Green Tea Polyphenols Reduced Fat Deposits in High Fat-Fed Rats via erk1/2-PPARγ-Adiponectin Pathway

• DOI: 10.1371/journal.pone.0053796
• Publication Date: 2013-01-15T22:30:54Z
• Authors: Chong Tian; Xiaolei Ye; Rui Zhang; Jia Long; Weiye Ren; Shibin Ding; Dan Liao; Xin Jin; Hongmei Wu; Shunqin Xu; Chenjiang Ying
• Keywords: Male; 0301 basic medicine; Science; Down-Regulation; Intra-Abdominal Fat; Diet, High-Fat; 03 medical and health sciences; Animals; Phosphorylation; Rats, Wistar; Extracellular Signal-Regulated MAP Kinases; Protein Kinase Inhibitors; Mitogen-Activated Protein Kinase 1; 2. Zero hunger; Mitogen-Activated Protein Kinase 3; Tea; Q; Body Weight; R; Polyphenols; Rats; 3. Good health; PPAR gamma; Medicine; Adiponectin; Research Article; Signal Transduction

Hypoadiponectinemia contributes to the development of obesity and related disorders such as diabetes, hyperlipidemia, and cardiovascular diseases. In this study we investigated the effects of green tea polyphenols (GTPs) on adiponectin levels and fat deposits in high fat (HF) fed rats, the mechanism of signaling pathway was explored as well.Male Wistar rats were fed with high-fat diet. GTPs (0.8, 1.6, 3.2 g/L) were administered via drinking water. Serum adiponectin and insulin were measured by ELISA, mRNA levels of adiponectin and PPARγ in visceral adipose tissue (VAT) were determined by Real-time PCR, protein levels of PPARγ, phospho (p) - PPARγ, extracellular signal regulated kinase (erk) 1/2 and p-erk1/2 in VAT were determined by western blot. GTPs treatment attenuated the VAT accumulation, hypoadiponectinemia and the decreased mRNA level of adiponectin in VAT induced by HF. Decreased expression and increased phosphorylation of PPARγ (the master regulator of adiponectin), and increased activation of erk1/2 were observed in HF group, and these effects could be alleviated by GTPs treatment. To explore the underlying mechanism, VAT was cultured in DMEM with high glucose to mimic the hyperglycemia condition in vitro. Similar to the results of in vivo study, decreased adiponectin levels, decreased expression and increased phosphorylation of PPARγ, and elevated erk1/2 phosphorylation in cultured VAT were observed. These effects could be ameliorated by co-treatment with GTPs or PD98059 (a selective inhibitor of erk1/2).GTPs reduced fat deposit, ameliorated hypoadiponectinemia in HF-fed rats, and relieved high glucose-induced adiponectin decrease in VAT in vitro. The signaling pathway analysis indicated that PPARγ regulation mediated via erk1/2 pathway was involved.