Nontargeted Metabolomics Revealed Novel Association Between Serum Metabolites and Incident Acute Coronary Syndrome: A Mendelian Randomization Study

BACKGROUND: This study was performed to identify metabolites associated with incident acute coronary syndrome (ACS) and explore causality of the associations. METHODS AND RESULTS: We performed nontargeted metabolomics in a nested case‐control study in the Dongfeng‐Tongji cohort, including 500 incident ACS cases and 500 age‐ and sex‐matched controls. Three metabolites, including a novel one (aspartylphenylalanine), and 1,5‐anhydro‐d‐glucitol (1,5‐AG) and tetracosanoic acid, were identified as associated with ACS risk, among which aspartylphenylalanine is a degradation product of the gut‐brain peptide cholecystokinin‐8 rather than angiotensin by the angiotensin‐converting enzyme (odds ratio [OR] per SD increase [95% CI], 1.29 [1.13–1.48]; false discovery rate–adjusted P=0.025), 1,5‐AG is a marker of short‐term glycemic excursions (OR per SD increase [95% CI], 0.75 [0.64–to 0.87]; false discovery rate–adjusted P=0.025), and tetracosanoic acid is a very‐long‐chain saturated fatty acid (OR per SD increase [95% CI], 1.26 [1.10–1.45]; false discovery rate–adjusted P=0.091). Similar associations of 1,5‐AG (OR per SD increase [95% CI], 0.77 [0.61–0.97]) and tetracosanoic acid (OR per SD increase [95% CI], 1.32 [1.06–1.67]) with coronary artery disease risk were observed in a subsample from an independent cohort (152 and 96 incident cases, respectively). Associations of aspartylphenylalanine and tetracosanoic acid were independent of traditional cardiovascular risk factors (P‐trend=0.015 and 0.034, respectively). Furthermore, the association of aspartylphenylalanine was mediated by 13.92% from hypertension and 27.39% from dyslipidemia (P<0.05), supported by its causal links with hypertension (P<0.05) and hypertriglyceridemia (P=0.077) in Mendelian randomization analysis. The association of 1,5‐AG with ACS risk was 37.99% mediated from fasting glucose, and genetically predicted 1,5‐AG level was negatively associated with ACS risk (OR per SD increase [95% CI], 0.57 [0.33–0.96], P=0.036), yet the association was nonsignificant when further adjusting for fasting glucose. CONCLUSIONS: These findings highlighted novel angiotensin‐independent involvement of the angiotensin‐converting enzyme in ACS cause, and the importance of glycemic excursions and very‐long‐chain saturated fatty acid metabolism.