Intestinal Microbiota in Early Life and Its Implications on Childhood Health

Abstract

Trillions of microbes reside in the human body and participate in multiple physiological and pathophysiological processes that affect host health throughout the life cycle. The microbiome is hallmarked by distinctive compositional and functional features across different life periods. Accumulating evidence has shown that microbes residing in the human body may play fundamental roles in infant development and the maturation of the immune system. Gut microbes are thought to be essential for the facilitation of infantile and childhood development and immunity by assisting in breaking down food substances to liberate nutrients, protecting against pathogens, stimulating or modulating the immune system, and exerting control over the hypothalamic-pituitary-adrenal axis. This review aims to summarize the current understanding of the colonization and development of the gut microbiota in early life, highlighting the recent findings regarding the role of intestinal microbes in pediatric diseases. Furthermore, we also discuss the microbiota-mediated therapeutics that can reconfigure bacterial communities to treat dysbiosis.

Keywords: Diseases; Early life; Gut–brain axis; Immunity; Intestinal microbiota; Microbiota manipulation.

Figure 1

Factors shaping the intestinal microbiota during early life and development The presence of microbes in the placenta and amniotic fluid suggests colonization of the fetus in utero with a Proteobacteria-dominated microbiome. During the neonatal period, gestational age and the mode of delivery influence the microbial colonization in the newborn. Changes in age and feeding mode, family lifestyle, geographical location, genetics of the infant, as well as the use of antibiotics further configure the microbiome in early life. The microbiota becomes more diverse over time, and the dominant microbes are Actinobacteria and Proteobacteria.

Figure 2

Schematic presentation of the relationship between the gut microbiome and the brain–gut axis The intestinal microbiota is involved in stimulating or modulating the gut immune system and exerting control over the hypothalamic–pituitary–adrenal axis indirectly. The dysbiosis of the intestinal microbiota is thought to be responsible for a series of pediatric diseases, including necrotizing enterocolitis, late-onset sepsis, eczema, asthma, food allergy, T1DM, obesity, irritable bowel syndrome, inflammatory bowel disease, and neuropsychiatric disorders. T1DM, type 1 diabetes mellitus.