L-arginine does not improve endothelial function in patients with metabolic syndrome

AIM: Metabolic syndrome (MS) is associated with impaired endothelial function. In this study we investigated whether L-Arginine improves endothelial dysfunction in patients with MS. METHODS: In a randomized double blind study, 38 subjects with MS received either 6.64 g/die of L-Arginine (n=19, group A) or placebo (n=19, group B) for 6 weeks. Flow mediated dilatation (FMD), systolic and diastolic blood pressure, visceral obesity, lipids, blood glucose, insuline, L-arginine, total NOx and symmetric and asymmetric dimethylarginine (SDMA and ADMA) were measured at baseline (T0) and at the end of the study (T6). RESULTS: At baseline, groups A and B differed just for waist circumference (100±7 vs. 107±12 cm; p<0.05). After treatment, beside the expected increases in both L-arginine (from 83±17 to 97±26 µM; p=0.002) and of L-arginine/ADMA ratio (from 215±40 to 243±53; p=0.002) no change was detected in L-arginine treated group. An increase of total cholesterol (from 173±47 to 184±44 mg/dL, p=0.027), LDL (from 95±26 to 109±34 mg/dL, p=0.012), HDL (from 44±7 to 46±8 mg/dL, p=0.003) and ADMA (from 0.39±0.07 to 0.42±0.09 µM, p=0.005) was observed in the placebo group. After data adjustment for possible confounders (age, pack-years and change in ADMA, arginine, blood glucose and pharmacological treatments) FMD significantly increased in the L-arginine treated group but not in the placebo group. Group A difference in FMD, however, lost its statistical significance after adjustment of the analysis for Brachial artery diameter measured at rest. CONCLUSIONS: The oral supply of L-Arginine does not influence the endothelial function in patients with MS.