Serum Myostatin and Follistatin Levels in Patients With Dermatomyositis and Polymyositis.

BACKGROUND

Myostatin is a protein in the TGF-β family that negatively regulates muscle mass, and follistatin is a myostatin antagonist.

OBJECTIVE

The aim of this study was to measure serum levels of myostatin and follistatin in idiopathic inflammatory myopathy patients and correlate these levels with muscle strength, fatigue, functional capacity, damage, and serum levels of muscle enzymes.

METHODS

This was a multicenter cross-sectional study including 50 patients (34 dermatomyositis and 16 polymyositis [PM]) and 52 healthy individuals (control group [CG]). The disease status was evaluated according to the International Myositis Assessment & Clinical Studies. Fatigue was rated according to the Fatigue Severity Scale, and body composition was measured using dual-energy x-ray emission densitometry. Myostatin and follistatin were measured using enzyme-linked immunosorbent assays.

RESULTS

Mean age was 50.9 ± 14.0 years, and mean disease duration was 89.2 ± 80.9 months. There were no differences in levels of myostatin (14.15 ± 9.65 vs. 10.97 ± 6.77 ng/mL; p = 0.131) or follistatin (0.53 ± 0.71 vs. 0.49 ± 0.60 ng/mL; p = 0.968) between patients and the CG. However, myostatin levels were higher in PM than CG (16.9 ± 12.1 vs. 11.0 ± 6.8 ng/mL; p = 0.036). There was no difference in serum myostatin among patients with and without low lean mass. Patients not treated with corticosteroids had higher serum levels of myostatin than the CG. There was a weak negative correlation between follistatin and Manual Muscle Testing and a Subset of Eight Muscles and a weak positive correlation between follistatin and Healthy Assessment Questionnaire.

CONCLUSIONS

Serum levels of myostatin and follistatin did not differ between dermatomyositis and PM patients and control subjects. The assessment of serum levels of myostatin and follistatin in idiopathic inflammatory myopathy patients seems not to be helpful in clinical practice.