Predictors and relationships of serum 25 hydroxyvitamin D concentration with bone turnover markers, bone mineral density, and vitamin D receptor genotype in Emirati women.
OBJECTIVE
To determine factors influencing serum 25 hydroxyvitamin D (25OHD) concentration and relationships between serum 25OHD concentration, bone turnover markers, bone mineral density (BMD), and vitamin D receptor (VDR) genotype in Emirati women.


METHODS
Serum 25OHD, parathyroid hormone (PTH), osteocalcin (OC), vitamin D binding protein (VDBP), and urinary deoxypyrdinoline (UDPD) concentrations and VDR genotype were determined in Emirati women volunteers who were participating in a study aiming at establishing a reference database for BMD.


RESULTS
Serum 25OHD concentration in the 259 women volunteers was 25.3 +/- 10.8 nmol/l (mean +/- SD), and all had vitamin D deficiency (25OHD <80 nmol/l). Mean serum 25OHD was highest in April (29.2 +/- 13.0 nmol/l), which marks the end of the short and cooler winter season, and lowest in August (18.2 +/- 5.9 nmol/l). No significant difference in 25OHD concentration was noted among Emirati women wearing different dress styles, but the mean serum 25OHD was significantly lower in comparison with non-Arab Caucasian women volunteers who dressed in a Western style (P < 0.001). Serum 25OHD correlated positively with age (r = 0.2), number of pregnancies (r = 0.16), dietary vitamin D intake (r = 0.15), serum calcium (r = 0.14), phosphorus (r = 0.14), VDBP (r = 0.15), and urinary calcium/creatinine (r = 0.2), and inversely with PTH (r = -0.22), OC (r = -0.13), and UDPD/creatinine (r = -0.15); P < 0.05 for all correlations. Multiple linear regression analysis showed that age, dietary vitamin D intake, multivitamin intake, and cooler season were independent positive predictors of serum 25OHD concentration (R(2) = 0.18). The frequencies of VDR genotypes were 36% GG, 44.1% AG, and 19.9% AA. Allele frequencies were 58% for G allele and 42% for A allele and were in Hardy-Weinberg equilibrium (x(2) = 1.44; P > 0.1). There was no statistically significant influence of VDR genotype on bone turnover or BMD.


CONCLUSIONS
Vitamin D deficiency is highly prevalent in Emirati women and appears largely attributable to insufficient sunlight exposure. It is associated with increased bone turnover. VDR genotype does not appear to influence bone turnover markers or BMD in Emirati women.
Saadi
Hussein F
HF
Department of Internal Medicine, Faculty of Medicine and Health Sciences, United Arab Emirates University, P O Box 17666, Al Ain, UAE. Electronic address: saadih@uaeu.ac.ae.
Nagelkerke
Nicolaas
N
Department of Community Medicine, Faculty of Medicine and Health Sciences, United Arab Emirates University, UAE.
Benedict
Sheela
S
Department of Internal Medicine, Faculty of Medicine and Health Sciences, United Arab Emirates University, P O Box 17666, Al Ain, UAE.
Qazaq
Hussein S
HS
Department of Nutrition, Ministry of Health, Tawam Hospital, General Authority for Health Services for Abu Dhabi, Al Ain, UAE.
Zilahi
Erica
E
Department of Medical Microbiology, Faculty of Medicine and Health Sciences, United Arab Emirates University, UAE.
Mohamadiyeh
Mohammad K
MK
Division of Nuclear Medicine, Tawam Hospital, General Authority for Health Services for Abu Dhabi, Al Ain, UAE.
Al-Suhaili
Abdulrahim I
AI
Division of Nuclear Medicine, Tawam Hospital, General Authority for Health Services for Abu Dhabi, Al Ain, UAE.
D000328:Adult; D000483:Alleles; D000596:Amino Acids / Q000652:urine; D000704:Analysis of Variance; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006801:Humans; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood; D011237:Predictive Value of Tests; D018167:Receptors, Calcitriol / Q000235:genetics*; D012621:Seasons; D014479:United Arab Emirates; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000097:blood / Q000175:diagnosis / Q000235:genetics; D014809:Vitamin D-Binding Protein / Q000097:blood
D000596:Amino Acids; C470125:PTH protein, human; D010281:Parathyroid Hormone; D018167:Receptors, Calcitriol; D014809:Vitamin D-Binding Protein; D015675:Osteocalcin; D014807:Vitamin D; C036020:deoxypyridinoline; C104450:25-hydroxyvitamin D