Non-thyroidal illness syndrome in chronic diseases: role of irisin as modulator of antioxidants.

Abstract

Non-thyroidal-illness syndrome (NTIS) refers to condition found in chronic diseases that is an adaptive mechanism. However, oxidative stress is related to NTIS in a vicious circle, due to deiodinases alteration and negative effects of low T3 on antioxidant levels or activity. Muscle is one of the main targets of thyroid hormones and it can secrete a myokine named irisin, which is able to induce the browning of white adipose tissue, energy expenditure and protect against insulin resistance. Inconclusive data have been reported about irisin role in chronic diseases. Moreover, no correlation with antioxidants has been investigated. Therefore, we performed a case-control study with the primary endpoint to evaluate irisin levels in two models of NTIS, such as chronic heart failure (CHF) and chronic kidney disease (CKD) during haemodialytic treatment. The secondary endpoint was the correlation with total antioxidant capacity (TAC) to establish a possible role of irisin in the modulation of antioxidant systems. Three groups of subjects were enrolled. Group A included CHF patients (n=18; aged 70.22 ± 2.78 ys; BMI ± 27.75 ± 1.28 kg/m2); Group B included CKD patients (n=29; aged 67.03 ± 2.64; BMI 24.53 ± 1.01); finally, 11 normal subjects (Group C) have been enrolled as controls. Irisin has been evaluated by ELISA method and Total Antioxidant Capacity (TAC) by spectrophotometric method. Irisin was significantly higher in Group B vs. A and C groups (Mean ± SEM: 20.18 ± 0.61 ng/ml vs. 2.77 ± 0.77 and 13.06 ± 0.56, respectively; p<0.05); a significant correlation between irisin and TAC was observed in group B. These preliminary data suggest a possible role of irisin in the modulation of antioxidants in two chronic syndromes with low T3 (i.e., CHF and CKD) with differential pattern in these two models studied. Further insights are needed to confirm this pilot study, which could be the basis for a longitudinal investigation, to assess a prognostic role of irisin with possible therapeutic implications.