Promoter variant -204A > C of the cholesterol 7α-hydroxylase gene: association with response to plant sterols in humans and increased transcriptional activity in transfected HepG2 cells.
OBJECTIVE
The bile acid pool influences intestinal cholesterol absorption because this process is strictly dependent on micellar solubilization, which is disrupted by plant sterols (PS). Plasma lipid variation relates to promoter variant -204A > C (rs3808607) of the CYP7A1 gene encoding for 7α-hydroxylase, an enzyme for bile acid synthesis. We hypothesized that this polymorphism would be associated with variability in lipid responses to PS.


METHODS
We investigated 67 subjects (31 AA and 36 AC + CC) with lipid responses to PS documented in two studies. To assess the functionality of the -204A > C variant, electrophoretic mobility gel shift assays were performed and luciferase reporter plasmids containing the promoter were transfected into HepG2 cells.


RESULTS
Compared to AA-subjects, C-carriers showed significantly higher adjusted mean reductions in total cholesterol (0.14 versus 0.43 mmol/L, P = 0.042) and increases in lathosterol-to-cholesterol ratios (0.10 versus 0.75, P = 0.013). The C-construct caused a 78% promoter activity increase and gel-shift assays showed lower affinity for nuclear transcription factors, while in silico experiments predicted a binding site for inhibitory nuclear factors RXR-CAR.


CONCLUSIONS
Results suggest that promoter -204A > C variant is associated with enhanced CYP7A1 activity. Increased intestinal bile acids and ensuing more efficient cholesterol absorption might explain why C-allele carriers show enhanced cholesterol lowering and increased feedback cholesterol synthesis to PS intervention.
De Castro-Orós
Isabel
I
Departamento de Bioquímica y Biología Molecular y Celular, Facultad de Ciencias, Universidad de Zaragoza, C. Pedro Cerbuna 12, 50009 Zaragoza, Spain. idecastro.iacs@aragon.es
Pampín
Sandra
S
Cofán
Montserrat
M
Mozas
Pilar
P
Pintó
Xavier
X
Salas-Salvadó
Jordi
J
Rodríguez-Rey
Jose C
JC
Ros
Emilio
E
Civeira
Fernando
F
Pocoví
Miguel
M
D000328:Adult; D000368:Aged; D001647:Bile Acids and Salts / Q000032:analysis; D002784:Cholesterol / Q000097:blood*; D002790:Cholesterol 7-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism; D004311:Double-Blind Method; D005260:Female; D005838:Genotype; D056945:Hep G2 Cells; D006801:Humans; D008156:Luciferases / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D010840:Phytosterols / Q000494:pharmacology*; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D047488:Retinoid X Receptors / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014162:Transfection; D055815:Young Adult
D001647:Bile Acids and Salts; D010840:Phytosterols; D047488:Retinoid X Receptors; D014157:Transcription Factors; C001521:lathosterol; D002784:Cholesterol; D008156:Luciferases; C553219:CYP7A1 protein, human; D002790:Cholesterol 7-alpha-Hydroxylase