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Citrulline a more suitable substrate than arginine to restore NO production and the microcirculation during endotoxemia.

Wijnands KA, Vink H, Briedé JJ, van Faassen EE, Lamers WH, Buurman WA, Poeze M - PLoS ONE (2012)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Maastricht University Medical Center, Maastricht, The Netherlands. n.wijnands@maastrichtuniversity.nl

ABSTRACT

Background: 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.

Methodology/principal findings: 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.

Conclusion/significance: 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.

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Amino-acid concentrations in plasma.(A) Citrulline plasma concentrations increased after L-Citrulline supplementation (LPS-Cit) compared to all other groups (P<0.0001). (B) Plasma arginine concentrations were significantly reduced in the LPS-Ala group compared to the control group (P<0.05), whereas this concentration was significantly increased by L-Arginine or L-Citrulline supplementation (LPS-Arg and LPS-Cit group) compared to both other groups (P<0.001). (C) Plasma ornithine levels increased in the LPS-Ala treated group compared to the control group (P<0.05) and increased further upon L-Arginine or L-Citrulline supplementation.
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pone-0037439-g004: Amino-acid concentrations in plasma.(A) Citrulline plasma concentrations increased after L-Citrulline supplementation (LPS-Cit) compared to all other groups (P<0.0001). (B) Plasma arginine concentrations were significantly reduced in the LPS-Ala group compared to the control group (P<0.05), whereas this concentration was significantly increased by L-Arginine or L-Citrulline supplementation (LPS-Arg and LPS-Cit group) compared to both other groups (P<0.001). (C) Plasma ornithine levels increased in the LPS-Ala treated group compared to the control group (P<0.05) and increased further upon L-Arginine or L-Citrulline supplementation.

Mentions: As expected L-Citrulline supplementation increased plasma citrulline concentration ∼20-fold (P<0.0001) compared to the control, the LPS-Ala and the LPS-Arg group (Figure 4A). L-Citrulline supplementation during physiological conditions (NaCl-Cit group) did also result in enhanced plasma citrulline and arginine concentrations versus control (see Figure S3). Endotoxemia resulted in a significantly decreased arginine plasma concentration in the LPS-Ala group compared to control (n = 13; P<0.05), comparable to the metabolic disturbances in man. For a complete description of the L-arginine concentration during prolonged endotoxemia infusion see also Figure S4. In the LPS-Cit group the plasma arginine concentration was significantly increased versus control mice (n = 13; P<0.0001) and the LPS-Ala group (n = 13; P<0.0001). Although, L-Arginine supplementation enhanced the arginine plasma concentrations in the LPS-Arg group compared to the concentrations in control mice (n = 13; P<0.001; Figure 4B) and compared to LPS-Ala treated mice (n = 13; P<0.0001), these enhanced arginine levels were significantly lower than those in the L-Citrulline supplemented group (n = 13; P<0.05). The plasma ornithine concentration was higher in all LPS-treated groups than in the control group (Figure 4C).


Citrulline a more suitable substrate than arginine to restore NO production and the microcirculation during endotoxemia.

Wijnands KA, Vink H, Briedé JJ, van Faassen EE, Lamers WH, Buurman WA, Poeze M - PLoS ONE (2012)

Amino-acid concentrations in plasma.(A) Citrulline plasma concentrations increased after L-Citrulline supplementation (LPS-Cit) compared to all other groups (P<0.0001). (B) Plasma arginine concentrations were significantly reduced in the LPS-Ala group compared to the control group (P<0.05), whereas this concentration was significantly increased by L-Arginine or L-Citrulline supplementation (LPS-Arg and LPS-Cit group) compared to both other groups (P<0.001). (C) Plasma ornithine levels increased in the LPS-Ala treated group compared to the control group (P<0.05) and increased further upon L-Arginine or L-Citrulline supplementation.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3362574&req=5

pone-0037439-g004: Amino-acid concentrations in plasma.(A) Citrulline plasma concentrations increased after L-Citrulline supplementation (LPS-Cit) compared to all other groups (P<0.0001). (B) Plasma arginine concentrations were significantly reduced in the LPS-Ala group compared to the control group (P<0.05), whereas this concentration was significantly increased by L-Arginine or L-Citrulline supplementation (LPS-Arg and LPS-Cit group) compared to both other groups (P<0.001). (C) Plasma ornithine levels increased in the LPS-Ala treated group compared to the control group (P<0.05) and increased further upon L-Arginine or L-Citrulline supplementation.
Mentions: As expected L-Citrulline supplementation increased plasma citrulline concentration ∼20-fold (P<0.0001) compared to the control, the LPS-Ala and the LPS-Arg group (Figure 4A). L-Citrulline supplementation during physiological conditions (NaCl-Cit group) did also result in enhanced plasma citrulline and arginine concentrations versus control (see Figure S3). Endotoxemia resulted in a significantly decreased arginine plasma concentration in the LPS-Ala group compared to control (n = 13; P<0.05), comparable to the metabolic disturbances in man. For a complete description of the L-arginine concentration during prolonged endotoxemia infusion see also Figure S4. In the LPS-Cit group the plasma arginine concentration was significantly increased versus control mice (n = 13; P<0.0001) and the LPS-Ala group (n = 13; P<0.0001). Although, L-Arginine supplementation enhanced the arginine plasma concentrations in the LPS-Arg group compared to the concentrations in control mice (n = 13; P<0.001; Figure 4B) and compared to LPS-Ala treated mice (n = 13; P<0.0001), these enhanced arginine levels were significantly lower than those in the L-Citrulline supplemented group (n = 13; P<0.05). The plasma ornithine concentration was higher in all LPS-treated groups than in the control group (Figure 4C).

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Surgery, Maastricht University Medical Center, Maastricht, The Netherlands. n.wijnands@maastrichtuniversity.nl

ABSTRACT

Background: 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.

Methodology/principal findings: 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.

Conclusion/significance: 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.

Show MeSH
Related in: MedlinePlus