Absence of mitochondrial dysfunction in polymyalgia rheumatica - Evidence based on a simultaneous molecular and biochemical approach

Objective: To investigate the molecular and biochemical profile of skeletal muscle mitochondria of patients with isolated polymyalgia rheumatica (PMR) . Patients and Methods: We included patients with a recent diagnosis of PMR a nd as control healthy individuals submitted to orthopedic surgery. Skeletal muscle was obtained from quadriceps, thus was mitochondria immediately iso lated. Long polymerase chain reaction and Southern blot transference were p erformed to detect deleted mtDNA molecules. Mitochondrial oxidative activit y using different substrates and individual enzyme activity of respiratory chain complexes were assessed to search for any biochemical dysfunction. Results: Fifty-one individuals (PMR=25, controls=26) were included. Mean ag e was 72 (11) years; 45% were females. We found no significant increase of deleted mtDNA molecules in PMR patients compared to controls. Both groups d iffered neither on oxygen consumption (p=NS for all substrates) nor enzymat ic activity (p=NS for all complexes). Conclusions: Skeletal muscle mitochondria are molecularly and biochemically unaffected in PMR.