| Background and Objective: Aberrant crypt foci(ACF)are the early manifestations of colorectal tumors in rodents,and eventually develop into cancerous tissues,which affect the body weight of rodents.Recent studies have found that Lactobacillus can inhibit the formation of ACF in colorectal cancer animal model and increase the body weight of tumor animal model,and β-glucuronidase and β-glucosidase in intestinal tract may be related to the formation of ACF.Through the systematic evaluation of the effect of Lactobacillus on the formation of ACF in the colon and rectum of tumor animal model,we hope to provide useful reference and inspiration for the follow-up research.Methods: Search the related articles in Embase,Cochrane library,Pub Med and Web of Science about the intervention of Lactobacillus on the formation of ACF in mouse or rat colon.The retrieval time is set up for each database to 2022-01-26.In the original literature,after being fed for 2-6 weeks,the experimental mice were roughly divided into three groups: Lactobacillus group,blank control group and tumor animal model control group.Mice in Lactobacillus group and tumor animal model control group were injected with appropriate amount of azoxymethane(AOM)or 1,2-dimethylhydrazine(DMH)to induce ACF formation.Mice or rats in Lactobacillus group were fed with various types of Lactobacillus and rodent diets for 4-32 weeks before and after injection of AOM or DMH.The blank control group and tumor animal model control group were fed with rodent diets for the same period of time.The body weight of the experimental mice was measured every week.At the end of the experiment,the mice were killed to take out the colorectal and its contents.Colorectum was stained in different ways,and ACF count was observed under light microscope.The bacterial enzyme activity samples from colorectal contents were added to phosphate buffer after centrifugation,and the supernatant was used to evaluate the levels of β-glucosidase and β-glucuronidase.The data were extracted by two researchers independently,and the literature quality was evaluated by SYRCLE animal experiment bias risk assessment form.Revman5.4 software was used for Meta analysis.Results: A total of 9 randomized controlled animal experiments were included,including279 mice,99 mice in Lactobacillus group,82 mice in the blank control group and 98 mice in the tumor animal model control group.The mice in the Lactobacillus group and the tumor animal model control group were injected with AOM or DMH to induce tumor formation.The results of Meta analysis showed that the number of ACF in the Lactobacillus group was significantly less than that in the tumor animal model control group [SMD=-2.04,95%C1(-2.94,-1.13),P<0.0001],and the body weight in the Lactobacillus group was significantly higher than that in the tumor animal model control group [SMD=5.32,95%C1(1.55,9.09),P=0.006].The level of β-glucuronidase in the Lactobacillus group was lower than that in the tumor animal model control group[SMD=-0.57,95%C1(-1.08,-0.06),P=0.03],but there was no significant difference in the level of β-glucuronidase between the Lactobacillus group and the tumor animal model control group [SMD=-0.26,95%Cl(-0.76,0.24),P=0.31].Conclusion: According to the included animal experiments,it is shown that:1.Lactobacillus can reduce the formation of ACF in the intestine of tumor model mice.2.Lactobacillus can increase the body weight level of tumor model mice.3.Lactobacillus may interfere with ACF formation by affecting the level ofβ-glucuronidase in the intestinal tract of tumor model mice.4.Lactobacillus had no significant effect on the level of β-glucosidase in the intestine of tumor model mice. |
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