Miettinen H E, Jauhiainen M, Gylling H, Ehnholm S, Palomäki A, Miettinen T A, Kontula K
Department of Medicine, University of Helsinki, Finland.
Arterioscler Thromb Vasc Biol. 1997 Nov;17(11):3021-32. doi: 10.1161/01.atv.17.11.3021.
We showed earlier that the apolipoprotein A-I Leu159-->Arg mutation (apoA-IFin) results in dominantly inherited hypoalphalipoproteinemia. In the present study we investigated the effect of the apoA-IFin mutation on lipoprotein profile, apoA-I kinetics, lecithin:cholesterol acyltransferase (LCAT) activation, and cholesterol efflux in vitro. Carriers (n = 9) of the apoA-IFin mutation exhibited several lipoprotein abnormalities. The serum HDL cholesterol level was diminished to 20% of normal, and nondenaturing gradient gel electrophoresis of HDL showed disappearance of particles at the 9.0- to 12-nm size range (HDL2-type) and the presence of small 7.8- to 8.9-nm (mostly HDL3-type) particles only. HDL3-type particles from both the mutation carriers and nonaffected family members were similarly converted to large, HDL2-type particles by phospholipid transfer protein in vitro. Studies on apoA-I kinetics in four affected subjects favored accelerated catabolism of apoA-I. Experiments with reconstituted proteoliposomes showed that the capacity of apoA-IFin protein to activate LCAT was reduced to 40% of that of the wild-type apoA-I. The impact of the apoA-IFin protein on cholesterol efflux was examined in vitro using [3H]cholesterol-loaded human fibroblasts and three different cholesterol acceptors: (1) total HDL, (2) total apoA-I combined with phospholipid, and (3) apoA-I isoform (apoA-IFin or wild-type apoA-I isoform 1) combined with phospholipid. ApoA-IFin did not impair phospholipid binding or cholesterol efflux from fibroblasts to any of the acceptors used. Only one of the nine apoA-IFin carriers appears to have evidence of clinically manifested atherosclerosis. In conclusion, although the apoA-IFin mutation does not alter the properties of apoA-I involved in promotion of cholesterol efflux, its ability to activate LCAT in vitro is defective. In vivo, apoA-IFin was found to be associated with several lipoprotein composition rearrangements and increased catabolism of apoA-I.
我们先前已表明，载脂蛋白A-I Leu159→Arg突变（apoA-IFin）会导致显性遗传的低α脂蛋白血症。在本研究中，我们调查了apoA-IFin突变对脂蛋白谱、apoA-I动力学、卵磷脂：胆固醇酰基转移酶（LCAT）激活以及体外胆固醇流出的影响。apoA-IFin突变携带者（n = 9）表现出多种脂蛋白异常。血清高密度脂蛋白（HDL）胆固醇水平降至正常水平的20%，HDL的非变性梯度凝胶电泳显示9.0至12纳米大小范围的颗粒（HDL2型）消失，仅存在7.8至8.9纳米的小颗粒（主要是HDL3型）。来自突变携带者和未受影响家庭成员的HDL3型颗粒在体外被磷脂转移蛋白同样转化为大的HDL2型颗粒。对四名受影响受试者的apoA-I动力学研究支持apoA-I的分解代谢加速。重组蛋白脂质体实验表明，apoA-IFin蛋白激活LCAT的能力降至野生型apoA-I的40%。使用[3H]胆固醇负载的人成纤维细胞和三种不同的胆固醇受体在体外检查了apoA-IFin蛋白对胆固醇流出的影响：（1）总HDL，（2）总apoA-I与磷脂结合，以及（3）apoA-I同工型（apoA-IFin或野生型apoA-I同工型1）与磷脂结合。apoA-IFin不会损害成纤维细胞与所使用的任何受体之间的磷脂结合或胆固醇流出。九名apoA-IFin携带者中只有一人似乎有临床显性动脉粥样硬化的证据。总之，尽管apoA-IFin突变不会改变参与促进胆固醇流出的apoA-I的特性，但其在体外激活LCAT的能力存在缺陷。在体内，发现apoA-IFin与几种脂蛋白组成重排以及apoA-I的分解代谢增加有关。
