Integrated Gut–Brain Axis Response to Freezing and Recovery in Freeze-Tolerant Fish, Perccottus glenii

The molecular mechanisms underlying freezing recovery in vertebrates, particularly in teleost fish, remain inadequately understood. This study utilized an integrated approach combining brain transcriptomics and gut microbiota analysis to investigate the recovery process in the freeze-tolerant species Perccottus glenii following experimental freezing and thawing. Significant transcriptomic reprogramming was observed in brain tissue, with the PPAR signaling pathway strongly activated immediately upon thawing (R0), potentially facilitating lipid metabolism and neuroprotection during ischemic stress. After 4 h of recovery (R4), circadian rhythm pathways were significantly upregulated, suggesting a potential role in coordinating metabolic recovery during reperfusion. Concurrently, gut microbiota analysis revealed substantial community shifts, characterized by a marked decrease in Bacillota and an increase in Pseudomonadota during the initial recovery phase. These findings suggest that successful freezing recovery in P. glenii is associated with coordinated changes in brain and gut, highlighting potential roles of metabolic adaptation and microbial ecological dynamics under the specific freezing protocol employed.