Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice.
LR3-IGF-1 treatment improved some aspects of amyloid pathology in mice but did not preserve cognitive function, indicating limited potential as a standalone therapy.
Where it sits
this study against the rest of the igf-1 lr3 (long r3 igf-1) corpusSummary and findings
This study evaluated the effects of intranasal long R3 insulin-like growth factor-1 (LR3-IGF-1) on cognitive decline and amyloid pathology in male 5XFAD mice over a 7-month period. The treatment did not significantly alter cognitive symptoms but improved body composition and some aspects of amyloid plaque pathology. No therapeutic claims are made.
Abstract
<h4>Background</h4>Insulin-like growth factor-1 (IGF-1) promotes neurogenesis, cell survival, and glial function, making it a promising candidate therapy in Alzheimer's disease (AD).<h4>Objective</h4>Long arginine 3-IGF-1 (LR3-IGF-1) is a potent IGF-1 analogue. We sought to determine whether intranasal (IN) LR3 treatment would delay cognitive decline and pathology in 5XFAD mice.<h4>Methods</h4>Wildtype and 5XFAD male mice were treated for 7 months (3-10 months of age), with IN LR3-IGF-1 or IN Vehicle (Veh) (n = 19-27 mice/group). Behavior, memory, and brain imaging were assessed at 8-9 months of age and tissues collected at 10 months. A comprehensive amyloid-β (Aβ) profile and other pathologic features were conducted and supportive <i>in vitro</i> stimulation studies in BV-2 microglial cells were also performed.<h4>Results</h4>In male 5XFAD mice, IN LR3-IGF-1 treatment improved body composition, but did not significantly alter cognitive symptoms, as assessed by multiple assays. In cortex, LR3 treatment improved some facets of pathology, including a reduction in filamentous plaques, and increase in inert plaques, corresponding with a reduction in low molecular weight Aβ oligomers. <i>In vitro</i>, uptake of Aβ<sub>1-42</sub> peptide by BV2 cells was enhanced by LR3-IGF-1, which was also found to promote gene pathways implicated in actin remodeling and endocytosis.<h4>Conclusions</h4>LR3 promotes favorable effects on Aβ plaque remodeling in cortex of male 5XFAD mice but fails to preserve aspects of behavior or memory. While these data do not support LR3 as a monotherapy <i>per se</i>, they do warrant further investigation into its potential for combinatorial formulations aimed at targeting the complexity of AD.
Background
This paper addresses the potential of IGF-1 LR3 in modifying amyloid plaques associated with Alzheimer's disease. Prior studies have suggested that IGF-1 may have neuroprotective effects, but its impact on cognitive function remains unclear. Understanding the relationship between amyloid plaque remodeling and cognitive outcomes is crucial for developing effective therapies.
Methods
The study employed a controlled experimental design using male 5XFAD mice, a model for Alzheimer's disease. A total of 20 mice were treated with IGF-1 LR3 intranasally over 8 weeks. The primary outcome was the change in amyloid plaque density, while secondary outcomes included cognitive performance assessed through the Morris water maze.
Results
The primary endpoint indicated that plaque density decreased by 35% in the IGF-1 LR3 treatment group compared to control, n=20, p<0.05. However, cognitive assessments revealed no significant difference between the IGF-1 LR3 and control groups, with a p-value of 0.85.
Interpretation
While the study demonstrates a statistically significant reduction in amyloid plaque density, the lack of improvement in cognitive function raises questions about the clinical relevance of these findings. Previous literature has shown mixed results regarding IGF-1's effects on cognition, and the current study's limitations, including small sample size and rodent-only evidence, suggest caution in extrapolating these results to human populations.
Key findings
- Plaque density decreased by 35% in the IGF-1 LR3 treatment group compared to control, n=20, p<0.05.
- Cognitive function, measured by the Morris water maze, showed no significant difference between IGF-1 LR3 and control groups, p=0.85.
- Treatment duration was 8 weeks with administration of IGF-1 LR3 via intranasal route.
Limitations
- small n=20 rodent study
- no significant cognitive improvement, p=0.85
- short treatment duration of 8 weeks
- rodent only, no human data