Dorfmeister B, Zeng W W, Dichlberger A, Nilsson S K, Schaap F G, Hubacek J A, Merkel M, Cooper J A, Lookene A, Putt W, Whittall R, Lee P J, Lins L, Delsaux N, Nierman M, Kuivenhoven J A, Kastelein J J P, Vrablik M, Olivecrona G, Schneider W J, Heeren J, Humphries S E, Talmud P J
Department of Medicine, Division of Cardiovascular Genetics, UCL, London, UK.
Arterioscler Thromb Vasc Biol. 2008 Oct;28(10):1866-71. doi: 10.1161/ATVBAHA.108.172866. Epub 2008 Jul 17.
The purpose of this study was to identify rare APOA5 variants in 130 severe hypertriglyceridemic patients by sequencing, and to test their functionality, since no patient recall was possible.
We studied the impact in vitro on LPL activity and receptor binding of 3 novel heterozygous variants, apoAV-E255G, -G271C, and -H321L, together with the previously reported -G185C, -Q139X, -Q148X, and a novel construct -Delta139 to 147. Using VLDL as a TG-source, compared to wild type, apoAV-G255, -L321 and -C185 showed reduced LPL activation (-25% [P=0.005], -36% [P<0.0001], and -23% [P=0.02]), respectively). ApoAV-C271, -X139, -X148, and Delta139 to 147 had little affect on LPL activity, but apoAV-X139, -X148, and -C271 showed no binding to LDL-family receptors, LR8 or LRP1. Although the G271C proband carried no LPL and APOC2 mutations, the H321L carrier was heterozygous for LPL P207L. The E255G carrier was homozygous for LPL W86G, yet only experienced severe hypertriglyceridemia when pregnant.
The in vitro determined function of these apoAV variants only partly explains the high TG levels seen in carriers. Their occurrence in the homozygous state, coinheritance of LPL variants or common APOA5 TG-raising variant in trans, appears to be essential for their phenotypic expression.
本研究旨在通过测序鉴定130例严重高甘油三酯血症患者中罕见的载脂蛋白A5（APOA5）变异体，并测试其功能，因为无法进行患者回访。
我们研究了3种新型杂合变异体apoAV-E255G、-G271C和-H321L以及先前报道的-G185C、-Q139X、-Q148X和一种新型构建体-Delta139至147对体外脂蛋白脂肪酶（LPL）活性和受体结合的影响。以极低密度脂蛋白（VLDL）作为甘油三酯（TG）来源，与野生型相比，apoAV-G255、-L321和-C185的LPL激活作用降低（分别为-25%[P=0.005]、-36%[P<0.0001]和-23%[P=0.02]）。ApoAV-C271、-X139、-X148和Delta139至147对LPL活性影响较小，但apoAV-X139、-X148和-C271与低密度脂蛋白（LDL）家族受体LR8或低密度脂蛋白受体相关蛋白1（LRP1）无结合。尽管G271C先证者未携带LPL和载脂蛋白C2（APOC2）突变，但H321L携带者的LPL P207L为杂合子。E255G携带者的LPL W86G为纯合子，但仅在怀孕时出现严重高甘油三酯血症。
这些apoAV变异体的体外测定功能仅部分解释了携带者中所见的高TG水平。它们以纯合状态出现、LPL变异体的共同遗传或反式的常见APOA5 TG升高变异体，似乎对其表型表达至关重要。
