Angiotensin I converting enzyme

Advances in the structural basis for angiotensin-1 converting enzyme (ACE) inhibitors

Human somatic angiotensin-converting enzyme (ACE) is a key zinc metallopeptidase that plays a pivotal role in the renin-angiotensin-aldosterone system (RAAS) by regulating blood pressure and electrolyte balance. Inhibition of ACE is a cornerstone in the management of hypertension, cardiovascular diseases, and renal disorders. Recent advances in structural biology techniques have provided invaluable insights into the molecular mechanisms underlying ACE inhibition, facilitating the design and development of more effective therapeutic agents. This review focuses on the latest advancements in elucidating the structural basis for ACE inhibition. High-resolution crystallographic studies of minimally glycosylated individual domains of ACE have revealed intricate molecular details of the ACE catalytic N- and C-domains, and their detailed interactions with clinically relevant and newly designed domain-specific inhibitors. In addition, the recently elucidated structure of the glycosylated form of full-length ACE by cryo-electron microscopy (cryo-EM) has shed light on the mechanism of ACE dimerization and revealed continuous conformational changes which occur prior to ligand binding. In addition to these experimental techniques, computational approaches have also played a pivotal role in elucidating the structural basis for ACE inhibition. Molecular dynamics simulations and computational docking studies have provided atomic details of inhibitor binding kinetics and energetics, facilitating the rational design of novel ACE inhibitors with improved potency and selectivity. Furthermore, computational analysis of the motions observed by cryo-EM allowed the identification of allosteric binding sites on ACE. This affords new opportunities for the development of next-generation allosteric inhibitors with enhanced pharmacological properties. Overall, the insights highlighted in this review could enable the rational design of novel ACE inhibitors with improved efficacy and safety profiles, ultimately leading to better therapeutic outcomes for patients with hypertension and cardiovascular diseases.

Association between Complex ACTN3 and ACE Gene Polymorphisms and Elite Endurance Sports in Koreans: A Case-Control Study

ACTN3 R577X and ACE I/D polymorphisms are associated with endurance exercise ability. This case-control study explored the association of ACTN3 and ACE gene polymorphisms with elite pure endurance in Korean athletes, hypothesizing that individuals with both ACTN3 XX and ACE II genotypes would exhibit superior endurance. We recruited 934 elite athletes (713 males, 221 females) and selected 45 pure endurance athletes (36 males, 9 females) requiring "≥90% aerobic energy metabolism during sports events", in addition to 679 healthy non-athlete Koreans (361 males, 318 females) as controls. Genomic DNA was extracted and genotyped for ACTN3 R577X and ACE I/D polymorphisms. ACE ID (p = 0.090) and ACTN3 RX+XX (p = 0.029) genotype distributions were significantly different between the two groups. Complex ACTN3-ACE genotypes also exhibited significant differences (p = 0.014), with dominant complex genotypes positively affecting endurance (p = 0.039). The presence of RX+II or XX+II was associated with a 1.763-fold higher likelihood of possessing a superior endurance capacity than that seen in healthy controls (90% CI = 1.037-3.089). Our findings propose an association of combined ACTN3 RX+XX and ACE II genotypes with enhanced endurance performance in elite Korean athletes. While causality remains to be confirmed, our study highlights the potential of ACTN3-ACE polymorphisms in predicting elite endurance.

Hypertension in Patients with Insulin Resistance: Etiopathogenesis and Management in Children

Insulin resistance (IR) is a key component in the etiopathogenesis of hypertension (HS) in patients with diabetes mellitus (DM). Several pathways have been found to be involved in this mechanism in recent literature. For the above-mentioned reasons, treatment of HS should be specifically addressed in patients affected by DM. Two relevant recently published guidelines have stressed this concept, giving specific advice in the treatment of HS in children belonging to this group: the European Society of HS guidelines for the management of high blood pressure in children and adolescents and the American Academy of Pediatrics Clinical Practice Guideline for Screening and Management of High Blood Pressure in Children and Adolescents. Our aim is to summarize the main pathophysiological mechanisms through which IR causes HS and to highlight the specific principles of treatment of HS for children with DM.

Modulation of insulin resistance by renin angiotensin system inhibitors: implications for cardiovascular prevention

Insulin resistance (IR) and the related hyperinsulinamia play a key role in the genesis and progression of the continuum of cardiovascular (CV) disease. Thus, it is reasonable to pursue in primary and secondary CV prevention, the pharmacological strategies that are capable to interfere with the development of IR. The renin-angiotensin-aldosterone system (RAAS) plays an important role in the pathogenesis of IR. In particular, angiotensin II (Ang II) through the generation of reactive oxygen species, induces a low grade of inflammation, which impairs the insulin signal transduction. The angiotensin converting enzyme (ACE) inhibitors are effective not only as blood pressure-lowering agents, but also as modulators of metabolic abnormalities. Indeed, experimental evidence indicates that in animal models of IR, ACE inhibitors are capable to ameliorate the insulin sensitivity. The Ang II receptor blockers (ARBs) modulate the peroxisome proliferator-activated receptor (PPAR)-γ activity. PPARâ€"γ is a transcription factor that controls the gene expression of several key enzymes of glucose metabolism. A further mechanism that accounts for the favorable metabolic properties of ARBs is the capability to modulate the hypothalamicâ€"pituitary-adrenal (HPA) axis. The available clinical evidence is consistent with the concept that both ACE inhibitors and ARBs are able to interfere with the development of IR and its consequences like type 2 diabetes. In addition, pharmacological inhibition of the RAAS has favourable effects on dyslipidaemias, metabolic syndrome and obesity. Therefore, the pharmacological antagonism of the RAAS, nowadays, represents the first choice in the prevention of cardio-metabolic diseases.

Role of Kinins in Hypertension and Heart Failure

The kallikrein-kinin system (KKS) is proposed to act as a counter regulatory system against the vasopressor hormonal systems such as the renin-angiotensin system (RAS), aldosterone, and catecholamines. Evidence exists that supports the idea that the KKS is not only critical to blood pressure but may also oppose target organ damage. Kinins are generated from kininogens by tissue and plasma kallikreins. The putative role of kinins in the pathogenesis of hypertension is discussed based on human mutation cases on the KKS or rats with spontaneous mutation in the kininogen gene sequence and mouse models in which the gene expressing only one of the components of the KKS has been deleted or over-expressed. Some of the effects of kinins are mediated via activation of the B2 and/or B1 receptor and downstream signaling such as eicosanoids, nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF) and/or tissue plasminogen activator (T-PA). The role of kinins in blood pressure regulation at normal or under hypertension conditions remains debatable due to contradictory reports from various laboratories. Nevertheless, published reports are consistent on the protective and mediating roles of kinins against ischemia and cardiac preconditioning; reports also demonstrate the roles of kinins in the cardiovascular protective effects of the angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor blockers (ARBs).

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.

Inhibitory Effects of Siegesbeckia orientalis Extracts on Advanced Glycation End Product Formation and Key Enzymes Related to Metabolic Syndrome

Metabolic syndrome typically includes Type 2 diabetes associated with hyperglycemia, central obesity, dyslipidemia and hypertension. It is highly related to oxidative stress, formation of advanced glycated end products (AGEs) and key enzymes, such as carbohydrate digesting enzymes like pancreatic α-amylase and intestinal α-glucosidase, pancreatic lipase and angiotensin I-converting enzyme (ACE). This study used an in vitro approach to assess the potential of four extracts of Siegesbeckia orientalis linne on key enzymes relevant to metabolic syndrome. In this research, S. orientailis was firstly extracted by ethanol. The ethanol extract (SE) was then partitioned sequentially with hexane, ethyl acetate and methanol, and these extracts were named SE-Hex, SE-EA and SE-MeOH, respectively. The experimental results showed that SE-EA had the highest total phenolic content (TPC, 76.9 ± 1.8 mg/g) and the total flavonoids content (TFC, 5.3 ± 0.3 mg/g). This extract exhibited the most significant antioxidant activities, including DPPH radical-scavenging capacity (IC₅₀ = 161.8 ± 2.4 μg/mL), ABTS radical-scavenging capacity (IC₅₀ = 13.9 ± 1.5 μg/mL) and reducing power. For anti-glycation activities, SE-EA showed the best results in the inhibition of AGEs, as well as inhibitory activities against α-glucosidase (IC₅₀ = 362.3 ± 9.2 μg/mL) and α-amylase (IC₅₀ = 119.0 ± 17.7 μg/mL). For anti-obesity activities, SE-EA indicated the highest suppression effect on pancreatic lipase (IC₅₀ = 3.67 ± 0.52 mg/mL). Finally, for anti-hypertension activity, SE-EA also demonstrated the strongest inhibitory activity on ACE (IC₅₀ = 626.6 ± 15.0 μg/mL). Close relationships were observed among the parameters of TPC, antioxidant activities, inhibitory activities on α-amylase, α-glucosidase, lipase and ACE (R > 0.9). Moderate correlations were found among the parameters of TFC, antioxidant activities, and suppression of dicarbonyl compounds formation (R = 0.5-0.9). Taken together these in vitro studies reveal the therapeutic potential of SE-EA extract in the prevention and treatment of metabolic disorders.

Mung-bean Protein Hydrolysates Obtained with Alcalase Exhibit Angiotensin I-converting Enzyme Inhibitory Activity

Mung-bean protein isolates were hydrolysed by two proteases alcalase and neutrase commercially available for food industry use, and the angiotensin I-converting enzyme (ACE) inhibitory activities of the enzymatic hydrolysates were measured at different hydrolysis times. The non-hydrolysed protein showed no inhibitory activity. Hydrolysates generated with neutrase displayed very low ACE inhibitory activity, while those obtained with alcalase exhibited high inhibitory activity. The highest ACE inhibitory activity with the IC50 value of 0.64 mg protein/mL was found in the hydrolysate obtained with alcalase at 2h of hydrolysis time. These results indicated that mung-bean protein is a good protein source of ACE inhibitory peptides when hydrolysed with the protease alcalase. The mung-bean protein hydrolysates prepared with alcalase might be utilised for physiologically functional foods with antihypertensive activity.

Involvement of Kallikrein-Kinin System on Cardiopulmonary Alterations and Inflammatory Response Induced by Purified Aah I Toxin from Scorpion Venom

Bradykinins are released from kininogen by kallikrein. They increase capillary lung permeability after their binding to β1 and especially β2 receptors before being metabolized by kininase enzyme. This study was performed to evaluate cardiopulmonary damages and inflammatory response on injected rats with Aah I toxin of scorpion venom and the involvement of Kallikrein-Kinin system in this pathogenesis. Obtained results revealed that Aah I toxin induces inflammatory cell infiltration accompanied by cellular peroxidase activities, a release of cytokine levels, pulmonary and myocardial damage, with altered metabolic activities and imbalanced redox status. Administration of aprotinin (bradykinin inhibitor) and especially icatibant (bradykinin β2 receptor antagonist) seemed to be able to protect animals against the toxicity of Aah I; nevertheless, the use of captopril (kininase II inhibitor) reduced partially some cardiac disorders. These findings indicate that the kallikrein-kinin system may contribute to the physiopathological effect and lung edema formation induced by toxin, which suggests a potential use of drugs with significant anti-kinin properties.

Peptides-Derived from Thai Rice Bran Improves Endothelial Function in 2K-1C Renovascular Hypertensive Rats

In recent years, a number of studies have investigated complementary medical approaches to the treatment of hypertension using dietary supplements. Rice bran protein hydrolysates extracted from rice is a rich source of bioactive peptides. The present study aimed to investigate the vasorelaxation and antihypertensive effects of peptides-derived from rice bran protein hydrolysates (RBP) in a rat model of two kidney-one clip (2K-1C) renovascular hypertension. 2K-1C hypertension was induced in male Sprague-Dawley rats by placing a silver clip around the left renal artery, whereas sham-operated rats were served as controls. 2K-1C and sham-operated rats were intragastrically administered with RBP (50 mg·kg⁻¹ or 100 mg·kg⁻¹) or distilled water continuously for six weeks. We observed that RBP augmented endothelium-dependent vasorelaxation in all animals. Administration of RBP to 2K-1C rats significantly reduced blood pressure and decreased peripheral vascular resistance compared to the sham operated controls (p < 0.05). Restoration of normal endothelial function and blood pressure was associated with reduced plasma angiotensin converting enzyme (ACE), decreased superoxide formation, reduced plasma malondialdehyde and increased plasma nitrate/nitrite (p < 0.05). Up-regulation of eNOS protein and down-regulation of p47^phox protein were found in 2K-1C hypertensive rats-treated with RBP. Our results suggest that RBP possesses antihypertensive properties which are mainly due to the inhibition of ACE, and its vasodilatory and antioxidant activity.

Assessment and Separation of Angiotensin I-Converting Enzyme Inhibitory Peptides in Chinese Soypaste

A Chinese soypaste-derived fraction with potent angiotensin I-converting enzyme (ACE) inhibitory activity (IC50 = 25.9 μg/mL) was obtained by treating soypaste extract with 80% ethanol. The result of gradient reversed-phase high-performance liquid chromatography (RP-HPLC) suggested that bioactive peptides bearing some polarity groups made a substantial contribution to the ACE inhibitory activity. By mass spectrometric analysis, a component was separated as Glu-Ser-Gly-Asp which was then found to act in a dose-dependent manner against ACE activity as a non-competitive inhibitor, with an IC50 value of 2.297 mM.

Biofunctional properties of enzymatic squid meat hydrolysate

Squid is one of the most important commercial fishes in the world and is mainly utilized or consumed as sliced raw fish or as processed products. The biofunctional activities of enzymatic squid meat hydrolysate were determined to develop value-added products. Enzymatic squid hydrolysate manufactured by Alcalase effectively quenched 1,1-diphenyl-2-picrylhydrazyl radical, hydroxyl radical, and hydrogen peroxide radical with IC₅₀ values of 311, 3,410, and 111.5 μg/mL, respectively. Angiotensin I-converting enzyme inhibitory activity of squid hydrolysate was strong with an IC₅₀ value of 145.1 μg/mL, while tyrosinase inhibitory activity with an IC₅₀ value of 4.72 mg/mL was moderately low. Overall, squid meat hydrolysate can be used in food or cosmetic industries as a bioactive ingredient and possibly be used in the manufacture of seasoning, bread, noodle, or cosmetics.

Molecular modelling studies for the discovery of new substituted pyridines derivatives with angiotensin II AT1 receptor antagonists

A QSAR study has been performed on a series of pyridines derivatives with potent angiotensin II AT1 receptor antagonists. Structural features responsible for the activity of the compounds were characterized by using topological, electrotopological, group based and 3D descriptors, calculated from the Molecular Design Suite software (V-life MDS 3.5). To elucidate the structural properties required for antihypertensive activity, four different molecular modeling techniques; two-dimensional, Group-based (G-QSAR), k-nearest neighbour and pharmacophore approach. A suitable set of molecular descriptors was calculated and stepwise - partial component regression (SW-PCR) was employed to select the descriptors that resulted in the models with the best fit to the data. This study was performed with twenty two compounds using sphere exclusion algorithm method for the division of the data set into training and test set. The statistically significant 2D QSAR model having r(2) = 0.8407 and q(2) = 0.7395 with pred_r(2) = 0.7971 was developed by stepwise-partial component regression (SW-PCR) and best Group based QSAR model having R(2) = 0.8132 and Q(2) = 0.6804 with pred_r(2) = 0.7661 was developed by SW-PCR. The analyzed k-nearest neighbour MFA model revealed a good fit, having q(2) value of 0.7635. The predictive power of the model generated was validated using a test set molecules with pred _r(2) value of 0.7314. The generated k-nearest neighbour models suggest that steric and electrostatic interactions play an important role in describing the variation in binding affinity. Additionally the pharmacophore model well corraborated with k-nearest neighbour studies as the contours of later were in good agreement with the 3D orientation of the pharmacophoric features. The present analysis has shown that the antihypertensive activity can be improved with the presence of specific steric substituent and electro-donating and electro-withdrawing groups nearby the pyridine moiety. The Pharmacophore information shows that the four features used were two AroC feature, one HAc, one AlaC features. The structural variations in the molecular fields at particular regions in the space provide underlying structural requirements and 3D-QSAR models generated give good predictive ability and aid in the design of potent antihypertensive activity.

The impact of fermentation and in vitro digestion on formation angiotensin converting enzyme (ACE) inhibitory peptides from pea proteins

Pea seeds were fermented by Lactobacillus plantarum 299v in monoculture under different time and temperature conditions and the fermented products were digested in vitro under gastrointestinal conditions. After fermentation and digestion ACE inhibitory activity was determined. In all samples after fermentation no ACE inhibitory activity was noted. Potentially antihypertensive peptides were released during in vitro digestion. The highest DH (68.62%) were noted for control sample, although the lowest IC50 value (0.19 mg/ml) was determined for product after 7 days fermentation at 22 °C. The hydrolysate characterised by the highest ACE inhibitory activity was separated on Sephadex G10 and two peptides fractions were obtained. The highest ACE inhibitory activity (IC50=64.04 μg/ml) for the first fraction was noted. This fraction was separated by HPLC and identified by LC-MS/MS and the sequence of peptide derived from pea proteins was determined as KEDDEEEEQGEEE.

LC-MS/MS coupled with QSAR modeling in characterising of angiotensin I-converting enzyme inhibitory peptides from soybean proteins

The importance of soy products in reducing the risk of cardiovascular disease is well documented. Our previous computation study has indicated the presence of several potent ACE inhibitory peptides within soybean proteins which needs to be identified. The aim of the study was to identify ACE inhibitory peptides from soy proteins using LC-MS/MS coupled with quantitative structure-activity relationship (QSAR) model. Soybean protein hydrolysate digested by thermolysin showed an IC50 value of 53.6 μg/mL, decreased slightly to 51.8 μg/mL after adding pepsin, and increased to 115.6 μg/mL after adding trypsin. A total of 34 peptides were characterised from LC-MS/MS. Five novel tripeptides, IVF, LLF, LNF, LSW and LEF, with predicted IC50 values lower than 10 μM were synthesized and validated. The results showed that soybean is an excellent source of ACE inhibitory peptides.

The kallikrein-kinin system as a regulator of cardiovascular and renal function

Autocrine, paracrine, endocrine, and neuroendocrine hormonal systems help regulate cardio-vascular and renal function. Any change in the balance among these systems may result in hypertension and target organ damage, whether the cause is genetic, environmental or a combination of the two. Endocrine and neuroendocrine vasopressor hormones such as the renin-angiotensin system (RAS), aldosterone, and catecholamines are important for regulation of blood pressure and pathogenesis of hypertension and target organ damage. While the role of vasodepressor autacoids such as kinins is not as well defined, there is increasing evidence that they are not only critical to blood pressure and renal function but may also oppose remodeling of the cardiovascular system. Here we will primarily be concerned with kinins, which are oligopeptides containing the aminoacid sequence of bradykinin. They are generated from precursors known as kininogens by enzymes such as tissue (glandular) and plasma kallikrein. Some of the effects of kinins are mediated via autacoids such as eicosanoids, nitric oxide (NO), endothelium-derived hyperpolarizing factor (EDHF), and/or tissue plasminogen activator (tPA). Kinins help protect against cardiac ischemia and play an important part in preconditioning as well as the cardiovascular and renal protective effects of angiotensin-converting enzyme (ACE) and angiotensin type 1 receptor blockers (ARB). But the role of kinins in the pathogenesis of hypertension remains controversial. A study of Utah families revealed that a dominant kallikrein gene expressed as high urinary kallikrein excretion was associated with a decreased risk of essential hypertension. Moreover, researchers have identified a restriction fragment length polymorphism (RFLP) that distinguishes the kallikrein gene family found in one strain of spontaneously hypertensive rats (SHR) from a homologous gene in normotensive Brown Norway rats, and in recombinant inbred substrains derived from these SHR and Brown Norway rats this RFLP cosegregated with an increase in blood pressure. However, humans, rats and mice with a deficiency in one or more components of the kallikrein-kinin-system (KKS) or chronic KKS blockade do not have hypertension. In the kidney, kinins are essential for proper regulation of papillary blood flow and water and sodium excretion. B2-KO mice appear to be more sensitive to the hypertensinogenic effect of salt. Kinins are involved in the acute antihypertensive effects of ACE inhibitors but not their chronic effects (save for mineralocorticoid-salt-induced hypertension). Kinins appear to play a role in the pathogenesis of inflammatory diseases such as arthritis and skin inflammation; they act on innate immunity as mediators of inflammation by promoting maturation of dendritic cells, which activate the body's adaptive immune system and thereby stimulate mechanisms that promote inflammation. On the other hand, kinins acting via NO contribute to the vascular protective effect of ACE inhibitors during neointima formation. In myocardial infarction produced by ischemia/reperfusion, kinins help reduce infarct size following preconditioning or treatment with ACE inhibitors. In heart failure secondary to infarction, the therapeutic effects of ACE inhibitors are partially mediated by kinins via release of NO, while drugs that activate the angiotensin type 2 receptor act in part via kinins and NO. Thus kinins play an important role in regulation of cardiovascular and renal function as well as many of the beneficial effects of ACE inhibitors and ARBs on target organ damage in hypertension.

The role of the renin-angiotensin system in the development of insulin resistance in skeletal muscle

The canonical renin-angiotensin system (RAS) involves the initial action of renin to cleave angiotensinogen to angiotensin I (ANG I), which is then converted to ANG II by the angiotensin converting enzyme (ACE). ANG II plays a critical role in numerous physiological functions, and RAS overactivity underlies many conditions of cardiovascular dysregulation. In addition, ANG II, by acting on both endothelial and myocellular AT1 receptors, can induce insulin resistance by increasing cellular oxidative stress, leading to impaired insulin signaling and insulin-stimulated glucose transport activity. This insulin resistance associated with RAS overactivity, when coupled with progressive ß-cell dysfunction, eventually leads to the development of type 2 diabetes. Interventions that target RAS overactivity, including ACE inhibitors, ANG II receptor blockers, and, most recently, renin inhibitors, are effective both in reducing hypertension and in improving whole-body and skeletal muscle insulin action, due at least in part to enhanced Akt-dependent insulin signaling and insulin-dependent glucose transport activity. ANG-(1-7), which is produced from ANG II by the action of ACE2 and acts via Mas receptors, can counterbalance the deleterious actions of the ACE/ANG II/AT1 receptor axis on the insulin-dependent glucose transport system in skeletal muscle. This beneficial effect of the ACE2/ANG-(1-7)/Mas receptor axis appears to depend on the activation of Akt. Collectively, these findings underscore the importance of RAS overactivity in the multifactorial etiology of insulin resistance in skeletal muscle, and provide support for interventions that target the RAS to ameliorate both cardiovascular dysfunctions and insulin resistance in skeletal muscle tissue.

Angiotensin I-converting enzyme inhibitory peptides derived from bovine casein and identified by MALDI-TOF-MS/MS

BACKGROUND

Hypertension is a major and common threat to the health of individuals around the world. Although agents such as captopril have been shown to regulate high blood pressure effectively, they bring unfavourable side effects such as dry cough and angioedema. If angiotensin I-converting enzyme (ACE) inhibitors derived from natural substances such as milk proteins can be shown to be safe and efficient at managing hypertension, such inhibitors will be a valuable auxiliary to agents such as captopril.

RESULTS

Low-molecular-weight casein-derived peptides hydrolysed by cell envelope proteinase of Lactobacillus casei subsp. casei (ATCC 15008) showed quite high ACE-inhibitory activity. The peptide fraction from α-casein with molecular weight between 5 and 10 kDa showed the highest ACE-inhibitory activity of 82.35%, with a 50% inhibition concentration (IC50 ) of 2.36 mg mL(-1). Peptides from β-casein exhibited lower ACE-inhibitory activity (56.67%, IC50 4.00 mg mL(-1)). Three distinct peptide sequences derived from α-casein (α(s1) -cn f95-105, f106-115 and f148-166) were identified using two-dimensional gel electrophoresis coupled with matrix-assisted laser desorption/ionisation time-of-flight tandem mass spectrometry.

CONCLUSION

This work investigated the ACE-inhibitory properties of casein-derived peptides. Three distinct peptide sequences derived from α-casein were identified. Characterisation of such peptides furthers the investigation of casein-derived ACE-inhibitory peptides from fermented dairy products.

A modern understanding of the traditional and nontraditional biological functions of angiotensin-converting enzyme

Angiotensin-converting enzyme (ACE) is a zinc-dependent peptidase responsible for converting angiotensin I into the vasoconstrictor angiotensin II. However, ACE is a relatively nonspecific peptidase that is capable of cleaving a wide range of substrates. Because of this, ACE and its peptide substrates and products affect many physiologic processes, including blood pressure control, hematopoiesis, reproduction, renal development, renal function, and the immune response. The defining feature of ACE is that it is composed of two homologous and independently catalytic domains, the result of an ancient gene duplication, and ACE-like genes are widely distributed in nature. The two ACE catalytic domains contribute to the wide substrate diversity of ACE and, by extension, the physiologic impact of the enzyme. Several studies suggest that the two catalytic domains have different biologic functions. Recently, the X-ray crystal structure of ACE has elucidated some of the structural differences between the two ACE domains. This is important now that ACE domain-specific inhibitors have been synthesized and characterized. Once widely available, these reagents will undoubtedly be powerful tools for probing the physiologic actions of each ACE domain. In turn, this knowledge should allow clinicians to envision new therapies for diseases not currently treated with ACE inhibitors.

Optimization of peptic hydrolysis parameters for the production of angiotensin I-converting enzyme inhibitory hydrolysate from Acetes chinensis through Plackett-Burman and response surface methodological approaches

BACKGROUND

Angiotensin I-converting enzyme (ACE) plays an important physiological role in regulating blood pressure. The elevation of blood pressure could be suppressed by inhibiting ACE. ACE inhibitory peptides derived from food proteins could exert antihypertensive effects without side effects. Acetes chinensis is a marine shrimp suitable for the production of ACE inhibitory peptides. The principal objective of this study was to screen for the significant variables, and further to optimize the levels of the selected variables, for the enzymatic production of ACE inhibitory peptides from Acetes chinensis.

RESULTS

Plackett-Burman design and response surface methodology were employed to optimize the peptic hydrolysis parameters of Acetes chinensis to obtain a hydrolysate with potent ACE inhibitory activity. The peptic hydrolysis variables were subject to a Plackett-Burman design for screening the main factors. The selected significant parameters such as pH, hydrolysis temperature and enzyme/substrate (E/S) ratio were further optimized using a central composite design. The optimized conditions were: pH 2.5, hydrolysis temperature 45 °C, E/S ratio 17 800 U kg(-1) shrimp and substrate concentration 200 g L(-1). The results showed that 3-5 h hydrolysis could result in a hydrolysate with ACE inhibition IC(50) of 1.17 mg mL(-1) and a high DH of 25-27%.

CONCLUSION

Plackett-Burman design and RSM performed well in the optimization of peptic hydrolysis parameters of Acetes chinensis to produce hydrolysate with ACE inhibitory activity. A hydrolysate with potent ACE inhibitory activity and high degree of hydrolysis was obtained, so that the yield of ACE inhibitory peptides in it was high.

Atherosclerotic renal artery stenosis--diagnosis and treatment

Renal artery stenosis (RAS) is characterized by a heterogeneous group of pathophysiologic entities, of which fibromuscular dysplasia and atherosclerotic RAS (ARAS) are the most common. Whether and which patients should undergo revascularization for ARAS is controversial. The general consensus is that all patients with ARAS should receive intensive medical treatment. The latest randomized clinical trials have increased confusion regarding recommendations for revascularization for ARAS. Although revascularization is not indicated in all patients with ARAS, experts agree that it should be considered in some patients, especially those with unstable angina, unexplained pulmonary edema, and hemodynamically significant ARAS with either worsening renal function or with difficult to control hypertension. A search of the literature was performed using PubMed and entering the search terms renal artery stenosis, atherosclerotic renal artery stenosis, and renal artery stenosis AND hypertension to retrieve the most recent publications on diagnosis and treatment of ARAS. In this review, we analyze the pathways related to hypertension in ARAS, the optimal invasive and noninvasive modalities for evaluating the renal arteries, and the available therapies for ARAS and assess future tools and algorithms that may prove useful in evaluating patients for renal revascularization therapy.

Increased risk of myocardial infarction associated with angiotensin-converting enzyme gene polymorphism is age dependent

The angiotensin-converting enzyme (ACE) gene is a candidate genetic locus for coronary artery disease (CAD). Studies investigating the relationship between the ACE-insertion/deletion (I/D) gene polymorphism and myocardial infarction (MI) have been inconsistent. The authors hypothesized that age may be an important modulating factor in this relationship. ACE-I/D allele and genotype distribution was determined in 3 groups: 104 men with a first MI at a young age (≤45 years old), 271 healthy young men (≤30 years old), and 28 healthy elderly men (>65 years old). All participants were French descendants from Quebec City, Canada. Frequency distribution of the ACE alleles and genotypes was similar among the healthy young, the healthy elderly, and the MI patients (P > .05). However, when considering the age at the time of the MI (≤40, ≤35, or ≤30 years old), a significant age-dependent effect with the prevalence of the ACE-DD genotype was found, as it increased by 22%, 61%, and 157%, respectively, compared with the healthy young group (P < .05). Similar observations were obtained versus the healthy elderly men (P < .05). The ACE-I/D polymorphism seems to be a genetic risk factor for MI in young men and becomes an important modulator of MI risk at a young age.

No altered blood pressure and serum markers of oxidative stress after a long time dietary fish oil in the genetically 9 month-old type-2 diabetes Zucker rat

In this study, we investigated the effect of a high n-3 fatty acid diet (eicosapentaenoic and docosahexaenoic acids) in Zucker obese and lean rats on blood pressure in association with physiological parameters, serum biochemistry and oxidative stress analysis. After 150 days of treatment, dietary fish oil supplementation in Zucker obese rats (9 months of age) reduces bodyweight gain and serum triglyceridemia and nitrite levels, increases serum glucose and angiotensin converting enzyme activity, but does not alter blood pressure, cholesterol levels and serum markers of oxidative stress (malondialdehyde, glutathione), compared to the Zucker rats fed control diet. According to these results, we can consider that after 150 days of treatment, fish oil is not enough to regulate parameters involved in the metabolic syndrome, such as cholesterolemia and blood pressure, in a 9 month-old genetically type-2 diabetes rat.

Influence of degree of hydrolysis on functional properties and angiotensin I-converting enzyme-inhibitory activity of protein hydrolysates from cuttlefish (Sepia officinalis) by-products

BACKGROUND

In Tunisia the cuttlefish-processing industry generates large amounts of solid wastes. These wastes, which may represent 35% of the original material and constitute an important source of proteins, are discarded without any attempt at recovery. This paper describes some functional properties and the angiotensin I-converting enzyme (ACE)-inhibitory activity of protein hydrolysates prepared by hydrolysis of cuttlefish (Sepia officinalis) by-products with crude enzyme extract from Bacillus licheniformis NH1.

RESULTS

Cuttlefish by-product protein hydrolysates (CPHs) with different degrees of hydrolysis (DH 5, 10 and 13.5%) were prepared. All CPHs contained 750-790 g kg(-1) proteins. Solubility, emulsifying capacity and water-holding capacity increased while fat absorption and foaming capacity decreased with increasing DH. All hydrolysates showed greater fat absorption than the water-soluble fraction from undigested cuttlefish by-product proteins and casein. CPHs were also analysed for their ACE-inhibitory activity. CPH3 (DH 13.5%) displayed the highest ACE inhibition (79%), with an IC(50) value of 1 mg mL(-1).

CONCLUSION

Hydrolysis of cuttlefish by-product proteins with alkaline proteases from B. licheniformis resulted in a product with excellent solubility over a wide pH range and high ACE-inhibitory activity. This study suggests that CPHs could be utilised to develop functional foods for prevention of hypertension.