In a volunteer fasted beyond 3 weeks, indirect calorimetry shows continued endogenous glucose production despite near-total depletion of liver glycogen. At this stage, which organ contributes roughly half of total gluconeogenesis, and what is its principal gluconeogenic substrate?

• A Adipose tissue, glycerol
• B Skeletal muscle, alanine
• C Small intestinal mucosa, lactate
• D Kidney cortex, glutamine ✓

Explanation

In late prolonged starvation the kidney cortex becomes a major gluconeogenic organ, contributing up to about half of blood glucose, using glutamine released mainly by skeletal muscle. Renal ammoniagenesis also provides ammonia to buffer the acidosis generated by ketoacid production, linking acid-base regulation to glucose output. Muscle lacks glucose-6-phosphatase so it cannot export glucose derived even from its own alanine.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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