Polymorphisms in the GC Gene for Vitamin D Binding Protein and Their Association with Vitamin D and Bone Mass in Young Adults.

OBJECTIVE

To identify DBP gene rs4588 and rs7041 polymorphisms and associate with participants' serum 25(OH)D and BMD levels.

STUDY DESIGN

Cross-sectional descriptive study design.

PLACE AND DURATION OF STUDY

Section of Chemical Pathology and Molecular Pathology, Department of Pathology and Laboratory Medicine, The Aga Khan University, Karachi, from July 2014 to September 2015.

METHODOLOGY

Blood samples from 98 young adults, out of 101 samples collected, were genotyped for GC rs4588 and rs7041 polymorphisms by polymerase chain reaction-based restriction fragment length polymorphism assay. Questionnaires were administered to obtain information on demographics and anthropometric characteristics, BMD was assessed with heel ultrasound and 25(OH)D was measured using a Chemiluminescence immunoassay.

RESULTS

High prevalence of vitamin D deficiency was noted in the study population n=87 (86.1%) having median (IQR) 25(OH)D levels of 14.9 (20.9) ng/ml, in males and 12.1 (51.8) ng/ml in females. The C/C genotype of SNP rs4588 had the highest proportion n=50 (51%), whereas for rs7041 genotype G/T was most frequently observed n=53 (54%) in subjects. Highest 25(OH)D levels were observed within the homozygous genotypes C/C median 25(OH)D 14.0 (49.6) and G/G (median 25(OH)D 14.9 (37.1) ng/ml. Statistically significant relationship was noted between rs7041 genotype G/T and BMD (p 0.037).

CONCLUSION

Hypovitaminosis D was frequently found in young adults. Furthermore, G/T variant of rs7041 polymorphism was associated with lower 25(OH)D serum levels.