Causal relationships of lipid metabolism in diabetic nephropathy risk: A two-sample Mendelian randomization study

Diabetic nephropathy (DN) represents the primary contributor to end-stage renal disease worldwide, and its prevalence continues to grow, even with improvements in therapies aimed at lowering glucose levels. The progression of DN has been associated with lipid metabolism, yet the direct involvement of particular lipid species is still not fully understood. This study employs two-sample Mendelian randomization (TSMR) to investigate the causal effects of 179 plasma lipid species on DN risk.

Lipid exposure genetic instruments were sourced from a genome-wide association study (GWAS) found in the GWAS Catalog, whereas data on the DN outcomes were collected from the FinnGen R12 cohort. The main analytical approach employed was inverse-variance weighted (IVW) regression. To evaluate pleiotropy and heterogeneity, tests such as MR-Egger intercept, Cochran's Q, MR-PRESSO, and leave-one-out analyses were performed. The analysis identified 13 lipid species with significant associations after sensitivity analyses. Among these, seven lipid species were risk factors for DN, including phosphatidylcholine (PC) (O-16:1_18:1, 15:0_18:2, 18:1_18:1, 18:1_20:2, 18:2_18:2) levels, phosphatidylethanolamine (PE) (18:1_18:1), and triacylglycerol (TAG) (56:4). Conversely, six lipid species demonstrated protective effects, including lysophosphatidylcholine (LPC) (20:4), lysophosphatidylethanolamine (LPE) (18:1), PC (17:0_20:4), sterol ester (SE) (27:1/15:0, 27:1/18:3), and TAG (52:6).

This study provides robust genetic evidence linking specific lipid species to DN risk. PC and PE species were identified as risk factors, whereas LPC, LPE, and SE exhibited protective effects. Additionally, TAG species demonstrated a bidirectional influence. These findings refine the understanding of lipid-mediated renal dysfunction in DN, highlighting lipid metabolism as a potential therapeutic target.