Mitochondrial DNA Copy Number Variation Research Articles

Mitochondrial DNA copy number variation across three generations: a possible biomarker for assessing perinatal outcomes

BackgroundMitochondria have their own circular multi-copy genome (mtDNA), and abnormalities in the copy number are implicated in mitochondrial dysfunction, which contributes to a variety of aging-related pathologies. However, not much is known about the genetic correlation of mtDNA copy number across multiple generations and its physiological significance.MethodsWe measured the mtDNA copy number in cord blood or peripheral blood from 149 three-generation families, specifically the newborns, parents, and grandparents, of 149 families, totaling 1041 individuals. All of the biological specimens and information were provided by the Tohoku Medical Megabank Project in Japan. We also analyzed their maternal factors during pregnancy and neonatal outcomes.ResultsWhile the maternal peripheral blood mtDNA copy number was lower than that of other adult family members, it was negatively correlated with cord blood mtDNA copy number in male infants. Also, cord blood mtDNA copy numbers were negatively correlated with perinatal outcomes, such as gestation age, birth weight, and umbilical cord length, for both male and female neonates. Furthermore, the mtDNA copy number in the infants born to mothers who took folic acid supplements during pregnancy would be lower than in the infants born to mothers who did not take them.ConclusionsThis data-driven study offers the most comprehensive view to date on the genetic and physiological significance of mtDNA copy number in cord blood or peripheral blood taken from three generations, totaling more than 1000 individuals. Our findings indicate that mtDNA copy number would be one of the transgenerational biomarkers for assessing perinatal outcomes, as well as that appropriate medical interventions could improve the outcomes via quantitative changes in mtDNA.

Assessment of mitochondrial DNA copy number variation relative to nuclear DNA quantity between different tissues

Mitochondrial DNA is a widely tested genetic marker in various fields of research and diagnostics. Nonetheless, there is still little understanding on its abundance and quality within different tissues.Aiming to obtain deeper knowledge about the content and quality of mtDNA, we investigated nine tissues including blood, bone, brain, hair (root and shaft), cardiac muscle, liver, lung, skeletal muscle, and buccal mucosa of 32 deceased individuals using two real-time quantitative PCR-based assays with differently sized mtDNA and nDNA targets.The results revealed that the quantity of nDNA is a weak surrogate to estimate mtDNA quantities among tissues of an individual, as well as tissues across individuals. Especially hair showed extreme variation, depicting a range of multiple magnitudes of mtDNA molecules per hair fragment. Furthermore, degradation can lead to fewer fragments being available for PCR. The results call for parallel determination of the quantity and quality of mtDNA prior to downstream genotyping assays.

Analysis of mitochondrial DNA copy number variation in Brazilian farmers occupationally exposed to pesticides

ABSTRACT The use of pesticide use has been linked to the higher production of reactive oxygen species, resulting in oxidative stress, which in turn can cause genomic instability. A marker for instability is the copy number variation of the mitochondrial genome (mtDNAcn), which has been found to be altered in diverse human diseases, including tumors. This research aimed to examine the variation of mtDNAcn in individuals occupationally exposed to pesticides. Real-time PCR assays were conducted on 154 individuals (78 exposed and 76 non-exposed). Pesticide-exposed ndividuals exhibited a significant reduction in mtDNAcn (1.11 ± 0.37mtDNAcn/genome) compared to non-exposed individuals (1.30 ± 0.33mtDNAcn/genome; p = 0.001). The multivariate analysis indicated that individuals who reported using haloxyfop and copper sulfate demonstrated an increase (β = 0.200, p = 0.053) and a decrease (β=-0.2, p = 0.021), respectively, in mtDNAcn. In conclusion, our findings suggest that chronic exposure to pesticides results in changes in mtDNAcn.

First Report of Mitochondrial DNA Copy Number Variation in Opsius heydeni (Insecta, Hemiptera, Cicadellidae) from Polluted and Control Sites.

Mitochondrial DNA easily undergoes alterations due to exposure to stress factors. In particular, mitochondrial DNA copy number (mtDNAcn) variation can be used as a biomarker of the effect of exposure to various environmental contaminants. In this study, a molecular investigation based on the evaluation of mtDNAcn variation was applied for the first time to individuals belonging to the species Opsius heydeni. A total of 20 samples were collected from two sites in eastern Sicily: Priolo Gargallo, a site with a strong anthropic impact, and the Simeto river Oasis, a control site. Specimens identified based on morphological traits were used to obtain COI gene sequences from this species that were not previously available in GenBank. After processing, the relative mtDNAcn was evaluated using real-time PCR of a portion of the COI and 18S genes. A decrease in the mtDNAcn in the specimens from the polluted site was observed. These results highlight how environmental contaminants can alter the mitochondrial genome and how Opsius heydeni can be considered a potential bioindicator species of environmental quality.

Bifenthrin disrupts cytochrome c oxidase activity and reduces mitochondrial DNA copy number through oxidative damage in pool barb (Puntius sophore)

Bifenthrin (BF), a synthetic pyrethroid is used worldwide for both agricultural and non-agricultural purposes due to its high insecticidal activity and low toxicity in mammals. However, its improper usage implies a possible risk to aquatic life. The study was aimed to correlate the association of BF toxicity with mitochondrial DNA copy number variation in edible fish Punitus sophore. The 96-h LC50 of BF in P. sophore was 3.4 μg/L, fish was treated with sub-lethal doses ((⅒ and ⅕ of LC50;0.34 μg/L, 0.68 μg/L) of BF for 15 days. The activity and expression level of cytochrome c oxidase (Mt-COI) were measured to assess mitochondrial dysfunction caused by BF. Results showed BF reduced the level of Mt-COI mRNA in treated groups, hindered complex IV activity and increased ROS generation leading to oxidative damage. mtDNAcn was decreased in the muscle, brain and liver after BF treatment. Furthermore, BF induced neurotoxicity in brain and muscle cells through the inhibition of AchE activity. The treated groups showed elevated level of malondialdehyde (MDA) and an imbalance of antioxidant enzymes activity. Molecular docking and simulation analysis also predicted that BF binds to the active sites of the enzyme and restricts the fluctuation of its residues. Hence, outcome of the study suggests reduction of mtDNAcn could be a potential biomarker to assess Bifenthrin induced toxicity in aquatic ecosystem.

Identification of two patterns of mitochondrial DNA-copy number variation in postcentral gyrus during aging, influenced by body mass index and type 2 diabetes.

Mitochondrial (mt) DNA replication is strongly associated with oxidative stress, a condition triggered by aging and hyperglycemia, both of which contribute to mitophagy disruption and inflammation. This observational exploratory study evaluated mtDNA-copy number (mtDNA-CN) and expression of genes involved in mitochondriogenesis (PPARGC1A, TFAM, TFB1M, TFB2M), mitophagy (PINK1, PRKN), and inflammatory pathways triggered by hyperglycemia (TXNIP, NLRP3, NFKB1), in the postcentral gyrus of adults and older individuals with and without type 2 diabetes mellitus (T2D). Quantitative real-time PCR was employed to evaluate mtDNA-CN and gene expression; tissue autofluorescence, a marker of aging and of cells with damaged organelles, was also quantified. No correlation was found between age and mtDNA-CN, but a direct correlation was observed for cases with mtDNA-CN >1000 (r=0.41). The mtDNA-CN >1000 group had greater tissue autofluorescence and higher body mass index compared to the mtDNA-CN <1000 group (BMI; 25.7 vs 22.0kg/m2, respectively). mtDNA-CN correlated with tissue autofluorescence in the overall sample (r=0.55) and in the T2D group (r=0.64). PINK and PRKN expressions were inversely correlated with age. Mitochondriogenesis genes and TXNIP expressions were higher in the T2D group, and correlations among the mitochondriogenesis genes were also stronger in this group, relative to the subgroup with mtDNA-CN >1000.

Quantification of cell-free circulating mitochondrial DNA copy number variation in hepatocellular carcinoma.

SUMMARYOBJECTIVE:Hepatocellular carcinoma is the most common primary malignant liver tumor. Mitochondrial DNA copy number has been shown to be associated with various malignancies. However, there has not been any study on the absolute quantification of mtDNA copy number in hepatocellular carcinoma. The aim of this study was to develop a new method for absolute quantification of mtDNA copy number and to relatively quantify the variations in the mtDNA copy number in hepatocellular carcinoma patients in comparison with healthy individuals.METHODS:Venous blood samples were collected from both hepatocellular carcinoma patients (34) and healthy individuals (34). Circulating cell-free DNAs were isolated and the relative quantification of mtDNA copy number variation was determined using quantitative polymerase chain reaction and digital polymerase chain reaction.RESULTS:It was found that the relative mtDNA copy number was significantly decreased in hepatocellular carcinoma patients in comparison with the control group (p<0.05). The median (range) and average of relative mtDNA/β-actin gene of the patients were determined as 42.8 cp/μL (11.1–88.5) and 45.1 cp/μL, respectively, while the median (range) and average relative mtDNA/β-actin gene of the control group were determined as 102.8 cp/μL (55.1–291.8) and 138.7 cp/μL, respectively (p<0.05). When quantitative polymerase chain reaction and digital polymerase chain reaction were compared, mtDNA/β-actin gene copy number ratio of digital polymerase chain reaction results was found to be 1.76-fold more than that of quantitative polymerase chain reaction results.CONCLUSION:Circulating mtDNA copy number was decreased in hepatocellular carcinoma patients in comparison with healthy individuals, and we suggest that it can be used as a noninvasive biomarker for hepatocellular carcinoma diagnosis in the future.

Ribosomal DNA copy number associated with blood metal levels in school-age children: A follow-up study on a municipal waste incinerator in Zhejiang, China

To evaluate the body burdens of heavy metals and explore the impact of environmental metal exposure on ribosomal DNA (rDNA) or mitochondrial DNA (mtDNA) copy number (CN) variation in school-age children living near a municipal waste incinerator (MWI), we conducted a follow-up study in 2019. A total of 146 sixth-grade children from a primary school located 1.2 km away from the MWI were recruited for our study. Metals, including vanadium (V), chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), stannum (Sn), stibium (Sb), thallium (Tl), and lead (Pb), were determined by an inductively coupled plasma mass spectrometer method. Real-time qPCR was used to measure the rDNA and mtDNA CN. The blood metal levels followed this order: Zn > Cu > Se > Pb > Mn > Sb > As > Ni > Cd > Co > Cr > Sn > V > Tl. Blood Cr level was significantly correlated with 18 S, 2.5 S, and 45 S CN (β = −0.25, −0.22, −0.26, p < 0.05); Ni was correlated with 5 S (β = −0.36, p < 0.01); Cu was correlated with 28 S, 18 S, and 5.8 S (β = −0.24, −0.24, −0.23, p < 0.05); while Zn was correlated with 18 S, 5.8 S, and 45 S (β = −0.28, −0.32, −0.26, p < 0.05). In conclusion, school-age children living near the MWI had lower blood metal levels compared to children recruited in 2013, while rDNA CN loss was found to be correlated to several heavy metals in these children.

Neither cardiac mitochondrial DNA variation nor copy number contribute to congenital heart disease risk

The well-established manifestation of mitochondrial mutations in functional cardiac disease (e.g., mitochondrial cardiomyopathy) prompted the hypothesis that mitochondrial DNA (mtDNA) sequence and/or copy number (mtDNAcn) variation contribute to cardiac defects in congenital heart disease (CHD). MtDNAcns were calculated and rare, non-synonymous mtDNA mutations were identified in 1,837 CHD-affected proband-parent trios, 116 CHD-affected singletons, and 114 paired cardiovascular tissue/blood samples. The variant allele fraction (VAF) of heteroplasmic variants in mitochondrial RNA from 257 CHD cardiovascular tissue samples was also calculated. On average, mtDNA from blood had 0.14 rare variants and 52.9 mtDNA copies per nuclear genome per proband. No variation with parental age at proband birth or CHD-affected proband age was seen. mtDNAcns in valve/vessel tissue (320 ± 70) were lower than in atrial tissue (1,080 ± 320, p = 6.8E−21), which were lower than in ventricle tissue (1,340 ± 280, p = 1.4E−4). The frequency of rare variants in CHD-affected individual DNA was indistinguishable from the frequency in an unaffected cohort, and proband mtDNAcns did not vary from those of CHD cohort parents. In both the CHD and the comparison cohorts, mtDNAcns were significantly correlated between mother-child, father-child, and mother-father. mtDNAcns among people with European (mean = 52.0), African (53.0), and Asian haplogroups (53.5) were calculated and were significantly different for European and Asian haplogroups (p = 2.6E−3). Variant heteroplasmic fraction (HF) in blood correlated well with paired cardiovascular tissue HF (r = 0.975) and RNA VAF (r = 0.953), which suggests blood HF is a reasonable proxy for HF in heart tissue. We conclude that mtDNA mutations and mtDNAcns are unlikely to contribute significantly to CHD risk.

Genome-wide association study of mitochondrial copy number.

Mitochondrial DNA copy number (mtDNAcn) variation has been associated with increased risk of several human diseases in epidemiological studies. The quantification of mtDNAcn performed with real-time PCR is currently considered the de facto standard among several techniques. However, the heterogeneity of the laboratory methods (DNA extraction, storage, processing) used could give rise to results that are difficult to compare and reproduce across different studies. Several lines of evidence suggest that mtDNAcn is influenced by nuclear and mitochondrial genetic variability, however this relation is largely unexplored. The aim of this work was to elucidate the genetic basis of mtDNAcn variation. We performed a genome-wide association study (GWAS) of mtDNAcn in 6836 subjects from the ESTHER prospective cohort, and included, as replication set, the summary statistics of a GWAS that used 295 150 participants from the UK Biobank. We observed two novel associations with mtDNAcn variation on chromosome 19 (rs117176661), and 12 (rs7136238) that reached statistical significance at the genome-wide level. A polygenic score that we called mitoscore including all known single nucleotide polymorphisms explained 1.11% of the variation of mtDNAcn (p = 5.93 × 10-7). In conclusion, we performed a GWAS on mtDNAcn, adding to the evidence of the genetic background of this trait.

Mitochondrial DNA copy number variation and pancreatic cancer risk in the prospective EPIC cohort

Mitochondrial DNA copy number variation and pancreatic cancer risk in the prospective EPIC cohort

Distinct Epigenetic Reprogramming, Mitochondrial Patterns, Cellular Morphology, and Cytotoxicity after Bee Venom Treatment.

Bee venom is a promising agent for cancer treatment due to its selective cytotoxic potential for cancer cells through apoptotic pathways. However, there is no evidence for changes in the epigenome and mitochondrial DNA copy numbers after bee venom application. The purpose of this study was to determine the impact of bee venom on cytosine modifications and mitochondrial DNA copy number variation. A broad range of methods was applied to elucidate the impact of bee venom on neoplastic cells. These included MTT assay for detection of cytotoxicity, immunostaining of cytosine modifications and mitochondria, assessment of cellular morphology by flow cytometry, and quantification of mitochondrial DNA copy numbers using QPCR. Bee venom-induced cell death was selective for cancer cells, where it triggered a response characterized by alteration of cytosine modification. In contrast, normal cells were more resistant to DNA modifications. Furthermore, application of the venom resulted in variation of mitochondrial membrane permeability and mitochondrial DNA copy numbers, together with alterations in cell morphology, manifesting as reduced affected cell size. The study findings suggest that bee venom can be used as a selective DNA (de)methylating agent in cancer. Various agents (such as decitabine and 5-azacytidine) have been synthesized and developed for cancer treatment, and a range of syntheses and preparation and application methods have been described for these patented drugs. However, to the best of our knowledge, no previous research has investigated the use of bee venom or any component thereof for epigenetic therapy in cancer cells.

Analysis of mitochondrial DNA copy number variation in blood and tissue samples of metastatic breast cancer patients (A pilot study)

Changes in mitochondrial DNA (mt-DNA) copy number in blood/tissue have been linked to increased risk of several cancers; however, studies on their association in breast cancer is still lacking. In this pilot study, we investigated mt-DNA copy number variation in peripheral blood and tissue samples from metastatic breast cancer patients and compared their differences. For the study, peripheral blood samples from non-cancer individuals (control) and breast cancer patients, along with resected tissues from adjacent and tumor sites from same breast cancer patients were collected. Total genomic DNA was isolated and changes in mt-DNA copy number were measured by relative quantification using SYBR green based quantitative real time PCR method. Our results indicated a significant reduction in mt-DNA copy number in blood samples of breast cancer patients compared to control. However, a significantly higher mt-DNA copy number was observed in tumor tissue when compared with paired non tumor tissue. There was no significant difference in mt-DNA copy number between blood and adjacent tumor tissue samples of the breast cancer patients. Overall, our study reports for the first time a comparison of mt-DNA copy number in blood and paired tissue together and suggested that mt-DNA copy number is differentially regulated in blood and tumor tissues in breast cancer.

Allostatic score and its associations with demographics, healthy behaviors, tumor characteristics, and mitochondrial DNA among breast cancer patients.

Allostatic load (AL), a composite index, has been used to capture variation in life-course stresses. However, few studies have been carried out among breast cancer patients. In this study, we examined the cross-sectional association of AL with demographics, healthy behaviors, tumor characteristics, and mitochondrial DNA copy number in breast cancer patients. The study used a sub-sample of 934 women with newly diagnosed breast cancer at M.D. Anderson from 2013 to 2018. To construct the AL score, the study used a battery of seventeen factors that represents the activity of five physiological systems: metabolic, cardiovascular, immunological, renal, and liver. AL was positively associated with the age of disease diagnosis (P = 0.002), and was higher in Black and Hispanic populations than White (P = 0.001 and 0.032, respectively). AL was also found more abundant in those who experienced marital dissolution (P = 0.006), lacked a college education (P = 0.045), currently smoked (P = 0.011), and had low levels of physical activity (P = 0.037) than their counterparts. The study then found that higher AL was associated with increased odds of having poorly differentiated tumors (Odds ratio (OR): 1.40, 95% confidence interval (CI): 1.28, 1.62). An additional significant association was observed between AL with estrogen receptor negative (ER-) (OR = 1.56, 95%CI: 1.02, 2.36) among Black patients. Finally, we observed a significant positive correlation between AL with leukocyte mitochondrial DNA copy number variation (P < 0.001). We conclude AL is influenced by selected demographics and healthy behaviors, and further is correlated with tumor characteristics and mitochondrial DNA copy number in breast cancer patients.

The genomic analysis of endometrial mitochondrial DNA copy number variation on recurrent implantation failure

ObjectiveAim of this study was to define the relationship between RIF (Recurrent Implantation Failure) and endometrial mtDNA copy number. Study DesignA total of 50 women of reproductive age including twenty-five patients clinically diagnosed with RIF and twenty-five fertile women as healthy controls were recruited into the study. Endometrial biopsy samples were obtained with a pipelle at the 20–24 days of the menstrual cycle of each participant. Total genomic DNA samples were isolated from endometrial tissues; MT-ND1 (mitochondrially encoded NADH dehydrogenase I) and MT-CO2 (mitochondrially encoded cytochrome C oxidase II) target genes were amplified by droplet digital PCR (ddPCR). Nuclear GAPDH (Glyceraldehyde-3-Phosphate Dehydrogenase) gene was also used for study normalization. The study has been conducted between February 2019 and June 2019. Result(s)Droplet digital PCR results were analyzed in “QuantaSoft” software. The concentration amount (copies/μl) of each participant’s mitochondrial gene was normalized according to the GAPDH gene concentrations as nuclear reference. mtDNA amounts were compared between RIF patients and healthy controls. Normalized data was statistically evaluated using Mann-Whitney U test and ROC curve analysis. Conclusion(s)It was concluded that the mitochondrial target gene (MT-ND1 and MT-CO2) copy number amount of RIF patients was higher than the one obtained from the healthy group in endometrial tissues. It is thought that higher mtDNA copy number at the RIF group may be related to increased oxidative stress in the endometrium. This stress factors may influence receptivity negatively and cause implantation failure. The receptivity of the endometrium is associated with the number of mtDNA copies and difference can be used as a biomarker for receptivity analysis.

Mitochondrial DNA copy number variation - A potential biomarker for early onset preeclampsia.

Oxidative stress has been hypothesized as a central component of both placental and endothelial dysfunction, leading to PE. This oxidative stress leading to mitochondrial dysfunction may be due to variations in mtDNA copy numbers as an adaptive response. In the present study we aimed to analyse mtDNA copy numbers in the placenta obtained after delivery from the women with PE as compared to the controls. It was a prospective case control study. A total of 32 placental samples were analyzed (Cases: 17; Controls: 15). Samples were collected ex vivo, after childbirth. MtDNA content was determined useing real-time quantitative PCR qRT-PCR) using TaqMan probes designed for two genes: MT-ND1 and a mitochondrial gene encoding for the NADH dehydrogenase 1 protein. We found that the median (IQR) mtDNA copy number was higher in PE cases 24.32 (9.260-33.51) as compared with controls 20.32 (13.33-26.22). On subgroup analysis, the median (IQR) mtDNA copy number was higher in early onset PE 28.06 (20.80-36.87) as compared to late onset PE 9.215 (4.150-56.45) as well as the controls 20.32 (13.33-26.22). Our findings support a higher mtDNA copy number in early onset PE as compared to late onset PE and control population. Although, mtDNA may only be increased in very severe cases of early onset preeclampsia. Future research may be directed to ascertain if mtDNA copy numbers can be a novel biomarker to predict or prognosticate early onset preeclampsia.

Ionizing radiation, genotoxic stress, and mitochondrial DNA copy-number variation in Caenorhabditis elegans: droplet digital PCR analysis

Mitochondria are vulnerable to the effects of ionizing radiation; damage to mitochondrial DNA (mtDNA) may be more extensive and persistent than damage to nuclear DNA (nDNA). Variation in mtDNA copy number has been proposed as a marker for mitochondrial dysfunction in response to ionizing radiation. We have developed a precise and sensitive duplex droplet digital PCR (ddPCR) method for quantitation of the mtDNA/nDNA ratio in the model organism Caenorhabditis elegans. The effect on this ratio was investigated over a wide range of doses (0.03–72 Gy) of chronic gamma irradiation. Five mitochondrial targets and two nuclear reference genes were amplified pairwise in duplex PCR format (one mitochondrial and one nuclear target per PCR) by both ddPCR and quantitative PCR (qPCR). The results showed that ddPCR but not qPCR enabled detection of a significant increase in mtDNA copy number (1.6 ± 0.1-fold) for nematodes exposed to high doses (≥24 Gy). Thus, ddPCR provided higher precision and greater sensitivity than qPCR for detection of mtDNA copy number variation. The variation followed a Hill-type dose response with threshold 10.3 ± 1 Gy. This strongly suggests that chronic genotoxic stress affects mtDNA replication. The duplex ddPCR method is a novel, high-precision, sensitive tool for determination of mitochondrial DNA copy number variation and function in C. elegans.

Mitochondrial DNA Copy-Number Variation and Pancreatic Cancer Risk in the Prospective EPIC Cohort.

Mitochondrial DNA (mtDNA) copy number in peripheral blood has been found to be associated with risk of developing several cancers. However, data on pancreatic ductal adenocarcinoma (PDAC) are very limited. To further our knowledge on this topic, we measured relative mtDNA copy number by a quantitative real-time PCR assay in peripheral leukocyte samples of 476 PDAC cases and 357 controls nested within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. We observed lower mtDNA copy number with advancing age (P = 6.54 × 10-5) and with a high body mass index (BMI) level (P = 0.004) and no association with sex, smoking behavior, and alcohol consumption. We found an association between increased mtDNA copy number and decreased risk of developing PDAC with an odds ratios (OR) of 0.35 [95% confidence interval (CI), 0.16-0.79; P = 0.01] when comparing the fifth quintile with the first using an unconditional logistic regression and an OR of 0.19 (95% CI, 0.07-0.52; P = 0.001) with a conditional analysis. Analyses stratified by BMI showed an association between high mtDNA copy number and decreased risk in the stratum of normal weight, consistent with the main analyses. Our results suggest a protective effect of a higher number of mitochondria, measured in peripheral blood leukocytes, on PDAC risk. Our findings highlight the importance of understanding the mitochondrial biology in pancreatic cancer.

Relative telomere length and mitochondrial DNA copy number variation with age: Association with plasma folate and vitamin B12

Telomere attrition and mitochondrial DNA variations are implicated in the biological aging process and genomic stability can be influenced by nutritional factors. This study aims to analyze the relative telomere length (rTL) and mitochondrial DNA copy number (mtCN) in aged individuals and their association with plasma folate and vitamin B12 levels. This community-based cross-sectional study involves 428 subjects (<60 years: 242 & ≥60 years: 186). Quantitative real-time PCR was used to measure rTL and mtCN variation, and radioimmunoassay to measure plasma folate and vitamin B12 levels. The subjects in the ≥60 years age group have significantly shorter telomeres and lower mtCN compared to the <60 years age group. A significant positive correlation was observed between the rTL and mtCN, and both of them were positively associated with plasma folate and vitamin B12 levels. In the ≥60 age group; folate and vitamin B12 positively correlated with rTL and vitamin B12 with mtCN. The study revealed a decline of rTL and mtCN with age in the Indian population and their association suggests that they may co-regulate each other with age. In conclusion, folate and vitamin B12 may delay aging by preventing the reduction in rTL length and mtCN.

Analysis of mitochondrial DNA sequence and copy number variation across five high-altitude species and their low-altitude relatives

High-altitude inhospitable environments impose a formidable life challenge for the local animals. Training and exposure to high-altitude environments produce both distinct physiological and phenotypic characteristics. The mitochondrion, an organelle crucial for the energy production, plays an important role in hypoxia adaptation. In this study, we investigated the mitochondrial DNA (mtDNA) polymorphism and copy number variation between the population pairs from distinct altitudes across the multi-species. Higher mitochondrial DNA control region’s genetic diversity is conspicuous in high-altitude animals versus low-altitude relatives. We also found an accordant decrease of mtDNA copy number in most of the tissues from high-altitude animals. Compared to mammals, chickens have significantly distinct mitogenomic characteristics, and more significant changes in the skeletal muscle mtDNA copy number between high- and low-altitude individuals. Our study catches a snapshot of the biological similarities and differences in the mitochondrial high-altitude acclimation across the species.