Effect of oleic acid level under constant n-6/n-3 and P/S ratios of dietary fats on lipid metabolism in rats

The effect of dietary oleate levels (18, 39, 57 and 74% of total fatty acids) on various lipid parameters was studied in rats given cholesterol-enriched diets containing fat with a constant P/S (3.1–3.2) and n-6/n-3 (5.4–6.2) ratio. High-oleic safflower oil was used as a source of oleic acid, and was replaced stepwise with a mixture of cotton seed and perilla seed oils. After three weeks of feeding, there were no significant differences in the concentrations of serum and liver cholesterol, although they tended to increase with an increasing dietary oleate level. A hypotriglyceridemic trend was observed toward an increasing proportion of oleic acid. The linoleate desaturation index, (dihomo-γ-linolenic acid + arachidonic acid)/linoleic acid, in tissue phosphatidylcholine tended to increase with an increasing proportion of oleate, whereas the production of prostacyclin by the aorta and thromboxane A₂by platelets was independent of the dietary oleate level. These results indicate that dietary oleate did not significantly modify the effect of polyunsaturated fatty acids on various lipid parameters under dietary conditions at which the P/S and n-6/n-3 ratios of the dietary fat were kept at an appropriate level to prevent ischemic heart disease.