Impact of interleukin 6 promoter polymorphisms (-174 G > C, -572 G > C and -597 G > A) on plasma IL-6 levels and their influence on the development of DVT: a study from India.

OBJECTIVES: To evaluate the association of interleukin 6 (IL-6) levels with deep vein thrombosis (DVT) and to assess the impact of IL-6 promoter polymorphisms (-174G > C, -572G > C and -597G > A) on its plasma levels and their influence in the development of DVT in India.

METHODS: One hundred DVT patients and 100 age and sex-matched healthy controls were study subjects. IL-6 polymorphisms were identified by polymerase chain reaction-restriction fragment length polymorphism. IL-6 levels were detected by enzyme-linked immunosorbent assay.

RESULTS: Significantly raised IL-6 levels were observed in patients as compared to controls. (Patients: 13.73 ± 6.30 pg/ml, Controls: 11.83 ± 4.47 pg/ml, p = 0.014). The prevalence of C allele of -572G > C polymorphism was significantly higher in patients than controls (Patients: 39.5%, Controls: 27.5%, p = 0.011, χ2 =6.463). Subjects with GC and CC genotype had significantly higher IL-6 levels than GG genotype (p=<0.001). Patients with GC and CC genotype increased the DVT risk by 1.39 fold (ORa : 1.39, CI: 0.74-2.62) and 2.69 fold (ORa : 2.42, CI: 1.08-6.70), respectively. IL-6 -174G > C and -597G > A polymorphisms were not associated with raised IL-6 levels and nor with thrombotic risk (-174G > C: p = 0.823 χ2 =0.369; -597G > A: p = 0.678 χ2 =1.08).

CONCLUSION: Our study emphasizes the importance of -572G > C polymorphism in increasing IL-6 levels, thereby showing its significant role in DVT in India. IL-6 -174G > C and -597G > A were neither associated with raised plasma IL-6 levels nor with thrombotic risk. Thus -572G > C polymorphism detection may be one of the connecting links between IL-6 and thrombotic risk in Indian DVT patients.