Yamada Yukiho, Urakawa Natsuho, Tamiya Hisato, Sakamoto Shuya, Takahashi Hiroki, Harada Naoki, Kitakaze Tomoya, Izawa Takeshi, Matsumua Shigenobu, Yoshihara Eiji, Inui Hiroshi, Mashimo Tomoji, Yamaji Ryoichi
Department of Applied Biological Chemistry, Graduate School of Agriculture, Osaka Metropolitan University, Sakai, Osaka, Japan.
Division of Applied Life Sciences, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, Japan.
J Biol Chem. 2025 May 21;301(6):110271. doi: 10.1016/j.jbc.2025.110271.
Pancreatic β-cells play a critical role in glucose homeostasis by secreting insulin. Chronic oxidative stress causes β-cell dysfunction, including β-cell loss; however, the underlying mechanisms remain unclear. Here, we demonstrate the critical role of the regulated in development and DNA damage response 2 (REDD2/DDiT4L/Rtp801L) in β-cell dysfunction. In INS-1 β-cells, Redd2 was induced by high glucose/palmitate or streptozotocin (STZ) exposure. Knockdown of Redd2 attenuated STZ-induced loss of cell viability, while REDD2 overexpression reduced cell viability and p70S6K phosphorylation, suggesting the involvement of suppression of mTORC1 activation. STZ also activated the transcription factors nuclear factor erythroid 2-related factor 2 (Nrf2) and p53, and overexpression of these transcription factors synergistically induced Redd2 expression. Reporter assays using the Redd2 promoter (-2328/-1) and chromatin immunoprecipitation identified the functional binding sites for Nrf2 (EpRE2, -349/-340) and p53 (p53RE1, -90/-81) on the Redd2 promoter. Purified recombinant p53 and Nrf2 bound directly. There were no noticeable changes in male global Redd2-knockout mice (C57BL/6J background), except for inguinal adipose tissue decrease when the mice were fed a standard diet. In contrast, when the mice were fed a high-fat diet (HFD), Redd2-knockout mice exhibited improved glucose tolerance relative to littermate controls. Redd2-knockout in HFD-fed mice increased β-cell mass due to reduced β-cell apoptosis and elevated plasma insulin concentrations, whereas insulin sensitivity remained unaffected. In both STZ-induced male and female and HFD-fed male models, β-cell-specific Redd2-knockout improved glucose tolerance without affecting insulin sensitivity. Our results identify REDD2 as a novel regulator of β-cell dysfunction under oxidative stress.
胰腺β细胞通过分泌胰岛素在葡萄糖稳态中发挥关键作用。慢性氧化应激会导致β细胞功能障碍，包括β细胞丢失；然而，其潜在机制仍不清楚。在此，我们证明了发育调控和DNA损伤反应2（REDD2/DDiT4L/Rtp801L）在β细胞功能障碍中的关键作用。在INS-1β细胞中，高糖/棕榈酸酯或链脲佐菌素（STZ）处理可诱导Redd2表达。敲低Redd2可减轻STZ诱导的细胞活力丧失，而REDD2过表达则降低细胞活力和p70S6K磷酸化，提示mTORC1激活受抑制。STZ还激活了转录因子核因子红系2相关因子2（Nrf2）和p53，这些转录因子的过表达协同诱导Redd2表达。使用Redd2启动子（-2328/-1）进行的报告基因分析和染色质免疫沉淀确定了Redd2启动子上Nrf2（EpRE2，-349/-340）和p53（p53RE1，-90/-81）的功能性结合位点。纯化的重组p53和Nrf2直接结合。雄性全局Redd2基因敲除小鼠（C57BL/6J背景）无明显变化，仅在喂食标准饮食时腹股沟脂肪组织减少。相比之下，当给小鼠喂食高脂饮食（HFD）时，Redd2基因敲除小鼠相对于同窝对照表现出改善的葡萄糖耐量。高脂饮食喂养的小鼠中Redd2基因敲除由于β细胞凋亡减少和血浆胰岛素浓度升高而增加了β细胞质量，而胰岛素敏感性未受影响。在STZ诱导的雄性和雌性以及高脂饮食喂养的雄性模型中，β细胞特异性Redd2基因敲除均改善了葡萄糖耐量而不影响胰岛素敏感性。我们的结果确定REDD2是氧化应激下β细胞功能障碍的一种新型调节因子。
