[Pentose phosphate pathway in neuromuscular diseases--evaluation of muscular glucose 6-phosphate dehydrogenase...

There have been several reports concerning elevated glucose 6 phosphate dehydrogenase (G6PDH), the rate-limiting enzyme of pentose phosphate pathway (PPP), in experimental muscle disturbances. PPP produces ribose, a substrate of RNA, and NADPH which is a cofactor of fatty acid synthesis. PPP also has a role of by-path pathway of glycolysis. Then, we evaluated G6PDH activity and RNA content in biopsied quadriceps muscle. The subjects were muscles from 23 neurogenic amyotrophy, 54 myopathy including 19 progressive muscular dystrophy (PMD), and 10 controls whose muscle was obtained at orthopedic surgery. Neurogenic amyotrophy consisted of 12 amyotrophic lateral sclerosis (ALS), 4 spinal muscular atrophy and 7 peripheral nerve disorders. Myopathy were 3 Duchenne dystrophy, 2 congenital muscular dystrophy, 8 limb-girdle type dystrophy, 6 facio-scapular +-humeral muscular dystrophy, 6 myotonic dystrophy, 6 mitochondrial myopathy, 5 endocrinological myopathy, 3 hypokalemic myopathy, 8 polymyositis and 4 other inflammatory myopathy. The assays of G6PDH and RNA were performed after Glock's and Fleck's methods, respectively. The control values were 3.6 +/- 0.8 nmol formed NADPH/mg protein/min (M +/- SD) in G6PDH and 0.69 +/- 0.17 micrograms/mg non-collagen protein in RNA. Most cases of PMD, as well as some cases of ALS, hyperthyroidism, mitochondria hypokalemic myopathy, inflammatory myopathy showed increased values (beyond M + 2SD of control) both in G6PDH and RNA. There were significant positive correlations between G6PDH activity and RNA content in PMD and motor neuron disease. Myotonic dystrophy showed normal values in both G6PDH and RNA. Half number of cases of mitochondrial myopathy demonstrated increased G6PDH alone.(ABSTRACT TRUNCATED AT 250 WORDS)