# Physiological Responses to Thermal Stress in the Liver of Gymnocypris eckloni Revealed by Multi-Omics

## TL;DR

This study explores how the liver of a cold-water fish adapts to heat stress, revealing molecular and metabolic changes that could help conserve similar species under climate change.

## Contribution

The study provides novel insights into the multi-omics responses of a cold-adapted fish to thermal stress, identifying key regulatory networks and metabolic pathways.

## Key findings

- Liver tissue showed structural damage and metabolic remodeling under heat stress.
- Key pathways like glutathione and tryptophan metabolism were central to the thermal stress response.
- MicroRNAs such as miR-196a-5p and miR-132-3p regulate metabolic genes during heat exposure.

## Abstract

As global temperatures rise, cold-adapted species such as Gymnocypris eckloni, endemic to the Tibetan Plateau, are increasingly threatened by thermal stress. This study investigates the physiological and molecular responses of Gymnocypris eckloni to prolonged heat exposure, with a focus on liver adaptation mechanisms. While no significant changes in growth were observed, histological and multi-omics analyses revealed substantial cellular and metabolic remodeling in the liver. The fish exhibited a shift in energy allocation, suppressing anabolic processes while enhancing stress-responsive pathways involved in protein homeostasis and cellular protection. Regulatory mechanisms, including microRNA-mediated gene expression, appear to play a key role in fine-tuning these adaptive responses. Overall, Gymnocypris eckloni demonstrates a complex but finite capacity to maintain physiological stability under elevated temperatures. These findings enhance our understanding of how climate change affects cold-adapted species and could guide future conservation efforts.

Climate-change-induced thermal stress poses a significant threat to cold-adapted aquatic species, particularly fish endemic to high-altitude ecosystems such as Gymnocypris eckloni, which is native to the Qinghai-Tibetan Plateau. To elucidate the molecular and metabolic mechanisms underlying their response to elevated temperatures, we integrated RNA-seq, miRNA-seq, and LC-MS-based metabolomic analyses of liver tissue from fish exposed to chronic thermal stress (HT) versus control (CT) conditions. Although no significant differences were observed in growth parameters, histopathological examination revealed structural damage under heat stress. Transcriptomic analysis identified widespread dysregulation of genes involved in energy metabolism, with significant downregulation of pathways related to amino acid, fatty acid, glucose, and oxidative phosphorylation. In contrast, upregulated DEGs were enriched in N-glycan biosynthesis, protein processing in the endoplasmic reticulum, and phagosome. Concomitant miRNA profiling revealed differentially expressed miRNAs, including miR-196a-5p, miR-132-3p, and miR-181b-5p, which were predicted to regulate key metabolic genes such as ugt1a1, pepck, and calr. Metabolomic analysis further demonstrated significant alterations in metabolic profiles, with glutathione metabolism, tryptophan metabolism, steroid hormone biosynthesis, and pyruvate metabolism emerging as central pathways in the heat stress response. Integrated multi-omics analysis confirmed coordinated regulation of these pathways, highlighting the critical role of glutathione and tryptophan, as well as disruptions in purine and energy metabolism. The DEMiR-DEG-DEM networks involving miR-196a-5p-pepck-PEP, miR-133a-3p-gne-UDP-GlcNAc, and miR-132-3p-ugt1a1-Bilirubin may play an important role in thermal stress. This study provided a new perspective on the molecular, regulatory, and metabolic adaptations of Gymnocypris eckloni to thermal stress, identifying potential biomarkers and regulatory networks that may inform conservation strategies for cold-water fish under global warming.