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Citrulline
Non-protein amino acid produced by enterocytes from glutamine and proline, exported to kidney, and converted to arginine, providing the most reliable route to elevate systemic arginine.
Plasma citrulline is a quantitative biomarker of enterocyte mass; it is reduced in short bowel syndrome, intestinal failure, and graft-versus-host disease. Oral citrulline bypasses splanchnic arginase and raises plasma arginine more efficiently than oral arginine. It is used in some urea cycle disorders (NAGS, CPS1, OTC deficiency) to provide an aspartate-conjugation substrate that captures nitrogen.
How one textbook covers it
Modern Nutrition in Health and Disease, 12th ed. — Ch 31: Arginine, Citrulline, and Glutamine
Plasma citrulline is a quantitative biomarker of enterocyte mass; it is reduced in short bowel syndrome, intestinal failure, and graft-versus-host disease. Oral citrulline bypasses splanchnic arginase and raises plasma arginine more efficiently than oral arginine. It is used in some urea cycle disorders (NAGS, CPS1, OTC deficiency) to provide an aspartate-conjugation substrate that captures nitrogen.
Related terms
Arginine, Short bowel syndrome, Urea cycle