Endothelial dysfunction in normotensive salt-sensitive subjects

Salt-sensitivity is associated with a more severe target organ injury and higher mortality, even in normotensive subjects. As endothelial dysfunction is predictive for future cardiovascular events, we evaluated whether normotensive salt-sensitive (NSS) subjects have more pronounced endothelial dysfunction compared with normotensive salt-resistant (NSR) subjects. Normotensive subjects (n=99, aged 25-50 years) were selected from a rural community in northern China. Salt sensitivity was assigned if mean BP increased by >= 10% from a 1-week high salt (18 g/day, NaCl) to low-salt diet (3 g/day, NaCl). Endothelial function was assessed by testing the flow-mediated dilatation (FMD) of the brachial artery using high-resolution ultrasound, as well as nitrogen oxide (NOx) levels, in plasma and urine at baseline. Blood pressure at baseline was similar be-tween NSS and NSR subjects, but diverged during salt intervention. Furthermore, FMD was significantly lower in 17 NSS subjects (10.2 +/- 2.5 vs 14.5 +/- 1.6%, P = 0.037) compared with NSR subjects. In addition, average plasma NOx levels were lower in NSS subjects than NSR subjects (61.2 +/- 3.23 mu M vs 82.5 +/- 1.61 mu M, P = 0.034). Moreover, Both FMD and plasma NOx levels were negatively correlated with the degree of salt sensitivity (r = -0.435 and r = -0.459, respectively, P<0.01). However, there was no difference in urine NOx between the two groups. Our study indicates that endothelial dysfunction could contribute to the long-term higher levels of target organ injury and higher mortality observed in NSS subjects. Journal of Human Hypertension (2012) 26, 247-252; doi: 10.1038/jhh. 2011.13; published online 24 February 2011