Biomarkers for mitochondrial respiratory chain disorders.

Mitochondrial respiratory chain deficiencies are a group of more than 100 disorders of adults and children, with highly variable phenotypes. Their diagnosis is a great challenge, in spite of the fact that knowledge on their molecular genetic background has increased considerably during the last 20 years. Muscle biopsy is the key diagnostic procedure, including histological and biochemical analysis of mitochondria. Less invasive, specific and sensitive diagnostic tools based on serum biomarkers are still lacking. Recent technological developments, especially in mass spectrometry, enable novel tools for identification of local and global molecular consequences of mitochondrial respiratory chain dysfunction in patient samples. Furthermore, emerging disease models, especially genetically modified mice, offer unique materials to tackle pathophysiology with modern transcriptomic, proteomic, and metabolomic approaches. Identified molecular signals or metabolic fingerprints have the potential to be highly useful biomarkers for future diagnosis of mitochondrial respiratory chain disorders.