Study of human NADH:ubiquinone oxidoreductase deficiency

NADH: ubiquinone oxidoreductase (complex I) is the most complicated enzyme of mitochondrial oxidative phosphorylation system (OXPHOS). Complex I is localised in the inner mitochondrial membrane and is composed of 45 subunits. Seven of them are coded by mtDNA, thirty eight subunits are coded by nDNA. Function of complex I is NADH oxidation and creation of proton gradient in intermembrane space by proton translocation. Mitochondrial disease caused by complex I defect are the most frequent OXPHOS disorders. Large-scale symptoms mostly affect organs with high energy demand like brain, muscle or heart. The aim of study was to characterize the impact of isolated complex I deficiency on cellular, enzymatic and protein level in patient-derived skin fibroblasts with m.3697G>A mutation in MTDN1 and c.[229C>T];[476C>A] mutations in NDUFS8. Both mutated subunits are parts of catalytic core of complex I. Heteroplasmy of mtDNA mutation m.3697G>A in fibroblast cells reached more than 90 %. Mitochondrial ultrastructure was disrupted in both patients compared to control. Mitochondrial network was nonhomogenous, mitochondrial ultrastructure showeed low cristae level and content of reactive oxygen species in both patients was significantly increased in comparison with control. Catalytic activity and protein level of..

Complex I of mitochondrial respiratory chain a its disorders.

NADH: ubiquinone oxidoreductase (Complex I) is a multisubunit protein complex of inner mitochondrial membrane. Complex I is the biggest and most complicated part of oxidative phosphorylation system, which is responsible for the cell ATP production. It consists of 45 subunits. 7 subunits are mitochondrial encoded, remainder 38 are nuclear encoded. NADH: ubiquinone oxidoreductase has L-shaped structure, which is built of two arms: membrane arm and matrix located peripheral arm. Complex I oxidize the NADH molecule. The electron transport is coupled with proton pumping across the inner mitochondrial membrane to intermembrane space, where proton gradient developed and which is used by ATP synthase to ATP synthesis. Deficiencies of NADH: ubiquinone oxidoreductase represent extensive, clinically and genetic heterogeneous group of mitochondrial diseases. Decrease of activity and amount of complex I, decrease of ATP production, changes of membrane potential, mitochondrial morphology and mitochondrial network and increasing of production of reactive oxygen species are found in cells with defects of NADH: ubiquinone oxidoreductase. Combination of this features lead to serious illnesses, which are almost fatal and we still haven't any useful therapy. Aim of this study is to summarize present knowledge about..

Deterioration of mitochondrial bioenergetics and ultrastructure impairment in skeletal muscle of a transgenic minipig model in the early stages of Huntington's disease

Skeletal muscle wasting and atrophy is one of the more severe clinical impairments resulting from the progression of Huntington's disease (HD). Mitochondrial dysfunction may play a significant role in the etiology of HD, but the specific condition of mitochondria in muscle has not been widely studied during the development of HD. To determine the role of mitochondria in skeletal muscle during the early stages of HD, we analyzed quadriceps femoris muscle from 24-, 36-, 48- and 66-month-old transgenic minipigs that expressed the N-terminal portion of mutated human huntingtin protein (TgHD) and age-matched wild-type (WT) siblings. We found altered ultrastructure of TgHD muscle tissue and mitochondria. There was also significant reduction of activity of citrate synthase and respiratory chain complexes (RCCs) I, II and IV, decreased quantity of oligomycin-sensitivity conferring protein (OSCP) and the E2 subunit of pyruvate dehydrogenase (PDHE2), and differential expression of optic atrophy 1 protein (OPA1) and dynamin-related protein 1 (DRP1) in the skeletal muscle of TgHD minipigs. Statistical analysis identified several parameters that were dependent only on HD status and could therefore be used as potential biomarkers of disease progression. In particular, the reduction of biomarker RCCII subunit SDH30 quantity suggests that similar pathogenic mechanisms underlie disease progression in TgHD minipigs and HD patients. The perturbed biochemical phenotype was detectable in TgHD minipigs prior to the development of ultrastructural changes and locomotor impairment, which become evident at the age of 48 months. Mitochondrial disturbances may contribute to energetic depression in skeletal muscle in HD, which is in concordance with the mobility problems observed in this model