Serum cholesterol levels and the ratio of polyunsaturated to saturated fatty acid as an indicator of lipid metabolism in rat liver.

Tne dietary effects of phytosterol and polyunsaturated fat (PUFA-fat) on the cholesterol and fatty acids levels in serum and liver of female rats were studied, with the following results. (1) Addition of 1% cholesterol with 0.25% cholic acid to a 10% butter diet increased cholesterol levels and decreased the ratio of polyunsaturated fatty acid (PUFA) to saturated fatty acid (SFA) in the serum and liver. These changes diminished upon additions of phytosterol and PUFA-fat (cod liver oil) to the 10% butter-cholesterol diet. (2) While the cholesterol-rich diet increased the fatty acid content of the liver, addition of phytosterol to the butter-cholesterol diet depressed this increase. On the other hand, addition of PUFA-fat to the butter-cholesterol diet caused an increase of total fatty acid in the liver. (3) A negative relationship was found between the cholesterol level and the ratio of PUFA to SFA in serum (r = -0.810) and also in liver (r = -0.548). There were significant positive correlations between the values for the serum and liver cholesterol levels (r = 0.720) and also between the respective values in the ratios of PUFA to SFA (r = 0.521). These results indicate that dietary phytosterol and PUFA-fat modulate the levels of cholesterol in proportion to the increase in the ratio of PUFA to SFA in both serum and liver with the cholesterol diet, and show that the changes in the values for the serum reflected in changes in the liver.