title: Mechanism for antioxidative effects of thiazolidinediones in pancreatic β-cells.
abstract: Thiazolidinediones (TZDs) are synthetic ligands of peroxisome proliferator-activated receptor-γ (PPARγ), a member of the nuclear receptor superfamily. TZDs are known to increase insulin sensitivity and also to have an antioxidative effect. In this study, we tested whether TZDs protect pancreatic β-cells from oxidative stress, and we investigated the mechanism involved in this process. To generate oxidative stress in pancreatic β-cells (INS-1 and βTC3) or isolated islets, glucose oxidase was added to the media. The extracellular and intracellular reactive oxygen species (ROS) were measured to directly determine the antioxidant effect of TZDs. The phosphorylation of JNK/MAPK after oxidative stress was detected by Western blot analysis, and glucose-stimulated insulin secretion and cell viability were also measured. TZDs significantly reduced the ROS levels that were increased by glucose oxidase, and they effectively prevented β-cell dysfunction. The antioxidative effect of TZDs was abolished in the presence of a PPARγ antagonist, GW9662. Real-time PCR was used to investigate the expression levels of antioxidant genes. The expression of catalase, an antioxidant enzyme, was increased by TZDs in pancreatic β-cells, and the knockdown of catalase significantly inhibited the antioxidant effect of TZDs. These results suggest that TZDs effectively protect pancreatic β-cells from oxidative stress, and this effect is dependent largely on PPARγ. In addition, the expression of catalase is increased by TZDs, and catalase, at least in part, mediates the antioxidant effect of TZDs in pancreatic β-cells.
authors.affiliation: Department of Internal Medicine, Seoul National University College of Medicine, Seoul, South Korea.
authors.forename: Sung Soo
authors.initials: SS
authors.lastname: Chung
authors.forename: Min
authors.initials: M
authors.lastname: Kim
authors.forename: Ji Seon
authors.initials: JS
authors.lastname: Lee
authors.forename: Byung Yong
authors.initials: BY
authors.lastname: Ahn
authors.forename: Hye Seung
authors.initials: HS
authors.lastname: Jung
authors.forename: Hak Mo
authors.initials: HM
authors.lastname: Lee
authors.forename: Kyong Soo
authors.initials: KS
authors.lastname: Park
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002478:Cells, Cultured; D004353:Drug Evaluation, Preclinical; D005947:Glucose / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000187:drug effects* / Q000378:metabolism; D051379:Mice; D047495:PPAR gamma / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D047490:Retinoid X Receptor alpha / Q000819:agonists / Q000235:genetics / Q000378:metabolism; D013552:Swine; D045162:Thiazolidinediones / Q000494:pharmacology*; D014162:Transfection
chemical_list: D000975:Antioxidants; D007004:Hypoglycemic Agents; D007328:Insulin; D047495:PPAR gamma; D047490:Retinoid X Receptor alpha; D045162:Thiazolidinediones; D006861:Hydrogen Peroxide; D005947:Glucose