Nutritional and metabolic effects of dietary trans fats depend on the intake of linoleic acid

This study aimed to investigate the differential effects of trans fatty acids (TFA) on the nutritional parameters, serum and tissue triacylglycerol (TAG) levels, as well as the mechanisms involved in their regulation, in male Wistar rats fed linoleic acid-enriched (+LA) or LA-deficient (−LA) diets. The TFA effects on nutritional parameters and TAG metabolism differed depending on the dietary LA status. In the +LA + TFA diet, compared to the +LA diet, TFA did not alter the serum TAG levels despite the increased epididymal adipose tissue (EAT) lipoprotein lipase (LPL) activity and the higher hepatic TAG content associated with a lower CPT-Ia activity. Otherwise, in –LA + TFA rats versus −LA, TFA increased the serum, liver, and adipose tissue TAG levels associated with higher FAS, G6PDH, and ME enzyme activities in both liver and adipose tissue, and a reduced TAG clearance by the adipose tissue LPL enzyme. Although TFA supplementation in both –LA and +LA-rats tended to decrease the CPT-Ib activity, the muscle TAG levels were not modified. We conclude that the nutritional and metabolic TFA effects depended mainly on the changes in the FA profile induced by dietary LA and, in a lesser extent, on the specific type of isomer retained in the tissues. Practical applications: Our approach involved growing animals in healthy physiological conditions with recommended levels of dietary fats, moderate intake of industrial TFA, and an unbalanced dietary LA:ALA ratio. These variables constitute a feasible situation to be observed in the human population. The present study might contribute to the understanding of how nutritional and lipid parameters are affected in the metabolic disorders induced by TFA. TAG regulation by TFA in rats fed LA enriched and deficient diets.