Trans fatty acid retention and conversion rates of fatty acids in tissues depend on dietary fat in mice

Given that the effects of trans fatty acids (TFA) may be associated with the type of TFA isomer and the proportion of n-3/n-6/n-9 fatty acids (FA), this work aimed to investigate the influence of different oils on the following parameters: content, incorporation, and retention of TFA; conversion of vaccenic acid (VA) to rumenic acid (RA) in different tissues; and hepatic output of TFA by VLDL. Another objective was to assess relative conversion rates of key FA and the potential alteration of FA composition induced by TFA in tissues. Male CF1 mice were fed (30-days) diets containing 7% olive, corn or rapeseed oils either supplemented with 0.75% of TFA or without added TFA. FA composition of liver, epididymal adipose tissue, gastrocnemius muscle, brain, and serum was assessed. With the exception of the brain, TFAs were incorporated into the analyzed tissues and serum. TFA retention and RA bioconversion from VA depended on the dietary unsaturated FA proportions. The higher levels of hepatic RA in the liver of mice fed an olive oil+TFA diet could be associated with a raised Δ9-desaturase index. The FA composition of tissues was scarcely modified by the consumption of partially hydrogenated vegetable oils containing similar proportions of t9-, t10-, and t11-18:1. Practical applications: The present study evaluates the interaction of hydrogenated vegetable oils with different edible oils and the impact on the FA profile and, specifically, TFA incorporation and retention in the tissues. Since the characterization of FA present in tissues might be determining the biological effects of edible fats, this study is relevant for elucidation of existing controversial findings associated with the intake of TFA and its effects on human metabolic alterations. The levels of trans fatty acids (TFA) in a particular tissue might be related to different variables including: type and level of the dietary TFA isomer; uptake, metabolization and release from the tissue, and interference with different dietary fatty acids.