Angiotensin converting enzyme (ACE) and ACE2 bind integrins and ACE2 regulates integrin signalling

The angiotensin converting enzymes (ACEs) are the key catalytic components of the renin-angiotensin system, mediating precise regulation of blood pressure by counterbalancing the effects of each other. Inhibition of ACE has been shown to improve pathology in cardiovascular disease, whilst ACE2 is cardioprotective in the failing heart. However, the mechanisms by which ACE2 mediates its cardioprotective functions have yet to be fully elucidated. Here we demonstrate that both ACE and ACE2 bind integrin subunits, in an RGD-independent manner, and that they can act as cell adhesion substrates. We show that cellular expression of ACE2 enhanced cell adhesion. Furthermore, we present evidence that soluble ACE2 (sACE2) is capable of suppressing integrin signalling mediated by FAK. In addition, sACE2 increases the expression of Akt, thereby lowering the proportion of the signalling molecule phosphorylated Akt. These results suggest that ACE2 plays a role in cell-cell interactions, possibly acting to fine-tune integrin signalling. Hence the expression and cleavage of ACE2 at the plasma membrane may influence cell-extracellular matrix interactions and the signalling that mediates cell survival and proliferation. As such, ectodomain shedding of ACE2 may play a role in the process of pathological cardiac remodelling.     

Angiotensin converting enzyme 2 (ACE2) activity in fetal calf serum: implications for cell culture research

Cell culture experiments often employ the use of culture media that contain fetal calf serum (FCS). The angiotensin peptides angiotensin II and angiotensin 1–7 have opposing effects with angiotensin converting enzyme 2 (ACE2) being the enzyme predominantly responsible for generating angiotensin 1–7 from angiotensin II. The effect of FCS on angiotensin peptides has not previously been described. We have shown that FCS has ACE2 enzyme activity capable of degrading angiotensin II and generating angiotensin 1–7. Researchers should be aware that FCS possesses ACE2 activity and that heat-treating FCS to 56 °C only partially inhibits this enzyme activity, whereas heat-treating to 70 °C completely abolishes ACE2 activity.     

Pathogenesis of hyperglycemia in diabetes mellitus type II (insulin-independent)

The most important causes of hyperglycaemia in the course of diabetes mellitus type 2 are discussed. Those include: insulin secretion disorders, resistance to the insulin and overproduction of glucose in the liver. Affected secretory function of B cells in the pancreatic islets results, first of all, from the primary genetic error and secondary regulatory disorders, chiefly hyperglycaemia. Resistance to the insulin caused by decreased insulin activity in the muscle tissue and adipose tissue includes so-called receptor and postreceptor defects. Mechanism of these disorders is partially explained. Overproduction of glucose in the liver is probably secondary to the above metabolic disturbances and decides on the basic hyperglycaemia. Pathogenetic aspects of the insulin independent diabetes mellitus therapy with particular reference to the role of sulfonylurea derivatives are also discussed.     

Beneficial effects of angiotensin converting enzyme inhibition on renal function in patients with diabetic nephropathy.

The effects of angiotensin converting enzyme inhibition with captopril were investigated in patients with diabetic nephropathy and hypertension. After nine days'' treatment with captopril glomerular filtration rate was unchanged in 13 patients, whereas renal plasma flow had increased from 265 to 302 ml/min/1.73 m2 body surface area (p less than 0.05) and the filtration fraction had decreased from 14.3 to 12.8% (p less than 0.025). During two years'' treatment with captopril in 14 patients the mean arterial blood pressure had fallen by 5 mm Hg (p less than 0.005) and the deterioration in glomerular filtration rate had decreased from 10.3 to 2.4 ml/min/year (p less than 0.005). There was no correlation between the fall in blood pressure and the reduction in the deterioration of glomerular filtration rate. These findings suggest that the effects of angiotensin converting enzyme inhibition on renal haemodynamics protect renal function. Inhibitors of angiotensin converting enzyme should be considered for lowering blood pressure in patients with diabetic nephropathy.     

Angiotensin I converting enzyme (ACE) inhibitory peptides from salmon byproduct protein hydrolysate by Alcalase hydrolysis

Angiotensin I converting enzyme (ACE) inhibitory peptides were produced from salmon byproduct proteins via enzymatic hydrolysis using Alcalase, flavourzyme, neutrase, pepsin, protamex and trypsin. Among them, Alcalase hydrolysate showed the highest ACE inhibitory activity, thus ACE inhibitory peptides were purified using consecutive chromatography. The purified ACE inhibitory peptides were identified to be Val-Trp-Asp-Pro-Pro-Lys-Phe-Asp (P1), Phe-Glu-Asp-Tyr-Val-Pro-Leu-Ser-Cys-Phe (P2), and Phe-Asn-Val-Pro-Leu-Tyr-Glu (P4) by time of flight-mass spectrometry/mass spectrometry (TOF-MS) analysis. The IC₅₀ values against ACE activity were 9.10 μM (P1), 10.77 μM (P2) and 7.72 μM (P4). The inhibition mode of P1, P2 and P4 was analyzed using the Lineweaver–Burk plots, demonstrating P1 to be a non-competitive inhibitor, P2 and P4 having a mixed inhibition mode. Taken together, the salmon byproduct protein hydrolysate and/or its active peptides can be used in foods for its benefits against hypertension and related diseases.     

Inhibition of angiotensin converting enzyme (ACE) activity by flavan-3-ols and procyanidins

It was determined that flavan-3-ols and procyanidins have an inhibitory effect on angiotensin I converting enzyme (ACE) activity, and the effect was dependent on the number of epicatechin units forming the procyanidin. The inhibition by flavan-3-ols and procyanidins was competitive with the two substrates assayed: N-hippuryl-L-histidyl-L-leucine (HHL) and N-[3-(2-furyl)acryloyl]-L-phenylalanylglycylglycine (FAPGG). Tetramer and hexamer fractions were the more potent inhibitors, showing Ki of 5.6 and 4.7 microM, respectively. As ACE is a membrane protein, the interaction of flavanols and procyanidins with the enzyme could be related to the number of hydroxyl groups on the procyanidins, which determine their capacity to be adsorbed on the membrane surface.     

Serum N-acetyl-beta-D-glucosaminidase (NAG) activity in patients with diabetes mellitus with reference to diabetic microangiopathy]

In 110 diabetics type I and type II and in 30 control subjects the total serum activity of NAG as well as of its isoenzymatic forms A and B was determined. In cases with diabetic nephropathy the GFR and serum creatinine was also analysed. It was found that NAG activity is correlated to the degree of clinical symptoms of diabetic vascular changes. Therefore it could be suggested that NAG plays a role in development of microangiopathy. NAG determination may also serve as an index differentiating the diabetic microangiopathy from other forms of microvessels.     

Angiotensin I-converting enzyme (ACE) activity and expression in rat central nervous system after sleep deprivation

Proteases are essential either for the release of neuropeptides from active or inactive proteins or for their inactivation. Neuropeptides have a fundamental role in sleep-wake cycle regulation and their actions are also likely to be regulated by proteolytic processing. Using fluorescence resonance energy transfer substrates, specific protease inhibitors and real-time PCR we demonstrate changes in angiotensin I-converting enzyme (ACE) expression and proteolytic activity in the central nervous system in an animal model of paradoxical sleep deprivation during 96 h (PSD). Male rats were distributed into five groups (PSD, 24 h, 48 h and 96 h of sleep recovery after PSD and control). ACE activity and mRNA levels were measured in hypothalamus, hippocampus, brainstem, cerebral cortex and striatum tissue extracts. In the hypothalamus, the significant decrease in activity and mRNA levels, after PSD, was only totally reversed after 96 h of sleep recovery. In the brainstem and hippocampus, although significant, changes in mRNA do not parallel changes in ACE specific activity. Changes in ACE activity could affect angiotensin II generation, angiotensin 1-7, bradykinin and opioid peptides metabolism. ACE expression and activity modifications are likely related to some of the physiological changes (cardiovascular, stress, cognition, metabolism function, water and energy balance) observed during and after sleep deprivation.     

Circadian rhythm of the angiotensin converting enzyme (ACE) activity in serum of healthy adult subjects

Angiotensin converting enzyme (ACE) activity was measured in the peripheral serum of 10 healthy, diurnally-active and nocturnally-resting adult subjects (5 women and 5 men). Blood was drawn serially at 4-h intervals throughout a 24-h cycle with the subjects hospitalized and synchronized. They were not kept in recumbency. Data were evaluated by conventional statistical analysis and by single- and population mean- cosinor procedures. A low-amplitude circadian rhythm was statistically validated for the group. Acrophase was located in the afternoon, at about 1630. The recognition that ACE activity oscillates physiologically in the peripheral blood according to a circadian rhythm may serve to amplify the clinical use of ACE measurements.     

Effect of angiotensin converting enzyme inhibitors on 1.25-(OH)2 D levels of hypertensive patients. Relationship with ACE polymorphisms.

BACKGROUND: The effect of angiotensin converting enzyme inhibitors (ACEIs) on 1.25-dihydroxyvitamin D [1.25-(OH)2D] levels has not been studied. The purpose of this study is to assess the relationship between 1.25-dihydroxyvitamin D levels and I/D angiotensin-converting enzyme polymorphism (ACE) in hypertensive patients. MATERIALS AND METHODS: The study included 60 individuals (31 females and 29 males) with systolic and/or diastolic hypertension. The 25-hydroxyvitamin D levels were measured by HPLC and the 1.25-(OH)2 D was determined by RIA. ACE polymorphism was analyzed by Polymerase Chain Reaction (PCR) using a modification of the original method described by Rigat. RESULTS: Treatment with ACEIs produced an increase in total calcium (p=0.003) and a decrease in the 1.25-(OH)2 D (p=0.0001). No relationship between final calcium and 1.25-(OH)2 D (r=-0.171, p=0.198) was observed. When the effects of enalapril and quinapril were analyzed separately, the results were similar. When the patients were divided according to genotype, the decrease in 1.25-(OH)2 D was observed only in patients with D allele, genotype Ins/Del (69+/-23 vs. 48+/-19, p=0.021 ) and in those of genotype Del/Del (64+/-19 vs. 17, p=0.004). CONCLUSION: The ACE inhibitors in combination with the presence of the DD genotype decrease the level of 1.25-(OH)2 D. There was no difference between enalapril and quinapril treated groups.     

Adiponectin gene polymorphisms in Egyptian type 2 diabetes mellitus patients with and without diabetic nephropathy

Recently, several reports addressed the associations of adiponectin (ADIPOQ) gene polymorphisms with abnormal adiponectin serum levels, type 2 diabetes mellitus (T2DM), and diabetic nephropathy (DN); however, results are inconsistent. This study aimed to investigate the possible association of ADIPOQ gene polymorphisms with T2DM and/or DN and whether they affect serum adiponectin levels in Egyptian population. Two hundred and ninety-six T2DM patients (100 normoalbuminuric patients, 103 microalbuminuric patients, and 93 macroalbuminuric patients) and 209 controls were enrolled in the present study. Polymorphisms of +45, ?11391, and +276 of the ADIPOQ gene were detected using polymerase chain reaction restriction fragment length polymorphism. Serum adiponectin was measured using ELISA. Our results revealed that ADIPOQ +45 TG and GG genotypes and G allele were significantly associated with T2DM, micro/macroalbuminuria, and decreased serum adiponectin level. ADIPOQ ?11391 AA genotype frequency was significantly increased in T2DM group. Moreover, GA and AA genotypes and A allele of ADIPOQ ?11391 were significantly associated with susceptibility to macroalbuminuria despite increased serum adiponectin concentrations. While, ADIPOQ +276 TT genotype and T allele were protective factors regarding the susceptibility to T2DM and micro/macroalbuminuria, and they were significantly associated with increased adiponectin levels. We observed also that the decrease of the serum Adiponectin level was accompanied by an insulin resistance, albuminuria, as well as an increase of serum creatinine. We concluded that ADIPOQ +45; ADIPOQ ?11391 gene polymorphisms are associated with T2DM and/or DN in Egyptian population. While, ADIPOQ +276 gene polymorphism is a protective factor regarding T2DM and/or DN susceptibility.     

Circulating levels of asprosin and its association with insulin resistance and renal function in patients with type 2 diabetes mellitus and diabetic nephropathy

Molecular Biology Reports - Adipokines play an important role in the development of type 2 diabetes mellitus (T2DM) and its complications like nephropathy. Asprosin is a newly discovered adipokine...     

Angiotensin I converting enzyme (ACE) inhibitory peptide derived from the sauce of fermented blue mussel, Mytilus edulis

The angiotensin I converting enzyme (ACE) inhibitory activity of fermented blue mussel sauce (FBMS) was investigated. Blue mussels were fermented with 25% NaCl (w/w) at 20 degrees C for 6 months and the resultant mixture was passed through a 40-mesh sieve, desalted using an electrodialyzer and then lyophilized. The IC(50) value of FBMS for ACE activity was 1.01 mg/ml. An ACE inhibitory peptide was purified from FBMS using Sephadex G-75 gel chromatography, SP-Sephadex C-25 ion exchange chromatography and reversed-phase high-performance liquid chromatography on a C(18) column. The IC(50) value of purified ACE inhibitory peptide was 19.34 microg/ml, and 10 amino acid residues of the N-terminal sequence was EVMAGNLYPG. The purified peptide was evaluated for antihypertensive effect in spontaneously hypertensive rats (SHR) following oral administration. Blood pressure significantly decreased after peptide ingestion. This result suggested that FBMS may have beneficial effects on hypertension.     

Evaluation of glucose utilization in patients with insulin-independent diabetes mellitus by using breathing test

Commonly used clinical and biochemical parameters, such as the content of glucose, insulin, somatotropic hormone, triglycerides, lactate, pyruvate, and free fatty acids (FFA) in blood of practically healthy subjects and in patients with insulin-independent diabetes mellitus (IIDM), were compared with the parameters obtained by mass-spectrometric analysis of 13CO2 in expired air after 13C-glucose loading. It was shown that, as opposed to healthy subjects, the content of blood glucose and free fatty acids in patients with IIDM increased, the level of glucose dropped in progression upon short-term fasting, and the concentration of lactate changed both upon fasting and after the administration of small test doses of glucose. The use of the 13C-glucose breathing test (13C-GBT), which presupposes the loading of safe small doses of glucose enriched in 13C-isotope permitted one to reveal a number of novel quantitative diagnostic criteria for the evaluation of glucose metabolism in patients with IIDM: a decrease in the rate of 13C withdrawal as a constituent of expired carbon dioxide after the administration of 13C-glucose; a reduction in the amount of exogenous glucose metabolized to carbon dioxide; and increased oxidation of endogenous substrates participating in carbon dioxide formation. Small glucose loads proposed by the authors in 13C-GBT are safe for patients with diabetes mellitus and have no effect on the level of blood glucose in healthy persons. The parameters determined by noninvasive 13C-GBT are more sensitive for diagnosis than commonly used biochemical characteristics of blood in patients with IIDM. The diagnostic criteria obtained allow the prediction of the maximum prohibited glucose loading for every patient.     

Modulation of metabolic control by angiotensin converting enzyme (ACE) inhibition

Angiotensin converting enzyme (ACE) inhibitors are a widely used intervention for blood pressure control, and are particularly beneficial in hypertensive type 2 diabetic subjects with insulin resistance. The hemodynamic effects of ACE inhibitors are associated with enhanced levels of the vasodilator bradykinin and decreased production of the vasoconstrictor and growth factor angiotensin II (ATII). In insulin-resistant conditions, ACE inhibitors can also enhance whole-body glucose disposal and glucose transport activity in skeletal muscle. This review will focus on the metabolic consequences of ACE inhibition in insulin resistance. At the cellular level, ACE inhibitors acutely enhance glucose uptake in insulin-resistant skeletal muscle via two mechanisms. One mechanism involves the action of bradykinin, acting through bradykinin B(2) receptors, to increase nitric oxide (NO) production and ultimately enhance glucose transport. A second mechanism involves diminution of the inhibitory effects of ATII, acting through AT(1) receptors, on the skeletal muscle glucose transport system. The acute actions of ACE inhibitors on skeletal muscle glucose transport are associated with upregulation of insulin signaling, including enhanced IRS-1 tyrosine phosphorylation and phosphatidylinositol-3-kinase activity, and ultimately with increased cell-surface GLUT-4 glucose transporter protein. Chronic administration of ACE inhibitors or AT(1) antagonists to insulin-resistant rodents can increase protein expression of GLUT-4 in skeletal muscle and myocardium. These data support the concept that ACE inhibitors can beneficially modulate glucose control in insulin-resistant states, possibly through a NO-dependent effect of bradykinin and/or antagonism of ATII action on skeletal muscle.     

Angiotensin converting enzyme (ACE) and neprilysin hydrolyze neuropeptides: a brief history, the beginning and follow-ups to early studies

Our investigations started when synthetic bradykinin became available and we could characterize two enzymes that cleaved it: kininase I or plasma carboxypeptidase N and kininase II, a peptidyl dipeptide hydrolase that we later found to be identical with the angiotensin I converting enzyme (ACE). When we noticed that ACE can cleave peptides without a free C-terminal carboxyl group (e.g., with a C-terminal nitrobenzylamine), we investigated inactivation of substance P, which has a C-terminal Met(11)-NH(2). The studies were extended to the hydrolysis of the neuropeptide, neurotensin and to compare hydrolysis of the same peptides by neprilysin (neutral endopeptidase 24.11, CD10, NEP). Our publication in 1984 dealt with ACE and NEP purified to homogeneity from human kidney. NEP cleaved substance P (SP) at Gln(6)-Phe(7), Phe(7)[see text]-Phe(8), and Gly(9)-Leu(10) and neurotensin (NT) at Pro(10)-Tyr(11) and Tyr(11)-Ile(12). Purified ACE also rapidly inactivated SP as measured in bioassay. HPLC analysis showed that ACE cleaved SP at Phe(8)-Gly(9) and Gly(9)-Leu(10) to release C-terminal tri- and dipeptide (ratio = 4:1). The hydrolysis was Cl(-) dependent and inhibited by captopril. ACE released only dipeptide from SP free acid. ACE hydrolyzed NT at Tyr(11)-Ile(12) to release Ile(12)-Leu(13). Then peptide substrates were used to inhibit ACE hydrolyzing Fa-Phe-Gly-Gly and NEP cleaving Leu(5)-enkephalin. The K(i) values in microM were as follows: for ACE, bradykinin = 0.4, angiotensin I = 4, SP = 25, SP free acid = 2, NT = 14, and Met(5)-enkephalin = 450, and for NEP, bradykinin = 162, angiotensin I = 36, SP = 190, NT = 39, Met(5)-enkephalin = 22. These studies showed that ACE and NEP, two enzymes widely distributed in the body, are involved in the metabolism of SP and NT. Below we briefly survey how NEP and ACE in two decades have gained the reputation as very important factors in health and disease. This is due to the discovery of more endogenous substrates of the enzymes and to the very broad and beneficial therapeutic applications of ACE inhibitors.     

The peptide network regulated by angiotensin converting enzyme (ACE) in hematopoiesis

The concept of a local bone marrow renin-angiotensin system (RAS) has been introduced and accumulating evidence suggests that the local RAS is actively involved in hematopoiesis. Angiotensin converting enzyme (ACE) is a key player in the RAS and makes the final effector angiotensin II. Besides angiotensin II, ACE also regulates a panel of bioactive peptides, such as substance P, Ac-SDKP and angiotensin 1-7. These peptides have also been individually reported in the regulation of pathways of hematopoiesis. In this setting, an ACE-regulated peptide network orchestrating hematopoiesis has emerged. Here, we focus on this peptide network and discuss the roles of ACE and its peptides in aspects of hematopoiesis. Special attention is given to the recent revelation that ACE is a bona fide marker of hematopoietic stem cells.