The current study examined the effects of sitagliptin (Januvia) on average blood glucose (sugar) levels and insulin production in type 2 diabetes patients.

Type 2 diabetes is a progressive disease. Insulin (the hormone needed to break down glucose) production decreases over time, and increasing medical treatments are needed to replace it. Sitagliptin is a treatment that increases insulin production. Sitagliptin also decreases HbA1c (average blood glucose over 3 months) and increases C-peptide levels (a substance in the blood associated with insulin production). Previous studies have examined the efficacy of sitagliptin in the short-term. It is not known what long-term effects sitagliptin has on HbA1c and C-peptide levels.

The current study examined the effects of sitagliptin on 285 type 2 diabetes patients who were treated for 2 years. HbA1c and C-peptide levels were measured at regular intervals over the 24 months following the start of the study (baseline). Patients were determined to be responders (180 patients) to sitagliptin if their HbA1c level decreased by more than 0.4%. Patients who saw less than a 0.4% change were labelled non-responders (105 patients).

In responders, HbA1c decreased significantly, from the baseline 8.3% to 7.5% at 3 months and to 7.0% at 24 months. Non-responders saw an initial decrease from the baseline 7.6% to 7.3% at 3 months, but an increase to 7.8% at 24 months.

C-peptide levels increased significantly from baseline to 24 months in responders. C-peptide levels did not change significantly in non-responders.

This study concluded that sitagliptin led to significant decreases in HbA1c and significant increases in insulin production, particularly in drug responders.

This study included only Japanese patients. Further studies should be done to determine whether the same results are seen in all races.