DPP4 and type 1 diabetes mellitus: A recent evaluation on the efficacy of combination therapy with γ-aminobutyric acid (GABA, which has regenerative effects on islet β cells (69)), DPP-4 inhibitors, PPI and insulin in T1D patients showed that this combination was associated with significant reductions in fasting blood glucose, HbA1c level, daily insulin dose, and fasting plasma C-peptide etc. After 26-42 weeks of treatments, it has been shown that this combination can improve glycemic control in T1D (51).