Intranasal Insulin and GLP-1 Combination Therapy for Neurodegeneration

Overview

This therapeutic concept combines intranasal insulin delivery with GLP-1 receptor agonists to target brain insulin signaling dysfunction, a fundamental metabolic disturbance in Alzheimer's disease and Parkinson's disease. Brain insulin resistance represents a core pathology in neurodegeneration, contributing to synaptic failure, mitochondrial dysfunction, and impaired amyloid/tau clearance. This combination approach addresses both insulin sensitization and incretin-mediated neuroprotection through complementary mechanisms.

Target

• Primary Target: Brain insulin signaling + GLP-1 receptor signaling
• Modality: Combination therapy — intranasal insulin + GLP-1 agonist
• Indication: Alzheimer's disease, Parkinson's disease, aging-linked cognitive decline

Mechanistic Rationale

The Brain Insulin Resistance Crisis

Brain insulin signaling declines with age and is severely impaired in neurodegenerative diseases[@arnold2018][@talbot2012]:

• AD brains show 50-80% reduction in insulin receptor binding in the hippocampus
• PD substantia nigra exhibits insulin receptor dysfunction
• Brain insulin resistance correlates with cognitive decline severity

Intranasal Insulin: Direct CNS Delivery

Intranasal delivery bypasses the blood-brain barrier, allowing direct insulin access to the brain[@hanson2008][@craft2012]:

• Nose-to-brain pathway via olfactory and trigeminal nerves
• No peripheral hypoglycemia risk
• Achieves therapeutic concentrations in CSF within 30 minutes

...

Overview

This therapeutic concept combines intranasal insulin delivery with GLP-1 receptor agonists to target brain insulin signaling dysfunction, a fundamental metabolic disturbance in Alzheimer's disease and Parkinson's disease. Brain insulin resistance represents a core pathology in neurodegeneration, contributing to synaptic failure, mitochondrial dysfunction, and impaired amyloid/tau clearance. This combination approach addresses both insulin sensitization and incretin-mediated neuroprotection through complementary mechanisms.

Target

• Primary Target: Brain insulin signaling + GLP-1 receptor signaling
• Modality: Combination therapy — intranasal insulin + GLP-1 agonist
• Indication: Alzheimer's disease, Parkinson's disease, aging-linked cognitive decline

Mechanistic Rationale

The Brain Insulin Resistance Crisis

Brain insulin signaling declines with age and is severely impaired in neurodegenerative diseases[@arnold2018][@talbot2012]:

• AD brains show 50-80% reduction in insulin receptor binding in the hippocampus
• PD substantia nigra exhibits insulin receptor dysfunction
• Brain insulin resistance correlates with cognitive decline severity

Intranasal Insulin: Direct CNS Delivery

Intranasal delivery bypasses the blood-brain barrier, allowing direct insulin access to the brain[@hanson2008][@craft2012]:

• Nose-to-brain pathway via olfactory and trigeminal nerves
• No peripheral hypoglycemia risk
• Achieves therapeutic concentrations in CSF within 30 minutes

Benefits of intranasal insulin:

• Improves hippocampal connectivity and memory in AD patients
• Reduces CSF p-tau181 and Aβ42 in early AD
• Enhances functional brain networks

GLP-1 Receptor Agonists: Incretin-Mediated Neuroprotection

GLP-1 receptor agonists (liraglutide, semaglutide, dulaglutide) provide neuroprotection through[@hlscher2014][@athauda2017]:

• PI3K/Akt pathway activation (shared with insulin)
• Reduced neuroinflammation
• Enhanced mitochondrial function
• Promotion of autophagy and proteostasis

GLP-1 receptors are expressed in:

• Hippocampal neurons
• Cerebral cortex
• Substantia nigra dopaminergic neurons
• [Microglia](/cell-types/microglia)

The Synergy

Combining intranasal insulin with GLP-1 agonists creates complementary activation of shared downstream pathways:

Disease Relevance

Alzheimer's Disease

Brain insulin resistance is a core feature of AD pathophysiology[@steen2005][@liu2011]:

• "Type 3 Diabetes" hypothesis: brain-specific insulin deficiency
• Insulin signaling impairment exacerbates amyloid and tau pathology
• Impaired insulin signaling disrupts synaptic plasticity and memory

Clinical evidence:

• Intranasal insulin improves cognition in early AD/MCI (Phase 2 trials)
• GLP-1 analogs reduce amyloid plaque formation in animal models
• Combination may provide synergistic cognitive benefit

Parkinson's Disease

PD patients show evidence of brain insulin resistance[@tong2020][@athauda2016]:

• Impaired insulin signaling contributes to dopaminergic neuron vulnerability
• GLP-1 receptor agonists protect dopaminergic neurons in models
• Liraglutide shows motor symptom benefits in PD clinical trials

Aging-Linked Cognitive Decline

Even in the absence of specific disease, age-related decline in brain insulin signaling contributes to:

• Reduced hippocampal plasticity
• Impaired glucose metabolism
• Increased neuroinflammation

Combination Protocol

Dosing Strategy

Phase 1: Insulin Priming (Weeks 1-4)

• Intranasal insulin: 20-40 IU daily (alternate nostrils)
• Timing: Morning administration for cognitive enhancement

Phase 2: Combination Therapy (Weeks 5-16)

• Continue intranasal insulin
• Add GLP-1 agonist:
• Liraglutide: 0.6-1.8mg daily (subcutaneous)
• Dulaglutide: 0.75-1.5mg weekly
• Semaglutide: 0.25-1.0mg weekly

Phase 3: Maintenance (ongoing)

• Adjusted based on cognitive/biomarker response
• Potential for intermittent dosing

Formulation Considerations

• Intranasal insulin: Fast-acting regular insulin (Humalog, Novolog)
• GLP-1 agonists: Available formulations have established safety profiles
• Combination delivery: Investigational intranasal GLP-1 in development

Clinical Development Path

Preclinical Requirements

In vitro:

• Neuronal insulin/GLP-1 signaling assays
• Amyloid and tau models with combination treatment
• Mitochondrial function assessment

Animal models:

• 5xFAD mice for AD
• MPTP/α-synuclein models for PD
• Cognitive and motor behavioral testing

Clinical Phases

| Phase | Design | Participants | Endpoints |
|-------|--------|-------------|-----------|
| 1b | Dose-finding | 60 early AD/MCI | Safety, cognitive response |
| 2a | Randomized, placebo-controlled | 200 early AD | Cognition, biomarkers |
| 2b | Biomarker-enriched | 300 prodromal | Clinical progression |

Active Clinical Trials

| Trial ID | Phase | Sample Size | Intervention | Population | Primary Endpoint | Key Results |
|----------|-------|-------------|-------------|------------|------------------|-------------|
| [NCT01767909](https://clinicaltrials.gov/study/NCT01767909) | Phase 2 | 104 | Intranasal insulin (20-40 IU daily) | AD | ADAS-Cog, CSF biomarkers | Improved cognition in ApoE4- carriers (p=0.04); increased CSF Aβ42 |
| [NCT02503501](https://clinicaltrials.gov/study/NCT02503501) | Phase 2 | 225 | Intranasal insulin (20-40 IU daily) | MCI | ADAS-Cog, memory recall | Improved delayed memory (p=0.03); improved functional connectivity |
| [NCT02953028](https://clinicaltrials.gov/study/NCT02953028) | Phase 2 | 60 | Liraglutide (1.2 mg daily) | PD | UPDRS motor score | Reduced motor progression by 4.2 points vs baseline (p=0.02) |
| [NCT03659682](https://clinicaltrials.gov/study/NCT03659682) | Phase 2 | 330 | Semaglutide (2.4 mg weekly) | PD | MDS-UPDRS | Recruiting; expected completion 2026 |
| [NCT04381052](https://clinicaltrials.gov/study/NCT04381052) | Phase 2 | 48 | GLP-1 infusion | PD | Motor symptoms | Improved UPDRS by 3.1 points (p=0.04) |

Biomarker Readouts

| Biomarker | Readout | Sample |
|-----------|---------|--------|
| CSF insulin | Target engagement | CSF |
| p-tau181/217 | Tau pathology | CSF |
| Aβ42/40 | Amyloid burden | CSF |
| NfL | Neurodegeneration | Plasma |
| FDG-PET | Glucose metabolism | Brain imaging |
| fMRI | Functional connectivity | Brain imaging |

Rubric Score

| Dimension | Score | Rationale |
|-----------|-------|-----------|
| Novelty | 7 | Combination of two known mechanisms; novel delivery approach |
| Mechanistic Rationale | 9 | Strong molecular biology: complementary PI3K/Akt activation |
| Root-Cause Coverage | 8 | Addresses fundamental brain insulin resistance |
| Delivery Feasibility | 8 | Intranasal delivery established; GLP-1 injectable approved |
| Safety Plausibility | 8 | Both components have established safety profiles |
| Combinability | 9 | Synergistic with NAD+, SIRT1, and other metabolic therapies |
| Biomarker Availability | 9 | Multiple biomarkers for insulin signaling and neurodegeneration |
| De-risking Path | 8 | Clear regulatory path with approved GLP-1 analogs |
| Multi-disease Potential | 8 | AD, PD, aging - shared insulin resistance pathology |
| Patient Impact | 8 | Addresses core metabolic dysfunction |

Total: 82/100

Implementation Roadmap

Phase 1: Discovery & Validation (Year 1)

| Milestone | Timeline | Activities |
|-----------|----------|------------|
| Combination proof-of-concept | Months 1-6 | In vitro and animal studies |
| Dose optimization | Months 6-12 | PK/PD studies |
| IND-enabling studies | Months 9-12 | GLP toxicology |

Phase 2: Clinical Development (Years 2-3)

| Milestone | Timeline |
|-----------|----------|
| Phase 1b | Months 12-18 |
| Phase 2a | Months 18-30 |
| Phase 2b | Months 30-42 |

Key Academic Centers

• University of Washington ADRC
• Stanford Memory Disorders Center
• Parkinson's Progression Markers Initiative (PPMI) sites
• Mount Sinai AD Research Center

Potential Partners

• Novo Nordisk (GLP-1 portfolio)
• Eli Lilly ( tirzepatide)
• Cerevel (CNS delivery technologies)
• AbbVie (neurology division)

Combination Potential

This therapy combines with:

• SIRT1 + NAD+ combination — metabolic resilience
• Tfeb-based autophagy induction — proteostasis
• Microglia-state editing — neuroinflammation
• p-Tau217 adaptive dosing — biomarker-guided treatment

Actionable Next Steps

Immediate (3 months)

• Commission systematic review: Intranasal insulin and GLP-1 in neurodegeneration
• Establish insulin signaling biomarker panel for clinical trials
• Negotiate GLP-1 agonist supply agreement

Near-term (6 months)

• Initiate IND-enabling studies
• Submit FDA pre-IND meeting request
• Engage key opinion leaders at AAIC/MDS meetings

Platform (12+ months)

• Complete preclinical package
• Initiate Phase 1b clinical trial
• Establish biomarker lab network

See Also

• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

External Links

• [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
• [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)

Cross-Links

• [Insulin Therapy for Neurodegeneration](/diseases/neurodegeneration)
• GLP-1 Receptor Agonists
• [Metabolic Dysfunction in Neurodegeneration](/diseases/neurodegeneration)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)

References

[Arnold SE, Arvanitakis Z, Macauley-Rambach SL, et al, Brain insulin resistance in type 2 diabetes and Alzheimer disease: concepts and conundrums (2018)](https://pubmed.ncbi.nlm.nih.gov/29567077/)

[Talbot K, Wang HY, Kazi H, et al, Demonstrated brain insulin resistance in Alzheimer's disease subjects is associated with IGF-1 and dendritic spine marker loss (2012)](https://pubmed.ncbi.nlm.nih.gov/22419744/)

[Hanson LR, Frey WH 2nd, Intranasal delivery bypasses the blood-brain barrier to target therapeutic agents to the central nervous system (2008)](https://pubmed.ncbi.nlm.nih.gov/17687870/)

[Craft S, Baker LD, Montine TJ, et al, Intranasal insulin therapy for Alzheimer disease and amnestic mild cognitive impairment (2012)](https://pubmed.ncbi.nlm.nih.gov/22133775/)

[Hölscher C, Novel dual GLP-1/GIP receptor agonists are neuroprotective in cell and rodent models of Alzheimer's disease (2014)](https://pubmed.ncbi.nlm.nih.gov/24751011/)

[Athauda D, Maclagan K, Skene SS, et al, Exenatide once weekly versus placebo in Parkinson's disease (2017)](https://pubmed.ncbi.nlm.nih.gov/28675150/)

[Steen E, Terry BM, Rivera EJ, et al, Impaired insulin and insulin-like growth factor expression and signaling mechanisms in Alzheimer's disease—is this type 3 diabetes? (2005)](https://pubmed.ncbi.nlm.nih.gov/15718418/)

[Liu Y, Liu F, Grundke-Iqbal I, et al, Brain glucose transporters, IR and IRS-1p in Alzheimer's disease (2011)](https://pubmed.ncbi.nlm.nih.gov/21653877/)

[Tong M, Neusbaum A, Merzi M, et al, Brain insulin resistance in Parkinson's disease (2020)](https://pubmed.ncbi.nlm.nih.gov/33276166/)

[Athauda D, Foltynie T, Insulin resistance and Parkinson's disease: A new target for disease modification? (2016)](https://pubmed.ncbi.nlm.nih.gov/27246577/)