-
1.
Meta-analysis identifies mitochondrial DNA sequence variants associated with walking speed.
Manini, TM, Buford, TW, Kairalla, JA, McDermott, MM, Vaz Fragoso, CA, Fielding, RA, Hsu, FC, Johannsen, N, Kritchevsky, S, Harris, TB, et al
GeroScience. 2018;(5-6):497-511
-
-
Free full text
-
Abstract
Declines in walking speed are associated with a variety of poor health outcomes including disability, comorbidity, and mortality. While genetic factors are putative contributors to variability in walking, few genetic loci have been identified for this trait. We examined the role of mitochondrial genomic variation on walking speed by sequencing the entire mitochondrial DNA (mtDNA). Data were meta-analyzed from 1758 Lifestyle Interventions and Independence for Elders (LIFE) Study and replication data from 730 Health, Aging, and Body Composition (HABC) Study participants with baseline walking speed information. Participants were 69+ years old of diverse racial backgrounds (African, European, and other race/ethnic groups) and had a wide range of mean walking speeds [4-6 m (0.78-1.09 m/s) and 400 m (0.83-1.24 m/s)]. Meta-analysis across studies and racial groups showed that m.12705C>T, ND5 variant was significantly associated (p < 0.0001) with walking speed at both short and long distances. Replication and meta-analysis also identified statistically significant walking speed associations (p < 0.0001) between the m.5460.G>A, ND2 and m.309C>CT, HV2 variants at short and long distances, respectively. All results remained statistically significant after multiple comparisons adjustment for 499 mtDNA variants. The m.12705C>T variant can be traced to the beginnings of human global migration and that cells carrying this variant display altered tRNA expression. Significant pooled effects related to stopping during the long-distance walk test were observed across OXPHOS complexes I (p = 0.0017) and III (p = 0.0048). These results suggest that mtDNA-encoded variants are associated with differences in walking speed among older adults, potentially identifying those at risk of developing mobility impairments.
-
2.
Mitochondrial DNA copy number variation, leukocyte telomere length, and breast cancer risk in the European Prospective Investigation into Cancer and Nutrition (EPIC) study.
Campa, D, Barrdahl, M, Santoro, A, Severi, G, Baglietto, L, Omichessan, H, Tumino, R, Bueno-de-Mesquita, HBA, Peeters, PH, Weiderpass, E, et al
Breast cancer research : BCR. 2018;(1):29
Abstract
BACKGROUND Leukocyte telomere length (LTL) and mitochondrial genome (mtDNA) copy number and deletions have been proposed as risk markers for various cancer types, including breast cancer (BC). METHODS To gain a more comprehensive picture on how these markers can modulate BC risk, alone or in conjunction, we performed simultaneous measurements of LTL and mtDNA copy number in up to 570 BC cases and 538 controls from the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. As a first step, we measured LTL and mtDNA copy number in 96 individuals for which a blood sample had been collected twice with an interval of 15 years. RESULTS According to the intraclass correlation (ICC), we found very good stability over the time period for both measurements, with ICCs of 0.63 for LTL and 0.60 for mtDNA copy number. In the analysis of the entire study sample, we observed that longer LTL was strongly associated with increased risk of BC (OR 2.71, 95% CI 1.58-4.65, p = 3.07 × 10- 4 for highest vs. lowest quartile; OR 3.20, 95% CI 1.57-6.55, p = 1.41 × 10- 3 as a continuous variable). We did not find any association between mtDNA copy number and BC risk; however, when considering only the functional copies, we observed an increased risk of developing estrogen receptor-positive BC (OR 2.47, 95% CI 1.05-5.80, p = 0.04 for highest vs. lowest quartile). CONCLUSIONS We observed a very good correlation between the markers over a period of 15 years. We confirm a role of LTL in BC carcinogenesis and suggest an effect of mtDNA copy number on BC risk.
-
3.
Next Generation Sequencing expression profiling of mitochondrial subunits in men with Klinefelter syndrome.
Salemi, M, Cimino, L, Marino, M, Cannarella, R, Condorelli, RA, Romano, C, La Vignera, S, Calogero, AE
International journal of medical sciences. 2018;(1):31-35
Abstract
Objectives: Klinefelter syndrome (KS) is one of the most common sex-chromosome disorders as it affects up to 1 in every 600-1000 newborn males. Men with KS carry one extra X chromosome and they usually present a 47,XXY karyotype, but less frequent variants have also been reported in literature. KS typical symptoms include tall stature, gynecomastia, broad hips, hypogonadism and absent spermatogenesis. The syndrome is also related to a wide range of cognitive deficits, among which language-based learning disabilities and verbal cognition impairment are frequently diagnosed. The present study was carried out to investigate the role of mitochondrial subunits in KS, since the molecular mechanisms underlying KS pathogenesis are not fully understood. Methods: The study was performed by the next generation sequencing analysis and qRT-PCR assay. Results: We were able to identify a significant down-expression of mitochondrial encoded NADH ubiquinone oxidoreductase core subunit 6 (MT-ND6) in men with KS. Conclusion: It is known that defects of the mtDNA encoding mitochondrial subunits are responsible for the malfunction of Complex I, which will eventually lead to the Complex I deficiency, the most common respiratory chain defect in human disorders. Since it has been shown that decreased Complex I protein levels could induce apoptosis, wehypothesizethat the above-mentioned MT-ND6 down-expression contributes to the wide range of phenotypes observed in men with KS.
-
4.
Mitochondrial biology and prostate cancer ethnic disparity.
Xiao, J, Cohen, P, Stern, MC, Odedina, F, Carpten, J, Reams, R
Carcinogenesis. 2018;(11):1311-1319
-
-
Free full text
-
Abstract
Prostate cancer remains the second most prevalent cancer in men. Its incidence, progression and mortality profiles vary significantly by race and ethnicity, with African-American men having the highest incidence rate and mortality rate in the world. Although these disparities can be partially explained by socioeconomic factors, the underlying molecular causes are complex and require careful research. A considerable amount of literature exists, supporting the association between mitochondrial health and the incidence, aggression and risk of prostate cancer. Genetic alterations in mitochondrial DNA are frequent in prostate cancer; therefore, the resulting mitochondrial dysfunction and metabolic dysregulation may contribute to or indicate oncogenesis. Many of the prominent features of cancer cells are also closely related to mitochondrial functions, such as resistance to apoptosis, excess reactive oxygen species production and altered oxidative phosphorylation. In addition, prostate cancer ethnic disparity is influenced by environmental and lifestyle factors, which involves differences in mitochondrial metabolism and retrograde signaling events.
-
5.
Cerebrospinal fluid cell-free mitochondrial DNA is associated with HIV replication, iron transport, and mild HIV-associated neurocognitive impairment.
Mehta, SR, Pérez-Santiago, J, Hulgan, T, Day, TR, Barnholtz-Sloan, J, Gittleman, H, Letendre, S, Ellis, R, Heaton, R, Patton, S, et al
Journal of neuroinflammation. 2017;(1):72
Abstract
BACKGROUND Mitochondria are abundant organelles critical for energy metabolism and brain function. Mitochondrial DNA (mtDNA), released during cellular injury and as part of the innate immune response to viral pathogens, contains CpG motifs that act as TLR-9 ligands. We investigated relationships between cerebrospinal fluid (CSF) cell-free mtDNA levels and HIV viral load (VL), biomarkers of inflammation and iron transport, and neurocognitive (NC) function in the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) cohort. METHODS We quantified cell-free mtDNA in CSF by droplet digital PCR in 332 CHARTER participants who underwent comprehensive neuropsychiatric evaluation. NC performance was assessed using the global deficit score (GDS) as either a continuous or a binary measure (GDS ≥ 0.5, impaired vs. GDS < 0.5, unimpaired). CSF, clinical, and biomarker data from the earliest available time point were analyzed. Cell-free mtDNA associations with CSF inflammation and iron-related biomarkers [CXCL10, IL-6, IL-8, TNF-a, transferrin (TF), ceruloplasmin (CP), and vascular endothelial growth factor (VEGF)], VL, and GDS were evaluated by multivariable regression. RESULTS CSF cell-free mtDNA levels were significantly lower in participants with undetectable (vs. detectable) VL in either plasma (p < 0.001) or CSF (p < 0.001) and in those on antiretroviral therapy (ART; p < 0.001). Participants on ART with undetectable VL in both CSF and plasma had lower mtDNA levels than those with detectable VL in both compartments (p = 0.001). Higher mtDNA levels were observed in participants in the highest vs. lowest tertile (T3 vs. T1) of CSF CXCL10 (T3 vs. T1, p < 0.001) and TNF-a (T3 vs. T1, p < 0.05) in unadjusted analyses. MtDNA levels also correlated with CSF leukocyte count. After adjusting for CSF leukocyte count and VL, mtDNA levels were also associated with other inflammation- and iron-related biomarkers in CSF, including TF (T3 vs. T1, p < 0.05) and CP (T3 vs. T1, p < 0.05). With additional correction for ART use, mtDNA was also negatively associated with CSF VEGF (p < 0.05) and IL-6 (p = 0.05). We observed no associations of CSF mtDNA levels with age or GDS-defined NC impairment. CONCLUSIONS CSF cell-free mtDNA levels were associated with HIV RNA and ART status, as well as with biomarkers of iron transport and VEGF, a growth factor with known effects on mitochondrial integrity and autophagy. CSF mtDNA may be a biomarker of iron dysregulation and/or neuroinflammation during HIV infection.
-
6.
Mitochondrial cytopathies and the kidney.
Emma, F, Salviati, L
Nephrologie & therapeutique. 2017;:S23-S28
Abstract
Mitochondrial cytopathies include a heterogeneous group of diseases that are characterized by impaired oxidative phosphorylation. Current evidence suggests that renal involvement is probably more frequent than originally suspected but remains subclinical in a significant number of patients or is underestimated due to the severity of other clinical manifestations. Until recently, these diseases were thought to develop primarily in pediatric patients but patients that become symptomatic only in adulthood are now well recognized. From a renal standpoint, many patients with severe systemic disease and several patients with oligo-symptomatic clinical pictures have tubular defects, ranging from isolated tubular wasting of electrolytes to complete forms of renal Fanconi syndrome. Aside from rare cases of tubulo-interstitial and cystic diseases, other patients present with glomerular diseases that correspond in the majority of cases to focal segmental glomerulosclerosis lesions. Two specific entities should be singled out, namely the 3243 A>G mutation in the gene encoding for the mitochondrial leucine tRNA because it represents the most frequent form of mitochondrial glomerulopathy, and defects in the biosynthesis of coenzyme Q10 because they represent one of the few treatable forms of mitochondrial cytopathies.
-
7.
Estimating mobility using sparse data: Application to human genetic variation.
Loog, L, Mirazón Lahr, M, Kovacevic, M, Manica, A, Eriksson, A, Thomas, MG
Proceedings of the National Academy of Sciences of the United States of America. 2017;(46):12213-12218
Abstract
Mobility is one of the most important processes shaping spatiotemporal patterns of variation in genetic, morphological, and cultural traits. However, current approaches for inferring past migration episodes in the fields of archaeology and population genetics lack either temporal resolution or formal quantification of the underlying mobility, are poorly suited to spatially and temporally sparsely sampled data, and permit only limited systematic comparison between different time periods or geographic regions. Here we present an estimator of past mobility that addresses these issues by explicitly linking trait differentiation in space and time. We demonstrate the efficacy of this estimator using spatiotemporally explicit simulations and apply it to a large set of ancient genomic data from Western Eurasia. We identify a sequence of changes in human mobility from the Late Pleistocene to the Iron Age. We find that mobility among European Holocene farmers was significantly higher than among European hunter-gatherers both pre- and postdating the Last Glacial Maximum. We also infer that this Holocene rise in mobility occurred in at least three distinct stages: the first centering on the well-known population expansion at the beginning of the Neolithic, and the second and third centering on the beginning of the Bronze Age and the late Iron Age, respectively. These findings suggest a strong link between technological change and human mobility in Holocene Western Eurasia and demonstrate the utility of this framework for exploring changes in mobility through space and time.
-
8.
Mitochondrial Epigenetics and Environmental Exposure.
Lambertini, L, Byun, HM
Current environmental health reports. 2016;(3):214-24
Abstract
The rising toll of chronic and debilitating diseases brought about by the exposure to an ever expanding number of environmental pollutants and socio-economic factors is calling for action. The understanding of the molecular mechanisms behind the effects of environmental exposures can lead to the development of biomarkers that can support the public health fields of both early diagnosis and intervention to limit the burden of environmental diseases. The study of mitochondrial epigenetics carries high hopes to provide important biomarkers of exposure and disease. Mitochondria are in fact on the frontline of the cellular response to the environment. Modifications of the epigenetic factors regulating the mitochondrial activity are emerging as informative tools that can effectively report on the effects of the environment on the phenotype. Here, we will discuss the emerging field of mitochondrial epigenetics. This review describes the main epigenetic phenomena that modify the activity of the mitochondrial DNA including DNA methylation, long and short non-coding RNAs. We will discuss the unique pattern of mitochondrial DNA methylation, describe the challenges of correctly measuring it, and report on the existing studies that have analysed the correlation between environmental exposures and mitochondrial DNA methylation. Finally, we provide a brief account of the therapeutic approaches targeting mitochondria currently under consideration.
-
9.
Cell-free circulating mitochondrial DNA content and risk of hepatocellular carcinoma in patients with chronic HBV infection.
Li, L, Hann, HW, Wan, S, Hann, RS, Wang, C, Lai, Y, Ye, X, Evans, A, Myers, RE, Ye, Z, et al
Scientific reports. 2016;:23992
Abstract
Recent studies have demonstrated a potential link between circulating cell-free mitochondrial DNA (mtDNA) content and cancers. However, there is no study evaluating the association between circulating mtDNA as a non-invasive marker of hepatocellular carcinoma (HCC) risk. We conducted a nested case-control study to determine circulating mtDNA content in serum samples from 116 HBV-related HCC cases and 232 frequency-matched cancer-free HBV controls, and evaluate the retrospective association between mtDNA content and HCC risk using logistic regression and their temporal relationship using a mixed effects model. HCC cases had significantly lower circulating mtDNA content than controls (1.06 versus 2.47, P = 1.7 × 10(-5)). Compared to HBV patients with higher mtDNA content, those with lower mtDNA content had a significantly increased risk of HCC with an odds ratio (OR) of 2.19 (95% confidence interval [CI] 1.28-3.72, P = 0.004). Quartile analyses revealed a significant dose-dependent effect (Ptrend = 0.001) for this association. In a pilot longitudinal sub-cohort of 14 matched cases-control pairs, we observed a trend of dramatically decreased mtDNA content in cases and slightly decreased mtDNA content in controls, with a significant interaction of case-control status with time (Pinteraction = 0.049). Our findings suggest that circulating mtDNA is a potential novel non-invasive biomarker of HCC risk in HBV patients.
-
10.
Functional annotation of introns in mitochondrial genome--a brief review.
Anandakumar, S, Ravindran, SP, Shanmughavel, P
Mitochondrial DNA. Part A, DNA mapping, sequencing, and analysis. 2016;(2):811-4
Abstract
The present study is to decipher the non-coding regions present in mitochondrial genomes that cause diseases in humans and predict their functional roles through comparative genomics approach followed by functional annotation of these segments.