Swiss and Italian scientists have demonstrated a correlation between the intestinal microbiota and the appearance of amyloid plaques in the brain, typical of Alzheimer’s disease, which is the most common cause of dementia.
Still incurable, this pathology directly affects almost one million people in Europe, and indirectly millions of family members, as well as society as a whole. In recent years, the scientific community has suspected that the gut microbiota plays a role in the development of the disease.
According to this new work, published in the Journal of Alzheimer’s Disease, proteins produced by certain intestinal bacteria, identified in the blood of patients, could indeed modify the interaction between the immune and nervous systems and trigger the disease. These results make it possible to envisage new prevention strategies based on the modulation of the microbiota of people at risk.
“We measured amyloid deposition and then quantified the presence in their blood.”
“We have already shown that the composition of the gut microbiota in patients with Alzheimer’s disease was altered compared to people without such disorders. Their microbiota has indeed a reduced microbial diversity, with an overrepresentation of certain bacteria and a strong decrease of other microbes. Moreover, we have also discovered an association between an inflammatory phenomenon detected in the blood, certain gut bacteria and Alzheimer’s disease; hence the hypothesis we wanted to test here: could inflammation in the blood be a mediator between the microbiota and the brain?” explains one of the authors, Giovanni Frisoni.
Gut bacteria can influence brain function and promote neurodegeneration through several pathways: indeed, they can influence the regulation of the immune system and, consequently, they can modify the interaction between the immune system and the nervous system.
Lipopolysaccharides, a protein located in the membrane of bacteria with proinflammatory properties, have been found in amyloid plaques and around the vessels of the brain of people with Alzheimer’s disease. In addition, the gut microbiota produces metabolites – in particular some short-chain fatty acids – which, having neuroprotective and anti-inflammatory properties, directly or indirectly affect brain function.
“To determine whether inflammatory mediators and bacterial metabolites constitute a link between gut microbiota and amyloid pathology in Alzheimer’s disease, we studied a cohort of 89 people aged 65 to 85 years. Some suffered from Alzheimer’s disease or other neurodegenerative diseases that caused similar memory problems, while others had no memory problems at all. Using PET imaging, we measured their amyloid deposition and then quantified the presence in their blood of several markers of inflammation and proteins produced by intestinal bacteria, such as lipopolysaccharides and short-chain fatty acids,” highlights another of the authors, Moira Marizzoni.
Dr. Mansi Shah
Functional Wellness Network