Influence of green tea on enzymes of carbohydrate metabolism, antioxidant defense, and plasma membrane in rat tissues

Objective Green tea, consumed worldwide since ancient times, is considered beneficial to human health. We hypothesized that green tea would enhance antioxidant defenses and specific metabolic activities of rat intestine, liver, and kidney to improve their functions. Methods The effect of green tea given to rats in the diet or drinking water for 25 d was determined on blood chemistry and on activities of enzymes of carbohydrate metabolism, brush border membrane, and antioxidant defense. Results Serum glucose, cholesterol, phosphate, and body weight decreased, whereas the activities of lactate and malate dehydrogenases and glucose-6- and fructose 1,6-bis-phosphatases increased in the intestine and kidney but slightly changed in the liver. Activity of glucose-6-phosphate dehydrogenase profoundly increased in the renal cortex but decreased in other tissues. Lipid peroxidation increased in the intestine and renal medulla and decreased in the renal cortex and liver; catalase increased in all tissues but the medulla. Superoxide dismutase activity decreased in the intestine but increased in renal tissues. Activities of brush border membrane enzymes in general increased in the intestine and kidney. Conclusion Green tea consumption resulted in enhanced enzyme activities of carbohydrate metabolism and antioxidant defenses, which may lead to improved health.