ACE genotype and ACE inhibitors induced renoprotection in chronic proteinuric nephropathies1

Precision Nephrology in Patients with Diabetes and Chronic Kidney Disease

Diabetes is the leading cause of kidney failure and specifically, diabetic kidney disease (DKD) occurs in up to 30% of all diabetic patients. Kidney disease attributed to diabetes is a major contributor to the global burden of the disease in terms of clinical and socio-economic impact, not only because of the risk of progression to End-Stage Kidney Disease (ESKD), but also because of the associated increase in cardiovascular (CV) risk. Despite the introduction of novel treatments that allow us to reduce the risk of future outcomes, a striking residual cardiorenal risk has been reported. This risk is explained by both the heterogeneity of DKD and the individual variability in response to nephroprotective treatments. Strategies that have been proposed to improve DKD patient care are to develop novel biomarkers that classify with greater accuracy patients with respect to their future risk (prognostic) and biomarkers that are able to predict the response to nephroprotective treatment (predictive). In this review, we summarize the principal prognostic biomarkers of type 1 and type 2 diabetes and the novel markers that help clinicians to individualize treatments and the basis of the characteristics that predict an optimal response.

OMICS in Chronic Kidney Disease: Focus on Prognosis and Prediction

Chronic kidney disease (CKD) patients are characterized by a high residual risk for cardiovascular (CV) events and CKD progression. This has prompted the implementation of new prognostic and predictive biomarkers with the aim of mitigating this risk. The ‘omics’ techniques, namely genomics, proteomics, metabolomics, and transcriptomics, are excellent candidates to provide a better understanding of pathophysiologic mechanisms of disease in CKD, to improve risk stratification of patients with respect to future cardiovascular events, and to identify CKD patients who are likely to respond to a treatment. Following such a strategy, a reliable risk of future events for a particular patient may be calculated and consequently the patient would also benefit from the best available treatment based on their risk profile. Moreover, a further step forward can be represented by the aggregation of multiple omics information by combining different techniques and/or different biological samples. This has already been shown to yield additional information by revealing with more accuracy the exact individual pathway of disease.

Precision medicine approaches for diabetic kidney disease: opportunities and challenges

The prevalence of end-stage kidney disease (ESKD) continuously increases worldwide. The increasing prevalence parallels the growth in the number of people with diabetes, which is the leading cause of ESKD. Early diagnosis of chronic kidney disease (CKD) in patients with diabetes and appropriate intervention is important to delay the progression of kidney function decline and prevent ESKD. Rate of CKD progression and response to treatment varies among patients with diabetes, highlighting the need to tailor individual treatment. In this review, we describe recent advances and areas for future studies with respect to precision medicine in diabetic kidney disease (DKD). DKD is a multi-factorial disease that is subject in part to genetic heritability, but is also influenced by various exogenous mediators, such as environmental or dietary factors. Genetic testing so far has limited utility to facilitate early diagnosis, classify progression or evaluate response to therapy. Various biomarker-based approaches are currently explored to identify patients at high risk of ESKD and to facilitate decision-making for targeted therapy. These studies have led to discovery and validation of a couple of inflammatory proteins such as circulating tumour necrosis factor receptors, which are strong predictors of kidney disease progression. Moreover, risk and drug-response scores based on multiple biomarkers are developed to predict kidney disease progression and long-term drug efficacy. These findings, if implemented in clinical practice, will pave the way to move from a one-size-fits-all to a one-fit-for-everyone approach.

Personalized medicine in diabetic kidney disease: a novel approach to improve trial design and patient outcomes

PURPOSE OF REVIEW

In the last decade many attempts have been made to reduce the high residual risk of end-stage kidney disease and cardiovascular disease in patients with diabetic kidney disease by targeting a variety of risk markers. Subsequent analyses revealed that the variation in individual drug response to the tested interventions partly explains why these trials did not result in additional kidney or cardiovascular protection. This review summarizes recent insights regarding individual variation in drug response. Additionally, we explore novel approaches to incorporate this drug response variability in the design of new clinical trials.

RECENT FINDINGS

Recent studies suggest that a plausible explanation for individual therapy resistance emanates from intrinsic individual characteristics such as genetic make-up or volume status and is likely only partially explained by drug characteristics such as the dose or type of intervention. Biomarker-based enrichment strategies to identify high-risk individuals and/or those who are more likely to respond to interventions offer opportunities to tailor therapies to individual patients.

SUMMARY

Individual drug response variability is a recognized phenomenon in clinical practice. It is time to implement novel approaches that take into account this response variability in the design of new trials in diabetic kidney disease in order to define optimal therapies for individual patients.

Early Proteinuria Lowering by Angiotensin-Converting Enzyme Inhibition Predicts Renal Survival in Children with CKD

Background Although pharmacotherapeutic proteinuria lowering was found to be nephroprotective in adults, the predictive value of early drug-induced proteinuria reduction for long-term renal survival in pediatric CKD is unknown. We analyzed data from the ESCAPE Trial for a potential association between initial antiproteinuric effect of standardized angiotensin-converting enzyme (ACE) inhibition and renal disease progression in children with CKD.Methods In total, 280 eligible children with CKD stages 2-4 (mean age 11.7 years old, median eGFR 46 ml/min per 1.73 m², 71% congenital renal malformations) received a fixed dose of ramipril (6 mg/m² per day) and were subsequently randomized to conventional or intensified BP control. We assessed initial proteinuria reduction from baseline to first measurement on ramipril (at 2.5±1.3 months). We used multivariable Cox modeling to estimate the association between initial proteinuria reduction and the risk of reaching a renal end point (50% eGFR decline or ESRD), which occurred in 80 patients during 5 years of observation.Results Ramipril therapy lowered proteinuria by a mean of 43.5% (95% confidence interval, 36.3% to 49.9%). Relative to proteinuria reduction <30%, 30%-60% and >60% reduction resulted in hazard ratios (95% confidence intervals) of 0.70 (0.40 to 1.22) and 0.42 (0.22 to 0.79), respectively. This association was independent of age, sex, CKD diagnosis, baseline eGFR, baseline proteinuria, initial BP, and concomitant BP reduction.Conclusions The early antiproteinuric effect of ACE inhibition is associated with long-term preservation of renal function in children with CKD. Proteinuria lowering should be considered an important target in the management of pediatric CKD.

Genetic Considerations in Pediatric Chronic Kidney Disease

Chronic kidney disease (CKD) in children is an irreversible process that, in some cases, may lead to end-stage renal disease. The majority of children with CKD have a congenital disorder of the kidney or urological tract arising from birth. There is strong evidence for both a genetic and epigenetic component to progression of CKD. Utilization of gene-mapping strategies, ranging from genome-wide association studies to single-nucleotide polymorphism analysis, serves to identify potential genetic variants that may lend to disease variation. Genome-wide association studies evaluating population-based data have identified different loci associated with CKD progression. Analysis of single-nucleotide polymorphisms on an individual level suggests that secondary systemic sequelae of CKD are closely related to dysfunction of the cardiovascular-inflammatory axis and may lead to advanced cardiovascular disease through abnormal vascular calcification and activation of the renin-angiotensin system. Similarly, genetic variants affecting cytokine control, fibrosis, and parenchymal development may modulate CKD through development and acceleration of renal interstitial fibrosis. Epigenetic studies evaluate modification of the genome through DNA methylation, histone modification, or RNA interference, which may be directly influenced by external or environmental factors directing genomic expression. Lastly, improved understanding of the genetic and epigenetic contribution to CKD progression may allow providers to identify a population at accelerated risk for disease progression and apply novel therapies targeted at the genetic mechanism of disease.

Response to angiotensin-converting enzyme inhibition is selectively blunted by high sodium in angiotensin-converting enzyme DD genotype: evidence for gene-environment interaction in healthy volunteers

BACKGROUND

Renin-angiotensin-aldosterone system blockade is a cornerstone in cardiovascular protection. Angiotensin-converting enzyme (ACE)-DD genotype has been associated with resistance to angiotensin-converting enzyme inhibition (ACEi), but data are conflicting. As sodium intake modifies the effect of ACEi as well as the genotype-phenotype relationship, we hypothesize gene-environment interaction between sodium-status, the response to ACEi, and ACE genotype.

METHOD

Thirty-five male volunteers (26 ± 9 years; II n = 6, ID n = 18, DD n = 11) were studied during placebo and ACEi (double blind, enalapril 20 mg/day) on low [7 days 50 mmol Na/day (low salt)] and high [7 days 200 mmol Na/day (high salt)] sodium, with a washout of 6 weeks in-between. After each period mean arterial pressure (MAP) was measured before and during graded infusion of angiotensin II (Ang II).

RESULTS

During high salt, ACEi reduced MAP in II and ID, but not in DD [II: 88 (78-94) versus 76 (72-88); ID: 87 (84-91) versus 83 (79-87); both P < 0.05 and DD: 86 (82-96) versus 88 (80-90); ns, P < 0.05 between genotypes]. However, during low salt, ACEi reduced MAP in all genotype groups [II: 83 (78-89) versus 77 (72-83); ID: 88 (84-91) versus 82 (78-86); DD: 84 (80-91) versus 81 (75-85); all P < 0.05]. During high salt + ACEi, the Ang II response was blunted in DD, with an 18% rise in MAP during the highest dose versus 22 and 31% in ID and II (P < 0.05). Low salt annihilated these differences.

CONCLUSION

In healthy participants, the MAP response to ACEi is selectively blunted in DD genotype during high salt, accompanied by blunted sensitivity to Ang II. Low salt corrects both abnormalities. Further analysis of this gene-environment interaction in patients may contribute to strategies for improvement of individual treatment efficacy.

Donor and recipient ACE I/D genotype are associated with loss of renal function in children following renal transplantation

Genetic polymorphisms of the RAS correlate with allograft function. We therefore analyzed common RAS polymorphisms in kidney donors and in children following RTx to determine the relationship between genotype and decline in GFR, blood pressure, and LVM. A total of 107 children who underwent RTx were included: 70 male, 37 female, mean age 8.8±4.9 yr, mean follow up 5.4 yr. The following RAS polymorphisms were studied in all 107 recipients, 48 donors, and 120 healthy controls: Renin (Renin Mbol 18G/A), ACE I/D; angiotensinogen (AGT M235T), and angiotensin II receptor type-1 (AT1R A1166C). Only patients homozygous for the ACE D allele had a significantly steeper decline in GFR compared with homozygous carriers of the ACE I allele (slope DD: -4.3±0.8 vs. II: -1.3±1.1 mL/min/1.73 m2 per yr; p=0.035). In four cases, a DD recipient received a kidney from a DD donor, and these patients showed a more pronounced decline in GFR (-5.2±0.5 mL/min/1.73 m2 per yr; p=0.002). MABP was not different before vs. after RTx and was independent of ACE I/D genotype. LVMI increased significantly in the majority of patients (36.6±13.9 g/m2.7 six months before RTx vs. 46.4±15.3 g/m2.7 12 months after RTx, p=0.015). However, this difference disappeared after stratification by ACE I/D genotype. The ACE DD genotype is a potential marker for identifying patients at high risk of poor allograft outcome.

Genetic polymorphisms related to the renin-angiotensin-aldosterone system and response to antihypertensive drugs

IMPORTANCE OF THE FIELD

Only 23 - 41% of hypertensive patients receiving antihypertensive drugs achieve adequate blood pressure control. Multiple physiological systems regulate blood pressure and variation in genes involved in these systems may account for enhanced or diminished blood pressure lowering response to antihypertensive therapy.

AREAS COVERED IN THIS REVIEW

We explored explanations for variation in blood pressure response to antihypertensive drugs by linking genetic polymorphisms in renin-angiotensin-aldosterone system (RAAS) genes to antihypertensive drug response on intermediate parameters (e.g., potassium excretion, aldosterone levels). A MEDLINE search (1966 - 2008) was performed to identify publications reporting effects of genetic polymorphisms in the RAAS on antihypertensive drug response with regard to intermediate parameters.

WHAT THE READER WILL GAIN

With regard to the ACE insertion/deletion and the angiotensinogen -217G/A polymorphism variation in blood pressure response could be explained by effects on intermediate parameters. However, most studies that were identified with our search varied in study design, population and outcome, which complicate adequate comparisons.

TAKE HOME MESSAGE

Little evidence is available that explains these pharmacogenetic interactions. In the future, a better understanding of these mechanisms should provide a more solid evidence base for the individualized hypertension treatment based on genetic variation.

Cost-effectiveness of ACE inhibitor therapy to prevent dialysis in nondiabetic nephropathy: influence of the ACE insertion/deletion polymorphism

INTRODUCTION

End-stage renal disease is associated with high health-care costs and low quality of life compared with chronic kidney disease. The renoprotective effectiveness of angiotensin-converting enzyme inhibitors (ACEi) is largely determined by the ACE insertion/deletion (I/D) polymorphism. We determined the cost-effectiveness of ACEi therapy in nondiabetic nephropathy for the ACE II/ID and for the ACE DD genotype separately. Furthermore, we considered a selective screen-and-treat strategy in which patients are prescribed alternative, more effective, therapy based on their ACE (I/D) polymorphism.

METHODS

Time-dependent Markov models were constructed; cohorts of 1000 patients were followed for 10 years. Data were mainly gathered from the Ramipril Efficacy In Nephropathy trial. Both univariate and probabilistic sensitivity analyses were performed.

RESULTS

ACEi therapy dominated placebo in both the ACE II/ID group (euro15 826, and 0.091 quality-adjusted life years gained per patient) and the ACE DD group (euro105 104 and 0.553 quality-adjusted life years gained). Sensitivity analyses showed 30.2% probability of ACEi being not cost-effective in the ACE II/ID group, against an almost 100% probability of cost-effectiveness in the ACE DD group. A selective screen-and-treat strategy should incorporate an alternative therapy for patients with the ACE II/ID genotype with an at least 9.1% increase in survival time compared with ACEi therapy to be cost-effective. Sensitivity analyses show that higher effectiveness and lower costs of the alternative therapy improve the cost-effectiveness of a screening strategy.

CONCLUSION

ACEi therapy is a cost-saving treatment compared with placebo in nondiabetic nephropathy, irrespective of ACE (I/D) genotype. However, ACEi therapy saved more costs and more health gains were achieved in the ACE DD genotype than in the ACE II/ID genotype. An alternative treatment featuring a modest increase in effectiveness compared with ACEi therapy for patients with the ACE II/ID genotype can be incorporated in a cost-effective or even cost-saving screen-and-treat strategy.

Can we personalize treatment for kidney diseases?

The idea of individualizing therapies to obtain optimal clinical results is not new but has only recently been applied to kidney diseases. Nonetheless, kidney disorders present a variety of opportunities to personalize medicine. Here, the heterogeneity of kidney disorders is reviewed to provide a rationale for pursuing personalized medicine. Data on adjusting therapy on the basis of pharmacogenetics/genomics and pharmacodynamics are summarized to demonstrate where the field is, and biomarker studies that reflect the future of personalized medicine are discussed. The goal of this review is to demonstrate that we can personalize therapy for kidney diseases but that considerable investment in new research will be required for personalized medicine to be routinely used in nephrology clinics.

Significance of genetic polymorphisms of the renin–angiotensin–aldosterone system in cardiovascular and renal disease

The angiotensin converting enzyme (ACE) is a component of the renin–angiotensin–aldosterone system (RAAS). The RAAS – involved primarily in blood pressure and sodium homeostasis – is activated in many renal and cardiovascular diseases, and therapy with ACE inhibitors and other blockers of the RAAS has proven to be clinically beneficial. Plasma and tissue levels of ACE are at least partially determined by a genetic polymorphism based on the presence (insertion [I]) or absence (deletion [D]) of a 287 base pair element in intron 16. In particular Asian subjects with the DD genotype (and increased ACE activity) have been reported to be at higher risk for cardiovascular disorders and nephropathy. Numerous studies evaluated the role of the ACE I/D polymorphism as well as other genetic variants of the RAAS in the context of RAAS inhibitor therapy. However, as race and environmental factors, such as salt intake also affect treatment response most studies were underpowered leading to conflicting results.

Angiotensin converting enzyme insertion/deletion polymorphism and renoprotection in diabetic and nondiabetic nephropathies

Despite the huge amount of studies looking for candidate genes, the ACE gene remains the unique, well-characterized locus clearly associated with pathogenesis and progression of chronic kidney disease, and with response to treatment with drugs that directly interfere with the renin angiotensin system (RAS), such as angiotensin converting enzyme (ACE) inhibitors and angiotensin II receptor antagonists (ARA). The II genotype is protective against development and progression of type I and type II nephropathy and is associated with a slower progression of nondiabetic proteinuric kidney disease. ACE inhibitors are particularly effective at the stage of normoalbuminuria or microalbuminuria in both type I and type II diabetics with the II genotype, whereas the DD genotype is associated with a better response to ARA therapy in overt nephropathy of type II diabetes and to ACE inhibitors in male patients with nondiabetic proteinuric nephropathies. The role of other RAS or non-RAS polymorphisms and their possible interactions with different ACE I/D genotypes are less clearly defined. Thus, evaluating the ACE I/D polymorphism is a reliable tool to identify patients at risk and those who may benefit the most of renoprotective therapy with ACE inhibitors or ARA. This may guide pharmacologic therapy in individual patients and help design clinical trials in progressive nephropathies. Moreover, it might help optimize prevention and intervention strategies at population levels, in particular, in countries where resources are extremely limited and 1 million patients continue to die every year of cardiovascular or renal disease.

ACE gene polymorphism and losartan treatment in type 2 diabetic patients with nephropathy

Losartan treatment reduced renal outcomes in proteinuric patients with type 2 diabetes in the Reduction of Endpoints in NIDDM with the Angiotensin II Antagonist Losartan (RENAAL) study. It is unknown whether an insertion (I)/deletion (D) polymorphism in the angiotensin I-converting enzyme (ACE) gene predicts renal outcomes and death and influences the effect of losartan in these patients. Pharmacogenetic analyses were performed comparing losartan with placebo administered with conventional blood pressure-lowering therapy in 1435 (95%) of the 1513 RENAAL study patients. The primary endpoint was the composite of doubling of baseline serum creatinine concentration, end-stage renal disease (ESRD) or death. Cox regression models were stratified on baseline proteinuria and included treatment, geographic region, ACE/ID genotype, and treatment x genotype interaction. Within the placebo group, subjects with the ID or DD genotype were more likely than those with the II genotype to reach the composite endpoint (by 17.5% and 38.1%, respectively, P = 0.029) or its individual components. Within the losartan group, genotype did not correlate with reaching the composite endpoint. Compared with placebo, however, losartan reduced the risk of reaching the composite endpoint by 5.8% (95% confidence interval, -23.3, 28.0), 17.6% (3.8, 29.4), and 27.9% (7.0, 44.1) among those with the II, ID, and DD genotypes, respectively. Similar trends were demonstrated for the individual endpoints. In conclusion, proteinuric type 2 diabetic patients with the D allele of the ACE gene have an unfavorable renal prognosis, which can be mitigated and even improved by losartan.

Impact of the preintervention rate of renal function decline on outcome of renoprotective intervention

BACKGROUND AND OBJECTIVES

Randomized clinical trials on progression of renal diseases usually include patients according to criteria for BP, renal function, and proteinuria. There are no data showing that this provides groups with similar baseline rates of renal function loss. Accordingly, the impact of preintervention rate of renal function loss (slope) on outcome of studies has not been established.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Preintervention slope was established in 60 of 89 renal patients without diabetes in whom a 4-yr prospective, randomized intervention had been performed (enalapril versus atenolol), and whether (1) preintervention slope was distributed equally over the groups; (2) treatment benefit, defined as slope improvement, corresponded to study outcome; and (3) preintervention slope was a determinant of intervention slope were analyzed.

RESULTS

The preintervention slope was different in the groups: -3.7 +/- 3.2 in the group to receive enalapril versus -2.2 +/- 3.3 ml/min per yr in the group to receive atenolol. The intervention slopes were similar: -1.9 +/- 0.8 enalapril and -1.8 +/- 0.7 ml/min per yr atenolol. Accordingly, slope improved during enalapril only. When analyzed by angiotensin-converting enzyme (I/D) genotype, slope improvement was found only in DD genotype. On multivariate analysis, the preintervention slope was a main predictor of the intervention slope.

CONCLUSIONS

Differences in preintervention slope are relevant to outcome of trials and can induce bias. For future studies, allocation according to preintervention slope, although time-consuming, may be useful to allow conduction of more valid studies in a smaller number of patients.

Cost-effectiveness of pharmacogenetic testing to predict treatment response to angiotensin-converting enzyme inhibitor

OBJECTIVE

This study aimed to assess the potential cost-effectiveness of testing patients with nephropathies for the I/D polymorphism before starting angiotensin-converting enzyme (ACE) inhibitor therapy, using a 3-year time horizon and a healthcare perspective.

METHODS

We used a combination of a decision analysis and Markov modeling technique to evaluate the potential economic value of this pharmacogenetic test by preventing unfavorable treatment in patients with nephropathies. The estimation of the predictive value of the I/D polymorphism is based on a systematic review showing that DD carriers tend to respond well to ACE inhibitors, while II carriers seem not to benefit adequately from this treatment. Data on the ACE inhibitor effectiveness in nephropathy were derived from the REIN (Ramipril Efficacy in Nephropathy) trial. We calculated the number of patients with end-stage renal disease (ESRD) prevented and the differences in the incremental costs and incremental effect expressed as life-years free of ESRD. A probabilistic sensitivity analysis was conducted to determine the robustness of the results.

RESULTS

Compared with unselective treatment, testing patients for their ACE genotype could save 12 patients per 1000 from developing ESRD during the 3 years covered by the model. As the mean net cost savings was euro 356,000 per 1000 patient-years, and 9 life-years free of ESRD were gained, selective treatment seems to be dominant.

CONCLUSION

The study suggests that genetic testing of the I/D polymorphism in patients with nephropathy before initiating ACE therapy will most likely be cost-effective, even if the risk for II carriers to develop ESRD when treated with ACE inhibitors is only 1.4% higher than for DD carriers. Further studies, however, are required to corroborate the difference in treatment response between ACE genotypes, before genetic testing can be justified in clinical practice.

ACE phenotyping as a first step toward personalized medicine for ACE inhibitors. Why does ACE genotyping not predict the therapeutic efficacy of ACE inhibition?

Angiotensin (Ang)-converting enzyme (ACE) inhibitors are widely used for the treatment of cardiovascular diseases. Not all patients respond to ACE inhibitors, and it has been suggested that genetic variation might be a useful marker to predict the therapeutic efficacy of these drugs. In particular, the ACE insertion (I)/deletion (D) polymorphism has been investigated in this regard. Despite a decade of intensive research involving the genotyping of thousands of patients, we still do not know whether ACE genotyping helps in predicting the success of ACE inhibition. This review critically addresses the concept that predictive information on therapeutic efficacy of ACE inhibitors might be obtained based on ACE genotyping. It answers the following questions: Do higher ACE levels really result in higher Ang II levels? Is ACE the only converting enzyme in humans? Does ACE inhibition affect ACE expression? Why does ACE have 2 catalytically active domains? What is the relevance of ACE inhibitor-induced signaling through membrane-bound ACE? The review ends with the proposal that ACE phenotyping may prove to be a better first step toward personalized medicine for ACE inhibitors than ACE genotyping.

Angiotensin converting enzyme gene polymorphisms do not predict the course of idiopathic nephrotic syndrome in Swiss children

AIM

Contradictory reports exist about a correlation of angiotensin I converting enzyme (ACE) gene polymorphisms to the outcome of idiopathic nephrotic syndrome (INS) in children. We investigated the frequency of ACE polymorphisms and their impact on the clinical course of INS in children in a Swiss hospital.

METHODS

The ACE gene polymorphism (I, insertion; D, deletion) was assessed in 32 children - 22 with steroid-sensitive INS and 10 with steroid-resistant INS - with a median age at onset of INS of 2.9 years (range 1.1-15.0). Polymerase chain reaction amplification was performed on genomic DNA isolated from blood leucocytes. Results were correlated to clinical course and renal morphology.

RESULTS

The ACE genotype was I/I, I/D and D/D in two, 12 and eight patients, respectively, with steroid-sensitive INS, and in one, eight and one patient, respectively, with steroid resistance. Renal morphology, available in 25 patients showed minimal change glomerulopathy in 17 patients (14 steroid-sensitive; three steroid-resistant) and focal segmental glomerulosclerosis in eight (one steroid-sensitive; seven steroid-resistant). There was no significant correlation between ACE genotype and steroid responsiveness, histology or outcome. ACE genotype was I/I, I/D and D/D in none, 12 and five patients, respectively, with minimal change glomerulopathy, and in one, five and two patients, respectively, with focal segmental glomerulosclerosis. Six patients with steroid-resistant nephrotic syndrome went into end stage renal disease; ACE genotype was I/I in one and I/D in five, but none were D/D.

CONCLUSION

In contrast to previous reports, ACE gene polymorphism is irrelevant for clinical outcome, steroid responsiveness or morphology in Swiss children with INS.

Angiotensin type 1 and type 2 receptor blockade in chronic allograft nephropathy

Angiotensin-II (Ang-II) type 1 (AT(1)) receptor blockers may delay the progression of chronic allograft nephropathy (CAN). However, neither the optimal time for initiating AT(1) receptor blockade in order to delay CAN potentially nor the role of Ang-II type 2 (AT(2)) receptors under AT(1) receptor blockade is known. Both AT receptors can regulate p53 expression and apoptosis. We investigated what time of initiation with AT(1) blockers most effectively delayed CAN as well as the role of the AT(2) receptor, and how angiotensin receptor blockade affected apoptosis and its regulating factors in this context in a rat model. Kidneys of Fisher (F344) rats were transplanted into Lewis rats. Animals were treated with AT(1) (candesartan) and/or AT(2) (PD123319) receptor antagonists, a calcium channel blocker, or vehicle (treatment periods: day -7 before to week 24 after transplantation (long term), week 12 to week 24 (late), day -7 to day +5 (early)) and observed the animals for 24 weeks. Reduction of proteinuria, grade of CAN, and number of apoptotic cells was most pronounced in animals receiving long-term AT(1) receptor blockade. A combined AT(1)/AT(2) blocker treatment reduced CAN similarly to AT(1) blocker treatment alone. The number of apoptotic cells and the level of p53 mRNA were significantly lower in long-term AT(1) blocker-treated animals. In summary, AT(1) receptor blockade delayed the progression of CAN, particularly in animals treated long term. Reduction of apoptosis could be related to these beneficial effects. The AT(2) receptor does not appear to play an important role in CAN.

The role of renin-angiotensin-aldosterone system in the progression of chronic kidney disease

The renin-angiotensin-aldosterone system (RAAS) is a well known regulator of blood pressure (BP) and determinant of target-organ damage. It controls fluid and electrolyte balance through coordinated effects on the heart, blood vessels, and Kidneys. Angiotensin II (AII) is the main effector of the RAAS and exerts its vasoconstrictor effect predominantly on the postglomerular arterioles, thereby increasing the glomerular hydraulic pressure and the ultrafiltration of plasma proteins, effects that may contribute to the onset and progression of chronic renal damage. AII may also directly contribute to accelerate renal damage by sustaining cell growth, inflammation, and fibrosis. Interventions that inhibit the activity of the RAAS are renoprotective and may slow or even halt the progression of chronic nephropathies. ACE inhibitors and angiotensin II receptor antagonists can be used in combination to maximize RAAS inhibition and more effectively reduce proteinuria and GFR decline in diabetic and nondiabetic renal disease. Recent evidence suggests that add-on therapy with an aldosterone antagonist may further increase renoprotection, but may also enhance the risk hyperkalemia. Maximized RAAS inhibition, combined with intensified blood pressure control (and metabolic control in diabetics) and amelioration of dyslipidemia in a multimodal approach including lifestyle modifications (Remission Clinic), may achieve remission of proteinuria and renal function stabilization in a substantial proportion of patients with proteinuric renal disease. Ongoing studies will tell whether novel drugs inhibiting the RAAS, such as the renin inhibitors or the vasopeptidase inhibitors, may offer additional benefits to those who do not respond, or only partially respond, to this multimodal regimen.

Renin–angiotensin system gene polymorphisms: association with susceptibility to Henoch–Schonlein purpura and renal involvement

The clinical course of Henoch-Schönlein Purpura (HSP) in children is variable, with some patients having a much more rapidly progressing course than others. We investigated whether polymorphisms of the renin-angiotensin system (RAS) genes are involved in HSP. Three RAS genotypes were examined in 114 children with HSP and in 164 healthy children: the angiotensin I converting enzyme (ACE) insertion/deletion polymorphism, the M235T mutation in the angiotensinogen gene (Agt), and the A1166C in the angiotensin II type I receptor (AT1R) gene. Significant differences were observed between HSP patients and control group in the frequency of ACE and Agt genotypes (p=0.004 and p=0.003, respectively). The TT genotype of Agt gene was associated with a 3.5-fold increased risk for Henoch-Schönlein nephritis (HSN) compared with the MM/MT genotype (odds ratio, 3.5; 95% confidence interval, 1.2-10.4). There was a trend to a higher prevalence of the TT genotype of the Agt gene among patients with nephrotic range proteinuria when compared to the patients with mild proteinuria, although the difference did not reach a statistical significance. The results of this study suggest that polymorphisms of ACE gene and Agt gene likely influence the risk of developing HSP. However, among the three genes of the RAS studies, only Agt gene was associated with the susceptibility to HSN. RAS gene polymorphisms studied are not associated with the presence of nephrotic range proteinuria. Additional studies are warranted to verify the correlation between RAS gene polymorphisms and susceptibility to HSP.

Mechanisms of progression and regression of renal lesions of chronic nephropathies and diabetes

The incidence of chronic kidney diseases is increasing worldwide, and these conditions are emerging as a major public health problem. While genetic factors contribute to susceptibility and progression of renal disease, proteinuria has been claimed as an independent predictor of outcome. Reduction of urinary protein levels by various medications and a low-protein diet limits renal function decline in individuals with nondiabetic and diabetic nephropathies to the point that remission of the disease and regression of renal lesions have been observed in experimental animals and even in humans. In animal models, regression of glomerular structural changes is associated with remodeling of the glomerular architecture. Instrumental to this discovery were 3D reconstruction studies of the glomerular capillary tuft, which allowed the quantification of sclerosis volume reduction and capillary regeneration upon treatment. Regeneration of capillary segments might result from the contribution of resident cells, but progenitor cells of renal or extrarenal origin may also have a role. This review describes recent advances in our understanding of the mechanisms and mediators underlying renal tissue repair ultimately responsible for regression of renal injury.

Does the Angiotensin-converting enzyme (ACE) gene insertion/deletion polymorphism modify the response to ACE inhibitor therapy?--A systematic review

Background

Pharmacogenetic testing to individualize ACE inhibitor therapy remains controversial. We conducted a systematic review to assess the effect modification of the insertion/deletion (I/D) polymorphism of the ACE gene on any outcome in patients treated with ACE inhibitors for cardiovascular and/or renal disease.

Methods

Our systematic review involved searching six electronic databases, then contacting the investigators (and pharmaceutical industry representatives) responsible for the creation of these databases. Two reviewers independently selected relevant randomized, placebo-controlled trials and abstracted from each study details on characteristics and quality.

Results

Eleven studies met our inclusion criteria. Despite repeated efforts to contact authors, only four of the eleven studies provided sufficient data to quantify the effect modification by genotypes. We observed a trend towards better response to ACE inhibitors in Caucasian DD carriers compared to II carriers, in terms of blood pressure, proteinuria, glomerular filtration rate, ACE activity and progression to end-stage renal failure. Pooling of the results was inappropriate, due to heterogeneity in ethnicity, clinical domains and outcomes.

Conclusion

Lack of sufficient genetic data from the reviewed studies precluded drawing any convincing conclusions. Better reporting of genetic data are needed to confirm our preliminary observations concerning better response to ACE inhibitors among Caucasian DD carriers as compared to II carriers.

A Prospective Open-Label Randomised Trial of Quinapril and/or Amlodipine in Progressive Non-Diabetic Renal Failure

BACKGROUND

Treatment of hypertension slows the progression of non-diabetic nephropathies, but the optimal regimen is unknown. Angiotensin-converting enzyme inhibitors are more effective than beta-blockers, but their merits relative to calcium channel blockers are less clear.

METHODS

73 hypertensive patients with progressive non-diabetic nephropathies were prospectively randomised to open-label quinapril (Q, n = 28), amlodipine (A, n = 28) or both drugs (Q&A, n = 17). Therapy was increased to achieve a diastolic blood pressure < 90 mm Hg. Patients were followed for 4 years or until death. The primary outcome was the combined endpoint of doubling serum creatinine, starting renal replacement therapy or death.

RESULTS

There was no significant difference in the primary outcome, or in the change of glomerular filtration rate. Blood pressure was equally controlled throughout the study period. 29 (40%) patients were withdrawn from the allocated therapy (Q 39%, A 36%, Q&A 47%). Because of the large crossover between trial arms, the data were re-analysed per protocol. The effect on preventing the need for renal replacement therapy then approached significance between the groups (p = 0.089) and the combined quinapril-containing groups were less likely than the amlodipine group to achieve the primary endpoint (p = 0.038), or the individual endpoints of renal replacement therapy (p = 0.030) or doubling creatinine (p = 0.051).

CONCLUSIONS

Quinapril is more effective than amlodipine at reducing the incidence of dialysis in patients with progressive renal failure, but only if they can tolerate the drug. The tolerability of these drugs in patients with advanced renal failure is poor.

Angiotensin-I converting enzyme insertion/deletion polymorphism and its association with diabetic nephropathy: a meta-analysis of studies reported between 1994 and 2004 and comprising 14,727 subjects

AIMS/HYPOTHESIS

The ACE insertion/deletion polymorphism has been examined for association with diabetic nephropathy over the past decade with conflicting results. To clarify this situation, we conducted a comprehensive meta-analysis encompassing all relevant studies that were published between 1994 and 2004 and investigated this potential genetic association.

METHODS

A total of 14,727 subjects from 47 studies was included in this meta-analysis. Cases (n=8,663) were type 1 or 2 diabetic subjects with incipient (microalbuminuria) or advanced diabetic nephropathy (proteinuria, chronic renal failure, end-stage renal disease). Control subjects (n=6,064) were predominantly normoalbuminuric.

RESULTS

No obvious publication bias was detected. Using a minimal-case definition based on incipient diabetic nephropathy, subjects with the II genotype had a 22% lower risk of diabetic nephropathy than carriers of the D allele (pooled odds ratio [OR]=0.78, 95% CI=0.69-0.88). While there was a reduced risk of diabetic nephropathy associated with the II genotype among Caucasians with either type 1 or type 2 diabetes, the association was most marked among type 2 diabetic Asians (Chinese, Japanese, Koreans) (OR=0.65, 95% CI=0. 51-0.83). This OR is significantly different from the OR of 0.90 (95% CI= 0.78-1.04) that was obtained for type 2 diabetic Caucasians (p=0.019). Using a stricter case definition based on advanced diabetic nephropathy, a comparable risk reduction of 24-32% was observed among the three subgroups, although statistical significance was reached only among Asians.

CONCLUSIONS/INTERPRETATION

The results of our meta-analysis support a genetic association of the ACE Ins/Del polymorphism with diabetic nephropathy. These findings may have implications for the management of diabetic nephropathy using ACE inhibitors especially among type 2 diabetic Asians.

Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers for IgA nephropathy

The lengthy course of IgA nephropathy and the possibility of good outcomes without therapy suggest nontoxic therapies such as angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs.) Among patients with IgA nephropathy, both ACE inhibitors and ARBs reduce the transglomerular passage of large, but not small, molecules, reducing proteinuria. The antiproteinuric effects of ACE inhibitors and ARBs are probably equivalent. Dual ACE inhibitor-ARB therapy reduces proteinuria by 54% to 73% and is more effective than either agent alone. To determine whether ACE inhibitors or ARBs preserve renal function long-term, one must rely on trials studying nondiabetic, proteinuric renal diseases rather than on trials specific to IgA nephropathy. Among this group of patients, several randomized, controlled trials, including the AIPRI trial, the REIN trial, and a metaanalysis of 11 randomized, controlled trials, have established clearly that the ACE inhibitors preserve renal function. There is no reason to believe that this information is not applicable to IgA nephropathy. The COOPERATE trial, in which 50% of the subjects had IgA nephropathy, established that ACE inhibitors and ARBs preserve renal function equally, and that dual ACE inhibitor-ARB therapy preserves renal function more effectively than either therapy alone. These data suggest that most individuals with proteinuric renal diseases, including IgA nephropathy, should be treated with ACE inhibitors and ARBs, ideally in combination. Polymorphisms of the angiotensinogen gene, the ACE gene, and the angiotensin II type I receptor gene have, so far, failed to predict either susceptibility to or progression of IgA nephropathy. However, the D allele of the ID polymorphism, particularly the DD genotype, could predict a favorable response to renin-angiotensin blockade.

Pharmacogenomics and renal drug disposition in the newborn

Genetic polymorphisms in the genes coding for drug metabolizing enzymes, drug transporters, and drug receptors are major determinants of an individual's response to drugs. The potential interactions of pharmacogenomics of renal drug transporters and drug receptors with renal drug disposition and the immature kidneys are briefly reviewed. Examples of gene polymorphisms seen in the RAAS (renin angiotensin system), beta-adrenergic receptors, dopamine receptors and cytochrome P450 and their potential clinical impact are discussed. The human newborn has deficient hepatic and renal drug metabolism and disposition. This immaturity in drug-handling capacity may potentially be superimposed to genetic polymorphisms determining drug metabolism and transport thereby substantially increasing interpatient variability in drug dose requirements and in drug responses in the newborn. Pharmacogenomics is a tool that can be used to individualize drug therapy in newborns to minimize adverse drug effects and to optimize efficacy.

Long-term renoprotective effects of losartan in diabetic nephropathy: interaction with ACE insertion/deletion genotype?

OBJECTIVE

Several observational follow-up studies have found that the D allele of the insertion (I)/deletion (D) polymorphism of the ACE gene (ACE/ID) is associated with an increased risk of renal function loss, even during ACE inhibition. Therefore, we investigated the long-term effect of the angiotensin II subtype-1 (AT1) receptor antagonist losartan (100 mg o.d.) on kidney function in II and DD type 1 diabetic patients with diabetic nephropathy.

RESEARCH DESIGN AND METHODS

A total of 54 hypertensive type 1 diabetic patients with diabetic nephropathy homozygous for the insertion (n = 26) or the deletion (n = 28) allele were included in the study. After a 4-week washout, the patients received losartan (tablet, 100 mg o.d.) and were followed prospectively with a mean follow-up period of 36 months. Patients and investigators were blinded to ACE genotypes. At baseline, after 2 and 4 months and every 6 months thereafter, glomerular filtration rate (GFR), albuminuria, and 24-h blood pressure were determined.

RESULTS

At baseline, GFR, albuminuria, and blood pressure were similar in the two genotype groups, II versus DD: mean (SD), 86 (22) vs. 88 (24) ml. min(-1). 1.73 m(-2); median (interquartile range), 1,134 (598-2,023) vs. 1,451 (893-1,766) mg/24 h; and mean (SD), 156/82 (17/9) vs. 153/80 (17/11) mmHg, respectively. GFR decreased similarly in both genotype groups, versus DD, respectively (P = 0.4): geometric mean (95% CI), 2.9 (2.0-4.2) vs. 3.4 (2.3-5.1) ml. min(-1). year(-1). Albuminuria and arterial blood pressure were significantly reduced during the study; no differences were noted between groups. During follow-up, albuminuria was decreased by 75% (95% CI 59-85) and 73% (56-83) in the II and DD groups, respectively (P < 0.01 vs. baseline). Mean systolic and diastolic blood pressures were 139/74 mmHg (14/8) in both genotype groups during the study (P < 0.01 vs. baseline).

CONCLUSIONS

In contrast to previous observational studies with ACE inhibitors, long-term treatment with losartan has similar beneficial renoprotective effects on progression of diabetic nephropathy in hypertensive type 1 diabetic patients with ACE II and DD genotypes.

Pharmacogenomics of angiotensin converting enzyme inhibitors in renal disease--pathophysiological considerations

Angiotensin converting enzyme (ACE) inhibitors preserve native kidney function in patients with renal disease better than other antihypertensive drugs, most likely because they more effectively reduce proteinuria. The plasma concentration of the ACE inhibitors target is, at least in part, under genetic control. A polymorphism of the ACE gene based on the presence or absence of a 287 base pair element in intron 16 accounts for 47% of the total phenotypic variance in the plasma ACE levels of healthy individuals. Unfortunately, pharmacogenetic studies performed so far do not provide a clear answer as to whether the efficacy of the reduction of proteinuria by ACE inhibitors is influenced by the ACE genotype - probably because these studies were not primarily designed to answer this question. This paper will try to outline some aspects that should be considered before an appropriate study on this topic is initiated.

Halting the progression of chronic nephropathy

The incidence of end-stage renal disease (ESRD) is increasing worldwide. In the United States alone, there were 372,000 patients requiring renal replacement therapy in the year 2000 and is expected to rise to 650,000 by the year 2010. The trends in Europe and Japan are forecasted to follow a similar path. These increases represent a significant burden to countries worldwide; not only due to the financial costs of providing ESRD care, but also because of lost productivity and significant morbidity and mortality for the affected patients. There is clearly a pressing need for the aggressive identification and early treatment of patients with nephropathy to prevent progression to ESRD. Research in the last 25 yr has made great advances in the understanding of the progression of chronic renal disease in diabetic and nondiabetic proteinuric nephropathy. There are now effective treatment options that can slow the progression of chronic nephropathies in many individuals, and ongoing research has raised the tantalizing prospect of the reversal of renal disease progression.

ACE genotype and ACE inhibitor response in kidney disease: a perspective

Angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce blood pressure and slow the progression of renal diseases. However, a substantial interindividual variability in treatment response also has been noted. The activity of ACE is partially dependent on the presence or absence of a 287-bp element in intron 16, and this insertion/deletion (I/D) polymorphism accounts for 47% of the total phenotypic variance in plasma ACE; DD subjects have the highest; ID subjects, intermediate; and II individuals, the lowest concentrations. Data suggest that genotype also determines tissue enzyme activity, and, at least under certain conditions, ACE activity is a rate-limiting step for angiotensin II formation. It therefore has been speculated that the ACE polymorphism also might affect therapeutic effects of ACE inhibitors. Unfortunately, clinical studies performed to date do not allow us to draw definite conclusions. Nonetheless, the rapidly evolving area of pharmacogenomics soon will also affect therapeutic decisions in the field of nephrology and hypertension.

Drug target pharmacogenomics: an overview

Pharmacogenomics is a field aimed at understanding the genetic contribution to variability in drug efficacy and toxicity. The goal is to be able to select the drugs with the greatest likelihood of benefit and the least likelihood of harm in individual patients, based on their genetic make-up. Pharmacogenetics has historically been a field focused primarily on genetic polymorphisms in drug metabolizing enzymes and their impact on drug efficacy and toxicity. More recently, investigators have begun to study the relationship between drug target polymorphisms and drug efficacy and toxicity. There are now numerous examples in the literature of associations between drug target polymorphisms and drug effect. Drug targets can be broken into three main categories: the direct protein target of the drug, signal transduction cascades or downstream proteins, and disease pathogenesis proteins. While the drug target pharmacogenetics literature provides 'proof of concept' that genetic variability contributes to the variability in drug response, the data are not to the point of being clinically useful in most cases. Specific problems to date include the inability of a single polymorphism to be highly predictive of response, and inconsistencies across studies of the same polymorphism. It seems likely that an important factor in the above limitations is the approach of focusing on a single polymorphism in a single gene. Given that most drug responses involve a large number of proteins, all of whose genes could have several polymorphisms, it seems unlikely that a single polymorphism in a single gene would explain a high degree of drug response variability in a consistent fashion. Thus, it seems that a polygenic, or genomic approach will be more appropriate. Candidate gene and genome scanning approaches to pharmacogenomics have shown promise in relating drug target polymorphisms to response or toxicity, and pharmacogenomic strategies for drug discovery and drug development are now being implemented by most major pharmaceutical companies. Pharmacogenomics has the potential to significantly enhance the ability of clinicians to use medications in a safe and effective manner and, as such, represents an exciting field with tremendous clinical potential.

Slowing the progression of renal failure

In recent years several multicentric prospective studies have demonstrated the efficacy of some therapeutic measures to slow the progression of renal diseases. Inhibition of renin-angiotensin system (RAS) both by ACE inhibitors (ACEI) and angiotensin II receptor antagonists (ARA) is probably the strongest therapeutic alternative: The antiproteinuric effect of these drugs is an excellent surrogate marker and a predictor of the beneficial influences on the progression of renal failure. The type of renal disease, an inadequate control of blood pressure, and the presence of obesity may counteract the beneficial influences of RAS inhibition, whereas early treatment of all patients with significant proteinuria before the appearance of renal insufficiency and combined therapy with an ACEI and an ARA may augment it. Dietary protein restriction is a classic treatment of chronic renal insufficiency whose effectiveness has been validated by multicentric studies. However, a poor compliance of the patient and the risk of malnutrition with very strict protein restriction could limit the benefits of this treatment. Treatment of hyperlipidemia, prevention of obesity, avoidance of smoking, and regular physical exercise are interventions whose therapeutic potential is progressively recognized, particularly in type 2 diabetic nephropathy. Early correction of anemia may contribute to the slowing of renal disease progression. Although further studies are required, the accumulated evidence and the likelihood of additive beneficial effect of these therapeutic measures advise their combined implementation in patients with chronic renal diseases.

Association of the D allele of the angiotensin I converting enzyme polymorphism with malignant vascular injury

AIMS

To determine whether there is an association between the insertion/deletion (I/D) polymorphism of the human angiotensin I converting enzyme (ACE) gene and malignant vascular injury (MVI).

METHODS

The polymerase chain reaction was used to genotype DNA extracted from archival, paraffin wax embedded renal biopsy material from 48 patients with MVI, made up from cases of malignant hypertension (n = 23), scleroderma (n = 10), and haemolytic uraemic syndrome (n = 15), and from whole blood samples from 191 healthy controls.

RESULTS

The D allele was found more frequently in cases of MVI than in healthy controls, (65% v 52%). Both the DD and I/D genotypes occurred significantly more frequently in patients with MVI than did the II genotype (chi(2) = 7.26, p = 0.007; and chi(2) = 4.06, p = 0.04, respectively).

CONCLUSIONS

Possession of at least one copy of the D allele is associated with an increased risk of developing MVI. Our data support a dominant mode of effect for the D allele. Use of the I/D polymorphism as a genetic marker for MVI may be of value clinically in identifying at risk individuals before the development of target end organ damage. Furthermore, those at risk may benefit from early ACE inhibition.

Pharmacogenomics: the inherited basis for interindividual differences in drug response

It is well recognized that most medications exhibit wide interpatient variability in their efficacy and toxicity. For many medications, these interindividual differences are due in part to polymorphisms in genes encoding drug metabolizing enzymes, drug transporters, and/or drug targets (e.g., receptors, enzymes). Pharmacogenomics is a burgeoning field aimed at elucidating the genetic basis for differences in drug efficacy and toxicity, and it uses genome-wide approaches to identify the network of genes that govern an individual's response to drug therapy. For some genetic polymorphisms (e.g., thiopurine S-methyltransferase), monogenic traits have a marked effect on pharmacokinetics (e.g., drug metabolism), such that individuals who inherit an enzyme deficiency must be treated with markedly different doses of the affected medications (e.g., 5%-10% of the standard thiopurine dose). Likewise, polymorphisms in drug targets (e.g., beta adrenergic receptor) can alter the sensitivity of patients to treatment (e.g., beta-agonists), changing the pharmacodynamics of drug response. Recognizing that most drug effects are determined by the interplay of several gene products that govern the pharmacokinetics and pharmacodynamics of medications, pharmacogenomics research aims to elucidate these polygenic determinants of drug effects. The ultimate goal is to provide new strategies for optimizing drug therapy based on each patient's genetic determinants of drug efficacy and toxicity. This chapter provides an overview of the current pharmacogenomics literature and offers insights for the potential impact of this field on the safe and effective use of medications.

Pharmacogenetics, pharmacogenomics, and cardiovascular therapeutics: the way forward

The completion of sequencing of the human genome will be the vanguard for numerous advances in medicine. The first discernible application is likely to occur in pharmacogenomics, a field focused on the influence of genetic differences on the variability in patients' response to medications. While an inherited basis for drug response has been recognized for some time, it is the confluence of molecular biology, high-throughput genotyping, and bioinformatics that has made it practical to study the genetic basis of variability to medications on a large scale. Pharmacogenomics may enable clinicians to prospectively identify patients most likely to derive benefit from a drug, with minimal likelihood of adverse events. This DNA-based approach to predicting clinical drug efficacy and toxicity would shift the current prescribing paradigm from its empirical nature to a more patient-specific model, ushering in a new era of personalized medicine. Polymorphisms in drug metabolizing enzymes, drug targets, and disease pathogenesis genes are associated with therapeutic effect to cardiovascular pharmacotherapy. Moreover, pharmacogenomics and functional genomics are expected to have a profound impact on the process of drug discovery and development. Finally, pharmacogenomics is likely to transform the way clinical trials are conducted by allowing for the selection of a more homogeneous study population, thereby reducing the size and cost of clinical investigation.

Genetic polymorphisms of the renin-angiotensin-aldosterone system in end-stage renal disease

BACKGROUND

Hypertension contributes to the progression to renal failure. A genetic susceptibility to hypertension may predispose to the development of end-stage renal disease (ESRD) and promote a more rapid progression to ESRD in patients with renal diseases. Genes encoding for angiotensinogen (AGT), angiotensin-converting enzyme (ACE), and aldosterone synthase (CYP11B2) are candidates for abnormal blood pressure regulation.

METHODS

Genotyping was performed in 327 control subjects and 260 ESRD patients for the M235T-AGT, the insertion/deletion (I/D)-ACE, and the -344T/C-CYP11B2 gene polymorphisms using polymerase chain reaction, gel analysis, and appropriate restriction digest when required.

RESULTS

Genotype frequencies did not differ significantly between ESRD patients and controls. When ESRD diabetic subjects were compared with diabetic patients without nephropathy, the prevalence of the AGT-MM genotype was lower (28.1 vs. 52.8%, P < 0.01), while the AGT-TT genotype was higher (15.6 vs. 2.7%, P < 0.05). The AGT-TT genotype was associated with a faster progression to ESRD in patients with glomerulonephritis (P < 0.05). In the total ESRD population, progression of renal disease was faster with the ACE-DD than with the DI and II alleles (P < 0.05). This association was particularly strong when the interaction with the AGT genotype was analyzed, with a rapid progression in ACE-DD as compared with ACE-DI and II in patients with the AGT-MM genotype (P < 0.01).

CONCLUSIONS

Susceptibility for ESRD and faster progression to ESRD are linked with the AGT genotype in diabetic patients. Faster progression to ESRD is associated with the ACE genotype when the total population with ESRD and with the AGT genotype when patients with glomerulonephritis are considered. Thus, genes of the renin-angiotensin-aldosterone system are candidate genes for further understanding of the interindividual differences in the development and course of ESRD.

Contribution of gene polymorphisms in the renin-angiotensin system to macroangiopathy in patients with diabetic nephropathy

The renin-angiotensin system is important in the control of hemodynamic status and pathogenesis of macrovascular disease, which is a major cause of morbidity and mortality in patients with type 2 diabetes with nephropathy. Serum angiotensin-converting enzyme (ACE) and angiotensinogen (Atg) levels are related to their respective gene polymorphisms. Seventy patients with type 2 diabetes with overt nephropathy (serum creatinine >/= 1.5 mg/dL) were studied. Serum ACE activity was measured by the spectrophotometric method. ACE deletion/insertion (D/I) and Atg M235T genotypes were determined by polymerase chain reaction. Patients with and without macroangiopathy were compared. Those with macroangiopathy had increased ACE activity (median, 60.9 U/L; range, 37.9 to 100 U/L versus without macroangiopathy, 47.9 U/L; range, 11.2 to 84.5 U/L; P = 0.01) and prevalence of ACE DD/DI genotypes (DD/DI:II: with macroangiopathy, 61%:39% versus without macroangiopathy, 34%:66%; P = 0.03). Multivariate analysis using age; sex; duration of diabetes; glycemic, blood pressure, and lipid level control; serum creatinine level; and presence of the ACE D allele showed that presence of the D allele (P = 0.03; odds ratio, 1.8; confidence interval, 1.1 to 3.1) and serum creatinine level (P = 0.0007) were independent risk factors for macroangiopathy. Association of the D allele became insignificant after serum ACE activity was included in the analysis in which only serum ACE activity (P = 0.004) and serum creatinine level (P = 0.01) were independent risk factors. Neither Atg M235T nor its synergistic effect with the ACE D allele showed an association with macroangiopathy. In conclusion, the ACE D allele is associated with macroangiopathy in Chinese patients with type 2 diabetes with nephropathy. The association is dependent on its effect on serum ACE activity, which is an independent risk factor for the development of macroangiopathy.