Seven-Day Salt Loading Impairs Microvascular Endothelium-Dependent Vasodilation without Changes in Blood Pressure, Body Composition and Fluid Status in Healthy Young Humans

Abstract

Objectives: We aimed to assess whether a 7-day high-salt (HS) diet affects endothelium-dependent and/or endothelium-independent microvascular function in the absence of changes in arterial blood pressure (BP), and to determine whether such microvascular changes are associated with changes in body composition and fluid status in healthy young humans. Materials and Methods: Fifty-three young healthy individuals (28 women and 25 men) were assigned to a 7-day low-salt diet (<3.5 g salt/day) followed by a 7-day HS diet (∼14 g salt/day). Skin microvascular blood flow in response to iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) was assessed by laser Doppler flowmetry, and BP, heart rate (HR), plasma renin activity (PRA), serum aldosterone, serum and 24 h-urine sodium, potassium, urea and creatinine levels, together with body composition and fluid status measurement with a 4-terminal portable impedance analyzer were measured before and after diet protocols. Results: BP, HR, body composition and fluid status were unchanged, and PRA and serum aldosterone level were significantly suppressed after HS diet. ACh-induced dilation (AChID) was significantly impaired, while SNP-induced dilation was not affected by HS diet. Impaired AChID and increased salt intake, as well as impaired AChID and suppressed renin-angiotensin system were significantly positively correlated. Changes in body composition and fluid status parameters were not associated with impaired AChID. Conclusion: 7-day HS diet impairs microvascular reactivity by affecting its endothelium-dependent vasodilation in young healthy individuals. Changes are independent of BP, body composition changes or fluid retention, but are the consequences of the unique effect of HS on endothelial function.

Effect of high-salt diet on blood pressure and body fluid composition in patients with type 1 diabetes: randomized controlled intervention trial

“…It may be noted that a recent study did not find any difference in ECFV after 1-week dietary salt loading in healthy individuals, in which the difference between LSD and HSD approximated 8 g (vs ±18 g in our study). 30 The similarity in ECFV in patients with type 1 diabetes and healthy controls on LSD and HSD is consistent with previous studies in normoalbuminuric patients with type 1 diabetes, since only in the presence of advanced chronic kidney disease ECFV was increased. 11 31 The mechanisms underlying the observed plasma volume response in patients with type 1 diabetes need further exploration.…”

Dietary Potassium Attenuates the Effects of Dietary Sodium on Vascular Function in Salt-Resistant Adults

“…While serum potassium was not significantly elevated, there is evidence to suggest that increases in dietary potassium may cause a feedforward mechanism by the gut to the kidney to increase potassium excretion without changes in serum potassium [38,39]. The significant elevation of PRA on the low sodium diet responded as expected and as previously demonstrated [12,40]. The response of Ang II was variable, but the pattern of response was as expected.…”

Mechanisms of Dietary Sodium-Induced Impairments in Endothelial Function and Potential Countermeasures

“…For instance, a high-sodium diet reduces the NO-mediated increase in skin blood flow in response to local heating in young, salt-resistant normotensive individuals [26]. In agreement with this finding, a high-sodium diet blunts the cutaneous blood flow response to ACh delivered via intradermal infusion [27] or iontophoresis [28,29]. Likewise, cutaneous post-occlusive reactive hyperemia is blunted in the absence of a change in BP following excess sodium consumption [28,30]; however, cutaneous reactive hyperemia appears to be mediated by endothelial release of prostaglandins rather than NO [30,31], and is beyond the scope of this review.…”