Mitochondrial genetic effect on atrial fibrillation: A case-control study

Mitochondrial DNA Polymorphisms of Peripheral Blood Mononuclear Cells Associated with Sustained Ventricular Tachycardia in Patients with Cardioverter-Defibrillator Implantation Indications

Background

Mitochondrial dysfunction in myocardium cells has been implicated in arrhythmogenesis, including ventricular tachycardia (VT). A carriage of point mitochondrial DNA (mtDNA) polymorphisms may contribute to the risk of certain arrhythmias. Therefore, it is hypothesized that mtDNA genotype could predict the risk of sustained VT (SVT). We aimed to explore whether specific mtDNA polymorphisms of peripheral blood mononuclear cells (PBMC) can serve as biomarkers for predicting the risk of SVT in patients with indications for an implantable cardioverter-defibrillator (ICD).

Methods

A total of 122 patients with ICD implantation indications who underwent transthoracic echocardiography (TTE) were enrolled in the study. Total DNA from PBMC was isolated using the phenol-chloroform extraction method. Genotyping of mtDNA polymorphisms A2706G, G3010A and G9055A was performed using restriction fragment length polymorphism analysis. Correlations between clinical parameters and mtDNA polymorphisms with SVT registered prior to ICD implantation were evaluated. Based on our data, we developed a risk model for SVT.

Results

Prior to ICD implantation, 70 (56.6%) patients had SVT (1st group) and 52 (43.4%) patients did not have SVT (2nd group). Patients with SVT were significantly older than patients without SVT (66.9 ± 9.9 year vs. 59.5 ± 10.6 year, p < 0.001), had a lower value estimated glomerular filtration rate (eGFR) (65.7 ± 19.7 mL/min/1.73 m2 vs. 77.9 ± 16.1 mL/min/1.73 m2, p < 0.001) and less frequently had A2706G mtDNA polymorphism (55.7% vs. 76.9%, p = 0.015). According to the multivariable logistic regression, age (odds ratio (OR) = 1.055, 95% confidence interval (CI) 1.009-1.103, p = 0.017), eGFR (OR = 0.974, 95% CI 0.949-0.999, p = 0.041) and absence of A2706G mtDNA polymorphism (OR = 0.335, 95% CI 0.141-0.797, p = 0.013) were independently associated with the SVT. We constructed a logistic equation with calculation of the cut-off value. The discriminative ability of the receiver operating characteristic curve (area under the curve) was 0.761 (95% confidence interval 0.675-0.833; sensitivity 65.71%; specificity 76.92%).

Conclusions

In patients with ICD implantation indications, a carriage of mtDNA polymorphism A2706G is associated with SVT. Our risk model including age, eGFR and absence of A2706G mtDNA substitution was able to distinguish patients with SVT. Further investigations of their predictive significance are warranted.

Clinical Trial Registration

NCT03667989 (https://clinicaltrials.gov/study/NCT03667989).

Concurrent Assessment of Oxidative Stress and MT-ATP6 Gene Profiling to Facilitate Diagnosis of Autism Spectrum Disorder (ASD) in Tamil Nadu Population

Autism spectrum disorder (ASD) is a neurodevelopmental disability that causes social impairment, debilitated verbal or nonverbal conversation, and restricted/repeated behavior. Recent research reveals that mitochondrial dysfunction and oxidative stress might play a pivotal role in ASD condition. The goal of this case-control study was to investigate oxidative stress and related alterations in ASD patients. In addition, the impact of mitochondrial DNA (mtDNA) mutations, particularly MT-ATP6, and its link with oxidative stress in ASD was studied. We found that ASD patient's plasma had lower superoxide dismutase (SOD) and higher catalase (CAT) activity, resulting in lower SOD/CAT ratio. MT-ATP6 mutation analysis revealed that four variations, 8865 G>A, 8684 C>T, 8697 G>A, and 8836 A>G, have a frequency of more than 10% with missense and synonymous (silent) mutations. It was observed that abnormalities in mitochondrial complexes (I, III, V) are more common in ASD, and it may have resulted in MT-ATP6 changes or vice versa. In conclusion, our findings authenticate that oxidative stress and genetics both have an equal and potential role behind ASD and we recommend to conduct more such concurrent research to understand their unique mechanism for better diagnosis and therapeutic for ASD.

Mitophagy: At the heart of mitochondrial quality control in cardiac aging and frailty

Cardiovascular disease is highly prevalent among older adults and poses a huge burden on morbidity, disability, and mortality. The age-related increased vulnerability of the cardiovascular system towards stressors is a pathophysiological trait of cardiovascular disease. This has been associated with a progressive deterioration of blood vessels and decline in heart function during aging. Cardiomyocytes rely mostly on oxidative metabolism for deploying their activities and mitochondrial metabolism is crucial to this purpose. Dysmorphic, inefficient, and oxidant-producing mitochondria have been identified in aged cardiomyocytes in association with cardiac structural and functional alterations. These aberrant organelles are thought to arise from inefficient mitochondrial quality control, which has therefore been place in the spotlight as a relevant mechanism of cardiac aging. As a result of alterations in mitochondrial quality control and redox dyshomeostasis, mitochondrial damage accumulates and contributes to cardiac frailty. Herein, we discuss the contribution of defective mitochondrial quality control pathways to cardiac frailty. Emerging findings pointing towards the exploitation of these pathways as therapeutic targets against cardiac aging and cardiovascular disease will also be illustrated.