The rs9982601 polymorphism of the region between the SLC5A3/MRPS6 and KCNE2 genes associated with a prevalence of myocardial infarction and subsequent long-term mortality

Genetic Variants Relate to Fasting Plasma Glucose, 2-Hour Postprandial Glucose, Glycosylated Hemoglobin, and BMI in Prediabetes

Diabetes mellitus (DM) is a chronic disease that seriously threatens human health. Prediabetes is a stage in the progression of DM. The level of clinical indicators including fasting plasma glucose (FPG), 2-h postprandial glucose (2hPG), and glycosylated hemoglobin (HbA1C) are the diagnostic markers of diabetes. In this genome-wide association study (GWAS), we aimed to investigate the association of genetic variants with these phenotypes in Hainan prediabetes. In this study, we recruited 451 prediabetes patients from the residents aged ≥18 years who participated in the National Diabetes Prevalence Survey of the Chinese Medical Association in 2017. The GWAS of FPG, 2hPG, HbA1C, and body mass index (BMI) in prediabetes was analyzed with a linear model using an additive genetic model with adjustment for age and sex. We identified that rs13052524 in MRPS6 and rs62212118 in SLC5A3 were associated with 2hPG in Hainan prediabetes (p = 4.35 × 10^-6, p = 4.05 × 10^-6, respectively). Another six variants in the four genes (LINC01648, MATN1, CRAT37, and SLCO3A1) were related to HbA1C. Moreover, rs11142842, rs1891298, rs1891299, and rs11142843 in TRPM3/TMEM2 and rs78432036 in MLYCD/OSGIN1 were correlated to BMI (all p < 5 × 10^-6). This study is the first to determine the genome-wide association of FPG, 2hPG, and HbA1C, which emphasizes the importance of in-depth understanding of the phenotypes of high-value susceptibility gene markers in the diagnosis of prediabetes.

The focal adhesion protein Testin modulates KCNE2 potassium channel β subunit activity

Coronary Artery Disease (CAD) typically kills more people globally each year than any other single cause of death. A better understanding of genetic predisposition to CAD and the underlying mechanisms will help to identify those most at risk and contribute to improved therapeutic approaches. KCNE2 is a functionally versatile, ubiquitously expressed potassium channel β subunit associated with CAD and cardiac arrhythmia susceptibility in humans and mice. Here, to identify novel KCNE2 interaction partners, we employed yeast two-hybrid screening of adult and fetal human heart libraries using the KCNE2 intracellular C-terminal domain as bait. Testin (encoded by TES), an endothelial cell-expressed, CAD-associated, focal adhesion protein, was identified as a high-confidence interaction partner for KCNE2. We confirmed physical association between KCNE2 and Testin in vitro by co-immunoprecipitation. Whole-cell patch clamp electrophysiology revealed that KCNE2 negative-shifts the voltage dependence and increases the rate of activation of the endothelial cell and cardiomyocyte-expressed Kv channel α subunit, Kv1.5 in CHO cells, whereas Testin did not alter Kv1.5 function. However, Testin nullified KCNE2 effects on Kv1.5 voltage dependence and gating kinetics. In contrast, Testin did not prevent KCNE2 regulation of KCNQ1 gating. The data identify a novel role for Testin as a tertiary ion channel regulatory protein. Future studies will address the potential role for KCNE2-Testin interactions in arterial and myocyte physiology and CAD.

Role of GTPases in Driving Mitoribosome Assembly

Mitoribosomes catalyze essential protein synthesis within mitochondria. Mitoribosome biogenesis is assisted by an increasing number of assembly factors, among which guanosine triphosphate hydrolases (GTPases) are the most abundant class. Here, we review recent progress in our understanding of mitoribosome assembly GTPases. We describe their shared and specific features and mechanisms of action, compare them with their bacterial counterparts, and discuss their possible roles in the assembly of small or large mitoribosomal subunits and the formation of the monosome by establishing quality-control checkpoints during these processes. Furthermore, following the recent unification of the nomenclature for the mitoribosomal proteins, we also propose a unified nomenclature for mitoribosome assembly GTPases.

The Diseased Mitoribosome

Mitochondria control life and death in eukaryotic cells. Harboring a unique circular genome, a by-product of an ancient endosymbiotic event, mitochondria maintains a specialized and evolutionary divergent protein synthesis machinery, the mitoribosome. Mitoribosome biogenesis depends on elements encoded in both the mitochondrial genome (the RNA components) and the nuclear genome (all ribosomal proteins and assembly factors). Recent cryo-EM structures of mammalian mitoribosomes have illuminated their composition and provided hints regarding their assembly and elusive mitochondrial translation mechanisms. A growing body of literature involves the mitoribosome in inherited primary mitochondrial disorders. Mutations in genes encoding mitoribosomal RNAs, proteins, and assembly factors impede mitoribosome biogenesis, causing protein synthesis defects that lead to respiratory chain failure and mitochondrial disorders such as encephalo- and cardiomyopathy, deafness, neuropathy, and developmental delays. In this article, we review the current fundamental understanding of mitoribosome assembly and function, and the clinical landscape of mitochondrial disorders driven by mutations in mitoribosome components and assembly factors, to portray how basic and clinical studies combined help us better understand both mitochondrial biology and medicine.

AKT and ERK1/2 activation via remote ischemic preconditioning prevents Kcne2-dependent sudden cardiac death

Sudden cardiac death (SCD) is the leading global cause of mortality. SCD often arises from cardiac ischemia reperfusion (IR) injury, pathologic sequence variants within ion channel genes, or a combination of the two. Alternative approaches are needed to prevent or ameliorate ventricular arrhythmias linked to SCD. Here, we investigated the efficacy of remote ischemic preconditioning (RIPC) of the limb versus the liver in reducing ventricular arrhythmias in a mouse model of SCD. Mice lacking the Kcne2 gene, which encodes a potassium channel β subunit associated with acquired Long QT syndrome were exposed to IR injury via coronary ligation. This resulted in ventricular arrhythmias in all mice (15/15) and SCD in 5/15 mice during reperfusion. Strikingly, prior RIPC (limb or liver) greatly reduced the incidence and severity of all ventricular arrhythmias and completely prevented SCD. Biochemical and pharmacological analysis demonstrated that RIPC cardioprotection required ERK1/2 and/or AKT phosphorylation. A lack of alteration in GSK‐3β phosphorylation suggested against conventional reperfusion injury salvage kinase (RISK) signaling pathway protection. If replicated in human studies, limb RIPC could represent a noninvasive, nonpharmacological approach to limit dangerous ventricular arrhythmias associated with ischemia and/or channelopathy‐linked SCD.

Kcne4 deletion sex-specifically predisposes to cardiac arrhythmia via testosterone-dependent impairment of RISK/SAFE pathway induction in aged mice

Sudden cardiac death (SCD) is associated with both electrical and ischemic substrates, and is a major cause of ischemic heart disease mortality worldwide. Male sex predisposes to SCD but the underlying mechanisms are incompletely understood. KCNE4, a cardiac arrhythmia-associated potassium channel β-subunit, is upregulated by 5α-dihydrotestosterone (DHT). Thus, ventricular Kcne4 expression is low in young adult female mice, but high in males and postmenopausal (12+ months) females. Despite causing a sex-independent electrical substrate at 13 months of age (22% QT prolongation in both males and females; P < 0.01), Kcne4 deletion preferentially predisposed aged male mice to ischemia/reperfusion (IR)-provoked ventricular tachyarrhythmias. Interestingly, Kcne4 deletion caused baseline induction of cardioprotective RISK and SAFE pathways in 13-m-old female, but not male, mice. IR-invoked RISK/SAFE induction was also deficient in male but not female Kcne4^-/- mice. Pharmacological inhibition of RISK/SAFE pathways in Kcne4^-/- females eliminated sex-specific differences in IR-invoked tachyarrhythmia predisposition. Furthermore, castration of Kcne4^-/- males eliminated sex-specific differences in both baseline and post-IR RISK/SAFE pathway induction, and tachyarrhythmia predisposition. Our results demonstrate for the first time that male sex can predispose in aged mice to dangerous ventricular tachyarrhythmias despite sex-independent electrical and ischemic substrates, because of testosterone-dependent impairment of RISK/SAFE pathway induction.

The rs2228145 polymorphism in the interleukin-6 receptor and its association with long-term prognosis after myocardial infarction in a pilot study

INTRODUCTION

Interleukin-6 (IL-6) is a cytokine with a complex function that is described as both pro- and anti-inflammatory. One factor that influences its function is the rs2228145 A/C single nucleotide polymorphism (SNP) of the IL-6 receptor (IL6R) gene. C allele carriers have a decreased inflammatory response and decreased prevalence of ischemic heart disease. The aim of the study was to investigate the association of the rs2228145 SNP of the IL6R gene with long-term total mortality in patients with ST-elevation myocardial infarction (STEMI) treated invasively.

MATERIAL AND METHODS

We analyzed the data of consecutive patients with ST elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI). Genotyping was performed with the TaqMan method. The analyzed end-point was total long-term mortality (median: 2875 days).

RESULTS

The registry comprised 553 patients (mean age: 62.4 ±11.9 years; 25.6% females, n = 142; TIMI 3 obtained in 91.7% of patients, n = 507). No significant differences in baseline characteristics were found between the genotypes. During long-term follow-up 171 (30.9%) patients died. There was non-significantly higher mortality in the rs2228145 AA homozygotes compared to C allele carriers (OR = 1.34, 95% CI: 0.93-1.93, p = 0.1).

CONCLUSIONS

The rs2228145 polymorphism of IL6R was not significantly associated with long-term mortality after STEMI. However, AA homozygotes (high-risk genotype for ischemic heart disease) showed a trend towards adverse outcome compared to C allele carriers. The observed trend is promising, but it requires independent replication studies.

Kcne2 deletion attenuates acute post-ischaemia/reperfusion myocardial infarction

AIMS

Most cardiac arrhythmia-associated genes encode ion channel subunits and regulatory proteins that are also expressed outside the heart, suggesting that diseases linked to their disruption may be multifactorial. KCNE2 is a ubiquitously expressed potassium channel β subunit associated with cardiac arrhythmia, atherosclerosis, and myocardial infarction (MI) in human populations. Here, we tested the hypothesis that Kcne2 disruption in mice would influence the acute outcome of experimentally induced MI.

METHODS AND RESULTS

One-year-old male Kcne2⁺/⁺ and Kcne2⁻/⁻ mice were subjected to cardiac ischaemia/reperfusion injury (IRI) by left anterior descending coronary artery ligation. After reperfusion (3 h), infarct size and markers of tissue damage were quantified. Unexpectedly, post-reperfusion, Kcne2⁻/⁻ mice exhibited 40% lower infarct size, decreased myocardial apoptosis and damage, and more than two-fold lower serum levels of damage markers, lactate dehydrogenase and creatine kinase, than Kcne2⁺/⁺ mice. Kcne2 deletion, despite increasing normalized heart weight and prolonging baseline QTc by 70%, helped preserve post-infarct cardiac function (quantified by a Millar catheter), with parameters including left ventricular maximum pressure, max dP/dt (P < 0.01), contractility index, and pressure/time index (P < 0.05) all greater in Kcne2⁻/⁻ compared with Kcne2⁺/⁺ mice. Western blotting indicated two-fold-increased glycogen synthase kinase 3β (GSK-3β) phosphorylation (inactivation) before and after IRI (P < 0.05) in Kcne2⁻/⁻ mice compared with Kcne2⁺/⁺ mice. GSK-3β inhibition by SB216763 mimicked in Kcne2⁺/⁺ mice the cardioprotective effects of Kcne2 deletion, but did not further enhance them in Kcne2⁻/⁻mice, suggesting that GSK-3β inactivation was a primary cardioprotective mechanism arising from Kcne2 deletion.

CONCLUSIONS

Kcne2 deletion preconditions the heart, attenuating the acute tissue damage caused by an imposed IRI. The findings contribute further evidence that genetic disruption of arrhythmia-associated ion channel genes has cardiac ramifications beyond abnormal electrical activity.

The 9p21 polymorphism is linked with atrial fibrillation during acute phase of ST-segment elevation myocardial infarction

The aim of the study was to find whether patients carrying polymorphic allele of the rs10757278 polymorphism from 9p21 locus have changed risk of arrhythmia (atrial fibrillation, AF; sustained ventricular tachycardia or ventricular fibrillation, sVT/VF) during acute phase of myocardial infarction. Retrospective analysis of data collected prospectively from two independent centers was performed. The clinical data were pooled from two independent cardiac registries: (1) the Warsaw ACS genetic registry (STEMI and NSTEMI/UA patients hospitalized in the years 2008-2011; only STEMI patients were analyzed); (2) the Bialystok STEMI genetic registry (STEMI patients hospitalized in years 2001-2005, who survived the first 48 h from hospital admission). Data regarding sVT/VF and AF within first 24 h were analyzed. The patients were genotyped with rs10757278 polymorphism. 1083 patients were included in the analysis; 62 (5.7 %) patients had sVT/VF during acute phase and 78 (7.2 %) patients had AF, 46 (4.2 %) patients had new-onset AF. Minor allele frequency in all patients with AF was significantly different from those without AF (0.40 vs 0.51, p = 0.0096). When only new-onset AF was analyzed, the trend was the same, with significant protective effect in recessive model [OR 0.41 (95 % CI 0.17-0.97), p = 0.025]. The effect was independent of age and GRACE score. No relationship was found between sVT/VF and rs10757278. Patients with STEMI, who survived until hospitalization with polymorphic allele of 9p21 rs10757278 SNP have less AF during acute phase of STEMI. SNP rs10757278 is not linked with sVT/VF in acute phase of STEMI.