High serum myostatin level suggests accelerated muscle senescence in active idiopathic inflammatory myositis

Introduction: Inflammation is the forerunner to fibrosis and premature aging in various systemic diseases. Hence, we hypothesized that idiopathic inflammatory myopathies (IIM) may exhibit accelerated senescence, and the serum myostatin (MSTN):follistatin system may be a reflection of early senescence events in the muscle. 

Methods: Patients with IIM (ACR/EULAR criteria) were recruited (2017-2019) for comparison with healthy and disease controls (DCs). Those with active infection, pregnancy, renal dysfunction, or chronic kidney disease were excluded from the study. MSTN and follistatin were estimated in sera using ELISA (R&D systems, USA). Juvenile myositis and young adults (18-40 years) were subsequently analyzed separately. Nonparametric tests were used for paired and unpaired analysis. Results expressed as median and interquartile range. 

Results: A total of 84 myositis (3 juvenile myositis, 40 DM, 30 PM, 11 overlap) patients (68 females) with median age 38 (27-47.0) years and median disease duration of 0.9 (2.3-5.1) years were included. Serum MSTN was lower in IIM than in healthy control (149.3 vs. 243.6 P < 0.0001) but higher in IIM as compared with DCs (149.3 vs. 85.11, P = 0.0174). MSTN levels were higher in active as compared with inactive myositis in young adults (189.6 vs. 115.8, P = 0.0349). Serum MSTN correlated with height (r = 0.3, P = 0.003) and weight (r = 0.2, P = 0.047) but not MMT8 or muscle enzymes. On follow-up, the serial MSTN estimation paralleled change in disease activity. 

Conclusion: Elevated serum MSTN levels in active myositis raise the possibility of accelerated senescence in the inflamed muscle tissues which need further investigation.