Associations of Serum 25-Hydroxyvitamin D3 Levels with Visceral Adipose Tissue in Chinese Men with Normal Glucose Tolerance

Objective: Decreased serum vitamin D level is a common observation in obese adults. Since no Chinese population-based study has yet evaluated the relationship between serum vitamin D levels and the accurate adiposity variables, this study investigated the association of serum vitamin D (assessed by 25-hydroxyvitamin D-3 [25(OH)D-3]) levels with precise body fat content and distribution in a cohort of Chinese men. Methods: Serum samples were collected from a total of 567 men with normal glucose tolerance (NGT) for assessment by electrochemiluminescence immunoassay to measure 25(OH)D-3 levels. In addition, each participant underwent bioelectrical impedance analysis to quantify total body fat and magnetic resonance imaging to measure visceral fat area (VFA) and subcutaneous fat area (SFA). Results: Overweight/obese (BMI >= 25 kg/m(2)) subjects had significantly lower serum 25(OH)D-3 levels than non-over weight/non-obese (BMI,25 kg/m(2)) subjects (P = 0.029). Greater fat mass and VFA were accompanied by a downward trend in serum 25(OH)D-3 levels (P for trend,0.01). Among overweight/obese subjects, those with body fat percent >= 25% also had significantly lower serum 25(OH)D-3 levels (P <0.05). Moreover, participants with VFA >= 80 cm(2) had significantly lower serum 25(OH)D-3 (P <0.05), regardless of BMI value. VFA was independently correlated with serum 25(OH) D3 levels (b = 20.023, P,<0.001), even after adjustments for confounding factors. In addition, serum 25(OH)D-3 levels were found to decrease by 0.26 ng/mL per 10 cm(2) increment of VFA.