Improvement effects of Chongqing Tuo tea extract on mice with type 2 diabetic

【Objective】To explore the hypoglycemic effect and mechanism of Chongqing Tuo tea extract on mice with type 2 diabetic（T2DM），and to provide theoretical basis for the study of health care function of Chongqing Tuo tea and the prevention and treatment of T2DM.【Method】Chongqing Tuo tea extract was prepared by hot water extraction and vacuum freeze-drying. The main quality components were detected by Folin-Ciocalteu method，anthrone colorimetry method，ninhydrin colorimetry method and high performance liquid chromatography（HPLC）. Twenty-four four-week-old specific pathogen-free（SPF）male C57BL/6J mice were selected as the research objects. Among them，6 mice were fed with basic diet as normal control group（NC group），18 mice were fed with high-fat diet，and then combined with streptozotocin（STZ）injection to induce T2DM mouse model. The low-dose（400 mg/kg，TTEL group，6 mice）and high-dose （800 mg/kg，TTEH group，6 mice）of Chongqing Tuo tea extract were given by gavage，and the T2DM model control group（MC group，6 mice）and NC group were given the same amount of normal saline by gavage. The intervention period was 8 weeks，once a day. During the experiment，the body weight，food intake and fasting blood glucose of the mice were measured and recorded. After the intervention，the effects on histopathological morphology，blood glucose，blood lipid and liver oxidative stress of the mice were analyzed.【Result】Among the main quality components of Chongqing Tuo tea extract，the content of tea polyphenols was the highest（34.45%）. Among the main components of tea polyphenols （catechins），the content of epigallocatechin gallate（EGCG）was the highest（18.22%）. The intervention of Chongqing Tuo tea extract could effectively alleviate the weight loss and pathological damage of liver and pancreas in T2DM mice. After 8 weeks of intervention，fasting blood glucose significantly decreased in the TTEL and TTEH groups compared with the MC group（P<0.05，the same below），the decreases were 23.95% in the TTEL group and 48.94% in the TTEH group. The extract of Chongqing Tuo tea could improve the glucose tolerance and insulin sensitivity of T2DM mice，among which the improvement effect of high dose of Chongqing Tuo tea extract was better. Compared with the MC group，the levels of serum triglyceride（TG），total cholesterol（TC），low density lipoprotein cholesterol（LDL-C）in TTEL group and TTEH group were significantly decreased，and the content of high density lipoprotein cholesterol（HDL-C）was significantly increased，indicating that the intervention of Chongqing Tuo tea extract could significantly improve the disorder of lipid metabolism. Compared with the MC group，the content of malondialdehyde（MDA）in liver of mice in TTEL group and TTEH group was significantly decreased，and the activities of superoxide dismutase（SOD），catalase （CAT）and glutathione peroxidase（GSH-Px）in liver were significantly increased，indicating that the intervention of Chongqing Tuo tea extract could significantly improve liver oxidative stress injury.【Conclusion】Chongqing Tuo tea extract has hypoglycemic effect and has the potential to be developed as a hypoglycemic functional food.