title: A comprehensive immunohistochemical examination of the distribution of the fat-burning protein irisin in biological tissues.
abstract: Irisin was first identified in skeletal muscle cells, but its precise location has not yet been demonstrated, and there is limited information about irisin protein in other human and rat tissues. The present immunohistochemical study was undertaken to screen skeletal muscle and other tissues for irisin immunoreactivity. İrisin staining was found in the brain (neurons and neuroglia), cardiac and skeletal muscle (fibers) and skin (sebaceous glands) tissues in male rats. In both human adult and fetal skeletal muscle, the most intense immunohistochemical staining was in the perimysium and endomysium, in the peripheral nerve (epineurium) and axon and nerve sheaths spreading among the cells, in the sarcoplasma and subendomysium. Irisin was also demonstrated in the testis (seminiferous tubules, some spermatogenic cells in fetal and Leydig cells in fetal and adult testis, ductus epididymis in fetal human epididymis); pancreas (islets of Langerhans, serous acini cells, intralobular and intralobular ducts cells); liver (hepatocytes; Kupffer cells and sinusoidal endothelial cells); spleen (subcapsular region and periarterial lymphatic sheets); the stomach (gastric parietal cells, tunica muscularis cells). We conclude that the fat-burning protein irisin locally produced in peripheral and central tissues could act as a gatekeeper of metabolic energy regulation in those tissues, since this myokine converts white into brown adipose tissue, enhancing energy expenditure.
authors.affiliation: Department of Medical Biochemistry and Clinical Biochemistry, (Firat Hormones Research Group), Medical School, Firat University, 23119 Elazig, Turkey. Electronic address: saydin1@hotmail.com.
authors.forename: Suleyman
authors.initials: S
authors.lastname: Aydin
authors.affiliation: Department of Histology and Embryology, Medical School, Firat University, 23119 Elazig, Turkey.
authors.forename: Tuncay
authors.initials: T
authors.lastname: Kuloglu
authors.affiliation: Department of Anatomy, Medical School, Firat University, 23119 Elazig, Turkey; Department of Cardiovascular Surgery, Elazig Training and Research Hospital, Elazig 23100, Turkey.
authors.forename: Suna
authors.initials: S
authors.lastname: Aydin
authors.affiliation: Department of Medical Biochemistry Laboratory, Elazig Training and Research Hospital, Elazig 23100, Turkey.
authors.forename: Mehmet
authors.initials: M
authors.lastname: Kalayci
authors.affiliation: Department of Medical Biochemistry and Clinical Biochemistry, (Firat Hormones Research Group), Medical School, Firat University, 23119 Elazig, Turkey.
authors.forename: Musa
authors.initials: M
authors.lastname: Yilmaz
authors.affiliation: Department of Cardiology, Ercis State Hospital, Van, Turkey.
authors.forename: Tolga
authors.initials: T
authors.lastname: Cakmak
authors.affiliation: Department of Brain Surgery, Elazig Training and Research Hospital, Elazig 23100, Turkey.
authors.forename: Serdal
authors.initials: S
authors.lastname: Albayrak
authors.affiliation: Department of Gynecology, Private Medical Hospital, Elazig 23100, Turkey.
authors.forename: Sami
authors.initials: S
authors.lastname: Gungor
authors.affiliation: Department of Histology and Embryology, Medical School, Firat University, 23119 Elazig, Turkey.
authors.forename: Neriman
authors.initials: N
authors.lastname: Colakoglu
authors.affiliation: Department of Medical Pathology, Medical School, Firat University, 23119 Elazig, Turkey.
authors.forename: Ibrahim Hanifi
authors.initials: IH
authors.lastname: Ozercan
mesh_terms: D000328:Adult; D000818:Animals; D004734:Energy Metabolism / Q000502:physiology*; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D009928:Organ Specificity / Q000502:physiology; D051381:Rats
chemical_list: C577593:FNDC5 protein, human; C583676:FNDC5 protein, rat; D005353:Fibronectins
keywords: Brain; Fetal skeletal muscle; Irisin; Spleen; Testis