Tea drinking effectively improves symptoms of diabetes and prevents hepatorenal damage in mice

Since type 2 diabetic patients often develop resistance to metformin as the progresses of diabetes, and almost all type 1 diabetic patients need receive insulin injection for hyperglycemia control. It is important to explore novel strategies with different mechanisms for diabetes management. Glucose-induced osmotic diuresis, known as polyuria, is the first clinical symptom in severe type 2 diabetes mellitus (T2DM) and type 1 diabetes mellitus (T1DM). Drinking green tea or black tea effectively mitigates diabetic symptoms including polyuria, polydipsia, polyphagia and hyperglycemia in db/db mice via regulating renal aquaporin 2 and urine transporter A1 (UT-A1), in favor renal water reabsorption. This unique mechanism of action of tea could be useful for the treatment of diabetes in humans. In this study, we found that drinking Large-leaf yellow tea (LYT) for 5 weeks effectively ameliorated polyuria, polydipsia, polyphagia, hyperglycemia and excessive body weight gain, as well as upregulated renal water reabsorption associated proteins, including protein kinase C-alpha (PKC-α), membrane PKC-α and glycosylated UT-A1 in db/db mice. Four-days experiment were also confirmed the rapidly response of these proteins in favor renal water reabsorption and the amelioration of diabetic symptoms by LYT. We also found that green tea drinking effectively mitigated symptoms of diabetes in a mouse model for T1DM via upregulating these proteins. Moreover, green tea drinking prevented hepatorenal damage caused by hyperglycemia as suggested by the reduced levels of aspartate aminotransferase and creatinine in serum and the enhanced antioxidant defense system in liver and kidney. These results suggest the possible application of tea or tea constitutes in the clinical treatment of severe T2DM and T1DM, and the kidney is the target organ.