mtDNA Copy Number In Peripheral Blood 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.

Mitochondrial DNA Copy Number in Peripheral Blood as a Potential Non-invasive Biomarker for Multiple Sclerosis.

The impaired mitochondrial function has been implicated in the pathogenicity of multiple sclerosis(MS), a chronicinflammatory, demyelinating,andneurodegenerative disease of the CNS. Circulating mtDNA copy number in body fluids has been proposed as an indicator for several neurodegenerative diseases, and the altered cerebrospinal fluid mtDNA has been shown as a promising marker for MS. The aim of this study was to determine changes and biomarker potential of circulating mtDNA in peripheral blood in MS. The mtDNA copy number was quantified by real-time PCR in blood samples from 60 patients with relapsing-remitting MS (RRMS) and 64 healthy controls. The RRMS patients had significantly lower circulating mtDNA copy number compared to controls. Subgroup analysis with stratification of RRMS patients based on disease duration under or over 10years revealed that the mtDNA copy number was significantly lower in the group with longer disease duration. A negative correlation was observed between mtDNA copy number and disease duration. The ROC curve analysis indicated a significant ability of mtDNA copy number to separate RRMS patients from controls with an AUC of 0.859. This is the first study to measure peripheral blood mtDNA copy number in MS patients. Current data suggest that the reduction in peripheral blood mtDNA copy number may be an early event in MS and correlate with the disease progression. The findings of this study indicate that circulating blood-based mtDNA copy number may be a potential non-invasive candidate biomarker for mitochondria-mediated neurodegeneration and MS. This can put forward the clinical applicability over other invasive markers.

Peripheral Blood Mitochondrial DNA Copy Number Obtained From Genome-Wide Genotype Data Is Associated With Neurocognitive Impairment in Persons With Chronic HIV Infection.

Mitochondrial DNA (mtDNA) copy number varies by cell type and energy demands. Blood mtDNA copy number has been associated with neurocognitive function in persons without HIV. Low mtDNA copy number may indicate disordered mtDNA replication; high copy number may reflect a response to mitochondrial dysfunction. We hypothesized that blood mtDNA copy number estimated from genome-wide genotyping data is related to neurocognitive impairment (NCI) in persons with HIV. In the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) study, peripheral blood mtDNA copy number was obtained from genome-wide genotyping data as a ratio of mtDNA single-nucleotide polymorphism probe intensities relative to nuclear DNA single-nucleotide polymorphisms. In a multivariable regression model, associations between mtDNA copy number and demographics, blood cell counts, and HIV disease and treatment characteristics were tested. Associations of mtDNA copy number with the global deficit score (GDS), GDS-defined NCI (GDS ≥ 0.5), and HIV-associated neurocognitive disorder (HAND) diagnosis were tested by logistic regression, adjusting for potential confounders. Among 1010 CHARTER participants, lower mtDNA copy number was associated with longer antiretroviral therapy duration (P < 0.001), but not with d-drug exposure (P = 0.85). mtDNA copy number was also associated with GDS (P = 0.007), GDS-defined NCI (P < 0.001), and HAND (P = 0.002). In all analyses, higher mtDNA copy number was associated with poorer cognitive performance. Higher mtDNA copy number estimated from peripheral blood genotyping was associated with worse neurocognitive performance in adults with HIV. These results suggest a connection between peripheral blood mtDNA and NCI, and may represent increased mtDNA replication in response to mitochondrial dysfunction.

Peripheral blood mitochondrial DNA copy number is a potential biomarker for progress of diabetic nephropathy in type 2 diabetes patients

Mitochondrial DNA (mtDNA) copy number is a surrogate measure of mitochondrial function, and altered mtDNA copy number has been associated with diabetic nephropathy (DN), a leading cause end stage renal disease in diabetic patients. We investigated whether mtDNA copy number in peripheral blood could be utilized as a biomarker for DN progress in type 2 diabetes (T2D) patients. A total of 50 non-diabetic and 100 diabetic subjects were recruited. The diabetic subjects were sub-divided based on urinary albumin-creatinine ratio (ACR) into T2D patients with normoalbuminuria (ACR < 30 mg/g, n = 50), DN patients with microalbuminuria (ACR 30–300 mg/g, n = 29), and DN patients with macroalbuminuria (ACR > 300 mg/g, n = 21). The mtDNA copy number was measured as relative quantity of mtDNA compared to nuclear DNA using real-time PCR. Overall, the mtDNA copy number was lower in T2D and DN patients than in controls (P < 0.001). Sub-group analyses by ACR showed that lower mtDNA copy number was significantly associated with high levels of albuminuria even after adjusting for conventional risk factors (odds ratio [OR] 0.47, confidence interval [CI] 0.299–0.74 for microalbuminuria and OR 0.21, 95% CI 0.1–0.436 for macroalbuminuria). Moreover, mtDNA copy number was correlated negatively with albuminuria (r = −0.546) and positively with glomerular filtration rate (r = 0.572). The areas under the receiver operating characteristic curves (AUCs) of mtDNA copy number in discriminating DN patients from T2D patients and healthy controls were 0.80 (P < 0.001) and 0.885 (P < 0.001), respectively. Our results showed that peripheral blood mtDNA copy number was associated with the development of DN and could serve as a biomarker during DN progression.

Peripheral blood mitochondrial DNA copy number, a potential marker of non‐alcoholic fatty liver disease?

IntroductionNonalcoholic fatty liver disease (NAFLD) includes a spectrum of histological findings ranging from simple steatosis (SS) to non‐alcoholic steatohepatitis (NASH). Although often considered the hepatic manifestation of metabolic syndrome (MS), longitudinal studies suggest that NAFLD precedes MS. To date, liver biopsy is the most accurate method to differentiate between SS and NASH. However, recent studies indicate an association between mitochondrial DNA (mtDNA) copy number and NAFLD severity in liver biopsies. If a similar association exists in peripheral blood, mtDNA copy number could represent a non‐invasive alternative for differentiating NAFLD disease stages.Given the above, we analyzed whether mtDNA copy number differs in individuals discordant for NAFLD and MS. We also probed for correlations between liver and peripheral blood mtDNA copy number, in addition to associations between NAFLD and mtDNA copy number.ObjectiveTo analyze whether mtDNA copy number is a useful blood‐based marker of NAFLD severity.Materials and methodsCohort = 73 peripheral blood samples and liver biopsies obtained from patients that were operated for gallstones; individuals were separated into 4 groups: controls (n = 27), NAFLD (n = 14), MS (n = 9) and MS + NAFLD (n = 23). NAFLD severity was determined according to the parameters described by Kleiner; mtDNA copy number was determined by semiquantitative PCR.ResultsWe found no significant differences in mtDNA copy number across the four groups analyzed (i.e. control, NAFLD, MS, MS+NAFLD). However, we did find an association between mtDNA copy number and NAFLD severity. In particular, we found that a significant increase in mtDNA copy number in SS relative to control samples, while mtDNA copy number was significantly reduced in NASH relative to SS.ConclusionAkin to the previously published data of mtDNA copy number in liver biopsies of individuals with NAFLD, we uncovered a dynamic relationship between mtDNA copy number and NAFLD severity in peripheral blood samples. This suggests that mtDNA copy number may be a promising blood‐based biomarker for differentiating between SS and NASH. To address this issue, we are currently probing for correlations between liver and peripheral blood mtDNA copy number.Support or Funding InformationMexican National Council for Science and Technology (CONACyT).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Mitochondrial DNA copy number variation as a potential predictor of renal cell carcinoma.

Peripheral blood mitochondrial DNA (mtDNA) copy number alteration has been suggested as a risk factor for several types of cancer. The aim of the present study was to assess the role of peripheral blood mtDNA copy number variation as a noninvasive biomarker in the prediction and early detection of renal cell carcinoma (RCC) in a cohort of Egyptian patients. Quantitative real-time polymerase chain reaction (qPCR) was used to measure peripheral blood mtDNA copy numbers in 57 patients with newly diagnosed, early-stage localized RCC and 60 age- and sex-matched healthy individuals as a control group. Median mtDNA copy number was significantly higher in RCC cases than in controls (166 vs. 91, p<0.001). Increased mtDNA copy number was associated with an 18-fold increased risk of RCC (95% confidence interval: 5.065-63.9). On receiver operating characteristic curve analysis, it was found that mtDNA could distinguish between RCC patients and healthy controls, with 86% sensitivity, 80% specificity, 80.3% positive predictive value and 85.7% negative predictive value at a cutoff value of 108.5. Our results showed that increased peripheral blood mtDNA copy number was associated with increased risk of RCC. Therefore, RCC might be considered as part of a range of potential tumors in cases with elevated blood mtDNA copy number.

No association between mitochondrial DNA copy number and colorectal adenomas.

Despite previously reported associations between peripheral blood mtDNA copy number and colorectal cancer, it remains unclear whether altered mtDNA copy number in peripheral blood is a risk factor for colorectal cancer or a biomarker for undiagnosed colorectal cancer. Though colorectal adenomas are well-recognized precursor lesions to colorectal cancer, no study has evaluated an association between mtDNA copy number and colorectal adenoma risk. Hence, we investigated an association between peripheral blood mtDNA copy number and incident, sporadic colorectal adenoma in 412 colorectal adenoma cases and 526 cancer-free controls pooled from three colonoscopy-based case-control studies that used identical methods for case ascertainment, risk factor determination, and biospecimen collection. We also evaluated associations between relative mtDNA copy number and markers of oxidative stress, including circulating F2 -isoprostanes, carotenoids, and fluorescent oxidation products. We measured mtDNA copy number using a quantitative real time polymerase chain reaction (PCR). We used unconditional logistic regression to analyze the association between mtDNA copy number and colorectal adenoma risk after multivariable adjustment. We found no association between logarithmically transformed relative mtDNA copy number, analyzed as a continuous variable, and colorectal adenoma risk (odds ratio = 1.02, 95%CI: 0.82-1.27; P = 0.86). There were no statistically significant associations between relative mtDNA copy number and other markers of oxidative stress. Our findings, taken together with those from previous studies, suggest that relative mtDNA copy number in peripheral blood may more likely be a marker of early colorectal cancer than of risk for the disease or of in vivo oxidative stress. © 2015 Wiley Periodicals, Inc.

Abstract 2771: Neutrophil specific mitochondrial DNA copy number as a biomarker for breast cancer

Abstract Background: We previously identified that mitochondrial DNA (mtDNA) copy number in pre-diagnostic peripheral blood samples collected up to 3 years prior to breast cancer diagnosis was associated with breast cancer risk. However, the biological mechanisms underlying this association remain poorly understood. To get a better understanding of the mtDNA copy number-breast cancer association we (a) evaluated the contribution of different cell subsets to whole blood mtDNA copy number and (b) developed a mouse model of early stage breast cancer that replicated the mtDNA copy number-breast cancer association observed in human populations. Methods: Since cell subsets in peripheral blood have different amounts of mtDNA copy number, we evaluated the contribution of five different cell subsets to mtDNA copy number in peripheral blood from 10 healthy volunteers that were sorted into the following cell subtypes using magnetic beads separation: neutrophils (CD15+), lymphocytes (CD3+), B-cells (CD19+), natural killer (NK) cells (CD56+) and monocytes (CD14+). We utilized a transgenic mouse model that relies on an inducible mouse mammary tumor virus (MMTV) promoter-driven inducible FGFR1 (iFGFR1) construct that represents a model of early stage mammary tumorigenesis to evaluate changes in peripheral blood mtDNA copy number. Results: The mtDNA copy number in the myeloid cell fractions (monocytes and neutrophils) were positively correlated with whole blood mtDNA copy number while the mtDNA copy number in the lymphocyte fractions (T and B lymphocytes and NK cells) were negatively correlated with whole blood mtDNA copy number. Specifically, the neutrophil mtDNA copy number was strongly correlated to the whole blood mtDNA copy number (r = 0.67), while the monocyte mtDNA copy number was weakly correlated with whole blood mtDNA copy number (r = 0.24). The lymphocyte cell subtypes (T lymphocytes, B lymphocytes and NK cells) showed weak negative correlations with whole blood mtDNA copy number (r = -0.16, r = -0.01 and r = -0.25 respectively). In the transgenic mouse model, we showed significant increase in mtDNA copy number in whole blood in treated mice (n = 4) versus control mice (n = 5) (2.87 vs. 1.53, p = 0.04), replicating our findings in human populations. Mitochondrial DNA copy number in sorted neutrophils from the transgenic mice also showed a similar trend. Conclusion: These data along with other studies that show altered neutrophil function in cancer patients, suggests that altered neutrophil phenotype may explain the mtDNA copy number-breast cancer association and neutrophil specific mtDNA copy number may be useful as an early detection tool in breast cancer diagnosis. The early stage breast tumorigenesis mouse model that replicates the mtDNA copy number-breast cancer association in human populations can be used to understand the biological mechanisms underlying the increase in mtDNA copy number observed in the peripheral blood of breast cancer patients. Citation Format: Helene Barcelo, Nicholas J. Brady, Kathryn L. Schwertfeger, Myron Gross, Bharat Thyagarajan. Neutrophil specific mitochondrial DNA copy number as a biomarker for breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2771. doi:10.1158/1538-7445.AM2015-2771

Higher mitochondrial DNA copy number is associated with lower prevalence of microalbuminuria

It has been suggested that mitochondrial dysfunction contributes to the initiation and development of atherosclerosis and cardiovascular disease. We examined the association between mitochondrial DNA (mtDNA) copy number and microalbuminuria in a cross-sectional community-based study. We measured peripheral blood mtDNA copy number in 694 adults without chronic kidney disease by a real-time PCR method. The overall prevalence of microalbuminuria (defined as an albumin creatinine ratio of 30 to 299 mg/g) was 4.5%. The prevalence of microalbuminuria decreased progressively from the lower to the upper quartiles of mtDNA copy number (6.9%, 5.7%, 2.9%, and 2.3% in quartiles 1, 2, 3, and 4, respectively, P=0.017 for trend). Multiple logistic regression models showed that the quartile of mtDNA copy number was independently associated with the prevalence of microalbuminuria (P=0.01 for trend). Compared with the lowest quartile, the highest quartile had an odds ratio of 0.22 for microalbuminuria (95% confidence interval, 0.05 to 0.87; P=0.03). Higher mtDNA copy number was associated with the lower prevalence of microalbuminuria in a community-based population.