L-Citruline

Chromatographia . 2018;81(6):911-921.

Quantitative Analysis of l-Arginine, Dimethylated Arginine Derivatives, l-Citrulline, and Dimethylamine in Human Serum Using Liquid Chromatography-Mass Spectrometric Method[Pubmed: 29887621]

Abstract Abstract: Nitric oxide (NO) is a small molecule involved in the regulation of many physiological processes. It plays a crucial role in the regulation of nervous system, immune and inflammatory responses, and blood flow. NO is synthesized by nitric oxide synthase (NOS) during two-step oxidation of l-arginine to l-citrulline. Intermediates and derivatives of NO metabolism, such as l-arginine, l-citrulline, asymmetrical dimethylarginine (ADMA), symmetrical dimethylarginine (SDMA), and dimethylamine (DMA), are investigated as potential biomarkers. In this article, we present a novel analytical method that allowed for simultaneous analysis of l-arginine, ADMA, SDMA, l-citrulline, and DMA, in a single-step extraction and derivatization using benzoyl chloride. In brief, aliquots of serum were mixed with internal standard solution mixture (50 μM D6-DMA, 20 μM D7-ADMA, and 100 μM D7-arginine) and 0.025 M borate buffer, pH 9.2 (10:1:5). The derivatization process was performed at 25 °C for 5 min using 10% benzoyl chloride. A reverse phase column was used for chromatographic separation. Quantitation was performed using following ions (m/z): 279.1457, 286.1749, 307.1717, 314.2076, 280.1297, 150.0919, and 156.1113 for l-arginine, D7-arginine, ADMA, SDMA, D7-ADMA, l-citrulline, DMA, and D6-DMA, respectively. The method was validated, and its assay linearity, accuracy and precision, recovery, and limits of detection (1.7 μM l-arginine, 0.03 μM ADMA, 0.02 μM SDMA, 0.36 μM l-citrulline, 0.06 μM DMA) and quantification (3.2 μM l-arginine, 0.08 μM ADMA, 0.05 μM SDMA, 1.08 μM l-citrulline, 0.19 μM DMA) were determined. The method is sensitive, reliable, repeatable, and reproducible. It can be applied in the routine clinical/diagnostic laboratory. Keywords: Amino acid derivatization; Asymmetric dimethylarginine; Citrulline; Dimethylamine; Liquid

The Journal of Clinical Hypertension Volume 17, Issue 1, pages 14–19, January 2015

Digital Plethysmography and Arginine Metabolism in Prehypertension—Effect of Nebivolol Therapy[Reference: WebLink]

Prehypertension is an important phenotype for cardiovascular risk and development of established hypertension.
METHODS AND RESULTS:
To better understand the early circulatory changes in this group, the authors studied 34 patients with prehypertension (blood pressure 120–139/80–89 mm Hg) using digital plethysmography for measurement of blood flow and reactive hyperemic index (RHI). Arterial augmentation index (AI) was also measured. Because prehypertension is associated with endothelial dysfunction and decreased availability of nitric oxide (NO), indices of arginine metabolism (l-arginine, asymmetric dimethylarginine (ADMA), symmetric dimethylarginine, and L-Citruline) were measured. Nebivolol (5 mg/d), a vasodilating β1-antagonist with β3-agonist activity, was studied in a double-blind fashion for 8 weeks.

Front Immunol. 2013 Dec 24;4:480.

l-Citrulline Protects from Kidney Damage in Type 1 Diabetic Mice.[Pubmed: 24400007]

Diabetic nephropathy (DN) is a major cause of end-stage renal disease, associated with endothelial dysfunction. Chronic supplementation of l-arginine (l-arg), the substrate for endothelial nitric oxide synthase (eNOS), failed to improve vascular function. L-Citruline (l-cit) supplementation not only increases l-arg synthesis, but also inhibits cytosolic arginase I, a competitor of eNOS for the use of l-arg, in the vasculature. To investigate whether l-cit treatment reduces DN in streptozotocin (STZ)-induced type 1 diabetes (T1D) in mice and rats and to study its effects on arginase II (ArgII) function, the main renal isoform.
METHODS AND RESULTS:
STZ-C57BL6 mice received l-cit or vehicle supplemented in the drinking water. For comparative analysis, diabetic ArgII knock out mice and l-cit-treated STZ-rats were evaluated. L-Citruline exerted protective effects in kidneys of STZ-rats, and markedly reduced urinary albumin excretion, tubulo-interstitial fibrosis, and kidney hypertrophy, observed in untreated diabetic mice. Intriguingly, l-cit treatment was accompanied by a sustained elevation of tubular ArgII at 16 weeks and significantly enhanced plasma levels of the anti-inflammatory cytokine IL-10. Diabetic ArgII knock out mice showed greater blood urea nitrogen levels, hypertrophy, and dilated tubules than diabetic wild type (WT) mice. Despite a marked reduction in collagen deposition in ArgII knock out mice, their albuminuria was not significantly different from diabetic WT animals. l-Cit also restored nitric oxide/reactive oxygen species balance and barrier function in high glucose-treated monolayers of human glomerular endothelial cells. Moreover, l-cit also has the ability to establish an anti-inflammatory profile, characterized by increased IL-10 and reduced IL-1β and IL-12(p70) generation in the human proximal tubular cells.
CONCLUSIONS:
L-Citruline supplementation established an anti-inflammatory profile and significantly preserved the nephron function during T1D.