Effects of dietarycis9,trans11–18: 2,trans10,cis12–18: 2, or vaccenic acid (trans11–18: 1) during lactation on body composition, tissue fatty acid profiles, and litter growth in mice

Abstract

Cis9,trans11 (c9,t11)-18: 2 andtrans10,cis12 (t10,c12)-18: 2 are the major conjugated linoleic acid (CLA) isomers in dietary supplements which reduce milk fat content in nursing women. The present study evaluated the effects of each CLA isomer or vaccenic acid on body composition and tissue fatty acids during lactation in mice. Dams were fed 30 g rapeseed oil (control)/kg diet or 20 g control plus 10 g 18: 0,trans11–18: 1 (t11–18: 1),c9,t11–18: 2, ort10,c12–18: 2. Dietaryt10,c12–18: 2 reduced food intake by 18 % and carcass fat weight of the dams by 49 % compared with the other treatments. Milk fat percentage ranked by treatment was 18: 0>t11–18: 1=c9,t11–18: 2>t10,c12–18: 2. The sum of saturated 12: 0 to 16: 0 in milk fat was lower whenc9,t11–18: 2 was fed compared with the control, 18: 0, ort11–18: 1 treatments. Dietaryt10,c12–18: 2 caused further reductions in milk fat 12: 0 to 16: 0. The proportion of CLA isomers was 3-fold greater in milk fat than in the carcasses of the dams. The pups nursing from the dams fedt10,c12–18: 2 had the lowest body weights and carcass fat, protein, and ash contents. Nursing from the dams fedc9,t11–18: 2 also resulted in lower carcass fat compared with the 18: 0 ort11–18: 1 treatments. The ratios ofcis9–16: 1:16: 0 orcis9–18: 1:18: 0, proxies for Δ9-desaturase activity, were markedly lower in the carcasses of the dams and pups fedt10,c12–18: 2. The ratio of 20: 4n-6:18: 2n-6, a proxy for Δ6- and Δ5-desaturase and elongase activity, in the liver of the dams and pups fedt10,c12–18: 2 also was lower. Dietaryt11–18: 1 enhanced the content ofc9,t11–18: 2 in milk fat and carcasses. As in previous studies, the reduction in food intake byt10,c12–18: 2 could not entirely account for the marked decrease in carcass fat content and milk fat concentration.T10,c12–18: 2 probably had a negative effect on Δ9-desaturase and mammaryde novofatty acid synthesis. Although these effects need to be confirmed in lactating women, the results suggest that the consumption of supplements containingt10,c12–18: 2 should be avoided during the nursing period.