Effect of arginine : lysine ratio in free amino acid and protein form on l-NAME induced hypertension in hypercholesterolemic Wistar rats

Abstract

Arginine plays an important role in cardiovascular diseases, especially as a nitric oxide precursor leading to vasodilation. The present study focuses, on the effect of the arginine/lysine (Arg : Lys) ratio in the protein form and free amino acid form on hypertension in hypercholesterolemic Wistar rats. Hypertension was induced by administration of L-NAME (Nω-nitro-L-arginine methyl ester hydrochloride) orally for 16 weeks in high cholesterol fed Wistar rats. Arginine : lysine ratio is high in Moringa seed protein isolate (MPI) compared to other oilseed proteins. After inducting, the treatment groups were supplemented with diets containing Moringa seed protein isolate (MPI-LN) and free amino acids (FAA-LN) for 6 weeks. A decrease in systolic blood pressure (SBP) was observed after treatment. The MPI-LN and FAA-LN exhibited 126.6 ± 2.2 mmHg and 127.5 ± 0.2 mmHg of SBP respectively, which is less compared to the hypertensive rats (146.7 ± 4.5 mmHg). The hypertensive markers such as angiotensin-I converting enzyme (ACE) and nitrate levels in kidney were analysed. The MPI-LN and FAA-LN exhibited 10.30 ± 3.7 nmoles per mg per min and 37.56 ± 3.7 nmoles per mg per min ACE activity respectively. In both treatment groups, a 50% decrease in ACE activity was observed compared to hypertensive rats. Increase (30%) in nitrate levels was observed in MPI-LN (0.47 ± 0.04 μM g⁻¹) and FAA-LN (0.4 ± 0.06 μM g⁻¹) compared to hypertensive rats. From the results, it is evident that Arg : Lys has a role in hypertension regulation. Lipid profiles of blood plasma showed a decrease in plasma triacylglyceride and liver triacyglyceride levels in the treatment groups. The Arg : Lys ratio in both the protein form (MPI) and free amino acid form strongly affects the metabolic pathways of hypertension with moderate effect on hypercholesterolemia.