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Associations between haptoglobin polymorphism, lipids, lipoproteins and inflammatory variables
L Braeckman1, D De Bacquer, J Delanghe
1Department of Public Health, University of Gent, Belgium. lutgart.braeckman@rug.ac.be
Atherosclerosis
|April 27, 1999
Summary
Haptoglobin (Hp) polymorphism influences lipid levels, with Hp 2-2 associated with higher cholesterol and apo B. Gene interactions, like Hp and apo E, affect cholesterol and Lp(a), potentially impacting coronary heart disease risk.
Area of Science:
- Human Genetics
- Biochemistry
- Cardiovascular Disease Risk Factors
Background:
- Haptoglobin (Hp) is a protein involved in hemoglobin binding.
- Hp polymorphism (Hp 1-1, Hp 1-2, Hp 2-2) is common in human populations.
- Lipoprotein metabolism is crucial for cardiovascular health.
Purpose of the Study:
- To determine haptoglobin allele and phenotype frequencies in Caucasian male workers.
- To investigate the association between haptoglobin polymorphism and clinical/biochemical parameters.
- To analyze potential interactions between haptoglobin and apolipoprotein E (apo E) polymorphisms on lipid traits.
Main Methods:
- Genotyping of haptoglobin and apo E polymorphisms in 741 male Caucasian workers (aged 35-59).
- Measurement of serum lipids (total cholesterol, free cholesterol, HDL cholesterol), lipoproteins (apo A-I, apo B, Lp(a)), and other biomarkers (fibrinogen, C-reactive protein).
- Statistical analysis to assess allele frequencies, phenotype distribution, Hardy-Weinberg equilibrium, and associations/interactions between genetic factors and biochemical parameters.
Main Results:
- Haptoglobin allele frequencies: Hp1 = 0.401, Hp2 = 0.599. Phenotype distribution was in Hardy-Weinberg equilibrium.
- Individuals with Hp 2-2 phenotype showed significantly higher serum total cholesterol, free cholesterol, and apo B levels compared to other Hp types.
- A significant multiplicative interaction was observed between Hp type and apo E genotype (specifically the apo epsilon4 allele) on free cholesterol levels, and between Hp type and apo E genotype (epsilon2 allele) on Lp(a) levels.
Conclusions:
- Haptoglobin polymorphism plays a role in regulating lipoprotein metabolism.
- The Hp 2-2 phenotype is associated with unfavorable lipid profiles, potentially increasing coronary heart disease risk.
- Gene-gene interactions, particularly between Hp and apo E, significantly influence lipid and lipoprotein levels, warranting further investigation in larger cohorts.