Mucus as Part of the Intestinal Barrier in Neurological Diseases

The objective of this paper is to review what is known about intestinal mucus in neurologic health and disease states. To set the stage, we summarize the physiology of mucus within the gastrointestinal tract and its role in gastrointestinal homeostasis and disease states. There is documentation of barrier dysfunction as well as damage to epithelial or mucosal defense mechanisms in prototypical neurological diseases, such as multiple sclerosis and Parkinson disease. The evidence is tabulated to summarize the data, and the strength of that evidence is appraised. Although there is relatively less evidence available regarding the association of abnormal mucus in these diseases, it is noted that changes in diet (such as the Western diet, emulsifiers, and lack of fiber) and specific microbial alterations, best exemplified by Akkermansia muciniphilia, result in deleterious alterations in mucin molecules or mucus (as a whole) in neurological diseases. These data suggest that further appraisal of the role of intestinal mucus and barrier may be relevant to the study of neurological diseases.