Effects of Polymannuronic Acid on the Intestinal Microbiota in Mice after Long-Term Intragastric Administration.

Polymannuronic acid (PM) is an alginate oligosaccharide derived from brown algae with a characterized structure and excellent biological activities. Herein, mice were given different doses of PM through 30-day-long-term intragastric administration, and the contents of the jejunum, ileum, and colon were analyzed by 16S rRNA gene sequencing technology for microbial diversity, and relevant experiments were verified according to the analysis results so as to comprehensively evaluate the effects of PM on the intestinal flora. The PM (400 mg/kg and 100 mg/kg) could regulate the microflora balance at the phylum level and increase the microflora richness in the jejunum, ileum, and colon of the mice. The PM could induce more strains that are negatively correlated with Escherichia, thereby reducing the relative abundance of Escherichia. Analysis of bacterial function showed that high and low doses of PM could promote lipid metabolism in the bacterial communities. Moreover, the PM could reduce serum total cholesterol and cholesterol ester levels in a concentration-dependent manner. High-dose PM could lead to colonic intestinal inflammation by increasing the relative abundance of multiple bacterial groups in the jejunum, ileum, and colon. Moreover, high-dose PM could increase lipopolysaccharide-binding protein and interleukin-1β levels. Therefore, the dose of PM plays an important role in its efficacy, and its biological activity is dosedifferent.