7-DAYS HIGH-SALT DIET AFFECTS NO-MEDIATED MICROVASCULAR ENDOTHELIAL VASODILATION IN YOUNG HEALTHY INDIVIDUALS

Abstract

Objective: We have previously reported that short-term (7-days) high-salt (HS) loading impairs microvascular endothelial function in young healthy individuals, independently of blood pressure (BP) or body composition and fluid status changes. This study aimed to functionally assess specifically nitric-oxide (NO) mediated endothelial vasodilation of skin microcirculation in response to 7-day HS diet in healthy salt-resistant individuals. Design and method: 20 young healthy individuals (10 women and 10 men), age ranged between 19–24 years, participated in the present study. All subjects adhered to a 7-day low-salt (LS) diet (3.5 g salt/day) followed by a 7-day high-salt (HS) diet (∼14.7 g salt/day) protocol. To confirm that subjects conformed to the diet protocol, daily salt intake based on 24-h urinary sodium excretion was calculated using appropriate formula before and after HS diet protocol. Blood pressure (BP) was measured before and after respective diet protocols and salt resistance was defined as a < 5 mmHg change in mean arterial pressure (MAP) determined on LS versus HS diet. NO-mediated microvascular endothelial vasodilation in response to local heating (42°C) was functionally assessed using laser Doppler Flowmetry (LDF) (moorVMS-LDF, Moor Instruments, UK) and skin heater controller (moorVMS-HEAT, Moor Instruments, UK). Results: 24-hour sodium excretion significantly increased following HS diet compared to LS conditions (salt/g LS 6.6 ± 2.6 vs. HS 14.3 ± 2.5, P < 0.001). Salt resistance was confirmed in all subjects undergoing study (MAP/mmHg LS 87 ± 7 vs. HS 86 ± 9, P = 0.829). 7-day HS diet significantly reduced skin microvascular flow increase in response to local heating compared to LS conditions (LDF HEAT LS 14.16 ± 6.01 vs. HS 10.67 ± 3.27, P = 0.006). Conclusions: Results of the present study have functionally demonstrated that 7-days HS diet alters specifically NO-mediated endothelium-dependent of skin microcirculation in salt-resistant young healthy individuals.