Lack of association of angiotensin converting enzyme gene polymorphism or serum enzyme activity with coronary artery disease in Japanese subjects

Endobiogeny: a global approach to systems biology (part 1 of 2)

Endobiogeny is a global systems approach to human biology that may offer an advancement in clinical medicine based in scientific principles of rigor and experimentation and the humanistic principles of individualization of care and alleviation of suffering with minimization of harm. Endobiogeny is neither a movement away from modern science nor an uncritical embracing of pre-rational methods of inquiry but a synthesis of quantitative and qualitative relationships reflected in a systems-approach to life and based on new mathematical paradigms of pattern recognition.

Fine-mapping angiotensin-converting enzyme gene: separate QTLs identified for hypertension and for ACE activity

Angiotensin-converting enzyme (ACE) has been implicated in multiple biological system, particularly cardiovascular diseases. However, findings associating ACE insertion/deletion polymorphism with hypertension or other related traits are inconsistent. Therefore, in a two-stage approach, we aimed to fine-map ACE in order to narrow-down the function-specific locations. We genotyped 31 single nucleotide polymorphisms (SNPs) of ACE from 1168 individuals from 305 young-onset (age ≤40) hypertension pedigrees, and found four linkage disequilibrium (LD) blocks. A tag-SNP, rs1800764 on LD block 2, upstream of and near the ACE promoter, was significantly associated with young-onset hypertension (p = 0.04). Tag-SNPs on all LD blocks were significantly associated with ACE activity (p-value: 10^–16 to <10^–33). The two regions most associated with ACE activity were found between exon13 and intron18 and between intron 20 and 3′UTR, as revealed by measured haplotype analysis. These two major QTLs of ACE activity and the moderate effect variant upstream of ACE promoter for young-onset hypertension were replicated by another independent association study with 842 subjects.

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.

Insertion/deletion polymorphism of the angiotensin-converting enzyme considerably changes postoperative outcome

STUDY OBJECTIVE

To evaluate the influence of insertion/deletion (ID) polymorphism of the angiotensin-converting enzyme (ACE) gene on clinical outcome of cardiac valve surgery.

DESIGN

Prospective, blinded observational study.

SETTING

Operating room and intensive care unit (ICU) of a university hospital.

PATIENTS

110 adult patients requiring elective cardiac valve surgery requiring cardiopulmonary bypass.

MEASUREMENTS

Patients' preoperative data (age, gender, body weight, New York Heart Association score, medication, biochemical data, and comorbid disorders), anesthetic management (blood pressure, heart rate, blood loss and transfusion, and cardiorespiratory complications and their treatment), and postoperative outcome (life-threatening complications, nosocomial infections, reintubation/reoperation, death, and duration of ICU stay and hospitalization) were recorded. ACE ID was detected by gel electrophoresis following conventional polymerase chain reaction. Patients were divided into two groups postoperatively; groups with II and non-II (ID and DD) genotypes, and group differences were analyzed.

MAIN RESULTS

Distribution of ACE ID in II, ID, and DD genotypes was 29%, 59%, and 12%, respectively. The non-II group had significantly greater postoperative blood loss and transfusion (P < 0.05), more common postoperative infections, and longer ICU stay duration than the II group (P < 0.01).

CONCLUSIONS

ACE ID polymorphism is associated with a higher incidence of postoperative complications, including postoperative infections, in patients undergoing cardiac valve surgery.

Impact of ACE and ApoE polymorphisms on myocardial perfusion: correlation with myocardial single photon emission computed tomographic imaging

Coronary artery disease is associated with multiple genetic and environmental risk factors. In this study, we evaluated the correlation of angiotensin l-converting enzyme (ACE) (I/D) and ApoE gene polymorphisms (E2, E3, E4 and g.-219G/T) with myocardial perfusion. We examined 410 patients using exercise-rest myocardial perfusion single photon emission computed tomography (SPECT), in which the summed stress score (SSS), summed rest score (SRS) and summed difference score (SDS) indexes were calculated. Homozygotes for the ACE D allele had greater mean values of SSS (P<0.001) and SDS (P<0.001). In addition, E3 homozygotes, E4 heterozygotes and E4 homozygotes had significantly higher values of SSS and SDS compared with E3 heterozygotes (P<0.001); E4 homozygotes had significantly higher values of SSS and SDS compared with E3 homozygotes. Furthermore, for the g.-219G>T polymorphic site at the promoter region of ApoE gene, the mean values of SSS and SDS were significantly higher for T heterozygotes/homozygotes than for GG homozygotes. Adjusting for all demographic and clinical data using multiple linear regression analysis it was found that ACE D and both ApoE genotypes were independent predictors with a cumulative contribution for the prediction of SSS and SDS. Furthermore, logistic regression analysis revealed that all three genotypes had an independent predictive ability for abnormal SSS (SSS>2). These data provide the first evidence of an association and significant cumulative contribution of the aforementioned genotypes in myocardial perfusion with E4 allele having the strongest association followed by ACE D and ApoE g.-219T alleles.

Five polymorphisms in gene candidates for cardiovascular disease in Afro-Brazilian individuals

Associations of polymorphisms in the angiotensin I-converting enzyme (ACE), apolipoprotein B (APOB) and apolipoprotein E (APOE) genes with hypertension and variations in lipid serum levels were evaluated in 184 Afro-Brazilians with a familial history of coronary artery disease (CAD). ACE (Ins/Del) and APOB (Ins/Del, XbaI, and EcoRI) and APOE (HhaI) polymorphisms were determined by polymerase chain reaction (PCR) and restriction fragment length polymorphism (RFLP) analyses on agarose, and polyacrylamide gel electrophoresis. Serum lipids were measured by means of routine enzymatic assays. The results showed a high frequency of hypertension (44%) in Afro-Brazilians that was increased in subjects >40 years old and those with a blood mass index (BMI) higher than 25 kg/m(2) (P<0.001). The ACE Del allele was associated with hypertension in men >40 years old (P<0.05). APOE (HhaI) and APOB (XbaI and Ins/Del) polymorphisms were not associated with hypertension or variations in serum concentrations of lipids, while subjects with the APOB E- allele had higher low-density lipoprotein cholesterol (LDL-C) levels than E+ carriers (P<0.05). These results suggest that ACE Ins/Del polymorphism is associated with hypertension, and APOB EcoRI polymorphism is associated with LDL-C variation in Afro-Brazilians.

Overestimation of genetic risks owing to small sample sizes in cardiovascular studies

We sought evidence of publication bias to explain conflicting findings in studies of angiotensin-converting enzyme deletion polymorphism (ACE D) and glycoprotein IIIa PlA2 (PLA2) polymorphism and the risk of myocardial infarction. Factor 5 Leiden (F5L), a well-established thrombotic risk factor, served as an internal comparison. We conducted systematic reviews of published studies involving ACE D, PLA2, F5L and relevant outcomes, searching medline (January 1990 through February, 2001), bibliographies, and meta-analyses. Random effects pooled odds ratios (95% confidence interval) for cardiovascular outcomes were as follows: PLA2 (n = 13,167 subjects): 1.13 (1.02, 1.26); ACE D (n = 42,140 subjects): 1.22 (1.11, 1.35); and F5L (n = 27,277 subjects): 4.43 (3.65, 5.38). However, funnel plots of ACE D and PLA2, but not F5L, showed an inverse relationship between sample size and odds ratios for ACE D (p = 0.02) and PLA2 (p = 0.04) but not F5L (p = 0.65) by Egger's test for potential publication bias. Despite research-based genotyping of over 50,000 subjects, the overall risk for myocardial infarction as a result of PLA2 and ACE D remains doubtful. Our study provides a clear example of how publication of underpowered studies can spuriously implicate polymorphisms as genetic risk factors.

Polymorphisms in the RAS and cardiac function

Since the discovery of the polymorphism in the angiotensin converting enzyme (ACE) and the consequences of this polymorphism on the activity levels of the enzyme, numerous association studies have been performed. However, these investigations do not often adhere to the most stringent criteria for such studies. The initial study reporting a positive association of the ACE polymorphism and myocardial infarction showed an increased risk of the DD genotype. This initial association was eventually refuted by a large, well conducted association study, which found a risk ratio of 1.02 after combining their own data with all published data. Although such large, well conducted association studies have not been performed in left ventricular (LV) hypertrophy, the association between DD genotype and hypertrophy is more convincing with a 192% excess risk of LV hypertrophy in untreated hypertensives. The role of ACE genotype in LV growth is well established, especially in athletes. In heart failure, large studies or meta-analyses have not been performed, because most studies have selected different end-points. This hampers a proper meta-analysis of the results obtained in associations with heart failure. As most association studies do not fulfill the criteria for good association studies and use too small sample sizes, it remains important to perform a meta-analysis to add meaning to the results of such studies. Above all, it is important to obey the rules set for association studies, large sample size, small P values, report associations that make biological sense and alleles that affect the gene product in a physiologically meaningful way.

Application of industrial scale genomics to discovery of therapeutic targets in heart failure

In recent years intense activity in both academic and industrial sectors has provided a wealth of information on the human genome with an associated impressive increase in the number of novel gene sequences deposited in sequence data repositories and patent applications. This genomic industrial revolution has transformed the way in which drug target discovery is now approached. In this article we discuss how various differential gene expression (DGE) technologies are being utilized for cardiovascular disease (CVD) drug target discovery. Other approaches such as sequencing cDNA from cardiovascular derived tissues and cells coupled with bioinformatic sequence analysis are used with the aim of identifying novel gene sequences that may be exploited towards target discovery. Additional leverage from gene sequence information is obtained through identification of polymorphisms that may confer disease susceptibility and/or affect drug responsiveness. Pharmacogenomic studies are described wherein gene expression-based techniques are used to evaluate drug response and/or efficacy. Industrial-scale genomics supports and addresses not only novel target gene discovery but also the burgeoning issues in pharmaceutical and clinical cardiovascular medicine relative to polymorphic gene responses.

Evidence for genetic factors in the development and progression of IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common glomerulonephritis in the world among patients undergoing renal biopsy. Once considered a relatively benign condition, longitudinal follow-up studies have revealed that in fact 9 to 50% of patients progress to end-stage renal disease within 20 years of disease onset. In the three decades since its first description by Jean Berger and Nicole Hinglais, clinical, epidemiologic, and immunologic studies of the pathogenesis of primary (idiopathic) mesangial glomerulonephritis with predominant IgA deposits have characterized the features of IgAN as a distinct glomerular disease entity. However, the basic molecular mechanism(s) underlying abnormal IgA deposition in the mesangium with ensuing extracellular matrix expansion and mesangial cell proliferation remains poorly understood. The task of elucidating the molecular basis of IgAN is made especially challenging by the fact that both environmental and genetic components likely contribute to the development and progression of IgAN.

METHODS AND RESULTS

We review here the evidence for genetic factors in the development and progression of IgAN, including a reappraisal of earlier conflicting results from small immunogenetic case-control studies, the evidence for racial differences in the prevalence of IgAN, a detailed summary of all reported occurrences of familial IgAN worldwide, and an exhaustive review of new insights gained through the study of two murine models of hereditary IgAN: the ddY and the uteroglobin-deficient mouse.

CONCLUSIONS

With the development of powerful molecular genetic approaches to the study of both Mendelian and complex human genetic diseases, and the successful efforts of investigators to identify and clinically characterize large IgAN multiplex families, we propose that genetic analysis of familial IgAN is the most promising approach to the identification of IgAN disease/susceptibility genes. Alternatively, if the case-control study design is employed to identify associations between particular candidate genes or markers and the development of IgAN, spurious associations caused by the effects of population stratification should be ruled out by confirming the findings using powerful and sensitive family-based methodologies such as the transmission/dysequilibrium test (TDT).

Large-scale test of hypothesised associations between the angiotensin-converting-enzyme insertion/deletion polymorphism and myocardial infarction in about 5000 cases and 6000 controls. International Studies of Infarct Survival (ISIS) Collaborators

BACKGROUND

The original report of a possible association between myocardial infarction and the insertion/deletion (I/D) polymorphism of the gene for the angiotensin-1-converting enzyme (ACE) indicated a risk ratio for myocardial infarction with the DD genotype of 1.34 (95% CI 1.05-1.70), and the association was claimed to be particularly strong in a retrospectively defined low-risk subgroup (3.2 [95% CI 1.7-5.9). Subsequent investigations reached varying conclusions, but all were small, and much larger studies were needed.

METHODS

4629 myocardial infarction cases and 5934 controls were compared. Cases were UK men aged 30-54 years and women aged 30-64 years recruited on presentation to hospital with confirmed myocardial infarction. Controls were aged 30-64 years with no history of cardiovascular disease, but were siblings or children of myocardial infarction survivors, or spouses of such relatives. All risk-ratio calculations allow for this relatedness of some of the controls. An updated meta-analysis of previous studies was also conducted.

FINDINGS

The ACE DD genotype was found in 1359 (29.4%) of the myocardial infarction cases and in 1637 (27.6%) of the controls (risk ratio 1.10 [95% CI 1.00-1.21]). The association between myocardial infarction and the DD genotype did not seem to be stronger in the subgroup defined as low risk by previously used criteria (234 [28%] of 836 cases and 911 [28%] of 3253 controls: risk ratio 1.04 [95% CI 0.87-1.24]), or in any other subgroup. Nor was the ACE I/D genotype predictive of subsequent survival.

INTERPRETATION

This study involved many more cases than any previously reported study of this question, but did not confirm the existence of any substantial association. In an updated meta-analysis of these results with those of previously published studies, the risk ratio for myocardial infarction with the DD genotype seems to lie in the range 1.0 to about 1.1. Although an increase in risk of up to about 10-15% cannot be ruled out, substantially more extreme risks can be. Moreover, there are not especially strong associations in the subgroups previously selected for emphasis. These findings illustrate the need for some studies of candidate genes to involve much larger populations than is customary, without undue emphasis on retrospectively defined subgroups.

Angiotensin-converting enzyme and cardiovascular disease risk

The published studies of the association of the angiotensin-converting enzyme (ACE) genotype with cardiovascular disease have used many different diagnostic criteria for cardiovascular disease and have drawn their samples from different patient groups and different populations. This review examines the association of the ACE DD genotype with cardiovascular disease risk in studies grouped by their case criterion, the geographical region of the population samples, and by the cardiovascular risk level of the patient sample. In studies where the underlying odds ratios are determined to be homogeneous, the overall odds ratios for myocardial infarction and coronary artery disease with regard to the ACE DD genotype are estimated using the Mantel-Haenszel method.

Angiotensin I-converting enzyme gene polymorphism in a low-risk European population for coronary artery disease

An insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) has been associated with an increased risk of coronary artery disease (CAD) and myocardial infarction (MI). However, this finding has not been fully investigated in European populations with very low CAD risk. In a case-control study on a population from Southern Europe (Toulouse, France), we evaluated the ACE I/D polymorphism in 405 men, aged 35-65 years, who underwent coronary angiography and in 357 representative control men within the same age range. We also explored associations in the patients between this polymorphism and CAD severity. The ACE genotype was not associated with the presence of either CAD or MI. The ACE genotype was not a marker for angiographically assessed CAD severity. In a sample in one of the European populations with the lowest CAD risk, ACE I/D polymorphism was not associated with an increased risk for CAD or MI and did not influence the extent of CAD.