Ghrelin tissue distribution: Comparison between gene and protein expression

Abstract

Ghrelin, the natural ligand of the GH secretagogue (GHS) receptor, was originally isolated from the stomach and detected in several tissues, but a systematic study of its tissue distribution has not been performed. In the present investigation, we evaluated ghrelin gene expression (by RT-PCR technique) and ghrelin protein concentration (by enzyme immunoassay technique) in tissues obtained from control rats as well as in rats subjected to 48-h fasting. The ghrelin gene was expressed in stomach, small intestine, brain, cerebellum, pituitary, heart, pancreas, salivary gland, adrenal, ovary and testis, with maximum expression occurring in the stomach, while no significant expression was detected by standard RT-PCR in liver, lung, kidney and skeletal muscle. Ghrelin protein was detected in stomach, small intestine, brain, cerebellum, pituitary, lung, skeletal muscle pancreas, salivary gland, adrenal, ovary and testis, at concentrations ranging from 0.05 to 1.43 ng/mg of homogenate protein (the highest concentration occurred in the lung, followed by the brain). Ghrelin was not detectable in the heart, liver and kidney. Therefore, gene and protein expression were dissociated. Fasting did not produce significant changes in ghrelin gene expression, while the distribution of ghrelin between different tissues was significantly modified: protein concentration increased in the brain, cerebellum, lung and salivary gland, while it decreased in the stomach.

Analysis of the network of feeding neuroregulators using the Allen Brain Atlas

“…These include the growth hormone secretagogue (GHS) receptor ligand, ghrelin, that has been shown to act as one of the most potent orexigens known to date. Ghrelin mRNA has been detected in the brains of both mice and rats (Ghelardoni et al, 2006;Zigman et al, 2006). Zigman et al performed a thorough analysis of the ghrelin mRNA distribution in the central nervous system of mice and found that its particularly high levels are present in the ARC, but also in the PVN and in the ventrolateral and capsule portions of the VMH (Zigman et al, 2006).…”

Central effects of ghrelin on the adrenal cortex: a morphological and hormonal study

“…Although it is mainly produced by the stomach mucosa, ghrelin and its receptors (GHS-R type 1a) are also expressed in the small intestine, hypothalamus, pituitary, adrenal and other tissues where it may have both endocrine and paracrine effects (Gnanapavan et al 2002;Ghelardoni et al 2006). Recent attention has been given to ghrelin activity, as it is one of the most important peripheral physiological signals of hunger, an important component of energy balance (Horvath et al 2001;Zigman and Elmquist 2003).…”

Diabetes, Ghrelin And Related Peptides: From Pathophysiology To Vasculopathy

“…Its expression was also described in other areas of the CNS and in some peripheral tissues as: thyroid gland, pancreas, spleen, myocardium, adrenal glands [11,14,42,43], rat testis, ovary [44], human T lymphocytes [12], morula, blastocyts and embryos [13]. There were identified binding sites in the myocardium (highest binding capacity), adrenal gland, gonads, arteries, lung, liver, skeletal muscle, kidney, pituitary, thyroid gland, adipose tissue, veins, uterus, skin and lymph nodes [45].…”

“…Ghrelin is also produced in the X/A cells of the intestine and in some others tissues such as the pancreas, kidney, placenta, lymphatics, *Address correspondence to this author at the Department of Physiology, Faculty of Medicine, Alameda Professor Hernâni Monteiro, 4200-319 Porto, Portugal; Tel: +351 225513644; Fax: +351 225513646; E.mail: arsousa@med.up.pt # Both authors had the same contribution to the article gonads, adrenal, thyroid gland, heart, lung, pituitary, hypothalamus, eye [10], human B-and T-lymphocytes, neutrophils [1,[10][11][12], morula, blastocyts and embryos [13]. Ghelardoni observed that ghrelin gene expression and its protein were, in some tissues, dissociated [14].In fetal life, ghrelin is mainly produced in the pancreas and lung [15]. The pancreas expresses ghrelin mRNA at midgestation being its mRNA levels six to seven times higher than in the fetal stomach [16].…”