Effect of fasting and refeeding on serum physiology, intestinal microbiota, and transcriptome in Pseudobagrus vachellii

Fasting is a common phenomenon caused by environmental factors. Here, changes in growth, serum biochemical parameters, intestinal microbiota, and liver transcriptome were investigated of Pseudobagrus vachellii subjected to fasting and refeeding. Fasting resulted in a significant decrease in body weight, but a compensatory growth occurred after refeeding. Serum biochemical indices including triglycerides, glucose, urea nitrogen, aspartate transaminase, and alanine transaminase were strongly affected by fasting and refeeding. Large amounts of glucose and fat were utilised during fasting, and liver functions can be returned to normal in P. vachellii after refeeding. 16 S rDNA analysis showed that fasting altered intestinal microbiota homeostasis and decreased intestinal alpha-diversity. At the phylum level, the dominant phyla were Proteobacteria, Firmicutes, Fusobacteriota, and Bacteroidota. Additionally, fasting significantly increased the abundance of the genera Plesiomonas, Edwardsiella, and Barnesiellaceae, whereas Romboutsia abundance decreased, indicating an increase in opportunistic pathogen abundance. However, after 7 days of refeeding, the composition of the gut microbiota was partially recovered. Additionally, the transcriptome analysis of the liver tissues showed that most of the identified DEGs, such as ACACA, FASN, Akt3, SCDb, and FADS2, were related to energy- and metabolism-related pathways, including fatty acid metabolism, glucagon-signalling pathway, AMPK-signalling pathway, apoptosis, carbon metabolism, and oxidative phosphorylation. Many DEGs detected during fasting were restored to normal levels after refeeding. These findings provide an important theoretical basis for future investigation of the fish physiological and ecological mechanisms underlying adaptations to food restriction.