The Regulation of Depot Fat by Linoleic Acid

Abstract

Matching groups of weanling male rats were fed purified diets containing either no fat, 20% of a mixture of saturated triglycerides (MCT) containing 7% of C₆, 78% of C₈, and 14% of C₁₀ acids, or 20% of a mixture of saturated triglycerides (LCT) containing 5% of C₁₀, 45% of C₁₂, 25% of C₁₄, 8% of C₁₆, and 16% of C₁₈ acids. The diets were supplemented with zero, 0.1, or 2% of linoleic acid. After the rats had received the diet for 71 days, they were killed and the testicular fat bodies pooled and subjected to gasliquid chromatography. When the fat-free diets were fed, the depot fat consisted of not more than 2% of acids having chains shorter than C₁₈. The main constituent was oleate, the level of which declined when 2% of linoleic acid was added to the diet. With the latter diet, 21% of linoleate was noted in the depot fat. With MCT and no linoleic acid, the depot fat was similar to that of the animals fed the corresponding fat-free diet. With 2% of linoleic acid, substantial amounts of C₈, C₁₀, and C₁₂ acids were deposited; the oleate content declined from 45 to 26%, and the linoleate level was 11%. With LCT, the depot fat contained a large amount of laurate and myristate. Linoleic acid supplementation increased their levels at the expense of oleate, with 0.1% of linoleic acid having a considerable effect. With 2% of linoleic acid in the diet, the depot fat contained 6% of linoleate. It is concluded that linoleate regulates the type of fat deposited; it leads to a decrease in neutral fat in relation to body weight and facilitates the laying down of a depot fat more representative of that in the diet.