A chemical compound produced by certain gut bacteria can increase the risk of developing Alzheimer's disease and accelerate memory decline, according to a study by researchers at the University of Wisconsin-Madison.
The scientists identified the substance as imidazole propionate, known as ImP. The compound is generated when specific intestinal bacteria metabolise histidine, an amino acid absorbed through food. The findings were published in the scientific journal Nature Communications.
Histidine is an essential amino acid found in protein-rich foods including meat, fish, eggs, dairy products, legumes, nuts, and certain grains. Because the human body cannot synthesize histidine on its own, it must be obtained through a standard daily diet to support tissue repair and metabolic function.
Impact on brain proteins and nerve cells
In laboratory experiments conducted on mice, the researchers demonstrated that ImP crosses into the brain and drives up the accumulation of beta-amyloid and tau protein. These two pathological proteins are the primary biological markers associated with Alzheimer's disease, and their buildup leads directly to the death of nerve cells.
Alzheimer's disease is a progressive neurodegenerative disorder that gradually destroys memory, thinking skills, and the ability to carry out simple tasks. It represents the most common cause of dementia among older adults globally.
To determine whether the mouse findings applied to humans, the research team evaluated data from nearly 1,200 participants enrolled in long-term observational monitoring studies.
Cognitive decline and genetic risk factors
Analysis of blood samples showed that individuals with the highest levels of ImP were more likely to display biomarkers of brain damage. Standardised cognitive tests further revealed that memory and reasoning abilities deteriorated noticeably faster in people with elevated ImP levels.
The investigators also identified a specific genetic variant present in approximately 43 percent of the population that encourages the accumulation of ImP in the human body.
The authors suggested that ImP could serve as a novel biological target for preventing Alzheimer's disease. They emphasized that removing histidine from the diet entirely is impossible because the amino acid is vital for human health.
Potential future treatments
Instead of dietary restrictions, researchers noted that medical treatments developed in the future could focus on reducing ImP levels in the blood.
The research builds on previous scientific findings showing that restricting sugar intake during the first 1,000 days of a child's life reduces the long-term risk of developing Alzheimer's disease.
