Abstract
Differentiation of the digestive tube and formation of the gut unit as a whole, are regulated by environmental factors through epigenetic modifications which enhance cellular plasticity. The critical period of DNA imprinting lasts from conception until approximately the 1,000th day of human life. During pregnancy, besides agents that may directly promote epigenetic programming (e.g., folate, zinc, and choline supplementation), some factors (e.g., antibiotic use, dietary components) can affect the composition of the mother's microbiota, in turn affecting the fetal microbiome which interacts with the offspring's intestinal epithelial cells. According to available literature that confirms intrauterine microbial colonization, the impact of the microbiome and its metabolites on the genome seems to be key in fetal development, including functional gut maturation and the general health status of the offspring, as well as later on in life. Although the origin of the fetal microbiome is still not well-understood, the bacteria may originate from both the vagina, as the baby is born, as well as from the maternal oral cavity/gut, through the bloodstream. Moreover, the composition of the fetal gut microbiota varies depending on gestational age, which in turn possibly affects the regulation of the immune system at the barrier between mother and fetus, leading to differences in the ability of microorganisms to access and survive in the fetal environment. One of the most important local functions of the gut microbiota during the prenatal period is their exposure to foreign antigens which in turn contributes to immune system and tissue development, including fetal intestinal Innate Lymphoid Cells (ILCs). Additional factors that determine further infant microbiome development include whether the infant is born premature or at term, the method of delivery, maternal antibiotic use, and the composition of the mother's milk, among others. However, the latest findings highlight the fact that a more diverse infant gut microbiome at birth facilitates the proliferation of stem cells by microbial metabolites and accelerates infant development. This phenomenon confirms the unique role of microbiome. This review emphasizes the crucial perinatal and postnatal factors that may influence fetal and neonatal microbiota, and in turn gut maturation.
Highlights
From the 3rd week of human embryogenesis, the digestive tube starts differentiating, leading to the formation of epithelial cells and eventually into the structural and functional gut unit, along with the development of the enteric nervous system in the weeks to follow [1]
It should be emphasized that the gut microbiota is a local community of organisms, but should be considered as an active “organ” which provides the host with metabolic, trophic, and immunological benefits [9]
After delivery a unique interaction or symbiotic relationship develops between the microbiome and host, which is necessary for survival
Summary
From the 3rd week of human embryogenesis, the digestive tube starts differentiating, leading to the formation of epithelial cells and eventually into the structural and functional gut unit (intestinal villi and crypts), along with the development of the enteric nervous system in the weeks to follow [1]. Besides for the wellknown genetic and transcription factors which directly influence organogenesis, the early colonization of the gut with microbiota is pivotal in the development of a functional intestine and in the general health status of the infant, as well as that of the human in adult life. The gut microbiome provides us with both genetic and metabolic agents that we have not been required to evolve on our own, including the synthesis of various inaccessible nutrients [3]. We emphasize the role of the gut microbiota in the transformation of the “dead” food consumed by the host into “living integrated food,” with immunological and nutritional benefits for the host
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