背景:严重烧伤通常并发由线粒体氧化应激相关的胰岛功能障碍引起的高血糖。沉默信息调节转录因子3(Sirt3)可以调控线粒体氧化应激。然而,Sirt3对严重烧伤后胰岛功能的作用和机制尚不清楚。因此,本研究旨在探讨Sirt3是否在严重烧伤后胰岛线粒体氧化应激和介导胰岛功能中发挥作用.
方法:建立30%全身表面积全层烧伤的小鼠模型和体外MIN6细胞缺氧模型。Sirt3KO小鼠用于进一步证明Sirt3在维持氧化还原稳态和调节胰岛功能中的作用。检测空腹血糖和葡萄糖刺激的胰岛素分泌(GSIS)以评估胰岛功能。线粒体ROS和脱乙酰的水平,并测定了Mn-SOD和IDH2的活性以评估氧化应激。检测线粒体膜电位(MMP)并测定细胞凋亡率。
结果:体外MIN6细胞,低氧处理显著降低Sirt3的表达,导致Mn-SOD和IDH2的脱乙酰作用增加,从而进一步导致线粒体ROS水平升高。此外,低氧降低MMP,增加细胞凋亡率,最终损害了GSIS。Sirt3的击倒引起了类似的改变。Sirt3的过表达可以逆转低氧诱导的线粒体ROS的高水平,凋亡和GSIS受损。同样,严重烧伤后,随着Mn-SOD的高水平脱乙酰,胰岛中Sirt3的表达显着降低,IDH2、线粒体ROS与细胞凋亡,和胰岛功能障碍。在Sirt3KO小鼠的胰岛中也发生氧化应激和细胞凋亡,伴有胰岛功能障碍。
结论:Sirt3和下游信号通过调节线粒体氧化应激和细胞凋亡来调节严重烧伤后的胰岛功能至关重要。
Severe burns are often complicated with hyperglycemia caused by mitochondrial oxidative stress-related pancreatic islet dysfunction. Silent information regulator of transcription 3 (Sirt3) can regulate mitochondrial oxidative stress. However, the role and mechanism of Sirt3 on islet function after severe burns remain unclear. Therefore, this study aimed to investigate whether Sirt3 played a role in both mitochondrial oxidative stress in islets and mediating islet function post severe burns.
A mouse model of 30% total body surface area full-thickness burn and an in vitro MIN6 cell hypoxia model were established. Sirt3 KO mice were used to demonstrate further the role of Sirt3 in maintaining redox homeostasis and regulating islet function. Fasting blood glucose and glucose-stimulated insulin secretion (GSIS) were detected to assess the islet function. The levels of mitochondrial ROS and deacetylation, and the activities of Mn-SOD and IDH2 were measured to evaluate oxidative stress. The mitochondrial membrane potential (MMP)was detected and the apoptosis rate measured.
In vitro MIN6 cells, the hypoxia treatment significantly reduced Sirt3 expression, resulting in increased deacetylation of Mn-SOD and IDH2, which further led to a higher level of mitochondrial ROS. In addition, hypoxia reduced MMP and increased apoptosis rate, which impaired GSIS eventually. Knockdown of Sirt3 caused similar alterations. The hypoxia-induced high level of mitochondrial ROS and apoptosis and impaired GSIS could be reversed by overexpression of Sirt3. Similarly, after severe burns, the expression of Sirt3 in islets decreased significantly with a high level of deacetylation of Mn-SOD, IDH2, mitochondrial ROS and apoptosis, and islet dysfunction. Oxidative stress and apoptosis also occurred in islets of Sirt3 KO mice, accompanied by islet dysfunction.
Sirt3 and downstream signalling are critical in modulating the islet function post severe burns by regulating mitochondrial oxidative stress and apoptosis.