PATH TO PEPTIDES GLP-1 AND THE BRAIN

CAN DIABETES DRUGS PROTECT AGAINST DEMENTIA?

One study showed a 45% lower dementia risk. Then a major trial failed. The full story is more interesting than either headline.

A STUDY OF OVER 100,000 PATIENTS FOUND THAT PEOPLE TAKING GLP-1 DRUGS HAD UP TO A 45% LOWER RISK OF DEVELOPING DEMENTIA. THEN A MAJOR CLINICAL TRIAL FOUND NO BENEFIT. SO WHICH IS IT?

The answer may be more nuanced — and more hopeful — than either headline suggests. The science of how GLP-1 drugs interact with the brain is still unfolding, and what researchers are learning
is fascinating.

WHY THIS MATTERS

Alzheimer’s disease affects over 6.9 million Americans and is the 7th leading cause of death in the United States.1 By 2060, that number is expected to nearly double.

Despite decades of research and billions of dollars invested, there are still very few effective treatments. The drugs that do exist (like lecanemab) only slow decline modestly and come with serious side effects.2

That’s why any hint that an existing, widely-used medication might protect the brain gets major attention. And GLP-1 drugs have generated some very intriguing signals.

HE SCIENCE: GLP-1 RECEPTORS IN YOUR BRAIN

Here’s something that surprised even scientists: your brain is loaded with GLP-1 receptors. They’re especially dense in areas critical for memory and learning — the hippocampus, cortex, and hypothalamus.3

Think of it this way: GLP-1 isn’t just a “gut hormone.” It’s also a brain chemical. Your body naturally makes GLP-1 in both your intestines AND in specific brain cells. The brain version helps with learning, memory, and protecting neurons from damage.4

Researchers believe GLP-1 drugs may protect the brain through several pathways:

Reducing brain inflammation: Chronic inflammation in the brain (called neuroinflammation) is a major driver of Alzheimer’s and Parkinson’s disease. GLP-1 drugs appear to calm this inflammatory response.5

Improving insulin signaling: The brain needs insulin to function properly. Alzheimer’s is sometimes called “type 3 diabetes” because brain insulin resistance appears to play a role. GLP-1 drugs may help restore healthy insulin signaling in brain cells.6

Protecting neurons: Lab studies show GLP-1 drugs can protect brain cells from the toxic effects of amyloid plaques — the protein clumps that build up in Alzheimer’s disease.7

Did You Know? Alzheimer’s disease is sometimes called “type 3 diabetes” by researchers because problems with insulin signaling in the brain appear to play a key role in the disease. That’s one
reason diabetes drugs caught neuroscientists’ attention.

WHAT THE RESEARCH SAYS

THE GOOD NEWS: LARGE OBSERVATIONAL STUDIES

Multiple large studies have found promising associations between GLP-1 drug use and lower dementia risk:

A study of over 120,000 patients with type 2 diabetes, published in Alzheimer’s & Dementia, found GLP-1 drug users had a 35% lower risk of developing Alzheimer’s and a 45% lower risk of ascular
dementia compared to those taking other diabetes medications.8

A 2024 meta-analysis combining data from multiple studies confirmed the pattern: GLP-1 drug users consistently showed lower rates of cognitive decline and dementia diagnoses.9

THE SETBACK: THE EVOKE TRIAL

In late 2024, the EVOKE trial — a randomized controlled trial of semaglutide in 1,840 patients with early Alzheimer’s disease — reported that the drug did not slow cognitive decline compared to
placebo over 2 years.10

This was disappointing. But researchers were quick to point out an important detail: the trial studied people who already had Alzheimer’s. It’s possible that GLP-1 drugs work as prevention, not
treatment.

THE KEY QUESTION:
PREVENTION VS. TREATMENT

Think of it like sunscreen. Sunscreen protects your skin if you apply it before sun damage happens. But it can’t reverse a sunburn that’s already there.

Many researchers now believe GLP-1 drugs may work the same way for the brain — protecting healthy neurons from damage over years or decades, rather than repairing neurons that are already damaged.11

New trials are now being designed to test this “prevention” hypothesis by studying GLP-1 drugs in people at risk for dementia but who haven’t been diagnosed yet.

BEYOND ALZHEIMER’S: PARKINSON’S DISEASE

The brain research doesn’t stop at Alzheimer’s. A Phase 2 trial found that the GLP-1 drug exenatide (Byetta) showed neuroprotective effects in Parkinson’s disease patients. After 1 year of treatment, patients on exenatide maintained better motor function than those on placebo.12

A larger Phase 3 trial (called NeuroPAS) is now underway to confirm these findings. If successful, it would be the first drug shown to slow the progression of Parkinson’s disease — not just treat symptoms.13

WHAT TO KNOW

KEY TAKEAWAYS:

• GLP-1 receptors are found throughout the brain, especially in memory regions.
• Large studies link GLP-1 drug use to 35-45% lower dementia risk.
• The EVOKE trial found no benefit for people who already had Alzheimer’s.
• Scientists believe these drugs may work as prevention, not treatment.
• Research in Parkinson’s disease is also showing promising early results.
• This is an active area of research — no brain-related uses are FDA-approved.
• Talk to a healthcare provider about any questions regarding brain health.

REFERENCES

1. Alzheimer’s Association. 2024 Alzheimer’s Disease Facts and Figures. Alzheimers Dement. 2024;20(5):3708-3821.
2. van Dyck CH, et al. Lecanemab in early Alzheimer’s disease. N Engl J Med. 2023;388(1):9-21.
3. Cork SC, et al. Distribution and characterisation of GLP-1 receptor expressing cells in the mouse brain. Mol Metab. 2015;4(10):718-731.
4. During MJ, et al. Glucagon-like peptide-1 receptor is involved in learning and neuroprotection. Nat Med. 2003;9(9):1173-1179.
5. Holscher C. Potential role of glucagon-like peptide-1 in the treatment of Alzheimer’s disease. CNS Drugs. 2012;26(10):871-882.
6. de la Monte SM, Wands JR. Alzheimer’s disease is type 3 diabetes — evidence reviewed. J Diabetes Sci Technol. 2008;2(6):1101-1113.
7. McClean PL, et al. The diabetes drug liraglutide prevents degenerative processes in a mouse model of Alzheimer’s disease. J Neurosci.2011;31(17):6587-6594.
8. Norgaard CH, et al. Treatment with GLP-1 receptor agonists and risk of dementia. Alzheimers Dement. 2022;8(1):e12268.
9. Cao Y, et al. GLP-1 receptor agonists and cognitive decline: systematic review and meta-analysis. Diabetes Obes Metab. 2024;26(3):1037-1048.
10. Novo Nordisk. EVOKE/EVOKE+ Phase 3 trial results for semaglutide in early Alzheimer’s disease. Press release. 2024.
11. Holscher C. Brain insulin resistance: role in neurodegenerative disease and potential for targeting. Expert Opin Investig Drugs. 2020;29(1):1-3.
12. Athauda D, et al. Exenatide once weekly versus placebo in Parkinson’s disease. Lancet. 2017;390(10103):1664-1675.
13. ClinicalTrials.gov. NeuroPAS: Phase 3 trial of exenatide for Parkinson’s disease. NCT04232969.

FOR RESEARCH AND EDUCATIONAL PURPOSES ONLY

This document is intended solely for educational purposes to increase awareness of emerging scientific research. It does not constitute medical advice and should not be used to make healthcare decisions.

Regulatory Status: GLP-1 receptor agonists are FDA-approved for type 2 diabetes and/or chronic weight management. Their use forneuroprotection, dementia prevention, or treatment of any
neurodegenerative disease is investigational and NOT FDA-approved.

All healthcare decisions should be made in consultation with qualified medical professionals.

This publication is part of an ongoing educational series designed to promote scientific literacy and awareness of developments in health research.