High-salt intake affects retinal vascular tortuosity in healthy males: an exploratory randomized cross-over trial

Eliane F E Wenstedt,Tien Y Wong,Emma Rademaker,Rosa D Wouda,Liffert Vogt,Esmee M Schrooten,Lisanne Beugelink,Nienke M G Rorije,Reinier O Schlingemann

doi:10.1038/s41598-020-79753-6

Abstract

The retinal microcirculation is increasingly receiving credit as a relatively easily accessible microcirculatory bed that correlates closely with clinical cardiovascular outcomes. The effect of high salt (NaCl) intake on the retinal microcirculation is currently unknown. Therefore, we performed an exploratory randomized cross-over dietary intervention study in 18 healthy males. All subjects adhered to a two-week high-salt diet and low-salt diet, in randomized order, after which fundus photographs were taken and assessed using a semi-automated computer-assisted program (SIVA, version 4.0). Outcome parameters involved retinal venular and arteriolar tortuosity, vessel diameter, branching angle and fractal dimension. At baseline, participants had a mean (SD) age of 29.8 (4.4) years and blood pressure of 117 (9)/73 (5) mmHg. Overall, high-salt diet significantly increased venular tortuosity (12.2%, p = 0.001). Other retinal parameters were not significantly different between diets. Changes in arteriolar tortuosity correlated with changes in ambulatory systolic blood pressure (r = − 0.513; p = 0.04). In conclusion, high-salt diet increases retinal venular tortuosity, and salt-induced increases in ambulatory systolic blood pressure associate with decreases in retinal arteriolar tortuosity. Besides potential eye-specific consequences, both phenomena have previously been associated with hypertension and other cardiovascular risk factors, underlining the deleterious microcirculatory effects of high salt intake.

Highlights

The retinal microcirculation is increasingly receiving credit as a relatively accessible microcirculatory bed that correlates closely with clinical cardiovascular outcomes
We aimed to study the effect of experimental high salt intake on the retinal microcirculation, involving venular and arterial tortuosity and other retinal vascular parameters including fractal dimension, arteriolar diameter, length diameter ratio and branching angle
One subject failed to meet the inclusion criteria, and one subject was excluded due to failure to adhere to the study protocol, 18 subjects remained for randomization and analysis, 10 of which were randomized to start with a high-salt diet and 8 to start with a low-salt diet

Summary

Introduction

The retinal microcirculation is increasingly receiving credit as a relatively accessible microcirculatory bed that correlates closely with clinical cardiovascular outcomes. Salt intake in the Western world generally exceeds the amount as recommended by g uidelines[1] The effect that this may have on microcirculatory vessels is important to establish, both with regard to the link to hypertension development as well as to expose potential blood pressure-independent deleterious effects. “twisted blood vessels”) and decreased arteriolar tortuosity were significantly associated with h ypertension[17] This is supported by other studies that showed a relation between hypertension and retinal vessel tortuosity[18,19,20,21,22,23]. We aimed to study the effect of experimental high salt intake on the retinal microcirculation, involving venular and arterial tortuosity and other retinal vascular parameters including fractal dimension, arteriolar diameter, length diameter ratio and branching angle

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Conclusion