Urinary titin reflects the severity of walking ability, muscle strength, and muscle and cardiac damage in patients with Becker muscular dystrophy.

BACKGROUND

Becker muscular dystrophy (BMD) is a dystrophinopathy caused by a pathological variant of the DMD gene. Urinary titin, a degradation product of the giant protein titin present in muscle sarcomeres, has been used as a biomarker to reflect muscle degradation in Duchenne muscular dystrophy, a more severe dystrophinopathy. However, the clinical significance of urinary titin levels in BMD remains unclear. This study aimed to investigate the relationship between urinary titin levels and the clinical data in patients with BMD.

METHODS

Urine samples were collected from 123 patients with BMD, and urinary titin levels were measured. The association of urinary titin with clinical data, including age, physical measurements, physical activity, blood tests, and cardiopulmonary test results, was examined.

RESULTS

A total of 257 urine samples were obtained from patients of 5-79 years of age. The median urinary titin level was 72.6 pmol/mg Cr (range 0.2-4325.0 pmol/mg Cr). No strong correlation was found between urinary titin levels and age, physical measurements, physical function, blood test results, or cardiopulmonary function. However, on comparing clinical data between the age-matched high urinary titin (N = 94) and normal (N = 29) groups, the high urinary titin group had a significantly greater number of non-ambulatory cases (23.9 % vs. 3.6 %), weaker grip strength (16.3 vs. 32.0 kg), and higher serum creatine kinase (1072 vs. 398 U/L) and cardiac troponin I (10.6 vs. 2.5 pg/mL) levels.

CONCLUSION

Urinary titin was identified as a biomarker reflecting walking ability, muscle strength, and skeletal and cardiac damage in patients with BMD.