The relationship of nitric oxide synthesis capacity, oxidative stress, and albumin-to-creatinine ratio in black and white men: the SABPA study

Abstract

Inadequate substrate availability and increased nitric oxide synthase inhibitor levels attenuate nitric oxide (NO) synthesis, whereas increased vascular oxidative stress may lead to inactivation of NO. We compared markers of NO synthesis capacity and oxidative stress in a bi-ethnic male population. Inter-relationships of ambulatory blood pressure and urinary albumin-to-creatinine ratio with NO synthesis capacity and oxidative stress markerswere investigated.NOsynthesis capacitymarkers (L-arginine, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA)) and oxidative stress markers (serum peroxides, total glutathione, glutathione peroxidase (GPx), glutathione reductase (GR), superoxide dismutase (SOD), and catalase) were measured. Black men displayed higher blood pressure and albuminto- creatinine ratio (all p < 0.001), while NO synthesis capacity was more favorable (higher L-arginine and lower ADMA (p ≤ 0.003)). Antioxidant enzyme activities were similar except for the redox status markers (GR activity and GR/GPx ratio), which were upregulated in black men (p < 0.001). In blackmen, ADMAwas inversely related to GPx activity (R$^2$ = 0.15; β = −0.20; p = 0.050) and GPx/ SOD ratio (R$^2$ = 0.24; β = −0.37; p < 0.001), but none of these markers related to blood pressure or albumin-tocreatinine ratio. In white men, albumin-to-creatinine ratio was positively associated with ADMA (R$^2$ = 0.18; β = 0.39; p < 0.001) while ADMA was inversely related to GR activity (R$^2$ = 0.26; β = −0.29; p = 0.002) and GR/ GPx ratio (R$^2$ = 0.25; β = −0.28; p = 0.003). Black men with elevated blood pressure and albumin-to-creatinine ratio displayed a favorable NO synthesis capacity. This may be counteracted by increased inactivation of NO, although it was not linked to vascular or renal phenotypes. In white men, reduced NO synthesis capacity may lower NO bio-availability, thereby influencing the albumin-tocreatinine ratio.