Antioxidants, diabetes and endothelial dysfunction

While a damaged endothelium is recognised to be a key accessory to diabetic macroangiopathy, awareness is developing that impairments concerning endot helium- and nitric oxide (NO)-dependent microvascular function, may contrib ute to several other corollaries of diabetes, such as hypertension, dyslipi daemia and in vivo insulin resistance. There are now several reports descri bing elevations in specific oxidant stress markers in both insulin resistan ce syndrome (IRS) and diabetes, together with determinations of reduced tot al antioxidant defence and depletions in individual antioxidants. Such a pr o-oxidant environment in diabetes may disrupt endothelial function through the inactivation of NO, resulting in the attenuation of a fundamental anti- atherogenic and euglycaemic vascular influence. Indeed, experimental and cl inical data suggest that the supplementation of insulin resistant or diabet ic states with antioxidants such as vitamin E, normalises oxidant stress an d improves both endothelium-dependent vasodilation and insulin sensitivity. However, the promising potential efficacy of antioxidant therapy in cardio vascular disease and diabetes, in either a primary or secondary preventativ e role, awaits definitive clinical demonstration. (C) 2000 Elsevier Science B.V. All rights reserved.