title: Cerebral antioxidant enzyme increase associated with learning deficit in type 2 diabetes rats.
abstract: In this study, we examined alterations in the enzymatic antioxidant defenses associated with learning deficits induced by type 2 diabetes, and studied the effects of the peroxisome proliferator-activated receptor γ agonist pioglitazone on these learning deficits. Learning ability was assessed by visual discrimination tasks in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, as a model of spontaneous type 2 diabetes. Levels of the antioxidant enzymes glutathione peroxidase (GPx), Cu(2+)-Zn(2+) superoxide dismutase (CuZn-SOD) and manganese SOD were measured in the cortex, hippocampus and striatum. Half the rats received oral pioglitazone (20mg/kg/day) from the early stage of diabetes (22 weeks old) to 27 weeks old. OLETF rats showed learning deficits compared with control, Long-Evans Tokushima Otsuka (LETO) rats. GPx levels in the cortex and hippocampus were increased in OLETF rats compared with LETO rats, with an inverse correlation between GPx in the hippocampus and learning score. CuZn-SOD levels were also increased in the hippocampus in OLETF rats. Pioglitazone reduced blood glucose and increased serum adiponectin levels, but had no effect on learning tasks or antioxidant enzymes, except for CuZn-SOD. These results suggest that an oxidative imbalance reflected by increased brain antioxidant enzymes plays an important role in the development of learning deficits in type 2 diabetes. Early pioglitazone administration partly ameliorated diabetic symptoms, but was unable to completely recover cerebral oxidative imbalance and functions. These results suggest that diabetes-induced brain impairment, which results in learning deficits, may have occurred before the appearance of the symptoms of overt diabetes.
authors.affiliation: Department of Physiology, Saitama Medical University, Moroyama, Iruma-gun, Saitama, Japan. rsuge@saitama-med.ac.jp
authors.forename: Rie
authors.initials: R
authors.lastname: Suge
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Shimazu
authors.forename: Hajime
authors.initials: H
authors.lastname: Hasegawa
authors.forename: Ikuo
authors.initials: I
authors.lastname: Inoue
authors.forename: Hidemasa
authors.initials: H
authors.lastname: Hayashibe
authors.forename: Hironori
authors.initials: H
authors.lastname: Nagasaka
authors.forename: Nobuo
authors.initials: N
authors.lastname: Araki
authors.forename: Shigehiro
authors.initials: S
authors.lastname: Katayama
authors.forename: Masahiko
authors.initials: M
authors.lastname: Nomura
authors.forename: Shu-Ichi
authors.initials: S
authors.lastname: Watanabe
mesh_terms: D052242:Adiponectin / Q000097:blood; D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001921:Brain / Q000201:enzymology; D002540:Cerebral Cortex / Q000201:enzymology; D003216:Conditioning, Operant / Q000187:drug effects / Q000502:physiology; D003342:Corpus Striatum / Q000201:enzymology; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism* / Q000503:physiopathology; D004195:Disease Models, Animal; D005979:Glutathione Peroxidase / Q000378:metabolism*; D006624:Hippocampus / Q000201:enzymology; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007859:Learning Disabilities / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D008569:Memory Disorders / Q000378:metabolism / Q000503:physiopathology; D000077205:Pioglitazone; D051381:Rats; D020334:Rats, Inbred OLETF; D013045:Species Specificity; D013482:Superoxide Dismutase / Q000378:metabolism*; D000072105:Superoxide Dismutase-1; D045162:Thiazolidinediones / Q000494:pharmacology; D000094765:Glutathione Peroxidase GPX1; D000099156:Superoxide Dismutase 2
chemical_list: D052242:Adiponectin; D000975:Antioxidants; D005979:Glutathione Peroxidase; D007004:Hypoglycemic Agents; D000077205:Pioglitazone; D013482:Superoxide Dismutase; D000072105:Superoxide Dismutase-1; D045162:Thiazolidinediones; D000094765:Glutathione Peroxidase GPX1; D000099156:Superoxide Dismutase 2; C000606292:Sod1 protein, rat; C000722069:Gpx1 protein, rat