Molecular characterization and frequency of transforming growth factor beta 1 gene polymorphism and its relation to bone complications in Egyptian patients with β-thalassemia

Abstract

Objective The objective of this study was to determine the frequency of transforming growth factor beta 1 (TGFβ1) C-509T gene polymorphism and its relation to bone complications in patients with β-thalassemia major in Egypt. Background Osteoporosis is the most prevalent bone complication in patients with β-thalassemia major despite regular blood transfusions and iron chelation therapy. It is characterized by low bone mineral density (BMD) resulting in reduced bone strength and increased risk of fractures. Genetic factors play an important role in the determination of BMD. The TGFβ1 gene, which encodes TGFβ1, is a strong candidate for susceptibility to osteoporosis, and several studies have reported associations between BMD and different polymorphisms of TGFβ1, although these studies have yielded conflicting results. Study design and methods Single nucleotide polymorphism in the TGFβ1 gene promoter (C-509T) was investigated in 100 regularly treated Egyptian children with β-thalassemia major by PCR/RFLP genotyping. BMD was measured by dual-energy radiograph absorptiometry and expressed as Z score. Results The frequency of TGFβ1 gene polymorphism C-509T genotypes in all studied patients was 6% for homozygous CC, 85% for heterozygous CT, and 9% for homozygous TT. C allele frequency was 48.5%, whereas T allele frequency was 51.5%. BMD Z score was significantly higher in TT genotype compared with CC genotype, with P value less than 0.05. Patients were grouped on the basis of BMD Z score: 51 (51%) patients with BMD deficit (Z score <−1) and 49 (49%) with normal BMD (Z score ≥−1). TGFβ1 gene polymorphism C-509T genotypes were distributed differently between the two groups; the TT genotype frequency was lower in patients with BMD deficit (P<0.05). Conclusion TGFB1 gene polymorphism C-509T is associated with BMD and genetic susceptibility to osteoporosis and may play a role in the pathogenesis and modification of bone complication in β-thalassemia major. BMD deficit is common in Egyptian children with β-thalassemia major. Analysis of this polymorphism at an early age could help in identification of thalassemic children at risk of osteoporosis and early management. However, large-scale studies are required to confirm these findings.