Catechins, compounds derived from green tea, have been shown to improve cholesterol metabolism in animal studies, but the molecular mechanisms underlying this function have not been fully understood. We performed DNA microarray analysis in order to clarify the effects of epigallocatechin gallate (EGCG), the dominant catechin in green tea, on cholesterol metabolism in HepG2 hepatocytes. This revealed that the expression levels of several genes related to cholesterol metabolism, including the LDL receptor, were changed by EGCG treatment. Using a real-time PCR technique, we confirmed that EGCG treatment up-regulated mRNA expression level of the LDL receptor. Moreover, EGCG decreased extracellular apoB levels. These findings indicated that EGCG improves cholesterol metabolism through the up-regulation of LDL receptor and also reduces extracellular apoB levels.

Epidemiological surveys suggest that a higher intake of tea may be associated with a lower risk of CHD. There is accumulating evidence that postprandial lipaemia makes a substantial contribution to the incidence of CHD. Our aim was, therefore, to evaluate the effect of tea catechins (major ingredients in green tea) on postprandial lipid responses in human subjects after the consumption of test meals. In a randomized triple-crossover design, nine male subjects with mild or borderline hypertriacylglycerolaemia consumed 10 (control), 224 (moderate dose) and 674 mg (high dose) of the assigned tea catechins three times each along with a standardized light meal consisting of a piece of bread spread with 20 g butter. Plasma lipids were measured in the fasting state and 1, 2, 3, 4 and 6 h after consuming the light meal. Results showed that, compared with the control, moderate and high doses of tea catechins reduced the incremental area under the plasma triacylglycerol curves by 15·1 and 28·7 %, respectively. Next, the rapid elevation of remnant-like particle cholesterol was significantly inhibited by a high dose of tea catechins 2 h after consuming the light meal (P<0·01). In the range of tea catechin dosages, no significant differences were observed in the postprandial responses for plasma total cholesterol or NEFA at any time point. In conclusion, this trial demonstrated that tea catechins attenuated the postprandial increase in plasma triacylglycerol levels following a fat load. These results may provide evidence for one of the possible mechanisms involved in lowering the incidence of CVD, and may prove useful in further studies on the beneficial health effects of tea drinking.