Abstracts
Résumé
La ghréline, peptide essentiellement produit par l’estomac endocrine, a été découverte en tant que ligand naturel du récepteur des sécrétagogues de l’hormone de croissance (GH). Très rapidement, elle s’est révélée être le premier facteur orexigène périphérique. À côté de cette fonction, la ghréline influence de nombreuses voies neuroendocriniennes, métaboliques et extraendocriniennes, notamment au sein du système cardiovasculaire. La liaison de la ghréline au récepteur des sécrétagogues de GH de type 1a (GHS-R 1a) nécessite la présence, sur le peptide, d’une acylation de la sérine située en position 3. Si cette modification est indispensable pour la stimulation de la GH et pour certains effets métaboliques, elle n’est pas requise pour les autres fonctions du peptide, dans lesquelles d’autres récepteurs sont probablement impliqués. Les souris invalidées pour le gène de la préproghréline ne sont ni anorexiques, ni naines. En revanche, les souris GHS-R–/– sont légèrement moins lourdes, et les actions GH-sécrétagogue et orexigène de la ghréline sont neutralisées chez ces animaux. Ainsi, l’histoire fascinante de la ghréline et ses implications physiopathologiques potentielles en endocrinologie et en médecine interne sont encore en devenir.
Summary
Ghrelin, a peptide predominantly produced by the stomach, has been discovered as a natural ligand of the growth hormone secretagogue receptor (GHS-R) type 1a. Shortly there after, it attracted enormous interest since it appeared as the first peripheral orexigenic factor. Besides, ghrelin exerts other neuroendocrine metabolic and non-endocrine actions (e.g. cardiovascular activities) that may rely on the widespread distribution of ghrelin and its receptor (GHS-R). The existence of several GHS-R subtypes and evidences that neuroendocrine and metabolic but not all other ghrelin actions are dependent on acylation on serine 3 add further complexity to the system whose major physiological role remains to be definitely elucidated. Ghrelin knockout(-/-) mice are neither anorectic nor dwarf though GHS-R-/- are slightly underweight and do not respond to ghrelin with increased GH secretion or appetite. Thus, the continuation of the fascinating ghrelin story as well as its potential pathophysiological implications in endocrinology and internal medicine remain open avenues for future investigations.
Appendices
Références
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