Gut Compound Imidazole Propionate Linked to Faster Cognitive Decline
A gut bacterial compound, imidazole propionate, is linked to faster cognitive decline and higher Alzheimer's disease biomarkers in a study of nearly 1,200 people.
Higher blood levels of the gut bacterial compound imidazole propionate (ImP) are associated with faster cognitive decline and increased Alzheimer's disease biomarkers. Researchers examined blood samples from almost 1,200 people enrolled in the Wisconsin Registry for Alzheimer's Prevention and related studies, finding that elevated ImP concentrations were linked to biological markers of abnormal proteins and impaired neuron function. ImP is produced by certain gut bacteria from histidine, an essential amino acid found in protein-rich foods, and can enter the bloodstream to reach the brain.
Past studies have linked ImP to type 2 diabetes and coronary artery disease. This new research connects it directly to Alzheimer's pathology in humans.
Genetic variation affects ImP clearance and Alzheimer's risk
About 43% of the study participants carried a genetic variant associated with substantially higher ImP levels. The genetic variation may affect how effectively the kidneys remove ImP from the blood. This same genetic variant has been previously associated with increased Alzheimer's risk in large genetic studies.
Federico Rey noted, "ImP-producing bacteria are present in a large fraction of people, but they're not very abundant in most people." The finding suggests a mechanism where reduced clearance combines with bacterial production to elevate circulating ImP.
Higher ImP levels predict faster cognitive decline
Participants with elevated ImP levels exhibited accelerated cognitive decline based on longitudinal cognitive testing. They also showed biological markers for neuron impairment. In mouse experiments, increased brain levels of ImP led to greater accumulation of beta amyloid and tau proteins, which are major hallmarks of Alzheimer's disease. The human data aligns with this, showing higher ImP blood concentrations were linked to these same pathological biomarkers.
Researchers propose blood-based treatments, not diet changes
Reducing ImP through diet alone may not be straightforward due to the essential nature of histidine. Barbara Bendlin cautioned against dietary elimination of histidine to reduce ImP, as histidine is necessary for human health and prevalent in protein-rich foods. She said, "Generally improving your diet would probably help."
Instead, researchers advocate for treatments that lower ImP levels in the bloodstream, similar to statins for cholesterol management. They suggest therapies could target ImP reduction in the bloodstream, offering a new mechanistic pathway for intervention.
