Antihypertensive pharmacogenetics: getting the right drug into the right patient

Measuring copeptin, a surrogate for vasopressin in patients with hypertension - Can it identify those who are volume Responsive?

BACKGROUND

Among hypertensive patients, plasma renin activity is lower and the response to diuretic monotherapy greater in volume responsive hypertensive patients. We hypothesized that hormones influencing extracellular volume such as vasopressin / antidiuretic hormone (ADH) might permit the development of a simple test to identify those with volume-related hypertension. Such a test might be of particular benefit to the Black population which is purported to have a higher incidence of volume-related and responsive hypertension. Thus, using copeptin, a surrogate marker for ADH, we studied if there were differences in this hormone between those with and without volume responsive hypertension.

METHODS

Serum copeptin was measured in biobanked blood samples from the Genetic Epidemiology of Responses to Antihypertensives (GERA) I study and analyzed with other variables from the study dataset.

RESULTS

There was no relationship between PRA and copeptin values nor could the response in blood pressure be predicted by the copeptin values. However, baseline copeptin levels were higher in Black than in White subjects (7.5 pmol/L vs 5.4 pmol/L, P < 0.001) while plasma sodium and calculated plasma osmolality were slightly lower in keeping with the concept that Black subjects have more volume-related hypertension. In addition, after hydrochlorothiazide (HCTZ), copeptin was significantly lower in Black (6.2 pmol/L, P = 0.004) but unchanged in White subjects (5.2 pmol/L, P = 0.901) and there were also changes in sodium.

CONCLUSION

The current study suggests differences in ADH physiology between hypertensive Black and White patients. However, the use of copeptin to identify volume responsive patients could not be confirmed.

Association of AGTR1 A1166C and CYP2C9∗3 Gene Polymorphisms with the Antihypertensive Effect of Valsartan

Background

The differences in the antihypertensive treatment with angiotensin type II receptor blockers (ARBs) may be attributed to polymorphisms in genes involving drug-targeted receptor and drug metabolism. The present study aimed to investigate whether the antihypertensive effect of the ARB drug valsartan was associated with angiotensin II type 1 receptor (AGTR1) gene polymorphism (A1166 C) and cytochrome P450 enzyme 2C9 (CYP2C9) gene polymorphism (CYP2C9∗3).

Methods

281 patients with hypertension who received valsartan monotherapy in the past month were included in this retrospective study. Polymerase chain reaction-melting curve analysis was performed to genotype the AGTR1 and CYP2C9 gene polymorphisms. Based on the systolic blood pressure (SBP) and diastolic blood pressure (DBP) at the time of visit, the patients were divided into well-controlled group (n = 144, SBP/DBP <140/90 mmHg) and poorly controlled group (n = 137, SBP/DBP ≥140/90 mmHg).

Results

Older age, decreased history of drinking, a higher proportion of mild-to-moderate hypertension, lower alanine aminotransferase levels, and higher high-density lipoprotein cholesterol levels were observed in the well-controlled group than the poorly controlled group. Higher frequencies of the C allele and AC + CC genotype of AGTR1 A1166C were detected in the well-controlled than the poorly controlled patients (P = 0.005 and P = 0.006). After adjustment for demographic and environmental factors, the CC + AC genotype of AGTR1 A1166C was markedly linked to better hypertension control with valsartan treatment compared to the AA genotype (odds ratio: 2.836, 95% confidence interval: 1.199–6.705, P = 0.018). No significant difference was observed in the allele or genotype distribution of CYP2C9∗3 polymorphism between well-controlled and poorly controlled patients.

Conclusions

The current data suggested that the AGTR1 A1166 C polymorphism may be associated with the antihypertensive effect of valsartan, and carriers with AC and CC genotypes may have a better antihypertensive efficacy response to valsartan treatment.

Distributive characteristics of the CYP2C9 and AGTR1 genetic polymorphisms in Han Chinese hypertensive patients: a retrospective study

Background

There is an individual variation in response to antihypertensive effect of the angiotensin II receptor antagonist. This study aimed to determine the allele and genotype frequencies of CYP2C9 and AGTR1 genetic polymorphisms and explore the potential role of these polymorphisms in guiding the selection of angiotensinIIreceptor antagonist in Han Chinese hypertensive patients.

Methods

Totally 2419 Han Chinese hypertensive patients and 126 normotensive controls were recruited in this study. Venous blood samples were collected from each patient, and the genetic polymorphisms of CYP2C9 and AGTR1 were assessed using a gene chip platform. The allele and genotype frequency of each gene and the combined genotypes in this study were analyzed respectively.

Results

The gene chip analysis identified an allelic frequency of 96.51% for CYP2C9*1 and 3.49% for CYP2C9*3 in the cohort of Han Chinese hypertensive patients. Statistical analysis showed that the frequency of wild-type homozygous for CYP2C9*1/*1 was 93.30%, while the frequency of heterozygous for *1/*3 or mutant homozygous for *3/*3 was 6.41% or 0.29%. Meanwhile, we detected allelic frequencies of 95.06% and 4.94% for the A and C allele of AGTR1, respectively. While the genotype frequency of wild-type homozygous for AA was 90.41%, the frequency of heterozygous for AC or mutant homozygous for CC was 9.30% or 0.29%. Notably, we observed that 84.66% (2048/2419) of the subjects exhibited a combined genotype of CYP2C9 and AGTR1 as *1/*1 + AA, while the combined genotypes *3/*3 + AC or *3/*3 + CC were not detected in hypertension patients. Besides, no significant association was found between normotensive controls and hypertensive patients, or among the three grades of hypertensive patients.

Conclusions

These data revealed the polymorphisms characteristics of CYP2C9 and AGTR1 in Han Chinese hypertensive patients, providing valuable information for genotype-based antihypertension therapy in prospective clinical studies in the future.

Hypertension genomics and cardiovascular prevention

Hypertension continues to be a major risk factor for global mortality, and recent genome-wide association studies (GWAS) have expanded in size, leading to the identification of further genetic loci influencing blood pressure. In light of the new knowledge from the largest cardiovascular GWAS to date, we review the potential impact of genomics on discovering potential drug targets, risk stratification with genetic risk scores, drug selection with pharmacogenetics, and exploring insights provided by gene-environment interactions.

ACE Phenotyping as a Guide Toward Personalized Therapy With ACE Inhibitors

Background:

Angiotensin-converting enzyme (ACE) inhibitors (ACEI) are widely used in the management of cardiovascular diseases but with significant interindividual variability in the patient’s response.

Objectives:

To investigate whether interindividual variability in the response to ACE inhibitors is explained by the “ACE phenotype”—for example, variability in plasma ACE concentration, activity, and conformation and/or the degree of ACE inhibition in each individual.

Methods:

The ACE phenotype was determined in plasma of 14 patients with hypertension treated chronically for 4 weeks with 40 mg enalapril (E) or 20 mg E + 16 mg candesartan (EC) and in 20 patients with hypertension treated acutely with a single dose (20 mg) of E with or without pretreatment with hydrochlorothiazide. The ACE phenotyping included (1) plasma ACE concentration; (2) ACE activity (with 2 substrates: Hip-His-Leu and Z-Phe-His-Leu and calculation of their ratio); (3) detection of ACE inhibitors in patient’s blood (indicator of patient compliance) and the degree of ACE inhibition (ie, adherence); and (4) ACE conformation.

Results:

Enalapril reduced systolic and diastolic blood pressure in most patients; however, 20% of patients were considered nonresponders. Chronic treatment results in 40% increase in serum ACE concentrations, with the exception of 1 patient. There was a trend toward better response to ACEI among patients who had a higher plasma ACE concentration.

Conclusion:

Due to the fact that “20% of patients do not respond to ACEI by blood pressure drop,” the initial blood ACE level could not be a predictor of blood pressure reduction in an individual patient. However, ACE phenotyping provides important information about conformational and kinetic changes in ACE of individual patients, and this could be a reason for resistance to ACE inhibitors in some nonresponders.

Genome-Wide and Gene-Based Meta-Analyses Identify Novel Loci Influencing Blood Pressure Response to Hydrochlorothiazide

This study aimed to identify novel loci influencing the antihypertensive response to hydrochlorothiazide monotherapy. A genome-wide meta-analysis of blood pressure (BP) response to hydrochlorothiazide was performed in 1739 white hypertensives from 6 clinical trials within the International Consortium for Antihypertensive Pharmacogenomics Studies, making it the largest study to date of its kind. No signals reached genome-wide significance (P<5×10-8), and the suggestive regions (P<10-5) were cross-validated in 2 black cohorts treated with hydrochlorothiazide. In addition, a gene-based analysis was performed on candidate genes with previous evidence of involvement in diuretic response, in BP regulation, or in hypertension susceptibility. Using the genome-wide meta-analysis approach, with validation in blacks, we identified 2 suggestive regulatory regions linked to gap junction protein α1 gene (GJA1) and forkhead box A1 gene (FOXA1), relevant for cardiovascular and kidney function. With the gene-based approach, we identified hydroxy-delta-5-steroid dehydrogenase, 3 β- and steroid δ-isomerase 1 gene (HSD3B1) as significantly associated with BP response (P<2.28×10-4 ). HSD3B1 encodes the 3β-hydroxysteroid dehydrogenase enzyme and plays a crucial role in the biosynthesis of aldosterone and endogenous ouabain. By amassing all of the available pharmacogenomic studies of BP response to hydrochlorothiazide, and using 2 different analytic approaches, we identified 3 novel loci influencing BP response to hydrochlorothiazide. The gene-based analysis, never before applied to pharmacogenomics of antihypertensive drugs to our knowledge, provided a powerful strategy to identify a locus of interest, which was not identified in the genome-wide meta-analysis because of high allelic heterogeneity. These data pave the way for future investigations on new pathways and drug targets to enhance the current understanding of personalized antihypertensive treatment.

Comparison of Blood Pressure Control Rates Among Recommended Drug Selection Strategies for Initial Therapy of Hypertension

BACKGROUND

Several approaches to initiation of antihypertensive therapy have been suggested. These include thiazide diuretics (TDs) as the first drug in all patients, initial drug selection based on age and race criteria, or therapy selection based on measures of plasma renin activity (PRA). It is uncertain which of these strategies achieves the highest control rate with monotherapy in Stage-I hypertension. We sought to compare control rates among these strategies.

METHODS

We used data from the Pharmacogenomic Evaluation of Antihypertensive Responses study (PEAR) to estimate control rates for each strategy: (i) TD for all, (ii) age- and race-based strategy: Hydrochlorothiazide (HCTZ) for all blacks and for whites ≥50 years and a renin-angiotensin system inhibitor (atenolol) for whites <50 years) or (iii) a PRA based strategy: HCTZ for suppressed PRA (<0.6ng/ml/h) and atenolol for non-suppressed PRA (≥0.6ng/ml/h) despite age or race. Hypertension was confirmed prior to treatment with HCTZ (148 blacks and 218 whites) or with atenolol (146 blacks and 221 whites).

RESULTS

In the overall sample, using clinic blood pressure (BP) response, the renin-based strategy was associated with the greatest control rate (48.9% vs. 40.8% with the age and race-based strategy (P = 0.0004) and 31.7% with the TD for all strategy (P < 0.0001)). The findings were similar using home or by 24-hour ambulatory BP responses and within each racial subgroup.

CONCLUSIONS

A strategy for selection of initial antihypertensive drug therapy based on PRA was associated with greater BP control rates compared to a thiazide-for-all or an age and race-based strategy.

Genome-wide response to antihypertensive medication using home blood pressure measurements: a pilot study nested within the HOMED-BP study

BACKGROUND

Patients with mild-to-moderate essential hypertension in the HOMED-BP trial were randomly allocated to first-line treatment with a calcium channel blocker (CCB), angiotensin-converting enzyme inhibitor (ACEI) or angiotensin II receptor blocker (ARB).

METHODS

We recruited 265 (93 for CCB, 71 for ACEI and 101 for ARB) patients who completed the genomic study. Home blood pressure was measured for 5 days off-treatment before randomization and for 5 days after 2-4 weeks of randomized drug treatment. Genotyping was performed by 500K DNA microarray chips. The blood pressure responses to the three drugs were analyzed separately as a quantitative trait. For replication of SNPs with p < 10(-4), we used the multicenter GEANE study, in which patients were randomized to valsartan or amlodipine.

RESULTS

SNPs in PICALM, TANC2, NUMA1 and APCDD1 were found to be associated with CCB responses and those in ABCC9 and YIPF1 were found to be associated with ARB response with replication.

CONCLUSION

Our approach, the first based on high-fidelity phenotyping by home blood pressure measurement, might be a step in moving towards the personalized treatment of hypertension.

The role of plasma renin activity, age, and race in selecting effective initial drug therapy for hypertension

BACKGROUND

Strategies for initial drug therapy of hypertension are a thiazide diuretic for all or drug selection based on age/race criteria or on plasma renin activity (PRA). It is uncertain which of these strategies will achieve the highest control rate among patients with stage 1 essential hypertension. We sought to compare control rates among 3 drug selection strategies: (i) thiazide diuretic for all, (ii) thiazide diuretic for all black subjects and white subjects aged ≥50 years and a renin-angiotensin system blocker for white subjects aged <50 years, or (iii) thiazide diuretic for PRA < 0.6ng/ml/h (suppressed PRA) and a renin-angiotensin system blocker for PRA ≥ 0.6ng/ml/h (nonsuppressed PRA).

METHODS

Blood pressure responses from the Genetic Epidemiology of Responses to Antihypertensives (GERA) study were used to determine control rates for each of the 3 strategies. In GERA, hypertensive adults were treated with hydrochlorothiazide (n = 286 black subjects and 284 white subjects) or with candesartan (n = 248 black subjects and 278 white subjects).

RESULTS

In the overall sample, the PRA strategy was associated with the highest control rate of 69.4% vs. 61.3% with the age/race strategy (P < 0.001) and 53.8% with the thiazide for all strategy (P < 0.001). This was also true in each racial subgroup (in black subjects: 62.1% vs. 55.2% for the other 2 strategies, P = 0.02; in white subjects: 76.3% vs. 67.1% with the age/race strategy (P < 0.001) and 52.4% with the thiazide for all strategy (P < 0.001)).

CONCLUSIONS

This exploratory analysis suggests that choice of initial therapy for hypertension using a PRA strategy may be associated with higher control rates than alternative strategies recommended in current guidelines.

Gene-environment interactions of selected pharmacogenes in arterial hypertension

Hypertension affects approximately 1 billion people worldwide. Owing to population aging, hypertension-related cardiovascular burden is expected to rise in the near future. In addition to genetic variants influencing the blood pressure response to antihypertensive drugs, several genes encoding for drug-metabolizing or -transporting enzymes have been associated with blood pressure and/or hypertension in humans (e.g., ACE, CYP1A2, CYP3A5, ABCB1 and MTHFR) regardless of drug treatment. These genes are also involved in the metabolism and transport of endogenous substances and their effects may be modified by selected environmental factors, such as diet or lifestyle. However, little is currently known on the complex interplay between environmental factors, endogenous factors, genetic variants and drugs on blood pressure control. This review will discuss the respective role of population-based primary prevention and personalized medicine for arterial hypertension, taking a pharmacogenomics' perspective focusing on selected pharmacogenes.

Genomic association analysis identifies multiple loci influencing antihypertensive response to an angiotensin II receptor blocker

To identify genes influencing blood pressure response to an angiotensin II receptor blocker, single nucleotide polymorphisms identified by genome-wide association analysis of the response to candesartan were validated by opposite direction associations with the response to a thiazide diuretic, hydrochlorothiazide. We sampled 198 white and 193 blacks with primary hypertension from opposite tertiles of the race-sex-specific distributions of age-adjusted diastolic blood pressure response to candesartan. There were 285 polymorphisms associated with the response to candesartan at P<10(-4) in whites. A total of 273 of the 285 polymorphisms, which were available for analysis in a separate sample of 196 whites, validated for opposite direction associations with the response to hydrochlorothiazide (Fisher χ(2) 1-sided P=0.02). Among the 273 polymorphisms, those in the chromosome 11q21 region were the most significantly associated with response to candesartan in whites (eg, rs11020821 near FUT4, P=8.98 × 10(-7)), had the strongest opposite direction associations with response to hydrochlorothiazide (eg, rs3758785 in GPR83, P=7.10 × 10(-3)), and had the same direction associations with response to candesartan in the 193 blacks (eg, rs16924603 near FUT4, P=1.52 × 10(-2)). Also notable among the 273 polymorphisms was rs11649420 on chromosome 16 in the amiloride-sensitive sodium channel subunit SCNN1G involved in mediating renal sodium reabsorption and maintaining blood pressure when the renin-angiotensin system is inhibited by candesartan. These results support the use of genomewide association analyses to identify novel genes predictive of opposite direction associations with blood pressure responses to inhibitors of the renin-angiotensin and renal sodium transport systems.

Genetic variation in renin predicts the effects of thiazide diuretics

BACKGROUND

While genetic variants of renin-angiotensin-aldosterone system (RAAS) may modify the blood pressure (BP) response to thiazide diuretics, there was no evidence of genetic variations in renin (REN) playing a role. This study aimed to address the potential effects of genetic variations of RAAS on the response to initial treatment of hydrochlorothiazide (HCTZ).

MATERIALS AND METHODS

We enrolled nondiabetic hypertensive patients with a systolic blood pressure (SBP) ≥140 or a diastolic blood pressure (DBP) ≥90mmHg, who were either previously untreated or unsatisfactorily treated. After lifestyle modification and diet instruction for 2weeks, 90 patients with persistently elevated BP were given HCTZ 50 mg every morning for 2 weeks. Single nucleotide polymorphism markers were selected from genes involving in RAAS, including rs7079 and rs699 of angiotensinogen, rs4293 and rs4353 of angiotensin-converting enzyme and rs1464816 and rs11240688 of REN.

RESULTS

The patients were divided into three groups according to the SBP response after HCTZ. The upper 1/3 responders had older age (P=0·035), higher SBP (P=0·039), higher pulse pressure (P=0·006) and lower plasma REN activity (PRA) (P=0·020) when compared with the lower 1/3 responders. Renin rs11240688 CC polymorphism (β=9·931, corrected P=0·012), Log PRA (β=7·451, P=0·004) and baseline SBP (β=0·299, P=0·006) were the independent predictors for the BP lowering response.

CONCLUSIONS

In addition to PRA, renin rs11240688 CC polymorphism may also independently predict the effect of HCTZ.

Pharmacogenetic interactions and their potential effects on genetic analyses of blood pressure

BACKGROUND

In observational studies, analyses of blood pressure (BP) typically require some correction for the use of antihypertensive medications by study participants. Different approaches to correcting for treatment have been compared, but the impact of pharmacogenetic interactions that influence the efficacy of antihypertensive treatments on estimates of genetic main effects has not been considered. This work demonstrates the potential influence of pharmacogenetic interactions in genetic analyses of BP.

METHODS

A simulation study is conducted to test the influence of pharmacogenetic interactions on approaches to the analysis of BP. Results from three plausible scenarios are presented.

RESULTS

Informative BP approaches (Fixed Treatment Effect, Non-parametric adjustment, Censored Normal Regression) perform well when there is no pharmacogenetic interaction, but yield biased estimates of the main effects of particular genetic variants when pharmacogenetic interactions exist. Substitution approaches (Binary Trait, Fixed Substitution, Random Substitution, Median Method) are unaffected by pharmacogenetic interactions, but consistently perform sub-optimally.

CONCLUSIONS

We recommend that the Informative BP approaches remain the most appropriate methods to use in practice, but stress that caution is required in the interpretation of their results-especially when an interaction between treatment and a genetic variant of interest is suspected. We make some suggestions as to how to check for possible interactions and confirm the results from genetic analyses of BP, but warn that these should be reviewed when data on real pharmacogenetic interactions become available.

Pharmacogenomics of antihypertensive drugs: past, present and future

Hypertension pharmacogenomics holds the promise of leading to individualized drug treatment approaches for the approximately 1 billion individuals worldwide with hypertension. Prior to 2000, the literature on hypertension pharmacogenomics was quite limited. The last decade has seen a substantial growth in the literature, with several examples of genes that appear to play an important role in antihypertensive response. The last decade has also made apparent the numerous challenges in hypertension pharmacogenomics, and addressing those challenges will be important. Moving forward, it seems clear that collaboration among researchers to allow replication or joint analyses will be essential in advancing the field, as will the use of genome-wide association approaches. The next decade should clearly define the clinical potential for hypertension pharmacogenomics.

Effects of Polymorphism of the β1 Adrenoreceptor and CYP2D6 on the Therapeutic Effects of Metoprolol

Metoprolol is a lipophilic β1 selective adrenergic receptor antagonist used in antihypertensive therapy. It is metabolized by the protein product of the cytochrome P450 2D6 ( CYP2D6) gene. Few studies have been performed on the association between the β1 adrenoreceptor, CYP2D6 polymorphism and blood pressure. The one reported here is a prospective, observational, clinical study in Chinese Han hypertensive patients on the combined influences of CYP2D6 and β1 adrenoreceptor polymorphisms on the therapeutic effects of metoprolol in 300 out-patients with essential hypertension. The same dose of metoprolol achieved different therapeutic effects in patients with different CYP2D6 and β1 adrenoreceptor polymorphisms. Additionally, different doses of metoprolol could achieve the same therapeutic effects in patients with different CYP2D6 and β1 adrenoreceptor polymorphisms. Knowledge of the combination of CYP2D6 and β1 adrenoreceptor polymorphisms may be used to guide antihypertensive therapy using β1 adrenoreceptor antagonists.

The relationship between the plasma concentration of irbesartan and the antihypertensive response is disclosed by an angiotensin II type 1 receptor polymorphism: results from the Swedish Irbesartan Left Ventricular Hypertrophy Investigation vs. Atenolol (SILVHIA) Trial

BACKGROUND

The aim of this study was to investigate the effect of the plasma concentration of irbesartan, a specific angiotensin II type 1 receptor (AT1R) antagonist, and the blood pressure response in relation to AT1R gene polymorphisms.

METHODS

Plasma irbesartan was analyzed in 42 patients with mild-to-moderate hypertension and left ventricular hypertrophy from the Swedish Irbesartan Left Ventricular Hypertrophy Investigation vs. Atenolol (SILVHIA) trial, who were treated with irbesartan as monotherapy for 12 weeks. Blood pressure and irbesartan concentration were measured at trough, i.e., 24 +/- 3 h after the last dose. Five AT1R gene polymorphisms were analyzed by minisequencing.

RESULTS

Neither the plasma concentration of irbesartan, nor any of the AT1R polymorphisms were associated with the blood pressure response to irbesartan treatment. However, the interaction term between the plasma concentration of irbesartan and the AT1R C5245T polymorphism was related to the reduction in systolic blood pressure after 12 weeks of treatment (P = 0.025). Furthermore, the plasma concentration of irbesartan was related to the change in systolic blood pressure in individuals homozygous for the AT1R 5245 T allele (r = -0.56, P = 0.030), but not for other genotypes.

CONCLUSIONS

There was an association between plasma concentrations of irbesartan and the blood pressure response for hypertensive patients with AT1R 5245 TT. Because of the small sample size, this study needs to be viewed as hypothesis generating. This is the first study, to our knowledge, indicating that the concentration-response relationship of an antihypertensive drug may be genotype dependent.

Genomic association analysis suggests chromosome 12 locus influencing antihypertensive response to thiazide diuretic

We conducted a genome-wide association study to identify novel genes influencing diastolic blood pressure (BP) response to hydrochlorothiazide, a commonly prescribed thiazide diuretic preferred for the treatment of high BP. Affymetrix GeneChip Human Mapping 100K Arrays were used to measure single nucleotide polymorphisms across the 22 autosomes in 194 non-Hispanic black subjects and 195 non-Hispanic white subjects with essential hypertension selected from opposite tertiles of the race- and sex-specific distributions of age-adjusted diastolic BP response to hydrochlorothiazide (25 mg daily, PO, for 4 weeks). The black sample consisted of 97 "good" responders (diastolic BP response [mean+/-SD]=-18.3+/-4.2 mm Hg; age=47.1+/-6.1 years; 51.5% women) and 97 "poor" responders (diastolic BP response=-0.18+/-4.3; age=47.4+/-6.5 years; 51.5% women). Haplotype trend regression identified a region of chromosome 12q15 in which haplotypes constructed from 3 successive single nucleotide polymorphisms (rs317689, rs315135, and rs7297610) in proximity to lysozyme (LYZ), YEATS domain containing 4 (YEATS4), and fibroblast growth receptor substrate 2 (FRS2) were significantly associated with diastolic BP response (nominal P=2.39 x 10(-7); Bonferroni corrected P=0.024; simulated experiment-wise P=0.040). Genotyping of 35 additional single nucleotide polymorphisms selected to "tag" linkage disequilibrium blocks in these genes provided corroboration that variation in LYZ and YEATS4 was associated with diastolic BP response in a statistically independent data set of 291 black subjects and in the sample of 294 white subjects. These results support the use of genome-wide association analyses to identify novel genes influencing antihypertensive drug responses.

Perindopril: beyond lowering blood pressure

Perindopril, a prodrug ester of perindoprilat, is an angiotensin-converting enzyme inhibitor that lowers angiotensin II and potentiates bradykinin. This agent has proven efficacy in a wide range of cardiovascular diseases. Its efficacy, safety and tolerability are well established in the treatment of hypertension. Beyond pharmacodynamic effects shown in lowering blood pressure, perindopril was also involved in the improvement of endothelial function and the normalization of vascular and cardiac structure and function. Large morbidity-mortality trials, such as the European Trial on Reduction of Cardiac Events with Perindopril in Patients with Stable Coronary Artery Disease (EUROPA), Perindopril Protection Against Recurrent Stroke Study (PROGRESS) and Anglo-Scandinavian Cardiac Outcomes Trial-Blood Pressure Lowering Arm (ASCOT-BPLA), have shown that treatment with perindopril reduces and prevents cardiovascular disease in a large range of patients with vascular diseases (including stable coronary disease), whether or not they are hypertensive.

Relationships of the appropriateness of left ventricular mass to left atrial size and function in arterial hypertension

OBJECTIVE

To investigate whether left ventricular mass (LVM) appropriateness may be related to left atrial changes in both size and performance in arterial hypertension.

METHODS

Three hundred and thirty-five hypertensive outpatients were studied by Doppler echocardiography and divided into two groups on the basis of LVM appropriateness. Left ventricular mass was defined inappropriate when greater than 128% of the value predicted from age, sex and stroke work (95th percentile of normal distribution) and appropriate for values <or= 128%. Left atrial volumes were obtained by two-dimensional echocardiography, left atrial ejection force was used as an index of systolic performance and calculated accordingly with Manning's formula.

RESULTS

Left ventricular mass was inappropriate in 58 patients (17%). Individuals with an inappropriate mass showed higher left atrial maximum and minimum volumes compared to those with appropriate mass (all P<0.001), independent of left ventricular geometry. Left atrial ejection fraction (44 +/- 13 versus 46 +/- 13%) and ejection force (8.4 +/- 4.8 versus 9.3 +/- 5.3 kdynes) were not statistically different between groups. In the whole group, left atrial volumes and stroke volume showed a close positive relationship with respect to crude values of LVM and inappropriate LVM, whereas left atrial ejection force was better related to left ventricular concentric geometry. This correlation was explained by the more pronounced diastolic dysfunction found in the highest quartile of left atrial ejection force.

CONCLUSIONS

In arterial hypertension, left atrial enlargement parallels an increase in LVM. Left atrial ejection force is at least in part independent of this mechanism, being mainly linked to concentric geometry and left ventricular diastolic function impairment.

Genetics of arterial hypertension and hypotension

Human hypertension affects affects more than 20% of the adult population in industrialized countries, and it is implicated in millions of deaths worldwide each year from stroke, heart failure and ischemic heart disease. Available evidence suggests a major genetic impact on blood pressure regulation. Studies in monogenic hypertension revealed that renal salt and volume regulation systems are predominantly involved in the genesis of these disorders. Mutations here affect the synthesis of mineralocorticoids, the function of the mineralocorticoid receptor, epithelial sodium channels and their regulation by a new class of kinases, termed WNK kinases. It has been learned from monogenic hypotension that almost all ion transporters involved in the renal uptake of Na(+) have a major impact on blood pressure regulation. For essential hypertension as a complex disease, many candidate genes have been analysed. These include components of the renin-angiotensin-aldosterone system, adducin, beta-adrenoceptors, G protein subunits, regulators of G protein signalling (RGS) proteins, Rho kinases and G protein receptor kinases. At present, the individual impact of common polymorphisms in these genes on the observed blood pressure variation, on risk for stroke and as predictors of antihypertensive responses remains small and clinically irrelevant. Nevertheless, these studies have greatly augmented our knowledge on the regulation of renal functions, cellular signal transduction and the integration of both. Together, this provides the basis for the identification of novel drug targets and, hopefully, innovative antihypertensive drugs.

New bearings in pharmacotherapeutic strategies: Pharmacogenetics and gene therapy

<zakljucak> Slicno drugim, novim terapijskim konceptima i genska terapija je puno obecavala, ali za sada je jos u razvoju. Glavni izazov ostaje unosenje pravog gena na pravo mesto, u pravu celiju i obezbedjenje adekvatne ekspresije, uz minimalna nezeljena dejstva. Iako se najvise radi na virusnim vektorima, smatra se da buducnost genske terapije cine znatno bezbedniji nevirusni sistemi. Bilo je izvesnih promasaja u genskoj terapiji, sto je dovelo do sumnje i zabrinutosti u siroj populaciji. Medjutim, razvoj genske terapije je realnost, kao i cinjenica da ona ima svoje mesto u medicini. Vazno je istaci da genskoj terapiji treba pristupati sa izuzetno visokim stepenom naucne, strucne i eticke odgovornosti, jer se ne moze iskljuciti mogucnost genetskih manipulacija opasnih za ljudsko zdravlje.

ACE phenotyping as a first step toward personalized medicine for ACE inhibitors. Why does ACE genotyping not predict the therapeutic efficacy of ACE inhibition?

Angiotensin (Ang)-converting enzyme (ACE) inhibitors are widely used for the treatment of cardiovascular diseases. Not all patients respond to ACE inhibitors, and it has been suggested that genetic variation might be a useful marker to predict the therapeutic efficacy of these drugs. In particular, the ACE insertion (I)/deletion (D) polymorphism has been investigated in this regard. Despite a decade of intensive research involving the genotyping of thousands of patients, we still do not know whether ACE genotyping helps in predicting the success of ACE inhibition. This review critically addresses the concept that predictive information on therapeutic efficacy of ACE inhibitors might be obtained based on ACE genotyping. It answers the following questions: Do higher ACE levels really result in higher Ang II levels? Is ACE the only converting enzyme in humans? Does ACE inhibition affect ACE expression? Why does ACE have 2 catalytically active domains? What is the relevance of ACE inhibitor-induced signaling through membrane-bound ACE? The review ends with the proposal that ACE phenotyping may prove to be a better first step toward personalized medicine for ACE inhibitors than ACE genotyping.

Preventing end stage renal disease in diabetic patients--genetic aspect (part I)

Diabetic nephropathy is a major cause of diabetes- related morbidity and mortality; however the clinical course of the disease and the renal prognosis is highly variable among individuals. The current review will discuss the genetic influence on the development of end stage renal disease (ESRD) in diabetic patients and potential improvements to the current treatment strategy to slow the loss of kidney function in these patients. In this first part, the growing evidence that glucose-induced activation of the intra-renal and systemic renin-angiotensin systems plays an essential role in processes leading to destruction of renal function is summarised. Genetic variations, especially the angiotensin-converting enzyme (ACE)/ID polymorphisms in the gene coding for ACE, are involved in activation of the renin-angiotensin system and seem to influence the clinical course of diabetic nephropathy during treatment with ACE inhibitors. In addition, this polymorphism may interact with other polymorphisms within the renin-angiotensin system, leading to high risk of ESRD. As new genetic approaches and methods develop, further understanding of diabetic nephropathy will evolve and genotyping will help prevent ESRD in diabetic patients.

Alcohol and the cardiovascular system: research challenges and opportunities

Excessive alcohol consumption has long been associated with cardiovascular disorders, including cardiomyopathy, hypertension, coronary artery disease, and stroke. However, recent evidence suggests that moderate alcohol intake can actually provide a measure of cardioprotection, particularly against coronary heart disease and ischemia-reperfusion injury. To explore the various dimensions of these opposing actions of alcohol, the National Institute on Alcohol Abuse and Alcoholism and the National Heart, Lung, and Blood Institute sponsored a state-of-the-art workshop on "Alcohol and the Cardiovascular System: Research Challenges and Opportunities" in Bethesda, Maryland, in May 2003. Speakers discussed the following topics: the epidemiology of alcohol and cardiovascular disease, clinical manifestations of alcohol, genetics of alcohol and cardiovascular disease, mechanisms underlying the molecular and cellular effects of alcohol, the application of new and emerging technology, and translation from discovery to therapeutic modalities of treatment. The panel concluded that future studies are needed to: 1) determine the role of genes and the environment in assessing mechanisms underlying the benefits of alcohol use and cardiovascular disease risk; 2) define the biological mechanisms underlying alcohol-induced peripheral vascular damage; 3) clarify the role of genetic variation in alcohol-metabolizing enzymes, genetic susceptibility, and pharmacogenomics in determining cardiovascular disease risk and effective treatment; 4) determine common mechanisms underlying alcohol-induced cardiovascular disease, such as oxidative stress and inflammation; 5) assess the role of insulin resistance, blood clotting, protein kinase C isoforms, and signal transduction mechanisms mediating alcohol's beneficial effects; and 6) explore the potential of stem cells in myocardial regeneration and repair in hearts damaged by alcohol.

Emerging drugs in the management of hypertension

Hypertension is a global health problem, affecting developing and developed countries alike. Most patients with hypertension are undiagnosed, and most diagnosed patients are either untreated or inadequately treated. Randomised controlled trial evidence suggests diuretic therapy for hypertension is as effective as newer drugs in reducing cardiovascular events. There is good evidence for the use of specific classes of drugs in hypertensive patients with a variety of associated clinical conditions, but for uncomplicated cases, the current emphasis in hypertension management is on blood pressure lowering rather than drug class. Individual patients vary in their responses to different drug classes, and optimal therapy for the individual is determined by trial and error. Pharmacogenomics may assist in tailoring therapy for individuals in the future. Emerging drugs include newer members of classes already established in clinical practice, for example, angiotensin II receptor antagonists, aldosterone receptor antagonists, calcium antagonists and centrally acting drugs; newer fixed-dose combination therapies; and more novel therapies, for example, endothelin (ET) receptor antagonists, activators of nitric oxide (NO)-sensitive guanylyl cyclase and vasopeptidase inhibitors.

Drug-gene interactions between genetic polymorphisms and antihypertensive therapy

Genetic factors may influence the response to antihypertensive medication. A number of studies have investigated genetic polymorphisms as determinants of cardiovascular response to antihypertensive drug therapy. In most candidate gene studies, no such drug-gene interactions were found. However, there is observational evidence that hypertensive patients with the 460 W allele of the alpha-adducin gene have a lower risk of myocardial infarction and stroke when treated with diuretics compared with other antihypertensive therapies. With regard to blood pressure response, interactions were found between genetic polymorphisms for endothelial nitric oxide synthase and diuretics, the alpha-adducin gene and diuretics, the alpha-subunit of G protein and beta-adrenoceptor antagonists, and the ACE gene and angiotensin II type 1 (AT(1)) receptor antagonists. Other studies found an interaction between ACE inhibitors and the ACE insertion/deletion (I/D) polymorphism, which resulted in differences in AT(1) receptor mRNA expression, left ventricular hypertrophy and arterial stiffness between different genetic variants. Also, drug-gene interactions between calcium channel antagonists and ACE I/D polymorphism regarding arterial stiffness have been reported. Unfortunately, the quality of these studies is quite variable. Given the methodological problems, the results from the candidate gene studies are still inconclusive and further research is necessary.

Renin–angiotensin system gene polymorphisms: relationship with blood pressure and microalbuminuria in telmisartan-treated hypertensive patients

This study analyzed the relationship between four renin-angiotensin system (RAS) gene polymorphisms and the response to blood pressure lowering and development of microalbuminuria in 206 patients with essential hypertension treated once daily for 12 months with telmisartan 80 mg. Seated cuff blood pressure and urinary albumin excretion (UAE) were measured throughout the study. Patients were screened for the presence of the A-6G variant of the angiotensinogen gene, angiotensin-converting enzyme insertion/deletion polymorphism, and the A1166C and C573T polymorphisms of the angiotensin II type 1 receptor gene. No significant association was found between the presence of any gene polymorphism and the reduction of blood or UAE following telmisartan treatment. The results indicate that these RAS gene polymorphisms do not affect the antihypertensive activity and renoprotection in mild-to-moderate hypertensive patients treated with telmisartan.

Single nucleotide polymorphisms in the apolipoprotein B and low density lipoprotein receptor genes affect response to antihypertensive treatment

BACKGROUND

Dyslipidemia has been associated with hypertension. The present study explored if polymorphisms in genes encoding proteins in lipid metabolism could be used as predictors for the individual response to antihypertensive treatment.

METHODS

Ten single nucleotide polymorphisms (SNP) in genes related to lipid metabolism were analysed by a microarray based minisequencing system in DNA samples from ninety-seven hypertensive subjects randomised to treatment with either 150 mg of the angiotensin II type 1 receptor blocker irbesartan or 50 mg of the beta1-adrenergic receptor blocker atenolol for twelve weeks.

RESULTS

The reduction in blood pressure was similar in both treatment groups. The SNP C711T in the apolipoprotein B gene was associated with the blood pressure response to irbesartan with an average reduction of 19 mmHg in the individuals carrying the C-allele, but not to atenolol. The C16730T polymorphism in the low density lipoprotein receptor gene predicted the change in systolic blood pressure in the atenolol group with an average reduction of 14 mmHg in the individuals carrying the C-allele.

CONCLUSIONS

Polymorphisms in genes encoding proteins in the lipid metabolism are associated with the response to antihypertensive treatment in a drug specific pattern. These results highlight the potential use of pharmacogenetics as a guide for individualised antihypertensive treatment, and also the role of lipids in blood pressure control.

Pharmacogenetics of Antihypertensive Drug Responses

The blood pressure (BP) response to any single antihypertensive drug is characterized by marked interindividual variation, and the known predictors of response are of limited value in identifying the optimum drug for an individual patient. Analysis of genetic variation has the potential to improve our understanding of determinants of antihypertensive drug response in order to individualize drug selection. Genetic variation can influence both pharmacokinetic and pharmacodynamic mechanisms underlying variation in drug response. Classic pharmacogenetic investigations have identified variations in single genes that have a large effect on antihypertensive drug metabolism and are inherited in a Mendelian fashion. These include a polymorphism in the CYP2D6 gene, encoding a cytochrome p450 family member involved in phase I drug metabolism, and polymorphisms in genes encoding enzymes involved in phase II drug metabolism, including N-acetyltransferase (NAT2), catechol-O-methyltransferase (COMT), and phenol sulfotransferase (P-PST, SULT1A1). Although these polymorphisms have major effects on the pharmacokinetic profiles of both commonly used antihypertensive drugs such as metoprolol (CYP2D6), and lesser used drugs such as hydralazine (NAT2), methyldopa (COMT), and minoxidil (SULT1A1), they have not been shown to influence variation in the antihypertensive effect of these drugs at conventional doses. Interest is now focused on identifying genetic polymorphisms that influence the pharmacodynamic determinants of antihypertensive response. Using a candidate gene approach, such polymorphisms have been identified in genes encoding alpha-adducin (ADD1), subunits of G-proteins (GNB3 and GNAS1), the beta(1)-adrenergic receptor (ADRB1), endothelial nitric oxide synthase (NOS3), and components of the renin-angiotensin-aldosterone system (angiotensinogen [AGT], angiotensin converting enzyme [ACE], the angiotensin type I receptor [AGTR1], and aldosterone synthase [CYP11B2]). These polymorphisms have been shown to influence the BP response to diuretics (ADD1, GNB3, NOS3, and ACE), beta-blockers (GNAS1 and ADRB1), ACE inhibitors (AGT, ACE, and AGTR1), angiotensin receptor blockers (ACE and CYP11B2), and clonidine (GNB3).An emerging consensus from these studies is that single gene effects on antihypertensive drug responses are small, and even the combined effects of all presently known polymorphisms do not account for enough variation in response to be clinically useful. New genome-wide scanning techniques may lead to the identification of genes previously unsuspected of influencing drug response. Additional requirements for pharmacogenetic approaches to become clinically useful are the characterization of the effects of haplotypes and multi-locus genotypes on drug response, and consideration of gene-by-environment interactions. Such studies will require huge sample sizes and novel statistical methods, but the theoretical and technical framework is in place to make this possible.

Pharmacogenetics of hypertension treatment

The extent of blood pressure lowering by anti-hypertensive agents is difficult to predict for individual patients, even when evaluated in the context of biochemical or demographic information. Genetic predictors (mainly single nucleotide polymorphisms, SNPs) have been the focus of several recent studies and are gaining much attention. We have conducted a literature search for studies in which the lowering of ambient blood pressure by specific drugs or drug classes in humans was related to specific genotypes. Twenty-eight studies were identified, of which six had a single-dose design, and the remaining 22 studied drug effects after more than 4 weeks of drug administration. Virtually all were association studies. Prospective trials that compared the prognostic value of genetic methods to routine clinical practice were not identified. Almost all studies used a candidate-gene design, usually with a very small number of SNPs (typically one). Gene-gene and gene-environment interactions were studied only rarely. Only one study targeted genes involved in drug metabolism. Most candidate-genes were part of the renin-angiotensin system. By far the most extensively studied has been the angiotensin-converting enzyme insertion/deletion polymorphism (15 studies) but, to date, no clear picture has emerged for this or other genetic variants. Thus, the potential for utility of genetic characterization of individual patients as a predictor of anti-hypertensive response has yet to be realized.

Essential hypertension

Hypertension is a frequent, chronic, age-related disorder, which often entails debilitating cardiovascular and renal complications. Blood pressure is usually noted in combination with other cardiovascular risk factors. Diagnosis of hypertension increasingly relies on automated techniques of blood pressure measurement. The pathophysiology of essential hypertension depends on the primary or secondary inability of the kidney to excrete sodium at a normal blood pressure. The central nervous system, endocrine factors, the large arteries, and the microcirculation also have roles in the disorder. Although monogenic forms of blood pressure dysregulation exist, hypertension mostly arises as a complex quantitative trait that is affected by varying combinations of genetic and environmental factors. Non-pharmacological strategies can reduce blood pressure. Antihypertensive drug treatment diminishes the complications of hypertension. The concept that a few major genes will provide the final clue to the pathogenesis of essential hypertension is an oversimplification that contradicts the heterogeneous nature of this disorder. Further integration of genetic, molecular, clinical, and epidemiological research could disclose subsets of patients in whom specific combinations of genetic and environmental factors raise blood pressure, and might lead to more individualised treatment.

Reduced nocturnal fall in blood pressure, assessed by two ambulatory blood pressure monitorings and cardiac alterations in early phases of untreated essential hypertension

To investigate whether in recently diagnosed essential hypertensives a reduced nocturnal fall in blood pressure (BP), established on the basis of two 24-h ambulatory blood pressure monitorings (ABPM) is related to a greater cardiovascular damage. In all, 355 consecutive, recently diagnosed, never-treated essential hypertensives referred for the first time to our outpatient clinic were included in the study. Each patient underwent the following procedures: (1) two 24-h ABPMs performed within 3 weeks, (2) 24-h urinary collection for microalbuminuria, (3) nonmydriatic photography of ocular fundi, (4) echocardiography, (5) carotid ultrasonography. We defined nondipping profile as a night-day systolic and diastolic fall < or =10 % (mean of two ABPMs). A dipper BP profile was found in 238 patients, whereas in 117 patients a nondipper profile was present. The two groups were similar for age, gender, body mass index, smoking habit, clinic BP, 48-h BP and heart rate, while, by definition, night-time systolic and diastolic BP were significantly higher in nondippers than in dippers (130/81 vs 121/74 mmHg, P < 0.0001).The prevalence of left ventricular hypertrophy (LVH) defined by four different criteria: (a) LV mass index (LVMI) > or = 125 g/m(2) in both genders; (b) LVMI > or = 134 gm(2) in men and > or = 110 in women; (c) LVMI> or = 125 g/m(2) in men and > or = 110 g/m(2) in women; (d) LVMI > or = 51 g/m(2.7) in men and > or = 47 g/m(2.7) in women was significantly higher in nondippers than in dippers (a: 12 vs 7%, P < 0.05; b: 16 vs 7%, P < 0.01; c: 20 vs 11%, P < 0.01; d: 35 vs 23% P < 0.02) and this finding was associated with a significant increase in aortic root and left atrium dimensions. There were no differences between the two groups in the prevalence of carotid and retinal changes and microalbuminuria. In conclusion our findings suggest that never-treated hypertensives with a reduced BP fall in the night time, defined on the basis of two ABPMs, have a higher prevalence of TOD than dippers, in terms of echocardiographic LVH. In this population setting, cardiac structural alterations are a more sensitive marker of the impact of the nocturnal BP load on cardiovascular system than other extracardiac signs of TOD.

A microarray minisequencing system for pharmacogenetic profiling of antihypertensive drug response

We aimed to develop a microarray genotyping system for multiplex analysis of a panel of single nucleotide polymorphisms (SNPs) in genes encoding proteins involved in blood pressure regulation, and to apply this system in a pilot study demonstrating its feasibility in the pharmacogenetics of hypertension. A panel of 74 SNPs in 25 genes involved in blood pressure regulation was selected from the SNP databases, and genotyped in DNA samples of 97 hypertensive patients. The patients had been randomized to double-blind treatment with either the angiotensin II type 1 receptor blocker irbesartan or the beta 1-adrenergic receptor blocker atenolol. Genotyping was performed using a microarray based DNA polymerase assisted 'minisequencing' single nucleotide primer extension assay with fluorescence detection. The observed genotypes were related to the blood pressure reduction using stepwise multiple regression analysis. The allele frequencies of the selected SNPs were determined in the Swedish population. The established microarray-based genotyping system was validated and allowed unequivocal multiplex genotyping of the panel of 74 SNPs in every patient. Almost 7200 SNP genotypes were generated in the study. Profiles of four or five SNP-genotypes that may be useful as predictors of blood pressure reduction after antihypertensive treatment were identified. Our results highlight the potential of microarray-based technology for SNP genotyping in pharmacogenetics.

Genetics of blood pressure, hypertensive complications, and antihypertensive drug responses

Hypertension is the most prevalent, treatable risk factor for diseases of the heart, brain and kidneys. In this review, we discuss advances in understanding of the genetics of blood pressure regulation, the development of hypertensive complications and the pharmacodynamics of antihypertensive drug responses. Discovery of single gene mutations that cause hypertension or hypotension in humans suggests that the common final pathway for regulation of blood pressure level is via alterations in renal sodium handling. Based on a working hypothesis that common genetic variations contributing to blood pressure variation in the population may also act on this same pathway, we summarize supporting evidence emerging from linkage and selected association studies of candidate genes--including those encoding components of the renin-angiotensin-aldosterone system, the epithelial sodium channel, adrenoceptors, G protein subunits, and other cellular signaling mediators and modifiers. We proceed to distinguish ischemic target organ complications due to arteriolosclerotic changes of the microvasculature from those due to atherosclerosis involving larger conduit and capacitance arteries. Using the example of subcortical white matter ischemia of the brain, we propose that interindividual variation in the arteriolosclerotic complications is more likely than atherosclerotic complications to be related to the same genetic (and environmental) mechanisms that contribute to hypertension. We conclude by summarizing the state-of-the-art of antihypertensive pharmacogenetics, which has succeeded in rejecting the null hypothesis that genetic variation does not influence blood pressure or protective target organ responses to drug therapy. In each of the three areas covered in this review, we indicate the many remaining obstacles to the routine clinical use of genetic measurements in the diagnosis, evaluation and treatment of hypertension.

Long-term angiotensin II inhibition increases mitochondrial nitric oxide synthase and not antioxidant enzyme activities in rat heart

OBJECTIVE

To provide insight into the subcellular mechanisms involved in the improvement of cardiovascular structure and function by long-term inhibition of the renin-angiotensin system.

DESIGN

The activities of antioxidant enzymes and mitochondrial free radical production were determined in the heart of control (C), enalapril-treated (E), and losartan-treated (L) rats to test the hypothesis of increased antioxidant enzyme activities and participation of mitochondria in the effects of chronic treatments with angiotensin II inhibitors.

METHODS

At 6 and 18 months of treatment, superoxide dismutases (SOD), Se-glutathione peroxidase, and catalase activities were determined in left ventricle homogenates by spectrophotometric methods and nitric oxide (NO) production in submitochondrial membranes by the oxyhemoglobin oxidation assay. The maximal rate of hydrogen peroxide (H2O2) production by submitochondrial membranes was also evaluated at 18 months by the scopoletin-horseradish peroxidase method.

RESULTS

No significant increase was found in the antioxidant enzymes measured. At 6 months, Mn-SOD was actually decreased in E and catalase in both E and L, whereas at 18 months Se-glutathione peroxidase was decreased in L. Production of NO by submitochondrial particles was 64% higher at 6 months in E and 105% higher at 18 months in E and L. Maximal hydrogen peroxide production was lower at 18 months in both groups.

CONCLUSIONS

Results do not support the hypothesis of an increase in antioxidant enzyme activity by long-term treatment with angiotensin II inhibitors as previously suggested and point towards a role for the NO produced by mitochondrial nitric oxide synthase (mtNOS) in the protective effect of these drugs.

Reproducibility of blood pressure response to hydrochlorothiazide

Few studies have investigated the reproducibility of responses to antihypertensive therapies. The purpose of this study was to assess the reproducibility of the blood pressure response to a thiazide diuretic, a preferred initial treatment for hypertension. Twenty-two subjects who underwent monotherapy with hydrochlorothiazide as part of a study to identify predictors of blood pressure response agreed to undergo the same protocol a second time, 26.6+/-11.8 (range, 4-52) months after their first participation. The mean systolic and diastolic blood pressure responses to hydrochlorothiazide did not differ significantly between the first and second participation (systolic response, -14.2+/-16.4 mm Hg vs. -16.0+/-16.5 mm Hg; diastolic response, -7.1+/-11.8 mm Hg vs. -6.6+/-8.6 mm Hg), and these responses were significantly correlated between the two trials (systolic response, r=0.61 and p<0.01; diastolic response, r=0.64 and p<0.01). However, both the direction and magnitude of responses for individual subjects varied considerably, with the limits of agreement between the first and second participations (i.e., 2 standard deviations above and below the mean difference between responses) ranging from 27.4 mm Hg to -23.8 mm Hg for systolic blood pressure response and from 17.4 mm Hg to -18.4 mm Hg for diastolic blood pressure response. These results show that the average systolic and diastolic blood pressure responses to hydrochlorothiazide for a group of subjects are reproducible; however, the responses for individual subjects are unpredictable.

Prevention of hypertension, hyperglycemia and vascular oxidative stress by aspirin treatment in chronically glucose-fed rats

OBJECTIVES

To examine whether an in vivo chronic treatment with aspirin could prevent insulin resistance, oxidative stress and blood pressure elevation associated with high glucose feeding in rats.

METHODS

Sprague-Dawley rats (SD) were given a normal chow diet for 3 weeks combined or not with a 10% glucose drinking solution with or without aspirin added to their drinking water, and were compared to control SD rats which received normal chow and tap water to drink for 3 weeks. Oxidative stress was evaluated by measuring superoxide anion (O2-) production in the aorta using the lucigenin-enhanced chemiluminescence method. Antioxidant reserve was assessed by measuring the activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) in the blood. Fasting blood sugar and insulin levels were measured at the end of the study.

RESULTS

The systolic blood pressure (SBP), the aortic basal superoxide production, plasma levels of insulin and glucose, as well as the insulin resistance index, were all significantly higher in rats fed glucose for 3 weeks, compared to control rats. The simultaneous treatment with aspirin prevented the increase in SBP, in plasma glucose levels and in aortic O2- production, and attenuated the rise in insulin levels as well as insulin resistance in the glucose-fed rats. Positive correlations between aortic O2- production and SBP, as well as between insulin resistance and SBP or between O2- production and insulin resistance, were found in control, glucose-fed and aspirin-treated, glucose-fed rats. The activities of GPx and SOD in the erythrocytes did not differ in the three groups. An increase in plasma SOD activity was observed in glucose-fed rats.

CONCLUSIONS

Chronic in vivo treatment with aspirin prevented the development of hypertension and reduced insulin resistance significantly in chronically glucose-fed rats. Aspirin seems to produce these effects through its antioxidative properties, since it was found to prevent the increase in aortic O2- production observed in chronically glucose-fed rats.

Plasma vascular endothelial growth factor in sleep apnea syndrome: effects of nasal continuous positive air pressure treatment

Sleep apnea syndrome is associated with recurrent episodic hypoxia during sleep, which has been implicated in the development of cardiovascular morbidity. Hypoxia is the major stimulus of vascular endothelial growth factor (VEGF), which is a potent angiogenic cytokine. In the present article we describe the results of three experiments in which plasma concentrations of VEGF were measured in patients with sleep apnea. In Experiment 1, apnea-hypopnea index was found to be a significant independent predictor of morning VEGF concentrations in 85 male subjects investigated in the sleep laboratory, of whom 47 had an apnea-hypopnea index greater than 20. In Experiment 2, VEGF concentrations measured hourly during the sleep period were found to be significantly higher in a group of five sleep apnea patients compared with six age-similar snorers and six normal young adults (129.1 +/- 43.4 versus 74.6 +/- 11.5 and 32.5 +/- 12.8 pg/ml, respectively [p < 0.007]). In Experiment 3, VEGF concentrations were compared in patients with sleep apnea before and 1 year after nasal continuous positive airway pressure treatment. A significant decrease in VEGF concentrations was found only in patients in whom nocturnal hypoxia improved after treatment (57.1 +/- 62.5 versus 39.6 +/- 46.9 pg/ml, p < 0.01). There was no comparable improvement in patients who did not accept treatment (53.9 +/- 23.6 versus 54.0 +/- 21.5 pg/ml, ns). These results raise the possibility that VEGF may contribute to the long-term adaptation of sleep apnea syndrome to recurrent nocturnal hypoxia.

Identification and ethnic distribution of major haplotypes in the gene GNB3 encoding the G-protein beta3 subunit

The 825T-allele of the gene GNB3 encoding the G protein beta3 subunit is associated with hypertension and obesity, and identifies individuals highly responsive to diuretic therapy. Gbeta3s, a Gbeta3 protein variant generated by alternative splicing in carriers of the 825T-allele, is linked to increased signal transduction and is a potential cause for the observed pathophysiology. Here, we searched the entire GNB3 gene for additional polymorphisms and analysed their prevalence in Caucasian, black African and Asian populations. We detected six novel single nucleotide polymorphisms which were termed according to their location as G76A, G1906T, G2906A, A3882C, G5177A, and G5249A. Furthermore, we found a CACA-insertion-deletion polymorphism at position 6496. Genotyping and association studies resulted in the definition of two major GNB3 haplotypes, termed 'C-haplotype' (alleles 825C, 3882A, 5249G, 6496CACA-) and 'T-haplotype' (alleles 825T, 3882C, 5249A, 6496CACA+). Molecular modelling studies revealed that the pre-mRNA structures of both haplotypes exhibit marked differences which may account for the alternative splicing predominantly observed with the T-haplotype. The prevalence of these haplotypes in major ethnic populations differs considerably. Furthermore, we detected additional frequent GNB3 polymorphisms. These variants were restricted to one or two major ethnic populations. Our results will aid future studies on population-specific effects of the GNB3 variants on risk and course of frequent diseases, including hypertension, obesity, stroke and myocardial infarction. Furthermore, they will contribute to the understanding of GNB3-related population-specific pharmacogenetic differences in the response to major drugs, as already shown for diuretics and antidepressants.

Double-blind, placebo-controlled crossover comparison of five classes of antihypertensive drugs

OBJECTIVE

Hypertension guidelines recommend initial treatment with a beta-blocker or diuretic and adding the other drug where blood pressure is not controlled. We hypothesized that systematic rotation through the major classes of antihypertensive drugs would demonstrate substantial differences in the pattern of an individual patient's response, and suggest a more rational approach to choosing best treatment.

DESIGN

Thirty-four young hypertensives (age 28-55, median 47) rotated in a double-blind, Latin-square, crossover fashion through 6 weeks of treatment each with amlodipine, doxazosin, lisinopril, bisoprolol, bendrofluazide and placebo. Blood pressure was measured at each visit. 'Best' drug, defined by efficacy and tolerability, was repeated at the end.

RESULTS

Rotation doubled the number of patients reaching target blood pressure (systolic < 140 mmHg) on one drug (P = 0.03). All five drugs were represented among the 'best' drugs. In six patients, the blood pressure on 'best' drug was at least 10 mmHg lower than on any other. Response to the 'best' drug was highly correlated (r = 0.79) with its previous administration. By contrast, there were only weak correlations between responses to pairs of drugs, except for angiotensin-converting enzyme (ACE) inhibitor (A) with beta-blocker (B), and calcium blocker (C) with diuretic (D) - each r = 0.71, P < 0.005). In these young patients, the majority of patients (23/34) responded best to a drug suppressing the renin system (A and B).

CONCLUSIONS

Patients vary reproducibly in their response to initial treatment, and switching among drugs can increase the efficacy of monotherapy. The results support an AB/CD scheme for choosing therapy, in which the first drug is taken from one of these pairs, and uncontrolled patients switch to one of the other pair.

Optimal blood pressure control and antihypertensive regimens in hypertensive renal disease: the potential of exploring the mechanisms of response variability

In renal patients rigorous blood pressure control is crucial to prevent renal and cardiovascular target organ damage. For renoprotection target blood pressure depends on the severity of proteinuria before treatment. For proteinuria of 1--3g/day a mean arterial pressure of 98 mmHg provides additional benefit, whereas the target should be as low as 92 mmHg if proteinuria exceeds 3g/day. The antiproteinuric effect of antihypertensive intervention predicts renoprotection; it is therefore recommended that therapy should be titrated not only on blood pressure, but also on reduction of proteinuria. All currently available classes of antihypertensives can be used to reduce blood pressure in renal patients. Interventions based on blockade of the renin-angiotensin-aldosterone system have additional antiproteinuric, and thus renoprotective, potential. Large individual differences in therapeutic benefit are common, even for interventions of proven efficacy at group level. Studies applying different classes of drugs in the same patient (rotation schedules) demonstrate that individual factors are main determinants of therapy response. Exploration of the mechanisms underlying these patient factors is important to improve treatment outcome. Analysis of genetic determinants of therapy response has great potential in this respect. However, therapy response is a complex phenotype. Thus, careful study of gene-gene and gene-environment interactions will be needed in order to turn this type of knowledge into benefit for the patient.