Ghrelin: a multifunctional hormone in non-mammalian vertebrates.
ABSTRACT In mammals, ghrelin is a non-amidated peptide hormone, existing in both acylated and non-acylated forms, produced mainly from the X/A or ghrelin cells present in the mucosal layer of the stomach. Ghrelin is a natural ligand of the growth hormone (GH) secretagogue-receptor (GHS-R), and functions primarily as a GH-releasing hormone and an orexigen, as well as having several other biological actions. Among non-mammalian vertebrates, amino acid sequence of ghrelin has been reported in two species of cartilaginous fish, seven species of teleosts, two species of amphibians, one species of reptile and six species of birds. The structure and functions of ghrelin are highly conserved among vertebrates. This review presents a concise overview of ghrelin biology in non-mammalian vertebrates.
Article: Ghrelin does not affect gastrointestinal contractility in rainbow trout and goldfish in vitro.[show abstract] [hide abstract]
ABSTRACT: Ghrelin has been identified in rainbow trout and goldfish, and it has been shown to regulate growth hormone release and food intake in these species as seen in mammals. The aim of this study was to investigate the functional role of ghrelin in regulation of gastrointestinal contractility in both fishes. Neither rainbow trout ghrelin nor rat ghrelin affected the contractility of gastrointestinal strips of rainbow trout. Similarly, goldfish ghrelin-17 and rat ghrelin did not cause marked contraction in the goldfish intestinal bulb. Detail examinations using the goldfish intestine revealed that human neurotensin, substance-P, goldfish neuromedine-U and carbachol showed apparent contractile activities in the intestinal strips. Electrical field stimulation (EFS, 1-20 Hz) caused a frequency-dependent contraction of the intestinal bulb. Atropine partially inhibited and tetrodotoxin abolished the EFS-induced contraction. Pretreatments with goldfish ghrelin-17 and rat ghrelin did not modify the EFS-induced contraction. The mRNAs of two types of growth hormone secretagogue receptor (GHS-R), GHS-R1a-1 and GHS-R1a-2, were detected in the goldfish intestine, and the expression level of GHS-R1a-2 was 4-times higher than that of GHS-R1a-1. The expression levels of GHS-R1a-1 and GHS-R1a-2 in four regions of the goldfish intestine (intestinal bulb, intestine-1, intestine-2 and intestine-3) were almost the same. In conclusion, ghrelin does not affect gastrointestinal contractility of the rainbow trout and goldfish, although GHSR-like receptor/GHS-R1a is expressed entire intestine. These results suggest diversity of ghrelin function in vertebrates.General and Comparative Endocrinology 07/2012; 178(3):539-45. · 3.27 Impact Factor
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ABSTRACT: Ghrelin O-acyl transferase (GOAT) is a recently identified enzyme responsible for the unique n-acyl modification of ghrelin, a multifunctional metabolic hormone. GOAT structure and activity appears to be conserved from fish to man. Since the acyl modification is critical for most of the biological actions of ghrelin, especially metabolic functions, GOAT emerged as a very important molecule of interest. The research on GOAT is on the rise, and several important results reiterating its significance have been reported. Notable among these discoveries are the identification of GOAT tissue expression patterns, effects on insulin secretion, blood glucose levels, feeding, body weight, and metabolism. Several attempts have been made to design and test synthetic compounds that can modulate endogenous GOAT, which could turn beneficial in favorably regulating whole body energy homeostasis. This paper will focus to provide an update on recent advances in GOAT research and its broader implications in the regulation of energy balance.International Journal of Peptides 01/2011; 2011:217957.
Article: Age-dependent reduction of ghrelin and motilin-induced contractile activity in the chicken gastrointestinal tract.[show abstract] [hide abstract]
ABSTRACT: Ghrelin is an endogenous ligand for growth hormone secretagogue-receptor 1a (GHS-R1a) and stimulates gastrointestinal (GI) motility in the chicken. Since ghrelin stimulates GH release, which regulates growth, it might be interesting to compare ghrelin-induced responses in GI tract of different-aged chickens. Motilin is a ghrelin-related gut peptide that induces strong contraction in the small intestine. Aim of this study was to clarify age-dependent changes in ghrelin- and motilin-induced contractions of the chicken GI tract and expression of their receptor mRNAs. Chicken ghrelin caused contraction of the crop and proventriculus. Ghrelin-induced contraction in the proventriculus decreased gradually up to 100 days after hatching, but the responses to ghrelin in the crop were the same during the growth period. GHS-R1a mRNA expression in the crop tended to increase, but that in the proventriculus decreased depending on the age. Chicken motilin caused contraction of the chicken GI tract. Atropine decreased the responses to motilin in the proventriculus but not in the ileum. Motilin-induced contraction in the proventriculus but not that in the ileum decreased depending on post-hatching days. On the other hand, motilin receptor mRNA expression in every region of the GI tract decreased with age, but the decrease was more marked in the proventriculus than in the ileum. In conclusion, ghrelin- and motilin-induced GI contractions selectively decreased in the chicken proventriculus depending on post-hatching days, probably due to the age-related decrease in respective receptors expression. The results suggest an age-related contribution of ghrelin and motilin to the regulation of chicken GI motility.Peptides 02/2013; · 2.43 Impact Factor