Contribution of genetic polymorphism in the renin-angiotensin system to the development of renal complications in insulin-dependent diabetes: Genetique de la Nephropathie Diabetique (GENEDIAB) study group

Role of ACE inhibitors in patients with diabetes mellitus

The adjective 'epidemic' is now attributed to the rapidly growing number of patients with diabetes mellitus, mainly type 2. and the specific complications linked to this disorder. Provided they are recognised early enough, these different complications can be treated; in some patients the evolutive course of these complications can be slowed or even stopped. Furthermore, some recent observations suggest that specific tissular lesions may be prevented or even reversed. Although glycaemic control is essential, other therapeutic measures that must also be taken include those to control blood pressure and to lower lipid levels. Of the agents available to control the complications of diabetes mellitus, cardiovascular drugs, and particularly ACE inhibitors, have a pre-eminent place. Experimental and epidemiological data suggest that activation of the renin-angiotensin-aldosterone system plays an important role in increasing in the micro- and macrovascular complications in patients with diabetes mellitus. Not only are ACE inhibitors potent antihypertensive agents but there is a growing body of data indicating that also they have a specific 'organ-protective' effect. For the same degree of blood pressure control, compared with other antihypertensive agents, ACE inhibitors demonstrate function and tissue protection of considered organs. ACE inhibitors have been reported to improve kidney, heart, and to a lesser extent, eye and peripheral nerve function of patients with diabetes mellitus. These favourable effects are the result of inhibition of both haemodynamic and tissular effects of angiotensin II. Finally, there are a growing number of arguments favouring the use of ACE inhibitors very early in patients with diabetes mellitus.

[The involvement of the renin-angiotensin system gene polymorphisms in coronary heart disease]

INTRODUCTION AND OBJECTIVES

Previous studies angiotensin-converting enzyme gene insertion/deletion polymorphism ACE (I/D), angiotensinogen gene polymorphism, and angiotensin II AT1 receptor polymorphism in relation to coronary heart disease controversial results. This study was designed to analyze the association between these gene polymorphisms and the first coronary event in individuals residing on Grand Canary Island, Spain.

PATIENTS AND METHOD

Case-control study. Case subjects (n = 304) were recruited at the first coronary event; age-matched controls (n = 315) were randomly selected from the Grand Canary population. Participants were examined for the usual risk factors. Blood samples were obtained for biochemical analyses and DNA extraction. Genotyping was performed by PCR and restriction analysis.

RESULTS

Neither ACE (I/D) nor AT1 receptor polymorphism was associated with coronary heart disease, whereas the frequency distribution of AGT M235T genotypes among patients and control subjects (TT: 29% and 19%; MT: 48% and 50%; MM: 22% and 31%, respectively) was statistically different (p = 0.003). Multiple logistic regression analysis identified the TT genotype of the angiotensinogen gene (OR = 1.9; 95% CI 1.1-3.4), diabetes (OR = 4.4; 95% CI 2.0-9.4) and hypertension (OR = 2.1; 95% CI 1.3-3.3) as risk factors predicting the coronary event.

CONCLUSIONS

Our results provide no evidence of an association between ACE (I/D) or AT1 receptor polymorphism and coronary heart disease. However, homozygosity for the T allele of the angiotensinogen gene, diabetes and hypertension independently place individuals at higher risk of experiencing a coronary event on Grand Canary Island.

The angiotensin-converting enzyme DD genotype is associated with glomerulopathy lesions in type 2 diabetes

Genetic factors are important in conferring diabetic nephropathy (DN) risk. The insertion/deletion (I/D) polymorphism of the ACE gene has been described to be associated with DN risk and progression. The renal lesions underlying DN in type 2 diabetes are heterogeneous; only a subset of patients, characterized by a faster decline of renal function, have diabetic glomerulopathy. This study explored the relations between diabetic glomerulopathy and the ACE genotype distribution in 77 type 2 diabetic patients with an albumin excretion rate > or = 20 microg/min. Using morphometric analysis of kidney biopsies, mesangial and mesangial matrix fractional volumes [Vv(mes/glom) and Vv(MM/glom)] and glomerular basement membrane (GBM) width were estimated. We found that 13 patients were II, 30 were ID, and 34 were DD. Clinical features and renal function were similar in the three groups; in contrast, the DD patients had the highest Vv(MM/glom) and GBM width. Subdividing patients in tertiles of GBM width and Vv(MM/glom), from the lowest (I) to the highest (III) values, the DD carriers had an odds ratio of 6.11 (95% CI 1.84-20.3) and 10.67 (2.51-45.36), respectively, for the likelihood of being in tertile III than I for GBM width and Vv(MM/glom). Multiple regression analysis revealed the I/D polymorphism as an independent determinant of GBM thickening in addition to diabetes duration and HbA(1c). In conclusion, the ACE DD genotype is associated with diabetic glomerulopathy lesions, making the study of this polymorphism helpful in identifying those type 2 diabetic patients at higher risk of fast DN progression.

Angiotensin II receptor polymorphisms in hypertension. Pharmacogenomic considerations

Molecular variants of individual components of the renin-angiotensin system (RAS) are thought to contribute to inherited predisposition towards essential hypertension. Polymorphisms in genes of angiotensinogen (AGT), angiotensin I-converting enzyme (ACE) and angiotensin II type 1 receptor (AT-1) have been related to differential responses to antihypertensive drugs. AT-1 receptor mediates the major pressor and trophic actions of angiotensin II (Ang II). At least 14 AT-1 polymorphisms have been described in the gene (AGT1R); in particular the +1166 A/C polymorphism has been associated with the severe form of essential hypertension. A relationship was suggested between this polymorphism and the humoral and renal hemodynamic responses to losartan, an antihypertensive drug acting as an AT-1 blocker. Variability in the individual response to AT-1 antagonists could also be due to variations in the pharmacokinetics of the drugs. This review presents current knowledge on Ang II-receptors and polymorphisms in AGT1R related to cardiovascular disease and antihypertensive therapy.

Risk predictors in patients with diabetic nephropathy

Diabetic nephropathy is currently the most common cause of end-stage renal disease in the Western countries. Only approximately one third of patients with type 1 diabetes develop nephropathy; thus, because it is not feasible to aggressively treat all patients, it becomes very important to find early markers in order to identify patients at high nephropathy risk. To date the best available predictor of overt nephropathy is microalbuminuria. In this article we review the validity of microalbuminuria as a predictor of overt nephropathy and consider other markers of nephropathy risk.

ACE gene polymorphism as a prognostic indicator in patients with type 2 diabetes and established renal disease

OBJECTIVE

To investigate whether the DD genotype is a predictor of mortality and of the decline in renal function in patients with type 2 diabetes and established nephropathy.

RESEARCH DESIGN AND METHODS

A total of 56 such patients of Maltese Caucasian descent were recruited, and their ACE genotype was determined. Serum creatinine was estimated approximately every 4 months. The glomerular filtration rate (GFR) was calculated according to the Cockroft-Gault formula, and rate of change was determined by regression analysis.

RESULTS

The rate of change in calculated GFR was -7.76 ml.min(-1).year(-1) in those with the DD genotype (n = 31) and -1.17 ml. min(-1). h(-1) in those with the ID or II genotype (n = 25) (P < 0.01). The 3-year mortality was 45.2% in the DD group compared with 20.0% in the ID/II group (P < 0.05).

CONCLUSIONS

The DD genotype of the ACE gene polymorphism is associated with a more rapid decline in renal function and higher mortality in type 2 diabetic patients with established nephropathy.

Angiotensin-converting enzyme gene polymorphism and microvascular complications in Turkish type 2 diabetic patients

The aim of this study was to investigate whether an association exists between the angiotensin converting enzyme (ACE) insertion/deletion (I/D) polymorphism and microvascular complications of type 2 diabetes mellitus in Turkish patients. A total of 239 type 2 diabetic patients and 138 sex and age matched control subjects were included into the study. The I/D polymorphism was determined by polymerase chain reaction (PCR). Nephropathy status was determined according to urinary albumin/creatinine ratio (microg/mg) (<30 normoalbuminuria, 30-300 microalbuminuria, >300 macroalbuminuria) and retinopathy was evaluated by fundoscopic examination and by flourescein fundus angiography. The distribution of ACE I/D polymorphism and allele frequencies in diabetic patients were not significantly different from controls, DD genotype 32.2 versus 37.2%; ID genotype 50.6 versus 47.1%; and II 17.2 versus 15.2%; D allele 57.5 versus 61.2%; I allele 42.5 versus 38.8%. Genotype distribution between normo-, micro- and macroalbuminuric patients did not differ significantly (DD:ID:II (%), normoalbuminuria, 35:46:19; microalbuminuria, 28:55:17; macroalbuminuria, 31:55:14). There was also no difference in genotype distribution between patients with and without retinopathy (DD:ID:II (%), retinopathy positive, 32:51:17; retinopathy negative, 33:49:18). In conclusion, the ACE I/D polymorphism does not seem to be associated with diabetic nephropathy and retinopathy in Turkish type 2 diabetic patients.

Angiotensinogen genotype and blood pressure response in the Dietary Approaches to Stop Hypertension (DASH) study

OBJECTIVE

To determine the relationship between angiotensinogen (ANG) genotype and blood pressure response to the dietary patterns of the Dietary Approaches to Stop Hypertension (DASH) trial. The angiotensin converting enzyme (ACE) gene was also tested.

DESIGN

The DASH trial was a randomized outpatient feeding study comparing the effects on blood pressure (BP) of three dietary patterns: a control diet, similar to typical American intake; a 'fruits and vegetables' diet (F/V) that is rich in fruits and vegetables but otherwise resembles the control diet; and the DASH diet that is reduced in fats and that emphasizes fruits, vegetables and low-fat dairy products. Participants' genotype was also determined.

SETTING

Four clinical sites.

PARTICIPANTS

Adults with above-optimal BP or stage 1 hypertension.

INTERVENTION

Participants ate one of the three dietary patterns for 8 weeks. Sodium intake and weight were held constant. In 355 of 459 DASH participants, DNA was extracted from leukocytes and genotyped for the G-6A ANG polymorphism and the D/I ACE polymorphism, by the polymerase chain reaction.

MAIN OUTCOMES

Genotype at ANG and ACE loci; BP after 8 weeks of intervention diet.

RESULTS

There was no association between ACE genotype and BP response. Associations with ANG polymorphism were significant: net systolic and diastolic BP response to the DASH diet was greatest in individuals with the AA genotype (-6.93/-3.68 mmHg) and least in those with the GG genotype (-2.80/0.20 mmHg). A similar relationship existed for the F/V diet.

CONCLUSIONS

ANG genotype is associated with BP response to the DASH diet. The AA genotype confers excess risk of hypertension and is associated with increased responsiveness to diet.

Dinucleotide repeat polymorphism of matrix metalloproteinase-9 gene is associated with diabetic nephropathy

BACKGROUND

Although genetic susceptibility has been proposed as an important factor for the development and progression of diabetic nephropathy, the definitive gene has not been identified. To identify the genetic marker for diabetic nephropathy, we examined the association between the (A-C)n dinucleotide repeat polymorphism upstream of the matrix metalloproteinase-9 (MMP-9) gene and diabetic nephropathy in a group of Japanese patients with type 2 diabetes.

METHODS

Patients were divided into three groups based on their urinary albumin excretion rate (AER) and the stage of diabetic retinopathy as follows: uncomplicated group (U), normal albuminuria (AER <20 microg/min) without proliferative retinopathy and with the duration of diabetes more than 20 years (N = 32); microalbuminuria group (M), 20 < or = AER < 200 microg/min (N = 155); overt nephropathy group (O), AER > or = 200 microg/min (N = 63). The region containing the dinucleotide repeat upstream of MMP-9 gene was amplified by polymerase chain reaction (PCR). The amplified products were analyzed with 7% formamide/urea acrylamide gel electrophoresis. The promoter constructs of the MMP-9 gene were transfected with the CMV-beta-galactosidase construct into 293 cells using the liposome method. Twenty-four hours after transfection, cells were harvested, and luciferase and beta-galactosidase activities were measured.

RESULTS

Nine alleles of the dinucleotide repeat polymorphism (17 to 25 repeats) were identified, and the frequency of each allele in diabetic subjects was not different from that in nondiabetic controls. The frequency of the allele containing 21 repeats (A21) was most abundant (42.4% in control and 45.6% in diabetic subjects), followed by the allele with 23 repeats (A23; 35.4% in control and 27.6% in diabetic subjects). The A21 allele was less frequent in M and O than U (O, 38.9%; M, 45.5%; U, 59.3%, chi2 = 7.18; P < 0.05, O vs. U), while the frequency of the alleles other than A21 was not different among each group. The calculated odds ratio for nephropathy in the noncarrier, heterozygote, or homozygote of A21 allele was 3.38, 1.97, and 0.2, respectively. Furthermore, the promoter assay for the MMP-9 gene revealed that the A21 allele had a higher promoter activity compared with other alleles. No significant correlation was observed between serum MMP-9 concentrations and the MMP-9 gene polymorphism.

CONCLUSION

These results indicate that the patients with A21 allele of the MMP-9 gene may be protected from the development and progression of diabetic nephropathy. Thus, the microsatellite polymorphism upstream of the MMP-9 gene could be a useful genetic marker for diabetic nephropathy.

Insertion-deletion polymorphism in the gene for angiotensin-converting enzyme is associated with obstetric cholestasis but not with preeclampsia

OBJECTIVE

Our purpose was to investigate the contribution of angiotensin-converting enzyme insertion-deletion polymorphism in the development of obstetric complications.

STUDY DESIGN

In a retrospective case-control study, angiotensin-converting enzyme insertion-deletion polymorphism was investigated in a control group of healthy women (n = 115) and in a group of women diagnosed with preeclampsia (n = 133) and obstetric cholestasis (n = 57). Polymerase chain reaction detection of insertion-deletion polymorphism was used to determine the presence of the two angiotensin-converting enzyme alleles in the groups; the frequencies in the general population in our area are presented for comparison.

RESULTS

The frequency of the D allele was 43.9% among women with obstetric cholestasis and 27% among healthy fertile women, which is close to the rate in the general population in our area (28%). The odds ratio for obstetric cholestasis associated with the DD genotype was 2.12 (95% CI, 1.08-4.12) compared with the pooled II and ID genotypes (P = .03). Neither the ID genotype distributions nor the allele frequencies differed significantly between preeclamptic and normotensive pregnancies (P = .36).

CONCLUSION

The present data indicate that the DD genotype is a genetic marker associated with an elevated risk of obstetric cholestasis, but this polymorphism of the angiotensin-converting enzyme gene is unlikely to play any significant role in preeclampsia.

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.

Characterization of a putative insulin-responsive element and its binding protein(s) in rat angiotensinogen gene promoter: regulation by glucose and insulin

We previously demonstrated that high glucose activates angiotensinogen (ANG) expression and that insulin inhibits this activation. The present studies aim to investigate whether insulin regulates ANG gene expression in kidney proximal tubular cells at the transcription level via interaction of the putative insulin-response element (IRE) with its binding protein(s) in the 5'-flanking region of the ANG gene. Fusion genes containing various lengths of the 5'-flanking region of the rat ANG gene fused to a human GH (hGH) gene as reporter were constructed and transiently introduced into rat immortalized renal proximal tubular cells (IRPTCs). The expression of the fusion genes was monitored by the amount of immunoreactive hGH secreted into the medium as assayed by a specific RIA for hGH. Insulin inhibited the expression of pOGH (rANG N-1498/+18), pOGH (rANG N-1120/+18) and pOGH (rANG N-882/+18) but not pOGH (rANG N-854/+18), pOGH (rANG N-820/+18), pOGH (rANG N-688/+18) and pOGH (rANG N-53/+18) in high-glucose (i.e. 25 mM) medium. Site-directed mutagenesis of nucleotides N-874 to N-867 (5' CCC GCC CT 3') in the 5'-flanking region of the rat ANG gene abolished the response to insulin. Insulin also inhibited the expression of the fusion gene containing the DNA fragment ANG N-882 to N-855 inserted upstream of the ANG gene promoter (N-53/+18), but had no effect on a mutant of N-882 to N-855. Gel mobility shift assays revealed that the labeled putative rat ANG-IRE motif (N-878 to N-864, 5' CCT TCC CGC CCT TCA 3') was bound to the nuclear proteins of IRPTCS: This binding was displaced by unlabeled ANG-IRE and IRE of human glyceraldehyde phosphate dehydrogenase but not by mutants of ANG-IRE and IRE of the rat glucagon gene. Southwestern blotting analysis revealed that the labeled putative ANG-IRE motif bound to a major nuclear protein with an apparent molecular mass of 48 kDA: Finally, high glucose levels enhanced 48-kDa nuclear protein expression and induced an additional 70-kDa nuclear protein expression in IRPTCs, as revealed by Southwestern blotting. Insulin inhibited both 48- and 70-kDa nuclear proteins expression induced by high glucose levels. Its inhibitory effect was reversed by the presence of PD98059 (an inhibitor of mitogen-activated protein kinase, MAPK) but not by wortmannin (an inhibitor of phosphatidylinositol 3- kinase). These studies demonstrate that insulin action on ANG gene expression is at the transcriptional level. The molecular mechanism (s) of insulin action is mediated, at least in part, via interaction of the functional IRE with unidentified 48- and 70- kDa nuclear proteins in the rat ANG gene and is MAPK dependent.

Association of angiotensinogen M235T and A(-6)G gene polymorphisms with coronary heart disease with independence of essential hypertension: the PROCAGENE study. Prospective Cardiac Gene

OBJECTIVES

We examined the relationship between the angiotensinogen (AGT) gene M235T polymorphism, the variant promoter of the AGT gene A(-6)G and the angiotensin-converting enzyme (ACE) gene insertion/deletion (I/D) polymorphism and coronary heart disease (CHD) in native Gran Canaria Island habitants, who have the highest rates of CHD in Spain.

BACKGROUND

Some studies subject that the ACE (I/D) polymorphism could be associated with CHD, while AGT (M235T) has been related to essential hypertension.

METHODS

We studied 304 subjects with angiographic evidence of coronary artery disease and a clinical diagnosis of myocardial infarction or unstable angina and 315 age- and gender-matched controls. Blood was drawn and DNA extracted. Angiotensin-converting enzyme (I/D) gene polymorphism was analyzed by polymerase chain reaction (PCR) and AGT gene polymorphisms by restriction fragment length polymorphism-PCR and mutagenically-separated PCR.

RESULTS

The ACE (I/D) polymorphism showed no association with CHD, whereas the frequency distribution of AGT (M235T) genotypes among patients and controls (235T: 29.1% and 19.0%; M235T: 48.5% and 50.2%; M235: 22.4% and 30.8%, respectively) was statistically different (p = 0.005) and not related to the presence of essential hypertension. Similar results were observed with the AGT A(-6)G polymorphism. In multiple logistic regression analysis, CHD odds ratio associated with 235T and M235 homozygotes were 1.7 (1.1 to 2.6) and 0.54 (0.36 to 0.82), respectively.

CONCLUSIONS

This study shows that genetic variation of the AGT (M235T), but not the ACE (I/D), genotypes contributes to the presence of CHD independently of blood pressure profile in a subset of the Spanish population with a high prevalence of cardiovascular disease.

Prognostic value of angiotensin-I converting enzyme I/D polymorphism for nephropathy in type 1 diabetes mellitus: a prospective study

Angiotensin-I converting enzyme (ACE) regulates renal hemodynamics. Its insertion/deletion (I/D) polymorphism, which determines most of ACE interindividual variance, was proposed as a genetic marker for diabetic nephropathy. A substitution (M235T) polymorphism in angiotensinogen (AGT) may interact with ACE I/D polymorphism for the risk of diabetic nephropathy, but their prognostic values have to be established by follow-up studies. A total of 310 type 1 diabetes mellitus patients who attended the diabetic clinic in Angers (France) took part in a prospective, observational, follow-up study. Glycohemoglobin, BP, plasma creatinine, and urinary albumin excretion were determined periodically. Nephropathy was classified as absent, incipient (microalbuminuria), established (proteinuria), advanced (plasma creatinine > or = 150 micromol/L), and terminal (renal replacement therapy). The main end point was the occurrence of a renal event defined as the progression to a higher stage of diabetic nephropathy. At baseline, 251 (81%) patients had no nephropathy, 35 (11%) had incipient nephropathy, 18 (6%) had established nephropathy, and 6 (2%) had advanced nephropathy. The ACE I/D and M235T AGT polymorphisms were in Hardy-Weinberg equilibrium in the patients. The median duration of follow-up was 6 yr (range, 2 to 9 yr). The occurrence of renal events was significantly influenced by ACE genotype (log-rank II versus ID versus DD, P < 0.03) with a dominant deleterious effect of the D allele: ID or DD versus II (adjusted hazard ratio, 5.0; 95% confidence interval, 1.5 to 16.6). Other contributors were high glycohemoglobin and systolic BP. In the patients who initially were free of nephropathy, baseline plasma ACE concentration was higher in patients who progressed to microalbuminuria (571 +/- 231 versus 466 +/- 181 microg/L; P = 0.0032); the D allele independently favored the occurrence of incipient nephropathy (adjusted hazard ratio, 4.5; 95% confidence interval, 1.1 to 19.4); other contributors were male gender, baseline systolic BP, and urinary albumin excretion. The AGT M235T polymorphism was not associated with renal events. The D allele of the ACE I/D polymorphism is an independent risk factor for both the onset and the progression of diabetic nephropathy in type 1 diabetes mellitus patients.

The DD genotype of the ACE gene polymorphism is associated with diabetic nephropathy in the type-1 diabetics

Genetic factors are involved in the development of diabetic nephropathy in type-1 diabetes. We are examining the association of the angiotensin-converting enzyme (ACE), insertion/deletion (I/D) polymorphism with the presence of diabetic nephropathy in type-1 diabetic patients. 52 type-1 diabetic patients with diabetic nephropathy (30 with either microalbuminuria or macroalbuminuria and 22 with end stage renal disease on dialysis) were compared with 10 type-1 diabetic patients with normoalbuminuria and duration of disease longer than 15 years and 27 non-diabetic healthy subjects. We found that the D-allele frequency was higher in patients with nephropathy than in the healthy and normoalbuminuric controls. There was an association in the DD polymorphism of the ACE gene with patients with diabetic nephropathy and not with the control subjects. We conclude that the DD genotype of ACE gene polymorphism is associated with diabetic nephropathy in patients with type-1 diabetes mellitus.

Loss of renal function following bone marrow transplantation: an analysis of angiotensin converting enzyme D/I polymorphism and other clinical risk factors

Chronic renal failure is an acknowledged late complication of BMT. It is related to the intensive chemotherapy, radiation and supporting medications. Polymorphism in the angiotensin converting enzyme (ACE) gene is associated with progression of nephropathy caused by diabetes and IgA nephropathy. We sought to determine whether ACE genotype and other clinical factors were associated with loss of renal function after BMT. We determined the genotype of 106 adult allogeneic BMT recipients, who received a similar preparative regimen, survived 1 year, and had assessment of renal function up to 3 years after BMT. We found that the distribution of genotypes was similar to the general population; 29%, 51%, and 20% for the DD, DI, and II genotypes, respectively. There was no statistical difference in patient survival between the three groups. Among all patients, the average creatinine clearance declined from 124 (95% CI 117, 131) to 89 (95% CI 78, 100) ml/min over the 36 months after BMT. Decline in renal function over time was less for patients with the DD compared to the II genotype (P = 0.040). Renal function in patients with the DD genotype was also better than those with the DI genotype, but this was of borderline statistical significance (P = 0.055). Renal shielding reduced decline in renal function compared to no shielding (P = 0.026). We conclude that the ACE genotype does not seem to influence survival, but the DD genotype may be protective against renal injury after BMT. Furthermore, we confirm that renal shielding during TBI reduces the renal injury after BMT.

Randomised controlled trial of dual blockade of renin-angiotensin system in patients with hypertension, microalbuminuria, and non-insulin dependent diabetes: the candesartan and lisinopril microalbuminuria (CALM) study

OBJECTIVES

To assess and compare the effects of candesartan or lisinopril, or both, on blood pressure and urinary albumin excretion in patients with microalbuminuria, hypertension, and type 2 diabetes.

DESIGN

Prospective, randomised, parallel group, double blind study with four week placebo run in period and 12 weeks' monotherapy with candesartan or lisinopril followed by 12 weeks' monotherapy or combination treatment.

SETTING

Tertiary hospitals and primary care centres in four countries (37 centres).

PARTICIPANTS

199 patients aged 30-75 years.

INTERVENTIONS

Candesartan 16 mg once daily, lisinopril 20 mg once daily.

MAIN OUTCOME MEASURES

Blood pressure and urinary albumin:creatinine ratio.

RESULTS

At 12 weeks mean (95% confidence interval) reductions in diastolic blood pressure were 9.5 mm Hg (7.7 mm Hg to 11.2 mm Hg, P<0.001) and 9.7 mm Hg (7.9 mm Hg to 11.5 mm Hg, P<0.001), respectively, and in urinary albumin:creatinine ratio were 30% (15% to 42%, P<0.001) and 46% (35% to 56%, P<0.001) for candesartan and lisinopril, respectively. At 24 weeks the mean reduction in diastolic blood pressure with combination treatment (16.3 mm Hg, 13.6 mm Hg to 18.9 mm Hg, P<0. 001) was significantly greater than that with candesartan (10.4 mm Hg, 7.7 mm Hg to 13.1 mm Hg, P<0.001) or lisinopril (mean 10.7 mm Hg, 8.0 mm Hg to 13.5 mm Hg, P<0.001). Furthermore, the reduction in urinary albumin:creatinine ratio with combination treatment (50%, 36% to 61%, P<0.001) was greater than with candesartan (24%, 0% to 43%, P=0.05) and lisinopril (39%, 20% to 54%, P<0.001). All treatments were generally well tolerated.

CONCLUSION

Candesartan 16 mg once daily is as effective as lisinopril 20 mg once daily in reducing blood pressure and microalbuminuria in hypertensive patients with type 2 diabetes. Combination treatment is well tolerated and more effective in reducing blood pressure.

Lack of relationship in long-term type 1 diabetic patients between diabetic nephropathy and polymorphisms in apolipoprotein epsilon, lipoprotein lipase and cholesteryl ester transfer protein. Genétique de la Nephropathie Diabétique Study Group. Données Epidémiologiques sur le Syndrome d'Insulino-Résistance Study Group

BACKGROUND

Genetic susceptibility contributes to the risk of diabetic nephropathy. Lipid disorders may favour diabetic nephropathy. Thus polymorphisms in lipid metabolism are candidates for the genetic component of risk for diabetic nephropathy.

METHODS

We searched for a contribution of the genetic polymorphisms of lipoprotein lipase (LPL), cholesteryl ester transfer protein (CETP) and apolipoprotein epsilon (Apo E) to the development of diabetic nephropathy by studying 494 type 1 diabetic patients with proliferative retinopathy and various stages of diabetic nephropathy (GENEDIAB Study). The selection process ensured that all patients had expressed their risk of chronic complications due to uncontrolled diabetes. Thus the nephropathy stages were largely influenced by genetic background. The lipid profile included fasting plasma total cholesterol (TC), triglycerides (TG), apolipoprotein A1 (Apo A1) and B (Apo B), and lipoprotein (a) (Lp(a)). Genetic polymorphisms were determined by PCR-based detection of Apo epsilon (e2/e3/e4), LPL (mutation Asn 291 Ser) and CETP (TAQ:IB B1/B2).

RESULTS

One hundred and fifty-seven patients (32%) had no nephropathy, 104 (21%) incipient nephropathy, 126 (25%) established nephropathy and 107 (22%) advanced nephropathy. There was a significant relationship between the stages of diabetic nephropathy and TC (P=0.002), TG (P<0.0001), Apo B (P=0.0007) or Lp(a) (P=0. 038), but not Apo A1. However the genetic polymorphism distributions of LPL, CETP and Apo epsilon did not differ in terms of renal complications. The study power to reject the null hypothesis was 58% for the Apo epsilon genotypes.

CONCLUSION

These results support no or only marginal effects of a genetic basis for lipid disturbances encountered in diabetic nephropathy.

High Levels of Glucose Stimulate Angiotensinogen Gene Expression Via the P38 Mitogen-Activated Protein Kinase Pathway in Rat Kidney Proximal Tubular Cells* *This work was supported by grants from the Medical Research Council of Canada (MT-13420 to J.S.D.C. and J.G.F., and MT-12573 to J.G.F.) and from the NIH (HL-48455 to J.R.I., and D.K-50836 to S.S.T.)

The present studies investigated whether the effect of high levels of glucose on angiotensinogen (ANG) secretion and gene expression in kidney proximal tubular cells is mediated at least in part via the activation of p38 mitogen-activated protein kinase (p38 MAPK). Rat immortalized renal proximal tubular cells (IRPTCs) were cultured in monolayer. The levels of immunoreactive rat ANG (IR-rANG) secreted into the medium and the levels of cellular ANG messenger RNA were determined by a specific RIA for rat ANG and a RT-PCR assay, respectively. Phosphorylation of cellular p38 MAPK was determined by Western blot analysis using the Phospho Plus p38 MAPK antibody kit. High levels of glucose (i.e. 25 mM) and phorbol 12-myristate 13-acetate (PMA; 10(-7) M) increased the secretion of IR-rANG and cellular ANG messenger RNA as well as phosphorylation of p38 MAPK in IRPTCs. This stimulatory effect of high levels of glucose and PMA was blocked by SB 203580 (a specific inhibitor of p38 MAPK), but not by SB 202474 (a negative control of SB 203580). High levels of D-sorbitol or 2-deoxy-D-glucose (i.e. > or = 35 mM) also stimulated the phosphorylation of p38 MAPK, but did not stimulate ANG secretion or gene expression. GF 109203X (an inhibitor of protein kinase C) blocked the stimulatory effect of high levels of glucose and PMA on ANG gene expression, whereas it did not block the effect of high levels of glucose, sorbitol, or 2-deoxy-D-glucose on p38 MAPK phosphorylation in IRPTCs. These studies demonstrate that the stimulatory effect of a high level of glucose (25 mM) on ANG gene expression in IRPTCS may be mediated at least in part via activation of p38 MAPK signal transduction pathway and is protein kinase C independent.

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

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

Angiotensin-converting enzyme gene insertion/deletion polymorphism and renal damage in childhood uropathies

BACKGROUND

The activation of the renin-angiotensin system in various renal disorders is well established. Congenital urological abnormalities, such as obstruction and reflux, are common causes of renal failure in children contributing to approximately 25% of chronic renal failure in this age group. While the outlook relates to the severity of initial renal damage, there is considerable heterogeneity in renal parenchymal destruction among individuals and the reasons for this heterogeneity are not fully understood. A polymorphism within intron 16 of the angiostensin-converting enzyme (ACE) gene has been shown to influence the activity of the renin-angiotensin system, thus, it may also have an impact on the expression of renal disorders. We have determined the incidence of this ID polymorphism of the ACE gene in 47 Kuwaiti children with different urological abnormalities leading to variable degrees of renal impairment and in 48 healthy control subjects with a similar ethnic background.

METHODS

Blood samples were collected from the patients (n = 47) and controls (n = 48), total genomic DNA extracted and the ACE genotypes were determined using a polymerase chain reaction-based method.

RESULTS

The DD genotype was detected in 27/47 (57%) cases compared with 25/48 (52%) controls (P = 0.439). The heterozygous genotype ID was found in 14/47 (29%) cases compared with 22/48 (46%) controls (P = 0.0138). The homozygous II genotype was detected in 6/47 (13%) cases compared with 1/48 (2%) controls (P = 0.0247). The D allele of ACE gene was detected in 41/47 (87%) uropathy cases when individuals with homozygous DD and heterozygous ID genotypes were considered collectively. The incidence of parenchymal damage was considerably higher in uropathy cases with DD genotype (62%) compared with those having ID (26%) and II (12%) genotypes.

CONCLUSIONS

Our data suggest an association of D allele of the ACE gene insertion/deletion polymorphism and congenital urological abnormalities, which result in parenchymal damage in Kuwaiti Arab children.

Comprehensive analysis of the renin-angiotensin gene polymorphisms with relation to hypertension in the Japanese

BACKGROUND

Components of the renin-angiotensin (R-A) system have been repeatedly investigated as candidate genes for essential hypertension. In particular, suggestive or significant association has been detected in some studies for the angiotensinogen M235T, angiotensin I-converting enzyme I/D, angiotensin II type 1 receptor A1166C, and aldosterone synthase C-344T polymorphisms, although the results remain inconclusive.

OBJECTIVE AND METHODS

To evaluate the importance of these candidate genes for hypertension, we undertook an extensive association study in the Japanese. This case-control study was conducted in a total of 1476 individuals using the four R-A gene polymorphisms. In the assessment of genotyping data, 843 hypertensive subjects were divided into three case subgroups according to severity of hypertension, while 633 normotensive subjects divided into two control subgroups by the age of enrollment. Each subgroup was further divided by sex. Subsequently, the presence of synergy (or gene-gene interaction) was evaluated among four R-A gene polymorphisms.

RESULTS

No significant association was observed between the individual R-A gene polymorphisms and hypertension status in our case-control study. The results were almost unchanged when severity of hypertension, sex-specificity, and synergy were taken into account

CONCLUSIONS

Despite a relatively large number of subjects, we did not find significant evidence for disease association in the Japanese population. Given confounding factors in the case-control strategy, the lack of association does not exclude the relevance of the R-A genes to hypertension. Further investigation needs to be performed in large-scale populations, where the use of not only hypertension status, but also 'intermediate' phenotypes would be useful.

The molecular basis of hypertension

More than 50 million Americans display blood pressures outside the safe physiological range. Unfortunately for most individuals, the molecular basis of hypertension is unknown, in part because pathological elevations of blood pressure are the result of abnormal expression of multiple genes. This review identifies a number of important blood pressure regulatory genes including their loci in the human, mouse, and rat genome. Phenotypes of gene deletions and overexpression in mice are summarized. More detailed discussion of selected gene products follows, beginning with proteins involved in ion transport, specifically the epithelial sodium channel and sodium proton exchangers. Next, proteins involved in vasodilation/natriuresis are discussed with emphasis on natriuretic peptides, guanylin/uroguanylin, and nitric oxide. The renin angiotensin aldosterone system has an important role antagonizing the vasodilatory cyclic GMP system.

Genetic polymorphisms of the renin-angiotensin system and complications of insulin-dependent diabetes mellitus

OBJECTIVE

Patients with insulin-dependent diabetes mellitus (IDDM) have a high risk of developing diabetic nephropathy, retinopathy and cardiovascular diseases. The contribution of gene polymorphisms of the renin angiotensin system to these complications is controversial and may differ among populations.

METHODS

In 257 Dutch IDDM patients (188 with urinary albumin excretion (UAE) <30 mg/24 h), logistic regression analysis was used to study the relationships among, on the one hand, the insertion/deletion gene polymorphism of the angiotensin-converting enzyme gene (ACE-ID), the M235T gene polymorphism of the angiotensinogen gene (AGT-M235T), and the A1166C gene polymorphism of the angiotensin type 1 receptor gene (AT1-A1166C), and, on the other hand, UAE, retinopathy, hypertension, and coronary heart disease.

RESULTS

The T-allele of the AGT-M235T polymorphism was associated with an increased risk of an elevated UAE (odds ratio (OR) 3.03; 95% confidence interval (CI) 1.06-8.61), but only when interaction with the D-allele of the ACE-ID polymorphism was considered. A previously described positive interaction between the T-allele of the AGT-M235T polymorphism and the D-allele of the ACE-ID polymorphism could not be confirmed. The T-allele was also associated with an increased risk of retinopathy (OR 3.89, 95% CI 1.79-8.47). The CC-genotype of the AT1-A1166C polymorphism was associated with hypertension (OR 3.58; 95% CI 1. 23-10.37).

CONCLUSIONS

In a Dutch IDDM population, including 69 patients with (incipient) diabetic nephropathy, the T-allele of the AGT-M235T polymorphism is associated with an elevated UAE and diabetic retinopathy and the CC-genotype of the AT1-A1166C polymorphism is associated with hypertension. A previously described interaction between the AGT-M235T and the ACE-ID polymorphisms could not be confirmed. Since the number of nephropathic patients in this study is small, these conclusions must be interpreted with caution.

Association between high von willebrand factor levels and the Thr789Ala vWF gene polymorphism but not with nephropathy in type I diabetes. The GENEDIAB Study Group and the DESIR Study Group

BACKGROUND

A genetic susceptibility for diabetic kidney disease is suspected since diabetic nephropathy occurs in only 30 to 40% of type I diabetic patients. As elevated von Willebrand factor (vWF) plasma concentrations have been reported to precede the development of microalbuminuria in type I diabetes, we addressed a possible implication of vWF as a genetic determinant for diabetic nephropathy.

METHODS

Three known vWF gene polymorphisms were genotyped in a group of 493 type I diabetic subjects, all showing proliferative retinopathy, but with various stages of renal involvement, which ranged from no microalbuminuria, despite a mean duration of diabetes of 31 years, to advanced nephropathy (GENEDIAB Study): Thr789Ala (Rsa I), M-/M+ (Msp I) (intron 19), and Ala1381Thr (Hph I). Plasma vWF and factor VIII (F VIII) levels were also measured in this population.

RESULTS

Plasma vWF and F VIII levels were increased in diabetic subjects with nephropathy (P < 0.001) or with coronary heart disease (CHD; P < 0.001), but there was no interaction of both conditions on plasma levels. The Msp I polymorphism (M-/M+) was weakly associated with nephropathy (P = 0. 04), but this association was not more significant when other risk factors were used in a logistic regression analysis. The vWF Thr789Ala polymorphism was associated with CHD (P = 0.002) and with plasma vWF levels. Logistic regression analysis indicated an independent and codominant effect of the Thr789Ala polymorphism on CHD, but not on nephropathy, with a maximal risk for Ala/Ala homozygotes (OR = 4.2, 95% CI, 1.8 to 9.9, P = 0.0008).

CONCLUSION

It is unlikely that polymorphisms in the vWF gene contribute to the risk for nephropathy in type I diabetic patients. However, the Thr789Ala polymorphism might affect the risk for CHD in this population through modulation of plasma vWF levels.

Genetic polymorphism of the renin-angiotensin system and organ damage in essential hypertension

BACKGROUND

The renin-angiotensin-aldosterone system (RAAS) plays a significant role in the development of hypertensive cardiac and vascular remodeling. Recently, several genetic variants of its key components, which may be clinically relevant and thus prove to be useful in the evaluation of cardiovascular risk, have been described. We therefore investigated the association between ACE I/D, AGT M235T, and AT1 A1266C gene polymorphisms and early signs of target organ damage in 215 untreated patients with essential hypertension (EH).

METHODS

Genotyping was based on the polymerase chain reaction technique, with further restriction analysis when required. Albuminuria was measured as the albumin-to-creatinine ratio (ACR). The left ventricular mass index (LVMI) was assessed by echocardiography (LVH = LVMI > or = 125 g/m2), carotid wall thickness (IMT) by an ultrasonographic (US) scan, and retinal vascular changes by direct ophthalmoscopy (Keith-Wagener classification).

RESULTS

The prevalence of microalbuminuria (Mi), LVH, and retinal vascular changes was 14, 46, and 74%, respectively. ACE, AGT, and AT1 genotype distribution was in agreement with the Hardy-Weinberg equilibrium. There was no difference in age, duration of disease, body mass index (BMI), blood pressure, and lipid profile when data were analyzed on the basis of genotype. Serum levels of angiotensin-converting enzyme (ACE) were related to the ACE genotype (10.2 +/- 0.5, DD; 8.2 +/- 0.3, ID; 6.5 +/- 0.4 IU/mL, II; P < 0. 0001 by analysis of variance). The ACE genotype independently influences serum ACE levels and accounts for approximately 14% of its variations (F = 26.7, r2 = 0.1393, df 1 to 214, P < 0.0001). Patients with DD and ID genotypes showed higher levels of ACR (1.59 +/- 0.2, DD + ID; 0.8 +/- 0.2 mg/mmol, II; P < 0.006 by ANOVA) and bigger LVMI (124.1 +/- 2.3, DD + ID vs. 117.8 +/- 3.6 g/m2, II; P < 0.01 by ANOVA). No differences in the prevalence and degree of target organ damage (TOD) were found when data were analyzed on the basis of the AGT and AT1 genotypes, respectively. Potentially unfavorable combinations of genotypes were also investigated by K-means cluster analysis. Two subgroups of patients were identified (cluster 1, N = 70; cluster 2, N = 57), and each differed significantly with regards to the presence and degree of TOD and patterns of RAAS gene polymorphisms (F, 15.97 for ACR; F, 7.19 for IMT; F, 217.03 for LVMI; F, 3.91 for ACE; F, 4.06 for AGT; and F, 5. 22 for AT1; df 1 to 214, P < 0.02, for each one of the variables examined).

CONCLUSION

The D allele of the ACE gene may be an independent risk factor for the development of target organ damage, and evaluating it could be useful for assessing cardiovascular risk in EH. Unfavorable patterns of RAAS genotypes seem to predispose patients to subclinical cardiovascular disease in EH.

[Possible genetic causes for late complications of diabetes mellitus]

BACKGROUND

Hyperglycemia occurs in every patient with diabetes mellitus. It is the most important factor in the development of diabetic complications. However, the onset, intensity and the progression of complications show large interindividual variations. Manifestation in families and the lack of complications in some diabetics with poor metabolic control indicate a genetic predisposition to develop diabetic complications like nephropathy, neuropathy and angiopathy.

NEPHROPATHY

Diabetic nephropathy occurs only in 25 to 40% of the diabetic patients. Therefore a genetic risk factor for this complication is very likely. Various variations in genes like ACE-gene and angiotensinogen-gene have been described, which could be associated with the development of diabetic nephropathy.

NEUROPATHY

Peripheral diabetic neuropathy occurs in up to 66% of all diabetics. Therefore and because of the possible pathological mechanisms genetic risk factors like variations in the Na/K-ATPase-gene and in the aldose reductase-gene are discussed.

RETINOPATHY

An association between diabetic retinopathy and polymorphisms in the ACE-gene and the aldose reductase-gene seems very unlikely, because up to 75% of the diabetic patients suffer from retinopathy after 15 years of diabetes.

MACROANGIOPATHY

A large number of studies show an association between diabetic macroangiopathy and genetic variations in the ACE-gene (I/D-variant) and the paraoxonase-gene (2 isoforms).

CONCLUSION

Based on the current evidence for associations of genetic markers with diabetic complications, the generation of an individual risk profile based on genetic markers seems to be possible. In addition to near euglycemia genetic markers could direct therapeutic strategies and lead to new therapeutic approaches.

Polymorphisms of angiotensin-converting enzyme and angiotensinogen genes in type 2 diabetic sibships in relation to albumin excretion rate

Familial clustering of altered albumin excretion and nephropathy risk has been described in both type 1 and type 2 diabetes; moreover, an association of micro-macroalbuminuria and diabetic retinopathy has been recently reported in a large number of white families with type 2 diabetes. Conflicting reports, mainly comparing affected with unaffected unrelated subjects, have suggested a possible role of some genotypes of the renin-angiotensin system in conferring nephropathy risk in type 2 diabetes. To examine the role of genetic factors in influencing albuminuria in families, we studied the relation of angiotensin-converting enzymes (ACE) and angiotensinogen (AGN) genotypes with albumin excretion rate in a population of affected siblings of type 2 diabetic probands. We determined ACE insertion/deletion polymorphism and two polymorphisms of the AGN gene (T174M and M235T) in 160 families with at least one affected member. Defining proband as the patient with the longest known duration of diabetes, we compared the allelic distribution in diabetic probands with and without altered albumin excretion and in their siblings. Allelic distribution of these polymorphisms was similar in the two groups of probands, as well as in their siblings. Identity-by-State (IBS) analysis showed a link between AGN locus and arterial hypertension in these siblings, which was independent from the degree of renal involvement. Thus, our findings suggest that in white families with type 2 diabetes, there is no linkage between the degree of albumin excretion and ACE and AGN polymorphisms, whereas the latter is related to arterial hypertension, as previously found in patients without diabetes but with essential hypertension.

Angiotensin I to angiotensin II conversion in the human forearm and leg. Effect of the angiotensin converting enzyme gene insertion/deletion polymorphism

OBJECTIVE

The angiotensin-converting enzyme (ACE) gene I/D polymorphism accounts for part of the variation in ACE concentration; subjects with one or two D alleles have approximately 25 and 50% higher ACE levels, respectively, than subjects with two I alleles. Data from studies on the pressor effects of angiotensin (Ang) I in DD compared with II subjects are inconsistent, because enhanced conversion in DD subjects may have been masked by a decreased responsiveness to Ang II. Here we quantify ACE genotype-related Ang I to Ang II conversion in the human forearm and leg using non-pressor 125I-Ang I infusions.

DESIGN AND METHODS

Infusions were given to 12 women and 17 men (age 24-67 years) who were undergoing renal vein sampling followed by renal angiography for diagnostic purposes. 125I-Ang I was infused for 20 min into the right antecubital vein, and blood samples for the measurement of 125I-labelled and endogenous Ang I and Ang II were taken from the aorta, the left antecubital vein and a femoral vein under steady-state conditions. Genotype frequencies were determined by polymerase chain reaction.

RESULTS

Fractional conversion (i.e. the percentage of arterially delivered 125I-Ang I that is converted to 125I-Ang II) in the forearm (38+/-4, 30+/-3 and 31+/-6% in 8 II, 16 ID and 5 DD subjects, respectively; mean +/- SEM) and leg (52+/-4, 48+/-3 and 42+/-5%) was similar in all three groups. In addition, no genotype-related differences in plasma Ang II/I ratio (a measure of ACE activity) were observed at the three sampling sites.

CONCLUSIONS

Regional Ang I to Ang II conversion does not parallel the previously described D allele-related differences in ACE concentration, suggesting that effects other than enhanced conversion may underlie the reported associations between the D allele and various cardiovascular diseases.

Genetic polymorphism of renin-angiotensin system is not associated with diabetic vascular complications in Japanese subjects with long-term insulin dependent diabetes mellitus

In a hospital cohort study, we examined whether or not ACE (Angiotensin-I converting enzyme) and AGT (Angiotensinogen) gene polymorphisms were associated with the development of nephropathy in long-term Japanese insulin-dependent diabetes mellitus (IDDM) patients with or without proliferative retinopathy, and whether or not the polymorphisms were associated with an arteriosclerotic family history in first degree relatives of the patients. A total of 201 patients with IDDM for more than 10 years and 159 patients with IDDM for more than 15 years were randomly selected in our hospital. All patients received uniform diabetes management and were divided into three groups, no nephropathy, incipient nephropathy and clinical nephropathy groups. There were no differences in clinical characteristics excluding urinary albumin to creatinine ratio and systolic blood pressure between the three groups. ACE I/D polymorphism was related to plasma ACE activity, but there were no associations between ACE I/D polymorphism and the development of diabetic nephropathy, nor was renal deterioration observed in patients with proliferative retinopathy even in those with a history of diabetes for more than 15 years. The AGT polymorphism did not have an additive effect on the association between ACE polymorphism and the development of diabetic nephropathy in patients with or without retinopathy. Development of diabetic nephropathy in the patients with or without proliferative retinopathy did not result in ACE or AGT polymorphisms. On the other hand, the ACE DD genotype was associated with a family history of ischemic heart disease in first degree relatives (X2 score = 9.04, P < 0.05). ACE and AGT gene polymorphisms may not play a role in the protective or accelerative effect against the development of diabetic nephropathy in the patients with or without proliferative retinopathy, but ACE gene polymorphism might be related to an arteriosclerotic family history in Japanese IDDM patients.

Renal response to captopril reflects state of local renin system in healthy humans

BACKGROUND

Heightened activity of the renin-angiotensin system has been linked to the development of both essential hypertension and diabetic nephropathy. Blunting of the renal vasoconstrictor response to Ang II, specifically when it is corrected by angiotensin converting enzyme (ACE) inhibition, is a feature which we have employed as a marker for activation of the intrarenal RAS. In this study we tested the hypothesis that variation in the renal vasodilator response to ACE inhibition in healthy humans reflected the variation in angiotensin-mediated renal vasoconstriction provoked by a low-salt diet.

METHODS

We studied 20 healthy people (ages 19 to 57; 15 males) who were in balance on a low sodium diet. Ang II was infused for 45 minutes (3 ng/kg/min), followed by 25 mg captopril and a repeat Ang II infusion; PAH clearance was measured at the end of each interval.

RESULTS

All subjects responded to captopril with a rise in renal plasma flow (range 43 to 242, mean 118 + 12 ml/min/1.73 m2). Individual vasodilator response to captopril was a strong inverse predictor of the precaptopril vasoconstrictor response to Ang II (P = 0.006, r = -0.59). There was a stronger, positive correlation of the vasodilator response to captopril and enhancement of Ang II responsiveness after captopril (r = 0.57). Plasma renin activity was significantly correlated with captopril response among the large responders (P = 0.003; r = 0.83), but not at all among those with little response.

CONCLUSION

These results suggest substantial variation in angiotensin-mediated control of the renal circulation in healthy individuals on a low sodium intake. Variation in the vasodilator response to captopril, correlated with responses to Ang II, provides a measure of that control.

Plasma renin and prorenin and renin gene variation in patients with insulin-dependent diabetes mellitus and nephropathy

BACKGROUND

The most striking abnormality in the renin angiotensin system in diabetic nephropathy (DN) is increased plasma prorenin. Renin is thought to be low or normal in DN. In spite of altered (pro)renin regulation the renin gene has not been studied for contribution to the development of DN.

METHODS

We studied plasma renin, prorenin, and four polymorphic markers of the renin gene in 199 patients with IDDM and DN, and in 192 normoalbuminuric IDDM controls matched for age, sex, and duration of diabetes. Plasma renin and total renin were measured by immunoradiometric assays. Genotyping was PCR-based.

RESULTS

Plasma renin was increased in patients with nephropathy (median (range), 26.3 (5.2-243.3) vs 18.3 (4.2-373.5) microU/ml in the normoalbuminuric group, P<0.0001). Prorenin levels were elevated out of proportion to renin levels in nephropathic patients (789 (88-5481) vs 302 (36-2226) microU/ml, P<0.0001). Proliferative retinopathy had an additive effect on plasma prorenin, but not on renin. DN was associated with a BglI RFLP in the first intron of the renin gene (bb-genotype: n=106 vs 82 in DN and normoalbuminuric patients respectively, P=0.037), but not with three other polymorphisms in the renin gene. A trend for association of higher prorenin levels with the DN-associated allele of this renin polymorphism was observed in a subgroup of patients with DN (bb vs Bb+BB, P=0.07).

CONCLUSIONS

The results indicate that in DN there is an increase in both renin and prorenin levels. A renin gene polymorphism may contribute weakly to DN. Although speculative, one of the renin gene alleles could lead to increased renin gene expression, leading to higher renin and prorenin levels. These may play a role in the pathogenesis of DN.

Pronatriodilatin gene polymorphisms, microvascular permeability, and diabetic nephropathy in type 1 diabetes mellitus

Approximately 30% of diabetic patients develop nephropathy, the appearance of which is partially under genetic control. Atrial natriuretic peptide (ANP) has associated physiologic effects on the kidney. This study was conducted to examine the relationship between a newly identified and known polymorphism at the pronatriodilatin (PND) gene locus and renal involvement in type 1 diabetic subjects. Of 454 type 1 diabetic patients (219 men, 235 women), 323 showed no sign of nephropathy, 79 had incipient renal involvement, and 52 established nephropathy; 58 healthy control subjects were examined for comparison. Allele frequencies (C708 versus T708) were: 0.95 and 0.05 in normoalbuminuric patients, respectively; 0.88 and 0.12 in microalbuminuric patients; 0.96 and 0.04 both in those with overt nephropathy and in healthy control subjects (P = 0.011). Patients with incipient nephropathy were in disequilibrium compared with the total diabetic cohort (P = 0.02). In the same populations, an additional genotype for ScaI polymorphism of the PND gene was tested. The A1 and A2 allele frequencies were: 0.21 and 0.79 in normoalbuminuric patients; 0. 13 and 0.87 in microalbuminuric patients; 0.06 and 0.94 in type 1 diabetic subjects with overt nephropathy; and 0.20 and 0.80 in healthy control subjects, respectively (P < 0.0001). A subset of 55 normotensive patients with type 1 diabetes, well matched for clinical features, plasma ANP levels, and microvascular permeability to macromolecules, was investigated on the basis of the C708/T and A2/A1 polymorphisms. Both transcapillary escape rate of albumin (TERalb) and plasma ANP levels were significantly lower in patients with the T708 than with C708 allele, as well as in the A1 than in A2 allele (TERalb: T708 versus C708: 5.5+/-1.7 versus 7.8+/-2.0%/h, P = 0.0001; plasma ANP levels: 8.3+/-3.9 versus 15.3+/-7.7 pg/ml, P = 0.0003; A1 versus A2: 6.05+/-2.2 versus 7.3+/-2.1%/h, P = 0.044; 8.53+/-4.6 versus 14.5+/-7.4 pg/ml, P = 0.0024, respectively). Thus, in a large ethnically homogeneous cohort of diabetic subjects, our data show: (1) a significant association of C708/T polymorphism with microalbuminuria in long-term diabetes and with both lower plasma ANP levels and widespread albumin leakage; and (2) a strong association between ScaI polymorphism and both diabetic nephropathy and plasma ANP concentrations. These results suggest a possible role of PND gene in conferring protection from nephropathy and microvascular damage in type 1 diabetes.

ACE, PAI-1, decorin and Werner helicase genes are not associated with the development of renal disease in European patients with type 1 diabetes

BACKGROUND

Genetic factors are involved in the development of diabetic nephropathy in Type 1 diabetes. We have examined the association of four candidate genes, angiotensin converting enzyme (ACE): insertion/deletion (I/D) polymorphism, plasminogen activator inhibitor-1 (PAI-1): 4G/5G polymorphism, decorin: 179/183/185 polymorphism and Werner syndrome helicase: C/R polymorphism, with the presence of diabetic nephropathy in Type 1 diabetic patients.

METHODS

175 Type 1 diabetic patients with albuminuria (59 with microalbuminuria and 116 with macroalbuminuria) were compared with 136 Type 1 diabetic patients with normoalbuminuria and duration of disease longer than 15 years (mean+/-SD: 25+/-8 years). 200 non-diabetic subjects were also studied as background population.

RESULTS

We found no association in the polymorphism of the four genes examined between patients with and without diabetic nephropathy and the control subjects.

CONCLUSIONS

The genes studied are unlikely to be involved in the susceptibility to nephropathy in Type 1 diabetic patients.

Increased bradykinin and "normal" angiotensin peptide levels in diabetic Sprague-Dawley and transgenic (mRen-2)27 rats

BACKGROUND

The transgenic (mRen-2)27 rat (TGR) is a high tissue renin, high angiotensin (Ang) II model of hypertension. When administered streptozotocin (STZ), TGRs develop a rapidly progressive diabetic nephropathy with renal failure over 12 weeks. Bradykinin (BK) and Ang II are potent vasoactive peptides that may participate in the vascular and metabolic abnormalities of diabetes.

METHODS

TGR and Sprague-Dawley (SD) rats were administered STZ (diabetic) or citrate buffer (nondiabetic) at six weeks of age. Diabetic rats received daily ultralente insulin to maintain moderate hyperglycemia ( approximately 18 mM). Rats were sacrificed four- and eight-weeks post-STZ or vehicle.

RESULTS

Diabetes did not modify the blood pressure of either SD rats or TGRs. Diabetes increased levels of BK-(1-9) and its metabolite BK-(1-7) in kidney, aorta, and heart of both SD rats and TGRs. Diabetes did not influence Ang II levels in plasma, kidney, aorta, heart, or adrenal gland of SD rats, but reduced to normal the elevated Ang II levels in plasma, kidney, aorta, and adrenal gland of TGRs.

CONCLUSIONS

STZ-induced diabetes was associated with elevated tissue levels of BK-(1-9) and "normal" circulating and tissue levels of Ang II. The increased BK-(1-9) levels were consistent with the participation of this peptide in the vascular and metabolic abnormalities of diabetes. However, the rapidly progressive nephropathy of diabetic TGRs was not associated with BK-(1-9) and Ang II levels in target organs that differed from those of diabetic SD rats.

Genetic susceptibility to end-stage renal disease

New methods have been developed to uncover the genotypes that result in complex diseases. End-stage renal disease is a complex disease, without a simple correspondence between genotype and phenotype. Both population-based and family-based epidemiological studies and analysis of model organisms suggest that the pathogenesis of end-stage renal disease may have a genetic component. A number of studies have analyzed candidate nephropathy genes with little success, but recently several well-designed studies of multiplex families with diabetic nephropathy have identified candidate nephropathy susceptibility loci. To date, kidney disease-oriented research has focused on effector mechanisms responsible for the initiation and progression of chronic renal disease. However, because end-stage renal disease is a complex disease, interruption of a single effector pathway is unlikely to result in significant therapeutic benefit. Further understanding of the pathogenesis of kidney disease and the development of new kidney disease therapies will require continued application of genetic and genomic tools to kidney disease research.

Angiotensin-converting enzyme gene and diabetes mellitus

AIMS

The association of the insertion/deletion polymorphism in the angiotensin-converting enzyme (ACE) gene with cardiovascular disease and diabetic nephropathy remains a controversial issue. This review aims to give an overview of the research to date assessing the impact of the ACE polymorphism in Type 1 and Type 2 diabetes mellitus (DM).

METHODS

A systematic review of the literature was performed in the databases of MEDLINE, PubMed and EMBASE for the key words 'diabetes mellitus', 'diabetic nephropathy', 'ACE polymorphism' and 'genotype' and relevant articles were considered.

RESULTS

A meta-analysis assessing the influence of the ACE polymorphism on disease susceptibility demonstrated significant odds ratios in individuals with the DD genotype for coronary heart disease, myocardial infarction and both diabetic and nondiabetic renal disease. No association was found for left ventricular hypertrophy or hypertension in nondiabetic subjects.

CONCLUSIONS

The ACE polymorphism appears to have a significant impact on the progression of diabetic nephropathy and may have therapeutic implications for identifying those individuals resistant to the effects of ACE inhibitors. It also appears to be indicative of an increased vascular risk in diabetic patients; however, larger prospective studies are required to clarify this situation.

Lack of association of angiotensin-converting enzyme (DD/II) and angiotensinogen M235T gene polymorphism with renal function among Chinese patients with type II diabetes

The prevalence of diabetic nephropathy is greater in nonwhite patients with type II diabetes, including the Chinese, and genetic variation appears to have a role. We examined angiotensin-converting enzyme (ACE) DD/II and angiotensinogen (Atg) M235T polymorphism in a cohort of Chinese patients with type II diabetes with an average duration of diabetes of 14 years. Group A (n = 88) did not have significant diabetic nephropathy (creatinine levels </= 130 micromol/L [</=1.48 mg/L], without macroalbuminuria), and group B (n = 80) had significant diabetic nephropathy (macroalbuminuria or creatinine level >130 micromol/L [>1.48 mg/d], and those undergoing dialysis). The two groups were matched in different aspects, including age, duration of diabetes, blood pressure, and glycemic control. The results showed: (1) no difference of genotype distribution between groups A and B (DD:DI:II, 14%:45%:41% v 8%:38%:54%; P = 0.20; TT:TM/MM, 70%:30% v 76%:24%; P = 0.43), (2) no evidence of synergistic effect of ACE (DD/II) and Atg M235T gene polymorphisms, (3) no difference of allele frequencies between groups A and B (D:I, 36%:64% v 27%:73%; P = 0.20 and T:M, 86%:16% v 86%:14%; P = 0.73), and (4) ACE activity was greatest in patients with DD genotype and least in those with II genotype (DD:DI:II = 66. 9 +/- 13.3 U/L:61.5 +/- 19.9 U/L:45.0 +/- 17.0 U/L; P < 0.005). The data do not support a role of ACE (DD/II) or Atg M235T polymorphism in the development of diabetic nephropathy in Chinese patients with type II diabetes, and no synergistic effect was found between them. Greater ACE activity was associated with DD genotype, and its role in diabetic nephropathy remains to be elucidated.

Expansion of cortical interstitium is limited by converting enzyme inhibition in type 2 diabetic patients with glomerulosclerosis. The Diabiopsies Group

Renal interstitial expansion is now considered a useful marker of progression of several nephropathies. This study describes a multicenter, prospective, double-blind, placebo-controlled, randomized trial of the effects of Perindopril (4 mg/d) on kidney structure and function over 2 yr in 26 type 2 diabetic patients with proteinuria ranging from 70 to 4210 mg/d and relatively preserved GFR (creatinine clearance >60 ml/min). All patients underwent baseline renal biopsy, but four (15%) were not randomized because of the presence of nondiabetic nephropathy. The remaining 22 were randomized ( 11 to Perindopril [PE], 11 to placebo [PO]), and 19 (9 PE, 10 PO) underwent follow-up biopsy at 2 yr. BP was controlled equally in both groups throughout. Proteinuria increased in PO patients (+1562 mg/d) but declined in PE patients (-156 mg/d) (P < 0.05). Morphometric analysis was performed by light microscopy using a Biocom computer. Over the 2 yr, mean cortical interstitial fractional volume identical at baseline increased significantly in PO patients (31.7 +/- 5.3 versus 40.2 +/- 11.1%; P = 0.001) but was unchanged in PE patients (33.8 +/- 4.9 versus 34.7 +/- 6.6%; P = 0.50). It is concluded that: (1) nondiabetic nephropathy is present in approximately 15% of albuminuric type 2 diabetic patients; and (2) Perindopril prevents interstitial expansion in hypertensive patients with biopsy-proven diabetic glomerulopathy. These results support a role of angiotensin II in the progression of interstitial changes in type 2 diabetic patients with nephropathy.

Angiotensin-converting enzyme gene polymorphism: is there a link to nephropathy in patients with type 1 diabetes?

OBJECTIVE

To evaluate the association between the angiotensin-converting enzyme (ACE) gene polymorphism and diabetic nephropathy in patients with type 1 diabetes.

DATA SOURCES

Citations were selected using the MEDLINE database. Only those citations involving human subjects and available in English were selected. Key search words included angiotensin-converting enzyme (ACE), polymorphism, nephropathy, and type 1 diabetes.

STUDY SELECTION

Selection criteria consisted of all MEDLINE-referenced clinical trials, review articles, and editorial comments assessing the potential link between the ACE gene polymorphism and diabetic nephropathy in insulin-dependent diabetes mellitus published between January 1990 and February 1998.

DATA SYNTHESIS

Because diabetic nephropathy is a serious complication of type 1 diabetes, focus has been placed on the early identification of and intervention with patients genetically susceptible to this complication. Because the ACE gene polymorphism has an effect on plasma ACE concentration variations among individuals, it has been investigated as a potential genetic marker for diabetic nephropathy. The best studies to date are reviewed in order to assess the utility of the ACE polymorphisms as a genetic marker of diabetic nephropathy in patients with type 1 diabetes, and to determine what implications this holds for drug treatment.

CONCLUSIONS

Although the ACE gene polymorphism's potential link to diabetic nephropathy in patients with type 1 diabetes has been debated, the most definitive studies show that an association exists. Large epidemiologic studies must now be conducted to determine the implications this polymorphism holds for the best treatment strategies in the care of these patients.