The expression level of myocardial β1-adrenergic receptor affects metoprolol antihypertensive effects: A novel mechanism for interindividual difference

Impact of CYP2D6 and ADRB1 polymorphisms on heart rate of post-PCI patients treated with metoprolol

Aim: To explore the effect of CYP2D6*10 (100C > T) and ADRB1 1165 G > C polymorphisms on heart rate of post-PCI (percutaneous coronary intervention) patients treated with metoprolol succinate sustained-release tablets. Methods: A total of 756 inpatients with metoprolol succinate sustained-release tablets were selected and the genotypes of CYP2D6*10 and ADRB1 1165G > C were detected in 319 patients using gene chip detection. The target heart rate was defined as a resting heart rate < 70 beats/min. Clinical data were collected. Results: A total of 319 inpatients were enrolled in the study. The mutant allele frequencies of CYP2D6 and ADRB1 were 57.21 and 69.44%, respectively. Whatever the dose of metoprolol, the heart rates were lower in patients with homozygous mutation of CYP2D6 than those with heterozygous mutation and wild-type (p < 0.05). Nevertheless, this effect was not seen between different genotypes of ADRB1. Logistic regression analysis showed that the dose of metoprolol and the genotypes of CYP2D6 were predictors of heart rate <70 beats/min in these patients. Further multivariate analysis indicated that patients with homozygous mutation had better control of heart rates compared with those with wild-type and heterozygous mutation of CYP2D6*10 genotypes (all: p < 0.001). Conclusion:CYP2D6*10 polymorphisms were associated with the heart rate of post-PCI patients treated with metoprolol succinate sustained-release tablets.

mRNA expression profile in peripheral blood mononuclear cells based on ADRB1 Ser49Gly and Arg389Gly polymorphisms in essential hypertension - a case-control pilot investigation in South Indian population

BACKGROUND

β1-Adrenoreceptor (ADRB1) genetic polymorphisms are widely studied for susceptibility to many cardiovascular diseases such as essential hypertension. However, the mRNA expression of ADRB1 is rarely studied.

METHODS

A case-control pilot study with 292 hypertensives and 324 controls was designed to evaluate the role of the Ser49Gly and Arg389Gly, which are commonly studied single nucleotide polymorphisms (SNP), in the mRNA levels of ADRB1, in conjunction with its genetic predisposition to essential hypertension.

RESULTS

Differential expression of ADRB1 mRNA was seen between hypertensives and controls (p<0.01) based on genetic variants of Ser49Gly. Among hypertensive subjects, Ser49Ser and Gly49Gly were highly expressed in comparison to Ser49Gly (p<0.05 and p<0.01, respectively), whereas genetic variants of Arg389Gly did not demonstrate any such variations. We found no association between the ADRB1 SNPs viz., Ser49Gly and Arg389Gly and essential hypertension.

CONCLUSIONS

The increased mRNA levels of Gly49Gly may indicate a plausible role in the interindividual variations in drug response. Further, ADRB1 polymorphisms did not contribute to the genetic risk of essential hypertension. Studies with larger sample size are warranted to confirm these observations in the South Indian population.

The Association of ADRB1 and CYP2D6 Polymorphisms With Antihypertensive Effects and Analysis of Their Contribution to Hypertension Risk

BACKGROUND

Genetic factors have a vital influence on the pathogenesis of hypertension. In this retrospective study, we aimed to evaluate the association of ADRB1 and CYP2D6 polymorphisms with antihypertensive effects and perform an analysis of their contribution to hypertension risk.

METHODS

A total of 261 healthy individuals and 261 essential hypertension patients treated with metoprolol for 12 weeks were enrolled. ADRB1 and CYP2D6 genotypes were identified by xTAG liquid chip technology. We used multivariate logistic regression and a generalized linear mixed model to assess hypertension-related risk factors.

RESULTS

The allele frequencies of ADRB1 and CYP2D6 variants were 59.8% and 64.6% in the essential hypertension group and 70.3% and 65.9% in the controls, respectively. The genotype and allele distribution of ADRB1 were significantly different between the 2 groups (P < 0.05), but there was no significant difference in CYP2D6 distribution (P = 0.91 and 0.88). By logistic regression analysis, high fasting plasma glucose, smoking, high triglyceride and the Gly/Gly polymorphism in Arg389Gly ADRB1 all emerged as independent risk factors for hypertension. Additionally, the ADRB1 genotype played a major role in the antihypertensive effect of metoprolol and the patients with the Gly389Gly genotype showed a significantly better response to metoprolol than did those with a heterozygous ADRB1 mutation (Arg389Gly) (P = 0.027).

CONCLUSIONS

The results demonstrate that Gly/Gly polymorphism in Arg389Gly ADRB1 was an independent risk factor together with high fasting plasma glucose, smoking and high triglyceride; moreover, the patients who carried the Gly389Gly genotype had a significantly improved metoprolol antihypertensive effect than those with ADRB1.

Downregulation of the β1 adrenergic receptor in the myocardium results in insensitivity to metoprolol and reduces blood pressure in spontaneously hypertensive rats

The β1‑adrenergic receptor (AR) is the primary β‑AR subtype in the heart and is the target of metoprolol (Met), which is commonly used to treat angina and hypertension. Previous studies have revealed a positive correlation between the methylation levels of the adrenoreceptor β1 gene (Adrb1) promoter in the myocardium with the antihypertensive activity of Met in spontaneously hypertensive rats (SHR), which affects β1‑AR expression in H9C2 cells. The aim of the present study was to investigate the effects of myocardial β1‑AR downregulation using short‑hairpin RNA (shRNA) against Adrb1 on the antihypertensive activity of Met in SHR. Recombinant adeno‑associated virus type 9 (rAAV9) vectors carrying Adrb1 shRNA (rAAV9‑Adrb1) or a negative control sequence (rAAV9‑NC) were generated and used to infect rat hearts via the pericardial cavity. The results of reverse transcription‑quantitative polymerase chain reaction, immunohistochemistry and western blotting analyses demonstrated that cardiac β1‑AR expression in the rAAV9‑Adrb1 group was significantly downregulated when compared with the rAAV9‑NC group (P<0.001, P<0.001 and P=0.032, respectively). In addition, a greater reduction in systolic blood pressure (SBP) was observed in the rAAV9‑NC group compared with the rAAV9‑Adrb1 group following Met treatment (P=0.035). Furthermore, downregulation of myocardial β1‑AR was associated with a significant decrease in SBP (P<0.001). In conclusion, these data suggest that suppression of β1‑AR expression in the myocardium reduces SBP and sensitivity to Met in SHR.

Pharmacoepigenetics: an element of personalized therapy?

INTRODUCTION

Epigenetics is a rapidly growing field describing heritable alterations in gene expression that do not involve DNA sequence variations. Advances in epigenetics and epigenomics have influenced pharmacology, leading to the development of a new specialty, pharmacoepigenetics, the study of the epigenetic basis for the individual variation in drug response. Areas covered: We present an overview of the major epigenetic mechanisms and their effects on the expression of drug metabolizing enzymes and drug transporters, as well as the epigenetic status of drug protein targets affecting therapy response. Recent advances in the development of pharmacoepigenetic biomarkers and epidrugs are also discussed. Expert opinion: There is growing evidence that pharmacoepigenetics has the potential to become an important element of personalized medicine. Epigenetic modifications influence drug response, but they can also be modulated by drugs. Moreover, they can be monitored not only in the affected tissue, but also in body fluids. Nevertheless, there are very few examples of epigenetic biomarkers implemented in the clinical setting. Explanation of the interplay between genomic and epigenomic changes will contribute to the personalized medicine approach. Ultimately, both genetic biomarkers and epigenetic mechanisms should be taken into consideration in predicting drug response in the course of successful personalized therapy.

Associations between ADRB1 and CYP2D6 gene polymorphisms and the response to β-blocker therapy in hypertension

OBJECTIVE

To investigate the associations between β1-adrenergic receptor (ADRB1) and cytochrome P450 2D6 (CYP2D6) gene polymorphisms and β-blocker treatment outcomes in patients with hypertension.

METHODS

Chinese patients with essential hypertension were treated with the β-blocker metoprolol and followed up for 12 weeks. xTAG® liquid-chip technology was used for CYP2D6 100 C > T and ADRB1 1165G > C genotyping. Associations between gene polymorphisms and antihypertensive therapy outcomes were assessed by generalized linear model fitting. A decrease of ≥ 10 mmHg in systolic blood pressure indicated an effective treatment outcome.

RESULTS

A total of 93 patients were included in the study. Mutant allele frequencies of 61.29% and 58.60% were obtained for ADRB1 and CYP2D6, respectively. There was no significant interaction between the effects of ADRB1 and CYP2D6 gene polymorphisms on treatment outcome. Patients homozygous for the mutant ADRB1 genotype (CC) had better treatment outcomes than those heterozygous for the mutation (GC). Interestingly, β-blocker treatment duration was an independent factor associated with treatment outcome.

CONCLUSIONS

The ADRB1 1165G > C gene polymorphism and β-blocker treatment duration are independent factors associated with β-blocker treatment outcome. These findings suggest that the selection of antihypertensive therapy should take into consideration the patient's genotype.