Insertion/deletion angiotensin converting enzyme gene polymorphism affects the microvascular structure of the kidney in patients with nondiabetic renal disease

The Genetic Determinants of Renal Impairment Following Cardiac Surgery

Cardiac surgery is frequently performed, and acute renal dysfunction is a common adverse event following this procedure. Cardiac surgery-related renal injury independently predicts longer hospital stays and greater rates of morbidity and mortality. Although much work has been completed toward better understanding of this phenomenon, the state of knowledge concerning surgery-related renal injury remains limited. Currently, there is no effective paradigm to identify patients who are at risk for this condition; the specific mechanisms of renal injury during surgery are incompletely understood; and few therapies exist to prevent or treat this phenomenon. To better understand this common clinical problem, recent research has focused on the importance of genetic variability within the physiological and patho-physiological systems that underlie renal dysfunction following cardiac surgery. Emphasizing the importance of using genetics to elucidate molecular mechanisms of this disease, this article reviews the current literature on genetic polymorphisms and post cardiac surgery-related renal dysfunction.

Angiotensinogen gene T235 variant: a marker for the development of persistent microalbuminuria in children and adolescents with type 1 diabetes mellitus

AIM

We examined genetic polymorphisms in the renin-angiotensin system (RAS) coding for angiotensin I-converting enzyme (ACE) insertion/deletion (I/D) for angiotensinogen (AGT) M235T and angiotensin II receptor type 1 (AGTR1) A1166C as predictors for the development of microalbuminuria (MA) in children with type 1 diabetes mellitus (T1DM).

METHODS

Four hundred fifty-three (215 males, 238 females) T1DM children [median (interquartile range): age, 16.7 years (13.9-18.3); diabetes duration, 6.9 years (3.3-10.8); age at diagnosis, 9.1 years (5.8-11.8)] were followed prospectively from diagnosis until the development of MA (two of three consecutive overnight urine samples with albumin excretion rates of > or =20 and <200 microg/min). Kaplan-Meier survival curves and Cox proportional multivariate model estimated the probability of developing MA and the relative risk for MA among different variables.

RESULTS

MA developed in 41 (9.1%) subjects. The frequencies of genotypes were as follows: ACE-II 112 (25%), ACE-ID 221 (49%), and ACE-DD 117 (26%) (n=450); AGT-MM 144 (32%), AGT-MT 231 (51%), and AGT-TT 77 (17%) (n=452); AGTR1-AA 211 (47%), AGTR1-AC 204 (45%), and AGTR1-CC 37 (8%) (n=452). The cumulative risk for the development of MA was higher in ACE-DD versus ACE-ID/II groups (log-rank test, P=.05), and a trend was noticed when AGT-TT was compared to AGT-MT/MM groups (log-rank test, P=.08). AGT-TT polymorphism conferred a fourfold increased risk for MA compared to AGT-MM/MT (hazard ratio=3.8; 95% confidence interval=1.43-10.3; P=.008).

INTERPRETATION

Our findings suggest that RAS gene polymorphism at AGT M235T is a strong predictor for early MA in young T1DM subjects.

The Influence of Angiotensin-Converting Enzyme Gene of Donor and Recipient on the Function of Transplanted Kidney

One of the genes that is supposed to influence renal graft function is the one encoding angiotensin I-converting enzyme (ACE). It shows polymorphism in the presence (I allele) or absence (D allele) of a 287-base pair fragment. The question arises whether ACE gene polymorphism of the recipient and donor influences renal graft survival. This prospective study included 94 recipients who underwent ACE genotyping (DD, DI, II) and measured their creatinine clearance after cimetidine administration. These factors were correlated with the occurrence of acute or chronic rejection and of pharmacologic treatment of hypertension. In 27 recipients it was possible to obtain the ACE genotype of the donor. Among the recipients, 36 proved to be DD genotype, 38 ID, and 20 II. Among the donors, 10 proved to be DD genotype, 10 ID, and 7 II. The changes in creatinine clearance after cimetidine administration were not significantly different among any of the genotype subgroups. Significantly higher creatinine concentrations were found among recipients with II genotype compared to the combined group of ID and DD among patients not treated with ACE inhibitors, but not among those receiving ACE I after kidney transplantation. No differences were found in the frequency of rejection episodes among the subgroups with different ACE genotypes. No significant influence of donor ACE genotype on renal graft function was observed. In summary, the I/D genotype was not an independent prognostic factor for renal graft survival in the first 4 years after transplantation. Possibly the use of ACE I alters the influence of genotype on some parameters.

Relation between the angiotensin-converting enzyme insertion/deletion polymorphism and blood pressure in Japanese male subjects

Inconsistent results have been reported regarding the association of the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism and hypertension. Recent studies of population-based samples of three different areas in Japan presented conflicting results regarding this association. We, thus, investigated the relation between the ACE I/D polymorphism and blood pressure (BP), or the frequency of hypertension, respectively, in 706 Japanese male subjects who participated in the health check-up programme of our hospital. The ACE I/D polymorphism was determined by the polymerase chain reaction technique. Of 706 subjects, 203 were found to have hypertension and the other 503 were found to be normotensive. In all subjects, the frequencies of the DD, ID, and II genotypes were 0.123, 0.432, and 0.445, respectively, and the allelic frequency of the D allele was 0.339. In the younger subjects aged <50 years (n=264), neither systolic nor diastolic BP differed significantly among the genotypes. Conversely, in the older subjects aged > or =50 years (n=442), the systolic BP was significantly higher by 5.9 mmHg in the subjects with the ID genotype than those with the II genotype (P<0.01), and the diastolic BP was significantly higher in the subjects with the DD and ID genotypes by 5.1 and 3.3 mmHg, respectively than those with the II genotype (P<0.05 for each), although age, BMI, percentage of smoking habits, drinking habits, or the use of antihypertensive drugs did not differ significantly among the genotypes. In addition, in the older subjects, the hypertensive subjects showed significantly higher frequencies of the DD and ID genotypes and the D allele than the normotensive subjects. These results demonstrated that there was no significant association of the ACE I/D polymorphism with BP or a prevalence of hypertension in younger Japanese men aged <50 years but there was in older Japanese men aged > or =50 years.

Effects of the Genetic Polymorphisms of the Renin-Angiotensin System on Focal Segmental Glomerulosclerosis

BACKGROUND/AIMS

We analyzed the influence of angiotensin-converting enzyme (ACE) I/D, angiotensinogen (AGT) M235T and angiotensin-II-type-1 receptor (AT1R) A1166C genetic polymorphisms on the clinical course of focal segmental glomerulosclerosis (FSGS).

METHODS

This study consisted of 71 patients with nephrotic syndrome due to biopsy proven FSGS and 100 healthy controls. According to the slope of the reciprocal serum creatinine (1/Cr, >or= or <-0.1 dl x mg(-1) x year(-1)) patients were classified into group A (slow progressors, n = 50) and group B (fast progressors, n = 21). Genotyping was performed using polymerase chain reaction (PCR).

RESULTS

There were no relevant differences in the allele frequencies of the investigated polymorphisms between patients with FSGS and controls. Patients carrying the T- allele of the AGT polymorphism required a larger number of antihypertensive agents (MM: 1.35 +/- 1.0 vs. MT/TT: 2.0 +/- 1.2, p < 0.05). The ACE-ID/DD genotypes were more frequently found in patients with fast progression (group A: II: 38.0%, ID/DD: 62.0% vs. group B: II: 14.3%, ID/DD: 85.7%, p < 0.05). The AT1R-A1166C polymorphism was not associated with any of the parameters studied.

CONCLUSION

The course of FSGS is in part genetically determined by polymorphisms of the renin-angiotensin-system. The ACE-I/D polymorphism was shown to be a risk factor of progression of renal disease and the AGT-M235T polymorphism was associated with the severity of arterial hypertension.

Lack of association of the renin-angiotensin system genes polymorphisms and left ventricular hypertrophy in hypertension

OBJECTIVE

The aim of the present study was to determine if there is an association of different gene polymorphisms of renin-angiotensin system and left ventricular hypertrophy (LVH) in patients with essential hypertension (EH) in St Petersburg population.

PATIENTS AND METHODS

We examined 156 patients (the mean age 49+/-8 years) with mild-to-moderate EH recruited from the general population of the outpatient clinic. Left ventricular mass was measured by echocardiography and left ventricular mass index (LVMI) was calculated. Subjects were genotyped for I/D polymorphism of the angiotensin-converting enzyme (ACE) gene, A1166C polymorphism of the AT1 receptor gene, M235T polymorphism of angiotensinogen gene and -6G/A polymorphism of its promoter region.

RESULTS

Genotype distribution of the sample obeyed Hardy-Weinberg equilibrium and was comparable to that reported previously for hypertensive individuals. Groups of patients with II, ID and DD polymorphism of ACE gene did not differ significantly in their LVMI levels. Furthermore, neither ID ACE-gene polymorphism nor ATI-receptor gene and angiotensinogen gene polymorphism was associated with LVH. Additionally, no any significant gene-gene interactions were found to be associated with LVH in the group studied.

CONCLUSIONS

In the light of these observations it seems reasonable to make a preliminary conclusion about lack of association between LVH and distinct polymorphisms of renin-angiotensin system genes in the population studied.

Different impact of deletion polymorphism of gene on the risk of renal and coronary artery disease

OBJECTIVE

An increased frequency of the angiotensin converting enzyme (ACE) D variant has recently been reported in patients with atheromatous renal artery disease (RAD), whereas controversy exists on the risk of coronary artery disease (CAD) associated with this polymorphism. In spite of the frequent coexistence of RAD and CAD, no studies have specifically compared ACE insertion/deletion (I/D) polymorphism in patients with coronary versus renal artery disease or defined the risk of each disease associated with the D variant.

DESIGN

We designed a large case-control study of subjects for whom objective renal or coronary angiographic documentation was available.

METHODS AND RESULTS

We analysed ACE I/D genotype and clinical-biochemical data of a total of 942 subjects (123 patients with and 137 without angiographic evidence of RAD, 420 patients with and 262 without angiographic evidence of CAD). Renal (with and without RAD) and coronary patients were similar for most conventional risk factors. There was no difference in DD frequency between CAD and CAD-free patients (38.1 versus 33.6%, NS) and DD homozygosity was not associated with CAD risk (OR = 1.27, 95% CI = 0.82-1.98). In contrast, the DD genotype was more frequent in RAD than in RAD-free patients (54.5 versus 39.4, P < 0.05) and was associated with a 2.25-fold increased risk of RAD in both the univariate and multivariate logistic regression models. Additional predictors of RAD were age and creatinine. In RAD/RAD-free patients with angiographically documented CAD, DD homozygosity was confirmed to be preferentially associated with RAD (P < 0.05).

CONCLUSIONS

ACE D variant is preferentially associated with atherosclerotic renal rather than with coronary disease, despite similar exposure to atherogenic noxae. DD homozygosity confers a 2.25-fold increased risk of RAD.

Renal function in relation to three candidate genes

We recently found that femoral intima media thickness, as well as the incidence of hypertension, is influenced by genes encoding the angiotensin-converting enzyme (ACE; insertion/deletion [I/D]) polymorphism, alpha-adducin (Gly460Trp), and aldosterone synthase (-344C/T). By interfering with blood pressure or sodium homeostasis, these genetic polymorphisms also may change renal function. We therefore investigated serum creatinine level, calculated and measured creatinine clearances, and 24-hour urinary protein excretion in subjects previously genotyped for these three polymorphisms. The 1,454 participants drawn at random from the population (64.3% of those invited) were aged 43.4 years and included 744 women (51.2%). Blood pressure, measured by study nurses at subjects' homes, averaged 123/76 mm Hg. Mean values were 90 micromol/L for serum creatinine; 84 and 88 mL/min/1.73 m(2) for calculated and measured (n = 855) creatinine clearances, respectively; and 90 mg/d of protein for proteinuria (n = 556). The prevalence of mild renal dysfunction (creatinine clearance </= 60 mL/min/1.73 m(2)) was nearly 11%. In single-gene analyses with adjustment for significant covariables, the risk for mild renal dysfunction was positively associated with the ACE D allele. However, multiple-gene analyses showed that these associations were restricted to carriers of the mutated alpha-adducin Trp allele (40.1% of all subjects). Findings remained similar after hypertensive patients and women on hormonal therapy were excluded. In this phenotypically more homogeneous subgroup, serum creatinine level was 3.6 micromol/L (P = 0.02) and relative risks for mild renal dysfunction and proteinuria were 1.7-fold (P < 0.001) and 26% (P = 0.02) greater in ACE D subjects than ACE II homozygotes, respectively. The aldosterone synthase T allele did not strengthen genetic associations with the ACE D allele considered alone or in combination with the alpha-adducin Trp allele. Thus, in the present cross-sectional analysis, renal function was slightly but consistently impaired when both the ACE D and alpha-adducin Trp alleles were present. These findings, together with experimental studies and our previous reports on femoral intima media thickness and the incidence of hypertension, constitute a growing body of evidence delineating a clinical entity genetically determined by the risk-carrying ACE D and alpha-adducin Trp alleles.

Apoptosis and glomerular injury after prolonged nitric oxide synthase inhibition in spontaneously hypertensive rats

This study was designed to investigate the relationship between apoptosis and glomerular injury in spontaneously hypertensive rats (SHR) with hypertensive disease that was exacerbated by inhibition of NO synthesis. Development of glomerular cell apoptosis was evaluated by assessment of renal hemodynamics, glomerular morphometric changes, and participation of the renin-angiotensin system. Three groups of 20-week-old SHR were investigated: control male SHR and 2 similar groups given 2 doses of N(G)-nitro-L-arginine methyl ester (L-NAME, 50 or 80 mg/L, respectively) for 3 weeks. Mean arterial pressure and renal vascular resistance increased, whereas effective renal plasma flow and glomerular filtration rate were diminished by L-NAME. The small artery wall/lumen ratio increased as the glomerular-tuft area diminished. Renal cortical tissue levels of angiotensin II increased in response to the L-NAME, thereby inducing afferent arteriolar injury. Apoptosis and proliferative index (PCNA) of nonsclerotic glomeruli were induced by the low-dose L-NAME as the glomerular cell number decreased. In contrast, the PCNA index was downregulated with the high-dose L-NAME. These results indicate that angiotensin II activation, induced by L-NAME, was related to glomerular cell deletion and apoptosis together with the pathophysiological changes of severe nephrosclerosis and impaired renal dynamics.

Pathology of progressive nephropathies

The role of cell cycle regulatory proteins in progression is elucidated. Human renal biopsy data show amelioration and even regression of structural injury with interventions. Data implicate new mechanisms of the renin-aldosterone-angiotensin system in progressive injuries, including immune modulation and a direct effect of aldosterone on progression. New approaches and interventions that target these fibrotic responses show promising results.

Apoptosis, coronary arterial remodeling, and myocardial infarction after nitric oxide inhibition in SHR

This study was designed to investigate the relationship between apoptosis (programmed cell death) and coronary arterial remodeling in spontaneously hypertensive rats (SHR) following prolonged nitric oxide synthesis inhibition. In addition, we evaluated whether the development of coronary arterial smooth muscular cell apoptosis was related to hemodynamics or to vascular hypertrophy. Three groups of 20-week-old male SHR were investigated: controls, and two groups that received two doses of N(G)-nitro-L arginine (L-NAME, 50 mg/L and 80 mg/L) each for 3 weeks. Mean arterial pressure and total peripheral resistance index increased whereas cardiac index diminished with L-NAME. Pathohistological study demonstrated increased pericardiac fibrosis and coronary arterial injury score in the L-NAME group in a dose-dependent manner. The high dose of L-NAME (Group 3) produced myocardial infarction in 78% of the rats. The wall:lumen ratio of epicardial coronary arteries was greater in L-NAME treated SHR (0.23+/-0.02 versus 0.16+/-0.02; P<0.05) and was associated with markedly increased apoptosis (15.3+/-6 versus 1. 9+/-1; P<0.05) without smooth muscle cell proliferation (PCNA positive cells). Apoptosis occurred predominantly in hypertrophic coronary arterial smooth muscular cells; myocardial infarction and ventricular fibrosis were exacerbated by impaired hemodynamics induced by L-NAME. These data suggest that coronary endothelial dysfunction and myocardial ischemic disease induced by L-NAME were responsible for apoptosis of coronary arterial smooth muscle cells, myocardial fibrosis, and infarction, all pathological findings that are consistent with what may be found in clinical hypertensive heart disease.