Dapagliflozin promotes browning of white adipose tissue through the FGFR1-LKB1-AMPK signaling pathway.

BACKGROUND: Obesity is associated with a wide variety of metabolic disorders that impose significant burdens on patients and society. The "browning" phenomenon in white adipose tissue (WAT) has emerged as a promising therapeutic strategy to combat metabolic disturbances. However, though the anti-diabetic drug dapagliflozin (DAPA) is thought to promote "browning," the specific mechanism of this was previously unclear. METHODS: In this study, C57BL/6 J male mice were used to establish an obesity model by high-fat diet feeding, and 3T3-L1 cells were used to induce mature adipocytes and to explore the role and mechanism of DAPA in "browning" through a combination of in vitro and in vivo experiments. RESULTS: The results show that DAPA promotes WAT "browning" and improves metabolic disorders. Furthermore, we discovered that DAPA activated "browning" through the fibroblast growth factor receptors 1-liver kinase B1-adenosine monophosphate-activated protein kinase signaling pathway. CONCLUSION: These findings provide a rational basis for the use of DAPA in treating obesity by promoting the browning of white adipose tissue.

Ginsenoside Rg3, enriched in red ginseng extract, improves lipopolysaccharides-induced suppression of brown and beige adipose thermogenesis with mitochondrial activation.

Brown adipose tissue (BAT) which is a critical regulator of energy homeostasis, and its activity is inhibited by obesity and low-grade chronic inflammation. Ginsenoside Rg3, the primary constituent of Korean red ginseng (steamed Panax ginseng CA Meyer), has shown therapeutic potential in combating inflammatory and metabolic diseases. However, it remains unclear whether Rg3 can protect against the suppression of browning or activation of BAT induced by inflammation. In this study, we conducted a screening of ginsenoside composition in red ginseng extract (RGE) and explored the anti-adipogenic effects of both RGE and Rg3. We observed that RGE (exist 0.25 mg/mL of Rg3) exhibited significant lipid-lowering effects in adipocytes during adipogenesis. Moreover, treatment with Rg3 (60 µM) led to the inhibition of triglyceride accumulation, subsequently promoting enhanced fatty acid oxidation, as evidenced by the conversion of radiolabeled 3H-fatty acids into 3H-H2O with mitochondrial activation. Rg3 alleviated the attenuation of browning in lipopolysaccharide (LPS)-treated beige adipocytes and primary brown adipocytes by recovered by uncoupling protein 1 (UCP1) and the oxygen consumption rate compared to the LPS-treated group. These protective effects of Rg3 on inflammation-induced inhibition of beige and BAT-derived thermogenesis were confirmed in vivo by treating with CL316,243 (a beta-adrenergic receptor agonist) and LPS to induce browning and inflammation, respectively. Consistent with the in vitro data, treatment with Rg3 (2.5 mg/kg, 8 weeks) effectively reversed the LPS-induced inhibition of brown adipocyte features in C57BL/6 mice. Our findings confirm that Rg3-rich foods are potential browning agents that counteract chronic inflammation and metabolic complications.

Guanidinoacetic acid ameliorates hepatic steatosis and inflammation and promotes white adipose tissue browning in middle-aged mice with high-fat-diet-induced obesity.

Guanidinoacetic acid (GAA) is a naturally occurring amino acid derivative that plays a critical role in energy metabolism. In recent years, a growing body of evidence has emerged supporting the importance of GAA in metabolic dysfunction. Hence, we aimed to investigate the effects of GAA on hepatic and adipose tissue metabolism, as well as systemic inflammatory responses in obese middle-aged mice models and attempted to explore the underlying mechanism. We found that dietary supplementation of GAA inhibited inguinal white adipose tissue (iWAT) hypertrophy in high-fat diet (HFD)-fed mice. In addition, GAA supplementation observably decreased the levels of some systemic inflammatory factors, including IL-4, TNF-α, IL-1ß, and IL-6. Intriguingly, GAA supplementation ameliorated hepatic steatosis and lipid deposition in HFD-fed mice, which was revealed by decreased levels of TG, TC, LDL-C, PPARγ, SREBP-1c, FASN, ACC, FABP1, and APOB and increased levels of HDL-C in the liver. Moreover, GAA supplementation increased the expression of browning markers and mitochondrial-related genes in the iWAT. Further investigation showed that dietary GAA promoted the browning of the iWAT via activating the AMPK/Sirt1 signaling pathway and might be associated with futile creatine cycling in obese mice. These results indicate that GAA has the potential to be used as an effective ingredient in dietary interventions and thus may play an important role in ameliorating and preventing HFD-induced obesity and related metabolic diseases.

trans-Palmitoleic acid promotes adipose thermogenesis to reduce obesity via hypothalamic FFAR1 signaling.

Diet-induced thermogenesis (DIT) is crucial for maintaining body weight homeostasis, and the role of dietary fatty acids in modulating DIT is essential. However, the underlying mechanism of fatty acid regulated diet-induced thermogenesis remains elusive. Utilizing the diet- and genetic ablation-induced obese mice models, we found that the C16 unsaturated fatty acids, trans-palmitoleic acid (TPA) and cis-palmitoleic acid (CPA), significantly increased the energy expenditure by promoting the thermogenesis of brown adipose tissues and the production of beige cells in white adipose. As a result, there is a significant reduction in the occurrence of obesity, associated hepatic steatosis and hyperglycemia. Notably, TPA exhibited more potent effects on promoting DIT and alleviating obesity than CPA did. Using inhibitor and gene deletion mice models, we unveiled that TPA acted as a signaling molecule to play a biological function, which could be sensed by the hypothalamic FFAR1 to activate the sympathetic nervous system in promoting adipose tissue thermogenesis. Together, these results demonstrate the underlying mechanism of free fatty acids associated-DIT and will provide fresh insights into the roles of trans-fatty acids in the development of obesity.

Role of Spexin in White Adipose Tissue Thermogenesis under Basal and Cold-Stimulated Conditions.

Spexin (SPX) is a novel adipokine that plays an emerging role in metabolic diseases due to its involvement in carbohydrate homeostasis, weight loss, appetite control, and gastrointestinal movement, among others. In obese patients, SPX plasma levels are reduced. Little is known about the relationship between SPX and white adipose tissue (WAT) thermogenesis. Therefore, the aim of the present study was to evaluate the role of SPX in this process. C57BL/6J male mice were treated or not with SPX for ten days. On day 3, mice were randomly divided into two groups: one kept at room temperature and the other kept at cold temperature (4 °C). Caloric intake and body weight were recorded daily. At the end of the protocol, plasma, abdominal (epididymal), subcutaneous (inguinal), and brown AT (EAT, IAT, and BAT, respectively) depots were collected for measurements. We found that SPX treatment reduced Uncoupling protein 1 levels in WAT under both basal and cold conditions. SPX also reduced cox8b and pgc1α mRNA levels and mitochondrial DNA, principally in IAT. SPX did not modulate the number of beige precursors. SPX decreased spx levels in IAT depots and galr2 in WAT depots. No differences were observed in the BAT depots. In conclusion, we showed, for the first time, that SPX treatment in vivo reduced the thermogenic process in subcutaneous and abdominal AT, being more evident under cold stimulation.

Glibenclamide promotes FGF21 secretion in interscapular BAT and attenuates depression-like behaviors in male mice with HFD-induced obesity.

AIMS: Epidemiological evidence suggests that comorbidity of obesity and depression is extremely common and continues to grow in prevalence. However, the mechanisms connecting these two conditions are unknown. In this study, we explored how treatment with KATP channel blocker glibenclamide (GB) or the well-known metabolic regulator FGF21 impact male mice with high-fat diet (HFD)-induced obesity and depressive-like behaviors. MATERIALS AND METHODS: Mice were fed with HFD for 12 weeks and then treated with recombinant FGF21 protein by infusion for 2 weeks, followed by intraperitoneal injection of 3 mg/kg recombinant FGF21 once per day for 4 days. Measurements were made of catecholamine levels, energy expenditure, biochemical endpoints and behavior tests, including sucrose preference and forced swim tests were. Alternatively, animals were infused with GB into brown adipose tissue (BAT). The WT-1 brown adipocyte cell line was used for molecular studies. KEY FINDINGS: Compared to HFD controls, HFD + FGF21 mice exhibited less severe metabolic disorder symptoms, improved depressive-like behaviors, and more extensive mesolimbic dopamine projections. FGF21 treatment also rescued HFD-induced dysregulation of FGF21 receptors (FGFR1 and co-receptor ß-klotho) in the ventral tegmental area (VTA), and it altered dopaminergic neuron activity and morphology in HFD-fed mice. Importantly, we also found that FGF21 mRNA level and FGF21 release were increased in BAT after administration of GB, and GB treatment to BAT reversed HFD-induced dysregulation of FGF21 receptors in the VTA. SIGNIFICANCE: GB administration to BAT stimulates FGF21 production in BAT, corrects HFD-induced dysregulation of FGF21 receptor dimers in VTA dopaminergic neurons, and attenuates depression-like symptoms.

Peripheral modulation of antidepressant targets MAO-B and GABAAR by harmol induces mitohormesis and delays aging in preclinical models.

Reversible and sub-lethal stresses to the mitochondria elicit a program of compensatory responses that ultimately improve mitochondrial function, a conserved anti-aging mechanism termed mitohormesis. Here, we show that harmol, a member of the beta-carbolines family with anti-depressant properties, improves mitochondrial function and metabolic parameters, and extends healthspan. Treatment with harmol induces a transient mitochondrial depolarization, a strong mitophagy response, and the AMPK compensatory pathway both in cultured C2C12 myotubes and in male mouse liver, brown adipose tissue and muscle, even though harmol crosses poorly the blood-brain barrier. Mechanistically, simultaneous modulation of the targets of harmol monoamine-oxidase B and GABA-A receptor reproduces harmol-induced mitochondrial improvements. Diet-induced pre-diabetic male mice improve their glucose tolerance, liver steatosis and insulin sensitivity after treatment with harmol. Harmol or a combination of monoamine oxidase B and GABA-A receptor modulators extend the lifespan of hermaphrodite Caenorhabditis elegans or female Drosophila melanogaster. Finally, two-year-old male and female mice treated with harmol exhibit delayed frailty onset with improved glycemia, exercise performance and strength. Our results reveal that peripheral targeting of monoamine oxidase B and GABA-A receptor, common antidepressant targets, extends healthspan through mitohormesis.

Secretin modulates appetite via brown adipose tissue-brain axis.

PURPOSE: Secretin activates brown adipose tissue (BAT) and induces satiation in both mice and humans. However, the exact brain mechanism of this satiety inducing, secretin-mediated gut-BAT-brain axis is largely unknown. METHODS AND RESULTS: In this placebo-controlled, single-blinded neuroimaging study, firstly using [18F]-fluorodeoxyglucose (FDG) PET measures (n = 15), we established that secretin modulated brain glucose consumption through the BAT-brain axis. Predominantly, we found that BAT and caudate glucose uptake levels were negatively correlated (r = -0.54, p = 0.037) during secretin but not placebo condition. Then, using functional magnetic resonance imaging (fMRI; n = 14), we found that secretin improved inhibitory control and downregulated the brain response to appetizing food images. Finally, in a PET-fMRI fusion analysis (n = 10), we disclosed the patterned correspondence between caudate glucose uptake and neuroactivity to reward and inhibition, showing that the secretin-induced neurometabolic coupling patterns promoted satiation. CONCLUSION: These findings suggest that secretin may modulate the BAT-brain metabolic crosstalk and subsequently the neurometabolic coupling to induce satiation. The study advances our understanding of the secretin signaling in motivated eating behavior and highlights the potential role of secretin in treating eating disorders and obesity. TRIAL REGISTRATION: EudraCT no. 2016-002373-35, registered 2 June 2016; Clinical Trials no. NCT03290846, registered 25 September 2017.

The effect of Xuezhikang capsule on gene expression profile in brown adipose tissue of obese spontaneously hypertensive rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Obesity is a critical threat to global health, and brown adipose tissue (BAT) is a potential target for the treatment of obesity and comorbidities. Xuezhikang Capsule (XZK), an extract of red yeast rice, has remarkable clinical efficacy and is widely used for the treatment of hyperlipidemia and coronary heart disease. However, its modulatory effect on BAT remains unknown. AIM OF THIS STUDY: The aim of this study was to investigate the protective mechanism of XZK in the obese spontaneously hypertensive rat (SHR) model by evaluating the regulatory effect of XZK on the BAT gene profile through transcriptome sequencing. MATERIALS AND METHODS: The SHRs were randomly divided into four groups: the standard chow diet (STD) group, the STD supplemented with 126 mg/kg of XZK group, the high-fat diet (HFD) group, and the HFD supplemented with 126 mg/kg of XZK group. All SHRs were fed for 18 weeks. The metabolic phenotypes, including body weight, fat mass, oral glucose tolerance test (OGTT), and serum glucose and lipid levels, was evaluated, and hematoxylin and eosin staining (H&E) staining was performed to evaluate the adipose tissue histopathological phenotype. Transcriptome sequencing was performed to determine the mechanism by which XZK improves the metabolic phenotype and the expression of key differential expression genes was verified by real-time quantitative polymerase chain reaction (qRT-PCR). RESULTS: XZK inhibited HFD-induced weight gain and adipose tissue remodeling in SHRs and prevented hypertrophy of epididymal adipocytes and maintained the brown fat phenotype. XZK intervention also improved glucose and lipid metabolism in SHRs, as suggested by a reduction in serum triglyceride (TG), low-density cholesterol (LDL-C), and fasting blood glucose (FBG) levels as well as increasing in serum high-density cholesterol (HDL-C) levels. Transcriptome sequencing analysis confirmed the regulatory effect of XZK on the gene expression profile of BAT, and the expression patterns of 45 genes were reversed by the XZK intervention. Additionally, the results of the transcriptome analysis of 10 genes that are important for brown fat function were in line with the results of qRT-PCR. CONCLUSIONS: XZK protected SHRs from HFD-induced obesity, inhibited fat accumulation and improved glucolipid metabolism. Additionally, the protective effect of XZK on the overall metabolism of obese SHRs might partly be related to its regulatory effect on the BAT gene expression profile. These findings might provide novel therapeutic strategies for obesity-related metabolic diseases in traditional Chinese medicine (TCM).

Apoptotic brown adipocytes enhance energy expenditure via extracellular inosine.

Brown adipose tissue (BAT) dissipates energy1,2 and promotes cardiometabolic health3. Loss of BAT during obesity and ageing is a principal hurdle for BAT-centred obesity therapies, but not much is known about BAT apoptosis. Here, untargeted metabolomics demonstrated that apoptotic brown adipocytes release a specific pattern of metabolites with purine metabolites being highly enriched. This apoptotic secretome enhances expression of the thermogenic programme in healthy adipocytes. This effect is mediated by the purine inosine that stimulates energy expenditure in brown adipocytes by the cyclic adenosine monophosphate-protein kinase A signalling pathway. Treatment of mice with inosine increased BAT-dependent energy expenditure and induced 'browning' of white adipose tissue. Mechanistically, the equilibrative nucleoside transporter 1 (ENT1, SLC29A1) regulates inosine levels in BAT: ENT1-deficiency increases extracellular inosine levels and consequently enhances thermogenic adipocyte differentiation. In mice, pharmacological inhibition of ENT1 as well as global and adipose-specific ablation enhanced BAT activity and counteracted diet-induced obesity, respectively. In human brown adipocytes, knockdown or blockade of ENT1 increased extracellular inosine, which enhanced thermogenic capacity. Conversely, high ENT1 levels correlated with lower expression of the thermogenic marker UCP1 in human adipose tissues. Finally, the Ile216Thr loss of function mutation in human ENT1 was associated with significantly lower body mass index and 59% lower odds of obesity for individuals carrying the Thr variant. Our data identify inosine as a metabolite released during apoptosis with a 'replace me' signalling function that regulates thermogenic fat and counteracts obesity.

Inhibition of STAT3 enhances UCP1 expression and mitochondrial function in brown adipocytes.

Extensive studies have shown that the increasing brown adipose tissue (BAT) mass/activity possesses a strong ability to prevent obesity and its related complications. The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signal pathway is known to play a role in adipocyte differentiation and development. However, its impact on thermogenic properties of mature brown adipocytes has not yet been clarified. Nifuroxazide (NFX), a potent inhibitor of STAT3, has received widespread attention due to its alternative anti-tumor and anti-inflammatory effects. Herein, we report that NFX induces lipolysis with subsequent downregulation of ACCα and FAS, while ATGL and pHSL levels are elevated in mature brown adipocytes. Furthermore, NFX treatment promotes the mitochondrial respiration of mature brown adipocytes, as evidenced by increased expression of thermogenic transcriptional factors and mitochondrial content. In addition, it also alleviates the IL-6 and TNFα inhibition on brown thermogenic programming via suppressing the STAT3/NF-κB/IL-6 signaling pathway. In general, these findings suggest that the blockade of the JAK/STAT3 pathway by NFX has a pro-thermogenic effect on mature brown adipocytes which opens new perspectives for NFX repurposing and potential therapeutic route to counteract obesity and related metabolic disorders.

ACSS3 in brown fat drives propionate catabolism and its deficiency leads to autophagy and systemic metabolic dysfunction.

Propionate is a gut microbial metabolite that has been reported to have controversial effects on metabolic health. Here we show that propionate is activated by acyl-CoA synthetase short-chain family member 3 (ACSS3), located on the mitochondrial inner membrane in brown adipocytes. Knockout of Acss3 gene (Acss3-/- ) in mice reduces brown adipose tissue (BAT) mass but increases white adipose tissue (WAT) mass, leading to glucose intolerance and insulin resistance that are exacerbated by high-fat diet (HFD). Intriguingly, Acss3-/- or HFD feeding significantly elevates propionate levels in BAT and serum, and propionate supplementation induces autophagy in cultured brown and white adipocytes. The elevated levels of propionate in Acss3-/- mice similarly drive adipocyte autophagy, and pharmacological inhibition of autophagy using hydroxychloroquine ameliorates obesity, hepatic steatosis and insulin resistance of the Acss3-/- mice. These results establish ACSS3 as the key enzyme for propionate metabolism and demonstrate that accumulation of propionate promotes obesity and Type 2 diabetes through triggering adipocyte autophagy.

Topical application of the pharmacological cold mimetic menthol stimulates brown adipose tissue thermogenesis through a TRPM8, UCP1, and norepinephrine dependent mechanism in mice housed at thermoneutrality.

Increasing whole-body energy expenditure via the pharmacological activation of uncoupling protein 1 (UCP1)-dependent brown adipose tissue (BAT) thermogenesis is a promising weight management strategy, yet most therapeutics studied in rodents to date either induce compensatory increases in energy intake, have thermogenic effects that are confounded by sub-thermoneutral housing temperatures or are not well tolerated in humans. Here, we sought to determine whether the non-invasive topical application of the pharmacological cold mimetic and transient receptor potential (TRP) cation channel subfamily M member 8 (TRPM8) agonist L-menthol (MNTH), could be used to stimulate BAT thermogenesis and attenuate weight gain in mice housed at thermoneutrality. Using three different strains of mice and multiple complimentary approaches to quantify thermogenesis in vivo, coupled with ex vivo models to quantify direct thermogenic effects, we were able to convincingly demonstrate the following: (1) acute topical MNTH application induces BAT thermogenesis in a TRPM8- and UCP1-dependent manner; (2) MNTH-induced BAT thermogenesis is sufficient to attenuate weight gain over time without affecting energy intake in lean and obese mice; (3) the ability of topical MNTH application to stimulate BAT thermogenesis is mediated, in part, by a central mechanism involving the release of norepinephrine. These data collectively suggest that topical application of MNTH may be a promising weight management strategy.

Cold Exposure Drives Weight Gain and Adiposity following Chronic Suppression of Brown Adipose Tissue.

Therapeutic activation of thermogenic brown adipose tissue (BAT) may be feasible to prevent, or treat, cardiometabolic disease. However, rodents are commonly housed below thermoneutrality (~20 °C) which can modulate their metabolism and physiology including the hyperactivation of brown (BAT) and beige white adipose tissue. We housed animals at thermoneutrality from weaning to chronically supress BAT, mimic human physiology and explore the efficacy of chronic, mild cold exposure (20 °C) and ß3-adrenoreceptor agonism (YM-178) under these conditions. Using metabolic phenotyping and exploratory proteomics we show that transfer from 28 °C to 20 °C drives weight gain and a 125% increase in subcutaneous fat mass, an effect not seen with YM-178 administration, thus suggesting a direct effect of a cool ambient temperature in promoting weight gain and further adiposity in obese rats. Following chronic suppression of BAT, uncoupling protein 1 mRNA was undetectable in the subcutaneous inguinal white adipose tissue (IWAT) in all groups. Using exploratory adipose tissue proteomics, we reveal novel gene ontology terms associated with cold-induced weight gain in BAT and IWAT whilst Reactome pathway analysis highlights the regulation of mitotic (i.e., G2/M transition) and metabolism of amino acids and derivatives pathways. Conversely, YM-178 had minimal metabolic-related effects but modified pathways involved in proteolysis (i.e., eukaryotic translation initiation) and RNA surveillance across both tissues. Taken together these findings are indicative of a novel mechanism whereby animals increase body weight and fat mass following chronic suppression of adaptive thermogenesis from weaning. In addition, treatment with a B3-adrenoreceptor agonist did not improve metabolic health in obese animals raised at thermoneutrality.

Mulberry leaf polysaccharides ameliorate obesity through activation of brown adipose tissue and modulation of the gut microbiota in high-fat diet fed mice.

Improving energy homeostasis and the gut microbiota is a promising strategy to improve obesity and related metabolic disorders. Mulberry leaf is one of the traditional Chinese medicines and functional diets. In this work, a mouse model induced by high-fat diet (HFD) was used to reveal the role of mulberry leaf polysaccharides (MLP). It was found that MLP had a significant effect in limiting body weight gain (reduced by 19.95%, 35.47% and 52.46%, respectively), ameliorating hepatic steatosis and regulating lipid metabolism in HFD induced obese mice (P < 0.05). RT-PCR and western blot analysis suggested that these metabolic improvements were mediated by inducing the development of brown-like adipocytes in inguinal white adipose tissue and enhancing brown adipose tissue activity. Besides, 16S rRNA sequencing results led to the inference that MLP could mitigate the composition and function of the gut microbiota. Together, these findings indicated that MLP possess great potential as a diet supplement or medication for obesity.

Withaferin A Promotes White Adipose Browning and Prevents Obesity Through Sympathetic Nerve-Activated Prdm16-FATP1 Axis.

The increasing prevalence of obesity has resulted in demands for the development of new effective strategies for obesity treatment. Withaferin A (WA) shows a great potential for prevention of obesity by sensitizing leptin signaling in the hypothalamus. However, the mechanism underlying the weight- and adiposity-reducing effects of WA remains to be elucidated. In this study, we report that WA treatment induced white adipose tissue (WAT) browning, elevated energy expenditure, decreased respiratory exchange ratio, and prevented high-fat diet-induced obesity. The sympathetic chemical denervation dampened the WAT browning and also impeded the reduction of adiposity in WA-treated mice. WA markedly upregulated the levels of Prdm16 and FATP1 (Slc27a1) in the inguinal WAT (iWAT), and this was blocked by sympathetic denervation. Prdm16 or FATP1 knockdown in iWAT abrogated the WAT browning-inducing effects of WA and restored the weight gain and adiposity in WA-treated mice. Together, these findings suggest that WA induces WAT browning through the sympathetic nerve-adipose axis, and the adipocytic Prdm16-FATP1 pathway mediates the promotive effects of WA on white adipose browning.

Pharmacological treatment with FGF21 strongly improves plasma cholesterol metabolism to reduce atherosclerosis.

AIMS: Fibroblast growth factor (FGF) 21, a key regulator of energy metabolism, is currently evaluated in humans for treatment of type 2 diabetes and non-alcoholic steatohepatitis. However, the effects of FGF21 on cardiovascular benefit, particularly on lipoprotein metabolism in relation to atherogenesis, remain elusive. METHODS AND RESULTS: Here, the role of FGF21 in lipoprotein metabolism in relation to atherosclerosis development was investigated by pharmacological administration of a half-life extended recombinant FGF21 protein to hypercholesterolaemic APOE*3-Leiden.CETP mice, a well-established model mimicking atherosclerosis initiation and development in humans. FGF21 reduced plasma total cholesterol, explained by a reduction in non-HDL-cholesterol. Mechanistically, FGF21 promoted brown adipose tissue (BAT) activation and white adipose tissue (WAT) browning, thereby enhancing the selective uptake of fatty acids from triglyceride-rich lipoproteins into BAT and into browned WAT, consequently accelerating the clearance of the cholesterol-enriched remnants by the liver. In addition, FGF21 reduced body fat, ameliorated glucose tolerance and markedly reduced hepatic steatosis, related to up-regulated hepatic expression of genes involved in fatty acid oxidation and increased hepatic VLDL-triglyceride secretion. Ultimately, FGF21 largely decreased atherosclerotic lesion area, which was mainly explained by the reduction in non-HDL-cholesterol as shown by linear regression analysis, decreased lesion severity, and increased atherosclerotic plaque stability index. CONCLUSION: FGF21 improves hypercholesterolaemia by accelerating triglyceride-rich lipoprotein turnover as a result of activating BAT and browning of WAT, thereby reducing atherosclerotic lesion severity and increasing atherosclerotic lesion stability index. We have thus provided additional support for the clinical use of FGF21 in the treatment of atherosclerotic cardiovascular disease.

Class-specific responses of brown adipose tissue to steroidal and nonsteroidal mineralocorticoid receptor antagonists.

Aldosterone exerts deleterious effects on the cardiovascular system and promotes adipose tissue expansion via mineralocorticoid receptor (MR) activation. We previously demonstrated that administration of steroidal mineralocorticoid receptor antagonists (MRA) in mice fed a moderate high-fat diet is able to reduce white adipose tissue (WAT) expansion, stimulate browning of WAT and activate interscapular brown adipose tissue (iBAT). Here, we aimed to compare the metabolic and adipose tissue-specific effects of the novel non-steroidal MRA finerenone (Fine) and spironolactone (Spiro) in a mouse model of very high-fat diet (HFD)-induced obesity. C57BL/6 J male mice were fed a 60% HFD containing or not Spiro or Fine for 12 weeks. WAT and iBAT morphology and adipose tissue gene expression analysis were assessed. After 12 weeks, both groups of mice showed similar weight gain compared to the HFD group. Histological and molecular analyses of WAT did not show significant differences among all experimental groups; differently, iBAT histological analysis revealed that Fine was able to increase recruitment of brown adipocytes in this depot, whereas mice treated with Spiro failed to elicit any iBAT response, as indicated by no changes in lipid droplets size and iBAT density, compared to HFD. Increased iBAT recruitment could explain, at least in part, the improved insulin resistance observed in mice treated with Fine, as shown by a significant reduction in homeostasis model assessment of insulin resistance (HOMA) index. These findings were confirmed by gene expression analysis of ucp-1, pgc1-α, and beta-3 adrenoreceptor (Adrb3) in iBAT, revealing significantly higher expression of these thermogenic genes in HFD + Fine group compared to HFD, whereas Spiro did not modify their expression. In summary, we demonstrated that, differently from Fine, Spiro did not induce iBAT recruitment. Our current study suggests that Fine, through its direct effects on iBAT, represents a promising pharmacologic tool to treat human metabolic diseases associated with adipose tissue dysfunctions.

Effect of Liothyronine Treatment on Dermal Temperature and Activation of Brown Adipose Tissue in Female Hypothyroid Patients: A Randomized Crossover Study.

Background: Thyroid hormones are essential for the full thermogenic response of brown adipose tissue (BAT) and have been implicated in dermal temperature regulation. Nevertheless, persistent cold-intolerance exists among a substantial proportion of hypothyroid patients on adequate levothyroxine (LT4) substitution. Materials and Methods: To assess if skin temperature and activation of BAT during treatment with liothyronine (LT3) differs from that of LT4 treatment, fifty-nine female hypothyroid patients with residual symptoms on LT4 or LT4/LT3 combination therapy were randomly assigned in a non-blinded crossover study to receive monotherapy with LT4 or LT3 for 12 weeks each. Change in supraclavicular (SCV) skin temperature overlying BAT, and sternal skin temperature not overlying BAT, during rest and cold stimulation were assessed by infrared thermography (IRT). In addition, abundance of exosomal miR-92a, a biomarker of BAT activation, was estimated as a secondary outcome. Results: Cold stimulated skin temperatures decreased less with LT3 vs. LT4 in both SCV (mean 0.009°C/min [95% CI: 0.004, 0.014]; P<0.001) and sternal areas (mean 0.014°C/min [95% CI: 0.008, 0.020]; P<0.001). No difference in serum exosomal miR-92a abundance was observed between the two treatment groups. Conclusion: LT3 may reduce dermal heat loss. Thermography data suggested increased BAT activation in hypothyroid patients with cold-intolerance. However, this finding was not corroborated by assessment of the microRNA biomarker of BAT activation. Clinical Trial Registration: ClinicalTrials.gov, identifier NCT03627611.

Comparative Transcriptome Profiling of Young and Old Brown Adipose Tissue Thermogenesis.

Brown adipose tissue (BAT) is a major site for uncoupling protein 1 (UCP1)-mediated non-shivering thermogenesis. BAT dissipates energy via heat generation to maintain the optimal body temperature and increases energy expenditure. These energetic processes in BAT use large amounts of glucose and fatty acid. Therefore, the thermogenesis of BAT may be harnessed to treat obesity and related diseases. In mice and humans, BAT levels decrease with aging, and the underlying mechanism is elusive. Here, we compared the transcriptomic profiles of both young and aged BAT in response to thermogenic stimuli. The profiles were extracted from the GEO database. Intriguingly, aging does not cause transcriptional changes in thermogenic genes but upregulates several pathways related to the immune response and downregulates metabolic pathways. Acute severe CE upregulates several pathways related to protein folding. Chronic mild CE upregulates metabolic pathways, especially related to carbohydrate metabolism. Our findings provide a better understanding of the effects of aging and metabolic responses to thermogenic stimuli in BAT at the transcriptome level.