Plasma Angiotensin I-converting Enzyme Levels Research Articles

Strong Association Between Angiotensin I-Converting Enzyme I/D Polymorphism and Unexplained Recurrent Miscarriage of Chinese Women—A Case–Control Study

The patients with recurrent miscarriage (RM) undergo multiple diagnostic tests to detect parental chromosomal anomalies, maternal thrombophilic, endocrine, or immunological disorders, and over 50% of the cases with RM are classified as idiopathic unexplained RM (URM). Angiotensin I-converting enzyme (ACE) is proposed to be a candidate gene in many common diseases, and the plasma ACE levels was associated with an insertion (I)/deletion (D) polymorphism involving about 287 bp situated in intron 16 of the ACE gene, the so-called ACE/ID polymorphism. In this study, we have estimated the ACE I/D polymorphism within a cohort of Chinese patients with URM. There were significant differences both in allele and genotype distribution between patients with URM and healthy controls. The association to URM reached significant both in dominate (1.63-fold, D allele) and in recessive mode (1.76-fold, DD genotype). To our knowledge, the present study is the first to establish the association between ACE I/D polymorphism and the development of URM and indicates that the D allele of the polymorphism possibly be a risk factor for URM in Chinese population.

Neutral endopeptidase and angiotensin I converting enzyme insertion/deletion gene polymorphism in humans.

Neutral endopeptidase (NEP) hydrolyses angiotensins (Ang) I and II and generates angiotensin-(1-7) [Ang-(1-7)]. In humans, the insertion/deletion (I/D) angiotensin-I converting enzyme (ACE) gene polymorphism determined plasma ACE levels by 40%. In rats, a similar polymorphism determines ACE levels which are inversely associated to NEP activity. The objective of this study is to evaluate the relationship between ACE expression and plasma NEP activity in normotensive subjects and in hypertensive patients. In total, 58 consecutive patients with hypertension, evaluated in our Hypertension Clinic, were compared according to their ACE I/D genotypes with 54 control subjects in terms of both plasma ACE activity and NEP activities. Plasma ACE activity was elevated 51 and 70% in both DD ACE groups (normotensives and hypertensives) compared with their respective ID and II ACE groups (P<0.001). A significant effect of the ACE polymorphism and of the hypertensive status on ACE activity was observed (P<0.001). In normotensive DD ACE subjects, NEP activity was 0.30+/-0.02 U/ml, whereas in the normotensive II ACE and in the normotensive ID ACE subjects NEP activity was increased 65 and 48%, respectively (P<0.001). In the hypertensive DD ACE patients, NEP activity was 0.47+/-0.03 U/mg. An effect of the I/D ACE genotypes on NEP activity (P<0.04) and an interaction effect between the I/D ACE genotype and the hypertensive status were also observed (P<0.001). These results are consistent with a normal and inverse relationship between the ACE polymorphism and NEP activity in normotensive humans (as is also observed in rats). This normal relationship is not observed in hypertensive patients.

Angiotensin-converting enzyme insertion/deletion polymorphism and risk of restenosis after directional coronary atherectomy followed by stent implantation.

The D allele of the insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene is associated with higher plasma and tissue ACE levels, which enhance the stimulus for neo-intimal hyperplasia. Plaque debulking before stenting reduces the plaque-related determinants of in-stent restenosis and provides an ideal clinical model for studying neointimal hyperplasia. We prospectively studied 113 consecutive patients undergoing elective DCA followed by stent implantation. The presence of I/D in ACE genome DNA was analysed by means of polymerase chain reaction. Follow-up coronary angiography was performed 6-12 months after DCA, and all of the angiograms were quantitatively analysed. The baseline clinical and angiographic characteristics of the patients with a D/D (33%), I/D (52%) and I/I (15%) genotype were well balanced. There were no significant differences in minimal lumen diameter before and after the procedure or at follow-up, and no significant differences in acute gain, late loss or the loss index. Our results indicate that ACE I/D polymorphism does not influence the risk of developing angiographic restenosis in patients undergoing DCA followed by stent implantation.

Angiotensin I-converting enzyme gene polymorphism and drug response.

An insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene has been described in chromosome 17q23 of the human genome. Subjects with the genotype DD have markedly higher plasma ACE levels than those with genotype II; although ACE concentration in plasma is not rate-limiting for the production of angiotensin II, it has been suggested that the renin-angiotensin system may have an enhanced role in cardiovascular homeostasis in subjects with DD genotype or D allele. Meta-analysis confirmed the association of the D allele with an increased risk of myocardial infarction and stroke, but these relations are still uncertain with longevity and renal deterioration. Otherwise, I allele seems to be related with an improved response to physical training. The I/D polymorphism of the ACE gene is not a marker for any form of hypertension, though some conflicting results have been described. Nevertheless this polymorphism may have an influence on the antihypertensive response, particularly when using ACE inhibitors (ACEI). For example, blood pressure normalization with captopril in patients suffering from cardiac failure would be more effective in II genotype; conversely, both regression in left ventricular hypertrophy and improvement in diastolic filling would be greater after long-term treatment with enalapril in patients with essential hypertension and DD genotype. Conflicting results were also described using ACEI as a renoprotective therapy. This review therefore supports the justification for further evaluation in appropriately powered studies.

Genetic variation in the renin-angiotensin system and athletic performance.

The D allele at the angiotensin-I-converting enzyme (ACE)-insertion/deletion polymorphism has been associated with an increased risk of developing several pathological processes, such as coronary heart disease and ventricular hypertrophy. Individuals with the DD genotype show a significantly increased left-ventricular mass in response to physical training, compared to the II genotype (which would be associated with the lowest plasma ACE levels) and the ID genotype. The II genotype has been linked to a greater anabolic response. In accordance with a role for ACE in the response to rigorous physical training, a higher frequency of the I allele has been reported to exist among elite rowers and high-altitude mountaineers. Sixty elite (professional) athletes (25 cyclists, 20 long-distance runners, and 15 handball players), and 400 healthy controls were genotyped for the DNA polymorphisms of the ACE, angiotensinogen (Ang) and angiotensin receptor type 1 (AT1) genes. Plasma ACE levels showed a strong correlation with the I/D genotype in our population. The I-allele occurred at a significantly higher frequency in athletes compared to controls (P = 0.0009). Gene and genotype frequencies for the Ang and AT1 polymorphisms did not differ between athletes and controls. Since the frequency of the ACE I allele was significantly increased among our elite athletes, we conclude that the ACE polymorphism represents a genetic factor that contributes to the development of an elite athlete.

Genotype-phenotype relationships for the renin-angiotensin-aldosterone system in a normal population.

The renin-angiotensin-aldosterone system plays an important role in blood pressure regulation by influencing salt-water homeostasis and vascular tone. The purpose of the present study was to search for associations of single nucleotide polymorphisms on 3 major candidate genes of this system with the plasma concentrations of the corresponding renin-angiotensin-aldosterone system components considered as quantitative phenotypes. Genotyping was performed in 114 normotensive subjects for different variants of the angiotensinogen (AGT) gene (C-532T, G-6A, M235T), the angiotensin I-converting enzyme (ACE) gene [4656(CT)(2/3)], the aldosterone synthase (CYP11B2), and the type 1 angiotensin II receptor (AT1R) gene (A1166C) by hybridization with allele-specific oligonucleotides (ASO) or enzymatic digestion of polymerase chain reaction products. Plasma levels of AGT, ACE, angiotensin II (Ang II), aldosterone, and immunoreactive active renin were measured according to standard techniques. Platelet binding sites for Ang II were analyzed by the binding of radioiodinated Ang II to purified platelets. B(max) and K(D) values of the Ang II binding sites on platelets of each individual were calculated to examine a possible relationship between these parameters and the AT1R genotype. A highly significant association of the ACE 4656(CT)(2/3) variant with plasma ACE levels was observed (P<0.0001). ANOVA showed a significant effect of the AGT C-532T polymorphism on AGT plasma levels (P=0.017), but no significant effect was detectable with the other AGT polymorphisms tested, such as the G-6A or the M235T. A significant effect association was also found between the C-344T polymorphism of the CYP11B2 gene and plasma aldosterone levels, with the T allele associated with higher levels (P=0.02). No genotype effect of the AT1R A1166C polymorphism was detected either on the B(max) or the K(D) value of the Ang II receptors on platelets.

The Angiotensin-Converting Enzyme (ACE) Gene Insertion/Deletion Dimorphism Tracks with Higher Serum ACE Activities in Both Younger and Older Subjects

The absence of a 287 base pair alu sequence in the ACE gene (D allele) is associated with higher ACE levels than its presence (I allele) in adults. We carried out a case-control study of the ACE*I/D dimorphism in relation to circulating ACE activities to evaluate associations between the two variables in adults, compared to younger (18 years or less) individuals. Genotypes of the ACE*I/D dimorphism were determined on DNA samples from a population of 164 random (unrelated) Emirate nationals, composed of two groups: 112 subjects above 18 years of age (range=20-77 years), and 52 subjects of 18 years or less (range=1-18), and analyzed for putative associations with serum ACE activities. ACE*I/D genotypes of the 164 individuals were determined by assays based on polymerase chain reaction. ACE activities were determined on serum samples of these subjects by colorimetric assays. The D allele was associated with increased ACE values in both adult and younger individuals. Mean ACE activity levels associated with II, ID and DD genotypes, however, were 42%-61% higher in the 18 years and under group of subjects. The ACE*I/D marker accounted for 28% of the variance of the phenomenon determining ACE levels in adults, and for 30% among youngsters. The ACE*I/D dimorphism correlated strongly with circulating ACE activities in both adult and young Emirati subjects, and the corresponding mean ACE activities were significantly higher among the youngsters.

The angiotensin-I converting enzyme (ACE) gene I/D polymorphism and ACE levels in Pima Indians.

An insertion/deletion (I/D) polymorphism of the angiotensin converting enzyme (ACE) gene is associated with plasma ACE levels in white populations. The occurrence of the I/D polymorphism and relationship to ACE levels was examined in a Pima Indian group (n = 305). The frequency of the D allele was lower in Pimas than whites (0.29 v 0.52 respectively). ACE levels were significantly associated with genotype in both groups (p = 0.0001), which accounted for 6.5% of the variation in ACE levels in Pimas and 18% in whites. The association of the I/D polymorphism with ACE levels confirms the relationship across ethnic groups. The low frequency of the D allele in Pima Indians shows that ethnic differences should be accounted for when studying the ACE gene.

Plasma fibronectin and angiotensin-converting enzyme: markers of primary pulmonary injury in burn patients

Plasma fibronectin (FBN) and angiotensin I-converting enzyme (ACE) were prospectively measured in 50 burn patients from the day of admission to day 28 after the trauma with the aim of finding biochemical markers of pulmonary injury by smoke inhalation. Patients were divided into three groups on the basis of fiberoptic bronchoscopy results (group I: healthy lungs; group II: burned lungs; group III: infected lungs). A decrease in FBN concentrations was observed in the three groups but was larger in group II than in the other groups, especially at day 2 ( P < 0.05). A similar profile was observed for plasma ACE activity. Factors other than lung injury may influence plasma FBN and ACE levels, in particular the burned body surface area, an acute event such as septicemia, or outcome. However, repeated measurements of both markers could help in the assessment of lung injury in the follow-up of burn patients.

Relationships Between Angiotensin I Converting Enzyme Gene Polymorphism, Plasma Levels, and Diabetic Retinal and Renal Complications

Insulin-dependent diabetes mellitus (IDDM), cardiovascular morbidity, and vital prognosis are linked to diabetic nephropathy, which is probably determined by renal hemodynamic abnormalities and by a genetic predisposition. Angiotensin I converting enzyme (ACE) regulates systemic and renal circulations through angiotensin II formation and kinins metabolism. Plasma and cellular ACE levels are genetically determined; an insertion/deletion polymorphism of the ACE gene is strongly associated with ACE levels, subjects homozygote for insertion (genotype II) having the lowest plasma values. We studied the relationship between the ACE gene polymorphism or plasma levels and microcirculatory disorders of IDDM through two independent studies: one involved 57 subjects with or without diabetic retinopathy, and the other compared 62 IDDM subjects with diabetic nephropathy to 62 diabetic control subjects with the same characteristics (including retinopathy severity) but with normal kidney function. The ACE genotype distribution was not different in diabetic subjects with or without retinopathy and in a healthy population. Conversely, an imbalance of ACE genotype distribution, with a low proportion of II subjects, was observed in IDDM subjects with diabetic nephropathy compared with their control subjects (P = 0.006). Plasma ACE levels were mildly elevated in all diabetic groups, independently of retinopathy, but they were higher in subjects with nephropathy than in those without nephropathy (P = 0.0022). The II genotype of ACE gene is a marker for reduced risk for diabetic nephropathy.

The Angiotensin I-Converting Enzyme (Kininase II)

The complete amino acid sequence of the human angiotensin I-converting enzyme (ACE) has been determined by protein sequencing of the purified kidney enzyme and cDNA cloning in endothelial cell libraries. The ACE molecule comprises 1,306 amino acids. It possesses a signal peptide of 29 residues cleaved off during maturation. The enzyme is most likely anchored to the plasma membrane by a short transmembrane domain situated near the carboxy-terminal extremity. Interestingly, the molecule presents a high degree of internal homology between two large peptidic domains. Each of these domains contains short sequences identical to zinc binding and active site sequences of other zinc metallopeptidases and therefore bears a putative active site. However, earlier experiments indicate only one zinc atom bound per molecule of ACE. Competitive inhibitors seem to interact with a unique class of high-affinity binding site. These observations may suggest that, despite the duplicated structure of the enzyme, there is only one functional active site per molecule of ACE. The respective role of the two homologous domains in this active site remains to be determined. A single gene coding for ACE is present in humans, transcribed as a 4.3-kilobase mRNA species in endothelial cells. In other studies, evidence for a genetic polymorphism in plasma ACE levels has been obtained by analyzing a large group of "healthy" nuclear families. A familial association of plasma ACE levels was observed. A major gene effect can possibly explain part of the interindividual variability observed in this enzyme.

Angiotensin-I-converting enzyme in germinomas.

Angiotensin-I-converting enzyme (ACE) was detected in 18 germinomas, both of testicular or extratesticular localization, and studied by immunohistochemical methods using specific polyclonal antibodies and by enzyme activity measurements. ACE was also detected in normal human germ cells. On the other hand, it was not present in other types of testicular tumors. Biochemical studies and immunohistochemical findings suggest that at least part of the enzyme is membrane bound. Plasma ACE levels appeared to be normal, indicating that measurement of plasma ACE levels in germinomas would be of little help for the diagnosis and follow-up of patients. However, the apparent specificity of ACE detection in germinomas among germ cell tumors might help in histologic diagnosis, especially for tumors of extragonadal localization.