Role of plasminogen activator inhibitor-1 gene polymorphisms in osteoporosis: A study in Chinese post-menopausal women

Abstract

Osteoporosis is a chronic multifactorial disease characterized by deterioration of bone mass and is vulnerable to bone fracture. Plasminogen activator inhibitor-1 (PAI-1) is an important molecule for maintenance of optimum bone mass. Several single-nucleotide polymorphisms (SNPs) in PAI-1 have been reported to alter PAI-1 expression and/or the translational level. In this report, we explored the possible role of common PAI-1 gene polymorphisms on predisposition to osteoporosis in a Chinese cohort. A total of 364 post-menopausal Chinese women diagnosed of having osteoporosis and 350 healthy females hailing from similar areas were enrolled in this study. Five common SNPs (−844G > A, −6754G/5G, +43G > A, +9785G > A and +11053T > G) were genotyped by polymerase chain reaction (PCR) followed by restriction fragment length polymorphism (RFLP). Relative expression of PAI-1 mRNA and plasma PAI-1 levels were quantified by reverse transcription polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. Prevalence of homozygous mutant (5G/5G) and minor allele (5G) of PAI-1 (−675 4G/5G) polymorphism was significantly more frequent in patients than in healthy controls (5G/5G: P < 0.0001, odds ratio (OR) = 3.18; 5G: P < 0.0001, OR = 1.65). Both plasma PAI-1 and relative mRNA expression levels were significantly lower in patients compared to healthy controls. Interestingly, the quantity of plasma PAI-1 and mRNA expression was correlated with PAI-1 (−675 4G/5G) polymorphism: subjects with 4G/4G genotype had elevated PAI-1 in comparison to homozygous mutant, and displayed lower quantity of PAI-1 protein and mRNA values. PAI-1 (−675 4G/5G) mutant is associated with susceptibility to development of osteoporosis in post-menopausal Chinese women. Furthermore, this variant in the promoter region alters plasma protein levels and relative expression of PAI-1.