Your Gut May Be Making A Molecule That Raises Alzheimer’s Risk

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A study published in Nature Communications links higher blood levels of imidazole propionate, a molecule made by some gut bacteria, to Alzheimer’s-related biological markers and faster cognitive decline. Mouse experiments also found changes involving amyloid and tau proteins, but the human findings do not show that ImP causes Alzheimer’s or that lowering it prevents the disease.

Researchers report that imidazole propionate (ImP), a molecule produced by some gut bacteria, may be connected to changes linked with Alzheimer’s disease. In mice, ImP reaching the brain increased the accumulation of abnormal amyloid and tau proteins; in a study of nearly 1,200 people, higher blood levels were associated with biological markers of disease and faster cognitive decline. The results suggest a possible research target, but do not establish that ImP causes Alzheimer’s or that reducing it would prevent dementia.

The study, published in Nature Communications, was led by researchers at the University of Wisconsin-Madison and included collaborators from the University of California, Los Angeles, and the University of Gothenburg. The team focused on ImP, a compound made by certain gut bacteria as they use histidine, an amino acid found in many foods. The amount people produce appears to vary: some have relatively high levels, while others have little.

In mouse experiments, the researchers found that ImP that reached the brain increased the accumulation of abnormal beta-amyloid and tau, proteins associated with Alzheimer’s disease. The report describes these changes as connected to processes that can damage neurons. The animal results offer a possible biological mechanism, but they cannot by themselves show that the same sequence causes disease in people.

The researchers also analyzed blood samples from nearly 1,200 participants in the Wisconsin Registry for Alzheimer’s Prevention and studies through the Wisconsin Alzheimer’s Disease Research Center. Higher blood ImP was associated with markers linked to abnormal proteins and impaired neuron function. Participants with the highest levels also showed faster decline on cognitive tests completed over time, according to the researchers. The report does not provide a specific rate of decline or establish that ImP was responsible for it.

A Possible Target in the Gut–Brain Link

The findings add a specific molecule to research into how the gut microbiome may relate to brain health. Nearly a decade ago, University of Wisconsin-Madison researchers Barbara Bendlin and Federico Rey reported differences in gut microorganisms between people with Alzheimer’s and healthy individuals. The new work investigates one possible connection: a bacterial product that can enter the bloodstream and, in mice, reach the brain.

If future studies show that ImP contributes to disease rather than simply tracking alongside it, lowering its levels could become a potential prevention or treatment strategy. The current results do not show that such an approach works in people. Nor do they support avoiding particular foods: histidine is essential and occurs in many foods, and the researchers say dietary restriction would not be a straightforward way to reduce ImP.

The findings may also help explain why Alzheimer’s risk differs among people. The team identified a genetic variation associated with substantially higher ImP in the blood. About 43% of study participants carried it. Researchers suspect the variation could affect how efficiently the kidneys clear ImP, but that explanation remains a hypothesis. Its association with higher ImP and prior links to Alzheimer’s risk make it a subject for further investigation, not a clinical risk test at this stage.

From Gut Bacteria to Blood

ImP is produced by certain gut bacteria during their processing of histidine. Although bacteria that make it are present in many people, Rey said they are not highly abundant in most. He noted that a microbe can affect its host without being common. Once produced, ImP can enter circulation and reach other parts of the body.

Earlier research had linked ImP to type 2 diabetes and coronary artery disease. The new study extends the question to brain changes associated with dementia. Bendlin and Rey’s team set out to investigate how differences in gut microorganisms might relate to changes in the brain. The work combines mouse experiments with blood and cognitive-test data from people, allowing the researchers to examine both a possible mechanism and associations in humans.

The research received support in part from the Wisconsin Partnership Program, the National Institutes of Health, and the U.S. Department of Agriculture. The published report lists multiple federal grant awards. Funding information describes support for the research; it does not independently establish the findings.

““Since then, we’ve been trying to figure out how this difference in the gut perhaps leads to changes in the brain.””

— Barbara Bendlin, professor of medicine at the University of Wisconsin-Madison

What the Study Cannot Yet Show

The human results show associations, not proof that ImP causes Alzheimer’s disease or speeds cognitive decline. The mouse experiments point to a possible mechanism, but whether the same effects occur in people, and at what levels of ImP, remains unclear. The report also does not establish whether high ImP precedes disease changes or partly reflects other factors.

Researchers have not shown that changing diet, gut bacteria, kidney clearance, or blood ImP levels changes a person’s risk or cognition. The proposed role of the genetic variation in kidney removal is also not confirmed. The report does not specify a tested ImP-lowering drug, a clinical threshold for high levels, or whether the findings apply equally across populations.

Testing ImP Reduction in People

The next research step is to determine whether ImP directly contributes to disease processes in people and whether safely lowering its blood levels can alter relevant outcomes. The researchers say the molecule could be a target for an inhibitor, but the study reports no such treatment trial. Further work would need to identify an approach, assess its safety, and test whether it affects Alzheimer’s-related markers or cognitive decline over time.

For now, the findings are a research lead rather than a basis for dietary changes or medical decisions. The study raises a more focused question about the gut–brain connection: whether ImP is an active contributor to disease, and whether it can be changed in a way that benefits patients.

Key Questions

What is imidazole propionate?

Imidazole propionate, or ImP, is a molecule made by some gut bacteria as they process histidine, an amino acid. It can enter the bloodstream and reach other parts of the body.

Does the study prove that ImP causes Alzheimer’s?

No. The human findings link higher blood ImP with Alzheimer’s-related markers and faster cognitive decline, while mouse experiments suggest a possible mechanism. These results do not prove that ImP causes the disease in people.

Should people avoid foods containing histidine?

The researchers do not recommend avoiding specific foods. Histidine is essential and is found in many foods, so the report says diet alone may not be a simple way to lower ImP.

Could a drug lower ImP?

The researchers propose that an inhibitor might one day reduce blood ImP levels. The study did not test such a drug or show that lowering ImP prevents Alzheimer’s or slows cognitive decline.

Source: rss