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Naim Terai, Fabian Helbig, Lisa Ramm, Richard P Stodtmeister, Lutz E Pillunat; The effect of dietary nitrate supplementation on retinal vessel responses in young healthy subjects. Invest. Ophthalmol. Vis. Sci. 2019;60(9):5725.
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© ARVO (1962-2015); The Authors (2016-present)
In peripheral arterial disease, dietary nitrate supplementation enhances patients exercise performance via an increase in nitric oxide (NO) bioavailability and an improvement of tissue oxygenation. Therefore, the aim of the present study was to investigate whether an oral intake of inorganic nitrate in form of beetroot juice may have an impact on retinal vessel responses in young healthy subjects as a sign of an increased NO bioavailability in the endothelium of retinal vessels.
In a prospective, placebo-controlled randomized study, retinal vessel response was measured in 62 healthy subjects before and two hours after oral intake of either beetroot juice (group I, 200 ml) or apple juice (group II, 200 ml) as a placebo. Static and dynamic vessel analysis was performed with the Dynamic Vessel Analyzer (DVA, Imedos Systems UG). Intraocular pressure (IOP), systemic blood pressure and blood glucose level were obtained before and after oral intake of both juices.
Mean age was 25.4 ± 2.3 years and 25.1 ± 2.8 years in group I and II with no statistical significant difference between both groups (p = 0.665). Systemic blood pressure, blood glucose level and IOP did not change significantly after supplementation of beetroot juice or apple juice. Dilatation responses of the arterioles and the venules (+ 3.84 ± 2.3 % and + 4.57 ± 2.96 %) did not change significantly after intake of beetroot juice (+ 3.76 ± 1.88 % and + 4.66 ± 2.26 %, p = 0.624 and p = 0.752). Also, the constriction responses of the arterioles (- 1.08 ± 1.18 %) did not change significantly after beetroot juice intake (- 0.990 ± 1.40 %, p = 0.310). Static vessel analysis revealed non-significant changes of the central retinal artery equivalent (197.42 ± 23.5 µm to 195.88 ± 15.1 µm, p = 0.477) and the central vein equivalent (221.19 ± 29.4 µm to 218.02 ± 17.18 µm, p = 0.848).
In the present study retinal vessel responses, as measured by the DVA, were not affected by dietary nitrate supplementation in young healthy subjects. It might be hypothesized that an unaffected endothelial function as seen in young subjects may not show any further improvement of vessel responses after additional nitrate intake. However, further studies should elucidate in how far patients with an endothelial dysfunction (e.g. glaucoma) may benefit from an nitrate supplementation.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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