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Relationship of apolipoprotein E phenotypes to hypocholesterolemia
S M Synder1, J F Terdiman, B Caan
1Department of Medicine, Kaiser Permanente Medical Center, South San Francisco, California.
The American Journal of Medicine
|November 1, 1993
Summary
Hypocholesterolemia in healthy adults is rarely due to diet or disease. Genetic factors, specifically altered apolipoprotein E (apo E) allele frequencies, are the primary cause of low cholesterol levels.
Area of Science:
- Biochemistry
- Genetics
- Clinical Medicine
Background:
- Hypocholesterolemia, defined as total cholesterol (TC) levels below 130 mg/dL, affects less than 1% of healthy individuals.
- Potential causes include restrictive diets, underlying diseases, genetic predispositions (e.g., low apolipoprotein B-100 [apo B-100] or specific apo E alleles), and certain medications.
Purpose of the Study:
- To investigate the underlying causes of hypocholesterolemia within a healthy population served by the Kaiser Foundation Health Plan (KFHP).
Main Methods:
- A comparative study involving 201 healthy hypocholesterolemic adults and 200 matched control subjects with average TC levels.
- Subgroup analysis included apolipoprotein E (apo E) phenotyping and measurements of lipids, apo A-1, and apo B-100 in 45 hypocholesterolemic individuals and 49 controls.
Main Results:
- No significant differences in dietary intake or prevalence of clinically relevant diseases were observed between hypocholesterolemic and control groups.
- Hypocholesterolemic subjects exhibited a significantly higher frequency of the apo E2 allele and a lower frequency of the apo E4 allele compared to controls (p < 0.0001).
- One case identified a mutation in the apo B gene leading to a truncated apo B-46 protein.
Conclusions:
- Hypocholesterolemia in this urban KFHP population is predominantly attributed to biochemical and genetic factors rather than diet or disease.
- An increased prevalence of the apo E-2 phenotype and a decreased prevalence of the apo E-4 phenotype are key biochemical determinants of hypocholesterolemia.