ULB Center for Diabetes Research, Université Libre de Bruxelles, CP-618, Route de Lennik 808, 1070, Brussels, Belgium.
Division of Endocrinology, Erasmus Hospital, Université Libre de Bruxelles, Brussels, Belgium.
BMC Genomics. 2020 Aug 26;21(1):590. doi: 10.1186/s12864-020-07003-0.
Prolonged exposure to elevated free fatty acids induces β-cell failure (lipotoxicity) and contributes to the pathogenesis of type 2 diabetes. In vitro exposure of β-cells to the saturated free fatty acid palmitate is a valuable model of lipotoxicity, reproducing features of β-cell failure observed in type 2 diabetes. In order to map the β-cell response to lipotoxicity, we combined RNA-sequencing of palmitate-treated human islets with iTRAQ proteomics of insulin-secreting INS-1E cells following a time course exposure to palmitate.
Crossing transcriptome and proteome of palmitate-treated β-cells revealed 85 upregulated and 122 downregulated genes at both transcript and protein level. Pathway analysis identified lipid metabolism, oxidative stress, amino-acid metabolism and cell cycle pathways among the most enriched palmitate-modified pathways. Palmitate induced gene expression changes compatible with increased free fatty acid mitochondrial import and β-oxidation, decreased lipogenesis and modified cholesterol transport. Palmitate modified genes regulating endoplasmic reticulum (ER) function, ER-to-Golgi transport and ER stress pathways. Furthermore, palmitate modulated cAMP/protein kinase A (PKA) signaling, inhibiting expression of PKA anchoring proteins and downregulating the GLP-1 receptor. SLC7 family amino-acid transporters were upregulated in response to palmitate but this induction did not contribute to β-cell demise. To unravel critical mediators of lipotoxicity upstream of the palmitate-modified genes, we identified overrepresented transcription factor binding sites and performed network inference analysis. These identified LXR, PPARα, FOXO1 and BACH1 as key transcription factors orchestrating the metabolic and oxidative stress responses to palmitate.
This is the first study to combine transcriptomic and sensitive time course proteomic profiling of palmitate-exposed β-cells. Our results provide comprehensive insight into gene and protein expression changes, corroborating and expanding beyond previous findings. The identification of critical drivers and pathways of the β-cell lipotoxic response points to novel therapeutic targets for type 2 diabetes.
长期暴露于升高的游离脂肪酸会导致β细胞衰竭（脂毒性），并有助于 2 型糖尿病的发病机制。体外β细胞暴露于饱和游离脂肪酸棕榈酸是脂毒性的一种有价值的模型，可再现 2 型糖尿病中观察到的β细胞衰竭特征。为了绘制β细胞对脂毒性的反应，我们结合了 RNA 测序和 iTRAQ 蛋白质组学，对棕榈酸处理后的人胰岛进行了时间过程暴露于棕榈酸后，对胰岛素分泌 INS-1E 细胞进行了研究。
跨转录组和棕榈酸处理的β细胞的蛋白质组学揭示了 85 个上调和 122 个下调基因在转录和蛋白质水平上。途径分析确定脂质代谢、氧化应激、氨基酸代谢和细胞周期途径是最丰富的棕榈酸修饰途径之一。棕榈酸诱导的基因表达变化与增加的游离脂肪酸线粒体导入和β氧化、减少的脂肪生成和修饰的胆固醇转运相兼容。棕榈酸修饰了调节内质网（ER）功能、ER 到高尔基体运输和 ER 应激途径的基因。此外，棕榈酸还调节了 cAMP/蛋白激酶 A（PKA）信号通路，抑制了 PKA 锚定蛋白的表达，并下调了 GLP-1 受体。SLC7 家族氨基酸转运体在棕榈酸的作用下上调，但这种诱导并不能导致β细胞死亡。为了在棕榈酸修饰基因之前阐明脂毒性的关键介质，我们鉴定了转录因子结合位点的过表达，并进行了网络推理分析。这些发现 LXR、PPARα、FOXO1 和 BACH1 是协调棕榈酸代谢和氧化应激反应的关键转录因子。
这是第一项结合了棕榈酸暴露β细胞的转录组学和敏感的时间过程蛋白质组学分析的研究。我们的结果提供了对基因和蛋白质表达变化的全面了解，证实并扩展了以前的发现。鉴定β细胞脂毒性反应的关键驱动因素和途径为 2 型糖尿病提供了新的治疗靶点。
