Role of the gut microbiota in inflammatory bowel disease pathogenesis: What have we learnt in the past 10 years?

Our understanding of the microbial involvement in inflammatory bowel disease (IBD) pathogenesis has increased exponentially over the past decade. The development of newer molecular tools for the global assessment of the gut microbiome and the identification of nucleotide-binding oligomerization domain-containing protein 2 in 2001 and other susceptibility genes for Crohn’s disease in particular has led to better understanding of the aetiopathogenesis of IBD. The microbial studies have elaborated the normal composition of the gut microbiome and its perturbations in the setting of IBD. This altered microbiome or “dysbiosis” is a key player in the protracted course of inflammation in IBD. Numerous genome-wide association studies have identified further genes involved in gastrointestinal innate immunity (including polymorphisms in genes involved in autophagy: ATG16L1 and IGRM), which have helped elucidate the relationship of the local innate immunity with the adjacent luminal bacteria. These developments have also spurred the search for specific pathogens which may have a role in the metamorphosis of the gut microbiome from a symbiotic entity to a putative pathogenic one. Here we review advances in our understanding of microbial involvement in IBD pathogenesis over the past 10 years and offer insight into how this will shape our therapeutic management of the disease in the coming years.

Gut microbiota absence and transplantation affect growth and intestinal functions:An investigation in a germ-free pig model

This study was conducted to investigate host-microbiota interactions and explore the effects of maternal gut microbiota transplantation on the growth and intestinal functions of newborns in a germ-free(GF)pig model.Twelve hysterectomy-derived GF Bama piglets were reared in 6 sterile isolators.Among them,6 were considered as the GF group,and the other 6 were orally inoculated with healthy sow fecal suspension as fecal microbiota transplanted(FMT)group.Another 6 piglets from natural birth were regarded as the conventional(CV)group.The GF and FMT groups were hand-fed with Co60-y-irradiated sterile milk powder,while the CV group was reared by lactating Bama sows.All groups were fed for 21 days.Then,all piglets and then were switched to sterile feed for another 21 days.Results showed that the growth performance,nutrient digestibility,and concentrations of short-chain fatty acids in the GF group decreased(P<0.05).Meanwhile,the serum urea nitrogen concentration and digesta pH values in the GF group increased compared with those in the FMT and CV groups(P<0.05).Compared with the CV group,the GF group demonstrated upregulation in the mRNA expression levels of intestinal barrier function-related genes in the small intestine(P<0.05).In addition,the mRNA abundances of intestinal development and absorption-related genes in the small intestine and colon were higher in the GF group than in the CV and FMT groups(P<0.05).The FMT group exhibited greater growth performance,lipase activity,and nutrient digestibility(P<0.05),higher mRNA expression levels of intestinal development and barrier-related genes in the small intestine(P<0.05),and lower mRNA abundances of pro-inflammatory factor in the colon and jejunum(P<0.05)than the CV group.In conclusion,the absence of gut microbes impaired the growth and nutrient digestibility,and healthy sow gut microbiota transplantation increased the growth and nutrient digestibility and improved the intestinal development and barrier function of newborn piglets,indicating the importance of intestinal microbes for intestinal development and functions.