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Adipose tissue's (AT) structural changes accompanying obesity may alter lipid transport protein expression and, thus, the fatty acids (FAs) transport and lipid balance of the body. Metabolic abnormalities within AT contribute to the elevated production of reactive oxygen species and increased oxidative/nitrosative stress. Although compounds such as N-acetylcysteine (NAC) and α-lipoic acid (ALA), which restore redox homeostasis, may improve lipid metabolism in AT, the mechanism of action of these antioxidants on lipid metabolism in AT is still unknown. This study aimed to examine the impact of NAC and ALA on the level and FA composition of the lipid fractions, and the expression of FA transporters in the visceral and subcutaneous AT of high-fat diet-fed rats.Male Wistar rats were randomly divided into four groups. The mRNA levels and protein expression of FA transporters were assessed using real-time PCR and Western Blot analyses. The collected samples were subjected to histological evaluation. The level of lipids (FFA, DAG, and TAG) was measured using gas-liquid chromatography.We found that antioxidants affect FA transporter expressions at both the transcript and protein levels, and, therefore, they promote changes in AT's lipid pools. One of the most remarkable findings of our research is that different antioxidant molecules may have a varying impact on AT phenotype.NAC and ALA exert different influences on AT, which is reflected in histopathological images, FA transport proteins expression patterns, or even the lipid storage capacity of adipocytes.

TBC1D4 (AS160) and TBC1D1 are Rab GTPase-activating proteins that play a key role in the regulation of glucose and possibly the transport of long chain fatty acids (LCFAs) into muscle and fat cells. Knockdown (KD) of TBC1D4 increased CD36/SR-B2 and FABPpm protein expressions in L6 myotubes, whereas in murine cardiomyocytes, TBC1D4 deficiency led to a redistribution of CD36/SR-B2 to the sarcolemma. In our study, we investigated the previously unexplored role of both Rab-GAPs in LCFAs uptake in human adipocytes differentiated from the ADMSCs of subcutaneous and visceral adipose tissue origin. To this end we performed a single- and double-knockdown of the proteins (TBC1D1 and TBC1D4). Herein, we provide evidence that AS160 mediates fatty acid entry into the adipocytes derived from ADMSCs. TBC1D4 KD resulted in quite a few alterations to the cellular phenotype, the most obvious of which was the shift of the CD36/SR-B2 transport protein to the plasma membrane. The above translated into an increased uptake of saturated long-chain fatty acid. Interestingly, we observed a tissue-specific pattern, with more pronounced changes present in the adipocytes derived from subADMSCs. Altogether, our data show that in human adipocytes, TBC1D4, but not TBC1D1, deficiency increases LCFAs transport via CD36/SR-B2 translocation.

Endothelial lipase (EL) is an enzyme capable of HDL phospholipids hydrolysis. Its action leads to a reduction in the serum high-density lipoprotein concentration, and thus, it exerts a pro-atherogenic effect. This study examines the impact of a single bout exercise on the gene and protein expression of the EL in skeletal muscles composed of different fiber types (the soleus—mainly type I, the red gastrocnemius—mostly IIA, and the white gastrocnemius—predominantly IIX fibers), as well as the diaphragm, and the heart. Wistar rats were subjected to a treadmill run: (1) t = 30 [min], V = 18 [m/min], (2) t = 30 [min], V = 28 [m/min], (3) t = 120 [min], V = 18 [m/min] (designated: M30, F30, and M120, respectively). We established EL expression in the total muscle homogenates in sedentary animals. Resting values could be ordered with the decreasing EL protein expression as follows: endothelium of left ventricle &gt, diaphragm &gt, red gastrocnemius &gt, right ventricle &gt, soleus &gt, white gastrocnemius. Furthermore, we observed that even a single bout of exercise was capable of inducing changes in the mRNA and protein level of EL, with a clearer pattern observed for the former. After 30 min of running at either exercise intensity, the expression of EL transcript in all the cardiovascular components of muscles tested, except the soleus, was reduced in comparison to the respective sedentary control. The protein content of EL varied with the intensity and/or duration of the run in the studied whole tissue homogenates. The observed differences between EL expression in vascular beds of muscles may indicate the muscle-specific role of the lipase.

Objectives Imbalanced diets (e.g., excessive protein, fat, and carbohydrates) may contribute to numerous disorders, such as steatosis. However, previous studies in the pancreas are scarce and limited to the evaluation of sphingolipid metabolism in the islets of Langerhans that constitute only ∼5% of the organ mass. The aim of this study was to assess the effects of high-fat, high-protein, and high-carbohydrate diets on the development of pancreatic steatosis in conjunction with sphingolipid profile in the organ. Methods The experiments were conducted on 40 male Wistar rats (initial age 8 wk) randomly allocated to experimental groups. After 8 wk, plasma and tissue sphingolipid levels were measured by means of high-performance liquid chromatography. Blood glucose levels were measured with a glucometer, whereas insulin concentration was determined using chemiluminescence. Results We demonstrated that a chronic feeding with three different types of improper diets exerts multifarious effects on sphingolipid metabolism in the pancreas. The most important finding of the present study was that all three diets predisposed toward the onset and development of pancreatic steatosis, as evidenced by an excessive ceramide accumulation. Conclusions As it has been established that pancreatic steatosis is a disease with growing prevalence and possible serious complications, further investigations of the topic are warranted. The complete and precise comprehension of pancreatic steatosis pathogenesis could contribute to the invention of novel therapies for the disease.

Pyrroloquinoline quinone (PQQ) acts as a powerful modulator of PGC‐1α activation and therefore regulates multiple pathways involved in cellular energy homeostasis. In the present study, we assessed the effects of L6 myotubes incubation with 0.5, 1, and 3 μM PQQ solution for 2 and 24 hr with respect to the cells' lipid metabolism. We demonstrated that PQQ significantly elevates PGC‐1α content in a dose‐ and time‐dependent manner with the highest efficiency for 0.5 and 1 µM. The level of free fatty acids was diminished (24 hr: −66%), while an increase in triacylglycerol (TAG) amount was most pronounced after 0.5 μM (2 hr: +93%, 24 hr: +139%) treatment. Ceramide (CER) content was elevated after 2 hr incubation with 0.5 µM and after prolonged exposure to all PQQ concentrations. The cells treated with PQQ for 2 hr exhibited decreased sphinganine (SFA) and sphinganine‐1‐phosphate (SFA1P) level, while 24 hr incubation resulted in an elevated sphingosine (SFO) amount. In summary, PGC‐1α activation promotes TAG and CER synthesis.

Acute pancreatic injury can be related to both parenchymal (responsible for exocrine functions) and islet (mainly β-cells, responsible for endocrine functions) damage. During embryonic development, both the salivary glands and the pancreas originate from the foregut, which explains many of the observed histological and functional similarities between these two organs. The relationship between several diseases of the pancreas and salivary glands, resulting from morphological and functional similarities, is well established. Sphingolipids constitute a class of biologically active molecules involved in numerous physiological and pathological processes, including acute pancreatitis (AP) and diabetes mellitus. However, the effect of AP on sphingolipid metabolism in the salivary glands remains uncertain. In the presented study, we examined the effect of AP and type 1 diabetes mellitus on sphingolipid metabolism in the salivary glands of rats. We demonstrated that acute pancreatic injury, related to both exocrine and endocrine functions, affects the metabolism of sphingolipids in the parotid, but not submandibular, salivary glands.

Diabetes is considered a major public health problem affecting millions of individuals worldwide. Remarkably, scientific reports regarding salivary glands sphingolipid metabolism in diabetes are virtually non-existent. This is odd given the well-established link between the both in other tissues (e.g., skeletal muscles, liver) and the key role of these glands in oral health preservation. The aim of this paper is to examine sphingolipids metabolism in the salivary glands in (pre)diabetes (evoked by high fat diet feeding or streptozotocin). Wistar rats were allocated into three groups: control, HFD-, or STZ-diabetes. The content of major sphingolipid classes in the parotid (PSG) and submandibular (SMSG) glands was assessed via chromatography. Additionally, Western blot analyses were employed for the evaluation of key sphingolipid signaling pathway enzyme levels. No changes in ceramide content in the PSG were found, whereas an increase in ceramide concentration for SMSG of the STZ group was observed. This was accompanied by an elevation in SPT1 level. Probably also sphingomyelin hydrolysis was increased in the SMSG of the STZ-diabetic rats, since we observed a significant drop in the amount of SM. PSG and SMSG respond differently to (pre)diabetes, with clearer pattern presented by the later gland. An activation of sphingomyelin signaling pathway was observed in the course of STZ-diabetes, that is, metabolic condition with rapid onset/progression. Whereas, chronic HFD lead to an inhibition of sphingomyelin signaling pathway in the salivary glands (manifested in an inhibition of ceramide de novo synthesis and accumulation of S1P).

The Akt substrate of 160 kDa (AS160) is a key regulator of GLUT4 translocation from intracellular depots to the plasma membrane in myocytes. Likely, AS160 also controls LCFAs transport, which requires relocation of fatty acid transporters. The aim of the present study was to determine the impact of AS160 knockdown on lipid milieu in L6 myotubes incubated with palmitate (PA). Therefore, we compared two different settings, namely: 1) AS160 knockdown prior to palmitate incubation (pre-PA-silencing, AS160- /PA); 2) palmitate incubation with subsequent AS160 knockdown (post-PA-silencing, PA/AS160- ). The efficiency of AS160 silencing was checked at mRNA and protein levels. The expression and localization of FA transporters were determined using Western Blot and immunofluorescence analyses. Intracellular lipid content (FFA, DAG, TAG, and PL) and FA composition were estimated by GLC, whereas basal palmitate uptake was analyzed by means of scintigraphy. Both groups with silenced AS160 were characterized by a greater expression of FA transporters (FAT/CD36, FATP-1, 4) which had contributed to an increased FA cellular influx. Accordingly, we observed that post-PA-silencing of AS160 resulted in a marked decrement in DAG, TAG, and PL contents, but increased FFA content (PA/AS160- vs. PA). The opposite effect was observed in the group with pre-PA-silencing of AS160 in which AS160 knockdown did not affect the lipid pools (AS160- /PA vs. PA). Our results indicate that post-PA-silencing of AS160 has a capacity to decrease the lipotoxic effect(s) of PA by decreasing the content of lipids (DAG and PL) that promote insulin resistance in myotubes. J. Cell. Physiol. 232: 2373-2386, 2017. © 2016 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals Inc.

Purpose The aim of this work was to assess the effect(s) of de novo ceramide synthesis inhibition on lipid metabolism in skeletal muscle tissue of type 1 diabetic rats. The latter seems to be of vital importance, since previous works have shown its positive influence on lipid metabolism and glucose homeostasis in the case of its counterpart – type 2 diabetes. Materials/methods The animals were randomly assigned to one of the following groups: C – control, M – myriocin (ceramide de novo synthesis inhibitor), D – diabetes (induced by streptozotocin injections); D + M – diabetes + myriocin. We have evaluated intracellular concentration of key sphingolipid species, via chromatography (GC and HPLC), and the activity of their most important enzymes, using radiometric approach. The aforementioned assessments were evaluated in respect to the three different types of muscle tissue representing different spectra of muscle metabolism (soleus – oxidative, red gastrocnemious – oxidative-glycolytic, white gastrocnemious – glycolytic). Results Interestingly, our therapeutic intervention not only lowered the level of ceramide, its precursors (sphinganine) and derivatives (sphingosine and sphingosine-1-phosphate), but also reduced other lipid species (triacylglycerols, diacylglycerols and free fatty acids) content, thus improving glucose homeostasis in type 1 diabetic animals. Conclusions In the light of the results ensuing from this study, it seems conceivable that the reduction of intramuscular ceramide production and accumulation could bestow an insulin-sensitizing effect. If so, then SPT inhibition could find potential future applications as a therapeutic intervention aimed to mitigate the effects of insulin resistance.

Nonalcoholic fatty liver disease (NAFLD) is characterized by excessive lipid accumulation in the liver. The disturbances in the fatty acid composition of stored lipids are more important than the lipid species itself, which may influence the overall effect caused by these molecules. Thus, uncovering time-dependent changes in the fatty acid composition of accumulated lipid fractions after a high fat diet seems to be a new marker of NAFLD occurrence. The experiments were conducted on high fat fed Wistar rats. The blood and liver samples were collected at the end of each experimental week and used to assess the content of lipid fractions and their fatty acid composition by gas liquid chromatography. The expression of proteins from lipid metabolism pathways and of fatty acid exporting proteins were detected by Western blotting. In the same high fat feeding period, decreased de novo lipogenesis, increased &beta, oxidation and lipid efflux were demonstrated. The observed effects may be the first liver protective mechanisms against lipotoxicity. Nevertheless, such effects were still not sufficient to prevent the liver from proinflammatory lipid accumulation. Moreover, the changes in liver metabolic pathways caused the plasma nervonic acid concentration in sphingomyelin to decrease simultaneously with NAFLD development, which may be a steatosis occurrence prognostic marker.

The aim of the present study was to investigate the time and intensity dependent effects of exercise on the heart components of the lipolytic complex. Wistar rats ran on a treadmill with the speed of 18 m/min for 30 min (M30) or 120 min (M120) or with the speed of 28 m/min for 30 min (F30). The mRNA and protein expressions of the compounds adipose triglyceride lipase (ATGL), comparative gene identification-58 (CGI-58), G0/G1 switch gene 2 (G0S2), hormone sensitive lipase (HSL) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1&alpha, ) were examined by real-time PCR and Western blot, respectively. Lipid content of free fatty acids (FFA), diacylglycerols (DG) and triacylglycerols (TG) were estimated by gas liquid chromatography. We observed virtually no changes in the left ventricle lipid contents and only minor fluctuations in its ATGL mRNA levels. This was in contrast with its right counterpart i.e., the content of TG and DG decreased in response to both increased duration and intensity of a run. This occurred in tandem with increased mRNA expression for ATGL, CGI-58 and decreased expression of G0S2. It is concluded that exercise affects behavior of the components of the lipolytic system and the lipid content in the heart ventricles. However, changes observed in the left ventricle did not mirror those in the right one.

Aims The aim of this study was to assess the effects of enterolactone (ENL) on lipid fractions fatty acids composition affecting hepatocyte inflammation development. Main methods The experiments were conducted in HepG2 cells incubated with ENL and/or palmitic acid (16 h). Intracellular contents of free fatty acids (FFA), di- (DAG) and tri- (TAG) acylglycerol as well as their fatty acids compositions were assessed by Gas-Liquid Chromatography. Moreover, the ω-6/ω-3 ratios in the above mentioned lipids fractions were estimated. The expression of proteins involved in eicosanoids and prostanoids production (COX-2, 15-LOX), inflammatory process (TNFα), as well as the proteins participating in the desaturation (SCD 1) and elongation (Elovl 3, Elovl 6) of fatty acids were evaluated by Western Blot. Key findings Enterolactone modified fatty acids composition in FFA, DAG and TAG fractions. In conjunction with lipid overload, it increased the content of ω-6 more than ω-3 PUFA. Moreover, it enhanced the expressions of Elovl 3, Elovl 6, COX-2 and TNFα, whereas it had no influence on SCD 1 and 15-LOX level. Significance Our study revealed that the supplementation with ENL affected intracellular hepatic composition of saturated as well as unsaturated fatty acids in each of the investigated lipid fractions. Based on the shift in the ω-6/ω-3 balance towards ω-6, as well as the increase in COX-2 and TNFα protein expressions, we may postulate a pro-inflammatory nature of the examined polyphenol. Moreover, our findings could prove to be useful in the future research in the topic of widespread diseases such as NASH.

OBJECTIVES Acute pancreatitis (AP) is a common and severe gastrointestinal inflammatory disease with poorly understood pathogenesis. We adopted cerulein-induced pancreatitis, a well-established rat model shearing similarities with human AP, to determine the disease background. Special interest was placed on sphingolipids, because their signaling pathways are involved in many pathological states including hepatic steatosis, heart infarction, or pancreatic origin type 1 diabetes. METHODS Sphingolipid levels in the blood and pancreas were determined by the means of chromatography (thin-layer and high-performance liquid chromatography). RESULTS We found that AP leads to activation of ceramide de novo synthesis pathway, as evidenced by a significant increment in sphinganine, that is, ceramide synthesis precursor, content (+3.8-fold). Surprisingly, despite the reported growth in sphinganine concentration, we observed a reduced (-38%) ceramide level in the pancreas of rats with AP. The results could be explained by subsequent hydrolysis of ceramide to other secondary messengers, that is, sphingosine (+4-fold) or sphingosine-1-phosphate (+3-fold). CONCLUSIONS Because it is known that sphingosine-1-phosphate and some of its analogs could have a protective role against AP complications, our findings may contribute to elaboration of new therapeutic strategies in the management of this severe medical condition.

Background NAFLD as a result of inappropriate diet and obesity, may progress to sever conditions such as: type 2 diabetes mellitus or steatohepatitis, and has recently become a prevalent topic of numerous investigations. Due to its dangerous aftermaths, finding new substances, such as polyphenols and their derivatives, which might reduce liver steatosis is the main target of research into NAFLD treatment. Hence, the aim of the present study was to evaluate the effect(s) of enterolactone (ENL), a metabolite of secoisolariciresinol (SECO), on lipid metabolism together with changes in the expression of fatty acid transporters in fatty liver. Methods The experiments were conducted on HepG2 cells incubated with either ENL and/or palmitic acid during 16 h exposure. The expression of selected fatty acid transport proteins: FATP2, FATP5, CD36, FABPpm, ABCA1, MTP, ACBP and L-FABP, as well as the proteins directly involved in lipogenesis (FAS), oxidation pathway (CPT 1), and lipid metabolism (PPARα, LXR, SREBP1c, pAMPK) was estimated by Western Blot. Intra and extracellular lipid contents were assessed by Gas-Liquid Chromatography. The data was analyzed with two-way analysis of variance (ANOVA), and results were considered to be statistically significant at p ≤ 0.05. Results ENL stimulated extracellular efflux of free fatty acids (FFA) and triacylglicerols (TAG) to the medium, while, it had no influence on FATP-family mediated intracellular fatty acid uptake. Moreover, ENL decreased the expression of CPT 1, pAMPK, PPARα, increased SREBP1c and had no effect on LXR, and FAS content. Conclusions The findings of our study demonstrate that ENL had opposite effect on liver steatosis in comparison with other polyphenols what suggests that it may be an inactive metabolite. ENL did not affect significantly the intracellular accumulation of FFA, DAG and TAG, yet it promoted their extracellular efflux. Furthermore, it inhibited ß-oxydation and intracellular lipid metabolism what may contribute to the progression of NAFLD.

Acute pancreatitis (AP) is a prevalent gastrointestinal disorder associated with systemic inflammatory response syndrome and, in the case of severe AP, a mortality rate ranging from 36% to 50%. Standard clinical treatment of AP includes intensive hydration, analgesia, and management of complications. Unfortunately, the direct treatment of AP at the level of its molecular pathomechanism has not yet been established. Recent studies indicate that the sphingolipid signaling pathway may be one of the important factors contributing to the development of inflammation in pancreatic diseases. In the current study, we sought to investigate this promising route. We examined the plasma sphingolipid profile of 44 patients with acute pancreatitis, dividing them into three groups: mild, moderate and severe AP. Samples were collected from these groups at days 1, 3 and 7 following their hospital admission. We demonstrated significant changes in blood plasma sphingolipids in relation to the time course of AP. We also found an inhibition of de novo ceramide synthesis in mild and moderate AP. However, the most important and novel finding was a significant elevation in sphingosine-1-phosphate (S1P) (a downstream metabolite of ceramide) in mild AP, as well as a dramatic reduction in the lipid molecule content in the early stage (days 1 and 3) of severe AP. This strongly indicates that plasma S1P could serve as a prognostic marker of AP severity.

Currently, obesity is a predominant medical condition and an important risk factor for the development of several diseases, including type 2 diabetes mellitus. Importantly, most research has indicated lipid-induced insulin resistance in skeletal muscles is a key link between the aforementioned pathological conditions. PGC-1α is a prominent regulator of myocellular energy metabolism orchestrating gene transcription programming in response to numerous environmental stimuli. Moreover, it is widely acknowledged that mitochondrial metabolism (primary metabolic target of PGC-1α) disturbances are widely acknowledged contributors to type 2 diabetes development. Therefore, it seems surprising that the exact physiological contribution of PGC-1α in the development of insulin resistance in skeletal muscle remains poorly understood. This review aims to reconcile these allegedly different findings by looking for a common denominator in the role(s) of PGC-1α in respect to lipid-induced insulin resistance in skeletal muscle. Our scrutiny of the literature indicates that interventions at the level of PGC-1α may exert beneficial effects on myocytes in respect to lipid-induced insulin resistance. The latter takes place as a result of a positive net energy balance (fatty acids oxidation surpassing their accumulation rate). Moreover, the aforementioned effects may not necessarily be limited to physically active states. They seem to occur, however, only within a physiologically observed range in muscle cells (approximately 1-fold changes in PGC-1α protein expression).

Nowadays diabetes is one of the most common metabolic diseases. Sphingolipids, which are vitally important constituents of intracellular signal transduction pathways, may be among the most pathogenic lipid moieties intermingled in the origin and development of diabetes. It is now well established that inhibition ofde novoceramide synthesis with myriocin exerts positive effects on lipid metabolism and glucose homeostasis in type 2 diabetes mellitus animal models. However, its influence on type I diabetes still remains unknown. Therefore, the scope of this paper is to fulfill that particular gap in our knowledge.

Nowadays, obesity and its complications are heavy burdens to western civilization. Surgical procedures remain one of the available therapies for obesity and obesity-associated diseases treatment. Among them, sleeve gastrectomy is the most common bariatric procedure. Despite the well-established fact that sleeve gastrectomy results in significant weight loss, some of its other divergent effects still need to be established. To fulfill this knowledge gap, we examined whether sleeve gastrectomy affects lipid metabolism in the plasma and liver of obese rats. We demonstrated that chronic high-fat diet feeding led to an increment in the level of Proprotein Convertase Subtilisin/Kexin (PCSK)&mdash, a regulator of plasma cholesterol concentration&mdash, in the liver, which was decreased after the gastrectomy. Moreover, we noticed significant increases in both plasma and liver contents of free fatty acids, diacylgycerides and triacylglycerides in the obese animals, with their reduction after the bariatric surgery. In conclusion, we revealed, presumably for the first time, that sleeve gastrectomy affects lipid metabolism in the liver of obese rats.

Bioactive sphingolipids are engaged with numerous cellular processes such as cell differentiation, proliferation and apoptosis. Sphingolipid metabolism in heart is regulated by physical exercise and PPARs. Ceramide, the main second messenger of sphingomyelin pathway of signal transduction, was found to be involved in development of cardiac dysfunction after ischemia/reperfusion. On the other hand ceramide derivative sphingosine- 1- phosphate has been shown to exert potent cardioprotective action and guards cardiomyocytes against ischemic/reperfusion injury. Pharmacological compounds, which regulate metabolism of sphingolipids can be potentially useful in treatment of selected cardiovascular diseases. The aim of this work is critical review of physiological and pathological role of sphingolipids in circulatory system.

Thyroid hormones (T3, T4) are well known modulators of different cellular signals including the sphingomyelin pathway. However, studies regarding downstream effects of T3 on sphingolipid metabolism in skeletal muscle are scarce. In the present work we sought to investigate the effects of hyperthyroidism on the activity of the key enzymes of ceramide metabolism as well as the content of fundamental sphingolipids. Based on fiber/metabolic differences, we chose three different skeletal muscles, with diverse fiber compositions: soleus (slow-twitch oxidative), red (fast-twitch oxidative-glycolytic) and white (fast-twitch glycolytic) section of gastrocnemius. We demonstrated that T3 induced accumulation of sphinganine, ceramide, sphingosine, as well as sphingomyelin, mostly in soleus and in red, but not white section of gastrocnemius. Concomitantly, the activity of serine palmitoyltransferase and acid/neutral ceramidase was increased in more oxidative muscles. In conclusion, hyperthyroidism induced fiber specific changes in the content of sphingolipids that were relatively more related to de novo synthesis of ceramide rather than to its generation via hydrolysis of sphingomyelin.

AIMS: To determine the presence and possible involvement of FAT/CD36, FABPpm and FATP-2, transporters in (i) fatty acids movement across plasma membrane and (ii) an induction of insulin resistance by palmitic (PA) and oleic (OA) fatty acids in primary hepatocytes. METHODS: Primary hepatocytes were treated with either PA and OA or combination of activators (AICAR, Insulin) or inhibitors (SSO, phloretin) of FA transport. Expression of FA and glucose transporters as well as insulin signalling proteins was determined using Western blot analyses. Palmitate and glucose transport was measured using radioactive isotopes. Intracellular lipid content [ceramide, diacylglycerols (DG) and triacylglycerols] and FA composition were estimated by GLC. RESULTS: In primary hepatocytes, adding phloretin diminished insulin, and AICAR stimulated palmitate transport. Both PA and OA fatty acids induced the protein expression of FAT/CD36 and FATP-2 with concomitant: (i) reduction in GLUT-2 protein content, (ii) inhibition of insulin-stimulated glucose uptake, (iii) reduction in insulin-stimulated activation of AKT and GSK, (iv) accumulation of either DG (PA and OA) or ceramide (only PA). CONCLUSIONS: FA transport into hepatocytes is, at least in part, protein-mediated process, and both PA and OA induce the protein expression of FAT/CD36 and FATP-2. Both saturated (PA) and unsaturated (OA) fatty acids induce insulin resistance in primary hepatocytes, associated with the accumulation of DG and/or ceramide.

Background Diabetes is one of the most common metabolic diseases. Moreover, previous studies indicate that diabetes may cause changes in the salivary glands phenotype and in the composition of saliva itself. Therefore, the main objective of this study was to determine the effects of streptozotocin induced diabetes on lipid profile of the rat salivary glands. Methods Male Wistar rats were divided into two groups: control and STZ-induced diabetes. At the end of the experiment all animals were sacrificed and samples of the parotid and submandibular salivary glands were excised. Major lipid fractions concentrations were determined by means of chromatography (TLC and GC). Results We observed a significant increase (∼3.5 fold) in the level of triacylglycerol in both the parotid and submandibular salivary glands of diabetic rats. The abovementioned changes were accompanied by significant, although less dramatic (i.e. from −60% to −90%), decrements in the levels of other lipid classes (phospholipids, free fatty acids and diacylglycerol). Conclusions In our study we have showed, presumably for the first time, that streptozotocin induced diabetes causes decrement in PH content with subsequent atrophy and malfunction in both parotid and submandibular salivary glands. Another novel finding of our research is that diabetic rats were characterized by an increased TG accumulation in both parotid and submandibular salivary glands. The later one could be a clinical manifestation of diabetes.

In today’s world wrong nutritional habits together with a low level of physical activity have given rise to the development of obesity and its comorbidity, insulin resistance. More specifically, many researches indicate that lipids are vitally involved in the onset of a peripheral tissue (e.g., skeletal muscle, heart, and liver) insulin resistance. Moreover, it seems that diabetes can also induce changes in respect of lipid composition of both the salivary glands and saliva. However, judging by the number of research articles, the salivary glands lipid profile still has not been sufficiently explored. In the current study we aim to assess the changes in the main lipid fractions, namely, triacylglycerols, phospholipids, free fatty acids, and diacylglycerols, in the parotid and the submandibular salivary glands of rats exposed to a 5-week high fat diet regimen. We observed that the high caloric fat diet caused a significant change in the salivary glands lipid composition, especially with respect to PH and TG, but not DAG or FFAs, classes. The observed reduction in PH concentration is an interesting phenomenon frequently signifying the atrophy and malfunctions in the saliva secreting organs. On the other hand, the increased accumulation of TG in the glands may be an important clinical manifestation of metabolic syndrome and type 2 diabetes mellitus.

IL-6 is a biologically active cytokine released during exercise by contracting skeletal muscles. It appears to be highly involved in the regulation of muscles energy substrate utilization. Whether an ablation of IL-6 (IL-6 KO) in mice subjected to a single bout of exercise affects lipid and/or glucose metabolism is currently unknown. In the present study we examined fatty acid (FAT/CD36, FABPpm, FATP-1, FATP-4) as well as glucose (GLUT-1, GLUT-4) transporters expression in IL-6 KO mice. In addition, intramuscular glycogen and lipid content was also evaluated. The expression of all fatty acid transporters (FAT/CD36: +25 %; FATP-1: +31 %; FABPpm: +12.7 %; FATP-4: +7.2 %) was increased in muscles from IL-6 KO mice compared to wild type (WT) mice. Accordingly intramuscular lipid content was also increased in these muscles (FFA: +38 %; DAG: +36 % and TAG: +160 %). Interestingly, IL-6 deficiency had only minor effect on glucose transporters expression (GLUT-1: -4 %, and GLUT-4: -5.1 %), with no apparent difference in muscular glycogen content. A single bout of exercise increased the glucose transporters (GLUT-1: +8 %; GLUT-4: +15 %) as well as FA transporters (FAT/CD36: +13 %; FABPpm: +4.5 %; FATP: +2.5 %, FATP-4: +10 %) expression but only in WT skeletal muscles. In muscles from IL-6 KO mice exercise induced changes only in glucose (GLUT-1: +20 %; GLUT-4: +35 %) but not in the content of FA transporters. Concomitantly, IL-6 KO mice displayed shorter time toward exhaustion with more pronounced reductions in intramuscular lipid and glycogen content. We may speculate, that IL-6 deficiency provokes more pronounced glucose utilization over lipid oxidation during a single bout of exhausting exercise.

Background/Aims: AS160 is a key intracellular regulator of energy utilization in cells. It was shown to regulate GLUT4 translocation from intracellular depots to the plasma membrane, with subsequent changes in facilitated glucose uptake into the skeletal muscles. Similarly, also free fatty acids (FFAs) transmembrane transport seems to be largely protein-mediated. Therefore, the objective of this study was to examine the effects of moderate AS160 depletion (-82% mRNA, -25% of protein content) on the expression of fatty acid transporters and subsequent changes in lipid profile in L6 myotubes. Results: Surprisingly, moderate down regulation of AS160 expression was followed by increased AS160 phosphorylation (∼40%). These resulted in a greater expression of fatty acid transporters, namely FABPpm and FAT/CD36, with subsequently increased FAs cellular influx. No changes in the expression of FATP1 and 4 were noticed. Accordingly, we have observed a reduction in total TAG content. This was mainly caused by a significant changes in TAG fatty acids composition favouring a decrease in the amount of palmitic and stearic fatty acid moieties. In contrast, our experimental intervention led to distinctively increased total content of DAG and PL, but concomitantly decreased the content of all measured sphingolipids, e.g. SFA, SA1P, CER, SFO and S1P, in the AS160 knockdown group. Conclusions: Modulation of AS160 level and activity led to significant increase in the concentration of DAG and PL, which was associated with changes in FAs composition and expression of fatty acid transporters. Interestingly, the intervention also simultaneously decreased the content of sphingolipids.

Obesity increases the risk for hepatic steatosis. Recent studies have demonstrated that high fat diet (HFD) may affect sphingolipid formation in skeletal muscles, heart, and other tissues. In this work we sought to investigate whether HFD feeding provokes changes in content and fatty acids (FAs) composition of sphingomyelin and ceramide at the level of liver and hepatic nuclei. Furthermore, we investigated whether the ceramide formation is related to the activity of either neutral sphingomyelinase (N-SMase) or acidic sphingomyelinase (A-SMase). Three weeks of HFD provision induced pronounced ceramide and sphingomyelin accumulation in both liver and hepatic nuclei, accompanied by increased activity of N-SMase but not A-SMase. Furthermore, a shift toward greater FAs saturation status in these sphingolipids was also observed. These findings support the conclusion that HFD has a major impact on sphingolipid metabolism not only in the liver, but also in hepatic nuclei.

Long-chain fatty acids (LCFAs) are an important source of energy for working skeletal muscles. The predominant mechanism of LCFA influx into skeletal muscle involves sarcolemmal proteins, namely fatty-acid transporters. Recent studies imply strong correlations between increased plasmalemmal expression of FA transporters and the development of insulin resistance in skeletal muscles. However, it seems that a major feature of myocyte insulin resistance is the imbalance in lipid transport into the cells and the capacity of mitochondria for LCFA oxidation. Excess deposition of myocelluar fatty acids leads to the accumulation of triacylglycerols, diacyloglycerols, and ceramides. Most likely, the accumulation of intramuscular lipid fractions is responsible for disturbances in the insulin signaling pathway and the subsequent development of skeletal muscle insulin resistance.

Nowadays wrong nutritional habits and lack of physical activity give a rich soil for the development of insulin resistance and obesity. Many researches indicate lipids, especially the one from the sphingolipids class, as the group of molecules heavily implicated in the progress of insulin resistance in skeletal muscle. Recently, scientists have focused their scrutiny on myriocin, a potent chemical compound that inhibits ceramide (i.e., central hub of sphingolipids signaling pathway)de novosynthesis. In the present research we evaluated the effects of myriocin application on type 2 diabetes mellitus in three different types of skeletal muscles: (1) slow-oxidative (red gastrocnemius), (2) oxidative-glycolytic (soleus), and (3) glycolytic (white gastrocnemius). For these reasons the animals were randomly divided into four groups: “control” (C), “myriocin” (M), “high fat diet” (HFD), “high fat diet” (HFD), and “high fat diet + myriocin” (HFD + M). Ourin vivostudy demonstrated that ceramide synthesis inhibition reduces intramuscular ceramide, its precursor sphinganine, and its derivatives sphingosine and sphingosine-1-phosphate concentrations. Moreover, FFA and TG contents were also decreased after myriocin treatment. Thus, myriocin presents potential therapeutic perspectives with respect to the treatment of insulin resistance and its serious consequences in obese patients.

Background: Thyroid hormones (THs) are key regulators of cardiac physiology as well as modulators of different cellular signals including the sphingomyelin/ceramide pathway. The objective of this study was to examine the effect of hyperthyroidism on the metabolism of sphingolipids in the muscle heart. Methods: Male Wistar rats were treated for 10 days with triiodothyronine (T3) at a dose of 50µg/100g of body weight. Animals were then anaesthetized and samples of the left ventricle were excised. Results: We have demonstrated that prolonged, in vivo, T3 treatment increased the content of sphinganine (SFA), sphingosine (SFO), ceramide (CER) and sphingomyelin (SM), but decreased the level of sphingosine-1-phosphate (S1P) in cardiac muscle. Accordingly, the changes in sphingolipids content were accompanied by a lesser activity of neutral sphingomyelinase and without significant changes in ceramidases activity. Hyperthyroidism also induced activation of AMP-activated protein kinase (AMPK) with subsequently increased expression of mitochondrial proteins: cytochrome c oxidase IV (COX IV), β-hydroxyacyl-CoA dehydrogenase (β-HAD), carnityne palmitoyltransferase I (CPT I) and nuclear peroxisome proliferator-activated receptor-γ coactivator-1α (PGC1α). Conclusions: We conclude that prolonged T3 treatment increases sphingolipids metabolism which is reflected by higher concentration of SFA and CER in heart muscle. Furthermore, hyperthyroidism-induced increase in heart sphingomyelin (SM) concentration might be one of the mechanisms underlying maintenance of CER at relatively low level by its conversion to SM together with decreased S1P content.

Incidence of colorectal cancer (CRC) is growing worldwide. Pathogenetic mechanisms responsible for its onset and progression need further clarification. Colorectal adenomatous polyps are precancerous lesions with malignant potential dependent on histological architecture and grade of nuclear dysplasia. One of the factors conditioning CRC development are abnormalities in sphingolipid metabolism. The aim of this study was to assess the levels of sphingolipids in human colorectal adenomas. The control group (C, n = 12) consisted of patients with no colonic polyps. The examined group consisted of patients with prior diagnosed colonic polyps, qualified to endoscopic polypectomy. This group was further divided due to histological architecture into tubular adenomas group (TA, n = 10), tubulovillous adenomas with low-grade dysplasia (LGD-TVA, n = 10), and tubulovillous adenomas group with high-grade dysplasia (HGD-TVA, n = 11). In tissue samples, sphingolipd metabolite contents were measured using high performance liquid chromatography (HPLC). In cases of polypoid lesions with low malignancy potential (tubular adenomas), concentration of ceramide, which is characterized by proapoptotic and anti-proliferative properties, increases compared with control group (p < 0.05), whereas content of sphingosine-1-phosphate with anti-apoptotic and stimulating cellular proliferation properties is reduced in comparison with control group (p < 0.05). On the contrary, in cases of more advanced form of adenomatous polyps (tubulovillous adenomas with high-grade dysplasia), the ceramide level decreases compared with control group (p < 0.05) while sphingosine-1-phosphate concentration is elevated (p < 0.05). We found that concentrations of pro-apoptotic ceramide are decreased and pro-proliferative S1P levels are increased in polypoid lesions with high malignancy potential, and it was the opposite in those with low malignancy potential.

Sphingolipids in digestive system are responsible for numerous important physiological and pathological processes. In the membrane of gut epithelial cells, sphingolipids provide structural integrity, regulate absorption of some nutrients, and act as receptors for many microbial antigens and their toxins. Moreover, bioactive sphingolipids such as ceramide or sphingosine-1-phosphate regulate cellular growth, differentiation, and programmed cell death—apoptosis. Although it is well established that sphingolipids have clinical implications in gastrointestinal tumorigenesis or inflammation, further studies are needed to fully explore the role of sphingolipids in neoplastic and inflammatory diseases in gastrointestinal tract. Pharmacological agents which regulate metabolism of sphingolipids can be potentially used in the management of colorectal cancer or inflammatory bowel diseases. The aim of this work is to critically the review physiological and pathological roles of sphingolipids in the gastrointestinal tract.