Ubiquinol: A potential biomarker for tissue energy requirements and oxidative stress

Background: Coenzyme Q (CoQ) has been suggested as a biomarker for tissue redox status. The aims are (1) to compare ubiquinol-9, ubiquinol-10, ubiquinone-9, ubiquinone-10, total CoQ content and CoQ redox ratio in quadriceps muscle, heart, brain and liver tissues of mdx mice with wild-type controls; and (2) to determine if ubiquinol content and CoQ redox ratio changes are associated with pathological findings in mdx mouse. Methods: CoQ contents were determined in homogenized quadriceps muscle, heart, liver and brain of age-matched mdx and wild-type control mice by HPLC-EC. Light and electron microscopy studies were conducted using standard pathology methods. Results: Ubiquinol-9 and ubiquinol-10 concentrations are significantly increased in quadriceps and heart muscle of mdx mouse. Increased redox ratios of coenzyme Q(9) and coenzyme Q(10) are also evident in quadriceps, heart and liver tissues in mdx mouse, but not brain. Pathological examination shows marked rnyofiber regeneration and evidence of mitochondrial proliferation for mdx muscle. Conclusions: Evidence that changes in ubiquinol content and CoQ redox ratio are related to pathological features in mdx skeletal and heart myofibers suggests that tissue ubiquinol content and CoQ redox ratio may be useful biomarkers for evaluating muscle disorders associated with mitochondrial proliferation and defects in oxidative phosphorylation. (c) 2005 Elsevier B.V. All rights reserved.