Angiotensin-converting enzyme activity and the ACE Alu polymorphism in autosomal dominant polycystic kidney disease

Association of Polymorphisms in Endothelial Nitric Oxide Synthesis and Renin-Angiotensin-Aldosterone System with Developing of Coronary Artery Disease in Bulgarian Patients

AIM

The purpose of this study was to evaluate the association of common polymorphisms in endothelial nitric oxide synthesis (eNOS; G894T) and renin-angiotensin-aldosterone system (angiotensin converting enzyme [ACE]-I/D, angiotensinogen-T704C, and angiotensin II receptor type 1-A1166C) as risk factors in the pathogenesis of coronary artery disease (CAD) in Bulgarian patients.

METHODS

This study included 171 patients with CAD and 123 control subjects. Polymerase chain reaction-restriction fragment length polymorphism was used for studying the single-nucleotide polymorphisms. Statistical analysis was performed using statistical software PASW for Windows.

RESULTS

A significantly higher percentage of the eNOS T894 allele was found in patients with acute coronary syndrome (ACS), compared to controls (p = 0.006) and patients with stable angina pectoris (SAP, p = 0.005). Results from a binary regression analysis suggested that eNOS T allele and ACE D allele carriers were more likely to develop ACS than controls (T allele odds ratio [OR] 2.585, p = 0.024; D allele OR 3.585, p = 0.046) and patients with SAP (T allele OR 2.955, p = 0.009; D allele OR 2.703, p = 0.05). Exploratory evaluation of gene-gene combinations showed a significant association between eNOS-G894T/ACE-I/D and ACS compared to controls (p = 0.022) and patients with SAP (p = 0.017).

CONCLUSIONS

The eNOS G894T and ACE I/D polymorphisms are associated with an increased risk of developing ACS after adjusting for classical risk factors for atherosclerosis in the Bulgarian cohort.

Hypertension and left ventricular hypertrophy in autosomal dominant polycystic kidney disease

Hypertension is a common problem in patients with autosomal dominant polycystic kidney disease affecting both renal and patient survival. Activation of the renin-angiotensin-aldosterone system due to cyst expansion and local renal ischemia has been proposed to play an important role in the development of hypertension in autosomal dominant polycystic kidney disease. Left ventricular hypertrophy, a major cardiovascular risk factor, is also common in patients with autosomal dominant polycystic kidney disease. Both hypertension and the activation of the renin-angiotensin-aldosterone system play a role in the development of left ventricular hypertrophy in these patients. Prospective randomized results indicate that aggressive control of blood pressure is important for the optimal reversal of left ventricular hypertrophy, thereby diminishing a major risk factor for cardiovascular morbidity and mortality of patients with autosomal dominant polycystic kidney disease. There is also substantial epidemiological support for aggressive control of blood pressure in slowing renal disease progression in autosomal dominant polycystic kidney disease patients. Blockade of the renin-angiotensin-aldosterone system should be the initial approach in the treatment of hypertension in these patients.

The polymorphism of the ACE gene affects left ventricular hypertrophy and causes disturbances in left ventricular systolic/diastolic function in patients with autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is one of the most frequently occurring autosomal diseases inherited in the dominant manner. Due to this, lesions in the cardiovascular system of ADPKD patients have caught the attention of clinical investigators worldwide. The aim of the study was to analyse cardiovascular complications in ADPKD patients with a focus on left ventricular hypertrophy (LVH) and selected components of its systolic/diastolic function based on echocardiography. The study was conducted on 55 patients with ADPKD (24 males, 31 females), subdivided into three groups according to the stage of chronic kidney disease (CKD). The patient group with ADPKD and ESRD (group C) manifested an increased incidence of the D allele as compared to group A and group B (χ² = 4.217, P = 0.04). In all ADPKD patients with the DD genotype, left ventricular mass (LVM), posterior wall thickness (PWT), and interventricular septal thickness (IVS) were significantly higher compared to patients possessing the II and ID genotypes (P < 0.02, P < 0.003, and P < 0.009, resp.). The DD genotype exists more frequently in ADPKD patients with ESRD and is associated with a higher occurrence of LVH and disturbances in systolic-diastolic function when compared to ADPKD ESRD patients with the II and ID genotypes.

Cardiovascular abnormalities in autosomal-dominant polycystic kidney disease

Cardiovascular problems are a major cause of morbidity and mortality in patients with autosomal-dominant polycystic kidney disease (ADPKD). Hypertension is a common early symptom of ADPKD, and occurs in approximately 60% of patients before renal function has become impaired. Hypertension is associated with an increased rate of progression to end-stage renal disease and is the most important potentially treatable variable in ADPKD. Left ventricular hypertrophy, which is a powerful, independent risk factor for cardiovascular morbidity and mortality, also occurs frequently in patients with ADPKD. Both hypertension and left ventricular hypertrophy have important roles in cardiovascular complications in these individuals. Moreover, biventricular diastolic dysfunction, endothelial dysfunction, increased carotid intima-media thickness, and impaired coronary flow velocity reserve are present even in young patients with ADPKD who have normal blood pressure and well-preserved renal function. These findings suggest that cardiovascular involvement starts very early in the course of ADPKD. Intracranial and extracranial aneurysms and cardiac valvular defects are other potential cardiovascular problems in patients with ADPKD. Early diagnosis and treatment of hypertension, with drugs that block the renin-angiotensin-aldosterone system, has the potential to decrease the cardiovascular complications and slow the progression of renal disease in ADPKD.

Influence of ACE I/D gene polymorphism in the progression of renal failure in autosomal dominant polycystic kidney disease: a meta-analysis

BACKGROUND

Autosomal dominant polycystic kidney disease (ADPKD) is a renal disease characterized by an important variability in clinical course, which cannot be fully explained by the genetic heterogeneity of the disease. Although the role for the angiotensin I-converting enzyme (ACE) insertion/deletion (I/D) polymorphism as a modifier factor in ADPKD renal deterioration has been suggested, direct evidence from genetic association studies remain inconclusive. To provide a more robust estimate of the putative effect of the ACE I/D polymorphism on the renal progression in ADPKD, we performed a meta-analysis pooling data from all relevant studies in which the role of the ACE I/D variant in ADPKD clinical features was evaluated.

METHODS

We applied a random-effects model to combine odds ratio and 95% confidence intervals. Q-statistic was used to evaluate the homogeneity, and both Egger's and Begg-Mazumdar tests were used to assess publication bias.

RESULTS

Altogether, three distinct meta-analyses were generated using data from 13 studies. Despite the absence of publication bias and the presence of homogeneity among study results, the DD genotype failed to show an influence on risk of end-stage renal disease (ESRD), mean age at ESRD or risk of hypertension in ADPKD patients when compared with I-allele carriers (DD vs ID+II). Likewise, meta-analyses carried out separately for Caucasian and Asian studies showed no indication of an association between the DD genotype and a faster renal deterioration in ADPKD.

CONCLUSION

These findings do not support the hypothesis that the enhanced ACE activity associated with the D allele might promote a significantly worse prognosis in patients with ADPKD.

Polymorphisms of the angiotensin converting enzyme and angiotensin II type 1 receptor genes and renal scarring in non-uropathic children with recurrent urinary tract infection

AIM

The aim of this study was to investigate whether the angiotensin converting enzyme (ACE) and angiotensin II type 1 receptor (A1166C) gene polymorphisms were associated with the renal scar formation secondary to recurrent urinary tract infection in children without uropathy.

METHODS

The polymorphisms were investigated by polymerase chain reaction in 97 children (81 females, 16 males; age, 2.5-13 years) with recurrent urinary tract infection and 100 healthy controls as a single centre study. Children with vesicoureteral reflux, bladder dysfunction and other uropathies were excluded. The dimercaptosuccinic acid (DMSA) scan performed at least 3 months after a proven urinary tract infection and the result of the last DMSA was taken into consideration.

RESULTS

Renal scarring was found in 30 patients (30.9%) using DMSA scan. The number of urinary tract infection attacks was significantly higher in patients with renal scarring compared with children without scarring (P<0.05). The follow-up period and male/female ratio of patients with or without renal scarring was similar (P>0.05). Age at the first urinary tract infection was lower in the group with scarring. The ACE insertion/deletion genotype distribution and D allele frequency were similar between patients and controls (P>0.05), and in patients with renal scarring and those without renal scarring. Also, the angiotensin II type 1 receptor gene polymorphism was not associated with renal parenchymal damage (P>0.05).

CONCLUSION

The results indicated that the ACE insertion/deletion and angiotensin II type 1 receptor gene polymorphisms were not independent risk factors for renal scar formation in recurrent urinary tract infection of paediatric patients without uropathy.

Modifier genes play a significant role in the phenotypic expression of PKD111See Editorial by Pei, p. 1630

BACKGROUND

Polycystic kidney disease type 1 (PKD1) is characterized by extreme variation in the severity and progression of renal and extrarenal phenotypes. There are significant familial phenotype differences; but it is not clear if this is due to differences in PKD1 mutations, differences in genetic background, or both.

METHODS

A total of 315 affected relatives (83 PKD1 families) without end-stage renal disease (ESRD) were evaluated for disease markers, including renal volume, creatinine clearance, proteinuria, liver cysts, and hypertension. Of these patients, 19% progressed to ESRD within 1 to 10 years after the initial examination. Nested analysis of variance was used to investigate interfamilial and intrafamilial differences in these phenotypes. Heritability analyses were used to estimate the effect of the genetic background on phenotypic variability. The age of onset of ESRD was also analyzed with an additional 389 family members from the same PKD1 families without clinical evaluation but with data on age of onset of ESRD (or age without ESRD).

RESULTS

There were significant phenotype differences between patients with the same mutation and different genetic backgrounds. The phenotypic variation between patients with different mutations and different genetic backgrounds was not significantly greater than the variation between patients with the same mutation and different genetic backgrounds. However, when the 389 family members were included, both the mutation and modifier genes had significant effects on the age of onset of ESRD. Inherited differences in genetic background were estimated to account for 18% to 59% of the phenotypic variability in PKD1 disease markers in patients prior to ESRD and in the subsequent progression to ESRD (43% heritability) in the 315 patients who were clinically evaluated.

CONCLUSION

Modifier loci in the genetic background are important factors in inter- and intrafamilial variability in the phenotypic expression of PKD1. The extreme intrafamilial phenotype differences are consistent with the hypothesis that one or a few modifier genes have a major effect on the progression and severity of PKD1.

Progressive Loss of Renal Function Is an Age-Dependent Heritable Trait in Type 1 Autosomal Dominant Polycystic Kidney Disease

Significant intrafamilial phenotypic variability is well documented in autosomal dominant polycystic kidney disease (ADPKD) and suggests a modifier effect. In this study, variance components analysis was performed to estimate the contribution of genetic factors for within-family renal disease variability in 406 patients from 66 type 1 ADPKD families. Overall, 39% of the study patients had ESRD at their last follow-up, and their renal survival did not differ by gender (P = 0.35, log-rank test). Because their frequency plot of creatinine clearance (Ccr) assumed a bimodal distribution with a marked kurtosis that was not improved by transformations, the study cohort was decomposed into two separate groups (non-ESRD [n = 247] and ESRD [n = 159]) in which the Ccr plots were normally distributed. The heritability (h(2)) of Ccr and age at ESRD (age(ESRD)) and the genetic correlations between these measures and their covariates were estimated. In patients without ESRD, a significant heritability was found for Ccr (h(2) = 0.42; P = 0.0015) after adjusting for age (P = 0.0001), systolic BP (P = 0.0006), and treatment with angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (P = 0.00001). Birth year, gender, BMI, diastolic and mean BP, and pack-years of cigarette smoking did not significantly influence the heritability of this trait. In patients with ESRD, age(ESRD) provides a better measure than Ccr, which was very narrowly distributed. A significant heritability was found for age(ESRD) (h(2) = 0.78; P = 0.00009) in these latter patients. None of the above covariates influenced the heritability of this trait. It is concluded that a significant modifier gene effect influences the progression of renal disease in type 1 ADPKD.

Angiotensin-converting enzyme and angiotensin type 2 receptor gene genotype distributions in Italian children with congenital uropathies

Angiotensin I-converting enzyme (ACE) and angiotensin type 2 receptor (AT2R) gene polymorphisms have been associated with an increased incidence of congenital anomalies of the kidney and urinary tract (CAKUT). We investigated the genotype distribution of these polymorphisms in Italian children with CAKUT. We also evaluated the association between the ACE insertion/deletion and the AT2R gene polymorphisms with the progression of renal damage in subgroups of CAKUT patients. We recruited 102 Italian children with CAKUT; 27 with vesicoureteral reflux; 12 with hypoplastic kidneys; 20 with multicystic dysplastic kidneys; 13 with ureteropelvic junctions stenosis/atresia; 18 with nonobstructed, nonrefluxing primary megaureters; and 12 with posterior urethral valves and compared them with 92 healthy control subjects. ACE and AT2R gene polymorphisms were analyzed by PCR. The identification of AT2R gene polymorphisms in intron 1 and in exon 3 was revealed by enzymatic digestion. ACE genotype distribution in children with CAKUT was no different from that of the control subjects, but the subgroup of patients with radiographic renal parenchymal abnormalities showed an increased occurrence of the D/D genotype. The frequency of the G allele of AT2R gene in children with CAKUT was increased in respect to that of the control subjects. By contrast, no significant difference in the frequency of the C and A alleles of the AT2R gene was found. Our findings indicate that the ACE gene can be a risk factor in the progression of renal parenchymal damage in CAKUT patients. Moreover, a major role of the AT2R gene in the development of CAKUT has been found, at least in Italian children.

Genotype-renal function correlation in type 2 autosomal dominant polycystic kidney disease

Autosomal dominant polycystic kidney disease (ADPKD) is a common Mendelian disorder that affects approximately 1 in 1000 live births. Mutations of two genes, PKD1 and PKD2, account for the disease in approximately 80 to 85% and 10 to 15% of the cases, respectively. Significant interfamilial and intrafamilial renal disease variability in ADPKD has been well documented. Locus heterogeneity is a major determinant for interfamilial disease variability (i.e., patients from PKD1-linked families have a significantly earlier onset of ESRD compared with patients from PKD2-linked families). More recently, two studies have suggested that allelic heterogeneity might influence renal disease severity. The current study examined the genotype-renal function correlation in 461 affected individuals from 71 ADPKD families with known PKD2 mutations. Fifty different mutations were identified in these families, spanning between exon 1 and 14 of PKD2. Most (94%) of these mutations were predicted to be inactivating. The renal outcomes of these patients, including the age of onset of end-stage renal disease (ESRD) and chronic renal failure (CRF; defined as creatinine clearance < or = 50 ml/min, calculated using the Cockroft and Gault formula), were analyzed. Of all the affected individuals clinically assessed, 117 (25.4%) had ESRD, 47 (10.2%) died without ESRD, 65 (14.0%) had CRF, and 232 (50.3%) had neither CRF nor ESRD at the last follow-up. Female patients, compared with male patients, had a later mean age of onset of ESRD (76.0 [95% CI, 73.8 to 78.1] versus 68.1 [95% CI, 66.0 to 70.2] yr) and CRF (72.5 [95% CI, 70.1 to 74.9] versus 63.7 [95% CI, 61.4 to 66.0] yr). Linear regression and renal survival analyses revealed that the location of PKD2 mutations did not influence the age of onset of ESRD. However, patients with splice site mutations appeared to have milder renal disease compared with patients with other mutation types (P < 0.04 by log rank test; adjusted for the gender effect). Considerable renal disease variability was also found among affected individuals with the same PKD2 mutations. This variability can confound the determination of allelic effects and supports the notion that additional genetic and/or environmental factors may modulate the renal disease severity in ADPKD.

The ENOS polymorphism is not associated with severity of renal disease in polycystic kidney disease 1

BACKGROUND

The renal phenotype in autosomal dominant polycystic kidney disease (ADPKD) is highly variable. Although genetic and allelic heterogeneity explain part of this variability, significant intrafamilial differences in time to end-stage renal disease (ESRD) indicate that genetic modifiers and the environment influence renal phenotype. Previously, a glutamic acid to aspartic acid polymorphism at residue 298 (E/D298) of the endothelial nitric oxide synthase (eNOS) gene ENOS was associated with disease severity in males with ADPKD.

METHODS

We typed the E/D298 polymorphism in 215 mutation-defined polycystic kidney disease 1 (PKD1) patients from 80 families. In this population, 96 patients had ESRD, with a median time to renal failure of 53 years.

RESULTS

Distribution of ENOS genotypes was 86 (40%), 106 (49.3%), and 23 (10.7%) for EE, ED, and DD, respectively. The occurrence of hypertension was not significantly different between genotypes. Kaplan-Meier renal survival analysis showed no significant difference between genotypes, with a median age to ESRD of 53 years for all genotypes in the total population and 52, 52, and 51 years (men) and 57, 53, and 55 years (women) for DD, DE, and EE, respectively.

CONCLUSION

Although the D298 ENOS allele may be associated with lower vascular activity of eNOS, this did not correlate with severity of renal disease in this PKD1 population. An important difference between this study and one finding a modifying role for ENOS was the rigor in defining the PKD1 population. This study shows the importance of using mutation-characterized populations for association studies in ADPKD.