Nutrition and the gastrointestinal tractCitrulline and the gutCuris, Emmanuela; Crenn, Pascalb,c; Cynober, Lucb,dAuthor Information aLaboratoire de Biomathématiques, Faculté de Pharmacie, Université Paris Descartes, Paris bLaboratoire de Biologie de la Nutrition, Faculté de Pharmacie, Université Paris Descartes, Paris cDépartement de Médecine Aiguë Spécialisée, Hôpital Raymond Poincaré, Assistance Publique – Hôpitaux de Paris, Université Versailles-Saint Quentin en Yvelines, Paris dService de Biochimie, Hôtel-Dieu, Assistance Publique – Hôpitaux de Paris, Paris, France Correspondence to M. Emmanuel Curis, Laboratoire de Biomathématiques; Faculté de Pharmacie; Université Paris Descartes, 4 Avenue de l'Observatoire, F-75006 Paris, France Tel: +33 1 53 73 98 37; fax: +33 1 53 73 97 77; e-mail: firstname.lastname@example.org Sponsorship: This study was supported by a grant (EA 2498) from the French Ministère de la Recherche et de la Technologie. Current Opinion in Clinical Nutrition and Metabolic Care: September 2007 - Volume 10 - Issue 5 - p 620-626 doi: 10.1097/MCO.0b013e32829fb38d Buy Metrics Abstract Purpose of review Citrulline, a nonprotein amino acid, is an important source of endogenous arginine. The gut is the main source of citrulline in humans. Hence, citrulline is a potential biomarker of short bowel function. Conversely, citrulline uptake by the gut is important for an oral supply of this amino acid as an alternative to arginine. This review discusses these two aspects of citrulline, as well as the recent developments in the understanding of its metabolism. Recent findings Citrullinemia is such an efficient marker when the active mass of the bowel is affected that it can be used as a prognostic marker for parenteral nutrition weaning (if citrullinemia is >20 μmol/l) and as a factor for deciding between parenteral and enteral nutrition (as long as the pathology is considered). Citrullinemia should be used with care as a marker either of the intestinal absorption or following small bowel transplantation. Summary Citrulline is easily taken up by the gut, with a broad set of transporters that can remove it from the lumen in the enterocytes. This is confirmed by pharmacokinetic studies and the efficacy is so great that oral complementation with citrulline seems more efficient than complementation with arginine to provide arginine. © 2007 Lippincott Williams & Wilkins, Inc.