Division of Metabolism and Biosystemic Science, Department of Medicine, Asahikawa Medical University, Asahikawa, Japan.
Diabetes. 2011 Mar;60(3):981-92. doi: 10.2337/db10-0655. Epub 2011 Jan 31.
Chronic hypoxia has been recognized as a key regulator in renal tubulointerstitial fibrosis, as seen in diabetic nephropathy, which is associated with the activation of hypoxia-inducible factor (HIF)-1α. We assess here the effects of the biguanide, metformin, on the expression of HIF-1α in diabetic nephropathy using renal proximal tubular cells and type 2 diabetic rats.
We explored the effects of metformin on the expression of HIF-1α using human renal proximal tubular epithelial cells (HRPTECs). Male Zucker diabetic fatty (ZDF; Gmi-fa/fa) rats were treated from 9 to 39 weeks with metformin (250 mg ⋅ kg(-1) ⋅ day(-1)) or insulin.
Metformin inhibited hypoxia-induced HIF-1α accumulation and the expression of HIF-1-targeted genes in HRPTECs. Although metformin activated the downstream pathways of AMP-activated protein kinase (AMPK), neither the AMPK activator, AICAR, nor the mTOR inhibitor, rapamycin, suppressed hypoxia-induced HIF-1α expression. In addition, knockdown of AMPK-α did not abolish the inhibitory effects of metformin on HIF-1α expression. The proteasome inhibitor, MG-132, completely eradicated the suppression of hypoxia-induced HIF-1α accumulation by metformin. The inhibitors of mitochondrial respiration similarly suppressed hypoxia-induced HIF-1α expression. Metformin significantly decreased ATP production and oxygen consumption rates, which subsequently led to increased cellular oxygen tension. Finally, metformin, but not insulin, attenuated tubular HIF-1α expression and pimonidazole staining and ameliorated tubular injury in ZDF rats.
Our data suggest that hypoxia-induced HIF-1α accumulation in diabetic nephropathy could be suppressed by the antidiabetes drug, metformin, through the repression of oxygen consumption.
慢性缺氧被认为是糖尿病肾病中肾小管间质纤维化的关键调节因素，这与缺氧诱导因子（HIF）-1α的激活有关。我们在此评估二甲双胍（一种双胍类药物）对糖尿病肾病中 HIF-1α表达的影响，使用的研究对象是肾近端小管细胞和 2 型糖尿病大鼠。
我们使用人肾近端小管上皮细胞（HRPTEC）探索了二甲双胍对 HIF-1α表达的影响。雄性 Zucker 糖尿病肥胖（ZDF；Gmi-fa/fa）大鼠从 9 至 39 周接受二甲双胍（250 mg ⋅ kg(-1) ⋅ day(-1))或胰岛素治疗。
二甲双胍抑制了 HRPTEC 中缺氧诱导的 HIF-1α积累和 HIF-1 靶向基因的表达。尽管二甲双胍激活了 AMP 激活的蛋白激酶（AMPK）的下游途径，但 AMPK 激活剂 AICAR 和 mTOR 抑制剂雷帕霉素均未抑制缺氧诱导的 HIF-1α表达。此外，AMPK-α 的敲低并未消除二甲双胍对 HIF-1α表达的抑制作用。蛋白酶体抑制剂 MG-132 完全消除了二甲双胍对缺氧诱导的 HIF-1α积累的抑制作用。线粒体呼吸抑制剂也同样抑制了缺氧诱导的 HIF-1α表达。二甲双胍显著降低了 ATP 生成和耗氧量，从而导致细胞内氧张力增加。最后，二甲双胍（而非胰岛素）减轻了 ZDF 大鼠的肾小管 HIF-1α表达和 pimonidazole 染色，并改善了肾小管损伤。
我们的数据表明，糖尿病肾病中缺氧诱导的 HIF-1α积累可被抗糖尿病药物二甲双胍通过抑制氧消耗来抑制。
