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A study published in Nature Communications links higher blood levels of imidazole propionate, a molecule made by some gut bacteria, with Alzheimer’s-related biological markers and faster cognitive decline. Mouse experiments also found brain changes after ImP exposure, but the human findings are observational and do not show that the molecule causes Alzheimer’s disease.
Researchers report that imidazole propionate (ImP), a molecule produced by some gut bacteria, is linked to Alzheimer’s-related biological markers and faster cognitive decline in people studied over time. The findings, published in Nature Communications, point to a possible gut-to-brain pathway and a potential research target, but do not establish that ImP causes Alzheimer’s disease in people.
Led by researchers at the University of Wisconsin–Madison, the study examined ImP, which certain intestinal bacteria produce while using histidine, an amino acid found in many foods. Production varies among people. The research team reports that ImP can enter the bloodstream and reach other parts of the body; earlier studies had associated it with type 2 diabetes and coronary artery disease.
In experiments with mice, the researchers found that ImP reaching the brain increased the accumulation of abnormal beta-amyloid and tau proteins. These proteins are associated with Alzheimer’s disease. The animal findings offer evidence of a possible biological mechanism, but results in mice alone cannot establish what the molecule does in human brains or whether changing its levels would alter disease risk.
The team also analyzed blood samples from nearly 1,200 people enrolled in the Wisconsin Registry for Alzheimer’s Prevention and studies through the Wisconsin Alzheimer’s Disease Research Center. Higher blood ImP was associated with biological markers tied to abnormal proteins and impaired neuron function. Participants with higher ImP levels also showed faster decline on cognitive tests over time, according to the researchers. The study additionally identified a genetic variation associated with higher blood ImP; about 43% of participants carried it.
A Possible Gut-to-Brain Pathway
The findings add a specific molecule to research into possible links between the gut microbiome and brain health. If further studies show that ImP contributes to harmful brain changes, researchers could investigate whether lowering it might help reduce Alzheimer’s risk or slow cognitive decline. That possibility is a research direction, not a proven prevention or treatment.
The genetic finding may help researchers understand why ImP levels differ between people. The team suspects the variation could affect how effectively the kidneys clear ImP from the blood, but the report presents this as a hypothesis that needs testing. Researchers say a molecule-specific approach could be more practical than trying to remove histidine from diets, since the amino acid is essential and present in many foods.
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From Gut Microbes to ImP
The study builds on work by the Wisconsin team nearly a decade ago, when researchers led by Barbara Bendlin and Federico Rey reported differences in gut microorganisms between people with Alzheimer’s and healthy individuals. Their subsequent work has sought to understand whether and how those microbial differences relate to changes in the brain.
ImP is produced by certain gut bacteria, but the researchers say those microbes are not highly abundant in most people. Its production can nevertheless vary substantially. Because the molecule can circulate beyond the intestine, it offers one possible route by which microbial activity could be associated with effects elsewhere in the body. The new research combines mouse experiments with human blood and cognitive-test data, but those lines of evidence answer different questions: the animal work probes possible effects, while the human analysis identifies associations.
Researchers cautioned against treating food restriction as an established way to lower ImP. Bendlin said that improving diet may help general health, but removing histidine-rich foods is not a simple solution because histidine is necessary for the body and occurs widely in the diet.
“Since then, we’ve been trying to figure out how this difference in the gut perhaps leads to changes in the brain.”
— Barbara Bendlin, University of Wisconsin–Madison professor of medicine
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Causation and Treatment Remain Open
The human results show an association between blood ImP and Alzheimer’s-related markers and cognitive decline; they do not prove that ImP caused either outcome. The source report does not provide enough detail to determine how other factors may have affected the observed relationship, or whether reducing ImP would change an individual’s risk or symptoms.
It also remains unclear how the genetic variation affects ImP levels. The researchers suspect it may influence kidney clearance, but that mechanism has not been confirmed in the material provided. No ImP-lowering treatment is reported as available, and the study does not establish that changing diet can safely or reliably lower the molecule.
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Testing ImP as a Treatment Target
The next research question is whether the association can be confirmed and whether deliberately lowering ImP changes brain-related outcomes. The team says a specific inhibitor could be investigated as a way to reduce ImP in blood, but the report gives no timetable for such a treatment or evidence that one has been developed. Further work would need to test the proposed kidney-clearance link and establish whether findings from mice apply to people.
For now, the study is a step toward understanding a possible biological connection, not a basis for Alzheimer’s prevention advice. Researchers from the University of California, Los Angeles, and the University of Gothenburg also contributed. The work received support from the Wisconsin Partnership Program, the National Institutes of Health and the U.S. Department of Agriculture.
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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. The study reports that ImP can enter the bloodstream.
Does the study prove that ImP causes Alzheimer’s disease?
No. The human data show associations between higher blood ImP, Alzheimer’s-related biological markers and faster cognitive decline. The findings do not prove that ImP causes Alzheimer’s in people.
Should people avoid histidine-rich foods to lower Alzheimer’s risk?
The research does not establish that avoiding particular foods lowers ImP or Alzheimer’s risk. Histidine is essential and is found in many foods; the researchers said reducing it through diet is not a straightforward approach.
Is there a treatment that lowers ImP?
The report describes an ImP-lowering inhibitor as a possible future research target. It does not report an approved or available treatment that lowers ImP to prevent or slow Alzheimer’s disease.
Source: rss
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