Respiratory chain activity in myopathies

ABSTRACT

Aim: The present study was conducted to find out whether disturbances of respiratory chain enzymes were involved in the pathogenesis of three types of myopathy Duchenne muscle dystrophy [DMD], limb girdle muscular dystrophy, and steroid-induced myopathies; to assess the extent and nature of these deficits among the three myopathic groups, and to investigate the relation between the severity of muscular disorders- assessed by creatine phosphokinase [CPK] level- and the extent of respiratory chain impairment. Subjects and Fourty myopathic patients as group I [GI]; 10 DMD [GIA], 16 limb girdle dystrophy [GIB], and 14 steroid-induced myopathy [GIC]; and 20 healthy controls as group II [GII] that matches the general features of GI. Cases and controls were subjected to history taking as well as physical examination. Diagnosis of myopathy was established using routine motor and sensory conduction study and concentric needle EMG. Cases and controls were subjected to estimation of respiratory chain complexes; RCI, RCII, RCIII, and RCIV, in neutrophil mitochondria. Results were analysed using t-test between GI and II and F test in between GIA, GIB and GIC. The results revealed a significant decrease of all respiratory chain complexes; RCI, RCII, RCIII, and RCIV; in GI as compared to controls [2878.04 +/- 1085.96 versus 5867.93 +/- 1000.03 micro mol/min/mg protein for RCII, 549.7 +/- 21574 versus 80382+/=119.41 micro mol/min/mg of protein for RCIV, 60654 +/- 162.35 versus 95949 +/- 136.14 micro mol/min/mg of protein for RCIII, and 58.73 +/- 18.08 versus 97.88 +/- 19.06 micro mol/min/mg protein for RCIV. On comparing the 3 subgroups; IA, IB, and IC; the following was found [1] A significant decrease of GIC when compared to GIA and when compared to GIB and when compared to GIB as regards RCI [3234.526 +/- 716.363, 3385.13 +/- 218.603, and 2043.894 +/- 631.967 micro mol/min/mg protein for GIA. GIB, and GIC, respectively, F - 4.331, and P = 0.03]; [2] A significant decrease of GIA when compared to GIB and when compared to GIC as regards RCIV [42.584 +/- 22,9177, 66.947 +/- 10.861, and 60.88 +/- 1532 micro mol/min/mg protein for GIA, GIB, and GIC, respectively, F = 3.67 and P = 0.47]. [3] Nonsignificant difference between GIA, GIB and GIC as regards RCII, and RCIII. Using multiple linear regression analysis between respiratory chain enzymes and CPK, only RCIV showed a statistically significant correlation with CPK. Conclusions: Myopathy could be associated with alterations in respiratory chain enzyme complexes that result in effort intolerance. Such an alteration could be detected in neutrophil mitochondria by an easier noninvasive technique. RCIV could be used as a predictive marker for the occurrence of muscle damage in myopathy