Comparison of the associations of apolipoprotein B and non-high-density lipoprotein cholesterol with other cardiovascular risk factors in patients with the metabolic syndrome in the Insulin Resistance Atherosclerosis Study

Background-The metabolic syndrome (MetS) as defined by the National Cholesterol Education Panel definition has been proposed as an indicator of cardiovascular disease risk. Both apolipoprotein (apo) B and non-HDL cholesterol (NHDLC) have been proposed as an additional indicator to identify patients at higher risk in MetS patients. Methods and Results-We studied 1522 individuals in the Insulin Resistance Atherosclerosis Study (IRAS) who were 40 to 69 years of age and from 3 ethnic groups. Their anthropometric measures, lipids, apoB, C-reactive protein, fibrinogen, plasminogen activator inhibitor-1, fasting and post-glucose load glucose, and insulin concentrations were measured, and insulin sensitivity was determined by intravenous glucose tolerance test. Differences in risk parameters in individuals with hyper-apoB/normo-NHDLC, and normo-apoB/hyper-NHDLC were compared in all IRAS subjects and again in those with MetS. In both cases, despite anticipated lower LDL cholesterol, the hyper-apoB/normo-NHDLC group had elevated risk indicated by greater waist circumference (both P<0.05) and fasting insulin (P<0.01) and lower insulin sensitivity (P<0.001). They also had higher C-reactive protein (P<0.05). Moreover, the Spearman correlation of apoB was significantly stronger (P<0.05) in the direction of greater associated risk than that of NHDLC with body mass index, waist circumference, systolic blood pressure, 2-hour glucose, fasting glucose, fasting insulin, 2-hour insulin, insulin sensitivity, C-reactive protein, fibrinogen, and plasminogen activator inhibitor-1. Conclusions-In conclusion, apoB is more closely associated with central adiposity, insulin resistance, thrombosis, and inflammation than NHDLC. Our data suggest that apoB is a better candidate risk parameter than NHDLC for identifying a subgroup of individuals with or without MetS with elevated cardiovascular risk.