| As an important component of lipids,Triglyceride(TG)plays an important role in energy metabolism,but the TG metabolism mechanism of Largemouth bass in hypoxic environment has not been fully revealed.To investigate the effects of acute hypoxic stress on the TG metabolism of Largemouth bass,we established a model of acute hypoxic stress in Largemouth bass by simulating a hypoxic environment under laboratory conditions.Three treatment groups(DO: 7.0 ± 0.15 mg/L,3.5 ± 0.12 mg/L,1.2 ± 0.2 mg/L)and six sampling time points(0 h,4 h,8 h,12 h,24 h and reoxygenation 12 h)were set in the experiment to measure the biochemical markers related to TG metabolism in the four of tissues liver,heart,brain and mesenteric fat of Largemouth bass after acute hypoxic stress and detect the expression of related genes.The results are as follows:1.Effect of acute hypoxic stress on TG metabolic index of Largemouth bassAfter acute hypoxic stress,the contents of TG and FFA in the four tissues of Largemouth bass were significantly increased(P < 0.05).After reoxygenation,only the TG content of the liver returned to normal level,and the TG content of the other three tissues was still significantly higher than that of the control(P < 0.05).While the FFA content of the four tissues all recovered to normal levels after reoxygenation.After acute hypoxic stress,LPS enzyme activity in liver,heart and brain increased significantly in different time(P < 0.05),but the activity of LPS enzyme in mesenteric fat was not significantly affected.The activity of LPS enzyme in the heart returned to normal level after reoxygenation,and the activity of LPS enzyme in liver and brain was still lower than normal(P < 0.05).The activity of LPL enzyme in heart tissue showed a significant increase after hypoxic stress(P < 0.05),which was contrary to the trend of the other three kinds of tissues.And after reoxygenation,only the activity of LPL enzyme returned to normal levels in the heart.According to the above results,the hypoxia inhibited the FFA oxidative decomposition and affected the activity of LPS and LPL enzymes,so as to change the synthesis and hydrolysis rate of TG.2.Effects of acute hypoxic stress on gene expression related to TG metabolism of Largemouth bassThis experiment successfully cloned some CDS sequences of three subtypes of PPARs.According to the results of tissue distribution,three subtypes were mainly expressed in tissues such as liver,heart,brain and mesenteric fat.Further studies showed that the expression levels of PPAR alpha gene in all four tissues were significantly up-regulated at 8 and 12 h of acute hypoxic stress(P < 0.05).After reoxygenation,only the gene expression quantity of PPAR alpha gene in the liver returned to normal levels.Without significant expression in the heart,PPAR beta was significantly up-regulated in the liver and brain(P < 0.05)and significantly down-regulated in mesenteric fat(P < 0.05).After reoxygenation,only gene expression quantity of PPAR beta in mesenteric fat returned to normal level.The expression quantity of PPAR gamma gene was significantly up-regulated in the liver(P < 0.05),but not obvious in the other three tissues.After reoxygenation,only the gene expression quantity of PPAR gamma in the mesenteric fat returned to normal levels.In addition,differential expression of the LPL gene is also induced by hypoxia.At 8 h of hypoxic stress,the expression quantity of LPL gene was significantly down-regulated in mesenteric fat(P < 0.05)and significantly up-regulated in the other three tissues(P < 0.05).After reoxygenation,only the expression quantity of LPL gene in the mesenteric fat returned to normal levels,and other three tissues were still above normal levels.According to these results,the expression difference of PPARs and its downstream gene LPL in four tissues is induced by hypoxia to regulate the TG metabolism in the hypoxic environment.These results provide opinions to explore the energy regulation pathways of Largemouth bass under acute hypoxic stress,and provide references for the breeding of hypoxia-resist Largemouth bass and healthy cultivation of Largemouth bass healthy farming. |
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