INS and type 1 diabetes mellitus: As shown in the study by Hari et al. [19], among patients with new-onset T1DM who presented with stimulated C-peptide levels ≥ 0.1 ng/mL, C-peptide was elevated by 0.0067 ± 0.19 ng/mL or −0.05 ± 0.28 ng/mL in the groups treated with sitagliptin alone or the combination of sitagliptin and insulin, respectively.