Spatiotemporal regulation of apolipoproteins LcApoa1 and LcApoa4 in lipid transport and anti-inflammatory response of Larimichthys crocea fed fishmeal-free diets

The global fishmeal shortage has necessitated the use of plant-derived proteins in aquafeeds, but their antinutritional factors often compromise nutrient utilization in carnivorous fish like large yellow croaker ( Larimichthys crocea ) . This study investigated the molecular mechanisms underlying divergent feed efficiency (FE) in L. crocea fed fishmeal-free diets. Individuals with contrasting FE (high-FE vs. low-FE) but comparable feed intake were selected for comparative proteomic profiling of foregut and hindgut tissues using data-independent acquisition mass spectrometry (DIA-MS). A total of 210 and 200 differentially expressed proteins (DEPs) were identified in the foregut and hindgut, respectively. Functional enrichment analysis revealed distinct regional specialization: foregut DEPs were primarily involved in acute inflammatory responses and steroid hormone biosynthesis, whereas hindgut DEPs were enriched in amino acid and carbohydrate metabolism pathways. Notably, we observed spatiotemporal regulation of apolipoproteins, with LcApoa1 upregulated in the liver and foregut, and LcApoa4 elevated in the liver and hindgut. Bioinformatic characterization indicated that Lcapoa1 (768 bp, 255 aa) and Lcapoa4 (765 bp, 254 aa) each contain a single apolipoprotein domain. In vitro assays demonstrated that recombinant LcApoa1 (1.5 mg/mL) and LcApoa4 (1.0 mg/mL) significantly alleviated β-conglycinin-induced intestinal inflammation in L. crocea intestinal cells (LYCI) by upregulating anti-inflammatory mediators ( TGF-β , IL-10 ) and downregulating pro-inflammatory mediators ( TNF-α , IL-1β , IL-6 ). Collectively, our findings demonstrate that coordinated, region-specific activation of apolipoproteins promotes efficient lipid absorption and inflammation control in L. crocea fed fishmeal-free diets. These insights provide promising molecular targets for breeding high-efficiency strains and optimizing plant-protein feed formulations in aquaculture.