The Agouti Related Protein and its Role in Human Obesity

刺鼠相关蛋白及其在人类肥胖中的作用

• 批准号: 6707543
• 负责人: GEORGE ARGYROPOULOS
• 金额: $ 29.4万
• 依托单位: LSU PENNINGTON BIOMEDICAL RESEARCH CTR
• 依托单位国家: 美国
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-03-01 至 2008-02-29
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6707543
• 关键词: gene expression; genetic polymorphism; genetic promoter element; genetic regulation; genetic regulatory element; genetic susceptibility; hormone inhibitor; human genetic material tag; human tissue; hypothalamus; leptin; obesity; overeating; secretory protein; single nucleotide polymorphism; transcription factor; weight control agent

DESCRIPTION (provided by applicant): The Agouti Related Protein (AGRP) is upregulated in obese and diabetic mice and stimulates hyperphagia and the development of obesity when overexpressed in transgenic mice. The human ortholog, hAGRP, has been isolated and has similar molecular and physiological properties, expressing one transcript in the arcuate nucleus and one in the periphery. We recently determined the gene structure and identified the minimal promoter of the human AGRP gene. Multiple binding sites for transcription factors were identified including putative binding sites for the STAT transactivators that may potentially mediate leptin's action in the hypothalamus. The 5' non-coding exon had significant promoter activity in a periphery cell line only, suggesting its role in the expression of the periphery-specific transcript. We also identified a polymorphism in the promoter that had significant impact on promoter activity and affinity to bind transcription factors, as tested in hypothalamus- and periphery-derived cell lines. The genotype with the high promoter activity was significantly associated with obesity and Type 2 Diabetes Mellitus (T2DM) in two different cohorts. Moreover, a polymorphism in the coding region of the gene was significantly associated with low body mass index and low abdominal adiposity but in older people only, suggesting a role for hAGRP in preventing late on set obesity. We hypothesize that increased amounts of hAGRP in the hypothalamus and the periphery, as determined by its promoter, will result in hyperphagia and the development of obesity. We therefore propose to completely characterize the promoter of hAGRP and identify the transcription factors and sequence motifs that regulate expression of the gene (Specific Aim 1). We will also determine the impact of hormones/fuel substrates on promoter activity and endogenous expression of AGRP, and identify the hormone/substrate response elements in the promoter of the gene (Specific Aim 2). Furthermore, we will investigate the association of hAGRP polymorphisms with obesity and T2DM, while the systemic levels of AGRP will be correlated with promoter polymorphisms as well as with the systemic levels of hormones/fuel substrates (Specific Aim 3). Given that hAGRP is a potent appetite effector, it is important that we identify the regulatory mechanisms for its expression and determine its role in food intake and the development of human obesity.

描述（由申请人提供）：AGRP相关蛋白（AGRP）在肥胖和糖尿病小鼠中上调，并且当在转基因小鼠中过表达时刺激摄食过多和肥胖的发展。人类直系同源物hAGRP已被分离出来，具有相似的分子和生理特性，在弓状核和外周分别表达一种转录本。我们最近确定了基因结构，并确定了人类AGRP基因的最小启动子。转录因子的多个结合位点被鉴定，包括可能潜在地介导瘦素在下丘脑中的作用的STAT反式激活因子的推定结合位点。5'非编码外显子仅在外周细胞系中具有显著的启动子活性，表明其在外周特异性转录物的表达中的作用。我们还确定了一个多态性的启动子，有显着的影响启动子的活性和亲和力结合转录因子，在下丘脑和外周衍生的细胞系进行测试。在两个不同的队列中，具有高启动子活性的基因型与肥胖和2型糖尿病（T2 DM）显著相关。此外，该基因编码区的多态性与低体重指数和低腹部肥胖显着相关，但仅在老年人中，这表明hAGRP在预防晚期肥胖中的作用。我们推测，hAGRP在下丘脑和外周的数量增加，由其启动子决定，将导致食欲过盛和肥胖的发展。因此，我们建议完全表征hAGRP的启动子，并确定调节基因表达的转录因子和序列基序（特异性目的1）。我们还将确定激素/燃料底物对AGRP启动子活性和内源表达的影响，并鉴定基因启动子中的激素/底物响应元件（具体目标2）。此外，我们将研究hAGRP多态性与肥胖和T2 DM的相关性，而AGRP的全身水平将与启动子多态性以及激素/燃料底物的全身水平相关（具体目标3）。鉴于hAGRP是一种有效的食欲效应子，我们确定其表达的调控机制并确定其在食物摄入和人类肥胖发展中的作用是很重要的。