Abstract
3-Methylhistidine (3 MH) is an amino acid synthesized by the posttranslational methylation of specific histidine residues in the peptide chains of actin and myosin in muscle fibers. When muscle protein is degraded, 3MH is released, but it does not participate in amino-acid reutilization, and is excreted unmetabolized. On the basis of these findings, it has been suggested that the rate of myofibrillar protein degradation may be estimated by relating the urinary 3MH concentration to an estimate of muscle mass such as urinary creatinine. We investigated the ratio of 3MH: creatinine in 21 children with neuromuscular diseases and 9 controls.
In controls, the mean ratio of 3MH: creatinine (mg/g) was 34.7±3.6 (mean±SD). In Duchenne muscular dystrophy (5 cases), Fukuyama type congenital muscular dystrophy (6 cases) and Werdnig-Hoffmann disease (5 cases), the ratios were 67.4±10.9, 73.4±9.9, 68.8±15.9, respectively, and they were significantly higher than that of controls (p<0.001), and about twice normal. Those of the cases of spinal type of arthrogryposis multiplex congenita, dermatomyositis and nemaline myopathy were 47.9, 55.6 and 39.9, respectively. These ratios were higher than the highest ratio (38.7) in controls. We suggested the clinical usefulness of urinary 3MH determination for the screening for neuromuscular diseases in childhood, not only in muscular dystrophy and Werdnig-Hoffmann disease, but also in other neurogenic muscular atrophy and congenital myopathy.
