Histological and biochemical assessment of mitochondrial function in dermatomyositis.
OBJECTIVE
Mitochondrial dysfunction in idiopathic inflammatory myopathies (IIM) remains a controversial issue. The aim of the present study was to investigate the correlation between histological abnormalities and the biochemical function of the skeletal muscle mitochondria from patients with dermatomyositis (DM).


METHODS
We evaluated 10 patients with a new diagnosis of DM and 15 healthy individuals, matched by age and gender. Muscle biopsy was routinely processed for histochemical studies and biochemical analysis of pure mitochondria. The percentages of ragged-red fibres (RRF), cytochrome c oxidase (COX)-negative fibres and succinic dehydrogenase (SDH) hyper-reactive fibres were calculated, oxygen utilization using different substrates was assessed polarographically, and enzymatic activity of individual complexes of the electron transport chain (ETC) and ATPase was measured spectrophotometrically.


RESULTS
We found an increased percentage of COX-negative and SDH hyper-reactive fibres in DM patients (0.82 and 1.82%, respectively) compared to controls (0.26 and 0.22%; P < 0.05 and P = 0.001, respectively); however, oxidation rates of different substrates and enzymatic activities of ETC and ATPase did not differ significantly between both groups.


CONCLUSIONS
The overall function of ETC from skeletal muscle mitochondria is not affected in DM.
Miró
O
O
Department of Internal Medicine, Hospital Clínic, Medical School, University of Barcelona, Catalonia, Spain.
Casademont
J
J
Grau
J M
JM
Jarreta
D
D
Urbano-Márquez
A
A
Cardellach
F
F
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy; D003882:Dermatomyositis / Q000201:enzymology / Q000473:pathology*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D005260:Female; D006801:Humans; D017243:MERRF Syndrome; D008297:Male; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000201:enzymology / Q000473:pathology*; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000473:pathology; D018482:Muscle, Skeletal / Q000201:enzymology / Q000473:pathology*; D011446:Prospective Studies; D013385:Succinate Dehydrogenase / Q000378:metabolism*
D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV; D000251:Adenosine Triphosphatases