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Urinary excretion of acid-soluble peptides in children with Duchenne muscular dystrophy
1Faculty of Science of Living, Osaka City University, Japan.
Insights
Urinary acid-soluble peptides (ASP) can indicate whole-body protein breakdown, especially in Duchenne muscular dystrophy (DMD). ASP levels correlate with muscle breakdown markers but are unaffected by diet, making them a convenient index.
Area of Science:
- Biochemistry
- Clinical Nutrition
- Pediatrics
Background:
- Protein catabolism assessment is crucial for understanding metabolic states.
- Existing biomarkers for protein breakdown, like 3-methylhistidine (3MH), have limitations.
- Acid-soluble peptides (ASP) in urine are proposed as a novel index for protein catabolism.
Purpose of the Study:
- To validate urinary ASP as a reliable index of whole-body protein catabolism.
- To compare ASP excretion in healthy children versus those with Duchenne muscular dystrophy (DMD).
- To assess the correlation of ASP with other protein breakdown and dietary intake markers.
Main Methods:
- Measured urinary ASP excretion in 46 normal children and 18 children with DMD.
- Correlated ASP levels with 3-methylhistidine (3MH) and 1-methylhistidine (1MH).
- Observed changes in urinary ASP following bestatin administration in DMD patients.
Main Results:
- Children with DMD exhibited significantly higher urinary ASP levels than controls.
- Urinary ASP concentration correlated positively with 3MH, indicating reflection of protein catabolism.
- No correlation was found between ASP and 1MH, suggesting dietary independence.
- Bestatin administration led to a marked increase in urinary ASP in DMD patients.
Conclusions:
- Urinary ASP serves as a valid and convenient index for whole-body protein catabolism.
- ASP is a more practical biomarker than 3MH due to fewer dietary restrictions.
- Caution is advised when using ASP as an index during bestatin treatment.
Abstract:
In order to investigate the validity of the hypothesis that acid-soluble peptides (ASP) in urinary excreta can be applied as an index of the protein catabolism of the whole body, we measured the urinary excretion of ASP in 46 normal children and in 18 children with Duchenne muscular dystrophy (DMD), in which continuous breakdown of skeletal muscle protein is presumed. The mean value of ASP in the children with DMD was significantly higher than that in normal controls. The concentration of ASP was correlated with that of 3-methylhistidine (3MH), which has been proposed as an index of muscle breakdown. This finding indicates that urinary ASP reflects the catabolism of body proteins. No correlation was observed between the concentration of ASP and that of 1-methylhistidine (1MH), which is used as an objective index of meat and fish ingestion. After the administration of bestatin, an inhibitor of leucine aminopeptidase, for 9 months, the urinary ASP concentration of children with DMD increased markedly. This increase is thought to have been directly caused by the bestatin itself. Urinary ASP is therefore apparently a more conveniently applied index of protein catabolism than is urinary 3MH, which requires the application of several restrictions. However, it should not be applied when the effect of bestatin administration is evident.