氧化鱼油对草鱼(Ctenopharyngodon idelluspond)肝胰脏、肠道胆固醇、胆汁酸合成代谢的影响

The Effect of Cholesterol and Bile Acid Metabolism Synthesis Pathway Related Enzymes in the Liver and Intestine under Oxidized Fish Oil in Ctenopharyngodon idelluspond

为了研究氧化鱼油对草鱼肝胰脏、肠道胆固醇、胆汁酸合成代谢的影响,本研究以豆油、鱼油、氧化鱼油作为饲料脂肪源,分别设计鱼油组(6F)、豆油组(6S)、2%氧化鱼油(2OF)、4%氧化鱼油(4OF)及6%氧化鱼油(6OF)5组等氮、等能半纯化饲料,在池塘网箱养殖平均体重为(74.8±1.2)g草鱼72 d。采用实时荧光定量PCR(q RT-PCR)的方法,测定了草鱼肝胰脏、肠道组织中四种胆固醇合成相关酶HMGCR、SREBP2、CETP、ABCA1和胆汁酸合成关键酶CYP7A1的基因表达活性,结合血清、肝胰脏和肠道TC、TBA含量分析了胆固醇、胆汁酸的合成强度的变化。结果显示:(1)添加氧化鱼油后,草鱼肝胰脏HMGCR基因表达活性显著上调(p<0.05),ABCA1和CYP7A1基因表达活性显著下调(p<0.05),肝胰脏TC、TBA含量显著增加(p<0.05);(2)添加氧化鱼油后,草鱼肠道HMGCR基因表达活性显著上调(p<0.05),CYP7A1基因表达活性显著下调(p<0.05),肠道TC含量显著增加(p<0.05),而TBA含量显著减少(p<0.05);(3)添加鱼油或氧化鱼油后,饲料∑PUFA含量与肝胰脏ABCA1基因表达活性呈显著正相关关系(p<0.05),饲料MDA含量与肠道ABCA1基因表达活性呈显著负相关关系(p<0.05)。结果表明,随着饲料氧化鱼油添加量的增加,在饲料∑PUFA含量减少和鱼油氧化产物MDA含量增加的交互影响下,肝胰脏和肠道细胞胆固醇合成能力、向细胞内转运胆固醇的能力增强,向细胞外转运胆固醇的能力、以胆固醇为原料合成胆汁酸的能力减弱,致使肝胰脏、肠道、血清胆固醇含量增加、而血清、肠道胆汁酸含量减少。肝胰脏胆汁酸含量增加,显示肝胰脏有胆汁酸淤积的发展趋势。预示着鱼体生理代谢可能需要更多的胆固醇以满足生理代谢的需要,而鱼体胆汁酸可能出现供给不足。

A 72-day expe riment was carried out to investigate the effect of grass carp cholesterol and bile acid metabolism synthesis pathway in liver and intestine under oxidized fish oil. Five diets containing different levels of soybean oil, fish oil and oxidized fish oil(6% fish oil, 6% soybean oil, 2% oxidized fish oil, 4% oxidized fish oil, 6%oxidized fish oil) were evaluated at the same nitrogen and energy. Using q RT-PCR method for quantitative detection of gene expression levels about cholesterol synthetic and regulation enzyme HMGCR, SREBP2, CETP,ABCA1 and bile acid synthetic enzyme CYP7A1 in liver and intestine, in addition the content of total bile acid(TBA) and total cholesterol(TC) in serum, liver and intestine. The results showed that under oxidized fish oil:(1) In the liver, the gene expression of HMGCR was significantly increased(p<0.05), the gene expressions of ABCA1 and CYP7A1 were significantly reduced( p<0.05), at the same time, the concentrations of TC and TBA were significantly increased(p<0.05);(2) In the intestine, the gene expression of HMGCR was significantly increased(p<0.05), the gene expression of CYP7A1 was significantly reduced(p<0.05), at the same time, the concentration of TC was significantly increased(p<0.05), and the concentration of TBA was significantly decreased(p<0.05);(3)The content of ΣPUFA was significant positive correlation with the ABCA1 gene expression(p<0.05) in the liver.The MDA content was significant negative correlation with the ABCA1 gene expression(p<0.05) in the intestine.Collectively, the present study demonstratesd under the fish oil nutritional and damaged interaction effects, the ability of cholesterol synthesis and intracellular transport cholesterol get enhance, and the capacity of extracellular transport cholesterol and bile acid synthesis get diminish in the liver and intestine. The result led to the cholesterol level increased in the serum, liver and intestine and the bile acid content decreased in the serum and intestine. As for the bile acid content increased in liver, it showed the trend of bile acid deposed in the liver. It indicated that the fish may need more cholesterol to meet the needs of the physiological metabolism, and bile acids may appear insufficient supply in fish.