Abstract
Plasma and tissue sulfur amino acid (SAA) availability are crucial for intracellular methylation reactions and cellular antioxidant defense, which are important processes during exercise and in recovery. In this randomized, controlled crossover trial among eight elite male cyclists, we explored the effect of exhaustive exercise and post-exercise supplementation with carbohydrates and protein (CHO+PROT) vs. carbohydrates (CHO) on plasma and urine SAAs, a potential new marker of methylation capacity (methionine/total homocysteine ratio [Met/tHcy]) and related metabolites. The purpose of the study was to further explore the role of SAAs in exercise and recovery. Athletes cycled to exhaustion and consumed supplements immediately after and in 30 min intervals for 120 min post-exercise. After ~18 h recovery, performance was tested in a time trial in which the CHO+PROT group cycled 8.5% faster compared to the CHO group (41:53 ± 1:51 vs. 45:26 ± 1:32 min, p < 0.05). Plasma methionine decreased by ~23% during exhaustive exercise. Two h post-exercise, further decline in methionine had occured by ~55% in the CHO group vs. ~33% in the CHO+PROT group (pgroup × time < 0.001). The Met/tHcy ratio decreased by ~33% during exhaustive exercise, and by ~54% in the CHO group vs. ~27% in the CHO+PROT group (pgroup × time < 0.001) post-exercise. Plasma cystathionine increased by ~72% in the CHO group and ~282% in the CHO+PROT group post-exercise (pgroup × time < 0.001). Plasma total cysteine, taurine and total glutathione increased by 12% (p = 0.03), 85% (p < 0.001) and 17% (p = 0.02), respectively during exhaustive exercise. Using publicly available transcriptomic data, we report upregulated transcript levels of skeletal muscle SLC7A5 (log2 fold-change: 0.45, FDR:1.8e−07) and MAT2A (log2 fold-change: 0.38, FDR: 3.4e−0.7) after acute exercise. Our results show that exercise acutely lowers plasma methionine and the Met/tHcy ratio. This response was attenuated in the CHO+PROT compared to the CHO group in the early recovery phase potentially affecting methylation capacity and contributing to improved recovery.
Highlights
Sulfur amino acids (SAAs) include proteinogenic methionine and cysteine as well as non-proteinogenic sulfur compounds such as homocysteine, cystathionine, taurine, and the tripeptide glutathione (Brosnan and Brosnan, 2006)
The Met/total homocysteine (tHcy) ratio, an indicator of methylation capacity, decreased by ∼33% during exhaustive exercise, and had further decreased by ∼54% in the CHO group 120 min post-exercise, whereas a decrease of ∼27% was observed in the CHO+PROT group (p for group × time interaction < 0.001)
We show that plasma concentrations of methionine and serine decrease after exhaustive exercise, whereas plasma concentrations of the other SAAs increased
Summary
Sulfur amino acids (SAAs) include proteinogenic methionine and cysteine as well as non-proteinogenic sulfur compounds such as homocysteine, cystathionine, taurine, and the tripeptide glutathione (Brosnan and Brosnan, 2006). The metabolism of SAAs involves the conversion of methionine to S-adenosylmethionine and subsequently to homocysteine (transmethylation), which in turn can undergo re-methylation to methionine or irreversible transsulfuration (see Figure 1 for details). Homocysteine is used to irreversibly form cystathionine and subsequently cysteine, which in turn can be converted to taurine or glutathione. SAA availability is crucial for synthesis of the major systemic antioxidant glutathione, a process that is activated by reactive oxidative species (ROS) (Banerjee et al, 2003; Stipanuk, 2004) formed during exercise (Radak et al, 2008, 2013)
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