Ghrelin
Ghrelin — A 28-amino acid peptide hormone produced primarily by the stomach that stimulates appetite, growth hormone release, and energy metabolism.
What Is Ghrelin?
Ghrelin is a 28-amino acid peptide hormone produced primarily by oxyntic cells of the gastric fundus. It is the only known circulating orexigenic (appetite-stimulating) hormone. Uniquely, ghrelin requires post-translational octanoylation (attachment of an 8-carbon fatty acid) at Ser3 for biological activity. Molecular weight: 3370.9 Da (acylated form). Ghrelin was identified in 1999 as the endogenous ligand of the GHS-R1a receptor.
Mechanism of Action
Acylated ghrelin binds GHS-R1a, the same receptor targeted by synthetic secretagogues GHRP-6, GHRP-2, ipamorelin, and hexarelin. Receptor activation in the hypothalamic arcuate nucleus stimulates appetite through NPY/AgRP neurons. In the pituitary, GHS-R1a activation stimulates growth hormone release, synergizing with GHRH signaling.
Research Significance
- Appetite regulation: Ghrelin levels rise before meals and fall after eating, functioning as a "hunger hormone"
- GH secretion: Synergizes with GHRH to amplify pulsatile GH release
- Metabolism: Promotes adipogenesis and glucose homeostasis through central and peripheral mechanisms
- Neuroprotection: Studies demonstrate protective effects in neuronal injury models
Handling
The octanoyl modification is labile; store at -80°C for long-term preservation. Use acidified buffers (pH 4-5) with protease inhibitors for plasma sampling. Des-acyl ghrelin (lacking the fatty acid) is biologically inactive at GHS-R1a but may have independent metabolic effects.
Frequently Asked Questions
What is Ghrelin?
A 28-amino acid peptide hormone produced primarily by the stomach that stimulates appetite, growth hormone release, and energy metabolism.
Why is Ghrelin important in peptide research?
Ghrelin is a fundamental concept in compound as it relates to peptide science. It directly influences experimental design, compound characterization, and the reliability of research outcomes across biochemistry and molecular biology disciplines.