Fish MicroRNA Responses to Thermal Stress: Insights and Implications for Aquaculture and Conservation Amid Global Warming.

In the context of global warming, heat tolerance is becoming a crucial physiological trait influencing fish species' distribution and survival. While our understanding of fish heat tolerance and stress has expanded from behavioral studies to transcriptomic analyses, knowledge at the transcriptomic level is still limited. Recently, the highly conserved microRNAs (miRNAs) have provided new insights into the molecular mechanisms of heat stress in fish. This review systematically examines current research across three main reference databases to elucidate the universal responses and mechanisms of fish miRNAs under heat stress. Our initial screening of 569 articles identified 13 target papers for comprehensive analysis. Among these, at least 214 differentially expressed miRNAs (DEMs) were found, with 15 DEMs appearing in at least two studies (12 were upregulated and 13 were downregulated). The 15 recurrent DEMs were analyzed using DIANA mirPath v.3 and the microT-CDS v5.0 database to identify potential target genes. The results suggest that multiple miRNAs target various genes, forming a complex network that regulates glucose and energy metabolism, maintains homeostasis, and modulates inflammation and immune responses. Significantly, , , , and were consistently differentially expressed in multiple studies, indicating their potential relevance in heat stress responses. However, these miRNAs should not be considered definitive biomarkers without further validation. Future research should focus on experimentally confirming their regulatory roles through functional assays, conducting transcriptomic comparisons across different species, and performing target validation studies. These miRNAs, conserved across species, could be valuable for monitoring wild fish health, enhancing aquaculture breeding, and guiding conservation strategies. However, the specific regulatory mechanisms of these miRNAs need clarification to confirm their reliability as biomarkers for thermal stress.