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Apolipoprotein E phenotypes in patients with myocardial infarction
Insights
Apolipoprotein E (apo E) isoform E4 is more frequent in myocardial infarction patients. Apo E2 homozygotes with hyperlipoproteinemia type III face higher coronary atherosclerosis risk.
Area of Science:
- Cardiovascular Genetics
- Lipid Metabolism
- Atherosclerosis Research
Background:
- Apolipoprotein E (apo E) genetic isoforms (E2, E3, E4) play a role in lipid metabolism and cardiovascular disease risk.
- Previous studies suggest associations between apo E isoforms and conditions like hyperlipoproteinemia and atherosclerosis.
Purpose of the Study:
- To investigate the frequencies of apo E isoforms in patients with myocardial infarction (MI) compared to healthy controls.
- To determine the specific role of apo E2 homozygosity in the context of MI and hyperlipoproteinemia.
Main Methods:
- Genotyping for apo E isoforms (E2, E3, E4) in 523 MI patients and 1031 blood donors.
- Comparison of isoform frequencies between patient and control groups.
- Analysis of lipid profiles (cholesterol, triglycerides) and clinical data in E2 homozygotes.
Main Results:
- Apo E4 frequency was significantly higher in MI patients than in controls.
- No significant difference in apo E3 or E2 frequencies was observed between groups.
- E2 homozygotes with MI consistently presented with hyperlipoproteinemia type III and elevated lipids.
- E2 homozygotes in the control group had primary dysbetalipoproteinemia but normal cholesterol levels.
Conclusions:
- Apo E4 is associated with an increased risk of myocardial infarction.
- E2 homozygotes with hyperlipoproteinemia type III have a substantially elevated risk for coronary atherosclerosis.
- The cardiovascular risk associated with E2 homozygosity may depend on plasma lipid levels, with normal levels potentially conferring lower risk.
Abstract:
The frequencies of genetic apo E isoforms E2, E3 and E4 were determined in 523 patients with myocardial infarction and compared to those in a control group (1031 blood donors). A significant difference in the frequency of apo E4 was noted between patients and controls (0.05 greater than P greater than 0.025). No differences in the frequencies of isoforms E3 and E2 were observed. In particular, there was no significant difference between the two groups in the frequency of apo E2 homozygosity, a condition that is associated with type III hyperlipoproteinemia. However, all E2 homozygote survivors of myocardial infarction had hyperlipoproteinemia type III (cholesterol 269 +/- 29 mg/dl; triglyceride 419 +/- 150 mg/dl; age 54 +/- 14 years; N = 5). On the contrary, E2 homozygote controls (all apo E-2/2 blood donors and their apo E-2/2 relatives who were from the same age range as the patients) had primary dysbetalipoproteinemia but normal or subnormal plasma cholesterol concentrations (cholesterol 184 +/- 28 mg/dl; triglyceride 151 +/- 52 mg/dl; age 56 +/- 13 years; N = 11). This indicates that E2 homozygotes with hyperlipoproteinemia type III who occur rarely in the population but comprise about 1% of myocardial infarction patients have a markedly increased risk for coronary atherosclerosis, whereas the risk for E2 homozygotes with normal or subnormal plasma cholesterol (= primary dysbetalipoproteinemia) may be considerably lower than for the general population. The data illustrate the complex relationship between apo E genes, lipid levels, and risk for atherosclerosis.