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

Adequacy Targets of Peritoneal Dialysis in the Asian Population

End-stage renal disease affects a large number of patients in Asia. The percentage of patients utilizing PD varies significantly in Asian countries. Continuous ambulatory peritoneal dialysis (CAPD) accounts for about 80% of the dialysis population in Hong Kong.

In this review, we address several questions related to adequacy targets in Asians: Are Asians different? Is dialysis adequacy important for Asians? What is the magnitude of the benefit and the optimal dose of dialysis prescription? Is the adequacy target realistic?

The current international recommendations, including the Dialysis Outcomes Quality Initiative guidelines, are compared with some of our own data for Asian patients. Our published data on dialysis adequacy, nutrition, residual renal function, and peritoneal membrane transport showed that those factors have a significant impact on the morbidity and mortality of PD patients in Hong Kong.

Our results show that solute clearance as measured by Kt/V has a significant impact on the outcome of Asian CAPD patients. Although Chinese PD patients have excellent medium-term patient and technique survival despite an apparently lower Kt/V as compared with the CANUSA standard, that favorable outcome should not prevent nephrologists from providing adequate dialysis to Asian patients. From our own data and analysis, we propose a target Kt/V of 1.9 in Asian CAPD populations. Small-volume dialysis (6 L daily) may be an acceptable compromise in some Asian populations with a smaller body size, especially with residual renal function, given the financial constraints in some developing countries.

Dialysis adequacy means more than a Kt/V value; other clinical parameters are equally if not more important. Thus we should also aim at achieving adequate fluid removal and volume homeostasis, blood pressure control, good nutrition, normal acid–base balance, normal mineral metabolism, minimal anemia, and normal lipid metabolism.

The Clinical and Epidemiological Aspects of Vascular Mortality in Chronic Peritoneal Dialysis Patients

This article reviews the clinical aspects of and epidemiological links between vascular mortality and the dialysis population, and emphasizes areas that warrant further clarification. In particular, we highlight potential pitfalls in interpretation of published observational and clinical studies, notably some of the issues related to reverse epidemiology of risk factors for cardiovascular disease. Recent published data from our own center in the Prince of Wales Hospital relating to the significance of residual renal function, inflammation, valvular calcification, as well as left ventricular hypertrophy were highlighted. Actions are needed to tackle both the traditional and the nontraditional factors for cardiovascular disease in order to treat this problem causing the highest mortality in peritoneal dialysis patients.

How to Have a Successful Peritoneal Dialysis Program

The proportion of end-stage renal disease patients on continuous ambulatory peritoneal dialysis (CAPD) has increased by twofold in Hong Kong over last two decades, accounting for 80% of the entire dialysis population. Our encouraging outcome results—a 2-year actuarial patient survival of 83%, and a 2-year technique survival of 72.8%—further testify to the success of CAPD in our territory. A relatively constant successful outcome has been achieved despite an increasing prevalence of diabetes mellitus and an aging population. The present review postulates the reasons behind our success. Apart from reimbursement policy, technique-related factors, and center effects, inherent patient factors—including baseline survival advantage of Chinese patients, genetic difference, cardiovascular risk factors, and possibly lower dialysis volume requirement and compliance—are thought to be contributory. As for the future, more efforts are needed to further improve the technique survival rate and the nutritional status, psychosocial well-being, and rehabilitation of CAPD patients. Judicious assessment of peritoneal dialysis adequacy and preservation of residual renal function should be constantly exercised to tailor treatment to the needs of Chinese CAPD patients.

The relationship between angiotensin-converting enzyme (ACE) insertion (I) / deletion (D) polymorphism, serum ACE activity and bone mineral density (BMD) in older Chinese

Objective:

In this study, we set out to investigate the relationship between angiotensin-converting enzyme (ACE) I/D polymorphism, serum ACE activity and bone mineral density (BMD) in older Chinese.

Methods:

A standardized, structured, face-to-face interview was performed to collect demographic information. BMD was measured using dual-energy X-ray absorptiometry (DXA). I/D genotypes of ACE were determined by polymerase chain reaction (PCR) amplification. Serum ACE activity was determined photometrically by a commercially available kinetic kit. Multiple linear regression analysis was used to examine the relationship between ACE I/D polymorphism, serum ACE activity and BMD.

Results:

A total of 1567 males and 1760 females were selected for analyzing the relationship between ACE I/D polymorphism and BMD. There was no significant difference in spine BMD, total hip BMD and femur neck BMD among different ACE I/D genotypes both in males and females. A total of 1699 males and 1739 females were selected for analyzing the relationship between serum ACE activity and BMD. There was also no significant difference in spine BMD, total hip BMD and femur neck BMD among different serum ACE activity groups both in males and females.

Conclusion:

There was no relationship between ACE I/D polymorphism, serum ACE activity and BMD in older Chinese.

Gender difference of serum angiotensin-converting enzyme (ACE) activity in DD genotype of ACE insertion/deletion polymorphism in elderly Chinese

INTRODUCTION

In this study we investigated the gender difference of serum angiotensin-converting enzyme (ACE) activity in a population of Hong Kong-dwelling elderly Chinese.

MATERIALS AND METHODS

A total of 1767 (843 male, 924 female) Hong Kong-dwelling elderly Chinese were recruited. ACE I/D genotypes were identified by polymerase chain reaction amplification and serum ACE activity was determined using a commercially available kinetic kit. ACE I/D genotype distribution was compared by chi-square test, the correlation between ACE I/D polymorphism and serum ACE activity was analysed by ANOVA test and gender difference of serum ACE activity of different genotypes was compared by independent sample t-test.

RESULTS

No statistically significant difference of genotype distribution between male and female subjects was found. Serum ACE activity was significantly correlated with ACE genotype. Overall, there was no gender difference of serum ACE activity; however, when sub-grouping the subjects by ACE I/D genotype, male subjects with DD genotype had higher serum ACE activity than female subjects with DD genotype.

CONCLUSIONS

No significant gender difference of genotype distribution was found in elderly Chinese. Serum ACE activity was significantly correlated with ACE I/D polymorphism in elderly Chinese. Male subjects with DD genotype had higher serum ACE activity than female subjects with DD genotype.

DD genotype of angiotensin-converting enzyme in type 2 diabetes mellitus with renal disease in Mexican Mestizos

AIM

The DD genotype of angiotensin-converting enzyme (ACE) has been suggested as a major contributor of diabetic nephropathy in several populations. The purpose of the present study was to determine whether micro/macroalbuminuria is associated with ACE insertion/deletion (I/D) polymorphism in Mexican Mestizos with type 2 diabetes mellitus.

METHODS

A total of 435 patients with type 2 diabetes mellitus, of whom 233 had albuminuria, were characterized for the ACE I/D polymorphism by the polymerase chain reaction method.

RESULTS

Clinical and biochemical characteristics and frequencies according to DD, ID and II genotypes in patients with and without albuminuria showed no significant differences. However, only females with micro/macroalbuminuria showed higher frequency of a DD genotype than those without albuminuria (27.9%, 21.2% and 10.5%, respectively; P <or= 0.044). In addition, female patients with macroalbuminuria without dialysis showed no significant differences with patients undergoing dialysis.

CONCLUSION

The ACE DD genotype is a risk factor for the development of renal disease in Mexican Mestizo females with type 2 diabetes, indicating a possible DD genotype-associated sex effect in renal disease.

The impact of the angiotensin-converting enzyme insertion/deletion polymorphism on severe hypoglycemia in Type 2 diabetes

The insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme gene (ACE) is associated with altered serum ACE activity. Raised ACE levels and the ACE DD genotype are associated with a 3.2 to 6.8-fold increased risk of severe hypoglycemia in type 1 diabetes. This relationship has not been assessed in type 2 diabetes. We aimed to test for association of the ACE I/D polymorphism with severe hypoglycemia in type 2 diabetes. Patients with type 2 diabetes (n = 308), treated with insulin (n = 124) or sulphonylureas (n = 184), were classified according to whether or not they had previously experienced severe hypoglycemia. Samples of DNA were genotyped for the ACE I/D polymorphism using two alternative polymerase chain reactions to prevent mistyping due to preferential amplification of the D allele. Overall, 12% of patients had previously experienced one or more episodes of severe hypoglycemia. This proportion did not differ between genotype groups (odds ratio (95% confidence limits) for carriers of D allele relative to II homozygotes: 0.79 (0.35-1.78)). This study found no evidence for association of the ACE I/D polymorphism with severe hypoglycemia frequency in patients with type 2 diabetes. However, we cannot rule out a smaller effect (odds ratio </= 1.78). Our results suggest that any effect of ACE genotype on severe hypoglycemia risk in type 2 patients is likely to be smaller than that seen in type 1 diabetes. We recommend future larger-scale studies.

Angiotensin-Converting Enzyme and Endothelial Constitutive Nitric Oxide Synthase Polymorphisms in Turkish Renal Transplant Population and Possible Influence on Renal Artery Atherosclerosis and Graft Survival

BACKGROUND

Renal transplant recipients are prone to accelerated atherosclerosis secondary to immunosuppressants, which may decrease graft survival. We sought to analyze the effects on renal graft survival of atherosclerotic degeneration in the renal artery and the influence of angiotensin-converting enzyme (ACE) endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphisms.

METHODS AND PATIENTS

Thirty three renal transplant recipients (25 men) of mean age 28.4 +/- 9.6 years, received organs from 11 living related donors and were followed for at least 36 months. Genotyping was performed for the insertion/deletion ACE (I/D), angiotensin (AGT) (M-->T, 235), angiotensine 1 receptor (A-->C, 1166), angiotensin 2-receptor (A-->G, 1223), and ecNOS (b-->a, intron4) gene polymorphisms. Renal artery biopsies were performed during transplantation surgery to analyze the presence of atherosclerosis.

RESULTS

Pathological examination indicated that 18 donor specimens and nine recipient specimens had atherosclerotic degeneration. Survival analysis (36 months) indicated that graft survival rates of recipients who had atherosclerosis in the renal artery and who received an organ from donors with an atherosclerotic renal artery were shorter than in their counterparts (P = .02, P = .04, respectively). Comparison of genetic variations of recipients revealed that CC/TC variation of AGT was higher in patients with atherosclerosis (81% vs 53%, P = .03). There was no significant difference between groups in means of other gene polymorphisms.

CONCLUSION

Renin-angiotensin system gene polymorphism analysis of patients in renal transplantation waiting list may provide information about allograft survival and posttransplant atherosclerotic degeneration at graft vasculature of young transplant recipients.

Genetics of common progressive renal disease

Familial aggregation of common chronic kidney diseases provides a unique opportunity to investigate the susceptibility genetic and environmental factors. In the past decade, a wealth of new data has become available concerning the genetic susceptibility leading to numerous nephropathies. Knowledge of the genetic components allows better understanding of initiation and progression of these chronic kidney diseases. In addition, one can envision that identification of genetically susceptible individuals might lead to earlier diagnosis and potential reversal of the current epidemic of end-stage renal disease. The goal of the current discussion is to review various issues pertaining to the role of genetic factors in common chronic kidney diseases, as exemplified by two leading causes of end-stage renal diseases worldwide, nephropathy of type 2 diabetes and IgA nephropathy. The genetic and environmental interplay leading to the nephropathies is highlighted.

The renin-angiotensin system and endothelial nitric oxide synthase gene polymorphisms and cyclosporine toxicity in renal transplant patients

Although cyclosporine has improved graft survival, the toxicity of the drug frequently causes problem for renal transplant patients. Cyclosporine displays deleterious effects due to direct toxicity to the nephrons and vasoconstriction of afferent arterioles, effects that may be due to increased angiotensin II and decreased nitric oxide activity. We sought to examine the relation between cyclosporine toxicity and the RAS (angiotensin-converting enzyme, angiotesinogen, angiotensin 1 and 2 receptors, and ecNOS) gene polymorphisms in 111 renal transplant patients. Retrospectively, we correlated the results of graft biopsies from these 111 patients, with the cumulative drug doses (mg), mean blood levels (mg/mL), mean daily doses (mg), and mean doses (mg/kg/d) of cyclosporine. Overall 125 patients (38 women, 87 men) were enrolled in the study. Their mean age was 34.47 +/- 11.04 years. Twenty patients displayed cyclosporine toxicity on graft biopsy; 91 showed no evidence of the disorder. We could not find any relation between cyclosporine toxicity and gene polymorphisms (P >.05), although the mean mg/kg/d dose was significantly high among cyclosporine toxicity group (P =.028, RR = 1.42). In recent studies angiotensin II and nitric oxide have been suggested to be related to cyclosporine toxicity; however, our results failed to reveal an association between cyclosporine toxicity and angiotensin II or nitric oxide-related gene polymorphisms.

Angiotensin-Converting enzyme gene polymorphism significantly affects renal posttransplantation erythrocytosis

Posttransplantation erythrocytosis (PE) is a frequent problem in renal transplant patients. The pathogenesis and mechanisms of both the problem and therapy strategy are unknown. Since ACE and angiotensin 2 receptor inhibitors have been used to successfully manage PE, we speculated a relation between gene polymorphisms and this complication. Ninety-six ( 30 women, 66 men, age 34.4 +/- 11.0 years) renal transplant patients evaluated retrospectively, for gene polymorphisms of ACE, angiotensinogen, angiotensin 1 and 2 receptors (ATR1 and ATR2), as well as endothelial nitric oxide synthase (ecNOS). They were divided into two groups; patients with versus without PE, which was defined as >15 g/dL hemoglobin levels during the first year after renal transplantation. PE was found to be significantly more prevalent among D/D than I/I gene polymorphism of ACE genes (P <.04). The distribution of D/D, I/D, and I/I polymorphisms were 39.1%, 45.9%, and 7.6%, respectively. There was no difference between D/D and I/D polymorphisms. Comparing the I/D and I/I polymorphisms showed PE to be statistically more prevalent in the I/D polymorphism (P <.01). Logistic regression analysis revealed that D/D and I/D polymorphisms were significant risk factors for PE (P <.05, RR = 7.714 and P <.03, RR = 10.199, respectively). While previous studies revealed a relation between angiotensin II and PE, our study discovered the contribution of ACE gene polymorphism.

Genetic aspects of diabetic nephropathy

BACKGROUND

Diabetic nephropathy from type 2 diabetes mellitus is the most common cause of end-stage renal disease (ESRD) in the United States and in Western Europe. Although patients with overt nephropathy generally experience greater cumulative glycemic exposure, the difference in glycemic control between patients developing nephropathy compared to those who did not, could not be demonstrated. This observation is consistent with the notion that perhaps other factors, in addition to glycemic control, have a bearing on the development of nephropathy. Genetic factors, which specifically increase the susceptibility to nephropathy in patients with diabetes, have been proposed.

METHODS

A range of linkage and association studies has been performed for revealing the genetic background of diabetic nephropathy.

RESULTS

Until now, no mutation has been identified which could explain the development of diabetic nephropathy in the majority of diabetic patients.

CONCLUSIONS

Because of relatively small case numbers of all studies being performed so far, conclusions from those studies are limited. With the development of better technologies for an affordable genome-wide association study using thousands of markers, it might become possible to unravel the genetic causes of diabetic nephropathy.

Is there a survival advantage in Asian peritoneal dialysis patients?

Over the last decade, epidemiological surveys and qualitative research literature have demonstrated and validated a better survival in the Asian peritoneal dialysis population. This review summarizes the current understanding of Asian peritoneal dialysis patient survival and attempts to scrutinize the supposed survival advantage of this population group. We outlined the published peritoneal dialysis survival data from a literature search, with reference to dialysis patient cohorts from 1983 through 2002 for prevalent cases and 1980 through 2002 for incident patients. Two-year and 5-year patient survival rates in excess of 80% and 60% respectively were demonstrated in Asian countries, which compared favorably with the CANUSA, ADEMEX and most Caucasian series. Better end-stage renal disease patient survival is apparent despite a dialysis adequacy disadvantage, for reasons yet to be identified. As is the case of other racial disparities in medical care, such a difference is a product of more than biological differences and include budgetary barrier, health care system and geographic variation, physician bias and statistical pitfalls. Particular efforts should therefore be made to explore the underlying reason(s) for the Asian peritoneal dialysis patient survival advantage. Alternative approach and guidelines to peritoneal dialysis delivery in Asia might be warranted.

Kidney disease, genotype and the pathogenesis of vasculopathy

PURPOSE OF REVIEW

The two leading causes of end-stage renal disease in the United States are diabetes mellitus and hypertensive nephrosclerosis, accounting for over two-thirds of all cases. In many patients both diseases are associated with small- and large-vessel disease, commonly attributed to hypertension or accelerated atherosclerosis. Recent investigations, however, have suggested that renal large-vessel and microvascular disease may be independent contributors to progressive kidney failure.

RECENT FINDINGS

Although genes have not been definitely linked to renal vascular disease, population- and family-based epidemiology of kidney disease, segregation analysis of Pima and Caucasian families in which diabetic nephropathy is clustered, and the positional cloning of genes responsible for rare, familial glomerulosclerosis syndromes support the hypothesis that genes regulate the pathogenesis of renal disease. This review highlights developments in our current understanding of vasculopathy and its role in renal disease, and it summarizes evidence suggesting that genetic determinants for the vascular phenotype are associated with common causes of chronic renal failure.

SUMMARY

With the application of genomics and proteomics methodologies to drug discovery, the identification of renal susceptibility genes should identify new mechanisms of progressive renal disease pathogenesis and generate novel target molecules for the treatment of kidney disease.

Prognostic role of serum ACE activity on outcome of type 2 diabetic patients on chronic ambulatory peritoneal dialysis

Overexpression of the renin-angiotensin system is important in the pathogenesis of macroangiopathy (MA). Patients with diabetes with end-stage renal failure have elevated serum angiotensin-converting enzyme (ACE) activity compared with their nonuremic counterparts. Because their major cause of death is MA, the significance of serum ACE activity on outcome of this group of patients is studied. We performed a prospective cohort study of 49 patients with type 2 diabetes on continuous ambulatory peritoneal dialysis (CAPD) therapy. Baseline serum ACE activity was determined by a modified spectrophotometric method and followed up at a median of 34 months. The prevalence of MA (defined as ischemic heart disease, sudden cardiac arrest, stroke, or peripheral vascular disease) and all-cause mortality rates were studied. Risk for MA is associated with serum ACE activity (median with MA, 69.0 U/L [range, 46.0 to 100.1 U/L] versus without MA, 57.2 U/L [range, 36.3 to 81.0 U/L]; P = 0.02). At the end of follow-up, 48% of patients (24 of 49 patients) died, 70% of MA. The group that died had increased baseline serum ACE activity (nonsurvivors, 65.0 U/L [range, 33.5 to 100.0 U/L] versus survivors, 49.4 U/L [range, 36.4 to 86.5 U/L]; P < 0.05) and MA rates (nonsurvivors, 77% versus survivors, 36%; P < 0.01). Cox regression analysis performed with age, sex, mean blood pressure, body mass index, metabolic control, Kt/V, residual renal function, serum albumin level, and ACE activity showed that baseline serum ACE activity (P = 0.033) is an independent predictor for mortality in patients with type 2 diabetes on CAPD therapy. Among patients with type 2 diabetes on CAPD therapy, serum ACE activity is associated with risk for MA and is an independent predictor for mortality. Whether ACE inhibition will have a beneficial effect on the outcome of these patients needs further investigation.