Vitamin D insufficiency predicts elevated levels of complement 3 independent of insulin resistance and BMI

Abstract

This study was to determine serum 25-hydroxyvitamin D (25(OH)D), the complement 3 (C3), and C-reactive protein (CRP) levels, and their association with the risk of insulin resistance (IR). A case-control study was carried out among 134 participants with body mass index (BMI) ≥30 kg/m2 and BMI518.5-24.99 kg/m2. Anthropometric and body composition indicators were measured. Serum levels of C3, CRP, 25(OH)D, insulin, and glucose were also measured. IR was assessed by the homeostasis model assessment (HOMAIR). C3, CRP, insulin, and HOMA-IR levels were higher in participants with obesity than that of controls (p<0.001). After adjustment for the potential confounders, anthropometric and body composition indicators were correlated positively with C3 (p<0.001), and negatively with 25(OH)D (p<0.05). C3, and 25(OH)D were correlated with HOMA-IR (r=0.350; r=-0.212; p<0.05). In logistic regression analyses, C3 and CRP were significantly related to increased odds of IR among participants with obesity as compared to controls after progressively adjusting for the potential confounders (p<0.001), whereas 25(OH)D was negatively, but insignificantly, related to decreased odds of IR among participants with obesity (p>0.05). C3 was associated positively with 25(OH)D insufficiency/deficiency independent of HOMA-IR and/or BMI (β=0.183, p<0.05). Obesity is associated with elevated levels of proinflammatory biomarkers and IR. 25(OH)D insufficiency/deficiency was associated with C3 regardless of HOMA-IR or BMI, which could in turn, have a role in the augmentation of IR during obesity.