Effects And Mechanism Of Cordyceps Militaris Polysaccharide On Alleviating Side-effects Of High-fat Diet

With changes in people’s lifestyles,obesity and its complications caused by highfat diets(HFD)have become a serious public health problem.Cordyceps militaris polysaccharide(CMP),as a special fungi polysaccharide,has little study on its effect of improving the side effects of HFD,and its mechanism remains unclear.This study aimed to investigate the anti-obesity effects of CMP in HFD-fed mice from the perspective of gut microbiota and metabolites,and explored the specific gut microbiota and metabolites that play a key regulatory role,which provides theoretical basis for further application of C.militaris.The main findings are as followed:(1)The composition,structural characteristics,and digestive and fermented characteristics of CMP were clarified.Firstly,CMP was extracted from C.militaris fruiting body using water extraction and ethanol precipitation.CMP was composed of 61.90 ± 1.22%carbohydrates,22.87 ± 0.51%proteins and 1.91 ± 0.07%uronic acid by sulfuric acid-phenol method,BCA protein determination method and hydroxybiphenyl method,respectively.Moreover,three fractions were identified in the CMP extract with Mw>670,4.58,and 1.29 kDa using HPLC-RI.Notably,the CMP extract mainly consisted of mannose,galactose,and glucose with a mole ratio of 1.55:0.84:1 by PMP pre-column derivatization.Based on in vitro simulated gastrointestinal digestion model and fermentation model,it was found that CMP cannot be digested by gastrointestinal fluid,but can be used by gut microbiota.(2)CMP had been found to have effects on allivating side effects of HFD,and improve HFD-induced disorders of gut microbiota and metabolites.Based on HFD-fed mice model,CMP supplementation reduced body weight,fat accumulation,proinflammatory cytokine levels(IL-1β IL-6、MCP-1 and LPS),and improved impaired glucose tolerance as well as gut barrier.Using 16S rRNA sequencing and non-targeted metabolome,CMP reversed the HFD-induced gut microbiota dysbiosis,as indicated by the elevated population of Alloprevotella,Parabacteroides,Butyricimonas,and Alistipes,which were negatively correlated with obesity-related indices;and decreased population of Negativebacillus,which were positively correlated with obesity-related indices,in addition to altered levels of metabolites,such as brassicasterol.The correlation analysis indicated that brassicasterol not only was positively associated with Alistipes and Parabacteroides,but also negatively associated with obesity-related indices,indicating it might be the potential mediator of anti-obesity effect of CMP.(3)It had been proved that brassicasterol was one of the important material bases of CMP,and can improve lipid accumulation through PPARy signal pathway.The contents of brassicasterol in serum,liver and epididymal fat were significantly increased by CMP supplementation using HPLC-MS/MS quantitation.Then CMP significantly promoted the enrichment of brassicasterol by fermentation with gut microbiota.Furthermore,we found that brassicasterol inhibited lipid accumulation in 3T3-L1 cells by down-regulating the expressions of PPARγ and C/EBPβ.In conclusion,this study demonstrated that CMP has positive effects on alleviating side effects of HFD,which is associated with gut microbiota and metabolites,and revealed that brassicasterol is the important material basis for the anti-obesity effect of CMP.