The purpose of this study was to investigate the hypoglycemic effect and mechanism of Dendrobium officinale polysaccharide (DOP) on type 2 diabetes mellitus (T2DM) mice established by high-fat diet and streptozotocin. The results showed that DOP improved glycolipid metabolism and serum inflammation levels, and inhibited intestinal-derived lipopolysaccharide (LPS) translocation, suggesting that inhibiting LPS-mediated intestinal barrier damage may be a key target for DOP to alleviate T2DM. Interestingly, the study found that DOP reduced intestinal inflammation and oxidative stress levels, significantly up-regulated the mRNA expression of tight junction proteins Claudin-1, Occludin and Zonula occluden-1 (ZO-1), and ameliorated intestinal epithelial damage. In addition, DOP strongly inhibited the intestinal pathogenic bacteria and LPS-producing bacteria Helicobacter, Enterococcus and Desulfovibrio with a reduction rate of 95%, 73% and 9%, respectively, and promoted the proliferation of anti-inflammatory bacteria Bifidobacterium and Lactobacillus by 139% and 8%, respectively. Taken together, the hypoglycemic effect of DOP was related to the protection of intestinal mucosal barrier, and its underlying mechanism lied in its excellent anti-inflammatory and gut microbiota-modulatory effects, providing a theoretical basis for developing DOP as a novel prebiotic in functional food for diabetes.

In this study, the structural characters, antioxidant activities and bile acid-binding ability of sea buckthorn polysaccharides (HRPs) obtained by the commonly used hot water (HRP-W), pressurized hot water (HRP-H), ultrasonic (HRP-U), acid (HRP-C) and alkali (HRP-A) assisted extraction methods were investigated. The results demonstrated that extraction methods had significant effects on extraction yield, monosaccharide composition, molecular weight, particle size, triple-helical structure, and surface morphology of HRPs except for the major linkage bands. Thermogravimetric analysis showed that HRP-U with filamentous reticular microstructure exhibited better thermal stability. The HRP-A with the lowest molecular weight and highest arabinose content possessed the best antioxidant activities. Moreover, the rheological analysis indicated that HRPs with higher galacturonic acid content and molecular weight showed higher viscosity and stronger crosslinking network (HRP-C, HRP-W and HRP-U), which exhibited stronger bile acid binding capacity. The present findings provide scientific evidence in the preparation technology of sea buckthorn polysaccharides with good antioxidant and bile acid binding capacity which are related to the structure affected by the extraction methods.