title: Novel evidence of ghrelin and growth hormone segretagogue receptor expression by human ocular tissues.
abstract: OBJECTIVE
  The gastrointestinal peptide hormone ghrelin (Ghr) was discovered in 1999 as the endogenous ligand for the growth hormone secretagogue receptor (GHSR-1a). It is a pleiotropic peptide that modulates a wide spectrum of biological activities, such as growth hormone (GH) release, feeding stimulation, adiposity and cardiovascular actions. The presence of Ghr mRNA in the iris and ciliary body (CB) epithelium was recently demonstrated in animal models, where a possible myorelaxing effect on the iris muscles has been suggested. Based on these observations, the aim of our study was to investigate the Ghr and GHSR-1a expression and localization in the normal human eye.
  
  
  METHODS
  Five different ciliary body/iris samples from normal eyes were subjected to Western blot analysis. Immunohistochemical detection was performed on three enucleated eyes. Twenty aqueous humor (AqH) samples obtained from patients submitted to cataract surgery were analyzed with an ELISA for the presence of Ghr.
  
  
  RESULTS
  Ghr and GHSR-1a were co-expressed by the pigmented epithelium (PE) of the CB, by the retinal pigmented epithelium (RPE) and by the anterior limiting layer (ALL) of the iris. No reaction was detected at the subepithelial level in the ciliary or pupillae smooth muscle cells. The AqH samples were positive for the presence of Ghr.
  
  
  CONCLUSIONS
  This study provides the first evidence that Ghr and GHSR-1a are expressed in the human eye by specific cells. The understanding of the functional role of Ghr at the human eye level needs more efforts and investigation, but a hypothetical action on the GH retinal synthesis and/or on the circadian clock system could be suggested.
authors.affiliation: Department of Medicine and Aging Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy.
authors.forename: Alessia
authors.initials: A
authors.lastname: Di Fonso
authors.affiliation: Department of Medicine and Aging Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Ghinassi
authors.affiliation: Department of Medicine and Aging Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy.
authors.forename: Pascal
authors.initials: P
authors.lastname: Izzicupo
authors.affiliation: Department of Experimental and Clinical Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy.
authors.forename: Roberta
authors.initials: R
authors.lastname: Zappacosta
authors.affiliation: Department of Experimental and Clinical Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy.
authors.forename: Marcella
authors.initials: M
authors.lastname: Liberatore
authors.affiliation: Department of Biomedical and Surgical Sciences University of Ferrara, 44123 Ferrara, Italy.
authors.forename: Carla Enrica
authors.initials: CE
authors.lastname: Gallenga
authors.affiliation: Department of Medicine and Aging Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy.
authors.forename: Maria Angela
authors.initials: MA
authors.lastname: D'Amico
authors.affiliation: Department of Experimental and Clinical Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy.
authors.forename: Pier Enrico
authors.initials: PE
authors.lastname: Gallenga
authors.affiliation: Department of Medicine and Aging Sciences, "G. d'Annunzio" University of Chieti-Pescara, 66013 Chieti, Italy. Electronic address: a.dibaldassarre@unich.it.
authors.forename: Angela
authors.initials: A
authors.lastname: Di Baldassarre
mesh_terms: D005123:Eye / Q000378:metabolism*; D054439:Ghrelin / Q000032:analysis* / Q000096:biosynthesis; D006801:Humans; D054440:Receptors, Ghrelin / Q000032:analysis* / Q000096:biosynthesis
chemical_list: D054439:Ghrelin; D054440:Receptors, Ghrelin
keywords: Circadian clock system; Ghrelin; Growth hormone secretagogue receptor-1a; Pigmented epithelium