A pilot study of a non-invasive oral nitrate stable isotopic method suggests that arginine and citrulline supplementation increases whole-body NO production in Tanzanian children with sickle cell disease

Alphonce I Marealle,Mario Siervo,Sara Wassel,Les Bluck,Andrew M Prentice,Omary Minzi,Philip Sasi,Appolinary Kamuhabwa,Deogratias Soka,Julie Makani,Sharon E Cox

doi:10.1016/j.niox.2017.12.009

Abstract

BackgroundLow bioavailability of nitric oxide (NO) is implicated in the pathophysiology of sickle cell disease (SCD). We designed a nested pilot study to be conducted within a clinical trial testing the effects of a daily ready-to-use supplementary food (RUSF) fortified with arginine (Arg) and citrulline (Citr) vs. non-fortified RUSF in children with SCD. The pilot study evaluated 1) the feasibility of a non-invasive stable isotope method to measure whole-body NO production and 2) whether Arg+Citr supplementation was associated with increased whole-body NO production. SubjectsTwenty-nine children (70% male, 9–11years, weight 16.3–31.3 kg) with SCD. MethodsSixteen children received RUSF+Arg/Citr (Arg, 0.2 g/kg/day; Citr, 0.1 g/kg/day) in combination with daily chloroquine (50 mg) and thirteen received the base RUSF in combination with weekly chloroquine (150 mg). Plasma amino acids were assessed using ion-exchange elution (Biochrom-30, Biochrom, UK) and whole-body NO production was measured using a non-invasive stable isotopic method. ResultsThe RUSF+Arg/Citr intervention increased plasma arginine (P = .02) and ornithine (P = .003) and decreased the ratio of asymmetric dimethylarginine to arginine (P = .01), compared to the base RUSF. A significant increase in whole-body NO production was observed in the RUSF-Arg/Citr group compared to baseline (weight-adjusted systemic NO synthesis 3.38 ± 2.29 μmol/kg/hr vs 2.35 ± 1.13 μmol/kg/hr, P = .04). No significant changes were detected in the base RUSF group (weight-adjusted systemic NO synthesis 2.64 ± 1.14 μmol/kg/hr vs 2.53 ± 1.12 μmol/kg/hr, P = .80). ConclusionsThe non-invasive stable isotopic method was acceptable and the results provided supporting evidence that Arg/Citr supplementation may increase systemic NO synthesis in children with SCD.

Highlights

nitric oxide (NO) synthase (NOS) converts L-arginine into equimolar amount of NO and citrulline [1]
The difference in NO synthesis between the treatment and washout periods was significant in the ready-to-use-supplementary food (RUSF)-Arg/Citr group (P = .04) but not in the RUSF group (P = .80) (Fig. 1B)
The isotopic decay of the stable isotope tracer was characterized by a good linear fit in both groups; the effect of the interventions on systemic NO production is described by the differences in isotopic decays in the RUSF (Fig. 1C) and RUSF+ARG/CIT (Fig. 1D) groups

Summary

Introduction

NO synthase (NOS) converts L-arginine into equimolar amount of NO and citrulline [1]. Siervo et al validated a non-invasive stable isotopic method to provide a quantitative and more accurate estimate of systemic whole-body NO synthesis in humans (Oral Nitrate Test, ONT) [9]. This method employs a very small oral dose of labelled sodium nitrate followed by the collection of repeated saliva samples over a period of 18 h [9]. Conclusions: The non-invasive stable isotopic method was acceptable and the results provided supporting evidence that Arg/Citr supplementation may increase systemic NO synthesis in children with SCD

Methods

Results

Conclusion