Ghrelin neurons produce ghrelin, the "hunger hormone" primarily secreted from the stomach but also synthesized in central nervous system neurons. Ghrelin is a 28-amino acid peptide that plays crucial roles in energy homeostasis, growth hormone secretion, and has emerged as an important modulator of neuroprotection, circadian rhythms, and neurodegenerative disease processes.
| Property | Value |
|----------|-------|
| Category | Neuroendocrine Neurons |
| Location | Hypothalamus (arcuate nucleus), pituitary, hippocampus |
| Cell Types | Ghrelin-producing neurons |
| Primary Neurotransmitter | Ghrelin (acyl-modified peptide) |
| Key Markers | GHRL (preproghrelin), GHSR (ghrelin receptor), MBOAT4 (acylating enzyme) |
| Gene | GHRL (Ghrelin gene) |
| Taxonomy |
ID |
Name / Label |
| Cell Ontology (CL) |
CL:0005018 |
ghrelin secreting cell |
The GHRL gene encodes preproghrelin, a 117-amino acid precursor that is processed to produce:
- Ghrelin: 28-amino acid active peptide (acyl-modified at serine-3)
- Obestatin: 23-amino acid peptide with distinct functions
Ghrelin's unique octanoyl modification (C8:0) at serine-3 is essential for biological activity:
- Enzyme: Ghrelin O-acyltransferase (GOAT/MBOAT4)
- Function: Acylation enables blood-brain barrier crossing and receptor binding
- GHSR (Growth Hormone Secretagogue Receptor): G protein-coupled receptor
- Distribution: Wide expression in brain (hypothalamus, hippocampus, substantia nigra)
- Signaling: Multiple pathways (Gq, Gi/o, β-arrestin)
- Arcuate nucleus (ARC): Primary site of ghrelin neurons
- Perifornical area: Secondary population
- Dorsomedial hypothalamus: Scattered neurons
- Hippocampus: Cortical ghrelin neurons
- Pituitary gland: Local production
- Pancreas: Peripheral ghrelin (not neurons)
- Substantia nigra: Dopaminergic neurons express GHSR
- Appetite Stimulation: Ghrelin is the only known orexigenic (appetite-stimulating) hormone
- Food Intake: Activates NPY/AgRP neurons, inhibits POMC neurons
- Energy Balance: Signals nutritional status to the brain
- GH Release: Potent stimulator of growth hormone secretion from pituitary
- IGF-1: GH-mediated growth factor production
- Linear Growth: Essential for normal growth
¶ Sleep and Circadian Regulation
- Sleep Architecture: Ghrelin modulates REM and non-REM sleep
- Circadian Rhythms: Ghrelin secretion follows diurnal pattern
- Interaction: Ghrelin-GH axis influences circadian function
- Glucose Homeostasis: Modulates insulin sensitivity
- Lipid Metabolism: Promotes fat storage
- Thermogenesis: Affects energy expenditure
- Anti-apoptotic: Activates pro-survival pathways (PI3K/Akt, MAPK/ERK)
- Anti-inflammatory: Reduces microglial activation
- Anti-oxidant: Enhances mitochondrial function
- Neurogenesis: Promotes hippocampal neurogenesis
- Learning and Memory: Ghrelin enhances hippocampal synaptic plasticity
- LTPmechanisms/long-term-potentiation): Long-term potentiation enhancement
- Cognitive Function: Spatial memory improvement
- Cardiovascular: Modulates heart rate and blood pressure
- Gastrointestinal: Regulates gut motility and secretion
- Thermoregulation: Influences body temperature
- Neuroprotection: Ghrelin may protect against Aβ toxicity
- Memory: Ghrelin improves cognitive function in AD models
- Amyloid: May reduce amyloid-β accumulation
- Clinical: Lower ghrelin levels in AD patients
- Nigral Protection: GHSR activation protects dopaminergic neurons
- Motor Function: Ghrelin may improve motor symptoms
- α-Synuclein: May reduce aggregation
- Clinical Trials: Ghrelin analogs in development
- Motor Neuron Protection: Ghrelin shows neuroprotective effects
- Appetite: Cachexia intervention
- Growth Hormone: GH/IGF-1 axis involvement
- Muscle: May improve muscle function
¶ Stroke and Ischemia
- Neuroprotection: Reduces infarct size in animal models
- Angiogenesis: Promotes blood vessel formation
- Recovery: May improve functional outcomes
- Obesity: Ghrelin antagonists for weight loss
- Cachexia: Ghrelin agonists to increase appetite
- Diabetes: Altered ghrelin in metabolic syndrome
- Tesamorelin: FDA-approved for HIV-associated lipodystrophy
- Anamorelin: Cancer cachexia (Phase 3)
- Exogenous Ghrelin: Appetite stimulation
- Growth Hormone Secretagogues: Synthetic GHSR activators
- Capromorelin: GH deficiency treatment
- Neuroprotective: Beyond GH release
- D-Lys3-GHRP-6: Research antagonist
- Compound 2a: Blood-brain barrier penetrating antagonist
- Potential: Obesity treatment
- Cachexia: Cancer, CHF, COPD-associated wasting
- Post-surgical: Recovery nutrition
- Elderly: Sarcopenia intervention
- Bcl-2: Upregulation of anti-apoptotic proteins
- Caspase-3: Inhibition of caspase activation
- Mitochondrial: Protection of mitochondrial function
- Microglia: Reduced activation
- Cytokines: Decreased TNF-α, IL-1β, IL-6
- NF-κB: Inhibited inflammatory signaling
- ROS: Reduced reactive oxygen species
- Mitochondria: Enhanced mitochondrial function
- Antioxidants: Upregulated Nrf2 pathway
- Glutamate: Modulated excitotoxicity
- Calcium: Reduced calcium dysregulation
- NMDA: Interaction with NMDA receptors
- GHRL-KO mice: Ghrelin gene knockout
- GHSR-KO mice: Receptor knockout
- GOAT-KO mice: Acyltransferase knockout
- Transgenic: fluorescent reporters
- ELISA: Ghrelin measurement
- IHC: Localization studies
- Electrophysiology: Neuronal recordings
- Behavioral: Feeding, memory tests
- Fasting: Highest levels before meals
- Obesity: Lower ghrelin (relative to lean)
- Cachexia: Elevated ghrelin
- Neurodegeneration: Often lower in AD/PD
- Growth Hormone: Response to ghrelin administration
- Food Intake: Appetite measures
- Body Weight: Weight change
The study of Ghrelin Neurons has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.