Effects of the oral administration of green tea polyphenol and tannic acid on serum and hepatic lipid contents and fecal steroid excretion in rats

Green tea polyphenol (Polyphenon) or tannic acid was administered orally to rats at a dose of 0.01-1.0 or 0.1-1.0 g/kg for 23 days, and changes both in serum and hepatic lipid concentrations and in fecal steroid excretion were examined. The administration of 0.2-1.0 g/kg of Polyphenon caused a significant decrease in levels of serum HDL-cholesterol, whereas tannic acid had no significant effect on serum lipid concentrations. The hepatic triglyceride concentration was significantly higher than controls in rats given more than 0.5 g/kg of Polyphenon, whereas both hepatic triglyceride and phospholipid concentrations were significantly higher after tannic acid administration. Serum thiobarbituric acid reactive substances were significantly low in rats given either 1.0 g/kg of Polyphenon or more than 0.1 g/kg of tannic acid. Fecal neutral steroid excretion increased significantly in rats given a dose of 1.0 gl kg of either Polyphenon or tannic acid. The excretion of fecal bile acids increased significantly in rats given 0.2 g/kg of tannic acid, but then tended to decrease at higher doses; however, excretion of fecal bile acids did not change after Polyphenon administration. We found that alterations in the compositions of fecal neutral steroids and bile acids were independent of the tannic acid or Polyphenon dose: the ratio of coprostanol to cholesterol decreased significantly in rats given 0.05-0.2 g/kg of Polyphenon or 0.5 g/kg of tannic acid; and the ratio of cholic-acid-derived bile acids to chenodeoxycholic-acid-derived bile acids decreased significantly after administration of 0.05, 0.2 and 0.5 g/ kg of Polyphenon or 0.1 and 0.5 g/kg of tannic acid. Primary bile acid excretion increased significantly only in rats given a dose of 0.1 g/kg of Polyphenon. This is the first report that documents the changes occurring in fecal steroid excretion induced by oral administration of green tea polyphenol or tannic acid.