Irisin is a
myokine involved in the browning of white adipose tissue and regulation of energy expenditure,
glucose homeostasis and
insulin sensitivity. Debated evidence exists on the metabolic role played by irisin in children with
overweight or
obesity, while few information exist in children with
Prader Willi Syndrome (PWS), a condition genetically prone to
obesity. Here we assessed serum irisin in relation to the metabolic profile and body composition in children and adolescents with and without PWS. In 25 PWS subjects [age 6.6-17.8y; body mass index standard deviation score (BMI SDS) 2.5 ± 0.3] and 25 age, and BMI-matched controls (age 6.8-18.0y; BMI SDS, 2.8 ± 0.1) we assessed irisin levels and metabolic profile inclusive of oral
glucose tolerance test (OGTT), and body composition by dual-energy X-ray absorptiometry (DXA). In PWS, we recorded lower levels of fat-free mass (FFM) (p <0.05), fasting (p<0.0001) and 2h post-OGTT
insulin (p<0.05) and lower
insulin resistance as expressed by homeostatic model of
insulin resistance (HOMA-IR) (p<0.0001). Irisin levels were significantly lower in PWS group than in controls with common
obesity (p<0.05). In univariate correlation analysis, positive associations linked irisin to
insulin OGTT0 (p<0.05),
insulin OGTT120 (p<0.005), HOMA-IR (p<0.05) and fasting
C-peptide (p<0.05). In stepwise multivariable regression analysis, irisin levels were independently predicted by
insulin OGTT120. These results suggest a link between irisin levels and
insulin sensitivity in two divergent models of
obesity.