Urea Cycle Metabolites and Atrial Fibrillation or Heart Failure Risk: Two Case-Control Studies in the PREDIMED Trial

OBJECTIVES: To prospectively analyze the associations between urea cycle metabolites and incident atrial fibrillation (AF) or heart failure (HF), and to evaluate the effect of a Mediterranean diet (MD) intervention on such associations. METHODS: We designed two nested case-control studies within the PREDIMED trial, a randomized controlled trial aimed to evaluate the effect of two MD interventions, supplemented with either extra virgin olive oil (EVOO) or nuts, on cardiovascular disease (CVD). Fasting blood samples were collected at baseline and urea cycle metabolites (arginine, citrulline, and ornithine) and methylarginines (asymmetric dimethylarginine/symmetric dimethylarginine ratio (ADMA/SDMA ratio)) were determined using liquid chromatography tandem mass spectrometry. We used conditional logistic regression models, adjusted for potential confounders, to analyze the associations between the metabolites and incident AF or HF. Potential interactions between metabolites and intervention (MD groups vs control group) were tested with the likelihood ratio test. RESULTS: The study population comprised a total of 1241 participants (509 cases) for AF case-control and 824 participants (326 cases) for HF case-control. Arginine was inversely associated with incident AF (OR per SD 0.83, 95% CI 0.73; 0.94) and HF (OR per SD 0.82, 95% CI 0.69; 0.97). Whereas ADMA/SDMA ratio was positively associated with AF (OR per SD 1.19, 95% CI 1.02; 1.41) but not with HF risk. A statistically significant interaction (P = 0.044) was found between arginine and intervention on HF risk. The lower risk of HF associated with arginine was only observed in participants of the MD groups (EVOO + nuts). CONCLUSIONS: The results of the present study suggest that urea cycle metabolites, arginine and ADMA/SDMA ratio specifically, could be involved in AF and HF pathophysiology. Moreover, the dietary intervention may modify the association between arginine and HF. FUNDING SOURCES: National Institutes of Health (NIH), Spanish Government Official Agency for funding biomedical research-Instituto de Salud Carlos III (ISCIII) and CIBEROBN