Effect of Sitagliptin in Type 1 or Type 2 Diabetic Patients with Absolute Insulin Deficiency: A 48 Weeks Observational Study

Aims: The aim of this study is to investigate the long-term efficacy of sitagliptin added to insulin in type 1 or type 2 diabetic patients with absolute insulin deficiency.
Study Design: 48 weeks open-label, observational study.
Place and Duration of Study: Department of Internal Medicine, Gyoda General Hospital, between June 2010 and December 2012.
Methodology: Sitagliptin 25-100 mg/day was added to the ongoing insulin therapy in those without any detectable post-meal C-peptide levels. HbA1c and other parameters were followed for 48 weeks.
Results: Effective reductions of HbA1c levels were already observed at 12 weeks and sustainable throughout the study period. However, 2 subjects had severe hypoglycemic evens. Post-meal C-peptide remained undetectable with all the subjects. Interestingly, significant increases of body weight were observed.
Conclusion: Sitagliptin as an adjunct to insulin in patients with absolute insulin deficiency may be effective and sustainable for at least 48 weeks, allowing for less intense therapy. However, it should be noted that some patients may have severe hypoglycemic events. In spite of the significant glycemic effects of sitagliptin in the setting of this study, endogenous insulin secretory capacity remained absent, suggesting that the glucose lowering effect of this drug may be mediated through GLP-1 independent pathway as well.