nicotianamine and Hypertension

Green asparagus (Asparagus officinalis) is known to be rich in functional components. In the present study, spontaneously hypertensive rats (SHR) were used to clarify whether green asparagus prevents hypertension by inhibition of angiotensin-converting enzyme (ACE) activity. Six-week-old male SHR were fed a diet with (AD group) or without (ND group) 5% asparagus for 10 weeks. Systolic blood pressure (SBP) (AD: 159 ± 4.8 mmHg, ND: 192 ± 14.7 mmHg), urinary protein excretion/creatinine excretion, and ACE activity in the kidney were significantly lower in the AD group compared with the ND group. Creatinine clearance was significantly higher in the AD group compared with the ND group. In addition, ACE inhibitory activity was observed in a boiling water extract of asparagus. The ACE inhibitor purified and isolated from asparagus was identified as 2″-hydroxynicotianamine. In conclusion, 2″-hydroxynicotianamine in asparagus may be one of the factors inhibiting ACE activity in the kidney, thus preventing hypertension and preserving renal function.

Topics: Angiotensin-Converting Enzyme Inhibitors; Animals; Antihypertensive Agents; Asparagus Plant; Azetidinecarboxylic Acid; Blood Pressure; Humans; Hypertension; Kidney; Male; Peptidyl-Dipeptidase A; Plant Preparations; Rats; Rats, Inbred SHR

Nicotianamine (NA) is a nonprotein amino acid that inhibits the angiotensin I-converting enzyme (ACE) in the renin-angiotensin system (RAS). The purpose of this study is to prove that NA contributes to the suppression of hypertension by preferential inhibition of ACE. On comparison with EDTA-a chelator-we found that the inhibition pattern of NA for ACE is that of mixed inhibition and that NA exhibits weak chelation effects for zinc, copper, and cobalt ions. Therefore, we investigated whether NA inhibited zinc-containing enzymes other than ACE in vitro. The results revealed that NA does not inhibit leucine aminopeptidase or alkaline phosphatase in rat serum. On the other hand, NA demonstrated specific inhibitory effects for rat serum ACE and aortic ACE. These results suggest that the preferential inhibition of circulatory and tissue ACE by NA can contribute to the suppression of hypertension.

Topics: Alkaline Phosphatase; Angiotensin-Converting Enzyme Inhibitors; Animals; Azetidinecarboxylic Acid; Chelating Agents; Cobalt; Copper; Edetic Acid; Hypertension; Inhibitory Concentration 50; Leucyl Aminopeptidase; Male; Peptidyl-Dipeptidase A; Rats; Rats, Inbred SHR; Renin-Angiotensin System; Zinc