INCREASE IN OXIDATIVE KEY ENZYMES IN A CASE OF MUSCLE UBIQUINOL-CYTOCHROME-C REDUCTASE DEFICIENCY

In a 29-year-old patient suffering from exertional muscle intolerance with a ubiquinol-cytochrome c reductase deficiency related to a cytoch rome b gene point mutation of the mitochondrial DNA, we conducted a st udy the aims of which were: (1) to test whether changes in the maximum activities of muscle key enzymes of the main energy-producing pathway s occur, (2) to address the issue of whether fibers of different types are equally affected in their enzymatic machinery involved in energy production, and (3) to correlate the results obtained with histochemic al and P-31 NMR spectroscopy data. When compared to results obtained i n six normal subjects, our study clearly shows that the type I fibers of the patient virtually all contained subsarcolemmal mitochondrial ag gregates and increased activities of succinate dehydrogenase and cytoc hrome c oxidase; microdissected type I fibers also displayed a signifi cant increase in both citrate synthase and beta-hydroxyacyl-CoA dehydr ogenase, two key enzymes of mitochondrial oxidative metabolism. Despit e these changes in the patient's muscle, its whole energy producing ma chinery remained impaired as revealed by a slowed post-exercise recove ry of phosphocreatine.