Exploring the causal relationship between plasma lipids and varicose veins of lower extremity: A comprehensive two-sample Mendelian randomization study.

Varicose veins of the lower extremities (VVs) is a common chronic vascular disease, with high prevalence rates in some countries; however, their pathogenesis remains unclear. Some studies have identified associations between changes in specific plasma lipid molecules, such as phosphatidylethanolamine (PE), phosphatidylcholine (PC), and sphingomyelin (SM), and the onset of VVs, but due to confounders and reverse causality, the causal relationship remains unclear. Meanwhile, studies on the potential link between other plasma lipids beyond PE, PC, and SM and the risk of VVs in the lower extremities are lacking. This study aimed to explore the potential causal relationship between VVs and plasma lipid levels to provide theoretical insights into the interrelation of plasma lipids and VVs in their occurrence and progression. We conducted a two-sample Mendelian randomization (MR) analysis to assess the potential connection between genetically predicted levels of individual plasma lipids and the risk of developing VVs. We utilized data from a large-scale genome-wide association study involving 7174 Finnish individuals for 179 plasma lipidomes along with VVs genome-wide association study data from 408,455 UK individuals. MR analysis employed methods, such as inverse-variance weighting, weighted median, Bayesian Weighted Mendelian Randomization, and MR-Egger regression. The inverse-variance weighting method was primarily used to assess causality. The validity of the results was demonstrated through sensitivity analysis. In total, 12 lipids were found to have their plasma levels associated with an increased risk of VVs. This includes 3 types of PE, 7 types of PC, and 2 types of phosphatidylinositol. However, no significant causal relationship was found between the plasma levels of 11 types of SM and VVs. These results support the existence of a potential causal relationship between specific types of lipid levels and the risk of VVs, which can provide clues for further studies on biological mechanisms and the exploration of potential therapeutic targets.