Physicochemical Characterization of a Polysaccharide from Green Microalga Chlorella pyrenoidosa and Its Hypolipidemic Activity via Gut Microbiota Regulation in Rats

A bioactive polysaccharide from microalga Chlorella pyrenoidosa (CPP) was successively prepared via DEAE-52 and G-100 columns. Nuclear magnetic resonance analysis showed that the main glycosidic bonds were composed of 1,2-linked-α- l -Fuc p, 1,4-linked-α- l -Rha p, 1,4-linked-β- l -Ara f, 1-linked-α- d -Glc p, 1,3-linked-β- d -Glc p A, 1,4-linked-β- d -Xyl p, and 1,3,6-linked-β- d -Man p . Its molecular weight was 5.63 × 10 6 Da. The hypolipidemic effect and intestinal flora regulation of CPP on diet-induced rats were evaluated through histopathology and biochemistry analyses. CPP could improve plasma and liver lipid metabolism and accelerate the metabolism of the cecal total bile acids and short-chain fatty acids. CPP has also upregulated the adenosine-monophosphate-activated protein kinase α and downregulated the acetyl-CoA carboxylase, sterol regulatory element-binding protein 1c, and β-hydroxy β-methylglutaryl-CoA expressions. Moreover, with the 16S rRNA gene sequencing, it was revealed that the composition of intestinal flora changed drastically after treatment, such as the bloom of Coprococcus _1, Lactobacillus, and Turicibacter, whereas there was a strong reduction of the [ Ruminococcus ]_ gauvreauii _group. The above results illustrated that CPP might be served as an effective ingredient to ameliorate lipid metabolism disorders and intestinal flora in hyperlipidemia rats.