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.