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

Katsuhiko Tsunekawa,Masami Murakami,Yoshimaro Yanagawa,Larasati Martha,Kazumi Ushiki,Kiyomi Nakajima,Yoshifumi Shoho,Akihiro Yoshida,Ryutaro Matsumoto,Hirotaka Ishigaki,Osamu Araki,Takao Kimura

doi:10.1186/s13102-020-00229-1

Katsuhiko Tsunekawa, Masami Murakami + Show 10 more

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https://doi.org/10.1186/s13102-020-00229-1

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Abstract

BackgroundFew 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.MethodsThe 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.ResultsCompared 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.ConclusionsIncreased 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.

Highlights

Few nutritional markers reflect the hypermetabolic state of athletes with high levels of skeletal muscle
Serum albumin concentration and branched-chain amino acids (BCAAs) to tyrosine ratio (BTR) were inversely correlated with skeletal muscle index (SMI), and serum Free 3 (FT3) concentration was inversely correlated with serum BTR, independently
The present study showed a decrease in serum BTR with increased skeletal muscle mass, it was not designed to assess the differences between enhanced BCAA consumption and reduced BCAA release in skeletal muscles

Summary

Introduction

Few nutritional markers reflect the hypermetabolic state of athletes with high levels of skeletal muscle. 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. Because of their branched structure, the essential amino acids valine, leucine, and isoleucine are collectively referred to as the branched-chain amino acids (BCAAs). BCAAs are involved in the regulation of protein metabolism in skeletal muscle cells; for example, leucine activates mammalian target of rapamycin complex 1 (mTORC1), which stimulates protein synthesis and suppresses proteolysis by autophagy [3] This activation of mTORC1 requires a high concentration of circulating leucine to be maintained [4]. We previously reported that wrestling athletes with high levels of skeletal muscle had high concentrations of LPL and GPIHBP1, and that increasing skeletal muscle mass improved effective energy use by promoting the hydrolysis of TGrich lipoproteins [11]

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