Serum vitamin d concentration does not predict insulin action or secretion in European subjects with the metabolic syndrome.

Objective: To investigate the relation between serum concentration of 25-hydroxyvitamin D [25(OH)D] and insulin action and secretion. Research Design and Methods: In a cross-sectional study of 446 Pan-European subjects with the metabolic syndrome insulin action and secretion were assessed by homeostasis model assessment (HOMA) indices and intravenous glucose tolerance test to calculate acute insulin response, insulin sensitivity and disposition index. Serum 25(OH)D was measured by HPLC/MS. Results: The mean (SD) 25(OH)D(3) concentration was 57.1 (26.0) nmol/l, and only 20% of the subjects had 25(OH)D(3) levels >/=75 nmol/l. In multiple linear analyses, 25(OH)D(3) concentrations were not associated withparameters of insulin action or secretion after adjustment for BMI and other covariates. Conclusion: In a large sample of subjects with the metabolic syndrome, serum concentrations of 25(OH)D(3) did not predict insulin action or secretion. Clear evidence that D-vitamin status directly influences insulin secretion or action is still lacking.