Epigenetic alterations are associated with gastric emptying disturbances in Diabetes Mellitus. Epigenetic alterations are associated with gastric emptying disturbances in Diabetes Mellitus

Introduction. Epigenetic modifications have been implicated to mediate several complications of diabetes mellitus (DM), especially nephropathy and retinopathy. Our aims were to ascertain if epigenetic alterations in whole blood discriminate among DM patients with normal, delayed and rapid gastric emptying (GE). Methods. Using ChIP-seq (Chromatin immunoprecipitation combined with next generation sequencing) assays, we compared the genome-wide enrichment of three histone modifications (ie, H3K4me3, H3K9ac and H3K27ac) in buffy coats from 20 DM patients with normal (n=6), delayed (n=8), or rapid (n=6) GE. Results. Between DM patients with delayed versus normal GE, there were 108 and 54 genes that were differentially-bound (FDR < 0.05) with H3K27ac and H3K9ac; 100 genes were differentially bound with H3K9ac in patients with rapid versus normal GE. The differentially bound genes with H3K27ac were functionally linked to the type 2 immune response, particularly Th2 cell activation and function (eg, CCR3, CRLF2, CXCR4, IL5RA, and IL1RL1) and glucose homeostasis (FBP-1, PDE4A, CMKLR1). For H3K9ac, the differentially occupied genes were related to T cell development and function (eg, ICOS and CCR3) and innate immunity (RELB, CD300LB, CLEC2D). Compared to normal, rapid GE had differential H3K9ac peaks at the promoter site of diverse immunity-related genes (eg, TNFRSF25 and CXCR4) and genes related to insulin resistance and glucose metabolism. The motif analysis disclosed enrichment of binding sites for several transcription factors relevant to the pathogenesis and complications of DM. Conclusions. GE disturbances in DM are associated with epigenetic alterations that may serve as biomarkers and provide clues to the pathogenesis Overall design: Comparison of 3 histone marks (H3K4me3, H3K9ac and H3K27ac) in buffy coat samples from DM patients with delayed versus normal GE and rapid versus normal GE.

引言：表观遗传修饰（epigenetic modifications）已被证实可介导糖尿病（diabetes mellitus, DM）的多种并发症，尤以肾病及视网膜病变最为突出。本研究旨在明确全血中的表观遗传改变是否可区分胃排空（gastric emptying, GE）正常、延迟与加速的糖尿病患者。
方法：本研究采用染色质免疫共沉淀测序（Chromatin immunoprecipitation combined with next generation sequencing, ChIP-seq）实验，对20例不同胃排空状态的糖尿病患者的血沉棕黄层（buffy coats）样本中3种组蛋白修饰（histone modifications，即H3K4me3、H3K9ac及H3K27ac）的全基因组富集水平进行比较；其中胃排空正常、延迟及加速的患者分别为6例、8例及6例。
结果：与胃排空正常的糖尿病患者相比，胃排空延迟的患者中，H3K27ac与H3K9ac分别存在108个及54个差异结合基因（错误发现率<0.05，false discovery rate, FDR <0.05）；而在胃排空加速与正常的患者中，共有100个基因的H3K9ac结合水平存在差异。H3K27ac的差异结合基因功能富集于2型免疫应答通路，尤其与Th2细胞活化及功能（如CCR3、CRLF2、CXCR4、IL5RA及IL1RL1）和葡萄糖稳态（FBP-1、PDE4A、CMKLR1）相关。对于H3K9ac而言，其差异结合基因与T细胞发育及功能（如ICOS及CCR3）和固有免疫（RELB、CD300LB、CLEC2D）相关。与胃排空正常的患者相比，胃排空加速的患者中，多种免疫相关基因（如TNFRSF25及CXCR4）以及胰岛素抵抗与糖代谢相关基因的启动子区域存在H3K9ac差异峰。基序分析（motif analysis）显示，多种与糖尿病发病机制及并发症相关的转录因子结合位点存在富集。
结论：糖尿病患者的胃排空紊乱与表观遗传改变密切相关，这些改变可作为生物标志物，并为糖尿病发病机制提供研究线索。
整体实验设计：比较胃排空延迟与正常、胃排空加速与正常的糖尿病患者血沉棕黄层样本中3种组蛋白修饰标记（H3K4me3、H3K9ac及H3K27ac）的富集差异。