共轭亚油酸同分异构体对肥胖Zucker大鼠的脂肪肝中的类二十烷酸的影响

Effect of Conjugated Linoleic Acid Isomers on Eicosanoids in Fatty Liver of Obese Zucker Rats

目的:检测使用共轭亚油酸(CLA)同分异构体后,Zucker大鼠肝脏中多种类二十烷酸水平以及探测与这些种类二十烷酸合成有关的酶的蛋白表达。方法:17周的雄性Zucker大鼠被随机分为对照组[瘦鼠对照组(lean control),和胖鼠对照组(fa/fa control)n=7]和治疗组[随机抽取的肥胖鼠(fa/fa 9,11CLA、fa/fa 10,12CLA),n=7],分别接受无CLA的对照饮食和加入0.4%(w/w)CLA的治疗饮食。8周后用高效液相质谱仪(HPLC/MS/MS)检测多种类二十烷酸水平;使用免疫印迹法(Westernblotting)探测与这些种类二十烷酸合成有关的酶的蛋白表达。结果:与对照组比较,t10,c12 CLA升高了肝组织中的白三烯4(LTB4)的水平(P<0.01)。然而,免疫印迹实验(Western blotting)显示,t10,c12 CLA(P<0.005)和c9,t11CLA(P<0.005)都抑制环氧合酶(COX2)的表达。与胖鼠对照组比较,瘦鼠对照组有较高的羟二十碳四烯酸(HODE)水平。结论:t10,c12 CLA减少脂肪肝里的总脂肪量,而抑制了COX2的蛋白表达、升高LTB4水平,两者对肝组织的影响,有待于组织学研究证实。胖鼠对照组有较低的13-HODE和9-HODE水平,与脂肪肝的饱和脂肪酸代谢酶的活性降低,引起亚油酸(LA)降低有关,不能反映血循环中的氧化应激状态。

[Objective] To investigate the eicosanoid levels and the related protein levels of enzymes involved in eicosanoid synthesis af- ter the supplementation of CLA isomers. [Method] Totally 17 week old male Zucker rats were randomly assigned into control groups （ lean control and faffa control） fed with control diet and treatment groups given 0. 4% （w/w） cis-9, trans-ll CLA （fa/fa c9, tll CLA） and trans-10, cis-12 CLA （fa/fa tl0, c12 CLA） respectively for 8 weeks. High performance liquid chromatography/mass spectrometry/ mass spectrometry （HPLC/MS/MS） was used for the measurement of eieosanods and Western blotting for the detection of protein expression of enzymes. [Result] HPLC/MS/MS showed that tl0, c12 CLA increased LTB4 levels （0. 12 _＋ 0. 04, n =7, P 〈0. 01 ） . Western blotting showed that both CLA isomers inhibited the protein levels of COX2. Compared withfa/fa control, lean control had higher levels of hydroxyocta- decadienoic acid （HODEs） . [Conclusion] tlO, c12 CLA reduced the total fat content of fatty liver, and then inhibited the protein levels of COX2. On the other hand, tl0, c12 CLA increased the LTB4 levels. The further histological analysis will help elucidate the final outcome of the inhibition of COX2 and the increase in LTB4. The lower 13-HODE and 9-HODE levels infa/fa control were caused by the alteration of decreased enzyme activity of unsaturated fatty acid in fatty liver and resultant decrease of LA, which did not reflect the oxidative stress in circulation.