Circulating osteopontin and body composition in systemic lupus erythematosus: a cross-sectional study

BACKGROUND: To evaluate the association between circulating osteopontin (OPN) levels and bioelectrical impedance analysis (BIA)-derived body composition measures in adults with systemic lupus erythematosus (SLE), with body fat percentage as the primary outcome and central adiposity and lean-mass surrogates as secondary outcomes.METHODS: Observational cross-sectional study with prospective recruitment of adults with SLE attending a tertiary referral center in Puebla, Mexico. Plasma OPN was quantified by ELISA (Quantikine®, R&D Systems; coefficient of variation 4.1%). Body composition was assessed by BIA (TANITA BC-545F FitScan) under fasting morning conditions. Associations between OPN and continuous body composition measures were examined using Spearman correlations (pairwise complete data). Sensitivity analyses used linear regression with ln(OPN) as the dependent variable, adjusting for age, sex, disease duration, SLEDAI-2K, and current prednisone exposure.RESULTS: Sixty-two patients were included (96.8% women), mean age 51.3±12.8 years; median disease duration 21.5 years (IQR 18.0-25.0). Disease activity was low (median SLEDAI-2K 0 [IQR 0-2]); 46.8% met LLDAS. Median OPN was 16.11 ng/mL (IQR 7.97-54.06). Mean BMI was 29.3±5.6 kg/m2, and 79.5% were overweight/obese. OPN showed no significant association with BMI, body fat percentage, visceral fat rating, muscle mass, or waist circumference. Adjusted regression analyses also remained non-significant.CONCLUSIONS: In this SLE cohort with predominantly low activity, circulating OPN levels were not associated with BIA-derived adiposity, central adiposity, or lean-mass surrogates, suggesting that OPN may reflect lupus-related inflammatory biology rather than body composition phenotypes.