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  • Short communication: change in plasma ghrelin in dairy cows following an intravenous glucose challenge. 18292256

    Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor and a potent orexigenic (appetite-stimulating) agent in humans and rodents, but little is known about its effect in dairy cows. Ten multiparous dairy cows 35 d in milk were subjected to an i.v. glucose challenge (300 mg of D-glucose/kg of body weight). Before infusion and at regular intervals after infusion, plasma glucose, insulin, nonesterified fatty acids (NEFA), growth hormone, epinephrine, and ghrelin concentrations were monitored. Plasma insulin rose (27.2 mU/L at 10 min) and NEFA, epinephrine, and ghrelin declined (nadir = 0.22 mmol/L, 22.2 microg/L, and 272 microg/L at 31, 13, and 22 min, respectively) after the glucose infusion. Ghrelin declined for 22 min before returning to suprabasal levels at approximately 75 min postinfusion. Sequential changes of the hormones and metabolites suggested a glucose transporter, type 2- and glucose transporter, type 4-mediated disposal of glucose, and an insulin-mediated reduction in NEFA. Ghrelin and epinephrine declined after glucose infusion and before the insulin peak, but the effect of insulin as a controlling factor in the hyperglycemic reduction in these hormones cannot be discounted. The post-nadir surge in ghrelin may be regulated by the decline in circulating concentrations of glucose and NEFA (an energy-deficit signal). The profile of change in plasma ghrelin in lactating dairy cows after a glucose challenge was similar to that in monogastric animals.
    Tipo de documento:
    Referencia
    Referencia del producto:
    GHRA-88HK
    Nombre del producto:
    Human Ghrelin (ACTIVE) RIA

  • Long-term infusions of ghrelin and obestatin in early lactation dairy cows. 19038949

    Ghrelin is an endogenous ligand of the growth hormone secretagogue receptor and a potential orexigenic agent in monogastrics and ruminants. Obestatin has been reported to have the opposite (anorexigenic) effect. Fifty one multiparous cows were randomly allocated to 1 of 3 groups (n = 17): a control group and 2 groups with cows continuously infused with 0.74 mumol/d of ghrelin (GHR group) or obestatin (OBE group) subcutaneously. Infusions began 21 d in milk, and treatments continued for 8 wk. Generalized linear models were used to determine the treatment effect on average daily and cumulative milk production and composition, and plasma ghrelin, growth hormone, insulin-like growth factor (IGF)-1, leptin, nonesterified fatty acids, and glucose. Mixed models, with cow included as a repeated effect, were used to determine if treatment effects differed by week postcalving for milk production, body weight, and body condition score (BCS; scale 1 to 10). Parity, breed, week of the year at calving, treatment, week postcalving, and the 2 wk preexperimental average of each measure (covariate) were included as fixed effects. Treatment did not affect dry matter intake. Cows infused with GHR lost more BCS (-0.71 units) over the 8-wk study period than the control (-0.23 BCS units) cows, and on average were thinner than cows in either of the other 2 treatments (0.2 BCS units). Consistent with the extra BCS loss in GHR cows, plasma IGF-1, glucose, and leptin concentrations were reduced and plasma nonesterified fatty acid concentrations were greater in GHR cows. Despite a numerical tendency for GHR cows to produce more milk (1,779 kg) than control (1,681 kg) or OBE (1,714 kg) cows during the 8-wk period, milk production differences were not statistically different. However, the timing of the numerical separation of the lactation curves coincided with the significant changes in BCS, IGF-1, and leptin. Results indicate a positive effect of ghrelin infusion on lipolysis. Further research is required to determine if the numerical increase in milk production, which coincides with the increased negative energy balance, is real.
    Tipo de documento:
    Referencia
    Referencia del producto:
    GHRA-88HK
    Nombre del producto:
    Human Ghrelin (ACTIVE) RIA

  • Upregulation of voltage-gated calcium channel cav1.3 in bovine somatotropes treated with ghrelin. 24455243

    Activation of the growth hormone (GH) secretagogue receptor (GHS-R) by synthetic GH releasing peptides (GHRP) or its endogenous ligand (Ghrelin) stimulates GH release. Though much is known about the signal transduction underlying short-term regulation, there is far less information on the mechanisms that produce long-term effects. In the current report, using an enzyme-linked immunosorbent assay for GH detection and whole-cell patch-clamp recordings, we assessed the long-term actions of such regulatory factors on voltage-activated Ca(2+) currents in bovine somatotropes (BS) separated on a Percoll gradient and detected by immunohistochemistry. After 24 h of treatment with Ghrelin (10 nM) or GHRP-6 (100 nM) enhanced BS secretory activity; GH secretion stimulated by GHS through the activation of GHS-R because treatment with the antagonist of GHS-R (D-Lys3-GHRP-6, 10 μM) blocked the GH secretion, and the effect was dose and time dependent (24, 48, and 72 h). GH secretion stimulated by GHRP-6 was abolished by nifedipine (0.5 μM), a blocker of L-type HVA Ca(2+) channels, and KN-62 (10 μM), an inhibitor of Ca(2+)/CaM-KII. After 72 h in culture, all recorded BS exhibited two main Ca(2+) currents: a low voltage-activated (LVA; T-type) and a high voltage-activated (HVA; mostly dihydropyridine-sensitive L-type) current. Interestingly, HVA and LVA channels were differentially upregulated by Ghrelin. Chronic treatment with the GHS induced a significant selective increase on the Ba(2+) current through HVA Ca(2+) channels, and caused only a small increase of currents through LVA channels. The stimulatory effect on HVA current density was accompanied by an augment in maximal conductance with no apparent changes in the kinetics and the voltage dependence of the Ca(2+) currents, suggesting an increase in the number of functional channels in the cell membrane. Lastly, in consistency with the functional data, quantitative real-time RT-PCR revealed transcripts encoding for the Cav1.2 and Cav1.3 pore-forming subunits of L-type channels. The treatment with Ghrelin significantly increased the Cav1.3 subunit expression, suggeting that the chronic stimulation of the GHS receptor with Ghrelin or GHRP-6 increases the number of voltage-gated Ca(2+) channels at the cell surface of BS.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB940

  • Growth hormone-releasing peptide hexarelin reduces neonatal brain injury and alters Akt/glycogen synthase kinase-3beta phosphorylation. 16081643

    Hexarelin (HEX) is a peptide GH secretagogue with a potent ability to stimulate GH secretion and recently reported cardioprotective actions. However, its effects in the brain are largely unknown, and the aim of the present study was to examine the potential protective effect of HEX on the central nervous system after injury, as well as on caspase-3, Akt, and extracellular signal-regulated protein kinase (ERK) signaling cascades in a rat model of neonatal hypoxia-ischemia. Hypoxic-ischemic insult was induced by unilateral carotid ligation and hypoxic exposure (7.7% oxygen), and HEX treatment was administered intracerebroventricularly, directly after the insult. Brain damage was quantified at four coronal levels and by regional neuropathological scoring. Brain damage was reduced by 39% in the treatment group, compared with vehicle group, and injury was significantly reduced in the cerebral cortex, hippocampus, and thalamus but not in the striatum. The cerebroprotective effect was accompanied by a significant reduction of caspase-3 activity and an increased phosphorylation of Akt and glycogen synthase kinase-3beta, whereas ERK was unaffected. In conclusion, we demonstrate for the first time that HEX is neuroprotective in the neonatal setting in vivo and that increased Akt signaling is associated with downstream attenuation of glycogen synthase kinase-3beta activity and caspase-dependent cell death.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • Comparison of Competitive Radioimmunoassays and Two-Site Sandwich Assays for the Measurement and Interpretation of Plasma Ghrelin Levels. 20194708

    Context: Ghrelin, an endogenous ligand for the GH secretagogue receptor, is an orexigenic peptide hormone produced primarily by the stomach. Recent studies suggest significant differences in the specificity of currently available ghrelin assays. Objective: The aim of the study was to compare four ghrelin assays (two commercially available and two developed by our group) of differing specificity, each used on the same set of more than 800 plasma samples from a human study. Design: Thirteen volunteers were sampled every 20 min for 6 h after consumption of one of three isocaloric drinks consisting of either 80% fat, 80% carbohydrate, or 80% protein. The samples were assayed by RIA for total and active ghrelin, as well as by sandwich assays for acyl and des-acyl ghrelin. The ghrelin profiles for each individual were smoothed using a statistical algorithm to lessen the effects of pulsatility and noise. Results: The sandwich assays for acyl and des-acyl ghrelin yielded ghrelin values that were lower than those from the corresponding RIAs. The ghrelin profiles after nutrient ingestion were similar, yet key differences among the four assays were apparent; in particular, percentage changes were significantly greater in the sandwich assays. Conclusions: The lower levels and greater relative changes in ghrelin values reported by the sandwich assays are consistent with greater assay specificity. When applied to the nutrient study, the sandwich assays were better able to distinguish the different responses to different nutrients than were the RIAs.
    Tipo de documento:
    Referencia
    Referencia del producto:
    Múltiplo
    Nombre del producto:
    Múltiplo

  • The role of C-terminal part of ghrelin in pharmacokinetic profile and biological activity in rats. 21291937

    Ghrelin is an endogenous ligand for growth hormone secretagogue receptor 1a (GHS-R1a), and consists of 28 amino acid residues with octanoyl modification at Ser(3). The previous studies have revealed that N-terminal part of ghrelin including modified Ser(3) is the active core for the activation of GHS-R1a. On the other hand, the role of C-terminal (8-28) region in ghrelin has not been clarified yet. In the present study, we prepared human ghrelin, C-terminal truncated ghrelin derivatives and anamorelin, a small molecular GHS compound which supposedly mimics the N-terminal active core, and examined GHS-R1a agonist activity in vitro, pharmacokinetic (PK) profile and growth hormone (GH) releasing activity in rats. All compounds demonstrated potent GHS-R1a agonist activities in vitro. Although the lack of C-terminal two amino acids did not modify PK profile and GH releasing activity, the deletion of C-terminal 8 and 20 amino acids affected them, and ghrelin(1-7)-Lys-NH(2) exhibited very short plasma half-life and low GH releasing activity in vivo. In rat plasma, ghrelin(1-7)-Lys-NH(2) was degraded more rapidly than ghrelin, suggesting that C-terminal part of ghrelin protected octanoylation of Ser(3) from plasma esterases. Subdiaphragmatic vagotomy significantly attenuated GH response to ghrelin but not to anamorelin. These results suggest that the C-terminal part of ghrelin has an important role in the biological activity in vivo. We also found that ghrelin stimulated GH release mainly via a vagal nerve pathway but anamorelin augmented GH release possibly by directly acting on brain in rats.
    Tipo de documento:
    Referencia
    Referencia del producto:
    EZRMGH-45K
    Nombre del producto:
    Rat/Mouse Growth Hormone ELISA

  • Immunohistochemical and quantitative analysis of ghrelin in Syzygium aromaticum. 21029042

    Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor, has been identified in mammals, fish, amphibians, birds, reptiles and some plants. The present investigation was designed to determine whether ghrelin is present in the appetite-stimulating plants Syzygium aromaticum and Salvadora persica, using IHC (immunohistochemistry) to indicate the location of the peptide and ELISA to measure the concentration. ELISA demonstrated that a ghrelin-like substance was present at concentrations of 4070.75±664.67 and 75.25±24.49 pg/mg in the tissues of flower bud of S. aromaticum and branch of S. persica, respectively. The concentration of ghrelin in human salivary gland tissue was 436.00±95.83 pg/mg. Ghrelin was predominantly localized to the T (trachea) and PCs (parenchyma cells) in the flower bud of S. aromaticum. However, no ghrelin immunoreactivity was observed in the PC or T of the branch of S. persica. The evolutionary role of this peptide hormone in plants and animals suggests that they have evolved in a more similar way than previously thought.
    Tipo de documento:
    Referencia
    Referencia del producto:
    EZGRT-89K
    Nombre del producto:
    Human Ghrelin (total) ELISA

  • Ghrelin and des-acyl ghrelin promote differentiation and fusion of C2C12 skeletal muscle cells. 17202410

    Ghrelin is an acylated peptidyl gastric hormone acting on the pituitary and hypothalamus to stimulate appetite, adiposity, and growth hormone release, through activation of growth hormone secretagogue receptor (GHSR)-1a receptor. Moreover, ghrelin features several activities such as inhibition of apoptosis, regulation of differentiation, and stimulation or inhibition of proliferation of several cell types. Ghrelin acylation is absolutely required for both GHSR-1a binding and its central endocrine activities. However, the unacylated ghrelin form, des-acyl ghrelin, which does not bind GHSR-1a and is devoid of any endocrine activity, is far more abundant than ghrelin in plasma, and it shares with ghrelin some of its cellular activities. In here we show that both ghrelin and des-acyl ghrelin stimulate proliferating C2C12 skeletal myoblasts to differentiate and to fuse into multinucleated myotubes in vitro through activation of p38. Consistently, both ghrelin and des-acyl ghrelin inhibit C2C12 proliferation in growth medium. Moreover, the ectopic expression of ghrelin in C2C12 enhances differentiation and fusion of these myoblasts in differentiation medium. Finally, we show that C2C12 cells do not express GHSR-1a, but they do contain a common high-affinity binding site recognized by both acylated and des-acylated ghrelin, suggesting that the described activities on C2C12 are likely mediated by this novel, yet unidentified receptor for both ghrelin forms.
    Tipo de documento:
    Referencia
    Referencia del producto:
    2500
    Nombre del producto:
    ReBlot Plus Kit

  • Obestatin, acylated and total ghrelin concentrations in the perinatal rat pancreas. 16733368

    BACKGROUND: Ghrelin and obestatin are encoded by the preproghrelin gene and originate from posttranslational processing of the preproghrelin peptide. The fetal rat pancreas contains acylated and desacylated ghrelin peptides, as well as growth hormone secretagogue receptor -1a mRNA. Acylated ghrelin inhibits insulin secretion. We investigated the plasma and tissue ontogeny of ghrelin and obestatin in the rat. METHODS: We measured obestatin and acylated and total ghrelin concentrations in plasma, pancreas and stomach from rat fetuses (F20) and neonates at postnatal day (PN) 1, 6, 12 and 21). RESULTS: Overall, obestatin concentrations were markedly lower than total ghrelin concentrations. In plasma, total ghrelin concentrations decreased abruptly after birth (p 0.05), contrasting with a 3 times increase in the concentration of acylated ghrelin between F20 and PN1 (p 0.05). In pancreas, total ghrelin and obestatin concentrations decreased progressively from PN1 to PN21 but acylated ghrelin concentrations increased 6-7 times from F20 (18 [6] pg/ml) to PN6 (122 [59] pg/ml). The percent of acylated ghrelin increased from 1.8 (0.6) at F20 to 39.7 (13.0) % of total ghrelin immunoreactivity at PN12 (p 0.05). There were significant positive correlations between postnatal obestatin, acylated or total ghrelin and insulin concentrations in the pancreas (all p 0.02, r(2) > 0.21) and between postnatal total ghrelin and obestatin (in pancreas, r(2) = 0.37) or acylated ghrelin (in stomach, r(2) = 0.27) (p 0.001). CONCLUSION: Ghrelin and obestatin are present in the perinatal pancreas where they could potentially affect insulin secretion.
    Tipo de documento:
    Referencia
    Referencia del producto:
    RI-13K
    Nombre del producto:
    Rat Insulin RIA

  • Ghrelin triggers the synaptic incorporation of AMPA receptors in the hippocampus. 24367106

    Ghrelin is a peptide mainly produced by the stomach and released into circulation, affecting energy balance and growth hormone release. These effects are guided largely by the expression of the ghrelin receptor growth hormone secretagogue type 1a (GHS-R1a) in the hypothalamus and pituitary. However, GHS-R1a is expressed in other brain regions, including the hippocampus, where its activation enhances memory retention. Herein we explore the molecular mechanism underlying the action of ghrelin on hippocampal-dependent memory. Our data show that GHS-R1a is localized in the vicinity of hippocampal excitatory synapses, and that its activation increases delivery of α-amino-3-hydroxy-5-methyl-4-isoxazole propionic-type receptors (AMPARs) to synapses, producing functional modifications at excitatory synapses. Moreover, GHS-R1a activation enhances two different paradigms of long-term potentiation in the hippocampus, activates the phosphatidylinositol 3-kinase, and increases GluA1 AMPAR subunit and stargazin phosphorylation. We propose that GHS-R1a activation in the hippocampus enhances excitatory synaptic transmission and synaptic plasticity by regulating AMPAR trafficking. Our study provides insights into mechanisms that may mediate the cognition-enhancing effect of ghrelin, and suggests a possible link between the regulation of energy metabolism and learning.
    Tipo de documento:
    Referencia
    Referencia del producto:
    AB15159