Which of the following correctly describes the pharmacological difference between sitagliptin and liraglutide in their action on the incretin axis?

• A Both act as GLP-1 receptor agonists but sitagliptin is shorter-acting
• B Sitagliptin directly stimulates pancreatic beta cells via cAMP; liraglutide inhibits glucagon secretion only
• C Sitagliptin inhibits DPP-4, preventing degradation of endogenous GLP-1 (achieves 2–3 fold elevation); liraglutide is a GLP-1 receptor agonist providing supraphysiological GLP-1 receptor stimulation ✓
• D Liraglutide inhibits DPP-4; sitagliptin is a GIP analogue

Explanation

Sitagliptin is a DPP-4 (dipeptidyl peptidase-4) inhibitor that prevents enzymatic degradation of endogenous GLP-1 and GIP, modestly raising their plasma levels 2–3 fold; its glucose-lowering effect is thus limited by the physiological incretin response. Liraglutide is a GLP-1 receptor agonist (acylated GLP-1 analogue with t½ ~13 hours) that provides continuous receptor stimulation at supraphysiological levels, resulting in greater HbA1c reduction, weight loss, and direct cardiovascular/renoprotective benefits. The two agents have complementary but distinct mechanisms.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.