HIGH SALT DIET ALTERS CEREBROVASCULAR RESISTANCE IN RESPONSE TO ORTHOSTATIC TEST IN HEALTHY YOUNG INDIVIDUALS

Abstract

Objective: High salt (HS) diet has been shown to impairs vascular reactivity in animal models, by increasing vasoconstriction to different stimuli. Response to orthostasis occurs via activation of baroreceptor reflex leading to increase in total peripheral resistance that prevents significant fall of arterial blood pressure (ABP) while standing up, aiming to preserve cerebral perfusion pressure. We recently showed that HS diet physiologically suppresses sympathetic arm of autonomic control in healthy humans (Stupin et al. Nutrients 2021; 13:1731. https://doi.org/10.3390/nu13051731). Present study aimed to assess the effect of HS diet on cerebral vasoreactivity in response to orthostatic load. Design and method: Twenty-seven young healthy participants (F:21, M:6, age range 19–24) consumed 7-day low-salt (LS) diet (<2.3 g NaCl /day) and afterwards 7-day HS diet (>11.2 g NaCl/day). In response to orthostatic test cerebral and systemic hemodynamic parameters, arterial blood pressure, heart rate variability and heart rate, and were recorded simultaneously with transcranial Doppler ultrasound and The Task Force® Monitor. Results: Subjects maintained normotension during HS diet. Diastolic blood pressure, as well as mean cerebral blood flow (CBF) and the velocity time integral decreased, while cerebral pulsatility index increased after standing up following both dietary protocols. However, while no change was observed in total peripheral resistance, cerebrovascular resistance significantly increased in response to orthostasis only after HS diet. Baroreflex sensitivity (BRS), sympathetic neural control, serum plasma renin activity and aldosterone, and urine noradrenaline and vanillylmandelic acid concentration was significantly decreased in HS diet. Conclusions: Results demonstrated that following 7-day HS diet, enhanced cerebral autoregulation preserves CBF and is manifested as increased cerebral vascular resistance, in conditions with blunted BRS and sympathetic activity. The study has been published in Eur J Appl Physiol. 2023 Jan 4. doi: 10.1007/s00421-022-05124-w. Online ahead of print.