Seven days of oral taurine supplementation does not increase muscle taurine content or alter substrate metabolism during prolonged exercise in humans

This study examined 1) the plasma taurine response to acute oral taurine supplementation (T), and 2) the effects of 7 days (d) of T on muscle amino acid content and substrate metabolism during 2 hr of cycling at ~60% VO2peak. 1) After an overnight fast seven volunteers (28±3yr, 184±2cm, 88.0±6.6kg) ingested 1.66g oral taurine doses with breakfast (8AM) and lunch (12noon) and blood samples were taken throughout the day. 2) Eight males (22±1yr, 181±1cm, 80.9±3.8kg, 4.21±0.16L.min-1 VO2peak) cycled for 2hr after 7d of placebo (P) ingestion (6g glucose/d) and again following 7d of T (5g/d). 1) Plasma taurine was 64±4µM prior to T and rose rapidly to 778±139µM by 10AM and remained elevated at noon (359±56µM). Plasma taurine reached 973±181µM at 1PM and was 161±31µM at 4PM. 2) Seven days of T had no effect on muscle taurine content (mmol/kg dry muscle) at rest (P, 44±15 vs. T, 42±15) or after exercise (P, 43±12 vs. T, 43±11). There was no difference in muscle glycogen or other muscle metabolites between conditions, but there were notable increases in muscle indispensable amino acid content following exercise after T. These data indicate that 1) acute T produces a 13 fold increase in plasma taurine concentration, 2) despite the ability to significantly elevate plasma taurine for extended periods throughout the day, 7 days of T does not alter skeletal muscle taurine content or carbohydrate and fat oxidation during exercise, and 3) T appears to alter muscle indispensable amino acid response to exercise