Weight cycling-induced reduction of linoleic acid in carcass and adipose tissue in rats

Abstract

Recent epidemiological studies have proposed the hypothesis that large fluctuations in body weight over time may increase the risk of cardiovascular disease. Several studies have demonstrated that there is an inverse correlation between adipose tissue linoleic acid content and the risk of coronary heart disease. This led us to consider whether several weight cyclings induced by food restriction followed by regain could affect metabolism of linoleic acid and α-linolenic acid and their longer-chain polyunsaturated fatty acids. Fifty rats were fed a semipurified diet containing 15% fat (30.5% kcal) in which linoleic acid and α-linolenic acid accounted for 7.2 and 3.5% of total fatty acids, respectively. They were randomly divided in two groups. The control (CTL) group was allowed free access to diet whereas the weight-cycled (W-CYC) rats were subjected to four cycles of partial food restriction (24% intake of ad libitum controls, about 5 g/day) for 3 or 4 days to reduce body weight followed by ad libitum refeeding until the weight reached the corresponding average of the CTL group. Four rats were killed as baseline values before weight cycle. The rest of the rats from each group were killed at the beginning ( n = 5), tge end of partial food restriction ( n = 9), and the end of ad libitum refeeding ( n = 10) in weight cycle 4. The fatty acid compositions of the liver, epididymal, and perirenal adipose tissue and carcass were determined by gas liquid chromatography. The W-CYC rats, compared with the CTL rats, increased significantly their food intake immediately after each partial food restriction but thereafter gradually reached that of the CTL. No differences in the weights of liver, epididymal, and perirenal adipose tissue were observed between the W-CYC and CTL group after four weight cycles. Contrary to ad libitum feeding, four weight cyclings decreased the content of linoleic acid in the carcass, epididymal and perirenal adipose tissue. α-linolenic acid was also lower in the W-CYC rats than in the CTL group, but a significant difference was observed only at the end of partial food restriction. Compared with those in the CTL, the liver fatty acids in the W-CYC rats were remarkably modified during the partial food restriction, showing an increase in linoleic, α-linolenic, and arachidonic acids but a decrease in oleic and palmitoleic acids. The food restriction-induced changes in liver fatty acids were reversed after the ad libitum refeeding. We conclude that weight cycling alters body fatty acid composition characterized by a selective decrease in the linoleic acid content of carcass and adipose tissues without significantly changing the total body fat content and the weight of perirenal and epididymal fat pads.