The protective role of ubiquinol-10 against formation of lipid hydroperoxides in human seminal fluid.

Defective sperm function in infertile men has been associated with increased lipid peroxidation and impaired function of antioxidant defenses in spermatozoa. Evidence strongly suggests that CoQ10, a lipid-soluble component of the respiratory chain acts, in its reduced form (ubiquinol), as a potent antioxidant in various biological systems, such as lipoproteins and membranes. In this study we assayed CoQ10 content in both the reduced and oxidized form (ubiquinol/ubiquinone), and hydroperoxide levels in seminal plasma and seminal fluid from 32 subjects with a history of infertility. Our results showed a significant correlation between ubiquinol content and sperm count (r = 0.62; P < 0.05) in seminal plasma. An inverse correlation between ubiquinol content and hydroperoxide levels both in seminal plasma and in seminal fluid (r = -0.56; P = 0.01) was found. Using multiple regression analysis we also found a strong correlation among sperm count, motility and ubiquinol-10 content (P < 0.01) in seminal fluid. An inverse correlation between ubiquinol/ubiquinone ratio and percentage of abnormal morphology was also observed in total fluid. These results suggest that ubiquinol-10 inhibits hydroperoxide formation in seminal fluid and in seminal plasma. Since peroxidation in sperm cells is an important factor affecting male infertility, ubiquinol could assume a diagnostic and/or a therapeutic role in these patients.