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 between 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 μM vs 82.5±1.61 μM, 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.