GNAS gene variants affect β-blocker-related survival after coronary artery bypass grafting

Inhibition of β1-AR/Gαs signaling promotes cardiomyocyte proliferation in juvenile mice through activation of RhoA-YAP axis

The regeneration potential of the mammalian heart is incredibly limited, as cardiomyocyte proliferation ceases shortly after birth. β-adrenergic receptor (β-AR) blockade has been shown to improve heart functions in response to injury; however, the underlying mechanisms remain poorly understood. Here, we inhibited β-AR signaling in the heart using metoprolol, a cardio-selective β blocker for β1-adrenergic receptor (β1-AR) to examine its role in heart maturation and regeneration in postnatal mice. We found that metoprolol enhanced cardiomyocyte proliferation and promoted cardiac regeneration post myocardial infarction, resulting in reduced scar formation and improved cardiac function. Moreover, the increased cardiomyocyte proliferation was also induced by the genetic deletion of Gnas, the gene encoding G protein alpha subunit (Gαs), a downstream effector of β-AR. Genome wide transcriptome analysis revealed that the Hippo-effector YAP, which is associated with immature cardiomyocyte proliferation, was upregulated in the cardiomyocytes of β-blocker treated and Gnas cKO hearts. Moreover, the increased YAP activity is modulated by RhoA signaling. Our pharmacological and genetic studies reveal that β1-AR-Gαs-YAP signaling axis is involved in regulating postnatal cardiomyocyte proliferation. These results suggest that inhibiting β-AR-Gαs signaling promotes the regenerative capacity and extends the cardiac regenerative window in juvenile mice by activating YAP-mediated transcriptional programs.

Polymorphic Variants in the GRK5 Gene Promoter Are Associated With Diastolic Dysfunction in Coronary Artery Bypass Graft Surgery Patients

BACKGROUND

The G-protein-coupled receptor kinase 5 (GRK5) is a mediator of cardiovascular homeostasis and participates in inflammation and cardiac fibrosis, both being involved in the development of diastolic dysfunction (DD). While mechanisms of transcriptional regulation of the GRK5 promoter are unclear, we tested the hypotheses, that (1) GRK5 expression varies depending on functional single nucleotide polymorphisms (SNPs) in the GRK5 promoter and (2) this is associated with DD in patients undergoing coronary artery bypass graft (CABG) surgery.

METHODS

We amplified and sequenced the GRK5 promoter followed by cloning, reporter assays, and electrophoretic mobility shift assays (EMSA). GRK5 messenger ribonucleic acid (mRNA) expression was determined in right atrial tissue sampled from 50 patients undergoing CABG surgery. In another prospective study, GRK5 genotypes were associated with determinants of diastolic function using transesophageal echocardiography in 255 patients with CABG with normal systolic left ventricular (LV) function. Specifically, we measured ejection fraction (EF), transmitral Doppler early filling velocity (E), tissue Doppler early diastolic lateral mitral annular velocity (E' lateral), and calculated E/E', E' norm and the difference of E' lateral and E' norm to account for age-related changes in diastolic function.

RESULTS

We identified 6 SNPs creating 3 novel haplotypes with the greatest promoter activation in haplotype tagging (ht) SNP T(-678)C T-allele constructs (P < .001). EMSAs showed allele-specific transcription factor binding proving functional activity. GRK5 mRNA expression was greatest in TT genotypes (TT: 131 fg/µg [95% CI, 108-154]; CT: 109 [95% confidence interval {CI}, 93-124]; CC: 83 [95% CI, 54-112]; P = .012). Moreover, GRK5 genotypes were significantly associated with determinants of diastolic function. Grading of DD revealed more grade 3 patients in TT compared to CT and CC genotypes (58% vs 38% vs 4%; P = .023). E´ lateral was lowest in TT genotypes (P = .007) and corresponding E/E' measurements showed 1.27-fold increased values in TT versus CC genotypes (P = .01), respectively. While E' norm values were not different between genotypes (P = .182), the difference between E' lateral and E' norm was significantly higher in TT genotypes compared to CC and CT genotypes (-1.2 [interquartile range {IQR}, 2.7], -0.5 [IQR, 3.4], and -0.4 [IQR, 4.2; P = .035], respectively).

CONCLUSIONS

A functional GRK5 SNP results in allele-dependent differences in GRK5 promoter activity and mRNA expression. This is associated with altered echocardiographic determinants of diastolic function. Thus, SNPs in the GRK5 promoter are associated with altered perioperative diastolic cardiac function. In the future, preoperative testing for these and other SNPs might allow to initiate more specific diagnostic and perioperative pathways to benefit patients at risk.

Quality Control Measures and Validation in Gene Association Studies: Lessons for Acute Illness

Acute illness is a complex constellation of responses involving dysregulated inflammatory and immune responses, which are ultimately associated with multiple organ dysfunction. Gene association studies have associated single-nucleotide polymorphisms (SNPs) with clinical and pharmacological outcomes in a variety of disease states, including acute illness. With approximately 4 to 5 million SNPs in the human genome and recent studies suggesting that a large portion of SNP studies are not reproducible, we suggest that the ultimate clinical utility of SNPs in acute illness depends on validation and quality control measures. To investigate this issue, in December 2018 and January 2019 we searched the literature for peer-reviewed studies reporting data on associations between SNPs and clinical outcomes and between SNPs and pharmaceuticals (i.e., pharmacogenomics) published between January 2011 to February 2019. We review key methodologies and results from a variety of clinical and pharmacological gene association studies, including trauma and sepsis studies, as illustrative examples on current SNP association studies. In this review article, we have found three key points which strengthen the potential accuracy of SNP association studies in acute illness and other diseases: providing evidence of following a protocol quality control method such as the one in Nature Protocols or the OncoArray QC Guidelines; enrolling enough patients to have large cohort groups; and validating the SNPs using an independent technique such as a second study using the same SNPs with new patient cohorts. Our survey suggests the need to standardize validation methods and SNP quality control measures in medicine in general, and specifically in the context of complex disease states such as acute illness.

Genetic variations in G-protein signal pathways influence progression of coronary artery calcification: Results from the Heinz Nixdorf Recall study

BACKGROUND AND AIMS

Coronary artery calcification (CAC) is one of the most sensitive and specific markers of coronary atherosclerosis and believed to be heritable. We hypothesized that functionally relevant single-nucleotide polymorphisms (SNPs) in the G-protein signal pathway, which have been previously related to coronary artery disease, are associated with CAC progression.

METHODS

3108 participants from the Heinz Nixdorf Recall study with CAC measurements at both baseline (CACb) and 5-year follow-up (CAC5y) were included. We genotyped SNPs rs1042714 (ADRB2), rs6026584 and rs12481583 (GNAS), and rs5443 (GNB3) and defined a priori risk alleles derived from literature data. Regression analyses were applied to measures of 5-year CAC progression, unadjusted, adjusted for age, sex, and adjusted for age, sex, log(CACb+1) as well as for cardiovascular risk factors.

RESULTS

The presence of one or more risk alleles was associated with a 26.9% (95% CI 5.5-52.4) increase in 5-year CAC progression (p = 0.011) and a 29.2% (95% CI 5.9-57.6) accelerated increase of CAC over the 5-year period compared to what was expected with respect to the baseline CAC percentile value (p = 0.012). Each of those risk alleles increased the 5-year CAC progression by 4.4% (95% CI 1.3-7.6, p = 0.006) and resulted in a 4.9% accelerated increase of CAC over the 5-year period (95% CI 1.6-8.4, p = 0.004). These unadjusted data did not change after adjustment.

CONCLUSIONS

Genetic variations in the G-protein signal pathway are associated with CAC progression in a cumulative fashion, indicating the importance of the pathway for genetic heritability in CAC progression and coronary artery disease.

GNAQ TT(-695/-694)GC Polymorphism Is Associated with Increased Gq Expression, Vascular Reactivity, and Myocardial Injury after Coronary Artery Bypass Surgery

BACKGROUND

Angiotensin II receptor type 1-mediated activation of the α-subunit of the heterotrimeric Gq protein evokes increased vasoconstriction and may promote hypertrophy-induced myocardial damage. The authors recently identified a TT(-695/-694)GC polymorphism in the human Gq promoter, the GC allele being associated with an increased prevalence of cardiac hypertrophy. In this article, the authors tested whether the TT(-695/-694)GC polymorphism is associated with differences in (1) myocardial Gq protein expression, (2) vascular reactivity, and (3) myocardial damage after coronary artery bypass grafting.

METHODS

Gq protein expression was measured in right atrial muscle from 55 patients undergoing coronary artery bypass grafting as were skin perfusion changes (n = 18; laser Doppler imaging), saphenous vein ring vascular reactivity (n = 50, organ bath) in response to angiotensin II, and myocardial damage (227 patients undergoing coronary artery bypass grafting), as assessed by postoperative cardiac troponin I concentration.

RESULTS

Myocardial Gq expression was greater in GC/GC genotypes (GC/GC vs.

TT/TT

1.27-fold change; P = 0.006). Skin perfusion after intradermal angiotensin II injection decreased only in GC/GC genotypes (P = 0.0002). Saphenous vein rings exposed to increasing angiotensin II concentrations showed an almost doubled maximum contraction in GC/GC compared with individuals with the TT/TT genotype (P = 0.022). In patients undergoing coronary artery bypass grafting, baseline cardiac ejection fraction was different (GC/GC: 55 ± 13%; GC/TT: 54 ± 14%; TT/TT: 48 ± 15%; P = 0.037) and postoperative peak cardiac troponin I was greater in patients with the GC/GC (11.5 ± 13.8 ng/ml) than in patients with the GC/TT (9.2 ± 9.2 ng/ml) or patients with the TT/TT genotype (6.6 ± 4.8 ng/ml, P = 0.015).

CONCLUSIONS

The GC/GC genotype of the TT(-695/-694)GC polymorphism is associated with increased Gq protein expression, augmented angiotensin II receptor type 1-related vasoconstriction, and increased myocardial injury after coronary artery bypass grafting, highlighting the impact of Gq genotype variation.

Polymorphisms in the GNAS Gene as Predictors of Ventricular Tachyarrhythmias and Sudden Cardiac Death: Results From the DISCOVERY Trial and Oregon Sudden Unexpected Death Study

Background

Population‐based studies suggest that genetic factors contribute to sudden cardiac death (SCD).

Methods and Results

In the first part of the present study (Diagnostic Data Influence on Disease Management and Relation of Genetic Polymorphisms to Ventricular Tachy‐arrhythmia in ICD Patients [DISCOVERY] trial) Cox regression was done to determine if 7 single‐nucleotide polymorphisms (SNPs) in 3 genes coding G‐protein subunits (GNB3, GNAQ, GNAS) were associated with ventricular tachyarrhythmia (VT) in 1145 patients receiving an implantable cardioverter‐defibrillator (ICD). In the second part of the study, SNPs significantly associated with VT were further investigated in 1335 subjects from the Oregon SUDS, a community‐based study analyzing causes of SCD. In the DISCOVERY trial, genotypes of 2 SNPs in the GNAS gene were nominally significant in the prospective screening and significantly associated with VT when viewed as recessive traits in post hoc analyses (TT vs CC/CT in c.393C>T: HR 1.42 [CI 1.11‐1.80], P=0.005; TT vs CC/CT in c.2273C>T: HR 1.57 [CI 1.18‐2.09], P=0.002). TT genotype in either SNP was associated with a HR of 1.58 (CI 1.26‐1.99) (P=0.0001). In the Oregon SUDS cohort significant evidence for association with SCD was observed for GNAS c.393C>T under the additive (P=0.039, OR=1.21 [CI 1.05‐1.45]) and recessive (P=0.01, OR=1.52 [CI 1.10‐2.13]) genetic models.

Conclusions

GNAS harbors 2 SNPs that were associated with an increased risk for VT in ICD patients, of which 1 was successfully replicated in a community‐based population of SCD cases. To the best of our knowledge, this is the first example of a gene variant identified by ICD VT monitoring as a surrogate parameter for SCD and also confirmed in the general population.

Clinical Trial Registration

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00478933.

Genetic Polymorphisms in Endothelin-1 as Predictors for Long-Term Survival and the Cardiac Index in Patients Undergoing On-Pump Cardiac Surgery

Genetic variants within the endothelin-1 gene (EDN1) have been associated with several cardiovascular diseases and may act as genetic prognostic markers. Here, we explored the overall relevance of EDN1 polymorphisms for long-term survival in patients undergoing on-pump cardiac surgery. A prospectively collected cohort of 455 Caucasian patients who underwent cardiac surgery with cardiopulmonary bypass was followed up for 5 years. The obtained genotypes and inferred haplotypes were analyzed for their associations with the five-year mortality rate (primary endpoint). The EDN1 T-1370G and K198N genotype distributions did not deviate from Hardy–Weinberg equilibrium and the major allele frequencies were 83% and 77%, respectively. The cardiovascular risk factors were equally distributed in terms of the different genotypes and haplotypes associated with the two polymorphisms. The five-year mortality rate did not differ among the different EDN1 T-1370G and K198N genotypes and haplotypes. Haplotype analysis revealed that carriers of the G-T (compound EDN1 T-1370G G/K198N T) haplotype had a higher cardiac index than did non-carriers (p = 0.0008); however, this difference did not reach significance after adjusting for multiple testing. The results indicate that common variations in EDN1 do not act as prognostic markers for long-term survival in patients undergoing on-pump cardiac surgery.

Noteworthy articles in 2014 for cardiothoracic anesthesiologists

In 2014, cardiothoracic anesthesiology again generated high-quality scientific work published in highly regarded journals. Our specialty continues to make significant strides in the creation and implementation of protocols to improve outcomes in our patients, which undoubtedly contribute to a safer hospital environment for patients and employees alike. Another theme that stirred a lot of interest in the past year is the search for patient-centered treatment plans. Even though we are still some time away from truly personalized medicine, our specialty starts to ask and answer exciting questions: Would we treat patient A any different from patient B if their genetic profiles were easily accessible? Could individualized treatment choices influence our patients' immediate and long-term outcomes? For this review, we selected a sample of relevant contributions to the field of cardiothoracic anesthesiology in 2014 with potential impact on our clinical routine.