Comparing arginine flux, catabolism and availability for NO synthesis in American, Indian, and Jamaican women

Abstract

We have reported that Indian women do not have increased Arg production during pregnancy like their American or Jamaican counterparts. There has not been a direct comparison of Arg flux, catabolism, and availability for NO synthesis in non‐pregnant American, Indian, and Jamaican women. The objective of this study was to determine whether Indian women are producing less Arg and/or catabolizing more Arg to Orn and therefore have less Arg available for anabolic pathways than their Jamaican and American counterparts. Ten healthy women of childbearing age from each country were given 6h primed, constant intravenous infusions of 15N2‐Arg, 2H2‐Cit, 15N2‐Orn, and 2H5‐Phe in both the fasted and fed states to measure Arg flux, hydrolysis, bioavailability, NO synthesis and Phe flux, an index of protein breakdown. USA India Jamaica P Value μmol/kg FFM/h μmol/kg FFM/h μmol/kg FFM/h Fasted Arg flux 56.1 ± 2.1a 54.2 ± 3.1a 66.1 ± 3.1 b 0.01 Arg hydrolysis 17.6 ± 1.5 a 23.7 ± 1.5 b 23.4 ± 1.6 b 0.01 Arg bioavailability 49.9 ± 1.3 ab 42.0 ± 2.6 a 55.5 ± 3.5 b 0.004 NO Synthesis 0.18 ± 0.01a 0.15 ± 0.01 b 0.21 ± 0.02 a 0.002 Phe flux 39.7 ± 0.9 39.0 ± 2.2 43.8 ± 2.3 0.17 Fed Arg flux 79.1 ± 3.3 a 80.3 ± 4.9 a 95.9 ± 2.9 b 0.008 Arg hydrolysis 27.3 ± 2.5 a 39.6 ± 3.7 b 37.2 ± 2.0 b 0.01 Arg bioavailability 51.8 ± 1.2 a 40.7 ± 3.5 b 57.5 ± 3.2 a <0.001 NO Synthesis 0.20 ± 0.01a 0.21 ± 0.03a 0.34 ± 0.04 b < 0.0001 Phe flux 58.8 ± 1.6 59.4 ± 3.0 63.3 ± 2.7 0.39 Means with different superscript letters are significantly different, P < 0.05 (post‐hoc Tukey's multiple comparison test).In conclusion, Indian women had increased Arg hydrolysis without a compensatory increase in Arg flux resulting in decreased bioavailability of Arg for the synthesis of proteins and other Arg‐derived biomolecules, including NO synthesis. Though American women also had slower Arg flux compared to Jamaican women, they were able to conserve Arg bioavailability because of decreased Arg hydrolysis. The results suggest that Indian women may need a higher dietary Arg intake.Supported by the Bill and Melinda Gates Foundation