Beneficial effects of melatonin on serum nitric oxide, homocysteine, and ADMA levels in fructose-fed rats

Context: Melatonin, a pineal hormone and a potent antioxidant, has important roles in metabolic regulation. Objective: This study investigated serum asymmetric dimethylarginine (ADMA), homocysteine (Hcy), nitric oxide (NO) levels, known to be reliable markers of cardiovascular diseases, and determined possible protective effects of melatonin in fructose-fed rats. Materials and methods: Sprague-Dawley rats were divided into four groups: control, fructose, melatonin, and fructose plus melatonin. Metabolic syndrome was induced in rats by 20% (w/v) fructose solution in tap water, and melatonin was administered at the dose of 20 mg/kg bw per day by oral gavage. After 8 weeks, serum lipids, glucose, insulin, ADMA, Hcy, and NOx (the stable end products of NO) levels were quantified. Results: Fructose administration caused a statistically significant increase in systolic blood pressure (SBP), serum insulin, triglycerides, and very low-density lipoprotein (VLDL)-cholesterol levels compared with the control group and the metabolic syndrome model was successfully demonstrated. In comparison with the control group, fructose caused a significant increase in serum ADMA, Hcy, and NOx levels. Melatonin counteracted the changes in SBP, serum ADMA, and Hcy levels found in rats both alone and administered with fructose. Discussion and conclusion: These results show that high fructose consumption leads to elevated SBP, atherogenic lipid profile, increased serum ADMA, and Hcy levels and melatonin treatment has beneficial effects on these biochemical parameters in rats. Melatonin might be beneficial for the prevention and/or treatment of the cardiovascular complications of metabolic syndrome not only by reducing the well-known risk factors of the disease but also by diminishing blood ADMA and Hcy levels.