Trans-vaccenic acid is desaturated to conjugated linoleic acid in mice

Mice were fed pure trans,, octadecenoic acid (trans-vaccenic acid; TVA) to determine whether it is desaturated to cis(9), trans(11) octadecadienoic ac id, a predominant isomer of conjugated linoleic acid (CLA). In a preliminar y trial, 12% of the TVA consumed during a 2-wk feeding period was recovered in the carcass as CLA. As a proportion of TVA in the tissues available for bioconversion, 48.8% was desaturated. We tested whether desaturation could be modified by supplementing no modifier, 0.5% clofibric acid to stimulate desaturation, or increasing the polyunsaturated fatty acids (PUFA) (10% co rn oil vs. 4% corn oil) to inhibit desaturation in diets with or without 1% TVA. These diets were fed to six groups of mice in a 3 x 2 factorial arran gement of treatments. Feeding 1% TVA with 10% corn oil decreased feed intak e (2.70 vs. 3.73 g/d, SEM 0.23; P < 0.05). Bioconversion of dietary TVA was 12.0, 7.5 and 5.1% for mice fed no modifier of desaturation, clofibrate an d increased PUFA, respectively. Conversion based on TVA available for desat uration was 52.6, 55.5 and 37.0%, respectively. Thus, clofibrate did not in crease bioconversion, but increasing PUFA decreased conversion by 30%, To t est whether TVA decreases food intake directly or after conversion to CLA, four groups of mice were fed diets containing 1% stearic, TVA, elaidic or c onjugated linoleic acid. Dietary CLA decreased food intake and body fat, bu t did not change body protein. CLA was found in the carcass only when TVA o r CLA was fed. CLA was found in both triacylglycerol and phospholipids when CLA was fed, but only in triacylglycerol when TVA was fed, suggesting that bioconversion occurred in the adipose tissue. In three trials, conversion of dietary TVA to CLA was 11.4 +/- 1.25%; conversion of stored n/A was 50.8 +/- 1.91%. Similar bioconversion of TVA in humans would increase current e stimates of CLA available for the general population by 6- to 10-fold.