Insulin Clearance: Candidate and Positional Genetic Determinants

描述（由申请人提供）：胰岛素敏感性/抵抗和胰岛素分泌在易患心血管疾病的代谢性疾病（如糖尿病、肥胖、代谢综合征和多囊卵巢综合征）的研究中受到了很多关注，而胰岛素清除在很大程度上被忽视了。胰岛素清除是一种高度遗传的特性。初步数据显示，单磷酸腺苷脱氨酶（AMPD1和AMPD2）基因的单倍型以及amp活化蛋白激酶（AMPK） 12亚基基因的单倍型与胰岛素代谢清除率（MCRI）的变化有关。因此，这一提议的假设是，参与腺嘌呤核苷酸（AMP， ADP， ATP）的相互转化和细胞对这些分子的反应（AMPK系统）的基因是胰岛素清除的决定因素。该申请提出了进一步的研究，阐明这些和相关基因在胰岛素清除中的作用，使用生物学候选基因方法以及全基因组连锁扫描鉴定的位置候选基因。在Aim 1中，与腺嘌呤核苷酸代谢和AMPK系统相关的约100个基因（基于功能的高优先级）中的1536个单核苷酸多态性（snp）将在墨西哥-美国冠状动脉疾病（MACAD）队列的前半部分（第1组）进行基因分型；这些snp及其衍生的单倍型将被分析与MCRI的关联。然后对显示与MCRI相关的前25个基因进行基因分型（384个snp），并在MACAD Set 2（该队列的后半部分）中检测与MCRI的相关性。目的3只评估两组患者中与MCRI相关的基因。在Aim 2中，MCRI的全基因组连锁扫描将在两个西班牙裔队列（MACAD和墨西哥裔美国高血压（MA-HTN）队列）中进行。在两个队列中发现的峰值（LOD> 1.4）和最显著的峰值（LOD>2）下的位置候选基因（预计50-70个基因）将被分析与MACAD中MCRI的关联。在Aims 3中，Aims 1和Aims 2中鉴定的与MCRI相关的基因将在MA-HTN队列中进行相关性测试，作为最终确认。在Aim 4中，将对证实相关的基因（在不同基因型和表型的受试者中）进行测序，以确定潜在的功能变异。通过测序确定的变异将在MACAD和MA-HTN联合队列中评估与MCRI的关联。这一建议在胰岛素清除的探索中是独一无二的，这是一个未被充分研究的高度遗传的特征。同样创新的是关注与腺嘌呤核苷酸和细胞能量状态相关的基因。该研究将在多个西班牙裔人群中检查这些基因，允许验证/复制正遗传关联，并受益于这两个队列已经被招募，并通过正血糖-高胰岛素钳进行了详细的全身胰岛素清除生理表型分析。考虑的新表型和基因可能导致胰岛素代谢的新见解。

DESCRIPTION (provided by applicant): Insulin sensitivity/resistance and insulin secretion have received much attention in the study of metabolic disorders (such as diabetes, obesity, the metabolic syndrome, and polycystic ovary syndrome) that predispose to cardiovascular disease, while insulin clearance has been largely overlooked. Insulin clearance is a highly heritable trait. Preliminary data show that haplotypes in the genes for adenosine monophosphate deaminase (AMPD1 and AMPD2) and the AMP-activated protein kinase (AMPK) 12 subunit are associated with variation in the metabolic clearance rate of insulin (MCRI). Thus, the hypothesis underlying this proposal is that genes involved in the interconversion of adenine nucleotides (AMP, ADP, ATP) and cellular response to these molecules (AMPK system) are determinants of insulin clearance. This application proposes further research elucidating the role of these and related genes in insulin clearance, using both a biologic candidate gene approach as well as positional candidate genes identified by whole-genome linkage scans. In Aim 1, 1536 single nucleotide polymorphisms (SNPs) in ~100 genes (high-priority based on function) related to adenine nucleotide metabolism and the AMPK system will be genotyped in the first half (Set 1) of the Mexican- American Coronary Artery Disease (MACAD) cohort; these SNPs and derived haplotypes will be analyzed for association with MCRI. The top 25 genes showing association with MCRI will then be genotyped (384 SNPs) and tested for association with MCRI in MACAD Set 2 (second half of that cohort). Only genes associated with MCRI in both Sets will be evaluated in Aim 3. In Aim 2, whole genome linkage scans for MCRI will be carried out in two Hispanic cohorts (MACAD, and the Mexican-American hypertension (MA-HTN) cohort). Positional candidate genes (50-70 genes anticipated) under peaks (LOD >1.4) found in both cohorts and under the most significant (LOD>2) peaks in either cohort will be analyzed for association with MCRI in MACAD. In Aim 3, the genes identified in Aims 1 and 2 as associated with MCRI will be tested for association in the MA-HTN cohort, as a final confirmation. In Aim 4, the genes with confirmed association will then be sequenced (in subjects of divergent genotype and phenotype) to identify potential functional variants. Variants identified by sequencing will be evaluated for association with MCRI in the combined MACAD and MA-HTN cohort. This proposal is unique in its exploration of insulin clearance, an understudied trait that is highly heritable. Also innovative is the focus on genes related to adenine nucleotides and cellular energy state. The study will examine these genes in multiple Hispanic populations, allowing for verification/replication of positive genetic associations, and benefits from the fact that both cohorts have already been recruited and have undergone detailed physiologic phenotyping of whole-body insulin clearance by the euglycemic-hyperinsulinemic clamp. The novel phenotype and genes considered are likely to lead to new insights in insulin metabolism. Project Narrative: The goal of this proposal is to discover genes that influence the body's ability to eliminate insulin. Abnormal levels of insulin are characteristic of several metabolic disorders, such as diabetes, obesity, the metabolic syndrome, and polycystic ovary syndrome, all of which are risk factors for cardiovascular disease. An understanding of the genes underlying insulin removal may lead to improvements in prevention and treatment of these disorders.