Dietary myristic acid modifies the HDL-cholesterol concentration and liver scavenger receptor BI expression in the hamster

Abstract

The influence of myristic acid in a narrow physiological range (0·5 to 2·4 % of total dietary energy) on the plasma and hepatic cholesterol metabolism was investigated in the hamster. The hamsters were fed on a diet containing 12·5 g fat/100 g and 0·05 g cholesterol/100 g with 0·5 % myristic acid (LA diet) for 3 weeks (pre-period). During the following 3 weeks (test period), they were divided into four dietary groups with 0·5 % (LA), 1·2 % (LM), 1·8 % (ML) or 2·4 % (M) myristic acid. Finally, half the hamsters in each group were again fed the LA diet for another 3 weeks (post-period). At the end of the test period, the hepatic expression of the scavenger receptor BI (SR-BI) was lower in the LM, ML and M groups than in the LA group whereas the hepatic cholesteryl ester concentration was higher. Cholesterol 7α hydroxylase activity was lower in the ML and M groups than in the LA and LM groups while the sterol 27 hydroxylase and 3-hydroxy-3-methyl glutaryl coenzyme A reductase activities were not modulated by dietary myristic acid. This is the first time a negative correlation has been observed between the HDL-cholesterol concentration and the hepatic mass of SR-BI (r-0·69;P<0·0001) under physiological conditions. An inverse linear regression was also shown between SR-BI and the percentage of myristic acid in the diet (r-0·75;P<0·0001). The hepatic mass of SR-BI in the M group had increased at the end of the post-period compared with the test-period values. The present investigation shows that myristic acid modulates HDL-cholesterol via a regulation of the SR-BI expression.