Journal Article

Citrulline a More Suitable Substrate than Arginine to Restore NO Production and the Microcirculation during Endotoxemia

Vink, Hans, van Faassen, Ernst E., Buurman, Wim A., Briedé, Jacob J., Wijnands, Karolina A. P., Lamers, Wouter H., Poeze, Martijn

2012

Overview

Impaired microcirculation during endotoxemia correlates with a disturbed arginine-nitric oxide (NO) metabolism and is associated with deteriorating organ function. Improving the organ perfusion in endotoxemia, as often seen in patients with severe infection or systemic inflammatory response syndrome (SIRS) is, therefore, an important therapeutic target. We hypothesized that supplementation of the arginine precursor citrulline rather than arginine would specifically increase eNOS-induced intracellular NO production and thereby improve the microcirculation during endotoxemia. To study the effects of L-Citrulline and L-Arginine supplementation on jejunal microcirculation, intracellular arginine availability and NO production in a non-lethal prolonged endotoxemia model in mice. C57/Bl6 mice received an 18 hrs intravenous infusion of endotoxin (LPS, 0.4 µg • g bodyweight(-1) • h(-1)), combined with either L-Citrulline (6.25 mg • h-1), L-Arginine (6.25 mg • h(-1)), or L-Alanine (isonitrogenous control; 12.5 mg • h(-1)) during the last 6 hrs. The control group received an 18 hrs sterile saline infusion combined with L-Alanine or L-Citrulline during the last 6 hrs. The microcirculation was evaluated at the end of the infusion period using sidestream dark-field imaging of jejunal villi. Plasma and jejunal tissue amino-acid concentrations were measured by HPLC, NO tissue concentrations by electron-spin resonance spectroscopy and NOS protein concentrations using Western blot. L-Citrulline supplementation during endotoxemia positively influenced the intestinal microvascular perfusion compared to L-Arginine-supplemented and control endotoxemic mice. L-Citrulline supplementation increased plasma and tissue concentrations of arginine and citrulline, and restored intracellular NO production in the intestine. L-Arginine supplementation did not increase the intracellular arginine availability. Jejunal tissues in the L-Citrulline-supplemented group showed, compared to the endotoxemic and L-Arginine-supplemented endotoxemic group, an increase in degree of phosphorylation of eNOS (Ser 1177) and a decrease in iNOS protein level. In conclusion, L-Citrulline supplementation during endotoxemia and not L-Arginine reduced intestinal microcirculatory dysfunction and increased intracellular NO production, likely via increased intracellular citrulline and arginine availability.

• Publisher: Public Library of Science,Public Library of Science (PLoS)
• Subject: Alanine / Amino acids / Animal tissues / Animals / Arginine / Arginine - metabolism / Arginine - pharmacology / Availability / Biological Availability / Biology / Citrulline / Citrulline - metabolism / Citrulline - pharmacokinetics / Citrulline - pharmacology / Clinical trials / Congenital diseases / Dietary Supplements / Electron spin / Endotoxemia / Endotoxemia - metabolism / Endotoxemia - pathology / Endotoxemia - physiopathology / Endotoxins / Gene Expression Regulation, Enzymologic - drug effects / Health aspects / Heart failure / Heart surgery / High-performance liquid chromatography / Infection / Inflammation / Inflammatory response / Intestine / Intracellular / Intracellular Space - drug effects / Intracellular Space - metabolism / Intravenous administration / Intravenous infusion / L-Alanine / Lipopolysaccharides / Liquid chromatography / Male / Medicine / Metabolism / Mice / Mice, Inbred C57BL / Microcirculation - drug effects / Microvasculature / Nitric oxide / Nitric Oxide - biosynthesis / Nitric Oxide - metabolism / Nitric Oxide Synthase Type II - metabolism / Nitric Oxide Synthase Type III - metabolism / Nitric-oxide synthase / Nutrition / Perfusion / Phosphorylation / Physiological aspects / Pulmonary hypertension / Rodents / Sepsis / Sickle cell disease / Spectroscopy / Spin resonance / Supplements / Systemic inflammatory response syndrome / Toxicology