Nicotinamide Protects Against Diet-Induced Body Weight Gain, Increases Energy Expenditure, and Induces White Adipose Tissue Beiging.

SCOPE: Interventions that boost NAD+ availability are of potential therapeutic interest for obesity treatment. The potential of nicotinamide (NAM), the amide form of vitamin B3 and a physiological precursor of nicotinamide adenine dinucleotide (NAD)+ , in preventing weight gain has not previously been studied in vivo. Other NAD+ precursors have been shown to decrease weight gain; however, their impact on adipose tissue is not addressed. METHODS AND RESULTS: Two doses of NAM (high dose: 1% and low dose: 0.25%) are given by drinking water to C57BL/6J male mice, starting at the same time as the high-fat diet feeding. NAM supplementation protects against diet-induced obesity by augmenting global body energy expenditure in C57BL/6J male mice. The manipulation markedly alters adipose morphology and metabolism, particularly in inguinal (i) white adipose tissue (iWAT). An increased number of brown and beige adipocyte clusters, protein abundance of uncoupling protein 1 (UCP1), mitochondrial activity, adipose NAD+ , and phosphorylated AMP-activated protein kinase (P-AMPK) levels are observed in the iWAT of treated mice. Notably, a significant improvement in hepatic steatosis, inflammation, and glucose tolerance is also observed in NAM high-dose treated mice. CONCLUSION: NAM influences whole-body energy expenditure by driving changes in the adipose phenotype. Thus, NAM is an attractive potential treatment for preventing obesity and associated complications.

The natural compound rutaecarpine promotes white adipocyte browning through activation of the AMPK-PRDM16 axis.

The prevalence of obesity is increasing globally and is associated with many metabolic disorders, such as type 2 diabetes and cardiovascular diseases. In recent years, a number of studies suggest that promotion of white adipose browning represents a promising strategy to combat obesity and its related metabolic disorders. The aim of this study was to identify compounds that induce adipocyte browning and elucidate their mechanism of action. Among the 500 natural compounds screened, a small molecule named Rutaecarpine, was identified as a positive regulator of adipocyte browning both in vitro and in vivo. KEGG pathway analysis from RNA-seq data suggested that the AMPK signaling pathway was regulated by Rutaecarpine, which was validated by Western blot analysis. Furthermore, inhibition of AMPK signaling mitigated the browning effect of Rutaecaripine. The effect of Rutaecaripine on adipocyte browning was also abolished upon deletion of Prdm16, a downstream target of AMPK pathway. In collusion, Rutaecarpine is a potent chemical agent to induce adipocyte browning and may serve as a potential drug candidate to treat obesity.

No Effect of Dietary Fish Oil Supplementation on the Recruitment of Brown and Brite Adipocytes in Mice or Humans under Thermoneutral Conditions.

SCOPE: Brown and brite adipocytes within the mammalian adipose organ provide non-shivering thermogenesis and thus, have an exceptional capacity to dissipate chemical energy as heat. Polyunsaturated fatty acids (PUFA) of the n3-series, abundant in fish oil, have been repeatedly demonstrated to enhance the recruitment of thermogenic capacity in these cells, consequently affecting body adiposity and glucose tolerance. These effects are scrutinized in mice housed in a thermoneutral environment and in a human dietary intervention trial. METHODS AND RESULTS: Mice are housed in a thermoneutral environment eliminating the superimposing effect of mild cold-exposure on thermogenic adipocyte recruitment. Dietary fish oil supplementation in two different inbred mouse strains neither affects body mass trajectory nor enhances the recruitment of brown and brite adipocytes, both in the presence and absence of a ß3-adrenoreceptor agonist imitating the effect of cold-exposure on adipocytes. In line with these findings, dietary fish oil supplementation of persons with overweight or obesity fails to recruit thermogenic adipocytes in subcutaneous adipose tissue. CONCLUSION: Thus, the authors' data question the hypothesized potential of n3-PUFA as modulators of adipocyte-based thermogenesis and energy balance regulation.

The Rosmarinus Bioactive Compound Carnosic Acid Is a Novel PPAR Antagonist That Inhibits the Browning of White Adipocytes.

Thermogenic brown and brite adipocytes convert chemical energy from nutrients into heat. Therapeutics that regulate brown adipocyte recruitment and activity represent interesting strategies to control fat mass such as in obesity or cachexia. The peroxisome proliferator-activated receptor (PPAR) family plays key roles in the maintenance of adipose tissue and in the regulation of thermogenic activity. Activation of these receptors induce browning of white adipocyte. The purpose of this work was to characterize the role of carnosic acid (CA), a compound used in traditional medicine, in the control of brown/brite adipocyte formation and function. We used human multipotent adipose-derived stem (hMADS) cells differentiated into white or brite adipocytes. The expression of key marker genes was determined using RT-qPCR and western blotting. We show here that CA inhibits the browning of white adipocytes and favors decreased gene expression of thermogenic markers. CA treatment does not affect ß-adrenergic response. Importantly, the effects of CA are fully reversible. We used transactivation assays to show that CA has a PPARα/γ antagonistic action. Our data pinpoint CA as a drug able to control PPAR activity through an antagonistic effect. These observations shed some light on the development of natural PPAR antagonists and their potential effects on thermogenic response.

Vitamin D ameliorates adipose browning in chronic kidney disease cachexia.

Patients with chronic kidney disease (CKD) are often 25(OH)D3 and 1,25(OH)2D3 insufficient. We studied whether vitamin D repletion could correct aberrant adipose tissue and muscle metabolism in a mouse model of CKD-associated cachexia. Intraperitoneal administration of 25(OH)D3 and 1,25(OH)2D3 (75 µg/kg/day and 60 ng/kg/day respectively for 6 weeks) normalized serum concentrations of 25(OH)D3 and 1,25(OH)2D3 in CKD mice. Vitamin D repletion stimulated appetite, normalized weight gain, and improved fat and lean mass content in CKD mice. Vitamin D supplementation attenuated expression of key molecules involved in adipose tissue browning and ameliorated expression of thermogenic genes in adipose tissue and skeletal muscle in CKD mice. Furthermore, repletion of vitamin D improved skeletal muscle fiber size and in vivo muscle function, normalized muscle collagen content and attenuated muscle fat infiltration as well as pathogenetic molecular pathways related to muscle mass regulation in CKD mice. RNAseq analysis was performed on the gastrocnemius muscle. Ingenuity Pathway Analysis revealed that the top 12 differentially expressed genes in CKD were correlated with impaired muscle and neuron regeneration, enhanced muscle thermogenesis and fibrosis. Importantly, vitamin D repletion normalized the expression of those 12 genes in CKD mice. Vitamin D repletion may be an effective therapeutic strategy for adipose tissue browning and muscle wasting in CKD patients.

Adipogenic commitment induced by green tea polyphenols remodel adipocytes to a thermogenic phenotype.

The potential contribution of green tea (GT) to the development of thermogenic/beige cells have been scarcely investigated. Here we investigated if the beneficial effects of GT in the induction of thermogenic/beige adipocytes results from an initial cell commitment during adipogenesis. Male C57Bl/6 mice (3 months) were divided into 3 groups: Control (chow diet), Obese (cafeteria diet), and Obese + GT. Mice received GT gavage (500 mg/kg of BW) over 12 weeks (5 days/week), after 4 weeks of diet, totalizing 16 weeks of experimentation. GT treatment increased energy expenditure (EE) in mice fed with cafeteria-diet leading to reduced BW gain, decreased adiposity, reduced inflammation, and improving insulin sensitivity. Those phenotypes were associated with enhanced expression of oxidative, thermogenic and beige genes. GT induced a futile cycle through de novo lipogenesis activating the thermogenic pathway. Induction of beige phenotype occurs autonomously in adipocytes and involves the PPARγ/FGF21/AMPK/UCP1 pathway. Our study identified that metabolic changes caused by GT may involve the temporal expression of PPARγ promoting the induction of thermogenic cells by reprogramming initial steps of adipocyte commitment.

Dietary apple polyphenols promote fat browning in high-fat diet-induced obese mice through activation of adenosine monophosphate-activated protein kinase α.

BACKGROUND: Promoting brown and beige adipogenesis contributes to adaptive thermogenesis, which provides a defense against obesity and related disorders. Apple polyphenols (APs) play a significant role in treating variety of metabolic diseases. This study was conducted to determine the effects of APs on the development of brown and beige adipocytes and thermogenesis and investigate whether these effects are mediated by adenosine monophosphate-activated protein kinase (AMPK). High-fat diet (HFD)-induced obese mice and differentiated 3T3-L1 adipocytes were subjected to APs treatment. The thermogenic program and associated regulatory factors, and the involvement of AMPKα was assessed. RESULTS: Dietary APs supplementation reduced adiposity and improved insulin sensitivity in HFD-induced obese mice. Moreover, APs increased the oxygen consumption and heat production and decreased respiratory exchange ratio, which were accompanied by the upregulation of thermogenic genes expression and the activation of AMPKα in brown fat and inguinal white fat. Further, APs treatment directly increased expression of brown adipogenic markers and induced phosphorylation of AMPKα in differentiated 3T3-L1 adipocytes, whereas the beneficial effects of APs were reversed by AMPK inhibition. CONCLUSION: Our results provide new insights into the function of APs in regulating brown/beige adipogenesis and adaptive thermogenesis and suggest the potential application of APs in the prevention and therapeutics of obesity and associated metabolic diseases. © 2020 Society of Chemical Industry.

Antiobesity effects of coumestrol through expansion and activation of brown adipose tissue metabolism.

Coumestrol is a dietary phytoestrogen with estrogen-mimicking characteristics. This study investigated the molecular mechanisms of antiobesity effects of coumestrol. Two weeks of coumestrol treatment reduced body weight and improved glucose tolerance of high-fat diet (HFD)-fed mice. Notably, coumestrol treatment reduced adiposity but expanded brown adipose tissue mass. In addition, coumestrol treatment induced up-regulation of brown adipocyte markers and lipolytic gene expression in adipose tissue. Mechanistically, coumestrol induced an increase in mitochondrial contents of brown adipose tissue, which was associated with up-regulation of adenosine monophosphate-activated protein kinase and sirtuin 1. In vitro knockdown of estrogen receptor 1 inhibited the effect of coumestrol on brown adipogenic marker expression, increase in mitochondrial contents and oxygen consumption rate in brown adipocytes. Furthermore, lineage tracing of platelet-derived growth factor receptor A-positive (PDGFRA+) adipocyte progenitors confirmed increased levels of de novo brown adipogenesis from PDGFRA+ cells by coumestrol treatment. In conclusion, our results indicate that coumestrol has antiobesity effects through the expansion and activation of brown adipose tissue metabolism.

Black Raspberry (Rubus coreanus Miquel) Promotes Browning of Preadipocytes and Inguinal White Adipose Tissue in Cold-Induced Mice.

The alteration of white adipose tissue (WAT) "browning", a change of white into beige fat, has been considered as a new therapeutic strategy to treat obesity. In this study, we investigated the browning effect of black raspberry (Rubus coreanus Miquel) using in vitro and in vivo models. Black raspberry water extract (BRWE) treatment inhibited lipid accumulation in human mesenchymal stem cells (hMSCs) and zebrafish. To evaluate the thermogenic activity, BRWE was orally administered for 2 weeks, and then, the mice were placed in a 4 °C environment. As a result, BRWE treatment increased rectal temperature and inguinal WAT (iWAT) thermogenesis by inducing the expression of beige fat specific markers such as PR domain zinc-finger protein 16 (PRDM16), uncoupling protein 1 (UCP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α), and t-box protein 1 (TBX1) in cold-exposed mice. Furthermore, ellagic acid (EA), a constituent of BRWE, markedly promoted beige specific markers: UCP1, PGC1α, TBX1, and nuclear respiratory factor 1 in beige differentiation media (DM)-induced 3T3-L1 adipocytes. Our findings indicate that BRWE can promote beige differentiation/activation, and EA is the active compound responsible for such effect. Thus, we suggest the nature-derived agents BRWE and EA as potential agents for obesity treatment.

Immature Citrus reticulata Extract Promotes Browning of Beige Adipocytes in High-Fat Diet-Induced C57BL/6 Mice.

Obesity has become a global public health issue. Promoting browning of white adipose tissue (WAT) helps to maintain energy homeostasis. Previous studies have found that citrus fruit exhibits a number of biological activities. Although most citrus fruit drop has been considered agricultural waste, the ability to use it may be desirable. In this study, we investigate the antiobesity effects of immature citrus fruits in high-fat diet (HFD)-fed mice. The main phytochemical components of immature Citrus reticulata in water extraction analyzed by HPLC are synephrine, narirutin, hesperidin, nobiletin, and tangeretin (16.0 ± 1.08, 4.52 ± 0.31, 9.14 ± 0.32, 2.54 ± 0.07, 1.67 ± 0.05 mg/g, respectively). Oral administration of 1% immature Citrus reticulata extract (ICRE) for 11 weeks markedly reduced body weight gain, epididymal fat weight, fasting blood glucose, serum triglyceride, and total cholesterol ( P < 0.05 for all). In addition, histological analysis revealed that dietary ICRE decreased adipocyte size and hepatic steatosis compared to the HFD group ( P < 0.05 for both). Furthermore, we found that mice treated with ICRE have improved cold tolerance during acute cold challenge. These effects were associated with increased expression of uncoupling protein 1 (UCP1) and thermogenic genes in inguinal WAT. Taken together, these results suggest that ICRE can prevent obesity and lipid accumulation through induction of brown-like adipocyte formation.

Raspberry promotes brown and beige adipocyte development in mice fed high-fat diet through activation of AMP-activated protein kinase (AMPK) α1.

Development of brown and beige/brite adipocytes increases thermogenesis and helps to reduce obesity and metabolic syndrome. Our previous study suggests that dietary raspberry can ameliorate metabolic syndromes in diet-induced obese mice. Here, we further evaluated the effects of raspberry on energy expenditure and adaptive thermogenesis and determined whether these effects were mediated by AMP-activated protein kinase (AMPK). Mice deficient in the catalytic subunit of AMPKα1 and wild-type (WT) mice were fed a high-fat diet (HFD) or HFD supplemented with 5% raspberry (RAS) for 10 weeks. The thermogenic program and related regulatory factors in adipose tissue were assessed. RAS improved the insulin sensitivity and reduced fat mass in WT mice but not in AMPKα1-/- mice. In the absence of AMPKα1, RAS failed to increase oxygen consumption and heat production. Consistent with this, the thermogenic gene expression in brown adipose tissue and brown-like adipocyte formation in subcutaneous adipose tissue were not induced by RAS in AMPKα1-/- mice. In conclusion, AMPKα1 is indispensable for the effects of RAS on brown and beige/brite adipocyte development, and prevention of obesity and metabolic dysfunction.

Phytol stimulates the browning of white adipocytes through the activation of AMP-activated protein kinase (AMPK) α in mice fed high-fat diet.

Stimulating the browning of white adipocytes contributes to the restriction of obesity and related metabolic disorders. This study aimed to investigate the browning effects of phytol on mice inguinal subcutaneous white adipose tissue (iWAT) and explore the underlying mechanisms. Our results demonstrated that phytol administration decreased body weight gain and iWAT index, and stimulated the browning of mice iWAT, with the increased expression of brown adipocyte marker genes (UCP1, PRDM16, PGC1α, PDH, and Cyto C). In addition, phytol treatment activated the AMPKα signaling pathway in mice iWAT. In good agreement with the in vivo findings, the in vitro results showed that 100 µM phytol stimulated brown adipogenic differentiation and formation of brown-like adipocytes in the differentiated 3T3-L1 by increasing the mitochondria content and oxygen consumption, and promoting mRNA and/or protein expression of brown adipocyte markers (UCP1, PRDM16, PGC1α, PDH, Cyto C, Cidea and Elovl3) and beige adipocyte markers (CD137 and TMEM26). Meanwhile, phytol activated the AMPKα signaling pathway in the differentiated 3T3-L1. However, the inhibition of AMPKα with Compound C totally abolished phytol-stimulated brown adipogenic differentiation and formation of brown-like adipocytes. In conclusion, these results showed that phytol stimulated the browning of mice iWAT, which was coincident with the increased formation of brown-like adipocytes in the differentiated 3T3-L1, and appeared to be primarily mediated by the AMPKα signaling pathway. These data provided new insight into the role of phytol in regulating the browning of WAT and suggested the potential application of phytol as a nutritional intervention for the restriction of obesity and related metabolic disorders.

Moderate alcohol intake induces thermogenic brown/beige adipocyte formation via elevating retinoic acid signaling.

Clinically, low and moderate alcohol intake improves human health with protection against metabolic syndromes, including type 2 diabetes; however, mechanisms that are associated with these effects remain to be elucidated. The aims of this study were to investigate the effects of moderate alcohol intake on thermogenic brown/beige adipocyte formation and glucose and lipid homeostasis, as well as the involvement of retinoic acid (RA) signaling in the entire process. C57BL6 male mice were supplemented with 8% (w/v) alcohol in water for 1 or 4 mo. Alcohol intake prevented body weight gain, induced the formation of uncoupling protein 1-positive beige adipocytes in white adipose tissue, and increased thermogenesis in mice, which is associated with decreased serum glucose and triacylglycerol levels. Mechanistically, alcohol intake increased RA levels in serum and adipose tissue, which was associated with increased expression of aldehyde dehydrogenase family 1 subfamily A1 (Aldh1a1). When RA receptor-α signaling was conditionally blocked in platelet-derived growth factor receptor-α-positive adipose progenitors, the effects of alcohol on beige adipogenesis were largely abolished. Finally, moderate alcohol prevented high-fat diet-induced obesity and metabolic dysfunction. In conclusion, moderate alcohol intake induces thermogenic brown/beige adipocyte formation and promotes glucose and lipid oxidation via elevation of RA signaling.-Wang, B., Wang, Z., de Avila, J. M., Zhu, M.-J., Zhang, F., Gomez, N. A., Zhao, L., Tian, Q., Zhao, J., Maricelli, J., Zhang, H., Rodgers, B. D., Du, M. Moderate alcohol intake induces thermogenic brown/beige adipocyte formation via elevating retinoic acid signaling.

Using Thermogenic Beige Cells to Identify Biologically Active Small Molecules and Peptides.

Incorporating molecular libraries in chemical biology screenings in cultured cells has been successfully used for gene discovery in many cellular processes. It has the unique potential to uncover novel mechanisms of complex cellular biology through the screening of small molecules and protein biologics in relevant cell-based assays. Recent development in the understanding and generation of thermogenic adipocytes provides opportunities for potential anti-obesity therapeutics discovery. In this chapter, we describe screening methods using thermogenic beige cells to identify novel compounds and peptides that activate adipocyte thermogenesis.

A Synergistic Antiobesity Effect by a Combination of Capsinoids and Cold Temperature Through Promoting Beige Adipocyte Biogenesis.

Beige adipocytes emerge postnatally within the white adipose tissue in response to certain environmental cues, such as chronic cold exposure. Because of its highly recruitable nature and relevance to adult humans, beige adipocytes have gained much attention as an attractive cellular target for antiobesity therapy. However, molecular circuits that preferentially promote beige adipocyte biogenesis remain poorly understood. We report that a combination of mild cold exposure at 17°C and capsinoids, a nonpungent analog of capsaicin, synergistically and preferentially promotes beige adipocyte biogenesis and ameliorates diet-induced obesity. Gain- and loss-of-function studies show that the combination of capsinoids and cold exposure synergistically promotes beige adipocyte development through the ß2-adrenoceptor signaling pathway. This synergistic effect on beige adipocyte biogenesis occurs through an increased half-life of PRDM16, a dominant transcriptional regulator of brown/beige adipocyte development. We document a previously unappreciated molecular circuit that controls beige adipocyte biogenesis and suggest a plausible approach to increase whole-body energy expenditure by combining dietary components and environmental cues.