Effect of sitagliptin on post-prandial glucagon and GLP-1 levels in patients with type 1 diabetes: investigator-initiated, double-blind, randomized, placebo-controlled trial

Peripheral insulin resistance in type 1 diabetes may be related to a paradoxical postprandial glucagon increase. This study evaluated the effects of sitagliptin (dipeptidyl peptidase-IV [DPP-IV] inhibitor, approved for patients with type 2 diabetes), in adults with type 1 diabetes to improve glycemic control through decreasing postprandial glucagon. This investigator-initiated, double-blind, randomized-parallel 20-week study enrolled 141 subjects. Subjects received sitagliptin 100 mg/day or placebo for 16 weeks. A subset of 85 patients wore blinded continuous glucose monitors (CGM) for 5 separate 7-day periods. The primary outcome was post-meal (Boost™) reduction in 4-hour glucagon area under the curve (AUC). Secondary endpoints included changes in glycated hemoglobin (A1c), CGM data, insulin dose, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and C-peptide levels. There were no differences at screening between groups; however, after a 4-week run-in phase, A1c was significantly lower in the sitagliptin vs. placebo group. Post-meal GLP-1 levels were higher (P