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Mechanism of muscle wasting in myotonic dystrophy
Author(s) -
Griggs Robert C.,
Jozefowicz Ralph,
Kingston William,
Nair K. Sreekumaran,
Herr Barbara E.,
Halliday David
Publication year - 1990
Publication title -
annals of neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.764
H-Index - 296
eISSN - 1531-8249
pISSN - 0364-5134
DOI - 10.1002/ana.410270509
Subject(s) - myotonic dystrophy , leucine , wasting , endocrinology , medicine , myotonia , atrophy , skeletal muscle , muscle biopsy , anabolism , muscle atrophy , muscular dystrophy , chemistry , biology , biochemistry , biopsy , amino acid
Myotonic dystrophy is associated with progressive muscular atrophy. In order to determine the mechanism of muscle wasting in this condition, we measured fractional mixed skeletal muscle protein synthesis in the postabsorptive state in 8 patients with myotonic dystrophy, and compared the results with those of 10 normal subjects. Fractional muscle protein synthesis was determined by measuring the increment of 13 C leucine in mixed skeletal muscle protein obtained by needle biopsy from the quadriceps muscle during a primed‐continuous infusion of L‐(1‐ 13 C) leucine. We used plasma 13 C α‐ketoisocaproate (representing intracellular leucine labeling) as the precursor pool for the calculation of fractional muscle protein synthesis and leucine kinetics. Fractional muscle protein synthesis was depressed in the patients with myotonic dystrophy (28% decrease, p < 0.02). Leucine flux, leucine oxidation, and the nonoxidative portion of leucine flux were not different between the patients with myotonic dystrophy and the normal control subjects. Muscle atrophy in myotonic dystrophy reflects a selective decrease in muscle protein synthesis without any similar decrease in nonmuscle protein synthesis. This decrease may result from an impaired end‐organ response to anabolic hormones or substrates.