title: Irisin in patients with nonalcoholic fatty liver disease.
abstract: OBJECTIVE
  Irisin is a recently discovered myokine proposed to increase thermogenesis-related energy expenditure and improve metabolism. We aimed to comparatively evaluate serum irisin levels in patients with biopsy-proven nonalcoholic fatty liver disease (NAFLD) vs. controls and study their association with disease severity.
  
  
  METHODS
  Fifteen and 16 consecutively enrolled patients with biopsy-proven nonalcoholic simple steatosis (NAFL) and steatohepatitis (NASH), respectively, and 24 lean and 28 obese controls without NAFLD were recruited. Irisin, established adipokines and biochemical tests were measured.
  
  
  RESULTS
  Serum irisin levels were statistically different in obese controls (33.7±2.7 ng/mL; p<0.001) and patients with NAFL (30.5±1.5 ng/mL; p<0.001) and NASH (35.8±1.9 ng/mL; p=0.001) compared with lean controls (47.7±2.0 ng/mL), but were similar among patients with NAFL, NASH and obese controls. This difference remained significant after adjustment for body mass index (or waist circumference), gender, age, insulin resistance (assessed by HOMA-IR or QUICKI), exercise and time since blood collection. Serum leptin and adiponectin, but not irisin, levels were independently from BMI correlated with insulin resistance and cardiometabolic factors. Serum irisin tended to be higher in patients with (36.7±2.4 ng/mL) than without (30.8±1.2 ng/mL; p=0.02) portal inflammation and independently associated with the latter; these data need to be confirmed by future studies.
  
  
  CONCLUSIONS
  Serum irisin levels differ between lean controls and obese controls or NAFLD patients. Despite similar circulating irisin levels between NAFL and NASH groups, irisin may be independently and positively associated with the presence of portal inflammation. Future clinical and mechanistic studies are needed to confirm and extend these data.
authors.affiliation: Department of Medicine, Second Medical Clinic, Aristotle University of Thessaloniki, Ippokration Hospital, Thessaloniki, Greece. Electronic address: stergios@endo.gr.
authors.forename: Stergios A
authors.initials: SA
authors.lastname: Polyzos
authors.affiliation: Department of Medicine, Second Medical Clinic, Aristotle University of Thessaloniki, Ippokration Hospital, Thessaloniki, Greece.
authors.forename: Jannis
authors.initials: J
authors.lastname: Kountouras
authors.affiliation: Department of Endocrinology, 424 General Military Hospital, Thessaloniki, Greece.
authors.forename: Athanasios D
authors.initials: AD
authors.lastname: Anastasilakis
authors.affiliation: Boston VA Healthcare system and Division of Endocrinology, Diabetes and Metabolism, Department of Internal Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Eleni V
authors.initials: EV
authors.lastname: Geladari
authors.affiliation: Boston VA Healthcare system and Division of Endocrinology, Diabetes and Metabolism, Department of Internal Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA.
authors.forename: Christos S
authors.initials: CS
authors.lastname: Mantzoros
mesh_terms: D054392:Adipokines / Q000097:blood*; D052242:Adiponectin / Q000097:blood; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D016022:Case-Control Studies; D018925:Chemokines / Q000097:blood; D005234:Fatty Liver / Q000097:blood*; D005260:Female; D005353:Fibronectins / Q000097:blood*; D006801:Humans; D007249:Inflammation / Q000097:blood; D007333:Insulin Resistance; D036341:Intercellular Signaling Peptides and Proteins; D020738:Leptin / Q000097:blood; D008297:Male; D008875:Middle Aged; D065626:Non-alcoholic Fatty Liver Disease; D009765:Obesity / Q000097:blood*; D011169:Portal Vein / Q000473:pathology*; D054839:Retinol-Binding Proteins, Plasma / Q000378:metabolism; D012307:Risk Factors; D012720:Severity of Illness Index; D013851:Thinness / Q000097:blood
chemical_list: D054392:Adipokines; D052242:Adiponectin; D015415:Biomarkers; D018925:Chemokines; C577593:FNDC5 protein, human; D005353:Fibronectins; D036341:Intercellular Signaling Peptides and Proteins; D020738:Leptin; C478630:RARRES2 protein, human; C101326:RBP4 protein, human; D054839:Retinol-Binding Proteins, Plasma
keywords: ALP; ALT; AST; BMI; Chemerin; FNDC; Fibronectin type III domain containing 5; GGT; HDL-C; HOMA-IR; IR; LDL-C; LETO; Long Evans Tokushima; Low density lipoprotein cholesterol; MetS; NAFL; NAFLD; NAFLD Activity Score; NAS; NASH; Nonalcoholic steatohepatitis; OLETF; Otsuka Long–Evans Tokushima Fatty; Portal inflammation; QUICKI; RBP; Retinol-binding protein-4; T2DM; WC; alanine transaminase; alkaline phosphatase; aspartate transaminase; body mass index; fibronectin type III domain containing; gamma-glutamyl transferase; high-density lipoprotein cholesterol; homeostatic model of assessment insulin resistance; insulin resistance; metabolic syndrome; non-alcoholic fatty liver disease; nonalcoholic steatohepatitis; quantitative insulin sensitivity check index; retinol-binding protein; simple nonalcoholic fatty liver; type 2 diabetes mellitus; waist circumference.