Identification of potential biomarkers for soybean meal-induced enteritis in juvenile pearl gentian grouper, Epinephelus lanceolatus♂ x Epinephelus fuscoguttatus♀

This study identifies the potential biomarkers of soybean meal-induced enteritis in juvenile pearl gentian grouper using ultra-performance liquid chromatography-mass spectrometry (UPLC-MS). There were 480 female juvenile grouper randomly assigned to two groups (n = 4), including the fish meal (FM) group (control) and 20% soybean meal (SBM20) group, which were fed by two iso-nitrogenous (50% crude protein) and isolipidic (10% crude lipid) diets for 10 weeks. The diets and distal intestinal (DI) content samples of FM and SBM20 groups were collected for metabonomics analysis. The data generated from the UPLC-MS was analysed using principal components analysis (PCA) and partial least-squares discriminant analysis (PLS-DA). The PLS-DA model with satisfactory explanatory and predictive ability can discriminate the SBM20 from the FM group. The area under the curve (AUC) was calculated as the cumulative ability to distinguish between dietary patterns. Results showed that 20% SBM substitution level induced distal intestinal physiological injury and enteritis of juvenile grouper, which can be reflected by hematoxylin and eosin staining and transmission electron microscope analysis. In diets, a total of 171 metabolites in positive mode and 104 metabolites in negative mode in SBM20 group were significantly distinguished from the FM group. In DI contents, a total of 395 metabolites in positive mode and 219 metabolites in negative mode in SBM20 group were significantly distinguished from the FM group. Between diets and DI contents, there are only 9 co-contained differential metabolites in positive mode and 4 co-contained differential metabolites in negative mode. The 17 most influential metabolites in DI contents were identified as the potential biomarkers in positive and negative modes via the metabonomics UPLC-MS profiles. In DI contents, compared with the FM group, the intestines of 5-methylbenzimidazole, Glycitin, Byakangelicol, Genistin, Malonylglycitin, Genistein 4'-O-glucuronide, Glycitein, 3,4-dihydroxyphenylacetic acid, Daidzein, FMNH2, Soyasaponin I, olmelin, Genistein, Ginsenoside Ro, 4-Phenolsulfonic acid, and Baicalin in the SBM20 group were significantly increased (p < .01); however, the intensity of amfonelic acid in SBM20 group decreased significantly (p < .01) (AUC > 0.9). The present study identified a broad array of DI content metabolites that differed between FM and SBM dietary patterns that could provide some valuable reference for further management of fish intestine health issues.