DNA甲基化年龄研究进展

表观遗传学的进展使得借助年龄生物标志物预测个体年龄成为了可能。DNA甲基化是表观遗传学的重要组成部分,通过筛选年龄相关的甲基化位点构建表观遗传时钟,衍生出新的衰老生物标志物-DNA甲基化年龄(DNAm年龄)。DNAm年龄广泛应用于衰老、衰老相关疾病、法医学年龄推断等研究领域,但目前尚缺乏针对DNAm年龄的文献综述。本文就DNAm年龄的主要特点、经典的3大表观遗传时钟(Horvath时钟、Hannum时钟、DNA PhenoAge)以及DNAm年龄与死亡率、癌症及其他衰老相关疾病关联进行综述和探讨。     

大骨节病与骨性关节炎DNA甲基化衰老时钟的比较研究

目的探讨大骨节病和骨性关节炎的软骨细胞是否存在过早衰老。方法收集大骨节病、骨性关节炎和对照组的膝关节软骨样本各5例,样本均来源于西安交通大学第二附属医院。提取膝关节软骨样本DNA,采用Illumina Infinium HumanMethylation450 BeadChip芯片技术对其进行DNA甲基化分析。同时,基于全基因组甲基化数据,利用线上DNA甲基化衰老时钟计算器(https://dnamage.genetics.ucla.edu/home)计算样本的DNA甲基化年龄,并与实际年龄进行比较。结果在大骨节病组与对照组的比较中,发现1212个差异甲基化CpG位点,包括497个高甲基化CpG位点和715个低甲基化CpG位点,分别对应264个高甲基化基因和368个低甲基化基因;在骨性关节炎组与对照组的比较中,发现656个差异甲基化CpG位点,包括343个高甲基化CpG位点和313个低甲基化CpG位点,分别对应177个高甲基化基因和174个低甲基化基因。在上述比较中,检测到367个重叠CpG位点(对应182个基因),这些位点在大骨节病组与对照组以及骨性关节炎组与对照组的比较中均存在差异甲基化表达。DNA甲基化衰老时钟结果表明,大骨节病、骨性关节炎以及对照组DNA甲基化年龄与实际年龄的平均年龄加速度差异分别为2.549、0.017、-5.364岁,大骨节病组和骨性关节炎组DNA甲基化年龄均大于实际年龄。结论大骨节病和骨性关节炎的软骨细胞均存在过早衰老。     

营养素与衰老标志物相关研究概述

衰老受遗传因素和环境因素的共同作用,其中营养素摄入在衰老的进程中起重要作用。在流行病学研究中,营养素摄入与衰老关系的研究主要集中在端粒-端粒酶学说、自由基学说和衰老的表观遗传学机制等衰老学说上。本文就营养素摄入与端粒长度、氧化损伤标志物及DNA甲基化水平等衰老标志物的关系进行综述,为延缓衰老对策的提出提供一定依据。     

体力活动影响衰老的研究进展

老化是生物体一种正常生理现象，体力活动对于延缓衰老、增强身体机能以及改善相关疾病具有重要意义。本文从端粒体、DNA甲基化以及线粒体等经典生物老化指标入手，尝试阐述体力活动与老化的关联，为解释体力活动影响衰老和身心健康的生物学机制提供参考。     

表观遗传学DNA甲基化与非创伤性产前诊断

表观遗传学研究与DNA序列改变无关，仅发生表现型改变的过程，DNA甲基化是表观遗传学最具特征的标志之一，DNA甲基化技术的进展将其应用领域扩大到非创伤性产前诊断。甲基化特异性PCR可快速、灵敏地根据胎儿和母亲之间DNA甲基化的差异从母血浆中检测胎儿DNA。     

DNA甲基化及其芯片技术研究进展

DNA甲基化是最早发现的、最基本的表观遗传学机制.大量研究表明DNA甲基化与人类疾病有密切关系.DNA甲基化改变包括全基因组水平DNA低甲基化和CpG岛局部高甲基化.DNA甲基化分析方法发展迅速,尤其是近年来,DNA甲基化芯片技术已成为高通量分析DNA甲基化的快速、有效的方法.DNA甲基化芯片主要包括CpG岛微阵列和甲基化寡核苷探针微阵列.本文围绕DNA甲基化相关概念、发生机制、与疾病的关系及主要研究方法等方面进行综述.     

一种改良的亚硫酸氢盐修饰微量DNA的甲基化分析方法

目的建立一种改良的亚硫酸氢盐修饰微量DNA的甲基化分析方法。方法应用低熔点琼脂糖包埋不同含量的DNA，进行亚硫酸氢盐修饰，通过MGMT基因甲基化与非甲基化特异PCR的扩增，与传统的亚硫酸氢盐修饰法进行分析比较。结果改良法对于低至15．625ng的DNA修饰均可获得MGMT基因甲基化扩增产物，而传统法对于62．5ng及其以下的DNA修饰难以获得MGMT基因甲基化扩增产物。结论改良的亚硫酸氢盐修饰方法可有效提高甲基化特异PCR的灵敏度，该方法为微量DNA的甲基化分析提供了一种较理想的研究手段。     

砷对DNA甲基化影响的研究进展

砷污染是全球性的问题,砷暴露与多种疾病密切相关,并能诱发癌症。细胞实验、动物模型实验和流行病学研究表明,砷暴露会影响全基因组DNA甲基化水平;另外,砷暴露也被证实会导致原癌基因和抑癌基因等多种基因启动子的甲基化异常。砷暴露干扰DNA甲基化的作用机制非常复杂。砷可能通过砷甲基化与DNA甲基化过程的耦合改变DNA甲基化状态,也可能通过调节DNA甲基化转移酶(DNMTs)的活力或通过氧化应激效应干扰DNA去甲基化来影响DNA甲基化状态。虽然最终的作用机制尚不明确,但是目前的DNA表观基因毒理学研究为砷暴露的环境健康研究提供了新视角。该文就砷对全基因组和特定基因启动子甲基化的影响及其分子作用机制进行综述。     

DNA甲基化在复发性流产病因中的研究进展

复发性流产（recurrent spontaneous abortion,RSA）是一种常见病理性妊娠,其中有约50%的患者病因和发病机制不明确。随着表观遗传学研究领域的发展,尤其是近年来DNA甲基化的研究,为RSA的病理生理机制提供了一个新视角。研究发现,基因DNA甲基化的功能缺陷、DNA的甲基化修饰调控及DNA甲基化介导的其他表观遗传修饰方式与RSA密切相关,印迹基因DNA甲基化、胎盘特有基因DNA甲基化以及精子DNA甲基化异常都直接或间接地影响胚胎的着床、生长及发育过程,最终导致RSA的发生。现阐述DNA甲基化在RSA发生、发展中的作用及其研究进展。     

DNA甲基化的分析与状态检测

DNA甲基化是指由甲基转移酶介导，以S-腺苷-L-甲硫氨酸为甲基供体，在胞嘧啶5位碳原子上加入一甲基基团，使之变成5-甲基胞嘧啶的化学反应。DNA甲基化是最常见的复制后调节方式之一，在基因表达调控、发育调节、基因组印迹等方面发挥重要作用，与某些肿瘤和遗传病的发生密切相关。CpG甲基化作用已成为阐明正常和病理基因表达现象的重要机制，因而成为当前分子生物学的研究热点之一，近年来，DNA甲基化检测技术有了很大的发展和完善。在此，本文按DNA甲基化检测的目的对DNA甲基化分析检测的技术方法的原理和特点作简要综述。     

A lifelong exposure to a Western-style diet,but not aging,alters global DNA methylation in mouse colon

BACKGROUND/OBJECTIVESPrevious studies have indicated that when compared to young mice, old mice have lower global DNA methylation and higher p16 promoter methylation in colonic mucosa, which is a common finding in colon cancer. It is also known that a Western-style diet (WSD) high in fat and calories, and low in calcium, vitamin D, fiber, methionine and choline (based on the AIN 76A diet) is tumorigenic in colons of mice. Because DNA methylation is modifiable by diet, we investigate whether a WSD disrupts DNA methylation patterns, creating a tumorigenic environment.SUBJECTVIES/METHODSWe investigated the effects of a WSD and aging on global and p16 promoter DNA methylation in the colon. Two month old male C57BL/6 mice were fed either a WSD or a control diet (AIN76A) for 6, 12 or 17 months. Global DNA methylation, p16 promoter methylation and p16 expression were determined by LC/MS, methyl-specific PCR and real time RT-PCR, respectively.RESULTSThe WSD group demonstrated significantly decreased global DNA methylation compared with the control at 17 months (4.05 vs 4.31%, P = 0.019). While both diets did not change global DNA methylation over time, mice fed the WSD had lower global methylation relative to controls when comparing all animals (4.13 vs 4.30%, P = 0.0005). There was an increase in p16 promoter methylation from 6 to 17 months in both diet groups (P < 0.05) but no differences were observed between diet groups. Expression of p16 increased with age in both control and WSD groups.CONCLUSIONSIn this model a WSD reduces global DNA methylation, whereas aging itself has no affect. Although the epigenetic effect of aging was not strong enough to alter global DNA methylation, changes in promoter-specific methylation and gene expression occurred with aging regardless of diet, demonstrating the complexity of epigenetic patterns.     

Prospects for Epigenetic Epidemiology

Epigenetic modification can mediate environmental influenceson gene expression and can modulate the disease risk associatedwith genetic variation. Epigenetic analysis therefore holdssubstantial promise for identifying mechanisms through whichgenetic and environmental factors jointly contribute to diseaserisk. The spatial and temporal variance in epigenetic profileis of particular relevance for developmental epidemiology andthe study of aging, including the variable age at onset formany common diseases. This review serves as a general introductionto the topic by describing epigenetic mechanisms, with a focuson DNA methylation; genetic and environmental factors that influenceDNA methylation; epigenetic influences on development, aging,and disease; and current methodology for measuring epigeneticprofile. Methodological considerations for epidemiologic studiesthat seek to include epigenetic analysis are also discussed. DNA methylation; environment; epigenesis, genetic; folic acid     

Older age and dietary folate are determinants of genomic and p16-specific DNA methylation in mouse colon

Older age and inadequate folate intake are strongly implicated as important risk factors for colon cancer and each is associated with altered DNA methylation. This study was designed to determine the effects of aging and dietary folate on select features of DNA methylation in the colon that are relevant to carcinogenesis. Old (18 mo; n = 34) and young (4 mo; n = 32) male C57BL/6 mice were randomly divided into 3 groups and fed diets containing 0, 4.5, or 18 mumol folate/kg (deplete, replete, and supplemented groups, respectively) for 20 wk. Genomic DNA methylation and p16 promoter methylation in the colonic mucosa were analyzed by liquid chromatography/electrospray ionization/MS and methylation-specific PCR, respectively. p16 gene expression was determined by real-time RT-PCR. Old mice had significantly lower genomic DNA methylation compared with young mice at each level of dietary folate (4.5 +/- 0.2, 4.8 +/- 0.1, and 4.9 +/- 0.1 vs. 6.0 +/- 0.1, 5.3 +/- 0.2, and 5.9 +/- 0.2%, in folate-deplete, -replete, and -supplemented groups, respectively, P < 0.05) and markedly higher p16 promoter methylation (61.0 +/- 2.7, 69.7 +/- 6.9, and 87.1 +/- 13.4 vs. 10.8 +/- 3.6, 8.4 +/- 1.8, and 4.9 +/- 1.7%, respectively, P < 0.05). In old mice, genomic and p16 promoter DNA methylation each increased in a manner that was directly related to dietary folate (P(trend) = 0.009). Age-related enhancement of p16 expression occurred in folate-replete (P = 0.001) and folate-supplemented groups (P = 0.041), but not in the folate-deplete group. In conclusion, aging decreases genomic DNA methylation and increases promoter methylation and expression of p16 in mouse colons. This effect is dependent on the level of dietary folate.     

Nutritional influences on epigenetics and age-related disease

Nutritional epigenetics has emerged as a novel mechanism underlying gene-diet interactions, further elucidating the modulatory role of nutrition in aging and age-related disease development. Epigenetics is defined as a heritable modification to the DNA that regulates chromosome architecture and modulates gene expression without changes in the underlying bp sequence, ultimately determining phenotype from genotype. DNA methylation and post-translational histone modifications are classical levels of epigenetic regulation. Epigenetic phenomena are critical from embryonic development through the aging process, with aberrations in epigenetic patterns emerging as aetiological mechanisms in many age-related diseases such as cancer, CVD and neurodegenerative disorders. Nutrients can act as the source of epigenetic modifications and can regulate the placement of these modifications. Nutrients involved in one-carbon metabolism, namely folate, vitamin B12, vitamin B6, riboflavin, methionine, choline and betaine, are involved in DNA methylation by regulating levels of the universal methyl donor S-adenosylmethionine and methyltransferase inhibitor S-adenosylhomocysteine. Other nutrients and bioactive food components such as retinoic acid, resveratrol, curcumin, sulforaphane and tea polyphenols can modulate epigenetic patterns by altering the levels of S-adenosylmethionine and S-adenosylhomocysteine or directing the enzymes that catalyse DNA methylation and histone modifications. Aging and age-related diseases are associated with profound changes in epigenetic patterns, though it is not yet known whether these changes are programmatic or stochastic in nature. Future work in this field seeks to characterise the epigenetic pattern of healthy aging to ultimately identify nutritional measures to achieve this pattern.     

饮食限制延缓衰老的表观遗传学机制

目的 近年来兴起的表观遗传学被认为在饮食影响健康、延缓衰老中发挥重要的作用。本文旨在从表观遗传学视角分析饮食限制延缓衰老的机制,为临床上抗衰老及其防治相关疾病提供理论参考。方法 系统综述了表观遗传学与衰老的关系,及饮食限制延缓衰老的表观遗传调控方式。结果 饮食限制通过DNA甲基化、组蛋白修饰、非编码RNA调控和染色质重塑等表观遗传修饰调节基因表达,进而影响衰老及其相关疾病的发生发展。结论 饮食限制是一种有效的可操作的环境因素,可通过调节表观遗传修饰进而延缓衰老,保持健康。     

DNA methylation changes in response to active smoking exposure are associated with leukocyte telomere length among older adults

Telomere length (TL) is associated with an increased risk of aging-related diseases. As a preventable environmental hazard of morbidity and mortality, smoking has been reported to promote TL attrition by producing a variety of oxidants and free radicals. Since DNA methylation has been demonstrated to play an important role in the pathways of smoking and smoking-induced diseases, this study aimed to address whether the smoking-associated DNA methylation changes could be associated with accelerated TL shortening. We obtained DNA methylation profiles in whole blood samples by Illumina Infinium Human Methylation 450 Beadchip array in two independent subsamples of the ESTHER study and measured their relative TL by quantitative PCR. Terminal Restriction Fragment analysis was additionally performed in a subsample to obtain absolute TL in base pairs. TL measurements across panels were standardized by z-transformation. After correction for multiple testing, we successfully confirmed that seven out of 151 smoking-related CpG sites were associated with TL (FDR <0.05). A smoking index based on the seven loci showed monotonic associations with TL, cumulative smoking exposure and time after smoking cessation. In conclusion, our study supports suggestions that epigenetic alterations could play a role in smoking-associated disproportionate aging as reflected by TL. Further research is required to examine whether the identified epigenetic signatures of smoking can be of value in clinical practice to assess individual aging across the lifespan.     

Is this environment making you older? Molecular biomarkers and new approaches to investigate the influences of environmental chemicals through aging

Aging is characterized by a gradual and progressive decline in system integrity that occurs with advancing chronological age. Although it is a physiological process, aging is associated with a myriad of age-related diseases (ARDs), including frailty, sarcopenia, chronic obstructive pulmonary disease, cardiovascular disease, cancer, and neurodegenerative diseases. While not exclusively ARDs, many of these diseases lead to death, a lesser quality of life, and increased healthcare costs for individuals and systems. ARDs share several underlying molecular mechanisms, such as cellular damage, inflammation, DNA methylation changes, stem cells exhaustion, and DNA mutations, which have been outlined as hallmarks of aging. Evidence suggests that environmental exposures, including but not limited to metals, air pollution, endocrine-disrupting chemicals, and noise, may accelerate biological aging. Over the past few years, aging research has identified new molecular biomarkers of the aging process. When applied to investigate environmental influences, these biomarkers can help identify individuals who are particularly susceptible to the influences of environmental exposures on aging processes and therefore guide in implementing possible preventive measures.