The prevalence of non-alcoholic fatty liver disease (NAFLD) is increasing annually, and emerging evidence suggests that the gut microbiota plays a causative role in the development of NAFLD. However, the role of gut microbiota in the development of NAFLD remains unclear and warrants further investigation. Thus, C57BL/6J mice were fed a high-fat diet (HFD), and we found that the HFD significantly induced obesity and increased the accumulation of intrahepatic lipids, along with alterations in serum biochemical parameters. Moreover, it was observed that the HFD also impaired gut barrier integrity. It was revealed via 16S rRNA gene sequencing that the HFD increased gut microbial diversity, which enriched Colidextribacter, Lachnospiraceae-NK4A136-group, Acetatifactor, and Erysipelatoclostridium. Meanwhile, it reduced the abundance of Faecalibaculum, Muribaculaceae, and Coriobacteriaceae-UCG-002. The predicted metabolic pathways suggest that HFD enhances the chemotaxis and functional activity of gut microbiota pathways associated with flagellar assembly, while also increasing the risk of intestinal pathogen colonization and inflammation. And the phosphotransferase system, streptomycin biosynthesis, and starch/sucrose metabolism exhibited decreases. These findings reveal the composition and predictive functions of the intestinal microbiome in NAFLD, further corroborating the association between gut microbiota and NAFLD while providing novel insights into its potential application in gut microbiome research for NAFLD patients.

Intestinal microbiota plays a crucial role in immune development and disease progression in mammals from birth onwards. The gastrointestinal tract of newborn mammals is rapidly colonized by microbes with tremendous biomass and diversity. Understanding how this complex of segmental communities evolves in different gastrointestinal sites over time has great biological significance and medical implications. However, most previous reports examining intestinal microbiota have focused on fecal samples, a strategy that overlooks the spatial microbial dynamics in different intestinal segments. Using intestinal digesta from six intestinal segments (duodenum, jejunum, ileum, cecum, colon and rectum) of newborn piglets, we herein conducted a large-scale 16S rRNA gene sequencing-based study to characterize the segmental dynamics of porcine gut microbiota at eight postnatal intervals (days 1, 7, 14, 21, 28, 35, 120 and 180). A total of 4,465 OTUs were obtained and showed that the six intestinal segments could be divided into three parts; in the duodenum-jejunum section, the most abundant genera included Lactobacillus and Bacteroides; in the ileum, Fusobacterium and Escherichia; and in the cecum-rectum section, Prevotella. Although the microbial communities of the piglets were similar among the six intestinal segments on postnatal day 1, they evolved and quickly differentiated at later intervals. An examination of time-dependent alterations in the dominant microbes revealed that the microbiome in the large intestine was very different from and much more stable than that in the small intestine. The gut microbiota in newborn piglets exhibited apparent temporal and spatial variations in different intestinal segments. The database of gut microbes in piglets could be a referable resource for future studies on mammalian gut microbiome development in early host growth phases.

Defects in gut barrier function are implicated in gastrointestinal (GI) disorders like inflammatory bowel disease (IBD), as well as in systemic inflammation. With the increasing incidence of IBD worldwide, more attention should be paid to dietary interventions and therapeutics with the potential to boost the natural defense mechanisms of gut epithelial cells. The current study aimed to investigate the protective effects of Limosilactobacillus reuteri ATCC PTA 4659 in a colitis mouse model and delineate the mechanisms behind it. Wild-type mice were allocated to the control group; or given 3% dextran sulfate sodium (DSS) in drinking water for 7 days to induce colitis; or administered L. reuteri for 7 days as pretreatment; or for 14 days starting 7 days before subjecting to the DSS. Peroral treatment with L. reuteri improved colitis severity clinically and morphologically and reduced the colonic levels of Tumor necrosis factor-α (TNF-α) (Tnf), Interleukin 1-β (Il1β), and nterferon-γ (Ifng), the crucial pro-inflammatory cytokines in colitis onset. It also prevented the CD11b⁺Ly6G⁺ neutrophil recruitment and the skewed immune responses in mesenteric lymph nodes (MLNs) of CD11b⁺CD11c⁺ dendritic cell (DC) expansion and Foxp3⁺CD4⁺ T-cell reduction. Using 16S rRNA gene amplicon sequencing and RT-qPCR, we demonstrated a colitis-driven bacterial translocation to MLNs and gut microbiota dysbiosis that were in part counterbalanced by L. reuteri treatment. Moreover, the expression of barrier-preserving tight junction (TJ) proteins and cytoprotective heat shock protein (HSP) 70 and HSP25 was reduced by colitis but boosted by L. reuteri treatment. A shift in expression pattern was also observed with HSP70 in response to the pretreatment and with HSP25 in response to L. reuteri-DSS. In addition, the changes of HSPs were found to be correlated to bacterial load and epithelial cell proliferation. In conclusion, our results demonstrate that the human-derived L. reuteri strain 4659 confers protection in experimental colitis in young mice, while intestinal HSPs may mediate the probiotic effects by providing a supportive protein–protein network for the epithelium in health and colitis.

Tight junction proteins are important for the maintenance and repair of the intestinal mucosal barrier. The present study investigated relationships among tight junction protein gene expression, porcine epidemic diarrhea virus (PEDV) infection, and intestinal mucosal morphology in piglets. We compared the expression of six tight junction proteins (ZO-1, ZO-2, Occludin, Claudin-1, Claudin-4, and Claudin-5) between seven-day-old piglets infected with PEDV and normal piglets, as well as in PEDV-infected porcine intestinal epithelial cells (IPEC-J2). We also evaluated differences in mucosal morphology between PEDV-infected and normal piglets. The expression of six tight junction protein genes was lower in PEDV-infected piglets than in the normal animals. The expression of ZO-1, ZO-2, Occludin, and Claudin-4 in the intestine tissue was significantly lower (p⟨0.05) in PEDV-infected than in normal piglets. The expression of Claudin-5 in the jejunum was significantly lower in PEDV-infected piglets than in the normal animals (p⟨0.01). The expression of Claudin-1 and Claudin-5 genes in the ileum was significantly higher in PEDV-infected piglets than in normal piglets (p⟨0.01). Morphologically, the intestinal mucosa in PEDV-infected piglets exhibited clear pathological changes, including breakage and shedding of intestinal villi. In PEDV-infected IPEC-J2 cells, the mRNA expression of the six tight junction proteins showed a downward trend; in particular, the expression of the Occludin and Claudin-4 genes was significantly lower (p⟨0.01). These data suggest that the expression of these six tight junction proteins, especially Occludin and Claudin-4, plays an important role in maintaining the integrity of the intestinal mucosal barrier and resistance to PEDV infection in piglets.