Methylation of adrenergic 1 receptor is a potential epigenetic mechanism controlling antihypertensive response to metoprolol.

Although metoprolol is used to treat hypertension, clinical responses are variable and unpredictable. Evidence suggests that adrenergic 1 receptor (ADRB1, designated Adrb1 in rodents) gene polymorphisms influence the level of blood pressure response to this drug therapy, but their presence can not predict the response of the individual patient. The question exists whether epigenetic modifications, such as DNA methylation could cause changes in the gene’s expression that are a determining factor in metoprolol’s efficacy. The aim of this study was to verify whether DNA methylation could change the expression of the ADRB1 gene, and epigenetic modification could explain why individuals with identical ADRB1 gene polymorphisms have different antihypertensive responses to metoprolol. H9c2 rat myocardial cells in vitro were randomly divided into 5-aza-2'-deoxycytidine (decitabine)-treated (0.5 to 10.0 μM) and control groups. For the in vivo experiments, 45 spontaneously hypertensive rats (SHRs) were divided into metoprolol-treated and control groups, and after a 4-week intervention myocardia were harvested. Genomic methylation-sensitive PCR was used to assess the methylation status of the Adrb1 promoter after DNA extraction from H9c2 cells and SHR myocardia. Real-time fluorescent quantitative RT-PCR was used to determine levels of Adrb1 mRNA. In H9c2 cells, the least degree of methylation was observed in the 5.0 μM decitabine treated group. Prolonged exposure of cells to 5.0 μM decitabine resulted in downregulating methylation of the Adrb1 promoter. Increased levels of Adrb1 mRNA of the 5.0 μM group demonstrated that this concentration resulted in the highest expression. Accordingly, DNA methylation resulted in the downregulation of Adrb1 transcription. In vivo, the lower level of methylation of the Adrb1 promoter from SHR myocardial samples demonstrated a better antihypertensive effect by metoprolol. The expression of Adrb1 mRNA in the effective group of SHRs was significantly upregulated. In conclusion, as shown in both H9c2 cells and SHRs, downregulated methylation of the Adrb1 promoter is likely to improve the antihypertensive efficacy of metoprolol.

Polymorphism of beta 3-adrenergic receptor gene and glycogen synthetase gene in polycystic ovary syndrome

To examine the association of polymorphisms of B3-adrenergic receptor and glycogen synthetase gene with obesity and insulin resistance in women with polycystic ovary.subfertile women with PCOS, n=43 [group I] were compared to matched age group of normoovulatory women [control group II [n=20]. Both groups were further subdivided according to Body mass index [BMI] into obese and non obese participants. Ultrasound examination and blood sampling were done and fasting blood glucose, insulin resistance, total cholesterol, and triglycerides were estimated. Trp64Arg polymorphism of the ADRB3 and A1Ae polymorphism of the GS gene were determined by PCR-RFLP analysis. The frequency of Trp64Arg variant was significantly higher in obese PCOS women [24%] compared with obese control group [0%]; p=0.044. A major effect of the Trp64Arg variant on insulin resistance [HOMA-IR] could not be demonstrated. On the other side, all women were normal for the glycogen synthetase gene [A1A1] whether obese or non obese, whether PCO or normoovulatory. Association between polycystic ovary and polymorphism of ADRB3 gene was found to be of high significance [Odds Ratio=10.03, 95% CI=2.73 to 36.72] p=0.00054. An association between Trp64Arg genetic variant and obesity in PCOS women was demonstrated. Polymorphism of glycogen synthetase does not appear to be higher in PCOS women compared to controls and it can be used as a marker for PCOS women