Leucine Supplementation Improves Effort Tolerance of Rats With Hyperthyroidism

et al. 2020

Preprint

Background Few nutritional markers reflect the hypermetabolic state of athletes with high levels of skeletal muscle. Although branched-chain amino acids (BCAA) play crucial roles in protein metabolism in skeletal muscle, the relationship between circulating BCAA concentration and skeletal muscle mass has not been fully understood. The aim of this study is to evaluate the association between skeletal muscle mass and serum BCAA to tyrosine ratio (BTR), a convenient indicator of circulating BCAA, in young Japanese men including wrestling athletes with high skeletal muscle mass. Methods The study enrolled 111 young Japanese men: 70 wrestling athletes and 41 controls. None were taking medications or undergoing extreme dietary restriction or an intense exercise regimen. Each participant’s body composition, serum concentrations of albumin and rapid turnover proteins including transthyretin and transferrin, BTR, and thyroid function were assessed. Results Compared to the controls, the athletes had significantly higher skeletal muscle index (SMI) (p < 0.001), and lower serum albumin concentration (p < 0.001) and BTR (p < 0.001). Kruskal–Wallis tests showed that serum albumin concentration and BTR were significantly lower in the participants with higher SMI. Serum albumin concentration and BTR were inversely correlated with SMI by multiple regression analysis (logarithmic albumin, β = −0.358, p < 0.001; BTR, β = −0.299, p = 0.001). SMI was inversely and transthyretin was positively correlated with serum albumin (SMI, β = −0.554, p < 0.001; transthyretin, β = 0.379, p < 0.001). Serum concentration of free 3,5,3'-triiodothyronine (FT3) was inversely correlated with BTR, and, along with SMI and albumin, was independent predictor of BTR (SMI, β = −0.321, p < 0.001; FT3, β = −0.253, p = 0.001; logarithmic albumin, β = 0.261, p = 0.003), but was not correlated with SMI or serum albumin. Serum concentrations of rapid turnover proteins were not correlated with BTR. Conclusions These results suggest that increased skeletal muscle mass enhances the consumption of circulating BCAAs, facilitated by thyroid hormones independently. Serum BTR may be a useful biomarker to assess the hypermetabolic state of wrestling athletes with high levels of skeletal muscle.

Section: Discussionsupporting

confidence: 67%

Significance of serum branched-chain amino acid to tyrosine ratio measurement in athletes with high skeletal muscle mass

et al. 2020

Preprint

“…However, we observed an inverse correlation between serum FT 3 concentration and serum BTR. A study of rats with hyperthyroidism showed that leucine supplementation improved their swimming performance [24]; this suggests that thyroid hormones increase BCAA metabolism in skeletal muscle, which may be relevant to our results. Further studies are needed to elucidate the mechanisms of BCAA metabolism in skeletal muscle involving thyroid hormones.…”

Section: Discussionsupporting

confidence: 67%

Circulating branched-chain amino acid concentrations are associated with skeletal muscle mass and thyroid function in young Japanese men

et al. 2020

Preprint

Background Few nutritional markers reflect the hypermetabolic state of athletes with high levels of skeletal muscle. Although branched-chain amino acids (BCAA) play crucial roles in protein metabolism in skeletal muscle, the relation between circulating BCAA concentration and skeletal muscle mass has not been fully understood. The aim of this study is to evaluate the association between skeletal muscle mass and serum BCAA to tyrosine ratio (BTR), a convenient indicator of circulating BCAA, in young Japanese men including wrestling athletes with high skeletal muscle mass. Methods The study enrolled 111 young Japanese men: 70 wrestling athletes and 41 controls. None were taking medications or undergoing extreme dietary restriction or an intense exercise regimen. Each participant’s body composition, serum concentrations of albumin and rapid turnover proteins, BTR, and thyroid function were assessed. Results Compared to the controls, the athletes had significantly higher weight-adjusted skeletal muscle mass (SMM) (p < 0.001) and skeletal muscle index (SMI) (p < 0.001), and lower serum albumin concentration (p < 0.001) and BTR (p < 0.001). Kruskal–Wallis tests with Bonferroni multiple comparison tests showed that serum albumin concentration and BTR were significantly lower in the participants with higher SMM and SMI. Spearman's correlation analyses showed that SMM and SMI were inversely correlated with serum albumin concentration (SMM, ρ = −0.315, p = 0.001; SMI, ρ = −0.511, p < 0.001) and BTR (SMM, ρ = −0.424, p < 0.001; SMI, ρ = −0.511, p < 0.001). Serum albumin concentration was positively correlated with BTR (ρ = 0.438, p < 0.001), transthyretin (ρ = 0.281, p = 0.003) and transferrin (ρ = 0.299, p = 0.001), but BTR was not correlated with other nutritional indicators. Serum concentration of free 3,5,3′-triiodothyronine was inversely correlated with BTR (ρ = −0.308, p = 0.001), but not with serum albumin or skeletal muscle mass. Conclusions These results suggest that the consumption of circulating BCAAs increases with increased skeletal muscle mass and is facilitated by thyroid hormones independent of skeletal muscle mass. Serum BTR may be a useful biomarker to assess the hypermetabolic state of athletes.

“…However, we did observe an inverse correlation between serum FT 3 concentration and serum BTR. A study of rats with hyperthyroidism showed that leucine supplementation improved their swimming performance [30]; this suggests that thyroid hormones increase BCAA metabolism in skeletal muscle. However, the mechanisms of thyroid hormone involvement in amino acid imbalances or BCAA metabolisms have not yet been studied.…”

Section: Discussionmentioning

confidence: 99%

Significance of serum branched-chain amino acid to tyrosine ratio measurement in athletes with high skeletal muscle mass

BMC Sports Sci Med Rehabil

et al. 2021

Background Few nutritional markers reflect the hypermetabolic state of athletes with high levels of skeletal muscle. Although branched-chain amino acids (BCAA) play crucial roles in protein metabolism in skeletal muscle, the relationship between skeletal muscle mass and amino acid imbalances caused by the metabolism of BCAA and aromatic amino acids remains unclear. The aim of this study is to test the hypothesis that athletes with high levels of skeletal muscle mass have plasma amino acid imbalances, assessed by serum BCAA to tyrosine ratio (BTR) which can be measured conveniently. Methods The study enrolled 111 young Japanese men: 70 wrestling athletes and 41 controls. None of them were under any medications, extreme dietary restrictions or intense exercise regimens. Each participant’s body composition, serum concentrations of albumin and rapid turnover proteins including transthyretin and transferrin, BTR, and thyroid function were assessed. Results Compared to the controls, the athletes had significantly higher skeletal muscle index (SMI) (p < 0.001), and lower serum albumin concentration (p < 0.001) and BTR (p < 0.001). Kruskal–Wallis tests showed that serum albumin concentration and BTR were significantly lower in the participants with higher SMI. Serum albumin concentration and BTR were inversely correlated with SMI by multiple regression analysis (logarithmic albumin, β = − 0.358, p < 0.001; BTR, β = − 0.299, p = 0.001). SMI was inversely and transthyretin was positively correlated with serum albumin (SMI, β = − 0.554, p < 0.001; transthyretin, β = 0.379, p < 0.001). Serum concentration of free 3,5,3′-triiodothyronine (FT3) was inversely correlated with BTR, and, along with SMI and albumin, was independent predictor of BTR (SMI, β = − 0.321, p < 0.001; FT3, β = − 0.253, p = 0.001; logarithmic albumin, β = 0.261, p = 0.003). However, FT3 was not correlated with SMI or serum albumin. Serum concentrations of rapid turnover proteins were not correlated with BTR. Conclusions Increased skeletal muscle mass enhances the circulating amino acid imbalances, and is independently facilitated by thyroid hormones. Serum BTR may be a useful biomarker to assess the hypermetabolic state of wrestling athletes with high levels of skeletal muscle.