Pediatric reference intervals for muscle coenzyme Q10

Coenzyme Q10 (CoQ10) is present in humans in both the reduced (ubiquinol, CoQ10H2) and oxidized (ubiquinone, CoQ10) forms. CoQ10 is an essential cofactor in mitochondrial oxidative phosphorylation, and is necessary for ATP production. Total, reduced and oxidized CoQ10 levels in skeletal muscle of 148 children were determined by HPLC coupled with electrochemical detection, and we established three level thresholds for total CoQ10 in muscle. We defined as "severe deficiency", CoQ10 levels falling in the range between 0.82 and 4.88 μmol/g tissue; as "intermediate deficiency", those ranging between 5.40 and 9.80 μmol/g tissue, and as "mild deficiency", the amount of CoQ10 included between 10.21 and 19.10 μmol/g tissue. Early identification of CoQ10 deficiency has important implications in children, not only for those with primary CoQ10 defect, but also for patients with neurodegenerative disorders, in order to encourage earlier supplementation with this agent also in mild and intermediate deficiency.