A Well-Established Gut Microbiota Enhances the Efficiency of Nutrient Metabolism and Improves the Growth Performance of Trachinotus ovatus.

The gut microbiota has become an essential component of the host organism and plays a crucial role in the host immune system, metabolism, and physiology. Nevertheless, our comprehension of how the fish gut microbiota contributes to enhancing nutrient utilization in the diet and improving host growth performance remains unclear. In this study, we employed a comprehensive analysis of the microbiome, metabolome, and transcriptome to analyze intestines of the normal control group and the antibiotic-treated model group of T. ovatus to investigate how the gut microbiota enhances fish growth performance and uncover the underlying mechanisms. First, we found that the growth performance of the control group was significantly higher than that of the antibiotic-treated model under the same feeding conditions. Subsequent multiomics analyses showed that the gut microbiota can improve its own composition by mediating the colonization of some probiotics represented by Lactobacillus in the intestine, improving host metabolic efficiency with proteins and lipids, and also influencing the expression of genes in signaling pathways related to cell proliferation, which together contribute to the improved growth performance of T. ovatus. Our results demonstrated the important contribution of gut microbiota and its underlying molecular mechanisms on the growth performance of T. ovatus.

What we need to know about the germ-free animal models.

The gut microbiota (GM), as a forgotten organ, refers to the microbial community that resides in the gastrointestinal tract and plays a critical role in a variety of physiological activities in different body organs. The GM affects its targets through neurological, metabolic, immune, and endocrine pathways. The GM is a dynamic system for which exogenous and endogenous factors have negative or positive effects on its density and composition. Since the mid-twentieth century, laboratory animals are known as the major tools for preclinical research; however, each model has its own limitations. So far, two main models have been used to explore the effects of the GM under normal and abnormal conditions: the isolated germ-free and antibiotic-treated models. Both methods have strengths and weaknesses. In many fields of host-microbe interactions, research on these animal models are known as appropriate experimental subjects that enable investigators to directly assess the role of the microbiota on all features of physiology. These animal models present biological model systems to either study outcomes of the absence of microbes, or to verify the effects of colonization with specific and known microbial species. This paper reviews these current approaches and gives advantages and disadvantages of both models.

Gut microbiota dynamics in KK-Ay mice: restoration following antibiotic treatment.

The primary aim of this study was to investigate the alterations in the microbial community of KK-Ay mice following antibiotic treatment. A comparative analysis of the gut microbiota was conducted between KK-Ay mice treated with antibiotics and those without treatment. The microbial community dynamics in antibiotic-treated KK-Ay mice were meticulously assessed over an eight-week period using 16S rDNA sequencing analysis. Simultaneously, dynamic renal function measurements were performed. The results demonstrated a marked decrease in bacterial DNA abundance following antibiotic intervention, coupled with a substantial reduction in bacterial diversity and a profound alteration in microbial composition. These observed microbiota changes persisted in the KK-Ay mice throughout the eight-week post-antibiotic treatment period. Particularly noteworthy was the reemergence of bacterial populations after two weeks or more, resulting in a microbiota composition resembling that of untreated KK-Ay mice. This transition was characterized by a significant increase in the abundance of clostridia at the class level, Lachnospirales and Oscillospirales at the order level, and Lachnospiraceae, Oscillospiraceae, and Ruminococcaceae at the family level. Concurrently, there was a notable decrease in Clostridia_UCG-014. The observed alterations in the gut microbiota of antibiotic-treated KK-Ay mice suggest a dynamic response to antibiotic intervention and subsequent restoration towards the original untreated state.

Bamboo shoot dietary fiber alleviates gut microbiota dysbiosis and modulates liver fatty acid metabolism in mice with high-fat diet-induced obesity.

Introduction: Obesity is a common nutritional disorder characterized by an excessive fat accumulation. In view of the critical role of gut microbiota in the development of obesity and metabolic diseases, novel dietary therapies have been developed to manage obesity by targeting the gut microbiome. In this study, we investigated anti-obesity effects of bamboo shoot dietary fiber (BSDF) and the potential mechanisms. Methods: After 12 weeks of intervention with BSDF in high-fat mice, we detected obesity-related phenotypic indicators, and made transcriptomic analysis of liver tissue. Then we analyzed the changes of gut microbiota using 16S rRNA gene sequencing, explored the effect of BSDF on gut microbiota metabolites, and finally verified the importance of gut microbiota through antibiotic animal model. Results and discussion: We found that BSDF was effective in reducing lipid accumulation in liver and adipose tissue and alleviating dyslipidemia and insulin resistance. Liver transcriptome analysis results showed that BSDF could improve lipid metabolism and liver injury by modulating peroxisome proliferator-activated receptor (PPAR) and fatty acid metabolic pathways. The 16S rRNA gene sequencing analysis of gut microbiota composition showed that BSDF significantly enriched beneficial bacteria such as Bifidobacterium, Akkermansia, Dubosiella, and Alloprevotella. Analysis of fecal metabolomics and gut microbiota metabolites revealed that BSDF increased the levels of several short-chain fatty acids and enriched bile acids, which may be important for improving lipid metabolism. Notably, the obesity-related metabolic disorders were abrogated after the abrogation of gut microbiota, suggesting that gut microbiota is a key factor in the beneficial effects of BSDF. Conclusion: Our study suggests that BSDF as a prebiotic supplement has the potential to improve obesity by improving gut microbiota and modulating host PPAR and fatty acid metabolic pathways.

Fecal Microbiota Transplantation Reshapes the Physiological Function of the Intestine in Antibiotic-Treated Specific Pathogen-Free Birds.

The topic about the interactions between host and intestinal microbiota has already caught the attention of many scholars. However, there is still a lack of systematic reports on the relationship between the intestinal flora and intestinal physiology of birds. Thus, this study was designed to investigate it. Antibiotic-treated specific pathogen-free (SPF) bird were used to construct an intestinal bacteria-free bird (IBF) model, and then, the differences in intestinal absorption, barrier, immune, antioxidant and metabolic functions between IBF and bacteria-bearing birds were studied. To gain further insight, the whole intestinal flora of bacteria-bearing birds was transplanted into the intestines of IBF birds to study the remodeling effect of fecal microbiota transplantation (FMT) on the intestinal physiology of IBF birds. The results showed that compared with bacteria-bearing birds, IBF birds had a lighter body weight and weaker intestinal absorption, antioxidant, barrier, immune and metabolic functions. Interestingly, FMT contributed to reshaping the abovementioned physiological functions of the intestines of IBF birds. In conclusion, the intestinal flora plays an important role in regulating the physiological functions of the intestine.

Dietary Luffa cylindrica (L.) Roem promotes branched-chain amino acid catabolism in the circulation system via gut microbiota in diet-induced obese mice.

High circulating branched-chain amino acid (BCAA) levels can be diagnosis indicators for obesity. Luffa cylindrica (luffa) is one of vegetables against obesity. However, whether the anti-obesity of luffa is associated with BCAA metabolism and gut microbiota remains unknown. Here, we used conventionally raised diet-induced obese (DIO) mice to prove dietary luffa could reduce higher circulating BCAA levels and upregulate the tissue-specific expressions of BCAA-catabolizing enzymes. Meanwhile, dietary luffa selectively decreased the relative abundances of g_Enterortabdus, g_Eubacterium_xylanophilum_group and g_Butyricicoccus that exhibited significantly positive correlations with BCAA levels, BMI and HOMA-IR. Bacterial functionality prediction indicated dietary luffa potentially inhibited bacterial BCAA biosynthesis for reducing BCAAs supplementation. More importantly, dietary luffa had no impacts on BCAA catabolism in germ-free-mimic DIO mice. Thus, dietary luffa improved BCAA dysfunction via gut microbiota to attenuate obesity. This study offers a novel insight into dietary intervention against obesity from the aspect of gut microbiota-amino acid metabolism.