Search

Natural rare sugars are an alternative category of sweeteners with positive physiologic and metabolic effects both in in vitro and animal models. D-allulose is a D-fructose epimer that combines 70% sucrose sweetness with the advantage of an extremely low energy content. However, there are no data about the effect of D-allulose against adipose dysfunction; thus, it remains to be confirmed whether D-allulose is useful in the prevention and in treatment of adipose tissue alterations. With this aim, we evaluated D-allulose's preventive effects on lipid accumulation in 3T3-L1 murine adipocytes exposed to palmitic acid (PA), a trigger for hypertrophic adipocytes. D-allulose in place of glucose prevented adipocyte hypertrophy and the activation of adipogenic markers C/EBP-β and PPARγ induced by high PA concentrations. Additionally, D-allulose pretreatment inhibited the NF-κB pathway and endoplasmic reticulum stress caused by PA, through activation of the Nrf2 pathway. Interestingly, these effects were also observed as D-allulose post PA treatment. Although our data need to be confirmed through in vivo models, our findings suggest that incorporating D-allulose as a glucose substitute in the diet might have a protective role in adipocyte function and support a unique mechanism of action in this sugar as a preventive or therapeutic compound against PA lipotoxicity through the modulation of pathways connected to lipid transport and metabolism. [ABSTRACT FROM AUTHOR]

Obesity is a metabolic disorder with excessive body fat accumulation, increasing incidence of chronic metabolic diseases. Hypertrophic obesity is associated with local oxidative stress and inflammation. Herein, we evaluated the in vitro activity of micromolar concentrations of α-lipoic acid (ALA) on palmitic acid (PA)-exposed murine hypertrophic 3T3-L1 adipocytes, focussing on the main molecular pathways involved in adipogenesis, inflammation, and insulin resistance. ALA, starting from 1 µM, decreased adipocytes hypertrophy, reducing PA-triggered intracellular lipid accumulation, PPAR-γ levels, and FABP4 gene expression, and counteracted PA-induced intracellular ROS levels and NF-κB activation. ALA reverted PA-induced insulin resistance, restoring PI3K/Akt axis and inducing GLUT-1 and glucose uptake, showing insulin sensitizing properties since it increased their basal levels. In conclusion, this study supports the potential effects of low micromolar ALA against hypertrophy, inflammation, and insulin resistance in adipose tissue, suggesting its important role as pharmacological supplement in the prevention of conditions linked to obesity and metabolic syndrome. [ABSTRACT FROM AUTHOR]

Natural rare sugars are an alternative category of sweeteners with positive physiologic and metabolic effects both in in vitro and animal models. D-allulose is a D-fructose epimer that combines 70% sucrose sweetness with the advantage of an extremely low energy content. However, there are no data about the effect of D-allulose against adipose dysfunction; thus, it remains to be confirmed whether D-allulose is useful in the prevention and in treatment of adipose tissue alterations. With this aim, we evaluated D-allulose’s preventive effects on lipid accumulation in 3T3-L1 murine adipocytes exposed to palmitic acid (PA), a trigger for hypertrophic adipocytes. D-allulose in place of glucose prevented adipocyte hypertrophy and the activation of adipogenic markers C/EBP-β and PPARγ induced by high PA concentrations. Additionally, D-allulose pretreatment inhibited the NF-κB pathway and endoplasmic reticulum stress caused by PA, through activation of the Nrf2 pathway. Interestingly, these effects were also observed as D-allulose post PA treatment. Although our data need to be confirmed through in vivo models, our findings suggest that incorporating D-allulose as a glucose substitute in the diet might have a protective role in adipocyte function and support a unique mechanism of action in this sugar as a preventive or therapeutic compound against PA lipotoxicity through the modulation of pathways connected to lipid transport and metabolism.

Background: Chronic unpredictable mild stress (CUMS) has been shown to exacerbate atherosclerosis, but the underlying mechanism remains unknown. Adipose tissue is an energy storage organ and the largest endocrine organ in the human body, playing a key role in the development of cardiovascular disease. In this research, it was hypothesized that CUMS may exacerbate the development of atherosclerosis by inducing the hypertrophy and dysfunction of white adipocytes. Methods: The CUMS-induced atherosclerosis model was developed in Western diet-fed apolipoprotein E (ApoE)-/- mice. White adipose tissue (WAT), serum, aortic root, and the brachiocephalic trunk were collected and tested after 12 weeks of CUMS development. The mouse model of CUMS was evaluated for depression-like behavior using the open field test (OFT) and the elevated plus maze (EPM) test. Enzyme-linked immunosorbent assay (ELISA) was conducted to detect serum noradrenaline and urine adrenaline protein levels. Serological assays were used to detect serum low-density lipoprotein (LDL), high-density lipoprotein (HDL), total cholesterol (TC), and free fatty acid (FFA) concentrations. Hematoxylin and eosin (H&E) staining and oil red O were used to detect atherosclerotic plaque area, lipid deposition, and adipocyte size. The mRNA levels of genes related to aberrant adipose tissue function were determined using real-time PCR. Immunofluorescence assay and western blotting were conducted to examine the expression of proteins in the adipose tissue samples. Results: CUMS aggravated vascular atherosclerotic lesions in ApoE-/- mice. It decreased body weight while increasing the percentage of WAT. The serological results indicated that the concentration of HDL decreased in CUMS mice. Notably, adipocyte hypertrophy increased, whereas the mRNA levels of Pparg and its target genes (Slc2a4 (encodes for GLUT4), Adipoq, and Plin1) decreased. Further investigation revealed that CUMS increased subcutaneous inguinal WAT (iWAT) lipid synthesis and adipocyte inflammation while decreasing lipid hydrolysis and the expression of HDL-associated protein ApoA-I. Moreover, CUMS aggravated insulin resistance in mice and inhibited the insulin pathway in iWAT. Conclusions: These findings indicated that CUMS induces adipose tissue dysfunction via a mechanism that leads to dyslipidemia, increased inflammation, and insulin resistance in the body, thereby exacerbating atherosclerosis. Notably, CUMS that is involved in decreasing the expression of HDL-associated proteins in adipose tissue may be a crucial link between adipose hypertrophy and advanced atherosclerosis. This study reveals a novel mechanism via which CUMS exacerbates atherosclerosis from the novel perspective of abnormal adipose function and identifies a novel potential therapeutic target for this disease. [ABSTRACT FROM AUTHOR]

Background Chronic unpredictable mild stress (CUMS) has been shown to exacerbate atherosclerosis, but the underlying mechanism remains unknown. Adipose tissue is an energy storage organ and the largest endocrine organ in the human body, playing a key role in the development of cardiovascular disease. In this research, it was hypothesized that CUMS may exacerbate the development of atherosclerosis by inducing the hypertrophy and dysfunction of white adipocytes. Methods The CUMS-induced atherosclerosis model was developed in Western diet-fed apolipoprotein E (ApoE)-/- mice. White adipose tissue (WAT), serum, aortic root, and the brachiocephalic trunk were collected and tested after 12 weeks of CUMS development. The mouse model of CUMS was evaluated for depression-like behavior using the open field test (OFT) and the elevated plus maze (EPM) test. Enzyme-linked immunosorbent assay (ELISA) was conducted to detect serum noradrenaline and urine adrenaline protein levels. Serological assays were used to detect serum low-density lipoprotein (LDL), high-density lipoprotein (HDL), total cholesterol (TC), and free fatty acid (FFA) concentrations. Hematoxylin and eosin (H&E) staining and oil red O were used to detect atherosclerotic plaque area, lipid deposition, and adipocyte size. The mRNA levels of genes related to aberrant adipose tissue function were determined using real-time PCR. Immunofluorescence assay and western blotting were conducted to examine the expression of proteins in the adipose tissue samples. Results CUMS aggravated vascular atherosclerotic lesions in ApoE-/- mice. It decreased body weight while increasing the percentage of WAT. The serological results indicated that the concentration of HDL decreased in CUMS mice. Notably, adipocyte hypertrophy increased, whereas the mRNA levels of Pparg and its target genes (Slc2a4 (encodes for GLUT4), Adipoq, and Plin1) decreased. Further investigation revealed that CUMS increased subcutaneous inguinal WAT (iWAT) lipid synthesis and adipocyte inflammation while decreasing lipid hydrolysis and the expression of HDL-associated protein ApoA-I. Moreover, CUMS aggravated insulin resistance in mice and inhibited the insulin pathway in iWAT. Conclusions These findings indicated that CUMS induces adipose tissue dysfunction via a mechanism that leads to dyslipidemia, increased inflammation, and insulin resistance in the body, thereby exacerbating atherosclerosis. Notably, CUMS that is involved in decreasing the expression of HDL-associated proteins in adipose tissue may be a crucial link between adipose hypertrophy and advanced atherosclerosis. This study reveals a novel mechanism via which CUMS exacerbates atherosclerosis from the novel perspective of abnormal adipose function and identifies a novel potential therapeutic target for this disease.

Ascorbic acid has been suggested to regulate obesity in obese male rodents. Moreover, increased adipocyte size has been associated with metabolic disease. Thus, we investigated the effects of ascorbic acid on adipocyte hypertrophy and insulin resistance in high-fat diet (HFD)-induced obese ovariectomized (OVX) C57BL/6J mice, an animal model of obese postmenopausal women. Administration of ascorbic acid (5% w/w in diet for 18 weeks) reduced the size of visceral adipocytes without changes in body weight and adipose tissue mass in HFD-fed obese OVX mice compared with obese OVX mice that did not receive ascorbic acid. Ascorbic acid inhibited adipose tissue inflammation, as shown by the decreased number of crown-like structures and CD68-positive macrophages in visceral adipose tissues. Ascorbic acid-treated mice exhibited improved hyperglycemia, hyperinsulinemia, and glucose and insulin tolerance compared with nontreated obese mice. Pancreatic islet size and insulin-positive β-cell area in ascorbic acid-treated obese OVX mice decreased to the levels observed in low-fat diet-fed lean mice. Ascorbic acid also suppressed pancreatic triglyceride accumulation in obese mice. These results suggest that ascorbic acid may reduce insulin resistance and pancreatic steatosis partly by suppressing visceral adipocyte hypertrophy and adipose tissue inflammation in obese OVX mice. [ABSTRACT FROM AUTHOR]

OBJECTIVE: The prolactin (PRL) system plays important behavioral, social, and metabolic roles, such as mediating social bonding and insulin secretion. Inherited dysfunction of the PRL pathway-related genes is associated with psychopathology and insulin resistance. We have previously suggested that the PRL system might be implicated in the comorbidity of psychiatric (depression) and type 2 diabetes (T2D) owing to the pleiotropy of PRL pathway-related genes. To our knowledge, no PRL variants have so far been reported in patients with either major depressive disorder (MDD) and/or T2D. PATIENTS AND METHODS: In this study, we analyzed 6 variants within the PRL gene and tested them for the presence of parametric linkage and/or linkage disequilibrium (LD, i.e., linkage and association) with familial MDD, T2D, and their comorbidity. RESULTS: We found, for the first time, that the PRL gene and its novel risk variants are linked to and in LD (i.e., linkage and association) with familial MDD, T2D, and MDD-T2D comorbidity. CONCLUSIONS: PRL might play a key role in mental-metabolic comorbidity and can be considered a novel gene in MDD and T2D. [ABSTRACT FROM AUTHOR]

Summary: Dysregulations in energy balance represent a major driver of obesity. Recent evidence suggests that environmental factors also play a pivotal role in inducing weight gain. Chronic exposure to fine particulate matter (PM2.5) is associated with white adipose tissue (WAT) expansion in animals and higher rates of obesity in humans. This review discusses metabolic adaptions in central and peripheral tissues that promote energy storage and WAT accumulation in PM2.5‐exposed animals and humans. Chronic PM2.5 exposure produces inflammation and leptin resistance in the hypothalamus, decreasing energy expenditure and increasing food intake. PM2.5 promotes the conversion of brown adipocytes toward the white phenotype, resulting in decreased energy expenditure. The development of inflammation in WAT can stimulate adipogenesis and hampers catecholamine‐induced lipolysis. PM2.5 exposure affects the thyroid, reducing the release of thyroxine and tetraiodothyronine. In addition, PM2.5 exposure compromises skeletal muscle fitness by inhibiting Nitric oxide (NO)‐dependent microvessel dilation and impairing mitochondrial oxidative capacity, with negative effects on energy expenditure. This evidence suggests that pathological alterations in the hypothalamus, brown adipose tissue, WAT, thyroid, and skeletal muscle can alter energy homeostasis, increasing lipid storage and weight gain in PM2.5‐exposed animals and humans. Further studies will enrich this pathophysiological model. [ABSTRACT FROM AUTHOR]

Abstract Obesity usually is accompanied by inflammation of fat tissue, with a prominent role of visceral fat. Chronic inflammation in obese fat tissue is of a lower grade than acute immune activation for clearing the tissue from an infectious agent. It is the loss of adipocyte metabolic homeostasis that causes activation of resident immune cells for supporting tissue functions and regaining homeostasis. Initially, the excess influx of lipids and glucose in the context of overnutrition is met by adipocyte growth and proliferation. Eventual lipid overload of hypertrophic adipocytes leads to endoplasmic reticulum stress and the secretion of a variety of signals causing increased sympathetic tone, lipolysis by adipocytes, lipid uptake by macrophages, matrix remodeling, angiogenesis, and immune cell activation. Pro-inflammatory signaling of adipocytes causes the resident immune system to release increased amounts of pro-inflammatory and other mediators resulting in enhanced tissue-protective responses. With chronic overnutrition, these protective actions are insufficient, and death of adipocytes as well as senescence of several tissue cell types is seen. This structural damage causes the expression or release of immunostimulatory cell components resulting in influx and activation of monocytes and many other immune cell types, with a contribution of stromal cells. Matrix remodeling and angiogenesis is further intensified as well as possibly detrimental fibrosis. The accumulation of senescent cells also may be detrimental via eventual spread of senescence state from affected to neighboring cells by the release of microRNA-containing vesicles. Obese visceral fat inflammation can be viewed as an initially protective response in order to cope with excess ambient nutrients and restore tissue homeostasis but may contribute to tissue damage at a later stage.

Glycerol is a key metabolite for lipid accumulation in insulin-sensitive tissues. We examined the role of aquaporin-7 (AQP7), the main glycerol channel in adipocytes, in the improvement of brown adipose tissue (BAT) whitening, a process whereby brown adipocytes differentiate into white-like unilocular cells, after cold exposure or bariatric surgery in male Wistar rats with diet-induced obesity (DIO) (n = 229). DIO promoted BAT whitening, evidenced by increased BAT hypertrophy, steatosis and upregulation of the lipogenic factors Pparg2, Mogat2 and Dgat1. AQP7 was detected in BAT capillary endothelial cells and brown adipocytes, and its expression was upregulated by DIO. Interestingly, AQP7 gene and protein expressions were downregulated after cold exposure (4 °C) for 1 week or one month after sleeve gastrectomy in parallel to the improvement of BAT whitening. Moreover, Aqp7 mRNA expression was positively associated with transcripts of the lipogenic factors Pparg2, Mogat2 and Dgat1 and regulated by lipogenic (ghrelin) and lipolytic (isoproterenol and leptin) signals. Together, the upregulation of AQP7 in DIO might contribute to glycerol influx used for triacylglycerol synthesis in brown adipocytes, and hence, BAT whitening. This process is reversible by cold exposure and bariatric surgery, thereby suggesting the potential of targeting BAT AQP7 as an anti-obesity therapy. [ABSTRACT FROM AUTHOR]

Here, we identify that Caveolin-2 (Cav-2), an integral membrane protein, controls adipocyte hypertrophy in association with nuclear lamina. In the hypertrophy stage of adipogenesis, pY19-Cav-2 association with lamin A/C facilitated the disengagement of CCAAT/enhancer-binding protein a (C/EBPa) and peroxisome proliferator-activated receptor γ (PPARγ) from lamin A/C and repressed Cav-2 promoter at the nuclear periphery for epigenetic activation of Cav-2, and thereby promoted C/EBPa and PPARγ-induced adipocyte hypertrophy. Stable expression of Cav-2 was required and retained by phosphorylation, deubiquitination, and association with lamin A/C for the adipocyte hypertrophy. However, obese adipocytes exhibited augmented Cav-2 stability resulting from the up-regulation of lamin A/C over lamin B1, protein tyrosine phosphatase 1B (PTP1B), and nuclear deubiquitinating enzyme (DUB), Uchl5. Our findings show a novel epigenetic regulatory mechanism of adipocyte hypertrophy by Cav-2 at the nuclear periphery. [ABSTRACT FROM AUTHOR]

The regulation of adipose deposition in broiler chickens is an important factor for production efficiency to poultry producers and health concerns to customers. Although vitamin A and its metabolite [all-trans retinoic acid (atRA)] have been used for studies on adipogenesis in mammals and avian, effects of embryonic atRA on adipose development in embryonic (E) and posthatch (D) ages in broiler chickens have not been studied yet. Different concentrations of atRA (0 M–2 μM) were injected in broiler eggs at E10, and adipose tissues were sampled at E16. Percentages of adipose tissues in chicken embryos were significantly increased in the group injected with 500 nM of atRA compared to the 0 M group (P

Obesity usually is accompanied by inflammation of fat tissue, with a prominent role of visceral fat. Chronic inflammation in obese fat tissue is of a lower grade than acute immune activation for clearing the tissue from an infectious agent. It is the loss of adipocyte metabolic homeostasis that causes activation of resident immune cells for supporting tissue functions and regaining homeostasis. Initially, the excess influx of lipids and glucose in the context of overnutrition is met by adipocyte growth and proliferation. Eventual lipid overload of hypertrophic adipocytes leads to endoplasmic reticulum stress and the secretion of a variety of signals causing increased sympathetic tone, lipolysis by adipocytes, lipid uptake by macrophages, matrix remodeling, angiogenesis, and immune cell activation. Pro-inflammatory signaling of adipocytes causes the resident immune system to release increased amounts of pro-inflammatory and other mediators resulting in enhanced tissue-protective responses. With chronic overnutrition, these protective actions are insufficient, and death of adipocytes as well as senescence of several tissue cell types is seen. This structural damage causes the expression or release of immunostimulatory cell components resulting in influx and activation of monocytes and many other immune cell types, with a contribution of stromal cells. Matrix remodeling and angiogenesis is further intensified as well as possibly detrimental fibrosis. The accumulation of senescent cells also may be detrimental via eventual spread of senescence state from affected to neighboring cells by the release of microRNA-containing vesicles. Obese visceral fat inflammation can be viewed as an initially protective response in order to cope with excess ambient nutrients and restore tissue homeostasis but may contribute to tissue damage at a later stage. [ABSTRACT FROM AUTHOR]

Adipocytes can increase in volume up to a thousand-fold, storing excess calories as triacylglycerol in large lipid droplets. The dramatic morphological changes required of adipocytes demands extensive cytoskeletal remodeling, including lipid droplet and plasma membrane expansion. Cell growth-related signalling pathways are activated, stimulating the production of sufficient amino acids, functional lipids and nucleotides to meet the increasing cellular needs of lipid storage, metabolic activity and adipokine secretion. Continued expansion gives rise to enlarged (hypertrophic) adipocytes. This can result in a failure to maintain growth-related homeostasis and an inability to cope with excess nutrition or respond to stimuli efficiently, ultimately leading to metabolic dysfunction. We summarize recent studies which investigate the functional and cellular structure remodeling of hypertrophic adipocytes. How adipocytes adapt to an enlarged cell size and how this relates to cellular dysfunction are discussed. Understanding the healthy and pathological processes involved in adipocyte hypertrophy may shed light on new strategies for promoting healthy adipose tissue expansion.

Glycyrrhiza glabra roots have been well studied for their pharmacological activities, whereas less research has been conducted on liquorice aerial parts. Leaves represent a good source of D-pinitol, useful in the treatment of insulin resistance-related pathologies. Herein, we analyzed the in vitro effects of a D-pinitol-rich methanolic extract from Glycyrrhiza glabra leaves (GGLME) against lipotoxicity-related hypertrophy, inflammation, and insulin resistance in 3T3-L1 adipocytes exposed to palmitic acid (PA), comparing its activity with D-pinitol. GGLME pretreatment decreased lipid deposition, PPAR-γ, and NF-κB pathway induced by PA, similarly to D-pinitol, and improved insulin sensitivity, in presence or not of PA, increasing PI3K, pAkt, and GLUT1 levels. This study confirms that liquorice leaves, considered a waste of resource, could potentially be reused, and support further in vivo studies on animal and human models. In conclusion, liquorice leaves extract represents a potential candidate for prevention of metabolically induced inflammation, frequently leading to metabolic disorders. [ABSTRACT FROM AUTHOR]

For the past several decades, the prevalence of obesity and type 2 diabetes (T2D) has continued to rise on a global level. The risk contributing to this pandemic implicates both genetic and environmental factors, which are functionally integrated by epigenetic mechanisms. While these conditions are accompanied by major abnormalities in fuel metabolism, evidence indicates that altered immune cell functions also play an important role in shaping of obesity and T2D phenotypes. Interestingly, these events have been shown to be determined by epigenetic mechanisms. Consistently, recent epigenome-wide association studies have demonstrated that immune cells from obese and T2D individuals feature specific epigenetic profiles when compared to those from healthy subjects. In this work, we have reviewed recent literature reporting epigenetic changes affecting the immune cell phenotype and function in obesity and T2D. We will further discuss therapeutic strategies targeting epigenetic marks for treating obesity and T2D-associated inflammation. [ABSTRACT FROM AUTHOR]

Central obesity is genetically complex, and its exponential increase in the last decades have made it a critical public health issue. The Lyon Hypertensive (LH) rat is a well-characterized hypertensive model that also exhibits spontaneous and profound differences in body weight and adiposity, relative to its metabolically healthy control, the Lyon Normotensive (LN) rat. The mechanisms underlying the body weight differences between these strains are not well-understood, thus a congenic model (LH17LNa) was developed where a portion of the proximal arm of LN chromosome 17 is introgressed on the LH genomic background to assess the contribution of LN alleles on obesity features. Male and female LH17LNa rats were studied, but male congenics did not significantly differ from LH in this study. Female LH17LNa rats exhibited decreases in total body growth, as well as major alterations to their body composition and adiposity. The LH17LNa female rats also showed decreases in metabolic rate, and a reduction in food intake. The increased adiposity in the female LH17LNa rats was specific to abdominal white adipose tissue, and this phenomenon was further explained by significant hypertrophy in those adipocytes, with no evidence of adipocyte hyperplasia. Sequencing of the parental strains identified a novel frameshift mutation in the candidate gene Ercc6l2 , which is involved in transcription-coupled DNA repair, and is implicated in premature aging. The discovery of the significance of Ercc6l2 in the context of female-specific adipocyte biology could represent a novel role of DNA repair failure syndromes in obesity pathogenesis. [ABSTRACT FROM AUTHOR]

Cyclooxygenase-2 (COX-2) plays a critical role in regulating innate immunity and metabolism by producing prostaglandins (PGs) and other lipid mediators. However, the implication of adipose COX-2 in obesity remains largely unknown. Using adipocyte-specific COX-2 knockout (KO) mice, we showed that depleting COX-2 in adipocytes promoted white adipose tissue development accompanied with increased size and number of adipocytes and predisposed diet-induced adiposity, obesity, and insulin resistance. The increased size and number of adipocytes by COX-2 KO were reversed by the treatment of prostaglandin E2 (PGE2) but not PGI2 and PGD2 during adipocyte differentiation. PGE2 suppresses PPARγ expression through the PKA pathway at the early phase of adipogenesis, and treatment of PGE2 or PKA activator isoproterenol diminished the increased lipid droplets in size and number in COX-2 KO primary adipocytes. Administration of PGE2 attenuated increased fat mass and fat percentage in COX-2 deficient mice. Taken together, our study demonstrated the suppressing effect of adipocyte COX-2 on adipogenesis and reveals that COX-2 restrains adipose tissue expansion via the PGE2-mediated paracrine mechanism and prevents the development of obesity and related metabolic disorders. [ABSTRACT FROM AUTHOR]

Obesity develops early in childhood and is accompanied by early signs of adipose tissue (AT) dysfunction and metabolic disease in children. In order to analyse the molecular processes during obesity-related AT accumulation in children, we investigated genome-wide expression profiles in AT samples, isolated adipocytes, and stromal vascular fraction (SVF) cells and assessed their relation to obesity as well as biological and functional AT parameters. We detected alterations in gene expression associated with obesity and related parameters, i.e., BMI SDS, adipocyte size, macrophage infiltration, adiponectin, and/or leptin. While differential gene expression in AT and adipocytes shared an enrichment in metabolic pathways and pathways related to extracellular structural organisation, SVF cells showed an overrepresentation in inflammatory pathways. In adipocytes, we found the strongest positive association for epidermal growth factor-like protein 6 (EGFL6) with adipocyte hypertrophy. EGFL6 was also upregulated during in vitro adipocyte differentiation. In children, EGFL6 expression was positively correlated to parameters of AT dysfunction and metabolic disease such as macrophage infiltration into AT, hs-CRP, leptin levels, and HOMA-IR. In conclusion, we provide evidence for early alterations in AT gene expression related to AT dysfunction in children and identified EGFL6 as potentially being involved in processes underlying the pathogenesis of metabolic disease. [ABSTRACT FROM AUTHOR]

Glycerol is a key metabolite for lipid accumulation in insulin-sensitive tissues. We examined the role of aquaporin-7 (AQP7), the main glycerol channel in adipocytes, in the improvement of brown adipose tissue (BAT) whitening, a process whereby brown adipocytes differentiate into white-like unilocular cells, after cold exposure or bariatric surgery in male Wistar rats with diet-induced obesity (DIO) (n = 229). DIO promoted BAT whitening, evidenced by increased BAT hypertrophy, steatosis and upregulation of the lipogenic factors Pparg2, Mogat2 and Dgat1. AQP7 was detected in BAT capillary endothelial cells and brown adipocytes, and its expression was upregulated by DIO. Interestingly, AQP7 gene and protein expressions were downregulated after cold exposure (4 °C) for 1 week or one month after sleeve gastrectomy in parallel to the improvement of BAT whitening. Moreover, Aqp7 mRNA expression was positively associated with transcripts of the lipogenic factors Pparg2, Mogat2 and Dgat1 and regulated by lipogenic (ghrelin) and lipolytic (isoproterenol and leptin) signals. Together, the upregulation of AQP7 in DIO might contribute to glycerol influx used for triacylglycerol synthesis in brown adipocytes, and hence, BAT whitening. This process is reversible by cold exposure and bariatric surgery, thereby suggesting the potential of targeting BAT AQP7 as an anti-obesity therapy.

The obesity pandemic increasingly causes morbidity and mortality from type 2 diabetes, cardiovascular diseases and many other chronic diseases. Fat cell size (FCS) predicts numerous obesity-related complications such as lipid dysmetabolism, ectopic fat accumulation, insulin resistance, and cardiovascular disorders. Nevertheless, the scarcity of systematic literature reviews on this subject is compounded by the use of different methods by which FCS measurements are determined and reported. In this paper, we provide a systematic review of the current literature on the relationship between adipocyte hypertrophy and obesity-related glucose and lipid dysmetabolism, ectopic fat accumulation, and cardiovascular disorders. We also review the numerous mechanistic origins of adipocyte hypertrophy and its relationship with metabolic dysregulation, including changes in adipogenesis, cell senescence, collagen deposition, systemic inflammation, adipokine secretion, and energy balance. To quantify the effect of different FCS measurement methods, we performed statistical analyses across published data while controlling for body mass index, age, and sex. [ABSTRACT FROM AUTHOR]

Estrogen and estrogen receptor (ER)-α suppress visceral fat development through actions in several organs via unclear mechanisms that we sought to identify. Using mice that express only nuclear ER-α [nuclear-only ER-α (NOER) mice] or plasma membrane ER-α [membrane-only ER-α (MOER) mice], we found that 10-wk-old mice that lacked either receptor pool showed extensive abdominal visceral fat deposition and weight gain compared with wild-type (WT) mice. Differentiation of cultured bone marrow stem cells (BMSCs) into the adipocyte lineage was suppressed by 17-β-estradiol (E2) in WT female mice but not in NOER or MOER mice. This finding correlated with E2 inhibition of prominent differentiation genes in WT BMSCs. In contrast, triglyceride content in differentiated BMSCs or 3T3-L1 cells was suppressed as a result of membrane ER-α signaling through several kinases to inhibit carbohydrate response element-binding protein-α and -β. We concluded that extranuclear and nuclear ER-α collaborate to suppress adipocyte development, but inhibition of lipid synthesis in mature cells does not involve nuclear ER-α.

Estrogen and estrogen receptor (ER)-α suppress visceral fat development through actions in several organs via unclear mechanisms that we sought to identify. Using mice that express only nuclear ER-α [nuclear-only ER-α (NOER) mice] or plasma membrane ER-α [membrane-only ER-α (MOER) mice], we found that 10-wk-old mice that lacked either receptor pool showed extensive abdominal visceral fat deposition and weight gain compared with wild-type (WT) mice. Differentiation of cultured bone marrow stem cells (BMSCs) into the adipocyte lineage was suppressed by 17-β-estradiol (E2) in WT female mice but not in NOER or MOER mice. This finding correlated with E2 inhibition of prominent differentiation genes in WT BMSCs. In contrast, triglyceride content in differentiated BMSCs or 3T3-L1 cells was suppressed as a result of membrane ER-α signaling through several kinases to inhibit carbohydrate response element-binding protein-α and -β. We concluded that extranuclear and nuclear ER-α collaborate to suppress adipocyte development, but inhibition of lipid synthesis in mature cells does not involve nuclear ER-α.

Tissue‐resident macrophages in white adipose tissue (WAT) dynamically adapt to the metabolic changes of their microenvironment that are often induced by excess energy intake. Currently, the exact contribution of these macrophages in obesity‐driven WAT remodeling remains controversial. Here, using a transgenic CD169‐DTR mouse strain, we provide new insights into the interplay between CD169+ adipose tissue macrophages (ATMs) and their surrounding WAT microenvironment. Using targeted in vivo ATM ablation followed by transcriptional and metabolic WAT profiling, we found that ATMs protect WAT from the excessive pathological remodeling that occurs during obesity. As obesity progresses, ATMs control not only vascular integrity, adipocyte function, and lipid and metabolic derangements but also extracellular matrix accumulation and resultant fibrosis in the WAT. The protective role of ATMs during obesity‐driven WAT dysfunction supports the notion that ATMs represent friends, rather than foes, as has previously assumed. SYNOPSIS: This study reveals that resident macrophages in the adipose tissue are important regulatory cells that restrain tissue dysregulation caused by obesity. Obesity alters adipose tissue macrophage (ATM) dynamics.CD11c+ ATM subset control lipid metabolism in obese adipose tissue.ATM depletion leads to adipocyte hypertrophy and dysregulation.ATMs support vascular integrity and hamper obesity‐induced fibrosis. [ABSTRACT FROM AUTHOR]

[Display omitted] • TBT+HCD exposure impairs TYG index compared with CON, TBT and HCD treatment. • TBT+HCD exposure increases adipocyte hypertrophy compared with CON, TBT and HCD treatment. • TBT+HCD exposure reduces AMH levels compared with CON, TBT and HCD treatment. • TBT+HCD exposure increases FSH levels compared with CON, TBT and HCD treatment • TBT+HCD exposure worse POF features compared with CON, TBT and HCD treatment. Exposure to the obesogen tributyltin (TBT) alone or high carbohydrate diet (HCD) alone leads to obesity and reproductive complications, such as premature ovary failure (POF) features. However, little is known about interactions between TBT and nutrition and their combined impact on reproduction. In this study, we assessed whether acute TBT and HCD exposure results in reproductive and metabolic irregularities. Female rats were treated with TBT (100 ng/kg/day) and fed with HCD for 15 days and metabolic and reproductive outcomes were assessed. TBT and HCD rats displayed metabolic impairments, such as increased adiposity, abnormal lipid profile and triglyceride and glucose (TYG) index, worsening adipocyte hypertrophy in HCD-TBT rats. These metabolic consequences were linked with reproductive disorders. Specifically, HCD-TBT rats displayed irregular estrous cyclicity, high follicle-stimulating hormone (FSH) levels, low anti-Müllerian hormone (AMH) levels, reduction in ovarian reserve, and corpora lutea (CL) number, with increases in atretic follicles, suggesting that HCD-TBT exposure exacerbated POF features. Further, strong negative correlations were observed between adipocyte hypertrophy and ovarian reserve, CL number and AMH levels. HCD-TBT exposure resulted in reproductive tract inflammation and fibrosis. Collectively, these data suggest that TBT plus HCD exposure leads to metabolic and reproductive abnormalities, exacerbating POF features in female rats. [ABSTRACT FROM AUTHOR]

For the past several decades, the prevalence of obesity and type 2 diabetes (T2D) has continued to rise on a global level. The risk contributing to this pandemic implicates both genetic and environmental factors, which are functionally integrated by epigenetic mechanisms. While these conditions are accompanied by major abnormalities in fuel metabolism, evidence indicates that altered immune cell functions also play an important role in shaping of obesity and T2D phenotypes. Interestingly, these events have been shown to be determined by epigenetic mechanisms. Consistently, recent epigenome-wide association studies have demonstrated that immune cells from obese and T2D individuals feature specific epigenetic profiles when compared to those from healthy subjects. In this work, we have reviewed recent literature reporting epigenetic changes affecting the immune cell phenotype and function in obesity and T2D. We will further discuss therapeutic strategies targeting epigenetic marks for treating obesity and T2D-associated inflammation.

Excessive adipose accretion causes health issues in humans and decreases feed efficiency in poultry. Although vitamin A has been known to be involved in adipogenesis, effects of all-trans retinoic acid (atRA), as a metabolite of vitamin A, on embryonic adipose development have not been studied yet. Avian embryos are developing in confined egg environments, which can be directly modified to study effects of nutrients on embryonic adipogenesis. With the use of quail embryos, different concentrations of atRA (0 M to 10 μM) were injected in ovo at embryonic day (E) 9, and adipose tissues were sampled at E14. Percentages of fat pad weights in embryo weights were significantly increased in the group injected with 300 nM of atRA. Also, among three injection time points, E5, E7, or E9, E7 showed the most significant increase in weight and percentage of inguinal fat at E14. Injection of atRA at E7 increased fat cell size in E14 embryos with up-regulation of pro-adipogenic marker genes (Pparγ and Fabp4) and down-regulation of a preadipocyte marker gene (Dlk1) in adipose tissues. These data demonstrate that atRA promotes hypertrophic fat accretion in quail embryos, implying important roles of atRA in embryonic development of adipose tissues.

Excessive adipose accretion causes health issues in humans and decreases feed efficiency in poultry. Although vitamin A has been known to be involved in adipogenesis, effects of all- trans retinoic acid (atRA), as a metabolite of vitamin A, on embryonic adipose development have not been studied yet. Avian embryos are developing in confined egg environments, which can be directly modified to study effects of nutrients on embryonic adipogenesis. With the use of quail embryos, different concentrations of atRA (0 M to 10 μM) were injected in ovo at embryonic day (E) 9, and adipose tissues were sampled at E14. Percentages of fat pad weights in embryo weights were significantly increased in the group injected with 300 nM of atRA. Also, among three injection time points, E5, E7, or E9, E7 showed the most significant increase in weight and percentage of inguinal fat at E14. Injection of atRA at E7 increased fat cell size in E14 embryos with up-regulation of pro-adipogenic marker genes (Pparγ and Fabp4) and down-regulation of a preadipocyte marker gene (Dlk1) in adipose tissues. These data demonstrate that atRA promotes hypertrophic fat accretion in quail embryos, implying important roles of atRA in embryonic development of adipose tissues. [ABSTRACT FROM AUTHOR]

Metabolic syndrome poses a great worldwide threat to the health of the patients. Increased visceral adiposity is recognized as the main determinant of the detrimental clinical effects of insulin resistance. Inflammation and immune system activation in the adipose tissue (AT) have a central role in the pathophysiology of metabolic syndrome, but the mechanisms linking increased adiposity to immunity in the AT remain in part elusive. In this review, we support the central role of adipocyte overload and relative adipose failure as key determinants in triggering immune aggression to AT. This provides a mechanistic explanation of the relative metabolic wellness of metabolically normal obese people and the disruption in insulin signaling in metabolically obese lean people. [Display omitted] • Adipocyte hypertrophy is linked to MHCII expression on the adipocyte membrane. • Adipocyte hypertrophy causes accumulation of immune cells in the adipose tissue. • Immune cells mediate adipocyte death. • Immune cells infiltration in the adipose tissue causes metabolic syndrome. [ABSTRACT FROM AUTHOR]

The brominated flame retardant tetrabromobisphenol A-bis(2,3-dibromo-2-methylpropyl ether) (TBBPA-DBMPE) is a recommended substitute for hexabromocyclododecane (HBCD), a banned persistent organic pollutant, yet its potential toxicities remains largely unexplored. Here, we investigated the effects of a long-term exposure to TBBPA-DBMPE at nominal doses of 50 and 1000 μg/kg/d on lipid homeostasis in CD-1 mice, in comparison with 50 μg/kg/d HBCD as a positive control. Male pups received chemical treatments through maternal administration via drinking water from postnatal day 0–21, followed by direct administration through drinking water after weaning. On the 23rd week after treatment, the oral lipid tolerance test revealed that low-dose TBBPA-DBMPE as well as HBCD affected lipid tolerance, although the fasting serum triglyceride (TG) levels were not altered. When chemical treatment was extended to the 32nd week, TBBPA-DBMPE-treated animals displayed adipocyte hypertrophy in both white adipose tissue (eWAT) and brown adipose tissue (BAT) and hepatic steatosis, which was largely consistent with the effects of HBCD. These findings indicate that like HBCD, TBBPA-DBMPE led to increased lipid load in mice. Interestingly, we also observed intestinal histological changes, coupled with increased expression of lipid absorption-related genes in both HBCD and TBBPA-DBMPE treatments, suggesting increased lipid absorption. This was supported by in vitro findings that both HBCD and TBBPA-DBMPE promoted lipid accumulation in IEC-6 cells under the stress of oleic acid for 6 h, implying that altered lipid absorption by the intestine may partly contributed to increased lipid load in mice. Overall, the effects of 50 μg/kg/d TBBPA-DBMPE in terms of some parameters were comparable with 50 μg/kg/d HBCD, suggesting that TBBPA-DBMPE may not be an ideal substitute of HBCD. [Display omitted] • Long-term exposure to TBBPA-DBMPE as well as HBCD led to lipid disorders in mice. • Lipid disorders involved adipocyte hypertrophy, hepatic steatosis, and increased lipid absorption. • The effects of low-dose TBBPA-DBMPE on some parameters were comparable with HBCD. [ABSTRACT FROM AUTHOR]

Cyclooxygenase-2 (COX-2) plays a critical role in regulating innate immunity and metabolism by producing prostaglandins (PGs) and other lipid mediators. However, the implication of adipose COX-2 in obesity remains largely unknown. Using adipocyte-specific COX-2 knockout (KO) mice, we showed that depleting COX-2 in adipocytes promoted white adipose tissue development accompanied with increased size and number of adipocytes and predisposed diet-induced adiposity, obesity, and insulin resistance. The increased size and number of adipocytes by COX-2 KO were reversed by the treatment of prostaglandin E2 (PGE2) but not PGI2 and PGD2 during adipocyte differentiation. PGE2 suppresses PPARγ expression through the PKA pathway at the early phase of adipogenesis, and treatment of PGE2 or PKA activator isoproterenol diminished the increased lipid droplets in size and number in COX-2 KO primary adipocytes. Administration of PGE2 attenuated increased fat mass and fat percentage in COX-2 deficient mice. Taken together, our study demonstrated the suppressing effect of adipocyte COX-2 on adipogenesis and reveals that COX-2 restrains adipose tissue expansion via the PGE2-mediated paracrine mechanism and prevents the development of obesity and related metabolic disorders.

Obesity develops early in childhood and is accompanied by early signs of adipose tissue (AT) dysfunction and metabolic disease in children. In order to analyse the molecular processes during obesity-related AT accumulation in children, we investigated genome-wide expression profiles in AT samples, isolated adipocytes, and stromal vascular fraction (SVF) cells and assessed their relation to obesity as well as biological and functional AT parameters. We detected alterations in gene expression associated with obesity and related parameters, i.e., BMI SDS, adipocyte size, macrophage infiltration, adiponectin, and/or leptin. While differential gene expression in AT and adipocytes shared an enrichment in metabolic pathways and pathways related to extracellular structural organisation, SVF cells showed an overrepresentation in inflammatory pathways. In adipocytes, we found the strongest positive association for epidermal growth factor-like protein 6 (EGFL6) with adipocyte hypertrophy. EGFL6 was also upregulated during in vitro adipocyte differentiation. In children, EGFL6 expression was positively correlated to parameters of AT dysfunction and metabolic disease such as macrophage infiltration into AT, hs-CRP, leptin levels, and HOMA-IR. In conclusion, we provide evidence for early alterations in AT gene expression related to AT dysfunction in children and identified EGFL6 as potentially being involved in processes underlying the pathogenesis of metabolic disease.

Emerging evidence highlights that dysfunction of adipose tissue contributes to impaired insulin sensitivity and systemic metabolic deterioration in obese state. Of note, adipocyte hypertrophy serves as a critical event which associates closely with adipose dysfunction. An increase in cell size exacerbates hypoxia and inflammation as well as excessive collagen deposition, finally leading to metabolic dysregulation. Specific mechanisms of adipocyte hypertrophy include dysregulated differentiation and maturation of preadipocytes, enlargement of lipid droplets, and abnormal adipocyte osmolarity sensors. Also, weight loss therapies exert profound influence on adipocyte size. Here, we summarize the critical role of adipocyte hypertrophy in the development of metabolic disturbances. Future studies are required to establish a standard criterion of size measurement to better clarify the impact of adipocyte hypertrophy on changes in metabolic homeostasis. [ABSTRACT FROM AUTHOR]

Sumary Objectives This study examines the hypothesis that lower adipose tissue lipoprotein lipase (LPL) activity and a limited capacity for subcutaneous adipocyte expansion will be associated with metabolic syndrome (MSyn) in postmenopausal women who are overweight and obese. Methods Women (N = 150; age 60 ± 1 year; BMI: 31.5 ± 0.3 kg m−2; mean ± standard errors of the means [SEM]) with and without MSyn had dual‐energy X‐ray absorptiometry scans for total body fat, CT scans for visceral and subcutaneous abdominal adipose tissue areas, lipid and glucose metabolic profiles, and abdominal and gluteal fat aspirations for subcutaneous fat cell weight (FCW; N = 150) and LPL activity (N = 100). Results Women with MSyn had similar total body fat, but 15% larger abdominal and 11% larger gluteal FCWs and more visceral fat (179 ± 7 vs. 134 ± 6 cm2) than women without MSyn (P's

Nobiletin is a major citrus flavonoid possessing several biological activities. Nobiletin has been reported to display anti-inflammatory activity and to reduce monocyte chemoattractant protein (MCP)-1 secretion by 3T3-L1 adipocytes. However, its mode of action remains unclear. In the present study, we investigated the suppressive effect of nobiletin on MCP-1 expression in 3T3-L1 cells and its underlying molecular mechanism. Nobiletin notably down-regulated the MCP-1 mRNA level during adipocyte differentiation. Nobiletin also reduced MCP-1 secretion by preadipocytes (undifferentiated cells), differentiated adipocytes, and hypertrophied adipocytes. Immunoblot analysis showed that nobiletin inhibits the phosphorylation level of extracellular signal-regulated kinase (ERK) in both preadipocytes and differentiated adipocytes. Moreover, nobiletin suppressed MCP-1 secretion by adipocytes induced by tumor necrosis factor (TNF)-α.

Asymmetric dimethylarginine (ADMA) is generated through the irreversible methylation of arginine residues. It is an independent risk factor for cardiovascular disease, currently thought to be due to its ability to act as a competitive inhibitor of the nitric oxide (NO) synthase enzymes. Plasma ADMA concentrations increase with obesity and fall following weight loss; however, it is unknown whether they play an active role in adipose pathology. Here, we demonstrate that ADMA drives lipid accumulation through a newly identified NO-independent pathway via the amino-acid sensitive calcium-sensing receptor (CaSR). ADMA treatment of 3T3-L1 and HepG2 cells upregulates a suite of lipogenic genes with an associated increase in triglyceride content. Pharmacological activation of CaSR mimics ADMA while negative modulation of CaSR inhibits ADMA driven lipid accumulation. Further investigation using CaSR overexpressing HEK293 cells demonstrated that ADMA potentiates CaSR signalling via G q intracellular Ca2+ mobilisation. This study identifies a signalling mechanism for ADMA as an endogenous ligand of the G protein-coupled receptor CaSR that potentially contributes to the impact of ADMA in cardiometabolic disease. • Asymmetric dimethylarginine promotes lipogenesis in adipocytes and hepatocytes. • Lipid accumulation is independent of nitric oxide blockade. • Asymmetric dimethylarginine can modulate Calcium-sensing receptor signalling. [ABSTRACT FROM AUTHOR]

Objective: Obesity induced by high-fat diet (HFD) elicits white adipose tissue dysfunction. In this study, we have hypothesized that the metabolic modulator eicosapentaenoic acid (EPA) combined with the antioxidant hydroxytyrosol (HT) attenuates HFD-induced white adipose tissue (WAT) alterations. Methods: C57BL/6J mice were administered with a HFD (60% fat, 20% protein, 20% carbohydrates) or control diet (CD; 10% fat, 20% protein, 70% carbohydrates), with or without EPA (50 mg/kg/day), HT (5 mg/kg/day), or both for 12 weeks. Determinations in WAT include morphological parameters, EPA and docosahexaenoic acid content in phospholipids (gas chromatography), lipogenesis, oxidative stress (OS) and inflammation markers, and gene expression and activities of transcription factors, such as sterol regulatory element-binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor-gamma (PPAR-γ), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) (p65 subunit) and nuclear factor erythroid 2-related factor 2 (Nrf2) (quantitative polymerase chain reaction and enzyme linked immunosorbent assay). Results: HFD led to WAT hypertrophy in relation to PPAR-γ downregulation. WAT metabolic dysfunction was characterized by upregulation of lipogenic SREBP-1c system, mitochondrial energy metabolism depression, loss of the antioxidant Nrf2 signaling with OS enhancement, n-3 long-chain polyunsaturated fatty acids depletion and activation of the pro-inflammatory NF-κB system. EPA and HT co-supplementation diminished HFD-dependent effects additively, reaching values close or similar to controls. Conclusion: Data presented strengthen the importance of combined protocols such as EPA plus HT to attenuate metabolic-inflammatory states triggered by obesity.

The concept of heterogeneity among obese individuals in their risk for developing metabolic dysfunction and associated complications has been recognized for decades. At the origin of the heterogeneity idea is the acknowledgement that individuals with central obesity are more prone to developing type 2 diabetes and cardiovascular disease than those with peripheral obesity. There have been attempts to categorize subjects according to their metabolic health and degree of obesity giving rise to different obese and non-obese phenotypes that include metabolically unhealthy normal-weight (MUHNW), metabolically healthy obese (MHO), and metabolically unhealthy obese (MUO). Individuals belonging to the MHO phenotype are obese according to their body mass index although exhibiting fewer or none metabolic anomalies such as type 2 diabetes, dyslipidemia, hypertension, and/or unfavorable inflammatory and fribinolytic profiles. However, some authors claim that MHO is only transient in nature. Additionally, the phenotype categorization is controversial as it lacks standardized definitions possibly blurring the distinction between obesity phenotypes and confounding the associations with health outcomes. To add to the discussion, the factors underlying the origin or protection from metabolic deterioration and cardiometabolic risk for these subclasses are being intensely investigated and several hypotheses have been put forward. In the present review, we compare the different definitions of obesity phenotypes and present several possible factors underlying them (adipose tissue distribution and cellularity, contaminant accumulation on the adipose tissue, dysbiosis and metabolic endotoxemia imposing on to the endocannabinoid tone and inflammasome, and nutrient intake and dietary patterns) having inflammatory activation at the center.

Background: Chronic unpredictable mild stress (CUMS) has been shown to exacerbate atherosclerosis, but the underlying mechanism remains unknown. Adipose tissue is an energy storage organ and the largest endocrine organ in the human body, playing a key role in the development of cardiovascular disease. In this research, it was hypothesized that CUMS may exacerbate the development of atherosclerosis by inducing the hypertrophy and dysfunction of white adipocytes., Methods: The CUMS-induced atherosclerosis model was developed in Western diet-fed apolipoprotein E (ApoE) -/- mice. White adipose tissue (WAT), serum, aortic root, and the brachiocephalic trunk were collected and tested after 12 weeks of CUMS development. The mouse model of CUMS was evaluated for depression-like behavior using the open field test (OFT) and the elevated plus maze (EPM) test. Enzyme-linked immunosorbent assay (ELISA) was conducted to detect serum noradrenaline and urine adrenaline protein levels. Serological assays were used to detect serum low-density lipoprotein (LDL), high-density lipoprotein (HDL), total cholesterol (TC), and free fatty acid (FFA) concentrations. Hematoxylin and eosin (H&E) staining and oil red O were used to detect atherosclerotic plaque area, lipid deposition, and adipocyte size. The mRNA levels of genes related to aberrant adipose tissue function were determined using real-time PCR. Immunofluorescence assay and western blotting were conducted to examine the expression of proteins in the adipose tissue samples., Results: CUMS aggravated vascular atherosclerotic lesions in ApoE -/- mice. It decreased body weight while increasing the percentage of WAT. The serological results indicated that the concentration of HDL decreased in CUMS mice. Notably, adipocyte hypertrophy increased, whereas the mRNA levels of Pparg and its target genes ( Slc2a4 (encodes for GLUT4), Adipoq , and Plin1 ) decreased. Further investigation revealed that CUMS increased subcutaneous inguinal WAT (iWAT) lipid synthesis and adipocyte inflammation while decreasing lipid hydrolysis and the expression of HDL-associated protein ApoA-I. Moreover, CUMS aggravated insulin resistance in mice and inhibited the insulin pathway in iWAT., Conclusions: These findings indicated that CUMS induces adipose tissue dysfunction via a mechanism that leads to dyslipidemia, increased inflammation, and insulin resistance in the body, thereby exacerbating atherosclerosis. Notably, CUMS that is involved in decreasing the expression of HDL-associated proteins in adipose tissue may be a crucial link between adipose hypertrophy and advanced atherosclerosis. This study reveals a novel mechanism via which CUMS exacerbates atherosclerosis from the novel perspective of abnormal adipose function and identifies a novel potential therapeutic target for this disease., Competing Interests: The authors declare that they have no competing interests., (© 2023 Mao et al.)

Histomorphometric analyses of adipose tissue usually require formalin fixation of fresh samples. Our objective was to determine if intact, flash-frozen whole adipose tissue samples stored at − 80 °C could be used for measurements developed for fresh-fixed adipose tissues. Portions of adipose tissue samples were either formalin-fixed immediately upon sampling or flash-frozen and stored at − 80 °C and then formalin-fixed during the thawing process. Mean adipocyte diameter was measured. Immunohistochemistry was performed on additional samples to identify macrophage subtypes (M1, CD14 + and M2, CD206 +) and total (CD68 +) number. All slides were counterstained using haematoxylin and eosin (H&E). Visual inspection of H&E-stained adipose tissue slides performed in a blinded fashion showed little or no sign of cell breakage in 74% of frozen-fixed samples and in 68% of fresh-fixed samples (p > 0.5). There was no difference in the distribution frequencies of adipocyte sizes in fresh-fixed vs. frozen-fixed tissues in both depots (p > 0.9). Mean adipocyte size from frozen-fixed samples correlated significantly and positively with adipocyte size from fresh-fixed samples (r = 0.74, p < 0.0001, for both depots). The quality of staining/immunostaining and appearance of tissue architecture were comparable in fresh-fixed vs. frozen-fixed samples. In conclusion, intact flash-frozen adipose tissue samples stored at − 80 °C can be used to perform techniques conventionally applied to fresh-fixed samples. This approach allows for retrospective studies with frozen human adipose tissue samples. [ABSTRACT FROM AUTHOR]

Rodent animal models take at least 18 months to develop aging phenotypes for researchers to investigate the mechanism of age-related metabolic complications. Senescence-accelerated mouse prone 8 (SAMP8) shortens the process of aging and may facilitate an alternative model for studying age-related insulin resistance. The short-lived strain SAMP8 and two long-lived strains SAM resistant 1 (SAMR1) mice and C57BL/6 mice at 12 (young) and 40 weeks old (old) were used in the present study. Glucose tolerance test, histology and signaling pathways involved in lipid metabolism in adipose tissue and liver and key components of insulin signaling pathway in the skeletal muscle were determined in these three strains. We found that short-lived SAMP8 mice developed symptoms of insulin resistance including hyperglycemia, hyperinsulinemia, and impaired glucose tolerance in association with adipocyte hypertrophy and ectopic lipid accumulation in liver and muscle at 40-wk.-old. Significantly increased serum IL-6, leptin, and resistin levels and adipogenic transcription factor PPARγ and macrophage marker F4/80 mRNA expression in adipose tissues were observed in old SAMP8 mice, compared with that in young SAMP8 mice. Marked increases in SREBP1 and PPARγ and a decrease in PPARα at mRNA level in accordance with activation of mTOR/Akt pathway were contributed to hepatic lipid accumulation in old SAMP8 mice. Down-regulation of insulin signaling pathway including IRβ, IRS1, and AS160 at protein level in skeletal muscle was observed in old SAMP8 mice. At 40-wk.-old, both long-lived SAMR1 and C57BL/6 mice have not been fully developed age-related metabolic disorders including insulin resistance and visceral fat expansion in line with fewer defects in lipid metabolism and skeletal muscle insulin signaling pathway. In conclusion, our data suggest the suitability of the SAMP8 mice as a model for studying age-related metabolic complications. [ABSTRACT FROM AUTHOR]