title: Angiotensin receptor blockade recovers hepatic UCP2 expression and aconitase and SDH activities and ameliorates hepatic oxidative damage in insulin resistant rats.
abstract: Metabolic syndrome (MetS) is commonly associated with elevated renin-angiotensin system, oxidative stress, and steatohepatitis with down-regulation of uncoupling proteins (UCPs). However, the mechanisms linking renin-angiotensin system, steatosis, and UCP2 to hepatic oxidative damage during insulin resistance are not described. To test the hypothesis that angiotensin receptor activation contributes to decreased hepatic UCP2 expression and aconitase activity and to increased oxidative damage after increased glucose intake in a model of MetS, lean and obese Long Evans rats (n = 10/group) were randomly assigned to the following groups: 1) untreated Long Evans Tokushima Otsuka (lean, strain control), 2) untreated Otsuka Long Evans Tokushima Fatty (OLETF) (MetS model), 3) OLETF + angiotensin receptor blocker (ARB) (10 mg olmesartan/kg·d × 6 wk), 4) OLETF + high glucose (HG) (5% in drinking water × 6 wk), and 5) OLETF + ARB + HG (ARB/HG × 6 wk). HG increased body mass (37%), plasma triglycerides (TGs) (35%), plasma glycerol (87%), plasma free fatty acids (28%), and hepatic nitrotyrosine (74%). ARB treatment in HG decreased body mass (12%), plasma TG (15%), plasma glycerol (23%), plasma free fatty acids (14%), and hepatic TG content (42%), suggesting that angiotensin receptor type 1 (AT1) activation and increased adiposity contribute to the development of obesity-related dyslipidemia. ARB in HG also decreased hepatic nitrotyrosine and increased hepatic UCP2 expression (59%) and aconitase activity (40%), as well as antioxidant enzyme activities (50-120%), suggesting that AT1 activation also contributes to protein oxidation, impaired lipid metabolism, and antioxidant metabolism in the liver. Thus, in addition to promoting obesity-related hypertension, AT1 activation may also impair lipid metabolism and antioxidant capacity, resulting in steatosis via decreased UCP2 and tricarboxylic acid cycle activity.
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Merced, CA 95343, USA.
authors.forename: Priscilla
authors.initials: P
authors.lastname: Montez
authors.forename: José Pablo
authors.initials: JP
authors.lastname: Vázquez-Medina
authors.forename: Rubén
authors.initials: R
authors.lastname: Rodríguez
authors.forename: Max A
authors.initials: MA
authors.lastname: Thorwald
authors.forename: José A
authors.initials: JA
authors.lastname: Viscarra
authors.forename: Lisa
authors.initials: L
authors.lastname: Lam
authors.forename: Janos
authors.initials: J
authors.lastname: Peti-Peterdi
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nakano
authors.forename: Akira
authors.initials: A
authors.lastname: Nishiyama
authors.forename: Rudy M
authors.initials: RM
authors.lastname: Ortiz
mesh_terms: D000154:Aconitate Hydratase / Q000096:biosynthesis*; D057911:Angiotensin Receptor Antagonists / Q000494:pharmacology*; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D005227:Fatty Acids / Q000378:metabolism; D005234:Fatty Liver; D015971:Gene Expression Regulation, Enzymologic; D007333:Insulin Resistance; D007473:Ion Channels / Q000096:biosynthesis*; D008099:Liver / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D024101:Mitochondrial Proteins / Q000096:biosynthesis*; D009765:Obesity / Q000378:metabolism; D018384:Oxidative Stress; D051381:Rats; D020318:Rats, Long-Evans; D013385:Succinate Dehydrogenase / Q000096:biosynthesis*; D000071246:Uncoupling Protein 2
chemical_list: D057911:Angiotensin Receptor Antagonists; D000975:Antioxidants; D005227:Fatty Acids; D007473:Ion Channels; D024101:Mitochondrial Proteins; C000604391:Ucp2 protein, rat; D000071246:Uncoupling Protein 2; D013385:Succinate Dehydrogenase; D000154:Aconitate Hydratase