Department of Biological Sciences, College of Medicine, Inha University, Incheon, Republic of Korea; Program in Biomedical Science and Engineering, Inha University, Incheon, Republic of Korea; Research Center for Controlling Intercellular Communication (RCIC), College of Medicine, Inha University, Incheon, Republic of Korea.
Department of Medicine, Columbia University, New York, New York.
Gastroenterology. 2023 Mar;164(3):439-453. doi: 10.1053/j.gastro.2022.11.019. Epub 2022 Nov 17.
BACKGROUND & AIMS: Obesity predisposes to type 2 diabetes (T2D) and nonalcoholic fatty liver disease (NAFLD), but underlying mechanisms are incompletely understood. Potassium channel tetramerization domain-containing protein 17 (Kctd17) levels are increased in livers from obese mice and humans. In this study, we investigated the mechanism of increased Kctd17 and whether it is causal to obesity-induced metabolic complications.
We transduced Rosa26-LSL-Cas9 knockin mice with AAV8-TBG-Cre (Control), AAV8-U6-Kctd17 sgRNA-TBG-Cre (L-Kctd17), AAV8-U6-Oga sgRNA-TBG-Cre (L-Oga), or AAV8-U6-Kctd17/Oga sgRNA-TBG-Cre (DKO). We fed mice a high-fat diet (HFD) and assessed for hepatic glucose and lipid homeostasis. We generated Kctd17, O-GlcNAcase (Oga), or Kctd17/Oga-knockout hepatoma cells by CRISPR-Cas9, and Kctd17-directed antisense oligonucleotide to test therapeutic potential in vivo. We analyzed transcriptomic data from patients with NAFLD.
Hepatocyte Kctd17 expression was increased in HFD-fed mice due to increased Srebp1c activity. HFD-fed L-Kctd17 or Kctd17 antisense oligonucleotide-treated mice show improved glucose tolerance and hepatic steatosis, whereas forced Kctd17 expression caused glucose intolerance and hepatic steatosis even in lean mice. Kctd17 induced Oga degradation, resulting in increasing carbohydrate response element-binding protein (Chrebp) protein, so concomitant Oga knockout negated metabolic benefits of hepatocyte Kctd17 deletion. In patients with NAFLD, KCTD17 messenger RNA was positively correlated with expression of Chrebp target and other lipogenic genes.
Srebp1c-induced hepatocyte Kctd17 expression in obesity disrupted glucose and lipid metabolism by stabilizing Chrebp, and may represent a novel therapeutic target for obesity-induced T2D and NAFLD.
肥胖可导致 2 型糖尿病（T2D）和非酒精性脂肪性肝病（NAFLD），但其潜在机制尚不完全清楚。钾通道四聚化结构域蛋白 17（Kctd17）在肥胖小鼠和人类的肝脏中表达增加。在本研究中，我们研究了 Kctd17 表达增加的机制，以及它是否与肥胖引起的代谢并发症有关。
我们通过 AAV8-TBG-Cre（对照）、AAV8-U6-Kctd17 sgRNA-TBG-Cre（L-Kctd17）、AAV8-U6-Oga sgRNA-TBG-Cre（L-Oga）或 AAV8-U6-Kctd17/Oga sgRNA-TBG-Cre（DKO）转导 Rosa26-LSL-Cas9 基因敲入小鼠。我们用高脂肪饮食（HFD）喂养小鼠，评估其肝葡萄糖和脂质稳态。我们通过 CRISPR-Cas9 生成 Kctd17、O-连接 N-乙酰氨基葡萄糖酶（Oga）或 Kctd17/Oga 敲除肝癌细胞，并用 Kctd17 导向的反义寡核苷酸在体内进行治疗潜力测试。我们分析了 NAFLD 患者的转录组数据。
由于 Srebp1c 活性增加，HFD 喂养的小鼠肝细胞中 Kctd17 的表达增加。L-Kctd17 或 Kctd17 反义寡核苷酸治疗的 HFD 喂养小鼠显示出改善的葡萄糖耐量和肝脂肪变性，而强制表达 Kctd17 甚至在瘦小鼠中也会导致葡萄糖不耐受和肝脂肪变性。Kctd17 诱导 Oga 降解，导致碳水化合物反应元件结合蛋白（Chrebp）蛋白增加，因此肝细胞 Kctd17 缺失的代谢益处可被同时敲除 Oga 所抵消。在 NAFLD 患者中，KCTD17 mRNA 与 Chrebp 靶标和其他脂肪生成基因的表达呈正相关。
肥胖时 Srebp1c 诱导的肝细胞 Kctd17 表达通过稳定 Chrebp 破坏葡萄糖和脂质代谢，可能成为肥胖引起的 T2D 和 NAFLD 的新治疗靶点。
