New Study Confirms Gut Microbiome’s Role in Alzheimer’s Disease
In a groundbreaking study, researchers have finally confirmed the role of the gut microbiome in the development of Alzheimer’s disease. Utilizing gut microbiota transplants, an international team of scientists demonstrated that memory impairments associated with Alzheimer’s can be passed on to young, healthy rats. This research also revealed a direct link between specific bacteria in the gut and cognitive decline in Alzheimer’s patients.
The findings highlight the gut microbiome as a crucial area of research for Alzheimer’s and other forms of dementia, potentially leading to new treatment approaches. Current therapeutic methods for Alzheimer’s are typically administered after the onset of cognitive symptoms. However, understanding the role of gut microbes during the early stages of dementia could open new avenues for therapy development and personalized interventions.
Recent evidence has suggested that changes in the gut microbiota could be a risk factor for Alzheimer’s. However, it was previously unclear whether these changes were merely associated with the disease or played a causal role. The new study provides confirmation that the gut microbiota indeed have a causal role in the development of Alzheimer’s symptoms.
Alzheimer’s is a devastating condition for which effective treatments are currently lacking. The study represents a significant step forward in our understanding of the disease, according to neuroscientist Sandrine Thuret from King’s College London (KCL). Thuret, along with collaborators from University College Cork (UCC), KCL, and IRCCS Saint John of God Clinical Research Centre of Bresci in Italy, aimed to investigate how the gut microbiota in Alzheimer’s patients affects brain health and behavior.
The study involved human participants, including 69 individuals with Alzheimer’s disease and 64 healthy controls. Blood samples were collected for research purposes, with some participants also providing stool samples to analyze their gut microbiota. Gut microbiota from Alzheimer’s patients were transplanted into young adult rats with depleted microbiomes, while a matching group of rats received gut microbiota from healthy control group individuals.
After the transplants, the rats underwent behavioral tests to evaluate memory performance and other traits associated with Alzheimer’s. Results showed that rats with microbiome transplants from Alzheimer’s patients exhibited impaired memory behaviors, particularly those dependent on adult hippocampal neurogenesis. Hippocampal neurogenesis refers to the production of new neurons in the hippocampus, a brain region crucial for memory and mood that is affected early in Alzheimer’s.
“The memory tests we investigated rely on the growth of new nerve cells in the hippocampus region of the brain,” explained Yvonne Nolan, a neuroscientist from UCC. “Animals with gut bacteria from people with Alzheimer’s produced fewer new nerve cells and had impaired memory.”
The study also revealed that rats with gut microbiota from Alzheimer’s patients experienced more severe impairments in hippocampal neurogenesis when the donors themselves had lower cognitive test scores. Furthermore, the researchers observed significant modifications in the rats’ hippocampal metabolome, which includes metabolites involved in cellular maintenance, growth, and normal function. These changes might contribute to the decreased growth of new neurons in the hippocampus.
While measuring hippocampal neurogenesis in living humans is challenging, laboratory experiments using human neural stem cells demonstrated that blood from Alzheimer’s patients decreased neurogenesis. Additionally, the expression levels of certain genes in the stem cells were linked to patients’ cognitive test performance and the types of bacteria present in their gut.
The study identified significant reductions in the bacteria genus Coprococcus, which is associated with healthy aging, in Alzheimer’s patients. These patients also had a higher abundance of bacteria from the Desulfovibrio genus, similar to previous research conducted in animal models of Alzheimer’s and Parkinson’s disease.
Future studies should consider evaluating other factors that could affect gut microbiota, such as health status, lifestyle, and medication history, according to the research team. The collaborative study has laid the groundwork for further research in this area, with the hope of advancing therapeutic interventions for Alzheimer’s.
The study has been published in the journal Brain.