Background/Aims: Vitamin D receptors are strongly expressed in pancreatic beta-cells and the active form of vitamin D may protect against insulin resistance in peripheral tissues. However, the evidence associating serum 25-hydroxyvitamin D (25(OH)D) concentrations and insulin resistance is inconsistent and most observational studies have been cross-sectional in design. We examined the prospective associations between serum 25(OH)D concentrations and insulin resistance from adolescence to young adulthood.
Methods: Serum 25(OH)D concentrations and homeostatic model assessment for insulin resistance (HOMA-IR) were measured at the 17 (n=1015) and 20 year (n=1118) follow-ups of the West Australian Pregnancy Cohort (Raine) Study. HOMA-IR was not normally distributed, so a log transformation was applied. Hierarchical linear mixed models with maximum likelihood estimation were used to investigate associations between serum 25(OH)D concentrations and ln HOMA-IR, with consideration given to potential confounders, including sex, race, BMI, physical activity, family income, smoking and alcohol intake.
Results: In a univariate model, serum 25(OH)D concentrations were inversely associated with ln HOMA-IR (Coefficient = -0.003; 95%CI -0.005, -0.002; p<0.001) and the inverse association was maintained after adjusting for BMI (Coefficient = -0.002; 95%CI -0.003, -0.001; p<0.001). The model shows that a one standard deviation increase (approximately 30 nmol/L) in serum 25(OH)D concentrations associated with a 6% decrease in HOMA-IR.
Conclusions: We found that serum 25(OH)D concentrations were inversely associated with insulin resistance. Well-designed randomised controlled trials may be warranted in order to determine any potential beneficial effect of vitamin D supplementation on insulin resistance in adolescents and young adults.
Funding source(s): NHMRC