Association between Vitamin D Receptor Polymorphism and Serum Vitamin D Levels in Children with Low-Energy Fractures

Abstract

Objective: Fractures of bones, especially forearm fractures, are very common in children and their number is increasing. This study was designed to determine the impact of vitamin D serum levels and vitamin D receptor (VDR) polymorphisms on the occurrence of low-energy fractures in children.

Methods: The study group consisted of 100 children with clinically relevant bone fractures and a control group consisted of 127 children without fractures. Total vitamin D [25(OH)D3 plus 25(OH)D2] serum concentrations were evaluated in every patient. Genotypes for 4 restriction fragment length polymorphisms of the vitamin D receptor gene (FokI, ApaI, TaqI, and BsmI) were determined by standard polymerase chain reaction–restriction fragment length polymorphism (PCR-RFLP) techniques.

Results: Differences in concentrations of vitamin D were observed between the group with bone fractures (median = 12 ng/ml) and the control group (median = 16 ng/ml; p = 0.000044).

Higher levels of vitamin D reduced the risk of fracture by 1.06 times (p = 0.0005). No impact of particular VDR polymorphism on the occurrence of low-energy fractures in children was detected. However, there were significant differences in the prevalence of FokI polymorphism genotypes between the fracture and control groups (p = 0.05). Furthermore, the recessive “aa” genotype of ApaI polymorphism and the dominant “TT” genotype of TaqI polymorphism were associated with higher levels of vitamin D (p = 0.005 and p = 0.036, respectively).

Conclusions: Vitamin D deficiency is an independent risk factor for fractures in children. ApaI polymorphism recessive “aa” and TaqI polymorphism dominant “TT” genotypes are associated with higher levels of vitamin D in serum.

Key words:

• 25-hydroxy-vitamin D
• children
• bone fractures
• vitamin D receptor polymorphism
• vitamin D deficiency

FUNDING

This study was supported from statutory funds of Department of Pediatric Orthopedics and Traumatology and Department of Medical Chemistry and conducted with the use of equipment purchased by the Medical University of Bialystok as part of the OP DEP 2007-2013, Priority Axis I.3, Contract No. POPW.01.03.00-20-008/09.