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In recent years, brown adipose tissue (BAT), which has a high heat-producing capacity, has been confirmed to exist even in adults, and it has become a focal point for the prevention and the improvement of obesity and lifestyle-related diseases. However, the influences of obesity and physical activity (PA) on the fluid factors secreted from BAT (brown adipokines) are not well understood. In this study, therefore, we focused on brown adipokines and investigated the effects of obesity and PA. The abnormal expressions of gene fluid factors such as galectin-3 (Lgals3) and Lgals3 binding protein (Lgals3bp), whose proteins are secreted from HB2 brown adipocytes, were observed in the interscapular BAT of obese mice fed a high-fat diet for 4 months. PA attenuated the abnormalities in the expressions of these genes. Furthermore, although the gene expressions of factors related to brown adipocyte differentiation such as peroxisome proliferator-activated receptor gamma coactivator 1-α were also down-regulated in the BAT of the obese mice, PA suppressed the down-regulation of these factors. On the other hand, lipogenesis was increased more in HB2 cells overexpressing Lgals3 compared with that in control cells, and the overexpression of Lgals3bp decreased the mitochondrial mass. These results indicate that PA attenuates the obesity-induced dysregulated expression of brown adipokines and suggests that Lgals3 and Lgals3bp are involved in brown adipocyte differentiation.

Activation of brown adipose tissue (BAT) has been proposed as a promising target against obesity due to its increased capacity for thermogenesis. In this study, we explored the effect of [Formula: see text]-Lapachone ([Formula: see text]L), a compound obtained from the bark of the lapacho tree, against obesity. In vivo administration of [Formula: see text]L into either high fat diet (HFD)-induced obese C57BL6 mice and genetically obese Lepr[Formula: see text] mice prevented body weight gain, which was associated with tissue weight loss of white adipose tissue (WAT). In addition, [Formula: see text]L elevated thermogenic proteins including uncoupling protein 1 (UCP1) and mitochondrial count in BAT and human adipose tissue-derived mesenchymal stem cells (hAMSCs). [Formula: see text]L also induced AMP-activated protein kinase (AMPK) phosphorylation, subsequent upregulation of acetyl-CoA carboxylase (ACC) and UCP1, and these effects were diminished by AMPK inhibitor compound C, suggesting that AMPK underlies the effects of [Formula: see text]L. Mitogen-activated protein kinase pathways participated in the thermogenesis of [Formula: see text]L, specifically p38, c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase 1/2 (ERK1/2) were activated by [Formula: see text]L treatment in hAMSCs. Additionally, inhibitors of p38/JNK/ERK1/2 abrogated the activity of [Formula: see text]L. Taken together, [Formula: see text]L exerts anti-obese effects by inducing thermogenesis mediated by AMPK signaling pathway, suggesting that [Formula: see text]L may have a potential therapeutic implication of obesity. Taken together, [Formula: see text]L exerts anti-obese effects by not only inducing thermogenesis on brown adipocytes but also inducing the browning of white adipocytes. The anti-obese effect of [Formula: see text]L is mediated by AMPK signaling pathway, suggesting that [Formula: see text]L may have potential therapeutic implication of obesity.

Obesity is a widespread health problem that brings about various adipose tissue dysfunctions. The balance of energy storage and energy expenditure is critical for normal fat accumulation and lipid metabolism. Therefore, understanding the molecular basis of adipogenesis and thermogenesis is essential to maintain adipose development and lipid homeostasis. Increasing evidence demonstrated that lncRNAs (long non-coding RNAs), a class of non-protein coding RNAs of >200 nucleotides in length, are identified as key regulators in obesity-related biological processes through diverse regulatory mechanisms. In this review, we concentrate on recent and relevant studies on the roles of lncRNAs in regulation of white adipogenesis, brown adipocyte differentiation and lipid metabolism. In addition, the diagnostic and therapeutic potential of lncRNAs is highlighted, and that will make recommendations for the future application of lncRNAs in the treatment of obesity.

Emerging evidence indicates that proper mitochondrial dynamics is critical for adipocyte differentiation and functional thermogenic capacity. We found that mitochondrial fission protein dynamin-related protein 1 (DRP1) is highly expressed in brown adipose tissue compared to white adipose tissue and their levels increase during brown adipocyte differentiation. Our results reveal that the inhibition of DRP1 using Mdivi-1 mitigates adipocyte differentiation and differentiation-associated mitochondrial biogenesis. We found that DRP1 is essential for the induction of the early phase of adipogenic transcriptional program. Intriguingly, inhibition of DRP1 is dispensable following the induction of adipogenesis and adipogenesis-associated mitochondrial biogenesis. Together, we demonstrate that DRP1 in the preadipocytes plays an essential role in brown and beige adipogenesis.

Brown adipose tissue (BAT) is a specialized organ that dissipates energy as heat by a unique mitochondrial protein, uncoupling protein 1 (UCP1). Sex differences on BAT function and abundance have been studied in many species: BAT of female mice has a greater thermogenic function due to a higher mitochondrial capacity than in males, and metabolically active BAT in the PET/CT imaging is more prevalent in women than in men. These sex-specific features are likely driven by sex hormones: estrogen and testosterone. However, the effect of progesterone, a major circulating female sex hormone during luteal phase and pregnancy, has been limitedly studied and available data are conflicting. We aimed to investigate the direct effects of progesterone on BAT differentiation and function using T37i, a female brown adipocyte cell line. T37i cells were differentiated with a standard regimen: 20 nM insulin and 2 nM triiodothyronine, with or without progesterone from 100 nM (a physiological circulating level) to 10 µM. After 9 days of differentiation, cells were collected for analysis or stimulated for 24 hours with 1 µM norepinephrine (NE). Progesterone dose-responsively reduced T37i differentiation. This is reflected by a 30% reduced lipid accumulation (quantified by Oil Red O staining), 37% decreased basal lipolytic activity (determined by glycerol release into the culture media), and decreased expression of adipogenic marker genes: Cd36 65%, Adipoq 68%, and Lep 93% reductions at the highest progesterone concentration. Concerning the thermogenic capacity of T37i cells, progesterone inhibited basal and NE-stimulated expressions of thermogenic genes (baseline Ucp1 98% and Ppargc1a 63% reductions; NE-stimulated Ucp1 97% and Ppargc1a 76% reductions) and reduced the NE-stimulated lipolysis by 50%. Moreover, short-term treatment with progesterone on differentiated T37i cells also reduced Ucp1, Adipoq, and Lep gene expressions. Interestingly, we could not detect Pgr mRNA expression in T37i cells. In conclusion, we demonstrated that progesterone inhibits the T37i brown adipocyte differentiation and thermogenic function, likely independently from the classical progesterone receptor, in a dose-dependent manner. Further studies are required to elucidate the mechanisms how progesterone inhibits BAT differentiation and functions.

Brown fat dissipates energy as heat by means of the uncoupling protein-1 (UCP1) on the mitochondrial inner membrane. Brown fat activity is inversely correlated with body mass index in humans, and pilot studies have shown that interventions such as chronic cold exposure successfully recruit human brown fat and increase systemic energy expenditure. Therefore, stimulating development and/or function of brown fat would be a novel strategy for the treatment of obesity and its complications. Here, we identified nuclear factor I-A (NFIA) as a transcriptional regulator of brown fat by a genome-wide open chromatin analysis of murine brown and white fat followed by motif analysis of the brown-fat-specific open chromatin regions. Introduction of NFIA into myoblasts results in brown adipocyte differentiation. Conversely, the brown fat of NFIA knockout mice displays impaired expression of the brown-fat-specific genes and reciprocal elevation of muscle genes. In human brown fat, expression of NFIA and the brown-fat-specific genes including UCP1 is positively correlated. Mechanistically, NFIA co-localizes with the master transcriptional regulator of adipogenesis, PPARgamma, selectively at the brown-fat-specific enhancers. Moreover, the binding of NFIA precedes and facilitates the binding of PPARgamma, leading to increased chromatin accessibility and active transcription. Most recently, we performed mass spectrometry analysis of NFIA protein complex to identify and characterize the crucial partner of NFIA-dependent brown-fat-specific chromatin regulation. Collectively, these results indicate that NFIA is a key transcription factor that activates the cell-type-specific enhancers and facilitates the binding of PPARgamma for controlling the brown fat gene program. Disclosure Y. Hiraike: Speaker's Bureau; Self; Novo Nordisk A/S. Research Support; Self; Novo Nordisk A/S, Mitsubishi Tanabe Pharma Corporation. H. Waki: Research Support; Self; MSD K.K., Novartis Pharma K.K., Boehringer Ingelheim Pharmaceuticals, Inc., Sanofi K.K., Ono Pharmaceutical Co., Ltd., Kyowa Hakko Kirin Co., Ltd., Takeda PHarmaceutical Co., Ltd.. S. Tsutsumi: None. H. Aburatani: None. T. Yamauchi: Research Support; Self; Novo Nordisk Inc., Daiichi Sankyo Company, Limited, Sanofi, Takeda, Tanabe-Mitsubishi. T. Kadowaki: Consultant; Self; Novo Nordisk A/S, AstraZeneca, Merck Sharp & Dohme Corp.. Research Support; Self; Kissei Pharmaceutical Co., Ltd., Taisho Pharmaceutical Co., Ltd., Sanofi, Kyowa Hakko Kirin Co., Ltd., Novo Nordisk A/S, Astellas Pharma, Daiichi Sankyo Company, Limited, Takeda, Mitsubishi Tanabe Pharma Corporation, Ono Pharmaceutical Co., Ltd., Merck Sharp & Dohme Corp., Nippon Boehringer Ingelheim Co. Ltd.. Speaker's Bureau; Self; Astellas Pharma, AstraZeneca, Merck Sharp & Dohme Corp., Ono Pharmaceutical Co., Ltd., Takeda, Eli Lilly and Company, Nippon Boehringer Ingelheim Co. Ltd., Novo Nordisk A/S.

Brown adipose tissue (BAT) is a unique thermogenic tissue in mammals that rapidly produces heat via nonshivering thermogenesis. Small mammalian hibernators have evolved the greatest capacity for BAT because they use it to rewarm from hypothermic torpor numerous times throughout the hibernation season. Although hibernator BAT physiology has been investigated for decades, recent efforts have been directed toward understanding the molecular underpinnings of BAT regulation and function using a variety of methods, from mitochondrial functional assays to ‘omics’ approaches. As a result, the inner-workings of hibernator BAT are now being illuminated. In this Review, we discuss recent research progress that has identified players and pathways involved in brown adipocyte differentiation and maturation, as well as those involved in metabolic regulation. The unique phenotype of hibernation, and its reliance on BAT to generate heat to arouse mammals from torpor, has uncovered new molecular mechanisms and potential strategies for biomedical applications.

GPR43, a G-protein coupled receptor recognizing short-chain fatty acids, has been reported to participate in many biological functions of white adipocytes, such as adipogenesis and lipolysis. However, the functional role of GPR43 in brown adipocytes is still not clear. In this study, we investigated the effects of the PPARγ agonist rosiglitazone on GPR43 expression in brown adipogenesis. The results demonstrated that GPR43 was expressed during the late phase of brown adipocyte differentiation, which could be further augmented by adipogenic agent rosiglitazone treatment. The PPARγ/RXR heterodimerization was found to be the key transcription factor for this enhancing effect of rosiglitazone on GPR43 expression. Taken together, these results suggested GPR43 levels might be regulated by PPARγ-activated events during brown adipocytes differentiation and reflect the adipogenesis status of brown adipocytes.

Brown adipose tissue (BAT) is specialized in non-shivering thermogenesis through the expression of the mitochondrial uncoupling protein-1 (UCP1). In this paper, we describe the relationship between UCP1 and proteins involved in ATP synthesis. By the use of BATIRKO mice, which have enhanced UCP1 expression in BAT, an increase in ATP synthase as well as in ubiquinol cytochrome c reductase levels was observed. Alterations in mitochondrial mass or variations in ATP levels were not observed in BAT of these mice. In addition, using a protocol of brown adipocyte differentiation, the concerted expression of UCP1 with ATP synthase was found. These two scenarios revealed that increases in the uncoupling machinery of brown adypocites must be concomitantly followed by an enhancement of proteins involved in ATP synthesis. These concerted changes reflect the need to maintain ATP production in an essentially uncoupling cell type.

Recent studies have demonstrated that adult humans have substantial amounts of functioning brown adipose tissue (BAT). Since BAT has been implicated as an anti-obese and anti-diabetic tissue, it is important to understand the signaling molecules that regulate BAT function. There has been a link between insulin signaling and BAT metabolism as deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function. Tribbles 3 (TRB3) is a pseudo kinase that has been shown to regulate metabolism and insulin signaling in multiple tissues but the role of TRB3 in BAT has not been studied. In this study, we found that TRB3 expression was present in BAT and overexpression of TRB3 in brown preadipocytes impaired differentiation and decreased expression of BAT markers. Furthermore, TRB3 overexpression resulted in significantly lower oxygen consumption rates for basal and proton leakage, indicating decreased BAT activity. Based on previous studies showing that deletion or pharmaceutical inhibition of insulin signaling impairs BAT differentiation and function, we assessed insulin signaling in brown preadipocytes and BAT in vivo. Overexpression of TRB3 in cells impaired insulin-stimulated IRS1 and Akt phosphorylation, whereas TRB3KO mice displayed improved IRS1 and Akt phosphorylation. Finally, deletion of IRS1 abolished the function of TRB3 to regulate BAT differentiation and metabolism. These data demonstrate that TRB3 inhibits insulin signaling in BAT, resulting in impaired differentiation and function.

Brown adipose tissue (BAT) is a specialized thermoregulatory organ that has a critical role in the regulation of energy metabolism. Specifically, energy expenditure can be enhanced by the activation of BAT function and the induction of a BAT-like catabolic phenotype in white adipose tissue (WAT). Since the recent recognition of metabolically active BAT in adult humans, BAT has been extensively studied as one of the most promising targets identified for treating obesity and its related disorders. In this review, we summarize information on the developmental origin of BAT and the progenitors of brown adipocytes in WAT. We explore the transcriptional control of brown adipocyte differentiation during classical BAT development and in WAT browning. We also discuss the neuronal control of BAT activity and summarize the recently identified non-canonical stimulators of BAT that can act independently of β-adrenergic stimulation. Finally, we review new findings on the beneficial effects of BAT activation and development with respect to improving metabolic profiles. We highlight the therapeutic potential of BAT and its future prospects, including pharmacological intervention and cell-based therapies designed to enhance BAT activity and development.

Until quite recently, brown adipose tissue was considered of metabolic significance only in small mammals and human newborns, since it was thought to disappear rapidly after birth in humans. However, nowadays this tissue is known to play a role in the regulation of energy balance not only in rodents, but also in humans. In this review we highlight new features regarding brown adipose tissue origin and function and revise old paradigms about brown adipocyte differentiation.

BackgroundBrown adipocytes play an important role in regulating the balance of energy, and as such, there is a strong correlation between obesity and the amount of brown adipose tissue. Although the molecular mechanism underlying white adipocyte differentiation has been well characterized, brown adipocyte differentiation has not been studied extensively. Here, we investigate the potential role of dual-specificity phosphatase 10 (DUSP10) in brown adipocyte differentiation using primary brown preadipocytes.Methods and resultsThe expression of DUSP10 increased continuously after the brown adipocyte differentiation of mouse primary brown preadipocytes, whereas the phosphorylation of p38 was significantly upregulated at an early stage of differentiation followed by steep downregulation. The overexpression of DUSP10 induced a decrease in the level of p38 phosphorylation, resulting in lower lipid accumulation than that in cells overexpressing the inactive mutant DUSP10. The expression levels of several brown adipocyte markers such as PGC-1α, UCP1, and PRDM16 were also significantly reduced upon the ectopic expression of DUSP10. Furthermore, decreased mitochondrial DNA content was detected in cells expressing DUSP10. The results obtained upon treatment with the p38 inhibitor, SB203580, clearly indicated that the phosphorylation of p38 at an early stage is important in brown adipocyte differentiation. The effect of the p38 inhibitor was partially recovered by DUSP10 knockdown using RNAi.ConclusionsThese results suggest that p38 phosphorylation is controlled by DUSP10 expression. Furthermore, p38 phosphorylation at an early stage is critical in brown adipocyte differentiation. Thus, the regulation of DUSP10 activity affects the efficiency of brown adipogenesis. Consequently, DUSP10 can be used as a novel target protein for the regulation of obesity.

Brown adipocytes burn chemical energy to produce heat for protection against hypothermia and obesity. Sellayah et al. now reveal that a secreted neuropeptide, Orexin, functions a key driver of brown adipocyte differentiation through direct actions on brown adipose precursors.