American Board of Internal Medicine (ABIM) Certification Practice Exam

What effect does Sitagliptin, a DPP-4 inhibitor, have on the digestive process?

1. Increases gastric emptying

2. Suppresses glucagon secretion

3. Enhances insulin sensitivity

4. Stimulates endogenous insulin production

The correct answer is: Suppresses glucagon secretion

Sitagliptin is a DPP-4 inhibitor, and its primary action relates to the incretin hormone system, which plays a crucial role in glucose metabolism. DPP-4 inhibitors like Sitagliptin increase the levels of incretin hormones such as GLP-1 (glucagon-like peptide-1) by inhibiting their degradation. One of the significant effects of increased GLP-1 levels is the suppression of glucagon secretion from the alpha cells of the pancreas. Glucagon is responsible for raising blood glucose levels by promoting gluconeogenesis and glycogenolysis in the liver. By suppressing glucagon, Sitagliptin helps to lower blood sugar levels, particularly after meals, contributing to better glycemic control. This suppression of glucagon is critical in the context of diabetes management, as it counters the hyperglycemic effect of glucagon and enhances the effectiveness of insulin. The other options primarily address different mechanisms not directly related to the primary actions of DPP-4 inhibitors like Sitagliptin. Enhancing insulin sensitivity and stimulating endogenous insulin production are important aspects of overall diabetes management, but they are not the direct actions of Sitagliptin. Instead, these conditions result from broader metabolic changes associated