Impact of renin-angiotensin-aldosterone system gene variants on the severity of hypertension in patients with newly diagnosed hypertension

AJH 2003; 16:1006 –1010 Impact of Renin-Angiotensin-Aldosterone System Gene Variants on the Severity of Hypertension in Patients With Newly Diagnosed Hypertension Armindo D. Tiago, Danelle Badenhorst, Benedicta Nkeh, Geoffrey P. Candy, Richard Brooksbank, Pinhas Sareli, Elena Libhaber, Nilesh J. Samani, Angela J. Woodiwiss, and Gavin R. Norton Background: The severity of hypertension has prognostic significance. Previous studies have assessed the relationship between renin-angiotensin-aldosterone system (RAAS) genotype and the severity of hypertension in either treated patients or those who have only recently discontinued treatment. Methods: We assessed the impact of RAAS genotype on ambulatory and office blood pressure (BP) in 231 newly diagnosed hypertensive patients of African ancestry who had never received therapy. Subjects were genotyped for variants of the angiotensin-converting enzyme (insertion/ deletion), angiotensinogen (M235T, ⫺20A3 C), and aldosterone synthase (CYP11B2)(⫺344C3 T) genes. Results: The CYP11B2 gene polymorphism was associated with systolic BP (SBP). In comparison to subjects with at least one copy of the ⫺344C allele (n ⫽ 75), patients who were homozygous for the ⫺344T allele (n ⫽ A 156) had both higher ambulatory SBP (150 ⫾ 1 v 144 ⫾ 1 mm Hg, P ⫽ .002 before and P ⫽ .01 after adjusting for multiple genotyping) and office SBP (163 ⫾ 2 v 156 ⫾ 2 mm Hg, P ⫽ .01 before and P ⫽ .05 after adjusting for multiple genotyping). Neither the angiotensin-converting enzyme insertion/deletion nor the angiotensinogen gene polymorphisms were associated with ambulatory or office SBP or diastolic BP (DBP). The CYP11B2 gene variant also did not affect DBP. Conclusion: A variant within the CYP11B2 locus has a clinically important impact on the severity of SBP changes in individuals with newly diagnosed hypertension who are of African ethnicity. Am J Hypertens 2003;16: 1006 –1010 © 2003 American Journal of Hypertension, Ltd. Key Words: Genes, angiotensinogen, angiotensin-converting enzyme, aldosterone, hypertension. number of studies have provided data to implicate genes that influence the activity of the reninangiotensin-aldosterone system (RAAS) in the control of blood pressure (BP) and the development of hypertension. Angiotensinogen (AGT),1–5 angiotensinconverting enzyme (ACE)6,7 and aldosterone synthase (CYP11B2)8 –12 gene variants have all been shown to produce effects on BP in humans in some studies. Because the severity of hypertension has prognostic significance,13,14 knowledge of the impact of candidate genes on BP in hypertension is of considerable importance. Studies conducted in previously treated patients that examined the relationship between RAAS genotype and the severity of hypertension have provided contradictory data.15,16 Preclinical studies indicate that prior therapy modifies the natural history of hypertension, probably through an impact on vascular remodeling.17 Therefore, in the present study we evaluated the impact of RAAS gene variants on Received April 14, 2003. First decision June 17, 2003. Accepted July 15, 2003. From the Cardiovascular Pathophysiology and Genomics Research Unit (ADT, DB, BN, GPC, PS, EL AJW, GRN), School of Physiology, and the Department of Cardiology and Nuclear Cardiology (GPC, EL), University of the Witwatersrand, Johannesburg, South Africa; and Division of Cardiology (NJS), Department of Medicine, University of Leicester, Leicester, United Kingdom. This work was supported by the University Research Council of the University of the Witwatersrand, the Medical Research Council of South Africa, and the Southern African Hypertension Society supported by an open educational grant from Astra Zeneca. Support was also provided by a grant from the Netherlands Organization for International Cooperation in Higher Education and BN from a grant from the Third World Organization of Women in Science (to ADT). 0895-7061/03/$30.00 doi:10.1016/j.amjhyper.2003.07.010 Address correspondence and reprint requests to Prof. Gavin Norton, School of Physiology, University of the Witwatersrand Medical School, 7 York Road, Parktown, Johannesburg 2193, South Africa; e-mail: © 2003 by the American Journal of Hypertension, Ltd. Published by Elsevier Inc. AJH–December 2003–VOL. 16, NO. 12 BP in newly diagnosed hypertensive patients who had never received previous therapy. Genotype effects were studied not only on office BP measurements but also on ambulatory BP, which has more prognostic relevance18 and allows the exclusion of isolated office hypertension.19 Methods This study was approved by the Committee for Research on Human Subjects of the University of the Witwatersrand (approval numbers M951122 and M010111). Study Groups, BP Measurements, and Hypertension Grading To avoid population stratification through ethnic diversity, only hypertensive patients of African ethnicity who were historically derived from the same gene pool (Nguni, Sotho and Venda chiefdoms) of South Africa living in urban and peri-urban areas of Johannesburg were selected. Consecutive hypertensive patients from district clinics in suburban areas of Johannesburg were recruited if they had provided consent, they had both conventional and daytime ambulatory BP ⱖ140 or ⱖ90 mm Hg, and were newly diagnosed with hypertension. Patients who had received prior antihypertensive therapy or who had secondary forms of hypertension, type 1 diabetes mellitus, uncontrolled type 2 diabetes mellitus (defined as an HbA1C ⬎ 10%), renal or endocrine disease, or clinically important cardiac pathology were excluded. All patients had ambulatory BP (ABP) measurements (SpaceLabs model 90207; SpaceLabs, Redmond, WA) performed at least half hourly during the day and hourly during the night from 10 PM to 6 AM, and ambulatory monitors were calibrated using standard techniques. All patients were advised not to smoke or to imbibe alcohol or ingest caffeine during this period. Daytime hours were predefined as 6 AM to approximately 8 PM and night hours from 8 PM to approximately 6 AM. Genotyping Deoxyribonucleic acid was extracted as previously described.20 Polymerase chain reaction (PCR) and PCRrestriction fragment length polymorphism-based techniques were performed to genotype patients for the insertion/deletion (I/D) polymorphism of the ACE gene,20 the M235T and ⫺20A3 C polymorphisms of the AGT gene,5 and the ⫺344C3 T polymorphism of the CYP11B2 gene,21 as previously described. Because strong concordance between the M235T polymorphism and the ⫺6G3 A, and ⫺532C3 T variants has previously been described by our group in the population sampled,5 the M235T polymorphism was used as a surrogate marker for the ⫺6G3 A, and ⫺532C3 T polymorphisms. We also considered genotyping patients for a previously described polymorphism of the angiotensin II type 1 receptor (AIIR) polymorphism. However, as the AIIR gene polymorphism IMPACT OF RAAS GENE VARIANTS ON HYPERTENSION 1007 Table 1. Demographic an (...truncated)