Protective Effects of Pre- and Post-biotics on Gut Inflammation, Microbiota Diversity, Epileptogenesis, and Quality of Life in Rett Syndrome

The gastrointestinal tract is the major site of exposure to environmental molecules where 1) dietary components are chemically transformed by the microbiota, and 2) gut-derived metabolites are disseminated to all organs, including the brain. The human gut microbiota directly affects human health, and its alteration can lead to gastrointestinal abnormalities and inflammation. Indeed, accumulating clinical and experimental evidences indicate that the gut microbiota impacts behavior, modulates neurotransmitter production in the gut and brain, influences brain development and myelination patterns. Specific gut-derived metabolites, such as 4-ethylphenyl sulfate (4-EPS) and isoamylamine (IAA) are known to alter brains activity and anxiety behavior in mice and/ or promoting neural cell death leading to cognitive decline. Rett syndrome (RTT; Online Mendelian Inheritance in Man, OMIM number #312750) is a severe and progressive neurological disorder that almost exclusively affects females with an incidence of ~1:10,000 live births. Loss-of-function mutations of the X-linked methyl-CpG binding protein 2 (MeCP2) gene is the major cause (approximately 90 %) of classical cases of RTT. Although a rare disorder, RTT represents a leading cause of severe cognitive impairment in the female gender. Affected individuals commonly show a period of apparent early normal development, followed by regression of hand and/or communication skills, and subsequent development of hand stereotypies, while gait is often abnormal in those who are learning to walk.

Despite a wide phenotypic variability, RTT is commonly associated with epilepsy, sleep disturbances, and gastrointestinal dysfunction thus suggesting a link between RTT's gastrointestinal abnormalities and the gut microbiota.

RTT is associated with a dysbiosis of both the bacterial and fungal component of the gut microbiota, suggesting that MeCP2 loss-of-function can favour the establishment of a peculiar microbial community with altered production of short chain fatty acids (SCFAs) possibly contributing to the RTT gastrointestinal physiopathology.

Modulation of the systemic inflammatory response using pre- and post-biotics is advocated as a possible global therapeutic approach in neurological diseases such as Alzheimer's dementia.

Alpha-lactalbumin (ALAC), is the predominant whey protein in human milk, provides essential amino acids for protein synthesis in the developing neonates. Its supplementation in adults are associated with improved cognition, better memory and sleep. The bioactive properties of ALAC relate to antimicrobial activity, pre-biotic features and epithelial restoration via selective apoptosis activity. Moreover, the antibacterial peptides released from ALAC during digestion can exert immunostimulatory effects inducing phagocytic activity. Overall, ALAC shows reduction of inflammation and oxidative stress status as well as improvement of insulin resistance and increase in the synthesis of brain serotonin, a central nervous system neurotransmitter with well-known antiepileptic activity.