Tirzepatide is a recently approved agent for type 2 diabetes and obesity. What distinguishes its mechanism from GLP-1 receptor agonists like semaglutide?
- A Tirzepatide is a GLP-1/glucagon dual agonist that improves hepatic glucose production while simultaneously increasing insulin secretion
- B Tirzepatide is a selective GIP agonist with GLP-1 receptor partial antagonism that paradoxically improves insulin sensitivity
- C Tirzepatide combines GLP-1 agonism with SGLT2 inhibition in a single molecule, providing renal glucose excretion and incretin effects
- D Tirzepatide is a GLP-1/GIP dual agonist — it activates both GLP-1 receptors (insulin secretion, appetite suppression) and GIP receptors (additional insulin secretion and adipocyte lipid metabolism), providing superior glycemic and weight reduction ✓
Explanation
Tirzepatide (Mounjaro/Zepbound) is a first-in-class dual GIP/GLP-1 receptor agonist ('twincretin'). It activates GIP receptors which enhance glucose-dependent insulin secretion (synergistic with GLP-1), suppress glucagon, improve adipocyte lipid handling (increasing adiponectin, reducing visceral fat), and may directly improve insulin sensitivity in peripheral tissues. GLP-1 receptor activation additionally slows gastric emptying and suppresses appetite centrally. The SURPASS trials demonstrated tirzepatide achieves greater HbA1c reduction and weight loss than semaglutide. The SURMOUNT trials showed impressive 20-22% body weight reduction. Approved by FDA in 2022 for type 2 diabetes and in 2023 for chronic weight management.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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