Decreased reactive oxygen species production in cells with mitochondrial haplogroups associated with longevity

Association between mtDNA haplogroups and skeletal fluorosis in Han population residing in drinking water endemic fluorosis area of northern China

To investigate the association between mtDNA genetic information and the risk of SF, individuals were conducted in the drinking water endemic fluorosis area in northern China, sequenced the whole genome of mtDNA, identified the SNPs and SNVs, analyzed the haplogroups, and diagnosed SF, and then, the effect of mtDNA genetic information on the risk of SF was evaluated. We find that, D5 haplogroup and its specific SNPs reduced the risk, while the D4 haplogroup and its specific SNPs increased the risk of SF. The number of SNVs in coding regions of mitochondrial respiratory chain (MRC) is different between the controls and cases. This suggests that D5 haplogroup may play a protective role in the risk of SF, while the opposite is observed for the D4 haplogroup, this may relate to their specific SNPs. And SNVs that encode the MRC complex may also be associated with the risk of SF.

Examining the Association between Mitochondrial Genome Variation and Coronary Artery Disease

Large-scale genome-wide association studies have identified hundreds of single-nucleotide variants (SNVs) significantly associated with coronary artery disease (CAD). However, collectively, these explain <20% of the heritability. Hypothesis: Here, we hypothesize that mitochondrial (MT)-SNVs might present one potential source of this “missing heritability”. Methods: We analyzed 265 MT-SNVs in ~500,000 UK Biobank individuals, exploring two different CAD definitions: a more stringent (myocardial infarction and/or revascularization; HARD = 20,405), and a more inclusive (angina and chronic ischemic heart disease; SOFT = 34,782). Results: In HARD cases, the most significant (p < 0.05) associations were for m.295C>T (control region) and m.12612A>G (ND5), found more frequently in cases (OR = 1.05), potentially related to reduced cardiorespiratory fitness in response to exercise, as well as for m.12372G>A (ND5) and m.11467A>G (ND4), present more frequently in controls (OR = 0.97), previously associated with lower ROS production rate. In SOFT cases, four MT-SNVs survived multiple testing corrections (at FDR < 5%), all potentially conferring increased CAD risk. Of those, m.11251A>G (ND4) and m.15452C>A (CYB) have previously shown significant associations with body height. In line with this, we observed that CAD cases were slightly less physically active, and their average body height was ~2.00 cm lower compared to controls; both traits are known to be related to increased CAD risk. Gene-based tests identified CO2 associated with HARD/SOFT CAD, whereas ND3 and CYB associated with SOFT cases (p < 0.05), dysfunction of which has been related to MT oxidative stress, obesity/T2D (CO2), BMI (ND3), and angina/exercise intolerance (CYB). Finally, we observed that macro-haplogroup I was significantly (p < 0.05) more frequent in HARD cases vs. controls (3.35% vs. 3.08%), potentially associated with response to exercise. Conclusions: We found only spurious associations between MT genome variation and HARD/SOFT CAD and conclude that more MT-SNV data in even larger study cohorts may be needed to conclusively determine the role of MT DNA in CAD.

Mitochondrial complex I as a therapeutic target for Alzheimer's disease

Alzheimer's disease (AD), the most prominent form of dementia in the elderly, has no cure. Strategies focused on the reduction of amyloid beta or hyperphosphorylated Tau protein have largely failed in clinical trials. Novel therapeutic targets and strategies are urgently needed. Emerging data suggest that in response to environmental stress, mitochondria initiate an integrated stress response (ISR) shown to be beneficial for healthy aging and neuroprotection. Here, we review data that implicate mitochondrial electron transport complexes involved in oxidative phosphorylation as a hub for small molecule-targeted therapeutics that could induce beneficial mitochondrial ISR. Specifically, partial inhibition of mitochondrial complex I has been exploited as a novel strategy for multiple human conditions, including AD, with several small molecules being tested in clinical trials. We discuss current understanding of the molecular mechanisms involved in this counterintuitive approach. Since this strategy has also been shown to enhance health and life span, the development of safe and efficacious complex I inhibitors could promote healthy aging, delaying the onset of age-related neurodegenerative diseases.

An atlas of mitochondrial DNA genotype-phenotype associations in the UK Biobank

Mitochondrial DNA (mtDNA) variation in common diseases has been underexplored, partly due to a lack of genotype calling and quality-control procedures. Developing an at-scale workflow for mtDNA variant analyses, we show correlations between nuclear and mitochondrial genomic structures within subpopulations of Great Britain and establish a UK Biobank reference atlas of mtDNA-phenotype associations. A total of 260 mtDNA-phenotype associations were new (P < 1 × 10-5), including rs2853822 /m.8655 C>T (MT-ATP6) with type 2 diabetes, rs878966690 /m.13117 A>G (MT-ND5) with multiple sclerosis, 6 mtDNA associations with adult height, 24 mtDNA associations with 2 liver biomarkers and 16 mtDNA associations with parameters of renal function. Rare-variant gene-based tests implicated complex I genes modulating mean corpuscular volume and mean corpuscular hemoglobin. Seven traits had both rare and common mtDNA associations, where rare variants tended to have larger effects than common variants. Our work illustrates the value of studying mtDNA variants in common complex diseases and lays foundations for future large-scale mtDNA association studies.

Is the NDUFV2 subunit of the hydrophilic complex I domain a key determinant of animal longevity?

Complex I, a component of the electron transport chain, plays a central functional role in cell bioenergetics and the biology of free radicals. The structural and functional N module of complex I is one of the main sites of the generation of free radicals. The NDUFV2 subunit/N1a cluster is a component of this module. Furthermore, the rate of free radical production is linked to animal longevity. In this review, we explore the hypothesis that NDUFV2 is the only conserved core subunit designed with a regulatory function to ensure correct electron transfer and free radical production, that low gene expression and protein abundance of the NDUFV2 subunit is an evolutionary adaptation needed to achieve a longevity phenotype, and that these features are determinants of the lower free radical generation at the mitochondrial level and a slower rate of aging of long-lived animals.

Mitochondria: The Retina's Achilles' Heel in AMD

Strong experimental evidence from studies in human donor retinas and animal models supports the idea that the retinal pathology associated with age-related macular degeneration (AMD) involves mitochondrial dysfunction and consequent altered retinal metabolism. This chapter provides a brief overview of mitochondrial structure and function, summarizes evidence for mitochondrial defects in AMD, and highlights the potential ramifications of these defects on retinal health and function. Discussion of mitochondrial haplogroups and their association with AMD brings to light how mitochondrial genetics can influence disease outcome. As one of the most metabolically active tissues in the human body, there is strong evidence that disruption in key metabolic pathways contributes to AMD pathology. The section on retinal metabolism reviews cell-specific metabolic differences and how the metabolic interdependence of each retinal cell type creates a unique ecosystem that is disrupted in the diseased retina. The final discussion includes strategies for therapeutic interventions that target key mitochondrial pathways as a treatment for AMD.

Intimate Relations-Mitochondria and Ageing

Mitochondrial dysfunction is associated with ageing, but the detailed causal relationship between the two is still unclear. We review the major phenomenological manifestations of mitochondrial age-related dysfunction including biochemical, regulatory and energetic features. We conclude that the complexity of these processes and their inter-relationships are still not fully understood and at this point it seems unlikely that a single linear cause and effect relationship between any specific aspect of mitochondrial biology and ageing can be established in either direction.

Mitochondrial DNA variation modulates alveolar development in newborn mice exposed to hyperoxia

Hyperoxia-induced oxidant stress contributes to the pathogenesis of bronchopulmonary dysplasia (BPD) in preterm infants. Mitochondrial functional differences due to mitochondrial DNA (mtDNA) variations are important modifiers of oxidant stress responses. The objective of this study was to determine whether mtDNA variation independently modifies lung development and mechanical dysfunction in newborn mice exposed to hyperoxia. Newborn C57BL6 wild type (C57ⁿ/C57^mt, C57WT) and C3H/HeN wild type (C3Hⁿ/C3H^mt, C3HWT) mice and novel Mitochondrial-nuclear eXchange (MNX) strains with nuclear DNA (nDNA) from their parent strain and mtDNA from the other-C57MNX (C57ⁿ/C3H^mt) and C3HMNX (C3Hⁿ/C57^mt)-were exposed to 21% or 85% O₂ from birth to postnatal day 14 (P14). Lung mechanics and histopathology were examined on P15. Neonatal mouse lung fibroblast (NMLF) bioenergetics and mitochondrial superoxide (O₂^-) generation were measured. Pulmonary resistance and mitochondrial O₂^- generation were increased while alveolarization, compliance, and NMLF basal and maximal oxygen consumption rate were decreased in hyperoxia-exposed C57WT mice (C57ⁿ/C57^mt) versus C57MNX mice (C57ⁿ/C3H^mt) and in hyperoxia-exposed C3HMNX mice (C3Hⁿ/C57^mt) versus C3HWT (C3Hⁿ/C3H^mt) mice. Our study suggests that neonatal C57 mtDNA-carrying strains have increased hyperoxia-induced hypoalveolarization, pulmonary mechanical dysfunction, and mitochondrial bioenergetic and redox dysfunction versus C3H mtDNA strains. Therefore, mtDNA haplogroup variation-induced differences in mitochondrial function could modify neonatal alveolar development and BPD susceptibility.

Mitochondrial DNA variation and the pathogenesis of osteoarthritis phenotypes

Mitochondria and mitochondrial DNA (mtDNA) variation are now recognized as important factors in the development of osteoarthritis (OA). Mitochondria are the energy powerhouses of the cell, and also regulate different processes involved in the pathogenesis of OA including inflammation, apoptosis, calcium metabolism and the generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS). Mitochondria contain their own genetic material, mtDNA, which evolved through the sequential accumulation of mtDNA variants to enable humans to adapt to different climates. The ROS and reactive metabolic intermediates that are by-products of mitochondrial metabolism are regulated in part by mtDNA and are among the signals that transmit information between mitochondria and the nucleus. These signals can alter nuclear gene expression and, when disrupted, affect a number of cellular processes and metabolic pathways, leading to disease. mtDNA variation influences OA-associated phenotypes, including those related to metabolism, inflammation and even ageing, as well as nuclear epigenetic regulation. This influence also enables the use of specific mtDNA haplogroups as complementary diagnostic and prognostic biomarkers of OA.

Cause or casualty: The role of mitochondrial DNA in aging and age-associated disease

The mitochondrial genome (mtDNA) represents a tiny fraction of the whole genome, comprising just 16.6 kilobases encoding 37 genes involved in oxidative phosphorylation and the mitochondrial translation machinery. Despite its small size, much interest has developed in recent years regarding the role of mtDNA as a determinant of both aging and age-associated diseases. A number of studies have presented compelling evidence for key roles of mtDNA in age-related pathology, although many are correlative rather than demonstrating cause. In this review we will evaluate the evidence supporting and opposing a role for mtDNA in age-associated functional declines and diseases. We provide an overview of mtDNA biology, damage and repair as well as the influence of mitochondrial haplogroups, epigenetics and maternal inheritance in aging and longevity.

Oldies but Goldies mtDNA Population Variants and Neurodegenerative Diseases

mtDNA is transmitted through the maternal line and its sequence variability, which is population specific, is assumed to be phenotypically neutral. However, several studies have shown associations between the variants defining some genetic backgrounds and the susceptibility to several pathogenic phenotypes, including neurodegenerative diseases. Many of these studies have found that some of these variants impact many of these phenotypes, including the ones defining the Caucasian haplogroups H, J, and Uk, while others, such as the ones defining the T haplogroup, have phenotype specific associations. In this review, we will focus on those that have shown a pleiotropic effect in population studies in neurological diseases. We will also explore their bioenergetic and genomic characteristics in order to provide an insight into the role of these variants in disease. Given the importance of mitochondrial population variants in neurodegenerative diseases a deeper analysis of their effects might unravel new mechanisms of disease and help design new strategies for successful treatments.

Ancestry and different rates of suicide and homicide in European countries: A study with population-level data

INTRODUCTION

There are large differences in suicide rates across Europe. The current study investigated the relationship of suicide and homicide rates in different countries of Europe with ancestry as it is defined with the haplotype frequencies of Y-DNA and mtDNA.

MATERIAL AND METHODS

The mortality data were retrieved from the WHO online database. The genetic data were retrieved from http://www.eupedia.com. The statistical analysis included Forward Stepwise Multiple Linear Regression analysis and Pearson Correlation Coefficient (R).

RESULTS

In males, N and R1a Y-DNA haplotypes were positively related to both homicidal and suicidal behaviors while I1 was negatively related. The Q was positively related to the homicidal rate. Overall, 60-75% of the observed variance was explained. L, J and X mtDNA haplogroups were negatively related with suicide in females alone, with 82-85% of the observed variance described.

DISCUSSION

The current study should not be considered as a study of genetic markers but rather a study of human ancestry. Its results could mean that research on suicidality has a strong biological but locally restricted component and could be limited by the study population; generalizability of the results at an international level might not be possible. Further research with patient-level data are needed to verify whether these haplotypes could serve as biological markers to identify persons at risk to commit suicide or homicide and whether biologically-determined ancestry could serve as an intermediate grouping method or even as an endophenotype in suicide research.

Mitochondrial genome variability: the effect on cellular functional activity

Mitochondria are the key players in cell metabolism, calcium homeostasis, and reactive oxygen species (ROS) production. Mitochondrial genome alterations are reported to be associated with numerous human disorders affecting nearly all tissues. In this review, we discuss the available information on the involvement of mitochondrial DNA (mtDNA) mutations in cell dysfunction.

Mitochondrial DNA mutations and cardiovascular disease

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is responsible for more morbidity and mortality worldwide than any other ailment. Strategies for reducing CVD prevalence must involve identification of individuals at high risk for these diseases, and the prevention of its initial development. Such preventive efforts are currently limited by an incomplete understanding of the genetic determinants of CVD risk. In this review, evidence for the involvement of inherited mitochondrial mutations in development of CVD is examined.

RECENT FINDINGS

Several forms of CVD have been documented in the presence of pathogenic mitochondrial DNA (mtDNA) mutations, both in isolation and as part of larger syndromes. Other 'natural' mtDNA polymorphisms not overtly tied to any pathology have also been associated with alterations in mitochondrial function and individual risk for CVD, but until very recently these studies have been merely correlative. Fortunately, novel animal models are now allowing investigators to define a causal relationship between inherited 'natural' mtDNA polymorphisms, and cardiovascular function and pathology.

SUMMARY

Cardiovascular involvement is highly prevalent among patients with pathogenic mtDNA mutations. The relationship between CVD susceptibility and 'natural' mtDNA polymorphisms requires further investigation, but will be aided in the near future by several novel experimental models.

The impact of oxidative stress and inflammation on RPE degeneration in non-neovascular AMD

The retinal pigment epithelium (RPE) is a highly specialized, unique epithelial cell that interacts with photoreceptors on its apical side and with Bruch's membrane and the choriocapillaris on its basal side. Due to vital functions that keep photoreceptors healthy, the RPE is essential for maintaining vision. With aging and the accumulated effects of environmental stresses, the RPE can become dysfunctional and die. This degeneration plays a central role in age-related macular degeneration (AMD) pathobiology, the leading cause of blindness among the elderly in western societies. Oxidative stress and inflammation have both physiological and potentially pathological roles in RPE degeneration. Given the central role of the RPE, this review will focus on the impact of oxidative stress and inflammation on the RPE with AMD pathobiology. Physiological sources of oxidative stress as well as unique sources from photo-oxidative stress, the phagocytosis of photoreceptor outer segments, and modifiable factors such as cigarette smoking and high fat diet ingestion that can convert oxidative stress into a pathological role, and the negative impact of impairing the cytoprotective roles of mitochondrial dynamics and the Nrf2 signaling system on RPE health in AMD will be discussed. Likewise, the response by the innate immune system to an inciting trigger, and the potential role of local RPE production of inflammation, as well as a potential role for damage by inflammation with chronicity if the inciting trigger is not neutralized, will be debated.

A replication study and meta-analysis of mitochondrial DNA variants in the radiographic progression of knee osteoarthritis

OBJECTIVE

To conduct a replication study and meta-analysis involving the study of mtDNA variants in the radiographic progression of OA in different cohorts worldwide, including Cohort Hip and Cohort Knee (CHECK), the OA Initiative and a cohort from Spain.

METHODS

The influence of the haplogroups in the rate of radiographic progression at 96 months in 431 subjects from CHECK was assessed in terms of Kellgren and Lawrence (KL) grade. Progression was defined as a change from KL ⩾ 1 at baseline to any higher grade during the follow-up. Extended Cox proportional hazard models were used to analyse the influence of mtDNA variants in the rate of radiographic knee OA progression. A subsequent meta-analysis of 1603 subjects following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines was conducted to combine the data of individual studies. A sensitivity analysis was performed to validate the stability of the results.

RESULTS

CHECK subjects carrying the haplogroup T showed the lowest rate of radiographic knee OA progression [hazard ratio (HR) 0.645 (95% CI 0.419, 0.978); P < 0.05]. When pooled, subjects within the superhaplogroup JT showed the same trend [HR 0.707 (95% CI 0.501, 0.965); P < 0.05]. BMI [HR 1.046 (95% CI 1.018, 1.073); P < 0.05] and bilateral OA [HR 2.266 (95% CI 1.733, 2.954); P < 0.05] at baseline are risk factors for radiographic knee OA progression as well. In the meta-analysis there was a reduced rate of radiographic progression in subjects with haplogroup T [HR 0.612 (95% CI 0.454, 0.824); P = 0.001] or in the superhaplogroup JT [HR 0.765 (95% CI 0.624, 0.938); P = 0.009]. Sensitivity analysis revealed that the results were robust.

CONCLUSION

The mtDNA variants in the superhaplogroup JT associate with a reduced rate of radiographic OA progression. The mtDNA polymorphisms in the superhaplogroup JT emerge as potential complementary genetic biomarkers for disease progression.

Mitochondrial Haplogroup Influences Motor Function in Long-Term HIV-1-Infected Individuals

Evolutionary divergence of the mitochondrial genome has given rise to distinct haplogroups. These haplogroups have arisen in specific geographical locations and are responsible for subtle functional changes in the mitochondria that may provide an evolutionary advantage in a given environment. Based on these functional differences, haplogroups could define disease susceptibility in chronic settings. In this study, we undertook a detailed neuropsychological analysis of a cohort of long-term HIV-1-infected individuals in conjunction with sequencing of their mitochondrial genomes. Stepwise regression analysis showed that the best model for predicting both working memory and declarative memory were age and years since diagnosis. In contrast, years since diagnosis and sub-haplogroup were significantly predictive of psychomotor speed. Consistent with this, patients with haplogroup L3e obtained better scores on psychomotor speed and dexterity tasks when compared to the remainder of the cohort, suggesting that this haplogroup provides a protective advantage when faced with the combined stress of HIV-1 infection and long-term antiretroviral therapies. Differential performance on declarative memory tasks was noted for individuals with other sub-L haplogroups, but these differences were not as robust as the association between L3e and psychomotor speed and dexterity tasks. This work provides evidence that mitochondrial haplogroup is related to neuropsychological test performance among patients in chronic disease settings such as HIV-1 infection.

Neurodegenerative Eye Disorders: Role of Mitochondrial Dynamics and Genomics

As a major source of cellular energy, mitochondria are critical for optimal ocular function. They are also essential for cell differentiation and survival. Mitochondrial mutations and oxidative damage to the mitochondrial DNA are important factors underlying the pathology of many ocular disorders. With increasing age, mitochondrial DNA damage accumulates and results in several eye diseases. It is evident that the mitochondrial genome is more susceptible to stress and damage than the nuclear genome, as it lacks histone protection, a nucleotide excision repair system, and recombination repair, and it is the source and target of free radicals. Accumulation of mitochondrial mutations beyond a certain threshold explains the marked variations in phenotypes seen in mitochondrial diseases and the molecular mechanisms related to the pathogenesis of several chronic disorders in the eye. This review details the structure and function of mitochondria and the mitochondrial genome along with the mitochondrial involvement in various neurodegenerative ophthalmic disorders.

Increased expression of ApoE and protection from amyloid-beta toxicity in transmitochondrial cybrids with haplogroup K mtDNA

Mitochondrial (mt) DNA haplogroups, defined by specific single nucleotide polymorphism (SNP) patterns, represent populations of diverse geographic origins and have been associated with increased risk or protection of many diseases. The H haplogroup is the most common European haplogroup while the K haplogroup is highly associated with the Ashkenazi Jewish population. Transmitochondrial cybrids (cell lines with identical nuclei, but mtDNA from either H (n=8) or K (n=8) subjects) were analyzed by the Seahorse flux analyzer, quantitative polymerase chain reaction (Q-PCR) and immunohistochemistry (IHC). Cybrids were treated with amyloid-β peptides and cell viabilities were measured. Other cybrids were demethylated with 5-aza-2'-deoxycytidine (5-aza-dC) and expression levels for APOE and NFkB2 were measured. Results show K cybrids have (a) significantly lower mtDNA copy numbers, (b) higher expression levels for MT-DNA encoded genes critical for oxidative phosphorylation, (c) lower Spare Respiratory Capacity, (d) increased expression of inhibitors of the complement pathway and important inflammasome-related genes; and (e) significantly higher levels of APOE transcription that were independent of methylation status. After exposure to amyloid-β1-42 peptides (active form), H haplogroup cybrids demonstrated decreased cell viability compared to those treated with amyloid-β42-1 (inactive form) (p<0.0001), while this was not observed in the K cybrids (p=0.2). K cybrids had significantly higher total global methylation levels and differences in expression levels for two acetylation genes and four methylation genes. Demethylation with 5-aza-dC altered expression levels for NFkB2, while APOE transcription patterns were unchanged. Our findings support the hypothesis that mtDNA-nuclear retrograde signaling may mediate expression levels of APOE, a key factor in many age-related diseases. Future studies will focus on identification of the mitochondrial-nuclear retrograde signaling mechanism(s) contributing to these mtDNA-mediated differences.

Relationship Between Mitochondrial DNA Mutations and Aging. Estimation of Age-at-death

Some studies have pointed to the relationship between mitochondrial DNA (mtDNA) mutations and age in different tissues, which are potentially interesting in aging research and in forensic identification because they could help to improve the estimation of age-at-death. The present study aims to evaluate the mutations in mtDNA from dentin and pulp and their relation with age. Healthy erupted third molars were extracted from individuals from two Spanish populations, aged 20-70. When analyzing the amplification of hypervariable region 2 of the mtDNA by real-time polymerase chain reaction, a negative strong linear correlation was found between the mtDNA amplification and age in dentin from both populations. In contrast, a significant correlation between mtDNA amplification and age in pulp was not discovered, probably due to the majority of the mitochondria are placed in dentin. A difference in mtDNA damage between these two populations was also detected, indicating the role of ancestry as a component. The findings from this research enrich the current studies related to aging and mitochondrial damage and provide a new quantitative tool for estimating the age-at-death that, in combination with traditional age markers, could improve identification accuracy in forensic cases.

Mitochondrial DNA D-loop AG/TC transition mutation in cortical neurons of mice after long-term exposure to nucleoside analogues

With the wide application of combined antiretroviral therapy, the prognosis of human immunodeficiency virus (HIV)-1 infected patient has been significantly improved. However, long-term administration of antiretroviral drugs can result in various drug-associated toxicities. Among them, nucleoside analogues were confirmed to inhibit DNA polymerase gamma, resulting in mitochondrial toxicity. Our previous study indicated that long-term exposure of mice to nucleoside analogue could induce mitochondria DNA (mtDNA) loss in cortical neurons. Herein, we further identify mitochondrial toxicity of four nucleoside analogues (zidovudine (AZT), stavudine (D4T), lamivudine (3TC), and didanosine (DDI)) by cloning and sequencing mtDNA D-loop region in mice neurons captured with laser capture microdissection. The results showed that mutation of neuronal mtDNA D-loop sequences increased in mice treated with each of the four nucleoside analogues for 4 months and D4T and DDI induced more severe D-loop lesion than the other two nucleoside analogues. The major type of D-loop point mutations induced by four nucleoside analogues was transition, in particular of "A→G" and "T→C" transition, but the point transition sites were variable. Our findings suggest that long-term exposure to nucleoside analogue can result in mtDNA D-loop region lesion in mouse cortical neurons.

mtDNA haplogroup and single nucleotide polymorphisms structure human microbiome communities

Background

Although our microbial community and genomes (the human microbiome) outnumber our genome by several orders of magnitude, to what extent the human host genetic complement informs the microbiota composition is not clear. The Human Microbiome Project (HMP) Consortium established a unique population-scale framework with which to characterize the relationship of microbial community structure with their human hosts. A wide variety of taxa and metabolic pathways have been shown to be differentially distributed by virtue of race/ethnicity in the HMP. Given that mtDNA haplogroups are the maternally derived ancestral genomic markers and mitochondria’s role as the generator for cellular ATP, characterizing the relationship between human mtDNA genomic variants and microbiome profiles becomes of potential marked biologic and clinical interest.

Results

We leveraged sequencing data from the HMP to investigate the association between microbiome community structures with its own host mtDNA variants. 15 haplogroups and 631 mtDNA nucleotide polymorphisms (mean sequencing depth of 280X on the mitochondria genome) from 89 individuals participating in the HMP were accurately identified. 16S rRNA (V3-V5 region) sequencing generated microbiome taxonomy profiles and whole genome shotgun sequencing generated metabolic profiles from various body sites were treated as traits to conduct association analysis between haplogroups and host clinical metadata through linear regression. The mtSNPs of individuals with European haplogroups were associated with microbiome profiles using PLINK quantitative trait associations with permutation and adjusted for multiple comparisons. We observe that among 139 stool and 59 vaginal posterior fornix samples, several haplogroups show significant association with specific microbiota (q-value < 0.05) as well as their aggregate community structure (Chi-square with Monte Carlo, p < 0.005), which confirmed and expanded previous research on the association of race and ethnicity with microbiome profile. Our results further indicate that mtDNA variations may render different microbiome profiles, possibly through an inflammatory response to different levels of reactive oxygen species activity.

Conclusions

These data provide initial evidence for the association between host ancestral genome with the structure of its microbiome.

Reactive oxygen species production and mitochondrial dysfunction in white blood cells are not valid biomarkers of ageing in the very old

Reliable and valid biomarkers of ageing (BoA) are needed to understand mechanisms, test interventions and predict the timing of adverse health events associated with ageing. Since increased reactive oxygen species (ROS) production and mitochondrial dysfunction are consequences of cellular senescence and may contribute causally to the ageing of organisms, we focused on these parameters as candidate BoA. Superoxide levels, mitochondrial mass and mitochondrial membrane potential in human peripheral blood mononuclear cells (PBMCs) and subpopulations (lymphocytes and monocytes) were measured in participants from the Newcastle 85+ study, a population-based study of the very old (aged 85 years and older). The intra- and inter-assay precision expressed as coefficient of variation (CV) for all parameters was acceptable (3% to 12% and 5 to 22% respectively). All parameters were stable in the short-term (1 week interval) in a sample of control individuals in the PBMCs and lymphocyte subpopulation, however they were unstable in the monocyte subpopulation; this rendered monocytes unreliable for further analysis. There was a significant association between superoxide levels and mitochondrial mass (positive in lymphocytes, p = 0.01) and between superoxide levels and mitochondrial membrane potential (negative in PBMCs, p = 0.01; positive in lymphocytes, p = 0.05). There were also significant associations between superoxide levels and mitochondrial parameters with other markers of oxidative stress-induced cellular senescence (p≤0.04), however some were in the opposite direction to expected. No associations were found between the measured parameters and age-related outcomes, including cognitive impairment, disability, co-morbidity and survival - questioning the validity of these parameters as candidate BoA in the very old.

mtDNA Mutations and Their Role in Aging, Diseases and Forensic Sciences

Mitochondria are independent organelles with their own DNA. As a primary function, mitochondria produce the energy for the cell through Oxidative Phosphorylation (OXPHOS) in the Electron Transport Chain (ETC). One of the toxic products of this process is Reactive Oxygen Species (ROS), which can induce oxidative damage in macromolecules like lipids, proteins and DNA. Mitochondrial DNA (mtDNA) is less protected and has fewer reparation mechanisms than nuclear DNA (nDNA), and as such is more exposed to oxidative, mutation-inducing damage. This review analyzes the causes and consequences of mtDNA mutations and their relationship with the aging process. Neurodegenerative diseases, related with the aging, are consequences of mtDNA mutations resulting in a decrease in mitochondrial function. Also described are "mitochondrial diseases", pathologies produced by mtDNA mutations and whose symptoms are related with mitochondrial dysfunction. Finally, mtDNA haplogroups are defined in this review; these groups are important for determination of geographical origin of an individual. Additionally, different haplogroups exhibit variably longevity and risk of certain diseases. mtDNA mutations in aging and haplogroups are of special interest to forensic science research. Therefore this review will help to clarify the key role of mtDNA mutations in these processes and support further research in this area.