Clinical Information

Coenzyme Q10 (CoQ10) is an essential cofactor in the mitochondrial respiratory chain responsible for oxidative phosphorylation where it functions as an electron carrier and acts as an antioxidant. It is found in all cell membranes and is carried by lipoproteins in the circulation. Approximately 60% of CoQ10 is associated with low-density lipoprotein (LDL), 25% with high-density lipoprotein, and 15% with other lipoproteins. CoQ10 is present in the body in both the reduced and oxidized forms, with the antioxidant activity of CoQ10 dependent on both its concentration and its reduction-oxidation (redox) status.

CoQ10 deficiencies, which are clinically and genetically diverse, can occur due to defects in genes involved in the biosynthesis of ubiquinone (primary CoQ10 deficiency) or due to other causes such as mitochondrial disorders (secondary or CoQ10 deficiency).

Five major clinical phenotypes of CoQ10 deficiency have been described:

-Encephalomyopathy (elevated serum creatine kinase [CK], recurrent myoglobinuria, lactic acidosis)

-Cerebellar ataxia and atrophy (neuropathy, hypogonadism)

-Severe multisystemic infant form (nystagmus, optic atrophy, sensorineural hearing loss, dystonia, rapidly progressing nephropathy)

-Nephropathy, steroid resistant nephrotic syndrome leading to end stage kidney disease

-Isolated myopathy (exercise intolerance, fatigue, elevated serum CK)

Treatment with CoQ10 in patients with mitochondrial cytopathies can improve mitochondrial respiration in both brain and skeletal muscle.

CoQ10 has been implicated in other disease processes, including Parkinson disease, diabetes, and Alzheimer disease, as well as in aging and oxidative stress. CoQ10 may also play a role in hydroxymethylglutaryl-CoA reductase inhibitor (statin) therapy; changes in CoQ10 may be relevant to statin-induced myalgia. Additionally, the redox status of CoQ10 may be a useful early marker for the detection of oxidative LDL modification.