Obestatin Partially Affects Ghrelin Stimulation of Food Intake and GH Secretion in Rodents

Unité Mixte de Recherche, 549 Institut National de la Santé et de la Recherche Médicale, Faculté de Médecine, Université Paris-Descartes, Paris, France.
Endocrinology (Impact Factor: 4.5). 05/2007; 148(4):1648-53. DOI: 10.1210/en.2006-1231
Source: PubMed


Administration of ghrelin, an endogenous ligand for the GH secretagogue receptor 1a (GHSR 1a), induces potent stimulating effects on GH secretion and food intake. However, more than 7 yr after its discovery, the role of endogenous ghrelin remains elusive. Recently, a second peptide, obestatin, also generated from proteolytic cleavage of preproghrelin has been identified. This peptide inhibits food intake and gastrointestinal motility but does not modify in vitro GH release from pituitary cells. In this study, we have reinvestigated obestatin functions by measuring plasma ghrelin and obestatin levels in a period of spontaneous feeding in ad libitum-fed and 24-h fasted mice. Whereas fasting resulted in elevated ghrelin levels, obestatin levels were significantly reduced. Exogenous obestatin per se did not modify food intake in fasted and fed mice. However, it inhibited ghrelin orexigenic effect that were evident in fed mice only. The effects of obestatin on GH secretion were monitored in superfused pituitary explants and in freely moving rats. Obestatin was only effective in vivo to inhibit ghrelin stimulation of GH levels. Finally, the relationship between octanoylated ghrelin, obestatin, and GH secretions was evaluated by iterative blood sampling every 20 min during 6 h in freely moving adult male rats. The half-life of exogenous obestatin (10 microg iv) in plasma was about 22 min. Plasma obestatin levels exhibited an ultradian pulsatility with a frequency slightly lower than octanoylated ghrelin and GH. Ghrelin and obestatin levels were not strictly correlated. In conclusion, these results show that obestatin, like ghrelin, is secreted in a pulsatile manner and that in some conditions; obestatin can modulate exogenous ghrelin action. It remains to be determined whether obestatin modulates endogenous ghrelin actions.

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    • "Its participation in the regulation of energetic homeostasis in humans has been suggested, and initial data pointed towards the idea that obestatin was driving an anorexigenic message in contraposition to the orexigenic effect of ghrelin. However, various recent studies have shown conflictive results regarding this (Nakahara et al. 2008; Nogueiras et al. 2007; Zhang et al. 2005; Zizzari et al. 2007). In a recent study, we found that obestatin was not associated to weight loss or diminished appetite or decreased eating behaviour frequently observed in the ageing phenomenon and referred to as anorexia of aged people (Mora et al. 2012a). "
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    ABSTRACT: Obestatin has been proposed to have anorexigenic and anti-ghrelin actions. The objective was to study obestatin concentrations in relation to handgrip strength, functional capacity and cognitive state in old women. The prospective study included 110 women (age, 76.93 ± 6.32) from the Mataró Ageing Study. Individuals were characterized by anthropometric variables, grip strength, Barthel and assessment of cognitive impairment [Mini Cognoscitive Examination (MCE) Spanish version], depressive status by the Geriatric Depression Scale (GDS) and frailty by the Fried criteria. Obestatin was measured by IRMA. Obestatin showed negative correlation to handgrip at basal time point (r = −0.220, p = 0.023) and at 2-year follow-up (r = −0.344, p = 0.002). Obestatin, divided into quartiles, showed a negative lineal association with handgrip: 11.03 ± 4.88 kg in first, 8.75 ± 4.08 kg in second, 8.11 ± 3.66 kg in third and 7.61 ± 4.08 kg in fourth quartile (p = 0.018). Higher obestatin levels were associated to increased weakness (categorized by handgrip of frailty criteria): 2.24 ± 0.42 ng/ml in weak vs. 1.87 ± 0.57 ng/ml in non-weak (p = 0.01). The decrease of either MCE or Barthel scores at 2-year follow-up was significantly higher in individuals in the fourth quartile of obestatin in comparison with individuals in the first quartile (p = 0.046 and p = 0.019, respectively). No association was found between obestatin and GDS score and neither with frailty as a condition. Obestatin is associated to low muscle strength, and impaired functional and cognitive capacity in old women participating in the Mataró Ageing Study.
    Journal of the American Aging Association 12/2013; 35(6). DOI:10.1007/s11357-013-9532-0 · 3.39 Impact Factor
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    • "It was previously described in the rat that intraperitoneal (ip) injection of native ghrelin in the early light phase induces feeding and cFos activation in the ArcN, NTS, and AP (Hewson and Dickson, 2000; Lawrence et al., 2002; Takayama et al., 2007). A dose of 30 nmol/30 g body weight was chosen here based on a published study showing that this dose stimulates food intake in mice (Zizzari et al., 2007). Although ghrelin was very potent in activating cFos in the ArcN, NTS, and AP in the present study, its effects on feeding did not reach statistical significance. "
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    ABSTRACT: The stimulatory effects of ghrelin, a 28-AA acylated peptide originally isolated from stomach, on GH secretion and feeding are exclusively mediated through the growth hormone secretagogue 1a receptor (GHS-R1a), the only ghrelin receptor described so far. Several GHS-R1a agonists and antagonists have been developed to treat metabolic or nutritional disorders but their mechanisms of action in the central nervous system remain poorly understood. In the present study, we compared the activity of BIM-28163, a GHS-R1a antagonist and of several agonists, including native ghrelin and the potent synthetic agonist, BIM-28131, to modulate food intake, GH secretion and c-Fos activity in ArcN, NTS and AP in wild-type and NPY-GFP mice. BIM-28131 was as effective as ghrelin in stimulating GH secretion, but more active than ghrelin in inducing feeding. It stimulated cFos activity similarly to ghrelin in the NTS and AP but was more powerful in the ArcN, suggesting that the super-agonist activity of BIM-28131 is mostly mediated in the ArcN. BIM-28163 antagonized ghrelin-induced GH secretion but not ghrelin-induced food consumption and cFos activation, rather it stimulated food intake and cFos activity without affecting GH secretion. The level of cFos activation was dependent on the region considered: BIM-28163 was as active as ghrelin in the NTS, but less active in the ArcN and AP. All compounds also induced cFos immunoreactivity in ArcN NPY neurons but BIM-28131 was the most active. In conclusion, these data demonstrate that two peptide analogs of ghrelin, BIM-28163 and BIM-28131, are powerful stimulators of appetite in mice, acting through pathways and key brain regions involved in the control of appetite that are only partially superimposable from those activated by ghrelin. A better understanding of the molecular pathways activated by these compounds could be useful in devising future therapeutic applications, such as for cachexia and anorexia.
    Frontiers in Endocrinology 03/2013; 4(7):25. DOI:10.3389/fendo.2013.00025
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    • "More recently, obestatin, a 23 amino acid peptide, derived from the cleavage of preproghrelin was discovered [14] and reported as an anorexigenic peptide ligand of the orphan receptor, GPR39, but these findings are controversial [15]–[18]. Nevertheless, when co-administered with ghrelin at equimolar doses, obestatin counteracts, for instance, ghrelin induced food intake and GH secretion in rodents [19]. The mechanism of action of obestatin and its interaction with ghrelin in the central nervous system remain poorly understood. "
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    ABSTRACT: Ghrelin and obestatin are two gut-derived peptides originating from the same ghrelin/obestatin prepropeptide gene (GHRL). While ghrelin stimulates growth hormone (GH) secretion and food intake and inhibits γ-aminobutyric-acid synaptic transmission onto GHRH (Growth Hormone Releasing Hormone) neurons, obestatin blocks these effects. In Humans, GHRL gene polymorphisms have been associated with pathologies linked to an unbalanced energy homeostasis. We hypothesized that one polymorphism located in the obestatin sequence (Q to L substitution in position 90 of the ghrelin/obestatin prepropeptide, rs4684677) may impact on the function of obestatin. In the present study, we tested the activity of native and Q90L obestatin to modulate ghrelin-induced food intake, GH secretion, cFos activity in GHRH and Neuropeptide Y (NPY) neurons and γ-aminobutyric-acid activity onto GHRH neurons. Food intake, GH secretion and electrophysiological recordings were assessed in C57BL/6 mice. cFos activity was measured in NPY-Renilla-GFP and GHRH-eGFP mice. Mice received saline, ghrelin or ghrelin combined to native or Q90L obestatin (30 nmol each) in the early light phase. Ghrelin stimulation of food intake and GH secretion varied considerably among individual mice with 59-77% eliciting a robust response. In these high-responders, ghrelin-induced food intake and GH secretion were reduced equally by native and Q90L obestatin. In contrast to in vivo observations, Q90L was slightly more efficient than native obestatin in inhibiting ghrelin-induced cFos activation within the hypothalamic arcuate nucleus and the nucleus tractus solitarius of the brainstem. After ghrelin injection, 26% of NPY neurons in the arcuate nucleus expressed cFos protein and this number was significantly reduced by co-administration of Q90L obestatin. Q90L was also more potent that native obestatin in reducing ghrelin-induced inhibition of γ-aminobutyric-acid synaptic transmission onto GHRH neurons. These data support the hypothesis that Q90L obestatin partially blocks ghrelin-induced food intake and GH secretion by acting through NPY and GHRH neurons.
    PLoS ONE 12/2012; 7(12):e51135. DOI:10.1371/journal.pone.0051135 · 3.23 Impact Factor
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