Immune cell-mediated effects of plasma lipids on heart failure: A two-step, two-sample Mendelian randomization study

A growing number of studies have shown that plasma lipids and immune cells are related to the occurrence and development of heart failure (HF), but the causal relationship between them is unclear. Therefore, it is critical to obtain a thorough understanding of the impact of plasma lipids and immune cells on the risk of developing HF. In addition, it is important to further explore whether immune cells play a mediating role in this relationship. First, a two-way, two-sample Mendelian randomization (MR) analysis was performed on 179 plasma lipids and HF, and the effect size (β) was obtained. Then, MR analysis was conducted on 731 kinds of immune cells in relation to HF. Moreover, the MR analysis of the screened plasma lipids in relation to immune cells produced an effect value of β1, and the MR analysis of immune cells causally related to plasma lipids with HF yielded an effect value of β2. Finally, the proportion of mediated effects of immune cells between plasma lipids and HF was calculated by the formula β1 × β2/β. During the study, we employed several analytical methods, including inverse-variance weighting, Bayesian weighted Mendelian randomization, MR-Egger regression, weighted median, weighted model, and simple model. Moreover, heterogeneity and pleiotropy tests were employed to validate the results. The results indicated a causal relationship between 7 types of plasma lipids and HF, and 4 types of immune cells mediated the causal relationship between plasma lipids and HF. The proportion of mediated effects in which HLA-DR+ CD4+ AC-mediated triacylglycerol (50:1) levels affecting HF was 5.77%. The results of this study were confirmed to be reliable by heterogeneity testing and sensitivity analysis. There was a causal relationship between 7 types of plasma lipids and HF, and 4 types of immune cells mediated the causal relationship between lipids and HF. This finding is expected to provide new ideas for the therapeutic strategy of HF.