||Exhibits correct molecular weight|
||Soluble in water|
Store in dry form at 0-5°C.|
For best results, rehydrate just before use.
After rehydration, keep solution at +4°C for up to 4 days or freeze for longer-term storage. Aliquot before freezing to avoid repeated freeze-thaw cycles.
||Each vial contains 100 µg of NET peptide.|
Ghrelin is a gut-brain peptide hormone that plays an important role in the control of energy metabolism. In the mouse, the expression of its receptor, growth hormone secretagogue receptor (GHSR), was reported to be highest in two brain regions, the arcuate nucleus (ARC) in the hypothalamus and non-preganglionic Edinger-Westphal nucleus (npEW) in the midbrain. The npEW is also the most dominant site of urocortin 1 (Ucn1) expression in the mammalian brain and the npEW-Ucn1 neurons play an important role in stress adaptation response. Despite the importance of ghrelin for regulating food intake and body weight, mice lacking ghrelin or GHSR show no, or only a modest metabolic phenotype. Because GHSR mRNA is abundantly present in the stress-sensitive npEW, we hypothesized that ghrelin is not only involved in metabolism control but also in the stress response. To test this we studied the ghrelin-KO mice, under basal non-stressed and acute stressed conditions. Under basal conditions, KO mice have higher activation of npEW-Ucn1 neurons as demonstrated by dual label Ucn-1 and Fos immunohistochemistry. After restraint stress both wild-type (WT) and KO mice revealed an increased activation of the npEW nucleus, but we found that stress recruited Ucn1-ir neurons only in WT, but not in KO mice. We also determined Ucn1 mRNA expression in stressed and non-stressed conditions in KO and WT mice by in situ hybridization and found a strong up-regulation of Ucn1 mRNA in KO than in WT mice. Moreover, KO but not WT mice revealed stress-induced Ucn1 mRNA expression. Taken together, our data provide evidence for ghrelin actions in stress response. We propose that Ucn1 neurons in the npEW are instrumental in ghrelin´s action on the animal´s stress adaptation response.
L. Xu et al., C137 Deletion of ghrelin alters the response of Edinger-Westphal nucleus to restraint stress in the mouse. Poster session presented at IBRO 2011. 8th International Brain Research Organization World Congress of Neuroscience; 2011 July 14-18; Florence, Italy.
Differential transport of mouse ghrelin, des-octanoyl mouse ghrelin, and human ghrelin across the blood-brain barrier in mice. Although octanoylated (bioactive) mouse ghrelin crosses the mouse BBB predominantly in the brain-to-blood direction, passage for des-octanoyl mouse ghrelin was observed only in the blood-to-brain direction. Human ghrelin, which differs from mouse ghrelin by two amino residues only, was transported in both directions in mice. The extent and direction in which the ghrelin can cross the BBB is therefore influenced by at least two features of its primary structure, its post-translationally added fatty acid side chain and its amino acid sequence.
We provide the first evidence for the existence in human plasma of peptides derived from the 66 carboxyl-terminal amino acids of pro-ghrelin (C-ghrelin). C-ghrelin immunoreactivity in plasma was higher than ghrelin, and did not significantly correlate with body mass index in normal health. In patients with myocardial infarction, plasma levels of both ghrelin and C-ghrelin were significantly decreased ( approximately 30%, P<0.05), whereas in patients with heart failure, C-ghrelin levels were significantly elevated ( approximately 32%, P<0.05) compared with controls. HPLC coupled with RIA showed circulating C-ghrelin to be primarily of low molecular weight (M(r) approximately 3500), but in chronic heart failure, a higher molecular weight form (M(r) approximately 7500) is also present. This is the first evidence for potential circulating hormones derived from the carboxyl terminus of pro-ghrelin and for their modulation in cardiovascular diseases.
Experimental studies have suggested that ghrelin plays a role in glucose homeostasis and in the regulation of blood pressure (BP). We therefore assessed the hypothesis that a low ghrelin concentration may be a risk factor for type 2 diabetes and hypertension. We also characterized the effect of the ghrelin Arg51Gln and Leu72Met mutations on ghrelin concentrations in the population-based hypertensive (n = 519) and control (n = 526) cohorts of our OPERA (Oulu Project Elucidating Risk of Atherosclerosis) study. The fasting plasma ghrelin concentrations of 1,040 subjects were analyzed using the radioimmunoassay method. Insulin sensitivity was assessed using the quantitative insulin sensitivity check index (QUICKI). Ghrelin concentrations were negatively associated with fasting insulin (P < 0.001), systolic (P = 0.026) and diastolic BP (P = 0.018), and the prevalence of type 2 diabetes (P = 0.015) and insulin resistance (P < 0.001) in the multivariate models. In the control cohort, low ghrelin was associated with hypertension (BP >140/90 mmHg) (P = 0.031). The subjects with the ghrelin 51Gln allele had lower ghrelin concentrations than the Arg51Arg homozygotes (P = 0.001). We conclude that low ghrelin is independently associated with type 2 diabetes, insulin concentration, insulin resistance, and elevated BP. Therefore, it might have some role in the etiology of type 2 diabetes and the regulation of BP. The ghrelin Arg51Gln mutation is associated with low plasma ghrelin concentrations.
FIGURE 1: Effect of acute bolus administration (i.v.) of acylated ghrelin (AG: 1.0 ¦Ìg/kg) or non-acylated ghrelin (UAG; 1.0 g/kg) or AG (1.0 g/kg) + UAG (1.0 g/kg) on insulin and glucose level.
A human study investigating the biological activities of non-acylated ghrelin revealed antagonizing properties of this peptide on the hyperglycemic effects of acylated (or active) ghrelin. More specifically, bolus injections (i.v.) of this inactive form of ghrelin caused a significant reversal of the active ghrelin-induced reduction in insulin levels and ghrelin-induced increase in plasma glucose levels. This indicates a novel mechanism for the control of glucose levels in the blood and hence may lead to potential therapeutic applications of the non-acylated form of ghrelin in the treatment of type II diabetes and insulin resistance-related conditions.
Broglio F, Prodam F, Benso A , et al.,Endo 2003, PHiladelphia, June 2003, Abstract #553.
Ghrelin, a growth hormone-releasing hormone produced by gastroenteropancreatic endocrine cells, hypothalamus, and pituitary, was recently identified in medullary thyroid carcinomas and derived cell lines. However, no data exist on its expression in either normal or neoplastic thyroid follicular cells. We analyzed ghrelin expression by immunohistochemistry, in situ hybridization, and reverse transcriptase-polymerase chain reaction in 15 fetal, 4 infant, and 10 adult thyroids, and in 54 tumors of follicular origin. We also analyzed the effects of ghrelin on cell proliferation in N-PAP and ARO thyroid carcinoma cell lines. Ghrelin-binding sites were investigated using reverse transcriptase-polymerase chain reaction to detect its growth hormone secretagogue receptor (GHS-R) mRNA and an in situ-binding localization procedure. Strong ghrelin immunoreactivity was found in fetal but not in infant or adult thyroids. Ghrelin protein and mRNA were present, in variable amounts, in benign and malignant tumors. Normal thyroids, thyroid tumors, and cell lines showed ghrelin binding sites by binding localization, in the absence of the specific GHS receptor mRNA (with the exception of one normal thyroid). Moreover, ghrelin induced dose-dependent inhibition of growth in cell lines. In conclusion, ghrelin is expressed in fetal but not in adult thyroid, and is re-expressed in tumors; the presence of ghrelin receptors other than GHS-R in normal and neoplastic adult thyroid is suggested; ghrelin inhibits cell proliferation of thyroid carcinoma cell lines in vitro.
Volante M., et al. American Journal of Pathology. 2003;162:645-654
Ghrelin and des-acyl ghrelin inhibit cell death in cardiomyocytes and endothelial cells through ERK1/2 and PI 3-kinase/AKT. Ghrelin is an acyl-peptide gastric hormone acting on the pituitary and hypothalamus to stimulate growth hormone (GH) release, adiposity, and appetite. Ghrelin endocrine activities are entirely dependent on its acylation and are mediated by GH secretagogue (GHS) receptor (GHSR)-1a, a G protein-coupled receptor mostly expressed in the pituitary and hypothalamus, previously identified as the receptor for a group of synthetic molecules featuring GH secretagogue (GHS) activity. Des-acyl ghrelin, which is far more abundant than ghrelin, does not bind GHSR-1a, is devoid of any endocrine activity, and its function is currently unknown. Ghrelin, which is expressed in heart, albeit at a much lower level than in the stomach, also exerts a cardio protective effect through an unknown mechanism, independent of GH release. Here we show that both ghrelin and des-acyl ghrelin inhibit apoptosis of primary adult and H9c2 cardiomyocytes and endothelial cells in vitro through activation of extracellular signal-regulated kinase-1/2 and Akt serine kinases. In addition, ghrelin and des-acyl ghrelin recognize common high affinity binding sites on H9c2 cardiomyocytes, which do not express GHSR-1a. Finally, both MK-0677 and hexarelin, a nonpeptidyl and a peptidyl synthetic GHS, respectively, recognize the common ghrelin and des-acyl ghrelin binding sites, inhibit cell death, and activate MAPK and Akt.These findings provide the first evidence that, independent of its acylation, ghrelin gene product may act as a survival factor directly on the cardiovascular system through binding to a novel, yet to be identified receptor, which is distinct from GHSR-1a.
Baldanzi G, et al. J Cell Biol 2002 Dec 23;159(6):1029-37
Acute effect of leptin and ghrelin injection on postprandial glycogen and lipid synthesis in rats.
Bassil MS, Mrayati MM, Hwalla NC, Obeid OA. Ann Nutr Metab. 2007;51(1):14-21.
Ghrelin inhibits proinflammatory responses and nuclear factor-kappaB activation in human endothelial cells.
Li WG, Gavrila D, Liu X, et al. Circulation. 2004;109(18):2221-6.
Ghrelin and des-octanoyl ghrelin promote adipogenesis directly in vivo by a mechanism independent of the type 1a growth hormone secretagogue receptor.
Thompson NM, Gill DA, Davies R, et al. Endocrinology. 2004;145(1):234-42.