Weiwei Cheng

Functional oligosaccharides, known as prebiotics, and ordinary dietary fiber have important roles in modulating the structure of intestinal microbiota. To investigate their effects on the intestinal microecosystem, three kinds of diets containing different prebiotics were used to feed mice for 3 weeks, as follows: GI (galacto-oligosaccharides (GOS) and inulin), PF (polydextrose and insoluble dietary fiber from bran), and a GI/PF mixture (GI and PF, 1:1), 16S rRNA gene sequencing and metabolic analysis of mice feces were then conducted. Compared to the control group, the different prebiotics diets had varying effects on the structure and diversity of intestinal microbiota. GI and PF supplementation led to significant changes in intestinal microbiota, including an increase of Bacteroides and a decrease of Alloprevotella in the GI-fed, but those changes were opposite in PF fed group. Intriguing, in the GI/PF mixture-fed group, intestinal microbiota had the similar structure as the control groups, and flora diversity was upregulated. Fecal metabolic profiling showed that the diversity of intestinal microbiota was helpful in maintaining the stability of fecal metabolites. Our results showed that a single type of oligosaccharides or dietary fiber caused the reduction of bacteria species, and selectively promoted the growth of Bacteroides or Alloprevotella bacteria, resulting in an increase in diamine oxidase (DAO) and/or trimethylamine oxide (TMAO) values which was detrimental to health. However, the flora diversity was improved and the DAO values was significantly decreased when the addition of nutritionally balanced GI/PF mixture. Thus, we suggested that maintaining microbiota diversity and the abundance of dominant bacteria in the intestine is extremely important for the health, and that the addition of a combination of oligosaccharides and dietary fiber helps maintain the health of the intestinal microecosystem.

Galacto-oligosaccharides (GOS) are prebiotics that positively affect the host's gut microbiota, which is important for the health of the host. Most previous studies focused on specific flora components (e.g. Bifidobacterium and Lactobacillus); very few have investigated the relationship between flora and metabolites. Here, we used 16S rRNA analysis and metabolomics to analyze the effect of GOS on microbiota and metabolites. Results show that the abundance of Ruminococcaceae and Oscillibacter decreased significantly in GOS-fed mice. Twenty-one metabolites, including oleic acid, arachidic acid, and behenic acid, decreased significantly in the GOS-fed mice. Fatty acid synthesis and blood triglyceride content significantly decreased in the GOS-fed mice compared with those in the control mice, suggesting that GOS may improve lipid metabolism in mice. Additionally, after three weeks of a GOS-rich diet, the mouse microbiota was significantly enriched in Alloprevotella, Bacteroides, and Parasutterella. The blood glucose level of the GOS-fed group was significantly higher than that of the control group, whereas the abundance of Coprococcus and Odoribacter (butyrate-producing bacteria) was significantly decreased. The metabolism of butyrate, known to reduce plasma glucose levels, was significantly downregulated in the GOS-fed mice, an effect potentially detrimental to the glucose metabolism of the host. This dual-omics analysis provided important information on the changes in host-microbe-metabolite interactions resulting from GOS supplementation. Our results provide evidence that GOS may improve lipid metabolism, and that long-term GOS supplementation had a detrimental effect on the host's glucose metabolism, which could be important for optimizing methods of prebiotic supplementation and developing approaches to prevent diseases using prebiotic interventions.

BACKGROUND: This study aimed to confirm the relationship between asthma, respiratory syncytial virus (RSV) infection, and the gut environment by analyzing the alterations in the gut microbiota of RSV-infected asthmatic mice. METHODS: Twenty-four male BALB/c mice were randomly separated into a control group (CON), ovalbumin (OVA) group, and an OVA + RSV group, (n=8 mice/group). At the end of experiments, we evaluated the RSV-infected asthma model using Wright-Giemsa staining, histopathology and immunoglobulin E (IgE) level using enzyme-linked immunosorbent assays (ELISA). Next, airway hyper-responsiveness (AHR) was measured using Buxco's modular and invasive system. Furthermore, IL cytokine expression were measured using ELISA. Moreover, feces were collected for 16S ribosome RNA (16S rRNA) sequencing and data analysis. RESULTS: We observed that the total BAL fluid lung cells in the OVA + RSV group was significantly higher than other group. We revealed that the inflammatory infiltration, edema, and collagen hyperplasia were more severe in the OVA + RSV group. The AHR of RSV-infected mice was aggravated compared with the other groups, (P<0.05 and P<0.01). We observed a higher expression of IgE, interleukin (IL)-5, IL-13, IL-25, and IL-33 levels in mice from the OVA and OVA + RSV groups (P<0.05 and P<0.01). The associations between Prevotellaceae_UCG_001, which is positive, and IgE, IL-13, IL-33 (P<0.001), IL-5 (P<0.01), and IL-25 (P<0.05) were highly significant. Lachnospiraceae_NK4A136_group is also positive and was significantly associated with IgE and IL-33. Helicobacter and Uncultured_Bacteroidales_bacteriumare_group, which are negative, were associated with IL-25 (P<0.05). CONCLUSIONS: Our results indicated that RSV-infected mice with asthma may have changes in the gut microbiota's major components and may influence the mutual relationship between the core operational taxonomic units (OTUs) and IgE as well as inflammatory cytokines.