Metabolic effects of trans fatty acids on an experimental dietary model.

The aim of the present study was to investigate the potential nutritional and metabolic impact of trans (t) fatty acids (FA) on an appropriate experimental dietary model. Since previously reported experimental designs have been matter of concern, we developed a dietary model to compare the effect of t isomers and/or the saturation of FA independently of other variables. Wistar rats were fed diets containing identical amounts of nutrients and high levels of dietary fats (200 g/kg) for 30 d. Dietary fat rich in t-FA was compared with fat rich in saturated (s) FA or rich in cis (c) FA, maintaining the same length of C chain of the FA. The fats were obtained through isomerization or hydrogenation of the c-FA present in the control fat. Apparent fat absorption, energy efficiency and triacylglycerol levels in serum and liver were different in rats fed t-FA or s-FA than c-FA. The apparent fat absorption was (%): s-FA 85.7 (sd 3.4)<t-FA 93.1 (sd 0.4)<c-FA 96.7 (sd 1.1) (P<0.05). The efficiency of energy utilization was lower in t-FA (11.7 %) and s-FA (18.5 %) diets, reaching statistical significance only between s-FA and c-FA. A striking finding was the change in the lipid profile in serum and liver. Serum and hepatic triacylglycerol levels were greater for t-FA and s-FA diets than in c-FA; however, the increases on serum triacylglycerol concentrations were greater with the s-FA diet and the increases on hepatic triacylglycerol content were greater with t-FA. Knowledge of the t-FA effects on this kind of experimental dietary model could contribute to determine the potential risk of t-FA intake for man.