Clinical nutrition : official journal of the European Society of Parenteral and Enteral Nutrition
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In human, citrulline (plasma concentration about 40 micromol/L) is an amino acid involved in intermediary metabolism and that is not incorporated in proteins. Circulating citrulline is mainly produced by enterocytes of the small bowel. For this reason plasma or serum citrulline concentration has been proposed as a biomarker of remnant small bowel mass and function. This article reviews this concept and its metabolic basis. ⋯ Reduced plasma citrulline levels are an innovative quantitative biomarker of significantly reduced enterocyte mass and function in different disease states in humans.