Integrated analysis of the involvement of nitric oxide synthesis in mitochondrial proliferation, mitochondrial deficiency and apoptosis in skeletal muscle fibres.

Nitric oxide (NO) is an important signaling messenger involved in different mitochondrial processes but only few studies explored the participation of NO in mitochondrial abnormalities found in patients with genetic mitochondrial deficiencies. In this study we verified whether NO synthase (NOS) activity was altered in different types of mitochondrial abnormalities and whether changes in mitochondrial function and NOS activity could be associated with the induction of apoptosis. We performed a quantitative and integrated analysis of NOS activity in individual muscle fibres of patients with mitochondrial diseases, considering mitochondrial function (cytochrome-c-oxidase activity), mitochondrial content, mitochondrial DNA mutation and presence of apoptotic nuclei.

Deletion of Kinin B2 Receptor Alters Muscle Metabolism and Exercise Performance.

Metabolic syndrome is a cluster of metabolic risk factors such as obesity, diabetes and cardiovascular diseases. Mitochondria is the main site of ATP production and its dysfunction leads to decreased oxidative phosphorylation, resulting in lipid accumulation and insulin resistance. Our group has demonstrated that kinins can modulate glucose and lipid metabolism as well as skeletal muscle mass.

Nitric oxide synthesis is increased in cybrid cells with m.3243A>G mutation.

Nitric oxide (NO) is a free radical and a signaling molecule in several pathways, produced by nitric oxide synthase (NOS) from the conversion of L-arginine to citrulline. Supplementation of L-arginine has been used to treat MELAS (mitochondrial encephalopathy with lactic acidosis and stroke like syndrome), a mitochondrial disease caused by the m.3243A>G mutation.

Complex I spectrophotometric assay in cultured cells: detailed analysis of key factors.

The diagnosis of mitochondrial encephalomyopathies caused by complex I (C-I) deficiency relies mainly on the spectrophotometric C-I assay. Considered difficult, this assay lacks reliability and has high nonspecific activity. We studied the key factors of this assay in cultured cells (cybrid and fibroblast): ubiquinone analogues, rotenone inhibition to determine specific activity, and mode of permeabilization of mitochondrial membranes.

The mutations m.5628T>C and m.8348A>G in single muscle fibers of a patient with chronic progressive external ophthalmoplegia.

We identified a double mutation in a patient with chronic progressive external ophthalmoplegia, located in the tRNA(Ala) (m.5628T>C) and tRNA(Lys) (m.8348A>G) genes.

Effects of short-term zidovudine exposure on mitochondrial DNA content and succinate dehydrogenase activity of rat skeletal muscle cells.

Long-term use of zidovudine (AZT) may cause mitochondrial abnormalities in various tissues, including a toxic myopathy in AIDS patients associated with mitochondrial DNA (mtDNA) depletion. In the present study, we examine the short-term (48 h) effect of AZT (10, 30 and 100 microg/ml) on the mitochondrial succinate dehydrogenase (SDH) and mtDNA content of rat cultured skeletal muscle. The effect of AZT on cytochrome c oxidase (COX) enzyme was also analyzed.

Progressive myopathy with a combined respiratory chain defect including Complex II.

Biochemical defects in the respiratory chain are mostly associated with deficiencies in Complexes I, III and IV, caused by nuclear or mitochondrial DNA mutations. Combined defects including Complex II have been reported very rarely and have muscular symptoms as the main manifestation, including muscle weakness, exercise intolerance and myoglobinuria. We report a patient with a fatal progressive myopathy and muscle biopsy showing diffuse reduction in succinate dehydrogenase activity, ragged red fibers and intense lipid accumulation.

Age-related mitochondrial DNA point mutations in patients with mitochondrial myopathy.

Mutations in the control region (D-loop) of mitochondrial DNA (mtDNA) have been described in normal old individuals and it is suggested that they originated from oxidative damage. Respiratory chain defects may lead to increased free radical generation, increased susceptibility to oxidative damage and further increased accumulation of age-related mutations. The objective of this study was to verify whether patients with a mitochondrial disease are more predisposed to accumulate the A189G and T408A mutations in the D-loop and confirm their age-associated nature.

The role of nitric oxide in muscle fibers with oxidative phosphorylation defects.

NO has been pointed as an important player in the control of mitochondrial respiration, especially because of its inhibitory effect on cytochrome c oxidase (COX). However, all the events involved in this control are still not completely elucidated. We demonstrate compartmentalized abnormalities on nitric oxide synthase (NOS) activity on muscle biopsies of patients with mitochondrial diseases.

Duchenne muscular dystrophy: alpha-dystroglycan immunoexpression in skeletal muscle and cognitive performance.

The Duchenne muscular dystrophy (DMD) is a muscular dystrophy with cognitive impairment present in 20-30% of the cases. In the present study, in order to study the relationship between the alpha-dystroglycan (alpha-DG) immunostaining in skeletal muscle and cognitive performance in DMD patients, 19 were assessed. Twelve patients performed the intelligence quotient (IQ) below the average.

Frequency of duplications in the D-loop in patients with mitochondrial DNA deletions.

Small duplications (miniduplications) of the D-loop of human mitochondrial DNA (mtDNA) have been described in patients with mtDNA deletions, mtDNA point mutations and in normal aged tissues. The origin of these miniduplications is still unknown but it is hypothesized that they could be formed after oxidative damage. The respiratory chain (RC) is the main source of free radicals in mitochondria and it is believed that a defect in RC increases free radical generation.