Supplementation of coenzyme Q 10 and α-tocopherol lowers glycated hemoglobin level and lipid peroxidation in pancreas of diabetic rats Cristina M. Sena a,b, ⁎ , Elsa Nunes a,b , Aline Gomes a , Maria S. Santos c , Teresa Proença d , Maria I. Martins e , Raquel M. Seiça a,b a Institute of Physiology, Faculty of Medicine, University of Coimbra, 3000-354 Coimbra, Portugal b Center for Neurosciences and Cell Biology of Coimbra, University of Coimbra, 3000-354 Coimbra, Portugal c Department of Zoology, University of Coimbra, 3000-354 Coimbra, Portugal d Laboratory of Neurochemistry, University Hospitals of Coimbra, 3000-075 Coimbra, Portugal e Department of Pathological Anatomy, University Hospitals of Coimbra, 3000-075 Coimbra, Portugal Received 2 May 2007; revised 27 November 2007; accepted 2 December 2007 Abstract The importance of nutritional supplementation in diabetes remains an unresolved issue. The present study was undertaken to examine the effects of α-tocopherol and CoQ 10 , powerful antioxidants, on metabolic control and on the pancreatic mitochondria of GK rats, a model of type 2 diabetes. We also evaluated the efficacy of these nutrients in preventing the diabetic pancreatic lesions observed in GK rats. Rats were divided into 4 groups, a control group of diabetic GK rats and 3 groups of GK rats administered with α-tocopherol and CoQ 10 alone or both in association, during 8 weeks. Fasting blood glucose levels were not significantly different between the groups, nor were blood glucose levels at 2 hours after a glucose load. HbA1c level was significantly reduced in the group supplemented with both antioxidants. Diabetes induced a decrease in coenzyme Q plasma levels that prevailed after treatment with antioxidants. In addition, the plasma α-tocopherol levels were higher after treatment with the antioxidants. An increment in some components of the antioxidant defense system was observed in pancreatic mitochondria of treated GK rats. Moreover, the antioxidants tested either alone or in association failed to prevent the pancreatic lesions in this animal model of type 2 diabetes. In conclusion, our results indicate that CoQ 10 and α-tocopherol decrease glycated HbA1c and pancreatic lipid peroxidation. These antioxidants increase some components of the antioxidant defense system but do not prevent pancreatic lesions. Thus, we cannot rule out the potential benefit of antioxidant treatments in type 2 diabetes in the prevention of their complications. © 2008 Elsevier Inc. All rights reserved. Keywords: α-tocopherol; Coenzyme Q 10 ; Pancreatic mitochondria; Type 2 diabetes; Goto-Kakizaki rats; Oxidative stress Abbreviations: CoQ 10 , Coenzyme Q 10 ; GK, Goto-Kakizaki rat; GSH-Px, glutathione peroxidase; HPLC, high-performance liquid chromatography; MDA, malondialdehyde; MnSOD, manganese superoxide dismutase; NBT, nitroblue tetrazolium; PAS, periodic acid-Schiff; reduced CoQ, ubiquinol 1. Introduction There is considerable interest in coenzyme Q (CoQ) and vitamin E (α-tocopherol) as nutritional supplements in type 2 diabetes because both can act as generators or quenchers of Available online at www.sciencedirect.com Nutrition Research 28 (2008) 113 – 121 www.elsevier.com/locate/nutres ⁎ Corresponding author. Institute of Physiology, Faculty of Medicine, University of Coimbra, 3000-354 Coimbra, Portugal. Tel.: +351 239 480013; fax: +351 239 480034. E-mail address: csena@ci.uc.pt (C.M. Sena). 0271-5317/$ – see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1016/j.nutres.2007.12.005