title: The effect of ascorbate supplementation on oxidative stress in the streptozotocin diabetic rat.
abstract: An increase in oxidative stress may contribute to the development of diabetic complications. The key aqueous-phase chain-breaking antioxidant ascorbate is known to be deficient in diabetes, and we have therefore investigated the effects of ascorbate supplementation on oxidative stress in the streptozotocin diabetic rat. Markers of lipid peroxidation (malondialdehyde [MDA] and diene conjugates) were increased in plasma and erythrocytes of untreated diabetic animals, and levels of the antioxidants ascorbate and retinol were reduced. Plasma tocopherol was unchanged. Insulin treatment normalized MDA and ascorbate levels, although ascorbate metabolism remained disturbed, as indicated by increased levels of dehydroascorbate. High-dose ascorbate supplementation in the absence of insulin treatment restored plasma ascorbate to normal and increased plasma retinol and tocopherol levels. However, MDA and diene conjugate levels remained unchanged, possibly as a result of increased iron availability. High-dose ascorbate supplementation should be approached with caution in diabetes, as ascorbate may exert both antioxidant and prooxidant effects in vivo.
authors.affiliation: Department of Clinical Biochemistry, Queen's University of Belfast, Northern Ireland.
authors.forename: I S
authors.initials: IS
authors.lastname: Young
authors.forename: J J
authors.initials: JJ
authors.lastname: Torney
authors.forename: E R
authors.initials: ER
authors.lastname: Trimble
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000378:metabolism / Q000494:pharmacology; D001205:Ascorbic Acid / Q000378:metabolism / Q000494:pharmacology*; D003683:Dehydroascorbic Acid / Q000378:metabolism; D003921:Diabetes Mellitus, Experimental / Q000188:drug therapy* / Q000378:metabolism; D005609:Free Radicals; D007328:Insulin / Q000494:pharmacology; D007501:Iron / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D013312:Stress, Physiological / Q000378:metabolism
chemical_list: D000975:Antioxidants; D005609:Free Radicals; D007328:Insulin; D007501:Iron; D001205:Ascorbic Acid; D003683:Dehydroascorbic Acid