Analysis of genetic markers for the optimization of an individualized approach to osteoporosis.

Abstract

Aim of this study: Osteoporosis is a systemic skeletal disease characterized by compromised bone structure and resistance and by an increased risk of fracture especially in postmenopausal women. Multiple factors including hormonal, environmental and genetic factors are involved in osteoporosis development and clinical outcome. It has been shown that Klotho and insulin-like growth factor-1 (IGF-1) have a significant effect on aging and osteoporosis risk. Actually, Insulin-like growth factor-1 (IGF-1) is a critical polypeptide that plays an important role in the regulation of bone metabolism, which promotes bone cell growth, differentiation, cell cycle progression. Klotho modulates aging in mice and humans, Klotho membrane-bound protein serves as a co-receptor required for the fibroblast growth factor 23 (FGF23), the link between Klotho and FGF23 creates a negative feedback that blocks the enzyme that converts 25-hydroxy Vitamin D to the active form (1,25 dihydroxy Vitamin D). Thus, klotho and FGF23 may function in a common signal transduction pathway in maintaining mineral ion homeostasis. Considering that some gene variant might influence production level and function of these mediators, we have started the evaluation of associations among IGF-1, IGF-1R and Klotho 1 SNPs and osteoporosis risk. Methods: In this preliminary approach, a total of 20 women with diagnosis of osteoporosis confirmed by radiograph or DEXA scan and a total of 72 healthy control women were included in the study. For the genetic analysis, peripheral blood samples were collected and genomic DNA was extracted from leukocytes. Genotypic analysis of polymorphisms of Klotho 1 (rs577912), IGF-1(rs35767), IGF-1R was conducted using a competitive allele specific PCR assays (KASpar) developed by Kbioscence. Genotype and allele frequencies were compared by statistical analysis using dominant, codominant, and recessive models. Results: In our study, the analysis of genotypic and allelic frequencies has highlighted, that IGF-I rs35767 genotypes positive for T allele are more represented in cases than in controls and could be associated with susceptibility to osteoporosis (P = 0.0327 OR= 4.529; 95% C.I.: 1.27 - 16.1). Instead, the SNP of Klotho 1 and IGF-I R have in our case subjects a frequency not different from that of the controls. Discussion and Conclusion: Our results are in full agreement with those from Zhang et al. (Genet Mol Res. 2015; 14: 7655-60) reporting association of T+ genotypes of rs35767 with lower BMD levels in the femoral neck. This preliminary result suggests that polymorphism in IGF-I rs35767 might play a role in osteoporosis risk and could be considered a potential indicator for risk of osteoporosis in postmenopausal women.