Tetradecylthioacetic acid reduces the amount of lipid droplets, induces megamitochondria formation and increases the fatty acid oxidation in rat heart

The effects of prolonged administration (3 months) of a 3-thia fatty acid analogue and omega-3-fatty acids on cardiac fatty acid oxidation and the volume fraction of lipid droplets and mitochondria in cardiomyocytes were investigated. Doses were 1 g/day/kg body weight, except 150 mg/day/kg body weight for tetradecylthioacetic acid (a 3-thia fatty acid). One group served as control and did not receive any treatment. The volume fraction of lipid droplets in cardiomyocytes was significantly lower in the tetradecylthioacetic acid group compared to the other groups. Mitochondrial beta-oxidation was 60% greater and fatty acyl-CoA oxidase activity was increased by 430% in the tetradecylthioacetic acid group compared to control. This was accompanied by a greater volume fraction of mitochondria in cardiomyocytes (0.514 +/- 0.032% in tetradecylthioacetic acid v 0.318 +/- 0.007% in control) which was due to an increased size of mitochondria. The volume fraction of mitochondria was also greater in eicosapentaenoic acid (EPA) treated rats compared to control, but the enzymic activities were unaffected. Docosahexaenoic acid (DHA) treatment resulted in a greater volume fraction of lipid droplets in the cardiomyocytes, but the volume fraction of mitochondria and enzyme activities were unaltered. These results indicate that EPA and DHA have different effects on the modulation of mitochondrial biogenesis. Tetradecylthioacetic acid treatment results in megamitochondria formation and increased peroxisomal and mitochondrial beta-oxidation with a concomitant reduction of lipid droplets in the cardiomyocytes.