Genetic polymorphisms of angiotensin-2 type 1 receptor and angiotensinogen and risk of renal dysfunction and coronary heart disease in type 2 diabetes mellitus

Association of the rs5186 polymorphism of the AGTR1 gene with decreased eGFR in patients with type 2 diabetes from Mexico City

BACKGROUND

Early biomarkers search for Diabetic Kidney Disease (DKD) in patients with Type 2 Diabetes Mellitus (T2DM), as genetic markers to identify vulnerable carriers of the disease even before Glomerular Filtration Rate (GFR) decline or microalbuminuria development, has been relevant during the last few years. The rs5186 (A116C) polymorphism of the Angiotensin II Receptor Type I gene (AGTR1), has been associated to multiple effects of renal injury risk, commonly detected in patients with Diabetes Mellitus (DM). It has been described that rs5186 could have an effect in stability proteins that assemble Angiotensin II Receptor Type I (AT1), modifying its action, which is why it should be considered as a risk factor for Chronic Kidney Disease (CKD), characterized by a GFR progressive reduction. Even though, the association between rs5186 AGTR1 gene polymorphism and DKD in patients with T2DM has been controversial, inconclusive, and even absent. This disputable issue might be as a result of association studies in which many and varied clinical phenotypes included are contemplated as CKD inductors and enhancers. Although, the sample sizes studied in patients with T2DM are undersized and did not have a strict inclusion criteria, lacking of biochemical markers or KDOQI classification, which have hindered its examination.

OBJECTIVE

The aim of our study was to establish an association between rs5186 AGTR1 gene polymorphism and GFR depletion, assessed as a risk factor to DKD development in patients with T2DM.

METHODS

We analyzed 297 not related patients with T2DM, divided into 221 controls (KDOQI 1) and 76 cases (KDOQI 2). Arterial pressure, anthropometric and biochemical parameters were measured. rs5186 of AGTR1 genotyping was performed by TaqMan assay real-time PCR method. Allele and genotype frequencies, and Hardy-Weinberg equilibrium were measured. Normality test for data distribution was analyzed by Shapiro-Wilk test, variable comparison by Student's t-test for continuous variables, and Chi-squared test for categorical variables; ANOVA test was used for mean comparison of more than two groups. Effect of rs5186 to DKD was estimated by multiple heritability adjustment models for risk variables of DKD. Statistical significance was indicated by p<0.05. Data was analyzed using Statistical Package STATA v11 software.

RESULTS

Dominant and Over-dominant models showed a likelihood ratio to GFR depletion of 1.89 (1.05-3.39, p=0.031) and 2.01 (1.08-3.73, p=0.023) in patients with T2DM. Risk factor increased to 2.54 (1.10-5.89) in women in Over-dominant model.

CONCLUSION

In clinical practice, most of nephropathies progress at a slow pace into a total breakdown of renal function, even asymptomatic. This is the first study, reporting that rs5186 polymorphism of AGTR1 gene contribution to GFR depletion, and this could be evaluated as a predisposing factor for DKD in patients with T2DM.

Angiotensin II Type I Receptor (AT1R): The Gate towards COVID-19-Associated Diseases

The binding of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike glycoprotein to its cellular receptor, the angiotensin-converting enzyme 2 (ACE2), causes its downregulation, which subsequently leads to the dysregulation of the renin-angiotensin system (RAS) in favor of the ACE-angiotensin II (Ang II)-angiotensin II type I receptor (AT1R) axis. AT1R has a major role in RAS by being involved in several physiological events including blood pressure control and electrolyte balance. Following SARS-CoV-2 infection, pathogenic episodes generated by the vasoconstriction, proinflammatory, profibrotic, and prooxidative consequences of the Ang II-AT1R axis activation are accompanied by a hyperinflammatory state (cytokine storm) and an acute respiratory distress syndrome (ARDS). AT1R, a member of the G protein-coupled receptor (GPCR) family, modulates Ang II deleterious effects through the activation of multiple downstream signaling pathways, among which are MAP kinases (ERK 1/2, JNK, p38MAPK), receptor tyrosine kinases (PDGF, EGFR, insulin receptor), and nonreceptor tyrosine kinases (Src, JAK/STAT, focal adhesion kinase (FAK)), and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase. COVID-19 is well known for generating respiratory symptoms, but because ACE2 is expressed in various body tissues, several extrapulmonary pathologies are also manifested, including neurologic disorders, vasculature and myocardial complications, kidney injury, gastrointestinal symptoms, hepatic injury, hyperglycemia, and dermatologic complications. Therefore, the development of drugs based on RAS blockers, such as angiotensin II receptor blockers (ARBs), that inhibit the damaging axis of the RAS cascade may become one of the most promising approaches for the treatment of COVID-19 in the near future. We herein review the general features of AT1R, with a special focus on the receptor-mediated activation of the different downstream signaling pathways leading to specific cellular responses. In addition, we provide the latest insights into the roles of AT1R in COVID-19 outcomes in different systems of the human body, as well as the role of ARBs as tentative pharmacological agents to treat COVID-19.

Diabetes and Renin-Angiotensin-Aldosterone System: Pathophysiology and Genetics

Diabetes mellitus (DM) is a metabolic disorder and characterized by hyperglycemia. Being a concern of both the developed and developing world, diabetes is a global health burden and is a major cause of mortality world-wide. The most common is the type 2 diabetes mellitus (T2DM), which is mainly caused by resistance to insulin. Long-term complications of diabetes cause microvascular related problems (eg. nephropathy, neuropathy and retinopathy) along with macrovascular complications (eg. cardiovascular diseases, ischemic heart disease, peripheral vascular disease). Renin-angiotensin-aldosterone system (RAAS) regulates homeostasis of body fluid that in turn, maintains blood pressure. Thus, RAAS plays pivotal role in the pathogenesis of long-term DM complications like cardiovascular diseases and chronic kidney diseases. T2DM is a polygenic disease, and the roles of RAAS components in insulin signaling pathway and insulin resistance have been well documented. Hyperglycemia has been found to be associated with the increased plasma renin activity, arterial pressure and renal vascular resistance. Several studies have reported involvement of single variants within particular genes in initiation and development of T2D using different approaches. This chapter aims to investigate and discuss potential genetic polymorphisms underlying T2D identified through candidate gene studies, genetic linkage studies, genome wide association studies.

Gender Differences in Diabetic Kidney Disease: Focus on Hormonal, Genetic and Clinical Factors

Diabetic kidney disease (DKD) is one of the most serious complications of both type 1 (T1DM) and type 2 diabetes mellitus (T2DM). Current guidelines recommend a personalized approach in order to reduce the burden of DM and its complications. Recognizing sex and gender- differences in medicine is considered one of the first steps toward personalized medicine, but the gender issue in DM has been scarcely explored so far. Gender differences have been reported in the incidence and the prevalence of DKD, in its phenotypes and clinical manifestations, as well as in several risk factors, with a different impact in the two genders. Hormonal factors, especially estrogen loss, play a significant role in explaining these differences. Additionally, the impact of sex chromosomes as well as the influence of gene-sex interactions with several susceptibility genes for DKD have been investigated. In spite of the increasing evidence that sex and gender should be included in the evaluation of DKD, several open issues remain uncovered, including the potentially different effects of newly recommended drugs, such as SGLT2i and GLP1Ras. This narrative review explored current evidence on sex/gender differences in DKD, taking into account hormonal, genetic and clinical factors.

Common genetic variants and pathways in diabetes and associated complications and vulnerability of populations with different ethnic origins

Diabetes mellitus is a complex and heterogeneous metabolic disorder which is often pre- or post-existent with complications such as cardiovascular disease, hypertension, inflammation, chronic kidney disease, diabetic retino- and nephropathies. However, the frequencies of these co-morbidities vary among individuals and across populations. It is, therefore, not unlikely that certain genetic variants might commonly contribute to these conditions. Here, we identified four single nucleotide polymorphisms (rs5186, rs1800795, rs1799983 and rs1800629 in AGTR1, IL6, NOS3 and TNFA genes, respectively) to be commonly associated with each of these conditions. We explored their possible interplay in diabetes and associated complications. The variant allele and haplotype frequencies at these polymorphic loci vary among different super-populations (African, European, admixed Americans, South and East Asians). The variant alleles are particularly highly prevalent in different European and admixed American populations. Differential distribution of these variants in different ethnic groups suggests that certain drugs might be more effective in selective populations rather than all. Therefore, population specific genetic architectures should be considered before considering a drug for these conditions.

Correlation between gene polymorphism in angiotensin II type 1 receptor and type 2 diabetes mellitus complicated by hypertension in a population of Inner Mongolia

Background

The role of angiotensin II type 1 receptor (AT1R) as a key player in type 2 diabetes mellitus (T2DM) complicated with hypertension remains controversial. The present case-control study systematically investigated the association between gene the correct variation type in the angiotensin II type 1 receptor (AT1R) gene and type 2 diabetes mellitus complicated with hypertension in the Han population from the Inner Mongolia region, China.

Method

Here, state which variants were analysis, including age, occupation, triglyceride, systolic, diastolic, sex, culture, marital status, smoking, alcohol, BMI (body mass index), SBP (systolic blood pressure), DBP (diastolic blood pressure), TG (triglyceride), TC (total cholesterol), HDL-C (high-density lipoprotein cholesterol), LDL-C (low-density lipoprotein cholesterol), FPG (fasting plasma glucose). Genomic DNA was extracted from samples from 202 type 2 diabetic patients with hypertension and 216 type 2 diabetic patients without hypertension.

Results

Non-conditional regression analysis showed that in comparison with the TT genotype, the presence of the CC genotype for the T573 site of the AT1R gene increased the risk for diabetes mellitus complicated with hypertension by 3.219-fold (OR = 3.219, 95% CI: 1.042–9.941, P = 0.042). The results from multivariate linear regression analysis suggested the rs5182 polymorphism in the AT1R gene to be associated with diastolic blood pressure (P = 0.032). No other associations were found between the incidence of disease and the correct variation type at other sites of the AT1R gene.

Conclusions

Our results suggest that the rs5182 polymorphism in the AT1R gene is associated with diabetes complicated by hypertension in the Han population of Inner Mongolia.

The Association Between Selected Molecular Biomarkers and Ambulatory Blood Pressure Patterns in African Chronic Kidney Disease and Hypertensive Patients Compared With Normotensive Controls: Protocol for a Longitudinal Study

Background

Chronic kidney disease (CKD) is a burgeoning epidemic in sub-Saharan Africa. Abnormal blood pressure variations are prevalent in CKD and potentiate the risk of cardiovascular morbidity and mortality. Certain genetic variants (angiotensin II receptor type 1 1166 A>C and angiotensin-converting enzyme insertion and deletion polymorphisms) and biomarkers such as interleukin–6, tumor necrosis factor, soluble (s) E-selectin, homocysteine, and highly sensitive C-reactive protein have been shown to affect blood pressure variability among non-African CKD, hypertensive. and nonhypertensive CKD population. However, the contributions of the pattern, genetic, and environmental determinants of ambulatory blood pressure in African CKD have not been characterized. Understanding these interactions may help to develop interventions to prevent major cardiovascular events among people with CKD.

Objective

The overarching objective of this study is to identify, document, and develop approaches to address related phenomic, genetic, and environmental determinants of ambulatory blood pressure patterns in African CKD and non-CKD hypertensive patients compared with normotensive controls.

Methods

This is a longitudinal short-term follow-up study of 200 adult subjects with CKD and 200 each of age-matched hypertensives without CKD and apparently healthy controls. Demographic information, detailed clinical profile, electrocardiography, echocardiography, and 24-hr ambulatory blood pressure measurements will be obtained. Blood samples will be collected to determine albumin-creatinine ratio, fasting plasma glucose, lipid profile, electrolytes, urea and creatinine, C-reactive protein, serum homocysteine, fibroblast growth factor–23, and complete blood count, while 2 mL blood aliquot will be collected in EDTA (ethylenediaminetetraacetic acid) tubes and mixed using an electronic rolling system to prevent blood clots and subsequently used for DNA extraction and genetic analysis.

Results

A total of 239 participants have been recruited so far, and it is expected that the recruitment phase will be complete in June 2020. The follow-up phase will continue with data analysis and publications of results.

Conclusions

This study will help stratify Nigerian CKD patients phenotypically and genotypically in terms of their blood pressure variations with implications for targeted interventions and timing of medications to improve prognosis.

International Registered Report Identifier (IRRID)

DERR1-10.2196/14820

Renin-angiotensin system gene polymorphisms and coronary artery disease in Saudi patients with diabetes mellitus

Polymorphisms of some genes of the renin-angiotensin system (RAS), such as angiotensinogen (AGT; M235T), angiotensin II type 2 receptor (AT2; C3123A), and angiotensin-converting enzyme (ACE; insertion/deletion (I/D)) are involved in the development and progression of coronary artery disease (CAD) in diabetic individuals. In the present study, we aimed to determine whether three polymorphisms, AGT-M235T, AT2-C3123A, and ACE I/D are associated with CAD in Saudi patients with type two diabetes mellitus (T2DM). In 266 patients with CAD (169 patients with T2DM and 97 without T2DM), restriction fragment length polymorphism analysis was used to detect polymorphisms in the three RAS genes. Within the CAD+T2DM group, for the ACE gene (I/D), homozygous DD was found in 65.68%, 25.44% carried the heterozygous ID, and 8.88% carried the homozygous II. Within the CAD-T2DM group, DD was found in 55.67%, 26.8% carried the ID, and 17.53% carried the II. The odds ratio (OR) of the ACE ID+DD vs. II was 2.18, with a 95% confidence interval (CI) of 1.04-4.60, and P = 0.04. Thus, we found an association between the ACE DD polymorphism and CAD in Saudi patients with T2DM, but not between the AT2 C3123A and AGT M235T polymorphisms and CAD.

A systematic review of the role of renin angiotensin aldosterone system genes in diabetes mellitus, diabetic retinopathy and diabetic neuropathy

BACKGROUND

The renin angiotensin aldosterone system (RAAS) plays a vital role in regulating glucose metabolism and blood pressure, electrolyte and fluid homeostasis. The aim of this systematic review is to assess the association of the RAAS genes with diabetes mellitus (DM) and its complications of retinopathy, neuropathy and cardiovascular disease (CVD).

MATERIALS AND METHODS

The relevant English-language studies were identified using the key words of DM, type 1 diabetes mellitus (T1DM), T2DM, renin angiotensin aldosterone polymorphisms or genotypes and RAAS from the search engines of MEDLINE/PubMed, and Scopus from January 1, 1995 to July 30, 2014. Inclusion criteria for selecting relevant studies were reporting the role of RAAS gene variants in the pathogenesis of T1DM or T2DM, diabetic retinopathy (DR), diabetic neuropathy and cardiovascular complication of DM.

RESULTS

The reviewers identified 204 studies of which 73 were eligible for inclusion in the present systematic review. The review indicates the angiotensinogen (AGT) M235T polymorphism might not affect the risk of DM. The role of angiotensin converting enzyme insertion/deletion (ACE I/D) and angiotensin II type 1 receptor gene (AT1R) A1166C polymorphisms in the pathogenesis of DM could not be established. Studies indicate the absence of an association between three polymorphisms of AGT M235T, ACE I/D and AT1R A1166C and DR in DM patients. A protective role for ACE II genotype against diabetic peripheral neuropathy has been suggested. Also, the ACE I/D polymorphism might be associated with the risk of CVD in DM patients.

CONCLUSION

More studies with adequate sample size that investigate the influence of all RAAS gene variants together on the risk of DM and its complications are necessary to provide a more clear picture of the RAAS genes polymorphisms involvement in the pathogenesis of DM and its complications.

Circulating adiponectin and cardiovascular mortality in patients with type 2 diabetes mellitus: evidence of sexual dimorphism

BACKGROUND

The pathogenesis of cardiovascular (CV) mortality, whose rate is increased in type 2 diabetes, is poorly understood.

METHODS

Three prospective cohorts were analyzed: 1) Gargano Heart Study (GHS; 359 patients, 58 events/1,934 person-years; py); 2) Health Professional Follow-up Study (HPFS; 833 men, 146 events/10,024 py); 3) Nurses' Health Study (NHS; 902 women, 144 events/15,074 py).

RESULTS

In GHS serum adiponectin predicted CV mortality in men (hazard ratio, HR, and 95% CI per standard deviation, SD, increment = 1.54, 1.19-2.01), but not women (HR = 0.98, 0.48-2.01).

CONCLUSIONS

This is the first report showing that high circulating adiponectin predicts increased CV mortality in men, but not in women with type 2 diabetes. Further studies are necessary to unravel the mechanisms through which adiponectin influences CV mortality in a sex-specific manner.

Extracellular water and blood pressure in adults with growth hormone (GH) deficiency: a genotype-phenotype association study

Objectives

Growth hormone deficiency (GHD) in adults is associated with decreased extracellular water volume (ECW). In response to GH replacement therapy (GHRT), ECW increases and blood pressure (BP) reduces or remains unchanged. Our primary aim was to study the association between polymorphisms in genes related to renal tubular function with ECW and BP before and 1 year after GHRT. The ECW measures using bioimpedance analysis (BIA) and bioimpedance spectroscopy (BIS) were validated against a reference method, the sodium bromide dilution method (Br⁻).

Design and Methods

Using a candidate gene approach, fifteen single-nucleotide polymorphisms (SNPs) in nine genes with known impact on renal tubular function (AGT, SCNN1A, SCNN1G, SLC12A1, SLC12A3, KCNJ1, STK39, WNK1 and CASR) were genotyped and analyzed for associations with ECW and BP at baseline and with their changes after 1 year of GHRT in 311 adult GHD patients. ECW was measured with the Br⁻, BIA, and BIS.

Results

Both BIA and BIS measurements demonstrated similar ECW results as the reference method. At baseline, after adjustment for sex and BMI, SNP rs2291340 in the SLC12A1 gene was associated with ECW volume in GHD patients (p = 0.039). None of the SNPs influenced the ECW response to GHRT. One SNP in the SLC12A3 gene (rs11643718; p = 0.024) and three SNPs in the SCNN1G gene [rs5723 (p = 0.02), rs5729 (p = 0.016) and rs13331086 (p = 0.035)] were associated with the inter-individual differences in BP levels at baseline. A polymorphism in the calcium-sensing receptor (CASR) gene (rs1965357) was associated with changes in systolic BP after GHRT (p = 0.036). None of these associations remained statistically significant when corrected for multiple testing.

Conclusion

The BIA and BIS are as accurate as Br⁻ to measure ECW in GHD adults before and during GHRT. Our study provides the first evidence that individual polymorphisms may have clinically relevant effects on ECW and BP in GHD adults.

ACACβ gene (rs2268388) and AGTR1 gene (rs5186) polymorphism and the risk of nephropathy in Asian Indian patients with type 2 diabetes

Patients with type 2 diabetes (T2DM) are usually obese and concurrent obesity results into activation of the renin-angiotensin-system (RAS) which is a risk factor for diabetic nephropathy (DN). Gene-gene interaction between acetyl-coenzymeA carboxylase beta (ACACβ) gene, which is involved in fatty acid metabolism and angiotensin II receptors (AGTR1) gene, which mediates RAS proteins actions on renal tissue, polymorphism with DN have not been studied earlier. The present study was designed with the aim to examine the association of an ACACβ (rs2268388) and AGTR1 (rs5186) gene polymorphism with the risk of DN in Asian Indians. 1,158 patients with T2DM belonging to two independently ascertained North Indian and one South Indian cohorts were genotyped for ACACβ (rs2268388) and AGTR1 (rs5186) polymorphism using real time PCR-based Taq-man assay and PCR-RFLP assays. In all the three cohorts, a significantly higher frequency of T allele and TT genotypes of ACACβ and C allele and CC genotypes of AGTR1 were found in patients with DN as compared to patients without nephropathy. Further, T allele of ACACβ and C allele of AGTR1 were found to be significantly associated with proteinuria, a hallmark of DN. We also found significant epistatic interactions between these two genes. TT genotypes of ACACβ gene and CC genotype of AGTR1 gene confers the risk of DN and both genes had significant epistatic interaction in Asian Indian patients with T2DM.

Association of angiotensin II type 1 receptor gene A1166C polymorphism with the presence of diabetes mellitus and metabolic syndrome in patients with documented coronary artery disease

BACKGROUND

There are relatively limited data available on the genetic susceptibility to diabetes mellitus and metabolic syndrome in the Iranian population. We have therefore investigated the association between the angiotensin II type I receptor gene polymorphism (AT(1)R/A1166C) and the presence of diabetes mellitus and metabolic syndrome in a well defined group of patients.

METHODS

Patients with angiographically defined coronary artery disease (CAD) (n=309) were evaluated for the presence of AT(1)R/A1166C polymorphism. These patients were classified into subgroups with (n=164, M/F: 109/55) and without (n=145, M/F: 84/61) diabetes mellitus. The AT(1)R polymorphism was assessed using a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) based method.

RESULTS

There was a higher frequency of polymorphic genotypes (AC+CC) in the diabetic compared with the non-diabetic group (p=0.01). When determined for each gender separately, this difference remained significant in the males (p=0.04) but not in females (p=0.09). With regard to the allele frequencies, the C allele was significantly higher and the A allele frequency was lower in the diabetic group (p=0.01). This remained significant after gender segregation for males (p=0.01) but not females. In the binary logistic regression analysis, only serum fasting glucose was found as the independent predictor for the presence of diabetes in the CAD patients (β=1.16, p<0.001 for total population and β=1.29, p<0.001 for male subjects). There was no significant difference in genotype or allele frequencies between subgroups with and without metabolic syndrome, this being unaffected by gender or the definition of metabolic syndrome used apart from a significantly lower frequency of C allele in male subjects with metabolic syndrome defined by the NCEP ATP III criteria (p=0.04).

CONCLUSION

The AT(1)R/A1166C polymorphism may be associated with the presence of diabetes mellitus in male subjects with documented CAD.

Identification of gene variants in NOS3, ET-1 and RAS that confer risk and protection against microangiopathy in type 2 diabetic obese subjects

The study aim was to investigate NOS3 VNTR, NOS3 G894T, EDN1 C8002T, ACE I/D, AGT M235T and AGTR1 A1166C in nonobese and obese T2DM patients, and their interaction with the incidence of microangiopathy. T2DM subjects (n=250; 166 nonobese, and 84 obese) were genotyped for the gene variants by PCR/RFLP. The interaction of these polymorphisms with obesity and their contribution to microangiopathy were analyzed by multivariate regression analysis. A higher frequency of NOS3 4a allele was found in obese (P=0.027) vs. nonobese subjects. ACE D (P=0.009) and AGT 235T (P=0.026) alleles were associated with the reduced risk of diabetic nephropathy in nonobese and obese patients, respectively. In obese subjects, NOS3 4a (P=0.011) had a converse effect to NOS3 894T (P=0.043), and EDN1 8002T (P=0.035) on the prevalence of combined microangiopathy (neuropathy/retinopathy/nephropathy) vs. microangiopathy-negative subjects. The study indicates association of RAS variants with obesity and nephropathy, and an opposite effect of NOS3 VNTR and NOS3 G894T on the occurrence of combined microangiopathy.

Renin-angiotensin-aldosterone system genotypes and haplotypes affect the susceptibility to nephropathy in type 2 diabetes patients

BACKGROUND

The association between renin C-4063T and angiotensinogen (AGT) T174M, M235T, and A-6G polymorphisms with diabetic nephropathy (DN) was investigated in Tunisian type 2 diabetes (T2DM) patients.

METHODS

Study subjects comprised 917 T2DM patients (405 normoalbuminuric, 329 microalbuminuric and 185 macroalbuminuric). Genotyping was done by PCR-RFLP.

RESULTS

Renin C-4063T allele and genotype frequencies were comparable between DN cases and normoalbuminuric controls. Although AGT 235T and -6G allele, and 235T/T and -6G/G genotype frequencies were higher in DN compared to normoalbuminuric patients, they were comparable between microalbuminuric or macroalbuminuric patients. Three-locus AGT haplotype analysis (A-6G/T174M/M235T) identified DN-protective (ATM, AMM, GTM) and DN-susceptible (GTM, ATT, GMT and AMT) haplotypes, and demonstrated enrichment of GTT haplotype in macroalbuminuric compared to microalbuminuric or normoalbuminuric patients. Regression analysis confirmed negative (AMM) and positive (GTM, ATT, GMT, AMT) association of AGT haplotypes with microalbuminuria, and negative (AMM) and positive (GTM and ATT) association of AGT haplotypes with macroalbuminuria. None of the AGT haplotypes was associated with DN severity.

CONCLUSIONS

Genetic variation at the AGT gene influences the risk of nephropathy in T2DM patients but not extent of DN severity, and thus represents a potential DN genetic susceptibility locus worthy of replication.

New evidence for the fetal insulin hypothesis: fetal angiotensinogen M235T polymorphism is associated with birth weight and elevated fetal total glycated hemoglobin at birth

BACKGROUND

Low birth weight is associated with an increased risk of cardiovascular events in later life. Insulin resistance is a key finding in adult patients with cardiovascular diseases. The neonatal phenotype of an individual with insulin resistance might be low birth weight, as insulin influences fetal growth. The renin-angiotensin-aldosterone system has been associated with cardiovascular disease and insulin resistance. We analyzed whether fetal polymorphisms of the angiotensinogen (AGT) and angiotensin-converting enzyme genes influence birth weight and/or fetal total glycated hemoglobin (fTGH), a surrogate parameter of fetal insulin resistance at birth.

METHOD

In 1132 white women delivering singletons, neonatal umbilical blood samples and clinical data of the mothers and newborns were obtained. Newborns were genotyped with respect to the AGT M235T and angiotensin-converting enzyme insertion/deletion polymorphism.

RESULTS

The AGT M235T TT polymorphism is associated with reduced birth weight (TT: 3288 g versus TM + MM: 3435 g, P < 0.05). Furthermore, newborns with a high percentage of fTGH (>6.5%) are more likely to have the TT genotype than those with normal fTGH (<or=6.5%, P < 0.05). With higher cutoffs for fTGH, the significance increases to P less than 0.005. No association was seen between these parameters and the fetal angiotensin-converting enzyme insertion/deletion phenotype.

CONCLUSION

The fetal AGT M235T polymorphism is associated with low birth weight and elevated fetal fTGH at birth. Previous findings show that elevated fetal fTGH correlates with low birth weight and that higher activity of the renin-angiotensin-aldosterone system is an independent risk factor for the development of diabetes mellitus and coronary artery disease. Therefore, our data are supportive of the fetal insulin hypothesis.

AGT M235T genotype/anxiety interaction and gender in the HyperGEN study

Background

Both anxiety and elevated heart rate (HR) have been implicated in the development of hypertension. The HyperGen cohort, consisting of siblings with severe and mild hypertension, an age-matched random sample of persons from the same base populations, and unmedicated adult offspring of the hypertensive siblings (N = 1,002 men and 987 women), was analyzed for an association of the angiotenisinogen AGTM235T genotype (TT, MT, MM) with an endophenotype, heart rate (HR) in high and low anxious groups.

Methodology

The interaction of AGTM genotype with anxiety, which has been independently associated with hypertension, was investigated adjusting for age, hypertension status, smoking, alcohol consumption, beta blocker medication, body mass index, physical activity and hours of television viewing (sedentary life style).

Principal Findings

Although there was no main effect of genotype on HR in men or women, high anxious men with the TT genotype had high HR, whereas high anxious men with the MM genotype had low HR. In women, HR was inversely associated with anxiety but there was no interaction with genotype.

Conclusion/Significance

The results suggest that high anxiety in men with the TT genotype may increase risk for hypertension whereas the MM genotype may be protective in high anxious men. This type of gene x environment interaction may be one reason why genome wide association studies sometimes fail to replicate. The locus may be important only in combination with certain environmental factors.

Cardiovascular Disease, Single Nucleotide Polymorphisms; and the Renin Angiotensin System: Is There a MicroRNA Connection?

Essential hypertension is a complex disorder, caused by the interplay between many genetic variants, gene-gene interactions, and environmental factors. Given that the renin-angiotensin system (RAS) plays an important role in blood pressure (BP) control, cardiovascular regulation, and cardiovascular remodeling, special attention has been devoted to the investigation of single-nucleotide polymorphisms (SNP) harbored in RAS genes that may be associated with hypertension and cardiovascular disease. MicroRNAs (miRNAs) are a family of small, ∼21-nucleotide long, and nonprotein-coding RNAs that recognize target mRNAs through partial complementary elements in the 3′-untranslated region (3′-UTR) of mRNAs and inhibit gene expression by targeting mRNAs for translational repression or destabilization. Since miRNA SNPs (miRSNPs) can create, destroy, or modify miRNA binding sites, this review focuses on the hypothesis that transcribed target SNPs harbored in RAS mRNAs, that alter miRNA gene regulation and consequently protein expression, may contribute to cardiovascular disease susceptibility.

The genetics of vascular complications in diabetes mellitus

Prospective identification of which individuals with diabetes mellitus (DM) are at greatest risk for developing cardiovascular disease (CVD) complications would have considerable public health importance by allowing the allocation of limited resources to be focused on those individuals who would most benefit from aggressive intervention. Over the past 20 years genetic disease association studies have demonstrated that polymorphisms at specific genetic loci may identify those individuals at greatest risk for developing CVD in the setting of DM. This article reviews the evidence accumulated to date on four polymorphic loci with the aim of explaining how these polymorphisms modify the risk for CVD in DM by modifying the functional activity of a specific gene. Use of the knowledge of these genetic differences among individuals in targeting drug therapy (pharmacogenomics) is also discussed.

Genotypic interactions of renin-angiotensin system genes with diabetes type 2 in a Tunisian population

AIMS

To explore the role of genetic variants of angiotensinogen (AGT M235T), angiotensin-converting enzyme (ACE I/D), and angiotensin type 1 receptor (AT1R A1166C) as predictors of diabetes risk and to examine their combined effects on type 2 diabetes mellitus (T2DM) patients.

MAIN METHODS

One hundred and fourteen T2DM patients were compared to 175 healthy controls with similar age and sex.

KEY FINDINGS

The genotypic frequencies for all three genes alone were significantly associated with increased risk of developing diabetes. Logistic regression analysis of classic coronary risk factors and the genetic polymorphisms demonstrated that hypertension and ACE DD genotype were the most significant contributors to T2DM. For the renin-angiotensin system (RAS) genes, the risk of T2DM in individuals with one risk genotype was 1.9 (95%CI: 1.1-3.0, p=0.017) higher than those with zero risk genotype. Individuals who carried two risk genotypes had a 4.0 (95%CI 1.7-9.4, p=0.001) times higher risk of T2DM than those who did not carry any risk genotypes of the RAS genes. Most interestingly, the risk of T2DM for individuals with three risk genotypes was 26.2 (95%CI: 5.8-117.9, p<0.001) higher than those with zero risk genotype.

SIGNIFICANCE

The results of the present study imply that genotyping of renin-angiotensin system genes could become an important part of the clinical process of risk identification for T2DM in Tunisian population.

Renin-angiotensin-aldosterone system gene polymorphisms in coronary artery bypass graft surgery patients

INTRODUCTION

Candidates for coronary artery bypass grafting (CABG) represent a group of patients with well documented, severe coronary artery disease (CAD). Genetic polymorphisms of renin-angiotensin-aldosterone system (RAAS) components have been associated with CAD. We examined the association of polymorphisms of angiotensin-converting enzyme (ACE), angiotensinogen (AGT), and angiotensin II type 1 receptor (AT(1) receptor) with severe CAD in CABG patients.

MATERIALS AND METHODS

One hundred and fifty-four CABG patients and 155 non-CAD controls were included in the study. Established PCR methods were used for genotyping of AGT M235T, AGT T174M, AT(1) receptor A1166C, and ACE I/D polymorphisms. Cumulative effect of analysed polymorphisms was assessed by calculation of each individual's RAAS gene score (addition of 0.5 points for each variant allele and then calculating the sum for all four polymorphisms).

RESULTS

No association between AGT M235T, AGT T174M, ACE I/D and AT(1) receptor A1166C polymorphisms and CAD was observed. Within CABG patients, the frequency of homozygous AGT 235TT genotype was higher in hypertensive compared to normotensive CABG patients (21.7% vs. 6.3%, p=0.03). RAAS gene score did not differ between CABG patients and non-CAD controls.

CONCLUSIONS

There is no association of the analysed RAAS polymorphisms with severe CAD in CABG patients. However, within these patients, an association was found between AGT 235TT genotype and hypertension.

Genetic clues to the etiology of Balkan endemic nephropathy: Investigating the role of ACE and AT1R polymorphisms

Balkan endemic nephropathy (BEN) was recognized as a distinct entity more than 50 years ago, but the exact environmental and genetic causes of the disease remain elusive. Considering the role of the renin-angiotensin system (RAS) in the emergence of various nephropathies, in the present study we evaluated the possible association with BEN of polymorphisms in two RAS genes: I/D ACE (an angiotensin-converting enzyme) and A1166C AT1R (an angiotensin type 1 receptor). The study groups consisted of 48 BEN patients from the endemic region in the district of Kolubara, Serbia, 33 patients with other nephropathies and 42 healthy individuals. The ACE DD genotype was significantly more represented in the NBEN group (OR=5.447; 95%CI=1.862-15.932, p<0.01). The frequency of the AT1R CC genotype was higher in BEN patients compared to controls (0.104 vs. 0.048), but the difference was not significant. Though the analyzed polymorphisms are associated with certain nephropathies, we found no support for their specific role in BEN susceptibility.