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.