Angiotensinogen Gene and Human Hypertension

To determine the role of the angiotensinogen gene in human hypertension.

Study Overview

• Status: Completed
• Conditions: Heart Diseases; Cardiovascular Diseases; Hypertension

Detailed Description

BACKGROUND:

Essential hypertension affects at least 25 percent of American adults, and it is a primary risk factor for heart failure, stroke, and kidney disease. Many, but not all, studies have shown that variants of the angiotensinogen gene (AGT) affect the risk of hypertension, but association studies conducted to date have been compromised by genetic heterogeneity and by the inherent complexity of hypertension as a phenotype.

DESIGN NARRATIVE:

A comprehensive study of the angiotensinogen (AGT) gene will be conducted in data collected from several large groups of individuals. The investigators will sequence or genotype a 14.4 kb region including AGT in more than 1,600 individuals sampled from populations throughout the world. This will permit them to explore fully the extent of allelic heterogeneity, haplotype variation, and potential for population stratification in the AGT gene. Approximately 600 of these individuals are clinically uncharacterized and will represent a broad range of worldwide human variation. Another 500 subjects are members of 40 Utah pedigrees that are part of the Centre d'Etude du Polymorphisme Humain (CEPH) collection. These unique families have been heavily characterized genetically, and they are now being phenotyped for variables that include anthropometrics, blood chemistries, blood pressure measures, and plasma and urinary angiotensinogen. They will address the issue of genetic heterogeneity by testing associations between multi-SNP AGT haplotypes, angiotensinogen levels, and blood pressure. In addition, linkage disequilibrium patterns will be assessed to determine the density and nature of SNPs best suited for localizing a gene underlying a complex trait. They will address the issue of phenotypic heterogeneity in hypertension by performing extensive SNP typing on a set of 400 hypertensives and 100 normotensives collected by Dr. Gordon Williams. These clinically well-characterized subjects have been tested for their response to infused angiotensin-II under high and low sodium intake. This direct probe provides a hypertension endophenotype that is closer to the function of the AGT gene, yielding a more realistic and informative assessment of the relationship between AGT haplotype variation and hypertension risk. A phylogenetic analysis of AGT sequence variation in the worldwide sample will help to assess population stratification in association studies. In addition, this sample will allow testing the hypothesis that the ancestral T235 AGT allele provided a selective advantage in the sodium-poor environment of sub-Saharan Africa. The results of this analysis may help to explain why African-Americans have elevated rates of hypertension. In summary, the extensive analysis of AGT variation in more than 1,600 subjects will clarify the role of this gene in essential hypertension and will test specific hypotheses about the evolution of AGT.

• Study Type: Observational

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Child; Adult; Older Adult
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

No eligibility criteria

Study Plan

How is the study designed?

Collaborators and Investigators

• Sponsor: University of Utah
• Collaborators: National Heart, Lung, and Blood Institute (NHLBI)
• Investigators: Lynn Jorde, University of Utah

Publications and helpful links

General Publications

• Nakajima T, Wooding S, Satta Y, Jinnai N, Goto S, Hayasaka I, Saitou N, Guan-Jun J, Tokunaga K, Jorde LB, Emi M, Inoue I. Evidence for natural selection in the HAVCR1 gene: high degree of amino-acid variability in the mucin domain of human HAVCR1 protein. Genes Immun. 2005 Aug;6(5):398-406. doi: 10.1038/sj.gene.6364215.

Study record dates

Study Major Dates

• Study Start: January 1, 2003
• Primary Completion (Actual): December 1, 2007
• Study Completion (Actual): December 1, 2007

Study Registration Dates

• First Submitted: June 30, 2003
• First Submitted That Met QC Criteria: June 30, 2003
• First Posted (Estimate): July 1, 2003

Study Record Updates

• Last Update Posted (Estimate): July 24, 2013
• Last Update Submitted That Met QC Criteria: July 23, 2013
• Last Verified: July 1, 2013

More Information

Terms related to this study

• Additional Relevant MeSH Terms: Vascular Diseases; Heart Diseases; Hypertension; Cardiovascular Diseases
• Other Study ID Numbers: 1215; R01HL070048 (U.S. NIH Grant/Contract)