Vitamin D3 identified from metabolomic analysis of intestinal contents promotes an antibacterial response in shrimp intestinal immunity

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Vibrio parahaemolyticus is a critical pathogenic bacterium for the kuruma shrimp, Marsupenaeus japonicus. Antibacterial drug application is the main method to control vibriosis in aquaculture; however, drug residues and the emergence of resistant bacteria have restricted their use. Therefore, the present study aimed to identify metabolites that are likely to play roles in the homeostasis of the intestinal microbiota, and to further explore their application in shrimp aquaculture. Metabolomic analysis, using high-performance liquid chromatography tandem mass spectrometry (HPLC/MS) of shrimp intestinal contents, was performed. The results showed that metabolic profiles changed distinctly in shrimp intestines after V. parahaemolyticus challenge compared with that in the control. The levels of 39 metabolites changed significantly after Vibrio challenge. Notably, vitamin D3 metabolism was enhanced in shrimp intestines after Vibrio challenge. Oral administration of 0.1 mg/kg vitamin D3 effectively improved the survival rate of shrimp infected with V. parahaemolyticus. Further studies indicated that vitamin D3 promoted bacterial clearance by regulating the expression of antimicrobial peptides genes in the shrimp intestines. Transcriptomics analysis revealed that vitamin D3 functioned in shrimp intestinal immunity by activating the prophenoloxidase system and Toll signaling pathway to induce the expression of certain antimicrobial peptides to maintain microbial homeostasis. Collectively, we identified vitamin D3 as an immunomodulatory factor that plays an important role in boosting the immune response against pathogenic bacteria in shrimp.