Causality between serum uric acid and diabetic microvascular complications - a mendelian randomization study

The aim of this study was to investigate whether a causal relationship exists between serum uric acid (SUA) and diabetic microvascular complications using a two-sample Mendelian randomization (MR) method.

We used the MR approach, utilizing genome-wide association study (GWAS) summary statistics, to estimate the causal effect of SUA on diabetic microvascular complications in European individuals. The summary statistical data of SUA were obtained from the open database (IEU OPEN GWAS PROJECT) (p < 5 × 10^- 8), and data on diabetic microvascular complications (diabetic nephropathy, diabetic neuropathy, diabetic retinopathy) were obtained from the FinnGen consortium. F-statistics were calculated to assess the correlation between instrumental variables (IVs) and SUA, and single nucleotide polymorphisms (SNPs) associated with confounders or outcomes were excluded by consulting the PhenoScanner database. Inverse variance weighting (IVW) was used for primary estimation, and MR‒Egger, weighted median (WM), and Mendelian randomization pleiotropy residuals sum and outliers (MR-PRESSO) were used for additional assessment. Heterogeneity was assessed using the Cochran's Q test, and polytropy was assessed using the MR‒Egger intercept.

MR analysis revealed a causal relationship between a genetically predicted increase in SUA and diabetic nephropathy [OR = 1.32, 95%(CI) = 1.07-1.63, p = 0.008]. The results were consistent with those after MR-PRESSO [OR = 1.30, 95%(CI) = 1.07-1.58, p = 0.008]. There was a causal relationship between type 2 diabetes mellitus (T2DM) and renal complication IVW [OR = 1.27, 95%(CI) = 1.00-1.62, p = 0.049]. These results were consistent with those after MR-PRESSO [OR = 1.27, 95%(CI) = 1.00-1.62, p = 0.050]. There was no significant causal relationship between the genetically predicted increase in SUA and diabetic retinopathy [OR 1.09, 95%(CI) = 0.94-1.26, p = 0.249] or diabetic neuropathy [OR = 1.08, 95%(CI) = 0.84-1.40, p = 0.549].

This MR analysis suggests a causal relationship between genetically predicted uric acid increases and diabetic microvascular complications. A significant causal relationship exists between SUA and diabetic nephropathy but not between SUA and diabetic retinopathy or diabetic neuropathy.