Tubular injury in a rat model of type 2 diabetes is prevented by metformin: a possible role of HIF-1α expression and oxygen metabolism.
Tubular injury in a rat model of type 2 diabetes is prevented by metformin: a possible role of HIF-1α expression and oxygen metabolism.
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作者：
Takiyama Y;Harumi T;Watanabe J;Fujita Y;Honjo J;Shimizu N;Makino Y;Haneda M
慢性缺氧已被认为是肾小管间质纤维化的关键调节因子，如糖尿病肾病，其与缺氧诱导因子（HIF）-1α的活化相关。我们在此利用肾近端小管细胞和2型糖尿病大鼠评估双胍类药物二甲双胍对糖尿病肾病中HIF-1α表达的影响。我们利用人肾近端小管上皮细胞（HRPTECs）研究二甲双胍对HIF-1α表达的影响。雄性Zucker糖尿病肥胖（ZDF; Gmi-fa/fa）大鼠接受二甲双胍（250 mg·kg-1·day-1）或胰岛素治疗9 - 39周。二甲双胍抑制缺氧诱导的HRPTECs中HIF-1α的积累和HIF-1靶向基因的表达。尽管二甲双胍激活了AMP活化蛋白激酶（AMPK）的下游途径，但AMPK激活剂AICAR和mTOR抑制剂雷帕霉素都不能抑制缺氧诱导的HIF-1α表达。此外，AMPK-α的敲低并不能消除二甲双胍对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蓄积的抑制。线粒体呼吸抑制剂同样抑制缺氧诱导的HIF-1α表达。甲硫氨酸显著降低ATP的产生和氧消耗速率，随后导致细胞氧张力增加。最后，二甲双胍（而非胰岛素）减弱了ZDF大鼠肾小管HIF-1α表达和哌莫硝唑染色，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积累可以被抗糖尿病药物二甲双胍通过抑制氧消耗来抑制。
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.