高脂饮食与低剂量TCDD联合作用对雌性肥胖易感大鼠肝脏脂质代谢的影响

Effects of high fat diet with low dose TCDD on hepatic lipid metabolism in female obesity-prone SD rats

目的探讨高脂饮食(high fat diet,HFD)引起的肥胖与低剂量持久性有机污染物--2,3,7,8-四氯二苯并二噁英(2,3,7,8-tetrachlorodibenzo-p-dioxin,TCDD)联合作用对肝脏脂质代谢的影响。方法采用2×2析因设计,研究HFD与低剂量TCDD(10 ng·kg^(-1)·d^(-1))联合作用对10周龄肥胖易感(obesity-prone,OP)雌性大鼠肝脏脂质代谢的影响。4组实验动物分别为:普通饮食无TCDD处理组(Cont+TCDD 0)、普通饮食低剂量TCDD处理组(Cont+TCDD 10)、高脂饮食无TCDD处理组(HFD+TCDD 0)及高脂饮食低剂量TCDD处理组(HFD+TCDD 10)。油红O染色观察肝脏脂肪沉积,酶法测定肝脏超氧化物歧化酶(superoxide dismutase,SOD)和谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-PX)的活性,实时荧光定量聚合酶链式反应(real-time fluorescence quantitative polymerase chain reaction,RT-qPCR)法检测肝脏脂质代谢相关基因mRNA表达。结果Cont+TCDD 0组、Cont+TCDD 10组、HFD+TCDD 0组及HFD+TCDD 10组大鼠体质量分别为(301.29±18.47)g、(312.16±20.45)g、(358.20±27.11)g及(373.83±26.50)g(F=7.43,P<0.01);肝脏油红O阳性区域比值分别为(1.26±0.16)%、(1.66±0.50)%,(9.06±1.54)%、(32.56±2.66)%(F=11.32,P<0.01),肝脏SOD酶活性分别为:(1.54±0.06)U/mg、(1.41±0.15)U/mg、(1.25±0.08)U/mg及(0.76±0.11)U/mg(F=4.31,P<0.05);肝脏GSH-PX酶活性分别为:(1511.00±69.30)U/mg、(1409.00±60.81)U/mg、(1232.00±65.05)U/mg及(965.00±83.44)U/mg(F=3.91,P<0.05)。对上述指标进行交互作用分析显示,高脂饮食与低剂量TCDD联合作用使肥胖易感的雌性SD大鼠体质量(F=6.33,P<0.05)及肝脏脂肪积聚(F=12.51,P<0.01)出现协同增加,肝脏抗氧化酶类SOD酶活性(F=4.15,P<0.05)和GPX酶活性(F=3.97,P<0.05)协同降低。对12种肝脏脂质代谢相关基因mRNA表达水平检测发现,高脂饮食与低剂量TCDD联合作用增加三酰甘油脂肪酶的限速酶(adipose triglyceride lipase,ATGL)(F=3.69,P<0.05)及脂肪酸转位酶(cluster of differentiation 36,CD36)的mRNA表达(F=5.58,P<0.01),抑制激素敏感脂肪酶(hormone-sensitive lipase,HSL)的mRNA表达(F=4.01,P<0.05),其余9种基因表达差异无统计学意义(P>0.05)。结论高脂饮食与低剂量TCDD联合作用可能协同增加肥胖诱导雌性大鼠肝脏脂质代谢异常。

Objective To study the effect of combination of high fat diet(HFD)induced obesity and low dose persistent organic pollutants 2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD)on liver lipid metabolism.Methods By 2×2 factorial design,the effects of combination of HFD and low dose TCDD(10 ng·kg^(-1)·d^(-1))on liver lipid metabolism in obesity-prone(OP)10-week-old female rats were studied.The four groups of experimental animals were:the group treated with no TCDD in chow diet(Cont+TCDD 0),the group treated with low dose TCDD in chow diet(Cont+TCDD 10),and the group high fat diet without TCDD(HFD+TCDD 0)and high fat diet group treated with low dose TCDD(HFD+TCDD 10).Lipid deposition in liver was observed by oil red O staining.The activities of superoxide dismutase(SOD)and glutathione peroxidase(GSH-PX)in liver were determined by enzyme method.mRNA expression of genes related to lipid metabolism in liver was detected by real-time fluorescence quantitative polymerase chain reaction(RT-qPCR).Results The body weight of rats in Cont+TCDD 0 group,Cont+TCDD 10 group,HFD+TCDD 0 group and HFD+TCDD 10 group were(301.29±18.47)g,(312.16±20.45)g,(358.20±27.11)g and(373.83±26.50)g,respectively(F=7.43,P<0.01),liver oil red O positive area ratios were(1.26±0.16)%,(1.66±0.50)%,(9.06±1.54)%,(32.56±2.66)%(F=11.32,P<0.01),liver SOD activity were(1.54±0.06)U/mg,(1.41±0.15)U/mg,(1.25±0.08)U/mg and(0.76±0.11)U/mg(F=4.31,P<0.05),respectively.Liver GSH-PX activity were Liver GSH-PX activity were(1511.00±69.30)U/mg,(1409.00±60.81)U/mg,(1232.00±65.05)U/mg and(965.00±83.44)U/mg(F=3.91,P<0.05).The interaction analysis of the above indexes suggested that the combination of high fat diet and low dose TCDD resulted in synergistic increases in the body weight(F=6.33,P<0.05)and liver fat accumulation(F=12.51,P<0.01)of obese-prone female SD rats,and the activities of antioxidant enzymes such as SOD in liver(F=4.15,P<0.05)and GSH-PX enzyme activity(F=3.97,P<0.05)were decreased synergistically.Analysis on mRNA expression levels of 12 genes related to lipid metabolism in liver showed that high fat diet combined with low dose TCDD increased adipose lipase(Atgl)(F=3.69,P<0.05),mRNA expression of cluster of differentiation 36(CD36)(F=5.58,P<0.01),inhibited the mRNA expression of hormone sensitive lipase(Hsl)(F=4.01,P<0.05),and there was no significant difference in the expression of other 9 genes(P>0.05).Conclusion The combination of high fat diet and low dose TCDD can synergistically increase the abnormal liver lipid metabolism in female obesity-prone female SD rats.