Research On Hypoglycemic Activity And Mechanism Of Phellinus Linteus Mycelial Extract From Solid-state Culture

Diabetes is a metabolic disease characterized by high blood glucose level(hyperglycemia)resulting from insulin secretion deficiency,insulin resistance,or these two factors in combination.Diabetes is considered to be one of the most common international health crises in the 21 st century.Literature of traditional Chinese medicine and modern scientific research proved that Phellinus linteus has the effect of adjuvant treatment of diabetes.Our research group expanded the source of high-quality P.linteus by solid-state culture techniques,and realized large-scale productions.However,the systemic research on the hypoglycemic effect and its molecular mechanism lacked.In the present study,hypoglycemic and hypolipidemic effects,and underlying molecular mechanisms of mycelial P.linteus extract(PLPE)were evaluated in type 2 diabetic rat models induced by high-fat diet(HFD)or low-dose streptozotocin(STZ)treatment.From the aspects of hepatic glucose and lipid metabolism,hepatic insulin signal transduction pathways,changes in intestinal microbial composition and intestinal barrier function,the mechanism of PLPE to reduce blood glucose and improve liver insulin resistance was explored.The main contents are as follows:1.The method to induce the type 2 diabetes(T2D)rats was: 6 weeks of feeding with HFD and intraperitoneal injection STZ with a dose of 45 mg/kg.BW.After 10 days,rats with fasting blood glucose(FBG)greater than 11.1 mmol/L were selected for follow-up experiments.2.The food intake,water intake and FBG of rats in the PLPE intervention group were significantly lower than those of the model group(MC)group at the 8th week.PLPE intervention effectively improved glucose tolerance and insulin sensitivity in T2 D rats.Glycated serum protein content and insulin resistance index of rats in PLPE intervention group were also significantly lower than those in MC group(P<0.01).PLPE also effectively reduced the concentration of triglyceride(TG),total cholesterol(T-CHO),free fatty acid(FFA)and low density lipoprotein(LDL)in the serum of T2 D rats.3.PLPE intervention reduced the expression of fructose-1,6-bisphosphatase(FBPase)and glucose-6-phosphatase(G6Pase)in the hepatic tissue of T2 D rats,and inhibited the process of gluconeogenesis and glycogen decomposition in liver.In addition,the expression of hepatic glucokinase(GCK)in the PLPE intervention group was restored.Glucose utilization rate was increased in liver.At the same time,PLPE accelerated the fatty acid β-oxidation process and enhanced expression of low-density lipoprotein receptor(LDLR)in the liver,which contributed to clearing lipid and LDL.Correspondingly,the content of liver glycogen in T2 D rats in MC group was significantly lower than that in normal rats.The hepatic gluconeogenesis was active,the output of hepatic glucose and liver fat content increased in the MC group.4.PLPE intervention effectively reduced the serum lipopolysaccharide(LPS)content and inflammatory factor levels,down-regulated the expression of TLR4 on the protein level and the phosphorylation level of JNK protein in the liver tissue.PLPE lightened the inflammatory response in liver.It was helped to reduce the phosphorylation of insulin receptor substrate 1(IRS1)protein at serine residue,restore insulin signaling in the liver and improve hepatic insulin resistance in T2 D rats.5.PLPE intervention could increase the content of propionic acid and butyric acid in the intestine of rats.The expression levels of Zonula Occluden1(ZO1),Occludin(Ocln)and Claudin 1(Cldn1)in small intestine tissue were also up-regulated which was beneficial to the recovery of intestinal barrier function in T2 D rats.6.PLPE intervention raised the microbial diversity of T2 D rats,making the intestinal microbial composition of T2 D rats closer to normal rats.Under the regulation of PLPE,the relative abundance of Lachnospiraceae-NK4A136,Lachnospiraceae-UCG-006,Roseburia,Eubacterium xylanophilum,etc.were increased.These bacteria have the ability to degrade polysaccharides and produce SCFAs.Compared with the MC group,the relative abundance of pathogens and opportunistic pathogens such as Clostridium-sensu-stricto-1 and Escherichia-Shigella were decreased in the PLPE group.7.Pathological sections of liver tissues showed abnormal liver morphology,swelling of liver cells,and blurring of nuclear boundaries in the MC group.At the same time,the kidney tissue of T2 D rats showed mesangial cell hyperplasia and glomerular hypertrophy.PLPE intervention could reduce oxidative damage of liver and kidney tissues.The results of this study provide a theoretical reference for the application of as an auxiliary hypoglycemic functional food.The research results of this study provide theoretical reference for the application of P.linteus in the development of auxiliary hypolycemic functional foods and the application of P.linteus combined with hypolycemic agents to improve diabetes complications.