Metabolic implications of distal atrophy. Carbohydrate metabolism in centronuclear myopathy

Centronuclear myopathy, like myotonic dystrophy, is characterized by muscle wasting and type 1 fiber atrophy. To determine whether this disorder might include a derangement in carbohydrate metabolism similar to that in myotonic dystrophy, 3 comparably wasted patients with centronuclear myopathy, myotonic dystrophy, and neurogenic atrophy were investigated. The patient with centronuclear myopathy had mild glucose intolerance and hypoinsulinemia after oral glucose ingestion in bold contrast to the normal glucose tolerance and hyperinsulinemia observed in the myotonic dystrophy patient. No abnormality was seen in oral glucose tolerance in the patient with neurogenic atrophy, and all 3 patients had normal insulin tolerance. Forearm insulin infusion demonstrated normal stimulation of muscle glucose uptake in the patients with centronuclear myopathy and neurogenic atrophy in contrast to the markedly diminished response to insulin seen in the patient with myotonic dystrophy. These data indicate that neither distal wasting or type 1 fiber atrophy are responsible for the abnormalities in carbohydrate metabolism in myotonic dystrophy.