Which of the following correctly describes the mechanism by which insulin lowers blood glucose in peripheral tissues?

• A Activates insulin receptor tyrosine kinase, leading to PI3K/Akt signaling and GLUT4 vesicle exocytosis ✓
• B Activates adenylyl cyclase, increasing cAMP, which promotes GLUT4 translocation
• C Opens voltage-gated calcium channels, stimulating glycogenolysis
• D Binds nuclear receptors to upregulate glucokinase gene transcription only

Explanation

Insulin binds its receptor (a transmembrane tyrosine kinase) on skeletal muscle and adipose cells. Autophosphorylation activates the receptor, which phosphorylates IRS (insulin receptor substrate) proteins. This activates PI3K, generating PIP3, which activates Akt/PKB. Akt phosphorylates AS160, promoting translocation of GLUT4-containing vesicles to the plasma membrane. GLUT4 is the primary glucose transporter responsible for insulin-stimulated glucose uptake in muscle and fat.

Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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