Studies On Effects And Mechanisms Of Anti-obesity For Dark Tea Aqueous Extracts

Obesity, which is attributed to the joint actions of energy intake, energy consuming and energy storage, is a nutritional and metabolic disorder. Previous studies have shown that teas and their bioactive ingredients possess lipid-lowering and anti-obesity functions. Dark tea is a unique tea in China. Complex chemical reactions during the long-time fermentation process of dark tea endow it with special flavor and features unlike other types of tea. The present study refers to3typical dark teas in China-Fuzhuan brick tea, Puer tea and Liupao tea. We evaluated the anti-obesity effects of the dark tea aqueous extracts (DTAEs) in a high-fat-diet (HFD) induced rat model, attempting to explore the possible underlying mechanisms and regulatory pathways of this function. This study aims to provide a theoretical basis for the development of organic, safe, lipid-lowering and weight-losing products of dark tea. The main results of the study are as follows:1. Study on anti-obesity effects of dark tea on ratsMale Sprague-Dawley rats were fed on by standard or high-fat diets. DTAEs were orally administrated to the treatment groups at dosages of75mg/kg·BW,150mg/kg·BW,300mg/kg·BW and the same amount of distilled water was orally administrated to normal control and HDF group for40days. The results revealed that the body weight gains and Lee's index were significantly decreased in the obese animals orally treated with DTAEs at different concentrations compared with the HDF group. Supplementation with DTAEs also significantly lowered the weights of perinephric fat pads and epididymal adipose tissues, fat coefficient and the values of the food utilization efficiency. Hepatoprotective effects were also dramatically observed in the liver histopathology. Histological analysis showed that DTAE had suppressive effects on the number and size of the adipose tissue fat cells.2. Study on mechanisms of anti-obesity effects of dark tea on ratsThe lipid profile of the high-fat-diet induced rats was measured with automatic biochemical analyzer, serum leptin and NPY level were determined by ELISA, and expression levels of the genes related to obesity in the rat liver were evaluated by RT-qPCR. The data showed that DTAEs has a hypolipidemic auxiliary function which improves the lipid profile of the high-fat-diet induced rats. Leptin resistance was significantly improved after the treatment. No significant effects were observed on the serum concentration of Neuropeptide Y (NPY) in the rats treated with DTAEs. Gene expression levels of acetyl CoA-carboxylase (ACC) in the liver were markedly increased compared with the HFD control group. In addition, DTAEs could also slightly increase the gene expression levels of NPY, uncoupling protein2(UCP2), malonyl CoA decarboxylase (MCD) and medium-chain acyl-CoA dehydrogenase (MCAD).3. Effects of dark tea aqueous extracts on proliferation and differentiation of3T3-L1preadipocytesThe effects of DTAEs on cell proliferation and differentiation were investigated using3T3-L1adipocytes by MTT assay and Oil Red O staining, respectively. Proliferation of preadipocytes was effectively inhibited in a dose-dependent manner by the DTAEs treatment with concentrations of100μg/mL,200μg/mL and400μg/mL after the24-hour treatment. Moreover, DTAEs could also significantly inhibit the differentiation of adipocytes at a concentration of200μg/mL.