Clinical aspects of coenzyme Q10 in relationship with its bioenergetic and antioxidant properties

For a number of years, coenzyme Q (CoQ10 in humans), was known for its key role in mitochondrial bioenergetics; later studies demonstrated its presence in other subcellular fractions and in plasma, and also extensively investigated its antioxidant role. This chapter discusses the relationship between the acknowledged bioenergetic role of CoQ10 and some clinical effects. The antioxidant properties of CoQ10 are then analyzed especially for their consequences on protection of circulating human low-density lipoproteins and prevention of atherogenesis. The relationship between CoQ 10 and statins is also discussed in the light of possible involvement of CoQ10 deficiency in the issue of statin side effects. New aspects of the antioxidant involvement of coenzyme Q are also discussed together with their relevance in cardiovascular disease. Data are reported on the efficacy of CoQ10 in ameliorating endothelial dysfunction in patients affected by ischemic heart disease. Many of the effects of CoQ10, which were classically ascribed to its bioenergetic properties, are now considered as the result of its biochemical interaction with nitric oxide (NO), NO synthase and reactive oxygen species capable of inactivating NO. Clinical studies are reported highlighting the effect of CoQ10 on extracellular SOD, which is deeply involved in endothelial dysfunction. Previous studies have shown decreased levels of CoQ10 in the seminal plasma and sperm cells of infertile men with different kinds of asthenospermia. Research has been extended to supplementation with CoQ10 of infertile men affected by idiopathic asthenozoospermia. CoQ10 levels increased significantly in seminal plasma and sperm cells after 6 months of treatment with concomitant improvement of sperm cell motility. © 2008 Springer Netherlands.