Green tea (Camellia sinensis) attenuates nephropathy by downregulating Nox4 NADPH oxidase in diabetic spontaneously hypertensive rats.

Green tea (GT), through its antioxidant properties, may be useful to treat or prevent human diseases. Because several lines of evidence suggest that oxidative stress contributes to the pathogenesis of diabetic nephropathy, we tested the hypothesis that GT prevents diabetes and hypertension-related renal oxidative stress, attenuating renal injury. Spontaneously hypertensive rats (SHR) with streptozotocin-induced diabetes and nondiabetic SHR were treated daily with tap water or freshly prepared GT (13.3 g/L). After 12 wk, the systolic blood pressure did not differ between treated and untreated nondiabetic or diabetic rats. However, body weight was less (P < 0.05) and glycemia was greater in diabetic SHR rats than in nondiabetic rats. Renal oxidative stress variables such as 8-hydroxy-2'-deoxyguanosine (8-OHdG) and nitrotyrosine expression, NADPH oxidase-dependent superoxide generation, and the expression of renal cortex Nox4 were greater (P < 0.05) in diabetic rats that received water (DW) than in nondiabetic rats that received water (CW). The 8-OHdG and NADPH oxidase-dependent superoxide generation were significantly less in rats treated with GT. Nitrotyrosine and Nox4 expression were significantly less in diabetic rats that received GT (DGT) than in DW. Likewise, the indices of renal injury, albuminuria, and renal expression of collagen IV were significantly greater in DW than in CW. These differences were significantly less in DGT than in DW. GT reestablished the redox state and reduced the indicators of nephropathy without altering glycemia and blood pressure levels in diabetic SHR. These findings suggest that the consumption of GT may ameliorate nephropathy in diabetic hypertensive patients.