A new brain imaging study has confirmed that insulin, delivered through a nasal spray, successfully reaches critical memory centers in the brain—offering a vital path forward for Alzheimer’s disease treatment trials.
The research, led by Wake Forest University School of Medicine and published in Alzheimer’s & Dementia: Translational Research & Clinical Interventions, not only validated the delivery system but also uncovered important differences in insulin absorption based on cognitive status and biological sex.
Tracking Insulin’s Journey to the Brain
Using a novel radiolabeled insulin tracer and PET scans, researchers monitored how insulin traveled from the nasal cavity to the brain. Sixteen older adults—seven cognitively normal and nine with mild cognitive impairment (MCI)—received the treatment via a specialized six-spray device. Scans showed that the insulin reached 11 memory-linked regions, including the hippocampus, amygdala, and temporal lobe.
One unexpected finding: people with early cognitive decline absorbed the drug differently. While cognitively normal participants had higher uptake that peaked later, those with MCI showed earlier spikes followed by rapid clearance.
Key Findings at a Glance
- Insulin reached 11 key brain regions involved in memory and cognition.
- People with mild cognitive impairment showed faster clearance of the drug.
- In women, insulin absorption was linked to cardiovascular health and amyloid burden.
- No serious side effects were reported; only two participants experienced mild headaches.
A New Tool for Drug Delivery Validation
“This study fills a critical gap in our understanding of how intranasal insulin reaches the brain,” said Suzanne Craft, Ph.D., who led the research. “We now have a roadmap directly to the brain.”
The PET tracer, [68Ga]Ga-NOTA-insulin, provided direct visual evidence of delivery—a step that previous trials lacked. This validation may explain why some past studies showed mixed outcomes. Importantly, the nasal spray had no measurable effect on blood insulin or glucose levels, reinforcing its safety.
Sex and Vascular Health Shape Brain Uptake
The study also revealed striking differences based on vascular health, insulin levels, and sex. In cognitively normal women, higher pulse pressure (a marker of arterial stiffness) was linked to better insulin absorption. But high levels of the Alzheimer’s-related protein ptau217 were associated with lower uptake across several brain regions.
These nuanced findings suggest that future therapies may need to account for individual biological factors.
Implications for Alzheimer’s Therapies
As Alzheimer’s drug development faces scrutiny over costly anti-amyloid treatments with limited effectiveness, this approach opens doors to metabolic strategies. The Wake Forest team is already planning larger studies to explore personalized treatment models based on vascular and metabolic profiles.
We now have the tools to validate whether treatments are actually reaching their intended brain targets, Craft said. This is promising news for developing more effective and accessible treatments for Alzheimer’s disease.
Journal: Alzheimer’s & Dementia: Translational Research & Clinical Interventions
DOI: 10.1002/trc2.70123
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