A recurrent theme with a new spin: ACE polymorphism and cardiovascular disease

Current perspectives on the use of gene therapy for hypertension

Systemic hypertension is a pathophysiological state that is manifested as high blood pressure and is a major risk factor for stroke, ischemic heart disease, peripheral vascular disease, and progressive renal damage. Pulmonary hypertension occurs in 3 distinct forms: primary pulmonary hypertension, pulmonary hypertension of the newborn, or secondary pulmonary hypertension attributable to a variety of lung and cardiovascular diseases. This review discusses the use of gene therapy in the control of systemic and pulmonary hypertension. Overexpression of vasodilator genes as well as antisense knockdown of vasoconstrictor genes has been successfully used in animal models of both forms of hypertension. Furthermore, the use of viral vectors to deliver these constructs has achieved long-term control of hypertension. The successful establishment of gene therapy techniques in the animal models of hypertension coupled with the anticipated advances in the genetic aspects of this disease would make it highly feasible to attempt gene delivery in the control of human hypertension.

Genetic polymorphism of the renin-angiotensin system and organ damage in essential hypertension

BACKGROUND

The renin-angiotensin-aldosterone system (RAAS) plays a significant role in the development of hypertensive cardiac and vascular remodeling. Recently, several genetic variants of its key components, which may be clinically relevant and thus prove to be useful in the evaluation of cardiovascular risk, have been described. We therefore investigated the association between ACE I/D, AGT M235T, and AT1 A1266C gene polymorphisms and early signs of target organ damage in 215 untreated patients with essential hypertension (EH).

METHODS

Genotyping was based on the polymerase chain reaction technique, with further restriction analysis when required. Albuminuria was measured as the albumin-to-creatinine ratio (ACR). The left ventricular mass index (LVMI) was assessed by echocardiography (LVH = LVMI > or = 125 g/m2), carotid wall thickness (IMT) by an ultrasonographic (US) scan, and retinal vascular changes by direct ophthalmoscopy (Keith-Wagener classification).

RESULTS

The prevalence of microalbuminuria (Mi), LVH, and retinal vascular changes was 14, 46, and 74%, respectively. ACE, AGT, and AT1 genotype distribution was in agreement with the Hardy-Weinberg equilibrium. There was no difference in age, duration of disease, body mass index (BMI), blood pressure, and lipid profile when data were analyzed on the basis of genotype. Serum levels of angiotensin-converting enzyme (ACE) were related to the ACE genotype (10.2 +/- 0.5, DD; 8.2 +/- 0.3, ID; 6.5 +/- 0.4 IU/mL, II; P < 0. 0001 by analysis of variance). The ACE genotype independently influences serum ACE levels and accounts for approximately 14% of its variations (F = 26.7, r2 = 0.1393, df 1 to 214, P < 0.0001). Patients with DD and ID genotypes showed higher levels of ACR (1.59 +/- 0.2, DD + ID; 0.8 +/- 0.2 mg/mmol, II; P < 0.006 by ANOVA) and bigger LVMI (124.1 +/- 2.3, DD + ID vs. 117.8 +/- 3.6 g/m2, II; P < 0.01 by ANOVA). No differences in the prevalence and degree of target organ damage (TOD) were found when data were analyzed on the basis of the AGT and AT1 genotypes, respectively. Potentially unfavorable combinations of genotypes were also investigated by K-means cluster analysis. Two subgroups of patients were identified (cluster 1, N = 70; cluster 2, N = 57), and each differed significantly with regards to the presence and degree of TOD and patterns of RAAS gene polymorphisms (F, 15.97 for ACR; F, 7.19 for IMT; F, 217.03 for LVMI; F, 3.91 for ACE; F, 4.06 for AGT; and F, 5. 22 for AT1; df 1 to 214, P < 0.02, for each one of the variables examined).

CONCLUSION

The D allele of the ACE gene may be an independent risk factor for the development of target organ damage, and evaluating it could be useful for assessing cardiovascular risk in EH. Unfavorable patterns of RAAS genotypes seem to predispose patients to subclinical cardiovascular disease in EH.

Cardiac genes and gene databases for cardiovascular disease genetics

Genes play a very important role in the etiology of hypertension. This paper reviews the current pool of candidate genes for human hypertension. Some of the genes studied in rat models of hypertension are also discussed. The methods for studying the genetics of hypertension are reviewed. A discussion of the role of cardiac gene libraries and gene databases in the characterization of cardiovascular disease is also included. This review is concluded by a discussion on the future role of genomics and cardiovascular gene databases in medical research.