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

A bioactive polysaccharide from microalga <i>Chlorella pyrenoidosa</i> (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<i>p</i>, 1,4-linked-α-l-Rha<i>p</i>, 1,4-linked-β-l-Ara<i>f</i>, 1-linked-α-d-Glc<i>p</i>, 1,3-linked-β-d-Glc<i>p</i>A, 1,4-linked-β-d-Xyl<i>p</i>, and 1,3,6-linked-β-d-Man<i>p</i>. Its molecular weight was 5.63 × 10⁶ 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 <i>Coprococcus</i>_1, <i>Lactobacillus</i>, and <i>Turicibacter</i>, whereas there was a strong reduction of the [<i>Ruminococcus</i>]_<i>gauvreauii</i>_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.