C-terminal pro-ghrelin peptides are present in the human circulation

doi:10.1016/j.bbrc.2003.09.045

Biochemical and Biophysical Research Communications

Volume 310, Issue 2, 17 October 2003, Pages 567-573

https://doi.org/10.1016/j.bbrc.2003.09.045 Get rights and content

Abstract

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 (∼30%, P<0.05), whereas in patients with heart failure, C-ghrelin levels were significantly elevated (∼32%, P<0.05) compared with controls. HPLC coupled with RIA showed circulating C-ghrelin to be primarily of low molecular weight (M_r ∼ 3500), but in chronic heart failure, a higher molecular weight form (M_r ∼ 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.

Section snippets

Materials and methods

Chemicals. Synthetic human pro-ghrelin(63–94) and ghrelin(1–28, n-octanoyl) were obtained from Phoenix Pharmaceuticals. Peptides derived from human pro-ghrelin(74–94) (Fig. 1) were synthesised by Chiron Mimotopes (Melbourne, Australia). All peptides were greater than 95% purity as assessed by ESI mass spectrometry.

Patient blood sampling groups. All protocols were approved by the Ethics Committee (Canterbury) of the Ministry of Health, New Zealand, in accordance with the guidelines of The

Radioimmunoassay for human carboxyl terminal ghrelin

The RIA for human C-ghrelin using antiserum A14 had an average zero binding of 33.7 ± 0.2%, a detection limit of 3.6 ± 0.3 fmol/tube (11.9 ± 1.1 pmol/L), 50% displacement of trace at 377.4 ± 61.3 pmol/L, and 3.2 ± 0.2% non-specific binding, over 15 assays. Dilutions of human plasma extracts were in parallel with both standard curves (Fig. 2).

Plasma levels of ghrelin and C-ghrelin in normal controls

In normal healthy volunteers, plasma C-ghrelin levels were significantly higher than corresponding ghrelin levels (202.8 ± 129.0 vs. 146.0 ± 97.3 pmol/L, P=0.026, Fig. 3A),

Discussion

Ghrelin is a potent stimulus for GH release [1], [2], [9] and it has a significant role in energy homeostasis [12]. However, a growing body of evidence also suggests that ghrelin may have in vivo effects upon blood pressure and cardiac function [13], [14], [15], [16]. Furthermore, in vitro studies suggest protective actions upon cardiomyocytes [7]. The tissue distribution of the GHS-R includes the heart and coronary vasculature [1], [6] and the heart itself synthesises bona fide ghrelin [14],

Acknowledgements

We thank Stephanie Moran for assistance with collection of blood samples and the staff of Endolab Laboratories for hormone measurements. P.W. was the recipient of a Canterbury Medical Research Foundation Summer Studentship. M.R. holds the National Heart Foundation Chair of Cardiovascular Studies. This work was supported by the Health Research Council, National Heart Foundation, and Canterbury Medical Research Foundation of New Zealand.

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Although this finding was not replicated in the kainate model, desacyl-ghrelin was anyway found to significantly delay the onset of status epilepticus in kainate-treated rats. This is indeed the first observation of an anticonvulsive effect of desacyl-ghrelin, whose plasma levels are physiologically more elevated than those of ghrelin (Pemberton et al., 2003). Similar to desacyl-ghrelin, hexarelin and EP-80317 were also able to counteract seizure induction.
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C-terminal pro-ghrelin peptides are present in the human circulation

Abstract

Section snippets

Materials and methods

Radioimmunoassay for human carboxyl terminal ghrelin

Plasma levels of ghrelin and C-ghrelin in normal controls

Discussion

Acknowledgements

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Biochem. Biophys. Res. Commun.

Biochem. Biophys. Res. Commun.

Atherosclerosis

J. Am. Coll. Cardiol.

J. Am. Coll. Cardiol.

Ghrelin is a growth-hormone-releasing acylated peptide from stomach

Nature

The novel hypothalamic peptide ghrelin stimulates food intake and growth hormone secretion

Endocrinology

Circulating ghrelin levels are decreased in human obesity

Diabetes

Plasma ghrelin concentrations in elderly subjects: comparison with anorexic and obese patients

J. Endocrinol.

Elevated circulating level of ghrelin in cachexia associated with heart failure

Circulation

[125I-His(9)]-ghrelin, a novel radioligand for localising GHS orphan receptors in human and rat tissue: upregulation of receptors with atherosclerosis

Br. J. Pharmacol.

Ghrelin and des-acyl ghrelin inhibit cell death in cardiomyocytes and endothelial cells through ERK1/2 and PI 3-kinase/AKT

J. Cell Biol.

[¹²⁵I-His(9)]-ghrelin, a novel radioligand for localising GHS orphan receptors in human and rat tissue: upregulation of receptors with atherosclerosis