Decreased nitric oxide end-products and its relationship with high density lipoprotein and oxidative stress in people with type 2 diabetes without complications

Abstract

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 μmol/l ( P<0.01); and 16.8±11.0 vs 28.8±11.3 μmol/l ( P<0.01), respectively). When the patients were divided into two groups according to HDL cholesterol levels (≤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 μmol/l ( P<0.01); women, 12.5±6.6 vs 21.4±6.6 μmol/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.