Multifunctional effects of green tea catechins on prevention of the metabolic syndrome

Tea catechins reduce serum cholesterol concentrations and suppress postprandial hypertriacylglycerolemia in experimental animals and humans. These effects are mainly ascribed to the gallate esters of catechins, (-)-epicatechin gallate (ECG) and (-)-epigallocatechin gallate (EGCG). During pasteurization of tea drinks, tea catechins are epimerized to so-called heat-treated tea catechins such as (-)-catechin gallate (CG) and (-)-gallocatechin gallate (GCG). We showed that both tea catechins and heat-treated tea catechins with the galloyl moiety lowered intestinal absorption of cholesterol by inhibiting micellar solubility of cholesterol. Since they inhibited pancreatic lipase in vitro and slowed down lymphatic absorption of triacylglycerols, it is suggested that delayed intestinal absorption of triacylglycerols after the feeding of catechin preparations causes suppression of postprandial hypertriacylglycerolemia. It has been reported that tea catechins and heat-treated tea catechins with the galloyl moiety suppress deposition of visceral fat in experimental animals and humans. Some studies suggest that the stimulation of hepatic β-oxidation might be a cause for reduced deposition of visceral fat. However, our study did not show any acceleration of β-oxidation in rat livers. Although there are some controversial observations, results obtained suggest a possibility that tea catechins and heat-treated tea catechins with the galloyl moiety improve lipid metabolism and contribute to the prevention of the metabolic syndrome.