RESUMO
The angiotensinogen gene locus has been associated with essential hypertension in most populations analyzed to date. Increased plasma angiotensinogen levels have been proposed as an underlying cause of essential hypertension in whites; however, differences in the genetic regulation of plasma angiotensinogen levels have also been reported for other populations. The aim of this study was to analyze the relationship between angiotensinogen gene polymorphisms and haplotypes with plasma angiotensinogen levels and the risk of essential hypertension in the Mexican population. We genotyped 9 angiotensinogen gene polymorphisms in 706 individuals. Four polymorphisms, A-6, C4072, C6309, and G12775, were associated with increased risk, and the strongest association was found for the C6309 allele (χ(2)=23.9; P=0.0000009), which resulted in an odds ratio of 3.0 (95% CI: 1.8-4.9; P=0.000006) in the recessive model. Two polymorphisms, A-20C (P=0.003) and C3389T (P=0.0001), were associated with increased plasma angiotensinogen levels but did not show association with essential hypertension. The haplotypes H1 (χ(2)=8.1; P=0.004) and H5 (χ(2)=5.1; P=0.02) were associated with essential hypertension. Using phylogenetic analysis, we found that haplotypes 1 and 5 are the human ancestral haplotypes. Our results suggest that the positive association between angiotensinogen gene polymorphisms and haplotypes with essential hypertension is not simply explained by an increase in plasma angiotensinogen concentration. Complex interactions between risk alleles suggest that these haplotypes act as "superalleles."
Assuntos
Indígena Americano ou Nativo do Alasca/genética , Angiotensinogênio/genética , Genótipo , Haplótipos/genética , Hipertensão/etnologia , Hipertensão/genética , Fenótipo , Idoso , Idoso de 80 Anos ou mais , Alelos , Indígena Americano ou Nativo do Alasca/etnologia , Angiotensinogênio/sangue , Estudos de Casos e Controles , Feminino , Predisposição Genética para Doença/genética , Humanos , Hipertensão/sangue , Masculino , México , Filogenia , Polimorfismo de Nucleotídeo Único/genética , Fatores de RiscoRESUMO
INTRODUCTION: The plasmatic angiotensinogen (AGT) level has been associated with essential hypertension. Linkage analysis has found a relationship between the AGT gene locus and hypertension in the Mexican-American population, but studies have failed to identify genetic variants associated with hypertension or plasma AGT levels. This study analyzes the relationship between polymorphisms in the AGT gene and plasmatic AGT levels in Mexican population. METHODS: Nine polymorphisms in AGT gene were genotyped, and plasma AGT level was determined by enzyme-linked immunosorbent assay. RESULTS: Differences in AGT plasma levels were associated with 2 polymorphisms: T-20G, TT = 25.3 ± 8.3 versus TG + GG = 21.6 ± 8.8 µg/mL; P = 0.008 and C3389T (T174M), CC = 25.8 ± 9.9 versus TC + TT = 20.5 ± 5.4 µg/mL; P = 0.0002. Haplotype 2 was associated with low plasma AGT (-5.1 µg/mL [95% confidence interval: -8.6 to -1.6], P = 0.004) and Haplotype 8 was associated with high plasma AGT (6.5 µg/mL [95% confidence interval: 2.5 to 10.6], P = 0.001). This association remained after adjustment for covariates. A Likelihood Ratio Test for haplotype-phenotype association adjusted for covariates resulted in χ = 38.9, P = 0.0005. The total effect of the haplotypes on plasma AGT level variance was 19.5%. No association was identified between haplotypes and quantitative traits of blood pressure. CONCLUSIONS: Two polymorphisms (T-20G and C3389T) and 2 haplotypes (H2 and H8) showed an association with plasma AGT levels in Mexican population.
Assuntos
Angiotensinogênio/genética , Polimorfismo de Nucleotídeo Único/genética , Idoso , Angiotensinogênio/sangue , Pressão Sanguínea/genética , Ensaio de Imunoadsorção Enzimática , Feminino , Genes/genética , Estudos de Associação Genética , Genótipo , Haplótipos/genética , Humanos , Hipertensão/genética , Masculino , México , Obesidade/genéticaRESUMO
To investigate the participation of purinergic P2 receptors in the regulation of renal function in ANG II-dependent hypertension, renal and glomerular hemodynamics were evaluated in chronic ANG II-infused (14 days) and Sham rats during acute blockade of P2 receptors with PPADS. In addition, P2X1 and P2Y1 protein and mRNA expression were compared in ANG II-infused and Sham rats. Chronic ANG II-infused rats exhibited increased afferent and efferent arteriolar resistances and reductions in glomerular blood flow, glomerular filtration rate (GFR), single-nephron GFR (SNGFR), and glomerular ultrafiltration coefficient. PPADS restored afferent and efferent resistances as well as glomerular blood flow and SNGFR, but did not ameliorate the elevated arterial blood pressure. In Sham rats, PPADS increased afferent and efferent arteriolar resistances and reduced GFR and SNGFR. Since purinergic blockade may influence nitric oxide (NO) release, we evaluated the role of NO in the response to PPADS. Acute blockade with N(ω)-nitro-l-arginine methyl ester (l-NAME) reversed the vasodilatory effects of PPADS and reduced urinary nitrate excretion (NO(2)(-)/NO(3)(-)) in ANG II-infused rats, indicating a NO-mediated vasodilation during PPADS treatment. In Sham rats, PPADS induced renal vasoconstriction which was not modified by l-NAME, suggesting blockade of a P2X receptor subtype linked to the NO pathway; the response was similar to that obtained with l-NAME alone. P2X1 receptor expression in the renal cortex was increased by chronic ANG II infusion, but there were no changes in P2Y1 receptor abundance. These findings indicate that there is an enhanced P2 receptor-mediated vasoconstriction of afferent and efferent arterioles in chronic ANG II-infused rats, which contributes to the increased renal vascular resistance observed in ANG II-dependent hypertension.