Influence of cardiovascular risk factors on relation between angiotensin converting enzyme-gene polymorphism and blood pressure in arterial hypertension

Genetic influences on 24 h blood pressure profiles in a hypertensive population: role of the angiotensin-converting enzyme insertion/deletion and angiotensin II type 1 receptor A1166C gene polymorphisms

OBJECTIVE

Data on the association of the ACE I/D and AT1R A1166C polymorphisms with hypertension are conflicting. Most studies, however, have focused on office blood pressure (BP) only. The objective of the present study was to investigate the association of BP with the angiotensin-converting enzyme insertion/deletion (ACE I/D) and angiotensin II type 1 receptor A1166C (AT1R A1166C) polymorphisms by means of both office and ambulatory blood pressure monitoring (ABPM).

METHODS AND RESULTS

A total of 348 hypertensive patients participated in this study. Office BP did not differ between the various ACE or AT1R genotype groups. However, ambulatory BP and BP load were positively associated with the ACE I/D polymorphism. This was more apparent in men than in women. There were no differences in heart rate, BP variability, and amount of dipping. The AT1R A1166C polymorphism showed no consistent association with blood pressure (load).

CONCLUSION

From these data we conclude that frequent measuring of blood pressure by ABPM is crucial to find an association of the ACE D allele with various aspects of blood pressure.

Effects of angiotensin-converting enzyme gene polymorphism and serum vitamin D levels on ambulatory blood pressure measurement and left ventricular mass in Turkish hypertensive population

INTRODUCTION

Regulation of angiotensin converting enzyme (ACE) and angiotensin II (ang-II) levels is under genetic control. 1,25(OH)2 vitamin D3 treatment has been shown to reduce the ang-II level, reduce myocardial hypertrophy and to decrease blood pressure. This study was designed to examine the effect of ACE gene polymorphisms on 24-h ambulatory blood pressure measurement (24 h) values, vitamin D levels and target organ damage in hypertensive patients.

METHODS

This study was carried on 118 patients with essential hypertension (female/male: 70/48, mean age: 49.1+/-7.6 years, hypertension duration: 56+/-40.5 months). All patients were assessed for target organ damage; the eye by retinal examination, the heart with echocardiography and the kidney with blood and 24-h urine analysis. 24-h ambulatory blood pressure measurement was performed in all patients. PCR amplification was employed to detect ACE genotypes.

RESULTS

ACE genotypes were as follows: DD (n=49) 41.5%; ID (n=37) 31.4% and II (n=32) 27.1%. No difference was present between groups of ACE polymorphism when 24-h ambulatory blood pressure measurement values, retinal vascular changes and microalbuminuria were taken into account. Statistically significant left ventricular mass index levels were obtained in the DD group when compared with the non-DD (ID+II) group (P : 0.009). Positive correlations have been noted between left ventricular mass index and day/night and early morning systolic pressures. A negative correlation exists between serum 25 (OH) vitamin D levels and 24-h ambulatory blood pressure measurement values (P<0.05).

CONCLUSIONS

The presence of the D allele is linked with a higher risk for left ventricular mass index in the Turkish hypertensive population.

Gender differences in left ventricular chamber and midwall systolic function in normotensive and hypertensive adults

OBJECTIVE

Whether left ventricular (LV) systolic function differs between healthy men and women independent of afterload, LV geometry, age, heart rate and body size is disputed.

METHODS

We studied 517 clinically healthy adults without history of cardiovascular or endocrinal disease (age range 20-70, 274 with essential arterial hypertension). Echocardiography was used to assess LV geometry and systolic function both at endocardial and midwall levels.

RESULTS

Normotensive and hypertensive women had higher LV systolic function at endocardial and midwall levels independent of afterload. After adjustment for age, body surface area, heart rate and LV geometry, LV systolic function remained higher in women than in men in hypertensive and normotensive subjects. In a second set of multivariate analyses adjusting for age, body mass index, LV geometry and heart rate, women had significantly higher LV systolic function than men, both among normotensive and hypertensive subjects. In a reference group of 95 subjects with optimal blood pressure and normal body mass index (mean age 34 +/- 10; 32 men) extracted from the study sample, lower limits (5th percentile) of parameters of LV systolic function were higher in women than in men. Use of gender-specific partition values revealed that subnormal LV chamber function was uncommon in overweight, normotensive subjects as well as in hypertensive subjects; vice versa, stress-corrected midwall dysfunction was frequently subnormal in both normotensive, overweight (14%, mostly women) and in hypertensive subjects (18%, mostly men). At the opposite end of the spectrum, gender-specific supranormal, stress-corrected LV systolic chamber function (> 95th percentile of the distribution in the reference group) was relatively frequent in both overweight, normotensive (14%) and in hypertensive subjects (27%).

CONCLUSIONS

Clinically healthy hypertensive and normotensive women have higher LV chamber and midwall systolic function than men, independent of left ventricular geometry, body size, age and heart rate. Use of gender-specific partition values to define subnormal and supranormal LV systolic function revealed that, both in hypertensive and overweight normotensive subjects, subnormal LV chamber function was uncommon, whereas stress-corrected LV chamber systolic function was frequently supranormal. Vice versa, myocardial contractility was subnormal in approximately one-sixth of asymptomatic, normotensive overweight and of hypertensive subjects, with potentially unfavorable prognostic impact.

Relations of pulse pressure and other components of blood pressure to preclinical echocardiographic abnormalities

OBJECTIVE

To evaluate the extent to which pulse pressure (PP) is associated with echocardiographic abnormalities, and in particular to whether PP is related to LV hypertrophy taking into account other blood pressure (BP) components.

DESIGN

Cross-sectional.

SETTING

University hospital, hypertension outpatient unit.

PARTICIPANTS

A total of 275 adults (mean age 47 years, range 19-69, 3% aged > or = 65) with essential hypertension. Overt coronary artery disease, valvular disease and secondary hypertension were exclusion criteria. Subjects were divided in two groups with PP < or = 50 or PP > 50 mmHg.

OUTCOME MEASURES

Left ventricular (LV) mass, hypertrophy, LV systolic dysfunction.

RESULTS

Prevalence of LV hypertrophy was higher in subjects with clinic PP > 50 mmHg. Subjects with PP > 50 mmHg had higher clinic and ambulatory systolic than subjects with PP < or = 50 mmHg while diastolic BP did not differ between groups. PP and systolic BP, either clinic or ambulatory, showed similar correlation to LV hypertrophy in separate logistic multivariate models. Using different methodologies, PP was not related to LV mass index or hypertrophy when the effect of its component systolic BP was taken into account. In separate analyses, PP was not significantly related to ejection fraction or midwall mechanics.

CONCLUSION

Middle-aged clinically healthy hypertensives with PP > 50 mmHg had two-fold higher prevalence of LV hypertrophy than those with PP < or = 50 mmHg, which may contribute to the higher cardiovascular risk in subjects with higher PP. However, in our sample, PP was not related to LV hypertrophy independently of systolic BP, suggesting that systolic BP is the explanatory link of the relation between PP and LV hypertrophy.

Inappropriate left ventricular mass in normotensive and hypertensive patients

We evaluated cardiovascular features of normotensive and hypertensive adults with left ventricular (LV) mass values exceeding levels predicted for given stroke work, gender, and height, termed "inappropriate" LV mass. Inappropriate LV mass is associated with overweight, concentric LV geometry, and low myocardial systolic function not only in hypertensive subjects, but also in normotensive subjects.

Lipoprotein lipase (C/G)447 polymorphism and blood pressure in the Stanislas Cohort

OBJECTIVE

Association between blood pressure and triglyceride levels, and between lipoprotein lipase (LPL) (C/G)447 polymorphism and triglyceride levels has been described. We investigated whether the LPL (C/G)447 polymorphism was associated with blood pressure (BP) levels and longitudinal changes.

DESIGN AND PARTICIPANTS

For cross-sectional analysis, 767 men and 816 women (29-55 years) were selected from the Stanislas Cohort, a cohort of volunteers for a free health check-up. Only subjects without anti-hypertensive or lipid-lowering medication were included in the study. A subset of this sample population, 359 men and 337 women, had been followed during the 11 years prior to recruitment in the Stanislas Cohort and was used for longitudinal analysis.

RESULTS

The cross-sectional study showed that serum triglyceride levels differed significantly according to LPL genotypes in both genders, the G447 allele being associated with the lowest triglyceride levels (P < or = 0.01). Univariate and multivariate analysis found that LPL polymorphism was not related to BP levels in men. In contrast, women with the LPL-G447 allele had lower systolic (SBP) and pulse (PP) pressure levels than those with the LPL-CC genotype (P < or = 0.01 and P < or = 0.05, respectively); this association being independent of triglyceride level. The longitudinal study showed LPL genotype was an independent predictor of PP and SBP follow-up levels in women; changes over 11 years being lower for LPL-G447 allele carriers (P < or = 0.05). These associations were independent of triglyceride level.

CONCLUSION

The LPL-G447 allele was found associated with lower PP and SBP independently of triglyceride level in women. This result suggests that the LPL gene may influence blood pressure.

Insertion/deletion polymorphism in the angiotensin-converting enzyme gene affects heart weight

BACKGROUND

Angiotensin (Ang) II, a major regulatory factor for left ventricular mass, is generated from Ang I by ACE. ACE levels are associated with an insertion/deletion (I/D) polymorphism in the ACE gene. The ACE polymorphism should result in varied Ang II concentrations and hence affect left ventricular mass. We therefore investigated whether ACE genotype is a predictor of heart weight.

METHODS AND RESULTS

From 693 consecutive patients autopsied between 1994 and 1998 in our hospital, patients with valvular disease, myocardial infarction, or cardiomyopathy were excluded. The remaining 443 autopsy patients were the subjects of our study. The heart weight at autopsy was corrected for body surface area. Genomic DNA was purified from the kidney, and ACE genotype was determined by polymerase chain reaction. Heart weight in the DD genotype (249. 9+/-49.9 g/m(2)) was significantly higher than that in the ID (230. 0+/-51.2 g/m(2); P<0.05) and II (226.8+/-49.8 g/m(2); P<0.01) genotypes. Heart weight was also positively related to age (r=0.145, P<0.0001) and coronary stenosis index (r=0.147, P=0.0019). Multiple regression analysis showed that a history of hypertension (P<0.0001), age (P=0.0001), and DD genotype (P=0.0154) were independent predictors of heart weight.

CONCLUSIONS

ACE genotype predicts cardiac mass; however, it was less effective than epigenetic factors such as hypertension or age.

Context-dependent associations of the ACE I/D polymorphism with blood pressure

The objective of the present study was to assess whether the influences of gender, age, or measures of body size on blood pressure are homogeneous among genotypes of the insertion/deletion (I/D) polymorphism of the gene that codes for angiotensin-converting enzyme (ACE). We studied a sample of 1875 non-Hispanic white individuals (988 female and 887 male subjects) between 5 and 90 years of age from the general population of Rochester, Minn. When statistical interactions between effects associated with the I/D polymorphism and age, height, and weight were not considered, there was no evidence of a significant relationship between variation in blood pressure level or diagnostic category (hypertension versus normotension) and variation in ACE genotype in either gender. However, in females 5 to 29.9 years of age, the linear regression relationships of systolic blood pressure level with age and weight and of diastolic blood pressure level with age were significantly heterogeneous among ACE genotypes. For these concomitant traits, the rank order of expected blood pressure levels associated with each genotype reversed from low values of the concomitant, in which blood pressure was lower for I/D heterozygotes than for II or DD homozygous, to high levels of the concomitant, in which blood pressure was higher for I/D heterozygotes than for II or DD homozygotes. In male subjects 50 to 90 years of age, the logistic regression relationship of the probability of having hypertension with height was also heterogeneous among ACE genotypes; it was statistically significant in II homozygotes but not statistically significant in either I/D heterozygotes or DD homozygotes. Findings of this study are consistent with the conclusion that the influence of variation in the ACE gene on interindividual variation in blood pressure is dependent on contexts that are indexed by gender, age, and measures of body size.

Cardiovascular risk factors, angiotensin-converting enzyme gene I/D polymorphism, and left ventricular mass in systemic hypertension

We investigated the influence of major cardiovascular risk factors (smoking, hypercholesterolemia, diabetes mellitus) on the association between angiotensin-converting enzyme (ACE) gene insertion (I)/deletion (D) polymorphism and echocardiographic left ventricular mass in 225 patients with sustained hypertension, assessed by ambulatory blood pressure monitoring. When the study population was analyzed as a whole, the 3 ACE genotypes did not differ in left ventricular mass (II, 47 g/m2.7; ID, 49 g/m2.7; DD, 51 g/m2.7; p = NS). No difference was found in subjects (n = 135) in whom at least 1 major cardiovascular risk factor was present (II, 51 g/m2.7; ID, 51 g/m2.7; DD: 52 g/m2.7; p = NS). In contrast, in the absence of cardiovascular risk factors, DD subjects (n = 32) exhibited left ventricular mass index higher than non-DD (ID/II) subjects (n = 75; p <0.05). After controlling for age and sex, in the absence of cardiovascular risk factors, the risk of left ventricular hypertrophy was 3.8-fold higher in DD than in non-DD patients (odds ratio 3.8; 95% confidence interval 1.2 to 12.1, p <0.02). We conclude that in the present setting of patients with established sustained systemic hypertension, the absence of risk factors potentially affecting cardiovascular adaptation allows for the detection of a positive association between homozygosity for the D allele of the ACE gene and left ventricular hypertrophy.