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Role of oxidative stress in physiological albumin glycation: A neglected interaction.


Free Radic Biol Med. 2013 Mar 18;


Authors: Vlassopoulos A, Lean M, Combet E


Abstract

BACKGROUND: Protein glycation is a key mechanism involved in chronic diseases development in both diabetic and non-diabetic individuals. About 12-18% of circulating proteins are glycated in vivo in normoglycaemic blood, but in-vitro studies have hitherto failed to demonstrate glucose-driven glycation below concentration of 30mM. METHODS: Bovine Serum Albumin (BSA), reduced BSA (mercaptalbumin), (both 40g/L) and human plasma were incubated with glucose concentrations 0-30mM for 4 weeks at 37°C. All were tested pre-oxidized for 8 hours prior to glycation with 10nM H202, or continuously exposed to 10nM H2O2 throughout the incubation period. Fructosamine was measured (nitroblue tetrazolium method) at two and four weeks. RESULTS: Oxidised BSA (both pre-oxidised and continuously exposed to H2O2) was more readily glycated than native BSA at all glucose concentrations (p=0.03). Moreover, only oxidised 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 oxidised than un-oxidised (p<0.05). Fructosamine concentration in human plasma was also significantly higher when oxidised and exposed to 5mM glucose, compared to non-oxidised plasma (p=0.03). The interaction between glucose concentration and oxidation was found to be significant in all protein models (p<0.05). CONCLUSION: The current 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.

PMID: 23517782 [PubMed - as supplied by publisher]