L-Arginine Supplementation Prevents the Development of Endothelial Dysfunction in Hyperglycaemia
Diabetes mellitus leads to the development of endothelial dysfunction which finally contributes to diabetic angiopathy. We investigated the effects of hyperglycaemia on nitric oxide (NO) liberation and a possible influence of L-arginine supplementation. Porcine endothelial aortic cells (PAEC) were cultured in Medium 199 containing 0.33 mmol/l L-arginine. During the entire third culture passage (= 4 days) cells were either exposed to 5 or 20 mmol/l D-glucose with or without additional 3 mmol/l L-arginine. For osmotic control, cells were exposed to 15 mmol/l mannitol. NO liberation was measured under basal conditions and after stimulation with 1 mmol/l ATP using the spectrophotometrical methemoglobin assay. Cells released 35 +/- 8 pmol NO/1 x 10(6) cells/10 min under basal conditions while hyperglycaemia led to a significant reduction in NO release to 16 +/- 6 pmol/1 x 10(6) cells/10 min. In osmotic control, NO release was unchanged (37 +/- 10 pmol/1 x 10(6) cells/10 min). Stimulation with 1 mmol/l ATP led to a significant increase in NO release to 103 +/- 11 pmol/1 x 10(6) cells/10 min (normoglycaemia) which was unchanged in osmotic controls. Under normoglycaemic conditions, additional L-arginine supplementation did not influence NO release from PAEC. In hyperglycaemia (0.33 mmol/l L-arginine) ATP stimulated NO release was reduced (48 +/- 8 pmol/1 x 10(6) cells/10 min, p < 0.05), which was completely prevented by 3 mmol/l L-arginine treatment (98 +/- 15 pmol/ 1 x 10(6) cells/10 min). Hyperglycaemia (but not enhanced osmotic pressure) leads to endothelial dysfunction with reduced NO release which is completely prevented by L-arginine. L-Arginine utilisation may be impaired in hyperglycaemia and L-arginine supplementation might be an interesting additional therapeutic tool in diabetic patients.
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