Arginine deficiency measured by global arginine bioavailability ratio in patients with acute coronary syndrome

Background: L-arginine and its related metabolites are associated with arginine bioavailability and subsequent nitric oxide production. The global L-arginine bioavailability ratio (GABR), defined as the ratio of the level of L-arginine to the sum of the levels of its major metabolites (L-arginine/[L-citrulline + L-ornithine]), has been reported as an index of arginine bioavailability. GABR in acute coronary syndrome (ACS) has not been fully investigated. Methods and results: The serum levels of L-arginine, L-citrulline, L-ornithine, asymmetric dimethylarginine (ADMA), and symmetric dimethylarginine (SDMA) were assessed in 134 patients who underwent coronary angiography. The patients were classified into the following three groups based on clinical presentation, electrocardiogram, and coronary angiogram: stable patients without coronary artery disease (CAD (−), n = 38), stable patients with CAD (CAD (+), n = 56), and patients with ACS (n = 40). The ACS patients included 13 with acute myocardial infarction and 27 with unstable angina pectoris. L-arginine and L-ornithine levels were not significantly different among the three groups, whereas L-citrulline levels were significantly increased in ACS patients (CAD (−): 135 ± 62, CAD (+): 148 ± 68, ACS: 174 ± 79 μmol/L; p = 0.043), resulting in a significant decrease in GABR (CAD (−): 0.51 ± 0.19, CAD (+): 0.49 ± 0.17, ACS: 0.39 ± 0.12; p = 0.003). Conclusion: Increased serum citrulline and decreased GABR were observed in patients with ACS, suggesting the presence of relative arginine deficiency in ACS.