Analysis of the Mitochondrial Complex I-V Enzyme Activities of Peripheral Leukocytes in Oxidative Phosphorylation Disorders

Abstract

Mitochondrial oxidative phosphorylation defects are a common cause of mitochondrial diseases, which are characterized by multiorgan involvement and clinically heterogeneous manifestations. Diagnosis is difficult because of the lack of clinically feasible methods. In this study, mitochondrial complex I-V enzyme activity was measured in 64 patients with suspected mitochondrial disease and 200 healthy controls. Spectrophotometric assay was used for the analysis of mitochondrial complex I-V enzyme activity in peripheral leukocytes. Diagnosis was based on clinical presentation, magnetic resonance imaging (MRI), muscle pathology, and point mutation screening in mitochondrial DNA. The differential diagnosis of aminoacidopathies, organic acidurias, and fatty acid β-oxidation defects was made. Thirty-five patients (54.7%) were diagnosed with Leigh syndrome based on characteristic brain MRI. Complex enzyme activity in controls was found to be stable. A deficiency in the oxidative phosphorylation was found in 29 patients (45.3%). Twenty (31.2%) patients had isolated complex defects, complex I deficiency (n = 2, 3.1%), complex II deficiency (n = 3, 4.7%), complex III deficiency (n = 5, 7.8%), complex IV deficiency (n = 5, 7.8%), and complex V deficiency (n = 5, 7.8%). Nine patients were found to have combined deficiencies, 3 (4.7%) had combined deficiencies of complex I and IV, 2 (3.1%) had combined deficiencies of complex III and V, and 2 (3.1%) had a combined deficiency of complex I and V. In conclusion, the peripheral leukocyte oxidative phosphorylation enzyme activity assay was found to be a reliable method for the diagnosis of mitochondrial diseases.

Stomatin-like Protein 2 Deficiency in T Cells Is Associated with Altered Mitochondrial Respiration and Defective CD4+ T Cell Responses

“…A paucity of immune manifestations is also observed in humans with complex I deficiency. Although these patients have a reduction of complex I activity in peripheral blood leukocytes, they do not show overt immune deficiency (47,48), likely due to a compensatory reliance on glycolysis for ATP production (49). However, these effects are not negligible as illustrated by the recent observation that complex I plays an important role in the activation of T cells (50,51) and also by the decrease in CD4 + T cell expansion under conditions of low NAD + levels from decreased complex I activity (47, 52-54).…”

COX6A2 variants cause a muscle‐specific cytochrome c oxidase deficiency

“…19,20 Each experiment was performed in triplicate. The assays for complexes I-IV and CS were performed as previously described.…”

Five novel SUCLG1 mutations in three Chinese patients with succinate-CoA ligase deficiency noticed by mild methylmalonic aciduria

“…The blood total amount of mitochondria protein was determined by Coomassie brilliant blue G-250 [8,9]. The activities of mitochondrial respiratory chain enzymes I-IV and ATP synthase in peripheral leukocytes were determined via spectrophotometric assay.…”

“…The activities of mitochondrial respiratory chain enzymes I-IV and ATP synthase in peripheral leukocytes were determined via spectrophotometric assay. The activity of each complex was expressed as the ratio to the rate of citrate synthase [8,10].…”