Metformin reduces endothelial cell expression of both the receptor for advanced glycation end products and lectin-like oxidized receptor 1.

Beyond its antihyperglycemic action, the antidiabetic oral drug metformin possesses antioxidant properties that may contribute to improve the cardiovascular deleterious effects of the diabetic disease. We explored whether metformin could modulate the redox-sensible expression of receptor for advanced glycation end products (RAGE) and lectin-like oxidized receptor 1 (LOX-1), 2 endothelial membrane receptors involved in the arterial endothelial dysfunction observed in diabetes. Bovine aortic endothelial cells, either unstimulated or activated by high levels of glucose (30 mmol/L) or advanced glycation end products, were incubated for 72 hours with metformin at therapeutically relevant concentrations (10(-5) to 5 x 10(-4) mol/L). The expressions of RAGE and LOX-1 were evaluated on cell extracts by Western blot analysis. Metformin was shown to reduce, in dose-dependent manner, such expression of the 2 receptors, both in stimulated (by either glucose or advanced glycation end products) and in unstimulated cells. The effect of metformin was associated with a decrease in intracellular reactive oxygen species as assessed using the 2',7'-dichlorodihydrofluorescein diacetate fluoroprobe. Taken together, our results suggest that the intracellular antioxidant properties of metformin may result in the inhibition of cell expression of both RAGE and LOX-1, possibly through a modulation of redox-sensible nuclear factors such as nuclear factor kappaB, that were shown to be involved in such receptor cell expression.

Metformin decreases intracellular production of reactive oxygen species in aortic endothelial cells.

Beyond its antidiabetic activity justifying its use in the treatment of the type 2 diabetes, metformin (MET [dimethylguanidine, Glucophage]) has been shown to exhibit antioxidant properties in vitro, which could contribute to limit the deleterious vascular complications of diabetes. We investigated whether MET, at the pharmacological level of 10 -5 mol/L, was able to modulate intracellular production of reactive oxygen species (ROS) both in quiescent bovine aortic endothelial cells (BAECs) and in BAECs stimulated by a short incubation with high levels of glucose (30 mmol/L, 2 hours) or angiotensin II (10 -7 mol/L, 1 hour). Intracellular ROS production was measured by fluorescence of the DCF (2,7-dichlorodihydrofluorescein) probe. Our results showed that MET was able to reduce the intracellular production of ROS in both nonstimulated BAECs (-20%, P < .05) and BAEC stimulated by high levels of glucose or angiotensin II (-28% and -72%, respectively, P < .01). Experiments performed in the presence of the nicotinamide adenine dinucleotide phosphate [NAD(P)H] oxidase inhibitor apocynin or the respiratory mitochondrial chain inhibitor rotenone indicated that MET exerted its effect partly through an inhibition of the formation of ROS produced mainly by NAD(P)H oxidase and also, to a lesser extent, by the respiratory mitochondrial chain.