The Contribution of Gut Microbiota–Brain Axis in the Development of Brain Disorders

Abstract

Different bacterial families colonize most mucosal tissues in the human organism such as the skin, mouth, vagina, respiratory, and gastrointestinal districts. In particular, the mammalian intestine hosts a microbial community of between 1,000 and 1,500 bacterial species, collectively called “microbiota.” Co-metabolism between the microbiota and the host system is generated and the symbiotic relationship is mutually beneficial. The balance that is achieved between the microbiota and the host organism is fundamental to the organization of the immune system. Scientific studies have highlighted a direct correlation between the intestinal microbiota and the brain, establishing the existence of the gut microbiota–brain axis. Based on this theory, the microbiota acts on the development, physiology, and cognitive functions of the brain, although the mechanisms involved have not yet been fully interpreted. Similarly, a close relationship between alteration of the intestinal microbiota and the onset of several neurological pathologies has been highlighted. This review aims to point out current knowledge as can be found in literature regarding the connection between intestinal dysbiosis and the onset of particular neurological pathologies such as anxiety and depression, autism spectrum disorder, and multiple sclerosis. These disorders have always been considered to be a consequence of neuronal alteration, but in this review, we hypothesize that these alterations may be non-neuronal in origin, and consider the idea that the composition of the microbiota could be directly involved. In this direction, the following two key points will be highlighted: (1) the direct cross-talk that comes about between neurons and gut microbiota, and (2) the degree of impact of the microbiota on the brain. Could we consider the microbiota a valuable target for reducing or modulating the incidence of certain neurological diseases?

Nutraceuticals and Cancer: Potential for Natural Polyphenols

“…If polyphenolic compounds cannot be absorbed in this district, they reach the colon where they are metabolized by the microbiota. It is, therefore, likely that an alteration of the gut microbiota will contribute to a reduction of polyphenol absorption and worsening of human health [225,226]. However, it should also be noted that polyphenols could have beneficial effects on the composition of the gut microbiota, acting as prebiotics [227].…”

The Potential of Probiotics in the Treatment of Schizophrenia

“…The bidirectional communication between the gastrointestinal tract and central nervous system through psychobiotics is called the microbiota-gut-brain axis [5]. It has been emphasized that abnormalities in the gut microbiota are associated with the onset of certain neuropsychiatric disorders, such as depression, anxiety disorders, autism spectrum disorders, multiple sclerosis, and Parkinson's disease [6]. These diseases are always caused by changes in brain neurons, and the mechanisms are assumed to include direct crosstalk between the gut microbiota and the central nervous system, and the effects of substances produced by the microbiota on the development of neural circuits.…”

Peripheral Vascular Abnormalities in Anorexia Nervosa: A Psycho-Neuro-Immune-Metabolic Connection

“…The microbiota supports the ENS formed at birth and participates in its homeostasis throughout adult life. A close correlation between the ENS and the microbiota has been demonstrated and we have to take into account the possibility of a close correlation between the dysfunction of the ENS, the microbiota, and the diseases of the central nervous system [ 62 ].…”