The incidence of diabetes mellitus is increasing among companion animals. This disease has similar characteristics in both humans and animals. Diabetes is frequently identified as an independent risk factor for infections associated with increased mortality. In the present study, homozygous diabetic (db/db) mice were infected with Listeria (L.) monocytogenes and then treated with the anti-diabetic drug exendin-4, a glucagon-like peptide 1 analogue. In aged db/db mice, decreased CD11b+ macrophage populations with higher lipid content and lower phagocytic activity were observed. Exendin-4 lowered high lipid levels and enhanced phagocytosis in macrophages from db/db mice infected with L. monocytogenes. Exendin-4 also ameliorated obesity and hyperglycemia, and improved ex vivo bacteria clearance by macrophages in the animals. Liver histology examined during L. monocytogenes infection indicated that abscess formation was much milder in exendin-4-treated db/db mice than in the control animals. Moreover, mechanistic studies demonstrated that expression of ATP binding cassette transporter 1, a sterol transporter, was higher in macrophages isolated from the exendin-4-treated db/db mice. Overall, our results suggest that exendin-4 decreases the risk of infection in diabetic animals by modifying the interaction between intracellular lipids and phagocytic macrophages.
ATP-Binding Cassette Transporters/metabolism ; Age Factors ; Animals ; Blood Chemical Analysis ; Cholesterol/metabolism ; Diabetes Mellitus, Type 2/*drug therapy/genetics ; Dyslipidemias/drug therapy/genetics ; Female ; Hyperglycemia/drug therapy/genetics ; Hypoglycemic Agents/*therapeutic use ; Injections, Intraperitoneal ; *Lipid Metabolism/drug effects ; Listeria monocytogenes/*drug effects/immunology ; Listeriosis/*drug therapy/immunology/microbiology ; Macrophages/drug effects/*metabolism ; Mice ; Obesity/drug therapy/genetics ; Peptides/*therapeutic use ; Phagocytosis/drug effects ; Venoms/*therapeutic use

Metabolic syndrome characterized by obesity, hyperglycemia and liver steatosis is becoming prevalent all over the world. Herein, a water insoluble polysaccharide (WIP) was isolated and identified from the sclerotium of Poria cocos, a widely used Traditional Chinese Medicine. WIP was confirmed to be a (1-3)-β-D-glucan with an average Mw of 4.486 × 10 Da by NMR and SEC-RI-MALLS analyses. Furthermore, oral treatment with WIP from P. cocos significantly improved glucose and lipid metabolism and alleviated hepatic steatosis in ob/ob mice. 16S DNA sequencing analysis of cecum content from WIP-treated mice indicated the increase of butyrate-producing bacteria Lachnospiracea, Clostridium. It was also observed that WIP treatment elevated the level of butyrate in gut, improved the gut mucosal integrity and activated the intestinal PPAR-γ pathway. Fecal transplantation experiments definitely confirmed the causative role of gut microbiota in mediating the benefits of WIP. It is the first report that the water insoluble polysaccharide from the sclerotium of P. cocos modulates gut microbiota to improve hyperglycemia and hyperlipidemia. Thereby, WIP from P. cocos, as a prebiotic, has the potential for the prevention or cure of metabolic diseases and may elucidate new mechanism for the efficacies of this traditional herbal medicine on the regulation of lipid and glucose metabolism.
Animals ; Bacteria ; classification ; genetics ; isolation & purification ; metabolism ; Butyrates ; metabolism ; Fatty Liver ; drug therapy ; Fungal Polysaccharides ; chemistry ; pharmacology ; therapeutic use ; Gastrointestinal Microbiome ; drug effects ; genetics ; Hyperglycemia ; drug therapy ; Hyperlipidemias ; drug therapy ; Intestines ; drug effects ; microbiology ; Male ; Metabolic Syndrome ; drug therapy ; Mice ; Mice, Obese ; Prebiotics ; Wolfiporia ; chemistry