title: Irisin as a predictor of glucose metabolism in children: sexually dimorphic effects.
abstract: BACKGROUND
  Irisin, a novel myokine, increases energy expenditure and glucose tolerance and, thus, improves carbohydrate homeostasis in humans. This hormone has potential therapeutic applications for weight loss and improvement in insulin resistance in subjects with obesity and diabetes mellitus type 2 (T2DM). In this cross-sectional study, we aimed to associate circulating levels of irisin and several anthropometric and metabolic parameters among Arab children.
  
  
  METHODS
  A cohort of 153 Saudi children, 81 boys [age: 12·4 ± 3·2 years; BMI: 19·5 ± 5·9 kg/m(2) ] and 72 girls: [age: 12·9 ± 3·2 years; BMI: 20·6 ± 5·2], were examined. Anthropometry was obtained, and fasted bloods were collected for biochemical analyses. Irisin was assessed by a specific enzyme-linked immunosorbent assay (ELISA).
  
  
  RESULTS
  Girls had higher circulating irisin levels than boys (P = 0·04). There were several significant correlations between circulating irisin and fasting blood glucose (FBG) (r = -0·35, P < 0·001), sagittal abdominal diameter (SAD) (r = -0·34, P < 0·001) and HDL cholesterol (r = 0·17, P = 0·04) across the entire cohort studied. Notably in girls, but not in boys, HOMA-IR correlated negatively with irisin levels (r = -0·32, P = 0·02), as previously noted in adults. FBG was a significant predictor of circulating irisin (R(2)  = 0·16) followed by SAD. In multivariate linear regression analysis, after controlling for potential confounders such as gender, age and BMI, irisin levels were independently associated with FBG (β = -0·34, P = 0·01), particularly in girls.
  
  
  CONCLUSIONS
  Serum irisin levels were higher in girls than in boys and correlated negatively with HOMA-IR. They were also independently associated with FBG predominantly in girls, suggesting that this hormone may play a crucial role in glucose metabolism from an early age.
authors.affiliation: Biochemistry Department, Biomarkers Research Program, College of Science, King Saud University, Riyadh, Saudi Arabia; Biochemistry Department, Prince Mutaib Chair for Biomarkers of Osteoporosis, King Saud University, Riyadh, Saudi Arabia.
authors.forename: Nasser M
authors.initials: NM
authors.lastname: Al-Daghri
authors.forename: Khalid M
authors.initials: KM
authors.lastname: Alkharfy
authors.forename: Shakilur
authors.initials: S
authors.lastname: Rahman
authors.forename: Osama E
authors.initials: OE
authors.lastname: Amer
authors.forename: Benjamin
authors.initials: B
authors.lastname: Vinodson
authors.forename: Shaun
authors.initials: S
authors.lastname: Sabico
authors.forename: Milan K
authors.initials: MK
authors.lastname: Piya
authors.forename: Alison L
authors.initials: AL
authors.lastname: Harte
authors.forename: Philip G
authors.initials: PG
authors.lastname: McTernan
authors.forename: Majed S
authors.initials: MS
authors.lastname: Alokail
authors.forename: George P
authors.initials: GP
authors.lastname: Chrousos
mesh_terms: D015415:Biomarkers / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism*; D002648:Child; D003430:Cross-Sectional Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005353:Fibronectins / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D008297:Male; D012737:Sex Factors
chemical_list: D015415:Biomarkers; D001786:Blood Glucose; C577593:FNDC5 protein, human; D005353:Fibronectins
keywords: Children; dimorphism; glucose; irisin