DPP4 and type 1 diabetes mellitus: In line with this hypothesis, our previous preliminary data obtained from a smaller cohort of patients (n = 46; 26 patients with T1D and 20 controls) showed that a VIDPP-4i regimen (with sitagliptin 100 mg/day plus vitamin D3 5,000 IU/day) in addition to insulin therapy was associated with a prolonged clinical remission phase (mean duration of 27.1 ± 18.9 months), along with a significant decrease in CD8+CD26+ T-cell count compared with a regimen with insulin alone in patients with T1D (32,33).