Efficiency of intestinal cholesterol absorption in humans is not related to apoE phenotype.
Level 4 - case-series / case-control
Cross-sectional comparative physiological study of homozygous phenotype groups
PubMed 12518038 · doi:10.1194/jlr.m200319-jlr200
What was done
Researchers measured intestinal cholesterol absorption, bile acid synthesis, and total cholesterol synthesis across 20 homozygous individuals divided into three groups: eight apoE4/4 subjects, six normocholesterolemic apoE2/2 subjects, and six apoE2/2 subjects with type III hyperlipoproteinemia. The relationship between cholesterol absorption and the plasma campesterol-to-cholesterol ratio was also evaluated.
What was found
Intestinal cholesterol absorption did not differ significantly among the groups, averaging 38 ± 2% (mean ± SEM) in normolipemic E2/2, 37 ± 4% in type III hyperlipemic E2/2, and 41 ± 3% in E4/4 subjects. Dietary intake of fat and cholesterol showed no influence on absorption efficiency. Across all subjects combined, cholesterol absorption efficiency correlated positively with the plasma campesterol-to-cholesterol ratio (r = 0.504; P < 0.02). Neither bile acid synthesis nor total cholesterol synthesis was affected by apoE allele status, though total cholesterol synthesis correlated with body weight (r = 0.574; P < 0.01).
Why it matters
The findings challenge the concept that variations in the apoE genotype directly alter baseline intestinal cholesterol absorption or synthesis in humans.
Limits
The sample size was very small (n = 20 total, with 6 to 8 per group), creating high risk of a false negative due to low statistical power. The study examined only homozygous extremes (E2/2 and E4/4) and did not include the most common E3/3 genotype or heterozygotes.
Cited by
- contradicts Individuals who are APOE4-positive absorb dietary fat better than those who are APOE4-negative.