A fast and accurate method for genotyping the angiotensin-converting enzyme I/D polymorphism

Investigation of ACE, ACE2 and AGTR1 genes for association with nephropathy in Type 1 diabetes mellitus

BACKGROUND

Polymorphisms in ACE and AGTR1 genes have been assessed in multiple studies for association with diabetic nephropathy; however, results are conflicting. The ACE2 gene has not been studied extensively for association with diabetic nephropathy.

METHODS

We investigated variants in ACE, ACE2 and AGTR1 for association with nephropathy in a case-control group (1467 participants with Type1 diabetes, case subjects n=718; control subjects n=749) of white descent with grandparents born in the British Isles. All recruited individuals were carefully phenotyped and genotyping was performed using Sequenom, Taqman and gel electrophoresis methods. The χ(2) -test for contingency tables was used to compare genotype and allele frequencies in case and control groups.

RESULTS

No departure from Hardy-Weinberg equilibrium was observed in cases or controls. Two variants within the ACE gene (rs4293, P(allelic) =0.02, P(genotypic) =0.008; rs4309, P(allelic) =0.02, P(genotypic) =0.01) were significantly associated with nephropathy at the 5% level. No variant remained statistically significant following adjustment for multiple comparisons. No single nucleotide polymorphisms in the ACE2 or AGTR1 genes were significantly associated with nephropathy when analysed either by genotype or allele frequencies.

CONCLUSIONS

Our independent case-control study provides no evidence that common variants in ACE, ACE2 and AGTR1 play a major role in genetic susceptibility to diabetic nephropathy in a white population with Type1 diabetes.

An alternative method for genotyping of the ACE I/D polymorphism

The mistyping of the angiotensin I-converting enzyme insertion/deletion (ACE I/D) has been well documented, and new methods have been suggested here to improve the genotyping efficiency. Buccal cell samples were collected from 157 young Caucasians, and genotyped using previously known and newly developed PCR amplification genotyping techniques, as well as PCR-RFLP tests for three single nucleotide polymorphisms (rs4327, rs4341 and rs4343). Inconsistent genotyping results were found when using only the PCR amplification genotyping techniques across repeated attempts (8% to 45%), however, individual SNP genotyping was highly consistent (100%). Two SNPs (rs4341 and rs4343) were in complete LD and SNP rs4327 was in high LD with the ACE I/D. The ACE I/D was in HW equilibrium in the portion of the population with consistent genotyping results, whereas the three SNPs were not in HW equilibrium. The mistyping of ACE I/D by only PCR amplification can be improved using alternative methods.

Methylenetetrahydrofolate reductase and angiotensin converting enzyme gene polymorphisms in two genetically and diagnostically distinct cohort of Alzheimer patients

The role of methylenetetrahydrofolate reductase (MTHFR) and angiotensin converting enzyme (ACE) gene polymorphisms as risk factors for the occurrence of Alzheimer's disease (AD) is still controversial. In this study, we investigated the common MTHFR C677-->T and ACE insertion/deletion (I/D) gene polymorphisms as risk factors for AD in two genetically and diagnostically distinct cohort of Alzheimer's patients. We analyzed a neuropathologically confirmed American cohort of 124 AD patients and 97 elderly controls, and a clinically diagnosed Italian cohort of 126 probable AD cases, 106 elderly controls, and a community-based sample of 1232 subjects aged under 65 years. No difference was found in polymorphism distribution between cases and controls in both study cohorts. We also tested a possible association between the polymorphisms investigated. No interaction was found between the MTHFR and ACE alleles. Moreover, no association was found for the ACE and MTHFR polymorphisms with age at onset, disease duration and MMSE score at observation. Thus, in our study, MTHFR C677-->T and ACE I/D polymorphisms do not appear to confer an added risk for AD.

PAI-1 4G/5G and ACE I/D gene polymorphisms and the occurrence of myocardial infarction in patients on intermittent dialysis

BACKGROUND

Myocardial infarction (MI) is a leading cause of death, particularly in high-risk settings such as uraemia, in which it is not yet known to what extent genetic factors contribute to the overall risk of MI. We have prospectively evaluated the effect of plasminogen activator inhibitor-1 (PAI-1) 4G/5G and angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphisms on the occurrence of MI in uraemics.

METHODS

All patients undergoing intermittent dialysis in an Italian district were enrolled as subjects. From the same area, 1307 individuals served as controls. Genomic DNA was obtained and ACE I/D and PAI-1 4G/5G gene polymorphisms were determined. After a baseline evaluation, patients were followed for 28.8+/-9.8 months. MIs and other causes of death were recorded.

RESULTS

A total of 461 patients (417 on haemodialysis and 44 on peritoneal dialysis) were investigated. At entry, their mean age was 58.2+/-16.2 years and dialytic age was 82+/-69 months. Genotype frequencies were not different between controls and uraemics and, in the latter group, between patients with or without cardiovascular diseases at baseline evaluation. During the follow-up, 22 fatal and 16 non-fatal MIs were recorded (mean incidence 1.99 and 1.45%/year, respectively). The adjusted risk of fatal and total MI was related to the presence at entry of a history of MI [hazard ratios (HR) 4.3; 95% confidence interval (CI) 1.5-12.0 and HR 6.8; 95% CI: 3.3-14.0, respectively] and to the PAI-1 4/4 genotype (HR 2.8; 95% CI 1.2-6.9 and HR 2.1; 95% CI 1.1-4.2, respectively).

CONCLUSIONS

In end-stage renal disease, PAI-1 4G/5G gene polymorphism may have a significant role in the occurrence of fatal and non-fatal MI.

ACE gene polymorphism and insulin action in older subjects and healthy centenarians

OBJECTIVES

To evaluate the possible relationship between angiotensin-converting enzyme (ACE) insertion-deletion (ID) genotype and insulin resistance in a population of healthy older Italian subjects.

DESIGN

Prospective recruitment of a convenience sample.

PARTICIPANTS

One hundred twenty-five subjects age 62 to 105 in good health and not taking any drug known to interfere with glucose metabolism.

RESULTS

In the sample population, the relative frequencies of the ACE genotypes deletion-deletion (DD) (0.424), ID (0.400), and insertion-insertion (II) (0.176) were not significantly different from values predicted by Hardy-Weinberg equilibrium. The genotype distribution was similar in men and women. Subjects carrying the II genotype had a higher FPG (P <.001) and FPI (P <.001) than did subjects with DD or ID genotype. Subjects with II genotype also had a significantly higher HOMA index than did subjects with DD or ID genotype (P for trend <.002). In a multivariate stepwise regression analysis, the ACE ID polymorphism was significantly and independently associated with the HOMA index (P <.001). The same result was confirmed performing multivariate analysis in the younger group and centenarians separately.

CONCLUSIONS

In an older population, the presence of II ACE genotype is associated with a high degree of insulin resistance independent of other anthropometric variables known to interfere with insulin action; this association is significant in both the younger subjects and the centenarians.

Cardiovascular risk factors, angiotensin-converting enzyme gene I/D polymorphism, and left ventricular mass in systemic hypertension

We investigated the influence of major cardiovascular risk factors (smoking, hypercholesterolemia, diabetes mellitus) on the association between angiotensin-converting enzyme (ACE) gene insertion (I)/deletion (D) polymorphism and echocardiographic left ventricular mass in 225 patients with sustained hypertension, assessed by ambulatory blood pressure monitoring. When the study population was analyzed as a whole, the 3 ACE genotypes did not differ in left ventricular mass (II, 47 g/m2.7; ID, 49 g/m2.7; DD, 51 g/m2.7; p = NS). No difference was found in subjects (n = 135) in whom at least 1 major cardiovascular risk factor was present (II, 51 g/m2.7; ID, 51 g/m2.7; DD: 52 g/m2.7; p = NS). In contrast, in the absence of cardiovascular risk factors, DD subjects (n = 32) exhibited left ventricular mass index higher than non-DD (ID/II) subjects (n = 75; p <0.05). After controlling for age and sex, in the absence of cardiovascular risk factors, the risk of left ventricular hypertrophy was 3.8-fold higher in DD than in non-DD patients (odds ratio 3.8; 95% confidence interval 1.2 to 12.1, p <0.02). We conclude that in the present setting of patients with established sustained systemic hypertension, the absence of risk factors potentially affecting cardiovascular adaptation allows for the detection of a positive association between homozygosity for the D allele of the ACE gene and left ventricular hypertrophy.