Zhang Hao, Cai Xu, Yi Bin, Huang Jing, Wang Jianwen, Sun Jian
Department of Nephrology, The Third Xiangya Hospital, Central South University, Changsha, Hunan 410013, P.R. China.
Department of Nephrology, The Second People's Hospital of Guangdong Province, Guangzhou, Guangdong 510317, P.R. China.
Mol Med Rep. 2014 Jun;9(6):2138-44. doi: 10.3892/mmr.2014.2067. Epub 2014 Mar 24.
Increasing evidence shows that DNA methylation is involved in the development and progression of diabetes mellitus (DM) and its complications. Previous studies conducted by our group have indicated that high glucose levels may induce the demethylation process of the connective tissue growth factor (CTGF) gene promoter and increase the expression of CTGF in human glomerular mesangial cells. Based on these findings, the aim of the present study was to investigate the methylation level of genomic DNA and the CTGF promoter in patients with type 2 DM and to analyze its possible correlation with CTGF expression. Methylation levels of the whole genomic DNA were detected by high-performance liquid chromatography in a non-diabetes control (NDM) group (n=29), a diabetes without nephropathy (NDN) group (n=37) and a diabetes with nephropathy (DN) group (n=38). CTGF promoter methylation levels were detected by methylation-specific polymerase chain reaction and bisulfite sequencing. The levels of serum CTGF were assessed using the enzyme-linked immunosorbent assay. The methylation levels of the whole genomic DNA were not significantly different among the three groups. However, the CTGF methylation levels in the two diabetes groups were significantly lower than those in the NDM group (P<0.05), with the lowest methylation level in the DN group (P<0.05). The CTGF protein levels in the DN group were significantly higher than those in the NDM and NDN groups (P<0.05). Levels of CTGF were negatively correlated with the estimated glomerular filtration rate (eGFR) and the methylation level of the promoter, while they were positively correlated with age, urinary albumin-to-creatinine ratio (UACR), blood urea nitrogen, creatinine, fasting blood sugar and postprandial blood glucose. Multiple stepwise regression analysis showed that CTGF expression was associated with the UACR, CTGF methylation level and eGFR. DNA methylation is a regulatory mechanism of CTGF expression, which is decreased in patients with DM, particularly in those with DN, and may contribute to the pathogenesis of nephropathy.
越来越多的证据表明，DNA甲基化参与了糖尿病（DM）及其并发症的发生和发展。我们团队之前进行的研究表明，高血糖水平可能会诱导结缔组织生长因子（CTGF）基因启动子的去甲基化过程，并增加人肾小球系膜细胞中CTGF的表达。基于这些发现，本研究的目的是调查2型糖尿病患者基因组DNA和CTGF启动子的甲基化水平，并分析其与CTGF表达的可能相关性。采用高效液相色谱法检测非糖尿病对照组（NDM，n = 29）、无肾病糖尿病组（NDN，n = 37）和糖尿病肾病组（DN，n = 38）的全基因组DNA甲基化水平。通过甲基化特异性聚合酶链反应和亚硫酸氢盐测序检测CTGF启动子甲基化水平。采用酶联免疫吸附测定法评估血清CTGF水平。三组之间全基因组DNA的甲基化水平无显著差异。然而，两个糖尿病组的CTGF甲基化水平显著低于NDM组（P < 0.05），DN组的甲基化水平最低（P < 0.05）。DN组的CTGF蛋白水平显著高于NDM组和NDN组（P < 0.05）。CTGF水平与估计肾小球滤过率（eGFR）和启动子甲基化水平呈负相关，而与年龄、尿白蛋白与肌酐比值（UACR）、血尿素氮、肌酐、空腹血糖和餐后血糖呈正相关。多元逐步回归分析表明，CTGF表达与UACR、CTGF甲基化水平和eGFR相关。DNA甲基化是CTGF表达的一种调节机制，在糖尿病患者中，尤其是糖尿病肾病患者中降低，可能参与了肾病的发病机制。
