The Renin-Angiotensin System and Cardiovascular Disease

ACE Inhibitory Activity and Molecular Docking of Gac Seed Protein Hydrolysate Purified by HILIC and RP-HPLC

Gac (Momordica cochinchinensis Spreng.) seed proteins (GSPs) hydrolysate was investigated for angiotensin I-converting enzyme (ACE) inhibitory activities. GSPs were hydrolyzed under simulated gastrointestinal digestion using a combination of enzymes, including pepsin, trypsin, and chymotrypsin. The screening of ACE inhibitory peptides from GSPs hydrolysate was performed using two sequential bioassay-guided fractionations, namely hydrophilic interaction liquid chromatography (HILIC) and reversed-phase high-performance liquid chromatography (RP-HPLC). Then, the peptides in the fraction with the highest ACE inhibitory activity were identified by LC-MS/MS. The flow-through (FT) fraction showed the most potent ACE inhibitory activity when HILIC fractionation was performed. This fraction was further separated using RP-HPLC, and the result indicated that fraction 8 (RP-F8) showed the highest ACE inhibitory activity. In the HILIC-FT/RP-F8 fraction, 14 peptides were identified using LC-MS/MS analysis coupled with de novo sequencing. These amino acid chains had not been recorded previously and their ACE inhibitory activities were analyzed in silico using the BIOPEP database. One fragment with the amino acid sequence of ALVY showed a significant ACE inhibitory activity (7.03 ± 0.09 µM). The Lineweaver-Burk plot indicated that ALVY is a competitive inhibitor. The inhibition mechanism of ALVY against ACE was further rationalized through the molecular docking simulation, which revealed that the ACE inhibitory activities of ALVY is due to interaction with the S1 (Ala354, Tyr523) and the S2 (His353, His513) pockets of ACE. Bibliographic survey allowed the identification of similarities between peptides reported as in gac fruit and other proteins. These results suggest that gac seed proteins hydrolysate can be used as a potential nutraceutical with inhibitory activity against ACE.

Effective treatment of hypertension by recombinant Lactobacillus plantarum expressing angiotensin converting enzyme inhibitory peptide

Background

Hypertension is considered the most serious risk factor for cardiovascular disease. Angiotensin-converting enzyme inhibitory peptides (ACEIPs), which are made from tuna frame protein (TFP) and yellow fin sole frame protein (YFP), have been used previously to treat hypertension. However, the production of these short peptides is usually dependent on enzymatic hydrolysis, resulting in a digested mixture that makes it difficult to purify the ACEIPs. Although it has been reported that ACEIPs could be produced in recombinant Escherichia coli strains, the use of lactic acid bacteria in the production of ACEIPs has not been demonstrated.

Results

In this study, the ACEIP coding sequences from TFP and YFP were joined through an arginine linker and expressed in the Lactobacillus plantarum (Lb. plantarum) NC8 strain by an inducible vector pSIP-409. Then, the antihypertensive effects were determined in the model of spontaneously hypertensive rats (SHRs) by measuring the blood pressure, hematology, blood biochemistry and nitric oxide (NO), endothelin (ET) and angiotensin II (Ang II) levels. The results showed that oral administration of recombinant Lb. plantarum NC8 (RLP) significantly decreased systolic blood pressure (P < 0.01) during treatment, which lasted for at least 10 days after the last dose. Furthermore, the presence of RLP resulted in an increased level of NO, as well as decreased levels of ET and Ang II in plasma, heart, and kidney. In addition, a dramatically decreased triglyceride level was also observed even though there was no significant change in hematology or blood biochemistry. Although some drawbacks were still observed, such as the presence of an antibiotic selection marker, no obvious side effects or bacterial translocation were observed in vivo, indicating the potential application of RLP in the treatment of hypertension.

Conclusion

These results demonstrated the effectiveness and safety of RLP on the treatment of hypertension.

Combination Therapy with Olmesartan and Amlodipine in the Treatment of Hypertension

Background: Combination therapy with antihypertensive agents utilises different mechanisms of action and may be responsible for a more effective decrease in blood pressure. Objective: To review the recently published trials on efficacy and safety of the combination therapy with olmesartan and amlodipine. Results: The double-blind American COACH (Combination of Olmesartan Medoxomil and Amlopdine Besylate in Controlling High Blood Pressure) study (2008) showed in 1,940 patients that after eight weeks of treatment the BP goals were most frequently achieved in the ‘combination therapy group’, with 56.3% (54.1–58.5%) and 54.0% (51.8–56.2%) of patients reaching adequate blood pressure of <140/90 mmHg with olmesartan/amlodipine 20/10 and 40/10 respectively. Combination therapy was generally well tolerated. The most common side effect was oedema [olmesartan 20 mg 9.9% (8.6–11.3%), amlodipine 10 mg 36.8% (34.7–39.0%), placebo 12.3% (10.9–13.8%)]. The frequency of oedema was lower in the groups combining amlodipine 10 mg with olmesartan 10 mg (26.5%, 24.5–28.5%), 20 mg (25.6%, 23.7–27.6%) or 40 mg (23.5%, 21.6–25.4%). In 2009 three double-blind controlled European studies including 500–1,000 patients each and performed independently of one another have confirmed the above study, and have demonstrated similar efficacy-safety effects from the combination of olmesartan medoxomil with amlodipine, particularly for patients not achieving adequate blood pressure control with olmesartan monotherapy. Conclusions: Combinations of olmesartan and amlodipine were significantly more effective at reducing blood pressure and realising guideline blood pressure goals in patients with mild to severe hypertension than monotherapy (with a placebo component). Combination therapy is well tolerated and is associated with a lower incidence of side effects, such as oedema, compared to monotherapy with high amlodipine dosages (10 mg).

New antihypertensive peptides isolated from rapeseed

Four potent angiotensin converting enzyme (ACE) inhibitory peptides, IY, RIY, VW and VWIS, were isolated from subtilisin digest of rapeseed protein. Among them RIY and VWIS are new peptides with IC(50) 28 and 30 microM, respectively. All isolated peptides lowered blood pressure of spontaneously hypertensive rats (SHR) following oral administration. The maximum effect in the case of RIY was observed 4h after administration, while maximum effect of other peptides on blood pressure occurred 2h after administration. Furthermore, the antihypertensive effect of RIY was observed even in old rats, in which ACE inhibitors become less effective, suggesting that a different mechanism other than ACE inhibition is also involved in lowering blood pressure by this peptide. Subtilisin digest of rapeseed protein also significantly lowered blood pressure of SHR after oral administration of a single dosage 0.15 g/kg, exerting maximum antihypertensive effect 4h after administration. This digest appears promising as a functional food, which may be useful in the prevention and treatment of hypertension.

Efficacy of valsartan in the therapy of persistent microalbuminuria in normotensive patients with type 1 diabetes mellitus

Aim. To determine the efficacy of AT1 receptor antagonist (valsartan) in decreasing of urinary excretion of albumin in normotensive patients with type 1 diabetes and incipient diabetic nephropathy (DN). Methods. This was a prospective, randomised, placebo-controlled study, which included 20 patients with insulin-dependent diabetes mellitus, mean age 25.15, and the duration of diabetes of 13.95 years. All the patients were normotensive, with persistent microalbuminuria (incipient phase of DN). Patients were randomly divided into two groups (10 patients each): valsartan group treated with 80 mg valsartan daily during 6 months, and the group treated with placebo during the same period. Both groups were similar and comparable concerning the observed parameters at the beginning of the study. Results. After 6 months therapy, valsartan caused significant decrease of urinary albumin excretion rate (UEAR) by 69.1% from 64.8 to 21.1 mg/24 h, while in placebo group there was an insignificant increase of UEAR by 29.8%. During the follow-up of UEA in the observed groups, at the beginning and the end of the mentioned period highly significant decrease of albumine secretion (p<0.001) was observed. Valsartan significantly lowered mean systolic blood pressure (from 122.0 ? 10.1 to 110.0 ? 11.8 mmHg). After 6 months therapy, the reduced values of total cholesterol and LDL-cholesterol fraction were registered in the valsartan group, while the difference in serum trigliceride values reached statistical significance (1.42 ? 0.79 vs. 1.21 ? 0.89 mmol/L; p<0.05). Neither significant difference in glycoregulation quality between the two groups, nor the occurence of hyperkalemia was detected throughout the study period. Conclusion. Valsartan's efficacy in the decrease of microalbuminuria after 6 months of therapy could justify the use of this group of renin/angiotensin blockers in delaying the clinically manifested DN. Valsartan was well tolerated and did not influence the quality of glycoregulation. It did not increase the level of serum lipids and could be recomended in the treatment of diabetic patients.