Renal Pathophysiology Laboratory, Investigation on Diabetes Complications, Faculty of Medical Sciences, State University of Campinas (Unicamp), Campinas, São Paulo, Brazil.
J Nutr Biochem. 2014 Jul;25(7):773-84. doi: 10.1016/j.jnutbio.2014.03.010. Epub 2014 Apr 2.
The aims of the present study were to investigate, in diabetes mellitus (DM), the mechanism of NOX4 up-regulation, its link with 5' adenosine monophosphate-activated protein kinase (AMPK) inactivation and transforming growth factor (TGF) ß-1 signaling in determining the accumulation of kidney extracellular matrix (ECM), and the possible action of cocoa enriched with polyphenols (CH) in these events. After 16 weeks of DM, spontaneously hypertensive rats showed increased kidney TGFβ-1 levels and expression of phosphorylated smad2, collagen IV and fibronectin in parallel with elevated NOX4 expression and reduced phosphorylated AMPK. CH treatment in diabetic rats prevented all of these abnormalities. In immortalized human mesangial cells exposed to high glucose (HG), or TGFβ-1, CH, nicotinamide adenine dinucleotide phosphate blocker, or silencing NOX4 ameliorated enhanced phosphorylated smad2 and collagen IV. Reduction in phosphorylated AMPK induced by HG or TGFβ-1 was ameliorated by CH or activation of AMPK, which reduced phosphorylation of smad2 and collagen IV via reduction in NOX4 expression. The effects of CH were abolished by AMPK blockade. These results suggest that inactivation in AMPK leads to NOX4 up-regulation, activation of TGFβ-1 signaling and increased ECM accumulation. Additionally, increased TGF-ß1 per se leads to the amplification of ECM production by reducing AMPK and promoting the activation of NOX4. It is suggested that the activation of AMPK by CH followed by reduction in NOX4/TGFβ-1 signaling may have a therapeutic potential in diabetic nephropathy.
本研究旨在探讨糖尿病（DM）中 NADPH 氧化酶 4（NOX4）上调的机制，及其与 5' 腺苷一磷酸激活蛋白激酶（AMPK）失活和转化生长因子（TGF）β-1 信号转导在决定肾脏细胞外基质（ECM）积聚中的关系，并研究富含多酚的可可（CH）在这些事件中的可能作用。在 DM 16 周后，自发性高血压大鼠（SHR）的肾脏 TGFβ-1 水平和磷酸化 smad2、胶原 IV 和纤维连接蛋白的表达均增加，同时 NOX4 表达升高，磷酸化 AMPK 减少。糖尿病大鼠用 CH 治疗可预防所有这些异常。在高糖（HG）或 TGFβ-1 暴露的永生化人肾小球系膜细胞中，CH、烟酰胺腺嘌呤二核苷酸磷酸（NADPH）抑制剂、沉默 NOX4 或激活 AMPK 可改善增强的磷酸化 smad2 和胶原 IV。HG 或 TGFβ-1 诱导的磷酸化 AMPK 减少可通过降低 NOX4 表达而得到改善，进而降低磷酸化 smad2 和胶原 IV。CH 的作用被 AMPK 阻断所废除。这些结果表明，AMPK 的失活导致 NOX4 上调，TGFβ-1 信号转导激活和 ECM 积聚增加。此外，TGF-β1 的增加本身通过降低 AMPK 和促进 NOX4 的激活，导致 ECM 产生的放大。提示 CH 通过降低 NOX4/TGFβ-1 信号转导激活 AMPK 可能具有治疗糖尿病肾病的潜力。
