Review article Clinical aspects of coenzyme Q 10 : An update Gian Paolo Littarru, M.D., Ph.D.,* and Luca Tiano, Ph.D. Department of Biochemistry, Biology and Genetics, Polytechnic University of the Marche, Ancona, Italy Manuscript received August 10, 2009; accepted August 13, 2009. Abstract The fundamental role of coenzyme Q 10 (CoQ 10 ) in mitochondrial bioenergetics and its well-acknowl- edged antioxidant properties constitute the basis for its clinical applications, although some of its effects may be related to a gene induction mechanism. Cardiovascular disease is still the main field of study and the latest findings confirm a role of CoQ 10 in improving endothelial function. The possible relation between CoQ 10 deficiency and statin side effects is highly debated, particularly the key issue of whether CoQ 10 supplementation counteracts statin myalgias. Furthermore, in cardiac patients, plasma CoQ 10 was found to be an independent predictor of mortality. Studies on CoQ 10 and physical exercise have confirmed its effect in improving subjective fatigue sensation and physical performance and in opposing exercise-related damage. In the field of mitochondrial myopathies, primary CoQ 10 deficiencies have been identified, involving different genes of the CoQ 10 biosynthetic pathway; some of these conditions were found to be highly responsive to CoQ 10 administration. The initial observations of CoQ 10 effects in Parkinson’s and Huntington’s diseases have been extended to Friedreich’s ataxia, where CoQ 10 and other quinones have been tested. CoQ 10 is presently being used in a large phase III trial in Parkinson’s disease. CoQ 10 has been found to improve sperm count and motility on asthenozoospermia. Moreover, for the first time CoQ 10 was found to decrease the incidence of preeclampsia in pregnancy. The ability of CoQ 10 to mitigate headache symptoms in adults was also verified in pediatric and adolescent populations. Ó 2010 Elsevier Inc. All rights reserved. Keywords: Coenzyme Q 10 ; Cardiovascular disease; Mitochondrial myopathies; Reproductive medicine Introduction Coenzyme Q (CoQ 10 in humans) is a key component of the mitochondrial respiratory chain and, for a number of years, it was mainly known for its role in oxidative phosphor- ylation; its presence was then demonstrated in other subcellu- lar fractions and in plasma lipoproteins, where it is endowed with antioxidant properties. CoQ 10 was also recognized to have an effect on gene expression [1]. These three functions underlie the rationale for its use in clinical practice and as a food supplement. This report constitutes an overview of new clinical findings in these past 4 y and is basically a further update of our previous report published in 2005 [2] (Table 1). Cardiovascular disease Cardiovascular effects of CoQ 10 can be ascribed to its bio- energetic role, to its capability of antagonizing oxidation of plasma low-density lipoprotein, and to its effect in ameliorat- ing endothelial function [3]. Among the recent data produced by our laboratory, CoQ 10 was found to improve endothelium- bound extracellular superoxide dismutase (ecSOD) [4] in patients affected by coronary artery disease. Patients with coronary artery disease have decreased levels of ecSOD, an enzyme that is thought to protect blood vessels against oxidant-induced damage. This was a double-blind, random- ized, controlled study of 35 patients with ischemic heart disease; the patients in the intervention group were treated with CoQ 10 at doses of 100 mg three times daily. CoQ 10 treatment determined a significant improvement in ecSOD activity, more pronounced in patients who had initial low values of ecSOD and therefore likely exposed to greater oxidative stress. This effect was accompanied by an increase of maximal oxygen uptake and of flow-mediated dilation, a recognized index of endothelial function. Since 1975 many studies have been conducted on the effect of CoQ 10 on hypertension. This issue was reviewed in 2007 by Rosenfeldt et al. [5] who carried out a meta- analysis of the clinical trials. The studies included three * Corresponding author. Tel.: þ39-071-2204674; fax: þ39-071-2801932. E-mail address: g.littarru@univpm.it (G. P. Littarru). 0899-9007/10/$ – see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.nut.2009.08.008 Nutrition 26 (2010) 250–254 www.nutritionjrnl.com