Serum Myokines Levels in Patients with Endogenous Cushing Syndrome and Acromegaly: Cross-Sectional Case−Control Study

Background : Myokines are produced and released by muscle cells in response to muscular contractions. Endogenous Cushing syndrome (CS) and acromegaly cause significant changes in muscle tissue leading to atrophy or hypertrophy. However, there is no data whether these endocrine abnormalities influence myokine secretion.  Aims : To evaluate serum levels of myostatin, interleukin-6 (IL6) and irisin in patients with CS and acromegaly.  Materials and methods : Fasting serum samples were taken and stored in aliquot at ≤-20°C from consecutive subjects with clinically evident and biochemically confirmed active CS, acromegaly and healthy volunteers matched by age, sex and body mass index (BMI). Commercially available kits were used to assay serum myokine levels. Grip strength was measured by a dynamometer. Insulin-like growth factor-1 (IGF1) was measured by immunochemiluminescence assay (Liaison), twenty-four hours urine free cortisol (24hUFC) ― by immunochemiluminescence assay (Vitros ECi), salivary free cortisol ― by electrochemiluminescence assay (Cobas). One-way ANOVA was utilized to assess the difference between groups.  Results : We enrolled 88 subjects: 30 patients suffered from CS (group 1), 28 ― acromegaly (2) and 30 matched healthy controls (3) with no difference among the groups in sex, age and BMI (p=0.492, 0.062 and 0.174 respectively). Mean 24hUFC in subjects with CS and mean IGF1 in subjects with acromegaly were significantly higher as compared to other groups (p<0.001). Right-hand grip strength was lower in patients with CS as compared to both patients with acromegaly and healthy subjects (p=0.04). However, among these young adults we did not find statistically significant differences in measured myokines levels: irisin ― p=0.15; IL6 ― p=0.34; myostatin ― p=0.50. There was a significant correlation between myostatin and irisin in the whole group of people and in every separately analyzed subset of patients (p<0.001), but no correlation was found between any measured myokines and 24hUFC or IGF1. Conclusions : Hypercortisolism or supraphysiological IGF1 levels do not significantly influence serum levels of myostatin, IL6 and irisin in young adults.