Association of Elevated Serum Branched-chain Amino Acid Levels With Longitudinal Skeletal Muscle Loss.

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Context: Branched-chain amino acids (BCAA) are substrates for protein synthesis. Although their intake may contribute to an increase in skeletal muscle mass, elevated serum BCAA levels have been reported to be associated with insulin resistance, potentially resulting in decreased skeletal muscle mass.Objective: This study aimed to explore the association between elevated serum BCAA levels and longitudinal skeletal muscle loss.Design and setting: A cohort analysis was conducted, in which serum amino acids were analyzed in healthy individuals who underwent a medical health checkup at Kameoka Municipal Hospital (HOZUGAWA study), Japan.Patients: Seventy-one participants (37 men and 34 women) underwent follow-up checkups after the baseline visit. The follow-up duration was 1.2 ± .4 years.Main outcome measures: The relationship between fasting baseline serum BCAA levels and lifestyle factors, body composition, blood test results, dietary history, and changes in skeletal muscle mass was evaluated.Results: In both men and women, serum BCAA levels were positively correlated with body weight, body mass index, skeletal muscle mass index (SMI), and serum triglycerides but inversely correlated with serum high-density lipoprotein cholesterol. In men, fasting serum BCAA levels were inversely associated with the rate of change in SMI (adjusted β = -.529, P = .006), and elevated BCAA levels were independently associated with a longitudinal decrease in skeletal muscle mass (odds ratio: 1.740; 95% confidence interval: 1.023-2.960 per 50 nmol/mL serum BCAAs increase).Conclusion: Increased circulating BCAAs could be an indicator of skeletal muscle loss in men.