title: ERK1/2 pathway is involved in renal gluconeogenesis inhibition under conditions of lowered NADPH oxidase activity.
abstract: 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.
authors.affiliation: Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland. Electronic address: k.winiarska@biol.uw.edu.pl.
authors.forename: Katarzyna
authors.initials: K
authors.lastname: Winiarska
authors.affiliation: Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
authors.forename: Robert
authors.initials: R
authors.lastname: Jarzyna
authors.affiliation: Department of Biochemistry, Faculty of Agriculture and Biology, Warsaw University of Life Sciences-SGGW, Nowoursynowska 159, 02-776 Warsaw, Poland.
authors.forename: Jolanta M
authors.initials: JM
authors.lastname: Dzik
authors.affiliation: Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
authors.forename: Adam K
authors.initials: AK
authors.lastname: Jagielski
authors.affiliation: Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Grabowski
authors.affiliation: Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
authors.forename: Agata
authors.initials: A
authors.lastname: Nowosielska
authors.affiliation: Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Focht
authors.affiliation: Department of Metabolic Regulation, Institute of Biochemistry, Faculty of Biology, University of Warsaw, I. Miecznikowa 1, 02-096 Warsaw, Poland.
authors.forename: Bartosz
authors.initials: B
authors.lastname: Sierakowski
mesh_terms: D000098:Acetophenones / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002070:Butadienes / Q000494:pharmacology; D017362:Cyclic AMP Response Element-Binding Protein / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D003497:Cyclic N-Oxides / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D005786:Gene Expression Regulation; D005943:Gluconeogenesis / Q000187:drug effects* / Q000235:genetics; D007004:Hypoglycemic Agents / Q000494:pharmacology; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D008297:Male; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009570:Nitriles / Q000494:pharmacology; D010729:Phosphoenolpyruvate Carboxykinase (GTP) / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D061251:Primary Cell Culture; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D051381:Rats; D011924:Rats, Zucker; D017382:Reactive Oxygen Species / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction; D013113:Spin Labels; D045162:Thiazolidinediones / Q000494:pharmacology
chemical_list: D000098:Acetophenones; D000975:Antioxidants; D002070:Butadienes; D017362:Cyclic AMP Response Element-Binding Protein; D003497:Cyclic N-Oxides; D007004:Hypoglycemic Agents; D047908:Intracellular Signaling Peptides and Proteins; D009570:Nitriles; D047428:Protein Kinase Inhibitors; D017382:Reactive Oxygen Species; D013113:Spin Labels; D045162:Thiazolidinediones; C113580:U 0126; C056165:acetovanillone; D019255:NADPH Oxidases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; C582554:Pck1 protein, rat; D010729:Phosphoenolpyruvate Carboxykinase (GTP); C001803:tempol
keywords: Diabetes; ERK1/2 pathway; Gluconeogenesis; NADPH oxidase; Phosphoenolpyruvate carboxykinase; Renal proximal tubules; ZDF rat