Association between variable number tandem repeats within the 3' flanking region of the interleukin-6 gene and systemic lupus erythematosus in Korean patients

The Association between Interleukin-6 Gene Polymorphisms and Risk of Systemic Lupus Erythematosus: A Meta-analysis with Trial Sequential Analysis

BACKGROUND

Molecular epidemiological studies have sought associations between interleukin-6 (IL-6) polymorphisms and the risk of systemic lupus erythematosus (SLE); however, the results are controversial. Therefore, we conducted a meta-analysis with trial sequential analysis to evaluate a more accurate estimation of the associations.

METHODS

Published literatures reporting the relationships of two IL-6 polymorphisms (G-174C and G-572C) and SLE risk were retrieved from electronic databases such as PubMed and EMBASE. The most appropriate genetic model was chosen for each polymorphism. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated. Trial sequential analysis (TSA) was introduced to assess the information size and the positive results.

RESULTS

With 17 studies (2780 cases and 3100 controls) included, a dominant association (CC+GC vs. GG) was suggested for G-174C polymorphism, and compared with the GG genotype, the CC+GC genotype of G-174C was associated with a decreased SLE risk (OR = 0.71; 95% CI = 0.56-0.88, P =.02). No association was found for G-572C under all genetic models (e.g. OR and 95%CI for CC+GC vs. GG: 0.89, 0.73-1.08, P =.22). Subgroup analyses indicated that SLE risk decreased in G-174C polymorphism by subgroups of Caucasian population, publications after 2010, studies with high quality, and studies complied with Hardy-Weinberg equilibrium (HWE). TSA suggested that the sample sizes used for G-572C were insufficient.

CONCLUSION

We found that the minor allele C of IL6G-174C polymorphism is a protective factor in SLE. Further studies with a larger sample size are needed to confirm the null association for G-572C.

Association of the interleukin-6 polymorphisms with systemic lupus erythematosus: a meta-analysis

BACKGROUND

Interleukin (IL)-6, an important proinflammatory cytokine, plays a potential pathological role in systemic lupus erythematosus (SLE). Studies on the relationship of IL-6 gene polymorphisms with SLE are inconclusive. The aim of this study was to estimate the relationship more precisely.

METHODS

The databases of PubMed and Web of Science updated to 30 August 2014 were retrieved. Meta-analysis was conducted using allelic contrast, dominant, recessive and homozygote contrast models. Fifteen studies were included in this study and ethnicity-specific meta-analysis was performed on European, Iranian and Asian populations.

RESULTS

Analysis for the IL-6-174 G/C polymorphism under all models except the homozygote contrast model indicated an association in the overall population (allelic contrast model: odds ratio (OR) 1.428, 95% confidence interval (CI) 1.124-1.812, dominant model: OR 1.382, 95% CI 1.037-1.842, recessive model: OR 1.610, 95% CI 1.158-2.240, homozygote contrast model: OR 1.759, 95% CI 0.989-3.127), as well as in European individuals under all four genetic models (allelic contrast model: OR 1.557, 95% CI 1.155-2.098, dominant model: OR 1.699, 95% CI 1.203-2.400, recessive model: OR 1.506, 95% CI 1.176-1.930, homozygote contrast model: OR 2.118, 95% CI 1.103-4.065). Analysis for the IL-6-572 G/C polymorphism indicated significant association in overall ethnicities under the recessive model (OR 1.491, 95% CI 1.104-2.014), but not under other models or in Asian individuals. In addition, significant association between the IL-6-174 G/C polymorphism and discoid skin lesions and antinuclear antibodies (ANAs) were found under the allelic contrast model and recessive model, respectively (discoid skin lesions: OR 2.271, 95% CI 1.053-4.895; ANAs: OR 2.244, 95% CI 1.141-4.416).

CONCLUSION

This meta-analysis provides evidence of the association between the IL-6 polymorphism and the risk of SLE, hinting that the IL-6-174 G/C and IL-6-572 G/C polymorphisms may play a role in SLE susceptibility.

Haematological manifestations of lupus

Our purpose was to compile information on the haematological manifestations of systemic lupus erythematosus (SLE), namely leucopenia, lymphopenia, thrombocytopenia, autoimmune haemolytic anaemia (AIHA), thrombotic thrombocytopenic purpura (TTP) and myelofibrosis. During our search of the English-language MEDLINE sources, we did not place a date-of-publication constraint. Hence, we have reviewed previous as well as most recent studies with the subject heading SLE in combination with each manifestation. Neutropenia can lead to morbidity and mortality from increased susceptibility to infection. Severe neutropenia can be successfully treated with granulocyte colony-stimulating factor. While related to disease activity, there is no specific therapy for lymphopenia. Severe lymphopenia may require the use of prophylactic therapy to prevent select opportunistic infections. Isolated idiopathic thrombocytopenic purpura maybe the first manifestation of SLE by months or even years. Some manifestations of lupus occur more frequently in association with low platelet count in these patients, for example, neuropsychiatric manifestation, haemolytic anaemia, the antiphospholipid syndrome and renal disease. Thrombocytopenia can be regarded as an important prognostic indicator of survival in patients with SLE. Medical, surgical and biological treatment modalities are reviewed for this manifestation. First-line therapy remains glucocorticoids. Through our review, we conclude glucocorticoids do produce a response in majority of patients initially, but sustained response to therapy is unlikely. Glucocorticoids are used as first-line therapy in patients with SLE with AIHA, but there is no conclusive evidence to guide second-line therapy. Rituximab is promising in refractory and non-responding AIHA. TTP is not recognised as a criteria for classification of SLE, but there is a considerable overlap between the presenting features of TTP and SLE, and a few patients with SLE have concurrent TTP. Myelofibrosis is an uncommon yet well-documented manifestation of SLE. We have compiled the cases that were reported in MEDLINE sources.