Ubiquinol Ameliorates Endothelial Dysfunction in Subjects with Mild-to-Moderate Dyslipidemia: A Randomized Clinical Trial

Randomized, double-blind clinical trial in men and post-menopausal women aged 35-65 years with mild-to-moderate dyslipidemia and moderate endothelial dysfunction, without clinical cardiovascular disease and not taking lipid-lowering therapy. Active-arm per-protocol analyses included 17 participants in the 200 mg/day group and 15 in the 100 mg/day group; the intention-to-treat population included all 51 randomized subjects.

Participants received oral ubiquinol (reduced CoQ10, Kaneka QH™) for 8 weeks in two active regimens: 100 mg/day or 200 mg/day, given as one capsule in the morning and one in the evening. The active regimens were compared with placebo.

Ubiquinol improved endothelial function over 8 weeks versus placebo, with no clear dose-response between 100 mg/day and 200 mg/day. Week 8 flow-mediated dilation increased in both active groups and was higher than placebo (F = 9.145; p < 0.001), with Cohen's d of 0.89 for 200 mg/day and 1.30 for 100 mg/day, versus -0.37 for placebo; post-hoc comparison between ubiquinol doses was not significant (p = 0.88). The intervention also raised plasma CoQ10 and nitric oxide bioavailability and improved LDL oxidation lag time; mediation analysis found a significant indirect effect of plasma CoQ10 on FMD through lag time (ab = 0.073, 95% BCa CI 0.007-0.141), accounting for 33.8% of the total effect. Lipid levels did not change, and no adverse events were reported.

The active-arm per-protocol samples were small, and the trial was short at 8 weeks. Outcomes were largely surrogate biomarkers in a selected dyslipidemic population, limiting generalizability, and key contextual factors such as ethnicity, diet, and physical activity were not reported. The findings also do not show a clear dose-response between 100 mg/day and 200 mg/day.