Because our patients harboured a glucose tolerance that spanned from normal to naive T2DM, and may have thus retained a superior beta-cell activity than patients with chronic T2DM, our results support the findings of Harris et al., who studied the effects of vitamin D supplementation in prediabetic obese patients and showed that the increase in 25(OH)D3 concentrations was associated with an increase of insulin secretion rate and C-peptide concentrations [51]. This evidence concerns the gene INS and type 2 diabetes mellitus.