This study was aimed to assess the levels of ghrelin in aqueous
humor and plasma of human eyes with primary open-angle glaucoma
(POAG) and to correlate their concentrations with the severity
of glaucoma.
Design: This was a case-control, prospective study.
Methods: Fifty patients with POAG and 35 patients with senile
nonpathologic cataract (control group) were enrolled in the study prospectively.
Aqueous humor samples were obtained by paracentesis from
patients with glaucoma and cataract who underwent elective surgery.
Aqueous humor and corresponding plasma samples were analyzed for
ghrelin concentrations by radioimmunoassay diagnostic kits assay.
Results: Ghrelin levels were significantly lower in aqueous humor of
patients with POAG with respect to the comparative group of patients
with cataract (P G 0.001). There was no significant difference in the
levels of ghrelin in the plasma of patients with POAG and that of patients
with cataract. A positive correlation was found between plasma/aqueous
humor ghrelin concentration in patients with POAG versus the control
group (P G 0.001). No significant correlation was found between the levels
of ghrelin and the severity of visual field loss.
Conclusions: Lower levels of aqueous humor ghrelin may be associated
with POAG and may be a consequence of glaucomatous damage.
Key Words: ghrelin, aqueous humor, POAG, cataract
(Asia-Pac J Ophthalmol 2014;3: 126Y129)
Glaucoma, which is characterized by retinal ganglion cell
apoptosis, is a major cause of blindness. Retinal ganglion
cell apoptosis may be the result of increased intraocular pressure
(IOP), neurotoxicity and apoptosis,1 extracellular matrix
changes,2 oxidative stress,3 and hypoxia due to ocular and
systemic vascular dysregulation.4
Ghrelin is the endogenous ligand for the human G proteincoupled
growth hormone secretagogue receptor type 1a (GHSR1a).
It is a 28-amino-acid peptide hormone described in the
rat’s stomach oxyntic mucosa in 1999 by Kojima and Hosoda.5
Production of ghrelin has also been identified in smaller amounts
in every tissue studied, including, for example, the brain (hypothalamus,
hippocampus, cerebral cortex),5 pituitary gland, small
intestine, adrenal gland, kidney, liver, myocardium, and eye.6,7
The acylated form of ghrelin is a relatively unstable molecule
and exerts mostly neuroendocrine effects after binding to
the GHS-R1a.5 The des-acylated form (des-acyl-ghrelin) of the
peptide, which constitutes more than 90% of the total circulating
ghrelin,5 does not bind to the GHS-R1a, and exhibits important
peripheral metabolic and cardiovascular effects.8,9
Ghrelin is a peptide that exerts both endocrine and paracrine
effects because it is involved in the regulation of metabolic
balance and energy homeostasis, as well as cardiovascular
function.8 Ghrelin expression in vascular endothelial cells and
its effects on vascular smooth muscle cells have been recently
described, including an endothelium-independent vasodilatory
effect of similar potency and efficacy between both the acylated
and des-acylated forms of ghrelin.7
In the present study, we measured the aqueous humor and
plasma levels of ghrelin in patients with primary open-angle
glaucoma (POAG) and senile nonpathologic cataract. In addition,
we assessed their relation to the severity of POAG. |
