Angiotensin-converting enzyme gene polymorphism in haemodialysis patients

Frequency of APOE, MTHFR and ACE polymorphisms in the Zambian population

Background

Polymorphisms within the apolipoprotein-E (APOE), Methylenetetrahydrofolate reductase (MTHFR) and Angiotensin I-converting enzyme (ACE) genes has been associated with cardiovascular and cerebrovascular disorders, Alzheimer’s disease and other complex diseases in various populations. The aim of the study was to analyze the allelic and genotypic frequencies of APOE, MTHFR C677T and ACE I/D gene polymorphisms in the Zambian population.

Results

The allele frequencies of APOE polymorphism in the Zambian populations were 13.8%, 59.5% and 26.7% for the ε2, ε3 and ε4 alleles respectively. MTHFR C677T and ACE I/D allele frequencies were 8.6% and 13.8% for the T and D minor alleles respectively. The ε2ε2 genotype and TT genotype were absent in the Zambian population. The genetic distances between Zambian and other African and non-African major populations revealed an independent variability of these polymorphisms.

Conclusion

We found that the APOE ε3 allele and the I allele of the ACE were significantly high in our study population while there were low frequencies observed for the MTHFR 677 T and ACE D alleles. Our analysis of the APOE, MTHFR and ACE polymorphisms may provide valuable insight into the understanding of the disease risk in the Zambian population.

High frequency of the D allele of the angiotensin-converting enzyme gene in Arabic populations

Background

The angiotensin-converting enzyme (ACE) gene in humans has an insertion-deletion (I/D) polymorphic state in intron 16 on chromosome 17q23. This polymorphism has been widely investigated in different populations due to its association with the renin-angiotensin system. However, similar studies for Arab populations are limited. This study addresses the distribution of the ACE gene polymorphism in three Arab populations (Egyptians, Jordanians and Syrians).

Findings

The polymorphisms of ACE gene were investigated using polymerase chain reaction for detection of an I/D mutation. The results showed a high frequency of the ACE D allele among the three Arab populations, Egyptians (0.67), Jordanians (0.66) and Syrians (0.60), which is similar to those obtained from previous studies for Arab populations.

Conclusion

The relationship between ACE alleles and disease in these three Arab populations is still not known, but the present results clearly suggest that geographic origin should be carefully considered in the increasing number of studies on the association between ACE alleles and disease etiology. This study adds to the data showing the wide variation in the distribution of the ACE alleles in different populations and highlights that great care needs to be taken when interpreting clinical data on the association of the ACE alleles with different diseases.

Angiotensin-converting enzyme gene polymorphism and the progression rate of focal segmental glomerulosclerosis in Iranian children

AIM

Focal segmental glomerulosclerosis (FSGS) is one of the most common forms of glomerulonephritis leading to end-stage renal disease (ESRD). A few clinical and paraclinical factors are considered as contributing factors in progression rate. However, there are controversial reports on the relationship between ACE gene polymorphism and rapidity of progression of FSGS to ESRD in different populations. To elucidate this issue, we investigated the relationship between the insertion (I) and deletion (D) ACE gene polymorphism and rapidity of progression of FSGS to ESRD in Iranian children.

METHODS

Forty-one children aged 1-18 years admitted to St AlZahra Hospital, Isfahan, and St Ali Asghar Hospital, Tehran, Iran, with idiopathic FSGS were enrolled. Renal death was defined as a glomerular filtration rate (GFR) of less than 50 mL/min per 1.73 m(2) or a decreased GFR to less than 50% compare to baseline. Reaching renal death in less or more than 2 years were labelled as rapid progressors (RP) or slow progressors (SP), respectively. Intron 16 of the ACE gene was amplified by the polymerase chain reaction technique.

RESULTS

Twenty-eight patients were male and 13 were female. In 15 RP patients, the genotype distribution was 26.6% DD, 6.7% II and 66.7% ID. In 26 SP patients, the genotype was similar (38.6% DD, 7.6% II and 53.8% ID, P > 0.05). There were no statistically significant differences for ACE I/D gene polymorphism between the two groups of patients (P > 0.05).

CONCLUSION

Our study revealed no correlation between ACE I/D gene polymorphism and rapidity of progression of FSGS to ESRD in Iranian children.

Angiotensin-converting enzyme (ACE) I/D genotype and renal ACE gene expression

BACKGROUND

The angiotensin-converting enzyme (ACE) I/D genotype affects serum ACE levels and the onset and progression of renal disease, but little is known about the mechanism. We investigated a possible association between the ACE I/D genotype and renal ACE mRNA levels in healthy subjects.

METHODS

Renal biopsy samples were obtained from 50 healthy kidney donors. The ACE I/D genotype was determined by polymerase chain reaction (PCR). Renal ACE mRNA quantification was performed by competitive RNA-PCR. In situ hybridization (ISH) for ACE mRNA on renal biopsy specimens was also performed.

RESULTS

The number of ACE transcripts in 100 ng of total RNA was significantly (P < 0.01) lower in subjects with II genotype (5.6 +/- 5.3 x 10(5), N = 20) compared with those with the ID (17.9 +/- 13.6 x 10(5), N = 23) or the DD genotype (36.9 +/- 14.6 x 10(5), N = 7) in healthy donors. The ISH studies showed that both tubular and glomerular ACE mRNA expressions were weak in subjects with the II genotype, intermediate in subjects with ID genotype, and strong in subjects with DD genotype.

CONCLUSIONS

It is suggested that renal ACE gene expression is associated with the ACE I/D genotype in healthy Japanese subjects.

Effect of ACE gene polymorphism on age at renal death in polycystic kidney disease in Japan

Polycystic kidney disease (PKD) is one of the most common genetic disorders and a major cause of renal death or end-stage renal disease (ESRD) requiring regular hemodialysis. The responsible genes recently have been cloned; however, genetic factors influencing the rate of progression to ESRD in patients with PKD have yet to be defined. Several studies have shown increased activity of the renin-angiotensin system (RAS) in patients with PKD. In addition, genetic polymorphisms of the RAS have been associated with the development of cardiovascular diseases. Therefore, these polymorphisms are good candidates for disease-modifying genetic factors or markers in PKD. In two previous reports of white subjects with a cumulative survival analysis, it was suggested that patients with P:KD1 homozygous for the deletion allele of the angiotensin-converting enzyme (ACE) gene are at increased risk for early renal death. To confirm this hypothesis in Japanese subjects, 103 individuals with PKD were genotyped for several components of the RAS, ie, ACE insertion/deletion (I/D) polymorphism, angiotensinogen (AGT) M235T, and angiotensin II type 1 receptor (AT1) A1166C. Seventy-six of the 103 patients (73.8%) reached ESRD at an average age of 52.1 +/- 11.3 years. The frequencies of each genotype of the genes were similar to those expected from Hardy-Weinberg equilibrium. There was a tendency to an excess of patients homozygous for the D allele in patients with ESRD (DD in patients with ESRD, 11.8%; DD in patients without ESRD, 3.7%; chi-square, 1.505; P: = 0.22). Cumulative renal survival was significantly less in those with the DD genotype compared with ID/II genotypes. Estimated mean renal survival was 46.4 years (95% confidence interval, 39.5 to 53.3) in subjects with the DD genotype and 57.2 years (95% confidence interval, 54.2 to 60.2) in ID/II genotypes (chi-square, 7.76; P: = 0.0053). There was no association between age at onset of ESRD and either M235T or A1166C polymorphism. These findings suggest that Japanese patients with PKD homozygous for the D allele of the ACE gene are at increased risk for developing ESRD at an early age.

Genetic polymorphisms in the renin-angiotensin system: relevance for susceptibility to cardiovascular disease

The renin-angiotensin system plays an important role in the pathogenesis of cardiovascular disease. Cloning of the human genes coding for the angiotensin-converting enzyme, angiotensinogen, and angiotensin II type 1 receptor has led to the discovery of several polymorphisms, which may be implicated in the pathogenesis of cardiovascular disease. The deletion/insertion (D/I) polymorphism of the angiotensin-converting enzyme gene is associated with hypertension in men, left ventricular hypertrophy in untreated hypertensive patients, various atherosclerotic cardiovascular complications, and microvascular disorders. The M235T polymorphism of the angiotensinogen gene may be associated with a higher risk of hypertension. The A1166C polymorphism of the angiotensin II type 1 receptor gene is probably correlated with hypertension and through an epistatic interaction with the D/I polymorphism of the angiotensin-converting enzyme gene possibly also with coronary heart disease. Several other gene polymorphisms, in particular those in the promoter area of the angiotensinogen gene, have been studied in relation to cardiovascular disease. Based on the insights gained from the reports summarized in this review article, population-based genetic studies of nuclear families are currently being conducted in Belgium and in the People's Republic of China with blood pressure and hypertension as the main outcome variables.

Angiotensin-converting enzyme gene polymorphisms in renal disease: clinically relevant?

The most recent studies of the effect of polymorphisms of the angiotensin-converting enzyme gene on the pathogenesis of renal diseases and the response to treatment with angiotensin-converting enzyme inhibitors continue to produce conflicting results. Large prospective studies are required before angiotensin-converting enzyme genotyping will provide information that will assist in the assessment of prognosis and response to angiotensin-converting enzyme inhibitor treatment in individual patients. Until such studies are performed, all patients with chronic renal disease, regardless of angiotensin-converting enzyme genotype, should be considered candidates for angiotensin-converting enzyme inhibitor therapy.

Angiotensin I-converting enzyme genotype significantly affects progression of IgA glomerulonephritis in an italian population

To evaluate the role of angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism in the progression of immunoglobulin A glomerulonephritis (IgA-GN), genotype distribution in 81 biopsy-proven cases of IgA-GN was studied. A logistic regression model showed that the risk for homozygous DD was not significantly elevated in patients with IgA-GN compared with healthy subjects (odds ratio = 1.16; confidence interval [CI], 0.4 to 3.3). However, the 5-year (78% v 90%) and 10-year (52% v 82%) renal survival rates for 47 patients with serum creatine (Cr) levels of 1.5 mg/dL or less at biopsy was significantly less in DD patients (n = 18; chi2 = 5.41; P = 0.02). The hazard ratio (HR) for DD (multivariate analysis from Cox proportional model after adjustment for known factors of progression, such as hypertension [HPT] and proteinuria [PTO]) was 3.07 (CI, 1.1 to 9.4). The HR for heavy PTO was 6.1 (CI, 1.9 to 19). The association of DD genotype with progression was even more striking when patients with other risk factors (heavy proteinuria) were excluded, as shown by DD-related risk in the absence (HR = 3.6; CI, 1.1 to 12) and presence (HR = 2; CI, 0.4 to 10) of PTO. The risk ratio was further increased by the coexistence of DD + PTO (HR = 9.16; CI, 1.8 to 15.7). Furthermore, in a cross-sectional study among patients with IgA-GN, a logistic regression model showed that the risk for homozygous DD was greater, although not at a statistically significant level in the end-stage renal failure subgroup compared with the normal renal function subgroup (odds ratio = 3.16; CI, 0.7 to 13.7) after adjustment by sex, age at biopsy, HPT, PTO, and therapy. Last, DD was significantly more frequent in those patients who started hemodialysis at an earlier age (chi2 for trend = 6.81; P = 0.009). Our study further supports that ACE genotype is a risk factor not for the development, but for the worsening of IgA-GN clinical course. However, on the basis of current knowledge, we cannot exclude that I/D polymorphism may simply serve as a prognostic marker, eventually linked with other discrete loci involved in the progression of renal damage.

Deletion polymorphism of the angiotensin converting enzyme gene predicts persistent proteinuria in Henoch-Schönlein purpura nephritis

OBJECTIVE

To study the influence of deletion/insertion polymorphism in the 16th intron of the angiotensin converting enzyme (ACE) gene on clinical manifestations of Henoch-Schönlein purpura nephritis.

STUDY DESIGN

Cross sectional study. ACE gene polymorphism was determined in patients (4-15 years old at onset) with Henoch-Schönlein purpura nephritis (n = 40) and compared with that in patients with IgA nephropathy (n = 79).

MAIN OUTCOME MEASURES

ACE genotypes, systemic blood pressures, urine protein excretion rate, haematuria, creatinine clearance, serum ACE activities.

RESULTS

The initial clinical manifestations of both Henoch-Schönlein purpura nephritis and IgA nephropathy were no different among homozygotes for insertion (II) and deletion (DD), and heterozygotes (ID) for the ACE gene. In patients with Henoch-Schönlein purpura nephritis, the incidence of moderate to heavy proteinuria at four and eight years after onset was more than five times higher in the DD genotype than in the II or ID genotypes. No such trend was seen in patients with IgA nephropathy. The number of patients with Henoch-Schönlein purpura nephritis in whom proteinuria resolved at four and eight years after onset was significantly lower in the DD genotype compared with the II genotype, whereas no differences were detected among the three different genotypes in patients with IgA nephropathy. Plasma ACE activities in patients with the DD genotype were significantly higher than in those with non-DD genotypes.

CONCLUSIONS

The ACE DD genotype predicts persistent proteinuria in Henoch-Schönlein purpura nephritis. The proteinuria might be related to a defective angiotensin system which is genetically determined by the D/I polymorphism.

The deletion/insertion polymorphism of the angiotensin converting enzyme gene and cardiovascular-renal risk

OBJECTIVE

This meta-analysis attempted to derive pooled estimates for the associations between various cardiovascular-renal disorders and the deletion/insertion (D/I) polymorphism of the angiotensin converting enzyme (ACE) gene.

METHODS

Case-control studies were combined, using the Mantel-Haenszel approach. Joint P values for continuous variables were calculated by Stouffer's method. Continuous measurements reported in different units were expressed on a percentage scale using the within-study mean of the II genotype as the denominator.

RESULTS

The computerized database used for this analysis included 145 reports with an overall sample size of 49 959 subjects. Overall, possession of the D allele was associated with an increased risk of atherosclerotic and renal microvascular complications. In comparison with the II reference group, the excess risk in DD homozygotes (P < 0.001) was 32% for coronary heart disease (CHD; 30 studies), 45% for myocardial infarction (20 studies), 94% for stroke (five studies) and 56% for diabetic nephropathy (11 studies). The corresponding risk in DI heterozygotes amounted to 11% (P= 0.02), 13% (P= 0.02), 22% (P= 0.10) and 40% (P < 0.001), respectively. Hypertension (23 studies), left ventricular hypertrophy (five studies), hypertrophic or dilated cardiomyopathy (eight studies) and diabetic retinopathy (two studies) were not related to the DI polymorphism. Publication bias was observed for CHD, myocardial infarction and microvascular nephropathy, but not hypertension. In studies with DNA amplification in the presence of insertion-specific primers, the risk associated with the DD genotype increased to 150% [95% confidence interval (CI) 76-256; four studies] for diabetic nephropathy, but decreased to 12% (95% CI -3 to 28; seven studies) for CHD and 14% (95% CI -6 to 37; four studies) for myocardial infarction. On the other hand, the pooled odds ratios did not materially change if the meta-analysis was limited to articles published in journals with an impact factor of at least 4. Furthermore, compared with the II control group, the circulating ACE levels (29 studies) were raised 58 and 31% (P < 0.001) in DD and DI subjects, respectively. In contrast, plasma renin (10 studies), systolic and diastolic blood pressure (46 studies) and body mass index (30 studies) were not associated with the D allele.

CONCLUSION

The D allele is not associated with hypertension, but behaves as a marker of atherosclerotic cardiovascular complications and diabetic nephropathy. These associations do not necessarily imply a causal relationship and may have been inflated by publication bias. Nevertheless, their possible therapeutic implications may be subject to further investigation in prospective (intervention) studies.

Association of the angiotensin I converting enzyme gene deletion polymorphism with early onset of ESRF in PKD1 adult polycystic kidney disease

To determine the effect of the ACE gene insertion/deletion (I/D) polymorphism, angiotensinogen gene M235T polymorphism and the angiotensin 1 receptor gene A1166C polymorphism on the age of onset of end-stage renal failure (ESRF) in PKD1 adult autosomal-dominant polycystic kidney disease (ADPKD), 189 individuals from 46 families with PKD1 were genotyped for each polymorphism. Of the 189 patients 52 (28%) reached ESRF at an average age of 48 +/- 1 year. In patients genotyped for the ACE gene insertion/deletion polymorphism the frequencies of the DD, ID and II genotypes were similar to those expected from Hardy Weinberg equilibrium. In patients with ESRF there was an excess of patients homozygous for the deletion allele (DD: 48% chi2 = 9.97 (1df) P = 0.002). Cumulative renal survival was significantly reduced among those with DD genotype compared to ID and II genotypes. The estimated mean renal survival (95% confidence intervals) were: DD, 52 years [48, 57]; II, 59 years [54, 63]; ID, 64 years [56, 72]; chi2 = 6.13 (1df) P = 0.013, DD versus ID/II. The mean age of renal failure was significantly younger in the DD genotype compared to ID and II genotypes (DD, ID, and II: 44 +/- 2, 49 +/- 2 and 54 +/- 3 years, respectively; P < 0.05 DD vs. ID, P < 0.05 DD vs. II). Ten of the eleven patients who reached ESRF before the age of 40 were homozygous for the deletion allele. The relative risk for ESRF below the age 40 for DD genotype was 17. For all ages there was an overall increased risk of 1.4 for ESRF with the DD genotype. There was no interaction between age of onset of ESRF and either the angiotensinogen M235T allele or angiotensin 1 receptor A1166C polymorphism. This study strongly suggests that PKD 1 patients homozygous for the deletion allele of the ACE gene are at increased risk of developing ESRF at a early age.

Angiotensin I converting enzyme gene polymorphism in non-insulin dependent diabetes mellitus

A total of 168 patients with non-insulin dependent diabetes (NIDDM) followed over 10 years were recruited in this study. The patients were divided into two groups: Group 1 patients had a stable renal function (N = 96) and Group 2 had a declining renal function (N = 72). Group 1 included those whose serum creatinine was normal five years ago but had increased to > or = 2 mg/dl or those who has reached end-stage renal failure (requiring dialysis) by the time of study. All patients were genotyped for the insertion/deletion (I/D) polymorphism of the ACE gene, the M235T polymorphism of the angiotensinogen (Atg) gene and the A1166C polymorphism of the angiotensin II type 1 receptor (AT1) gene. The genotype frequency distributions of M235T Atg and the A116C AT1 gene polymorphisms were not different between Group 1 versus Group 2. While the frequency of the ACE DD genotype in Group 1 (7.3%) was comparable to that of the general population, the DD frequency was significantly higher in Group 2 (26.4%) than in Group 1 (odds ratio, 4.56; 95% confidence interval, 1.80 approximately 11.56, P < 0.001). Among all 168 patients studied, the renal survival rate was significantly lower among DD than ID (P < 0.005) or II patients (P < 0.001). In patients with a declining renal function (Group 2), those with the DD genotype had a significantly shorter time interval from onset of diabetes to the initiation of dialysis (13.4 +/- 1.4 years) than those with ID (20.7 +/- 1.2 years, P < 0.01) or II genotypes (17.5 +/- 1.1 year, P < 0.01). Analysis of the clinical course of the three ACE genotypes revealed that the majority (95%) of patients with the DD genotype who had albuminuria progressed to end-stage renal disease within 10 years of diagnosis of diabetes. Our analysis also revealed that initiation and continuation of dialysis are associated with a progressive decrease in the frequency of the DD genotype. These results indicate that, in NIDDM, the ACE DD genotype has a high prognostic value for progressive deterioration of renal function. Moreover, the DD genotype appears to increase the mortality once dialysis is initiated.

Association between a polymorphism in the angiotensin-converting enzyme gene and microvascular complications in Japanese patients with NIDDM

The relationship between diabetic nephropathy and an insertion (I)/deletion (D) polymorphism in intron 16 of the angiotensin-converting enzyme (ACE) gene is still under debate. The association of ACE gene polymorphism with nephropathy and retinopathy was therefore examined in 362 Japanese patients with non-insulin-dependent diabetes mellitus (NIDDM) and 105 healthy control subjects. Distribution of the ACE genotype did not differ between healthy control subjects and diabetic patients without complications. However, the frequency of the D allele was significantly higher in the diabetic subjects with nephropathy than in those without (0.32 in normoalbuminuric patients vs 0.44 in albuminuria patients with albuminuria) (chi 2 = 7.7; p = 0.006). There was no significant association between ACE genotype and retinopathy. These observations thus demonstrate a significant association of the ACE gene polymorphism with nephropathy, but not with retinopathy, in Japanese patients with NIDDM.

Role of the deletion of polymorphism of the angiotensin converting enzyme gene in the progression and therapeutic responsiveness of IgA nephropathy

Studies conducted over the last decade demonstrated variable therapeutic efficacy of angiotensin converting enzyme (ACE) inhibitor on the progression of glomerular diseases, including IgA nephropathy. In this study, among patients with biopsy-proven IgA nephropathy, 53 patients in whom creatinine clearance had been monitored over 5 yr were recruited for study. These patients were classified into two groups according to whether or not renal function had declined as determined by the slope of creatinine clearance against time: group 1 had stable renal function; group 2 had declining renal function (average: -6.7 +/- 1.3 ml/min/yr). 21 of 53 patients were treated with ACE inhibitor and followed for 48 wk. Gene polymorphism consisting of insertion (I) or deletion (D) of a 287-bp DNA fragment (presumed to be a silencer element) of the ACE gene was determined by PCR. 46 age-matched individuals without history of proteinuria were analyzed as controls. The DD genotype was significantly more frequent in group 2 (43%) than in controls (7%) or group 1 patients with stable renal function (16%). 48 wk after ACE inhibitor administration, proteinuria significantly decreased in patients with DD genotype but not in those with ID or II genotypes. The results indicate that deletion polymorphism in the ACE gene, particularly the homozygote DD, is a risk factor for progression to chronic renal failure in IgA nephropathy. Moreover, this deletion polymorphism predicts the therapeutic efficacy of ACE inhibition on proteinuria and, potentially, on progressive deterioration of renal function.

Insertion/deletion polymorphism in the angiotensin-I-converting enzyme gene is associated with coronary heart disease in IDDM patients with diabetic nephropathy

Insulin-dependent diabetic (IDDM) patients with diabetic nephropathy have a highly increased morbidity and mortality from coronary heart disease. An insertion (I) /deletion (D) polymorphism in the angiotensin-I-converting enzyme (ACE) gene has been shown to be associated with coronary heart disease. Therefore, we have investigated the role of this ACE/ID polymorphism in 198 IDDM patients with diabetic nephropathy and 190 normoalbuminuric IDDM patients. The prevalence of myocardial infarction and other coronary heart disease was significantly elevated in patients with nephropathy, 19% (38/198) vs 8% (15/190), p < 0.001. In the nephropathic group 12 of 63 (19%), 23 of 95 (24%), and 3 of 40 (7.5%) patients with the DD, ID and II genotypes, respectively had a history of coronary heart disease, II vs DD and ID, p < 0.05 when compared to nephropathic patients without coronary heart disease. Multiple logistic regression analysis of the risk factors associated with coronary heart disease in univariate analysis revealed that the II genotype acts as an independent protective factor against coronary heart disease, odds ratio II/DD + ID 0.27 (95% confidence interval 0.07-0.97, p < 0.05). There was no difference in genotype or allele frequency (D/I) between patients with and without nephropathy, 0.56/0.44 in both groups, but plasma ACE concentration was elevated in patients with nephropathy 609 (151-1504) ng/ml as compared to patients with normoalbuminuria, 428 (55-1630) ng/ml, p < 0.001. We suggest that ACE/ID polymorphism may influence the frequency of life-threatening cardiac complications in IDDM patients suffering from diabetic nephropathy, a condition characterized by increased plasma ACE concentration.

Similarity of blood pressure for each genotype of the insertion/deletion polymorphism of the dipeptidyl carboxypeptidase-1 gene in different age groups of patients with severe, familial essential hypertension

1. The association of alleles of an insertion/deletion polymorphism (I/D) of the dipeptidyl carboxypeptidase-1 gene with hypertension is controversial. If a particular allele makes a major contribution to blood pressure, then hypertensives homozygous for this allele could be expected to have higher high blood pressure than those homozygous for the alternate allele. 2. The present study examined this hypothesis by comparing pretreatment blood pressures of hypertensives who had been genotypes for the I/D polymorphism. Blood pressures for different age groups (< 50, 50-59 and > or = 60 years) were also examined for each genotype. In addition, several other parameters were examined. 3. Systolic blood pressures were found to be 167 +/- 3, 167 +/- 3 and 170 +/- 6 mmHg (mean +/- s.e.) for the genotypes II, ID and DD, respectively. Diastolic blood pressures were 113 +/- 4, 111 +/- 2 and 111 +/- 4, for the respective genotypes. One-way ANOVA showed that the respective blood pressure values did not differ significantly across genotypes. Blood pressures for different age groups of hypertensives were also similar. 4. In addition, body mass index, mean age and sex did not differ between genotypes, either for the group as a whole or for the different age groups. 5. In conclusion, the present study could find no evidence to support a genetic association between the I/D polymorphism of DCP1 and blood pressure in a group with severe, familial hypertension living in Sydney.

Different frequencies of angiotensin-converting enzyme genotypes in older hypertensive individuals

The frequency of the D allele of an insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene has been reported to be elevated in myocardial infarction and other patients. We therefore hypothesized that death rate of DD individuals should be increased in the population as a whole and this should be evident as a decrease in DD frequency with age. This hypothesis was tested in 118 Caucasian subjects who were already at high risk of cardiovascular events by having severe, early onset, familial hypertension (HT). A group of 196 age-, sex- and body mass index-matched normotensives (NTs) was used as a control. In the NT group II, ID, and DD genotype frequencies were similar for different age groups. DD frequency was 0.42 in NTs, but in HTs was 0.28, 0.26, and 0.10 for the age groups < 50, 50-59, and > or = 60 yr, respectively. Corresponding D allele frequencies were 0.52, 0.46, and 0.40 in the respective age groups of HTs, compared with 0.61 in NTs (by chi 2-analysis, P = 0.1, 0.047, and 0.0006, respectively). In HTs aged > or = 60, DD frequency was only 14% of expected. Plasma ACE activity tracked similarly with I/D genotype in HTs (P = 0.027; n = 35) as in NTs (P = 0.0001; n = 94) and Michaelis constant was identical for DD and II. Neither blood pressure, body mass index, nor sex bore any relationship with I/D genotype. In conclusion, in a group of severely HT patients not selected for cardiac pathology, there appeared to be a marked, selective decrease, in subgroups of increasing age, in frequency of the ACE DD genotype. One possibility suggested by this data might be that DD increases risk of premature death, at least in HTs who have two HT parents.