Effects of (−)-epigallocatechin-3-gallate on pancreatic beta-cell damage in streptozotocin-induced diabetic rats

Abstract

Oxygen free radicals, which are produced as a result of chronic hyperglycemia, are implicated in many diabetic complications. (−)- Epigallocatechin-3-gallate (EGCG), a green tea polyphenol, has been shown to have both antioxidant and pro-oxidant activities, but its effect on oxidative stress of pancreatic beta cells in vivo is unclear. Here we evaluated the effects of nanomolar concentrations of EGCG on beta-cell survival and the response to high glucose loading in streptozotocin-induced diabetic rats. A 4-day intraperitoneal treatment with EGCG (5 mg/kg/ day) further impaired the beta-cell response to high glucose in the diabetic rats. EGCG exacerbated the loss of islet cell mass and insulinimmunoreactivity in beta cells. These results suggest that, even at nanomolar plasma concentrations, EGCG acts as a pro-oxidant rather than an antioxidant, at least in beta cells in vivo. © 2006 Elsevier B.V. All rights reserved. Keywords: (−)-Epigallocatechin-3-gallate; Oxygen free radical; Streptozotocin; Glucose; Insulin