Partially Acid-Hydrolyzed Porphyran Improved Dextran Sulfate Sodium-Induced Acute Colitis by Modulation of Gut Microbiota and Enhancing the Mucosal Barrier

The pharmacological values of marine algal polysaccharides on gut health are being recognized in recent research. However, the protective effect of degraded polysaccharides from Porphyra haitanensis (PHP-D) on the colonic mucosal barrier damaged in ulcerative colitis is poorly understood. The purpose of this study was to investigate how PHP-D could maintain the integrity of colonic mucosal layer mediated by microbiota in a dextran sulfate sodium (DSS)-induced colitis mouse model. Structural analysis revealed that PHP-D had a typical porphyran structure having a backbone of alternating (1 → 3)-linked β-d-galactopyranose units linked to either (1 → 4)-3,6-anhydro-α-l-galactopyranose units or (1 → 4)-linked α-l-galactose-6-sulfate units. An in vivo study demonstrated that PHP-D treatment reduced the severity of DSS-induced ulcerative colitis. 16S rRNA phylogenetic sequencing revealed that PHP-D affected the diversity of gut microbiota with an increase of Bacteroides, Muribaculum, and Lactobacillus species. Similarly, PHP-D increased levels of short-chain fatty acids. Furthermore, PHP-D restored mucus thickness and improved the expression of tight junction proteins. This work demonstrates that PHP-D is capable of enhancing a colonic mucosal barrier. These outcomes offer unique perspectives on the potential application of P. haitanensis as a promising natural product for the management of ulcerative colitis.