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

Diabetes mellitus is highly prevalent worldwide. High-fat-diet (HFD) consumption can lead to liver fat accumulation, impair hepatic glycometabolism, and cause insulin resistance and the development of diabetes. Resveratrol has been shown to improve the blood glucose concentration of diabetic mice, but its effect on the abnormal hepatic glycometabolism induced by HFD-feeding and the mechanism involved are unknown. In this study, we determined the effects of resveratrol on the insulin resistance of high-fat-diet-fed mice and a hepatocyte model by measuring serum biochemical indexes, key indicators of glycometabolism, glucose uptake, and glycogen synthesis in hepatocytes. We found that resveratrol treatment significantly ameliorated the HFD-induced abnormalities in glucose metabolism in mice, increased glucose absorption and glycogen synthesis, downregulated protein phosphatase 2A (PP2A) and activated Ca2+/CaM-dependent protein kinase kinase β (CaMKKβ), and increased the phosphorylation of AMP-activated protein kinase (AMPK). In insulin-resistant HepG2 cells, the administration of a PP2A activator or CaMKKβ inhibitor attenuated the effects of resveratrol, but the administration of an AMPK inhibitor abolished the effects of resveratrol. Resveratrol significantly ameliorates abnormalities in glycometabolism induced by HFD-feeding and increases glucose uptake and glycogen synthesis in hepatocytes. These effects are mediated through the activation of AMPK by PP2A and CaMKKβ.

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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

Frontiers in Pharmacology ◽

10.3389/fphar.2021.614406 ◽

2021 ◽

Vol 12 ◽

Author(s):

Jianfei Lai ◽

Qianyu Qian ◽

Qinchao Ding ◽

Li Zhou ◽

Ai Fu ◽

...

Keyword(s):

Adipose Tissue ◽

Protein Kinase ◽

White Adipose Tissue ◽

High Fat Diet ◽

Sirtuin 1 ◽

Male Mice ◽

High Fat ◽

Sirt1 Expression ◽

Salvianolic Acid ◽

Amp Activated Protein Kinase

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.

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A High-Fat Diet Attenuates Amp-Activated Protein Kinase α1 in Adipocytes to Induce Exosome Shedding and Nonalcoholic Fatty Liver Development in Vivo

10.2337/figshare.13259768 ◽

2020 ◽

Author(s):

Ada Admin ◽

Chenghui Yan ◽

Xiaoxiang Tian ◽

Jiayin Li ◽

Dan Liu ◽

...

Keyword(s):

Adipose Tissue ◽

Protein Kinase ◽

Fatty Liver ◽

Lipid Accumulation ◽

High Fat Diet ◽

Liver Development ◽

High Fat ◽

Tissue Specific ◽

Nonalcoholic Fatty Liver ◽

Amp Activated Protein Kinase

Exosomes are important for intercellular communication, but the role of exosomes in the communication between adipose tissue (<a>AT</a>) and the liver remains unknown. The aim of this study is to determine the contribution of AT-derived exosomes in nonalcoholic fatty liver disease (<a>NAFLD</a>). Exosome components, liver fat content, and liver function were monitored in AT in mice fed a <a>high-fat diet </a>(<a>HFD</a>) or treated with metformin- or GW4869 and with AMP-activated protein kinase (AMPKα1) floxed (Prkaα1fl/fl/WT), <a>Prkaα1-/-</a>, liver tissue-specific Prkaα1-/-, or AT-specific Prkaα1-/- modification. In cultured adipocytes and white adipose tissue (WAT), the absence of <a>AMPKα1</a> increased exosome release and exosomal proteins by elevating <a>tumor susceptibility gene 101 (TSG101</a>)-mediated exosome biogenesis. In adipocytes treated with palmitic acid, TSG101 facilitated scavenger receptor class B (CD36) sorting into exosomes. CD36-containing exosomes were then endocytosed by hepatocytes to induce lipid accumulation and inflammation. Consistently, an HFD induced more severe lipid accumulation and cell death in <a>Prkaα1-/- </a>and adipose tissue-specific Prkaα1-/- mice than in WT and liver-specific Prkaα1-/- mice. AMPK activation by metformin reduced adipocyte-mediated exosome release and mitigated fatty liver development in WT and liver specific Prkaα1-/- mice. Moreover, administration of the exosome inhibitor GW4869 blocked exosome secretion and alleviated HFD-induced fatty livers in Prkaα1-/- and adipocyte-specific Prkaα1-/- mice. We conclude that HFD-mediated AMPKα1 inhibition promotes NAFLD by increasing numbers of AT C<a>D36</a>-containing exosomes.

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