Effects of Add-On Treatment with Sitagliptin on Narrowing the Range of Glucose Fluctuations in Japanese Type 2 Diabetes Patients Receiving Insulin Therapy

Background: In an earlier continuous glucose monitoring (CGM)-based study, we reported that sitagliptin not only reduced 24-h mean glucose levels but also suppressed postprandial glucose increases, thus reducing the range of glycemic fluctuations in type 2 diabetes patients. In this study, we investigated whether sitagliptin might provide similar benefits in type 2 diabetes patients receiving insulin therapy by using CGM. Patients and Methods: The study included a total of 13 type 2 diabetes patients in whom stable glycemic control had been achieved after admission for glycemic control. Insulin regimens used included long-acting insulin preparations once daily in four patients and biphasic insulin preparations twice daily in nine, with the daily insulin dose being 19.0 +/- 12.7 U. During the CGM-based study, the patients were given insulin therapy alone on Days 1 and 2 and were given sitagliptin 50 mg/day as add-on treatment on Days 3-6, with their daily insulin doses maintained. Results: The add-on treatment with sitagliptin led to significant decreases in 24-h mean glucose levels and SDs of 288 glucose levels measured by CGM for 24 h, as well as in the indices for magnitude of glucose variability and proportion of time in hyperglycemia, compared with insulin therapy alone (P<0.01), whereas there was no significant change seen in regard to the proportion of time in hypoglycemia with or without add-on treatment with sitagliptin. Conclusions: This CGM-based study clearly demonstrated that insulin therapy alone, whether with long-acting or biphasic insulin preparations, does not provide adequate glycemic control in type 2 diabetes patients. In contrast, add-on sitagliptin was shown to narrow the range of 24-h glucose fluctuations in these patients, suggesting that add-on treatment with sitagliptin is effective for postprandial glucose control in type 2 diabetes patients receiving insulin therapy.