控制摄食对小鼠肝脏及肾上腺胆固醇代谢的影响

Effects of Dietary Restriction on Cholesterol Metabolism in Liver and Adrenal Gland of Mice

本试验旨在研究控制摄食对小鼠肝脏及肾上腺胆固醇代谢的影响。采用雄性ICR小鼠为试验对象,先适应性饲养3 d,在体重达24~25 g后,随机分为5组,每组6只,分别为正常对照组(自由摄食)、摄食4.0 g组[摄食量:4.0 g/(只·d);控食比例:正常摄食量的88%]、摄食3.0 g组[摄食量:3.0 g/(只·d);控食比例:正常摄食量的66%]、摄食2.0 g组[摄食量:2.0 g/(只·d);控食比例:正常摄食量的44%]和摄食1.5 g组[摄食量:1.5 g/(只·d);控食比例:正常摄食量的22%]。各组自由饮水,控食14 d后处死小鼠,取心脏、肝脏、肾脏、脾脏、胸腺及睾丸称重并计算脏器指数,取肝脏和肾上腺组织分别抽提总RNA和总蛋白,以实时荧光定量PCR技术检测胆固醇代谢相关基因mRNA的相对表达量,以W estern blot方法检测类固醇合成急性调节蛋白(St AR)蛋白的相对表达量,并以酶联免疫吸附测定(ELISA)方法检测血清皮质酮含量。结果表明:1)与正常对照组相比,各控食组小鼠体重均有不同程度的减轻,心脏、肝脏、肾脏、脾脏、胸腺均有不同程度的萎缩。2)与正常对照组相比,摄食3.0 g组、摄食2.0 g组和摄食1.5 g组小鼠肝脏低密度脂蛋白受体(Ldlr)、B类清道夫受体1(Scarb1)、羟甲基戊二酰辅酶A还原酶(Hmgcr)、激素敏感脂酶(Lipe)、载脂蛋白E(Apoe)、ATP结合盒转运体G5(Abcg5)、ATP结合盒转运体G8(Abcg8)、细胞色素P450家族成员7A1(Cyp7a1)、固醇调节元件结合蛋白裂解激活蛋白(Scap)、肝脏X受体β(Nr1h2)、过氧化物酶体增殖剂激活受体α(Ppara)、过氧化物酶体增殖剂激活受体γ(Pparg)基因的表达均显著上调(P<0.05或P<0.01),而胰岛素诱导基因2(Insig2)基因的表达则显著下调(P<0.05)。3)与正常对照组相比,摄食2.0 g组和摄食1.5 g组小鼠肾上腺细胞色素P450家族成员11A1(Cyp11a1)、细胞色素P450家族成员21A1(Cyp21a1)基因的表达均显著上调(P<0.05),摄食1.5 g组小鼠肾上腺St AR和细胞色素P450家族成员11B1(Cyp11b1)基因的表达也显著上调(P<0.05),而摄食3.0 g组、摄食2.0 g组和摄食1.5 g组细胞色素P450家族成员11B2(Cyp11b2)基因的表达显著下调(P<0.05)。此外,与正常对照组比较,各控食组小鼠肾上腺St AR蛋白表达均增强且随着摄食量的降低而增强。由此可见,严格控制摄食会影响小鼠免疫器官脾脏与胸腺,同时代谢器官肝脏也受到严重影响,进而影响胆固醇在肝脏与肾上腺的代谢与转化。

This experiment was conducted to study the effects of dietary restriction on cholesterol metabolism in liver and adrenal gland of mice.ICR male mice were used as the study subjects,with adaptive feeding 3 days.After weighing up to 24 to 25 g,they were randomly divided into 5 groups with 6 mice in each group,inclu-ding normal control group(free feeding),4.0 g feeding group[feed intake:4.0 g/d per mouse;restriction ratio:88%of normal feed intake],3.0 g feeding group[feed intake:3.0 g/d per mouse;restriction ratio:66%of normal feed intake],2.0 g feeding group[feed intake:2.0 g/d per mouse;restriction ratio:44%of normal feed intake]and 1.5 g feeding group[feed intake:1.5 g/d per mouse;restriction ratio:22%of nor-mal feed intake].It was free drinking for all groups.After feeding restriction for 14 days,the mice were exe-cuted,and the heart,liver,kidney,spleen,thymus and testis were weighed and the organic indexes were cal-culated.The total RNA and total protein of hepatic and adrenal tissues were extracted.Then,cholesterol metab-olism related genes mRNA relative expression levels were detected by real-time quantitative PCR technology,and steroidogenic acute regulatory protein(StAR)relative expression level was assayed by Western blot meth-od,and serum corticosterone content were tested by enzyme-linked immuno sorbent assay(ELISA)method.The results showed as follows:1)compared with the normal control group,the body weight of mice in dietary restriction groups was lost in different degrees,and the heart,liver,kidney,spleen and thymus of mice in di-etary restriction groups were shrunken in different degrees.2)Compared with the normal control group,the expression of low-density lipoprotein receptor(Ldlr),scavenger receptor class B member 1(Scarb1),hydroxymethyl glutaric acyl coenzyme A reductase(Hmgcr),hormone-sensitive triglayceride lipase(Lipe),apolipoprotein E(Apoe),ATP-binding cassette transporter G5(Abcg5),ATP-binding cassette transporter G8(Abcg8),cytochromes P450 7A1(Cyp7a1),sterol regulatory element binding protein cleavage active protein(Scap),liver X receptorβ(Nr1h2),peroxisome proliferators-activated receptorα(Ppara)and peroxisome proliferators-activated receptorγ(Pparg)genes in liver of 3.0 g feeding group,2.0 g feeding group and 1.5 g feeding group were significantly up-regulated(P<0.05 or P<0.01),while the expression of insulin induced gene 2(Insig2)gene was significantly down-regulated(P<0.05).3)Compared with the normal control group,the expression of adrenal cytochromes P450 11A1(Cyp11a1)and cytochromes P450 21A1(Cyp21a1)genes in ad-renal gland of 2.0 g feeding group and 1.5 g feeding group were significantly up-regulated(P<0.05),the expres-sion of StAR and cytochromes P450 11B1(Cyp11b1)genes in adrenal gland of 1.5 g feeding group were signifi-cantly up-regulated(P<0.05),and the expression of cytochromes P450 11B2(Cyp11b2)in 3.0 g feeding group,2.0 g feeding group and 1.5 g feeding group was significantly down-regulated(P<0.05).Additionally,the adrenal StAR protein expression of all dietary restriction groups was strengthen,and it was strengthen with the feed intake decreasing.In conclusion,the organism metabolism such as spleen,thymus and liver are affected by extreme dieta-ry restriction,and then the hepatic and adrenal cholesterol metabolism and conversion are affected.