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Interorgan amino acid exchange in humans: consequences for arginine and citrulline metabolism.

Authors :
van de Poll MC
Siroen MP
van Leeuwen PA
Soeters PB
Melis GC
Boelens PG
Deutz NE
Dejong CH
Source :
The American journal of clinical nutrition [Am J Clin Nutr] 2007 Jan; Vol. 85 (1), pp. 167-72.
Publication Year :
2007

Abstract

Background: The liver plays a central role in amino acid metabolism. However, because of limited accessibility of the portal vein, human data on this subject are scarce.<br />Objective: We studied hepatic amino acid metabolism in noncirrhotic fasting patients undergoing liver surgery.<br />Design: Twenty patients undergoing hepatectomy for colorectal metastases in a normal liver were studied. Before resection, blood was sampled from a radial artery, portal vein, hepatic vein, and renal vein. Organ blood flow was measured by duplex ultrasound scan.<br />Results: The intestine consumed glutamine and released citrulline. Citrulline was taken up by the kidney. This was accompanied by renal arginine release, which supports the view that glutamine is a precursor for arginine synthesis through an intestinal-renal pathway. The liver was found to extract citrulline from this pathway at a rate that was dependent on intestinal citrulline release (P < 0.0001) and hepatic citrulline influx (P = 0.03). Fractional hepatic extractions of citrulline (8.4%) and arginine (11.5%) were not significantly different. Eighty-eight percent of arginine reaching the liver passed it unchanged. Splanchnic citrulline release could account for one-third of renal citrulline uptake.<br />Conclusions: This is the first study of hepatic and interorgan amino acid metabolism in humans with a normal liver. The data indicate that glutamine is a precursor of ornithine, which can be converted to citrulline by the intestine; citrulline is transformed in the kidneys to arginine. Hepatic citrulline uptake limits the amount of gut-derived citrulline reaching the kidney. These findings may have implications for interventions aimed at increasing systemic arginine concentrations.

Details

Language :
English
ISSN :
0002-9165
Volume :
85
Issue :
1
Database :
MEDLINE
Journal :
The American journal of clinical nutrition
Publication Type :
Academic Journal
Accession number :
17209193
Full Text :
https://doi.org/10.1093/ajcn/85.1.167