Alzheimer's disease, whose factors are still poorly understood, still has no effective treatment. However, a hypothesis around the role of the intestinal microbiota is emerging, sparking hope for new therapeutic avenues.
Alzheimer's disease, which affects more than 35 million people around the world, is associated with memory loss, language and comprehension problems, attention and concentration problems, apraxia (loss of dexterity), and, in some cases, agnosia (problems recognizing objects or faces). Added to these cognitive symptoms, which worsen over time, are behavioral symptoms such as anxiety, apathy, irritability, sleep problems, disinhibition, and agitation.
Causes still unknown
Several genetic and environmental risk factors have been identified for the disease: hypertension, hypercholesterolemia, smoking, sedentary lifestyle, unbalanced diet, and lack of cognitive stimulation, among others. Lesions in the brain are also a well-known component of the disease, particularly the accumulation of amyloid beta plaques and neuron degeneration. However, the causes of the disease have yet to be clearly determined.
The hypothesis of intestinal microbiota
Researchers are considering whether the intestinal microbiota is involved in Alzheimer’s disease: certain proteins (amyloid peptides) produced by “negative” bacteria in the intestinal flora may favor the development of the disease. Conversely, “beneficial” bacteria may play a protective role, by slowing the formation of amyloid plaques.
Break the therapeutic deadlock
Intestinal microbiota could represent a new avenue for therapeutic research, as no current curative therapy exists for Alzheimer’s disease. Only a few medications lessen symptoms, and their effectiveness is very limited. Some researchers are, therefore, considering carrying out future work on the disease via the microbiota, through dietary changes or by ingesting probiotics.
La démence. OMS. Avril 2016. http://www.who.int/mediacentre/factsheets/fs362/fr/
Inserm. Alzheimer [en ligne]. Dossier réalisé en collaboration avec le Pr Phiippe Amouyel. Disponible à l'adresse : http://www.inserm.fr/thematiques/neurosciences-sciences-cognitives-neurologie-psychiatrie/dossiers-d-information/alzheimer
Hill JM, Lukiw WJ. Microbial-generated amyloids and Alzheimer's disease (AD). Front Aging Neurosci. 2015 ;7:9. Published 2015 Feb 10.
Wang D, Ho L, Faith J, et al. Role of intestinal microbiota in the generation of polyphenol-derived phenolic acid mediated attenuation of Alzheimer’s disease β-amyloid oligomerization. Mol Nutr Food Res 2015 ; 59 : 1025-40.
Pistollato F, Sumalla Cano S, Elio I, Masias Vergara M, Giampieri F, Battino M. Role of gut microbiota and nutrients in amyloid formation and pathogenesis of Alzheimer disease. Nutr Rev. 2016;74(10):624-634.
Bhattacharjee S. & Lukiw W. J. Alzheimer’s disease and the microbiome. Front Cell Neurosci. 2013 ; 7, 153