Background According to modern data, one of important genetic determinants of bone metabolic disorders is a calcitonin receptor gene (CALCR), encoding a protein receptor for indicated hormone. Polymorphism of 1377 C>T gene CALCR is a SNP mutation, which leads to a decrease in density and increase the risk of disorders of bone metabolism.
Objectives The purpose of this study is to investigate the prevalence of genotypic variants of polymorphism of 1377 C>T gene CALCR at patients with OA and estimation of the possible association of this marker with the risk of OP.
Methods The study was conducted on DNA samples of 56 patients with OA in combination with OP (I subgroup) and 44 patients with OA, but without OP (II subgroup). Diagnosis was made according to clinical and instrumental data. The control group was composed of 37 unrelated healthy individuals of Uzbek nationality, without any OA/OP associated diseases.
Genotyping of polymorphism was performed by standard PCR-analysis on a thermocycler Applied Biosistems-2720 (USA) with using sets of “MedLab”. Statistical processing of the results was performed by using the statistical software package “GenePop” and “OpenEpi 2009, Version 2.3”.
Results In the studied patients at I subgroup and control levels of observed and expected heterozygosis matched Hardy-Weinberg equilibrium (P<0.05). The observed and expected level of homo-and heterozygosis in the group of patients were 0.86/0.14 and 0.86/0.13 respectively (P<0.05). Wright's fixation index value was D =-0.07. In the control group, these figures corresponded to 0.81/0.19 and 0.82/0.17 at D =-0.012.
A comparative analysis of the frequency distribution of genotypic variants of polymorphism of 1377 C>T gene CALCR wasn't detected in any single case of homozygous genotype TT in both studied groups. This leaded to the conclusion of an extremely high prevalence of C allele in our population. Thus, the frequency of allele C was prevalent in patients group and healthy donors (92.8% and 90.5%, respectively). At the same time, there was no any significant differences obtained in the occurrence of a particular allele of this polymorphism in the observation group compared with the population (χ2=0.06; P=0.8; OR=0.89; 95% CI 0.3531-2.239).
The frequency of C/C and C/T genotypes in I subgroup of patients was 85.7% and 14.3%, respectively. In the control group, the figures were 81.1% and 18.9%, respectively. The frequencies of adverse distribution of C/C genotype CALCR gene between patients and controls also didn't show any statistically significant differences (χ2=0.06; P=0.79; OR=1.4; 95% CI 0.4301, 3.018).
Exactly the same frequencies of alleles and genotypes were obtained in the II subgroup of patients (OA without OP). Differences between this subgroup of patients and I subgroup were not statistically reliable (χ2=0.6; P=0.4; OR=1.5; 95% CI 0.541-4.39).
Conclusions Thus, despite the expected relationship between CALCR gene with the risk of OP in patients with OA has not been obtained reliable data indicating the decisive role of genetic variant of 1377 C>T this gene in the formation of osteometabolism in these patients.
Disclosure of Interest None declared