Association between serum uric acid and muscle function in underweight young women: An exploratory cross-sectional study

INTRODUCTION: Uric acid (UA), a major endogenous antioxidant involved in oxidative stress regulation and energy metabolism, has been linked to skeletal muscle health. However, evidence regarding its association with muscle function and muscle mass in underweight young women is limited. This study investigated the associations between serum UA levels, handgrip strength, and skeletal muscle mass in underweight young women. METHODS: This cross-sectional study included 73 underweight female university students (body mass index <18.5 kg/m²) who underwent detailed assessments following annual health checkups at Shimane University, Japan, between 2022 and 2024. Participants were categorized by muscle mass and handgrip strength status based on the Asian Working Group for Sarcopenia (AWGS) 2019 cut-off values. Serum UA levels were compared among groups. Associations between UA and muscle-related parameters were examined using correlation analyses. Multivariable linear regression analyses were performed with handgrip strength as the dependent variable and serum UA as the independent variable, adjusting for age, skeletal muscle index (SMI), estimated glomerular filtration rate (eGFR), daily energy intake, and physical activity. RESULTS: Serum UA was positively correlated with handgrip strength (r = 0.273, p = 0.013) but not with SMI (r = 0.080, p = 0.503). Participants with low muscle mass and reduced handgrip strength had significantly lower UA levels than those with low muscle mass only (3.4 ± 0.7 vs. 4.1 ± 0.6 mg/dL, p = 0.020). In multivariable linear regression analyses, serum UA was independently associated with handgrip strength after adjustment for age, SMI, eGFR, daily energy intake, and physical activity. CONCLUSIONS: Serum UA was associated with handgrip strength but not with skeletal muscle mass in underweight young women. These findings suggest that serum UA may be more closely related to muscle function than muscle mass in this population. Further studies are needed to clarify the mechanisms underlying this association.