Study On The Effect And Mechanism Of Gut Microbiota Changes On Osteoporosis

ObjectiveOsteoporosis is a kind of systemic skeletal disease,which is characterized by the decrease of bone mass,the destruction of bone microstructure and the increase of bone fragility.Experimental studies using germ-free mice and antibiotic intervention had shown that there was a relationship between gut microbiota and bone metabolism.Clinical studies have found that there were several gut microbiota disorder in the pathogenesis of osteoporosis.The results of various studies were not consistent,thus,the related role and mechanism of gut microbiota on bone mass still need further study.In this study,we first explored the change rules and mechanisms of gut microbiota in the pathogenesis of osteoporosis by using the rat model of type I and II osteoporosis.Then,the gut microbiota of osteoporosis was transplanted to the healthy rats to explore the influence of gut microbiota on the bone mass and the possible pathogenic mechanism of microflora,so as to provide the theoretical basis for the pathogenesis of osteoporosis.In order to provide new directions for the prevention and treatment of osteoporosis,healthy gut microbiota was transplanted to osteoporosis rats to explore the feasibility of fecal microbiota transplantation(FMT)and its related mechanism of micrflora.Methods1.Bone mass,bone turnover factor and other biochemical indicators were measured to evaluate the intestinal mucosal barrier function in ovariectomized rat model.16 S rRNA and metagenomics sequencing method were used to clarify the changes of gut microbiota structure and functional genes in the pathogenesis of type I osteoporosis.2.The bone histomorphometric parameters were measured in the old rat model,16 S rRNA and metagenomics sequencing were used to compare the differences of gut microbiota structure and functional genes between type II osteoporosis rats and healthy rats.3.The fecal microbiota of osteoporotic rats were transplanted to healthy rats.The bone morphometric,bone turnover indexes and intestinal mucosal barrier function of the FMT group and the control group were detected before and after transplantation for 12 W and 24 W respectively.16 S rRNA sequencing was used to compare the structural and functional differences of the gut microbiota of the two groups.4.The fecal microbiota of healthy rats were transplanted to the aged osteoporosis rats.The bone morphometric and bone turnover indexes of the FMT group and the control group were detected before and after transplantation for 12 W and 24 W respectively,the structure and function changes of gut microbiota of the two groups were compared by 16 S rRNA sequencing.Results1.After ovariectomy,the barrier function of intestinal mucosa was weakened,the number of OTUs and α diversity of gut microbiota increased significantly.Using analysis of correlation and significant differences,we found that Ruminococcus flavefaciens and Prevotella were related to the reduction of bone mass after ovariectomy,and the genes related to the synthesis and metabolism of monosaccharide,and nucleotide,the genes related to microbial structure were significantly decreased.2.In osteoporosis rats,the number of OTUs of gut microbiota increased,the α diversity and F/B value decreased.The abundance and function of Helicobacter were closely related to osteoporosis.The contents of genes of disaccharide and oligosaccharide,gram-negative cell wall components and electron donor effect factors decreased significantly.3.Compared with the control group,the bone mass decreased significantly,the abundance of gut microbiota decreased with the increase of diversity after FMT,which led to the gut microecology disorder.The abundance of latobacillus and clostridium XIVa decreased significantly.4.After 24 weeks of FMT in healthy rats,the bone turnover rate of osteoporosis rats decreased significantly,the bone loss stopped and kept at the level before transplantation,the structure and function of gut microbiota tended to rebuild the homeostasis.Conclusions1.There were significant differences in the composition and structure of gut microbiota before and after ovariectomy in rats.The increase of intestinal permeability and cotents of Ruminofocus flavefaciens,Prevotella and their related metabolic pathways were the important pathogenesis of type I osteoporosis.2.Senile osteoporosis was closely related to the structural changes of gut microbiota,Helicobacter and Lachnospiraceae may be the main pathogenic microflora.Gut microbiota could cause host immune disorder through metabolic pathway and participate in the pathological process of senile osteoporosis.3.Osteoporosis caused by aging can be transferred to healthy rats by FMT.Intestinal homeostasis disorder was the pathogenic factor of osteoporosis.Lactobacillus and Clostridium XIVa were the key species to produce these change.4.FMT could reduce the rate of bone turnover and delay the loss of bone mass.The structure and function of gut microbiota tended to rebuild the homeostasis.Proteobacteria and Helicobater were the key factors to prevent the continuous deterioration of osteoporosis.