Taurine included abundantly in skeletal muscle, particularly in the slow-twitch fibers, enhances exercise performance. However, the exact mechanisms for this effect have been unclear. The present study investigated the influence of taurine supplementation on amino acids profile in skeletal muscles as one of mechanisms in the enhancement of exercise performance induced by taurine. In the rats that received taurine solution, amino acids concentrations were comprehensively quantified in two portions with different fiber compositions in the fast-twitch fiber dominant (FFD) gastrocnemius muscle after 2 weeks, and in the gastrocnemius and additional other FFD muscles, liver, and plasma with exhausted exercise after 3 weeks. In the FFD muscles after 2 weeks, a common phenomenon that decreased concentrations of threonine (-16%), serine (-15~-16%), and glycine (-6~-16%) were observed, and they are categorized in the pyruvate precursors for hepatic gluconeogenesis rather than biosynthesis, polar, and side-chain structures. The decreases in the three amino acids were significantly emphasized after an additional week of taurine supplementation in the FFD muscles (p values in three amino acids in these tissues were less than 0.001-0.05), but not in the liver and plasma, accompanied with significantly increase of running time to exhaustion (p <0.05). In contrast, the three amino acids (threonine and serine; p < 0.05, glycine; p < 0.01) and alanine (p < 0.01) in the liver were significantly decreased and increased, respectively, following the exhaustive exercise. In conclusion, the taurine-induced reductions of these amino acids in skeletal muscle might be one of the mechanisms which underpin the enhancement of exercise performance by taurine. Key pointsTaurine ingestion significantly decreased certain amino acids in skeletal muscles accompanied with enhanced exercise performance.The decreased amino acids in common were threonine, serine, and glycine, but not alanine; pyruvate precursor for gluconeogenesis.The alteration of three amino acids in muscles was maintained after exhausted exercise.The muscular alterations of them might be one of taurine-induced roles on exercise performance.
Keywords: Serine; gluconeogenic precursor; glycine; threonine; treadmill.