Association between mitochondrial DNA copy number and cardiovascular disease: Current evidence based on a systematic review and meta-analysis

Mitochondrial DNA copy number and risk of cardiovascular disease and all-cause mortality: a systematic review and meta-analysis of observational studies

Increasing studies have explored the correlation of mitochondrial DNA copy number (mtDNA-CN) abnormalities with cardiovascular disease (CVD) and all-cause mortality; however, their findings are contradictory. This systematic review and meta-analysis sought to quantitatively summarize current studies to elucidate the impact of mtDNA-CN on CVD outcomes and all-cause mortality. Relevant studies were searched for in PubMed, Embase and Web of Science databases, up to 23 October 2023. Summary relative risks (RRs) and 95% confidence intervals (CIs) were calculated with the random-effects model. In total, 22 articles were included in the systematic review, 13 of which were included in the meta-analysis of CVD outcomes and 8 in all-cause mortality. Compared to the highest mtDNA-CN level, the summary RR (95% CI) for the lowest mtDNA-CN level was 2.09 (95% CI 1.59-2.75) for CVD, 1.70 (95% CI 1.29-2.24) for coronary heart disease (CHD), 1.43 (95% CI 1.15-1.79) for heart failure (HF), 1.88 (95% CI 1.08-3.28) for stroke and 1.33 (95% CI 1.21-1.47) for all-cause mortality. Lower mtDNA-CN may increase the risk of CVD, including CHD, HF and stroke, as well as all-cause mortality. MtDNA-CN is a potential predictor of CVD and all-cause mortality.

Crosstalk between mitochondrial homeostasis and AMPK pathway mediate the receptor-mediated cardioprotective effects of estradiol in ovariectomized female rats

Estrogen (E2) deficiency is a risk factor for cardiovascular disease (CVD), however, the exact mechanism for the E2 protective effect on CVD remains unclear. This study aimed to investigate the estrogen receptor (ER) and non-receptor mediated effects of E2 treatment on the cardiac expression of adenosine monophosphate-dependent protein kinase (AMPK), autophagic, mitophagy and mitochondrial homeostasis-regulating genes in ovariectomized (OVX) rats. Female rats were divided into two main groups; sham and bilaterally OVX rats, then each group was subdivided into four subgroups according to treatment; untreated, subcutaneously treated with E2 (30 μg/kg), or Fulvestrant (F) (5 mg/Kg), or a combination of both drugs for 28 days. The OVX rats or F-treated sham rats showed dyslipidemia, and marked disturbances in parameters of AMPK signaling, autophagy, mitophagy, mitochondrial fission, fusion and biogenesis. E2 administration to OVX or F-treated sham rats has corrected the disturbed lipid and cardiac profiles, increased AMPK, and restored the balance of cardiac autophagy, mitophagy, and mitochondrial dynamics and homeostasis. Most of these effects in OVX rats were blocked by the ER antagonist (F). Estrogen treatment has cardioprotective effects in OVX females through modulating cardiac mitochondrial homeostasis, mitophagy and autophagy and restoring the AMPK signaling pathway. As witnessed by Fulvestrant, these effects suggest the main role of ER-mediated signaling in regulating mitophagy and plasma and cardiac lipids along with the existence of a post-translational control mechanism or the involvement of estrogenic non-receptor pathway controlling the postmenopausal cardiac mitochondrial energy production machinery that needs further investigation.

The role of mitochondrial dysfunction in the association between trace metals and QTc prolongation in the aged population

This study delves into the relationship between environmental metal exposure and QT interval corrected for heart rate (QTc) prolongation, a critical marker for cardiovascular risk in the elderly. Although the interplay between metal exposure and QTc prolongation is important for predicting sudden cardiac death, it remains underexplored. Our analysis of 6478 participants from the Shenzhen aging-related disorder cohort involved measuring urinary concentrations of 22 trace metals and using mitochondrial DNA copy number (mtDNA-CN) as an indicator of mitochondrial dysfunction. Utilizing Bayesian kernel machine regression, and structural equation modeling, we assessed the effects of mixed trace metals on QTc prolongation. Our findings indicated a direct association between certain metals (Sb, Cu, Zn) and a 7 % increase in QTc prolongation risk, while Li, V, and Rb were associated with a 5 % reduction in risk. Elevated levels of V, Ti, and Cr corresponded to higher mtDNA-CN. Notably, restricted cubic splines revealed a U-shaped, nonlinear relationship between mtDNA-CN and QTc prolongation. After adjusting for metal exposure, an inverse correlation was observed between mtDNA-CN and QTc prolongation, suggesting mitochondrial dysfunction as a partial mediator.

Changes in TP53 Gene, Telomere Length, and Mitochondrial DNA in Benign Prostatic Hyperplasia Patients

BACKGROUND

Benign prostatic hyperplasia (BPH) is a growing issue due to an ageing population. Our study investigated the possible associations between BPH and ageing hallmarks, including the telomere length (TL) and mitochondrial genome copy number (mtDNA CN), along with genetic variations in the TP53 gene and mtDNA.

METHODS

Prostate tissue samples were obtained from 32 patients with BPH, together with 30 blood samples. As a healthy control group, age-matching blood DNA samples were used. For the comparison of mtDNA sequence data, 50 DNA samples of the general Latvian population were used. The full mtDNA genome was analyzed by using Next-Generation Sequencing (NGS), the TP53 gene by Sanger sequencing, and the mtDNA copy number (mtDNA CN) and telomere length (TL) byqPCR assay.

RESULTS

The results showed that in BPH patients, telomeres in the prostate tissue were significantly longer than in blood cells, while the TL in blood cells of the healthy controls was the shortest. Also, the mtDNA amount in the prostate tissue of BPH patients was significantly greater in comparison with blood cells, and controls had the smallest mtDNA CN. We did not find any mutations in the TP53 gene that could be linked to BPH; however, in mtDNA, we found several unique mutations and heteroplasmic changes, as well as genetic changes that have been previously associated with prostate cancer.

CONCLUSIONS

In conclusion, prolonged telomeres and changes in the mtDNA amount might be involved in the molecular mechanisms of BPH. Some of the heteroplasmic or homoplasmic mtDNA variants might also contribute to the development of BPH. Additional studies are needed to substantiate these findings.

Leukocyte mitochondrial DNA copy number and cardiovascular disease: A systematic review and meta-analysis of cohort studies

Increasing cohort studies have examined the link between mitochondrial DNA copy number (mtDNA-CN) and cardiovascular disease (CVD), with inconsistent findings. We searched PubMed, EMBASE, and Web of Science up to July 11, 2023 and used a random-effects model to calculate summary hazard ratios (HRs) and 95% confidence intervals (CIs). This systematic review and meta-analysis included 8 articles encompassing 29 studies with 646,398 participants. Individuals with the lowest mtDNA-CN had a summary HR of 1.27 (95% CI 1.02-1.59) for CVD, 1.18 (95% CI 0.92-1.50) for coronary heart disease (CHD), 1.10 (95% CI 0.89-1.37) for stroke, and 1.30 (95% CI 1.07-1.56) for heart failure (HF). Decreased mtDNA-CN is linked to an increased risk of CVD and HF but not CHD and stroke. These findings suggest mtDNA-CN from leukocytes may be a potential early biomarker for CVD. However, more prospective studies with long follow-up are needed.

A nomogram prediction of coronary artery dilation in Kawasaki diseases based on mtDNA copy number

Objective

The level of mitochondrial DNA copy number (mtDNA-CN) in peripheral blood cells had been identified to be involved in several immune and cardiovascular diseases. Thus, the aim of this study is to evaluate the levels of mtDNA-CN in Kawasaki disease (KD) and to construct a nomogram prediction for coronary artery lesions in children with KD.

Methods

One hundred and forty-four children with KD diagnosed from March 2020 to March 2022 were involved in the study. The clinical features and laboratory test parameters of these children were assessed between the KD and normal groups. Univariable and multivariable analyses were performed sequentially to identify the essential risk factors. Subsequently, a nomogram prediction was constructed.

Results

A total of 274 children were included in the analysis. Of these, 144 (52.6%) represented the KD group. Peripheral blood DNA mtDNA qPCR showed that the -log value of mtDNA-CN in the KD group (6.67 ± 0.34) was significantly higher than that in the healthy group (6.40 ± 0.18) (P<0.001). The area under the ROC curve for mtDNA-CN in distinguishing KD was 0.757. MtDNA-CN (OR = 13.203, P = 0.009, 95% CI 1.888-92.305), RBC (OR = 5.135, P = 0.014, 95% CI 1.394-18.919), and PA (OR = 0.959, P = 0.014, 95% CI 0.927-0.991) were identified as independent risk factors for coronary artery dilation in children with KD. Finally, the nomogram predictive was established based on the results of multivariable analysis, demonstrating the satisfied prediction and calibration values.

Conclusion

The results of this study revealed that mtDNA-CN could be used as a biomarker in predicting the development of KD. Furthermore, the higher the mtDNA-CN was significantly associated with coronary artery dilation in KD.

Associations between mitochondrial copy number, exercise capacity, physiologic cost of walking, and cardiac strain in young adult survivors of childhood cancer

PURPOSE

Childhood cancer survivors are at risk for cardiac dysfunction and impaired physical performance, though underlying cellular mechanisms are not well studied. In this cross-sectional study, we examined the association between peripheral blood mitochondrial DNA copy number (mtDNA-CN, a proxy for mitochondrial function) and markers of performance impairment and cardiac dysfunction.

METHODS

Whole-genome sequencing, validated by quantitative polymerase chain reaction, was used to estimate mtDNA-CN in 1720 adult survivors of childhood cancer (48.5% female; mean age = 30.7 years, standard deviation (SD) = 9.0). Multivariable logistic regression was performed to evaluate the associations between mtDNA-CN and exercise intolerance, walking inefficiency, and abnormal global longitudinal strain (GLS), adjusting for treatment exposures, age, sex, and race and ethnicity.

RESULTS

The prevalence of exercise intolerance, walking inefficiency, and abnormal GLS among survivors was 25.7%, 10.7%, and 31.7%, respectively. Each SD increase of mtDNA-CN was associated with decreased odds of abnormal GLS (adjusted odds ratio (OR) = 0.88, p = 0.04) but was not associated with exercise intolerance (OR = 1.02, p = 0.76) or walking inefficiency (OR = 1.06, p = 0.46). Alkylating agent exposure was associated with increased odds of exercise intolerance (OR = 2.25, p < 0.0001), walking inefficiency (OR = 2.37, p < 0.0001), and abnormal GLS (OR = 1.78, p = 0.0002).

CONCLUSIONS

Increased mtDNA-CN is associated with decreased odds of abnormal cardiac function in childhood cancer survivors.

IMPLICATIONS FOR CANCER SURVIVORS

These findings demonstrate a potential role for mtDNA-CN as a biomarker of early cardiac dysfunction in this population.

The predictive value of peripheral blood cell mitochondrial gene expression in identifying the prognosis in pediatric sepsis at preschool age

Background

Sepsis represents a severe manifestation of infection often accompanied by metabolic disorders and mitochondrial dysfunction. Notably, mitochondrial DNA copy number (mtDNA-CN) and the expression of specific mitochondrial genes have emerged as sensitive indicators of mitochondrial function. To investigate the utility of mitochondrial gene expression in peripheral blood cells for distinguishing severe infections and predicting associated outcomes, we conducted a prospective cohort study.

Methods

We established a prospective cohort comprising 74 patients with non-sepsis pneumonia and 67 cases of sepsis induced by respiratory infections, aging from 2 to 6 years old. We documented corresponding clinical data and laboratory information and collected blood samples upon initial hospital admission. Peripheral blood cells were promptly isolated, and both total DNA and RNA were extracted. We utilized absolute quantification PCR to assess mtDNA-CN, as well as the expression levels of mt-CO1, mt-ND1, and mt-ATP6. Subsequently, we extended these comparisons to include survivors and non-survivors among patients with sepsis using univariate and multivariate analyses. Receiver operating characteristic (ROC) curves were constructed to assess the diagnostic potential.

Results

The mtDNA-CN in peripheral blood cells was significantly lower in the sepsis group. Univariate analysis revealed a significant reduction in the expression of mt-CO1, mt-ND1, and mt-ATP6 in patients with sepsis. However, multivariate analysis did not support the use of mitochondrial function in peripheral blood cells for sepsis diagnosis. In the comparison between pediatric sepsis survivors and non-survivors, univariate analysis indicated a substantial reduction in the expression of mt-CO1, mt-ND1, and mt-ATP6 among non-survivors. Notably, total bilirubin (TB), mt-CO1, mt-ND1, and mt-ATP6 levels were identified as independent risk factors for sepsis-induced mortality. ROC curves were then established for these independent risk factors, revealing areas under the curve (AUCs) of 0.753 for TB (95% CI 0.596-0.910), 0.870 for mt-CO1 (95% CI 0.775-0.965), 0.987 for mt-ND1 (95% CI 0.964-1.000), and 0.877 for mt-ATP6 (95% CI 0.793-0.962).

Conclusion

MtDNA-CN and mitochondrial gene expression are closely linked to the severity and clinical outcomes of infectious diseases. Severe infections lead to impaired mitochondrial function in peripheral blood cells. Notably, when compared to other laboratory parameters, the expression levels of mt-CO1, mt-ND1, and mt-ATP6 demonstrate promising potential for assessing the prognosis of pediatric sepsis.

Associations of Epigenetic Age Acceleration With CVD Risks Across the Lifespan: The Bogalusa Heart Study

Although epigenetic age acceleration (EAA) might serve as a molecular signature of childhood cardiovascular disease (CVD) risk factors and further promote midlife subclinical CVD, few studies have comprehensively examined these life course associations. This study sought to test whether childhood CVD risk factors predict EAA in adulthood and whether EAA mediates the association between childhood CVD risks and midlife subclinical disease. Among 1,580 Bogalusa Heart Study participants, we estimated extrinsic EAA, intrinsic EAA, PhenoAge acceleration (PhenoAgeAccel), and GrimAge acceleration (GrimAgeAccel) during adulthood. We tested prospective associations of longitudinal childhood body mass index (BMI), blood pressure, lipids, and glucose with EAAs using linear mixed effects models. After confirming EAAs with midlife carotid intima-media thickness and carotid plaque, structural equation models examined mediating effects of EAAs on associations of childhood CVD risk factors with subclinical CVD measures. After stringent multiple testing corrections, each SD increase in childhood BMI was significantly associated with 0.6-, 0.9-, and 0.5-year increases in extrinsic EAA, PhenoAgeAccel, and GrimAgeAccel, respectively (P < 0.001 for all 3 associations). Likewise, each SD increase in childhood log-triglycerides was associated with 0.5- and 0.4-year increases in PhenoAgeAccel and GrimAgeAccel (P < 0.001 for both), respectively, whereas each SD increase in childhood high-density lipoprotein cholesterol was associated with a 0.3-year decrease in GrimAgeAccel (P = 0.002). Our findings indicate that PhenoAgeAccel mediates an estimated 27.4% of the association between childhood log-triglycerides and midlife carotid intima-media thickness (P = 0.022). Our data demonstrate that early life CVD risk factors may accelerate biological aging and promote subclinical atherosclerosis.

The mitochondrial link: Phthalate exposure and cardiovascular disease

Phthalates' pervasive presence in everyday life poses concern as they have been revealed to induce perturbing health defects. Utilized as a plasticizer, phthalates are riddled throughout many common consumer products including personal care products, food packaging, home furnishings, and medical supplies. Phthalates permeate into the environment by leaching out of these products which can subsequently be taken up by the human body. It is previously established that a connection exists between phthalate exposure and cardiovascular disease (CVD) development; however, the specific mitochondrial link in this scenario has not yet been described. Prior studies have indicated that one possible mechanism for how phthalates exert their effects is through mitochondrial dysfunction. By disturbing mitochondrial structure, function, and signaling, phthalates can contribute to the development of the foremost cause of death worldwide, CVD. This review will examine the potential link among phthalates and their effects on the mitochondria, permissive of CVD development.

Extrapulmonary manifestations of pulmonary arterial hypertension

INTRODUCTION

Extrapulmonary manifestations of pulmonary arterial hypertension (PAH) may play a critical pathobiological role and a deeper understanding will advance insight into mechanisms and novel therapeutic targets. This manuscript reviews our understanding of extrapulmonary manifestations of PAH.

AREAS COVERED

A group of experts was assembled and a complimentary PubMed search performed (October 2023 - March 2024). Inflammation is observed throughout the central nervous system and attempts at manipulation are an encouraging step toward novel therapeutics. Retinal vascular imaging holds promise as a noninvasive method of detecting early disease and monitoring treatment responses. PAH patients have gut flora alterations and dysbiosis likely plays a role in systemic inflammation. Despite inconsistent observations, the roles of obesity, insulin resistance and dysregulated metabolism may be illuminated by deep phenotyping of body composition. Skeletal muscle dysfunction is perpetuated by metabolic dysfunction, inflammation, and hypoperfusion, but exercise training shows benefit. Renal, hepatic, and bone marrow abnormalities are observed in PAH and may represent both end-organ damage and disease modifiers.

EXPERT OPINION

Insights into systemic manifestations of PAH will illuminate disease mechanisms and novel therapeutic targets. Additional study is needed to understand whether extrapulmonary manifestations are a cause or effect of PAH and how manipulation may affect outcomes.

The role of mitochondrial DNA copy number in cardiometabolic disease: a bidirectional two-sample mendelian randomization study

BACKGROUND

This study used a bidirectional 2-sample Mendelian randomization study to investigate the potential causal links between mtDNA copy number and cardiometabolic disease (obesity, hypertension, hyperlipidaemia, type 2 diabetes [T2DM], coronary artery disease [CAD], stroke, ischemic stroke, and heart failure).

METHODS

Genetic associations with mtDNA copy number were obtained from a genome-wide association study (GWAS) summary statistics from the UK biobank (n = 395,718) and cardio-metabolic disease were from largest available GWAS summary statistics. Inverse variance weighting (IVW) was conducted, with weighted median, MR-Egger, and MR-PRESSO as sensitivity analyses. We repeated this in the opposite direction using instruments for cardio-metabolic disease.

RESULTS

Genetically predicted mtDNA copy number was not associated with risk of obesity (P = 0.148), hypertension (P = 0.515), dyslipidemia (P = 0.684), T2DM (P = 0.631), CAD (P = 0.199), stroke (P = 0.314), ischemic stroke (P = 0.633), and heart failure (P = 0.708). Regarding the reverse directions, we only found that genetically predicted dyslipidemia was associated with decreased levels of mtDNA copy number in the IVW analysis (β= - 0.060, 95% CI - 0.044 to - 0.076; P = 2.416e-14) and there was suggestive of evidence for a potential causal association between CAD and mtDNA copy number (β= - 0.021, 95% CI - 0.003 to - 0.039; P = 0.025). Sensitivity and replication analyses showed the stable findings.

CONCLUSIONS

Findings of this Mendelian randomization study did not support a causal effect of mtDNA copy number in the development of cardiometabolic disease, but found dyslipidemia and CAD can lead to reduced mtDNA copy number. These findings have implications for mtDNA copy number as a biomarker of dyslipidemia and CAD in clinical practice.

Arsenic-Induced Cardiovascular Diseases and their Correlation with Mitochondrial DNA Copy Number, Deletion, and Telomere Length in Bangladeshi Population

Arsenic contamination is a global health concern, primarily through contaminated groundwater and its entry into the food chain. The association between arsenic exposure and cardiovascular diseases (CVDs) is particularly alarming due to CVDs being the leading cause of death worldwide. Arsenic exposure has also been linked to changes in telomere length, mitochondrial DNA copy number (mtDNAcn), and deletion, further increasing the risk of CVDs. We aimed to determine whether arsenic exposure alters telomere length and mtDNAcn and deletion in a total of 50 CVD patients who underwent open heart surgery hailed from known arsenic-affected and unaffected areas in Bangladesh. Amount of arsenic was determined from the collected nails and cardiac tissues. Relative telomere length and mtDNAcn and deletion were quantified by qRT-PCR. The patients from arsenic-contaminated areas had higher average arsenic deposits in their fingers and toenails (P < 0.05) and higher cardiac tissue injury scores (P < 0.05). Moreover, approximately 1.5-fold shorter telomere length (P < 0.05, r =  - 0.775), 1.2-fold decreased mtDNAcn (P < 0.05, r = - 0.797), and an 81-fold higher amount of mitochondrial DNA deletion (P < 0.05, r = 0.784) were observed in the patients who had higher arsenic deposition in their nails. Higher levels of arsenic exposure were found to be linked to shorter telomere length, decreased mtDNAcn, and increased mitochondrial DNA deletion in the patients from As-affected areas. It can also be anticipated that the correlation of arsenic exposure with telomere length, mtDNAcn, and deletion can be used as biomarkers for early diagnosis of arsenic-induced cardiovascular diseases.

Association of sleep quality and mitochondrial DNA copy number in healthy middle-aged adults

OBJECTIVES

Mitochondria contribute to various compromised health, yet the association between sleep and mitochondria remains unclear. This study investigated the association between sleep quality and mitochondrial function in healthy middle-aged adults in the Republic of Korea.

METHOD

This cross-sectional study recruited 238 middle-aged adults using convenience sampling. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI). Mitochondrial function, represented by mitochondrial DNA copy number (mtDNAcn), was measured using real-time quantitative polymerase chain reaction on peripheral blood leukocytes. Multivariate linear regression analyses were performed to determine the association between sleep quality and mtDNAcn.

RESULTS

Sleep quality was negatively associated with mtDNAcn (r = -.15, p = .025); the poor sleep quality group had a notably lower mtDNAcn compared to the good sleep quality group (t = 2.40, p = .017). Among the PSQI components, sleep latency was significantly associated with reduced mtDNAcn (r = -.18, p = .005). Univariate regression analysis revealed that mtDNAcn was significantly associated with education level (β = 0.15, p = .017), shift work (β = -0.17, p = .010), global PSQI score (β = -0.15, p = .025), and sleep latency (β = -0.18, p = .005). After adjusting for educational level and shift work in the final model, longer sleep latency was independently associated with reduced mtDNAcn (β = -.16, p = .011).

CONCLUSIONS

Poor sleep quality is associated with reduced mtDNAcn, suggesting a potential biological mechanism whereby poor sleep quality, specifically long sleep latency, accelerates cellular aging and impairs health through mitochondrial dysfunction. These findings enhance our understanding of the health effects of sleep quality and highlight the importance of screening and intervention strategies for mitochondrial dysfunction.

Low mitochondrial DNA copy number in peripheral blood mononuclear cells is associated with future mortality risk: a long-term follow-up study from Japan

OBJECTIVES

The mitochondrial DNA (mtDNA) is unique and circular with multiple copies of the genome. The lower mtDNA copy number (mtDNA-CN) in leukocytes is associated with the risk of all-cause mortality. However, its long-term association is unknown. Thus, the study examined the association between mtDNA-CN and the risk of all-cause mortality in a long-term follow-up study in the Japanese population.

DESIGN

This longitudinal study included the study cohort from an annual, population-based health checkup in the town of Yakumo, Hokkaido, Japan.

SETTING AND PARTICIPANTS

814 participants (baseline age range: 38-80 years, mean: 56.3 years) were included in this study in 1990. They were followed-up regarding mortality for about 30 years (median: 28.1 years) till 2019.

MEASURES

The genomic DNA was extracted from peripheral blood mononuclear cells and the mtDNA-CN was measured using real-time polymerase chain reaction. The level of the mtDNA-CN was divided into tertiles (low, middle, and high). The participants were categorized based on their age into middle-aged (<60 years old) or old-aged (≥60 years old). Survival analysis was performed for tertile of mtDNA-CN and compared using the log-rank test. Univariate and multivariable Cox proportional hazard regression analyses were performed to assess the association between mtDNA-CN and all-cause mortality. The model adjusted with age, sex, body mass index, systolic blood pressure, smoking habit, alcohol consumption, exercise habit, and education level.

RESULTS

The low levels of mtDNA-CN resulted in a significant decrease in cumulative survival rate (P <  0.05). The risk of mortality was significantly higher in the middle-aged cohort when mtDNA-CN levels were low (hazard ratios [95% confidence intervals]: 1.98 [1.10-3.56]).

CONCLUSION

This study demonstrated that leukocyte mtDNA-CN is associated with future mortality risk. Our study findings may lead to further research on the early prediction of mortality and its underlying mechanisms.

Complete mitochondrial DNA profile in stroke: A geographical matched case-control study in Spanish population

INTRODUCTION

Stroke, the second leading cause of death worldwide, is a complex disease influenced by many risk factors among which we can find reactive oxygen species (ROS). Since mitochondria are the main producers of cellular ROS, nowadays studies are trying to elucidate the role of these organelles and its DNA (mtDNA) variation in stroke risk. The aim of the present study was to perform a comprehensive evaluation of the association between mtDNA mutations and mtDNA content and stroke risk.

MATERIAL AND METHODS

Homoplasmic and heteroplasmic mutations of the mtDNA were analysed in a case-controls study using 110 S cases and their corresponding control individuals. Mitochondrial DNA copy number (mtDNA-CN) was analysed in 73 of those case-control pairs.

RESULTS

Our results suggest that haplogroup V, specifically variants m.72C > T, m.4580G > A, m.15904C > T and m.16298 T > C have a protective role in relation to stroke risk. On the contrary, variants m.73A > G, m.11719G > A and m.14766C > T appear to be genetic risk factors for stroke. In this study, we found no statistically significant association between stroke risk and mitochondrial DNA copy number.

CONCLUSIONS

These results demonstrate the possible role of mtDNA genetics on the pathogenesis of stroke, probably through alterations in mitochondrial ROS production.

Protective Effects of Micronutrient Supplements, Phytochemicals and Phytochemical-Rich Beverages and Foods Against DNA Damage in Humans: A Systematic Review of Randomized Controlled Trials and Prospective Studies

Accumulation of deoxyribonucleic acid (DNA) damage diminishes cellular health, increases risk of developmental and degenerative diseases, and accelerates aging. Optimizing nutrient intake can minimize accrual of DNA damage. The objectives of this review are to: 1) assemble and systematically analyze high-level evidence for the effect of supplementation with micronutrients and phytochemicals on baseline levels of DNA damage in humans, and 2) use this knowledge to identify which of these essential micronutrients or nonessential phytochemicals promote DNA integrity in vivo in humans. We conducted systematic literature searches of the PubMed database to identify interventional, prospective, cross-sectional, or in vitro studies that explored the association between nutrients and established biomarkers of DNA damage associated with developmental and degenerative disease risk. Biomarkers included lymphocyte chromosome aberrations, lymphocyte and buccal cell micronuclei, DNA methylation, lymphocyte/leukocyte DNA strand breaks, DNA oxidation, telomere length, telomerase activity, and mitochondrial DNA mutations. Only randomized, controlled interventions and uncontrolled longitudinal intervention studies conducted in humans were selected for evaluation and data extraction. These studies were ranked for the quality of their study design. In all, 96 of the 124 articles identified reported studies that achieved a quality assessment score ≥ 5 (from a maximum score of 7) and were included in the final review. Based on these studies, nutrients associated with protective effects included vitamin A and its precursor β-carotene, vitamins C, E, B1, B12, folate, minerals selenium and zinc, and phytochemicals such as curcumin (with piperine), lycopene, and proanthocyanidins. These findings highlight the importance of nutrients involved in (i) DNA metabolism and repair (folate, vitamin B12, and zinc) and (ii) prevention of oxidative stress and inflammation (vitamins A, C, E, lycopene, curcumin, proanthocyanidins, selenium, and zinc). Supplementation with certain micronutrients and their combinations may reduce DNA damage and promote cellular health by improving the maintenance of genome integrity.

Mitochondrial DNA copy number is associated with incident chronic kidney disease and proteinuria in the AIDS linked to the intravenous experience cohort

We evaluated the prospective association of mitochondrial DNA copy number (mtDNA CN) with markers of kidney function among a cohort of persons who inject drugs (PWID). This is a Prospective cohort study nested in the AIDS linked to the intravenous experience cohort (community-based cohort of PWID in Baltimore, MD). mtDNA CN was measured at two time-points 5 years apart using a real-time polymerase chain reaction. Kidney function (estimated glomerular filtration rate [eGFR], serum creatinine, urine protein) was measured annually. We used linear mixed effects models to evaluate kidney function trajectories (N = 946) and Cox regression models to assess hazard of incident CKD (eGFR < 60 at two consecutive visits, N = 739) and proteinuria (urine protein:creatinine ratio > 200, N = 573) by level of mtDNA CN (Low [lowest quartile], vs high [other three quartiles]. Models were adjusted for demographic and behavioral characteristics, HIV and/or HCV infection, and comorbidity burden. Low mtDNA CN was independently associated with higher hazard of incident CKD (aHR: 2.33, 95% CI 1.42, 3.80) and proteinuria (aHR: 1.42, 95% CI 1.04, 1.96). Participants with low mtDNA CN had greater declines in eGFR and greater increases in serum creatinine over time. Low mtDNA CN is associated with more rapid kidney function decline and risk of incident CKD and proteinuria.

Moringa oleifera Leaves Extract Ameliorates Doxorubicin-Induced Cardiotoxicity via Its Mitochondrial Biogenesis Modulatory Activity in Rats

Background

Doxorubicin, an anthracycline class of anticancer, is an effective chemotherapeutic agent with serious adverse effects, mainly cardiotoxicity. Several possible causes of doxorubicin cardiotoxicity are increased oxidative stress, nucleic acid and protein synthesis inhibition, cardiomyocyte apoptosis, and mitochondrial biogenesis disruptions. Moringa oleifera (MO), a naturally derived medicine, is known for its antioxidative properties and activity in alleviating mitochondrial dysfunction. To determine the potency and possible cardioprotective mechanism of MO leaves aqueous extract via the mitochondrial biogenesis pathway in doxorubicin-induced rats.

Methods

Twenty-four Sprague-Dawley rats were divided into four groups of six. The first group was normal rats; the second group was treated with doxorubicin 4 mg/kg BW intraperitoneally once weekly for four weeks; the third and fourth groups were treated with doxorubicin 4 mg/kg BW intraperitoneally once weekly, and MO leaves extract at 200 mg/kg BW or 400 mg/kg BW orally daily, for four weeks. At the end of the fourth week, blood and cardiac tissues were obtained and analyzed for cardiac biomarkers, mitochondrial DNA copy number, mRNA expressions of peroxisome-activated receptor-gamma coactivator-1 alpha (PGC-1α), the nuclear factor erythroid 2-related factor 2 (Nrf2), superoxide dismutase 2 (SOD2), caspase 3, the activity of glutathione peroxidase (GPx), levels of 8-hydroxy-2-deoxyguanosine (8-OH-dG), and malondialdehyde.

Results

MO leaves extract was shown to decrease biomarkers of cardiac damage (LDH and CK-MB), malondialdehyde levels, and GPx activity. These changes align with the reduction of mRNA expressions of caspase-3, the increase of mRNA expressions of PGC-1α and Nrf2, and the elevation of mitochondrial DNA copy number. MO leaves extracts did not influence the mRNA expressions of superoxide dismutase 2 (SOD2) or the levels of 8-OH-dG.

Conclusion

Moringa oleifera leaves extract ameliorates doxorubicin-induced cardiotoxicity by reducing apoptosis and restoring gene expression of PGC-1α and Nrf2, a key regulator in mitochondrial biogenesis.

The Relationship between All-Cause Natural Mortality and Copy Number of Mitochondrial DNA in a 15-Year Follow-Up Study

We explored the relationship between the copy number of mitochondrial DNA (mtDNA-CN) and all-cause natural mortality. We examined a random population sample in 2003/2005 (n = 9360, men/women, 45-69, the HAPIEE project) and followed up for 15 years. Using a nested case-control design, we selected non-external deaths among those free from baseline cardiovascular diseases (CVD) and cancer (n = 371), and a sex- and age-stratified control (n = 785). The odds ratios (ORs) of death were 1.06 (95%CI 1.01-1.11) per one-decile decrease in mtDNA-CN independent of age, sex, metabolic factors, smoking, alcohol intake and education. The age-sex-adjusted ORs of death in the second and first tertiles of mtDNA-CN vs. the top tertile were 2.35 (95% CI 1.70-3.26) and 1.59 (1.16-2.17); an increased risk was confined to the second tertile after controlling for smoking and metabolic factors. The multivariable-adjusted OR of CVD death was 1.92 (95% CI 1.18-3.15) in tertile 2 vs. the top tertile of mtDNA-CN, and for cancer-related death the ORs were 3.66 (95% CI 2.21-6.05) and 2.29 (95% CI 1.43-3.68) in tertiles 2 and 1 vs. the top tertile. In the Siberian population cohort, the mtDNA-CN was an inverse predictor of the 15-year risk of natural mortality, due to the greatest impact of CVD and cancer-related death. The findings merit attention for exploring further the role of mtDNA in human ageing and the diversity of mortality.

The prenatal environment and its influence on maternal and child mitochondrial DNA copy number and methylation: A review of the literature

Mitochondrial DNA (mtDNA) is sensitive to environmental stressors and associated with human health. We reviewed epidemiological literature examining associations between prenatal environmental, dietary, and social exposures and alterations in maternal/child mtDNA copy number (mtDNAcn) and mtDNA methylation. Evidence exists that prenatal maternal exposures are associated with alterations in mtDNAcn for air pollution, chemicals (e.g. metals), cigarette smoke, human immunodeficiency virus (HIV) infection and treatment. Evidence for their associations with mtDNA methylation was limited. Given its potential implications as a disease pathway biomarker, studies with sufficient biological specificity should examine the long-term implications of prenatal and early-life mtDNA alterations in response to prenatal exposures.

Cardiovascular disease treatment using traditional Chinese medicine：Mitochondria as the Achilles' heel

Cardiovascular disease (CVD), involving the pathological alteration of the heart or blood vessels, is one of the main causes of disability and death worldwide, with an estimated 18.6 million deaths per year. CVDs are caused by a variety of risk factors, including inflammation, hyperglycemia, hyperlipidemia, and increased oxidative stress. Mitochondria, the hub of ATP production and the main generator of reactive oxygen species (ROS), are linked to multiple cellular signaling pathways that regulate the progression of CVD and therefore are recognized as an essential target for CVD management. Initial treatment of CVD generally focuses on diet and lifestyle interventions; proper drugs or surgery can prolong or save the patient's life. Traditional Chinese medicine (TCM), a holistic medical care system with an over 2500-year history, has been proven to be efficient in curing CVD and other illnesses, with a strengthening effect on the body. However, the mechanisms underlying TCM alleviation of CVD remain elusive. Recent studies have recognized that TCM can alleviate cardiovascular disease by manipulating the quality and function of mitochondria. This review systematically summarizes the association of mitochondria with cardiovascular risk factors, and the relationships between mitochondrial dysfunction and CVD progression. We will investigate the research progress of managing cardiovascular disease by TCM and cover widely used TCMs that target mitochondria for the treatment of cardiovascular disease.

Ripretinib induced skeletal muscle toxicity through mitochondrial impairment in C2C12 myotubes

Ripretinib is a multikinase inhibitor drug approved in 2020 by the FDA and in 2021 by EMA for use in the treatment of advanced gastrointestinal stromal tumors (GIST) which have not adequately responded to previous treatments with kinase inhibitors. The most common side effects of the drug are myalgia and fatigue, which likely causes interruption of the treatment or reduction of the dose. Skeletal muscle cells highly depend on ATP to perform their functions and mitochondrial damage may play a role in skeletal muscle toxicity induced by kinase inhibitors. However, the molecular mechanism has not been clearly identified in the literature yet. In this study, it has been aimed to elucidate the role of mitochondria in the toxic effect of ripretinib on skeletal muscle using the mouse C2C12 myoblast-derived myotubes. The myotubes were exposed to ripretinib at the range of 1-20 μM concentrations for 24 h. To determine the potential role of mitochondrial impairment in ripretinib-induced skeletal muscle toxicity, intracellular ATP level, mitochondrial membrane potential (MMP), mitochondrial ROS production (mtROS), mitochondrial DNA (mtDNA) copy number, and mitochondrial mass were examined after ripretinib treatment. Furthermore, changes in PGC 1α/NRF 1/NRF 2 expression levels that play a role in mitochondrial biogenesis and mitophagy were investigated. Additionally, the mitochondrial electron transport chain (ETC) enzyme activities were evaluated. Lastly, a molecular docking study was done to see ripretinib's possible interaction with DNA polymerase gamma (POLG) which is important for DNA replication in the mitochondria. According to the findings, ripretinib decreases the ATP level and mtDNA copy number, induces loss of MMP, and reduces mitochondrial mass. The activities of the ETC complexes were inhibited with ripretinib exposure which is in line with the observed ATP depletion and MMP loss. The molecular docking study revealed that ripretinib has inhibitory potential against POLG which supports the observed inhibition of mtDNA. The expression of PGC 1α was reduced in the nuclear fraction indicating that PGC-1α was not activated since the NRF 1 expression was reduced and NRF 2 level did not show significant change. Consequently, mtROS production increased in all treatment groups and mitophagy-related gene expressions and Parkin protein expression level were up-regulated at high doses. In conclusion, mitochondrial damage/loss can be one of the underlying causes of ripretinib-induced skeletal muscle toxicity. However, further studies are needed to confirm the results in vivo.

The potential role of environmental factors in modulating mitochondrial DNA epigenetic marks

Many studies implicate mitochondrial dysfunction in the development and progression of numerous chronic diseases. Mitochondria are responsible for most cellular energy production, and unlike other cytoplasmic organelles, mitochondria contain their own genome. Most research to date, through investigating mitochondrial DNA copy number, has focused on larger structural changes or alterations to the entire mitochondrial genome and their role in human disease. Using these methods, mitochondrial dysfunction has been linked to cancers, cardiovascular disease, and metabolic health. However, like the nuclear genome, the mitochondrial genome may experience epigenetic alterations, including DNA methylation that may partially explain some of the health effects of various exposures. Recently, there has been a movement to understand human health and disease within the context of the exposome, which aims to describe and quantify the entirety of all exposures people encounter throughout their lives. These include, among others, environmental pollutants, occupational exposures, heavy metals, and lifestyle and behavioral factors. In this chapter, we summarize the current research on mitochondria and human health, provide an overview of the current knowledge on mitochondrial epigenetics, and describe the experimental and epidemiologic studies that have investigated particular exposures and their relationships with mitochondrial epigenetic modifications. We conclude the chapter with suggestions for future directions in epidemiologic and experimental research that is needed to advance the growing field of mitochondrial epigenetics.

Mitochondrial oxidative stress contributes to diastolic dysfunction through impaired mitochondrial dynamics

Diastolic dysfunction (DD) underlies heart failure with preserved ejection fraction (HFpEF), a clinical syndrome associated with aging that is becoming more prevalent. Despite extensive clinical studies, no effective treatment exists for HFpEF. Recent findings suggest that oxidative stress contributes to the pathophysiology of DD, but molecular mechanisms underpinning redox-sensitive cardiac remodeling in DD remain obscure. Using transgenic mice with mitochondria-targeted NOX4 overexpression (Nox4TG618) as a model, we demonstrate that NOX4-dependent mitochondrial oxidative stress induces DD in mice as measured by increased E/E', isovolumic relaxation time, Tau Glantz and reduced dP/dtmin while EF is preserved. In Nox4TG618 mice, fragmentation of cardiomyocyte mitochondria, increased DRP1 phosphorylation, decreased expression of MFN2, and a higher percentage of apoptotic cells in the myocardium are associated with lower ATP-driven and maximal mitochondrial oxygen consumption rates, a decrease in respiratory reserve, and a decrease in citrate synthase and Complex I activities. Transgenic mice have an increased concentration of TGFβ and osteopontin in LV lysates, as well as MCP-1 in plasma, which correlates with a higher percentage of LV myocardial periostin- and ACTA2-positive cells compared with wild-type mice. Accordingly, the levels of ECM as measured by Picrosirius Red staining as well as interstitial deposition of collagen I are elevated in the myocardium of Nox4TG618 mice. The LV tissue of Nox4TG618 mice also exhibited increased ICaL current, calpain 2 expression, and altered/disrupted Z-disc structure. As it pertains to human pathology, similar changes were found in samples of LV from patients with DD. Finally, treatment with GKT137831, a specific NOX1 and NOX4 inhibitor, or overexpression of mCAT attenuated myocardial fibrosis and prevented DD in the Nox4TG618 mice. Together, our results indicate that mitochondrial oxidative stress contributes to DD by causing mitochondrial dysfunction, impaired mitochondrial dynamics, increased synthesis of pro-inflammatory and pro-fibrotic cytokines, activation of fibroblasts, and the accumulation of extracellular matrix, which leads to interstitial fibrosis and passive stiffness of the myocardium. Further, mitochondrial oxidative stress increases cardiomyocyte Ca2+ influx, which worsens CM relaxation and raises the LV filling pressure in conjunction with structural proteolytic damage.

No Mediation Effect of Telomere Length or Mitochondrial DNA Copy Number on the Association Between Adverse Childhood Experiences (ACEs) and Central Arterial Stiffness

Background

Adverse childhood experiences (ACEs) have been linked to increased cardiovascular disease (CVD) risk. Previous reports have suggested that accelerated biological aging—indexed by telomere length (TL) and mitochondrial DNA copy number (mtDNAcn)—may contribute to associations between ACEs and cardiovascular health outcomes. Here, we examine the potential mediating effects of TL and mtDNAcn on the association between ACEs and central arterial stiffness—an intermediate cardiovascular health outcome—as a novel pathway linking ACEs to CVD risk among young adults.

Methods and Results

One hundred and eighty‐five (n=102 women; mean age, 22.5±1.5 years) individuals provided information on ACEs. TL (kb per diploid cell) and mtDNAcn (copies per diploid cell) were quantified using quantitative polymerase chain reaction techniques. Central arterial stiffness was measured as carotid‐femoral pulse wave velocity (cfPWV; m/s). Multiple linear regression analyses were used to examine the associations between ACEs, TL, mtDNAcn, and cfPWV. ACEs were positively associated with cfPWV ( β =0.147, P =0.035). TL ( β =−0.170, P =0.011) and mtDNAcn ( β =−0.159, P =0.019) were inversely associated with cfPWV. Neither TL ( β =−0.027, P =0.726) nor mtDNAcn ( β =0.038, P =0.620) was associated with ACEs. Neither marker mediated the association between ACEs and cfPWV.

Conclusions

An increasing number of ACEs were associated with a faster cfPWV and thus, a greater degree of central arterial stiffness. ACEs were not associated with either TL or mtDNAcn, suggesting that these markers do not represent a mediating pathway linking ACEs to central arterial stiffness.

Mitochondrial Genome Variants as a Cause of Mitochondrial Cardiomyopathy

Mitochondria are small double-membraned organelles responsible for the generation of energy used in the body in the form of ATP. Mitochondria are unique in that they contain their own circular mitochondrial genome termed mtDNA. mtDNA codes for 37 genes, and together with the nuclear genome (nDNA), dictate mitochondrial structure and function. Not surprisingly, pathogenic variants in the mtDNA or nDNA can result in mitochondrial disease. Mitochondrial disease primarily impacts tissues with high energy demands, including the heart. Mitochondrial cardiomyopathy is characterized by the abnormal structure or function of the myocardium secondary to genetic defects in either the nDNA or mtDNA. Mitochondrial cardiomyopathy can be isolated or part of a syndromic mitochondrial disease. Common manifestations of mitochondrial cardiomyopathy are a phenocopy of hypertrophic cardiomyopathy, dilated cardiomyopathy, and cardiac conduction defects. The underlying pathophysiology of mitochondrial cardiomyopathy is complex and likely involves multiple abnormal processes in the cell, stemming from deficient oxidative phosphorylation and ATP depletion. Possible pathophysiology includes the activation of alternative metabolic pathways, the accumulation of reactive oxygen species, dysfunctional mitochondrial dynamics, abnormal calcium homeostasis, and mitochondrial iron overload. Here, we highlight the clinical assessment of mtDNA-related mitochondrial cardiomyopathy and offer a novel hypothesis of a possible integrated, multivariable pathophysiology of disease.

New Perspectives on the Importance of Cell-Free DNA Biology

Body fluids are constantly replenished with a population of genetically diverse cell-free DNA (cfDNA) fragments, representing a vast reservoir of information reflecting real-time changes in the host and metagenome. As many body fluids can be collected non-invasively in a one-off and serial fashion, this reservoir can be tapped to develop assays for the diagnosis, prognosis, and monitoring of wide-ranging pathologies, such as solid tumors, fetal genetic abnormalities, rejected organ transplants, infections, and potentially many others. The translation of cfDNA research into useful clinical tests is gaining momentum, with recent progress being driven by rapidly evolving preanalytical and analytical procedures, integrated bioinformatics, and machine learning algorithms. Yet, despite these spectacular advances, cfDNA remains a very challenging analyte due to its immense heterogeneity and fluctuation in vivo. It is increasingly recognized that high-fidelity reconstruction of the information stored in cfDNA, and in turn the development of tests that are fit for clinical roll-out, requires a much deeper understanding of both the physico-chemical features of cfDNA and the biological, physiological, lifestyle, and environmental factors that modulate it. This is a daunting task, but with significant upsides. In this review we showed how expanded knowledge on cfDNA biology and faithful reverse-engineering of cfDNA samples promises to (i) augment the sensitivity and specificity of existing cfDNA assays; (ii) expand the repertoire of disease-specific cfDNA markers, thereby leading to the development of increasingly powerful assays; (iii) reshape personal molecular medicine; and (iv) have an unprecedented impact on genetics research.

Preanalytical Variables in the Analysis of Mitochondrial DNA in Whole Blood and Plasma from Pancreatic Cancer Patients

Given the crucial role of mitochondria as the main cellular energy provider and its contribution towards tumor growth, chemoresistance, and cancer cell plasticity, mitochondrial DNA (mtDNA) could serve as a relevant biomarker. Thus, the profiling of mtDNA mutations and copy number variations is receiving increasing attention for its possible role in the early diagnosis and monitoring therapies of human cancers. This applies particularly to highly aggressive pancreatic cancer, which is often diagnosed late and is associated with poor prognosis. As current diagnostic procedures are based on imaging, tissue histology, and protein biomarkers with rather low specificity, tumor-derived mtDNA mutations detected from whole blood represents a potential significant leap forward towards early cancer diagnosis. However, for future routine use in clinical settings it is essential that preanalytics related to the characterization of mtDNA in whole blood are thoroughly standardized, controlled, and subject to proper quality assurance, yet this is largely lacking. Therefore, in this study we carried out a comprehensive preanalytical workup comparing different mtDNA extraction methods and testing important preanalytical steps, such as the use of different blood collection tubes, different storage temperatures, length of storage time, and yields in plasma vs. whole blood. To identify analytical and preanalytical differences, all variables were tested in both healthy subjects and pancreatic carcinoma patients. Our results demonstrated a significant difference between cancer patients and healthy subjects for some preanalytical workflows, while other workflows failed to yield statistically significant differences. This underscores the importance of controlling and standardizing preanalytical procedures in the development of clinical assays based on the measurement of mtDNA.

Sex differences in heart mitochondria regulate diastolic dysfunction

Heart failure with preserved ejection fraction (HFpEF) exhibits a sex bias, being more common in women than men, and we hypothesize that mitochondrial sex differences might underlie this bias. As part of genetic studies of heart failure in mice, we observe that heart mitochondrial DNA levels and function tend to be reduced in females as compared to males. We also observe that expression of genes encoding mitochondrial proteins are higher in males than females in human cohorts. We test our hypothesis in a panel of genetically diverse inbred strains of mice, termed the Hybrid Mouse Diversity Panel (HMDP). Indeed, we find that mitochondrial gene expression is highly correlated with diastolic function, a key trait in HFpEF. Consistent with this, studies of a "two-hit" mouse model of HFpEF confirm that mitochondrial function differs between sexes and is strongly associated with a number of HFpEF traits. By integrating data from human heart failure and the mouse HMDP cohort, we identify the mitochondrial gene Acsl6 as a genetic determinant of diastolic function. We validate its role in HFpEF using adenoviral over-expression in the heart. We conclude that sex differences in mitochondrial function underlie, in part, the sex bias in diastolic function.

Mitochondrial DNA Is a Vital Driving Force in Ischemia-Reperfusion Injury in Cardiovascular Diseases

According to the latest Global Burden of Disease Study, cardiovascular disease (CVD) is the leading cause of death, and ischemic heart disease and stroke are the cause of death in approximately half of CVD patients. In CVD, mitochondrial dysfunction following ischemia-reperfusion (I/R) injury results in heart failure. The proper functioning of oxidative phosphorylation (OXPHOS) and the mitochondrial life cycle in cardiac mitochondria are closely related to mitochondrial DNA (mtDNA). Following myocardial I/R injury, mitochondria activate multiple repair and clearance mechanisms to repair damaged mtDNA. When these repair mechanisms are insufficient to restore the structure and function of mtDNA, irreversible mtDNA damage occurs, leading to mtDNA mutations. Since mtDNA mutations aggravate OXPHOS dysfunction and affect mitophagy, mtDNA mutation accumulation leads to leakage of mtDNA and proteins outside the mitochondria, inducing an innate immune response, aggravating cardiovascular injury, and leading to the need for external interventions to stop or slow the disease course. On the other hand, mtDNA released into the circulation after cardiac injury can serve as a biomarker for CVD diagnosis and prognosis. This article reviews the pathogenic basis and related research findings of mtDNA oxidative damage and mtDNA leak-triggered innate immune response associated with I/R injury in CVD and summarizes therapeutic options that target mtDNA.

Molecular mechanisms of coronary microvascular endothelial dysfunction in diabetes mellitus: focus on mitochondrial quality surveillance

Coronary microvascular endothelial dysfunction is both a culprit and a victim of diabetes, and can accelerate diabetes-related microvascular and macrovascular complications by promoting vasoconstrictive, pro-inflammatory and pro-thrombotic responses. Perturbed mitochondrial function induces oxidative stress, disrupts metabolism and activates apoptosis in endothelial cells, thus exacerbating the progression of coronary microvascular complications in diabetes. The mitochondrial quality surveillance (MQS) system responds to stress by altering mitochondrial metabolism, dynamics (fission and fusion), mitophagy and biogenesis. Dysfunctional mitochondria are prone to fission, which generates two distinct types of mitochondria: one with a normal and the other with a depolarized mitochondrial membrane potential. Mitochondrial fusion and mitophagy can restore the membrane potential and homeostasis of defective mitochondrial fragments. Mitophagy-induced decreases in the mitochondrial population can be reversed by mitochondrial biogenesis. MQS abnormalities induce pathological mitochondrial fission, delayed mitophagy, impaired metabolism and defective biogenesis, thus promoting the accumulation of unhealthy mitochondria and the activation of mitochondria-dependent apoptosis. In this review, we examine the effects of MQS on mitochondrial fitness and explore the association of MQS disorders with coronary microvascular endothelial dysfunction in diabetes. We also discuss the potential to treat diabetes-related coronary microvascular endothelial dysfunction using novel MQS-altering drugs.

DNA damage, serum metabolomic alteration and carcinogenic risk associated with low-level air pollution

Outdoor air pollution has been classified as carcinogenic to humans (Group 1) for lung cancer, but the underlying mechanism and key toxic components remain incompletely understood. Since DNA damage and metabolite alterations are associated with cancer progression, exploring potential mechanisms linking air pollution and cancer might be meaningful. In this study, a real-time ambient air exposure system was established to simulate the real-world environment of adult male SD rats in Beijing from June 13th, 2018, to October 8th, 2018. 8-OHdG in the urine, γ-H2AX in the lungs and mtDNA copy number in the peripheral blood were analyzed to explore DNA damage at different levels. Serum non-targeted metabolomics analysis was performed. Pair-wise spearman was used to explore the correlation between DNA damage biomarkers and serum differential metabolites. Carcinogenic risks of heavy metals and PAHs via inhalation were assessed according to US EPA guidelines. Results showed that PM_2.5 and O₃ were the major air pollutants in the exposure group and not detected in the control group. Compared with control group, higher levels of 8-OHdG, mtDNA copy number, γ-H2AX and PCNA-positive nuclei cells were observed in the exposure group. Histopathological evaluation suggested ambient air induced alveolar wall thickening and inflammatory cell infiltration in lungs. Perturbed metabolic pathways identified included glycolysis/gluconeogenesis metabolism, purine and pyrimidine metabolism, etc. γ-H2AX was positively correlated with serum ADP, 3-phospho-D-glyceroyl phosphate and N-acetyl-D-glucosamine. The BaPeq was 0.120 ng/m³. Risks of Cr(VI), As, V, BaP, BaA and BbF were above 1 × 10^-6. We concluded that low-level air pollution was associated with DNA damage and serum metabolomic alterations in rats. Cr(VI) and BaP were identified as key carcinogenic components in PM_2.5. Our results provided experimental evidence for hazard identification and risk assessment of low-level air pollution.

Reduced mitochondrial DNA copy number in occupational workers from brominated flame retardants manufacturing plants

Decabrominated diphenyl ether (BDE-209) and its substitute decabromodiphenyl ethane (DBDPE) are two flame retardants that have similar structure and are widely used in various industrial products. The accumulation and potential toxicity of them to human health have already aroused attention, and some research showed that they may affect mitochondrial function. Therefore, this study focused on the population with high exposure to brominated flame retardants (BFRs) and the related changes in mtDNA copy number (mtDNAcn) in whole blood. 334 blood samples were collected from three groups of people in Shandong Province, including 42 BDE-209 occupational exposure workers from the BDE-209 manufacturing plant, 131 DBDPE occupational exposure workers from the DBDPE manufacturing plant, and 161 non-BFRs occupational exposure residents from the BFRs contaminated area. We measured the levels of BDE-209, DBDPE in serum sample, and the mtDNAcn in whole blood sample and analyzed these data by multiple linear regression. The average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in BDE-209 occupational workers were 3510, 639 and 4600 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in DBDPE occupational workers were 229, 4040 and 4470 ng/g lw, respectively; the average concentrations of BDE-209, DBDPE and ∑(BDE-209 + DBDPE) in non-BFRs occupational exposure residents were 66.3, 45.7 and 137 ng/g lw, respectively. The relative mtDNAcn was 0.823 in BDE-209 occupational workers, 0.845 in DBDPE occupational workers and 0.989 in non-BFRs occupational exposure residents. A 10-fold increase in BDE-209, DBDPE concentrations was separately associated with a 0.068 and 0.063 decrease in mtDNAcn. Therefore, our study implied that BFRs may affect mitochondrial function. As increasing BFRs exposure has emerged in recent years, the relationship between BFRs exposure and mitochondrial function needs further study.

The Role of Mitochondrial DNA Mutations in Cardiovascular Diseases

Cardiovascular diseases (CVD) are one of the leading causes of morbidity and mortality worldwide. mtDNA (mitochondrial DNA) mutations are known to participate in the development and progression of some CVD. Moreover, specific types of mitochondria-mediated CVD have been discovered, such as MIEH (maternally inherited essential hypertension) and maternally inherited CHD (coronary heart disease). Maternally inherited mitochondrial CVD is caused by certain mutations in the mtDNA, which encode structural mitochondrial proteins and mitochondrial tRNA. In this review, we focus on recently identified mtDNA mutations associated with CVD (coronary artery disease and hypertension). Additionally, new data suggest the role of mtDNA mutations in Brugada syndrome and ischemic stroke, which before were considered only as a result of mutations in nuclear genes. Moreover, we discuss the molecular mechanisms of mtDNA involvement in the development of the disease.

Peripheral Blood Mitochondrial DNA Levels Were Modulated by SARS-CoV-2 Infection Severity and Its Lessening Was Associated With Mortality Among Hospitalized Patients With COVID-19

Introduction

During severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, the virus hijacks the mitochondria causing damage of its membrane and release of mt-DNA into the circulation which can trigger innate immunity and generate an inflammatory state. In this study, we explored the importance of peripheral blood mt-DNA as an early predictor of evolution in patients with COVID-19 and to evaluate the association between the concentration of mt-DNA and the severity of the disease and the patient’s outcome.

Methods

A total 102 patients (51 COVID-19 cases and 51 controls) were included in the study. mt-DNA obtained from peripheral blood was quantified by qRT-PCR using the NADH mitochondrial gene.

Results

There were differences in peripheral blood mt-DNA between patients with COVID-19 (4.25 ng/μl ± 0.30) and controls (3.3 ng/μl ± 0.16) (p = 0.007). Lower mt-DNA concentrations were observed in patients with severe COVID-19 when compared with mild (p= 0.005) and moderate (p= 0.011) cases of COVID-19. In comparison with patients with severe COVID-19 who survived (3.74 ± 0.26 ng/μl) decreased levels of mt-DNA in patients with severe COVID-19 who died (2.4 ± 0.65 ng/μl) were also observed (p = 0.037).

Conclusion

High levels of mt-DNA were associated with COVID-19 and its decrease could be used as a potential biomarker to establish a prognosis of severity and mortality of patients with COVID-19.

Probes for Fluorescent Visualization of Specific Cellular Organelles

The defining characteristic of eukaryotic cells is the segregation of critical cellular functions within various membrane bound cellular organelles, including the nucleus, endoplasmic reticulum, Golgi apparatus, lysosomes, and mitochondria. Cell biologists therefore have extensively utilized organelle specific counterstains to help identify the localization of specific proteins or other targets of interest in order to garner an understanding of either their potential functions or their effects on the cell. There currently is a wide array of fluorescent dyes and reagents that can be utilized in live and fixed cells to identify organelles, thereby creating challenges in both choosing between the plethora of options and optimizing their use. Here we present a discussion of commonly utilized commercially available organelle dyes and summarize the factors that influence selection of the various dyes for: a given organelle; live versus fixed cellular conditions; adaptation to a specific protocol; spectral multiplexing; or matching excitation/emission spectra to available imaging equipment. Also presented are recommended protocols for a typical example reagent that can be reliably utilized to visualize its target cellular organelle.

Mitochondrial Dynamin-Related Protein Drp1: a New Player in Cardio-oncology

PURPOSE OF REVIEW

This study is aimed at reviewing the recent progress in Drp1 inhibition as a novel approach for reducing doxorubicin-induced cardiotoxicity and for improving cancer treatment.

RECENT FINDINGS

Anthracyclines (e.g. doxorubicin) are one of the most common and effective chemotherapeutic agents to treat a variety of cancers. However, the clinical usage of doxorubicin has been hampered by its severe cardiotoxic side effects leading to heart failure. Mitochondrial dysfunction is one of the major aetiologies of doxorubicin-induced cardiotoxicity. The morphology of mitochondria is highly dynamic, governed by two opposing processes known as fusion and fission, collectively known as mitochondrial dynamics. An imbalance in mitochondrial dynamics is often reported in tumourigenesis which can lead to adaptive and acquired resistance to chemotherapy. Drp1 is a key mitochondrial fission regulator, and emerging evidence has demonstrated that Drp1-mediated mitochondrial fission is upregulated in both cancer cells to their survival advantage and injured heart tissue in the setting of doxorubicin-induced cardiotoxicity. Effective treatment to prevent and mitigate doxorubicin-induced cardiotoxicity is currently not available. Recent advances in cardio-oncology have highlighted that Drp1 inhibition holds great potential as a targeted mitochondrial therapy for doxorubicin-induced cardiotoxicity.

Extensive analysis of mitochondrial DNA quantity and sequence variation in human cumulus cells and assisted reproduction outcomes

STUDY QUESTION

Are relative mitochondrial DNA (mtDNA) content and mitochondrial genome (mtGenome) variants in human cumulus cells (CCs) associated with oocyte reproductive potential and assisted reproductive technology (ART) outcomes?

SUMMARY ANSWER

Neither the CC mtDNA quantity nor the presence of specific mtDNA genetic variants was associated with ART outcomes, although associations with patient body mass index (BMI) were detected, and the total number of oocytes retrieved differed between major mitochondrial haplogroups.

WHAT IS KNOWN ALREADY

CCs fulfil a vital role in the support of oocyte developmental competence. As with other cell types, appropriate cellular function is likely to rely upon adequate energy production, which in turn depends on the quantity and genetic competence of the mitochondria. mtDNA mutations can be inherited or they can accumulate in somatic cells over time, potentially contributing to aging. Such mutations may be homoplasmic (affecting all mtDNA in a cell) or they may display varying levels of heteroplasmy (affecting a proportion of the mtDNA). Currently, little is known concerning variation in CC mitochondrial genetics and how this might influence the reproductive potential of the associated oocyte.

STUDY DESIGN, SIZE, DURATION

This was a prospective observational study involving human CCs collected with 541 oocytes from 177 IVF patients. mtDNA quantity was measured in all the samples with a validated quantitative PCR method and the entire mtGenome was sequenced in a subset of 138 samples using a high-depth massively parallel sequencing approach. Associations between relative mtDNA quantity and mtGenome variants in CCs and patient age, BMI (kg/m2), infertility diagnosis and ART outcomes were investigated.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Massively parallel sequencing permitted not only the accurate detection of mutations but also the precise quantification of levels of mutations in cases of heteroplasmy. Sequence variants in the mtDNA were evaluated using Mitomaster and HmtVar to predict their potential impact.

MAIN RESULTS AND THE ROLE OF CHANCE

The relative mtDNA CC content was significantly associated with BMI. No significant associations were observed between CC mtDNA quantity and patient age, female infertility diagnosis or any ART outcome variable. mtGenome sequencing revealed 4181 genetic variants with respect to a reference genome. The COXI locus contained the least number of coding sequence variants, whereas ATPase8 had the most. The number of variants predicted to affect the ATP production differed significantly between mitochondrial macrohaplogroups. The total number of retrieved oocytes was different between the H-V and J-T as well as the U-K and J-T macrohaplogroups. There was a non-significant increase in mtDNA levels in CCs with heteroplasmic mitochondrial mutations.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

Although a large number of samples were analysed in this study, it was not possible to analyse all the CCs from every patient. Also, the results obtained with respect to specific clinical outcomes and macrohaplogroups should be interpreted with caution due to the smaller sample sizes when subdividing the dataset.

WIDER IMPLICATIONS OF THE FINDINGS

These findings suggest that the analysis of mtDNA in CCs is unlikely to provide an advantage in terms of improved embryo selection during assisted reproduction cycles. Nonetheless, our data raise interesting biological questions, particularly regarding the interplay of metabolism and BMI and the association of mtDNA haplogroup with oocyte yield in ovarian stimulation cycles.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by National Institutes of Health grant 5R01HD092550-02. D.J.N. and C.R. co-hold patent US20150346100A1 and D.J.N. holds US20170039415A1, both for metabolic imaging methods. D.W. receives support from the NIHR Oxford Biomedical Research Centre. The remaining authors have no conflicts of interest to declare.

Unlocking the Complexity of Mitochondrial DNA: A Key to Understanding Neurodegenerative Disease Caused by Injury

Neurodegenerative disorders that are triggered by injury typically have variable and unpredictable outcomes due to the complex and multifactorial cascade of events following the injury and during recovery. Hence, several factors beyond the initial injury likely contribute to the disease progression and pathology, and among these are genetic factors. Genetics is a recognized factor in determining the outcome of common neurodegenerative diseases. The role of mitochondrial genetics and function in traditional neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, is well-established. Much less is known about mitochondrial genetics, however, regarding neurodegenerative diseases that result from injuries such as traumatic brain injury and ischaemic stroke. We discuss the potential role of mitochondrial DNA genetics in the progression and outcome of injury-related neurodegenerative diseases. We present a guide for understanding mitochondrial genetic variation, along with the nuances of quantifying mitochondrial DNA variation. Evidence supporting a role for mitochondrial DNA as a risk factor for neurodegenerative disease is also reviewed and examined. Further research into the impact of mitochondrial DNA on neurodegenerative disease resulting from injury will likely offer key insights into the genetic factors that determine the outcome of these diseases together with potential targets for treatment.

Role of mitochondrial DNA copy number in incident cardiovascular diseases and the association between cardiovascular disease and type 2 diabetes: A follow-up study on middle-aged women

BACKGROUND AND AIMS

Mitochondrial DNA copy number (mtDNA-CN) is a surrogate biomarker of mitochondrial dysfunction and is associated with type 2 diabetes (T2D) and cardiovascular disease (CVD). However, despite being associated with both CVD and T2D, it is not known what role mtDNA-CN has in the association between T2D and CVD. Our aims were to investigate whether, (1) baseline mtDNA-CN is associated with CVD incidence and (2) mtDNA-CN has a role as a mediator between T2D and CVD.

METHOD

We quantified absolute mtDNA-CN by droplet digital PCR method in a population-based follow-up study of middle aged (52-65 years) women (n = 3062). The median follow-up period was 17 years.

RESULTS

Our results show that low baseline levels of mtDNA-CN (<111 copies/μL) were associated with an increased risk of CVD (HR = 1.32, 95% CI = 1.08; 1.63) as well as with specific CVDs: coronary heart disease (HR = 1.28, 95% CI = 0.99; 1.66), stroke (HR = 1.26, 95% CI = 0.87; 1.84) and abdominal aortic aneurysm (HR = 2.61, 95% CI = 1.03; 6.62). The associations decreased but persisted even after adjustment for potential confounders. Furthermore, our results show that the total effect of T2D on future risk of CVD was reduced after controlling for mtDNA-CN and the proportion mediated by mtDNA-CN was estimated to be 4.9%.

CONCLUSIONS

Lower baseline mtDNA-CN is associated with incident CVD and may have a mediating effect on the association between T2D and CVD; however, this novel observation needs to be confirmed in future studies.

Prospective Associations of Early Pregnancy Metal Mixtures with Mitochondria DNA Copy Number and Telomere Length in Maternal and Cord Blood

BACKGROUND

Metal exposure during pregnancy influences maternal and child health. Oxidative stress and inflammation may mediate adverse effects of heavy metals, whereas essential metals may act as antioxidants. Mitochondrial DNA is a prime target for metal-induced oxidative damage. Telomere dysfunction is attributed to imbalances between reactive oxidant species and antioxidants.

OBJECTIVES

We evaluated individual and joint associations of prenatal metals with mitochondrial DNA copy number (mtDNAcn) and telomere length (TL) in maternal and cord blood as biomarkers of inflammation and oxidative stress.

METHODS

We measured six nonessential metals (arsenic, barium, cadmium, cesium, lead, mercury) and four essential metals (magnesium, manganese, selenium, zinc) in first-trimester maternal red blood cells in Project Viva, a U.S. prebirth cohort. We measured relative mtDNAcn (n=898) and TL (n=893) in second-trimester maternal blood and mtDNAcn (n=419) and TL (n=408) in cord blood. We used multivariable linear regression and quantile g-computation to estimate associations between prenatal metals and the biomarkers. We used generalized additive models and Bayesian kernel machine regression to examine nonlinearity and interactions.

RESULTS

A 2-fold increase in maternal magnesium was associated with lower maternal [β=-0.07, 95% confidence interval (CI): -0.10, -0.01] and cord blood (β=-0.08, 95% CI: -0.20, -0.01) mtDNAcn. Lead was associated with higher maternal mtDNAcn (β=0.04, 95% CI: 0.01, 0.06). Selenium was associated with longer cord blood TL (β=0.30, 95% CI: 0.01 0.50). An association was observed between the nonessential metal mixture and higher maternal mtDNAcn (β=0.04, 95% CI: 0.01, 0.07). There was a nonlinear relationship between cord blood mtDNAcn and magnesium; maternal mtDNAcn and barium, lead, and mercury; and maternal TL and barium.

DISCUSSION

Maternal exposure to metals such as lead, magnesium, and selenium was associated with mtDNAcn and TL in maternal second trimester and cord blood. Future work will evaluate whether these biomarkers are associated with child health. https://doi.org/10.1289/EHP9294.

Mitochondrial Epigenetics and Environmental Health: Making a Case for Endocrine Disrupting Chemicals

Recent studies implicate mitochondrial dysfunction in the development and progression of numerous chronic diseases, which may be partially due to modifications in mitochondrial DNA (mtDNA). There is also mounting evidence that epigenetic modifications to mtDNA may be an additional layer of regulation that controls mitochondrial biogenesis and function. Several environmental factors (eg, smoking, air pollution) have been associated with altered mtDNA methylation in a handful of mechanistic studies and in observational human studies. However, little is understood about other environmental contaminants that induce mtDNA epigenetic changes. Numerous environmental toxicants are classified as endocrine disrupting chemicals (EDCs). Beyond their actions on hormonal pathways, EDC exposure is associated with elevated oxidative stress, which may occur through or result in mitochondrial dysfunction. Although only a few studies have assessed the impacts of EDCs on mtDNA methylation, the current review provides reasons to consider mtDNA epigenetic disruption as a mechanism of action of EDCs and reviews potential limitations related to currently available evidence. First, there is sufficient evidence that EDCs (including bisphenols and phthalates) directly target mitochondrial function, and more direct evidence is needed to connect this to mtDNA methylation. Second, these and other EDCs are potent modulators of nuclear DNA epigenetics, including DNA methylation and histone modifications. Finally, EDCs have been shown to disrupt several modulators of mtDNA methylation, including DNA methyltransferases and the mitochondrial transcription factor A/nuclear respiratory factor 1 pathway. Taken together, these studies highlight the need for future research evaluating mtDNA epigenetic disruption by EDCs and to detail specific mechanisms responsible for such disruptions.

Mitochondrial DNA copy number and trimethylamine levels in the blood: New insights on cardiovascular disease biomarkers

Among cardiovascular disease (CVD) biomarkers, the mitochondrial DNA copy number (mtDNAcn) is a promising candidate. A growing attention has been also dedicated to trimethylamine-N-oxide (TMAO), an oxidative derivative of the gut metabolite trimethylamine (TMA). With the aim to identify biomarkers predictive of CVD, we investigated TMA, TMAO, and mtDNAcn in a population of 389 coronary artery disease (CAD) patients and 151 healthy controls, in association with established risk factors for CVD (sex, age, hypertension, smoking, diabetes, glomerular filtration rate [GFR]) and troponin, an established marker of CAD. MtDNAcn was significantly lower in CAD patients; it correlates with GFR and TMA, but not with TMAO. A biomarker including mtDNAcn, sex, and hypertension (but neither TMA nor TMAO) emerged as a good predictor of CAD. Our findings support the mtDNAcn as a promising plastic biomarker, useful to monitor the exposure to risk factors and the efficacy of preventive interventions for a personalized CAD risk reduction.

Differentiation of THP-1 monocytes to macrophages increased mitochondrial DNA copy number but did not increase expression of mitochondrial respiratory proteins or mitochondrial transcription factor A

Monocytes are differentiated into macrophages. In this study, mitochondrial DNA copy number (mtDNAcn) levels and downstream events such as the expression of respiratory chain mRNAs were investigated during the phorbol 12-myristate 13-acetate (PMA)-induced differentiation of monocytes. Although PMA treatment increased mtDNAcn, the expression levels of mRNAs encoded in mtDNA were decreased. The levels of mitochondrial transcription factor A mRNA and protein were also decreased. The levels of coenzyme Q10 remained unchanged. These results imply that, although mtDNAcn is considered as a health marker, the levels of mtDNAcn may not always be consistent with the parameters of mitochondrial functions.

Mitochondria-DNA copy-number and incident venous thromboembolism among middle-aged women: a population-based cohort study

Venous thromboembolism (VTE) is the third most common cardiovascular disease. Low amount of mitochondrial DNA copy number (mtDNA-CN) has been associated with arterial cardiovascular disease (CVD) and reflects mitochondrial dysfunctions. However, whether mtDNA-CN is associated with VTE has not been determined. To examine the association between mtDNA-CN and incident VTE among middle-aged women. 6917 women aged 50-64 years, followed for 20 years in the Women's Health In the Lund Area (WHILA) study. DNA samples for mtDNA quantification were available from 2521 women. Quantification of mtDNA-CN was performed using a well-optimized droplet digital PCR method. After exclusions of women with anticoagulant treatment, women living in nursing homes, and women who were diagnosed with cancer, stroke, VTE, or coronary heart disease at baseline, a cohort of 2117 women remained for analysis. Cox regression was used to analyze the relationship between mtDNA-CN and time to VTE (hazard ratio = HR). In total, 87 women were diagnosed with VTE during follow-up, corresponding to an incidence rate of 2.8 per 1000 person-years. Neither crude nor adjusted HR for mtDNA-CN were significantly associated with incident VTE. A sensitivity analysis with inclusion of excluded women did not change the results. MtDNA-CN was not significantly associated with VTE. The present study suggests that mtDNA-CN, reflecting mitochondrial dysfunction, should not be considered a biomarker that plays a major role for developing VTE. However, due to limited study size we may not exclude minor associations.

Role of Oxidative DNA Damage and Repair in Atrial Fibrillation and Ischemic Heart Disease

Atrial fibrillation (AF) and ischemic heart disease (IHD) represent the two most common clinical cardiac diseases, characterized by angina, arrhythmia, myocardial damage, and cardiac dysfunction, significantly contributing to cardiovascular morbidity and mortality and posing a heavy socio-economic burden on society worldwide. Current treatments of these two diseases are mainly symptomatic and lack efficacy. There is thus an urgent need to develop novel therapies based on the underlying pathophysiological mechanisms. Emerging evidence indicates that oxidative DNA damage might be a major underlying mechanism that promotes a variety of cardiac diseases, including AF and IHD. Antioxidants, nicotinamide adenine dinucleotide (NAD⁺) boosters, and enzymes involved in oxidative DNA repair processes have been shown to attenuate oxidative damage to DNA, making them potential therapeutic targets for AF and IHD. In this review, we first summarize the main molecular mechanisms responsible for oxidative DNA damage and repair both in nuclei and mitochondria, then describe the effects of oxidative DNA damage on the development of AF and IHD, and finally discuss potential targets for oxidative DNA repair-based therapeutic approaches for these two cardiac diseases.

Yoga improves mitochondrial health and reduces severity of autoimmune inflammatory arthritis: A randomized controlled trial

BACKGROUND

Oxidative stress (OS) and mitochondrial alterations have been implicated in the pathogenesis of rheumatoid arthritis (RA). Various environmental triggers like air pollutants, smoking, unhealthy social habits and sedentary lifestyle induce OS, which may compromise mitochondrial integrity. This trial was designed to explore the effect of 8-weeks yoga practice on mitochondrial health and disease severity in an active RA group compared with a usual-care control group.

METHODS

A total of 70 subjects were randomized into two groups: yoga group and non-yoga group. Mitochondrial health was assessed by calculation of mitochondrial DNA copy number (mtDNA-CN), OS markers, mitochondrial activity, mitochondrial membrane potential (ΔΨm), circadian rhythm markers and transcripts associated with mitochondrial integrity: AMPK, TIMP-1, KLOTHO, SIRT-1, and TFAM. Parameters of disease activity and disability quotient were also assessed by disease activity score - erythrocyte sedimentation rate (DAS28-ESR) and health assessment questionnaire-disability index (HAQ-DI), respectively.

RESULTS

In yoga group, there was a significant upregulation of mtDNA-CN, mitochondrial activity markers, ΔΨm, and transcripts that maintain mitochondrial integrity after 8-weeks of yoga. There was optimization of OS markers, and circadian rhythm markers post 8-weeks practice of yoga. Yoga group participants showed significant improvements in DAS28-ESR (p < 0.05) and HAQ-DI (p < 0.05) over the non-yoga group.

CONCLUSION

Adoption of yoga by RA patients holds the key to enhance mitochondrial health, improve circadian rhythm markers, OS marker regulation, upregulation of transcripts that maintain mitochondrial integrity, reduce disease activity and its associated consequences on health outcome and hence can be beneficial as an adjunct therapy.

Metabolism in Pulmonary Hypertension

Pulmonary arterial hypertension (PAH) is characterized by impaired regulation of pulmonary hemodynamics and vascular growth. Alterations of metabolism and bioenergetics are increasingly recognized as universal hallmarks of PAH, as metabolic abnormalities are identified in lungs and hearts of patients, animal models of the disease, and cells derived from lungs of patients. Mitochondria are the primary organelle critically mediating the complex and integrative metabolic pathways in bioenergetics, biosynthetic pathways, and cell signaling. Here, we review the alterations in metabolic pathways that are linked to the pathologic vascular phenotype of PAH, including abnormalities in glycolysis and glucose oxidation, fatty acid oxidation, glutaminolysis, arginine metabolism, one-carbon metabolism, the reducing and oxidizing cell environment, and the tricarboxylic acid cycle, as well as the effects of PAH-associated nuclear and mitochondrial mutations on metabolism. Understanding of the metabolic mechanisms underlying PAH provides important knowledge for the design of new therapeutics for treatment of patients.

Diabetic cardiomyopathy attenuated the protective effect of ischaemic post-conditioning against ischaemia-reperfusion injury in the isolated rat heart model

The present study was designed to investigate the efficacy of post-conditioning (POC) in the diabetic heart with myopathy (DCM) against ischaemia-reperfusion (I/R) injury in an isolated rat heart model. Present work includes three groups of male Wistar rat viz., (i) normal, (ii) diabetes mellitus (DM) and (iii) DCM and each group was subdivided into normal perfusion, I/R, and POC. Isolated heart from the rats was analysed for tissue injury, contractile function, mitochondrial function, and oxidative stress. Results demonstrated that unlike in DM heart and normal heart, POC procedure failed to recover the DCM heart from I/R induced cardiac dysfunction (measured via cardiac hemodynamics and infarct size. POC was unsuccessful in preserving mitochondrial subsarcolemmal fraction during I/R when compared with DM and normal heart. To conclude, the development of myopathy in diabetic heart abolished the cardioprotective efficacy of POC and the underlying pathology was linked with the mitochondrial dysfunction.KEY MESSAGESEarly studies reported contradicting response of diabetic heart towards post-conditioning mediated cardioprotection.Deteriorated mitochondrial function underlines the failure of post-conditioning in DCM.Efficacy of cardioprotection depends on the varying pathology of different diabetes stages.