Dose-dependent long-term effects of nitrate on lipid profile in male rats

Background. This study aims to investigate the long-term effects of different doses of nitrate on the lipid profile in male rats. Methods. Male Wistar rats (n = 60) were assigned to 6 groups (n = 10 per group). The control group received drinking water, and 5 treatment groups received nitrate at doses of 50, 100, 150, 250, and 500 mg/L for 6 months. Nitric oxide (NO) metabolite levels (NOx) were determined at months 0 and 6. Lipid profile [cholesterol, triglyceride (TG), low-density lipoprotein cholesterol (LDL), and high-density lipoprotein cholesterol (HDL)] in the serum was measured at months 0, 3, and 6. Results. Nitrate administration for 6 months (at doses of 50, 100, 150, 250, and 500 mg/L) could increase serum NOX levels by 29.5% (P = 0.0115), 39.6% (P = 0.0002), 65.2% (P < 0.0001), 91.4% (P < 0.0001), and 181.6% (P < 0.0001), respectively. Nitrate administration for 6 months (at doses of 50, 100, and 150 mg/L) decreased serum TG [7.8% (P = 0.0508), 7.4% (P = 0.0654), and 8.3% (P = 0.0331)] and cholesterol [12.7% (P = 0.0066), 15.2% (P = 0.0009), and 15.2% (P = 0.0009)] levels. In addition, it increased serum HDL at doses of 50, 100, and 250 mg/L [24.4% (P = 0.0005), 13.9% (P= 0.0910), and 17.5% (P = 0.0172)], while it had no significant effect on serum LDL levels in comparison to the control group. Conclusion. Long-term nitrate administration at low doses (50‒150 mg/L) prevented dyslipidemia (improved lipid profile) in male rats. These beneficial effects of nitrate can be mainly due to increased serum levels of NO metabolites. Practical Implications. These findings imply that long-term nitrate administration at low doses, achieved by consuming a diet containing vegetables, can potentially be utilized to manage dyslipidemia.