Brown Adipose Tissue Research Articles

Deceptive Brown Adipose Tissue.

Deceptive Brown Adipose Tissue.

#972 A Novel Single Compound from Chinese Herbs as a Potential Candidate for Reducing obesity induced diabetic nephropathy via ATF3-RARRES1 axis pathway

Abstract Background and Aims Billions of people have obesity induced diabetic nephropathy. Promoting the browning of white adipose tissue has been suggested as a potential strategy for, but a drug still needs to be identified. Method First, WT and ATF3 knockout mice fed a high-fat diet were treated with STZ to determine that ATF3 plays an important role in obesity-induced diabetic nephropathy. Second, DBA mice fed a high-fat diet were infused with STZ, and db/db KO mice were fed a high-fat diet, and the two mouse models were injected intraperitoneally with or without the ATF3 inducer ST32da (the structure is a single drug designed based on the traditional Chinese medicine Salvia miltiorrhiza). After about one and a half months, all related kidneys function values were measured. Results After analysis the relationship between ATF3 and diabetic nephropathy in human GEO DataSet Browser indicated that the gene expression of ATF3 was lower in patients groups. Genetic deletion of activating transcription factor 3 (ATF3−/−) in mice under a high-fat diet (HFD) and STZ treatment resulted in more aggravated nephropathy phenomenon syndrome including higher urine albumin, lower creatinine clearance and high risk in death. ST32da, a synthetic ATF3 inducer isolated from Salvia miltiorrhiza, promoted ATF3 expression to downregulate inflammatory genes and ameliorated foot process effacement resulting in reduced diabetic nephropathy by suppressing the podocyte apoptosis via interleukin (IL)-6 and retinoic acid receptor responder protein 1 (RARRES1) axis. Conclusion Our study identified the ATF3 inducer ST32da and Salvia miltiorrhiza extraction, may as a promising therapeutic drug for treating diet-induced obesity induced diabetic nephropathy.

UV Irradiation Increases Appetite and Prevents Body Weight Gain through the Upregulation of Norepinephrine in Mice

UV irradiation of the human skin downregulates lipid synthesis and adipokine production in subcutaneous fat. Recent evidence has suggested that UV exposure limits body weight gain in mouse models of obesity. However, the relationship between norepinephrine and UV irradiation has not been previously reported. Chronic UV exposure stimulated food intake but prevented body weight gain. Leptin, an appetite-suppressing hormone, was significantly reduced in the serum of the UV-irradiated mice. In contrast, UV irradiation induced browning of subcutaneous white adipose tissues without increasing physical activity. Notably, UV irradiation significantly increased norepinephrine levels, and the inhibition of norepinephrine production reversed the effects of chronic UV irradiation on food intake and body weight gain. In conclusion, chronic UV irradiation induces norepinephrine release, resulting in the stimulation of food intake due to the downregulation of leptin levels, but it prevents weight gain by inducing the browning process and elevating energy expenditure.

Aging impairs cold-induced beige adipogenesis and adipocyte metabolic reprogramming.

The energy-burning capability of beige adipose tissue is a potential therapeutic tool for reducing obesity and metabolic disease, but this capacity is decreased by aging. Here, we evaluate the impact of aging on the profile and activity of adipocyte stem and progenitor cells (ASPCs) and adipocytes during the beiging process in mice. We found that aging increases the expression of Cd9 and other fibro-inflammatory genes in fibroblastic ASPCs and blocks their differentiation into beige adipocytes. Fibroblastic ASPC populations from young and aged mice were equally competent for beige differentiation in vitro, suggesting that environmental factors suppress adipogenesis in vivo. Examination of adipocytes by single nucleus RNA-sequencing identified compositional and transcriptional differences in adipocyte populations with aging and cold exposure. Notably, cold exposure induced an adipocyte population expressing high levels of de novo lipogenesis (DNL) genes, and this response was severely blunted in aged animals. We further identified Npr3, which encodes the natriuretic peptide clearance receptor, as a marker gene for a subset of white adipocytes and an aging-upregulated gene in adipocytes. In summary, this study indicates that aging blocks beige adipogenesis and dysregulates adipocyte responses to cold exposure and provides a resource for identifying cold and aging-regulated pathways in adipose tissue.

Quantitative Assessment of Morphological Changes in Lipid Droplets and Lipid-Mito Interactions with Aging in Brown Adipose.

The physical characteristics of brown adipose tissue (BAT) are defined by the presence of multilocular lipid droplets (LD) within the brown adipocytes and a high abundance of iron-containing mitochondria, which give it its characteristic color. Normal mitochondrial function is, in part, regulated by organelle-to-organelle contacts. Particularly, the contact sites that mediate mitochondria-LD interactions are thought to have various physiological roles, such as the synthesis and metabolism of lipids. Aging is associated with mitochondrial dysfunction, and previous studies show that there are changes in mitochondrial structure and proteins that modulate organelle contact sites. However, how mitochondria-LD interactions change with aging has yet to be fully clarified. Therefore, we sought to define age-related changes in LD morphology and mitochondria-lipid interactions in BAT. We examined the three-dimensional morphology of mitochondria and LDs in young (3-month) and aged (2-year) murine BAT using serial block face-scanning electron microscopy and the Amira program for segmentation, analysis, and quantification. Analysis showed reductions in LD volume, area, and perimeter in aged samples compared to young samples. Additionally, we observed changes in LD appearance and type in aged samples compared to young samples. Notably, we found differences in mitochondrial interactions with LDs, which could implicate that these contacts may be important for energetics in aging. Upon further investigation, we also found changes in mitochondrial and cristae structure for mitochondria interacting with LD lipids. Overall, these data define the nature of LD morphology and organelle-organelle contacts during aging and provide insight into LD contact site changes that interconnect biogerontology and mitochondrial functionality, metabolism, and bioactivity in aged BAT.

Characterizing the Dynamic Expression of C1q/TNF-α-Related Protein 6 (CTRP6) during Pregnancy in Humans and Mice with Gestational Diabetes Mellitus.

C1q/TNF-related protein 6 (CTRP6) is a novel adipokine involved in insulin resistance. Thus, we aim to investigate the expression profile of CTRP6 in the plasma, adipose tissue and placenta of GDM patients and mice. Chinese Han pregnant women (GDM n = 9, control n = 10) with a scheduled caesarean section delivery were recruited. A number of high-fat diet (HFD) induced-pregnancy C57BL/6 mice were chosen as an animal model of GDM. Circulating levels of CTRP6 and adiponectin were examined by ELISA. CTRP6 expression in adipose tissue and placenta were detected by real-time qPCR and WB. Plasma CTRP6 levels were decreased during the first and second trimesters in mice, as well as the second and third trimesters in patients, while they were increased at delivery in GDM patients and mice. Plasma CTRP6 levels were significantly correlated with WBC, systolic pressure, diastolic pressure and fasting blood glucose. Moreover, CTRP6 mRNA expression in the subcutaneous (sWAT) and omental white adipose tissue (oWAT), as well as in the placenta, was significantly higher in GDM human patients at cesarean delivery. Furthermore, the mRNA expression of Ctrp6 was increased in the sWAT and visceral WAT (vWAT), whilst decreased in the interscapular brown adipose tissue (iBAT), of GDM mice at cesarean delivery. Dynamically expressed CTRP6 may be served as a candidate target for treatment of GDM.

Early Life Programming of Adipose Tissue Remodeling and Browning Capacity by Micronutrients and Bioactive Compounds as a Potential Anti-Obesity Strategy.

The early stages of life, especially the period from conception to two years, are crucial for shaping metabolic health and the risk of obesity in adulthood. Adipose tissue (AT) plays a crucial role in regulating energy homeostasis and metabolism, and brown AT (BAT) and the browning of white AT (WAT) are promising targets for combating weight gain. Nutritional factors during prenatal and early postnatal stages can influence the development of AT, affecting the likelihood of obesity later on. This narrative review focuses on the nutritional programming of AT features. Research conducted across various animal models with diverse interventions has provided insights into the effects of specific compounds on AT development and function, influencing the development of crucial structures and neuroendocrine circuits responsible for energy balance. The hormone leptin has been identified as an essential nutrient during lactation for healthy metabolic programming against obesity development in adults. Studies have also highlighted that maternal supplementation with polyunsaturated fatty acids (PUFAs), vitamin A, nicotinamide riboside, and polyphenols during pregnancy and lactation, as well as offspring supplementation with myo-inositol, vitamin A, nicotinamide riboside, and resveratrol during the suckling period, can impact AT features and long-term health outcomes and help understand predisposition to obesity later in life.

A device for rapid calorimetric measurements on small biological tissue samples

A new calorimetric technique is described that allows high-throughput heat production rate measurements on small biological tissue samples. The technique is based on the widely used thermopile chip technology combined with an innovative method for precise transport and positioning of samples of different biological materials at the thermal power detector inside the calorimeter. The new transport and positioning technique is a combination of fluidic and mechanical transport, where the latter is realized by a magneto-motor drive. The transport facility ensures good diffusive oxygen penetration into the sample, which is essential for highly metabolically active materials. The proper functioning of the device is demonstrated by measuring the heat production of metabolically active brown adipose tissue, biopsied tegu lizard muscle, and live Drosophila larvae at different stages and temperatures.

The novel adrenergic agonist ATR-127 targets skeletal muscle and brown adipose tissue to tackle diabesity and steatohepatitis

ObjectiveSimultaneous activation of β2- and β3-adrenoceptors (ARs) improves whole-body metabolism via beneficial effects in skeletal muscle and brown adipose tissue (BAT). Nevertheless, high-efficacy agonists simultaneously targeting these receptors whilst limiting activation of β1-ARs – and thus inducing cardiovascular complications – are currently non-existent. Therefore, we here developed and evaluated the therapeutic potential of a novel β2-and β3-AR, named ATR-127, for the treatment of obesity and its associated metabolic perturbations in preclinical models. MethodsIn the developmental phase, we assessed the impact of ATR-127's on cAMP accumulation in relation to the non-selective β-AR agonist isoprenaline across various rodent β-AR subtypes, including neonatal rat cardiomyocytes. Following these experiments, L6 muscle cells were stimulated with ATR-127 to assess the impact on GLUT4-mediated glucose uptake and intramyocellular cAMP accumulation. Additionally, in vitro, and in vivo assessments are conducted to measure ATR-127's effects on BAT glucose uptake and thermogenesis. Finally, diet-induced obese mice were treated with 5 mg/kg ATR-127 for 21 days to investigate the effects on glucose homeostasis, body weight, fat mass, skeletal muscle glucose uptake, BAT thermogenesis and hepatic steatosis. ResultsExposure of L6 muscle cells to ATR-127 robustly enhanced GLUT4-mediated glucose uptake despite low intramyocellular cAMP accumulation. Similarly, ATR-127 markedly increased BAT glucose uptake and thermogenesis both in vitro and in vivo. Prolonged treatment of diet-induced obese mice with ATR-127 dramatically improved glucose homeostasis, an effect accompanied by decreases in body weight and fat mass. These effects were paralleled by an enhanced skeletal muscle glucose uptake, BAT thermogenesis, and improvements in hepatic steatosis. ConclusionsOur results demonstrate that ATR-127 is a highly effective, novel β2- and β3-ARs agonist holding great therapeutic promise for the treatment of obesity and its comorbidities, whilst potentially limiting cardiovascular complications. As such, the therapeutic effects of ATR-127 should be investigated in more detail in clinical studies.

Low expression of ELOVL6 may be involved in fat loss in white adipose tissue of cancer-associated cachexia

BackgroundCancer-associated cachexia (CAC) arises from malignant tumors and leads to a debilitating wasting syndrome. In the pathophysiology of CAC, the depletion of fat plays an important role. The mechanisms of CAC-induced fat loss include the enhancement of lipolysis, inhibition of lipogenesis, and browning of white adipose tissue (WAT). However, few lipid-metabolic enzymes have been reported to be involved in CAC. This study hypothesized that ELOVL6, a critical enzyme for the elongation of fatty acids, may be involved in fat loss in CAC.MethodsTranscriptome sequencing technology was used to identify CAC-related genes in the WAT of a CAC rodent model. Then, the expression level of ELOVL6 and the fatty acid composition were analyzed in a large clinical sample. Elovl6 was knocked down by siRNA in 3T3-L1 mouse preadipocytes to compare with wild-type 3T3-L1 cells treated with tumor cell conditioned medium.ResultsIn the WAT of patients with CAC, a significant decrease in the expression of ELOVL6 was found, which was linearly correlated with the extent of body mass reduction. Gas chromatographic analysis revealed an increase in palmitic acid (C16:0) and a decrease in linoleic acid (C18:2n-6) in these tissue samples. After treatment with tumor cell-conditioned medium, 3T3-L1 mouse preadipocytes showed a decrease in Elovl6 expression, and Elovl6-knockdown cells exhibited a reduction in preadipocyte differentiation and lipogenesis. Similarly, the knockdown of Elovl6 in 3T3-L1 cells resulted in a significant increase in palmitic acid (C16:0) and a marked decrease in oleic acid (C18:1n-9) content.ConclusionOverall, the expression of ELOVL6 was decreased in the WAT of CAC patients. Decreased expression of ELOVL6 might induce fat loss in CAC patients by potentially altering the fatty acid composition of adipocytes. These findings suggest that ELOVL6 may be used as a valuable biomarker for the early diagnosis of CAC and may hold promise as a target for future therapies.

The Role of Exerkines in Obesity-Induced Disruption of Mitochondrial Homeostasis in Thermogenic Fat.

There is a notable correlation between mitochondrial homeostasis and metabolic disruption. In this review, we report that obesity-induced disruption of mitochondrial homeostasis adversely affects lipid metabolism, adipocyte differentiation, oxidative capacity, inflammation, insulin sensitivity, and thermogenesis in thermogenic fat. Elevating mitochondrial homeostasis in thermogenic fat emerges as a promising avenue for developing treatments for metabolic diseases, including enhanced mitochondrial function, mitophagy, mitochondrial uncoupling, and mitochondrial biogenesis. The exerkines (e.g., myokines, adipokines, batokines) released during exercise have the potential to ameliorate mitochondrial homeostasis, improve glucose and lipid metabolism, and stimulate fat browning and thermogenesis as a defense against obesity-associated metabolic diseases. This comprehensive review focuses on the manifold benefits of exercise-induced exerkines, particularly emphasizing their influence on mitochondrial homeostasis and fat thermogenesis in the context of metabolic disorders associated with obesity.

Dynamic changes of immunocyte subpopulations in thermogenic activation of adipose tissues.

The effects of cold exposure on whole-body metabolism in humans have gained increasing attention. Brown or beige adipose tissues are crucial in cold-induced thermogenesis to dissipate energy and thus have the potential to combat metabolic disorders. Despite the immune regulation of thermogenic adipose tissues, the overall changes in vital immune cells during distinct cold periods remain elusive. This study aimed to discuss the overall changes in immune cells under different cold exposure periods and to screen several potential immune cell subpopulations on thermogenic regulation. Cibersort and mMCP-counter algorithms were employed to analyze immune infiltration in two (brown and beige) thermogenic adipose tissues under distinct cold periods. Changes in some crucial immune cell populations were validated by reanalyzing the single-cell sequencing dataset (GSE207706). Flow cytometry, immunofluorescence, and quantitative real-time PCR assays were performed to detect the proportion or expression changes in mouse immune cells of thermogenic adipose tissues under cold challenge. The proportion of monocytes, naïve, and memory T cells increased, while the proportion of NK cells decreased under cold exposure in brown adipose tissues. Our study revealed dynamic changes in immune cell profiles in thermogenic adipose tissues and identified several novel immune cell subpopulations, which may contribute to thermogenic activation of adipose tissues under cold exposure.

Characterization of a novel adipose tissue located between abdominal lymph nodes and cervix/prostate in mice.

Perigonadal adipose tissue is a homogeneous white adipose tissue (WAT) in adult male mice without any brown adipose tissue (BAT). However, there are congenital differences in the gonads between male and female mice. Whether heterogeneity existed in perigonadal adipose tissues (ATs) in female mice remains unknown. This study reported a perigonadal brown-like AT located between abdominal lymph nodes and the uterine cervix in female mice, termed lymph node-cervical adipose tissue (LNCAT). Its counterpart, lymph node-prostatic adipose tissue (LNPAT), exhibited white phenotype in adult virgin male mice. When exposed to cold, LNCAT/LNPAT increased uncoupling protein 1 (UCP1) expression via activation of tyrosine hydroxylase (TH), in which abdominal lymph nodes were involved. Interestingly, the UCP1 expression in LNCAT/LNPAT varied under different reproductive stages. The UCP1 expression in LNCAT was upregulated at early pregnancy, declined at midlate pregnancy, and reverted in weaning dams. Mating behavior stimulated LNPAT browning in male mice. We found that androgen but not estrogen or progesterone inhibited UCP1 expression in LNCAT. Androgen administration reversed the castration-induced LNPAT browning. Our results identified a perigonadal brown-like AT in female mice and characterized its UCP1 expression patterns under various conditions.NEW & NOTEWORTHY A novel perigonadal brown-like AT (LNCAT) of female mice was identified. Abdominal lymph nodes were involved in cold-induced browning in this newly discovered adipose tissue. The UCP1 expression in LNCAT/LNPAT was also related to ages, sexes, and reproductive stages, in which androgen acted as an inhibitor role.

C-fos induction in the choroid plexus, tanycytes and pars tuberalis is an early indicator of spontaneous arousal from torpor in a deep hibernator.

Hibernation is an extreme state of seasonal energy conservation, reducing metabolic rate to as little as 1% of the active state. During the hibernation season, many species of hibernating mammals cycle repeatedly between the active (aroused) and hibernating (torpid) states (T-A cycling), using brown adipose tissue (BAT) to drive cyclical rewarming. The regulatory mechanisms controlling this process remain undefined but are presumed to involve thermoregulatory centres in the hypothalamus. Here, we used the golden hamster (Mesocricetus auratus), and high-resolution monitoring of BAT, core body temperature and ventilation rate, to sample at precisely defined phases of the T-A cycle. Using c-fos as a marker of cellular activity, we show that although the dorsomedial hypothalamus is active during torpor entry, neither it nor the pre-optic area shows any significant changes during the earliest stages of spontaneous arousal. Contrastingly, in three non-neuronal sites previously linked to control of metabolic physiology over seasonal and daily time scales - the choroid plexus, pars tuberalis and third ventricle tanycytes - peak c-fos expression is seen at arousal initiation. We suggest that through their sensitivity to factors in the blood or cerebrospinal fluid, these sites may mediate metabolic feedback-based initiation of the spontaneous arousal process.

Exploring the Therapeutic Potential of β-Hydroxybutyrate (BHB) in Clear Cell Renal Cell Carcinoma: A Journey into Fat Browning, Autophagy, and Tumor Slimming

This study delves into the therapeutic potential of β-hydroxybutyrate (BHB) in clear cell renal cell carcinoma (ccRCC), a cancer known for its complex pathogenesis and resistance to conventional treatments. The research specifically explores the impact of BHB on cell viability, autophagy induction, and lipid metabolism in Caki-1 cells. The findings reveal that BHB significantly reduces ccRCC cell viability, particularly under low-glucose conditions. The combination of glucose and BHB treatment activates autophagy pathways, as evidenced by increased expression of autophagy-related genes (Beclin-1, LC3IIβ, and ATG5) and decreased expression of P62 after 48 and 72 hours. Moreover, the combined therapy enhances lipid metabolism, as indicated by elevated expression of PGC-1α and UCP-1, along with upregulation of ACSL3 and CPT1A, which are associated with lipid droplet formation and facilitate lipid breakdown within cells. The study concludes that BHB holds promise as a therapeutic agent for ccRCC, targeting abnormal lipid metabolism, inducing autophagy-mediated cell death, and promoting fat browning. The results suggest potential avenues for precision-guided nutritional therapies in ccRCC treatment, highlighting the innovative role of BHB in addressing the challenges posed by this cancer.

Collagen-derived dipeptide prolyl-hydroxyproline cooperates with Foxg1 to activate the PGC-1α promoter and induce brown adipocyte-like phenotype in rosiglitazone-treated C3H10T1/2 cells.

The global obesity epidemic is a significant public health issue, often leading to metabolic disorders such as diabetes and cardiovascular diseases. Collagen peptides (CP) and their bioactive component, Prolyl-hydroxyproline (Pro-Hyp), have shown potential in reducing adipocyte size, with unclear mechanisms concerning brown adipocyte differentiation. We investigated the effects of Pro-Hyp on the differentiation of brown adipocytes in C3H10T1/2 mesenchymal stem cells, focusing on its impact on adipocyte size, gene expression related to brown fat function, and mitochondrial activity. Pro-Hyp treatment decreased adipocyte size and upregulated brown fat-specific genes, including C/EBPα, PGC-1α, and UCP-1. Remarkably, it did not alter PPARγ expression. Pro-Hyp also elevated mitochondrial activity, suggesting enhanced brown adipocyte functionality. A Pro-Hyp responsive element was identified in the PGC-1α gene promoter, which facilitated the binding of the Foxg1 transcription factor, indicating a novel regulatory mechanism. Pro-Hyp promotes brown adipocyte differentiation, potentially offering a therapeutic strategy for obesity management. This study provides a molecular basis for the anti-obesity effects of CP, although further in vivo studies are needed to confirm these findings and to investigate the potential impact on beige adipocyte differentiation.

Intranasal insulin treatment ameliorates spatial memory, muscular strength, and frailty deficits in 5xFAD mice

The 5xFAD mouse model shows age-related weight loss as well as cognitive and motor deficits. Metabolic dysregulation, especially impaired insulin signaling, is also present in AD. This study examined whether intranasal delivery of insulin (INI) at low (0.875 U) or high (1.750 U) doses would ameliorate these deficits compared to saline in 10-month-old female 5xFAD and B6SJL wildtype (WT) mice. INI increased forelimb grip strength in the wire hang test in 5xFAD mice in a dose-dependent manner but did not improve the performance of 5xFAD mice on the balance beam. High INI doses reduced frailty scores in 5xFAD mice and improved spatial memory in both acquisition and reversal probe trials in the Morris water maze. INI increased swim speed in 5xFAD mice but had no effect on object recognition memory or working memory in the spontaneous alternation task, nor did it improve memory in the contextual or cued fear memory tasks. High doses of insulin increased the liver, spleen, and kidney weights and reduced brown adipose tissue weights. P-Akt signaling in the hippocampus was increased by insulin in a dose-dependent manner. Altogether, INI increased strength, reduced frailty scores, and improved visual spatial memory. Hypoglycemia was not present after INI, however alterations in tissue and organ weights were present. These results are novel and important as they indicate that intra-nasal insulin can reverse cognitive, motor and frailty deficits found in this mouse model of AD.

Valine induces inflammation and enhanced adipogenesis in lean mice by multi-omics analysis.

The branched-chain amino acids (BCAAs) are essential to mammalian growth and development but aberrantly elevated in obesity and diabetes. Each BCAA has an independent and specific physio-biochemical effect on the host. However, the exact molecular mechanism of the detrimental effect of valine on metabolic health remains largely unknown. This study showed that for lean mice treated with valine, the hepatic lipid metabolism and adipogenesis were enhanced, and the villus height and crypt depth of the ileum were significantly increased. Transcriptome profiling on white and brown adipose tissues revealed that valine disturbed multiple signaling pathways (e.g., inflammation and fatty acid metabolism). Integrative cecal metagenome and metabolome analyses found that abundances of Bacteroidetes decreased, but Proteobacteria and Helicobacter increased, respectively; and 87 differential metabolites were enriched in several molecular pathways (e.g., inflammation and lipid and bile acid metabolism). Furthermore, abundances of two metabolites (stercobilin and 3-IAA), proteins (AMPK/pAMPK and SCD1), and inflammation and adipogenesis-related genes were validated. Valine treatment affects the intestinal microbiota and metabolite compositions, induces gut inflammation, and aggravates hepatic lipid deposition and adipogenesis. Our findings provide novel insights into and resources for further exploring the molecular mechanism and biological function of valine on lipid metabolism.

Oral supplementation with resveratrol improves hormonal profile and increases expression of genes associated with thermogenesis in oophorectomy mice

Menopause causes important bodily and metabolic changes, which favor the increased occurrence of cardiovascular diseases, obesity, diabetes, and osteoporosis. Resveratrol exerts proven effects on body metabolism, improving glucose and lipid homeostasis and reducing inflammation and oxidative stress in various organs and tissues. Accordingly, this study evaluates the effects of resveratrol supplementation on the expression of markers associated with thermogenesis in brown adipose tissue, and on the body, metabolic and hormonal parameters of female mice submitted to bilateral oophorectomy. Eighteen female mice were randomized into three groups: G1: control (CONTROL), G2: oophorectomy (OOF), and G3: oophorectomy + resveratrol (OOF + RSV); the animals were kept under treatment for twelve weeks, being fed a standard diet and treated with resveratrol via gavage. Body, biochemical, hormonal, and histological parameters were measured; in addition to the expression of markers associated with thermogenesis in brown adipose tissue. The results showed that animals supplemented with resveratrol showed reduced body weight and visceral adiposity, in addition to glucose, total cholesterol, and triglyceride levels; decreased serum FSH levels and increased estrogen levels were observed compared to the OOF group and mRNA expression of PRDM16, UCP1, and SIRT3 in brown adipose tissue. The findings of this study suggest the important role of resveratrol in terms of improving body, metabolic, and hormonal parameters, as well as modulating markers associated with thermogenesis in brown adipose tissue of female mice submitted to oophorectomy.

Sulfonylureas exert antidiabetic action on adipocytes by inhibition of PPARγ serine 273 phosphorylation

ObjectiveSulfonylureas (SUs) are still among the mostly prescribed antidiabetic drugs with an established mode of action: release of insulin from pancreatic β-cells. In addition, effects of SUs on adipocytes by activation of the nuclear receptor peroxisome proliferator-activated receptor γ (PPARγ) have been described, which might explain their insulin-sensitizing potential observed in patients. However, there is a discrepancy between the impact of SUs on antidiabetic action and their rather moderate in vitro effect on PPARγ transcriptional activity. Recent studies have shown that some PPARγ ligands can improve insulin sensitivity by blocking PPARγ Ser-273 phosphorylation without having full agonist activity. It is unknown if SUs elicit their antidiabetic effects on adipocytes by inhibition of PPARγ phosphorylation. Here, we investigated if binding of SUs to PPARγ can interfere with PPARγ Ser-273 phosphorylation and determined their antidiabetic actions in vitro in primary human white adipocytes and in vivo in high-fat diet (HFD) obese mice. MethodsPrimary human white preadipocytes were differentiated in the presence of glibenclamide, glimepiride and PPARγ ligands rosiglitazone and SR1664 to compare PPARγ Ser-273 phosphorylation, glucose uptake and adipokine expression. Transcriptional activity at PPARγ was determined by luciferase assays, quantification of PPARγ Ser-273 phosphorylation was determined by Western blotting and CDK5 kinase assays. In silico modelling was performed to gain insight into the binding characteristics of SUs to PPARγ. HFD mice were administered SUs and rosiglitazone for 6 days. PPARγ Ser-273 phosphorylation in white adipose tissue (WAT), body composition, glucose tolerance, adipocyte morphology and expression levels of genes involved in PPARγ activity in WAT and brown adipose tissue (BAT) were evaluated. ResultsSUs inhibit phosphorylation of PPARγ at Ser-273 in primary human white adipocytes and exhibit a positive antidiabetic expression profile, which is characterized by up regulation of insulin-sensitizing and down regulation of insulin resistance-inducing adipokines. We demonstrate that SUs directly bind to PPARγ by in silico modelling and inhibit phosphorylation in kinase assays to a similar extend as rosiglitazone and SR1664. In HFD mice SUs reduce PPARγ phosphorylation in WAT and have comparable effects on gene expression to rosiglitazone. In BAT SUs increase UCP1 expression and reduce lipid droplets sizes. ConclusionsOur findings indicate that a part of SUs extra-pancreatic effects on adipocytes in vitro and in vivo is probably mediated via their interference with PPARγ phosphorylation rather than via classical agonistic activity at clinical concentrations.