نبذة مختصرة : Research background. Sparassis latifolia polysaccharides can regulate lipids and cholesterol in serum and liver. However, little is known about the regulation mechanism of the polysaccharides on cholesterol metabolism and especially the causal relationship with gut microbiota regulation. This study will provide a theoretical basis for the cholesterol-lowering mechanism of S. latifolia polysaccharides and further development of functional foods. Experimental approach. In this study, we investigated how the regulation mechanism of Sparassis latifolia polysaccharides affects intestinal cholesterol metabolism in high-fat and high-cholesterol diet-fed rats. Briefly, enzymatic colorimetric microplate assay was used to determine the concentration of faecal bile acid. Gas chromatography-mass spectrometry was used to detect the content of cholesterol and alcohol in faeces. Haematoxylin and eosin staining method was applied to observe the changes in the structure of the small intestine tissue. The related gene expressions in jejunum and ileum were detected by real-time fluorescent quantitative polymerase chain reaction. The related protein expressions in jejunum were studied by using Western blot. High-throughput sequencing was used to detect the intestinal flora changes of the caecal contents. Gas chromatography-mass spectrometry was applied to detect the concentration of short-chain fatty acids in the caecal content. Results and conclusions. The results showed that Sparassis latifolia polysaccharides could improve the intestinal morphological structure and physiological indices in rats fed high-fat and high-cholesterol diet. Moreover, it could improve intestinal cholesterol metabolism disorder induced by high-fat and high-cholesterol diets via the reduction of the expression of HMGCR, NPC1L1, ACAT2, MTP, ASBT and IBABP mRNA or protein, increasing ABCG8 mRNA expression. In addition, it could also increase the relative abundance of Bacteroides, Butyricicoccus, Parabacteroides, Parasutteerella and Alloprevotella and the short-chain fatty acid concentration, to comprehensively regulate the intestinal cholesterol metabolism. The metabolomics analysis found that Sparassis latifolia polysaccharides could affect lipid, carbohydrate and other related metabolites. Some biomarkers associated with cholesterol metabolism correlated significantly with the abundance of specific intestinal microbiota. Novelty and scientific contribution. These findings indicate that Sparassis latifolia polysaccharides could attenuate intestinal cholesterol metabolism disorder, correlating with modulating gut microbiota and improving host metabolism. They provide theoretical support for the development of Sparassis latifolia as a new food resource.
Pozadina istraživanja. Polisaharidi iz gljive Sparassis latifolia mogu regulirati udjel lipida i kolesterola u serumu i jetri. Međutim, mehanizam regulacije metabolizma kolesterola i osobito njegova povezanost s regulacijom crijevne mikrobiote slabo su poznati. U ovom je radu teorijski opisan mehanizam snižavanja udjela kolesterola pomoću polisaharida iz gljive S. latifolia, te je istražena mogućnost razvoja funkcionalne hrane s ispitanim polisaharidima. Eksperimentalni pristup. U ovom smo radu ispitali kako mehanizam regulacije polisaharida iz gljive S. latifolia utječe na metabolizam kolesterola u crijevima miševa hranjenih hranom s velikim udjelom masti i kolesterola. Ukratko, određena je koncentracija žučne kiseline u stolici pomoću kolorimetrijskog testa na mikrotitracijskim pliticama. Tekućinskom kromatografijom spregnutom s masenom spektrometrijom određeni su udjeli kolesterola i alkohola u fecesu. Promjene strukture tkiva tankog crijeva praćene su bojenjem hematoksilinom i eozinom. Ekspresije gena u jejunumu i ileumu određene su kvantitativnom lančanom reakcijom polimeraze u stvarnom vremenu, dok je ekspresija proteina u jejunumu ispitana pomoću metode Western blot. Metodom sekvenciranja visoke propusnosti praćene su promjene crijevne flore u slijepom crijevu. Koncentracija kratkolančanih masnih kiselina u slijepom crijevu određena je plinskom kromatografijom spregnutom s masenom spektrometrijom. Rezultati i zaključci. Rezultati pokazuju da polisaharidi iz gljive S. latifolia mogu poboljšati morfološku strukturu i fiziološke značajke crijeva miševa hranjenih hranom s velikim udjelom masti i kolesterola. Osim toga, s obzirom na to da smanjuju ekspresiju HMGCR, NPC1L1, ACAT2, MTP, ASBT i IBABP mRNA ili proteina, te povećavaju ekspresiju ABCG8 mRNA, polisaharidi mogu ublažiti poremećaj metabolizma kolesterola u crijevima uzrokovan masnom prehranom. Također mogu povećati broj bakterija iz rodova Bacteroides, Butyricicoccus, Parabacteroides, Parasutteerella i Alloprevotella, te koncentraciju kratkolančanih masnih kiselina, čime reguliraju metabolizam kolesterola u crijevima. Metabolomička je analiza pokazala da polisaharidi iz gljive S. latifolia mogu utjecati na lipide, ugljikohidrate i ostale metabolite. Neki su biomarkeri metabolizma kolesterola bili u bitnoj korelaciji s povećanim udjelom specifične crijevne mikrobiote. Novina i znanstveni doprinos. Dobiveni rezultati pokazuju da polisaharidi iz gljive S. latifolia mogu ublažiti poremećaj metabolizma kolesterola u crijevima te regulirati crijevnu mikrobiotu, što pozitivno utječe na metabolizam domaćina. Time je osigurana teorijska podloga za razvoj gljive S. latifolia kao novog izvora hrane.
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