Exploring the causal pathway from omega-6 levels to coronary heart disease: A network Mendelian randomization study

Background and aims: Evidence on the effect of omega-6 fats on coronary heart disease (CHD) risk remains inconclusive. We applied a network MR framework to determine the causal effects between omega-6 levels and CHD and the potential cholesterol metabolic risk factors (Total cholesterol, TC; Low-density lipoprotein cholesterol, LDL-C; High-density lipoprotein cholesterol, HDL-C; Triglycerides, TG) which might act as mediators in the link between omega-6 levels and CHD by integrating summary-level genome wide association study (GWAS) data. Methods and results: Network MR analysis-an approach using genetic variants as the instrumental variables for both the exposure and mediator to infer causality was performed to examine the causal effects between omega-6 levels and CHD and cholesterol metabolic risk factors. Summary statistics from the Kettunen et al. 's consortium were used (n = 13506) for omega-6, CARDIoGRAMplusC4D consortium data were used (n = 184305) for CHD, and GLGC consortia data were used (n = 108363) for TC, LDL-C, HDL-C, and TG. The IVW method estimate indicated that the odds ratio (OR) (95% confidence interval [CI]) for CHD was 1.210 (1.118-1.310) per standard deviation increase in omega-6. Results were consistent in MR Egger method (OR, 1.418; 95% CI, 1.087-1.851; P = 0.050) and weighted median methods (OR, 1.239; 95% CI, 1.125-1.364; P = 0.000). Omega-6 was positively causal associated with TC, LDL-C, and TG but was not associated with HDL-C. Moreover, TC, LDL-C, and TG were positively associated with CHD. Conclusions: Using a network MR framework, we provided evidence supporting a positive causal relationship between omega-6 and CHD, which might be partially mediated by TC, LDL-C, and TG. (C) 2019 The Italian Society of Diabetology, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition, and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V.