Genetic and environmental determinants of 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels in Hispanic and African Americans.
BACKGROUND
Vitamin D deficiency is associated with many adverse health outcomes, yet little is known about the genetic epidemiology of vitamin D or its metabolites.


OBJECTIVE
Our objective was to examine the relationship among three vitamin D-related genes and levels of 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25(OH)2D] in Hispanics (HAs) and African Americans (AAs).


METHODS
The cross-sectional Insulin Resistance Atherosclerosis Family Study recruited and examined subjects in: Los Angeles, California (AAs; 513 individuals from 42 families); San Luis Valley (SLV), Colorado (HAs; 513 individuals from 30 families); and San Antonio (SA), Texas (HAs; 504 individuals from 58 families).


METHODS
Plasma levels of 25(OH)D and 1,25(OH)2D were measured.


RESULTS
Levels of 25(OH)D were highest in SLV-HAs [18.3 +/- 7.7 ng/ml (45.7 +/- 19.2 nmol/liter)], lower in SA-HAs [14.6 +/- 6.4 ng/ml (36.4 +/- 16.0 nmol/liter)], and lowest in AAs [11.0 +/- 5.4 ng/ml (27.5 +/- 13.5 nmol/liter)]. Levels of 1,25(OH)2D were similar in AAs [43.5 +/- 13.9 pg/ml (113.1 +/- 36.1 pmol/liter)] and SLV-HAs [43.2 +/- 13.3 pg/ml (112.3 +/- 34.6 pmol/liter)], but higher in SA-HAs [48.6 +/- 17.0 pg/ml (126.4 +/- 44.2 pmol/liter)]. After adjusting for gender and age within the site, two single nucleotide polymorphisms (SNPs) in the vitamin D binding protein gene (DBP), rs4588 and rs7041, were associated with 25(OH)D, and one SNP in the DBP, rs4588, was associated with 1,25(OH)2D at all three study centers.


CONCLUSIONS
SNPs in the DBP are associated with levels of 25(OH)D and 1,25(OH)2D in HA and AA participants in the Insulin Resistance Atherosclerosis Family Study.
Engelman
Corinne D
CD
Department of Population Health Sciences, University of Wisconsin School of Medicine and Public Health, 610 Walnut Street, 1007A WARF, Madison, Wisconsin 53726-2397, USA. cengelman@wisc.edu
Fingerlin
Tasha E
TE
Langefeld
Carl D
CD
Hicks
Pamela J
PJ
Rich
Stephen S
SS
Wagenknecht
Lynne E
LE
Bowden
Donald W
DW
Norris
Jill M
JM
D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics; D000293:Adolescent; D000328:Adult; D001741:Black or African American / Q000235:genetics*; D002117:Calcitriol / Q000097:blood* / Q000235:genetics; D003430:Cross-Sectional Studies; D005260:Female; D006630:Hispanic or Latino / Q000235:genetics*; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D008875:Middle Aged; D020641:Polymorphism, Single Nucleotide; D018167:Receptors, Calcitriol / Q000235:genetics; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood / Q000235:genetics; D014808:Vitamin D Deficiency / Q000097:blood / Q000208:ethnology* / Q000235:genetics*; D014809:Vitamin D-Binding Protein / Q000235:genetics
D018167:Receptors, Calcitriol; D014809:Vitamin D-Binding Protein; D014807:Vitamin D; C104450:25-hydroxyvitamin D; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase; D002117:Calcitriol