Division of Food Functionality Research, Korea Food Research Institute, Jeollabuk-do, 55365, Republic of Korea.
Department of Food and Nutrition, Gangseo Univ., Seoul, 07661, Republic of Korea.
Exp Mol Med. 2023 Jan;55(1):143-157. doi: 10.1038/s12276-022-00919-5. Epub 2023 Jan 6.
Dynamic alteration of DNA methylation leads to various human diseases, including nonalcoholic fatty liver disease (NAFLD). Although C-Maf-inducing protein (Cmip) has been reported to be associated with NAFLD, its exact underlying mechanism remains unclear. Here, we aimed to elucidate this mechanism in NAFLD in vitro and in vivo. We first identified alterations in the methylation status of the Cmip intron 1 region in mouse liver tissues with high-fat high-sucrose diet-induced NAFLD. Knockdown of DNA methyltransferase (Dnmt) 1 significantly increased Cmip expression. Chromatin immunoprecipitation assays of AML12 cells treated with oleic and palmitic acid (OPA) revealed that Dnmt1 was dissociated and that methylation of H3K27me3 was significantly decreased in the Cmip intron 1 region. Conversely, the knockdown of Tet methylcytosine dioxygenase 2 (Tet2) decreased Cmip expression. Following OPA treatment, the CCCTC-binding factor (Ctcf) was recruited, and H3K4me3 was significantly hypermethylated. Intravenous Cmip siRNA injection ameliorated NAFLD pathogenic features in ob/ob mice. Additionally, Pparγ and Cd36 expression levels were dramatically decreased in the livers of ob/ob mice administered siCmip, and RNA sequencing revealed that Gbp2 was involved. Gbp2 knockdown also induced a decrease in Pparγ and Cd36 expression, resulting in the abrogation of fatty acid uptake into cells. Our data demonstrate that Cmip and Gbp2 expression levels are enhanced in human liver tissues bearing NAFLD features. We also show that Dnmt1-Trt2/Ctcf-mediated reversible modulation of Cmip methylation regulates the Gbp2-Pparγ-Cd36 signaling pathway, indicating the potential of Cmip as a novel therapeutic target for NAFLD.
DNA 甲基化的动态改变导致了各种人类疾病，包括非酒精性脂肪性肝病（NAFLD）。虽然 C-Maf 诱导蛋白（Cmip）已被报道与 NAFLD 相关，但它的确切潜在机制尚不清楚。在这里，我们旨在体外和体内阐明 NAFLD 中的这一机制。我们首先在高脂肪高蔗糖饮食诱导的 NAFLD 小鼠肝组织中鉴定了 Cmip 内含子 1 区域甲基化状态的改变。DNA 甲基转移酶（Dnmt）1 的敲低显著增加了 Cmip 的表达。用油酸和棕榈酸（OPA）处理的 AML12 细胞的染色质免疫沉淀实验显示，Dnmt1 解离，Cmip 内含子 1 区域的 H3K27me3 甲基化显著减少。相反，Tet 甲基胞嘧啶双加氧酶 2（Tet2）的敲低降低了 Cmip 的表达。OPA 处理后，CCCTC 结合因子（Ctcf）被募集，H3K4me3 被显著超甲基化。静脉注射 Cmip siRNA 可改善 ob/ob 小鼠的 NAFLD 发病特征。此外，在接受 siCmip 治疗的 ob/ob 小鼠肝脏中，Pparγ 和 Cd36 的表达水平显著降低，RNA 测序显示 Gbp2 参与其中。Gbp2 的敲低也诱导 Pparγ 和 Cd36 表达的减少，导致细胞内脂肪酸摄取减少。我们的数据表明，在具有 NAFLD 特征的人类肝组织中，Cmip 和 Gbp2 的表达水平增强。我们还表明，Dnmt1-Trt2/Ctcf 介导的 Cmip 甲基化的可逆调节调节 Gbp2-Pparγ-Cd36 信号通路，表明 Cmip 作为 NAFLD 的一种新的治疗靶点的潜力。
