The Role of the Intestinal Fatty Acid Binding Protein in Insulin Resistance

我们以前的研究确定了一个区域， 染色体4 q与胰岛素作用的测量有关。一 该区域中的候选基因是FABP 2，其编码人 肠脂肪酸结合蛋白（IFABP）。我们确定了一个 该基因中的多态性导致丙氨酸（Ala 54） IFABP的氨基酸54处的苏氨酸（Thr 54）取代。我们 发现Thr 54编码的IFABP与 基因型（频率= 0.29）和空腹脂质氧化增加 率和胰岛素抵抗，并进一步表明， 重组Thr 54蛋白对长链脂肪酸具有更高的亲和力， 与重组Ala 54蛋白相比，我们进一步 研究IFABP的生理后果 替代，通过分析脂肪酸运输永久 表达Ala 54和Thr 54 IFABP的转染细胞。我们 发现3 H脂质以更快的速度通过 Thr 54表达细胞与Ala 54表达细胞相比。 研究Ala 54和Thr 54之间的结构差异 IFABP，我们与J.汉密尔顿和利用3-D 核磁共振技术解决了两种蛋白质结合时的结构 长链脂肪酸我们目前正在分析 来自Ala 54纯合个体的IFABP基因 等位基因和胰岛素敏感的个体， Thr 54等位基因，并且是胰岛素抵抗的。我们已经确定 几个多态性和两个缺失， 与Ala到Thr取代的不平衡。我们计划分析 这些不同的启动子通过连接 将它们与报告基因进行比较， 在转染的细胞中。

Our previous studies identified a region on chromosome 4q that was linked to measures of insulin action. A candidate gene in this region is FABP2 which encodes the human intestinal fatty acid binding protein (IFABP). We identified a polymorphism in this gene which results in an alanine (Ala54) to threonine (Thr54) substitution at amino acid 54 of IFABP. We found a significant association between the Thr54-encoding IFABP genotype (frequency = 0.29) and increased fasting lipid oxidation rates and insulin resistance, and have further shown that recombinant Thr54 protein has a higher affinity for long-chain fatty acids as compared to recombinant Ala54 protein. We further investigated the physiologic consequences of the IFABP substitution, by analyzing fatty acid transport across permanently transfected cells expressing either Ala54 and Thr54 IFABP. We found that 3H lipid was transported at a faster rate across the Thr54-expressing cells as compared to the Ala54-expressing cells. To investigate the structural differences between Ala54 and Thr54 IFABP, we have collaborated with J. Hamilton and utilized 3-D NMR to solve the structure of both proteins when bound to long-chain fatty acids. We are currently analyzing the promoters of the IFABP gene from individuals who are homzygous for the Ala54 allele and are insulin sensitive and individuals who are homzygous for the Thr54 allele and are insulin resistant. We have identified several polymorphisms and two deletions which are in total linkage disequilibration with the Ala to Thr substitution. We plan to assay the functional consequences of these varied promoters by ligating them to a reporter gene and comparing their transcriptional activity in transfected cells.