Department of Burns and Plastic Surgery, The Fourth Medical Center, Chinese PLA General Hospital, Beijing, 100048, China.
Department of Burns and Plastic Surgery, The Fourth Medical Center, Chinese PLA General Hospital, Beijing, 100048, China.
Free Radic Biol Med. 2023 Mar;198:59-67. doi: 10.1016/j.freeradbiomed.2023.01.027. Epub 2023 Feb 3.
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.
严重烧伤常伴有线粒体氧化应激相关胰岛功能障碍引起的高血糖症。沉默信息调节因子 3（Sirt3）可以调节线粒体氧化应激。然而，Sirt3 在严重烧伤后对胰岛功能的作用及其机制尚不清楚。因此，本研究旨在探讨 Sirt3 是否在胰岛的线粒体氧化应激和调节胰岛功能方面发挥作用。
建立 30%总体表面积全层烧伤小鼠模型和 MIN6 细胞缺氧模型。使用 Sirt3 KO 小鼠进一步证明 Sirt3 在维持氧化还原平衡和调节胰岛功能中的作用。检测空腹血糖和葡萄糖刺激胰岛素分泌（GSIS）评估胰岛功能。测量线粒体 ROS 和去乙酰化水平以及 Mn-SOD 和 IDH2 的活性来评估氧化应激。检测线粒体膜电位（MMP）和细胞凋亡率。
在体外 MIN6 细胞中，缺氧处理显著降低 Sirt3 的表达，导致 Mn-SOD 和 IDH2 的去乙酰化增加，从而导致线粒体 ROS 水平升高。此外，缺氧降低了 MMP 并增加了细胞凋亡率，最终损害了 GSIS。Sirt3 的敲低也导致了类似的改变。缺氧诱导的线粒体 ROS 水平升高、细胞凋亡和 GSIS 受损可以通过 Sirt3 的过表达逆转。同样，在严重烧伤后，胰岛中 Sirt3 的表达明显下降，Mn-SOD、IDH2、线粒体 ROS 和细胞凋亡的去乙酰化水平升高，胰岛功能受损。氧化应激和细胞凋亡也发生在 Sirt3 KO 小鼠的胰岛中，伴有胰岛功能障碍。
Sirt3 及其下游信号在调节严重烧伤后胰岛功能方面起着至关重要的作用，通过调节线粒体氧化应激和细胞凋亡。
