[Heat-inactivated Streptococcus thermophilus MN002 alleviate lipid metabolism of high fat diet-fed induced obese mice through modulating gut microbiota structure and bile acids].

Objective: To explore the effects of heat-inactivated Streptococcus thermophilus MN-ZLW-002(MN002) on glucose metabolism, lipid metabolism, gut microbiota and bile acids in high-fat diet fed obese mice.

Methods: Sixty 3-week-old male C57BL/6 mice were randomly divided into control group, high-fat group and intervention group(n=20). After 1 week of adaptive feeding, the control group was fed with normal chow and continued intragastric administration of normal saline for 12 weeks, the high-fat group was fed with high-fat diet and continued intragastric administration of normal saline for 12 weeks, and the intervention group was fed with high-fat diet and continued intragastric of MN002 for 12 weeks. During the experiment, the body weight, food intake, fasting blood glucose content of mice were measured and feces were collected. At the end of the experiment, the oral glucose tolerance of mice was measured and blood, periintestinal fat, peritestosterone fat and perirenal fat samples were collected. The histopathological changes of liver were observed by hematoxylin-eosin staining. Triglyceride, low density lipoprotein, high density lipoprotein and total cholesterol were detected by automatic biochemical analyzer, bile acids content in feces was detected by liquid chromatography-mass spectrometry, gut microbiota structure of mice was analyzed by 16S rDNA sequencing.

Results: Compared with high fat group, serum triglyceride, total cholesterol and perirenal fat in intervention group were significantly decreased(P<0.05), the content of fossil cholic acid sulfate in feces was significantly increased, while the content of ursodeoxycholic acid, porcine deoxycholic acid and deoxycholic acid were significantly decreased(P<0.01). Heat inactivation of MN002 could significantly increase the relative abundance of Ruminiclostridium and Alistipes and reduce the relative abundance of Lactobacillus(P<0.01).

Conclusion: Heat-inactivated Streptococcus thermophilus MN002 can regulate the gut microbiota structure and bile acid composition and content of high-fat diet fed mice, thereby alleviating the lipid metabolic disorders caused by high-fat diet.