Effect of dietary cholesterol and polyunsaturated fats on plasma and liver lipids in guinea pigs.

Weanling male Hartley guinea pigs were fed for 6 weeks on a regular chow supplemented with 5% polyunsaturated fats (safflower, linseed, or evening primrose oil) or 5% saturated fats (hydrogenated coconut oil) with or without the addition of 1% cholesterol to the diet. Cholesterol feeding resulted in slower growth, hyperlipidemia, and a fatty liver. Cholesterol contents (predominantly in the form of cholesterol esters) in plasma and liver were increased, but the increase of plasma cholesterol was significantly reduced when unsaturated fats in place of saturated fat were added to the diet. The essential fatty acid contents in plasma and liver lipids were modulated by the dietary fats and by the cholesterol feeding. The latter reduced the proportions of 20:4 (n-6), but increased or had no effect on the levels of 18:2 (n-6). These results led to a reduced ratio of 20:4 (n-6)/18:2 (n-6), suggesting that cholesterol feeding may impair the desaturase activities.