Hyperglycemia-induced DNA damage as a driver of genomic instability

描述(申请人提供)：肥胖导致一系列相互关联的疾病，包括高血糖、胰岛素抵抗、高脂血症和2型糖尿病，统称为代谢综合征。这种情况极大地增加了患结肠癌、肝癌、胰腺癌、肾癌、乳腺癌、宫颈癌和子宫内膜癌的风险；然而，其发病机制尚不清楚。肥胖和2型糖尿病的许多病理并发症是由于高血糖和随后糖基化终末产物(AGEs)的积累引起的，这是由葡萄糖衍生的α-氧代醛与蛋白质、脂肪和脱氧核糖核酸反应引起的。虽然蛋白质-AGEs在代谢性疾病中的病理后果已被认识多年，但DNA-AGEs积累的程度及其在肥胖/糖尿病病理中的潜在作用在很大程度上还没有被探索。使用高度敏感的 和定性质谱学方法，我们已经表明，一个主要的DNA-AGE，CEdG，在人体组织中存在显著水平，其水平在代谢综合征动物模型中显著高于正常血糖对照组。我们最近发现CEdG在人类细胞中是诱变的，核苷酸切除修复(NER)是将DNA-AGE诱导的基因组不稳定性降至最低的主要途径。由于肥胖和糖尿病导致NER表达下调，我们推测，代谢综合征患者体内突变DNA-AGEs的积累显著增加了他们的癌症易感性。我们的长期目标是确定代谢性疾病中DNA-AGE水平升高如何导致基因组不稳定和癌症易感性增加。我们将测试这一假设，即高血糖诱导的突变DNA-AGE的积累与减弱的DNA修复一起推动基因组的不稳定性，并显著增加癌症的易感性。我们认为，DNA-AGE积累和突变的组织特异性变异是与肥胖相关的癌症范围有限的部分原因。为了实现我们的长期目标，需要阐明主要DNA-AGE的结构和化学稳定性，以便确定最有可能导致体内基因组不稳定的产物(目标1)。为了研究DNA-AGEs在肥胖中的遗传毒性病理学，我们将建立代谢综合征的动物模型，并测量组织特异性突变和DNA-AGE水平作为NER状态的函数(目标2)。为了更定量地确定代谢性疾病导致的DNA修复能力的下降，我们将使用肥胖/糖尿病小鼠在疾病进展阶段制备的提取物来测量DNA-AGEs的修复动力学(目标3)。这些特定目标的成功实现将极大地有助于我们理解癌症与肥胖病理后果引起的分子变化之间的这种联系。此外，我们预计，加强我们对高血糖诱导的DNA-AGE病理的了解将对人类健康产生重大的整体影响，并刺激新疗法的开发，以降低与肥胖相关的特定癌症的风险。

DESCRIPTION (provided by applicant): Obesity endgenders a wide spectrum of interrelated pathologies including hyperglycemia, insulin resistance, hyperlipidemia, and Type 2 diabetes, collectively termed the metabolic syndrome. This condition significantly increases risk for cancers of the colon, liver, pancreas, kidney, breast, cervix, and endometrium; however, the mechanisms responsible remain unknown. Many pathological complications of obesity and Type 2 diabetes arise from hyperglycemia and the subsequent accumulation of advanced glycation end products (AGEs) resulting from reactions of glucose-derived α-oxo aldehydes with proteins, lipids, and DNA. Although the pathological consequences of protein-AGEs in metabolic disease have been recognized for many years, the extent of DNA-AGE accumulation and its potential role in obese/diabetic pathology are largely unexplored. Using a highly sensitive and determinative mass spectrometric method, we have shown that a major DNA-AGE, CEdG, is present at significant levels in human tissue, and its levels are substantially elevated in animl models of metabolic syndrome relative to lean euglycemic controls. We recently showed that CEdG is mutagenic in human cells, and that nucleotide excision repair (NER) is the major pathway for minimizing DNA-AGE induced genomic instability. Because NER is downregulated as consequence of adiposity and diabetes we theorize that the accumulation of mutagenic DNA-AGEs in individuals with metabolic syndrome substantially elevates their cancer susceptibility. Our long term goal is to determine how elevated DNA-AGE levels in metabolic disease contribute to genomic instability and increased vulnerability to cancer. We will test the hypothesis that hyperglycemia-induced accumulation of mutagenic DNA-AGEs in conjunction with attenuated DNA repair propels genomic instability and substantially increases cancer susceptibility. We propose that tissue-specific variations in DNA-AGE accumulation and mutagenesis account in part for the restricted range of cancers associated with obesity. Progress toward our long term goal requires elucidating the structures and chemical stabilities of the major DNA-AGEs in order to identify products most likely to contribute to genomic instability in vivo (Aim 1). To study the genotoxic pathology of DNA-AGEs in obesity, we will generate animal models of metabolic syndrome and measure tissue-specific mutations and DNA-AGE levels as a function of NER status (Aim 2). To more quantitatively define the decline in DNA repair capacity due to metabolic disease, we will measure the repair kinetics of DNA-AGEs using extracts prepared from obese/diabetic mice at progressive stages of disease (Aim 3). Successful implementation of these Specific Aims will contribute greatly toward our understanding of this link between cancer and a molecular change induced by a pathologic consequence of obesity. Moreover, we anticipate that enhancing our knowledge of hyperglycemia-induced DNA-AGE pathology will have a significant overall impact on human health and stimulate the development of novel treatments to reduce the risk of specific cancers associated with obesity.