Oral Hypoglycemic Effects Of Polysaccharides From Amillariella Mellea And Their Mechanisms

Currently,diabetes is a global health problem with high morbidity and mortality.Since clinical therapeutic drugs are often accompanied by obvious side effects,looking for natural products as a safe and non-toxic hypoglycemic health food has become a research hotspot.Amillariella mellea is an edible fungus,and polysaccharides are the main active ingredients.Studies have shown that polysaccharides from Amillariella mellea have biological activities such as antioxidation,immune enhancement,and hypoglycemic activity,but the mechanism of hypoglycemic action has not yet been elucidated.Therefore,this paper intends to study the oral hypoglycemic effect and mechanism of polysaccharides from Amillariella mellea.The fruit body was subjected to hot water boiling,ethanol precipitation,papain and cellulase enzyme hydrolysis to obtain the total AMP of Amillariella mellea.The DEAEcellulose ion exchange chromatography was used to separate and purify the AMP.We obtained the neutral fraction AMP-N eluated by distilled water and acidic fraction AMPA eluated by 0.4 M NaCl.The monosaccharide composition was analyzed by high performance liquid chromatography.The results showed that the content ratio of glucose to galactose in AMP and AMP-N was 1:1,indicating that they contained galactoglucan domain,and the content ratio of glucose and galactose in AMP-A was 10:1,presumably containing glucan domain.In vitro,the insulin resistance cell model induced by high glucose and high fat was used to compare the improvement activity of three polysaccharides of Amillariella mellea on insulin resistance.AMP and AMP-N showed better improvement activity,and insulin resistance was improved by activating the IR-Akt-AMPK signaling pathway,while AMPA did not improve the effect,suggesting that galactoglucan may be the main active domain.Then using cells stably expressing GFP-LC3 and human hepatocellular carcinoma cells,the expression of autophagosomes and autophagy-related proteins were analyzed,and the abilities of three polysaccharides to induce autophagy were compared.AMP and AMP-N promote the formation of autophagosomes.At the same time,the degradation of p62 protein and the conversion of LC3-I to LC3-II were increased,indicating that AMP and AMP-N have abilities to induce autophagy significantly.In contrast,AMP-A induces less autophagy.Combined with the improvement in insulin resistance,we speculated that AMP and AMP-N may improve insulin resistance via autophagy activation.In vivo,using db/db diabetic mice optimized the oral hypoglycemic dose and duration of administration of polysaccharides from Amillariella mellea to determine the optimal dose of 50 mg/kg/d for 4 weeks.From the results of blood glucose,GTT and ITT,it was shown that AMP and AMP-N have significant oral hypoglycemic effects,and AMP-N is better than AMP,while AMP-A does not have hypoglycemic effect.Serum biochemical analysis showed that AMP and AMP-N reduced serum triglycerides and free fatty acids,indicating that lipid metabolism was regulated in diabetic mice,and alanine aminotransferase and aspartate aminotransferase were reduced,indicating protection of liver function in diabetic mice;decreased serum insulin content,indicating improved insulin resistance.HE stainning showed that AMP-N reduced the number of lipid droplets in the liver and interfered with the formation of lipid droplets,indicating that hepatic fat accumulation in mice was inhibited.Analysis of liver autophagy-related protein expression,AMP-N significantly increased the degradation of p62 protein,and the conversion of LC3-I to LC3-II,indicating that the level of autophagy was upregulated in mice liver.At the same time,the results of islet morphology analysis showed that AMP-N protected the integrity and compactness of islet in diabetic mice and restored the function of damaged islets.In addition,the toxicity of polysaccharides from Amillariella mellea was also analyzed.During the administration,the polysaccharides had no effect on body weight,blood sugar,liver weight and fat mass of mice,indicating that polysaccharides from Amillariella mellea are safe and non-toxic.In summary,the total polysaccharide AMP and neutral fraction AMP-N have obvious oral hypoglycemic activity,and AMP-N is superior to AMP in its hypoglycemic effect.Combining the results of monosaccharide composition,it was speculated that galactoglucan may be its main active domain.The mechanism of hypoglycemic effect of AMP-N,on the one hand,it improves the level of autophagy in the liver of diabetic mice,reduces fat accumulation and improves insulin sensitivity;on the other hand,it protects islets of diabetic mice and improves impaired function.The results of the paper will lay the foundation for the development and utilization of Amillariella mellea,providing a basis for the development of hypoglycemic health foods.