Relative mtDNA Research Articles

Investigation of Mitochondrial Related Variants in a Cerebral Small Vessel Disease Cohort

Monogenic forms of cerebral small vessel disease (CSVD) can be caused by both variants in nuclear DNA and mitochondrial DNA (mtDNA). Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) is known to have a phenotype similar to Cerebral Autosomal Dominant Arteriopathy with Sub-cortical Infarcts and Leukoencephalopathy (CADASIL), and can be caused by variants in the mitochondrial genome and in several nuclear-encoded mitochondrial protein (NEMP) genes. The aim of this study was to screen for variants in the mitochondrial genome and NEMP genes in a NOTCH3-negative CADASIL cohort, to identify a potential link between mitochondrial dysfunction and CSVD pathology. Whole exome sequencing was performed for 50 patients with CADASIL-like symptomology on the Ion Torrent system. Mitochondrial sequencing was performed using an in-house designed protocol with sequencing run on the Ion GeneStudio S5 Plus (S5 +). NEMP genes and mitochondrial sequencing data were examined for rare (MAF < 0.001), non-synonymous variants that were predicted to have a deleterious effect on the protein. We identified 29 candidate NEMP variants that had links to either MELAS-, encephalopathy-, or Alzheimer’s disease–related phenotypes. Based on these changes, variants affecting POLG, MTO1, LONP1, NDUFAF6, NDUFB3, and TCIRG1 were thought to play a potential role in CSVD pathology in this cohort. Overall, the exploration of the mitochondrial genome identified a potential role for mitochondrial related proteins and mtDNA variants contributing to CSVD pathologies.

Quantitative and structural characteristics of mitochondrial DNA in varicose veins

ObjectiveWe examined quantitative (in terms of mtDNA/nuclear DNA) and structural (in terms of common deletions in the MT-ND4 gene region) characteristics of mitochondrial DNA (mtDNA) in varicose veins (VVs) and venous wall layers by comparing mitochondrial genome parameters, as well as mitochondrial function (in terms of mitochondrial membrane potential (MtMP)), in varicose vein (VV) vs. non-varicose vein (NV) tissue samples. MethodsWe analyzed paired great saphenous vein samples (VV vs. NV segments from each patient left after venous surgery) harvested from patients with VVs. Relative mtDNA level and the proportion of no-deletion mtDNA were determined by a multiplex quantitative PCR (qPCR), confirming the latter with a more sensitive method – droplet digital PCR (ddPCR). Mitochondria's functional state in VVs was assessed using fluorescent (dependent on MtMP) live-staining of mitochondria in venous tissues. ResultsTotal mtDNA level was lower in VV than in NV samples (predominantly in the t. media layer). ddPCR analysis showed lower proportion of no-deletion mtDNA in VVs. Because of the decrease in relative MtMP in VVs, our results suggest a possible reduction of mitochondrial function in VVs. ConclusionQuantitative and structural changes (copy number and integrity) of mtDNA are plausibly involved in VV pathogenesis. Future clinical studies implementing the mitochondrial targeting may be eventually fostered after auxiliary mechanistic studies.

Serum from pediatric dilated cardiomyopathy patients promotes dysregulation of cardiolipin biosynthesis and mitochondrial dysfunction in primary cardiomyocytes

Pediatric dilated cardiomyopathy (DCM) is a devastating and poorly understood disease with most clinical treatment paradigms extrapolated from the adult population. Our studies showed that aspects of metabolism and mitochondrial function are dysregulated in pediatric hearts. Cardiolipin (CL), a unique phospholipid in the inner mitochondrial membrane, is essential for optimal mitochondrial function and was shown to be dysregulated in failing adult and pediatric human heart. Our objective is to investigate if serum circulating factors from pediatric DCM patients can remodel CL resulting in mitochondrial dysfunction in vitro, similar to what is observed in the failing pediatric heart. Using a novel in vitro model that consists of treating neonatal rat ventricular myocytes (NRVMs) with serum from pediatric DCM patients or from non-failing (NF) healthy controls, mitochondrial respiration was assessed using the Agilent Seahorse, and reactive oxygen species (ROS) was assessed using Electron Paramagnetic Resonance Spectroscopy. Relative mtDNA copy number was determined by qPCR and expression of enzymes involved in CL biosynthesis were analyzed using RT-qPCR. Mass-spectrometry was used to quantitate total and specific CL species and to investigate the metabolite composition of NRVMs treated with NF or DCM serum. While mitochondrial ROS and mtDNA copy number were not significantly altered, we show that DCM serum decreases mitochondrial function, which is associated with alterations in CL content and composition and the downregulation of enzymes implicated in CL biosynthesis. Analysis of metabolite content showed an alteration of pathways involved in fatty acid metabolism, mitochondrial biogenesis and regulation of β-oxidation by PPARα. In conclusion, pediatric DCM serum circulating factors can promote CL remodeling resulting in mitochondrial dysfunction in primary cardiomyocytes. These findings suggest that CL could be a novel therapeutic target for this particular population.

MtDNA content in cumulus cells does not predict development to blastocyst or implantation.

STUDY QUESTIONIs relative mitochondrial DNA (mtDNA) content in cumulus cells (CCs) related to embryo developmental competence in humans and/or the bovine model?SUMMARY ANSWERmtDNA content in CCs provides a poor predictive value of oocyte developmental potential, both in vitro and following embryo transfer.WHAT IS KNOWN ALREADYCCs are closely connected to the oocyte through transzonal projections, serving essential metabolic functions during folliculogenesis. These oocyte-supporting cells are removed and discarded prior to ICSI, thereby providing interesting biological material on which to perform molecular analyses designed to identify markers that predict oocyte developmental competence. Previous studies have positively associated oocyte mtDNA content with developmental potential in animal models and women. However, it remains debatable whether mtDNA content in CCs could be used as a proxy to infer oocyte developmental potentialSTUDY DESIGN, SIZE, DURATIONmtDNA content was analyzed in CCs obtained from 109 human oocytes unable to develop to blastocyst, able to develop to blastocyst but failing to establish pregnancy or able to develop to blastocyst and to establish pregnancy. mtDNA analysis was also performed on bovine cumulus samples collected from 120 oocytes unable to cleave, oocytes developing into cleaved embryos but arresting development prior to the blastocyst stage or oocytes developing to blastocysts.PARTICIPANTS/MATERIALS, SETTING, METHODSHuman CCs samples were obtained from women undergoing IVF. Only unfrozen oocytes and embryos not submitted to preimplantation genetic testing were included in the analysis. Bovine samples were obtained from slaughtered cattle and individually matured, fertilized and cultured in vitro. Relative mtDNA was assessed by quantitative PCR analysis.MAIN RESULTS AND THE ROLE OF CHANCEmtDNA content in human and bovine CCs did not differ according to the developmental potential of their enclosed oocyte. Moreover, mtDNA content in bovine oocytes did not correlate with that of their corresponding CCs.LARGE SCALE DATAN/A.LIMITATIONS, REASONS FOR CAUTIONThe lack of correlation found between mtDNA content in human CCs and oocytes was also assessed in bovine samples. Although bovine folliculogenesis, mono-ovulatory ovulation and early embryo development exhibit considerable similarities with that of humans, they may not be fully comparable.WIDER IMPLICATIONS OF THE FINDINGSThe use of molecular markers for oocyte developmental potential in CCs could be used to enhance success rates following single embryo transfer. However, our data indicate that mtDNA in CCs is not a good proxy for oocyte quality.STUDY FUNDING/COMPETING INTEREST(S)This research was supported by the Industrial Doctorate Project IND2017/BIO-7748 funded by the Madrid Region Government. The authors declare no competing interests.

Morphological variation and genealogical discordance in Caatinga sand lizards Calyptommatus Rodrigues 1991 (Squamata: Gymnophthalmidae) with the description of a new species.

In the last decades, a remarkable fauna of psammophilous and fossorial squamates was discovered in sandy habitats of the semiarid Caatinga of northeast Brazil. Despite the increasing accumulation of genetic data from this unique fauna, an incomplete knowledge of its diversity still hampers a better understanding of its origins and diversification. The fossorial lizard genus Calyptommatus (Gymnophthalmidae) is endemic to sandy habitats of the Caatinga, being currently represented by four allopatric species. In this study, we used morphological and molecular data to assess population-level variation in Calyptommatus. We found a new morphotype of Calyptommatus from the state of Bahia, Brazil, readily distinguished from congeners by the presence of a frontal scale. Morphological, nuDNA and geographic data support the recognition of a new species herein described as Calyptommatus frontalis sp. nov. Nevertheless, genetic data revealed mito-nuclear+morphology discordance, with populations with frontal scales distributed in three distantly related mtDNA clades, suggesting either potential historical and/or current introgressions or incomplete lineage sorting. Further data are needed to clarify the status of the two other mtDNA clades displaying a frontal scale.

Glyphosate and AMPA exposure in relation to markers of biological aging in an adult population-based study.

Glyphosate, a broad-spectrum herbicide, and its main metabolite aminomethylphosphonic acid (AMPA) are persistent in the environment. Studies showed associations between glyphosate or AMPA exposure and several adverse cellular processes, including metabolic alterations and oxidative stress. To determine the association between glyphosate and AMPA exposure and biomarkers of biological aging. We examined glyphosate and AMPA exposure, mtDNA content and leukocyte telomere length in 181 adults, included in the third cycle of the Flemish Environment and Health Study (FLEHSIII). DNA was isolated from leukocytes and the relative mtDNA content and telomere length were determined using qPCR. Urinary glyphosate and AMPA concentrations were measured by Gas Chromatography-Tandem Mass Spectrometry (GC-MS-MS). We used multiple linear regression models to associate mtDNA content and leukocyte telomere length with glyphosate or AMPA exposure while adjusting for confounding variables. A doubling in urinary AMPA concentration was associated with 5.19% (95% CI: 0.49 to 10.11; p=0.03) longer leukocyte telomere length, while no association was observed with urinary glyphosate concentration. No association between mtDNA content and urinary glyphosate nor AMPA levels was observed. This study showed that AMPA exposure may be associated with telomere biology in adults.

Detection of Mitochondrial DNA Copy Number in Plasma Exosomes of Patients with Non-small Cell Lung Cancer

For the prevalence of lung cancer and its poor diagnosis, the seeking of the efficient biomarkers for this disease is an urgent requirement, especially from non-invasive samples such as plasma. The mitochondria DNA (mtDNA) copy number change has been evaluated as a potential indicator of cancer risk, however, there have been few studies regarding mtDNA in plasma derived exosomes. In this study, the mtDNA copy number was measured on 29 plasma exosome samples of patients with non-small cell lung cancer (NSCLC) and 29 plasma exosome samples of cancer-free controls by real-time PCR assay, then being statistically analyzed to evaluate the relationship between these figures and several pathological features of NSCLC patients. As the results, the existence of mtDNA in exosomes isolated from plasma was detected through PCR assay using primers covering most of the mtDNA length. The relative mtDNA copy numbers determined in the exosomes of the disease and control groups were 1619.1 ± 2589.0 and 1207.0 ± 1550.0, respectively, whereas these values in two disease stages were 783.6 ± 759.3 (stage I-II) and 2647.0 ± 3584.0 (stage III-IV). Comparing among these groups, the difference was only statistically significant between the disease groups of stage I-II and stage III-IV (p&lt;0.05), the group of stage III-IV and the control group (p&lt;0.05). Indeed, the mtDNA copy number is associated with tumor stage and stage N (p&lt;0.05). On the other aspect, the smoking habit of NSCLC patients could be an underlying reason behind the alteration in mtDNA copy number in the plasma exosomes. In short, our study demonstrates that the mtDNA copy number in exosomes resourced from plasma could be a potential biomarker for the detection and prognosis of NSCLC.

Effects of Melatonin Supplementation during Pregnancy on Reproductive Performance, Maternal-Placental-Fetal Redox Status, and Placental Mitochondrial Function in a Sow Model.

Melatonin (MT) is a bio-antioxidant that has been widely used to prevent pregnancy complications, such as pre-eclampsia and IUGR during gestation. This experiment evaluated the impacts of dietary MT supplementation during pregnancy on reproductive performance, maternal–placental–fetal redox status, placental inflammatory response, and mitochondrial function, and sought a possible underlying mechanism in the placenta. Sixteen fifth parity sows were divided into two groups and fed each day of the gestation period either a control diet or a diet that was the same but for 36 mg of MT. The results showed that dietary supplementation with MT increased placental weight, while the percentage of piglets born with weight < 900 g decreased. Meanwhile, serum and placental MT levels, maternal–placental–fetal redox status, and placental inflammatory response were increased by MT. In addition, dietary MT markedly increased the mRNA levels of nutrient transporters and antioxidant-related genes involved in the Nrf2/ARE pathway in the placenta. Furthermore, dietary MT significantly increased ATP and NAD+ levels, relative mtDNA content, and the protein expression of Sirt1 in the placenta. These results suggested that MT supplementation during gestation could improve maternal–placental–fetal redox status and reproductive performance by ameliorating placental antioxidant status, inflammatory response, and mitochondrial dysfunction.

Abstract 13349: Circulating Factors Promote Metabolic Remodeling and Mitochondrial Dysfunction in Single Ventricle Congenital Heart Disease

Introduction: While heart failure (HF) remains a leading cause of death and indication for transplant in single ventricle heart disease (SV) patients, the molecular mechanisms associated with the progression to HF are poorly understood. The purpose of this study is to investigate if serum circulating factors from failing SV patients remodel cardiomyocyte metabolism, as is seen in the failing SV heart. Additionally, we investigated the effect of sildenafil on cardiomyocyte metabolism in vitro. Methods: We used a novel in vitro model that consists of primary cardiomyocytes (NRVMs) treated with serum from failing SV patients (SVHF) or bi-ventricular non-failing (BVNF) controls, +/- sildenafil. Mass spectroscopy was used to quantitate mitochondrial cardiolipin and investigate the metabolite composition of serum-treated NRVMs. Mitochondrial respiration was assessed using the Seahorse Bioanalyzer (Agilent), and reactive oxygen species (ROS) were quantified using the Amplex Red (Thermo Fisher). Enzyme and gene expression were analyzed using RT-qPCR and western blot, and relative mtDNA copy numbers were determined by qPCR. Results: While relative mitochondrial copy number was not significantly altered, failing SV serum decreases NRVM mitochondrial function (Fig. 1A-C), which is associated with decreased mitochondrial cardiolipin, increased reactive oxygen species (Fig. 1D), and altered expression of enzymes implicated in lipid and metabolic remodeling. Importantly, many of these changes are abrogated by sildenafil (Fig 1A-D). Conclusions: Together these data suggest that SV serum circulating factors promote lipid and metabolic remodeling in cardiomyocytes and that mitochondria represent a novel therapeutic target of sildenafil in the failing SV heart. Elucidation of the molecular mechanisms involved in modulation of cardiac energy metabolism in SV will be important to improve cardiac function and enhance transplant-free SV survival.

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

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? 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. 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. 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. 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. 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. N/A. 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. 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. 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.

Constitutive activation of the PI3K-Akt-mTORC1 pathway sustains the m.3243\u2009A\u2009>\u2009G mtDNA mutation

Mutations of the mitochondrial genome (mtDNA) cause a range of profoundly debilitating clinical conditions for which treatment options are very limited. Most mtDNA diseases show heteroplasmy – tissues express both wild-type and mutant mtDNA. While the level of heteroplasmy broadly correlates with disease severity, the relationships between specific mtDNA mutations, heteroplasmy, disease phenotype and severity are poorly understood. We have carried out extensive bioenergetic, metabolomic and RNAseq studies on heteroplasmic patient-derived cells carrying the most prevalent disease related mtDNA mutation, the m.3243 A > G. These studies reveal that the mutation promotes changes in metabolites which are associated with the upregulation of the PI3K-Akt-mTORC1 axis in patient-derived cells and tissues. Remarkably, pharmacological inhibition of PI3K, Akt, or mTORC1 reduced mtDNA mutant load and partially rescued cellular bioenergetic function. The PI3K-Akt-mTORC1 axis thus represents a potential therapeutic target that may benefit people suffering from the consequences of the m.3243 A > G mutation.

P–219 mtDNA content in bovine cumulus cells does not predict oocytés developmental competence

Abstract Study question Does cumulus cell mtDNA content correlate with oocyte developmental potential in the bovine model? Summary answer The relative amount of mtDNA content did not vary significantly in oocytes showing different developmental outcomes following IVF What is known already Cumulus cells are closely connected to the oocyte through transzonal projections, serving essential metabolic functions during folliculogenesis. These oocyte-supporting cells are removed and discarded prior to ICSI, thereby constituting an interesting biological material on which to perform molecular analysis aimed to predict oocyte developmental competence. Previous studies have positively associated oocytés mtDNA content with developmental potential in both animal models and women. However, it remains debatable whether mtDNA content in cumulus cells could be used as a proxy to infer oocyte developmental potential. Study design, size, duration Bovine cumulus cells were allocated into three groups according to the developmental potential of the oocyte: 1) oocytes developing to blastocysts following IVF (Bl+Cl+), 2) oocytes cleaving following IVF but arresting their development prior to the blastocyst stage (Bl-Cl+), and 3) oocytes not cleaving following IVF (Bl-Cl-). Relative mtDNA content was analysed in 40 samples/group, each composed by the cumulus cells from one cumulus-oocyte complex (COC). Participants/materials, setting, methods Bovine cumulus-oocyte complexes were obtained from slaughtered cattle and individually matured in vitro (IVM). Following IVM, cumulus cells were removed by hyaluronidase treatment, pelleted, snap frozen in liquid nitrogen and stored at –80 ºC until analysis. Cumulus-free oocytes were fertilized and cultured in vitro individually and development was recorded for each oocyte. Relative mtDNA abundance was determined by qPCR, amplifying a mtDNA sequence (COX1) and a chromosomal sequence (PPIA). Statistical differences were tested by ANOVA. Main results and the role of chance Relative mtDNA abundance did not differ significantly (ANOVA p &amp;gt; 0.05) between the three groups exhibiting different developmental potential (1±0.06 vs. 1.19±0.05 vs. 1.11±0.05, for Bl+Cl+ vs. Bl-Cl+ vs. Bl-Cl-, mean±s.e.m.). Limitations, reasons for caution Experiments were conducted in the bovine model. Although bovine folliculogenesis, monoovulatory ovulation and early embryo development exhibit considerable similarities with that of humans, caution should be taken when extrapolating these data to humans. Wider implications of the findings: The use of molecular markers for oocyte developmental potential in cumulus cells could be used to enhance success rates following single-embryo transfer. Unfortunately, mtDNA in cumulus cells was not found to be a good proxy for oocyte quality. Trial registration number Not applicable

Design of a digital-PCR assay to quantify fragmented human mitochondrial DNA.

Digital PCR (dPCR) has been adapted to quantify the proportion of mitochondrial DNA (mtDNA) molecules without and with double-strand DNA breaks (DSBs). This is based on a break-apart approach of two differentially labeled target sequences distantly located in the circular DNA molecule. When the two targets amplify in separated reaction partitions, the original mtDNA molecule should be fragmented by two DSBs at least, each in a different segment between targets. When both targets amplify in the same partition, it must correspond to a circular or linear mtDNA molecule. These two possibilities may be distinguished through a restriction endonuclease (RE) induced unique DSB within a DNA segment between the targets. After RE-digestion, separation of both target signals in different partitions must indicate the presence of a previous linear mtDNA molecule. Otherwise, joint amplification in the same partition would correspond to an initial circular mtDNA that has been linearized by the endonuclease. The procedure was validated by assaying different proportions of mtDNA fragmented by in vitro digestion with REs, evidencing a perfect accordance between the expected theoretical values and dPCR quantification. Samples from peripheral blood cells, cellular and extracellular DNA from the U2OS cell line, as well as cells incubated with ethidium bromide to induce mtDNA depletion, were evaluated. The technique may be of interest to complement the studies of mtDNA in relation to aging and human disease, as well as to assess possible adverse effects of certain drugs that could be related to affectation of mtDNA.

Serum from pediatric dilated cardiomyopathy patients promotes dysregulation of cardiolipin biosynthesis and mitochondrial dysfunction

Pediatric dilated cardiomyopathy (DCM) is a devastating and poorly understood disease with most clinical treatment paradigms extrapolated from the adult population. Our studies showed that aspects of metabolism and mitochondria function are dysregulated in pediatric hearts. Cardiolipin (CL), a unique phospholipid in the inner mitochondrial membrane, is essential for optimal mitochondrial function and was shown to be dysregulated in failing adult hearts. We investigate if serum circulating factors from pediatric DCM patients can remodel CL resulting in mitochondrial dysfunction similar to what is observed in the failing pediatric heart. Using a novel in vitro model that consists of treating neonatal rat ventricular myocytes (NRVMs) with serum from pediatric DCM patients or from non-failing (NF) healthy controls, mitochondrial respiration was assessed using Seahorse assay, and reactive oxygen species (ROS) was assessed using Electron Paramagnetic Resonance Spectroscopy. Expression of enzymes involved in CL biosynthesis and remodeling were analyzed using RT-qPCR and relative mtDNA copy number determined by qPCR. Mass spectroscopy was used to quantitate total and specific CL species and to investigate the metabolite composition of NRVMs treated with NF or DCM serum. While mitochondrial ROS and copy number were not significantly altered, we showed that DCM serum decreases mitochondrial function, which is associated with alterations in CL content and composition and gene expression of enzymes implicated in CL biosynthesis and remodeling. Analysis of metabolite content showed an alteration of pathways involved in fatty acid metabolism, mitochondrial biogenesis and regulation of β-oxidation by PPARα. Pediatric DCM serum circulating factors can promote CL remodeling resulting in mitochondrial dysfunction in cardiomyocytes. These findings suggest that CL could be a therapeutic target for this particular population.

Telomere length and outcome of treatment for pulmonary tuberculosis in a gold mining community

Telomere length (TL) is a marker of ageing and mitochondrial DNA (mtDNA) is an early marker of inflammation caused by oxidative stress. We determined TL and mtDNA content among active pulmonary tuberculosis (PTB) patients to assess if these cellular biomarkers differed between artisanal miners and non-miners, and to assess if they were predictive of treatment outcome. We conducted a prospective cohort study from August 2018 to May 2019 involving newly diagnosed PTB patients at three outpatient TB clinics in a rural Democratic Republic of Congo. We measured relative TL and mtDNA content in peripheral blood leukocytes (at inclusion) via qPCR and assessed their association with PTB treatment outcome. We included 129 patients (85 miners and 44 non-miners) with PTB (median age 40 years; range 5–71 years, 22% HIV-coinfected). For each increase in year and HIV-coinfection, TL shortened by − 0.85% (− 0.19 to − 0.52) (p ≤ 0.0001) and − 14% (− 28.22 to − 1.79) (p = 0.02) respectively. Independent of these covariates, patients with longer TL were more likely to have successful TB treatment [adjusted hazard ratio; 95% CI 1.27 for a doubling of leucocyte telomere length at baseline; 1.05–1.44] than patients with a shorter TL. Blood mtDNA content was not predictive for PTB outcome. For a given chronological age, PTB patients with longer telomeres at time of diagnosis were more likely to have successful PTB treatment outcome.

STAMP: a multiplex sequencing method for simultaneous evaluation of mitochondrial DNA heteroplasmies and content.

Human mitochondrial genome (mtDNA) variations, such as mtDNA heteroplasmies (the co-existence of mutated and wild-type mtDNA), have received increasing attention in recent years for their clinical relevance to numerous diseases. But large-scale population studies of mtDNA heteroplasmies have been lagging due to the lack of a labor- and cost-effective method. Here, we present a novel human mtDNA sequencing method called STAMP (sequencing by targeted amplification of multiplex probes) for measuring mtDNA heteroplasmies and content in a streamlined workflow. We show that STAMP has high-mapping rates to mtDNA, deep coverage of unique reads and high tolerance to sequencing and polymerase chain reaction errors when applied to human samples. STAMP also has high sensitivity and low false positive rates in identifying artificial mtDNA variants at fractions as low as 0.5% in genomic DNA samples. We further extend STAMP, by including nuclear DNA-targeting probes, to enable assessment of relative mtDNA content in the same assay. The high cost-effectiveness of STAMP, along with the flexibility of using it for measuring various aspects of mtDNA variations, will accelerate the research of mtDNA heteroplasmies and content in large population cohorts, and in the context of human diseases and aging.

MITOCHONDRIAL DNA QUANTITY AND SEQUENCE VARIATION IN HUMAN CUMULUS CELLS ARE ASSOCIATED WITH PATIENT BMI BUT NOT AGE OR ASSISTED REPRODUCTION OUTCOMES

Cumulus cells (CCs) fulfil a vital role in support of oocyte developmental competency. The appropriate function of CCs relies on adequate energy production, which in turn depends on the quantity and genetic competence of mitochondria. We sought to characterize the mitochondrial DNA content of a large number of human CCs samples via a combination of quantitative (relative mtDNA copy number) and qualitative (DNA sequence) analyses. Results were considered in relation to factors of relevance to oocyte reproductive potential, such as female age and body mass index (BMI), as well as to embryo characteristics and assisted reproductive technology (ART) outcomes.

Somatic Mitochondrial DNA Point Mutations Used as Biomarkers to Demonstrate Genomic Heterogeneity in Primary Prostate Cancer.

Primary prostate tumor heterogeneity is poorly understood, leaving research efforts with challenges regarding the initiation and advancement of the disease. The growth of tumor cells is accompanied by mutations in nuclear and in mitochondrial genomes. Thus, mitochondrial DNA mutations may be used as tumor cell markers. By the use of laser capture microdissection coupled with assays for mitochondrial point mutation detection, mtDNA mutations were used to trace mutated cells at a histological level. Point mutations in mtDNA were determined in 12 primary prostate cancers. The tumors represent different pathology-prognostic grade groups. Known mutational hotspots of the mtDNA were scanned for heteroplasmy. All specimens with mtDNA heteroplasmy were subsequently subsampled by laser capture microdissection. From a total number of 1728 microsamples, mitochondrial DNA target sequences were amplified and base substitutions detected by cycling temperature capillary electrophoresis. Real-time PCR was used as a quantitative assay to determine the relative mtDNA copy number of 12 tumors studied, represented by two samples from each (N = 24); a high degree (75%) demonstrated tumor specimen heterogeneity. A grid of 96 spots isolated by laser capture microdissection demonstrated interfocal sample heterogeneity and increased the limit of detection. The spots demonstrated a wide range of mutant fractions from 0 to 100% mutant copies. The mitochondrial DNA copy number in the samples was determined by real-time PCR. No correlation between copy number and pathology-prognostic grade groups was observed. Somatic mitochondrial DNA point mutations represent traceable biomarkers demonstrating heterogeneity in primary prostate cancer. Mutations can be detected in areas before changes in tissue histopathology are evident to the pathologist.

Mitochondrial DNA Copy Number is Associated with Attention Deficit Hyperactivity Disorder.

Attention deficit hyperactivity disorder (ADHD) is the most common psychiatric disorder in children. Several hypotheses have been proposed to explain its etiology. Mitochondrial dysfunction (MD) is suggested to be one of the causes of Attention Deficit Hyperactivity Disorder. The objective of the study was to evaluate the relationship between MD and ADHD by investigating mitochondrial DNA (mtDNA) levels from peripheral blood leukocytes, one of the best biomarkers of mitochondrial dysfunction. This study included 56 children aged 6-16 years who were diagnosed with ADHD for the first time and 56 age- and sex-matched children without ADHD. Real-time PCR was performed to determine the relative mtDNA copy number in each study participant. The mean mtDNA copy number of the case group was 57.623±24.827 and that of the control group was 44.204±18.926 (p=0.002). The mtDNA copy number of the case group was higher than that of the control group. Results of ROC curve analysis provided a mtDNA cutoff value of 45. Significantly higher mtDNA copy number in ADHD group may suggest mitochondrial dysfunction in the etiopathogenesis of ADHD.

Association of mitochondrial DNA content and displacement loop region sequence variations with cancer-related fatigue in breast cancer survivors receiving chemotherapy

Cancer-related fatigue (CRF) is characterized by a lack of energy, and mitochondrial dysfunction is postulated to contribute to its etiology. This prospective cohort study assesses the self-reported fatigue levels of early-stage breast cancer patients using the validated Multi-Dimensional Fatigue Symptom Inventory–Short Form (MFSI-SF) and blood samples drawn at three time points: before treatment, approximately 6 weeks, and 12 weeks after the initiation of chemotherapy. The aim of this study is to evaluate mitochondrial measures with CRF, over the course of chemotherapy using mitochondrial DNA (mtDNA content) and displacement loop (D-loop) region sequence variations at nucleotide positions 303, 489 and 514. The relative mtDNA copy number was determined via real-time quantitative polymerase chain reaction and compared between study time points and D-loop sequence variants. The association of mtDNA content with MFSI-SF total and sub-domain scores was analyzed in a sample of 155 patients (mean age ± SD: 51.7 ± 8.8 years). The median mtDNA content decreased over 12 weeks after the initiation of chemotherapy (p < 0.001). Baseline mtDNA content was lower for nucleotide position 303 in sequence variations than for the reference sequence (67.2 copies vs 79.1 copies, p = 0.03). Physical fatigue negatively correlated with mtDNA content in both unadjusted (β = −0.0075, p = 0.048) and adjusted models (β = −0.0062, p = 0.042), accounting for age, anxiety, insomnia, haemoglobin levels and body mass index. Our findings add to the literature indicating that mitochondrial function serves as an important target for mitigating CRF.