Lactobacillus T3L Imppoves Bone Loss And Intestinal Immune Mechanism In Obese Mice

High-fat diets not only lead to overweight,but also induce abnormal bone metabolism and absorption,leading to reduced bone mass and decreased bone strength,leading to an increased risk of spontaneous and traumatic bone damage and severely impairing bone health.However,the relationship between long-term high-fat diets and reduced bone performance has not been clearly explained.The improvement of bone health by probiotics is mainly through the regulation of the immune system to influence the activity of osteoclasts,so as to adjust the balance of bone resorption and bone remodeling.Therefore,we speculate that intestinal flora may be a new target for the treatment of osteoporosis.However,the specific relationship between probiotics and the immune system and bone resorption still needs further exploration.In summary,the purpose of this study was to clarify the mechanism by which L.coryniformis subsp.torquens T3（T3L）protects obese mice from bone loss.We believe that T3 L inhibits bone mass loss in obese mice by altering the short-chain fatty acid-producing bacteria.This study selected the probiotic strain T3 L which showed significant obesity inhibition in Balb/c mice induced by high fat diet,and studied the inhibition of bone damage in high-fat diet mice;Effects on intestinal flora and fecal short-chain fatty acids;Impact on the systemic immune system,and then infer the mechanism of Lactobacillus promote bone health in mice with high-fat diet.（1）By means of intragastric administration,T3 L was given a dose of 2×10¹⁰CFU/kg.bw and short-chain fatty acids（Sodium Acetate:Sodium Propionate:Sodium Butyrate=1:1:1）at a dose of 0.576 g/kg.bw to give obese Balb/c mice that had been successfully modeled for 6 weeks.The results showed that there was no significant difference between the mice fed the short-chain fatty acid group and the high-fat group,while the T3 L strain has a significant effect on suppressing obesity and blood lipids in mice caused by a high-fat diet.（2）Inhibitory effect of lactobacillus on bone loss in high-fat diet mice:After intervention of T3 L Lactobacillus,the biomechanical properties of the femur of high-fat diet mice were enhanced.In addition,observed by staining,intragastric administration of short-chain fatty acids inhibited bone damage in high-fat diet mice,but there was no significant difference from high-fat diet group.In the T3 L group,the trabecular structure of the mouse was more evenly arranged,with less cartilage damage and more red staining of the collagen,which was significantly different from that of the high-fat group.（3）High-throughput sequencing was used to analyze the intestinal flora diversity in mice.Obesity induced by high-fat diet caused differences in intestinal microflora in mice,both intragastric administration of short-chain fatty acids and T3 L reduced the ratio of thick-walled bacteria to Bacteroidetes in the feces of mice,and there was a significant difference in mice in the high-fat group.In addition,after gavage of Lactobacillus T3 L,the diversity of intestinal microflora in mice changed and the number of strains producing short-chain fatty acids increased.（4）To detect the expression of Foxp3,a specific cytokine of Tregs in colonic tissue,the results showed that intragastric administration of short-chain fatty acids and T3 L mouse colon tissue Foxp3 infiltration increased,and the high-fat group had significant differences.Detection of systemic immune organ expression by RT-qPCR,including large intestine,small intestine,spleen,lymph node IL-10,TGF-β1,Foxp3Ffar2 acetylase HDAC6,-9.The expression of IL-10,Foxp3 and Ffar2,in colonic tissue was significantly increased after administration with T3 L,and the expression level is close to the control group（p<0.05）.And the intervention of T3 L Lactobacillus reduced HDAC6 and-9 and expression.In summary,the content of short-chain fatty acids in feces after intragastric administration of T3 L Lactobacillus increased.Probiotics may increase the proportion of short-chain fatty acid-producing bacteria by regulating intestinal flora.Further,the use of short-chain fatty acids affects the systemic immune function of mice through the HDAC pathway and then interferes with the mechanism of bone remodeling to complete the protection of the bone.