Brain metabolism is abnormal in the mdx model of Duchenne muscular dystrophy

Abstract

Duchenne muscular dystrophy (DMD) is an X-linked genetic disorder primarily affecting young boys, often causing mental retardation in addition to the well-known progressive muscular weakness. Normal dystrophin expression is lacking in skeletal muscle and the CNS of both DMD children and the mdx mouse model. To date, 31P-magnetic resonance spectroscopy (MRS) has shown in vivo several abnormalities within skeletal muscle of mdx mice and DMD boys. In this study, we determined whether similar abnormalities occur in mdx brain in vivo by using 31P-MRS in addition to metabolite and enzyme analysis to study cerebral metabolism. An increased inorganic phosphate (P(i))/phosphocreatine (PCr) and pH was found in vivo for mdx brain compared with controls, and biochemical analysis showed a reduction in total creatine, an increased extracellular and decreased intracellular volume in mdx brain. No differences were found in any glycolytic or mitochondrial maximal enzyme activities. These changes are discussed with respect to the biochemical changes found in muscle from DMD patients and mdx mice. It is proposed that these biochemical changes may be a factor in the reduced cognitive capacity of mdx mice and some DMD children.