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

TL;DR

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A study published in Nature Communications found that the gut bacterial molecule imidazole propionate (ImP) was linked to Alzheimer’s-related biological markers and faster cognitive decline in a cohort of nearly 1,200 people. Experiments in mice also associated ImP reaching the brain with increased abnormal amyloid and tau; whether lowering ImP could prevent or slow dementia in people remains unknown.

Researchers report that imidazole propionate (ImP), a molecule produced by some gut bacteria, was associated with Alzheimer’s-related brain changes in mice and with faster cognitive decline among people followed in a study of nearly 1,200 participants. The findings, published in Nature Communications, point to a possible research target but do not establish that ImP causes Alzheimer’s disease in people.

The University of Wisconsin-Madison-led team studied ImP because certain intestinal bacteria produce it while using histidine, an amino acid found in many foods. ImP levels vary between people. The researchers say bacteria capable of producing the molecule are common, though they are not highly abundant in most people. After formation in the gut, ImP can enter the bloodstream and reach other parts of the body.

In mouse experiments, the researchers found that ImP reaching the brain was associated with increased accumulation of abnormal beta-amyloid and tau, proteins linked to Alzheimer’s disease. The team also analyzed blood samples from almost 1,200 people enrolled in the Wisconsin Registry for Alzheimer’s Prevention and studies through the Wisconsin Alzheimer’s Disease Research Center. Participants with higher blood ImP had more biological markers associated with abnormal proteins and impaired neuron function.

Because participants had taken cognitive tests over time, researchers compared ImP concentrations with changes in thinking and memory. Those with the highest ImP levels experienced faster cognitive decline, the team reported. The study also identified a genetic variation associated with substantially higher blood ImP; about 43% of participants carried it. The researchers suspect the variation may affect how effectively the kidneys clear ImP, but that explanation remains a hypothesis.

A Possible Target Beyond Diet

The findings suggest a potential connection between the gut microbiome and brain health that researchers can investigate at the level of a specific molecule. If further work confirms that ImP contributes to disease processes, lowering its levels could become a possible avenue for prevention or treatment research. The study does not show that an ImP-lowering intervention works, or that changing gut bacteria will prevent dementia.

The researchers caution against treating food avoidance as an established response. Gut bacteria produce ImP while metabolizing histidine, which is essential to human health and present in many foods, particularly protein-rich foods. Barbara Bendlin of UW-Madison said that improving diet may help generally, but reducing ImP is not as simple as eliminating eggs or red meat. The team instead raises the possibility of developing treatments that lower ImP more specifically.

From Gut Differences to ImP

Nearly a decade before this report, a team led by UW-Madison researchers Barbara Bendlin and Federico Rey found that the mix of microorganisms in the intestines differed between people with Alzheimer’s disease and healthy individuals. The group has since investigated whether gut-related differences might be connected to changes in the brain.

ImP had already been linked in previous research to type 2 diabetes and coronary artery disease. The new study extends the question to dementia, combining mouse experiments with human blood measurements and cognitive testing. Scientists from the University of California, Los Angeles, and the University of Gothenburg also contributed. The research received support from the Wisconsin Partnership Program, the National Institutes of Health and the U.S. Department of Agriculture.

“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

Cause and Treatment Still Unproven

The human findings show an association between blood ImP levels, biological markers and cognitive decline; they do not establish that ImP caused those changes. The reported mouse results add experimental evidence, but effects in animals do not by themselves show what will happen in people. The study report does not establish whether lowering ImP would reduce Alzheimer’s risk or slow decline.

It is also unclear how much of the difference in people’s ImP levels comes from bacterial production, kidney clearance, genetics or other factors. The proposed kidney explanation for the genetic association requires further testing. The report does not identify a proven diet, drug or other intervention for reducing ImP.

Testing Ways to Lower ImP

The next research question is whether ImP directly contributes to disease-related changes in people and whether its concentration can be lowered safely. The researchers suggest that a targeted inhibitor could be investigated, but no such treatment was established by this study. Further studies would need to test both the biological mechanism and whether changing ImP levels alters cognitive or disease outcomes.

For now, the result is a research lead, not clinical guidance. The source report does not describe a confirmed next trial or treatment timeline, and it provides no basis for people to restrict histidine-containing foods to reduce Alzheimer’s risk.

Key Questions

What is imidazole propionate?

Imidazole propionate, or ImP, is a molecule produced by certain gut bacteria as they use histidine, an amino acid. It can enter the bloodstream after being produced in the gut.

Does this study prove that ImP causes Alzheimer’s disease?

No. The human results show that higher blood ImP was associated with Alzheimer’s-related biological markers and faster cognitive decline. The study does not prove that ImP causes Alzheimer’s in people.

Should people avoid eggs or red meat to lower ImP?

The study does not support avoiding particular foods as a way to prevent Alzheimer’s. Histidine is essential and occurs in many foods; the researchers say reducing ImP through diet alone may not be straightforward.

Could a treatment that lowers ImP prevent dementia?

That is a possibility for future research, not a demonstrated benefit. The researchers propose investigating targeted ways to lower ImP, but this study did not test an ImP-lowering treatment or show that it prevents dementia.

Source: rss