The effect of 25-hydroxyvitamin D on insulin sensitivity in obesity: is it mediated via adiponectin?

ABSTRACT

There has been substantial recent interest in using vitamin D to improve insulin sensitivity and preventing/delaying diabetes in those at risk. There is little consensus on the physiological mechanisms and whether the association is direct or indirect through enhanced production of insulin-sensitising chemicals, including adiponectin. We examined cross-sectional associations between serum 25-hydroxyvitamin D (25(OH)D) and insulin sensitivity (Matsuda index), parathyroid hormone (PTH), waist circumference, body mass index (BMI), triglycerides (TG), total and high molecular weight (HMW) adiponectin, HMW total adiponectin ratio (HMW total adiponectin), and total cholesterol HDL cholesterol ratio (TCHDL cholesterol) in 137 Caucasian adults of mean age 43.3 ± 8.3 years and BMI 38.8 ± 6.9 kg/m(2). Total adiponectin (standardised ß = 0.446; p < 0.001), waist circumference (standardised ß = -0.216; p < 0.05), BMI (standardised ß = -0.212; p < 0.05), and age (standardised ß = -0.298; p < 0.001) were independently associated with insulin sensitivity. Serum 25(OH)D (standardised ß = 0.114; p = 0.164) was not associated with insulin sensitivity, total or HMW adiponectin, HMW total adiponectin, or lipids. Our results provide the novel finding that 25(OH)D is not associated with HMW adiponectin or HMW total adiponectin in nondiabetic, obese adults and support the lack of association between 25(OH)D and lipids noted by others in similar groups of patients.