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编程在健康和疾病中的关键作用。有证据 下丘脑的表观遗传重编程与肥胖有关。下丘脑包括核心 控制能量平衡、体重和代谢稳态的神经回路。值得注意的是，95%以上的已知 人类肥胖相关基因影响大脑神经通路和活动。然而，转录因子和 负责下丘脑神经元的表观遗传重编程的表观遗传酶是未知的。段塞 一种转录抑制因子，已知在发育和癌症中促进上皮-间质转化 转移Slug通过其C-末端DNA结合结构域和其N-末端SNAG结构域与E2盒结合 结合EZH 2和HDAC 1/2并募集表观遗传酶以靶向启动子/增强子。EZH 2是 多梳阻遏复合物2的催化亚基，并与EED（结构抑制剂）结合催化 亚基），组蛋白3赖氨酸-27（H3 K27 me 2/3）的二甲基化和三甲基化，抑制性表观遗传标记。我们发现 Slug在下丘脑神经元的一个子集中表达，并且在肥胖症中上调。删除Slug 表达长型瘦素受体LepRb的神经元可防止高脂饮食（HFD）诱导的肥胖， 2糖尿病和肝脂肪变性。同样，在腹内侧下丘脑（VMH）中缺失Slug也 减轻HFD诱导的肥胖。相反，野生型Slug的过表达，而不是表观遗传缺陷型Slug的过表达， 突变体，在下丘脑内侧基底部促进肥胖和代谢紊乱。值得注意的是， 注射EZH 2-选择性或EED-选择性抑制剂可改善由Slug 过表达或HFD喂养。下丘脑瘦素信号转导与脑源性神经营养因子（BDNF） 已知信号传导可以防止肥胖和代谢综合征。我们观察到鼻涕虫直接结合 与LepRb启动子连接并诱导H3 K27 me 2/3，从而抑制LepRb表达。Slug也 抑制脑源性神经营养因子在下丘脑的表达基于这些发现，我们假设鼻涕虫 在LepRb、BDNF和其他肥胖的启动子/增强子上组装EZH 2/EED表观遗传复合物 基因，其沉积存款H3 K27 me 2/3以抑制基因。下丘脑SLUG/EZH 2/EED表观遗传 重编程驱动肥胖和代谢紊乱的发展。我们进一步建议， 药理学逆转SLUG/EZH 2/EED表观遗传重编程减轻肥胖和代谢 疾病我们将在三个目标中检验这些假设。目的1是确定VMH Slug是否促进 肥胖症是由表观遗传机制引起的。目的2是确定EZH 2/EED 1复合物是否介导SLUG 支持肥胖的行动。目的3是确定EZH 2和EED抑制剂是否减轻肥胖和代谢紊乱。 通过逆转SLUG/EZH 2/EED表观遗传重编程来治疗疾病。预计这些成果将建立一个 新的下丘脑SLUG/EZH 2/EED表观遗传范式在肥胖和代谢疾病领域。

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.