Low density lipoprotein cholesterol level inversely correlated with coronary flow velocity reserve in patients with Type 2 diabetes

OBJECTIVES: To evaluate the association of coronary artery endothelial function and plasma levels of low density lipoprotein cholesterol (LDL-C) and high density lipoprotein cholesterol (HDL-C) in patients with Type 2 Diabetes Mellitus (DM). METHODS: We investigated 90 participants from our institution between October 2007 to March 2010: non-DM (n = 60) and DM (n = 30). As an indicator of coronary endothelial dysfunction, we used non-invasive Doppler echocardiography to quantify coronary flow velocity reserve (CFVR) in the distal part of the left descending artery after rest and after intravenous adenosine administration. RESULTS: Plasma level of LDL-C was significantly higher in patients with DM than in non-DM (3.21 ± 0.64 vs. 2.86 ± 0.72 mmo/L, P < 0.05), but HDL-C level did not differ between the groups (1.01 ± 0.17 vs. 1.05 ± 0.19 mmo/L). Furthermore, the CFVR value was lower in DM patients than non-diabetics (2.45 ± 0.62 vs. 2.98 ± 0.68, P < 0.001). Plasma levels of LDL-C were negatively correlated with CFVR in all subjects (r = −0.35, P < 0.001; 95% confidence interval (CI): −0.52 – −0.15) and in the non-DM (r = −0.29, P < 0.05; 95% CI: −0.51– −0.05), with an even stronger negative correlation in the DM group (r = −0.42, P < 0.05; 95% CI: −0.68 – −0.06). Age (β = −0.019, s = 0.007, sβ = −0.435, 95% CI: −0.033 – −0.005, P = 0.008), LDL-C (β = −0.217, s = 0.105, sβ = −0.282, 95% CI: −0.428 – −0.005, P = 0.045) remained independently correlated with CFVR in the DM group. However, we found no correlation between HDL-C level and CFVR in any group. CONCLUSIONS: Diabetes may contribute to coronary artery disease (CAD) by inducing dysfunction of the coronary artery endothelium. Increased LDL-C level may adversely impair coronary endothelial function in DM. HDL-C may lose its endothelial-protective effects, in part as a result of pathological conditions, especially under abnormal glucose metabolism.