Modulation of cholesterol metabolism by the green tea polyphenol (-)-epigallocatechin gallate in cultured human liver (HepG2) cells

Epidemiological and animal studies have found that green tea is associated with lower plasma cholesterol. This study aimed to further elucidate how green tea modulates cholesterol metabolism. When HepG2 cells were incubated with the main green tea constituents, the catechins, epigallocatechin gallate (EGCG) was the only catechin to increase LDL receptor binding activity (3-fold) and protein (2.5-fold) above controls. EGCG increased the conversion of sterol regulatory element binding protein-1 (SREBP-1) to its active form (+56%) and lowered the cellular cholesterol concentration (-28%). At 50 microM, EGCG significantly lowered cellular cholesterol synthesis, explaining the reduction in cellular cholesterol. At 200 microM EGCG, cholesterol synthesis was significantly increased even though cellular cholesterol was lower, but there was a significant increase seen in medium cholesterol. This indicates that, at 200 microM, EGCG increases cellular cholesterol efflux. This study provides mechanisms by which green tea modulates cholesterol metabolism and indicates that EGCG might be its active constituent.