The Acute Effects of Elevated Blood Lipid Levels on Endothelial Function

by Nissen, Alexander

The association between prolonged elevation of blood lipid levels and coronary artery disease is well established. Research focusing on the acute effects of hyperlipidemia is not as abundant, and often looks only at large-sized arteries. The purpose of our study was to measure the acute effects of elevated blood lipid levels on microvascular endothelial function, non-invasively, by means of laser Doppler flowmetry and the administration of vasoactive challenges.

With IRB approval, six healthy subjects were recruited for a three-session study in which they were given isocaloric meals with variable fat content (non-fat meal = NM; fatty meal = FM; or fatty meal with atorvastatin = FML). Two hours after ingesting the meal, the subjects microvasculature was examined using laser Doppler flowmetry. Our analysis looked at the ratio of low to high frequency microvascular oscillations (increases if parasympathetically mediated oscillations are inhibited) both at baseline and during a vasoconstrictive challenge; as well as endothelium-independent versus endothelium-dependent vasodilation using topical administration of acetylcholine and nitroglycerin.

We found a greater low to high frequency ratio after the FM compared to the NM both at baseline (mean ratio after FM was 222 +/-109% of that after NM, p = 0.016) and during the vasoconstrictive challenge (mean ratio after FM was 321 +/-242% of that after NM, p = 0.05), indicating a relative impairment in parasympathetic oscillations after the FM. Additionally, the mean ratio of endothelium-independent to endothelium-dependent vasodilation after the FM was 177.6 +/-98% of that after the NM, p = 0.036.

We concluded that elevated blood lipid levels acutely impair endothelial function.