Trans-octadecenoic Acid Positional Isomers Have Different Accumulation and Catabolism Properties in Mice

Trans fatty acids (TFA) are considered risk factors for cardiovascular disease (CVD), while the details of distribution and metabolism of the individual isomers are not clear. Here we investigated the accumulation and catabolic rate of TFA positional isomers of octadecenoic acid (18:1) in mice. ICR mice were fed deuterium- and [1-(13)C] stable isotope-labeled trans-9-18:1 (9t-18:1*), trans-10-18:1 (10t-18:1*), or trans-11-18:1 (11t-18:1*) for 2 or 4 weeks, or a TFA mixture (9t-18:1*, 10t-18:1*, and 11t-18:1*) for 3 weeks. Analysis of whole-body tissues by gas chromatography-chemical ionization mass spectrometry revealed the highest 9t-18:1* levels in the heart. Significant differences in the accumulation of the respective trans-18:1 were observed in the heart and erythrocytes, where 9t- > 11t- > 10t-18:1*, but no significant difference was observed in the liver or white adipose tissue (WAT). Mice fed on 11t-18:1 demonstrated accumulation of endogenously synthesized conjugated linoleic acid in the liver, WAT, and heart, but any other metabolites were not found in other groups. Furthermore, we analyzed catabolic rates of single-dose-administered trans-18:1* isomers into [(13)C]-labeled CO2 using isotope-ratio mass spectrometry, and the 10t-18:1*catabolic rate was significantly higher than those of 9t- and 11t-18:1*. We found that the accumulation and catabolism of trans-18:1 positional isomers varied in these mice. Differential accumulation in tissues suggests that individual TFA positional isomers may play different roles in human health.