Browning Of White Adipose Tissue Research Articles

1507-P: Carnosic Acid–Induced Browning in 3T3-L1 Adipocytes Is Dependent on AMPK Activation

Background: Increased adiposity has long been associated with insulin resistance and adipose tissue plays a crucial role in regulating metabolic homeostasis, as its dysfunction in obesity leads to insulin resistance and type 2 diabetes (T2D). The primary function of white adipose tissue (WAT) is to store energy as lipids while brown adipose tissue (BAT) regulates thermogenesis by dissipating energy in a form of heat. The process of browning involves transdifferention of WAT into brown-like or beige adipocytes, which exhibit the same functional properties as BAT. Browning of WAT is an attractive approach against obesity and insulin resistance. In addition, evidence indicate that activation of the energy sensor AMP-activated protein kinase (AMPK) could counteract insulin resistance. The aim of this study is to examine if carnosic acid (CA), induces browning via activation of AMPK in 3T3-L1 white adipocytes. Material and methods: Cell morphology, lipid accumulation, mitochondrial density, and browning markers such as uncoupling protein-1 (UCP-1) and peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) levels were assessed using Cytation5 microscope, Oil-O-Red (ORO), MitoTracker Red, immunoblotting and immunocytochemistry. Results: Microscopic investigation revealed that CA reduced the size and number of lipid droplets in the cells, giving a rise to a brown-like phenotype. The reduction of lipid accumulation was also confirmed by ORO stain. Next, CA increased mitochondrial density and protein expression of UCP-1 and PGC-1-α in 3T3-L1 adipocytes. Most importantly, pre-treatment with compound C, prevented the CA-induced reduction in lipid accumulation, and mitochondrial density and blocked the CA-induced increase in UCP-1 and PGC-1 expression. Conclusion: This study demonstrates that CA has a pronounced potential in stimulating browning of adipocytes via AMPK-dependent mechanism. Future in vivo studies are required to fully examine the effects of CA. Disclosure F.Vlavcheski: None. N.Tsakiridis: None. A.Giacca: None. E.Tsiani: None. Funding Natural Science and Engineering Research Council of Canada (RGPIN-2018-06666)

233-LB: Role of SUMO-Specific Protease 2 (SENP2) in Modulating Brown Adipose Tissue Activity

Brown adipose tissue (BAT) is a metabolically active endocrine organ. Activation of BAT contributes to increased energy expenditure through systemic glucose and lipid utilization. SUMO-specific protease 2 (SENP2) is a post-translational protein modifier that is involved in regulation of metabolism in different tissues. We had previously showed that while SENP2 suppresses browning of white adipose tissues, morphologic defect in BAT was observed in adipose specific SENP2 deficient mice fed with high fat diet. How SENP2 may modulate BAT activity has not been elucidated yet. BAT-specific Senp2 knockout (Senp2-BKO, Ucp1-Cre;Senp2f/f) mice were more insulin resistant in response to high fat diet than controls. They were also intolerant to acute cold exposure. Mechanistically, knockdown of Senp2 in brown adipocytes resulted in reduced levels of Ucp1 and Cidea through SUMOylation of ERRα. SUMOylation of ERRα interrupted binding of ERRα to ERRα response element (ERRE) in the Ucp1 promoter, and deSUMOylation of ERRα via SENP2 enhanced the synergistic effect of ERRα/PGC-1α complex required for the transcription of Ucp1. Collectively, these results suggest that SENP2 is intimately involved in modulating the activity of Ucp1 in BAT through deSUMOylation of ERRα/PGC-1α complex, especially ERRα. Disclosure H. Choe: None. J. Lee: None. J. Park: None. S. Lee: None. S. Chung: None. K. Park: None. Funding National Research Foundation of Korea (2015R1D1A1A09059551, 2016R1A2B3010373, 2019R1A2C3009517)

1562-P: Hepatic ChREBP-ß Overexpression Enhances Peripheral Glucose and Lipid Homeostasis Independently of FGF21

Carbohydrate Response Element-Binding Protein (ChREBP) is a key transcription factor activated by carbohydrate metabolites which transactivates metabolic gene programs involved in the glycolytic and lipogenic response to dietary and circulating sugars. Genetic variants in the ChREBP locus associate with multiple aspects of cardiometabolic disease including dyslipidemia and risk of type 2 diabetes (T2D). Studies overexpressing ChREBP in the liver suggest that ChREBP can play a protective role in preserving glucose and lipid homeostasis. We hypothesized that this protective effect may be mediated through ChREBP’s effect to increase hepatic expression and circulating levels of the beneficial hepatokine, FGF21. To test this hypothesis, we transduced male mice with liver-specific knockout of FGF21 (L-FGF21KO) and lox/lox controls with adenovirus (ADV) containing the constitutively active isoform of murine ChREBP, ChREBP-β, versus ADV-GFP control (N = 4-7 / group). ADV-ChREBP-β transduction induced a 5-fold increase in hepatic (p<0.001) and circulating FGF21 (p<0.0001) in control mice and this was fully abrogated in L-FGF21KO mice. While no significant changes in body weight were detected, ADV-ChREBP-β transduction reduced fasting glycemia and enhanced glucose tolerance in both controls and L-FGF21KO mice. ADV-ChREBP-β transduction induced glycolytic and lipogenic genes similarly in L-FGF21KO and control mice, increased hepatic triglyceride content (3-fold, p<0.005) and induced steatosis, while reducing circulating triglycerides and increasing browning of white adipose tissue. In conclusion, hepatic FGF21 does not mediate the beneficial effect of hepatic ChREBP-β overexpression on peripheral glucose and lipid homeostasis. Disclosure S.Hannou: None. A.Sargsyan: Employee; AstraZeneca. W.Tong: None. J.An: None. C.B.Newgard: Advisory Panel; Eli Lilly and Company, Novo Nordisk, AstraZeneca. I.Astapova: None. M.A.Herman: Research Support; Eli Lilly and Company. Funding National Institutes of Health (R01DK100425)

76-OR: Axon Guidance Molecule Slit3 Is Essential for Cold-Induced Remodeling of BAT Neurovasculature and Thermogenesis

Brown adipose tissue (BAT) is primarily responsible for regulating body temperature through adaptive thermogenesis. Enhancing energy expenditure through the activation of BAT thermogenesis is a promising strategy to prevent and reverse obesity and its cardiometabolic sequelae. Brown adipocytes are embedded in a dense network of blood vessels and sympathetic nerves that supports their thermogenic activity. Increasing the density of blood vessels and sympathetic innervation is essential for enhanced thermogenesis in cold. However, how these distinct processes are spatiotemporally regulated is not clear. To define the mediators of intercellular crosstalk in the BAT, we used single-cell transcriptomic analysis of BAT to build a network of ligand-receptor interactions. We identified Slit guidance ligand 3 (Slit3) as a new adipokine that mediates the crosstalk among adipocyte progenitors, endothelial cells, and sympathetic nerves. Using a combination of in vivo gain and loss of function studies, we showed that Slit3 is essential for cold-induced angiogenesis and sympathetic innervation in BAT. Loss of Slit3 reduced the density of blood vessels and sympathetic neurites in BAT. Consequently, mice lacking Slit3 expression in BAT exhibited severe cold intolerance, increased lipid accumulation and whitening of BAT, and reduced expression of thermogenic and mitochondrial genes in BAT. Conversely, the overexpression of Slit3 enhanced cold-induced BAT thermogenesis. Our mechanistic studies identified the key regulatory events that control Slit3 signaling in BAT. Collectively, these findings established the essential role of Slit3 signaling in regulation of BAT thermogenesis and introduced Slit3 as a new niche factor that promotes adipose tissue health. These studies introduced a potential node of intervention for improving systemic metabolism through the expansion of thermogenic fat. Disclosure T.Duarte afonso serdan: None. H.E.Cervantes: None. F.M.Neto: None. Y.Tseng: Consultant; Cellarity, LyGenesis. F.Shamsi: None. Funding National Institutes of Health (K01DK125608)

Natural products as novel anti-obesity agents: insights into mechanisms of action and potential for therapeutic management.

Obesity affects more than 10% of the adult population globally. Despite the introduction of diverse medications aimed at combating fat accumulation and obesity, a significant number of these pharmaceutical interventions are linked to substantial occurrences of severe adverse events, occasionally leading to their withdrawal from the market. Natural products serve as attractive sources for anti-obesity agents as many of them can alter the host metabolic processes and maintain glucose homeostasis via metabolic and thermogenic stimulation, appetite regulation, pancreatic lipase and amylase inhibition, insulin sensitivity enhancing, adipogenesis inhibition and adipocyte apoptosis induction. In this review, we shed light on the biological processes that control energy balance and thermogenesis as well as metabolic pathways in white adipose tissue browning, we also highlight the anti-obesity potential of natural products with their mechanism of action. Based on previous findings, the crucial proteins and molecular pathways involved in adipose tissue browning and lipolysis induction are uncoupling protein-1, PR domain containing 16, and peroxisome proliferator-activated receptor-γ in addition to Sirtuin-1 and AMP-activated protein kinase pathway. Given that some phytochemicals can also lower proinflammatory substances like TNF-α, IL-6, and IL-1 secreted from adipose tissue and change the production of adipokines like leptin and adiponectin, which are important regulators of body weight, natural products represent a treasure trove for anti-obesity agents. In conclusion, conducting comprehensive research on natural products holds the potential to accelerate the development of an improved obesity management strategy characterized by heightened efficacy and reduced incidence of side effects.

22-LB: MiRNA Profiling of Exosomes Derived from Perivascular Adipocyte Tissue in Type 2 Diabetic Mice

Background: Exosomes (EXs), a major type of extracellular vesicles, are emerging as a novel type of intercellular communicators. MicroRNAs (miRs) are one of the major executors of EXs. The previous study shows that lean and obesity adipocyte tissue EXs could elicit different effects in response to insulin sensitivity, the underlying mechanism is related to their carried miRs. Given EX cargoes and function vary on their cellular status, we speculate the miR profiling of EXs derived from the perivascular adipose tissue (PVAT) is altered in diabetic conditions. Methods: EXs were isolated from the PVAT tissue of type 2 diabetic db/db and control db/c mice. EX size and concentration were analyzed by nanoparticle tracking analysis. The miR profiling of PVAT-EXs was analyzed by mmu-miR miRome profiling kit. The miRs of interest were further validated by qRT-PCR. Results: 1) The PVAT-EXs level was higher in diabetic db/db mice than that in non-diabetic db/c mice; 2) In db/db mice, exosomal miRs profile was changed. The exosomal miRs, miR-223, miR-181a, miR-146a, miR-34a, and miR-210, were either down-regulated or up-regulated > 3-fold when comparing that in db/c mice. Among these candidate miRs, miR-181a, miR-223, miR-210, and miR-146a might be involved in modulating adipose tissue inflammation and/or vascular function. MiR-34a could participate in white adipose tissue browning, macrophage polarization, and glucose tolerance. Conclusion: Our data have demonstrated that the miR profiling of PVAT-derived EXs is changed in type 2 diabetic conditions, which suggests the functions of these EXs might be altered in diabetic conditions. Disclosure S. Chen: None. V. Polaki: None. J. Bihl: None. J. Wang: None.

75-OR: Cold-Responsive Proteolytic Rewiring of Mitochondria Safeguards White Fat Thermogenic Remodeling

Mitochondrial proteases are emerging as key regulators of mitochondrial plasticity acting both as protein quality surveillance and regulatory enzymes. It remains unclear, however, whether the regulated mitochondrial proteolysis is mechanistically linked to cell identity switch such as white-to-beige conversion of adipocytes. Here we report that cold-responsive mitochondrial proteolysis is a prerequisite for conversion from white-to-beige adipocytes during white adipose tissue (WAT) browning. MitoTimer reporter and chemical thiol probe analysis reveal that thermogenic stimulation selectively promotes mitochondrial proteostasis in WAT via mitochondrial protease LONP1 both in vivo and in vitro. Disruption of LONP1-dependent proteolysis substantially impairs cold or b3-AR agonist induced adipocyte identity programming, evidenced by the remarkably attenuated formation of UCP1+ multilocular adipocytes in IWAT from Lonp1 f/f/Adipoq-Cre (LONP1 AKO) mice. LONP1 AKO mice exposed to cold had lower body temperature, elevated serum TG and FFA levels. Chow-fed LONP1 AKO mice also developed glucose intolerance. “AdipoChaser” system “pulse-chase” lineage tracing experiments confirm that LONP1 ablation markedly blocks the direct cell fate programming of pre-existing mature adipocytes. Importantly, augmented LONP1 expression corrects aging-related impairments in white-to-beige adipocytes conversion. 10-month-old adipocyte-specific Lonp1 overexpression mice had significantly lower body weight and fat mass as a result of elevated energy expenditure. Thus, the identification of LONP1 as a critical safeguard of WAT beiging holds promise for translational applications in enhancing white-to-beige adipocytes conversion capacity relevant to a variety of metabolic disease states and during aging. Disclosure T.Fu: None. W.Sun: None. Z.Zhou: None. Z.Xu: None. M.Yan: None. L.Yang: None. Y.Yin: None. Z.Gan: None.

Effects of Melatonin Supplementation on Lipid Metabolism and Body Fat Accumulation in Ovariectomized Rats.

Postmenopausal obesity is a rising problem. Melatonin (Mel) is a hormone secreted by the pineal gland that regulates the circadian rhythms and improves obesity. In this experiment, ovariectomized (OVX) rats were used as a menopause model to explore the effects of Mel supplementation on lipid metabolism, body fat accumulation, and obesity. Nine-week-old female rats underwent an OVX surgery and were assigned to the following groups: control group (C), low-dose group (L, 10 mg/kg body weight (BW) Mel), medium-dose group (M, 20 mg/kg BW Mel), and high-dose group (H, 50 mg/kg BW Mel), administered by gavage for 8 weeks. The results showed that the OVX rats supplemented with low, medium, and high doses of Mel for 8 weeks exhibited reduced BW gain, perirenal fat mass, and gonads fat mass, and an increased serum irisin level. Low and high doses of Mel induced brite/beige adipocytes in the white adipose tissues. In addition, the messenger RNA levels of the fatty acid synthesis enzymes were significantly reduced after the high-dose Mel supplementation. Thus, Mel can reduce the hepatic fatty acid synthesis and promote the browning of white adipose tissues through irisin; thereby, improving obesity and body fat accumulation in OVX rats.

Combination of Panax ginseng and Diospyros kaki Leaf Inhibits White Adipocyte Differentiation and Browning Process through AMP-Activated Protein Kinase (AMPK) Activation In Vitro and In Vivo.

Activating brown adipose tissue (BAT) and stimulating white adipose tissue (WAT) browning is a prospective obesity treatment method. Dietary components derived from plants are the most effective approach to activate BAT and promote WAT browning in rodents. This study investigated the synergistic effects of Panax ginseng (PG) and Diospyros kaki leaf (DKL) extract on adipocyte differentiation and browning, as well as the molecular mechanism underlying their beneficial effects. The administration of PG and DKL to HFD-induced obese mice significantly decreased body weight and epididymal and abdominal adipose tissue mass. In in vitro, PG inhibited the adipogenesis of 3T3-L1 adipocytes by regulating the expression of key adipogenic regulators, such as peroxisome proliferator-activated receptor (PPAR)γ and CCAAT/enhancer-binding protein (C/EBP)-α. In contrast, DKL negligibly influenced the adipogenesis of 3T3-L1 adipocytes but greatly increased the protein expression of UCP-1, PGC-1α, and PPARα in BAT and/or WAT. Moreover, PG and DKL inhibited adipogenesis synergistically and activated white adipocyte browning via AMP-activated protein kinase (AMPK) and sirtuin 1 (SIRT1) pathways. These results suggest that a combination of PG and DKL regulates adipogenesis in white adipocytes and browning in brown adipocytes by activating AMPK/SIRT1 axis. The potential use of PG and DKL may represent an important strategy in obesity management that will be safer and more effective.

Inherited stress resiliency prevents the development of metabolic alterations in diet-induced obese mice.

Chronic stress promotes obesity and metabolic comorbidities. The ability of individuals to cope with stress may serve as an important parameter in the development of obesity-related metabolic outcomes. The aim of this study was to clarify whether differences in stress response affect metabolic health under obesity. The study was performed in a selectively bred mouse model of social dominance (Dom) and submissiveness (Sub), which exhibit stress resilience or vulnerability, respectively. Mice were given a high-fat diet (HFD) or standard diet, followed by physiological, histological, and molecular analyses. The HFD caused hyperleptinemia, glucose intolerance, insulin resistance, steatosis of the liver and pancreas, and brown adipose tissue whitening in Sub mice, whereas Dom mice were protected from these consequences of the HFD. The HFD increased circulating levels of interleukin (IL)-1β and induced the expression of proinflammatory genes in the liver and in epididymal white adipose tissue of Sub mice, with no changes in Dom mice. The Cox2 inhibitor celecoxib (15 mg/kg/d) reduced serum IL-1β, improved glucose tolerance and insulin sensitivity, and prevented hepatic and brown adipose tissue whitening in HFD-fed Sub mice. The extent of stress resiliency is associated with inflammation and contributes to population heterogeneity in the development of healthy or unhealthy obesity.

Leucine-Restricted Diet Ameliorates Obesity-Linked Cognitive Deficits: Involvement of the Microbiota-Gut-Brain Axis.

Leucine restriction (LR) improves insulin resistance and promotes white adipose tissue browning. However, the effect of LR on obesity-associated cognitive impairment remains unclear. The present study found that an 8-week LR dramatically improved high-fat diet (HFD)-induced cognitive decline by preventing synaptic dysfunction, increasing the expressions of neurotrophic factors, and inhibiting neuroinflammation in memory-related brain regions. Moreover, LR notably reshaped the structure of gut microbiota, which was manifested by downregulating the Firmicutes/Bacteroidetes ratio, reducing the relative abundance of inflammation-related bacteria including Acetatifactor, Helicobacter, Mucispirillum, and Oscillibacter but increasing short-chain fatty acid (SCFA)-producing bacterial genera including Alistipes, Allobaculum, Odoribacter, and Olsenella. Notably, HFD-caused SCFA reduction, gut barrier damage, and LPS leakage were recovered by LR. Our findings suggested that LR could serve as an effective approach to attenuate obesity-induced cognitive deficits, which may be achieved by balancing gut microbiota homeostasis and enhancing SCFA production.

Maresin 1 activates brown adipose tissue and promotes browning of white adipose tissue in mice

ObjectiveMaresin 1 (MaR1) is a docosahexaenoic acid-derived proresolving lipid mediator with insulin-sensitizing and anti-steatosis properties. Here, we aim to unravel MaR1 actions on brown adipose tissue (BAT) activation and white adipose tissue (WAT) browning. MethodsMaR1 actions were tested in cultured murine brown adipocytes and in human mesenchymal stem cells (hMSC)-derived adipocytes. In vivo effects of MaR1 were tested in diet-induced obese (DIO) mice and lean WT and Il6 knockout (Il6−/−) mice. ResultsIn cultured differentiated murine brown adipocytes, MaR1 reduces the expression of inflammatory genes, while stimulates glucose uptake, fatty acid utilization and oxygen consumption rate, along with the upregulation of mitochondrial mass and genes involved in mitochondrial biogenesis and function and the thermogenic program. In Leucine Rich Repeat Containing G Protein-Coupled Receptor 6 (LGR6)-depleted brown adipocytes using siRNA, the stimulatory effect of MaR1 on thermogenic genes was abrogated. In DIO mice, MaR1 promotes BAT remodeling, characterized by higher expression of genes encoding for master regulators of mitochondrial biogenesis and function and iBAT thermogenic activation, together with increased M2 macrophage markers. In addition, MaR1-treated DIO mice exhibit a better response to cold-induced BAT activation. Moreover, MaR1 induces a beige adipocyte signature in inguinal WAT of DIO mice and in hMSC-derived adipocytes. MaR1 potentiates Il6 expression in brown adipocytes and BAT of cold exposed lean WT mice. Interestingly, the thermogenic properties of MaR1 were abrogated in Il6−/− mice. ConclusionsThese data reveal MaR1 as a novel agent that promotes BAT activation and WAT browning by regulating thermogenic program in adipocytes and M2 polarization of macrophages. Moreover, our data suggest that LGR6 receptor is mediating MaR1 actions on brown adipocytes, and that IL-6 is required for the thermogenic effects of MaR1.

THE ASSOCIATION OF CIRCULATING SERUM IRISIN LEVELS WITH GLUCOSE AND LIPID METABOLISM IN CHINESE ADOLESCENTS AGED 12∼18 YEARS

Objective: Irisin is an exercise-regulated myokine inducing browning of white adipose tissue and has gained interest as a potential new strategy to combat type 2 diabetes mellitus and dyslipidemia. The aim of this study was to evaluate the possible relationships between circulating serum irisin levels with glucose and lipid metabolism in Chinese adolescents. Design and method: This cross-sectional study included 1219 adolescents aged 12 to 18 years. Serum irisin levels were evaluated by enzyme-linked immunosorbent assay and all participants’ fasting blood glucose (FBG) and lipids,including totalcholesterol(TC),triglyceride(TG),low-density lipoprotein cholesterol(LDL-C) and high-density lipoprotein cholesterol(HDL-C) were measured. Multiple linear regression was used to study the effect of irisin on glucose and lipid metabolism. Results: There were several significant negative correlations between circulating irisin and FBG (r = -0.120, P<0.001), TC(r = -0.091, P<0.001), LDL-C(r = -0.088, P = 0.002) and HDL-C(r = -0.094, P<0.001) across the study. In multivariate linear regression analysis, after controlling for potential confounders such as gender, age and BMI, irisin levels were independently associated with FBG( = -0.115, P<0.001), TC( = -0.078, P = 0.003), LDL-C( = -0.073, P = 0.005) and HDL-C(r = -0.087, P = 0.001). Conclusions: We found that serum irisin levels were inversely correlated with glucose and lipid metabolic parameters including FPG, TC, LDL-C and HDL-C,suggesting that irisin may play a crucial role in glucose and lipid metabolism from an early age.

PRMT4 facilitates white adipose tissue browning and thermogenesis by methylating PPARγ.

Obesity is a global health threat, and the induction of white adipose tissue (WAT) browning presents a promising therapeutic method for it. Recent publications revealed the essential role of protein arginine methyltransferase 4 (PRMT4) in lipid metabolism and adipogenesis, but its involvement in WAT browning has not been investigated. Our initial studies found that the expression of PRMT4 in adipocytes was upregulated in cold-induced WAT browning but downregulated in obesity. Besides, PRMT4 overexpression in inguinal adipose tissue accelerated WAT browning and thermogenesis to protect against high-fat diet (HFD)-induced obesity and metabolic disruptions. Mechanistically, our work demonstrated that PRMT4 methylated peroxisome proliferator-activated receptor-γ (PPARγ) on Arg240 to enhance its interaction with the co-activator PR domain-containing protein 16 (PRDM16), leading to the increased expression of thermogenic genes. Taken together, our results uncover the essential role of PRMT4/PPARγ/PRDM16 axis in the pathogenesis of WAT browning.

Transcriptomic analysis reveals the effects of maternal exposure to bisphenol AF on hypothalamic development in male neonatal mice

Fragmented data suggest that bisphenol AF (BPAF), a chemical widely used in a variety of products, might have potential impacts on the hypothalamus. Here, we employed male neonatal mice following maternal exposure to explore the effects of low-dose BPAF on hypothalamic development by RNA-sequencing. We found that maternal exposure to approximately 50 µg/(kg·day) BPAF from postanal day (PND) 0 to PND 15 altered the hypothalamic transcriptome, primarily involving the pathways and genes associated with extracellular matrix (ECM) and intercellular adhesion, neuroendocrine regulation, and neurological processes. Further RNA analysis confirmed the changes in the expression levels of concerned genes. Importantly, we further revealed that low-dose BPAF posed a stimulatory impact on pro-opiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus and induced the browning of inguinal white adipose tissue. All findings indicate that developmental exposure to low-dose BPAF could interfere with hypothalamic development and thereby lead to alterations in the metabolism. Interestingly, 5000 µg/(kg·day) BPAF caused slighter, non-significant or even inverse alterations than the low dose of 50 µg/(kg·day), displaying a dose-independent effect. Further observations suggest that the the dose-independent effects of BPAF might be associated with oxidative stress and inflammatory responses caused by the high dose. Overall, our study highlights a risk of low-dose BPAF to human neuroendocrine regulation and metabolism.

PPARγ Acetylation in Adipocytes Exacerbates BAT Whitening and Worsens Age-Associated Metabolic Dysfunction.

Aging and obesity are the two prominent driving forces of metabolic dysfunction, yet the common underlying mechanisms remain elusive. PPARγ, a central metabolic regulator and primary drug target combatting insulin resistance, is hyperacetylated in both aging and obesity. By employing a unique adipocyte-specific PPARγ acetylation-mimetic mutant knock-in mouse model, namely aKQ, we demonstrate that these mice develop worsened obesity, insulin resistance, dyslipidemia, and glucose intolerance as they age, and these metabolic deregulations are resistant to intervention by intermittent fasting. Interestingly, aKQ mice show a whitening phenotype of brown adipose tissue (BAT) manifested in lipid filling and suppressed BAT markers. Diet-induced obese aKQ mice retain an expected response to thiazolidinedione (TZD) treatment, while BAT function remains impaired. This BAT whitening phenotype persists even with the activation of SirT1 through resveratrol treatment. Moreover, the adverse effect of TZDs on bone loss is exacerbated in aKQ mice and is potentially mediated by their increased Adipsin levels. Our results collectively suggest pathogenic implications of adipocyte PPARγ acetylation, contributing to metabolic dysfunction in aging and thus posing as a potential therapeutic target.

6‐Gingerol induces browning of white adipose tissue to improve obesity through PI3K/AKT‐RPS6‐mediated thermogenesis pathway

AbstractThe browning of white fat has become a hot topic as it could help to lose weight and improve metabolic health. Therefore, this study aims to explore the in vivo browning or thermogenesis effect of 6‐gingerol (6G), a natural bioactive compound of ginger, and to clarify the underlying mechanism. The results showed that 6G limited weight gain, improved cold tolerance, and increased energy expenditure in high‐fat diet‐induced obese mice. Moreover, histological and immunohistochemical analysis revealed that 6G activated brown adipose tissue (BAT) and induced more beige cells in epididymal adipose tissue (eWAT). Meanwhile, eWAT browning was marked by appearance of multilocular lipid droplets, a higher level of uncoupling protein 1 (UCP1), and increased mitochondrial content. The potential molecular mechanism of eWAT browning was further investigated by RNA‐seq, qPCR, and western blot assays. Results indicated that 6G significantly induced the expression of beige and thermogenesis‐specific markers in eWAT and triggers thermogenesis mainly through a phosphoinositide 3‐kinase (PI3K) / protein kinase B (AKT)‐ribosomal protein S6 (RPS6) axis. Consistently, in vitro, data showed that pretreatment of primary white adipocytes with PI3K/AKT pathway inhibitor significantly counteracted the 6G‐induced effects. This study reveals, for the first time, that 6G induces browning in adipose tissue by modulating the PI3K/AKT‐RPS6 and thermogenesis pathways, thereby alleviating obesity.

Reduced hepatic bradykinin degradation accounts for cold-induced BAT thermogenesis and WAT browning in male mice

An important role for liver in the regulation of adipose tissue thermogenesis upon cold exposure has been suggested; however, the underlying mechanisms remain incompletely defined. Here, we identify elevated serum bradykinin levels in response to acute cold exposure in male mice. A bolus of anti-bradykinin antibodies reduces body temperature during acute cold exposure, whereas bradykinin has the opposite effect. We demonstrate that bradykinin induces brown adipose tissue thermogenesis and white adipose tissue browning, and bradykinin increases uncoupling protein 1 (UCP1) expression in adipose tissue. The bradykinin B2 receptor (B2R), adrenergic signaling and nitric oxide signaling are involved in regulating bradykinin-increased UCP1 expression. Moreover, acute cold exposure inhibits hepatic prolyl endopeptidase (PREP) activity, causing reduced liver bradykinin degradation and increased serum bradykinin levels. Finally, by blocking the breakdown of bradykinin, angiotensin-converting enzyme inhibitors (ACEIs) increase serum bradykinin levels and induce brown adipose tissue thermogenesis and white adipose tissue browning via B2R. Collectively, our data provide new insights into the mechanisms underlying organ crosstalk in whole-body physiology control during cold exposure and also suggest bradykinin as a possible anti-obesity target.

The Role of Acetyl-CoA Synthetase Short Chain Family Member-1 on Adipocyte Thermogenic Capacity

Obesity is characterized by an increase in adipose mass and is the leading risk factor for type 2 diabetes. Recent research suggests that activation of brown or beige fat and white adipose tissue browning represent a new therapeutic strategy for metabolic diseases. Fatty acid oxidation is required for the browning of white adipose tissue (WAT) and the induction of uncoupling protein 1 (UCP1) in WAT. The Acyl-CoA Synthetase Short Chain Family Member-1 (ACSS1), an established SIRT3 deacetylation target, is central to fatty acid oxidation (FAO) and mitochondrial bioenergetics by converting acetate and CoA to acetyl-CoA. However, the biological function of ACSS1 acetylation (ACSS1-Ac) in thermogenic adipose tissue and how it contributes to metabolic changes in adipocytes has not been investigated. We have generated a novel acetylation mimic mouse where lysine 635 (K635) was mutated to glutamine (K635Q), representing constitutive ACSS1-K635-Ac. Male mice expressing Acss1 K635Q/K635Q exhibited a reduction in size and body weight. Upon 48-hour fasting, these mice exhibited hypothermia as well as decreased ATP and lactate levels. Interestingly, UCP1 gene expression was upregulated in brown adipose tissue (BAT) of the Acss1 K635Q/K635Q compared to WT and also in WAT from fasted animals. Differentiated beige adipocytes also showed higher UCP1, PGC1a and adiponectin gene expression in cells isolated from Acss1 K635Q/K635Q mice compared to WT cells. Oxygen consumption rate of these cells was lower with lower basal and ATP-coupled respiration. Acss1 K635Q/K635Q beige adipocytes failed to respond to beta-adrenergic stimulation and did not increase their respiration capacity when compared to WT cells. No differences were observed in glucose uptake and lipolysis functional assays. These results suggest that the mutation leads to a disruption of downstream signaling of UCP1. In conclusion, ACSS1-K635-Ac is a novel thermoregulator in adipose tissue that could lead to further development of new therapies for metabolic diseases. 1. Mays Cancer Center CCSG (P30 CA054174); 2. National Institute of Diabetes and Digestive and Kidney Diseases of the National Institutes of Health, under Award Number F32-0DK122754 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Acetyl-CoA carboxylase 1 is a suppressor of the adipocyte thermogenic program

Disruption of adipocyte de novo lipogenesis (DNL) by deletion of fatty acid synthase (FASN) in mice induces browning in inguinal white adipose tissue (iWAT). However, adipocyte FASN knockout (KO) increases acetyl-coenzyme A (CoA) and malonyl-CoA in addition to depletion of palmitate. We explore which of these metabolite changes triggers adipose browning by generating eight adipose-selective KO mouse models with loss ofATP-citrate lyase (ACLY), acetyl-CoA carboxylase 1 (ACC1), ACC2, malonyl-CoA decarboxylase (MCD) or FASN, or dual KOs ACLY/FASN, ACC1/FASN, and ACC2/FASN. Preventing elevation of acetyl-CoA and malonyl-CoA by depletion of adipocyte ACLY or ACC1 in combination with FASN KO does not block the browning of iWAT. Conversely, elevating malonyl-CoA levels in MCD KO mice does not induce browning. Strikingly, adipose ACC1 KO induces a strong iWAT thermogenic response similar to FASN KO while also blocking malonyl-CoA and palmitate synthesis. Thus, ACC1 and FASN are strong suppressors of adipocyte thermogenesis through promoting lipid synthesis rather than modulating the DNL intermediates acetyl-CoA or malonyl-CoA.