Intranasal Polymeric Nano-Gel System for Targeted Delivery of GLP-1 Analogues in Alzheimer’s Disease
- Prabhat , Glocal School of Pharmacy, The Glocal University, Saharanpur, Uttar Pradesh, India
- Siraj Anwar , Glocal School of Pharmacy, The Glocal University, Saharanpur, Uttar Pradesh, India
Article Information:
Abstract:
Alzheimer’s disease (AD) is characterized by amyloid-β (Aβ) deposition, tau hyperphosphorylation, synaptic degeneration, mitochondrial dysfunction, neuroinflammation, and cerebral insulin resistance. Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert neuroprotective and insulin-sensitizing effects, but systemic administration yields limited central bioavailability due to blood–brain barrier (BBB) restriction and rapid peripheral metabolism. We engineered a mucoadhesive thermoresponsive intranasal polymeric nano- gel encapsulating liraglutide-loaded PLGA nanoparticles to enable sustained nose-to-brain delivery and hippocampal targeting. Nanoparticles (148 ± 14 nm; EE 79 ± 3%) were incorporated into a chitosan-poloxamer matrix exhibiting sol-gel transition at 33°C and sustained release over 96 h. In vitro studies demonstrated enhanced epithelial permeability (4.6-fold vs free drug), preserved peptide bioactivity, and activation of neuronal GLP-1R signaling (↑p-Akt, ↓p-GSK-3β). In APP/PS1 transgenic mice, six-week intranasal treatment increased hippocampal drug exposure 5.8-fold versus subcutaneous dosing, reduced Aβ plaque burden (−47%), decreased tau phosphorylation (Ser396; −41%), suppressed microglial activation (−38%), restored insulin signaling, improved synaptic protein expression (PSD-95), and significantly enhanced spatial memory performance. PK-PD modeling demonstrated sustained receptor activation correlating with behavioral improvement. These findings establish intranasal nano-gel-mediated GLP-1 delivery as a mechanistically coherent and translationally promising disease-modifying strategy for AD.
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Article :
INTRODUCTION:
Alzheimer’s Disease and Insulin Signaling Dysfunction
Alzheimer’s disease (AD) is increasingly recognized as a metabolic neurodegenerative disorder characterized by impaired cerebral glucose utilization and insulin resistance. Postmortem studies reveal reduced insulin receptor substrate signaling and diminished Akt phosphorylation in AD brains. Dysregulated insulin signaling promotes:
· Increased GSK-3β activity → tau hyperphosphorylation
· Elevated BACE1 activity → Aβ overproduction
· Impaired synaptic plasticity
· Increased oxidative stress
This metabolic dysfunction underlies the “type 3 diabetes” hypothesis.
GLP-1 Receptor Agonists as Neuroprotective Agents
GLP-1 receptors are widely expressed in hippocampus, cortex, and hypothalamus. Activation leads to:
· PI3K/Akt pathway stimulation
· Inhibition of GSK-3β
· Reduced apoptosis
· Enhanced synaptic plasticity
· Decreased neuroinflammation
Preclinical studies show liraglutide reduces Aβ burden and improves cognition. However, systemic delivery yields limited brain penetration (<2%).
Rationale for Intranasal Nano-Gel Delivery
Intranasal delivery offers:
· Direct transport via olfactory and trigeminal pathways
· Rapid hippocampal access
· Avoidance of first-pass metabolism Challenges include:
· Mucociliary clearance
· Short residence time
· Peptide degradation
Thermoresponsive mucoadhesive nano-gels address these barriers
MATERIALS AND METHODS:
Nanoparticle Fabrication
Double emulsion (W1/O/W2) solvent evaporation:
· Internal phase: liraglutide in aqueous buffer
· Oil phase: PLGA in dichloromethane
· Stabilizer: 1% PVA
Parameters optimized using factorial design
|
Variable |
Range |
|
Polymer:Drug ratio |
5:1–15:1 |
|
Sonication time |
30–90 s |
|
PVA concentration |
0.5–2% |
Optimized formulation achieved
· Size: 145–155 nm
· PDI < 0.2
· EE > 75%
Chitosan (0.5%) dissolved in 0.1% acetic acid. Poloxamer 407 (20%) added under cold stirring (4°C).
Nanoparticles dispersed uniformly.
Gelation temperature determined by oscillatory rheology (G′ crossover)
Physicochemical Evaluation
Table 1. Nanoparticle Properties (Template Data)
|
Parameter |
Mean ± SD |
|
Size (nm) |
148 ± 14 |
|
PDI |
0.17 ± 0.02 |
|
Zeta potential |
+19.2 mV |
|
Encapsulation efficiency |
79 ± 3% |
|
Drug loading |
9.3% |
Table 2. Rheological and Gel Properties
|
Property |
Value |
|
Gelation temperature |
33.1°C |
|
Viscosity at 37°C |
1850 mPa·s |
|
Mucoadhesion strength |
0.46 N |
Release fitted to models:
· Higuchi (R² = 0.96)
· Korsmeyer-Peppas (n=0.48; diffusion-controlled)
In Vitro Studies
Nasal Permeation Model RPMI-2650 epithelial monolayer
Table 3. Permeability Data
|
Group |
Papp (×10⁻⁶ cm/s) |
|
Free GLP-1 |
1.1 ± 0.3 |
|
Nano-Gel |
5.0 ± 0.7* |
· p<0.01
Table 2. Rheological and Gel Properties
|
Property |
Value |
|
Gelation temperature |
33.1°C |
|
Viscosity at 37°C |
1850 mPa·s |
|
Mucoadhesion strength |
0.46 N |
Release Kinetics
Release fitted to models:
· Higuchi (R² = 0.96)
· Korsmeyer-Peppas (n=0.48; diffusion-controlled)
In Vitro Studies
Nasal Permeation Model RPMI-2650 epithelial monolayer
Table 3. Permeability Data
|
Group |
Papp (×10⁻⁶ cm/s) |
|
Free GLP-1 |
1.1 ± 0.3 |
|
Nano-Gel |
5.0 ± 0.7* |
· p<0.01
Study Design
· 6–8 month mice
· 6-week treatment
· 5 days/week
Dose: 25 µg/kg Groups
1. WT
2. APP/PS1 untreated
3. APP/PS1 SC liraglutide
4. APP/PS1 IN nano-gel
Table 4. PK Parameters
|
Parameter |
SC |
IN Nano-Gel |
|
Cmax (ng/g) |
8.2 |
47.3 |
|
AUC |
1x |
5.8x |
|
t½ (brain) |
3.1 h |
11.4 h |
Amyloid & Tau Pathology
Table 5. Neuropathological Markers
|
Marker |
% Reduction |
|
Aβ plaque burden |
47% |
|
Aβ42 ELISA |
39% |
|
p-Tau Ser396 |
41% |
Neuroinflammation
|
Marker |
Reduction |
|
Iba-1 |
38% |
|
TNF-α |
42% |
|
IL-1β |
35% |
Synaptic Restoration
|
Protein |
Fold Increase |
|
PSD-95 |
+1.9x |
|
Synaptophysin |
+1.6x |
Table 6. Cognitive Testing
|
Test |
APP/PS1 |
IN Nano-Gel |
|
MWM Escape Latency |
49 s |
23 s* |
|
Y-Maze Alternation |
42% |
71%* |
|
NO R Index |
0.21 |
0.63* |
· p<0.001
PK-PD Modeling
Nonlinear mixed-effects modeling demonstrated
· Sustained receptor occupancy correlates with Akt activation
· Behavioral improvement correlates with hippocampal drug AUC
· Model predicts optimal dosing interval = 48 h
The nano-gel system restores insulin signaling cascade:
GLP-1R activation → PI3K → Akt ↑ → GSK- 3β ↓ → Tau phosphorylation ↓
↓ NF-κB → ↓ Cytokines → ↓ Microglial activation
↑ CREB → ↑ Synaptic proteins
This multi-target modulation suggests disease- modifying potential.
Safety Evaluation
· No nasal mucosal damage
· Stable body weight
· No hepatotoxicity markers
· Repurposing FDA-approved GLP-1 analogues
· Chronic administration feasibility
· Potential for early-stage AD intervention
· Scalable polymer system
CONCLUSION :
This thermoresponsive intranasal nano-gel platform provides sustained hippocampal GLP-1 delivery, restores insulin signaling, reduces pathological hallmarks of AD, and improves cognition. The system represents a promising translational strategy for disease modification in Alzheimer’s diseaset.
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