BACKGROUND:Gut microbiota is closely related to host energy balance and metabolism.The metabolites of intestinal flora can regulate the occurrence and development of obesity and can be a new target for the prevention and treatment of obesity. OBJECTIVE:To summarize the interaction between the intestinal flora and obesity,as well as the specific mechanism underlying regulation of obesity by metabolites of intestinal flora,thereby providing a new reference and basis for the prevention and treatment of obesity. METHODS:"Intestinal microbiota,intestinal bacteria,intestinal microbiota metabolites,short-chain fatty acids,bile acids,ipopolysaccharide,trimethylamine N-oxide,medium-chain fatty acids,tryptophan derivatives,obesity"were used as search terms in Chinese and English.Literature related to obesity from 1990 to 2022 was retrieved in PubMed and CNKI databases.According to inclusion and exclusion criteria,88 articles were finally selected. RESULTS AND CONCLUSION:Intestinal flora is closely related to the occurrence and development of obesity.For example,changes in the Firmicutes to Bacteroidetes ratio can be used as a biomarker for the diagnosis of obesity,and the occurrence of obesity can be delayed by the colonization of probiotics such as Bifidobacterium breve,Lactobacillus and Akkermansia.Intestinal flora is mainly mediated by the metabolites of intestinal flora to participate in the regulation of obesity.For example,short-chain fatty acid can regulate adipogenesis by regulating signaling pathways such as G protein-coupled receptors 41,43 and peroxisome proliferator-activated receptor γ,thus delaying the occurrence and development of obesity.Bile acids can increase insulin sensitivity and body energy expenditure by promoting the activation of G protein-coupled receptor 5 and farnesol X receptor.In addition,lipopolysaccharide,trimethylamine oxide,medium-chain fatty acids and tryptophan derivatives are also widely involved in the occurrence and development of obesity through various signaling pathways.Further studies have found that metabolites of the same bacterial community exert heterogeneous effects in the specific process of regulating obesity via different signaling pathways.For example,under the influence of high-fat diet,acetic acids can activate the parasympathetic nervous system,leading to hyperphagia and liver insulin resistance and thus accelerating the physiological course of obesity.

BACKGROUND:Intestinal flora and its metabolites can participate in the pathological process of osteoporosis and play an important role in the diagnosis and treatment of osteoporosis.In addition,exercise can regulate the intestinal flora and thus affect the occurrence and development of osteoporosis. OBJECTIVE:To summarize the effects and mechanism of intestinal flora on osteoblasts,osteoclasts,and bone marrow mesenchymal stem cells,and the potential role of exercise-mediated intestinal flora in regulating osteoporosis. METHODS:"Intestinal flora,intestinal bacteria,metabolites of intestinal flora,bone metabolism,osteoporosis,exercise"were selected as keywords.Literatures from 1990 to 2023 were retrieved from PubMed and CNKI databases. RESULTS AND CONCLUSION:Changes in the abundance and diversity of intestinal flora and changes in the levels of intestinal flora metabolites such as trimethylamine oxide and bile acid can be used as biomarkers for the diagnosis of osteoporosis.The imbalance of intestinal flora can lead to intestinal barrier dysfunction and excessive production of lipopolysaccharides and trimethylamine oxide,induce the secretion of tumor necrosis factor-α and other inflammatory cytokines,activate the nuclear factor κB signaling pathway and aggravate oxidative stress,thus promoting osteoclast differentiation,inducing osteoblast apoptosis and affecting bone marrow mesenchymal cell migration.Remodeling intestinal flora homeostasis can inhibit inflammatory response,downregulate oxidative stress,inhibit osteoclast differentiation,promote osteoblast differentiation,and regulate the osteogenic migration of bone marrow mesenchymal cells to prevent and treat osteoporosis.Exercise can regulate intestinal flora homeostasis,improve intestinal barrier function,promote the secretion of short-chain fatty acids and bile acids,down-regulate serum lipopolysaccharide level,reduce oxidative stress,and then inhibit osteocyte apoptosis,inhibit osteoclast differentiation,promote osteoblast differentiation,and regulate osteocyte nutrient metabolism to exert the potential of preventing and treating osteoporosis.