Supplementary Material for: Circulating irisin levels in preadolescents and adolescents born preterm

Introduction. Prematurity is associated with increased cardiometabolic risk later in life. The adipomyokine irisin has been acknowledged as a modulator of energy metabolism and insulin sensitivity. The aim of this study was to investigate circulating levels of irisin and their relation to anthropometric measurements and cardiometabolic phenotype in a population of preterm-born children vs. full-term-born peers. Methods. A total of 160 children (87 born preterm aged 8.1-14.8 years and 73 born full-term of similar age and gender distribution) were studied. Arterial blood pressure, anthropometry, body composition assessments with dual energy X-ray absorptiometry (DXA) and skin fold measurements were performed. Blood biochemistry and circulating levels of irisin, insulin, cortisol, leptin, and adiponectin were also determined. Results. The preterm group had higher diastolic blood pressure, triceps skin fold, subscapular skin fold (SSF) and abdominal skin fold measurements and more central adiposity than the full-term group. Irisin was significantly lower (p=0.002), whereas leptin was higher (p=0.03), in the preterm than the full-term group. Irisin correlated positively with gestational age (r=0.19, p=0.01), birthweight (r=0.23, p=0.003) and high-density lipoprotein cholesterol (r=0.20, p=0.01), and negatively with SSSF (r=-0.25 p=0.003) and chronological age (r=-0.21, p=0.008). Conclusion. Lower levels of irisin and a slightly unhealthy adiposity and cardiometabolic pattern were detected in preterm-born children in comparison to their full-term-born peers. Whether low irisin levels in preadolescents and adolescents born prematurely could be of prognostic value for the development of cardiometabolic sequelae later in life remains to be further studied.