Gut Dysbiosis-caused Alteration Of Mouse Fecal Digestive Enzymes,Intervention,and Effects On Immune Homeostasis

As the research moves along,a growing number of diseases are associated with intestinal dysbiosis.Gut dysbiosis caused the loss of key probiotic flora,increased pathogenic bacteria,decreased diversity of gut microbiota,and altered metabolic functions.Then triggered inflammatory bowel diseases(IBD)such as ulcerative colitis and Crohn’s disease,metabolic disorders,autoimmune diseases,and neurological disorders.However,the causal role of gut dysbiosis in disease development and the underlying mechanism of potential long-term adverse effects on intestinal immune homeostasis are unclear.Studies have reported that elevated fecal serine protease activity in patients(Pouchitis and diarrhea-irritable bowel syndrome)and antibiotic treated mice.In addition,increased proteases could impair gut barrier and trigger inflammation reaction.In this study,oral gavage four broad-spectrum antibiotics to mice for 2 weeks to establish a model of gut dysbiosis.16 S rRNA gene sequencing showed that antibiotics caused the alteration of diversity and composition of mice gut microbiota.The analysis at phylum level showed that the flora of Proteobacteria in the sample increased significantly.At genus level,a significant increase in Klebsiella and decrease in Lactobacillus and norank-f-muribaculaceae was observed in the antibiotic group.Oral gavage of antibiotics caused a significant increase in mice fecal protease activity(neutral and alkalic protease)and glucoamylase activity.The overall fecal protein concentration and protein diversity was decreased in antibiotics treated mice.Oral gavage trypsin could decrease neutral and alkalic protease activity but did not restore to the level of mice that never treated with antibiotics.Then oral gavage of trypsin enteric-coated capsules to mice fed with trypsin for two weeks restored the protease activity to levels close to the control,while the fecal protease activity of mice that were halt antibiotic treatment and did not receive other treatments remained at high level.The glucoamylase activity was decreased to normal level when administrated trypsin for 2 weeks.The diversity of gut microflora could be increased and restored to normal level after administrating trypsin or trypsin enteric-coated capsules to mice with gut dysbiosis.By measuring inflammatory factors in mice serum,the results showed that the level of IFN-α was significantly increased in antibiotic mice(171.5 ± 6.5 pg/mL)compared to that in the control(198.7 ± 5.2 pg/mL,p<0.05).In addition,the fecal supernatants of antibiotics treated mice induced to decrease phagocytosis of macrophage(Ana-1 cell)and microglia(N9 cell)and was recovered by trypsin or trypsin enteric-coated capsules.The results of the study show that intestinal enzymes activity is not only related to food digestion,but also has an important effect on homeostasis of gut microbiota and immune.The homeostasis of gut microbiota is essential for intestinal enzyme activity.Intestinal enzyme activity increases after antibiotics destroy the homeostasis of gut microbiota.The elevated enzymes might impair the mucosal barrier,affect the function of phagocytes,and disturb the immune homeostasis.This work expands a new understanding of the function of digestive enzymes and is expected to become a new indicator for judging intestinal function.