Pycnogenol® Induces Browning of White Adipose Tissue through the PKA Signaling Pathway in Apolipoprotein E-Deficient Mice

Flavonoid-enriched extract from Millettia speciosa Champ prevents obesity by regulating thermogenesis and lipid metabolism in high-fat diet-induced obese C57BL/6 mice

Millettia speciosa (M. speciosa) Champ is a medicinal and edible plant. The roots are rich in flavonoids, which possess multiple biological activities, including lipid-lowering effects. This study aimed to explore the effect of flavonoid-enriched extract from M. speciosa (FMS) on obesity. The UPLC-Q-TOF-MS analysis and chromatographic analysis were adopted to identify flavonoid compounds in FMS. Male C57BL/6J mice were fed with a high-fat diet for 3 months and were then treated with FMS (50 or 100 mg/kg/d) or Orlistat (10 mg kg-1 d-1) for another 8 weeks. A total of 35 flavonoids were identified in the extract of M. speciosa root. FMS reduced body weight gain, liver weight gain, white adipose tissue, lipid accumulation, and blood glucose. The levels of TG, ALT, AST, and inflammatory-related adipokines (TNF-α and IL-6) in serum were also reduced by FMS. In addition, FMS promoted thermogenesis in brown adipose tissue and induced the activation of lipolysis, fatty acid oxidation, and oxidative phosphorylation in white adipose tissues. In summary, long-term administration of FMS could ameliorate high-fat diet-induced obesity by stimulating adipose thermogenesis and lipid metabolism.

Activation of AMP-Activated Protein Kinase-Sirtuin 1 Pathway Contributes to Salvianolic Acid A-Induced Browning of White Adipose Tissue in High-Fat Diet Fed Male Mice

Background: Salvianolic acid A (Sal A), a natural polyphenolic compound extracted from Radix Salvia miltiorrhiza (Danshen), exhibits exceptional pharmacological activities against cardiovascular diseases. While a few studies have reported anti-obesity properties of Sal A, the underlying mechanisms are largely unknown. Given the prevalence of obesity and promising potential of browning of white adipose tissue to combat obesity, recent research has focused on herbal ingredients that may promote browning and increase energy expenditure.

Purpose: The present study was designed to investigate the protective antiobesity mechanisms of Sal A, in part through white adipose browning.

Methods: Both high-fat diet (HFD)-induced obese (DIO) male mice model and fully differentiated C3H10T1/2 adipocytes from mouse embryo fibroblasts were employed in this study. Sal A (20 and 40 mg/kg) was administrated to DIO mice by intraperitoneal injection for 13-weeks. Molecular mechanisms mediating effects of Sal A were evaluated.

Resluts: Sal A treatment significantly attenuated HFD-induced weight gain and lipid accumulation in epididymal fat pad. Uncoupling protein 1 (UCP-1), a specialized thermogenic protein and marker for white adipocyte browning, was significantly induced by Sal A treatment in both white adipose tissues and cultured adipocytes. Further mechanistic investigations revealed that Sal A robustly reversed HFD-decreased AMP-activated protein kinase (AMPK) phosphorylation and sirtuin 1 (SIRT1) expression in mice. Genetically silencing either AMPK or SIRT1 using siRNA abolished UCP-1 upregulation by Sal A. AMPK silencing significantly blocked Sal A-increased SIRT1 expression, while SIRT1 silencing did not affect Sal A-upregulated phosphorylated-AMPK. These findings indicate that AMPK was involved in Sal A-increased SIRT1.

Conclusion: Sal A increases white adipose tissue browning in HFD-fed male mice and in cultured adipocytes. Thus, Sal is a potential natural therapeutic compound for treating and/or preventing obesity.

Recent developments in natural products for white adipose tissue browning

Excess accumulation of white adipose tissue (WAT) causes obesity which is an imbalance between energy intake and energy expenditure. Obesity is a serious concern because it has been the leading causes of death worldwide, including diabetes, stroke, heart disease and cancer. Therefore, uncovering the mechanism of obesity and discovering anti-obesity drugs are crucial to prevent obesity and its complications. Browning, inducing white adipose tissue to brown or beige (brite) fat which is brown-like fat emerging in WAT, becomes an appealing therapeutic strategy for obesity and metabolic disorders. Due to lack of efficacy or intolerable side-effects, the clinical trials that promote brown adipose tissue (BAT) thermogenesis and browning of WAT have not been successful in humans. Obviously, more specific means still need to be developed to activate browning of white adipose tissue. In this review, we summarized seven kinds of natural products (alkaloids, flavonoids, terpenoids, long chain fatty acids, phenolic acids, else and extract) promoting white adipose tissue browning which can ameliorate the metabolic disorders, including obesity, dislipidemia, insulin resistance and diabetes. Since natural products are important drug sources and the browning property plays a significant role in not only obesity treatment but also in type 2 diabetes (T2DM) improvement, natural products of inducing browning may be an irreplaceable drug discovery orientation for obesity, diabetes and even other metabolic disorders.

The Gintonin-Enriched Fraction of Ginseng Regulates Lipid Metabolism and Browning via the cAMP-Protein Kinase a Signaling Pathway in Mice White Adipocytes

Obesity is a major health concern and is becoming an increasingly serious societal problem worldwide. The browning of white adipocytes has received considerable attention because of its potential protective effect against obesity-related metabolic disease. The gintonin-enriched fraction (GEF) is a non-saponin, glycolipoprotein component of ginseng that is known to have neuroprotective and anti-inflammatory effects. However, the anti-obesity and browning effects of GEF have not been explored to date. Therefore, we aimed to determine whether GEF has a preventive effect against obesity. We differentiated 3T3-L1 cells and mouse primary subcutaneous adipocytes for 8 days in the presence or absence of GEF, and then measured the expression of intermediates in signaling pathways that regulate triglyceride (TG) synthesis and browning by Western blotting and immunofluorescence analysis. We found that GEF reduced lipid accumulation by reducing the expression of pro-adipogenic and lipogenic factors, and increased lipolysis and thermogenesis, which may be mediated by an increase in the phosphorylation of protein kinase A. These findings suggest that GEF may induce fat metabolism and energy expenditure in white adipocytes and therefore may represent a potential treatment for obesity.

Polymethoxyselenoflavones exert anti-obesity effects through activation of lipolysis and brown adipocyte metabolism

BACKGROUND/OBJECTIVES

Polymethoxyselenoflavone (PMSF) is a compound that substitutes the oxygen atom in a flavonoid with selenium. This study aimed to investigate the effects of PMSFs on lipid metabolism in adipocytes and their anti-obesity potential.

SUBJECTS/METHODS

To test lipolytic and thermogenic effects of the compounds in vitro, adipocytes differentiated from immortalized pre-brown adipocyte progenitors and pre-white adipocyte cell lines were treated with 19 PMSFs. The expression levels of brown adipocyte markers and genes related to mitochondrial metabolism were analyzed by qPCR and western blot. In vivo anti-obesity effect was investigated using diet-induced obesity mouse models and adipocyte-specific ATGL knockout mice.

RESULTS

The qPCR analysis identified 2-(3,4-dimethoxyphenyl)-4H-selenochromen-4-one (DMPSC) as the most potent brown adipogenic candidate among the 19 compounds tested in this study. DMPSC treatment significantly increased the mitochondrial content and oxidative metabolism in adipocytes in vitro. Mechanistically, DMPSC treatment increased lipolysis through activation of PKA downstream signaling. Consistently, the in vivo treatment of DMPSC increased energy consumption, reduced body weight, and improved glucose tolerance in mice fed with high-fat diets. Moreover, DMPSC treatment increased brown adipocyte marker expression and mitochondrial content in adipose tissue of mice. The anti-obesity effects were absent in adipocyte-specific ATGL knockout mice, indicating that the DMPSC effect is mediated by cytosolic lipase-dependent mechanisms.

CONCLUSIONS

Collectively, our results indicated that DMPSC exerted anti-obesity effects partially through the PKA signaling-mediated activation of lipolysis and brown adipose tissue metabolism.