Malondialdehyde levels in diabetic retinopathy patients: a systematic review and meta-analysis

BACKGROUND: It remains unclear whether circulating malondialdehyde (MDA) levels change in people with diabetic retinopathy (DR). This systematic review compared circulating MDA levels in diabetic people with and without DR. METHODS: PubMed, Medline (Ovid), Embase (Ovid), and Web of Science were searched for case-control studies conducted before May 2022 in English that compared circulating MDA levels in people with and without DR. The following MeSH search terms were used: (“malondialdehyde” or “thiobarbituric acid reactive substances [TBARS]” or “lipid peroxidation” or “oxidative stress”) and “diabetic retinopathy.” Newcastle–Ottawa Quality Assessment Scale was used to evaluate the quality of the included studies. Random-effects pairwise meta-analysis pooled the effect size with standardized mean difference (SMD) and 95% confidence intervals (CIs). RESULTS: This meta-analysis included 29 case-control studies with 1680 people with DR and 1799 people with diabetes but not DR. Compared to people without DR, the circulating MDA levels were higher in those with DR (SMD, 0.897; 95% CI, 0.631 to 1.162; P < 0.001). The study did not identify credible subgroup effects or publication bias and the sensitivity analysis confirmed the robustness of the study. CONCLUSIONS: Circulating MDA levels are higher in people with DR compared to those without. Future comparative studies that use more specific methods are required to draw firm conclusions. REGISTRATION: PROSPERO; https://www.crd.york.ac.uk/PROSPERO/; No. CRD42022352640.