Amuc_1100 pretreatment alleviates acute pancreatitis in a mouse model through regulating gut microbiota and inhibiting inflammatory infiltration.

Amuc_1100 is a membrane protein from Akkermansia muciniphila, which has been found to play a role in host immunological homeostasis in the gastrointestinal tract by activating TLR2 and TLR4. In this study we investigated the effects and underlying mechanisms of Amuc_1100 on acute pancreatitis (AP) induced in mice by intraperitoneal injection of caerulein and lipopolysaccharide (LPS). The mice were treated with the protein Amuc_1100 (3 μg, i.g.) for 20 days before caerulein injection. Cecal contents of the mice were collected for 16S rRNA sequencing. We found that pretreatment with Amuc_1100 significantly alleviated AP-associated pancreatic injury, reduced serum amylase and lipase. Amuc_1100 pretreatment significantly inhibited the expression of proinflammatory cytokines (TNF-α, IL-1β, IFN-γ and IL-6) in spleen and pancreas through inhibiting NF-κB signaling pathway. Moreover, Amuc_1100 pretreatment significantly decreased the inflammatory infiltration, accompanied by the reduction of Ly6C macrophages and neutrophils in the spleen of AP mice. Gut microbiome analysis showed that the abundance of Bacteroidetes, Proteobacteria, Desulfobacterota and Campilobacterota was decreased, while the proportion of Firmicutes and Actinobacteriota was increased in AP mice pretreated with Amuc_1100. We further demonstrated that Amuc_1100 pretreatment restored the enrichment of tryptophan metabolism, which was mediated by intestinal flora. These results provide new evidence that Amuc_1100 lessens the severity of AP through its anti-inflammatory properties with a reduction of macrophages and neutrophil infiltration, as well as its regulation of the composition of intestinal flora and tryptophan metabolism.