Objective: This study aimed to make an early diagnosis of endothelial dysfunction, the initial pathology of atherosclerosis in metabolic syndrome (MS) patients, and to investigate the usefulness of serum asymmetric dimethylarginine (ADMA) levels as a marker of cardiovascular risk.

Methods: Thirty-eight patients (24 women and 14 men) who were diagnosed with MS, according to the National Cholesterol Education Program Adult Treatment Panel III, were included in the study. Patients with a history of systemic diseases, except components of MS, and smokers were excluded from the study. The control group comprised 25 and 12 healthy women and men, respectively; with similar age profiles. Serum ADMA levels and carotid intima-media thickness (CIMT) were measured in patients and controls.

Results: Lower serum ADMA levels and higher CIMT measurements were observed in the patient group than in the control group (p<0.001 and p<0.001, respectively). C-reactive protein (CRP) was significantly higher in patients than in controls (p<0.001). Correlation analysis revealed a significant and inverse correlation between plasma ADMA concentrations and fasting blood glucose (p<0.001, r=-0.421), HbA1c (p=0.001, r=-0.361), CRP (p=0.003, r=-0.335), and CIMT measurements (p=0.024, r=-0.261). Among the patients with MS, 32 were diagnosed with type 2 DM; among whom 29 were receiving metformin treatment. ADMA levels in MS patients with and without metformin therapy were 4.5±1.7 nmol/mL and 7.3±1.2 nmol/mL, respectively; and the ADMA levels were significantly lower in the former than in the latter (p=0.007).

Conclusion: MS is a cluster of diseases in which pro-atherosclerotic processes such as DM, hypertension, obesity, and hypercholesterolemia coexist. In our study, when increased CIMT values were considered as evidence for the presence of atherosclerosis in patients, the low serum ADMA levels may be related to metformin therapy, poor glycemic control, and/or problems in the immune-assay.