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.

Integrated UHPLC-QE/MS, transcriptomics and network pharmacology reveal the mechanisms via which Liang-Yan-Yi-Zhen-San promotes the browning of white adipose tissue.

We have previously shown that Liang-Yan-Yi-Zhen-San (LYYZS), an ancient Chinese herbal formula, can promote the browning of white adipose tissue. In this study, we sought to determine which active ingredients of LYYZS mediated its effects on the browning of white adipose tissue. Employing ultra-high performance liquid chromatography-Q-Exactive HF mass spectrometry, a total of 52 LYYZS ingredients were identified. On this basis, 1,560 ingredient-related targets of LYYZS were screened using the HERB databases. Meanwhile, RNA sequencing analysis of the inguinal white adipose tissue of mice produced a total of 3148 genes that were significantly differentially expressed following LYYZS treatment and differentially expressed genes regarded as browning-related targets. Through the network pharmacological analysis, a total of 136 intersection targets were obtained and an ingredient-target-pathway network was established. According to network pharmacology analysis, 10 ingredients containing trans-cinnamaldehyde, genistein, daidzein, calycosin, arginine, coumarin, oleic acid, isoleucine, palmitic acid and tyrosine were regarded as active ingredients of browning of white adipose tissue. Integrated evaluation using chemical analysis, transcriptomics and network pharmacology provides an efficient strategy for discovering the active ingredients involved in how LYYZS promotes the browning of white adipose tissue.

Extracellular thiamine concentration influences thermogenic competency of differentiating neck area-derived human adipocytes.

Introduction: Brown adipose tissue (BAT) dissipates energy in the form of heat majorly via the mitochondrial uncoupling protein 1 (UCP1). The activation of BAT, which is enriched in the neck area and contains brown and beige adipocytes in humans, was considered as a potential therapeutic target to treat obesity. Therefore, finding novel agents that can stimulate the differentiation and recruitment of brown or beige thermogenic adipocytes are important subjects for investigation. The current study investigated how the availability of extracellular thiamine (vitamin B1), an essential cofactor of mitochondrial enzyme complexes that catalyze key steps in the catabolism of nutrients, affects the expression of thermogenic marker genes and proteins and subsequent functional parameters during ex vivo adipocyte differentiation. Methods: We differentiated primary human adipogenic progenitors that were cultivated from subcutaneous (SC) or deep neck (DN) adipose tissues in the presence of gradually increasing thiamine concentrations during their 14-day differentiation program. mRNA and protein expression of thermogenic genes were analyzed by RT-qPCR and western blot, respectively. Cellular respiration including stimulated maximal and proton-leak respiration was measured by Seahorse analysis. Results: Higher thiamine levels resulted in increased expression of thiamine transporter 1 and 2 both at mRNA and protein levels in human neck area-derived adipocytes. Gradually increasing concentrations of thiamine led to increased basal, cAMP-stimulated, and proton-leak respiration along with elevated mitochondrial biogenesis of the differentiated adipocytes. The extracellular thiamine availability during adipogenesis determined the expression levels of UCP1, PGC1a, CKMT2, and other browning-related genes and proteins in primary SC and DN-derived adipocytes in a concentration-dependent manner. Providing abundant amounts of thiamine further increased the thermogenic competency of the adipocytes. Discussion: Case studies in humans reported that thiamine deficiency was found in patients with type 2 diabetes and obesity. Our study raises the possibility of a novel strategy with long-term thiamine supplementation, which can enhance the thermogenic competency of differentiating neck area-derived adipocytes for preventing or combating obesity.

DHA alleviated hepatic and adipose inflammation with increased adipocyte browning in high-fat diet-induced obese mice.

Obesity is associated with accumulation of inflammatory immune cells in white adipose tissue, whereas thermogenic browning adipose tissue is inhibited. Dietary fatty acids are important nutritional components and several clinical and experimental studies have reported beneficial effects of docosahexaenoic acid (DHA) on obesity-related metabolic changes. In this study, we investigated effects of DHA on hepatic and adipose inflammation and adipocyte browning in high-fat diet-induced obese C57BL/6J mice, and in vitro 3T3-L1 preadipocyte differentiation. Since visceral white adipose tissue has a close link with metabolic abnormality, epididymal adipose tissue represents current target for evaluation. A course of 8-week DHA supplementation improved common phenotypes of obesity, including improvement of insulin resistance, inhibition of macrophage M1 polarization, and preservation of macrophage M2 polarization in hepatic and adipose tissues. Moreover, dysregulated adipokines and impaired thermogenic and browning molecules, considered obesogenic mechanisms, were improved by DHA, along with parallel alleviation of endoplasmic reticulum (ER) stress, mitochondrial dysfunction, and mitochondrial DNA stress-directed innate immunity. During 3T3-L1 preadipocytes differentiation, DHA treatment decreased lipid droplet accumulation and increased the levels of thermogenic, browning, and mitochondrial biogenesis molecules. Our study provides experimental evidence that DHA mitigates obesity-associated inflammation and induces browning of adipose tissue in visceral epididymal adipose tissue. Since obesity is associated with metabolic abnormalities across tissues, our findings indicate that DHA may have potential as part of a dietary intervention to combat obesity.

Low Dose of Curcumin Combined with Exercise Synergistically Induces Beige Adipocyte Formation in Mice.

Curcumin (Cur) has various biological effects, including anti-obesity and anti-diabetic properties. However, the molecular mechanisms by which Cur exerts these effects remain unclear. In addition, high doses of Cur have been administered in most animal and human trials to date, due mainly to the poor water solubility of native Cur and its low oral bioavailability. In our previous study, we demonstrated that a highly bioavailable Cur formulation (4.5 mg/kg) induces the formation of beige adipocytes in inguinal white adipose tissue (iWAT) in mice. In the present study, to enhance Cur-mediated beige adipocyte formation and reduce the required functional Cur dose, we investigated whether a low dose of Cur combined with exercise synergistically induced beige adipocyte formation. Cur (1.5 mg Cur/kg, daily) combined with exercise for 4 wk significantly induced beige adipocyte formation in iWAT in mice. This effect was associated with the elevation of interleukin-6 level following subsequent Cur administration combined with exercise. These results indicate that exercise combined with Cur synergistically enhances biological activity and reduces the required Cur dose. These findings suggest that Cur could be used as a dietary supplement during exercise to enhance exercise-mediated health benefits.

Green Tea Epigallocatechin Gallate Inhibits Preadipocyte Growth via the microRNA-let-7a/HMGA2 Signaling Pathway.

SCOPE: This study investigates the effect of epigallocatechin gallate (EGCG) on white and beige preadipocyte growth and explores the involvement of the miR-let-7a/HMGA2 pathway. METHODS AND RESULTS: 3T3-L1 and D12 cells are treated with EGCG. The effect of EGCG on cell proliferation and viability is evaluated, as well as microRNA (miRNA)-related signaling pathways. EGCG inhibits 3T3-L1 and D12 preadipocyte growth, upregulates miR-let-7a expression, and downregulates high-mobility group AT-hook 2 (HMGA2) mRNA and protein levels in a time- and dose-dependent manner. In addition, overexpression of miR-let-7a significantly inhibits the growth of 3T3-L1 and D12 cells and decreases HMGA2 mRNA and protein levels. MiR-let-7a inhibitor antagonizes the inhibitory effects of EGCG on the number and viability of 3T3-L1 and D12 cells. Furthermore, miR-let-7a inhibitor reverses the EGCG-induced increase in miR-let-7a expression levels and decrease in HMGA2 mRNA and protein levels. HMGA2 overexpression induces an increase in cell number and viability and antagonizes EGCG-suppressed cell growth and HMGA2 expression in 3T3-L1 and D12 preadipocytes. CONCLUSION: EGCG inhibits the growth of 3T3-L1 and D12 preadipocytes by modulating the miR-let-7a and HMGA2 pathways.

Hyperoside prevents high-fat diet-induced obesity by increasing white fat browning and lipophagy via CDK6-TFEB pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Hypericum perforatum L. (genus Hypericum, family Hypericaceae) is a flowering plant native to Europe, North Africa and Asia, which can be used in the treatment of psychiatric disorder, cardiothoracic depression and diabetes. Crataegus pinnatifida Bunge (genus Crataegus pinnatifida Bunge, family Rosaceae) was another traditional Chinese medicine for treating hyperlipidemia. Hyperoside (Hype), a major flavonoid glycoside component of Hypericum perforatum L. and Crataegus pinnatifida Bunge, possesses multiple physiological activities, such as anti-inflammatory and antioxidant effects. However, the role of Hype on obesity and related metabolic diseases still needs to be further investigated. AIM OF THE STUDY: We explored the effect of Hype on high-fat diet (HFD)-induced obesity and its metabolic regulation on white fat tissues. MATERIALS AND METHODS: In vivo four-week-old male C57BL/6J mice were randomly assigned to vehicle (0.5% methycellulose) and Hype (80 mg/kg/day by gavage) group under a normal chow diet (NCD) or HFD for 8 weeks. In vitro, 3T3-L1 preadipocyte cell line and primary stromal vascular fraction (SVF) cells from inguinal white adipose tissue (iWAT) of mice were used to investigate the molecular mechanisms of Hype regulation on adipocyte energy metabolism. RESULTS: Hype treatment in vivo promotes UCP1-dependent white to beige fat transition, increases glucose and lipid metabolism, and resists HFD-induced obesity. Meanwhile, Hype induces lipophagy, a specific autophagy that facilitates the breakdown of lipid droplets, and blocking autophagy partially reduces UCP1 expression. Mechanistically, Hype inhibited CDK6, leading to the increased nuclear translocation of TFEB, while overexpression of CDK6 partially reversed the enhancement of UCP1 by Hype. CONCLUSIONS: Hype protects mice from HFD-induced obesity by increasing energy expenditure of white fat tissue via CDK6-TFEB pathway.

Dietary selenomethionine attenuates obesity by enhancing beiging process in white adipose tissue.

Imbalanced nutrient intake causes abnormal energy metabolism, which results in obesity. There is feasible evidence that selenium-rich (Se-rich) foods may alleviate obesity and enhance general public health, but the underlying mechanisms remain elusive. Herein we examined the effect of Se supplementation on white adipose tissue beiging process. The mice were fed with a normal diet or a Se-deficient high-fat diet (DHFD) until significant differences in terms of body weight, glucose tolerance and insulin sensitivity. Next, mice in the DHFD group were changed to a high-fat diet (HFD) containing specified amounts of selenomethionine (SeMet) (0, 150, 300, and 600 µg/kg) and continued to feed for 14 weeks. Notably, 150 µg/kg SeMet supplement highly protected mice from DHFD-induced obesity, insulin resistance, and lipid deposits in the liver and kidney, and featured by the enhanced beiging process in white adipose tissue and increased energy expenditure. Moreover, upon cold challenge, 150 µg/kg SeMet supplement enhanced cold tolerance in mice by inducing adipose beiging to promote energy expenditure, as evidenced by the increased expression of uncoupling protein-1 (UCP1) in adipocytes. Similarly, SeMet (10 µM) promoted the differentiation of beige adipocytes from the stromal vascular fraction. Collectively, our data support that optimal supplementation of SeMet could enhance the beiging process to attenuate HFD-induced obesity, which provides new insights into the relationship between dietary SeMet and type 2 diabetes.

The effects of taurine supplementation on obesity and browning of white adipose tissue in high-fat diet-fed mice.

Background: In recent years, a new type of adipose tissue (beige adipose tissue) has been mentioned, unlike white adipose tissue (WAT) and brown adipose tissue (BAT). Beige cells are capable of thermogenesis like BAT. In response to various agents, beige cells can develop within WAT through a process called "browning." Therefore, the prevention of obesity and related diseases by providing WAT browning with new potential agents has been extensively studied in recent years. Taurine has many physiological functions in the body and has beneficial effects on obesity and related metabolic disorders. For this reason, we aimed to investigate whether taurine supplementation has effects on browning of WAT and attenuating obesity. Methods: Thirty-two male C57BL/6 mice were used for the study. Mice were divided into 4 groups as control, control + taurine, high fat diet (HFD) and HFD + taurine, and fed for 20 weeks. Taurine was given in drinking water (5%). Epididymal WAT samples were obtained from mice and RNA was extracted from these tissues. Expression levels of FLCN, mTOR, TFE3, PGC-1α, PGC1-1ß, AMPK, S6K and UCP1 genes were measured by real-time PCR. Results: Taurine supplementation reduced HFD-induced obesity. No UCP1 expression was detected in any of the groups studied. Any of the gene expressions were not significantly different between HFD and HFD + taurine groups. Reduced PGC-1α and PGC-1ß expressions were observed in both HFD and HFD + taurine groups. Conclusions: Taurine reduced the obesity in HFD fed mice, but had no effect on browning of epididymal WAT in this study.

Lipolysis-derived linoleic acid drives beige fat progenitor cell proliferation.

De novo beige adipocyte biogenesis involves the proliferation of progenitor cells in white adipose tissue (WAT); however, what regulates this process remains unclear. Here, we report that in mouse models but also in human tissues, WAT lipolysis-derived linoleic acid triggers beige progenitor cell proliferation following cold acclimation, ß3-adrenoceptor activation, and burn injury. A subset of adipocyte progenitors, as marked by cell surface markers PDGFRα or Sca1 and CD81, harbored cristae-rich mitochondria and actively imported linoleic acid via a fatty acid transporter CD36. Linoleic acid not only was oxidized as fuel in the mitochondria but also was utilized for the synthesis of arachidonic acid-derived signaling entities such as prostaglandin D2. Oral supplementation of linoleic acid was sufficient to stimulate beige progenitor cell proliferation, even under thermoneutral conditions, in a CD36-dependent manner. Together, this study provides mechanistic insights into how diverse pathophysiological stimuli, such as cold and burn injury, promote de novo beige fat biogenesis.

Low-dose lithium supplementation promotes adipose tissue browning and sarco(endo)plasmic reticulum Ca2+ ATPase uncoupling in muscle.

Sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) uncoupling in skeletal muscle and mitochondrial uncoupling via uncoupling protein 1 (UCP1) in brown/beige adipose tissue are two mechanisms implicated in energy expenditure. Here, we investigated the effects of glycogen synthase kinase 3 (GSK3) inhibition via lithium chloride (LiCl) treatment on SERCA uncoupling in skeletal muscle and UCP1 expression in adipose. C2C12 and 3T3-L1 cells treated with LiCl had increased SERCA uncoupling and UCP1 protein levels, respectively, ultimately raising cellular respiration; however, this was only observed when LiCl treatment occurred throughout differentiation. In vivo, LiCl treatment (10 mg/kg/day) increased food intake in chow-fed diet and high-fat diet (HFD; 60% kcal)-fed male mice without increasing body mass-a result attributed to elevated daily energy expenditure. In soleus muscle, we determined that LiCl treatment promoted SERCA uncoupling via increased expression of SERCA uncouplers, sarcolipin and/or neuronatin, under chow-fed and HFD-fed conditions. We attribute these effects to the GSK3 inhibition observed with LiCl treatment as partial muscle-specific GSK3 knockdown produced similar effects. In adipose, LiCl treatment inhibited GSK3 in inguinal white adipose tissue (iWAT) but not in brown adipose tissue under chow-fed conditions, which led to an increase in UCP1 in iWAT and a beiging-like effect with a multilocular phenotype. We did not observe this beiging-like effect and increase in UCP1 in mice fed a HFD, as LiCl could not overcome the ensuing overactivation of GSK3. Nonetheless, our study establishes novel regulatory links between GSK3 and SERCA uncoupling in muscle and GSK3 and UCP1 and beiging in iWAT.

Natural bioactive constituents from herbs and nutraceuticals promote browning of white adipose tissue.

Obesity is a significant public health problem worldwide that is characterized by abnormal or excessive fat accumulation. Unfortunately, the application of available weight-loss drugs has been restricted because of their serious adverse effects. Browning of white adipose tissue (WAT), which refers to the transformation of white adipocytes to beige adipocytes under certain stimulations, is regarded as a new strategy to solve the obesity problem. Numerous studies have recently evidenced that traditional Chinese medicine (TCM) could promote browning of WAT with multi-component and multi-target characteristics. This article summarizes natural constituents from TCM with stimulatory effects on browning of WAT in the past two decades. The active ingredients can be generally divided into polyphenols, saponins, alkaloids, terpenoids, phenylpropanoids and others, such as resveratrol, quercetin, curcumin, genistein, capsaicin, epigallocatechin gallate (EGCG), berberine, menthol, emodin and ginsenosides. Simultaneously, the chemical structures, source, model, efficacy and mechanism of these monomeric compounds are also described. And the mechanisms of these active ingredients are mainly involved in the regulation of PRDM16, PGC-1α, PPARγ, SIRT1, AMPK, ß3-adrenergic receptors, TRPV1 and TRPM8 channels, FGF21 and miRNAs. The present article opens opportunities for developing novel drugs or supplements from TCM with wide acceptability to prevent obesity progression and its associated metabolic disorders.

Local hyperthermia therapy induces browning of white fat and treats obesity.

Beige fat plays key roles in the regulation of systemic energy homeostasis; however, detailed mechanisms and safe strategy for its activation remain elusive. In this study, we discovered that local hyperthermia therapy (LHT) targeting beige fat promoted its activation in humans and mice. LHT achieved using a hydrogel-based photothermal therapy activated beige fat, preventing and treating obesity in mice without adverse effects. HSF1 is required for the effects since HSF1 deficiency blunted the metabolic benefits of LHT. HSF1 regulates Hnrnpa2b1 (A2b1) transcription, leading to increased mRNA stability of key metabolic genes. Importantly, analysis of human association studies followed by functional analysis revealed that the HSF1 gain-of-function variant p.P365T is associated with improved metabolic performance in humans and increased A2b1 transcription in mice and cells. Overall, we demonstrate that LHT offers a promising strategy against obesity by inducing beige fat activation via HSF1-A2B1 transcriptional axis.

Conditional gene targeting using UCP1-Cre mice directly targets the central nervous system beyond thermogenic adipose tissues.

OBJECTIVE: Uncoupling protein 1 (UCP1) is a mitochondrial protein critical for adaptive thermogenesis in adipose tissues, and it is typically believed to be restricted to thermogenic adipose tissues. UCP1-Cre transgenic mice are utilized in numerous studies to provide "brown adipose-specific" conditional gene targeting. Here, we examined the distribution of Cre and UCP1 throughout the body in UCP1-Cre reporter mice. METHODS: UCP1-Cre mice crossed to Ai14-tdTomato and Ai9-tdTomato reporter mice were used to explore the tissue distribution of Cre recombinase and Ucp1 mRNA in various tissues. UCP1-Cre mice were independently infected with either a Cre-dependent PHP.eB-tdTomato virus or a Cre-dependent AAV-tdTomato virus to determine whether and where UCP1 is actively expressed in the adult central nervous system. In situ analysis of the deposited single cell RNA sequencing data was used to evaluate Ucp1 expression in the hypothalamus. RESULTS: As expected, Ucp1 expression was detected in both brown and inguinal adipose tissues. Ucp1 expression was also detected in the kidney, adrenal glands, thymus, and hypothalamus. Consistent with detectable Ucp1 expression, tdTomato expression was also observed in brown adipose tissue, inguinal white adipose tissue, kidney, adrenal glands, and hypothalamus of both male and female UCP1-Cre; Ai14-tdTomato and UCP1-Cre; Ai9-tdTomato mice by fluorescent imaging and qPCR. Critically, expression of tdTomato, and thus UCP1, within the central nervous system was observed in regions of the brain critical for the regulation of energy homeostasis, including the ventromedial hypothalamus (VMH). CONCLUSIONS: TdTomato expression in UCP1-Cre; tdTomato mice is not restricted to thermogenic adipose tissues. TdTomato was also expressed in the kidneys, adrenal glands, and throughout the brain, including brain regions and cell types that are critical for multiple aspects of central regulation of energy homeostasis. Collectively, these data have important implications for the utility of UCP1-Cre mice as genetic tools to investigate gene function specifically in brown adipose tissue.

Theobromine enhances the conversion of white adipocytes into beige adipocytes in a PPARγ activation-dependent manner.

The adipocytes play an important role in driving the obese-state-white adipose tissue (WAT) stores the excess energy as fat, wherein brown adipose tissue (BAT) is responsible for energy expenditure via the thermoregulatory function of uncoupling protein 1 (UCP1)-the imbalance between these two onsets obesity. Moreover, the anti-obesity effects of brown-like-adipocytes (beige) in WAT are well documented. Browning, the process of transformation of energy-storing into energy-dissipating adipocytes, is a potential preventive strategy against obesity and its related diseases. In the present study, to explore an alternative source of natural products in the regulation of adipocyte transformation, we assessed the potential of theobromine (TB), a bitter alkaloid of the cacao plant, inducing browning in mice (in vivo) and primary adipocytes (in vitro). Dietary supplementation of TB significantly increased skin temperature of the inguinal region in mice and induced the expression of UCP1 protein. It also increased the expression levels of mitochondrial marker proteins in subcutaneous adipose tissues but not in visceral adipose tissues. The microarray analysis showed that TB supplementation upregulated multiple thermogenic and beige adipocyte marker genes in subcutaneous adipose tissue. Furthermore, in mouse-derived primary adipocytes, TB upregulated the expression of the UCP1 protein and mitochondrial mass in a PPARγ ligand-dependent manner. It also increased the phosphorylation levels of PPARγ coactivator 1α without affecting its protein expression. These results indicate that dietary supplementation of TB induces browning in subcutaneous WAT and enhances PPARγ-induced UCP1 expression in vitro, suggesting its potential to treat obesity.

Anthocyanin oligomers stimulate browning in 3T3-L1 white adipocytes via activation of the ß3-adrenergic receptor and ERK signaling pathway.

Microbial fermentation of grape-skin extracts is found to synthesize anthocyanin oligomers (AO), which are more active than the monomeric anthocyanins that are effective for some metabolic diseases such as diabetes and obesity. This study investigated the functional role of AO in 3T3-L1 white adipocyte metabolism, with a focus on inducing browning. To achieve this, we determined the expressions of core genes and protein markers responsible for browning and lipid metabolism in response to AO treatment of 3T3-L1 white adipocytes. AO exposure significantly increases the expressions of beige-specific genes (Cidea, Cited1, Ppargc1α, Prdm16, Tbx1, Tmem26, and Ucp1) and brown-fat signature proteins (UCP1, PRDM16, and PGC-1α), and suppresses the expressions of lipogenic marker proteins while enhancing the protein levels of lipolysis in white adipocytes. The mechanistic study revealed stimulation of white fat browning via activation of the ß3-AR/PKA/p38 axis and ERK/CREB signaling pathway subsequent to AO treatment. In conclusion, our current findings indicate the beneficial effects of AO for the treatment of obesity with interesting properties such as regulating the browning of adipocytes and increasing thermogenic activity. Although further research based on animal models or clinical trials remains, AO treatment can bring more insights into the treatment of obesity and metabolic syndrome.

Omega-3 Polyunsaturated Fatty Acids Prevent Nonalcoholic Steatohepatitis (NASH) and Stimulate Adipogenesis.

The increasing impact of obesity on global human health intensifies the importance of studies focusing on agents interfering with the metabolism and remodeling not only of the white adipose tissue (WAT) but also of the liver. In the present study, we have addressed the impact of n-3 PUFA in adipose cells' proliferation and adipogenesis, as well as in the hepatic lipid profile and morphology. Mice were induced to obesity by the consumption of a high-fat diet (HFD) for 16 weeks. At the 9th week, the treatment with fish oil (FO) was initiated and maintained until the end of the period. The FO treatment reduced the animals' body mass, plasma lipids, glucose, plasma transaminases, liver mass, triacylglycerol, and cholesterol liver content when compared to animals consuming only HFD. FO also decreased the inguinal (ing) WAT mass, reduced adipocyte volume, increased adipose cellularity (hyperplasia), and increased the proliferation of adipose-derived stromal cells (AdSCs) which corroborates the increment in the proliferation of 3T3-L1 pre-adipocytes or AdSCs treated in vitro with n-3 PUFA. After submitting the in vitro treated (n-3 PUFA) cells, 3T3-L1 and AdSCs, to an adipogenic cocktail, there was an increase in the mRNA expression of adipogenic transcriptional factors and other late adipocyte markers, as well as an increase in lipid accumulation when compared to not treated cells. Finally, the expression of browning-related genes was also higher in the n-3 PUFA treated group. We conclude that n-3 PUFA exerts an attenuating effect on body mass, dyslipidemia, and hepatic steatosis induced by HFD. FO treatment led to decreasing adiposity and adipocyte hypertrophy in ingWAT while increasing hyperplasia. Data suggest that FO treatment might induce recruitment (by increased proliferation and differentiation) of new adipocytes (white and/or beige) to the ingWAT, which is fundamental for the healthy expansion of WAT.

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.

Trigonelline induces browning in 3T3-L1 white adipocytes.

Trigonelline, a major alkaloid component of fenugreek, has been demonstrated to have several biological activities, including antidiabetic and anticancer effects. This study aimed to examine the possible application of trigonelline as an anti-obesity compound based on an investigation of its enhancement of lipid catabolism and induction of browning in white adipocytes. Trigonelline induces browning of 3T3-L1 white adipocytes by enhancing the expressions of brown-fat signature proteins and genes as well as beige-specific genes, including Cd137, Cited1, Tbx1, and Tmem26. Trigonelline also improves lipid metabolism in white adipocytes by decreasing adipogenesis and lipogenesis as well as promotes lipolysis and fatty acid oxidation. Moreover, trigonelline increases the expression of Cox4, Nrf1, and Tfam genes that are responsible for mitochondrial biogenesis. Mechanistic studies revealed that the browning effect of trigonelline in 3T3-L1 white adipocytes is mediated by activating ß3-AR and inhibiting PDE4, thereby stimulating the p38 MAPK/ATF-2 signaling pathway. Considering its high bioavailability in humans and the results of this study, trigonelline may have potential as an anti-obesity compound.

A Peripheral CB1R Antagonist Increases Lipolysis, Oxygen Consumption Rate, and Markers of Beiging in 3T3-L1 Adipocytes Similar to RIM, Suggesting that Central Effects Can Be Avoided.

With the increased prevalence of obesity and related co-morbidities, such as type 2 diabetes (T2D), worldwide, improvements in pharmacological treatments are necessary. The brain- and peripheral-cannabinoid receptor 1 (CB1R) antagonist rimonabant (RIM) has been shown to induce weight loss and improve glucose homeostasis. We have previously demonstrated that RIM promotes adipose tissue beiging and decreased adipocyte cell size, even during maintenance on a high-fat diet. Given the adverse side-effects of brain-penetrance with RIM, in this study we aimed to determine the site of action for a non-brain-penetrating CB1R antagonist AM6545. By using in vitro assays, we demonstrated the direct effects of this non-brain-penetrating CB1R antagonist on cultured adipocytes. Specifically, we showed, for the first time, that AM6545 significantly increases markers of adipose tissue beiging, mitochondrial biogenesis, and lipolysis in 3T3-L1 adipocytes. In addition, the oxygen consumption rate (OCR), consisting of baseline respiratory rate, proton leak, maximal respiratory capacity, and ATP synthase activity, was greater for cells exposed to AM6545, demonstrating greater mitochondrial uncoupling. Using a lipolysis inhibitor during real-time OCR measurements, we determined that the impact of CB1R antagonism on adipocytes is driven by increased lipolysis. Thus, our data suggest the direct role of CB1R antagonism on adipocytes does not require brain penetrance, supporting the importance of focus on peripheral CB1R antagonism pharmacology for reducing the incidence of obesity and T2D.