Recent studies have shown that seaweed
polysaccharides can ameliorate high-fat-diet (HFD)-induced
metabolic syndromes associated with the regulatory function of gut microbiota. However, kelp, a natural source of seaweed
polysaccharides, is highly viscous, making it difficult to prepare
dietary fiber by simple degradation. Therefore, we developed a novel method of preparing low-molecular-weight
polysaccharides from Laminaria japonica by combining high-pressure pretreatment and composite enzymatic degradation and evaluated the
obesity prevention activity of these
polysaccharides. Seaweed L. japonica
polysaccharides (SJP) were rapidly utilized by the human fecal microbiota in vitro, resulting in the generation of
short-chain fatty acids (SCFAs), specifically
acetate and
propionate. The in vivo effects of SJP on the intestinal microbiota were also investigated using HFD-fed C57BL/6J mice. SJP reduced
weight gain and fat deposition in HFD-fed mice and increased the concentration of total SCFAs, including
acetate,
propionate, and
butyrate in the feces. SJP ameliorated HFD-induced gut microbiota
dysbiosis, resulting in increased abundance of Faecalibaculum, Romboutsia, and Clostridium sensu stricto 1 and decreased abundance of Blautia and Lactobacillus. Further, SJP enhanced the abundance of Akkermansia muciniphila in mice provided with HFD and normal chow. Single-strain culture experiments also revealed that SJP promoted the growth of A. muciniphila. This study highlights the potential use of SJP, prepared using composite enzymatic degradation (
cellulase and recombinant
alginate lyase), in preventing
obesity and restoring intestinal homeostasis in obese individuals.