The endothelium is the thin layer of cells that lines the interior surface of blood vessels. It forms an interface between circulating blood in the lumen and the rest of the vessel wall. Endothelial cells line the entire circulatory system, from the heart to the smallest capillary. These cells reduce turbulence of the flow of blood, allowing the fluid to be pumped farther. Endothelial cells protect against atherosclerosis by helping to prevent blood clotting, because they contain heparan sulfate. Heparan sulfate acts as an anticoagulant.
The health of the endothelial cells is an important factor in preventing atherosclerosis. A meta-analysis that appeared in the journal Atherosclerosis (epublished ahead of print Oct 25, 2011) included MEDLINE, Cochrane Library, Scopus, and EMBASE to identify studies up to 1 July 2011 looked at randomized, controlled studies dealing with CoQ10 supplementation and endothelial function. The analysis found that CoQ10 supplementation significantly improved endothelial function.