Opposing associations of muscle and fat mass changes on serum uric acid levels: a 2-year longitudinal cohort study

BACKGROUND/AIMS: Obesity elevates serum uric acid (SUA) levels, but the influence of muscle mass remains unclear. As a major endogenous purine pool, skeletal muscle may affect SUA dynamics. We evaluated the impact of changes in body components, including skeletal muscle mass index (SMI), fat mass index (FMI), and waist-to-hip ratio (WHR), on SUA in a large cohort of healthy Koreans. METHODS: We analyzed 39,505 adults (24,623 men; 14,180 premenopausal and 702 postmenopausal women) who underwent health checkups in 2015-2017. Body composition was assessed using bioimpedance analysis. Participants were categorized into seven groups based on 2-year changes in SMI, FMI, and WHR (tertiles of increase, decrease, and no change). Hyperuricemia was defined as SUA ≥ 7 mg/dL in men and ≥ 6 mg/dL in women. Odds ratios (ORs) for achieving optimal SUA levels (< 6 mg/dL) and regression coefficients for SUA changes were calculated. RESULTS: Mean SUA levels were 6.25 ± 1.21 mg/dL in men, 4.23 ± 0.88 mg/dL in premenopausal women, and 4.34 ± 0.91 mg/dL in postmenopausal women. SUA changed dose-dependently with body component: SMI increases were associated with reduced SUA (OR [95% CI] for the highest tertile = 1.45 [1.32-1.59] in men; 1.48 [1.06-2.06] in premenopausal women), while FMI and WHR increases correlated positively with SUA. CONCLUSION: Two-year changes in body composition significantly influenced SUA levels, particularly in men and premenopausal women. Increasing muscle mass and reducing adiposity may be associated with improved urate control in individuals with hyperuricemia or those prone to gout.