Lactobacillus gasseri LA39 promotes hepatic primary bile acid biosynthesis and intestinal secondary bile acid biotransformation / 浙江大学学报（英文版）（B辑：生物医学和生物技术）

A growing body of evidence has linked the gut microbiota to liver metabolism. The manipulation of intestinal microflora has been considered as a promising avenue to promote liver health. However, the effects of Lactobacillus gasseri LA39, a potential probiotic, on liver metabolism remain unclear. Accumulating studies have investigated the proteomic profile for mining the host biological events affected by microbes, and used the germ-free (GF) mouse model to evaluate host-microbe interaction. Here, we explored the effects of L. gasseri LA39 gavage on the protein expression profiles of the liver of GF mice. Our results showed that a total of 128 proteins were upregulated, whereas a total of 123 proteins were downregulated by treatment with L. gasseri LA39. Further bioinformatics analyses suggested that the primary bile acid (BA) biosynthesis pathway in the liver was activated by L. gasseri LA39. Three differentially expressed proteins (cytochrome P450 family 27 subfamily A member 1 (CYP27A1), cytochrome P450 family 7 subfamily B member 1 (CYP7B1), and cytochrome P450 family 8 subfamily B member 1 (CYP8B1)) involved in the primary BA biosynthesis pathway were further validated by western blot assay. In addition, targeted metabolomic analyses demonstrated that serum and fecal β‍-muricholic acid (a primary BA), dehydrolithocholic acid (a secondary BA), and glycolithocholic acid-3-sulfate (a secondary BA) were significantly increased by L. gasseri LA39. Thus, our data revealed that L. gasseri LA39 activates the hepatic primary BA biosynthesis and promotes the intestinal secondary BA biotransformation. Based on these findings, we suggest that L. gasseri LA39 confers an important function in the gut‒liver axis through regulating BA metabolism.

Fecal microbiota transplantation from growing pigs with different feed efficiency to pseudo-germ-free mice can result in reappearance of the original phenotype / 中国实验动物学报

Objective The aim of this experiment was to explore the effect and mechanism of intestinal microbiota on shaping the growth performance by fecal microbiota transplantation from pigs to pseudo-germ-free mice. Methods Thirty-six barrows with a similar initial body weight of 30 kg were raised for 42 days(ad libitum)within individual metabolic cages. Feed intake and body weight of each pig were recorded every week to calculate the feed conversion rate and average daily gain. At the end of the experiment,feed conversion ratio and average daily gain were integrated to divide the pigs into 3 groups, namely, high growth performance(HP), moderate growth performance(MP)and low growth performance(LP)groups. Feces were collected to calculate the total intestinal nutrient digestibility and prepare for fecal microbiota transplantation to pseudo-germ-free mice, which were induced with several antibiotics for four weeks. Fecal microbiome structure was assayed by profiling V3-V4 region of the 16S rRNA gene. Results Fecal microbiota transplantation from pigs to pseudo-germ-free mice resulted in reappearance of the original phenotype. Compared with the LP pigs, the microbial species richness and microbial diversity in feces were higher in the HP pigs. The HP pigs had improved digestibility of gross energy(P =0.01)and higher abundance of Methanobrevibacter. Enterococcus and Akkermansia were also more abundant in the recipient pseudo-germ-free mice from the HP pigs which may be correlated with a high energy utilization. Conclusions Fecal microbiota transplantation from pigs to mice results in reappearance of the original phenotype and microbial species richness,microbial diversity,and their growth ability. Different nutritional metabolism is shown among pigs with different feed efficiency and the HP pigs have improved energy utilization(P=0.01). At the same time, the bacteria correlated with high energy utilization are more abundant in feces of HP pigs than in LP pigs.

Application of germ-free mice in colorectal cancer research / 中国实验动物学报

Accumulated evidence shows that gut microbial composition is closely related to the development of colorectal cancer. Germ-free animal models, especially germ?free murine models, have been shown to be simple and easy to access, which provide a valuable tool for studying the correlation between microbiota, colorectal neoplasms and the host. These models are mainly established by cesarean section followed by rearing and breeding the pups in sterile isolators. Sim?ilarly, some special models, such as transgenic and drug?induced murine models, can also be developed according to the study purposes. To date the germ?free murine models have been widely used in the field of colorectal cancer research, showing that certain microbes or microorganisms can promote the occurrence and development of colorectal cancer by activa?ting immune response and inducing inflammation. Results from germ?free murine models have demonstrated that gut micro?bial dysbiosis and colorectal cancer development influence each other and are reciprocal causation. Taken together, germ?free murine models are important tools for investigating the mechanisms of the tumorigenesis in colon and rectum, especially dysbiosis?induced colorectal cancer.

A review on immune regulation by intestinal microbiota / 中国实验动物学报

In a"superorganism" of human being, commensal bacteria play vital roles in regulating many aspects of host physiology. Germ-free mice have been proven to be a valuable tool to unravel the underlying mechanisms how microbes interact with the host. This review discusses the recent research progress on microbiota and immune regulation.

The Second Brain

The ability of the microbiota of the gut to communicate with the brain and influence behaviour is an emerging topic of research.The enteric microbiota interacts with the host to form a relationship that governs homeostasis. Despite the unique enteric bacterial fingerprintof each individual there appears to be a certain balance that confers health benefits. A decrease in desirable bacteria therefore leads to a disturbed gastrointestinal, neuroendocrinal and immune relationship leading to a diseased condition. Studies are focussing on the impact of the microbiota on the host specially its effect on the brain.There are many studies which have demonstrated germ free mice displaying altered stress response, neurochemistry and anxiety in comparison to normal mice. Data obtained from such experiments show that modulation of enteric microbiota may be a useful strategy in stress related disorders, gastrointestinal disorders such as Irritable Bowel Syndrome (IBS) and Inflammatory bowel disease