title: Dietary oxidised frying oil causes oxidative damage of pancreatic islets and impairment of insulin secretion, effects associated with vitamin E deficiency.
abstract: We previously reported that, in rodents, a diet with a high oxidised frying oil (OFO) content leads to glucose intolerance associated with a reduction in insulin secretion. The present study aimed at investigating the impairment of pancreatic islets caused by dietary OFO. C57BL/6J mice were divided into three groups to receive a low-fat basal diet containing 5 g/100 g of fresh soyabean oil (LF group) or a high-fat diet containing 20 g/100 g of either fresh soyabean oil (HF group) or OFO (HO group). After 8 weeks, mice in the HO group showed glucose intolerance and hypoinsulinaemia, and their islets showed impaired glucose-stimulated insulin secretion (P < 0·05; HO group v. LF and HF groups). Significantly higher oxidative stress and a lower mitochondrial membrane potential were observed in the islets in the HO group compared with the LF and HF groups. Immunoblots showed that the reduction in insulin levels in HO islets was associated with activation of the c-Jun NH2-terminal kinase and a reduction in levels of pancreatic and duodenal homeobox factor-1. In a second study, when dietary OFO-induced tissue vitamin E depletion was prevented by large-dose vitamin E supplementation (500 IU(1·06 mmol all-rac-α-tocopherol acetate)/kg diet; HO+E group), the OFO-mediated reduction in islet size and impairment of glucose tolerance and insulin secretion were significantly attenuated (P < 0·05; HO group v. HO+E group). We conclude that a high level of dietary OFO ingestion impairs glucose metabolism by causing oxidative damage and compromising insulin secretion in pancreatic islets, and that these effects can be prevented by vitamin E supplementation.
authors.affiliation: Institute of Nutrition, China Medical University, Taichung, Taiwan, ROC.
authors.forename: Ya-Fan
authors.initials: YF
authors.lastname: Chiang
authors.forename: Huey-Mei
authors.initials: HM
authors.lastname: Shaw
authors.forename: Mei-Fang
authors.initials: MF
authors.lastname: Yang
authors.forename: Chih-Yang
authors.initials: CY
authors.lastname: Huang
authors.forename: Cheng-Hsien
authors.initials: CH
authors.lastname: Hsieh
authors.forename: Pei-Min
authors.initials: PM
authors.lastname: Chao
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism; D001786:Blood Glucose; D003296:Cooking; D004042:Dietary Fats, Unsaturated / Q000009:adverse effects* / Q000032:analysis*; D004435:Eating; D004586:Electrophoresis; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism; D018149:Glucose Intolerance; D005951:Glucose Tolerance Test; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects*; D048670:MAP Kinase Kinase 4 / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D010084:Oxidation-Reduction; D013024:Soybean Oil; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014811:Vitamin E Deficiency / Q000139:chemically induced*
chemical_list: D000975:Antioxidants; D001786:Blood Glucose; D004042:Dietary Fats, Unsaturated; D018398:Homeodomain Proteins; D007328:Insulin; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein; D013024:Soybean Oil; D048670:MAP Kinase Kinase 4; D005947:Glucose