有机硒缓解达氏鳇热应激肝损伤的抗氧化机制及转录谱特征OACHSSCD

[Objective]To investigate the molecular mechanisms by which organic selenium alleviates hepatic damage induced by thermal stress in Huso dauricus,providing theoretical basis for nutrition regulation strategy against heat stress in sub-cold water fish.[Method]Four experiment groups,such as control group(C,18℃),heat stress group(R,28℃),organic selenium group(S,18℃+5 mg/kg Se),and heat stress+organic Se group(RS,28℃+5 mg/kg Se).After 28 days of feeding,the growth performance indicators were determined,and liver tissue was collected for antioxidant parameters measurement and transcriptome sequencing using Illumina HiSeq 2500 platform.Subsequently,GO and KEGG databases were used for the function enrichment analysis of differentially expressed genes(DEGs),and the relative expression levels of critical candidate genes were validated by qRT-PCR.[Results]High temperature stress significantly inhibited the growth of juvenile H.dauricus,with the specific growth rate(SGR)in group R decreasing by 32.4%compared to group C(P<0.05).After mitigation with organic selenium,the SGR in group RS recovered to 86.6%of the control.Hepatic antioxidant parameters showed that group RS exhibited the lowest MDA molarity[(4.21±7.41)nmol/mg]and the highest SOD activity[(12.31±2.14)U/mg],confirming the antioxidant protective effect of organic selenium at physiological level.A total of 8 715 DEGs were identified in the R vs C comparison,with 58.2%being downregulated.Function enrichment analysis showed that thermal stress significantly activated immune response,heat shock response,and inflammation-related pathways(AGE-RAGE,p53,and PI3K-Akt signaling pathways),while suppressing energy metabolism-related pathways(pyrimidine metabolism,lipid metabolism,etc.).In the S vs C comparison,485 DEGs were detected,primarily enriched in cell cycle regulation,DNA repair,and glutathione metabolism pathways.qRT-PCR validation demonstrated that organic selenium significantly down-regulated the heat stress-induced hsp90 and ptenb gene expression levels(P<0.05);furthermore,the expression levels of mtor,ccnd1,tsc2,and ptenb genes in the RS group were significantly further down-regulated compared to group R,indicating a synergistic suppressive effect of organic selenium and heat stress on the PI3K-Akt-mTOR pathway.[Conclusion]Thermal stress causes hepatic damage in H.dauricus by inducing transcriptional reprogramming and metabolic disorders.In contrast,organic selenium effectively alleviated heat stress-induced liver injury at both physiological and molecular levels by enhancing antioxidant defense capacity,maintaining protein synthesis homeostasis,promoting DNA repair process,and profoundly suppressing the ptenb gene to regulate the PI3K-Akt-mTOR signaling axis,thereby actively down-regulating energy-consuming anabolic pathways on the basis of antioxidant protection to achieve an adaptive"metabolic throttling-repair priority"regulatory strategy.