补锌通过激活AKT-Nrf2-MT信号通路预防糖尿病肝损伤的研究

Oxidative stress is the key pathogenesis of diabetes-induced liver injury. Zinc is one of the most important metallic element for human, which induces antioxidative effect. As we know, zinc deficiency is the one of the key feature of diabetes. Our preliminary studies indicated zinc supplementation can efficiently prevent diabetes-induced liver injury. But the preventive mechanism of zinc is still unclear. Both metallothionein (MT) and nuclear factor-E2 related factor2 (Nrf2) are well-known antioxidant and their expression are significantly suppressed under diabetic condition. Our previous studied showed that zinc deficiency further decreased the expressions of hepatic MT and Nrf2 in diabetic mice. But the phenomenon can be reversed by zinc supplementation. An recent study demonstrated that MT is downstream of Nrf2 and partially mediates sulforaphane prevention of diabetic cardiomyopathy. Therefore whether Nrf2 and MT mediated zinc-induced hepatic protective effect via same signaling pathway is still unknown. Additionally, under certain circumstances, zinc induces antioxidative effect via activation of Akt signaling pathway. Other studies mention that Akt activation is also required for induction of Nrf2 expression and activation. Based on the above evidence and preliminary studied, the objective of the present project is to explore whether Akt-Nrf2 mediated zinc induced prevention on diabetic liver injury via MT-dependent or MT-independent pathway. In order to do that, we will apply multiple transgenic mice, in combination of mechanistic studies in vitro, to evaluate the role of Nrf2, MT or Akt in zinc induced prevention on diabetic liver injury, respectively; and to identify whether Akt-Nrf2-MT signaling pathway mediated zinc-induced liver protection in type 2 diabetic mice.

氧化应激是糖尿病肝损伤的关键致病机制。锌是机体内的重要金属元素且与抗氧化关系密切。已知锌缺乏是糖尿病的重要特征，我们前期研究证实补锌能有效预防糖尿病肝损伤，但其保护机制仍不明确。金属硫蛋白（MT）及核因子E2相关因子2（Nrf2）是机体内重要的抗氧化蛋白，在糖尿病状态下表达降低。预实验显示祛锌能进一步降低糖尿病小鼠肝脏MT及Nrf2的表达，这一现象在补锌后能被改善。证据显示Nrf2可以调控MT生物学作用的发挥。在某些情况下锌能通过激活Akt发挥抗氧化作用。另外Akt活化也能调控Nrf2的表达及功能发挥。本课题目标是探索补锌治疗是否通过激活Akt-Nrf2信号通路诱导的MT依赖性或非依赖性抗氧化效应预防2型糖尿病肝损伤。本课题将采用多种转基因小鼠并配合体外研究，解析Nrf2、MT及Akt在锌诱导的肝脏保护中的作用，明确Akt-Nrf2-MT信号通路是否是介导锌预防2型糖尿病肝损伤的分子机制。

已知肝脏是糖尿病损伤的主要靶器官之一。研究显示近年来由终末期肝病导致死亡的糖尿病患者数量逐年增加，已经成为威胁糖尿病患者生命健康的重要并发症。确凿证据显示氧化应激是导致糖尿病肝损伤的关键分子机制。锌是维持人类正常生命活动的重要微量元素，在诱导抗氧化方面发挥着卓越作用，有报道指出锌能通过调节AKT激酶活性影响核因子E2相关因子2（Nrf2）和金属硫蛋白（MT）发挥抗氧化作用。课题组前期研究证实缺锌能加重糖尿病肝损伤；而补锌能有效预防糖尿病肝损伤。基于上述线索本课题旨在探索抗氧化在补锌预防糖尿病肝损伤中的作用，同时解析AKT、Nrf2以及MT在补锌诱导抗氧化作用预防糖尿病肝损伤中扮演的角色和相互关系。课题组紧紧围绕研究目标，积极跟踪前沿，创造性的完成了如下研究工作：（1）为明确MT在补锌预防糖尿病肝损伤的作用，课题组引入MT-KO小鼠并利用高脂饮食配合药物刺激诱导2型糖尿病模型，后给予补锌处理。研究证实MT缺失加剧糖尿病肝损伤同时阻断补锌诱导的肝脏保护作用，表明MT参与介导补锌对2型糖尿病肝损伤的预防作用；（2）为明确Nrf2在补锌预防糖尿病肝损伤的作用及其对肝源性MT表达的影响，课题组引入Nrf2-KO小鼠并利用高脂饮食配合药物刺激诱导2型糖尿病模型，后给予补锌处理。研究证实Nrf2缺失加剧糖尿病肝损伤，并且阻断补锌诱导的肝脏保护作用及其对肝脏MT表达的正向调控作用，表明Nrf2-MT参与介导慢性补锌处理对2型糖尿病肝损伤的预防作用；（3）利用高脂饮食配合药物刺激诱导2型糖尿病模型，后给予补锌处理和/或Akt抑制剂处理。研究证实Akt抑制能阻断补锌诱导的肝脏保护作用同时阻断补锌对肝脏Nrf2和MT活性/表达的正向调节作用，表明补锌对糖尿病肝损伤的预防作用是通过激活Akt-Nrf2-MT抗氧化信号通路而实现的。.通过该课题的研究，本课题组发表高水平SCI研究论文3篇（皆有标注），课题负责人受邀参加浙江省内分泌学会并做口头发言（2020）。同时本课题资助培养硕士研究生2名。