Concentration of Catechins and Caffeine in Black Tea Affects Suppression of Fat Accumulation and Hyperglycemia in High-fat Diet-fed Mice

In this study, we investigated preventive effects of black tea on obesity and hyperglycemia in C57BL/6 mice fed a high-fat diet for 14 weeks. During the feeding period, mice were given the following black teas: BT1 containing 3,000 mg/L total catechins and 864 mg/L caffeine; and BT2 containing 1,437 mg/L total catechins and 594 mg/L caffeine. Both BT1 and BT2 suppressed high-fat diet-caused body weight gain, deposition of white adipose tissue, and increases in plasma lipids and glucose. Moreover, both BT1 and BT2 counteracted the high-fat diet-caused decrease in the expression of insulin receptor (IR)-beta and glucose transporter 4 (GLUT4), markers for insulin resistance. Of these effects, BT2 were stronger than that of BT1. In conclusion, black tea prevents hyperglycemia and insulin resistance through maintenance of IR-beta and GLUT4 expression in high-fat diet-fed mice, with an appropriate concentration of tea producing maximal effectiveness.