Institute of Clinical Biochemistry, Hannover Medical School, 30625 Hannover, Germany.
Department of Anesthesiology and Intensive Care Medicine, University Hospital Jena, 07740 Jena, Germany.
Int J Mol Sci. 2021 Oct 8;22(19):10893. doi: 10.3390/ijms221910893.
Elevated levels of free fatty acids (FFAs) have been related to pancreatic beta-cell failure in type 2 diabetes (T2DM), though the underlying mechanisms are not yet fully understood. FFAs have been shown to dysregulate formation of bioactive sphingolipids, such as ceramides and sphingosine-1 phosphate (S1P) in beta-cells. The aim of this study was to analyze the role of sphingosine-1 phosphate lyase (SPL), a key enzyme of the sphingolipid pathway that catalyzes an irreversible degradation of S1P, in the sensitivity of beta-cells to lipotoxicity. To validate the role of SPL in lipotoxicity, we modulated SPL expression in rat INS1E cells and in human EndoC-βH1 beta-cells. SPL overexpression in INS1E cells (INS1E-SPL), which are characterized by a moderate basal expression level of SPL, resulted in an acceleration of palmitate-mediated cell viability loss, proliferation inhibition and induction of oxidative stress. SPL overexpression affected the mRNA expression of ER stress markers and mitochondrial chaperones. In contrast to control cells, in INS1E-SPL cells no protective effect of oleate was detected. Moreover, expression and lipid droplet formation were strongly reduced in OA-treated INS1E-SPL cells. Silencing of SPL in human EndoC-βH1 beta-cells, which are characterized by a significantly higher SPL expression as compared to rodent beta-cells, resulted in prevention of FFA-mediated caspase-3/7 activation. Our findings indicate that an adequate control of S1P degradation by SPL might be crucially involved in the susceptibility of pancreatic beta-cells to lipotoxicity.
游离脂肪酸 (FFAs) 水平升高与 2 型糖尿病 (T2DM) 中的胰岛 β 细胞衰竭有关，但潜在机制尚不完全清楚。FFAs 已被证明可扰乱生物活性鞘脂，如 β 细胞中神经酰胺和 1-磷酸鞘氨醇 (S1P) 的形成。本研究旨在分析鞘氨醇-1-磷酸裂解酶 (SPL) 的作用，SPL 是鞘脂途径的关键酶，可催化 S1P 的不可逆降解，在β细胞对脂毒性的敏感性中起作用。为了验证 SPL 在脂毒性中的作用，我们在大鼠 INS1E 细胞和人 EndoC-βH1 β 细胞中调节了 SPL 的表达。SPL 在 INS1E 细胞中的过表达（INS1E-SPL），其 SPL 的基础表达水平适中，导致棕榈酸介导的细胞活力丧失、增殖抑制和氧化应激诱导加速。SPL 过表达影响 ER 应激标记物和线粒体伴侣的 mRNA 表达。与对照细胞不同，在 INS1E-SPL 细胞中未检测到油酸盐的保护作用。此外，在 OA 处理的 INS1E-SPL 细胞中，表达和脂滴形成强烈减少。与啮齿动物 β 细胞相比，人 EndoC-βH1 β 细胞中 SPL 的表达明显更高，SPL 在人 EndoC-βH1 β 细胞中的沉默导致 FFA 介导的 caspase-3/7 活化得到预防。我们的研究结果表明，SPL 对 S1P 降解的适当控制可能对胰岛 β 细胞对脂毒性的敏感性至关重要。
