Glycerol Release Research Articles

Cortisol and epinephrine alter the adipose functions and the mobilization of PCBs in adipose tissue slices from elephant seal

Marine mammals are exposed to increasing intensities of anthropogenic stressors such as acoustic disturbance and contaminants. Correlative studies have suggested concerning shifts in behavioral and physiological status of stress-exposed individuals, which could alter the health and survival of marine mammal populations. However, functional studies of the effects of multiple stressors on marine mammals are lacking. To fill in this gap, we recently developed an ex vivo approach of precision-cut adipose tissue slices (PCATS) to study the impact of stressors on the function of an essential endocrine organ: the adipose tissue. In the present study, we investigated the impact of hormones associated with the stress response on adipose tissue from northern elephant seals (Mirounga angustirostris). Blubber biopsies were collected from 17 weaned northern elephant seal pups, separated into inner and outer layers, dissected into PCATS, and cultured for 48 hours. To mimic prolonged and short-term exposure to physiological stress, PCATS were treated with 2 µM cortisol (CORT) for the entire 48 hours or 100 nM epinephrine (EPI) for the last 12 hours of culture, respectively. Hormones were applied individually or in combination. CORT and EPI exhibited an interacting, blubber layer-dependent, effect on adipose tissue biology, as quantified by gene expression in PCATS, and release of glycerol, free fatty acids, leptin and polychlorinated biphenyls into culture media. EPI stimulated a higher rate of lipolysis than CORT in PCATS from both blubber layers. The combination of CORT and EPI upregulated the expression of adipose triglyceride lipase in inner blubber PCATS and downregulated hormone-sensitive lipase in outer blubber-derived PCATS. Expression of the leptin gene and secretion of the leptin adipokine were both decreased by EPI, while addition of CORT attenuated this effect in inner blubber PCATS only. CORT also increased the expression of the antioxidant enzyme glutathione peroxidase 3 in PCATS from both blubber layers. Polychlorinated biphenyls exhibited selective and limited mobilization from PCATS treated with stress hormones, highlighting the lipophilic properties of these toxic compounds. This study showed that physiological stress can impact several essential functions of marine mammal blubber, such as lipolysis and adipokine production.

Anti‑adipogenic effect and underlying mechanism of lignan‑enriched nutmeg extract on 3T3‑L1 preadipocytes.

Nutmeg is the seed derived from Myristica fragrans. Nutmeg seeds contain alkylbenzene derivatives such as myristicin, which are toxic to the human organism, and lignan compounds such as nectandrin B, which possess anti-aging and anti-diabetic properties. However, the anti-adipogenic, prolipolytic and anti-inflammatory effects of lignan-enriched nutmeg extract (LNX) on preadipocytes remain unclear. In the present study, the effects of LNX on lipid accumulation, glycerol release and inflammatory cyclooxygenase-2 (COX-2) expression in differentiated 3T3-L1 preadipocytes were investigated. Oil red O staining demonstrated that treatment with LNX resulted in a concentration-dependent reduction in lipid accumulation in differentiating 3T3-L1 preadipocytes without affecting cell growth. Mechanistically, LNX treatment at 6 µg/ml led to a reduction in phosphorylation levels of signal transducer and activator of transcription 3 (STAT3), whereas it did not influence the peroxisome proliferator-activated receptor gamma (PPAR-γ) and CCAAT enhancer binding protein alpha (C/EBP-α) expression levels during 3T3-L1 preadipocyte differentiation. In addition, LNX treatment at 6 µg/ml led to a decrease in fatty acid synthase (FAS) expression levels on day (D) 2, but not D5 and D8, during preadipocyte differentiation. Treatment with LNX at 6 µg/ml did not affect the expression levels of perilipin A during preadipocyte differentiation. In differentiated 3T3-L1 adipocytes, LNX treatment at 6 µg/ml did not stimulate glycerol release and hormone-sensitive lipase phosphorylation, which are known lipolysis hallmarks. Furthermore, LNX treatment at the doses tested had no effect on tumor necrosis factor alpha-induced COX-2 expression in 3T3-L1 preadipocytes. Collectively, these results demonstrated that LNX has an anti-adipogenic effect on differentiating 3T3-L1 preadipocytes, which is mediated by the downregulation of STAT3 phosphorylation and FAS expression.

Benzyl isothiocyanate inhibits TNFα-driven lipolysis via suppression of the ERK/PKA/HSL signaling pathway in 3T3-L1 adipocytes

Tumor necrosis factor α (TNFα), an inflammatory cytokine, induces lipolysis and increases circulating concentrations of free fatty acids. In addition, TNFα is the first adipokine produced by adipose tissue in obesity, contributing to obesity-associated metabolic disease. Given that benzyl isothiocyanate (BITC) is a well-known anti-inflammatory agent, we hypothesized that BITC can ameliorate TNFα-induced lipolysis and investigated the working mechanisms involved. We first challenged 3T3-L1 adipocytes with TNFα to induce lipolysis, which was confirmed by increased glycerol release, decreased protein expression of peroxisome proliferator-activated receptor γ (PPARγ) and perilipin 1 (PLIN1), and increased phosphorylation of ERK, protein kinase A (PKA), and hormone-sensitive lipase (HSL). However, inhibition of ERK or PKA significantly attenuated the lipolytic activity of TNFα. Meanwhile, pretreatment with BITC significantly ameliorated the lipolytic activity of TNFα; the TNFα-induced phosphorylation of ERK, PKA, and HSL; the TNFα-induced ubiquitination of PPARγ; the TNFα-induced decrease in PPARγ nuclear protein binding to PPAR response element; and the TNFα-induced decrease in PLIN1 protein expression. Our results indicate that BITC ameliorates TNFα-induced lipolysis by inhibiting the ERK/PKA/HSL signaling pathway, preventing PPARγ proteasomal degradation, and maintaining PLIN1 protein expression.

FRI020 Adipocyte Subpopulations Regulate Growth Hormone-induced Lipolysis And Insulin Resistance

Abstract Disclosure: S. Siyar: None. J. Huang: None. R. Sharma: None. J.J. Kopchick: None. V. Puri: None. K.Y. Lee: None. Growth Hormone (GH) administration has long been known to increase lipolysis in adipose tissue leading to increased circulating free fatty acid levels and insulin resistance. Previous studies from our lab have found that this effect is mediated, at least in part, through transcriptional repression of the lipid droplet associated protein Fat specific protein (FSP27 also known as CIDEC). Furthermore, recent studies suggest that within a single adipose tissue depot there are different subpopulations of adipocytes. We have identified three distinct subpopulations of adipocytes with unique gene expression profiles and metabolic activities. We have found that one of these subpopulations of adipocytes, termed Type 2 adipocytes, are highly responsive to GH stimulation. In order to assess the physiological role of GH-mediated lipolysis mediated by this subpopulation, we specifically expressed human FSP27 (hFSP27) in Type 2 adipocytes (Type2Ad-hFSP27tg mice). Type2AdhFSP27tg mice had reduced systemic plasma glycerol release after acute GH treatment, and improvement in acute, but not chronic, GH-induced glucose intolerance. These mice exhibited an 45% increase in fat mass and significant increase in adipocyte cell size further indicating a decreased lipolytic response to GH. This decreased lipolytic response was associated with improved hepatic insulin signaling and insulin-induced gene expression in Type2Ad-hFSP27tg mice. Taken together, these results indicate that specifically targeting a subpopulation of adipocytes is sufficient to reduce GH-induced lipolysis and insulin resistance and may provide a platform for improved medical therapies for growth and endocrine disorders. Presentation: Friday, June 16, 2023

FRI025 Succinate Receptor Activation Increases Respiration In Human But Not Murine Brown Adipocytes

Abstract Disclosure: B.T. McNeill: None. A. Kelman: None. L.E. Ramage: None. K.J. Suchacki: None. S.J. Wakelin: None. N.M. Morton: None. R.H. Stimson: None. Brown adipose tissue (BAT) is a thermogenic tissue that generates heat to maintain body temperature. BAT activation is a potential therapeutic target for treating obesity-related cardiometabolic disease. We performed RNA sequencing of human primary brown and white adipocytes and identified SUCNR1, which encodes the succinate receptor, as highly differentially expressed (20-fold) in brown versus white adipocytes. Succinate is known to increase BAT thermogenesis, while SUCNR1 activation inhibits lipolysis in white adipose tissue (WAT). We hypothesized that SUCNR1 activation increases BAT thermogenesis in humans and in mice. To test this, we investigated the effect of succinate and the selective SUCNR1 agonist cis-epoxysuccinic acid (C-ESA) in human and murine primary brown/ beige adipocytes. In addition, we determined the metabolic effects of disruption of Sucnr1 in mice either fed control or a high fat (HFD) for 12 weeks and measured energy expenditure when housed at standard room temperature (21°C) and during cold exposure (4°C). In human brown and white adipocytes, succinate increased basal and noradrenaline-stimulated respiration, while C-ESA increased basal respiration only in human brown adipocytes without altering UCP1 mRNA levels. SUCNR1 activation reduced glycerol release only in human white adipocytes. Male (but not female) Sucnr1-/- mice exhibited impaired glucose tolerance versus Sucnr1+/+ littermates after 2 weeks of HFD, and greater fat mass was also observed in the Sucnr1-/- mice following chronic HFD. However, energy expenditure, locomotor activity and tail vein temperature were unchanged in male Sucnr1-/- mice either at 21°C or 4°C. In addition, expression of Ucp1 and Pgc1α in BAT and inguinal WAT were similar between genotypes. Sucnr1 deletion had no effect on fat mass or glucose tolerance in mice fed a control diet. In vitro, differentiated brown adipocytes from Sucnr1-/- mice demonstrated comparable cellular respiration and Ucp1 mRNA levels both basally and during noradrenaline stimulation to Sucnr1+/+ adipocytes. Succinate and C-ESA did not stimulate respiration in murine brown or white adipocytes. These data reveal that SUCNR1 activation enhances brown adipocyte respiration in human but not murine brown adipocytes, highlighting a novel pathway regulating BAT function in addition to differences between species. These data also reveal novel sex-specific differences in the metabolic effects of SUCNR1, although the mechanisms through which female mice are protected from the adverse metabolic effects of Sucnr1 deletion are unclear. SUCNR1 activation may be a novel therapeutic target to treat obesity and associated metabolic disease, but requires further research in humans to determine the specific mechanisms through which SUCNR1 regulates BAT thermogenesis. Presentation: Friday, June 16, 2023

Altered Adipocyte Cell Size Distribution Prior to Weight Loss in the R6/2 Model of Huntington's Disease.

Metabolic alterations contribute to disease onset and prognosis of Huntington's disease (HD). Weight loss in the R6/2 mouse model of HD is a consistent feature, with onset in mid-to-late stage of disease. In the present study, we aimed to investigate molecular and functional changes in white adipose tissue (WAT) that occur at weight loss in R6/2 mice. We further elaborated on the effect of leptin-deficiency and early obesity in R6/2 mice. We performed analyses at 12 weeks of age; a time point that coincides with the start of weight loss in our R6/2 mouse colony. Gonadal (visceral) and inguinal (subcutaneous) WAT depot weights were monitored, as well as adipocyte size distribution. Response to isoprenaline-stimulated glycerol release and insulin-stimulated glucose uptake in adipocytes from gonadal WAT was assessed. In R6/2 mice, WAT depot weights were comparable to wildtype (WT) mice, and the response to insulin and isoprenaline in gonadal adipocytes was unaltered. Leptin-deficient R6/2 mice exhibited distinct changes compared to leptin-deficient WT mice. At 12 weeks, female leptin-deficient R6/2 mice had reduced body weight accompanied by an increased proportion of smaller adipocytes, while in contrast; male mice displayed a shift towards larger adipocyte sizes without a significant body weight reduction at this timepoint. We here show that there are early sex-specific changes in adipocyte cell size distribution in WAT of R6/2 mice and leptin-deficient R6/2 mice.

Adipocyte Subpopulations Mediate Growth Hormone-induced Lipolysis and Glucose Tolerance in Male Mice.

In adipose tissue, growth hormone (GH) stimulates lipolysis, leading to an increase in plasma free fatty acid levels and a reduction in insulin sensitivity. In our previous studies, we have found that GH increases lipolysis by reducing peroxisome proliferator-activated receptor γ (PPARγ) transcription activity, leading to a reduction of tat-specific protein 27 (FSP27, also known as CIDEC) expression. In previous studies, our laboratory uncovered 3 developmentally distinct subpopulations of white adipocytes. In this manuscript, we show that one of the subpopulations, termed type 2 adipocytes, has increased GH-induced signaling and lipolysis compared to other adipocyte subtypes. To assess the physiological role of GH-mediated lipolysis mediated by this adipocyte subpopulation, we specifically expressed human FSP27 (hFSP27) transgene in type 2 adipocytes (type2Ad-hFSP27tg mice). Systemically, male type2Ad-hFSP27tg mice displayed reduced serum glycerol release and nonesterified fatty acids levels after acute GH treatment, and improvement in acute, but not chronic, GH-induced glucose intolerance. Furthermore, we demonstrate that type2Ad-hFSP27tg mice displayed improved hepatic insulin signaling. Taken together, these results indicate that this adipocyte subpopulation is a critical regulator of the GH-mediated lipolytic and metabolic response. Thus, further investigation of adipocyte subpopulations may provide novel treatment strategies to regulate GH-induced glucose intolerance in patients with growth and metabolic disorders.

Exosomal EIF5A derived from Lewis lung carcinoma induced adipocyte wasting in cancer cachexia

Cancer cachexia is a systemic inflammation-driven syndrome, characterized by muscle atrophy and adipose tissue wasting, with progressive weight loss leading to serious impairment of physiological function. Extracellular vesicles (EVs) derived from cancer cells play a significant role in adipocyte lipolysis, yet the mechanism remain uneclucidated. In this study, EVs derived from Lewis lung carcinoma (LLC) cells were extracted and characterized. 3T3-L1 and HIB1B adipocytes were cultured with conditioned medium or EVs from LLC, and LLC cells were used to establish a cancer cachexia mouse model. EVs derived from LLC cells were taken up by 3T3-L1 and HIB1B adipocytes, and derived exosomal EIF5A protein-induced lipolysis of adipocytes. High level of EIF5A was expressed in EVs from LLC cells, exosomal EIF5A is linked to lipid metabolism. Elevated expression of EIF5A is associated with shorter overall survival in lung cancer patients. Western blots, glycerol release and Oil red O staining assays were used to evaluate lipolysis of adipocytes. The reduction of lipolysis in 3T3-L1 and HIB1B adipocytes is achieved through silencing EIF5A or treating with pharmacologic inhibitor GC7 in vitro, and suppressing the expression of EIF5A in LLC cells by infected with shRNA or GC7 treatment partly alleviated white and brown adipose tissue lipolysis in vivo. Mechanistically, EIF5A directly binds with G protein-coupled bile acid receptor 1 (GPBAR1) mRNA to promote its translation and then activates cAMP response element binding protein (CREB) signaling pathway to induce lipolysis. This study demonstrates that exosomal EIF5A from LLC cells, with hypusinated EIF5A, has a lipolytic effect on adipocyte and adipose tissues in cancer cachexia model. Exosomal EIF5A could be involved in lipolysis and these findings indicate that a novel regulator and potential target for cachexia treatment.

Regulatory effects of baicalin, a flavonoid compound, on adipocyte metabolism.

Baicalin is a plant-derived, biologically active compound exerting numerous advantageous effects. Adipocytes store and release energy in the process of lipogenesis and lipolysis. Rodent studies have shown that baicalin treatment positively affects fat tissue, however, data on the direct influence of this compound on adipocyte metabolism is lacking. In the present research, the short-term effects of 25, 50, and 100 μM baicalin on glucose transport, conversion to lipids, and oxidation, and also on lipolysis in primary rat adipocytes were explored. Lipolysis was measured as glycerol release from adipocytes. It was shown that 100 μM baicalin reduced glucose oxidation but at any concentration did not affect glucose transport and lipogenesis. Baicalin significantly increased the adipocyte response to physiological and pharmacological lipolytic stimuli (such as epinephrine - adrenergic agonist, DPCPX - adenosine A1 receptor antagonist, and amrinone - cAMP phosphodiesterase inhibitor). The stimulatory effects of baicalin on epinephrine-induced lipolysis were markedly diminished by insulin (activator of cAMP phosphodiesterases) and H-89 (PKA inhibitor). It was also demonstrated that baicalin evoked a similar rise in epinephrine-induced lipolysis in the presence of glucose and alanine. Our results provided evidence that baicalin may reduce glucose oxidation and is capable of enhancing lipolysis in primary rat adipocytes. The action on lipolysis is glucose-independent and covers both the adrenergic and adenosine A1 receptor pathways. The rise in cAMP content is proposed to be responsible for the observed potentiation of the lipolytic process.

Black Wheat Extracts (Arriheuk) Regulate Adipogenesis and Lipolysis via Adenosine Monophosphate (AMP) Activated Protein Kinase (AMPK)/Sirtuin 1 (SIRT1) Signaling Pathways.

Polyphenols and other compounds with antioxidant properties are found in plants and are one of the main antioxidants proven to reduce body weight and the risk of insulin resistance. Still, the mechanism behind the protective effects against obesity remains unclear. Thus, the study aims to assess the impact of flavonoid-rich arriheuk extract, a purple wheat extract, on mitochondrial function using 3T3-L1 adipocytes and investigate the molecular mechanism behind its protective effects against adipogenesis and lipolysis. The study findings strongly indicate that arriheuk significantly suppressed triglyceride levels and inhibited the expression of transcription factors like C/EBPα and PPARγ in 3T3-L1 adipocytes. Furthermore, treatment with arriheuk suppressed the expression of SREBP1c and FAS proteins linked to lipogenesis. In addition, treatment with arriheuk extract decreased the mRNA levels of adipogenic transcription factors, increased glycerol release, and inhibited adipocyte differentiation. Interestingly, the arriheuk-mediated PGC-1α expression triggered mitochondrial biogenesis by promoting the AMPK phosphorylation and SIRT1 expression in adipocytes. Also, arriheuk suppressed adipogenesis and elicited browning through the AMPK- and SIRT1-associated pathways. Collectively, these findings strongly suggest that arriheuk extract regulates browning in 3T3-L1 white adipocytes by triggering the AMPK/SIRT1 pathway, indicating the prospective applications of arriheuk as a functional food to control obesity.

5-OR: Adipocyte ANGPTL8 Regulates Insulin Sensitivity and Thermogenic Programing

ANGPTL8 (A8), expressed mainly in the liver and adipocytes, regulates lipoprotein lipase (LPL) and lipid metabolism. Hepatic A8 and ANGPTL3 form a complex that inhibits LPL. However, the precise intracellular role of A8 in adipocytes is yet to be explored. We observed that RNAi-knockdown of A8 in mouse primary subcutaneous (SC) pre-adipocytes reduces adipocyte differentiation, glycerol, and fatty acid release at day 7 post-differentiation. RNAseq analysis of A8 siRNA or control siRNA transfected SC pre-adipocytes on days 0, 2, 4 and 7 of differentiation showed that A8 silencing impeded adipogenic and oxidative phosphorylation pathways and reduced expression of insulin signaling pathway genes IRS1, IRS2, PPARG, mTOR, early during differentiation, suggesting a role for A8 in the regulation of insulin sensitivity. Next, we investigated the functional role of adipose A8 by generating conditional adipocyte-specific A8 Knockout (AT-A8-KO) mice. AT-A8-KO mice on 45% high fat diet (HFD) with 30% fructose for 20 weeks showed a decrease in body weight gain, glycemia, brown fat mass, plasma TG and smaller cell size of SC adipocytes, while increased rectal temperature compared to controls. Interestingly, OGTT revealed AT-A8-KO mice in control diet or in HFD have significantly lower insulinemia. ITT results confirmed significant improvement of insulin sensitivity of AT-A8-KO mice on HFD. In addition, upon exposure to 6°C for 24h, AT-A8-KO mice exhibited elevated body temperature and energy expenditure compared to control mice, indicating that adipose tissue A8 negatively modulates cold-induced thermogenesis. Our results reveal that A8 regulates in vitro adipocyte differentiation, probably by modulating insulin signaling and mitochondrial respiration, and that deletion of adipocyte A8 in mice enhances insulin sensitivity, cold induced body temperature and energy expenditure. Therefore, targeting adipose specific A8 may be beneficial in promoting insulin sensitivity and preventing obesity. Disclosure A.Ghosh: None. I.Al-khairi: None. J.Abubaker: None. F.Al-mulla: None. M.Abu-farha: None. M.Prentki: None. Y.H.Leung: None. J.C.Y.Yu: None. R.M.Sladek: None. I.Chenier: None. A.Oppong: None. M.Peyot: None. M.Madiraju: None. Funding Dasman Diabetes Institute (731)

Effect of Crocetin on Basal Lipolysis in 3T3-L1 Adipocytes.

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

Assessment of Antidiabetic and Anti-Inflammatory Activities of Carissa carandas Linn Extract: In Vitro and In Vivo Study

This study investigated the effects of aqueous fruit extracts of Carissa carandas (CCA) on inflammation and insulin resistance using an in vitro cellular model, in vivo high-fat diets, and a streptozotocin-induced type 2 diabetic (T2DM) rat model. CCA significantly ameliorated inflammation by decreasing nitric oxide production in lipopolysaccharide (LPS)-induced RAW 264.7 macrophages. Interestingly, CCA showed anti-insulin resistance activities, as it significantly improved glucose uptake and decreased glycerol release in LPS-induced 3T3-L1 adipocytes. In vivo studies showed that a high dose of 12-week oral supplementation of CCA (400 mg/kg BW/day) significantly reduced visceral fat, triglycerides, and cholesterol level in the blood of diabetic rats. Importantly, the metabolic parameters in both fasting and postprandial states, including fasting plasma glucose, HOMA-IR, and glucose intolerance, significantly improved, indicating its antihyperglycemic benefit in diabetic rats. Moreover, the results of the HOMA-β and histological examination suggested that pancreatic β-cell function and pancreatic morphological changes of the CCA and metformin treatments appeared to be better than those in non-treated diabetes, indicating the protective effect of CCA against pancreatic damage caused by hyperglycemia. In conclusion, the present study first reported that the C. carandas fruit extract has anti-inflammation and anti-insulin resistance, and subsequently improved glycemic control in the T2DM rat model.

Bone marrow adipocytes alteration in an in vitro model of Gaucher Disease

Gaucher disease (GD) is caused by biallelic pathogenic variants in GBA1 gene that encodes the lysosomal enzyme glucocerebrosidase. Up to now, specific treatment for GD cannot completely reverse bone complications. Bone is composed of different cell types; including osteoblasts, osteocytes and osteoclasts. Osteoblasts are present on bone surfaces and are derived from local mesenchymal stem cells (MSCs). Depending on environment conditions, MSCs could differentiate into osteoblasts and adipocytes. Mature adipocytes-secreted adipokines and free fatty acids affect both osteoblasts and osteoclasts formation/activity and therefore mediate skeletal homeostasis. The aim of this study was to evaluate possible alterations in GD adipocyte (GD Ad) that could contribute to bone complications. MSCs were grown in adipogenic media in order to evaluate expression of differentiation markers as PPAR-γ. PPAR-γ was observed into the nucleus of GD Ad, indicating that these cells are properly stimulated. However, these cells accumulate lesser lipid droplets (LDs) than Control Ad. In order to study lipid droplet metabolism, we evaluated the lipolysis of these structures by the measurement of free glycerol in culture supernatant. Our results indicated that GD Ad had an alteration in this process, evidenced by an increase in glycerol release. We have also evaluated two enzymes involved in LDs synthesis: fatty acid synthase (FASN) and stearoyl-coenzyme A desaturase 1 (SCD1). The transcription of these genes was decreased in GD Ad, suggesting a dysfunction in the synthesis of LDs. In conclusion, our results show an alteration in LDs metabolism of GD Ad, independent of adipocyte differentiation process. This alteration would be caused by an increase in lipolysis in early stages of differentiation and also by a reduction of lipid synthesis, which could contribute with the skeletal imbalance in GD.

Sudachitin and Nobiletin Stimulate Lipolysis via Activation of the cAMP/PKA/HSL Pathway in 3T3-L1 Adipocytes.

Polymethoxyflavones are flavonoids that are abundant in citrus fruit peels and have beneficial effects on human health. Previous studies have demonstrated that the polymethoxyflavones, namely sudachitin and nobiletin, ameliorate obesity and diabetes in humans and rodents. Although nobiletin induces lipolysis in adipocytes, lipolytic pathway activation by sudachitin has not been clarified in adipocytes. In this study, the effect of sudachitin on lipolysis was elucidated in murine 3T3-L1 adipocytes. Glycerol release into the medium and activation of the cyclic AMP (cAMP)/protein kinase A (PKA)/hormone-sensitive lipase (HSL) pathway was evaluated in 3T3-L1-differentiated adipocytes. Treatment with sudachitin and nobiletin for 24 and 48 h did not induce cytotoxicity at concentrations of up to 50 μM. Sudachitin and nobiletin at concentrations of 30 and 50 μM increased intracellular cAMP and medium glycerol levels in 3T3-L1 adipocytes. Western blotting revealed that sudachitin and nobiletin dose-dependently increased protein levels of phosphorylated PKA substrates and phosphorylated HSL. Sudachitin- and nobiletin-induced glycerol release, phosphorylation of PKA substrates, and HSL phosphorylation were suppressed by pharmacological inhibition of adenylate cyclase and PKA. These findings indicated that sudachitin, similar to nobiletin, exerts anti-obesogenic effects, at least in part through the induction of lipolysis in adipocytes.

Adipose tissue specific CCL18 associates with cardiometabolic diseases in non-obese individuals implicating CD4+ T cells

AimObesity is linked to cardiometabolic diseases, however non-obese individuals are also at risk for type 2 diabetes (T2D) and cardiovascular disease (CVD). White adipose tissue (WAT) is known to play a role in both T2D and CVD, but the contribution of WAT inflammatory status especially in non-obese patients with cardiometabolic diseases is less understood. Therefore, we aimed to find associations between WAT inflammatory status and cardiometabolic diseases in non-obese individuals.MethodsIn a population-based cohort containing non-obese healthy (n = 17), T2D (n = 16), CVD (n = 18), T2D + CVD (n = 19) individuals, seventeen different cytokines were measured in WAT and in circulation. In addition, 13-color flow cytometry profiling was employed to phenotype the immune cells. Human T cell line (Jurkat T cells) was stimulated by rCCL18, and conditioned media (CM) was added to the in vitro cultures of human adipocytes. Lipolysis was measured by glycerol release. Blocking antibodies against IFN-γ and TGF-β were used in vitro to prove a role for these cytokines in CCL18-T-cell-adipocyte lipolysis regulation axis.ResultsIn CVD, T2D and CVD + T2D groups, CCL18 and CD4+ T cells were upregulated significantly compared to healthy controls. WAT CCL18 secretion correlated with the amounts of WAT CD4+ T cells, which also highly expressed CCL18 receptors suggesting that WAT CD4+ T cells are responders to this chemokine. While direct addition of rCCL18 to mature adipocytes did not alter the adipocyte lipolysis, CM from CCL18-treated T cells increased glycerol release in in vitro cultures of adipocytes. IFN-γ and TGF-β secretion was significantly induced in CM obtained from T cells treated with CCL18. Blocking these cytokines in CM, prevented CM-induced upregulation of adipocyte lipolysis.ConclusionWe suggest that in T2D and CVD, increased production of CCL18 recruits and activates CD4+ T cells to secrete IFN-γ and TGF-β. This, in turn, promotes adipocyte lipolysis – a possible risk factor for cardiometabolic diseases.

Spheroids derived from the stromal vascular fraction of adipose tissue self-organize in complex adipose organoids and secrete leptin

BackgroundAdipose tissue-derived stromal vascular fraction (SVF) harbors multipotent cells with potential therapeutic relevance. We developed a method to form adipose spheroids (AS) from the SVF with complex organoid structure and enhanced leptin secretion upon insulin stimulation.MethodsSVF was generated from the interscapular brown adipose tissue of newborn mice. Immunophenotype and stemness of cultured SVF were determined by flow cytometry and in vitro differentiation, respectively. Spheroids were generated in hanging drops and non-adherent plates and compared by morphometric methods. The adipogenic potential was compared between preadipocyte monolayers and spheroids. Extracellular leptin was quantified by immunoassay. Lipolysis was stimulated with isoprenaline and quantified by colorimetric methods. AS viability and ultrastructure were determined by confocal and transmission electron microscopy analyses.ResultsCultured SVF contained Sca1 + CD29 + CD44 + CD11b- CD45- CD90- cells with adipogenic and chondrogenic but no osteogenic potential. Culture on non-adherent plates yielded the highest quantity and biggest size of spheroids. Differentiation of AS for 15 days in a culture medium supplemented with insulin and rosiglitazone resulted in greater Pparg, Plin1, and Lep expression compared to differentiated adipocytes monolayers. AS were viable and maintained leptin secretion even in the absence of adipogenic stimulation. Glycerol release after isoprenaline stimulation was higher in AS compared to adipocytes in monolayers. AS were composed of outer layers of unilocular mature adipocytes and an inner structure composed of preadipocytes, immature adipocytes and an abundant loose extracellular matrix.ConclusionNewborn mice adipose SVF can be efficiently differentiated into leptin-secreting AS. Prolonged stimulation with insulin and rosiglitazone allows the formation of structurally complex adipose organoids able to respond to adrenergic lipolytic stimulation.

Breast cancer cell-derived exosome-delivered microRNA-155 targets UBQLN1 in adipocytes and facilitates cancer cachexia-related fat loss.

Cachexia occurrence and development are associated with loss of white adipose tissues, which may be involved with cancer-derived exosomes. This study attempted to characterize the functional mechanisms of bc cell-derived exosomes-loaded microRNA (miR)-155 in cancer cachexia-related fat loss. Exosomes were incubated with preadipocytes and cellular lipid droplet accumulation was observed using oil red O staining. Western blots evaluated the cellular levels of lipogenesis marker peroxisome proliferator activated receptor gamma (PPARγ) and adiponectin, C1Q and collagen domain containing (AdipoQ). Differentiated adipocytes were incubated with exosomes, and phosphate hormone sensitive lipase (P-HSL), adipose triglyceride lipase (ATGL), and glycerol were detected in adipocytes, in addition to uncoupling protein 1 (UCP1) and leptin levels. A mouse model of cancer cachexia was established where cancer exosomes were injected intravenously. The changes in body weight and tumor-free body weights were recorded and serum glycerol levels and lipid accumulation in adipose tissues were determined. Also, the relationship between miR-155 and UBQLN1 was predicted and verified. bc exosome treatment reduced PPARγ and AdipoQ protein levels, promoted the levels of P-HSL and ATGL proteins, facilitated glycerol release, increased UCP1 expression, and lowered leptin expression in adipocytes. Exosomal miR-155 inhibited lipogenesis in preadipocytes and boosted the browning of white adipose tissues. miR-155 downregulation alleviated cancer exosome-induced browning of white adipose tissues and fat loss. Mechanistically, miR-155 targeted UBQLN1, and UBQLN1 upregulation reversed the impacts of cancer exosomes. miR-155 loaded by bc cell-derived exosomes significantly affects white adipose browning and inhibition of cancer-derived exosomes.

Measuring the Rate of Lipolysis in Ex vivo Murine Adipose Tissue and Primary Preadipocytes Differentiated In Vitro.

Adipocytes store energy in the form of triglycerides in lipid droplets. This energy can be mobilized via lipolysis, where the fatty acid side chains are sequentially cleaved from the glycerol backbone, resulting in the release of free fatty acids and glycerol. Due to the low expression of glycerol kinase in white adipocytes, glycerol re-uptake rates are negligible, while fatty acid re-uptake is dictated by the fatty acid binding capacity of media components such as albumin. Both glycerol and fatty acid release into media can be quantified by colorimetric assays to determine the lipolytic rate. By measuring these factors at multiple time points, one can determine the linear rate of lipolysis with high confidence. Here, we provide a detailed protocol for the measurement of lipolysis in in vitro differentiated adipocytes and ex vivo adipose tissue from mice. This protocol may also be optimized for other preadipocyte cell lines or adipose tissue from other organisms; considerations and optimization parameters are discussed. This protocol is designed to be useful in determining and comparing the rate of adipocyte lipolysis between mouse models and treatments.

The impact of hepatocyte-specific deletion of hypoxia-inducible factors on the development of polymicrobial sepsis with focus on GR and PPARα function.

Polymicrobial sepsis causes acute anorexia (loss of appetite), leading to lipolysis in white adipose tissue and proteolysis in muscle, and thus release of free fatty acids (FFAs), glycerol and gluconeogenic amino acids. Since hepatic peroxisome proliferator-activated receptor alpha (PPARα) and glucocorticoid receptor (GR) quickly lose function in sepsis, these metabolites accumulate (causing toxicity) and fail to yield energy-rich molecules such as ketone bodies (KBs) and glucose. The mechanism of PPARα and GR dysfunction is not known. We investigated the hypothesis that hypoxia and/or activation of hypoxia inducible factors (HIFs) might play a role in these issues with PPARα and GR. After cecal ligation and puncture (CLP) in mice, leading to lethal polymicrobial sepsis, bulk liver RNA sequencing illustrated the induction of the genes encoding HIF1α and HIF2α, and an enrichment of HIF-dependent gene signatures. Therefore, we generated hepatocyte-specific knock-out mice for HIF1α, HIF2α or both, and a new HRE-luciferase reporter mouse line. After CLP, these HRE-luciferase reporter mice show signals in several tissues, including the liver. Hydrodynamic injection of an HRE-luciferase reporter plasmid also led to (liver-specific) signals in hypoxia and CLP. Despite these encouraging data, however, hepatocyte-specific HIF1α and/or HIF2α knock-out mice suggest that survival after CLP was not dependent on the hepatocyte-specific presence of HIF proteins, which was supported by measuring blood levels of glucose, FFAs, and KBs. The HIF proteins were also irrelevant in the CLP-induced glucocorticoid resistance, but we found indications that the absence of HIF1α in hepatocytes causes less inactivation of PPARα transcriptional function. We conclude that HIF1α and HIF2α are activated in hepatocytes in sepsis, but their contribution to the mechanisms leading to lethality are minimal.