Department of Molecular BiologyHebei Key Lab of Laboratory Animal Science, Hebei Medical University, Shijiazhuang, China.
Department of BiochemistryHebei Key Laboratory of Medical Biotechnology, Hebei Medical University, Shijiazhuang, China.
J Mol Endocrinol. 2018 Jul;61(1):47-56. doi: 10.1530/JME-18-0009.
Activation of transforming growth factor β1 (TGFB1)/SMAD3 signaling may lead to additional synthesis of collagen type IV (COL4), which is a major contributor to extracellular matrix (ECM) accumulation in diabetic nephropathy (DN). C-peptide can attenuate fibrosis to have unique beneficial effects in DN. However, whether and how C-peptide affects TGFB1/SMAD3-activated COL4 synthesis is unclear. In this study, pathological changes, expression of COL4 a1-a5 chains (), COL4 distribution and protein and TGFB1 and SMAD3 protein were first assessed in a rat model of diabetes. Then, rat mesangial cells were treated with high glucose (HG) and/or C-peptide to investigate the underlying mechanism. expression, COL4 protein and secretion, TGFB1 protein, SMAD3 nuclear translocation and binding of SMAD3 to its cognate sites in the promoters of , and were measured. It was found that C-peptide attenuated glomerular pathological changes and suppressed renal mRNA expression, COL4 protein content and TGFB1 protein content. C-peptide had a dose-dependent effect to inhibit mRNA expression, COL4 protein content and secretion, in HG-stimulated mesangial cells. In addition, the HG-induced increase in TGFB1 protein content was significantly reduced by C-peptide. Although not apparently affecting SMAD3 nuclear translocation, C-peptide prevented SMAD3 from binding to its sites in the , and promoters in HG-stimulated mesangial cells. In conclusion, C-peptide could prevent SMAD3 from binding to its sites in the , and promoters, to inhibit COL4 generation. These results may provide a mechanism for the alleviation of fibrosis in DN by C-peptide.
转化生长因子β1（TGFB1）/SMAD3 信号的激活可能导致胶原 IV 型（COL4）的进一步合成，这是糖尿病肾病（DN）中细胞外基质（ECM）积累的主要原因。C 肽可以减轻纤维化，在 DN 中具有独特的有益作用。然而，C 肽是否以及如何影响 TGFB1/SMAD3 激活的 COL4 合成尚不清楚。在这项研究中，首先在糖尿病大鼠模型中评估了 COL4 a1-a5 链（）、COL4 分布和蛋白以及 TGFB1 和 SMAD3 蛋白的病理变化、表达。然后，用高葡萄糖（HG）和/或 C 肽处理大鼠系膜细胞，以研究其潜在机制。测量了 表达、COL4 蛋白和分泌、TGFB1 蛋白、SMAD3 核易位以及 SMAD3 与其启动子中同源位点的结合。结果发现，C 肽减轻了肾小球的病理变化，抑制了肾脏 mRNA 表达、COL4 蛋白含量和 TGFB1 蛋白含量。C 肽呈剂量依赖性抑制 HG 刺激的系膜细胞中 mRNA 表达、COL4 蛋白含量和分泌。此外，C 肽显著减少 HG 诱导的 TGFB1 蛋白含量增加。尽管 C 肽对 SMAD3 核易位没有明显影响，但它阻止了 SMAD3 在 HG 刺激的系膜细胞中与 、 和 启动子中的其结合位点结合。总之，C 肽可以防止 SMAD3 与其在 、 和 启动子中的结合位点结合，从而抑制 COL4 的产生。这些结果可能为 C 肽减轻 DN 纤维化提供了一种机制。
