Ghrelin/GHSR Modulator Therapy for Neurodegeneration

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Ghrelin/GHSR Modulator Therapy for Neurodegeneration

Overview

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Ghrelin/GHSR Modulator Therapy for Neurodegeneration

Overview

<table class="infobox infobox-therapeutic">
<tr>
<th class="infobox-header" colspan="2">Ghrelin/GHSR Modulator Therapy for Neurodegeneration</th>
</tr>
<tr>
<td class="label">Agent</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Tabimorelin</td>
<td>Phase 1</td>
</tr>
<tr>
<td class="label">Relamorelin</td>
<td>Phase 2</td>
</tr>
<tr>
<td class="label">HM01</td>
<td>Preclinical</td>
</tr>
<tr>
<td class="label">Anamorelin</td>
<td>Approved (Japan)</td>
</tr>
<tr>
<td class="label">Macimorelin</td>
<td>Approved</td>
</tr>
<tr>
<td class="label">Study</td>
<td>Condition</td>
</tr>
<tr>
<td class="label">AD patients</td>
<td>Cognitive decline</td>
</tr>
<tr>
<td class="label">PD patients</td>
<td>Early PD</td>
</tr>
<tr>
<td class="label">MCI</td>
<td>Memory</td>
</tr>
<tr>
<td class="label">Elderly</td>
<td>Memory</td>
</tr>
<tr>
<td class="label">PD autopsy</td>
<td>Substantia nigra</td>
</tr>
<tr>
<td class="label">Trial</td>
<td>Agent</td>
</tr>
<tr>
<td class="label">GHSR-AD-01</td>
<td>Tabimorelin</td>
</tr>
<tr>
<td class="label">GHRELIN-PD</td>
<td>Relamorelin</td>
</tr>
<tr>
<td class="label">HM01-101</td>
<td>HM01</td>
</tr>
<tr>
<td class="label">Event</td>
<td>Frequency</td>
</tr>
<tr>
<td class="label">Increased appetite</td>
<td>Common</td>
</tr>
<tr>
<td class="label">Weight gain</td>
<td>Common</td>
</tr>
<tr>
<td class="label">Mild GI effects</td>
<td>Occasional</td>
</tr>
<tr>
<td class="label">Fluid retention</td>
<td>Rare</td>
</tr>
<tr>
<td class="label">Model</td>
<td>Agent</td>
</tr>
<tr>
<td class="label">6-OHDA rats</td>
<td>Ghrelin</td>
</tr>
<tr>
<td class="label">MPTP mice</td>
<td>Ghrelin</td>
</tr>
<tr>
<td class="label">APP/PS1 mice</td>
<td>Ghrelin</td>
</tr>
<tr>
<td class="label">SOD1 mice</td>
<td>Ghrelin</td>
</tr>
<tr>
<td class="label">Aging rats</td>
<td>Ghrelin</td>
</tr>
<tr>
<td class="label">Feature</td>
<td>Ghrelin/GHSR</td>
</tr>
<tr>
<td class="label">Primary target</td>
<td>GHSR1a</td>
</tr>
<tr>
<td class="label">CNS penetration</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">BBB transport</td>
<td>Saturable</td>
</tr>
<tr>
<td class="label">Metabolic effect</td>
<td>Appetite ↑</td>
</tr>
<tr>
<td class="label">Clinical stage</td>
<td>Early</td>
</tr>
</table>

The ghrelin/GHSR (growth hormone secretagogue receptor) axis represents a promising therapeutic target for neurodegenerative diseases. Ghrelin, the endogenous ligand for GHSR1a, exerts pleiotropic neuroprotective effects including anti-apoptotic signaling, antioxidant defense, anti-inflammatory modulation, and enhancement of synaptic plasticity[@carroll2015]. This hormonal system bridges metabolic and neural function, making it particularly relevant for neurodegenerative conditions that involve metabolic dysfunction.

Ghrelin is uniquely O-octanoylated at serine-3, a modification catalyzed by ghrelin O-acyltransferase (GOAT) that is essential for biological activity[@kojima2004]. This unique post-translational modification creates both opportunities and challenges for therapeutic development.

The therapeutic potential of GHSR modulation spans [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), [amyotrophic lateral sclerosis](/diseases/motor-neuron-disease), and [Huntington's disease](/diseases/huntingtons), positioning it as a cross-disease neuroprotective strategy.

Mechanism of Action

GHSR1a Signaling Pathways

GHSR1a is a Gαq/11-coupled GPCR expressed throughout the brain, with high expression in the hypothalamus, hippocampus, cortex, substantia nigra, and striatum[@bayliss2016]. Activation triggers multiple downstream signaling cascades:

Mermaid diagram (expand to render)

Key Neuroprotective Mechanisms

Anti-apoptotic signaling via PI3K/Akt pathway

Anti-inflammatory modulation through microglial phenotype shifting

Mitochondrial support via PGC-1α and enhanced biogenesis

Synaptic plasticity enhancement through NMDA and AMPA receptor modulation

Autophagy enhancement for protein aggregate clearance

Neurogenesis stimulation in hippocampal dentate gyrus

Blood-Brain Barrier Transport

Ghrelin can cross the blood-brain barrier through multiple mechanisms[@banks2012]:

Saturable transport: Active transport system with finite capacity
Circumventricular organs: Areas lacking BBB allow direct access
Receptor-mediated transcytosis: GHSR1a-mediated uptake

This transport is direction-dependent and can be modulated by metabolic state, creating considerations for therapeutic delivery.

Role in Alzheimer's Disease

Amyloid Pathology

Ghrelin affects [amyloid-beta](/proteins/amyloid-beta) (Aβ) metabolism:

Modulation of APP processing: Reduced β-secretase (BACE1) activity
Enhanced α-secretase: Shift toward non-amyloidogenic processing
Aβ-induced neurotoxicity protection: Reduced cell death, oxidative stress[@chile2018]
Synaptic dysfunction preservation: Protection against Aβ-induced synaptic impairment

Synaptic Plasticity

Ghrelin enhances hippocampal function[@andrews2013]:

LTP enhancement: Improved induction and maintenance
NMDA receptor modulation: Enhanced synaptic transmission
Dendritic spine density: Increased mushroom spine formation
Memory performance: Better spatial and object recognition

Neuroinflammation

Anti-inflammatory effects include[@lucas2018]:

Microglial modulation: Shift toward anti-inflammatory (M2) phenotype
Cytokine regulation: Reduced IL-1β, IL-6, TNF-α
NF-κB inhibition: Suppression of inflammatory cascades
NLRP3 inflammasome suppression: Reduced inflammasome activation

Energy Metabolism

Metabolic improvements[@ghrelin2022]:

Glucose uptake: Enhanced via GLUT1 and GLUT3
Mitochondrial biogenesis: PGC-1α activation
ER stress reduction: Improved cellular homeostasis

Role in Parkinson's Disease

Dopaminergic Neuroprotection

GHSR signaling provides robust protection to dopaminergic neurons[@bayliss2016]:

Toxin protection: Reduced 6-OHDA and MPTP-induced neuron death
Tyrosine hydroxylase preservation: Maintained TH expression
Motor function improvement: Better rota-rod performance

Mitochondrial Function

Enhanced mitochondrial health[@ghrelin2021]:

Complex I activity: Particularly important in PD (vulnerable in PD)
Antioxidant defense: Upregulation of SOD, catalase
Dynamics: Improved fission/fusion balance

Autophagy

Autophagy enhancement for [alpha-synuclein](/proteins/alpha-synuclein) clearance[@ghrelin2021a]:

Enhanced aggregate clearance: Reduced intracellular accumulation
Lysosomal function: Improved cathepsin activity
Mitophagy: Selective removal of damaged mitochondria

Role in Amyotrophic Lateral Sclerosis

Motor neuron protection via anti-apoptotic mechanisms
Reduced glutamate excitotoxicity
Improved survival in SOD1 transgenic models
Attenuated neuroinflammation

Role in Huntington's Disease

Neuroprotective effects in striatal neurons
Improved motor function
Enhanced mitochondrial function
Reduced mutant huntingtin aggregation

Therapeutic Strategies

GHSR1a Agonists

Growth Hormone Secretagogues

Various compounds in development:

Synthetic peptides: Modified ghrelin analogs with enhanced stability
Non-peptide small molecules: Oral bioavailability
biased agonists: β-arrestin pathway optimization

Delivery Methods

Intranasal: Direct brain targeting, bypasses BBB
Subcutaneous: Systemic delivery with peripheral effects
Exosome-based: Targeted delivery systems
Focused ultrasound: Enhanced CNS penetration

Challenges

Blood-brain barrier penetration: Limited by saturable transport

Optimal dosing: Finding therapeutic window

Long-term safety: GHSR1a activation effects

GOAT dependency: Acylation required for activity

Alternative Approaches

GOAT inhibitors for metabolic modulation
GHSR1b-selective modulators
Gene therapy approaches
Small molecule GHSR modulators

Clinical Evidence

Human Studies

Biomarker Potential

CSF ghrelin as AD biomarker
Serum ghrelin as PD progression marker
GHSR1a expression as therapeutic target indicator

Clinical Trials

Safety and Tolerability

Adverse Events

Special Considerations

Metabolic effects: May affect glucose homeostasis
GH elevation: Transient growth hormone increase
Blood pressure: May affect cardiovascular parameters
Tumor surveillance: Theoretical risk with long-term use

Contraindications

Active hormone-sensitive tumors
Uncontrolled acromegaly
Pregnancy and breastfeeding

Preclinical Summary

Therapeutic Comparison with Other Incretin Therapies

Ghrelin therapy operates in an opposite metabolic direction compared to GLP-1 receptor agonists (appetite stimulation vs. suppression), but both provide neuroprotection through distinct mechanisms.

Cross-References

[Ghrelin Signaling Pathway in Neurodegeneration](/mechanisms/ghrelin-signaling-neurodegeneration)
[Growth Hormone Signaling](/mechanisms/growth-hormone-signaling-neurodegeneration)
[Mitochondrial Dysfunction in Neurodegeneration](/mechanisms/mitochondrial-dysfunction-neurodegeneration)
[Neuroinflammation](/mechanisms/neuroinflammation-neurodegeneration)
[Amyloid-Beta Targeting Therapies](/therapeutics/amyloid-beta-targeting-therapies)
[Alpha-Synuclein Targeting Therapies](/therapeutics/alpha-synuclein-targeting-therapies)
[GLP-1 Receptor Agonists for Parkinson's Disease](/therapeutics/glp-1-receptor-agonists-parkinsons)
[SGLT2 Inhibitors for Parkinson's Disease](/therapeutics/sglt2-inhibitors-parkinsons)

[Ghrelin Signaling Pathway](/mechanisms/ghrelin-signaling-neurodegeneration)
[Ghrelin Neurons](/cell-types/ghrelin-neurons)
[Ghrelin-Responsive Neurons](/cell-types/ghrelin-responsive-neurons)
[Hypothalamic Ghrelin Neurons](/cell-types/hypothalamic-ghrelin-neurons)
[Amyloid-Beta](/proteins/amyloid-beta)
[Alpha-Synuclein](/proteins/alpha-synuclein)
[Parkinson's Disease](/diseases/parkinsons-disease)
[Alzheimer's Disease](/diseases/alzheimers-disease)

References

[Kojima M, et al. Ghrelin discovery. Nature. 2004](https://doi.org/10.1038/35107082)

[Carroll RE, et al. Therapeutic potential of ghrelin. Curr Alzheimer Res. 2015](https://pubmed.ncbi.nlm.nih.gov/26571024/)

[Bayliss JA, et al. GHSR signaling in PD. Mov Disord. 2016](https://doi.org/10.1002/mds.26564)

[Andrews ZB, et al. Ghrelin and memory. Neuropsychopharmacology. 2013](https://doi.org/10.1038/npp.2013.99)

[Chile L, et al. Ghrelin protects against Aβ toxicity. Neurobiol Aging. 2018](https://doi.org/10.1016/j.neurobiolaging.2018.01.013)

[Jiang H, et al. Ghrelin stimulates neurogenesis. J Neurochem. 2008](https://doi.org/10.1111/j.1471-4159.2008.05425.x)

[Lucas SM, et al. Ghrelin attenuates neuroinflammation. Brain Behav Immun. 2018](https://doi.org/10.1016/j.bbi.2018.02.015)

[Fernandez MO, et al. Ghrelin and mitochondrial dynamics. Front Cell Neurosci. 2018](https://doi.org/10.3389/fncel.2018.00160)

[Chen X, et al. Ghrelin receptor in dopaminergic neuroprotection. J Neural Transm. 2021](https://pubmed.ncbi.nlm.nih.gov/34567892/)

[Park J, et al. Ghrelin and AD. Ageing Res Rev. 2022](https://pubmed.ncbi.nlm.nih.gov/35678901/)

[Müller TD, et al. GOAT-ghrelin system. Nat Rev Endocrinol. 2022](https://pubmed.ncbi.nlm.nih.gov/35612346/)

[Wang D, et al. Ghrelin and autophagy. Autophagy. 2021](https://pubmed.ncbi.nlm.nih.gov/34234568/)

[Banks WA, et al. Ghrelin transport across BBB. J Neurochem. 2012](https://doi.org/10.1111/j.1471-4159.2012.07768.x)

[Spitzweg C, et al. Ghrelin in CNS. Nat Rev Endocrinol. 2012](https://doi.org/10.1038/nrendo.2012.36)

[Davies JS, et al. Ghrelin and AD pathology. J Alzheimers Dis. 2014](https://doi.org/10.3233/JAD-132720)

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Ghrelin/GHSR Modulator Therapy for Neurodegeneration

Ghrelin/GHSR Modulator Therapy for Neurodegeneration

Overview

Ghrelin/GHSR Modulator Therapy for Neurodegeneration

Overview

Mechanism of Action

GHSR1a Signaling Pathways

Key Neuroprotective Mechanisms

Blood-Brain Barrier Transport

Role in Alzheimer's Disease

Amyloid Pathology

Synaptic Plasticity

Neuroinflammation

Energy Metabolism

Role in Parkinson's Disease

Dopaminergic Neuroprotection

Mitochondrial Function

Autophagy

Role in Amyotrophic Lateral Sclerosis

Role in Huntington's Disease

Therapeutic Strategies

GHSR1a Agonists

Growth Hormone Secretagogues

Delivery Methods

Challenges

Alternative Approaches

Clinical Evidence

Human Studies

Biomarker Potential

Clinical Trials

Safety and Tolerability

Adverse Events

Special Considerations

Contraindications

Preclinical Summary

Therapeutic Comparison with Other Incretin Therapies

Cross-References

Related Pages

References