Alzheimer's disease and gut microbiota: link confirmed

Alzheimer's disease is a degenerative disease of the CNS and is the most common cause of dementia whose causes are still unknown. Still incurable, it directly affects nearly one million people in Europe with heavy repercussions for families who have to care for their loved ones.

In recent years, the scientific community has observed a close correlation between the composition of the gut microbiota and the appearance of amyloid plaques in the brain, characteristic of Alzheimer's disease.

A recent study published in the international journal JAD (Journal of Alzheimer's Disease) clearly showed this correlation. The study was conducted by a team of Italian researchers-Department of Chemical Sciences, University of Naples Federico II-, I.B.B.-. C.N.R. Naples, SDN Research Center-Naples, Fatebenefratelli National Research and Treatment Center for Alzheimer's and Psychiatric Diseases in Brescia in collaboration with Prof. Frisoni, director of the HUG memory center in Geneva, a professor of geriatrics at the Swiss University, has been studying the connections between the gut microbiota and neurodegenerative diseases in the elderly for many years.

This study confirmed the correlation in humans between an imbalance in the gut microbiota and the development of amyloid plaques in the brain, which are at the origin of the neurodegenerative disorders characteristic of Alzheimer's disease. In fact, proteins produced by certain gut bacteria, identified in patients' blood, could alter the interaction between the immune and nervous systems and trigger the disease. The results the scientists arrived at allow them to hypothesize new preventive strategies based on modulating the microbiota of people at risk.

The results of the clinical trial highlighted that the malfunctioning (or alteration of the basal composition) of the gut microbiota can contribute with a high probability to interfere with amyloid plaques in the brain and accelerate their progressive deterioration causing the onset of the disease in patients. In particular, the substances and compounds responsible for this irreversible process were found to be short-chain fatty acids and lipopolysaccharides.

It is known that patients with overt Alzheimer's disease have altered intestinal flora, poor bacterial diversity and abnormal production of short-chain free fatty acids. These molecules, as reported extensively in the literature, have a protective effect and anti-inflammatory action at both enteric and brain levels.

This study involved patients aged 65-85 years, one group with already diagnosed Alzheimer's disease, a second with milder symptoms, (memory loss) and a third without obvious neurodegenerative problems. Among the diagnostic investigations performed, Pet Imaging showed that the subjects with A.D. had numerous amyloid plaques in the brain while the appearance of pro-inflammatory molecules, lipopolysaccharides and altered production of short-chain fatty acids were observed in the blood. For these acids, dosed appropriately, it was clearly verified that high levels of acetic acid and valeric acid are associated with increased amyloid deposits in the brain while high levels of butyric acid have an anti-inflammatory and protective effect.

These results help us to better understand some aspects of the disease, an aid to prevention can come from diet, a diet particularly rich in fiber, adequately supplemented by pre and probiotic supplements can promote the development of good bacteria in the gut and strengthen immune defenses.

These results again reveal the fundamental role that the gut microbiota and microbiome play in the onset of certain diseases, the causes of which are unfortunately not yet well understood. Further studies will be conducted to try to modulate the production of short-chain fatty acids, thus averting the onset of this tremendous disease.

 

Keywords: brain amyloidosis, inflammation, lipopolysaccharide, microbiota, short chain fatty acids

Bibliography
Moira Marizzoni, Annamaria Cattaneo, Peppino Mirabelli, Cristina Festari, Nicola Lopizzo, Valentina Nicolosi, Elisa Mombelli, Monica Mazzelli, Delia Luongo, Daniele Naviglio, Luigi Coppola, Marco Salvatore, Giovanni B Frisoni, Short-Chain Fatty Acids and Lipopolysaccharide as Mediators Between Gut Dysbiosis and Amyloid Pathology in Alzheimer's Disease, Journal of Alzheimer's Disease, 78(2), 683-697, 2020.

DOI: 10.3233/JAD-200306