Epigenome modification by a dietary pattern rich in polyunsaturated fatty acids

修订后的项目摘要/摘要 拟议研究的总体目标是确定与保护Yup'ik阿拉斯加原住民食用传统饮食的2型糖尿病（T2 D）相关的生物途径的表观遗传变化。Yup'ik的传统饮食模式的特点是高蛋白质，高脂肪和低碳水化合物的摄入量，以及n-3多不饱和脂肪酸水平，比一般美国人口高出20倍。在Yup'ik人中，高水平的传统食物摄入与脂联素呈正相关，与C-反应蛋白、甘油三酯和瘦素：脂联素比率呈负相关，提示胰岛素敏感性增加。然而，Yup'ik人的饮食正在过渡到增加对高度加工的市场食品的消费，超重和肥胖的流行开始反映美国普通人口的情况。即便如此，Yup'ik人的代谢综合征（15%）和T2 D（3%）的患病率仍然低于美国普通人群。坚持Yup'ik传统的饮食模式可能对Yup'ik人有保护作用，尽管保护机制尚不清楚。我们将使用氮稳定同位素比值（δ 15 N）作为传统饮食模式的有效、客观指标来探索这些机制。 虽然在鉴定导致代谢性疾病的遗传因素方面已经取得了相当大的进展，但已知的遗传变异解释了T2 D表型的遗传性的不到10%。表观遗传机制最近被认为是遗传风险和环境暴露（如饮食）之间的联系，从而为遗传易感性的改变提供了一种机制，并深入了解了90%尚未解释的遗传性。这项拟议中的研究将在20个最有希望的候选基因中精细绘制表观遗传生物标志物，这些基因是使用Illumina MethylationEPIC微阵列对569名Yup'ik人的外周血DNA样本进行鉴定的，这些样本来自传统饮食摄入量的最高和最低十分位数。（DK 104347）使用靶向亚硫酸氢盐测序来揭示在阵列数据中不明显的详细DNA甲基化模式，并鉴定影响这些基因甲基化的遗传变异。这些研究结果将在格陵兰因努伊特人群体中得到复制，以确定Yup'ik人研究结果的普遍性。候选基因中甲基化模式的下游功能后果将使用基因表达测定法在192个外周血RNA样本中进行评估，这些样本来自我们的饮食测量值δ 15 N分布的极端个体。通过确定与坚持传统饮食和胰岛素敏感性相关的表观基因组生物标志物，拟议的研究将测试传统Yup'ik饮食修改有助于Yup'ik人代谢健康的关键基因下游转录的假设。

Revised Project Summary/Abstract The overall goal of the proposed research is to identify epigenetic changes in biological pathways associated with protection from Type 2 Diabetes (T2D) in Yup’ik Alaska Native people consuming a traditional diet. The Yup’ik traditional dietary pattern is characterized by high protein, high fat, and low carbohydrate intakes, as well as n-3 polyunsaturated fatty acid levels that are up to 20 times higher than in the general U.S. population. High levels of traditional food intake in Yup’ik people are positively associated with adiponectin and inversely associated with c-reactive protein, triglycerides, and the leptin:adiponectin ratio, suggestive of increased insulin sensitivity. However, the diet of Yup’ik people is transitioning to increased consumption of highly processed market foods, and the prevalence of overweight and obesity is beginning to mirror that of the general U.S. population. Even so, the prevalence of metabolic syndrome (15%) and T2D (3%) among Yup’ik people remains lower than in the general U.S. population. Adherence to a Yup’ik traditional dietary pattern is likely to be protective in Yup’ik people, although the mechanisms of protection are not well understood. We will use the nitrogen stable isotope ratio (δ15N) as a validated, objective measure of the traditional dietary pattern to explore these mechanisms. Although considerable advances have been made in the identification of genetic factors contributing to metabolic diseases, less than 10% of the heritability of T2D phenotypes is explained by known genetic variation. Epigenetic mechanisms have recently been proposed as a link between genetic risk and environmental exposures such as diet, thereby providing a mechanism for the modification of genetic predisposition and insight into 90% of the heritability that is not explained. The proposed research will fine map epigenetic biomarkers in the 20 most promising candidate genes identified using Illumina MethylationEPIC microarrays on stored peripheral blood DNA samples from 569 Yup’ik people at the highest and lowest deciles of traditional dietary intake (DK104347) using targeted bisulfite sequencing to reveal detailed DNA methylation patterns not apparent in the array data, and to identify genetic variants that influence methylation at these genes. These findings will be replicated in a Greenlandic Inuit cohort to determine the generalizability of the findings from Yup’ik people. The downstream functional consequences of methylation patterns in the candidate genes will be assessed using gene expression assays in 192 peripheral blood RNA samples from individuals at the extremes of the distribution of our dietary measure, δ15N. By identifying epigenomic biomarkers associated both with adherence to a traditional diet and with insulin sensitivity, the proposed research will test the hypothesis that a traditional Yup’ik diet modifies the downstream transcription of key genes that contribute to metabolic health of Yup’ik people.