Adipose tissue-derived non-esterified saturated long-chain fatty acid palmitate (PA) decisively contributes to β-cell demise in type 2 diabetes mellitus in part through the excessive generation of hydrogen peroxide (HO). The endoplasmic reticulum (ER) as the primary site of oxidative protein folding could represent a significant source of HO. Both ER-oxidoreductin-1 (ERO-1) isoenzymes, ERO-1α and ERO-1β, catalyse oxidative protein folding within the ER, generating equimolar amounts of HO for every disulphide bond formed. However, whether ERO-1-derived HO constitutes a potential source of cytotoxic luminal HO under lipotoxic conditions is still unknown. Here, we demonstrate that both ERO-1 isoforms are expressed in pancreatic β-cells, but interestingly, PA only significantly induces ERO-1α. Its specific deletion significantly attenuates PA-mediated oxidative ER stress and subsequent β-cell death by decreasing PA-mediated ER-luminal and mitochondrial HO accumulation, by counteracting the dysregulation of ER Ca homeostasis, and by mitigating the reduction of mitochondrial membrane potential and lowered ATP content. Moreover, ablation of ERO-1α alleviated PA-induced hyperoxidation of the ER redox milieu. Importantly, ablation of ERO-1α did not affect the insulin secretory capacity, the unfolded protein response, or ER redox homeostasis under steady-state conditions. The involvement of ERO-1α-derived HO in PA-mediated β-cell lipotoxicity was corroborated by the overexpression of a redox-active ERO-1α underscoring the proapoptotic activity of ERO-1α in pancreatic β-cells. Overall, our findings highlight the critical role of ERO-1α-derived HO in lipotoxic ER stress and β-cell failure.

中文翻译：

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非酯化脂肪酸棕榈酸酯通过上调 ERO-1α 表达促进氧化内质网应激和 β 细胞凋亡

脂肪组织来源的非酯化饱和长链脂肪酸棕榈酸酯 (PA) 在 2 型糖尿病中通过过度产生过氧化氢 (H2O) 来决定性地导致 β 细胞死亡。内质网（ER）作为氧化蛋白折叠的主要位点可能是 H2O 的重要来源。 ER-氧化还原素-1 (ERO-1) 同工酶 ERO-1α 和 ERO-1β 均催化 ER 内的氧化蛋白折叠，为每个形成的二硫键生成等摩尔量的 H2O。然而，ERO-1衍生的H2O是否构成脂毒性条件下细胞毒性管腔H2O的潜在来源仍不清楚。在这里，我们证明两种 ERO-1 亚型均在胰腺 β 细胞中表达，但有趣的是，PA 仅显着诱导 ERO-1α。它的特异性缺失通过减少 PA 介导的 ER 腔和线粒体 H2O 积累、抵消 ER Ca 稳态失调、减轻线粒体膜电位的降低和降低，显着减轻 PA 介导的氧化 ER 应激和随后的 β 细胞死亡。 ATP 含量。此外，ERO-1α 的消融减轻了 PA 诱导的 ER 氧化还原环境的过度氧化。重要的是，ERO-1α 的消除不会影响稳态条件下的胰岛素分泌能力、未折叠蛋白反应或 ER 氧化还原稳态。氧化还原活性 ERO-1α 的过表达证实了 ERO-1α 衍生的 H2O 参与 PA 介导的 β 细胞脂毒性，这强调了 ERO-1α 在胰腺 β 细胞中的促凋亡活性。总的来说，我们的研究结果强调了 ERO-1α 衍生的 H2O 在脂毒性 ER 应激和 β 细胞衰竭中的关键作用。