Tuula Hannila-Handelberg

Common variants of the beta and gamma subunits of the epithelial sodium channel and their relation to plasma renin and aldosterone levels in essential hypertension

BackgroundRare mutations of the epithelial sodium channel (ENaC) result in the monogenic hypertension form of Liddles syndrome. We decided to screen for common variants in the ENaC βand γ subunits in patients with essential hypertension and to relate their occurrence to the activity of circulating renin-angiotensin-aldosterone system.MethodsInitially, DNA samples from 27 patients with low renin/low aldosterone hypertension were examined. The DNA variants were subsequently screened for in 347 patients with treatment-resistant hypertension, 175 male subjects with documented long-lasting normotension and 301 healthy Plasma renin and aldosterone levels were measured under baseline conditions and during postural and captopril challenge tests.ResultsTwo commonly occurring βENaC variants (G589S and a novel intronic i12-17CT substitution) and one novel γENaC variant (V546I) were detected. One of these variants occurred in a heterozygous form in 32 patients, a prevalence (9.2%) significantly higher than that in normotensive males (2.9%, p = 0.007) and blood donors (3.0%, p = 0.001). βENaC i12-17CT was significantly more prevalent in the hypertension group than in the two control groups combined (4.6% vs. 1.1%, p = 0.001). When expressed in Xenopus oocytes, neither of the two ENaC amino acid-changing variants showed a significant difference in activity compared with ENaC wild-type. No direct evidence for a mRNA splicing defect could be obtained for the βENaC intronic variant. The ratio of daily urinary potassium excretion to upright and mean (of supine and upright values) plasma renin activity was higher in variant allele carriers than in non-carriers (p = 0.034 and p = 0.048).ConclusionsAt least 9% of Finnish patients with hypertension admitted to a specialized center carry genetic variants of β and γENaC, a three times higher prevalence than in the normotensive individuals or in random healthy controls. Patients with the variant alleles showed an increased urinary potassium excretion rate in relation to their renin levels.

Laboratory tests as predictors of the antihypertensive effects of amlodipine, bisoprolol, hydrochlorothiazide and losartan in men: results from the randomized, double-blind, crossover Genres Study

Objective Individual blood pressure responses to antihypertensive therapy are difficult to predict. To improve optimization of antihypertensive therapy, we analyzed correlations of relevant laboratory tests with blood pressure responses to four antihypertensive monotherapies. Methods In the GENRES study, 208 Finnish men aged 35–60 years with moderate hypertension used amlodipine 5 mg, bisoprolol 5 mg, hydrochlorothiazide 25 mg and losartan 50 mg daily, each for 4 weeks as a monotherapy in a double-blind, randomized, placebo-controlled crossover study; that is, each subject received each type of monotherapy in a random order. The treatment periods were preceded and separated by 4-week placebo periods. Ambulatory 24-h and office blood pressure measurements were carried out after all study periods. Data from several biochemical tests were correlated to antihypertensive drug responses. Results Serum total calcium concentration was negatively correlated with blood pressure responses to amlodipine (P values 0.001–0.002). Plasma renin activity was positively correlated with blood pressure responses to losartan (P values 0.001–0.005) and bisoprolol (P values 0.03–0.17), and negatively with blood pressure responses to hydrochlorothiazide (P values 0.01–0.07). Daily urinary excretion of sodium was negatively correlated with ambulatory blood pressure responses to amlodipine (P values 0.001–0.01). Conclusions In this carefully controlled study, marked individual variations in antihypertensive drug responsiveness were found to correlate to several baseline laboratory parameters. The negative correlation between serum calcium levels and amlodipine responses is intriguing and suggests an underlying mechanistic association. Collectively, our data imply that laboratory tests may have some value in prediction of the efficacy of various antihypertensive drug therapies, although great patient-to-patient variation remains an obstacle for exact predictive classification.

Relationship of electrocardiographic repolarization measures to echocardiographic left ventricular mass in men with hypertension.

Objective Arterial hypertension often leads to an increase in left ventricular mass (LVM). Marked left ventricular hypertrophy (LVH) is associated with potentially arrhythmogenic ventricular repolarization abnormalities, which may contribute to the increased risk of sudden cardiac death in this disorder. We studied whether electrocardiographic repolarization changes are already detectable in mild LVM increase associated with hypertension. Methods In 220 men (mean age 51 ± 6 years) attending the GENRES hypertension study, we measured QT intervals (QTend and QTpeak), T-wave peak to T-wave end (TPE) intervals, and novel T-wave morphology parameters (principal component analysis ratio, T-wave morphology dispersion, total cosine R-to-T, and T-wave residuum) from a digital standard 12-lead electrocardiogram, and related them to echocardiographically determined LVM. Results In this group of moderately hypertensive men, the mean LVM index (LVMI; LVM divided by body surface area) was 99 ± 19 g/m2, with only 18% of the subjects showing evidence of echocardiographic LVH (LVMI > 116 g/m2). LVMI correlated significantly with QT intervals (r = 0.16–0.21, P = 0.018–0.002), TPE intervals (r = 0.23–0.27, P < 0.001), and T-wave morphology parameters (r = 0.22–0.39, P < 0.001). Except for the QTpeak interval, the relationship between LVMI and electrocardiographic repolarization parameters was independent in multivariate analyses. Conclusion Altered electrocardiographic ventricular repolarization, indicating reduced repolarization reserve and possibly increased repolarization heterogeneity, is already present in hypertensive men with only mild LVM increase. At a population level, this may carry important risk implications for the large group of hypertensive patients.

Common genetic variation of β1- and β2-adrenergic receptor and response to four classes of antihypertensive treatment

Varying results have been reported on the association of β-adrenergic receptor polymorphisms with blood pressure (BP) response to β-blockers. We investigated the influence of ADRB1 Ser49Gly and Arg389Gly, and ADRB2 Gly16Arg and Glu27Gln polymorphisms on ambulatory BP response to bisoprolol and three other antihypertensive drug monotherapies in a placebo-controlled, double-blind, cross-over study with 233 moderately hypertensive men. ADRB1 Ser49Ser homozygotes tended to have a better ambulatory BP response to bisoprolol but the difference was statistically nonsignificant. ADRB1 Arg389Arg homozygotes did not show better BP response to bisoprolol than the other genotypes. There were no significant associations of ADRB2 polymorphisms with BP responses to any of the study drugs. The results from this controlled study in hypertensive men do not support clinical use of common polymorphisms in ADRB1 and ADRB2 in predicting BP responses to β-blockers or to three other antihypertensive drugs.

Renin–Angiotensin System and α-Adducin Gene Polymorphisms and Their Relation to Responses to Antihypertensive Drugs: Results From the GENRES Study

BACKGROUND Polymorphisms in genes coding for components of the renin-angiotensin system (RAS) and alpha-adducin (ADD1) have been reported to be associated with blood pressure (BP) responses to antihypertensive agents. The results, however, have not been consistent and most of the earlier studies have been small and lacked placebo-control. Therefore, the association of common polymorphisms in these genes with BP responses to four different antihypertensive drugs was analyzed in a controlled study. METHODS The study included 208 hypertensive Finnish men from the GENRES study. All of them used amlodipine 5 mg, bisoprolol 5 mg, hydrochlorothiazide (HCT) 25 mg, and losartan 50 mg daily, each for 4 weeks as a monotherapy in a double-blind, randomized, study. The treatment periods were separated by 4-week placebo periods. Both 24-h ambulatory (ABP) and office BP (OBP) measurements were carried out. The polymorphisms analyzed were ADD1 Gly460Trp, angiotensinogen (AGT) Met235Thr, angiotensin converting enzyme (ACE) insertion/deletion (I/D), and angiotensin II type 1 receptor (AGTR1) 1166A/C. RESULTS The presence of 460Trp allele of ADD1, previously suggested to be a marker of thiazide responsiveness, did not predict a better response to HCT. There was no significant association of AGT Met235Thr, ACE I/D, and AGTR1 1166A/C polymorphisms with BP responses to the study drugs. ADD1 460Trp and AGT 235Thr alleles were associated with higher systolic white coat effect (WCE) during the placebo periods (P values 0.03 and 0.01, respectively). CONCLUSIONS Common polymorphisms of ADD1, AGT, ACE, and AGTR1 do not markedly predict BP responses to amlodipine, bisoprolol, HCT, and losartan, at least in white hypertensive men.

Common genetic variations of the renin-angiotensin-aldosterone system and response to acute angiotensin I-converting enzyme inhibition in essential hypertension

Objective In order to get insight into possible genetic determinants of antihypertensive drug action, we analysed the relations between polymorphisms of the genes of the renin–angiotensin–aldosterone system and acute effects of ACE inhibition on blood pressure as well as circulating renin and aldosterone levels in hypertensive patients. Methods A total of 315 hypertensive patients referred for problems in drug treatment were given a single 50 mg dose of captopril. Plasma renin and aldosterone were measured before and 60 min after the drug administration. Four DNA variants, including angiotensin type I receptor (AGTR1) 1166 A/C, angiotensin-converting enzyme (ACE) I/D, angiotensinogen (AGT) M235T and AGT –217 G/A, were genotyped in the patients and normotensive men (n = 175). A replication study on the relation between AGTR1 1166 A/C and plasma renin and aldosterone levels was carried out in the 244 hypertensive men of the pharmacogenetic GENRES Study. Results Referred hypertensive patients with the AGTR1 CC genotype had higher aldosterone at baseline (P = 0.02) and after 60 min of captopril administration (P = 0.01) compared with the AA genotype. Replicate analysis in the GENRES patients showed a similar trend. When the two studies were combined (315 and 244 patients, respectively), plasma aldosterone level (P = 0.007) as well as aldosterone/renin ratio (P = 0.04) were significantly higher in the CC genotype (n = 13) than in the AA genotype (n = 370). Transfection studies in cultured HEK293 cells indicated that the 1166C allele was associated with higher mRNA levels than the 1166A allele. Conclusion The AGTR1 1166C allele when present in homozygous form may be associated with a form of essential hypertension characterized by high plasma aldosterone and low plasma renin levels, possibly due to increased AGTR1 mRNA levels and augmented angiotensin II action.

CYP2C9 genotype modifies activity of the renin-angiotensin-aldosterone system in hypertensive men.

Background Two variants of the CYP2C9 gene, CYP2C9*2 and CYP2C9*3, have been indicated to have impaired enzyme function, and thus suspected to reduce the formation of the active metabolite of losartan. Cytochrome P450 (CYP) enzymes are also involved in eicosanoid biosynthesis and regulation of blood pressure (BP) and sodium homeostasis. Methods We studied the impact of these variants on BP response to losartan and three other antihypertensive drugs and on baseline indicators of the activity of the renin–angiotensin–aldosterone system. The participants were 217 moderately hypertensive Finnish men that participated in the double-blind, cross-over, placebo-controlled GENRES Study. Results BP responses to losartan did not differ between CYP2C9*2 or CYP2C9*3 allele carriers and CYP2C9*1*1 patients. A suggestive finding of less pronounced ambulatory BP response to losartan in CYP2C9*1*3 patients with low–normal kidney function was made. At baseline of the GENRES Study, CYP2C9*1*3 patients had significantly lower plasma renin activity and aldosterone levels than CYP2C9*1*1 patients (both P values 0.004). In a replication study in patients with treatment-resistant hypertension, men with CYP2C9*3 allele also had lower plasma renin activity (P = 0.03) and aldosterone levels (P = 0.18). In addition, these men had attenuated renin and aldosterone responses in captopril challenge test (P = 0.29 and 0.006, respectively). Conclusion The CYP2C9*3 allele was associated with lower activity of the renin–angiotensin–aldosterone system in hypertensive men, which may reflect a more efficient sodium reabsorption capacity. CYP2C9*2 and CYP2C9*3 alleles do not influence the antihypertensive effect of losartan in men with essential hypertension and normal kidney function.

STK39 variation predicts the ambulatory blood pressure response to losartan in hypertensive men.

Large-scale genome-wide association studies (GWASs) have identified significant associations of common genetic variants with blood pressure (BP) levels. To obtain more evidence for the role of these variants in BP regulation, we studied their association with BP responses to four different antihypertensive drug monotherapies. We selected 19 single-nucleotide variants based on data from five GWASs. The study group consisted of more than 200 hypertensive Finnish men from the GENRES study. Ambulatory BP responses to 4-week treatments with losartan, bisoprolol, hydrochlorothiazide and amlodipine were the primary targets of the study. Secondarily, baseline indicators of the activity of the renin–angiotensin–aldosterone system were studied. After correction for multiple comparisons, the variant rs6749447 in the STK39 gene was significantly associated with BP responses. Thus, the minor rs6749447 allele was associated with a lower systolic and diastolic BP response to losartan (P=0.0005 and 0.0002, respectively). rs6749447 minor allele homozygotes had marginally higher serum aldosterone/plasma renin activity (PRA) ratios (P=0.04) than those without this allele. In a replication study on aldosterone and renin levels, another cohort of hypertensive patients (n=311) showed a similar trend. When the two cohorts were combined, the aldosterone level (P=0.02) and the aldosterone/PRA ratio (P=0.01) were higher in subjects homozygous for the minor rs6749447 allele than in other subjects. The present study shows that pharmacogenetic approaches may provide evidence that complements systematic genome-wide strategies by identifying gene loci that not only affect the BP level but also might modify its response to pharmacologic interventions.

Short-term electrophysiological effects of losartan, bisoprolol, amlodipine, and hydrochlorothiazide in hypertensive men

Background and aim. Hypertension-induced left ventricular structural remodelling associates with repolarization abnormalities. We investigated if antihypertensive drugs can modulate ventricular repolarization. Methods. A total of 183 hypertensive men received for 4 weeks drugs (losartan 50 mg, bisoprolol 5 mg, amlodipine 5 mg, hydrochlorothiazide (HCTZ) 25 mg) in a randomized order, separated by 4-week placebo periods. Electrocardiograms (ECG) were recorded at the end of placebo and drug periods. Measurements of repolarization duration (QT intervals), repolarization heterogeneity (T-wave peak to T-wave end (TPE) intervals), and T-wave morphology (T-wave principal component analysis (PCA) ratio, T-wave morphology dispersion (TMD), and total cosine R-to-T (TCRT)) during each drug were compared to placebo measurements. Results. Losartan and bisoprolol shortened maximum and mean rate-adjusted QT intervals as well as mean TPE interval, decreased TMD, and increased TCRT. Losartan also shortened precordial maximum TPE interval and decreased PCA ratio. Amlodipine had no repolarization effects, whereas HCTZ prolonged precordial maximum TPE interval and mean TPE interval. Conclusion. Losartan and bisoprolol have beneficial short-term ECG repolarization effects. Amlodipine seems to have no repolarization effects. HCTZ seems to prolong the ECG TPE interval, potentially reflecting increased repolarization heterogeneity. These findings show that antihypertensive drugs may relatively rapidly and treatment-specifically modulate ECG markers of ventricular repolarization.

Licorice-induced hypertension and common variants of genes regulating renal sodium reabsorption

Abstract Aim. To study if gene alterations affecting renal sodium reabsorption associate with susceptibility to licorice-induced hypertension. Methods. Finnish subjects (n = 30) with a previously documented incident of licorice-induced hypertension were recruited for the study using a newspaper announcement. Their previous clinical and family histories as well as serum electrolyte levels were examined. DNA samples from all individuals were screened for variants of the genes encoding 11β-hydroxysteroid dehydrogenase type 2 (11βHSD2) and α-, β-, and γ-subunits of the epithelial sodium channel (ENaC). Results. Upon licorice predisposition, the patients had a mean blood pressure of 201/118 mmHg. Circulating potassium, renin, and aldosterone levels were low. No significant DNA variations were identified in the 11βHSD2 gene. Four subjects were heterozygous for β- and γENaC variants previously shown to be associated with hypertension. Furthermore, a novel G insertion (2004–2005insG) in the SCNN1A gene encoding the αENaC was identified in two subjects. The frequency of these ENaC variants was significantly higher in subjects with licorice-induced hypertension (6/30 i.e. 20%) than in blood donors (11/301 i.e. 3.7%, P = 0.002). Conclusions. Defects of the 11βHSD2 gene do not constitute a likely cause for licorice-induced hypertension. Variants of the ENaC subunits may render some individuals sensitive to licorice-induced metabolic alterations and hypertension.