Zhang Yan, Dong Yuan, Xiong Zhenyu, Zhu Zhengru, Gao Fanya, Wang Tingting, Man Wanrong, Sun Dong, Lin Jie, Li Tongbin, Li Congye, Zhao Zhijing, Shen Min, Sun Dongdong, Fan Yanhong
Department of Cardiology, Xijing Hospital, Fourth Military Medical University, Xi'an, People's Republic of China.
Department of Otolaryngology Head and Neck Surgery, First Hospital of Lanzhou University, Lanzhou, People's Republic of China.
Diabetes Metab Syndr Obes. 2020 Dec 7;13:4801-4808. doi: 10.2147/DMSO.S287287. eCollection 2020.
Endothelial-to-mesenchymal transition (EndMT) is an important source of myofibroblasts that directly affects cardiac function in diabetic cardiomyopathy (DCM) via an unknown underlying mechanism. Sirt6 is a member of the Sirtuin family of NAD(+)-dependent enzymes that plays an important role in glucose and fatty acid metabolism. In this study, we investigated whether Sirt6 participates in EndMT during the development of T2DM and the possible underlying regulatory mechanisms.
Endothelium-specific Sirt6 knockout (Sirt6-KO) mice (C57BL/6 genetic background) were generated using the classic Cre/loxp gene recombination system. T2DM was induced in eight-week-old male mice by feeding with a high-fat diet for three weeks followed by i.p. injection with 30 mg/kg of streptozotocin. The weight, lipids profiles, insulin, food intake and water intake of experimental animals were measured on a weekly basis. Cardiac microvascular endothelial cells (CMECs) were obtained from adult male mice; the isolated cells were cultured with high glucose (HG; 33 mmol/L) and palmitic acid (PA; 500 μmol/L) in DMEM for 24 h, or with normal glucose (NG; 5 mmol/L) as the control.
Sirt6 expression is significantly downregulated in CMECs treated with HG+PA. Additionally, Sirt6-KO was found to worsen DCM, as indicated by aggravated perivascular fibrosis, cardiomyocyte hypertrophy, and decreased cardiac function. In vitro, Sirt6 knockdown exacerbated the proliferation, and migration of CMECs exposed to HG+PA. Mechanistically, Sirt6 knockdown significantly enhanced Notch1 activation in CMECs treated with HG+PA, whereas Notch1 adenoviral interference significantly blunted the effects of Sirt6 knockdown on CMECs.
This study is the first to demonstrate that Sirt6 participates in EndMT via the Notch1 signaling pathway in CMECs stimulated with HG+PA. Therefore, the findings of this study suggest that Sirt6 could provide a potential treatment strategy for DCM.
内皮-间充质转化（EndMT）是肌成纤维细胞的重要来源，其通过未知的潜在机制直接影响糖尿病性心肌病（DCM）的心脏功能。Sirt6是烟酰胺腺嘌呤二核苷酸（NAD⁺）依赖性酶的沉默调节蛋白家族成员，在葡萄糖和脂肪酸代谢中起重要作用。在本研究中，我们调查了Sirt6是否参与2型糖尿病（T2DM）发展过程中的EndMT以及可能的潜在调控机制。
使用经典的Cre/loxp基因重组系统构建内皮特异性Sirt6基因敲除（Sirt6-KO）小鼠（C57BL/6遗传背景）。8周龄雄性小鼠通过高脂饮食喂养3周，随后腹腔注射30 mg/kg链脲佐菌素诱导T2DM。每周测量实验动物的体重、血脂谱、胰岛素、食物摄入量和饮水量。从成年雄性小鼠中获取心脏微血管内皮细胞（CMECs）；将分离的细胞在含有高糖（HG；33 mmol/L）和棕榈酸（PA；500 μmol/L）的DMEM中培养24小时，或用正常葡萄糖（NG；5 mmol/L）作为对照。
用HG+PA处理的CMECs中Sirt6表达显著下调。此外，发现Sirt6-KO会加重DCM，表现为血管周围纤维化加重、心肌细胞肥大和心脏功能下降。在体外，Sirt6基因敲低加剧了暴露于HG+PA的CMECs的增殖和迁移。机制上，Sirt6基因敲低显著增强了用HG+PA处理的CMECs中的Notch1激活，而Notch1腺病毒干扰显著减弱了Sirt6基因敲低对CMECs的影响。
本研究首次证明Sirt6在HG+PA刺激的CMECs中通过Notch1信号通路参与EndMT。因此，本研究结果表明Sirt6可为DCM提供潜在的治疗策略。
