The influence of dietary branched‐chain fatty acids on the fatty acid composition of tissue lipids of rats

Abstract

AbstractBranched‐chain fatty acids (BCFA) were prepared as a concentrate from the adiposetissue lipids of barley‐fed lambs. The BCFA was included in a stock Oxoid ration at levels of 2.5–15% by weight and these diets were given to appetite to female weanling rats for up to 14 days. The influence of the diets on inter alia growth‐rate and fatty acid composition of tissue lipids was compared with the effect of the same stock diet with inclusions at a level of 5% by weight of 3‐methylhexadecanoic acid (3‐MHD), 4‐methylhexadecanoic acid (4‐MHD), 3,7,11,15‐tetramethylhexadecanoic (phytanic) acid and n‐hexadecanoic (palmitic) acid which, with the stock ration, served as control. Rats receiving diets containing up to 7.5% BCFA grew almost as well as did those given palmitic acid whereas the animals offered the diets containing 3‐MHD, 4‐MHD or 10% BCFA barely subsisted. Rats given 10% BCFA or phytanic acid became moribund within 3 days. BCFA accumulated to widely varying degrees in the lipids of the main internal organs. The higher proportions of these acids constituted some 40–60% of the total fatty acids of the lipids of kidney, liver and heart and were associated with diets containing 10% and 15% BCFA and 5% 3‐MHD. The lower proportions of the branched acids in the lipids of these organs were in the range 15–25% of the total fatty acids and related to diets that included 2.5% BCFA and 5% 4‐MHD. In contrast to the changes in fatty acid composition of the lipids of the main internal organs, those of the central and peripheral nervous systems were only minor, the proportions of branched acids amounting to some 3% in brain tissue and up to 14% in sciatic nerve. Clearance of branched acids from tissue lipids of the main internal organs was almost complete after the animals were returned to the basal diet for 14 days but the loss of branched acids from nerve tissue was evidently less rapid.