Effects of green tea on serum paraoxonase/arylesterase activities in streptozotocin-induced diabetic rats

In recent years, green tea has become a subject of interest because of its beneficial effects on human health. The purpose of this study was to determine the effects of green tea on serum paraoxonase/arylesterase activities and lipoprotein oxidizability in streptozotocin-induced diabetic rats (65 mg/kg [intraperitoneal]). Green tea was given in tap water (2%) for 3 and 6 weeks to control (CGT-3w and CGT-6w) and diabetic (DGT-3w and DGT-6w) rats, and they were compared with the control and diabetic groups (D-3w and D-6w), respectively. Serum insulin level was significantly increased in the DGT-6w group; serum lipid and plasma and tissue malondialdehyde levels were reduced in the DGT-3w and DGT-6w groups. Oxidizability of apolipoprotein B-containing lipoprotein fraction was found to be significantly reduced in the DGT-6w group. Serum total antioxidant capacity showed a significant increase in the CGT-6w and DGT-6w groups. Paraoxonase activity was significantly reduced in the D-3w and D-6w groups and increased in the DGT-6w group. We conclude that green tea might have antihyperlipidemic and antioxidative effects and may slow the progression of atherogenesis by reducing oxidation of lipoproteins and preserving paraoxonase activity.