Microbiota in Health and Diseases

*Human Microbiome*

[65] Ramachandran G, Bikard D. Editing the microbiome the CRISPR way. Philosophical

[66] Burstein D, Harrington LB,

2019;**374**(1772):20180103

Transactions of the Royal Society B.

Strutt SC, Probst AJ, Anantharaman K, Thomas BC, et al. New CRISPR—Cas systems from uncultivated microbes. Nature. 2017;**542**(7640):237-241

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**Chapter 2**

**Abstract**

"Dialogue" between the Human

In conditions of severe gut dysbiosis, there is a risk of developing diseases of the host organism in general and of the brain in particular, as evidenced by a growing number of studies. This chapter focuses on several groups of low-molecular-weight compounds that originate primarily from the gut microbiota. It discusses the results of experimental and clinical studies on the effect of microbial metabolites (such as short-chain fatty acids, phenolic metabolites of tyrosine, indolic metabolites of tryptophan, trimethylamines) on the brain. Several studies have proven that the microbial metabolite profiles in the gut and serum are interlinked and reflect a disruption of the gut microbial community. Using 16S ribosomal RNA gene sequencing, it was found that the gut microbiota of patients with positive or negative dynamics of neurological status differ taxonomically. The chapter also presents data obtained from animal germ-free (GF) models. Many researchers would like to consider the gut microbiota as a new therapeutic target, including for the treatment of brain diseases, stroke prevention, reduction of neuroinflammation, and more

Microbiome and the Brain

*Natalia Beloborodova and Andrey Grechko*

successful neurorehabilitation of patients.

critical ill patients, neurorehabilitation

over the past 10 years (**Figure 1**).

and in patients with various diseases.

**1. Introduction**

**Keywords:** human microbiome, microbial metabolites, brain damage, gut microbiota dysbiosis, mental health, Alzheimer's disease, autism, stroke,

The human gut microbiome is a community of trillions of microorganisms that

Today, modern technologies allow us to identify hundreds of types of microorganisms in the human gut. Various microbial metabolites are also available for measurement in biological material samples, including feces, blood, urine, cerebrospinal fluid (CSF), and so on [1–3]. Thus, the possibilities of determining microbiota metabolites have expanded to studying their role both in healthy people

produce and use many molecules of microbial origin. Normally, the epithelial– immune–gut barrier supports homeostasis in the host body. The importance of the function of the gut microbiota for the host organism allows us to consider it as a large but "invisible organ" [1]. In conditions of severe gut dysbiosis, there is a risk of developing diseases of the host organism in general and of the brain in particular, as evidenced by a growing number of studies [2, 3]. The relevance of studying the relationship between the human microbiome and the brain is confirmed by a 20-fold increase in the number of publications on this topic in the PubMed database
