Effect of triiodothyronine (T3) excess on fatty acid metabolism in the soleus muscle from endurance-trained rats.Effect of triiodothyronine (T3) excess on fatty acid metabolism in the soleus muscle from endurance-trained rats.

We studied whether short-term T3 administration at the end of endurance training will influence the rate of palmitic acid (PA) uptake and metabolism in rat soleus muscle in vitro. Training per se did not affect the rate of PA uptake by the soleus, however, T3 excess increased the rate of this process at 1.5mM PA and the rate of PA incorporation into intramuscular triacylglycerols (TG). In trained euthyroid rats the rate of TG synthesis was reduced after exercise (1.5mM PA). In all trained rats immediately after exercise the rate of PA oxidation was enhanced compared to sedentary value. Hyperthyroidism additionally increased the rate of this process at 1.5mM PA. After recovery the rate of PA oxidation returned to control value in both groups. High-energy phosphates content demonstrated that elevated PA oxidation after exercise-training in euthyroid rats was associated with stable ATP concentration and increased ADP and AMP content thus reducing energy cellular potential (ECP). In hyperthyroid rats ADP and AMP were increased in sedentary and exercise-trained rats. After recovery in hyperthyroid rats ECP was high resulting from high ATP and decreased ADP and AMP. In conclusion, already short-term hyperthyroidism accelerates PA utilization in well-trained soleus muscle.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author