Winiarska Katarzyna, Jarzyna Robert, Dzik Jolanta M, Jagielski Adam K, Grabowski Michal, Nowosielska Agata, Focht Dorota, Sierakowski Bartosz
Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
Free Radic Biol Med. 2015 Apr;81:13-21. doi: 10.1016/j.freeradbiomed.2014.12.024. Epub 2015 Jan 16.
The aim of this study was to elucidate the mechanisms involved in the inhibition of renal gluconeogenesis occurring under conditions of lowered activity of NADPH oxidase (Nox), the enzyme considered to be one of the main sources of reactive oxygen species in kidneys. The in vitro experiments were performed on primary cultures of rat renal proximal tubules, with the use of apocynin, a selective Nox inhibitor, and TEMPOL (4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl), a potent superoxide radical scavenger. In the in vivo experiments, Zucker diabetic fatty (ZDF) rats, a well established model of diabetes type 2, were treated with apocynin solution in drinking water. The main in vitro findings are the following: (1) both apocynin and TEMPOL attenuate the rate of gluconeogenesis, inhibiting the step catalyzed by phosphoenolpyruvate carboxykinase (PEPCK), a key enzyme of the process; (2) in the presence of the above-noted compounds the expression of PEPCK and the phosphorylation of transcription factor CREB and ERK1/2 kinases are lowered; (3) both U0126 (MEK inhibitor) and 3-(2-aminoethyl)-5-((4-ethoxyphenyl)methylene)-2,4-thiazolidinedione (ERK inhibitor) diminish the rate of glucose synthesis via mechanisms similar to those of apocynin and TEMPOL. The observed apocynin in vivo effects include: (1) slight attenuation of hyperglycemia; (2) inhibition of renal gluconeogenesis; (3) a decrease in renal PEPCK activity and content. In view of the results summarized above, it can be concluded that: (1) the lowered activity of the ERK1/2 pathway is of importance for the inhibition of renal gluconeogenesis found under conditions of lowered superoxide radical production by Nox; (2) the mechanism of this phenomenon includes decreased PEPCK expression, resulting from diminished activity of transcription factor CREB; (3) apocynin-evoked inhibition of renal gluconeogenesis contributes to the hypoglycemic action of this compound observed in diabetic animals. Thus, the study has delivered some new insights into the recently discussed issue of the usefulness of Nox inhibition as a potential antidiabetic strategy.
本研究的目的是阐明在NADPH氧化酶（Nox）活性降低的情况下肾糖异生受到抑制的相关机制，Nox被认为是肾脏中活性氧的主要来源之一。体外实验在大鼠肾近端小管的原代培养物上进行，使用了选择性Nox抑制剂阿朴吗啡和有效的超氧阴离子自由基清除剂TEMPOL（4-羟基-2,2,6,6-四甲基哌啶-1-氧基）。在体内实验中，用饮用水中的阿朴吗啡溶液处理Zucker糖尿病脂肪（ZDF）大鼠，这是一种成熟的2型糖尿病模型。主要的体外研究结果如下：（1）阿朴吗啡和TEMPOL均减弱糖异生速率，抑制该过程的关键酶磷酸烯醇丙酮酸羧激酶（PEPCK）催化的步骤；（2）在上述化合物存在下，PEPCK的表达以及转录因子CREB和ERK1/2激酶的磷酸化降低；（3）U0126（MEK抑制剂）和3-（2-氨基乙基）-5-（（4-乙氧基苯基）亚甲基）-2,4-噻唑烷二酮（ERK抑制剂）通过与阿朴吗啡和TEMPOL类似的机制降低葡萄糖合成速率。观察到的阿朴吗啡的体内作用包括：（1）轻度减轻高血糖；（2）抑制肾糖异生；（3）肾PEPCK活性和含量降低。鉴于上述总结的结果，可以得出以下结论：（1）ERK1/2途径活性降低对于在Nox产生超氧阴离子自由基减少的情况下发现的肾糖异生抑制很重要；（2）这种现象的机制包括由于转录因子CREB活性降低导致PEPCK表达减少；（3）阿朴吗啡引起的肾糖异生抑制有助于在糖尿病动物中观察到的该化合物的降血糖作用。因此，该研究为最近讨论的Nox抑制作为潜在抗糖尿病策略的有用性问题提供了一些新的见解。
