Introduction: It remains unknown whether dipeptidyl peptidase-4 (DPP-4) inhibitors improve early-phase insulin secretion in Japanese patients with type 2 diabetes (T2D), a disease characterized by impaired insulin secretion. We investigated the changes in insulin secretion before and after treatment with the DPP-4 inhibitor teneligliptin in patients with T2D with a low insulinogenic index (IGI) determined by the oral glucose tolerance test (OGTT).
Methods: An open-label, prospective clinical study was conducted. Thirteen drug-naïve patients (mean age 55.5 ± 3.9 years) with T2D underwent OGTT before and after teneligliptin 20 mg/day monotherapy. Plasma levels of glucose (PG), insulin, and C-peptide were measured at 0, 30, 60, 90, and 120 min after glucose loading in the OGTT. Homeostasis model assessment (HOMA)-β, IGI, and the total or incremental area under the curve (AUC) for PG and insulin were measured. AUC120min for the secretory units of islets in transplantation (SUIT) index was also measured.
Results: HbA1c significantly decreased from 8.3 ± 0.4% at baseline to 6.3 ± 0.2% after 12 weeks of teneligliptin treatment (p < 0.05). Incremental AUC120min PG also significantly decreased, and β-cell function assessed by IGI30min, AUC120min insulin, and the AUC120min SUIT index significantly increased (0.16 ± 0.05 vs. 0.28 ± 0.06, 2692 ± 333 µU·2h/mL vs. 3537 ± 361 µU·2h/mL, and 4261 ± 442 vs. 8290 ± 1147, respectively; all p < 0.05). HOMA-β was unchanged. The reduction in incremental AUC120min PG was significantly associated with the augmentation of IGI30min and the AUC120min SUIT index. No severe adverse events were observed.
Conclusions: Twelve weeks of teneligliptin treatment improved IGI30min, AUC120min, and the SUIT index in drug-naïve Japanese patients with T2D.