title: Role of oxidative stress in physiological albumin glycation: a neglected interaction.
abstract: Protein glycation is a key mechanism involved in chronic disease development in both diabetic and nondiabetic individuals. About 12-18% of circulating proteins are glycated in vivo in normoglycemic blood, but in vitro studies have hitherto failed to demonstrate glucose-driven glycation below a concentration of 30mM. Bovine serum albumin (BSA), reduced BSA (mercaptalbumin) (both 40g/L), and human plasma were incubated with glucose concentrations of 0-30mM for 4 weeks at 37°C. All were tested preoxidized for 8h before glycation with 10nM H2O2 or continuously exposed to 10nM H2O2 throughout the incubation period. Fructosamine was measured (nitroblue tetrazolium method) at 2 and 4 weeks. Oxidized BSA (both preoxidized and continuously exposed to H2O2) was more readily glycated than native BSA at all glucose concentrations (p = 0.03). Moreover, only oxidized BSA was glycated at physiological glucose concentration (5mM) compared to glucose-free control (glycation increased by 35% compared to native albumin, p < 0.05). Both 5 and 10mM glucose led to higher glycation when mercaptalbumin was oxidized than when unoxidized (p < 0.05). Fructosamine concentration in human plasma was also significantly higher when oxidized and exposed to 5mM glucose, compared to unoxidized plasma (p = 0.03). The interaction between glucose concentration and oxidation was significant in all protein models (p < 0.05). This study has for the first time demonstrated albumin glycation in vitro, using physiological concentrations of albumin, glucose, and hydrogen peroxide, identifying low-grade oxidative stress as a key element early in the glycation process.
authors.affiliation: Human Nutrition, School of Medicine, College of Medical, Veterinary & Life Sciences, University of Glasgow, Glasgow G3 8SJ, UK.
authors.forename: A
authors.initials: A
authors.lastname: Vlassopoulos
authors.forename: M E J
authors.initials: ME
authors.lastname: Lean
authors.forename: E
authors.initials: E
authors.lastname: Combet
mesh_terms: D000818:Animals; D002417:Cattle; D005947:Glucose / Q000737:chemistry* / Q000378:metabolism; D006442:Glycated Hemoglobin / Q000737:chemistry / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D006861:Hydrogen Peroxide / Q000737:chemistry; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism
chemical_list: D005947:Glucose; D006442:Glycated Hemoglobin; D006861:Hydrogen Peroxide; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; C001702:mercaptoalbumin