Review: Effect of Gut Microbiota and Its Metabolite SCFAs on Radiation-Induced Intestinal Injury.

Yangyang Li,Junrui Hua,Yongqi Liu,Liying Zhang,Jinpeng He,Ting Zhou,Yiming Zhang,Tongfan Shi,Fan Niu,Gucheng Zhou,Nan Ding,Kongxi Wei

doi:10.3389/fcimb.2021.577236

Abstract

Gut microbiota is regarded as the second human genome and forgotten organ, which is symbiotic with the human host and cannot live and exist alone. The gut microbiota performs multiple physiological functions and plays a pivotal role in host health and intestinal homeostasis. However, the gut microbiota can always be affected by various factors and among them, it is radiotherapy that results in gut microbiota 1 2 dysbiosis and it is often embodied in a decrease in the abundance and diversity of gut microbiota, an increase in harmful bacteria and a decrease in beneficial bacteria, thereby affecting many disease states, especially intestine diseases. Furthermore, gut microbiota can produce a variety of metabolites, among which short-chain fatty acids (SCFAs) are one of the most abundant and important metabolites. More importantly, SCFAs can be identified as second messengers to promote signal transduction and affect the occurrence and development of diseases. Radiotherapy can lead to the alterations of SCFAs-producing bacteria and cause changes in SCFAs, which is associated with a variety of diseases such as radiation-induced intestinal injury. However, the specific mechanism of its occurrence is not yet clear. Therefore, this review intends to emphasize the alterations of gut microbiota after radiotherapy and highlight the alterations of SCFAs-producing bacteria and SCFAs to explore the mechanisms of radiation-induced intestinal injury from the perspective of gut microbiota and its metabolite SCFAs.

Highlights

Gut microbiota, second genome of the human body, as the genes that it carries are about 100 times more than the human genome (Singh et al, 2017; Chassaing and Cascales, 2018; Knauf et al, 2019)
An increasing number of evidence demonstrated that radiotherapy can lead to gut microbiota dysbiosis and cause the alterations in the gut microbial communities such as the alterations of Bacteroidetes and Firmicutes counts, which disrupts intestinal homeostasis and thereby promoting the occurrence and development of various diseases
The gut microbiota metabolites such as short-chain fatty acids (SCFAs) play a pivotal role in health and disease

Summary

INTRODUCTION

Second genome of the human body, as the genes that it carries are about 100 times more than the human genome (Singh et al, 2017; Chassaing and Cascales, 2018; Knauf et al, 2019). The gut microbiota can produce a variety of small molecules and metabolites, among which short chain fatty acids (SCFAs) can connect intestinal flora and host to play a key physiological role (Xing et al, 2020). Hou et al have studied the effects of intestinal bacterial depletion on mice receiving 12Gy single-dose wholebody irradiation (TBI) They found that the use of broadspectrum antibiotics that disrupt commensal bacteria to be harmful to mammals receiving lethal TBI, indicating that the gut microbiota plays a pivotal role in the body (Hou et al, 2007). The specific classification of radiotherapy affecting the intestinal flora is still uncertain (Nam et al, 2013).The gut microbiota plays an important role in regulating immune homeostasis in the host. Patients undergoing radiotherapy resulting in cytotoxicity showed significant changes in the intestinal flora, the most common of which were the decrease of Bifidobacterium, Clostridium cluster XIVa and Faecalibacterium prausnitzii and increase of Enterobacteriaceae and Bacteroides

Sequencing Method

Findings

CONCLUSIONS AND PERSPECTIVES