Beige Adipocyte Formation Research Articles

Seabuckthorn Reverses High-Fat-Diet-Induced Obesity and Enhances Fat Browning via Activation of AMPK/SIRT1 Pathway.

Seabuckthorn possesses various bioactive compounds and exhibits several positive pharmacological activities. The present trial aims to determine the effect of seabuckthorn powder intake on high-fat diet (HFD)-induced obesity prevention in mice. The results suggest that seabuckthorn powder intake decreased body weight, fat mass, and circulating lipid levels, and improved insulin sensitivity in HFD-fed mice. Moreover, dietary seabuckthorn powder alleviated hepatic steatosis and hepatic lipid accumulation induced by the HFD. Furthermore, seabuckthorn exhibited obvious anti-inflammatory capacity in white adipose tissue (WAT) by regulating the abundance of inflammation-related cytokines, such as interleukins 4, 6, and 10; tumor necrosis factor α; and interferon-γ. More importantly, dietary seabuckthorn powder promoted a thermogenic program in BAT and induced beige adipocyte formation in iWAT in HFD-fed mice. Interestingly, we found that seabuckthorn powder effectively restored AMPK and SIRT1 activities in both BAT and iWAT in HFD-fed mice. Collectively, these results potentiate the application of seabuckthorn powder as a nutritional intervention strategy to prevent obesity and related metabolic diseases by promoting thermogenesis in BAT and improving beige adipocyte formation in WAT.

200-LB: Persistent cAMP Signaling Induces Adipocyte Browning through Biphasic Transcriptional and Epigenetic Remodeling

Beige adipocytes are inducible thermogenic cells formed in response to cold exposure and other environmental cues within white adipose tissue. Their capacity to produce heat would provide metabolic benefits against obesity and type 2 diabetes; however, the mechanisms underlying beige adipocyte recruitment, so-called adipocyte browning, induced by different stimuli remain unclear. Using our new adipocyte cell line with improved browning potentials, we compared adipocyte browning responses induced by cAMP (forskolin) versus PPARɣ activation (rosiglitazone) . Time-course RNA-seq revealed that chronic activation of cAMP but not PPARɣ resulted in a biphasic response. The cAMP signaling promoted tissue remodeling at the early phase and subsequently activated energy metabolism while inhibiting cell cycle, which resembles the kinetics of in vivo cold-induced browning. Those late-phase changes were highly correlated with those by PPARɣ activation. Consistently, the cAMP-driven effects were abolished by treatment with PPARɣ antagonists, suggesting PPARɣ as a converging point of its thermogenic actions. Assay for transposase-accessible chromatin sequencing (ATAC-seq) revealed unique dynamics of chromatin landscape distinct from transcriptional changes during cAMP-induced browning. Chromatin at early-induced genes opened acutely and stayed open until the late phase despite the rapid return of gene expression. The chromatin regions at late-induced genes also opened early, preceding transcriptional activation. Using a motif discovery method, we identified NFIL3 that was enriched in both early and late phases of cAMP-induced browning. Reduced thermogenic gene expression and mitochondrial respiration by NFIL3 knockdown suggest NFIL3 as a putative transcription factor mediating the biphasic response of adipocyte browning. These findings define new mechanisms that orchestrate transcriptional and epigenetic remodeling underlying beige adipocyte formation. Disclosure J. So: None. S. Taleb: None. J. Wann: None. O. Strobel: None. H. Roh: None. Funding American Diabetes Association (7-21-JDF-056) , National Institute of Health (DK129289)

SOX4 promotes beige adipocyte-mediated adaptive thermogenesis by facilitating PRDM16-PPARγ complex.

Brown and beige fat protect against cold environments and obesity by catabolizing stored energy to generate heat. This process is achieved by controlling thermogenesis-related gene expression and the development of brown/beige fat through the induction of transcription factors, most notably PPARγ. However, the cofactors that induce the expression of thermogenic genes with PPARγ are still not well understood. In this study, we explored the role of SOX4 in adaptive thermogenesis and its relationship with PPARγ. Methods: Whole transcriptome deep sequencing (RNA-seq) analysis of inguinal subcutaneous white adipose tissue (iWAT) after cold stimulation was performed to identify genes with differential expression in mice. Indirect calorimetry detected oxygen consumption rate and heat generation. mRNA levels were analyzed by qPCR assays. Proteins were detected by immunoblotting and immunofluorescence. Interaction of proteins was detected by endogenous and exogenous Co-IP. ChIP-qPCR, FAIRE assay and luciferase reporter assays were used to investigate transcriptional regulation. Results: SOX4 was identified as the main transcriptional effector of thermogenesis. Mice with either adipocyte-specific or UCP1+ cells deletion of SOX4 exhibited significant cold intolerance, decreased energy expenditure, and beige adipocyte formation, which was attributed to decreased thermogenic gene expression. In addition, these mice developed obesity on a high-fat diet, with severe hepatic steatosis, insulin resistance, and inflammation. At the cell level, loss of SOX4 from preadipocytes inhibited the development of beige adipocytes, and loss of SOX4 from mature beige adipocytes reduced the expression of thermogenesis-related genes and energy metabolism. Mechanistically, SOX4 stimulated the transcriptional activity of Ucp1 by binding to PPARγ and activating its transcriptional function. These actions of SOX4 were, at least partly, mediated by recruiting PRDM16 to PPARγ, thus forming a transcriptional complex to elevate the expression of thermogenic genes. Conclusion: SOX4, as a coactivator of PPARγ, drives the thermogenic gene expression program and thermogenesis of beige fat, promoting energy expenditure. It has important physiological significance in resisting cold and obesity.

Imaging Adipose Tissue Browning using Mitochondrial Complex-I Tracer [18F]BCPP-EF.

Browning of white adipose tissue (WAT) into beige adipocytes has been proposed as a strategy to tackle the ongoing obesity epidemic. Thermogenic stimuli have been investigated with the aim of converting existing white adipose tissue, primarily used for energy storage, into beige adipocytes capable of dissipating energy; however, evaluation is complicated by the dearth of noninvasive methodologies to quantify de novo beige adipocytes in WAT. Imaging with [18F]FDG is commonly used to measure brown adipose tissue (BAT) and beige adipocytes but the relationship between beige adipocytes, thermogenesis and [18F]FDG uptake is unclear. [18F]BCPP-EF, a tracer for mitochondrial complex-I (MC-I), acts as a marker of oxidative metabolism and may be useful for the detection of newly formed beige adipocytes. Mice received doses of the β3-adrenergic agonist CL-316,243 subchronically for 7 days to induce formation of beige adipocytes in inguinal white fat. PET imaging was performed longitudinally with both [18F]FDG (a marker of glycolysis) and [18F]BCPP-EF (an MC-I marker) to assess the effect of thermogenic stimulation on uptake in browning inguinal WAT and interscapular BAT. Treatment with CL-316,243 led to significant increases in both [18F]FDG and [18F]BCPP-EF in inguinal WAT. The uptake of [18F]BCPP-EF in inguinal WAT was significantly increased above control levels after 3 days of stimulation, whereas [18F]FDG only showed a significant increase after 7 days. The uptake of [18F]BCPP-EF in newly formed beige adipocytes was blocked by pretreatment with an adrenoceptor antagonist suggesting that beige adipocyte formation may be associated with the activation of MC-I. However, in BAT, uptake of [18F]BCPP-EF was unaffected by β3-adrenergic stimulation, potentially due to the high expression of MC-I. [18F]BCPP-EF can detect newly formed beige adipocytes in WAT generated after subchronic treatment with the β3-adrenergic agonist CL-316,243 and displays both higher inguinal WAT uptake and earlier detection than [18F]FDG. The MC-I tracer may be a useful tool in the evaluation of new therapeutic strategies targeting metabolic adipose tissues to tackle obesity and metabolic diseases.

Combination of Exercise and Intake of Amino Acid Mixture Synergistically Induces Beige Adipocyte Formation in Mice.

Exercise combined with dietary factors may have significant effects on the suppression of body fat accumulation. Several trials suggest that amino acid mixtures containing alanine, arginine, and phenylalanine (ARF) combined with exercise can significantly reduce body fat accumulation in overweight adults and high-fat diet-induced obesity in mice. We therefore hypothesized that combining ARF and exercise would significantly induce beige adipocyte formation and that this would contribute to reducing body weight, whereas administration of ARF or exercise alone would not. Administration of ARF (1 g/kg body weight, daily) combined with exercise (5 sessions per week) for 4 wk significantly induced formation of beige adipocytes in inguinal white adipose tissue (iWAT) in mice, although ARF or exercise alone did not. Metabolomic analysis showed that plasma lactate concentration was significantly elevated in the exercise+ARF group relative to the exercise group. Furthermore, lactate dehydrogenase B, which increases redox stress by converting lactate to pyruvate in iWAT and triggers induction of uncoupling protein 1 expression was significantly upregulated in iWAT of the exercise+ARF group. These findings demonstrate the unique effect of ARF combined with exercise for inducing beige adipocyte formation, which may be associated with the suggested lactate-mediated pathway. Appropriate mixtures of amino acids could be used as a dietary supplement before exercise and contributed to increasing energy expenditures.

Apolipoprotein E deficiency activates thermogenesis of white adipose tissues in mice through enhancing β-hydroxybutyrate production from precursor cells.

White adipose tissue (WAT) has the capacity to undergo a white-to-beige phenotypic switch, known as browning, in response to stimuli such as cold. However, the mechanism underlying beige adipocyte formation is largely unknown. Apolipoprotein E (ApoE) is highly induced in WAT and has been implicated in lipid metabolism. Here, we show that ApoE deficiency in mice increased oxygen consumption and thermogenesis and enhanced adipose browning pattern in inguinal WAT (iWAT), with associated characteristics such as increased Ucp1 and Pparγ expression. At the cellular level, ApoE deficient beige adipocytes had increased glucose uptake and higher mitochondrial respiration than wild-type cells. Mechanistically, we showed that ApoE deficient iWAT and primary adipose precursor cells activated the thermogenic genes program by stimulating the production of ketone body β-hydroxybutyrate (βHB), a novel adipose browning promoting factor. This was accompanied by increased expression of genes involved in ketogenesis and could be compromised by the treatment for ketogenesis inhibitors. Consistently, ApoE deficient mice show higher serum βHB level than wild-type mice in the fed state and during cold exposure. Our results further demonstrate that the increased βHB production in ApoE deficient adipose precursor cells could be attributed, at least in part, to enhanced Cd36 expression and CD36-mediated fatty acid utilization. Our findings uncover a previously uncharacterized role for ApoE in energy homeostasis via its cell-autonomous action in WAT.

Intercellular and inter-organ crosstalk in browning of white adipose tissue: molecular mechanism and therapeutic complications.

Adipose tissue (AT) is highly plastic and heterogeneous in response to environmental and nutritional changes. The development of heat-dissipating beige adipocytes in white AT (WAT) through a process known as browning (or beiging) has garnered much attention as a promising therapeutic strategy for obesity and its related metabolic complications. This is due to its inducibility in response to thermogenic stimulation and its association with improved metabolic health. WAT consists of adipocytes, nerves, vascular endothelial cells, various types of immune cells, adipocyte progenitor cells, and fibroblasts. These cells contribute to the formation of beige adipocytes through the release of protein factors that significantly influence browning capacity. In addition, inter-organ crosstalk is also important for beige adipocyte biogenesis. Here, we summarize recent findings on fat depot-specific differences, secretory factors participating in intercellular and inter-organ communications that regulate the recruitment of thermogenic beige adipocytes, as well as challenges in targeting beige adipocytes as a potential anti-obese therapy.

Therapeutic efficacy of 6-Gingerol and 6-Shogaol in promoting browning of white adipocytes vis-à-vis enhanced thermogenesis portrayed in high fat milieu

Ginger is a culinary spice, well documented for its inherent potent health beneficial effects, with Gingerols and Shogaols contributing as major bioactive constituents (23–25% and 18–25%) respectively. The present study aims to assess the therapeutic potential of 6-Gingerol (40 μM) and 6-Shogaol (40 μM) in promoting browning of white adipocytes vis-à-vis thermogenesis, tested in pre-adipocyte cell line (3T3-L1), and stromal vascular fraction (SVF)/obesogenic milieu derived from WNIN/Gr-Ob mutant rats. We investigated for anti-adipogenic potential of 6-Gingerol and 6-Shogaol (Oil-Red-O Staining), and evaluated for: (i) expression of brown specific markers like Ucp1, Pgc1α, Prdm16, Fgf21, Tmem26, Cidea and Pparγ, (ii) immunofluorescence for UCP-1, PGC-1α and PRDM16, (iii) thermogenesis using MitoTracker staining and (iv) oxygen consumption rate/OCR (assay kit). Further, we quantitated for beige progenitors/CD137+ve using flow cytometry, and measured multilocular vs unilocular adipocytes. To gain insights, molecular interactions of 6-Gingerol and 6-Shogaol with β3-adrenergic receptor membrane protein (β3-AR) were determined using in-silico docking studies. Our results demonstrate the potent efficacy of 6-Gingerol > 6-Shogaol as: (i) anti-adipogenic, (ii) enhanced formation of beige adipocytes (significant up-regulation of beige markers Fgf21, Tmem26 and Cidea, Ucp1, Prdm16, Pgc-1α, (iii) increased mitochondrial turnover, (iv) higher OCR, (v) induction of beige progenitors, (vi) preponderance of multilocular cells compared to unilocular cells, and (vii) better binding efficiency of 6-Gingerol > 6-Shogaol with β3-AR arrived from bond length and binding energy. Our present findings does advocate the promise(s) of Ginger, more so with 6-Gingerol as a potent therapeutic nutraceutical agent in obesity management.

Adipose-specific ATGL ablation reduces burn injury-induced metabolic derangements in mice.

Hypermetabolism following severe burn injuries is associated with adipocyte dysfunction, elevated beige adipocyte formation, and increased energy expenditure. The resulting catabolism of adipose leads to detrimental sequelae such as fatty liver, increased risk of infections, sepsis, and even death. While the phenomenon of pathological white adipose tissue (WAT) browning is well‐documented in cachexia and burn models, the molecular mechanisms are essentially unknown. Here, we report that adipose triglyceride lipase (ATGL) plays a central role in burn‐induced WAT dysfunction and systemic outcomes. Targeting adipose‐specific ATGL in a murine (AKO) model resulted in diminished browning, decreased circulating fatty acids, and mitigation of burn‐induced hepatomegaly. To assess the clinical applicability of targeting ATGL, we demonstrate that the selective ATGL inhibitor atglistatin mimics the AKO results, suggesting a path forward for improving patient outcomes.

Progenitor-like characteristics in a subgroup of UCP1+ cells within white adipose tissue

Thermogenic beige fat found in white adipose tissue is a potential therapeutic target to curb the global obesity and diabetes epidemic. However, these inducible thermogenic beige adipocytes have been thought to be short-lived and to rapidly convert to "white-like" adipocytes after discontinuing stimuli. In this study, using effective labeling techniques and genetic mouse tools, we demonstrate that a subset of UCP1+ cells that exist within white adipose tissue are able to self-divide and contribute to new beige adipocyte recruitment in response to β3 stimuli. When these cells are depleted or their adipogenic capability is blocked, β3-induced beige adipocyte formation is impaired. We also identify a cell-cycle machinery of p21 and CDKN2A as a molecular basis of beige adipocyte regulation. Collectively, our findings provide new insights into the cellular and molecular mechanisms of beige adipocyte regulation and potential therapeutic opportunities to induce the beige phenotype and treat metabolic disease.

MECHANISMS IN ENDOCRINOLOGY: Human brown adipose tissue as a therapeutic target: warming up or cooling down?

Excessive accumulation of white adipose tissue leads to obesity and its associated metabolic health consequences such as type 2 diabetes and cardiovascular disease. Several approaches to treat or prevent obesity including public health interventions, surgical weight loss, and pharmacological approaches to reduce caloric intake have failed to substantially modify the increasing prevalence of obesity. The (re-)discovery of active brown adipose tissue (BAT) in adult humans approximately 15 years ago led to a resurgence in research into whether BAT activation could be a novel therapy for the treatment of obesity. Upon cold stimulus, BAT activates and generates heat to maintain body temperature, thus increasing energy expenditure. Activation of BAT may provide a unique opportunity to increase energy expenditure without the need for exercise. However, much of the underlying mechanisms surrounding BAT activation are still being elucidated and the effectiveness of BAT as a therapeutic target has not been realised. Research is ongoing to determine how best to expand BAT mass and activate existing BAT; approaches include cold exposure, pharmacological stimulation using sympathomimetics, browning agents that induce formation of thermogenic beige adipocytes in white adipose depots, and the identification of factors secreted by BAT with therapeutic potential. In this review, we discuss the caloric capacity and other metabolic benefits from BAT activation in humans and the role of metabolic tissues such as skeletal muscle in increasing energy expenditure. We discuss the potential of current approaches and the challenges of BAT activation as a novel strategy to treat obesity and metabolic disorders.

Inducible beige adipocytes improve impaired glucose metabolism in interscapular BAT-removal mice

Inducible beige adipocytes are emerging as an interesting issue in obesity and metabolism research. There is a neglected possibility that brown adipocytes are equally activated when external stimuli induce the formation of beige adipocytes. Thus, the question is whether beige adipocytes have the same functions as brown adipocytes when brown adipose tissue (BAT) is lacking. This question has not been well studied. Therefore we determine the beneficial effects of beige adipocytes upon cold challenge or CL316243 treatments in animal models of interscapular BAT (iBAT) ablation by surgical denervation. We found that denervated iBAT were activated by cold exposure and CL316243 treatments. The data show that beige adipocytes partly contribute to the improvement of impaired glucose metabolism resulting from denervated iBAT. Thus, we further used iBAT-removal animal models to abolish iBAT functions completely. We found that beige adipocytes upon cold exposure or CL316243 treatments improved impaired glucose metabolism and enhanced glucose uptake in iBAT-removal mice. The insulin signaling was activated in iBAT-removal mice upon cold exposure. Both the activation of insulin signaling and up-regulation of glucose transporter expression were observed in iBAT-removal mice with CL316243 treatments. The data show that inducible beige adipocytes may have different mechanisms to improve impaired glucose metabolism. Inducible beige adipocytes can also enhance energy expenditure and lipolytic activity of white adipose tissues when iBAT is lacking. We provide direct evidences for the beneficial effect of inducible beige adipocytes in glucose metabolism and energy expenditure in the absence of iBAT in vivo.

Studying Brown Adipose Tissue in a Human in vitro Context.

New treatments for obesity and associated metabolic disease are increasingly warranted with the growth of the obesity pandemic. Brown adipose tissue (BAT) may represent a promising therapeutic target to treat obesity, as this tissue has been shown to regulate energy expenditure through non-shivering thermogenesis. Three different strategies could be employed for therapeutic targeting of human thermogenic adipocytes: increasing BAT mass through stimulation of BAT progenitors, increasing BAT function through regulatory pathways, and increasing WAT browning through promotion of beige adipocyte formation. However, these strategies require deeper understanding of human brown and beige adipocytes. While murine studies have greatly increased our understanding of BAT, it is becoming clear that human BAT does not exactly resemble that of the mouse, highlighting the need for human in vitro models of brown adipocytes. Several different human brown adipocyte models will be discussed here, along with the potential to improve brown adipocyte culture through recreation of the BAT microenvironment.

Prenatal PPARα Activation Moved Forward Transient Browning of WAT at Neonates and Increased HFD-Induced UCP1 Expression in WAT of Male Mice at Adulthood

Abstract Objectives To test the hypothesis that prenatal administration of PPARα agonist clofibrate may increase the developmental beige adipocytes and permanently increased the browning capacity of white adipose tissue (WAT). Methods Pregnant C57BL/6 J mice received a basal diet, without (C) or with 0.5% clofibrate (CF, a PPARα agonist) throughout pregnancy. After parturition, only male offspring were used; all suckled their mothers (who were eating the C diet) and after weaning, they ate a standard chow diet for 4 wk, followed by a high-fat diet (HFD) for 5 wk. Results CF administration significantly increased the expression of PPARα and its target genes. CF elevated serum concentrations and hepatic expression of FGF21 (a thermogenic hormone) in fetuses, with a return to basal levels after CF withdrawal. At postnatal day 84 (P84), CF-offspring had significantly higher mRNA and protein levels of UCP1 in response to HFD in inguinal (iWAT) but not in visceral fats. Based on UCP1 levels in iWAT on P7, P14, and P21, the appearance of the transient brown-adipocyte phenotype seemed to be hastened by prenatal CF exposure. The mRNA level of UCP1 is peaked at P14 in CF-offspring, unlike C-offspring which peaked at P21. However, the mRNA level of beige cell markers (Cd137, Tmem26, Tbx1) maintained the same across this time window (P7–21). Microarray analysis of global gene expression in iWAT during this time window is conducting, as well as serum level of leptin, since leptin surge is essential to the formation of beige adipocytes during this time window. Conclusions Giving CF to pregnant mice programmed greater HFD-induced WAT browning in subcutaneous, but not in visceral fat, in their male offspring at adulthood. We foresee the transient browning of iWAT occurred at critical window may offer clues for elucidating this interesting phenomenon. Funding Sources Ministry of Science and Technology, Taiwan.

Resveratrol-Loaded Liposomes: Browning Subcutaneous White Adipose Tissue for Combating Obesity in C57BL/6 J Mice

Abstract Objectives Trans-resveratrol (R) is a potential browning compound and can induce beige adipocyte formation in subcutaneous white adipose tissue (WAT). However, R's low aqueous solubility and high hepatic metabolism limit its application in combating obesity. Hence, we synthesized R-loaded liposomes (Rlipo). The objectives of this study are to measure Rlipo characteristics and determine the browning and anti-obesity efficacy for local delivery of Rlipo to inguinal WAT (I-WAT) in obese mice. Methods The particle size and zeta potential of Rlipo and void liposomes (Vlipo) were measured using a Brookhaven BI-MAS particle size and ZetaPALS analyzer, respectively. Their physical stability was measured daily at 4, 22 and 37°C for 7 days. The in vitro R release pattern of Rlipo was measured using a dialysis method. For determining anti-obesity activities, C57BL/6 J mice were fed the high-fat diet (HFD) for 9 weeks. During week 5–9, mice were treated with saline, free R, Vlipo, or Rlipo via I-WAT injection twice per week. Food intake, body weight, and body composition were measured weekly, and the glucose tolerance test was conducted at week 9. After sacrifice, we collected and measured the mass of liver and fat depots. The mRNA levels of uncoupling protein-1 (UCP-1) and other beige markers in I-WAT were measured using real-time PCR. Results As compared to free R, Rlipo increased R's aqueous solubility by more than 30 times. The particle sizes of Rlipo and Vlipo were about 100 nm. Their zeta potentials were around −25 mV. Both Rlipo and Vlipo have good physical stability at 3 tested temperatures for 7 days and Rlipo exhibited a prolonged-release manner. In the animal study, Rlipo-treated compared to free R-treated mice had 1.2-, 1.4-, 1.6-, 1.5-fold lower body weight, fat %, I-WAT, and gonadal WAT mass, respectively, which were correlated with 1.8- and 2.6-fold higher UCP-1 and TMEM26 mRNA levels in I-WAT. However, no significant differences were found in food intake and the glucose tolerance test. Conclusions Rlipo increased R's aqueous solubility and improved its sustained release manner. Rlipo had higher anti-obesity activities than free R, which were correlated with increased expression of beige markers in I-WAT of mice. Browning subcutaneous WAT using Rlipo might provide an innovative and efficient approach for combating obesity. Funding Sources NIH 1R15AT010395.

SAT-LB103 Glucose-Dependent Insulinotropic Polypeptide Promotes Proliferation, Inhibits Apoptosis and Modifies Adipogenesis in Human Omental Adipose-Derived Stem Cells

Increased visceral fat correlates with a high risk of morbidity and mortality from diabetes and other metabolic diseases. To cope with changes of nutritional status, the adipose tissue undergoes dynamic remodeling, during which adipose derived stem cells (ADSCs) participate through cell proliferation and adipogenic differentiation into mature adipocytes. Besides, beige adipocytes formation from ADSCs, to dissipate energy as heat in mitochondrial via uncoupling protein1 (UCP1) has been proved to improve energy expenditure. Thus, modifying adipose remodeling and promoting beige adipogenesis of ADSCs in visceral fat bring much metabolic benefits. Newly listed LY3298176, an agonist targeted on glucose-dependent insulinotropic polypeptide (GIP) /glucagon-like peptide-1 (GLP-1) receptor, shows outstanding effect of reducing glucose and weight. Due to superior efficacy in dual-target agonist to GLP-1 monotherapy, and the unknown role of GIP in human visceral adipose, we aimed to clarify GIP’s role in undifferentiated ADSCs in vivo. We selected cell model derived from abdominal omental adipose tissue by obtaining ADSCs via primary culture from patients, because of wide-distributed GIP receptors in fat, and the dominant role of abdominal fat in metabolism. Then the cells were allowed to proliferate, or differentiate into adipocytes in the differentiation medium (DM), with or without co-treated with GIP or GIP3-42 (GIP receptor antagonist), followed by subsequently measurement. CCK-8, EdU incorporation, and cell cycle analysis were conducted to assess cellular proliferation. Annexin V FITC/PI stain, TUNEL and cleaved caspase3 detection were performed to evaluate apoptosis. The related signaling pathway was measured by Western blot and the validation was conducted by using pathway inhibitors followed with the above proliferation and apoptosis analysis. Besides, at the early stage of adipogenesis, mitotic clonal expansion (MCE) was reflected by cell cycle detection. Western blot analysis, quantitative real time-PCR (qRT-PCR), and Oil Red O staining were performed to evaluate adipogenesis. We found that GIP facilitated ADSCs viability and DNA synthesis, accelerated cell cycle progress and reduced palmitate-induced apoptosis by promoting phosphorylation of ERK1/2, AKT, PKA and AMPK. We further confirmed that ADSCs after confluence underwent MCE once induced by DM. GIP also modified adipogenesis by accelerating MCE, upregulating core transcription factor (PPARγ and C/EBPα), increasing beige-related markers (UCP1, PGC1α, PRDM16, et al) while suppressing white-related genes (ZFP423 and TLE3). In summary, we illustrated the efficacies of GIP on proliferation, apoptosis and adipogenesis (especially the beige adipocyte formation) of ADSCs, providing evidence of the additional metabolic benefits of GIP/GLP-1 dual-target agonist over GLP-1 agonist monotherapy in vivo.

Transferrin Receptor 1 Regulates Thermogenic Capacity and Cell Fate in Brown/Beige Adipocytes.

Iron homeostasis is essential for maintaining cellular function in a wide range of cell types. However, whether iron affects the thermogenic properties of adipocytes is currently unknown. Using integrative analyses of multi‐omics data, transferrin receptor 1 (Tfr1) is identified as a candidate for regulating thermogenesis in beige adipocytes. Furthermore, it is shown that mice lacking Tfr1 specifically in adipocytes have impaired thermogenesis, increased insulin resistance, and low‐grade inflammation accompanied by iron deficiency and mitochondrial dysfunction. Mechanistically, the cold treatment in beige adipocytes selectively stabilizes hypoxia‐inducible factor 1‐alpha (HIF1α), upregulating the Tfr1 gene, and thermogenic adipocyte‐specific Hif1α deletion reduces thermogenic gene expression in beige fat without altering core body temperature. Notably, Tfr1 deficiency in interscapular brown adipose tissue (iBAT) leads to the transdifferentiation of brown preadipocytes into white adipocytes and muscle cells; in contrast, long‐term exposure to a low‐iron diet fails to phenocopy the transdifferentiation effect found in Tfr1‐deficient mice. Moreover, mice lacking transmembrane serine protease 6 (Tmprss6) develop iron deficiency in both inguinal white adipose tissue (iWAT) and iBAT, and have impaired cold‐induced beige adipocyte formation and brown fat thermogenesis. Taken together, these findings indicate that Tfr1 plays an essential role in thermogenic adipocytes via both iron‐dependent and iron‐independent mechanisms.

Sesaminol induces brown and beige adipocyte formation through suppression of myogenic program.

Adipocytes are key players in maintaining energy homeostasis and are classified into two different categories: white and brown adipocytes. While white adipocytes store energy as triacylglycerols in lipid droplets, brown adipocytes combust excess chemical energy and release in the form of heat through uncoupled respiration. This characteristic phenomenon of brown fat attracts researchers and pharmacological industries to view brown fat as one of the potential therapeutic targets for obesity and associated metabolic disease. In the current study, we investigated the effect of a small molecule, sesaminol (SML) on brown fat activity and found that SML induces the thermogenic program in primary white adipocytes as well as chow diet fed mice. In particular, SML treatment to mice elevated mitochondrial complex proteins and the rate of oxygen consumption in brown and white fat. Administration of SML to high fat diet (HFD) challenged mice decreased weight gain, adiposity and cholesterol levels along with an increase of brown fat gene program in brown and white fat. Mechanistically, SML repressed the myogenic gene program in C2C12 myoblasts and increased all mitochondrial marker genes as appeared in brown adipose cells. Together, our results demonstrate that SML stimulates brown adipose function and protects mice against diet-induced weight gain.

Sustained mitochondrial biogenesis is essential to maintain caloric restriction-induced beige adipocytes

BackgroundCaloric restriction (CR) delays the onset of metabolic and age-related disorders. Recent studies have demonstrated that formation of beige adipocytes induced by CR is strongly associated with extracellular remodeling in adipose tissue, decrease in adipose tissue inflammation, and improved systemic metabolic homeostasis. However, beige adipocytes rapidly transition to white upon CR withdrawal through unclear mechanisms. Materials and methodsSix-week old C57BL6 mice were fed with 40% CR chow diet for 6 weeks. Subsequently, one group of mice was switched back to ad libitum chow diet, which was continued for additional 2 weeks. Adipose tissues were assessed histologically and biochemically for beige adipocytes. ResultsBeige adipocytes induced by CR rapidly transition to white adipocytes when CR is withdrawn independent of parkin-mediated mitophagy. We demonstrate that the involution of mitochondria during CR withdrawal is strongly linked with a decrease in mitochondrial biogenesis. We further demonstrate that beige-to-white fat transition upon β3-AR agonist-withdrawal could be attenuated by CR, partly via maintenance of mitochondrial biogenesis. ConclusionIn the model of CR, our study highlights the dominant role of mitochondrial biogenesis in the maintenance of beige adipocytes. We propose that loss of beige adipocytes upon β3-AR agonist withdrawal could be attenuated by CR.

Mosaic Mutant Analysis Identifies PDGFRα/PDGFRβ as Negative Regulators of Adipogenesis.

Adipocyte progenitors (APs) express platelet-derived growth factor receptors (PDGFRs), PDGFRα and PDGFRβ. Elevated PDGFRα signaling inhibits adipogenesis and promotes fibrosis; however, the function of PDGFRs in APs remains unclear. We combined lineage tracing and functional analyses in a sequential dual-recombinase approach that creates mosaic Pdgfr mutant cells by Cre/lox recombination with a linked Flp/frt reporter to track individual cell fates. Using mosaic lineage labeling, we show that adipocytes are derived from the Pdgfra lineage during postnatal growth and adulthood. In contrast, adipocytes are only derived from the mosaic Pdgfrb lineage during postnatal growth. Functionally, postnatal mosaic deletion of PDGFRα enhances adipogenesis and adult deletion enhances β3-adrenergic-receptor-induced beige adipocyte formation. Mosaic deletion of PDGFRβ also enhances white, brown, and beige adipogenesis. These data show that both PDGFRs are cell-autonomous inhibitors of adipocyte differentiation and implicate downregulation of PDGF signaling as a critical event in the transition from AP to adipocyte.