Department of Epidemiology, Erasmus University Medical Center, Rotterdam, the Netherlands; Department of Epidemiology, Harvard T.H. Chan School of Public Health, Boston, Massachusetts.
Department of Epidemiology, Erasmus University Medical Center, Rotterdam, the Netherlands; Department of Genetics, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.
Gastroenterology. 2017 Oct;153(4):1096-1106.e2. doi: 10.1053/j.gastro.2017.06.003. Epub 2017 Jun 15.
BACKGROUND & AIMS: Epigenetic mechanisms might be involved in the regulation of liver enzyme level. We aimed to identify CpG sites at which DNA methylation levels are associated with blood levels of liver enzymes and hepatic steatosis.
We conducted an epigenome-wide association study in whole blood for liver enzyme levels, including gamma-glutamyl transferase (GGT), alanine aminotransferase (ALT), and aspartate aminotransferase (AST), among a discovery set of 731 participants of the Rotterdam Study and sought replication in a non-overlapping sample of 719 individuals. Significant DNA methylation changes were further analyzed to evaluate their relation with hepatic steatosis. Expression levels of the top identified gene were measured in 9 human liver cell lines and compared with expression profiles of its potential targets associated with lipid traits. The candidate gene was subsequently knocked down in human hepatoma cells using lentiviral vectors expressing small hairpin RNAs.
Eight probes annotated to SLC7A11, SLC1A5, SLC43A1, PHGDH, PSORS1C1, SREBF1, ANKS3 were associated with GGT and 1 probe annotated to SLC7A11 was associated with ALT after Bonferroni correction (1.0 × 10). No probe was identified for AST levels. Four probes for GGT levels including cg06690548 (SLC7A11), cg11376147 (SLC43A1), cg22304262 (SLC1A5), and cg14476101 (PHGDH), and 1 for ALT cg06690548 (SLC7A11) were replicated. DNA methylation at SLC7A11 was associated with reduced risk of hepatic steatosis in participants (odds ratio, 0.69; 95% CI= 0.55-0.93; P value: 2.7 × 10). In functional experiments, SLC7A11 was highly expressed in human liver cells; its expression is positively correlated with expression of a panel of lipid-associated genes, indicating a role of SLC7A11 in lipid metabolism.
Our results provide new insights into epigenetic mechanisms associated with markers of liver function and hepatic steatosis, laying the groundwork for future diagnostic and therapeutic applications.
表观遗传机制可能参与了肝脏酶水平的调控。我们旨在鉴定与血液中肝脏酶和肝脂肪变性相关的 DNA 甲基化水平的 CpG 位点。
我们在全血中进行了一项与肝脏酶水平（包括 γ-谷氨酰转移酶（GGT）、丙氨酸氨基转移酶（ALT）和天冬氨酸氨基转移酶（AST））相关的全基因组关联研究，该研究在鹿特丹研究的 731 名参与者的发现集中进行，并在 719 名非重叠样本中寻求复制。进一步分析显著的 DNA 甲基化变化，以评估其与肝脂肪变性的关系。在 9 个人类肝母细胞瘤细胞系中测量了鉴定出的 top 基因的表达水平，并与与脂质特征相关的其潜在靶基因的表达谱进行了比较。随后，使用表达小发夹 RNA 的慢病毒载体在人肝癌细胞中敲低候选基因。
在 Bonferroni 校正（1.0×10）后，有 8 个探针注释到 SLC7A11、SLC1A5、SLC43A1、PHGDH、PSORS1C1、SREBF1、ANKS3 与 GGT 相关，1 个探针注释到 SLC7A11 与 ALT 相关。未鉴定出与 AST 水平相关的探针。与 GGT 水平相关的 4 个探针，包括 cg06690548（SLC7A11）、cg11376147（SLC43A1）、cg22304262（SLC1A5）和 cg14476101（PHGDH），与 ALT 的 1 个探针 cg06690548（SLC7A11）被复制。SLC7A11 的 DNA 甲基化与参与者肝脂肪变性的风险降低相关（比值比，0.69；95%CI=0.55-0.93；P 值：2.7×10）。在功能实验中，SLC7A11 在人肝母细胞瘤细胞中高表达；其表达与一组脂质相关基因的表达呈正相关，表明 SLC7A11 在脂质代谢中起作用。
我们的研究结果为与肝功能和肝脂肪变性标志物相关的表观遗传机制提供了新的见解，为未来的诊断和治疗应用奠定了基础。
