The association between small dense low density lipoprotein, apolipoprotein B, apolipoprotein B/apolipoprotein A1 ratio and coronary artery stenosis

Background: Recently, small dense low density lipoprotein (sdLDL) has been highlighted as a new risk factor for the coronary artery disease (CAD).Small dense LDLs are believed to be atherogenic since these particles are taken up more easily by arterial wall. They are readily oxidized and have reduced affinity for low density lipoprotein (LDL) receptor and increased affinity for arterial proteoglicans. LDL cholesterol is only a measure of the cholesterol level in the LDL whereas apolipoprotein B(apo B) is a measure of the cholesterol levels of all the atherogenic particles, including very low density lipoprotein, intermediate density, and low density lipoproteins. Therefore, it might be a better marker than other traditional lipids. The aim of the present study was to evaluate the association between serum small dense LDL, apolipoprotein B, apolipoprotein A1 (apo A1) and apoB/apoA1 ratio and the coronary stenosis. Methods: 86 patients with coronary stenosis , 35 patients without coronary stenosis identified by angiography who were referred to Rajaii Heart Center , and 30 healthy individuals were studied. SdLDL was measured by a direct homogenous LDL-C assay in the supernatant of serum which remained after heparin-magnesium precipitation. Serum apolipoprotein A1 and apolipoprotein B were measured by using immunoturbidimetric method. Results: The results showed that the sdLDL levels were higher in patients with coronary stenosis than patients without coronary stenosis and healthy individuals (21.54±7.1, 16.88±4.4 and 15.45±5mg/dl, p=0.001, respectively). In addition the level of apoB (with stenosis: 113.71±21.8, without stenosis:100.88±18.7 and healthy: 102.30±9.6, p=0.003) and apoB/apoA1 ratio (with stenosis:1.100±0.24, without stenosis :0.589±0.26 and healthy:0.751±0.16, p=0.001) were significantly higher in patients with coronary stenosis. SdLDL levels were positively correlated with the level of apoB(r=0.589), apoB/apoA1 ratio(r=0.416), triglyceride(r=0.494), LDL-C (r=0.749), Total cholesterol(r=0.354) and were inversely correlated with the level of HDL-C (r = -0.586)(p<0.01). Conclusion: The elevated levels of small dense LDL, apoB and apoB/apoA1 ratio were associated with coronary artery stenosis.