Evaluation of enzymatic assays and compounds affecting ATP production in mitochondrial respiratory chain complex I deficiency

Abstract Isolated complex I deficiency is the most common oxidative phosphorylation defect and is associated with substantial morbidity and mortality. The diagnosis is made by enzymatic analysis and for most patients the molecular pathology remains undefined. Various cofactors and vitamins are frequently administered, but their efficacy have been difficult to assess. We employed determination of ATP production in fibroblast cell lines from patients with complex I deficiency to evaluate the usefulness of therapeutic agents. The effect of each additive varied among the different patients with certain agents favorably affecting ATP production rate in some of the patients and adversely affecting it in others. The reduced nicotinamide adenine dinucleotide (NADH)–ferricyanide reductase assay in muscle mitochondria correlated better than the NADH–coenzyme Q and NADH–cytochrome c assays with ATP production rate in fibroblasts. Our results underscore the necessity of evaluation of different agents for each patient separately. The NADH–ferricyanide reductase assay play a helpful role in directing mutation analysis and identifying patients which are more likely to have their cells amenable for ATP production assessment.