Abstract

CONTEXT: Vitamin D regulates glucose homeostasis pathways, but effects of vitamin D supplementation on insulin sensitivity and beta-cell function remain unclear.OBJECTIVE: To investigate the effects of vitamin D3 supplementation on insulin sensitivity and beta-cell function.METHODS: This is a pre-specified secondary analysis of the Vitamin D and type 2 diabetes (D2d) study. Overweight/obese adults at high risk for type 2 diabetes were randomly treated with vitamin D3 4000 IU or matching placebo daily for 24 months.MAIN OUTCOME: Disposition index (DI), as an estimate of beta-cell function, was calculated as the product of HOMA2%Scpep and C-peptide response during the first 30 minutes of a 75-gram oral glucose tolerance test (OGTT).RESULTS: Mean age was 60.5±9.8 years and BMI was 31.9±4.4kg/m 2. Mean serum 25(OH)D level increased from 27.9±10.3ng/mL at baseline to 54.9ng/mL at two years in the vitamin D group and was unchanged (28.5±10.0ng/mL) in the placebo group. The baseline DI predicted incident diabetes independent of the intervention. In the entire cohort, there were no significant differences in changes in DI, HOMA2%Scpep, or C-peptide response between the two groups. Among participants with baseline 25(OH)D level <12ng/mL, the mean percent differences for DI between the vitamin D and placebo groups was 8.5% (95%CI 0.2-16.8).CONCLUSIONS: Supplementation with vitamin D3 for 24 months did not improve an OGTT-derived index of beta-cell function in people with prediabetes not selected based on baseline vitamin D status; however, there was benefit among those with very low baseline vitamin D status.

View details for DOI 10.1210/clinem/dgab649

View details for PubMedID 34473295