title: Role of NADPH oxidase-4 in saturated fatty acid-induced insulin resistance in SK-Hep-1 cells.
abstract: We aimed to develop a cell culture model of type 2 diabetes by treating SK-Hep-1 cells with four free fatty acids [i.e., palmitic acid, stearic acid (SA), linoleic acid and oleic acid]. The results showed that Akt phosphorylation was increased in SK-Hep-1 cells treated with insulin in a time- and concentration-dependent manner, which was inhibited by saturated fatty acids, but not by unsaturated fatty acids. Moreover, protein levels of NADPH oxidase (NOX) 4 but not NOX2 were increased following SA treatment and, consequently, increased reactive oxygen species production and decreased cellular glutathione were observed. Apocynin, a NOX4 inhibitor, restored the SA-induced inhibition of Akt phosphorylation, suggesting the role of NOX4 in insulin resistance induced by SA. Neither phosphorylation level nor protein level of the stress signaling kinases, such as c-Jun N-terminal kinase or p38 mitogen activated protein kinase, was changed by SA treatment. Although binding immunoglobulin protein, a marker of endoplasmic reticulum stress, was transiently increased in SKHep-1 cells treated with SA, 4-phenyl butyric acid, a chemical chaperone, had no effect on the insulin-mediated Akt phosphorylation inhibited by SA. The present study provides a useful model for screening anti-insulin resistance drugs and finding new drug targets for treatment of diabetes.
authors.affiliation: College of Pharmacy, Chungnam National University, Daejeon 305-764, Republic of Korea.
authors.forename: Jung Min
authors.initials: JM
authors.lastname: Oh
authors.affiliation: College of Pharmacy, Chungnam National University, Daejeon 305-764, Republic of Korea.
authors.forename: Jong Min
authors.initials: JM
authors.lastname: Choi
authors.affiliation: College of Pharmacy, Chungnam National University, Daejeon 305-764, Republic of Korea.
authors.forename: Ji Yoon
authors.initials: JY
authors.lastname: Lee
authors.affiliation: Bio-Evaluation Center, KRIBB, Ochang, Chungbuk, Republic of Korea.
authors.forename: Soo Jin
authors.initials: SJ
authors.lastname: Oh
authors.affiliation: College of Pharmacy, Chungnam National University, Daejeon 305-764, Republic of Korea.
authors.forename: Bong Hee
authors.initials: BH
authors.lastname: Kim
authors.affiliation: College of Pharmacy, Chungnam National University, Daejeon 305-764, Republic of Korea. Electronic address: sangkim@cnu.ac.kr.
authors.forename: Sang Kyum
authors.initials: SK
authors.lastname: Kim
mesh_terms: D002461:Cell Line, Transformed; D005227:Fatty Acids / Q000494:pharmacology*; D006801:Humans; D007333:Insulin Resistance; D008315:Malondialdehyde / Q000378:metabolism; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism*; D018384:Oxidative Stress / Q000187:drug effects; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D017382:Reactive Oxygen Species; D008315:Malondialdehyde; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human
keywords: Akt; Insulin resistance; NOX4; Reactive oxygen species; Stearic acid