Multi-omics integrated analysis reveals the physiological response of large yellow croaker (Larimichthys crocea) to starvation and refeeding during overwintering

This study aimed to investigate the physiological response to starvation and refeeding during the overwintering period of large yellow croaker (Larimichthys crocea) using physiological and biochemical assays, microbiomics and transcriptomics. Fish were sampled at the beginning of starvation (Fa0 group), after 8 weeks (Fa8 group), after 16 weeks (Fa16 group), and after 8 weeks of refeeding (Fe group). Results indicated that compared to the Fa0 group, the viscerosomatic index (VSI) and intestinal digestive enzyme activities (trypsin, lipase, and amylase) significantly decreased in the Fa8 and Fa16 groups (P < 0.05), but these indicators recovered in the Fe group. Prolonged starvation significantly reduced triglyceride (TG) levels in both serum and liver, but these levels rebounded after 8 weeks of refeeding. Chronic starvation also led to a notable increase in serum low-density lipoprotein (LDL) levels, accompanied by a significant decrease in liver LDL content. As the duration of starvation increasing, the antioxidant and immune capabilities in the serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), lysozyme (LZM), alkaline phosphatase (AKP), acid phosphatase (ACP) significantly enhanced (P < 0.05), and these indicators significantly declined in the Fe group (P < 0.05). Intestinal flora analysis showed that the Alpha diversity gradually decreased with the prolongation of starvation but recovered after 8 weeks of refeeding, with the abundance of Akkermansia muciniphila significantly increasing (P < 0.05) in the Fa16 group compared to the other groups. Liver transcriptomic analysis revealed that upregulated genes enriched in pathways such as "Ribosome biogenesis in eukaryotes", "Proteasome", "RNA transport", "Biosynthesis of unsaturated fatty acids", "Fatty acid metabolism", "Fatty acid degradation", and "PPAR signaling pathway" (P < 0.05), while downregulated genes significantly enriched in "metabolic pathways" (P < 0.05) in the Fa16 group. Genes related to immune responses were significantly downregulated (P < 0.05) in the Fe group. The correlation analysis of intestinal flora and transcriptome revealed LOC104925398 (complement C3-like) and LOC113745439 (heat shock 70 kDa protein) exhibited significant positive correlations with Levilactobacillus brevis, unclassified Lachnoclostridium, Escherichia coli, and Akkermansia muciniphila (P < 0.05). In conclusion, prolonged starvation was more advantageous to the safe overwintering of large yellow croaker. Our study revealed the physiological response of large yellow croaker to starvation and refeeding during the overwintering period, providing a theoretical foundation for the formulation of safe overwintering strategies.