Background – Epigallocatechin gallate (EGCG), considered to be the active component of green tea, has yet to be shown to lower cholesterol in the cholesterol-fed hypercholesterolaemic rabbit model. Furthermore, cholesterol reduction by EGCG may involve the reduction of cholesterol synthesis through inhibition of squalene epoxidase. Objectives – To determine the effects of EGCG on serum cholesterol and on the cholesterol synthesis precursor, lathosterol, in the cholesterol-fed rabbit model of hypercholesterolaemia.
Design – Twelve NZ White rabbits were fed, for two weeks, a rabbit chow to which was added 0.25% (w/w) cholesterol. For the next four weeks, one group (6 controls) continued on the 0.25% (w/w) cholesterol chow while the other group (6 treated) was fed the 0.25% (w/w) cholesterol diet with 2% (w/w) EGCG added. Serum cholesterol (enzymatic assay) and lathosterol (GC) were measured and expressed as mean ± SEM.
Outcomes – The EGCG effectively lowered serum cholesterol by 85% (P = 0.02) from 8.6 ± 2.3 at week 2 to 1.3 ± 0.1 mmol/L at week 6. In contrast, serum cholesterol did not change significantly (P = 0.72) in the control group, going from 8.6 ± 2.3 at week 2 to 7.9 ± 4.0 mmol/L at week 6. Serum lathosterol decreased from 2.4 ± 0.5 at week 2 to 0.25 ± 0.05 μmol/L at week 6 (P < 0.01) in the treatment group and from 3.1 ± 1.1 at week 2 to 0.93 ± 0.32 μmol/L at week 6 (P < 0.01) in the control group and was significantly lower in the treatment group at week 6 compared to the control group (P = 0.03). However, when serum lathosterol was normalised using serum cholesterol (lathosterol/cholesterol) to account for lipoprotein carrier capacity, there were no differences between the groups. Conclusions – The green tea catechin, EGCG, effectively lowered cholesterol and lathosterol in the cholesterol-fed hypercholesterolaemic rabbits but it did not have any effect on the serum lathosterol to cholesterol ratio.