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Combining exercise with fasting is known to boost fat mass-loss, but detailed analysis on the consequential mobilization of visceral and subcutaneous WAT-derived fatty acids has not been performed. In this study, a subset of fasted male rats (66 h) was submitted to daily bouts of mild exercise. Subsequently, by using gas chromatography—flame ionization detection, the content of 22 fatty acids (FA) in visceral (v) versus subcutaneous (sc) white adipose tissue (WAT) depots was compared to those found in response to the separate events. Findings were related to those obtained in serum and liver samples, the latter taking up FA to increase gluconeogenesis and ketogenesis. Each separate intervention reduced scWAT FA content, associated with increased levels of adipose triglyceride lipase (ATGL) protein despite unaltered AMP-activated protein kinase (AMPK) Thr172 phosphorylation, known to induce ATGL expression. The mobility of FAs from vWAT during fasting was absent with the exception of the MUFA 16:1 n-7 and only induced by combining fasting with exercise which was accompanied with reduced hormone sensitive lipase (HSL) Ser563 and increased Ser565 phosphorylation, whereas ATGL protein levels were elevated during fasting in association with the persistently increased phosphorylation of AMPK at Thr172 both during fasting and in response to the combined intervention. As expected, liver FA content increased during fasting, and was not further affected by exercise, despite additional FA release from vWAT in this condition, underlining increased hepatic FA metabolism. Both fasting and its combination with exercise showed preferential hepatic metabolism of the prominent saturated FAs C:16 and C:18 compared to the unsaturated FAs 18:1 n-9 and 18:2 n-6:1. In conclusion, depot-specific differences in WAT fatty acid molecule release during fasting, irrelevant to their degree of saturation or chain length, are mitigated when combined with exercise, to provide fuel to surrounding organs such as the liver which is correlated with increased ATGL/ HSL ratios, involving AMPK only in vWAT.

Crocetin (CCT) is a natural saffron-derived apocarotenoid that possesses healthy properties such as anti-adipogenic, anti-inflammatory, and antioxidant activities. Lipolysis is enhanced in obesity and correlates with a pro-inflammatory, pro-oxidant state. In this context, we aimed to investigate whether CCT affects lipolysis. To evaluate CCT’s possible lipolytic effect, 3T3-L1 adipocytes were treated with CCT10μM at day 5 post-differentiation. Glycerol content and antioxidant activity were assessed using colorimetric assays. Gene expression was measured using qRT-PCR to evaluate the effect of CCT on key lipolytic enzymes and on nitric oxide synthase (NOS) expression. Total lipid accumulation was assessed using Oil Red O staining. CCT10μM decreased glycerol release from 3T3-L1 adipocytes and downregulated adipose tissue triglyceride lipase (ATGL) and perilipin-1, but not hormone-sensitive lipase (HSL), suggesting an anti-lipolytic effect. CCT increased catalase (CAT) and superoxide dismutase (SOD) activity, thus showing an antioxidant effect. In addition, CCT exhibited an anti-inflammatory profile, i.e., diminished inducible NOS (NOS2) and resistin expression, while enhanced the expression of adiponectin. CCT10μM also decreased intracellular fat and C/EBPα expression (a transcription factor involved in adipogenesis), thus revealing an anti-adipogenic effect. These findings point to CCT as a promising biocompound for improving lipid mobilisation in obesity.

Neutral lipid storage disease type M (NLSD-M) is an ultra-rare, autosomal recessive disorder that causes severe skeletal and cardiac muscle damage and lipid accumulation in all body tissues. In this hereditary pathology, the defective action of the adipose triglyceride lipase (ATGL) enzyme induces the enlargement of cytoplasmic lipid droplets and reduction in the detachment of mono- (MG) and diglycerides (DG). Although the pathogenesis of muscle fiber necrosis is unknown, some studies have shown alterations in cellular energy production, probably because MG and DG, the substrates of Krebs cycle, are less available. No tests have been tried with medium-chain fatty acid molecules to evaluate the anaplerotic effect in NLSD cells. In this study, we evaluated the in vitro effect of triheptanoin (Dojolvi®), a highly purified chemical triglyceride with seven carbon atoms, in fibroblasts obtained from five NLSD-M patients. Glycolytic and mitochondrial functions were determined by Seahorse XF Agylent Technology, and cellular viability and triglyceride content were measured through colorimetric assays. After the addition of triheptanoin, we observed an increase in glycolysis and mitochondrial respiration in all patients compared with healthy controls. These preliminary results show that triheptanoin is able to induce an anaplerotic effect in NLSD-M fibroblasts, paving the way towards new therapeutic strategies.

Hintergrund: Im Kontext der Herzinsuffizienz werden verschiedene neurohumorale Systeme aktiviert, unter anderem der Sympathikus mit einer kontinuierlichen Katecholaminenfreisetzung. Während dies zunächst die verringerte Herzleistung kompensiert, trägt eine chronische Überstimulation durch strukturelle und funktionelle Veränderungen zur Progression der Herzinsuffizienz bei, insbesondere bei reduzierter Ejektionsfraktion. Ferner führt die Sympathikusaktivierung zur Lipolyseinduktion im Fettgewebe, was weiter zum Fortschreiten der Erkrankung beitragen kann. Kürzlich wurde gezeigt, dass eine Verringerung der Fettgewebslipolyse durch eine adipozytenspezifische Deletion des Schlüsselenzyms Adipozyten-Triglycerid-Lipase (ATGL) vor der Entwicklung einer druckinduzierten Herzinsuffizienz bei Mäusen schützt. In der vorliegenden Studie wurde daher die Hypothese aufgestellt, dass die pharmakologische Inhibition der Fettgewebslipolyse durch Atglistatin, einem adipozytenspezifischen ATGL-Inhibitor, einen Katecholamin-induzierten Herzschaden positiv beeinflusst. Methoden: Der Katecholamin-vermittelte Herzschaden wurde in 129/Sv-Mäusen durch viertägige subkutane Injektionen von Isoproterenol (ISO) induziert. Die orale Behandlung mit Atglistatin oder Kontrollfutter wurde fünf Tage zuvor begonnen und bis zum Ende des Versuchs fortgesetzt. Zwei und zwölf Tage nach der letzten ISO-Applikation wurde der Herzschaden mittels Echokardiographie einschließlich Speckle-Tracking-Technik, (Immun-)Histologie, Western Blot und RT-qPCR analysiert. Mechanistische Untersuchungen umfassten die massenspektrometrische Lipidomanalysen von Serum und Herzgewebe sowie Experimente in einem in vitro Modell zum kardialen Einfluss von Adipozyten. Ergebnisse: Langfristige Analysen zwölf Tage nach ISO zeigten eine ausgeprägte subendokardiale Fibrose, einen beeinträchtigten globalen longitudinalen Strain sowie eine pro-fibrotische Geninduktion, die durch Atglistatinbehandlung deutlich verbessert wurde. Mechanistische Analysen zwei Tage nach ISO ergaben eine pro-apoptotische Reaktion auf Gen- und Proteinebene, die durch die Atglistatintherapie nahezu vollständig blockiert wurde. Weiterhin verringerte Atglistatin den ISO-vermittelten Anstieg der lipotoxischen Diacylglyceride und Ceramide im Blut. Mehrere Ceramid-Spezies waren zudem auch in Herzen von Atglistatin behandelten ISO-Mäusen reduziert. In vitro reduzierte Atglistatin die ISO-vermittelte Freisetzung spezifischer Fettsäuren - Palmitinsäure, Palmitoleinsäure und Ölsäure - aus Adipozyten, die pro-apoptotische Effekte in Kardiomyozyten auslösten. Schlussfolgerung: Die vorliegende Arbeit deutet auf eine wichtige Rolle der Fettgewebslipolyse in der Entwicklung des Katecholamin-induzierten Herzschadens hin. Die Modifikation durch pharmakologische ATGL-Inhibition in Adipozyten stellt dabei eine neue Strategie zur Behandlung von kardiovaskulären Erkrankungen dar, die mit neurohumoraler Aktivierung und erhöhten Katecholaminspiegeln einhergehen., Background: Several neurohormonal systems are activated during heart failure, including the sympathetic nervous system with a sustained release of catecholamines. This response compensates for reduced cardiac output at first. However, chronic overactivation becomes detrimental by direct impairment of myocardial structure and function, particularly in heart failure with reduced ejection fraction. Moreover, exaggerated sympathetic activity results in a strong induction of adipose tissue lipolysis which may be another mechanism underlying the progression of heart failure. Recently, reduction of adipose tissue lipolysis by adipocyte-specific deletion of rate-limiting enzyme adipose triglyceride lipase (ATGL) has been shown to prevent pressure-mediated heart failure in mice. In this study, we hypothesized that pharmacological inhibition of adipose tissue lipolysis using Atglistatin, an adipocyte-specific ATGL inhibitor, attenuates catecholamine-induced cardiac damage. Methods: Catecholamine-mediated cardiac injury was induced in 129/Sv mice by subcutaneous injections of isoproterenol (ISO) for four days. Oral treatment with Atglistatin or control was started five days prior to ISO and continued throughout the experiment. Two and twelve days after final ISO application, cardiac damage was analyzed by echocardiography including speckle-tracking technique, (immuno-)histology, western blot and RT-qPCR. Mechanistic studies included mass spectrometry-based lipidome analyses of serum and cardiac tissue as well as investigations in an in vitro model of adipose tissue – heart crosstalk. Results: Long-term investigations twelve days after ISO revealed profound subendocardial fibrosis, an impaired global longitudinal strain and pro-fibrotic gene induction which was significantly ameliorated by treatment with Atglistatin. Mechanistic analyses two days after ISO showed strong pro-apoptotic gene and protein expression. Application of Atglistatin significantly blocked this pro-apoptotic response in the heart. Moreover, Atglistatin treatment significantly blocked the ISO-mediated increase of lipotoxic diacylglycerol und ceramide blood levels. Several ceramide species were also reduced in cardiac tissue of mice treated with ISO and Atglistatin. In vitro, Atglistatin attenuated the release of specific fatty acids - palmitic acid, palmitoleic acid, and oleic acid - by adipocytes in response to ISO stimulation, which exhibited pro-apoptotic signals in cardiomyocytes. Conclusion: This study highlights the importance of adipose tissue lipolysis in the development of catecholamine-induced cardiac injury. In this regard, modification of adipose tissue lipolysis by pharmacological adipocyte-specific ATGL inhibition may represent a novel strategy for the treatment of cardiovascular diseases associated with neurohormonal activation and elevated catecholamine levels.

Ubiquitin/ISG15-conjugating enzyme E2 L6 (UBE2L6/Ube2l6) catalyzes protein ISGylation and ubiquitylation, post-translational modifications which regulate protein stability. Ube2l6 plays a role in promoting in vitro adipogenesis; however, its mechanism(s) of action and in vivo effects remain unknown. Here, we discovered that UBE2L6 levels were upregulated, and UBE2L6 and adipose triglyceride lipase (ATGL/Atgl) levels were negatively correlated, in white adipose tissue (WAT) from obese humans and obese mice. Therefore, we employed adipose-specific Ube2l6 knockout (Ube2l6AKO) mice and age-matched Ube2l6flox/flox controls to assess adipocyte Ube2l6's role in high-fat diet (HFD)-induced obesity, insulin resistance, and hepatic steatosis. HFD-fed Ube2l6AKO mice displayed lower subcutaneous and visceral WAT mass levels relative to controls. HFD-fed Ube2l6AKO mice also showed WAT adipocyte hypoplasia and hypotrophy as well as enhanced whole-body metabolic activity relative to controls. Furthermore, glucose intolerance, insulin resistance, compensatory hyperinsulinemia, hypercholesterolemia, and hepatic steatosis were lower in HFD-fed Ube2l6AKO mice as compared to controls. Mechanistically, we found that Atgl protein expression and Atgl-mediated lipolysis were negatively regulated by Ube2l6's promotion of Atgl protein ubiquitylation. Collectively, adipocyte Ube2l6 functions as a negative regulator of Atgl protein stability and, consequently, promotes HFD-induced obesity, insulin resistance, and hepatic steatosis.

(1) Background: The glucocorticoid receptor (GR) plays a key role in lipid metabolism, but investigations of GR activation as a potential therapeutic approach have been hampered by a lack of selective agonists. Ginsenoside compound K (CK) is natural small molecule with a steroid-like structure that offers a variety of therapeutic benefits. Our study validates CK as a novel GR agonist for the treatment of obesity. (2) Methods: By using pulldown and RNA interference, we determined that CK binds to GR. The anti-obesity potential effects of CK were investigated in obese mice, including through whole-body energy homeostasis, glucose and insulin tolerance, and biochemical and proteomic analysis. Using chromatin immunoprecipitation, we identified GR binding sites upstream of lipase ATGL. (3) Results: We demonstrated that CK reduced the weight and blood lipids of mice more significantly than the drug Orlistat. Proteomics data showed that CK up-regulated autophagy regulatory proteins, enhanced fatty acid oxidation proteins, and decreased fatty acid synthesis proteins. CK induced lipophagy with the initial formation of the phagophore via AMPK/ULK1 activation. However, a blockade of autophagy did not disturb the increase in CK on lipase expression, suggesting that autophagy and lipase are independent pathways in the function of CK. The pulldown and siRNA experiments showed that GR is the critical target. After binding to GR, CK not only activated lipophagy, but also promoted the binding of GR to the ATGL promoter. (4) Conclusions: Our findings indicate that CK is a natural food candidate for reducing fat content and weight.

In response to inflammatory activation by pathogens, macrophages accumulate triglycerides in intracellular lipid droplets. The mechanisms underlying triglyceride accumulation and its exact role in the inflammatory response of macrophages are not fully understood. Here, we aim to further elucidate the mechanism and function of triglyceride accumulation in the inflammatory response of activated macrophages. Lipopolysaccharide (LPS)-mediated activation markedly increased triglyceride accumulation in macrophages. This increase could be attributed to up-regulation of the hypoxia-inducible lipid droplet-associated (HILPDA) protein, which down-regulated adipose triglyceride lipase (ATGL) protein levels, in turn leading to decreased ATGL-mediated triglyceride hydrolysis. The reduction in ATGL-mediated lipolysis attenuated the inflammatory response in macrophages after ex vivo and in vitro activation, and was accompanied by decreased production of prostaglandin-E2 (PGE2) and interleukin-6 (IL-6). Overall, we provide evidence that LPS-mediated activation of macrophages suppresses lipolysis via induction of HILPDA, thereby reducing the availability of proinflarnmatory lipid precursors and suppressing the production of PGE2 and IL-6.

Adipose triglyceride lipase (ATGL) has been discovered 14 years ago and revised our view on intracellular triglyceride (TG) mobilization – a process termed lipolysis. ATGL initiates the hydrolysis of TGs to release fatty acids (FAs) that are crucial energy substrates, precursors for the synthesis of membrane lipids, and ligands of nuclear receptors. Thus, ATGL is a key enzyme in whole-body energy homeostasis. In this review, we give an update on how ATGL is regulated on the transcriptional and post-transcriptional level and how this affects the enzymes' activity in the context of neutral lipid catabolism. In depth, we highlight and discuss the numerous physiological functions of ATGL in lipid and energy metabolism. Over more than a decade, different genetic mouse models lacking or overexpressing ATGL in a cell- or tissue-specific manner have been generated and characterized. Moreover, pharmacological studies became available due to the development of a specific murine ATGL inhibitor (Atglistatin®). The identification of patients with mutations in the human gene encoding ATGL and their disease spectrum has underpinned the importance of ATGL in humans. Together, mouse models and human data have advanced our understanding of the physiological role of ATGL in lipid and energy metabolism in adipose and non-adipose tissues, and of the pathophysiological consequences of ATGL dysfunction in mice and men., Highlights • Summary of mouse models with genetic or pharmacological manipulation of ATGL. • Summary of patients with mutations in the human gene encoding ATGL. • In depth discussion of the role of ATGL in numerous physiological processes in mice and men.

Background and Aim: Obesity is an excessive accumulation of fat and its storage due to an imbalance between energy intake and energy consumption. High-fat diets, through inhibition of lipolysis enzymes can lead to increase in obesity and also many metabolic diseases. While exercise can activate these enzymes and lead to a change in the amount of visceral adipose tissue and reduce obesity. The purpose of this study was to investigate the effect of high intensity interval training (HIIT) and moderate intensity continuous training (MICT) on the content of perilipin 1, ATGL, and CGI-58 in visceral adipose tissue of obese male rats. Material and Methods: Forty male Wistar rats were divided into five groups of eight. A group of 8 rats consumed standard diet (SD) for 10 weeks, and 32 other rats used high-fat diet (HFD) for 10 weeks. After induction of obesity, 8 rats from high fat diet group and 8 rats from standard dietary group were killed, and the samples were collected to study the effects of high-fat diet. Other obese rats were randomly divided into three groups: high-fat diet sedentary (HFD+SED), moderate-intensity continuous training protocol (MICT), and high-intensity interval training protocol (HIIT). The HIIT protocol consisted of 10 times of running, each time for 4 minutes, on a treadmill with an intensity of 90-85% VO2max, with 2 minutes active rest periods, and the MICT protocol included running on treadmill with an intensity of 70-65% VO2max, which had been matched with the HIIT protocol in terms of distance. 5 sessions of The training scheduals were performed per week for 12 weeks. Finally, the samples were collected by western blot method to measure the content of perilipin 1, ATGL, CGI-58. Results: The results of this study showed that obesity caused a significant reduction in the content of prilipin 1, ATGL and CGI-58. While both moderate-intensity continuous training and high-intensity interval training significantly increased the content of perilipin 1 and ATGL (p≤ 0.05). Also, the high-intensity interval training led to a significant increase in CGI-58 content (p

Hibernation is an adaptive survival strategy in response to cold and foodless winter. To determine the underlying mechanisms of seasonal adaptions, transcriptome sequencing studies have been conducted in bears, ground squirrels and bats. Despite advances in identifying differentially expressed genes involved in metabolism, the precise mechanisms of these physiological adaptions remain unclear. In the present study, we examined liver of Chinese Soft-Shelled Turtle (Pelodiscus sinensis) and found that the contents of lipid droplet (LD) and triglyceride (TG) were significantly decreased during hibernation. Increases in mRNA expression levels of lipolysis-related genes and decreased levels of lipogenesis-related genes during hibernation indicated that LD hydrolysis was stimulated during hibernation. To continuously release fatty acids (FAs) from LD, adipose triglyceride lipase (ATGL) was recruited and accumulated on the surface of LDs via activation of Cyclic Adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling. Meanwhile, increased phosphorylation of the LD-associated protein, perilipin-5, activated the enzyme activity of ATGL via interaction between comparative gene identification-58 (CGI-58) and ATGL. Taken together, our results indicated that ATGL accumulation on the LD surface and its induced enzyme activity during hibernation promoted LD breakdown in the liver of Chinese Soft-Shelled Turtle (Pelodiscus sinensis), thereby enhancing mitochondrial β-oxidation to maintain energy hemostasis.

Background In the last decades, the concept of metabolic rewiring as a cancer hallmark has been expanded beyond the “Warburg effect” and the importance of other metabolic routes, including lipid metabolism, has emerged. In cancer, lipids are not only a source of energy but are also required for the formation of membranes building blocks, signaling and post-translational modification of proteins. Since lipid metabolism contributes to the malignancy of cancer cells, it is an attractive target for therapeutic strategies. Methods Over-expression of the adipose triglyceride lipase (ATGL) was used to boost lipid catabolism in cervical cancer cells. The cervical cancer cell line HeLa was employed as the primary experimental model for all subsequent studies. The lipolytic activity of ATGL was mimicked by caproate, a short-chain fatty acid that is efficiently oxidized in mitochondria. Results Here, we provide evidence of the association between boosted lipid catabolism and the increased proliferation and migration capability of cervical cancer cells. These pro-tumoral effects were ascribed to the reactive oxygen species (ROS)-mediated induction of hypoxia-inducible factor-1α (HIF1α) triggered by the increased mitochondrial fatty acids (FAs) oxidation. HIF1α activation increases glycolytic flux and lactate production, promoting cell proliferation. At the same time, HIF1α increases protein and mRNA levels of its known target BCL2 and adenovirus E1B 19-kDa-interacting protein 3 (BNIP3), which in turn activates mitophagy as a pro-survival process, as demonstrated by the induction of apoptosis upon inhibition of mitophagy. These effects were mimicked by the short-chain fatty acid caproate, confirming that forcing lipid catabolism results in HIF1α induction. Conclusions Boosting lipid catabolism by ATGL over-expression has a pro-tumor role in cervical cancer cells, dependent on ROS production and HIF1α induction. Together with the bioinformatics evidence of the correlation of ATGL activity with the aggressiveness of cervical cancer cells, our data suggest that ATGL could be a promising prognostic marker for cervical cancer and highlight the need of further investigations on the role of this lipase in cancer cells. This evidence could be exploited to develop new personalized therapy, based on the functionality of the antioxidant equipment of cancer cells, considering that ROS content could affect ATGL role.

International audience; In hepatocytes, peroxisome proliferator-activated receptor α (PPARα) orchestrates a genomic and metabolic response required for homeostasis during fasting. This includes the biosynthesis of ketone bodies and of fibroblast growth factor 21 (FGF21). Here we show that in the absence of adipose triglyceride lipase (ATGL) in adipocytes, ketone body and FGF21 production is impaired upon fasting. Liver gene expression analysis highlights a set of fasting-induced genes sensitive to both ATGL deletion in adipocytes and PPARα deletion in hepatocytes. Adipose tissue lipolysis induced by activation of the β3-adrenergic receptor also triggers such PPARα-dependent responses not only in the liver but also in brown adipose tissue (BAT). Intact PPARα activity in hepatocytes is required for the cross-talk between adipose tissues and the liver during fat mobilization.

International audience; Branched esters of palmitic acid and hydroxy stearic acid are antiinflammatory and antidiabetic lipokines that belong to a family of fatty acid (FA) esters of hydroxy fatty acids (HFAs) called FAHFAs. FAHFAs themselves belong to oligomeric FA esters, known as estolides. Glycerol-bound FAHFAs in triacylglycerols (TAGs), named TAG estolides, serve as metabolite reservoir of FAHFAs mobilized by lipases upon demand. Here, we characterized the involvement of two major metabolic lipases, adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL), in TAG estolide and FAHFA degradation. We synthesized a library of 20 TAG estolide isomers with FAHFAs varying in branching position, chain length, saturation grade, and position on the glycerol backbone and developed an in silico mass spectra library of all predicted catabolic intermediates. We found that ATGL alone or coactivated by comparative gene identification-58 efficiently liberated FAHFAs from TAG estolides with a preference for more compact substrates where the estolide branching point is located near the glycerol ester bond. ATGL was further involved in transesterification and remodeling reactions leading to the formation of TAG estolides with alternative acyl compositions. HSL represented a much more potent estolide bond hydrolase for both TAG estolides and free FAHFAs. FAHFA and TAG estolide accumulation in white adipose tissue of mice lacking HSL argued for a functional role of HSL in estolide catabolism in vivo. Our data show that ATGL and HSL participate in the metabolism of estolides and TAG estolides in distinct manners and are likely to affect the lipokine function of FAHFAs.

Previously, we demonstrated that a 5% ethanol extract of unripe Rubus coreanus (5-uRCK) and ellagic acid has hypocholesterolemic and antiobesity activity, at least partially mediated by the downregulation of adipogenic and lipogenic gene expression in high-fat diet (HFD)-fed animals. The present study investigated the thermogenic and lipolytic antiobesity effects of 5-uRCK and ellagic acid in HFD-induced obese C57BL/6 mice and explored its mechanism of action. Mice fed an HFD received 5-uRCK or ellagic acid as a post-treatment or pretreatment. Both post-treated and pretreated mice showed significant reductions in body weight and adipose tissue mass compared to the HFD-fed mice. The protein levels of lipolysis-associated proteins, such as adipose triglyceride lipase (ATGL), phosphorylated hormone-sensitive lipase (p-HSL), and perilipin1 (PLIN1), were significantly increased in both the 5-uRCK- and ellagic acid-treated mouse epididymal white adipose tissue (eWAT). Additionally, thermogenesis-associated proteins, such as peroxisome proliferator-activated receptor α (PPARα), carnitine palmitoyl transferase-1 (CPT1), uncoupling protein 1 (UCP1), and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α), in inguinal white adipose tissue (ingWAT) were clearly increased in both the 5-uRCK- and ellagic acid-treated mice compared to HFD-fed mice. These results suggest that 5-uRCK and ellagic acid are effective for suppressing body weight gain and enhancing the lipid profile.

Monocytes are key players in innate immunity mechanisms. They originate from the bone marrow and contribute to the whole-body homeostasis maintenance by being mobilized to the blood circulation in case of injury or chronic inflammation for example. There, monocytes can either stay in the blood circulation, or be recruited to peripheral tissues where they can differentiate into macrophages. Since the 70’s the metabolic control of immune cell survival, function and fate, mostly in macrophages that are involved in numerous cardio-metabolic diseases, gained great interest from the scientific community. However, the monocyte-specific metabolic control is still ill-defined. Interestingly, in steady state, blood monocyte numbers oscillate throughout the day on a 24h basis. Moreover, we highlighted a correlation between circulating monocyte number oscillation pattern and fatty acid levels during the day. Therefore, during my Ph.D. I focused on deciphering the possible causality that unites those phenomena and more particularly on studying the impact of energetic metabolites such as fatty acids on the control of monocytes. In this purpose, we generated a genetic mouse model deficient for the lipolysis adipose tissue key enzyme, namely Atgl. Here, we show that the inhibition of adipose tissue lipolysis leads to stress and specific chronic inflammation in the brown adipose tissue, associated to a local monocyte recruitment in a CCR2-dependant manner. This brown adipose tissue monocyte recruitment was paralleled to a decrease in blood monocyte numbers. However, we failed to see alterations in the bone marrow compartment, responsible for hematopoiesis and blood cell production. Thus, we highlighted the major role of adipose tissue lipolysis and monocyte recruitment on brown adipose tissue homeostasis., Les monocytes font partie des acteurs majeurs de l’immunité innée. Ils sont générés dans la moelle osseuse et contribuent à garantir le maintien de l’homéostasie de l’organisme en cas de blessure ou d’inflammation chronique par leur mobilisation dans le sang et leur recrutement dans les tissus où ils ont la capacité de se différencier en macrophages. Depuis les années 1970, l’étude du contrôle exercé par le métabolisme sur la survie, la fonction et le devenir des cellules immunitaires, et plus particulièrement des macrophages, impliqués dans de nombreuses pathologies cardio-métaboliques, a gagné un grand intérêt auprès de la communauté scientifique. Cependant, les données recueillies sur l’impact du métabolisme sur les monocytes restent très limitées. De façon intéressante à l’état physiologique, le nombre de monocytes dans la circulation sanguine varie au cours de la journée. De plus, nous avons mis en évidence une corrélation entre le nombre de monocytes présents dans la circulation et les taux d’acides gras circulants au cours de la journée. Ainsi, durant ma thèse je me suis intéressée à l’étude de la potentielle causalité qui unit ces deux phénomènes et plus particulièrement à l’impact des métabolites énergétiques tels que les acides gras sur le contrôle des monocytes. Pour ce faire, nous avons utilisé un modèle murin génétiquement déficient pour l’enzyme clé responsable de la libération des acides gras à travers la lipolyse du tissu adipeux, appelée Atgl. Nous avons pu mettre en évidence que l’altération de la lipolyse du tissu adipeux entraine un stress et une inflammation chronique spécifique du tissu adipeux brun, associés à un recrutement local massif des monocytes de façon dépendante de l’expression du récepteur aux chimiokines CCR2. Le recrutement accru des monocytes dans le tissu adipeux brun est également associé à une diminution des taux de monocytes dans la circulation sanguine. Cependant chez ces souris, nous n’avons pas observé d’altération du compartiment médullaire, siège de l’hématopoïèse et de la production des cellules sanguines. Nos résultats permettent ainsi de mettre en évidence l’importance de la lipolyse ainsi que du recrutement des monocytes sur le maintien de l’homéostasie du tissu adipeux brun.

Monocytes are key players in innate immunity mechanisms. They originate from the bone marrow and contribute to the whole-body homeostasis maintenance by being mobilized to the blood circulation in case of injury or chronic inflammation for example. There, monocytes can either stay in the blood circulation, or be recruited to peripheral tissues where they can differentiate into macrophages. Since the 70’s the metabolic control of immune cell survival, function and fate, mostly in macrophages that are involved in numerous cardio-metabolic diseases, gained great interest from the scientific community. However, the monocyte-specific metabolic control is still ill-defined. Interestingly, in steady state, blood monocyte numbers oscillate throughout the day on a 24h basis. Moreover, we highlighted a correlation between circulating monocyte number oscillation pattern and fatty acid levels during the day. Therefore, during my Ph.D. I focused on deciphering the possible causality that unites those phenomena and more particularly on studying the impact of energetic metabolites such as fatty acids on the control of monocytes. In this purpose, we generated a genetic mouse model deficient for the lipolysis adipose tissue key enzyme, namely Atgl. Here, we show that the inhibition of adipose tissue lipolysis leads to stress and specific chronic inflammation in the brown adipose tissue, associated to a local monocyte recruitment in a CCR2-dependant manner. This brown adipose tissue monocyte recruitment was paralleled to a decrease in blood monocyte numbers. However, we failed to see alterations in the bone marrow compartment, responsible for hematopoiesis and blood cell production. Thus, we highlighted the major role of adipose tissue lipolysis and monocyte recruitment on brown adipose tissue homeostasis.; Les monocytes font partie des acteurs majeurs de l’immunité innée. Ils sont générés dans la moelle osseuse et contribuent à garantir le maintien de l’homéostasie de l’organisme en cas de blessure ou d’inflammation chronique par leur mobilisation dans le sang et leur recrutement dans les tissus où ils ont la capacité de se différencier en macrophages. Depuis les années 1970, l’étude du contrôle exercé par le métabolisme sur la survie, la fonction et le devenir des cellules immunitaires, et plus particulièrement des macrophages, impliqués dans de nombreuses pathologies cardio-métaboliques, a gagné un grand intérêt auprès de la communauté scientifique. Cependant, les données recueillies sur l’impact du métabolisme sur les monocytes restent très limitées. De façon intéressante à l’état physiologique, le nombre de monocytes dans la circulation sanguine varie au cours de la journée. De plus, nous avons mis en évidence une corrélation entre le nombre de monocytes présents dans la circulation et les taux d’acides gras circulants au cours de la journée. Ainsi, durant ma thèse je me suis intéressée à l’étude de la potentielle causalité qui unit ces deux phénomènes et plus particulièrement à l’impact des métabolites énergétiques tels que les acides gras sur le contrôle des monocytes. Pour ce faire, nous avons utilisé un modèle murin génétiquement déficient pour l’enzyme clé responsable de la libération des acides gras à travers la lipolyse du tissu adipeux, appelée Atgl. Nous avons pu mettre en évidence que l’altération de la lipolyse du tissu adipeux entraine un stress et une inflammation chronique spécifique du tissu adipeux brun, associés à un recrutement local massif des monocytes de façon dépendante de l’expression du récepteur aux chimiokines CCR2. Le recrutement accru des monocytes dans le tissu adipeux brun est également associé à une diminution des taux de monocytes dans la circulation sanguine. Cependant chez ces souris, nous n’avons pas observé d’altération du compartiment médullaire, siège de l’hématopoïèse et de la production des cellules sanguines. Nos résultats permettent ainsi de mettre en évidence l’importance de la lipolyse ainsi que du recrutement des monocytes sur le maintien de l’homéostasie du tissu adipeux brun.

Adaptation to nutrient availability is crucial for survival. Upon nutritional stress, such as during prolonged fasting or cold exposure, organisms need to balance the feeding of tissues and the maintenance of body temperature. The mechanisms that regulate the adaptation of brown adipose tissue (BAT), a key organ for non-shivering thermogenesis, to variations in nutritional state are not known. Here we report that specific deletion of the activin receptor ALK7 in BAT resulted in fasting-induced hypothermia due to exaggerated catabolic activity in brown adipocytes. After overnight fasting, BAT lacking ALK7 showed increased expression of genes responsive to nutrient stress, including the upstream regulator KLF15, aminoacid catabolizing enzymes, notably proline dehydrogenase (POX), and adipose triglyceride lipase (ATGL), as well as markedly reduced lipid droplet size. In agreement with this, ligand stimulation of ALK7 suppressed POX and KLF15 expression in both mouse and human brown adipocytes. Treatment of mutant mice with the glucocorticoid receptor antagonist RU486 restored KLF15 and POX expression levels in mutant BAT, suggesting that loss of BAT ALK7 results in excessive activation of glucocorticoid signaling upon fasting. These results reveal a novel signaling pathway downstream of ALK7 which regulates the adaptation of BAT to nutrient availability by limiting nutrient stress-induced overactivation of catabolic responses in brown adipocytes.

Nearly all cell types have the ability to store excess energy as triglycerides in specialized organelles called lipid droplets. The formation and degradation of lipid droplets is governed by a diverse set of enzymes and lipid droplet-associated proteins. One of the lipid droplet-associated proteins is Hypoxia Inducible Lipid Droplet Associated (HILPDA). HILPDA was originally discovered in a screen to identify novel hypoxia-inducible proteins. Apart from hypoxia, levels of HILPDA are induced by fatty acids and adrenergic agonists. HILPDA is a small protein of 63 amino acids in humans and 64 amino acids in mice. Inside cells, HILPDA is located in the endoplasmic reticulum and around lipid droplets. Gain- and loss-of-function experiments have demonstrated that HILPDA promotes lipid storage in hepatocytes, macrophages and cancer cells. HILPDA increases lipid droplet accumulation at least partly by inhibiting triglyceride hydrolysis via ATGL and stimulating triglyceride synthesis via DGAT1. Overall, HILPDA is a novel regulatory signal that adjusts triglyceride storage and the intracellular availability of fatty acids to the external fatty acid supply and the capacity for oxidation.

Background and Aim: The purpose of this study was to investigate the effect of endurance training intensity (low, moderate and high) on the expression of skeletal muscle ATGL protein and serum levels of insulin and glucose in male diabetic rats. Material and Method: 40 streptozotocin induced diabetic male Wistar rats were randomly assigned to five groups of eight, including low (DL , moderate (DM) and high intensity (DH) endurance training diabetic groups, diabetic control group (D), and healthy control group (Con). Three sessions of endurance training with low intensity (DL( equivalent to 5-8 m / min, moderate intensity (DM) equivalent to 17-14 m / min and high intensity (DH) equivalent to 25-22 m / min were performed every week for eight weeks. The relative expression of ATGL protein was measured with western blot technique. Serum insulin and glucose levels were measured by ELISA method. To determine the difference between the groups we used one way ANOVA test. Result: The results showed a significant difference in the expression of ATGL between the control and training groups (with low, moderate and high intensity) (p=0.0002). This difference was significant between DH and D (p=0.0049), DH and DL (p = 0.0053) and also between DH and DM (P = 0.0136) groups. Serum glucose levels were also significantly different between the DH group with the groups D (p = 0.002) and DL (p = 0.039), also, the DM group with groups D (p = 0.0018) and DL (p = 0.0165). There was a significant difference in the amount of insulin in the DH group compared to the groups DL (p = 0.011), D (p = 0.0002), and the DM group with D (p = 0.014). Conclusion: Moderate and high intensity endurance training can to some extent compensate for diabetes-induced reduction in the expression of ATGL protein and cause reduction of serum insulin and glucose levels in diabetic rats. It seems higher intensity of endurance training can lead to greater increase in expression of ATGL in diabetic rats. Keywords: Diabetes, ATGL, Endurance training intensity, Insulin, Glucose. Received: Oct 17, 2017 Accepted: Jan 29, 2018

IntrodutionThe purpose of this study was investigating the effect of endurance training on protein expression of CGI-58, ATGL and serum levels of insulin and glucose in streptozotocin-induced diabetic rats. Methods: 24 male Wistar rats were randomly assigned to three groups of eight, including diabetic group with endurance exercise (D-E), diabetic (D) and healthy control groups (Con). After induction of diabetic rats by injection streptozotocin was administered intraperitoneal , endurance exercise was applied for eight weeks, three sessions pre week in diabetic rats. Exercise intensity was equal to a speed of 21-25 m / min. The relative expression of CGI-58 and ATGL protein was measured with western blot technique and serum insulin and glucose levels were measured with a specialized kit. One-way ANOVA test was performed using SPSS-20 software and at a significance level less than 5%. Results: Results showed that ATGL and CGI-58 values were significantly different between the three groups (p

Objective Brown adipose tissue (BAT) thermogenesis depends on the mobilization and oxidation of fatty acids from intracellular lipid droplets (LD) within brown adipocytes (BAs); however, the identity and function of LD proteins that control BAT lipolysis remain incomplete. Proteomic analysis of mouse BAT subcellular fractions identified vacuolar protein sorting 13C (VPS13C) as a novel LD protein. The aim of this work was to investigate the role of VPS13C on BA LDs. Methods Biochemical fractionation and high resolution confocal and immuno-transmission electron microscopy (TEM) were used to determine the subcellular distribution of VPS13C in mouse BAT, white adipose tissue, and BA cell culture. Lentivirus-delivered shRNA was used to determine the role of VPS13C in regulating lipolysis and gene expression in cultured BA cells. Results We found that VPS13C is highly expressed in mouse BAT where it is targeted to multilocular LDs in a subspherical subdomain. In inguinal white adipocytes, VPS13C was mainly observed on small LDs and β3-adrenergic stimulation increased VPS13C in this depot. Silencing of VPS13C in cultured BAs decreased LD size and triglyceride content, increased basal free fatty acid release, augmented the expression of thermogenic genes, and enhanced the lipolytic potency and efficacy of isoproterenol. Mechanistically, we found that BA lipolysis required activation of adipose tissue triglyceride lipase (ATGL) and that loss of VPS13C greatly increased the association of ATGL to LDs. Conclusions VPS13C is present on BA LDs where is targeted to a distinct subdomain. VPS13C limits the access of ATGL to LD and loss of VPS13C elevates lipolysis and promotes oxidative gene expression., Highlights • VPS13C is highly expressed on mouse brown adipose tissue lipid droplets. • VPS13C is present on lipid droplets in a unique subspheric pattern. • VPS13C silencing in BAs decreases lipid droplet size and triglyceride content. • VPS13C silencing in BAs increases lipolysis and oxidative gene expression. • VPS13C silencing in BAs enhances ATGL but not HSL targeting to LDs.

Lipolysis is a catabolic reaction that is mediated by adipose triglyceride lipase (ATGL) and its inhibitor such as G0/G1 switch gene 2 (G0S2) protein during the first step of hydrolysis. The hydrophobic domain of G0S2 protein interacts and binds to the patatin-like domain in ATGL. Although conservation of the hydrophobic domain has been reported across species, sheep G0S2 amino acids and its hydrophobic domain have not been sequenced and studied. In this study, the hydrophobic region of G0S2 which plays an important role in inhibition of ATGL-mediated lipolysis was highly conserved as shown in other species. Phylogenetic analysis revealed that ruminant G0S2 proteins showed greater homologies within the ruminant species compared to other mammalian species. Moreover, adipose-specific expression of G0S2 for sheep was observed. Together with an abundant expression of ATGL protein in adipose tissue of sheep, G0S2 protein may play a critical role in inhibiting ATGL-mediated triacylglycerol (TAG) hydrolysis in the adipose tissue. Fil: Ahn, Jinsoo. Ohio University; Estados Unidos Fil: Wu, Huiguang. Ohio University; Estados Unidos. Inner Mongolia University for Nationalities; China Fil: Suh, Yeunsu. Ohio University; Estados Unidos Fil: Carranza Martin, Ana Cristina. Ohio University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Relling, Alejandro Enrique. Ohio University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Shin, Sangsu. Kyungpook National University; Corea del Sur Fil: Lee, Sang Suk. Ohio University; Estados Unidos. Sunchon National University; Corea del Sur Fil: Lee, Kichoon. Ohio University; Estados Unidos

The excessive accumulation of body fat has become a serious problem in the broiler industry. However, the molecular mechanisms underlying the regulation of lipid metabolism-related genes in broiler chickens are not fully understood. In the present study, we investigated the role of glucagon on the expression of lipid metabolism-related genes in chicken white adipose tissue (WAT). Four hours of fasting significantly increased plasma levels of free fatty acid in broiler chickens. The mRNA levels of adipose triglyceride lipase (ATGL) and pyruvate dehydrogenase kinase 4 (PDK4) in abdominal WAT significantly increased by fasting, whereas the mRNA levels of diacylglycerol O-acyl-transferase homolog 2 (DGAT2) and peroxisome proliferator-activated receptor-γ (PPARγ) significantly decreased. The results suggest that fasting stimulates lipolysis and suppresses adipogenesis and re-esterification of TG in chicken WAT. Glucagon significantly increased the mRNA levels of PDK4 in chicken primary adipocytes, whereas there were no significant changes in the mRNA levels of ATGL, DGAT2, and PPARγ. Our findings suggest that glucagon upregulates PDK4 expression and may stimulate lipolysis without affecting the expression of ATGL in chicken WAT.

Aberrant fatty acid (FA) metabolism is a hallmark of proliferating cells, including untransformed fibroblasts or cancer cells. Lipolysis of intracellular triglyceride (TG) stores by adipose triglyceride lipase (ATGL) provides an important source of FAs serving as energy substrates, signaling molecules, and precursors for membrane lipids. To investigate if ATGL-mediated lipolysis impacts cell proliferation, we modified ATGL activity in murine embryonic fibroblasts (MEFs) and in five different cancer cell lines to determine the consequences on cell growth and metabolism. Genetic or pharmacological inhibition of ATGL in MEFs causes impaired FA oxidation, decreased ROS production, and a substrate switch from FA to glucose leading to decreased AMPK-mTOR signaling and higher cell proliferation rates. ATGL expression in these cancer cells is low when compared to MEFs. Additional ATGL knockdown in cancer cells did not significantly affect cellular lipid metabolism or cell proliferation whereas the ectopic overexpression of ATGL increased lipolysis and reduced proliferation. In contrast to ATGL silencing, pharmacological inhibition of ATGL by Atglistatin© impeded the proliferation of diverse cancer cell lines, which points at an ATGL-independent effect. Our data indicate a crucial role of ATGL-mediated lipolysis in the regulation of cell proliferation. The observed low ATGL activity in cancer cells may represent an evolutionary selection process and mechanism to sustain high cell proliferation rates. As the increasing ATGL activity decelerates proliferation of five different cancer cell lines this may represent a novel therapeutic strategy to counteract uncontrolled cell growth., Highlights • ATGL deficiency increases cell proliferation and decreases phosphorylation of AMPK in murine embryonic fibroblasts. • ATGL silencing does not reduce lipolysis or increase proliferation of diverse cancer cells. • Increasing ATGL activity represses cell proliferation in a panel of cancer cells. • Atglistatin© exhibits an ATGL independent tumor suppressive effect.

Summary: Obesity leads to a state of chronic, low-grade inflammation that features the accumulation of lipid-laden macrophages in adipose tissue. Here, we determined the role of macrophage lipid-droplet accumulation in the development of obesity-induced adipose-tissue inflammation, using mice with myeloid-specific deficiency of the lipid-inducible HILPDA protein. HILPDA deficiency markedly reduced intracellular lipid levels and accumulation of fluorescently labeled fatty acids. Decreased lipid storage in HILPDA-deficient macrophages can be rescued by inhibition of adipose triglyceride lipase (ATGL) and is associated with increased oxidative metabolism. In diet-induced obese mice, HILPDA deficiency does not alter inflammatory and metabolic parameters, despite markedly reducing lipid accumulation in macrophages. Overall, we find that HILPDA is a lipid-inducible, physiological inhibitor of ATGL-mediated lipolysis in macrophages and uncouples lipid storage in adipose tissue macrophages from inflammation and metabolic dysregulation. Our data question the contribution of lipid droplet accumulation in adipose tissue macrophages in obesity-induced inflammation and metabolic dysregulation. : Lipid-laden macrophages are believed to play a key role in obesity-induced adipose tissue inflammation. Van Dierendonck et al. show that the lipid-droplet-associated protein HILPDA regulates intracellular triglyceride breakdown by directly inhibiting ATGL and that reduced lipid accumulation in adipose tissue macrophages surprisingly does not affect adipose tissue inflammation. Keywords: Hilpda, ATGL, fatty acid metabolism, lipid droplets, macrophages, inflammation, obesity

When administered to rats receiving a high-fat diet (HFD), 3,5-diiodo-L-thyronine (3,5-T2) [at a dose of 25 &mu, g/100 g body weight (BW)] is known to increase energy expenditure and to prevent HFD-induced adiposity. Here, we investigated which cellular and molecular processes in visceral white adipose tissue (VAT) contributed to the beneficial effect of 3,5-T2 over time (between 1 day and 4 weeks following administration). 3,5-T2 programmed the adipocyte for lipolysis by rapidly inducing hormone sensitive lipase (HSL) phosphorylation at the protein kinase A-responsive site Ser563, accompanied with glycerol release at the 1-week time-point, contributing to the partial normalization of adipocyte volume with respect to control (N) animals. After two weeks, when the adipocyte volumes of HFD-3,5-T2 rats were completely normalized to those of the controls (N), 3,5-T2 consistently induced HSL phosphorylation at Ser563, indicative of a combined effect of 3,5-T2-induced adipose lipolysis and increasing non-adipose oxidative metabolism. VAT proteome analysis after 4 weeks of treatment revealed that 3,5-T2 significantly altered the proteomic profile of HFD rats and produced a marked pro-angiogenic action. This was associated with a reduced representation of proteins involved in lipid storage or related to response to oxidative stress, and a normalization of the levels of those involved in lipogenesis-associated mitochondrial function. In conclusion, the prevention of VAT mass-gain by 3,5-T2 occurred through different molecular pathways that, together with the previously reported stimulation of resting metabolism and liver fatty acid oxidation, are associated with an anti adipogenic/lipogenic potential and positively impact on tissue health.

Neutral lipid storage disease with myopathy (NLSDM) and with ichthyosis (NLSDI) are rare autosomal recessive disorders caused by mutations in the PNPLA2 and in the ABHD5/CGI58 genes, respectively. These genes encode the adipose triglyceride lipase (ATGL) and α-β hydrolase domain 5 (ABHD5) proteins, which play key roles in the function of lipid droplets (LDs). LDs, the main cellular storage sites of triacylglycerols and sterol esters, are highly dynamic organelles. Indeed, LDs are critical for both lipid metabolism and energy homeostasis. Partial or total PNPLA2 or ABHD5/CGI58 knockdown is characteristic of the cells of NLSD patients; thus, these cells are natural models with which one can unravel LD function. In this review we firstly summarize genetic and clinical data collected from NLSD patients, focusing particularly on muscle, skin, heart, and liver damage due to impaired LD function. Then, we discuss how NLSD cells were used to investigate and expand the current structural and functional knowledge of LDs.

Purpose The cornea is richly innervated by the trigeminal ganglion (TG) and its function supported by secretions from the adjacent lacrimal (LG) and meibomian glands (MG). In this study we examined how pigment epithelium-derived factor (PEDF) gene deletion affects the cornea structure and function. Methods We used PEDF hemizygous and homozygous knockout mice to study effects of PEDF deficiency on corneal innervation assessed by beta tubulin staining, mRNA expression of trophic factors, and PEDF receptors by adjacent supporting glands, corneal sensitivity measured using a Cochet-Bonnet esthesiometer, and tear production using phenol red cotton thread wetting. Results Loss of PEDF was accompanied by reduced corneal innervation and sensitivity, increased corneal surface injury and tear production, thinning of the corneal stroma and loss of stromal cells. PEDF mRNA was expressed in the cornea and its supporting tissues, the TG, LG, and MG. Deletion of one or both PEDF alleles resulted in decreased expression of essential trophic support in the TG, LG, and MG including nerve growth factor, brain-derived neurotrophic growth factor, and GDNF with significantly increased levels of NT-3 in the LG and decreased EGF expression in the cornea. Decreased transcription of the putative PEDF receptors, adipose triglyceride lipase, lipoprotein receptor-related protein 6, laminin receptor, PLXDC1, and PLXDC2 was also evident in the TG, LG and MG with the first three showing increased levels in corneas of the Pedf+/- and Pedf-/- mice compared to wildtype controls. Constitutive inactivation of ERK1/2 and Akt was pronounced in the TG and cornea, although their protein levels were dramatically increased in Pedf-/- mice. Conclusions This study highlights an essential role for PEDF in corneal structure and function and confirms the reported rescue of exogenous PEDF treatment in corneal pathologies. The pleiotropic effects of PEDF deletion on multiple trophic factors, receptors and signaling molecules are strong indications that PEDF is a key coordinator of molecular mechanisms that maintain corneal function and could be exploited in therapeutic options for several ocular surface diseases.

SummaryLipolysis provides metabolic fuel; however, aberrant adipose lipolysis results in ectopic lipid accumulation and lipotoxicity. While adipose triacylglycerol lipase (ATGL) catalyzes the first step of lipolysis, its regulation is not fully understood. Here, we demonstrate that adipocyte Snail1 suppresses both ATGL expression and lipolysis. Adipose Snail1 levels are higher in fed mice than in fasted mice and higher in obese mice as opposed to lean mice. Insulin increases Snail1 levels in both murine and human adipocytes, wherein Snail1 binds to the ATGL promoter to repress its expression. Importantly, adipocyte-specific deletion of Snail1 increases adipose ATGL expression and lipolysis, resulting in decreased fat mass and increased liver fat content in mice fed either a normal chow diet or a high-fat diet. Thus, we have identified a Snail1-ATGL axis that regulates adipose lipolysis and fatty acid release, thereby governing lipid partitioning between adipose and non-adipose tissues.

The balance of lipid storage and utilization of lipids as a substrate of energy is maintained by complex biological signals. During nutrient-deficient condition or excess physical activity, fatty acids are produced through lipolysis of lipid droplets by lipases and provide energy, or autophagy is induced. This review will summarize the regulators of lipolysis that maintain energy homeostasis and cellular signaling.

Previously, we demonstrated that a 5% ethanol extract of unripe Rubus coreanus (5-uRCK) and ellagic acid has hypocholesterolemic and antiobesity activity, at least partially mediated by the downregulation of adipogenic and lipogenic gene expression in high-fat diet (HFD)-fed animals. The present study investigated the thermogenic and lipolytic antiobesity effects of 5-uRCK and ellagic acid in HFD-induced obese C57BL/6 mice and explored its mechanism of action. Mice fed an HFD received 5-uRCK or ellagic acid as a post-treatment or pretreatment. Both post-treated and pretreated mice showed significant reductions in body weight and adipose tissue mass compared to the HFD-fed mice. The protein levels of lipolysis-associated proteins, such as adipose triglyceride lipase (ATGL), phosphorylated hormone-sensitive lipase (p-HSL), and perilipin1 (PLIN1), were significantly increased in both the 5-uRCK- and ellagic acid-treated mouse epididymal white adipose tissue (eWAT). Additionally, thermogenesis-associated proteins, such as peroxisome proliferator-activated receptor &alpha, (PPAR&alpha, ), carnitine palmitoyl transferase-1 (CPT1), uncoupling protein 1 (UCP1), and peroxisome proliferator-activated receptor-&gamma, coactivator-1&alpha, (PGC1&alpha, ), in inguinal white adipose tissue (ingWAT) were clearly increased in both the 5-uRCK- and ellagic acid-treated mice compared to HFD-fed mice. These results suggest that 5-uRCK and ellagic acid are effective for suppressing body weight gain and enhancing the lipid profile.

Soy isoflavones are bioactive phytoestrogens with known health benefits. Soybean embryo extract (SEE) has been consumed as a source of isoflavones, mainly daidzein, glycitein, and genistein. While previous studies have reported the anti-obesity effects of SEE, this study investigates their molecular mechanisms and the synergistic effects of co-treatment with SEE and enzymatically modified isoquercitrin (EMIQ). SEE upregulated genes involved in lipolysis and brown adipocyte markers and increased mitochondrial content in differentiated C3H10T1/2 adipocytes in vitro. Next, we use a high-fat diet-induced obesity mouse model to determine the anti-obesity effect of SEE. Two weeks of single or combined treatment with SEE and EMIQ significantly reduced body weight gain and improved glucose tolerance. Mechanistically, SEE treatment increased mitochondrial content and upregulated genes involved in lipolysis in adipose tissue through the cAMP/PKA-dependent signaling pathway. These effects required a cytosolic lipase adipose triglyceride lipase (ATGL) expression, confirmed by an adipocyte-specific ATGL knockout mouse study. Collectively, this study demonstrates that SEE exerts anti-obesity effects through the activation of adipose tissue metabolism and exhibits a synergistic effect of co-treatment with EMIQ. These results improve our understanding of the mechanisms underlying the anti-obesity effects of SEE related to adipose tissue metabolism.

In adipose tissue, adipose triglyceride lipase (ATGL) and perilipin5 (PLIN5) play an important role in the regulation of lipolysis. However, little is known about the effect of interval training intensity on ATGL and PLIN5 in visceral adipose tissue of type 2 diabetic male rats. In this study, forty male Wistar rats were assigned into two groups as follows: healthy control (HC) (n=8) and T2D (n=32) groups which were fed with their corresponding diets for 10 weeks. After the induction of diabetes, CD animals and 8 rats from the D group were sacrificed (first experiment), and the remaining T2D animals were divided to moderate intensity interval training (MIIT), high intensity interval training (HIIT) and control (DC2) groups. Interval training (HIIT, MIIT) was applied for 12 weeks, 5 sessions per week. The MIIT protocol included 13 bouts of 4-minute activity with equivalent intensity of 60-65% vo2max and the HIIT protocol included 10 bouts of 4-minute activity with equivalent intensity of 85-90% vo2max with 2-minute active rest periods. The Western Blot method was used to measure PLIN5 and ATGL protein levels. ANOVA and Tukey's test were used for data analysis. The results indicated that type 2 diabetes resulted in a significant increase in the protein levels of PLIN5 (p

Background To determine whether adipocyte-derived lipids could be transferred into breast cancer cells and investigate the underlying mechanisms of subsequent lipolysis and fatty acid trafficking in breast cancer cells. Methods A Transwell co-culture system was used in which human breast cancer cells were cultured in the absence or presence of differentiated murine 3 T3-L1 adipocytes. Migration/invasion and proliferation abilities were compared between breast cancer cells that were cultivated alone and those co-cultivated with mature adipocytes. The ability of lipolysis in breast cancer cells were measured, as well as the expression of the rate-limiting lipase ATGL and fatty acid transporter FABP5. ATGL and FABP5 were then ablated to investigate their impact on the aggressiveness of breast cancer cells that were surrounded by adipocytes. Further, immunohistochemistry was performed to detect differential expression of ATGL and FABP5 in breast cancer tissue sections. Results The migration and invasion abilities of cancer cells were significantly enhanced after co-culture with adipocytes, accompanied by elevated lipolysis and expression of ATGL and FABP5. Abrogation of ATGL and FABP5 sharply attenuated the malignancy of co-cultivated breast cancer cells. However, this phenomenon was not observed if a lipid emulsion was added to the culture medium to substitute for adipocytes. Furthermore, epithelial-mesenchymal transaction was induced in co-cultivated breast cancer cells. That may partially due to the stimulation of PPARβ/δ and MAPK, which was resulted from upregulation of FABP5. As evidenced by immunohistochemistry, ATGL and FABP5 also had higher expression levels at the invasive front of the breast tumor, in where the adipocytes abound, compared to the central area in tissue specimens. Conclusions Lipid originating from tumor-surrounding adipocytes could be transferred into breast cancer cells. Adipocyte-cancer cell crosstalk rather than lipids alone induced upregulation of lipases and fatty acid transport protein in cancer cells to utilize stored lipids for tumor progression. The increased expression of the key lipase ATGL and intracellular fatty acid trafficking protein FABP5 played crucial roles in this process via fueling or signaling. Electronic supplementary material The online version of this article (10.1186/s12964-018-0221-6) contains supplementary material, which is available to authorized users.

Globally, approximately 10-25% of women smoke during pregnancy. Since nicotine is highly addictive, women may use nicotine containing products like nicotine replacement therapies for smoking cessation, but the long-term consequences of early life exposure to nicotine remain poorly defined. Our laboratory has previously demonstrated that maternal nicotine exposed (MNE) rat offspring exhibit hypertriglyceridemia due to increased hepatic de novo lipogenesis. Hypertriglyceridemia may also be attributed to impaired white adipose tissue (WAT) lipid storage; however, the effects of MNE on WAT are not completely understood. We hypothesize that nicotine-induced alterations in adipose function (e.g. lipid storage) underlie dyslipidemia in MNE adults. Female 6 month old rats exposed to nicotine during gestation and lactation exhibited significantly decreased visceral adipocyte cell area by 40%, attributed, in part, to a 3-fold increase in adipose triglyceride lipase (ATGL) protein expression compared to vehicle. Given ATGL has antioxidant properties and in utero nicotine exposure promotes oxidative stress in various tissues, we next investigated if there was evidence of increased oxidative stress in MNE WAT. At both 3 weeks and 6 months, MNE offspring expressed 37-48% higher protein levels of SOD1 and SOD2 in WAT. Since oxidative stress can induce inflammation, we examined the inflammatory profile of WAT and found increased expression of cytokines (IL-1β, TNFα, and IL-6) by 44-61% at 6 months. Collectively, this suggests that the expression of WAT ATGL may be induced to counter MNE-induced oxidative stress and inflammation. However, higher levels of ATGL would further promote lipolysis in WAT, culminating in impaired lipid storage and long-term dyslipidemia.

Introduction Cardiac metabolism undergoes changes in response to pathological left ventricular hypertrophy (LVH) and heart failure (HF), characterized by increased reliance on glycolysis, decreased fatty acid (FA) oxidation and a loss of metabolic flexibility. In addition to the heart, non-cardiac organs are involved in these metabolic changes. In this context, the influence of white adipose tissue (WAT) and its release of FA on the development of LVH and HF are not well investigated. The aim of this study was to investigate the effect of Adipose Triglyceride Lipase (ATGL) in WAT on the development of LVH and HF in a pressure overload-induced cardiac hypertrophy model in mice. Methods Male adipose tissue-specific ATGL knock-out (atATGL-KO) and wild-type mice (WT) underwent transverse aortic constriction (TAC-surgery) or sham- surgery. Echocardiography 1 week before, 5 and 11 weeks after Sham/TAC-surgery were performed to evaluate wall thickness, left ventricular mass (LVM) and cardiac function. In addition, histological and gene expression analysis of hearts were performed. Insulin sensitivity, body composition, glucose tolerance and FA serum levels were measured to investigate metabolic changes. Results TAC-surgery caused a significant increase in LVM compared to Sham- surgery in atATGL-KO and WT mice 5 weeks post-surgery. However, there were no significant differences in LVM between atATGL-KO and WT mice. 11 weeks after TAC-surgery, LVM in WT was significantly larger compared to atATGL-KO (LVM [mg] WT-TAC: 211.16±19.73; atATGL-KO-TAC: 124.32±9.06; p, Einleitung Der kardiale Metabolismus ändert sich während der Entwicklung einer linksventrikulären Hypertrophie (LVH) und einer Herzinsuffizienz (HF), welche gekennzeichnet ist durch eine erhöhte Abhängigkeit von Glykolyse, einer erniedrigten Oxidation von Fettsäuren (FA) und einem Verlust der metabolischen Flexibilität. Neben dem Herzen sind auch nicht-kardiale Organe von diesen metabolischen Veränderungen betroffen. In diesem Zusammenhang ist der Einfluss von weißen Fettgewebe (WAT) und seiner Freisetzung von FA auf die Entwicklung der LVH und HF wenig untersucht. Das Ziel dieser Studie war es, den Effekt von Adipozyten Triglycerid Lipase (ATGL) im WAT auf die Entwicklung einer LVH und HF in einem Model der druckinduzierenten kardialen Hypertrophie in der Maus zu untersuchen. Methoden Männliche fettgewebsspezifische ATGL knock-out (atATGL- KO) und Wildtyp Mäuse (WT) wurden einer transversen Aortenkonstriktion (TAC- OP) oder Scheinoperation (Sham-OP) unterzogen. 1 Woche vor, 5 und 11 Wochen nach der Sham/TAC-OP wurde die linksventrikuläre Masse (LVM) und die kardiale Funktion echokardiographisch untersucht. Zusätzlich wurden histologische und Genexpressions-Analysen der Herzen durchgeführt. Die Insulinsensitivität, Glukosetoleranz, Körperzusammensetzung und FA-Serumspiegel wurden gemessen, um metabolische Veränderungen zu untersuchen. Ergebnisse Die TAC-OP resultierte in einer signifikanten Zunahme der LVM im Vergleich zur Sham-OP bei atATGL-KO und WT Mäusen 5 Wochen nach OP. Es lagen jedoch keine signifikanten Unterschiede in der LVM zwischen atATGL-KO und WT Mäusen vor. 11 Wochen nach TAC-OP, LVM in WT war signifikant größer im Vergleich zu atATGL-KO (LVM [mg] WT-TAC: 211,16±19,73; atATGL-KO-TAC: 124,32±9,06; p

// Xiaoying Zhou 1, 2, * , Jiazhang Wei 1, * , Fu Chen 3 , Xue Xiao 1 , Tingting Huang 1 , Qian He 1 , Shumin Wang 1 , Chunping Du 1 , Yingxi Mo 1, 4 , Longde Lin 5 , Ying Xie 1 , Lili Wei 1 , Ying Lan 1 , Mairiko Murata 4 , Guangwu Huang 1 , Ingemar Ernberg 2 , Liudmila Matskova 2 , Zhe Zhang 1 1 Department of Otolaryngology-Head & Neck Surgery, First Affiliated Hospital of Guangxi Medical University, Guangxi, China 2 Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna, Sweden 3 Department of Radiation Oncology, Eye Ear Nose & Throat Hospital of Fudan University, Shanghai, China 4 Department of Environmental and Molecular Medicine, Mie University Graduate School of Medicine, Mie, Japan 5 School of Public Health, Guangxi Medical University, Guangxi, China * These authors have contributed equally to this work Correspondence to: Ingemar Ernberg e-mail: ingemar.ernberg@ki.se Zhe Zhang e-mail: zhangzhe@gxmu.edu.cn Keywords: UBE2L6, nasopharyngeal carcinoma, DNA methylation, tumor suppressor gene, ATGL Received: April 30, 2015 Accepted: August 20, 2015 Published: October 12, 2015 ABSTRACT We identified the UBE2L6 gene, encoding the ISG15-conjugating enzyme UbcH8, as one gene significantly downregulated by promoter hypermethylation in nasopharyngeal carcinoma (NPC). Reduced expression of the UbcH8 protein correlated with poor outcome in NPC patients. Restored expression of UBE2L6 suppressed proliferation and colony formation in NPC cells, while inducing apoptosis. Of particular interest, we found that aberrant lipid turnover was controlled by UbcH8 in NPC through ISG15-conjugation of valosin-containing protein (VCP). Tumor tissue and NPC cell lines showed conspicuously strong accumulation of lipid droplets (LDs) compared to control nasopharyngeal epithelium and non-cancerous cell lines. We demonstrated that UbcH8 counteracts degradation of adipocyte triglyceride lipase (ATGL), a key enzyme in lipid catabolism.

Background & AimsAdipose tissue (AT)-derived fatty acids (FAs) are utilized for hepatic triacylglycerol (TG) generation upon fasting. However, their potential impact as signaling molecules is not established. Herein we examined the role of exogenous AT-derived FAs in the regulation of hepatic gene expression by investigating mice with a defect in AT-derived FA supply to the liver.MethodsPlasma FA levels, tissue TG hydrolytic activities and lipid content were determined in mice lacking the lipase co-activator comparative gene identification-58 (CGI-58) selectively in AT (CGI-58-ATko) applying standard protocols. Hepatic expression of lipases, FA oxidative genes, transcription factors, ER stress markers, hormones and cytokines were determined by qRT-PCR, Western blotting and ELISA.ResultsImpaired AT-derived FA supply upon fasting of CGI-58-ATko mice causes a marked defect in liver PPARα-signaling and nuclear CREBH translocation. This severely reduced the expression of respective target genes such as the ATGL inhibitor G0/G1 switch gene-2 (G0S2) and the endocrine metabolic regulator FGF21. These changes could be reversed by lipid administration and raising plasma FA levels. Impaired AT-lipolysis failed to induce hepatic G0S2 expression in fasted CGI-58-ATko mice leading to enhanced ATGL-mediated TG-breakdown strongly reducing hepatic TG deposition. On high fat diet, impaired AT-lipolysis counteracts hepatic TG accumulation and liver stress linked to improved systemic insulin sensitivity.ConclusionsAT-derived FAs are a critical regulator of hepatic fasting gene expression required for the induction of G0S2-expression in the liver to control hepatic TG-breakdown. Interfering with AT-lipolysis or hepatic G0S2 expression represents an effective strategy for the treatment of hepatic steatosis.

The G0/G1 switch gene 2 (G0S2) is methylated and silenced in a wide range of human cancers. The protein encoded by G0S2 is an endogenous inhibitor of lipid catabolism that directly binds adipose triglyceride lipase (ATGL). ATGL is the rate-limiting step in triglyceride metabolism. Although the G0S2 gene is silenced in cancer, the impact of ATGL in the growth and survival of cancer cells has never been addressed. Here we show that ectopic expression of G0S2 in non-small cell lung carcinomas (NSCL) inhibits triglyceride catabolism and results in lower cell growth. Similarly, knockdown of ATGL increased triglyceride levels, attenuated cell growth and promoted apoptosis. Conversely, knockdown of endogenous G0S2 enhanced the growth and invasiveness of cancer cells. G0S2 is strongly induced in acute promyelocytic leukemia (APL) cells in response to all trans retinoic acid (ATRA) and we show that inhibition of ATGL in these cells by G0S2 is required for efficacy of ATRA treatment. Our data uncover a novel tumor suppressor mechanism by which G0S2 directly inhibits activity of a key intracellular lipase. Our results suggest that elevated ATGL activity may be a general property of many cancer types and potentially represents a novel target for chemotherapy.

Lipolysis is the biochemical pathway responsible for the catabolism of cellular triacylglycerol (TG). Lipolytic TG breakdown is a central metabolic process leading to the generation of free fatty acids (FA) and glycerol, thereby regulating lipid, as well as energy homeostasis. The precise tuning of lipolysis is imperative to prevent lipotoxicity, obesity, diabetes and other related metabolic disorders. Here, we present our finding that miR-124a attenuates RNA and protein expression of the major TG hydrolase, adipose triglyceride lipase (ATGL/PNPLA2) and its co-activator comparative gene identification 58 (CGI-58/ABHD5). Ectopic expression of miR-124a in adipocytes leads to reduced lipolysis and increased cellular TG accumulation. This phenotype, however, can be rescued by overexpression of truncated Atgl lacking its 3'UTR, which harbors the identified miR-124a target site. In addition, we observe a strong negative correlation between miR-124a and Atgl expression in various murine tissues. Moreover, miR-124a regulates the expression of Atgl and Cgi-58 in murine white adipose tissue during fasting as well as the expression of Atgl in murine liver, during fasting and re-feeding. Together, these results point to an instrumental role of miR-124a in the regulation of TG catabolism. Therefore, we suggest that miR-124a may be involved in the regulation of several cellular and organismal metabolic parameters, including lipid storage and plasma FA concentration.

Hepatic lipid droplet (LD) catabolism is thought to occur via cytosolic lipases such as adipose triglyceride lipase (ATGL) or through autophagy of LDs, a process known as lipophagy. We tested the potential interplay between these metabolic processes and its effects on hepatic lipid metabolism. We show that hepatic ATGL is both necessary and sufficient to induce both autophagy and lipophagy. Moreover, lipophagy is required for ATGL to promote LD catabolism and the subsequent oxidation of hydrolyzed fatty acids (FAs). Following previous work showing that ATGL promotes sirtuin 1 (SIRT1) activity, studies in liver-specific SIRT1−/− mice and in primary hepatocytes reveal that SIRT1 is required for ATGL-mediated induction of autophagy and lipophagy. Taken together, these studies show that ATGL-mediated signaling via SIRT1 promotes autophagy/lipophagy as a primary means to control hepatic LD catabolism and FA oxidation.

cope In recent years, several studies reported the role of eIF4E-binding proteins (4E-BPs) on the development of diet-induced obesity and insulin resistance. Our aim was to investigate the effect of 4E-BP protein deletion on lipid accumulation and metabolism in skeletal muscle in response to a high fat diet-induced obesity in 4E-BP1/2 DKO mice. Methods and results Diet-induced obesity engendered increased ectopic accumulation of lipotoxic species in skeletal muscle of 4E-BP1 and 4E-BP2 double-knockout mice (4E-BP1/2 DKO), namely diacylglycerols and ceramides. Increased lipid accumulation was associated with alterations in the expression of genes involved in fatty acid transport (FATP, CD36), diacylglycerol/triacylglycerol biosynthesis (GPAT1, AGPAT1, DGAT1) and β-oxidation (CPT1b, MCAD). Diet-induced obesity resulted in increased lean mass and muscle in 4E-BP1/2 DKO mice despite the development of a more severe systemic insulin resistance. Since increased expression of genes of several proteolytic systems (MuRF1, Atrogin/MAFbx and Cathepsin-L) in 4EBP1/2 DKO skeletal muscle was reported, the increased of skeletal muscle mass in 4E-BP1/2 DKO mice suggests that ablation of 4E-BPs compensate with activation of muscle anabolism. Conclusions These findings indicate that 4E-BP proteins may prevent excess lipid accumulation in skeletal muscle and suggest that 4E-BPs are key regulators of muscle homeostasis regardless of insulin sensitivity. This article is protected by copyright. All rights reserved

Synucleins are a family of homologous, predominantly neuronal proteins known for their involvement in synaptic transmission and neurodegeneration. γ-synuclein is predominantly localized in axons and presynaptic terminals of selected populations of peripheral and central neurons but is also highly expressed in human white adipose tissue (WAT) and increased in obesity. We have recently shown that γ-synuclein is nutritionally regulated in murine adipocytes while its loss protects mice from high fat diet (HFD)-induced obesity and associated metabolic complications. This protection was coupled with increased adipocyte lipolysis, lipid oxidation, and energy expenditure in HFD-fed γ-synuclein-null mutant compared with wild-type mice. Cellular studies suggest that relocalization of ATGL to the lipid droplet in γ-synuclein-deficient adipocytes may contribute to increased lipolysis in these cells. Loss of γ-synuclein in adipocytes also attenuates the assembly of SNARE complexes, an important component of lipid droplet fusion machinery, possibly due to reduced chaperoning of SNAP-23 to the assembling SNARE complex by γ-synuclein. Together our data suggests that not only is γ-synuclein a novel regulator of lipid handling in adipocytes but also that the deficiency of this protein has a significant effect on whole body energy expenditure.

My PhD research work was focused on the role of muscle lipids in the regulation of energy metabolism and insulin sensitivity. Lipids can be found under two different forms in skeletal muscle: adipocytes located between muscle fibers/bundles and lipid droplets inside muscle fibers (i.e. intramyocellular triacylglycerols or IMTG). These depots, when present in excess, have both been associated with insulin-resistance in humans, mainly because of intracellular lipotoxic lipid accumulation known to impair insulin signaling for IMTG, and through a yet unknown mechanism for adipocytes. First, we isolated and characterized two distinct populations of progenitor cells from human muscle biopsies. The first population is composed of satellite cells (muscle progenitor cells) and display a myogenic differentiation potential in vitro. The second population is composed of cells that acquire the phenotypic and metabolic properties of functional white adipocytes, called fibro/adipogenic progenitors (FAPs). By using these cell models, we showed that FAPs-derived adipocytes secretions are able to impair insulin signaling and action in human skeletal muscle fibers in vitro. This paracrine effect could explain, at least partly, the inverse relationship observed between intramuscular adipocyte content and insulin sensitivity in humans. Secondly, we studied the role of two proteins, G0/G1 Switch Gene 2 (G0S2) and perilipin 5 (PLIN5), in lipid droplets dynamics as well as their impact on lipid metabolism and insulin sensitivity. We showed in vitro that these two proteins play a key role in the control of muscle lipolysis (i.e. IMTG hydrolysis) via the adipose triglyceride lipase (ATGL, catalyzing the limiting step of muscle lipolysis), and that G0S2 and PLIN5 inhibit ATGL activity through direct and indirect mechanisms, respectively. Furthermore, our data showed that G0S2 and PLIN5 invalidation in vivo in mouse skeletal muscle activates lipolysis, increases lipotoxicity and impairs insulin sensitivity. We have also highlighted an important role for PLIN5 in the regulation of fatty acids oxidation, by finely adjusting their availability to energy demand. Overall, these results clearly show on one hand that a crosstalk between adipocytes and fibers within skeletal muscle can lead to an alteration of insulin sensitivity in humans, and on the other hand that G0S2 and PLIN5, two lipid droplet proteins, play a central role in the control of muscle lipid homeostasis and insulin sensitivity. These data help to develop our current understanding of the link between muscle lipids and insulin sensitivity in humans.; Mon travail de thèse a été axé sur l'étude du rôle des lipides musculaires dans la régulation du métabolisme énergétique et la sensibilité à l'insuline. Les lipides sont présents sous deux formes au sein du muscle squelettique : soit sous forme d'adipocytes insérés entre les fibres/faisceaux musculaires, soit sous forme de gouttelettes lipidiques à l'intérieur des fibres musculaires (i.e. triglycérides intramyocellulaires ou IMTG). Ces deux dépôts de lipides, lorsqu'ils sont présents en excès, sont associés à la mise en place de l'insulino-résistance musculaire chez l'homme, via l'accumulation intracellulaire d'espèces lipidiques lipotoxiques altérant la signalisation insulinique pour les IMTG, et par un mécanisme inconnu pour les adipocytes. Dans un premier temps, nous avons isolé et mieux caractérisé, à partir de biopsies musculaires humaines, deux populations de cellules progénitrices. La première population présente un potentiel de différenciation myogénique en culture, il s'agit des cellules satellites (cellules progénitrices musculaires). La deuxième population est composée de cellules capables d'acquérir les propriétés phénotypiques et métaboliques d'adipocytes blancs matures, il s'agit des progéniteurs fibro/adipocytaires (FAPs). Grace à ces modèles d'étude, nous avons mis en évidence que les sécrétions des adipocytes dérivés des FAPs sont capables d'altérer la voie de signalisation et les effets de l'insuline sur des fibres musculaires humaines in vitro. Cet effet paracrine pourrait en partie expliquer la corrélation négative observée entre le contenu en adipocytes intramusculaires et la sensibilité à l'insuline chez l'homme. Dans un second temps, nous avons étudié le rôle de deux protéines, G0/G1 Switch Gene 2 (G0S2) et la périlipine 5 (PLIN5), dans la dynamique des gouttelettes lipidiques ainsi que leur impact sur le métabolisme des lipides et la sensibilité à l'insuline. Nous avons montré in vitro que ces deux protéines jouent un rôle clé dans le contrôle de la lipolyse musculaire (i.e. hydrolyse des IMTG) via l'adipose triglyceride lipase (ATGL, enzyme limitante de la lipolyse musculaire), et que G0S2 et PLIN5 inhibent l'activité de l'ATGL par des mécanismes directs et indirects, respectivement. Par ailleurs, nos données ont montré que l'invalidation de G0S2 et PLIN5 dans le muscle squelettique active la lipolyse, augmente la lipotoxicité et diminue la sensibilité à l'insuline in vivo chez la souris. Nous avons également démontré un rôle important de PLIN5 dans la régulation de l'oxydation des acides gras en ajustant finement leur disponibilité aux besoins énergétiques des cellules. En résumé, ces travaux démontrent d'une part qu'une communication entre adipocytes et fibres au sein du muscle peut entraîner une altération de la sensibilité à l'insuline musculaire chez l'homme, et d'autre part que G0S2 et PLIN5, deux protéines de la gouttelette lipidique, sont au centre du contrôle de l'homéostasie lipidique et du maintien de l'insulino-sensibilité musculaire. Ces données permettent ainsi d'élargir les connaissances existantes sur le lien entre les lipides musculaires et la sensibilité à l'insuline chez l'homme.

Background Obesity is closely related to the metabolism of triacylglycerol (TG) in adipocytes. Adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) are rate-limiting enzymes that control the hydrolysis of TG. Effects on ATGL and HSL to increase lipolysis may counteract obesity. Berberine (BBR) is a compound derived from the Chinese medicine plant Coptis chinensis. In the present study we show the effects of BBR on ATGL and HSL and explore the potential underlying mechanisms of these effects. Methods The TG content in cells was measured using a colorimetric assay. The expressions of HSL, ATGL and GPAT3 were evaluated by Western-blotting. The expression of ATGL was also evaluated by real-time PCR and radioimmunoassay. Compound C, an inhibitor of AMP-activated protein kinase (AMPK), was used to explore the possible pathway that involved in the effect of BBR on ATGL. Results TG content of differentiated 3T3-L1 cells was significantly decreased by more than 10% after treated with BBR. In differentiated 3T3-L1 adipocytes, BBR increased the expression of p-HSL and ATGL, and these effects were time-depended (p

Triglycerides (TG) hydrolysis in adipose tissue is initialized by the action of the adipose TG lipase (ATGL) and its cofactor, the CGI-58 protein. Mutations in the gene coding the CGI-58 or ATGL proteins are the cause of the syndrome of Chanarin-Dorfman and of neutral lipids storage disease, respectively. CGI-58 protein belongs to the a/ß-hydrolase family, harboring the catalytic triad Ser-Asp/Glu-His, characteristic of carboxylester hydrolases, as well as the HX4D motif, characteristic of acyltransferase activity. Nowadays, the role and the enzymatic activity of the CGI-58 protein, in mammalians and plants, are not quite clear. In order to better understand the function of CGI-58 protein in lipid metabolism, we developed a new strategy using a new set of plasmids that enabled us, with the use of pET28b(+) plasmid, to express and purify the CGI-58 protein of mice and plants as well as the murine ATGL. These proteins were expressed in different E. coli strains, to test in vitro their activity. In addition, we have set up, using the generated plasmids and different E. coli strains, a system that allowed us to test the in vivo acyltransferase activity (LPAAT and/or LPGAT) of the CGI-58 proteins expressed in E. coli. Using these techniques, we demonstrated in vivo and in vitro that both mice and plant CGI-58 proteins, are neither able to catalyze a LPAAT or a LPGAT reaction, and that the plant CGI-58 protein is devoid of TG lipase or phospholipase activity. However we have shown, by analyzing lipid extracts, by thin layer chromatography and by mass spectrometry of different E. coli strains expressing the CGI-58 protein, that the expression of the plant CGI-58 protein, but not the mice one, results in a decrease of phosphatidylglycerol (PG) content in the different strains tested. However the mutation of the serine or histidine residue of the putative catalytic triad restores the wild-typephenotype. These results allowed us to propose that plant CGI-58 protein is involved in the metabolism of PG, L’hydrolyse des triglycérides (TG) du tissu adipeux est initialisée par l’action de l’adipocyte TG lipase (ATGL), activée par son cofacteur la protéine CGI-58. Des mutations du gène codant les protéines CGI-58 ou ATGL sont respectivement à l’origine du syndrome de Chanarin-Dorfmann et de maladies de stockagede lipides neutres. La protéine CGI-58 appartient à la famille des a/ß-hydrolases, elle en possède la triade catalytique Ser-Asp/Glu-His caractéristique des carboxylester hydrolases, ainsi que le motif HX4D, caractéristique d’une activité acyltransférase. A ce jour, le rôle de la protéine CGI-58, chez les mammifères ou chez les plantes, n’est pas totalement éclairci, de même que son activité enzymatique. Dans le but de mieux comprendre le rôle de cette protéine CGI-58 dans le métabolisme lipidique, nous avons développé une nouvelle stratégie, en générant notamment de nouveaux plasmides qui nous ont permis d’exprimer et de purifier la protéine CGI-58 de souris et de plantes, ainsi que l’ATGL murine, dans différents souches d’E. coli, pour tester l’activité in vitro de ces protéines. De plus, nous avons mis en place, en utilisant ces plasmides générés et différentes souches E. coli, un système qui nous a permis de tester in vivo, dans E. coli, l’activité acyltransférase (LPAAT et/ou LPGAT) de la protéine CGI-58. En utilisant ces différentes techniques, nous avons pu montrer, aussi bien in vivo qu’in vitro, que la protéine CGI-58 de plante, ainsique celle de mammifère, ne possède ni activité LPAAT ni activité LPGAT, et que la protéine CGI-58 de plante est dépourvue d’activité TG lipase ou phospholipase. Cependant, nous avons montré, en analysant, par chromatographie sur couche mince et par spectrométrie de masse, des extraits lipidiques des différentes souches d’E. coli exprimant la protéine CGI-58, que l’expression de la protéine de plante, et non celle de mammifère, aboutit à une diminution du taux de phosphatidylglycérol (PG) dans les différentes souchestestées, et a contrario nous avons montré que la mutation de la sérine, ainsi que la mutation de l’histidine de la triade catalytique potentielle, restaure le phénotype sauvage. Ces résultats nous ont permis de proposer que la protéine CGI-58 de plante est impliquée dans le métabolisme du PG

Fatty acids are derived from the hydrolysis of triacylglycerol (TG) found in white adipose tissue, muscle tissue and circulating lipoproteins. The mobilization of free fatty acids (FFA) from white adipose tissue contributes to about 50% of the FFA utilized during moderate-intensity exercise. The delivery of FFA from white adipose tissue is improved by hormone-stimulated lipolytic events in white adipocytes (WA). Thus, the lipolysis in WA that provides fuel for metabolism has been a highly conserved function throughout the course of evolution. This short review outlines our current understanding of the molecular regulation of TG lipases via the lipolytic cascade in WA, as well as provides an account of our recent findings concerning changes in the lipolytic molecules of WA that result from acute and habitual exercise.

Introduction: Trans-10, cis-12 conjugated linoleic acid (CLA) and resveratrol have been shown to reduce TG content in cultured 3T3-L1 adipocyte acting on different pathways. In recent years, the method of simultaneously targeting several signal transduction pathways with multiple natural products in order to achieve additive or synergistic effects has been tested. However, the combined effect of both molecules on lipid metabolism has not been described before. Objective: The aim of the present work was to analyze the effect of the combination of trans-10, cis-12 CLA and resveratrol on TG accumulation as well as on FAS, HSL and ATGL expression in 3T3-L1 mature adipocytes, in order to assess a potential interaction between both molecules. Methods: For this purpose, 3T3-L1 mature adipocytes were treated with the two molecules, both separately and combined, in 10 and 100 μM for 20 hours. TG content and FAS, ATGL and HSL expression were measured by spectrophotometry and Real Time RT-PCR respectively. Results: Both doses of CLA and 100 M resveratrol decreased TG content in mature adipocytes. The combination of both molecules reduced TG accumulation to the same extent as each one separately. No change in FAS and HSL mRNA levels after CLA and resveratrol treatment was observed. ATGL was not modified by CLA but it was increased by resveratrol and by the combination. This combination did not increase the effect caused by resveratrol on its own. Conclusion: Lipolysis increase via ATGL is involved in the TG reduction induced by resveratrol and the combination of both molecules. The combination of these two molecules does not increase the efficacy of each molecule separately in mature adipocytes and thus it does not represent an advantage for obesity treatment or prevention.Introducción: Se ha demostrado que el ácido linoleico trans-10, cis-12 conjugado (ALC) y el resveratrol reducen el contenido de TG en el adipocito 3T3-L1 cultivado actuando sobre distintas vías. En los últimos años, se ha probado el método de llegar a diferentes vías de transducción de señal simultáneamente con múltiples productos naturales con el fin de alcanzar efectos aditivos o sinérgicos. Sin embargo, el efecto combinado de ambas moléculas sobre el metabolismo de los lípidos no se ha descrito previamente. Objetivo: El objetivo de este estudio fue analizar el efecto de la combinación del ALC trans-10, cis-12 y el resveratrol sobre la acumulación de TG así como sobre la expresión de FAS, HSL y ATGL en los adipocitos maduros 3T3-L1 con el propósito de evaluar la interacción potencial entre ambas moléculas. Métodos: Para este propósito, se trató a adipocitos maduros 3T3-L1 con las dos moléculas, de forma separada y combinada, en 10 y 100 μM durante 20 horas. El contenido de TG y la expresión de FAS, ATGL y HSL se midieron con espectrofotometría y en RT-PCR en tiempo real, respectivamente. Resultados: ambas dosis de ALC y 100 μM de resveratrol disminuyeron el contenido de TG en los adipocitos maduros. La combinación de ambas moléculas redujo la acumulación de TG en el mismo grado que cada una de ellas por separado. No se observaron cambios en los niveles de ARNm de FAS y HSL tras el tratamiento con ALC y resveratrol. El ATGL no se modificó por el ALC pero se incrementó por el resveratrol y la combinación. Esta combinación no aumentó el afecto causado por el resveratrol solo. Conclusión: el aumento de la lipólisis vía ATGL está implicado en la reducción de TG inducida por resveratrol y la combinación de ambas moléculas. Esta combinación no aumenta la eficacia de cada una de las moléculas por separado en los adipocitos maduros y, por lo tanto, no representa una ventaja en la prevención ni el tratamiento de la obesidad.

Keratinocyte differentiation is essential for skin development and the formation of the skin permeability barrier. This process involves an orchestrated remodeling of lipids. The cleavage of precursor lipids from lamellar bodies by β-glucocerebrosidase, sphingomyelinase, phospholipases and sterol sulfatase generates ceramides, non-esterified fatty acids and cholesterol for the lipid-containing extracellular matrix, the lamellar membranes in the stratum corneum. The importance of triacylglycerol (TAG) hydrolysis for the formation of a functional permeability barrier was only recently appreciated. Mice with defects in TAG synthesis (acyl-CoA:diacylglycerol acyltransferase-2-knock-out) or TAG catabolism (comparative gene identification-58, -CGI-58-knock-out) develop severe permeability barrier defects and die soon after birth because of desiccation. In humans, mutations in the CGI-58 gene also cause (non-lethal) neutral lipid storage disease with ichthyosis. As a result of defective TAG synthesis or catabolism, humans and mice lack ω-(O)-acylceramides, which are essential lipid precursors for the formation of the corneocyte lipid envelope. This structure plays an important role in linking the lipid-enriched lamellar membranes to highly cross-linked corneocyte proteins. This review focuses on the current knowledge of biochemical mechanisms that are essential for epidermal neutral lipid metabolism and the formation of a functional skin permeability barrier.