Structural characterisation of Cistanche tubulosa polysaccharides and their effects against non-alcoholic steatohepatitis via gut microbiota regulation

Non-alcoholic steatohepatitis (NASH) is a growing global health burden for which there are no approved drugs. Cistanche tubulosa is a traditional Chinese medicine, with polysaccharide as one of its active components. However, its physicochemical structure is unclear, and no research has assessed its effect on NASH. In this study, polysaccharides from C. tubulosa were extracted using an aqueous alcoholic precipitation method. Two polysaccharides, named CTAN and CTBN, were successfully obtained after separation and purification through column chromatography. CTAN was identified as a polysaccharide composed of →6)α-D-Glcp-(1→. Meanwhile, CTBN was revealed to be polysaccharide with a → 4)α-D-Glcp-(1 → backbone and α-D-Glcp-(1 → branches attached to →3,4)α-D-Glcp-(1→. In vitro experimental studies demonstrated that the two polysaccharides exhibited no significant toxicity, with CTBN showing pronounced lipid-regulating and anti-inflammatory effects. We systematically analysed the effects of CTBN on high-fat high-cholesterol diet (HFHCD)–induced NASH in mice. Results showed that CTBN alleviated NASH by improving lipid metabolism disorders, reducing hepatic inflammation and fibrosis induced by HFHCD and protecting the intestinal mucosal barrier. Additionally, the metabolism of intestinal microbiota and SCFAs could been regulated by CTBN. Beneficial effects about liver and colon were associated with the modulation of intestinal flora, as confirmed by experiments in pseudo- germfree mice.