BackgroundThe aim of this study was to investigate the efficacy and safety of vildagliptin as an add-on therapy for patients with type 2 diabetes mellitus inadequately controlled with basal insulin.MethodsTwenty-four patients treated with basal insulin and oral anti-diabetes drugs were randomly allocated into two groups: the control group (did not receive any add-on drugs) and vildagliptin group (received vildagliptin 100 mg/day for 6 months). The primary outcome was changes in hemoglobin A1c (HbA1c) from baseline to end of study.ResultsTreatment with vildagliptin significantly reduced HbA1c from 8.1±0.7% at baseline to 7.1±0.7% (P < 0.01), while there was no significant change of HbA1c in the control group. Vildagliptin group showed significant reduction of HbA1c compared with control group (-1.0±0.3% vs. 0.2±0.8%, P < 0.01). In addition, vildagliptin group showed a significant increase in 1,5-anhydroglucitol compared with the control group (4.5 ± 3.4 vs. 0.5 ± 4.1 μg/mL, P < 0.05). Mild hypoglycemia was reported in one patient of the vildagliptin group and two patients of the control group.ConclusionVildagliptin improved glycemic control without increasing hypoglycemia in Japanese type 2 diabetes inadequately controlled with basal insulin treatment and other oral anti-diabetes drugs. This study was registered with UMIN (University Hospital Medical Information Network ID#000010849).

Pancreatic polypeptide (PP), secreted from γ cells of the islets of Langerhans, is a 36 amino-acid peptide encoded by the Ppy gene. Although previous studies have reported that PP causes a decrease in appetite, the molecular mechanism that regulates PP secretion has not been fully elucidated. Lack of understanding of the regulatory mechanism of PP secretion may be partially owing to the lack of assay systems that can specifically detect PP. We recently developed the mouse monoclonal antibody 23-2D3 that specifically recognizes PP. In the present study, we developed a sandwich enzyme-linked immunosorbent assay for the measurement of mouse PP, and directly monitored intracellular Ca2+ concentrations in Ppy-expressing cells from a newly developed reporter mouse. Using these systems, we identified agonists, such as carbachol and glucose-dependent insulinotropic polypeptide (GIP), which stimulate PP secretion. We further demonstrated that, unlike the case of GIP-induced insulin secretion from β cells, there is a unique mechanism by which PP secretion is triggered by an increase in intracellular Ca2+ concentrations via voltage-dependent calcium channels even in low-glucose conditions.

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