童年受不良對待經驗與憂鬱症的影響之研究：透過NR3C1基因的DNA甲基化

Abstract

重度憂鬱症是精神疾病當中最常見的，患者通常會有不正常的情緒起伏，並且可能會有睡眠問題、自殺行為等等造成工作場合、社交人際關係的嚴重干擾。因此，了解情緒疾病以及其生物機制是很重要的，其中影響的因子包含了環境和遺傳層面。童年受到不良對待的經驗是最顯著的環境因子之一，而環境的影響有可能對基因的表現有長期的作用，透過啟動子的甲基化影響特定基因表現。因此，本篇研究將針對孩童時期不良對待經驗以及情緒疾病候選基因NR3C1的甲基化程度，分別探討兩者在情感性疾患和健康對照組之間比例的差異，並進一步分析甲基化程度是否在幼年不良對待經驗與憂鬱症扮演中介因子。我們使用自填式的童年受到不良對待經驗量表計算比例以及利用焦磷酸測序的技術測定NR3C1啟動子的甲基化程度，作為環境與遺傳變項。收入81位憂鬱症個案以及151位健康對照受試者，以病例對照研究的方式建立各項因子之間的相關性資料。結果，在早期失去父母(p=0.0003)、情感虐待(p=0.0002)、身體虐待(p=0.0277)、性虐待(p=0.0001)與情感忽略(p<.0001)發現和憂鬱症有顯著相關。除此之外，在控制年紀、教育程度以及職業狀態以後，幼年的情感虐待有最高的勝算比，OR=5.11 (p<.0001)。在10個測定的CpG位點，甲基化程度的平均分別在憂鬱症和健康對照組介於0.13%到1.64%和0.12% 到 1.76%。其中，只有CpG位點10在憂鬱症組較健康對照組有顯著高的甲基化程度(p=0.038)。本篇研究發現NR3C1甲基化程度和憂鬱症的風險存在顯著相關，但和孩童時期不良經驗之間的關係需要進一步、更完整的研究才能下結論。

Major depressive disorder (MDD) is a severe mental illness with severe functional impairments. Adverse childhood experiences (ACE) have been found to play important roles in the risk of developing MDD due to their potential effects in the early stage of brain development, which may exert the impacts in emotion and behaviors in adulthood. ACE may be recognized as stress to the body and induce dysregulation of stress response system, in particular the Hypothalamo-Pituitary-Adrenal (HPA) Axis. One of the possible mechanisms is through the DNA methylation (DNAm) on HPA axis related genes, which can be altered under stressful conditions. Therefore, the aim of the current study is to examine the relationship between ACE and the specific DNA methylation patterns to the risk of depression. In addition, we also detected the possible mediating effects of DNA methylation levels on the relationship between ACE and depression. We recruited 81 DSM-V diagnosed MDD patients and 151 healthy controls from psychiatric outpatient units and communities. Each participant completed semi-structured interviews and Childhood Trauma Questionnaire (CTQ), including assessments of five types of childhood maltreatment and early parental loss, and also provided their blood samples. Furthermore, we tested the DNA methylation levels of the promoter region on NR3C1, for which are related to the HPA axis and are implicated in the regulation of stress responses. Possible transcription factor binding sites were predicted to further locate major CpG sites. We determined the mean methylation levels of promoter regions on NR3C1 using pyrosequencing method with bisulfite converted genomic DNA. Linear and logistic regressions were applied to analyze the relationships between ACE, DNAm and depression. We found a significant association between early parental loss (p=0.0003), emotional abuse (p=0.0002), physical abuse (p=0.0277), sexual abuse (p=0.0001), and emotional neglect (p<.0001). In addition, participants with emotional abuse in childhood have higher risk at depression (OR=5.11, p<.0001) adjusted for age, education level and employment status. The mean methylation levels for the analyzed ten CpG sites were ranged from 0.13% to 1.64% and 0.12% to 1.76% in case and control respectively. Only one CpG site exhibited significant higher methylation level in MDD compared to healthy control (p=0.038). In conclusion, the current study found significant association between NR3C1 methylation status and the risk of depression; however, further investigation is needed to further establish the relationship between adverse childhood experiences and methylation levels.