title: Circulating Irisin Levels Are Not Regulated by Nutritional Status, Obesity, or Leptin Levels in Rodents.
abstract: Irisin is a cleaved and secreted fragment of fibronectin type III domain containing 5 (FNDC5) that is mainly released by skeletal muscle and was proposed to mediate the beneficial effects of exercise on metabolism. In the present study we aim to investigate the regulation of the circulating levels of irisin in obese animal models (diet-induced obese (DIO) rats and leptin-deficient (ob/ob) mice), as well as the influence of nutritional status and leptin. Irisin levels were measured by Enzyme-Linked Immunosorbent Assay (ELISA) and Radioimmunoassay (RIA). Serum irisin levels remained unaltered in DIO rats and ob/ob mice. Moreover, its circulating levels were also unaffected by fasting, leptin deficiency, and exogenous leptin administration in rodents. In spite of these negative results we find a negative correlation between irisin and insulin in DIO animals and a positive correlation between irisin and glucose under short-term changes in nutritional status. Our findings indicate that serum irisin levels are not modulated by different physiological settings associated to alterations in energy homeostasis. These results suggest that in rodents circulating levels of irisin are not involved in the pathophysiology of obesity and could be unrelated to metabolic status; however, further studies should clarify its precise role in states of glucose homeostasis imbalance.
authors.affiliation: Department of Physiology, CIMUS, University of Santiago de Compostela, Sanitary Research Institute of Santiago de Compostela (IDIS), 15782 Santiago de Compostela, Spain ; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 15706 Santiago de Compostela, Spain.
authors.forename: Mar
authors.initials: M
authors.lastname: Quiñones
authors.affiliation: Department of Physiology, CIMUS, University of Santiago de Compostela, Sanitary Research Institute of Santiago de Compostela (IDIS), 15782 Santiago de Compostela, Spain ; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 15706 Santiago de Compostela, Spain ; Endocrine Physiopathology Group, Sanitary Research Institute of Santiago de Compostela (IDIS), University Hospital Complex of Santiago (CHUS/SERGAS), 15706 Santiago de Compostela, Spain.
authors.forename: Cintia
authors.initials: C
authors.lastname: Folgueira
authors.affiliation: Department of Physiology, CIMUS, University of Santiago de Compostela, Sanitary Research Institute of Santiago de Compostela (IDIS), 15782 Santiago de Compostela, Spain ; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 15706 Santiago de Compostela, Spain.
authors.forename: Estrella
authors.initials: E
authors.lastname: Sánchez-Rebordelo
authors.affiliation: Department of Physiology, CIMUS, University of Santiago de Compostela, Sanitary Research Institute of Santiago de Compostela (IDIS), 15782 Santiago de Compostela, Spain ; CIBER Physiopathology of Obesity and Nutrition (CIBERobn), 15706 Santiago de Compostela, Spain.
authors.forename: Omar
authors.initials: O
authors.lastname: Al-Massadi
mesh_terms: D000818:Animals; D001823:Body Composition; D005353:Fibronectins / Q000097:blood*; D020738:Leptin / Q000097:blood*; D008297:Male; D009752:Nutritional Status; D009765:Obesity / Q000097:blood* / Q000209:etiology; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: C583676:FNDC5 protein, rat; D005353:Fibronectins; D020738:Leptin