Effect of VDR gene polymorphisms on osteocalcin secretion in calcitriol-stimulated human osteoblasts.
BACKGROUND
The impact of vitamin D receptor (VDR) gene polymorphisms in bone metabolism remains controversial. Some authors have found a beneficial effect of some VDR gene polymorphisms, while others found no differences, or even a lower bone mass in subjects with the same type of polymorphisms. The aim of this study was to assess if the VDR gene polymorphisms could have an effect on the calcitriol-stimulated osteocalcin in human osteoblasts.


METHODS
Osteoblasts were obtained from human femoral necks replaced because of osteoarthritis. Bones were cut into pieces of 1 to 2 mm and placed in a nylon mesh. After the migration of osteoblasts, the pieces were collected and cultured with different concentrations of calcitriol (10(-8), 10(-9), and 10(-1)0 mol/L). After 48 hours of incubation with calcitriol, the osteocalcin secreted into the medium (corrected by either total proteins or total DNA content) was measured. The DNA was extracted from the osteoblasts, amplified by polymerase chain reaction (PCR), and analyzed for target sequences sites of the BsmI, ApaI, TaqI, and FokI restriction enzymes.


RESULTS
The response observed in osteocalcin secretion in the bb or TT genotypes doubled the response observed in the BB or tt genotypes (calcitriol 10(-8) and 10(-9) mol/L). A slight trend was also observed with the aa genotype. Men showed higher levels of osteocalcin secretion than women. Age did not show any influence in osteocalcin secretion.


CONCLUSIONS
VDR alleles and gender demonstrated an effect on the osteocalcin secretion. BB or tt genotypes, and also the "A" allele, showed the lowest calcitriol-stimulated osteocalcin secretion.
Naves
Manuel
M
Bone and Mineral Research Unit, Instituto Reina Sofía de Investigación, Oviedo, Spain.
Alvarez-Hernández
Daniel
D
Fernández-Martín
José L
JL
Paz-Jiménez
José
J
García-Prado
Pedro
P
Fernández-Coto
Teresa
T
Santamaría
Iñigo
I
Cannata-Andía
Jorge
J
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism; D002117:Calcitriol / Q000494:pharmacology*; D002478:Cells, Cultured; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010006:Osteoblasts / Q000187:drug effects / Q000378:metabolism*; D015675:Osteocalcin / Q000378:metabolism*; D011110:Polymorphism, Genetic / Q000235:genetics*; D018167:Receptors, Calcitriol / Q000235:genetics*; D012044:Regression Analysis; D012727:Sex Characteristics; D013268:Stimulation, Chemical
D018167:Receptors, Calcitriol; D015675:Osteocalcin; D002117:Calcitriol