Fig 1: Hypothesis schema depicting the mechanism of L-fucose in HSD-promoted inflammation. Mice received CD or HSD for 8 consecutive weeks. The CD-fed mice possess a normal gut microbiota, which leads to a higher abundance of an intestinal microbial metabolite L-fucose. L-fucose has anti-inflammatory properties, and when CD-fed mice are stimulated with inflammatory injuries, the inflammatory response in CD-fed mice is controlled at a reasonable level. On the contrary, the HSD consumption altered the composition of gut microbiota in the HSD-fed mice and significantly reduced the abundance of L-fucose. When HSD-fed mice are stimulated with inflammatory injuries, reduced L-fucose levels in the gut contributed to a more substantial inflammatory response, as evidenced by the increased accumulation of inflammatory cells and elevated levels of inflammatory cytokines including TNF-α, IL-6, and MCP-1.