Lipoproteins and apolipoproteins in the young and familial risk of coronary atherosclerosis

Decreased lipoprotein lipase activity and increased postprandial concentrations of triglyceride-rich lipoproteins in offspring of elderly survivors of myocardial infarction

BACKGROUND AND AIM

A family history of myocardial infarction (MI) is an independent risk factor for future coronary events. Decreased plasma lipoprotein lipase (LPL) activity is associated with delayed clearance of triglyceride-rich lipoproteins (TRL) and low fasting HDL cholesterol. The aim of the study was to investigate the relations between plasma LPL activity, postprandial TRL and HDL cholesterol in offspring of MI patients.

METHODS AND RESULTS

A case-control study was performed in 17 healthy middle-aged offspring of MI patients and 13 healthy age-and sex-matched controls. Fasting blood samples were collected and each subject was given a standardized oral fat load (1g fat/kg body weight) with subsequent blood samples collected for an 8-h period. Offspring of MI patients had significantly lower postheparin LPL activity (62.9 mU/ml+/-22.8 mU/ml) (mean+/-SD) than healthy controls (93.0 mU/ml+/-21.7 mU/ml) (p=0.002). Decreased postheparin LPL activity was accompanied by significantly increased and delayed clearance of postprandial TRL and subsequent lower fasting HDL cholesterol in offspring of MI patients. Postheparin LPL activity was associated with HDL cholesterol (r=0.40, p=0.036) and trend analysis revealed a decrease in incremental area under the curve (AUCi) for chylomicrons with increasing LPL activity (p=0.013).

CONCLUSIONS

Offspring of MI patients had decreased postheparin LPL activity accompanied by increased postprandial TRL and subsequent decreased HDL cholesterol, an unfavourable lipid profile which may contribute to their increased risk for future coronary events.

Comparison of laboratory parameters as risk factors for the presence and the extent of coronary or carotid atherosclerosis: the significance of apolipoprotein B to apolipoprotein all ratio

We compared several "new" risk factors (autoantibodies to oxidatively modified low density lipoprotein (LDL), sialic acid content of LDL, bilirubin and C-reactive protein) with "conventional" risk factors (apolipoprotein (apo) AI, AII and B, lipoprotein(a), triglycerides, and total, LDL and high density lipoprotein (HDL) cholesterol) for the presence and the extent of coronary or carotid atherosclerosis. Forty male patients with angiographically proven coronary atherosclerosis and 31 male patients with ultrasound-proven extracranial carotid atherosclerosis were compared to 40 age matched (53+/-5 years) healthy males as control subjects, with negative parental history of atherosclerosis, no clinical signs of systemic or organ-related ischemic disease and normal extracranial carotid arteries. The apo B/apo All ratio most powerfully indicated the presence and the extent of coronary or carotid atherosclerosis. Elevated lipoprotein(a) contributed significant additional information in the assessment of the atherosclerotic risk. Increase in C-reactive protein indicated the presence (but not the extent) of coronary or carotid atherosclerosis with a similar power as lipoprotein(a). Decreased values of total bilirubin indicated the presence of atherosclerosis only in smokers. Autoantibodies to oxidatively modified LDL additionally described the atherosclerotic process, but were less important than apolipoproteins, lipoprotein(a), C-reactive protein or bilirubin. Sialic acid content of LDL added no information to the parameters discussed above. We demonstrated that in male patients apolipoproteins, especially the apo B/apo All ratio, were better indicators of the presence and the extent of coronary or carotid atherosclerosis than C-reactive protein, bilirubin, autoantibodies to oxidatively modified LDL or sialic acid content of LDL.