Effect of RAS Polymorphism on Essential Blood Pressure

Effect of RAS Polymorphism on Essential Blood Pressure Pharmacogenetic Association of RAS Polymorphism on Essential Blood Pressure in Relation to Enalapril/Lisinopril among Malay male newly diagnosed hypertensives Abstract Objective: It has been suggested that genetic backgrounds, which have an association with essential hypertension, may also determine the responsiveness to ACE inhibitor. We determined the association of angiotensin-converting enzyme (I/D, G2350A), angiotensinogen (M235T, T174M and A-6G) and renin (Bg/I and Mbo/I) gene polymorphisms with essential hypertension and the relationship between genetic variant of interest and high blood pressure response to ACE inhibitor (enalapril, lisinopril) in patients with essential hypertension subjects from Seremban, Malaysia. Methods: A newly hypertensive Malay male population (n=142) was recruited for a mono-trophy[ah1] pharmacogenetic study. Hypertensive patients were treated with ACEI drugs, particularly enalapril or lisinopril alone. We differentiated between those who controlled their HT with those who did not. Each group’s characteristics were compared to determine the risk of non-controlled HT associated with RAS polymorphisms by adjusting for different variables. Results: Statistically significant associations of I, G, T and M alleles were observed with essential hypertension in I/D, G2350A, M235T, and T175M. The decrease in systolic blood pressure and diastolic blood pressure after 24 weeks of treatment of the patients carrying II, GG, and TT genotypes was greater than the groups carrying DD, AA, MM and MM genotypes. In contrast, no significant difference was shown between renin gene polymorphisms (Bg/I and MboI). Conclusions: Although this study shows a possible association of polymorphisms of RAAS genes[ah2] with the risk of non-controlled HT in ACEI-treated patients and indicates the importance of all components in this system in regulating HT, it needs to be replicated in other data sources. Keywords: Essential hypertension; renin-angiotensin-aldosterone system; single-nucleotide polymorphism; ACE inhibitors; pharmacogenetic INTRODUCTION Essential hypertension (EH) is an increasingly important medical and public health issue [1]. In Malaysia, the National Health and Morbidity Survey (NHMS) 2013 has shown that the prevalence of hypertension in adults ≠¥18 years increased from 33.2% in 2006 to 35.7% in 2013 [2]. Furthermore, the prevalence increased from 42.6% to 43.5% for those >30 years old. Unfortunately, 60.6% of total hypertensives were â€Å"undiagnosed† [3]. These poor rates of high blood pressure (BP) control are not explained by the lack of treatment, as one study estimated approximately 30% of treated hypertensive patients take one antihypertensive drug, 40% take two antihypertensive drugs and 30% take three or more antihypertensive drugs [4]. These data suggest that the present trial and error approach for high blood pressure management is suboptimal, and alternative approaches for identifying the optimal antihypertensive regimen in a specific patient are needed. Using genetic make-up of an indiv idual along with the association between single-nucleotide polymorphisms (SNPs) and angiotensin-converting enzyme (ACE) inhibitors for hypertensive response offers a new preventive approach to lower adverse drug interaction risk. A renin-angiotensin system (RAS) is an important component of blood pressure regulation, and it has been suspected to be involved in hypertension [5]. Moreover, the major active peptide of the RAS is angiotensin II. Produced from the precursor molecule, angiotensinogen (AGT), via an enzyme cascade involving ACE enzyme, angiotensin II exerts numerous effects on the homeostatic regulation of blood pressure, the vast majority of which are mediated via the angiotensin II type 1 receptor (AT1R) [6]. The presence of polymorphisms in the ACE, AGT and renin (REN) genes of the RAS has been associated with adverse EH changes in several studies [7,8,9]. For example, the insertion/deletion (I/D) polymorphisms of the ACE gene have been associated with increased blood pressure, urinary albumin excretion (UAE) and target-organ damage in hypertensive patients [10]. Moreover, ACE G2350A gene polymorphisms in exon 17 were reported as a remarkable genetic variant mostly associated through hypertension with an average increase of 3.2 mmHg in SBP by having the G allele [11]. It has been reported that the presence of A-6G polymorphism of AGT gene among Chinese hypertensives increased body weight gain in hypertensive patients [12]. The Mb/I and Bg/I polymorphisms of the REN gene have been associated with hypertension, left ventricular hypertrophy, aortic stiffness and exaggerated vasoconstriction; additionally, the Bg/I polymorphism in the same gene appears to confer protection against the development of microalbuminuria in patients with hypertension [13]. The purpose of the present study was to evaluate the impact of four RAS gene polymorphisms on the antihypertensive response in newly detected hypertensives receiving two ACEIs (enalapril and lisinopril). The polymorphisms investigated were A-6G, the A for G substitution of the AGT gene 6 nucleotides upstream from the start site; the ACE I/D polymorphism corresponding to an insertion or deletion of a 287bp alu repeat; and two polymorphisms of the REN gene, Bg/I and MboI and both in the coding area of intron 9. There are compelling reasons hypothesizing that variations in genes of the system may be predictive of variations in BP response. Therefore, genetic variation of the RAS has been investigated in relation to antihypertensive response to ACE inhibitors in various population and dosage (Table 1) as the most common lowering BP agent in Malaysia [14]; however, previously publications have had somewhat conflicting results elsewhere [15-19]. We hypothesized those genetic polymorphisms in RAS genes, including ACE I/D, G2350A, AGT M235T, T174M, A-6G along with REN MboI and Bg/I were associated with the incidence of EHT. Therefore, the aim of this pharmacogenetic study was to investigate the association between seven RAS gene polymorphisms of interest among 142 newly diagnosed Malay male hypertensives that never took BP medications. They were treated once daily for 24 weeks with 20 mg of enalapril or lisinopril. MATERIAL AND METHODS Patient Populations Malay male patients >18 years of age with three-generation Malay family who were newly diagnosed with essential mild-to-moderate hypertension were collected from clinics for non-communicable disease Seremban, Malaysia. The information includes age (25-60 years old), onset (25-60 years old), systolic BP > 140 mmHg and a diastolic BP > 90 mmHg on 2 consecutive visits for those untreated, absence of secondary forms of hypertension. Subjects with a history of diabetes mellitus, renal failure and major infectious disease were excluded. They had no metabolic or endocrine disorder, as well as any acute illness. They were not on any antihypertensive treatment and were drug-naive patients. Written informed consent was obtained from each patient before being included in the clinical trial, and patient’s identity was kept strictly confidential. A specific consent form was requested for genetic testing permission. BLOOD PRESSURE REDUCTION PATTERN Lifestyle Modification For patients, lifestyle modification for a period of three months was advised. The patients were seen three times during this period to assess the efficacy of the non-pharmacological management including weight loss, regular exercise, and ingestion of a high-fiber, low-fat, and low-salt diet. Follow-up Mon-trophy[ah3] Management Dispensed ACEIs (lisinopril or enalapril) on the same date for individuals have recorded. Each patient received lisinopril or enalapril (20 mg, once daily) for 24 weeks on a regular basis. Patients’ BP was measured using the same device and protocol; follow-up visits were made 12 times (once per two weeks). Of the 152 patients, 10 lost to the follow-up along monitoring due to relocation, travelling and/or change of medication. Eventually 142 hypertensives (92.6%) completed the study. This subsample was divided into two groups; individuals whose HT was not controlled as the non-responded (n=35), and individuals whose HT was under control as the responded (n=107). Figure 1 presents how responded and non-responded HT groups are categorized. Fig. 1. The flowchart of sample collection. Genotyping procedures A blood sample was taken in two separate tubes; one was used for colorimetric analysis of total cholesterol (TC), high density lipid profile (HDL), low density lipid profile (LDL), triacylglycerol (TG) and fasting glucose (FBG) using Diays Commercial Kits (Diagnostic System, GmBH, D66559 Holzheim, Germany), and the other test tube contained venous blood samples collected on EDTA was subjected to DNA extraction, which was obtained from individuals in the morning after a minimum of 8 hours fasting at the time of randomization. Eventually, the samples were stored at -20 °C for further molecular and biochemical analysis. DNAs were extracted from 5 mL blood samples as explained elsewhere [20]. ACE I/D polymorphism was genotyped using DNA amplification with oligonucleotides as described elsewhere [21]. For ACE G2350A, DNA amplification followed the approach by Zhu et al. [22]. Reactions were conducted using DNA amplification in a final volume of 25 mL containing 20 pmol of each primer, 0.4 mmol/L of each deoxynucleotide triphosphate (dNTP), 2 mmol/L of MgCl2, 1XTaq buffer and one unit of NEB Taq DNA polymerase (New England Biolabs, Beverly, MA, USA). The PCR cycling conditions were carried out in an iCycler machine (BioRad Laboratories, Hercules, CA, USA). Were chosen[ah4] for genotyping using the polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) approach, and the details are presented in Table 2. Eventually, DNA fragments were stained in ethidium bromide and visualized by Alpha Imager (Alpha Innotech, San Leandro, CA, USA) under ultraviolet (UV) light. Statistical Analysis SPSS 20 statistical package (SPSS, Chicago, USA) was used for analysis. Allele frequencies were calculated from the genotypes of all subjects. Hardy-Weinberg equilibrium (HWE) was assessed by χ2 analysis. Continuous data are presented as mean  ± SD. Differences between groups were tested by an χ2 test for qualitative parameters and by one-way analysis of variance (ANOVA). All tests were two-tailed and the values of p