Differential effect of dietary fat saturation and cholesterol on hepatic apolipoprotein gene expression in rats.

The effects of dietary cholesterol and fat saturation on hepatic apolipoprotein A-I, A-II, A-IV, B, C-I, C-III, E and LDL receptor mRNA levels were studied in male rats. Animals were maintained for 2 months on a high fat diet (40% w/w) containing 0.1% cholesterol. Two groups of control animals received either chow diet or chow plus 0.1% cholesterol, while experimental groups received as their fat supplement coconut, corn or olive oil. Olive oil fed animals had higher levels of hepatic apo A-I than the control cholesterol group (1.6 +/- 0.3 vs. 0.8 +/- 0.2). Apo E mRNA levels were 50% and 72% higher in animals consuming the saturated (coconut) and unsaturated (corn and olive) fat diet than the control cholesterol group. Apo B and apo C-I mRNA levels were not affected by the experimental conditions. Apo A-IV mRNA increased between 66% and 127% in groups in which cholesterol was present. LDL receptor mRNA increased 2 times in the corn fed group compared with the control groups. These results indicate that the expression of genes coding for products involved in lipoprotein metabolism have a differential susceptibility to dietary fat saturation and cholesterol.

Hepatic expression of apolipoprotein A-I gene in rats is upregulated by monounsaturated fatty acid diet.

The effect of the degree of dietary fat saturation on the hepatic expression of apolipoprotein A-I mRNA was studied in male rats. Animals were maintained for two months on a high fat diet (40% w/w) containing 0.1% cholesterol. Two groups of control animals received either chow diet or chow plus 0.1% cholesterol, while experimental groups received their fat supplement as coconut, corn or olive oil respectively. Dietary cholesterol did not affect apolipoprotein A-I mRNA levels as compared to control animals. Corn oil fed animals had significantly higher levels of hepatic apolipoprotein A-I mRNA than those receiving cholesterol, or coconut oil plus cholesterol. Olive oil fed animals had significantly higher levels of hepatic apolipoprotein A-I mRNA when compared to all other dietary groups. Our data indicate that monounsaturated fatty acids supplied as olive oil play a major role in regulating the hepatic expression of apolipoprotein A-I in male rats.