Professional and Linguistic Assessments Board (PLAB) Practice Exam

What is one of the key effects of sitagliptin on glucose metabolism?

1. Stimulates glucagon secretion

2. Promotes insulin release

3. Increases glucose production

4. Suppresses release of glucagon

The correct answer is: Suppresses release of glucagon

Sitagliptin is classified as a DPP-4 inhibitor, which plays a significant role in the regulation of glucose metabolism. One of its primary functions is to enhance the incretin system. By inhibiting the DPP-4 enzyme, sitagliptin prolongs the action of incretin hormones, which are essential for increasing insulin secretion in response to meals. A crucial aspect of this process is that sitagliptin also suppresses the release of glucagon, a hormone produced by the alpha cells of the pancreas that typically stimulates glucose production by the liver. By preventing glucagon secretion, sitagliptin helps reduce hepatic glucose output, which is particularly beneficial in managing blood glucose levels in people with type 2 diabetes. In contrast, stimulating glucagon secretion or increasing glucose production would counteract the desirable effect of lowering blood glucose levels, making those choices inconsistent with sitagliptin's action. Additionally, while sitagliptin does promote insulin release indirectly through incretin enhancement, its most notable effect is in suppressing glucagon, which is vital for effective glucose homeostasis.