The role of hypothalamic Slug in the regulation of leptin sensitivity, energy balance, and body weight

摘要 最近的研究强调了表观遗传重新编程在健康和疾病中的关键作用。有证据表明 下丘脑的表观遗传重编程与肥胖有关。下丘脑围绕核心 控制能量平衡、体重和代谢动态平衡的神经回路。值得注意的是，已知的95% 人类肥胖相关基因影响脑神经通路和活动。然而，转录因子和 负责下丘脑神经元表观遗传重编程的表观遗传酶尚不清楚。弹头是 一种转录抑制因子，在发育和癌症中促进上皮-间充质转化 转移。Slug通过其C-末端DNA结合域和N-末端SNAG结构域与E2盒结合 结合EZH2和HDAC1/2并招募表观遗传酶来靶向启动子/增强子。EZH2是 多梳抑制络合物2的催化亚基，并与EED(一种结构 亚单位)，组蛋白3赖氨酸-27(H3K27me2/3)的二甲基化和三甲基化，抑制性表观遗传标记。我们发现 该粘蛋白在下丘脑神经元的一个子集中表达，并在肥胖时上调。删除中的弹出程序 长型瘦素受体LepRb表达神经元对高脂饮食(HFD)诱导的肥胖型的保护作用 2糖尿病和肝脏脂肪变性。同样，下丘脑腹内侧区(VMH)中的Slug的缺失也 减轻高脂饮食引起的肥胖。相反，野生型鼻涕虫过表达，但不是表观遗传缺陷 突变的下丘脑内侧基底区会促进肥胖和代谢紊乱。值得注意的是，中央 注射EZH2选择性或EED选择性抑制剂可改善由任一种鼻涕引起的肥胖 过度表达或HFD进食。下丘脑瘦素信号与脑源性神经营养因子 众所周知，信号可以预防肥胖和代谢综合征。我们观察到鼻涕虫直接结合 与LepRb启动子结合，诱导H3K27me2/3，从而抑制LepRb的表达。鼻涕虫也 抑制BDNF在下丘脑的表达。基于这些发现，我们假设弹头 在LepRb、BDNF和其他肥胖的启动子/增强子上组装EZH2/EED表观遗传复合体 基因，沉积H3K27me2/3以抑制基因。下丘脑鼻涕虫/EZH2/EED表观遗传学 重新编程会导致肥胖和代谢紊乱的发展。我们进一步建议 Slug/EZH2/EED表观遗传重编程的药理学逆转减轻肥胖和代谢 疾病。我们将在三个目标上检验这些假设。目标1是确定VMH插件是否会提升 由表观遗传机制引起的肥胖。目的2是确定EZH2/EED1复合体是否介导鼻涕虫 支持肥胖的行动。目标3是确定EZH2和EED抑制剂是否可以减轻肥胖和代谢 通过逆转Slug/EZH2/EED表观遗传重新编程而致病。预计结果将建立一个 肥胖和代谢性疾病领域中新的下丘脑Slug/EZH2/EED表观遗传学范式。

Abstract Recent research highlights pivotal roles of epigenetic reprogramming in health and disease. There is evidence that epigenetic reprogramming in the hypothalamus is linked to obesity. The hypothalamus encompasses core neural circuits controlling energy balance, body weight, and metabolic homeostasis. Of note, >95% of known human obesity-related genes affect brain neural pathways and activities. However, transcription factors and epigenetic enzymes responsible for epigenetic reprogramming of hypothalamic neurons are unknown. Slug is a transcriptional repressor and known to promote epithelial-mesenchymal transition in development and cancer metastasis. Slug binds to E2 boxes via its C-terminal DNA-binding domain, and its N-terminal SNAG domain binds to EZH2 and HDAC1/2 and recruits the epigenetic enzymes to target promoters/enhancers. EZH2 is the catalytic subunit of the polycomb repressive complex 2, and catalyzes, in conjunction with EED (a structural subunit), di- and tri-methylations of histone 3 lysine-27 (H3K27me2/3), repressive epigenetic marks. We found that Slug is expressed in a subset of hypothalamic neurons and upregulated in obesity. Deletion of Slug in long-form leptin receptor LepRb-expressing neurons protects against high fat diet (HFD)-induced obesity, type 2 diabetes, and liver steatosis. Likewise, deletion of Slug in the ventromedial hypothalamus (VMH) also mitigates HFD-induced obesity. Conversely, overexpression of wild-type Slug, but not epigenetic-defective mutants, in the mediobasal hypothalamus promotes obesity and metabolic disorders. Remarkably, central injection of EZH2-selective or EED-selective inhibitors ameliorates obesity induced by either Slug overexpression or HFD feeding. Hypothalamic leptin signaling and brain-derived neurotrophic factor (BDNF) signaling are known to protect against obesity and metabolic syndromes. We observed that Slug directly binds to the LepRb promoter and induces H3K27me2/3, thereby suppressing LepRb expression. Slug also suppresses BDNF expression in the hypothalamus. Based on these findings, we hypothesize that Slug assembles EZH2/EED epigenetic complexes on the promoters/enhancers of LepRb, BDNF, and other obesity genes, which deposit H3K27me2/3 to repress the genes. Hypothalamic SLUG/EZH2/EED epigenetic reprogramming drives the development of obesity and metabolic disorders. We further propose that pharmacological reversal of the SLUG/EZH2/EED epigenetic reprogramming mitigates obesity and metabolic disease. We will test these hypotheses in three aims. Aim 1 is to determine whether VMH Slug promotes obesity by an epigenetic mechanism. Aim 2 is to determine whether EZH2/EED1 complex mediates SLUG’s pro-obesity action. Aim 3 is to determine whether EZH2 and EED inhibitors mitigate obesity and metabolic disease by reversing SLUG/EZH2/EED epigenetic reprogramming. The outcomes are expected to establish a new hypothalamic SLUG/EZH2/EED epigenetic paradigm in the field of obesity and metabolic disease.