Diabetes mellitus is associated with hyperglycaemia, hyperlipoproteinaemia, increased oxidative stress and decreased nitric oxide production from endothelial cells. In the present study the aim was to determine the relationships between serum lipids, lipoproteins, erythrocyte malondialdehyde (eMDA), as a marker for oxidative stress, and serum nitrite and nitrate levels, as degradation products of nitric oxide in type 2 diabetic patients without complications. The study group included 30 patients and 30 sex- and age-matched healthy volunteers. Total cholesterol, triacylglycerol, LDL cholesterol, apo B, HbA(1c) and glucose levels in patients were significantly higher than in controls, and HDL cholesterol levels lower. Increased eMDA levels and decreased nitrate and nitrite + nitrate levels SD) were observed in patients compared to controls (87 +/- 22 vs 59 +/- 17 nmol/g-Hb (P < 0.01); 11.8 +/- 8.6 vs 22.8 +/- 10.8 mu mol/l (P < 0.01); and 16.8 +/- 11.0 vs 28.8 +/- 11.3 mu mol/l (P < 0.01), respectively). When the patients were divided into two groups according to HDL cholesterol levels (less than or equal to 0.91 and > 0.91 mmol/l), total plasma nitric oxide end-products were found to be decreased in patients with low HDL levels compared to those patients with high HDL levels [men, 11.7 +/- 6.4 vs 24.6 +/- 14.9 mu mol/l (P < 0.01); women, 12.5 +/- 6.6 vs 21.4 +/- 6.6 mu mol/l (P < 0.01]. Nitrite and nitrate levels were correlated with HDL cholesterol (r = 0.50, P < 0.05) and eMDA (r = -0.52, P < 0.05). It was concluded that the patients with unregulated blood glucose levels have abnormal lipid and lipoprotein metabolism and decreased nitric oxide end-products, with relationships between nitric oxide products and dyslipidaemia, especially between low HDL cholesterol levels and increased oxidative stress. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.