Interleukin-6 and Diabetic Retinopathy: A Systematic Review and Meta-Analysis

ABSTRACT

Background: Interleukin-6 (IL-6) is produced by a variety of cells involved in inflammation and acts as local intensification signals in pathological processes associated with chronic eye inflammation. This meta-analysis was performed to provide a better understanding of the relationship between IL-6 and diabetic retinopathy.

Methods: The study was started with systematic search for literatures by using the PubMed, Web of Science and Embase online databases. The standard mean difference (SMD) and its 95% confidence intervals (CIs) were was included and then pooled with a random effects model.

Results: Thirty-one articles, containing1099 DR patients and 1010 controls, were included in this meta-analysis. The level of IL-6 in the DR group was found to be higher than that in the control group (SMD: 2.12, 95% CI: 1.53−2.70, p < 0.00001).Obvious heterogeneity existed between the studies (p < 0.00001, I² = 96%). So a subgroup analysis and sensitivity analysis were performed. Removing the sensitivity studies, the stability of the overall treatment effect was good. Subgroup analysis showed that the levels of IL-6 in case group were observed to be higher than those in the control group; and the IL-6 levels in the proliferative diabetic retinopathy (PDR) group were also higher than those in the non-proliferative diabetic retinopathy (NPDR) group. (SMD: 0.78, 95% CI: 0.26–1.31, p=  0.003)

Conclusion: The results from this current meta-analysis indicated that increased level of IL-6 generally exist in DR patients. And it may associated with the severity of DR. However, large-scale and high-quality studies in future are required to confirm the present findings.

KEYWORDS:

• Interleukin-6
• diabetic retinopathy
• meta-analysis

Acknowledgments

We do not have someone to acknowledge to.

Abbreviations

IL-6, Interleukin-6; SMD, standard mean difference; CI, confidence interval; DR, diabetic retinopathy; NPDR, non-proliferative diabetic retinopathy; PDR, proliferative diabetic retinopathy; Anti-VEGF, anti-vascular endothelial growth factor; BMI, body mass index; NOS, Newcastle-Ottawa scale; MOOSE, meta-analysis of observation studies in epidemiology; DM, diabetes mellitus; ELISA, Enzyme-linked immuno sorbent assay; TNF-a, tumour necrosis factor-alpha;

Availability of data and materials

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Author’s contributions

RL and XNL collected the data. YY and JUD assessed the quality of the included studies. XNL and YY performed the statistical analysis. RL drafted the manuscript. LHL and NL conceived and designed the study. YY reviewed and revised the manuscript. All authors have read and approved the final manuscript.

Competing interests

The authors declare the have no competing interest.

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Ethics and consent to participate

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Additional information

Funding

This work was supported by the National Natural Science Foundation of China (NO.81500726), the Medical Research Project of Xi’an Science Technology Bureau [No.201805097YX5SF31(4)]the Medical Research Project of Xi’an Science Technology Bureau [[No.201805097YX5SF31(4)]];the National Natural Science Foundation of China [NO.81500726];the third batch of key disciplines construction project of Xi’an Medical University.