Leukocyte Mitochondrial DNA Copy Number Research Articles

MEG3 polymorphisms associated with peripheral blood leukocyte mitochondrial DNA copy number in PAHs-exposure workers

BackgroundEpidemiological studies have shown that exposure to Polycyclic aromatic hydrocarbons (PAHs) is associated with reduced mitochondrial DNA copy number (mtDNA-CN). Long non-coding RNA maternally expressed gene 3 (MEG3) is involved in mitochondrial function regulation. However, it is unknown whether single-nucleotide polymorphisms in the MEG3 can regulate the mtDNAcn in PAHs exposed populations. The aim of this study was to examine the effect of MEG3 genetic polymorphisms on the mtDNA-CN in PAHs exposed populations. Materials and methodsWe recruited 544 coke oven workers and 238 controls using random cluster sampling. High-performance liquid chromatography was used to detect the concentrations of four OH-PAHs (1-hydroxypyrene [1-OHPyr], 1-hydroxynathalene [1-OHNap], 2-hydroxynathalene [2-OHNap], and 3-hydroxyphenanthrene [3-OHPhe]) in urine. The mtDNA-CN of peripheral blood leukocytes was measured using the quantitative polymerase chain reaction method. Sequenom Mass ARRAY matrix-assisted laser desorption/ionization-time of flight mass spectrometry platform was used to detect ten polymorphisms in MEG3. ResultsThe OH-PAHs levels in the exposure group were significantly higher than those in the control group (P < 0.001). The mtDNA-CN in the exposure group was significantly lower than that in the control group (P < 0.001). A linear regression model revealed that PAHs-exposure (β [95% confidence interval, CI], −0.428 [-0.475, −0.381], P < 0.001), male gender (−0.052 [-0.098, −0.005], P = 0.029), genotype TT for MEG3 rs11859 (−0.088 [-0.142, −0.035], P = 0.001), and genotype GG for MEG3 rs7155428 (−0.114 [-0.210, −0.017], P = 0.021) were associated with decreased mtDNA-CN. ConclusionPAHs-exposure, male gender, genotype TT for rs11859, and genotype GG for rs7155428 were risk factors for mtDNA-CN.

Leukocyte telomere length and mitochondrial DNA copy number associate with endothelial function in aging-related cardiovascular disease.

We investigated the association between leukocyte telomere length, mitochondrial DNA copy number, and endothelial function in patients with aging-related cardiovascular disease (CVD). In total 430 patients with CVD and healthy persons were enrolled in the current study. Peripheral blood was drawn by routine venipuncture procedure. Plasma and peripheral blood mononuclear cells (PBMCs) were collected. Cell-free genomic DNA (cfDNA) and leukocytic genomic DNA (leuDNA) were extracted from plasma and PBMCs, respectively. Relative telomere length (TL) and mitochondrial DNA copy number (mtDNA-CN) were analyzed using quantitative polymerase chain reaction. Endothelial function was evaluated by measuring flow-mediated dilation (FMD). The correlation between TL of cfDNA (cf-TL), mtDNA-CN of cfDNA (cf-mtDNA), TL of leuDNA (leu-TL), mtDNA-CN of leuDNA (leu-mtDNA), age, and FMD were analyzed based on Spearman's rank correlation. The association between cf-TL, cf-mtDNA, leu-TL, leu-mtDNA, age, gender, and FMD were explored using multiple linear regression analysis. cf-TL positively correlated with cf-mtDNA (r = 0.1834, P = 0.0273), and leu-TL positively correlated with leu-mtDNA (r = 0.1244, P = 0.0109). In addition, both leu-TL (r = 0.1489, P = 0.0022) and leu-mtDNA (r = 0.1929, P < 0.0001) positively correlated with FMD. In a multiple linear regression analysis model, both leu-TL (β = 0.229, P = 0.002) and leu-mtDNA (β = 0.198, P = 0.008) were positively associated with FMD. In contrast, age was inversely associated with FMD (β = -0.426, P < 0.0001). TL positively correlates mtDNA-CN in both cfDNA and leuDNA. leu-TL and leu-mtDNA can be regarded as novel biomarkers of endothelial dysfunction.

High leukocyte mitochondrial DNA copy number contributes to poor prognosis in breast cancer patients

BackgroundCompelling evidence has indicated a significant association between leukocyte mitochondrial DNA copy number (mtDNAcn) and prognosis of several malignancies in a cancer-specific manner. However, whether leukocyte mtDNAcn can predict the clinical outcome of breast cancer (BC) patients has not been well investigated.MethodsThe mtDNA copy number of peripheral blood leukocytes from 661 BC patients was measured using a Multiplex AccuCopy™Kit based on a multiplex fluorescence competitive PCR principle. Kaplan–Meier curves and Cox proportional hazards regression model were applied to investigate the association of mtDNAcn with invasive disease-free survival (iDFS), distant disease-free survival (DDFS), breast cancer special survival (BCSS), and overall survival (OS) of patients. The possible mtDNAcn-environment interactions were also evaluated by the Cox proportional hazard regression models.ResultsBC patients with higher leukocyte mtDNA-CN exhibited a significantly worse iDFS than those with lower leukocyte mtDNAcn (5-year iDFS: fully-adjusted model: HR = 1.433[95%CI 1.038–1.978], P = 0.028). Interaction analyses showed that mtDNAcn was significantly associated with hormone receptor status (adjusted p for interaction: 5-year BCSS: 0.028, 5-year OS: 0.022), so further analysis was mainly in the HR subgroup. Multivariate Cox regression analysis demonstrated that mtDNAcn was an independent prognostic factor for both BCSS and OS in HR-positive patients (HR+: 5-year BCSS: adjusted HR (aHR) = 2.340[95% CI 1.163–4.708], P = 0.017 and 5-year OS: aHR = 2.446 [95% CI 1.218–4.913], P = 0.011).ConclusionsFor the first time, our study demonstrated that leukocyte mtDNA copy number might influence the outcome of early-stage breast cancer patients depending on intrinsic tumor subtypes in Chinese women.

Abstract P198: Associations Between Plasma Proteome and Leukocyte Mitochondrial DNA Copy Number: The Atherosclerosis Risk in Communities Study (ARIC)

Introduction: The number of copies of the mitochondrial genome, termed mitochondrial DNA copy number (MTCN), is a proxy for mitochondrial function and varies by cell. Critically, lower MTCN has been associated with aging and chronic diseases such as dementia and cancer. We conducted a large-scale proteomics analysis of leukocyte MTCN (L-MTCN) to elucidate pathways modulated by L-MTCN that may be involved in diseases of aging. Hypothesis: We hypothesize that L-MTCN is significantly associated to plasma proteins that have been implicated in biological pathways of L-MTCN and related diseases. Methods: Based on whole genome sequencing (WGS) data measured in samples collected in ARIC visits 1, 2, and 3 (i.e., baseline for the current study), L-MTCN was calculated as (2 * coverage of the mitochondrial genome) / coverage of the autosome, using the median coverage of 1000 base pair bins overlapping the mitochondrial genome (16 total) and the median coverage of ~142,000 higher quality autosomal bins. Only samples with read lengths of 150 or 151 were included in subsequent analyses, and L-MTCN estimates were inverse normalized within read length group and WGS group before being merged together. This normalized L-MTCN was then analyzed as a predictor for an association with 4,870 plasma proteins measured by SOMAscan v4 in ARIC visit 3 in race-specific generalized linear models, adjusting for the following covariates at baseline: WGS sample visit, age, gender, field center, smoking status, and a measure of kidney function. Bonferroni correction was applied to account for the number of proteins tested in 5,007 White participants (p≤1x10 -5 ). Associations were tested for replication in 1,178 Black participants and considered significant if protein estimates had the same direction of association as Whites at p-value ≤ 2.2x10 -4 . Results: Among White participants, 230 proteins were significantly associated with L-MTCN. Of these proteins S100A9, GP1Bα, EGFR, THBS2, and FCGR3B were significantly replicated among Black participants. Strongest associations with L-MTCN were seen with GP1Bα (Estimate: 0.121) and S100A9 (Estimate: -0.191). Biologically S100A9 is a calgranulin and together with S100A8 forms calprotectin, which have roles mediating inflammatory processes. GP1Bα helps mediate platelet activation and forms the glycoprotein Ib-IX-V complex which acts as a platelet surface receptor for von Willebrand factor facilitating platelet adhesion. Conclusion: This large proteomics analysis identified 230 plasma proteins significantly associated with L-MTCN. Some of the proteins have been connected to inflammatory diseases, cardiovascular disease, and cancer in the literature. These results provide insight into proteins involved in biological pathways related to L-MTCN.

Leukocyte telomere length and mitochondrial DNA copy number association with colorectal cancer risk in an aging population

In this study, we evaluated the association of blood leukocyte telomere length (LTL) and mitochondrial DNA copy number (mtDNA-CN) with the risk of incident colorectal cancer (CRC). We studied and followed-up a cohort of Russian men and women (aged 45 – 69 years, n = 9360, 54% female) from the HAPIEE study for 15 years. Using the nested case-control design, we selected cases with incident CRC among those free from any baseline cancer (n = 146) and sex- and age-stratified controls among those free from baseline cancer and cardiovascular disease and alive at the end of the follow-up (n = 799). We employed multivariable-adjusted logistic regression to estimate the odds ratios (ORs) of CRC per 1 decile of LTL or mtDNA-CN. We observed an inverse association of LTL and mtDNA-CN baseline values with the 15-year risk of incident CRC. Carriers of shorter telomeres had an increased 15-year risk of incident CRC with adjusted OR 3.2 (95% CI: 2.56 – 3.87, P &lt; 0.001) per 1 decile decrease in LTL, independent of baseline age, sex, smoking, body mass index, blood pressure, lipid levels, and education. Similarly, lower mtDNA-CN was associated with the higher risk of incident CRC with adjusted OR 1.7 (95% CI: 1.12 – 1.89, P &lt; 0.001) per 1 decile decrease in mtDNA-CN, independent of the aforementioned factors. Using the modified values of LTL and mtDNA-CN adjusted for multiple factors and their interactions with a case–control status, the ORs of CRC were 2.53 and 1.52 per 1 decile decrease in adjusted baseline LTL and mtDNA-CN, respectively. In conclusion, LTL and mtDNA-CN were independent inverse predictors of the 15-year risk of CRC in the Russian cohort. These findings highlight the relevance for subsequent research to exploit the mechanisms through which LTL and mtDNA-CN may reflect human health.

Telomere and mitochondria mediated the association between dietary inflammatory index and mild cognitive impairment: A prospective cohort study

BackgroundDiet and chronic inflammation might play a major role in the pathogenesis of mild cognitive impairment (MCI). In addition, peripheral blood leukocyte telomere length (LTL) and mitochondrial DNA copy number (mtDNAcn) might mediate the relationship between inflammation and MCI risk. The purpose of the present study is to evaluate whether inflammatory potential of diet assessed by dietary inflammatory index (DII), chronic inflammation, peripheral blood LTL, and mtDNAcn were associated with the risk of MCI.ResultsA population-based cohort study was conducted with a total of 2944 participants. During a median follow-up of 2 years, 438 (14.90%) individuals were new-onset MCI. After adjustment, a higher score of DII (hazard ratio [HR]: 1.056, 95% CI: 1.005, 1.109), a higher log systemic immune inflammation index (SII) (HR: 1.333, 95% CI: 1.089, 1.633) and log system inflammation response index (SIRI) (HR: 1.487, 95% CI: 1.024, 2.161) predicted elevated risk of MCI. An increased mtDNAcn (HR: 0.843, 95% CI: 0.712, 0.997), but not LTL, predicted a decreased risk of MCI. Negative associations of log SII with LTL (β:-0.359, 95% CI: -0.445, -0.273) and mtDNAcn (β:-0.048, 95% CI: -0.090, -0.006) were found. Additionally, negative associations of log SIRI with LTL (β: -0.035, 95% CI: -0.052, -0.017) and mtDNAcn (β:-0.136, 95% CI: -0.216, -0.056) were also found. Path analysis suggested that SIRI, LTL, and mtDNAcn, in series, have mediation roles in the association between DII score and MCI risk.ConclusionsHigher DII, SII, and SIRI might predict a greater risk of MCI, while a longer LTL and an increased mtDNAcn were linked to a reduced risk of MCI among the older population. LTL and mtDNAcn could play mediation roles in the association between DII and MCI risk.

Leukocyte Telomere Length Predicts Severe Disability in Relapsing-Remitting Multiple Sclerosis and Correlates with Mitochondrial DNA Copy Number.

Multiple sclerosis (MS) is a chronic autoimmune inflammatory disease that affects the nervous system. Peripheral blood leukocyte telomere length (LTL) and mitochondrial DNA copy number (mtDNA-CN) are potential biomarkers of neurological disability and neural damage. Our objective was to assess the LTL and mtDNA-CN in relapsing-remitting MS (RRMS). We included 10 healthy controls, 75 patients with RRMS, 50 of whom had an Expanded Disability Status Scale (EDSS) from 0 to 3 (mild to moderate disability), and 25 had an EDSS of 3.5 to 7 (severe disability). We use the Real-Time Polymerase Chain Reaction (qPCR) technique to quantify absolute LTL and absolute mtDNA-CN. ANOVA test show differences between healthy control vs. severe disability RRMS and mild-moderate RRMS vs. severe disability RRMS (p = 0.0130). LTL and mtDNA-CN showed a linear correlation in mild-moderate disability RRMS (r = 0.378, p = 0.007). Furthermore, we analyzed LTL between RRMS groups with a ROC curve, and LTL can predict severe disability (AUC = 0.702, p = 0.0018, cut-off < 3.0875 Kb, sensitivity = 75%, specificity = 62%), whereas the prediction is improved with a logistic regression model including LTL plus age (AUC = 0.762, p = 0.0001, sensitivity = 79.17%, specificity = 80%). These results show that LTL is a biomarker of disability in RRMS and is correlated with mtDNA-CN in mild-moderate RRMS patients.

Association of leukocyte mitochondrial DNA copy number with longitudinal C-reactive protein levels and survival in older adults: a cohort study.

Systemic chronic inflammation occurs with age. The association of the leukocyte mitochondrial DNA copy number, a measure of mitochondrial function in aging, with the temporal profile of serum high-sensitivity C-reactive protein and mortality risk remains uncertain. The objectives of this study were to examine the association of the leukocyte mitochondrial DNA copy number with longitudinal high-sensitivity C-reactive protein levels and the association of the longitudinal high-sensitivity C-reactive protein levels with mortality risk. This prospective cohort study included 3928 adults aged ≥ 55years without systemic inflammation in the baseline examination of the Healthy Aging Longitudinal Study in Taiwan, which started in 2009. Each participant received leukocyte mitochondrial DNA copy number measurement using a fluorescence-based quantitative polymerase chain reaction at baseline, serum high-sensitivity C-reactive protein measurements at baseline and the follow-up examination five years later, and the ascertainment of all-cause death (until November 30, 2021). The relationships among the leukocyte mitochondrial DNA copy number, longitudinal serum high-sensitivity C-reactive protein levels, and time to all-cause mortality were examined using the joint longitudinal and survival modeling analysis. Of the 3928 participants (mean age: 69years; 2060 [52%] were women), 837 (21%) died during follow-up. In the adjusted analysis, one standard deviation lower natural log-transformed baseline leukocyte mitochondrial DNA copy number was associated with an increase of 0.05 (95% confidence interval [CI], 0.02 to 0.08) standard deviation in serum high-sensitivity C-reactive protein in subsequent years. An increase of 1 standard deviation in instantaneous high-sensitivity C-reactive protein levels was associated with a hazard ratio (HR) for all-cause mortality of 1.22 (95% CI, 1.14 to 1.30). Similar results were obtained after further adjusting for baseline high-sensitivity C-reactive protein levels (HR [95% CI], 1.27 [1.16 to 1.38]) and after excluding those with serum high-sensitivity C-reactive protein above 10mg/L (HR [95% CI], 1.21[1.11 to 1.31]) or 3mg/L (HR [95% CI], 1.19 [1.06 to 1.31]) during follow-up. A lower leukocyte mitochondrial DNA copy number was associated with persistently higher high-sensitivity C-reactive protein levels. Moreover, these higher time-varying high-sensitivity C-reactive protein levels were instantaneously associated with a higher risk of death.

Markers related to oxidative stress in peripheral blood in children with autism spectrum disorder

BackgroundOxidative stress in the brain contributes to neuronal damage in genetically susceptible children, which might be involved in the pathophysiology of autism spectrum disorder(ASD). However, clinical data were inconsistent. The goal of this study was to investigate whether oxidative stress markers (vitamin A and vitamin E concentrations and leukocyte mitochondrial DNA copy number and telomere length) in peripheral blood are related to ASD in Chinese children aged 6–9 years. MethodSixty seven individuals with ASD and 134 sex- and age-matched neurotypical controls participated. The relative mitochondrial DNA copy number (mtDNAcn) and telomere length of leukocytes in peripheral blood were measured using quantitative real-time polymerase chain reaction. The vitamin A and vitamin E concentrations in plasma were determined using reversed-phase high-performance liquid chromatography. ResultsASD group had a higher leukocyte mtDNAcn (1.36 ± 0.49 vs. 1.03 ± 0.24, p < 0.001) and vitamin E concentration (5.79 ± 1.70 ng/ml vs. 5.30 ± 0.96 ng/ml, p = 0.044) than the control group, but no significant differences in vitamin A concentration and leukocyte telomere length were detected between groups. Leukocyte mtDNAcn in the highest tertile increased the risk of ASD by 4.259 times (odds ratio:4.259, 95% confidence interval: 1.427–12.707, p = 0.009) compared with the lowest tertile after adjustment for confounders, and a significant dose–response relationship between mtDNAcn and ASD risk was observed (p-trend = 0.032). ConclusionsChildren with ASD had higher levels of leukocyte mtDNAcn.

Reduced leukocyte mitochondrial copy number in metabolic syndrome and metabolically healthy obesity.

ObjectiveThis study aimed to investigate the associations between peripheral blood leukocyte mitochondrial copy number, metabolic syndrome, and adiposity-related body composition phenotypes in a high prevalence population.MethodsA single center cross-sectional study was conducted, consisting of 521 middle-aged subjects of Maltese-Caucasian ethnicity. Participants were stratified according to the presence of metabolic syndrome and different metabolic health definitions based on NCEP-ATP III criteria. Relative leukocyte mitochondrial DNA copy number was determined by quantitative polymerase chain reaction and corrected for leukocyte and platelet count. The associations between mitochondrial copy number and metabolic syndrome components was evaluated and adjusted for age and gender.ResultsSignificant negative correlations between mtDNA copy number and BMI, waist circumference, triglyceride levels, fasting plasma glucose, HbA1c, HOMA-IR and hsCRP were observed, along with a positive correlation with HDL-C levels. Mitochondrial copy number was lower in individuals with metabolic syndrome. When compared to metabolically healthy normal weight subjects, a reduction in mtDNA copy number was observed in both the metabolically healthy and unhealthy obese categories.ConclusionOur data supports the association between reduced leukocyte mtDNA copy number, obesity, and metabolic syndrome. This investigation expands on the spectrum of associations between mtDNA copy number and metabolic phenotypes in different populations and underpins the role of mitochondrial dysfunction in the development and progression of metabolic syndrome and its components.

Leukocyte mitochondrial DNA copy number is a potential non-invasive biomarker for psoriasis.

Abnormalities in the mitochondria have been linked to psoriasis, a chronic immune-mediated inflammatory skin disease. The mitochondrial DNA (mtDNA) is present in thousands of copies per cell and altered mtDNA copy number (mtDNA-CN), a common indicator of mitochondrial function, has been proposed as a biomarker for several diseases including autoimmune diseases. In this case-control study, we investigated whether the mtDNA-CN is related to psoriasis, correlates with the disease duration and severity, and can serve as a disease biomarker. Relative mtDNA-CN as compared with nuclear DNA was measured by a quantitative real-time polymerase chain reaction in peripheral blood buffy coat samples from 56 patients with psoriasis and 44 healthy controls. The receiver operating characteristic (ROC) curve analysis was performed to evaluate the value of mtDNA-CN as a biomarker. We found that the mtDNA-CN was significantly decreased in patients with psoriasis compared to healthy controls (93.6±5.3 vs. 205±71; P = 0.04). Sub-group analyses with stratification of patients based on disease duration under or over 10 years and disease severity indicated that the mtDNA-CN was significantly lower in patients with longer disease duration (74±4.3 in disease duration >10 years vs. 79±8.3 in disease duration <10 years, P = 0.009), and higher disease severity (72±4.3 in moderate-to-severe index vs. 88.3 ± 6 in mild index, P = 0.017). Moreover, the mtDNA-CN was negatively correlated with the disease duration and disease severity (r = -0.36, P = 0.006; r = -0.41, P = 0.003 respectively). The ROC analysis of mtDNA-CN showed an area under the curve (AUC) of 0.84 (95% confidence interval: 0.69-0.98; P = 0.002) for differentiating patients from healthy controls. Our study suggests that low mtDNA-CN may be an early abnormality in psoriasis and associates with the disease progression. Our study also suggests that mtDNA-CN may be a novel blood-based biomarker for the early detection of psoriasis.

Advanced glycation end products, leukocyte telomere length, and mitochondrial DNA copy number in patients with coronary artery disease and alterations of glucose homeostasis: From the GENOCOR study

Background and aimAlterations of glucose homeostasis can increase advanced glycation end products (AGEs) that exacerbate vascular inflammatory disease and may increase vascular senescence and aging. This study examined the relationships between carboxymethyl-lysine (CML) and soluble receptor for AGEs (sRAGE) with leukocyte telomere length (LTL) and mitochondrial DNA copy number (mtDNAcn), as cell aging biomarkers, in patients with established coronary artery disease (CAD). Methods and resultsWe studied 459 patients with CAD further categorized as having normal glucose homeostasis (NG, n = 253), pre-diabetes (preT2D, n = 85), or diabetes (T2D, n = 121). All patients were followed up for the occurrence of major adverse cardiovascular events (MACEs). Plasma concentrations of sRAGE and CML were measured by ELISA. mtDNAcn and LTL were measured by qRT-PCR. CML levels were significantly higher in patients with preT2D (p < 0.007) or T2D (p < 0.003) compared with those with NG. mtDNAcn resulted lower in T2D vs preT2D (p = 0.04). At multivariate Cox proportional hazard analysis, short LTL (HR: 2.89; 95% CI: 1.11–10.1; p = 0.04) and high levels of sRAGE (HR: 2.20; 95% CI: 1.01–5.14; p = 0.04) were associated with an increased risk for MACEs in patients with preT2D and T2D, respectively. T2D patients with both short LTL and high sRAGE levels had the highest risk of MACEs (HR: 3.11; 95% CI: 1.11–9.92; p = 0.04). ConclusionsHigh levels of sRAGE and short LTL were associated with an increased risk of MACEs, especially in patients with diabetes, supporting the usefulness of both biomarkers of glycemic impairment and aging in predicting cardiovascular outcomes in patients with CAD.

Association of Obstructive Sleep Apnea with the Aging Process.

Rationale: Evidence suggests that the physiopathologic consequences of obstructive sleep apnea (OSA) resemble those induced by aging. Some studies report that the deleterious effects associated with OSA might be age dependent. Objectives: To evaluate the association of OSA with the aging process and to determine whether this association is maintained across different age groups. Methods: This was an observational, prospective study including 599 patients with suspected OSA. Five hallmarks of aging were evaluated: alteration of cellular communication (serum CRP [C-reactive protein] concentration), deregulation of nutrient sensing (insulin resistance), telomere attrition (leukocyte telomeric length), mitochondrial dysfunction (leukocyte mitochondrial DNA copy number), and genomic instability (urinary 8-hydroxy-2-deoxyguanosine concentration). For age-stratified analyses, subjects were divided into four groups according to the apnea-hypopnea index (AHI) and the median age (50 yr): young patients without OSA (age < 50 yr old, AHI < 15 events/h), young patients with OSA (age < 50 yr old, AHI ⩾ 15 events/h), older patients without OSA (age ⩾ 50 yr old, AHI < 15 events/h), and older patients with OSA (age ⩾ 50 yr old, AHI ⩾ 15 events/h). Results: A dose-response relationship was found between the AHI, arousal index, and time during the night spent with an oxygen saturation less than 90% and the following hallmarks: alteration of cellular communication, deregulation of nutrient sensing, mitochondrial dysfunction, and genomic instability. Considering age-stratified analyses, OSA was associated with an increase in several hallmarks of aging in young patients, but no significant association of OSA was identified in older patients. Conclusions: In subjects under 50 years of age, OSA is associated with an increase in specific hallmarks of aging, independent of several known confounding factors.

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 effects of everyday-life exposure to polycyclic aromatic hydrocarbons on biological age indicators

BackgroundFurther knowledge on modifiable aging risk factors is required to mitigate the increasing burden of age-related diseases in a rapidly growing global demographic of elderly individuals. We explored the effect of everyday exposure to polycyclic aromatic hydrocarbons (PAHs), which are fundamental constituents of air pollution, on cellular biological aging. This was determined via the analysis of leukocyte telomere length (LTL), mitochondrial DNA copy number (LmtDNAcn), and by the formation of anti-benzo[a]pyrene diolepoxide (B[a]PDE–DNA) adducts.MethodsThe study population consisted of 585 individuals living in North-East Italy. PAH exposure (diet, indoor activities, outdoor activities, traffic, and residential exposure) and smoking behavior were assessed by questionnaire and anti-B[a]PDE–DNA by high-performance-liquid-chromatography. LTL, LmtDNAcn and genetic polymorphisms [glutathione S-transferase M1 and T1 (GSTM1; GSTT1)] were measured by polymerase chain reaction. Structural equation modelling analysis evaluated these complex relationships.ResultsAnti-B[a]PDE–DNA enhanced with PAH exposure (p = 0.005) and active smoking (p = 0.0001), whereas decreased with detoxifying GSTM1 (p = 0.021) and in females (p = 0.0001). Subsequently, LTL and LmtDNAcn reduced with anti-B[a]PDE–DNA (p = 0.028 and p = 0.018), particularly in males (p = 0.006 and p = 0.0001). Only LTL shortened with age (p = 0.001) while elongated with active smoking (p = 0.0001). Besides this, the most significant determinants of PAH exposure that raised anti-B[a]PDE–DNA were indoor and diet (p = 0.0001), the least was outdoor (p = 0.003).ConclusionNew findings stemming from our study suggest that certain preventable everyday life exposures to PAHs reduce LTL and LmtDNAcn. In particular, the clear association with indoor activities, diet, and gender opens new perspectives for tailored preventive measures in age-related diseases.CapsuleEveryday life exposure to polycyclic aromatic hydrocarbons reduces leukocyte telomere length and mitochondrial DNA copy number through anti-B[a]PDE-DNA adduct formation.

Leukocyte mitochondrial DNA copy number and built environment in Mexican Americans: a cross-sectional study

Mitochondrial DNA (mtDNA) copy number in leukocytes has been regarded as a biomarker for various environmental exposures and chronic diseases. Our previous study showed that certain demographic factors (e.g. age, gender, BMI, etc.) significantly affect levels of leukocyte mtDNA copy number in Mexican Americans. However, the effect of the built environment on leukocyte mtDNA copy number has not been studied previously. In this cross-sectional study, we examined the association between multiple components of the built environment with leukocyte mtDNA copy number among 5,502 Mexican American adults enrolled in Mano-A-Mano, the Mexican American Cohort Study (MACS). Based on the median levels of mtDNA copy number, the study population was stratified into low mtDNA copy number group (< median) and high mtDNA copy number group (≥ median). Among all built environment exposure variables, household density and road/intersection ratio were found to be statistically significant between groups with low and high mtDNA copy number (P < 0.001 and 0.002, respectively). In the multivariate logistic regression analysis, individuals living in areas with elevated levels of household density had 1.24-fold increased odds of having high levels of mtDNA copy number [Odds ratio (OR) = 1.24, 95% confidence interval (CIs) 1.08, 1.36]. Similarly, those living in areas with elevated levels of road/intersection ratio had 1.12-fold increased odds of having high levels of mtDNA copy number (OR = 1.12, 95% CI 1.01, 1.27). In further analysis, when both variables were analyzed together in a multivariate logistic regression model, the significant associations remained. In summary, our results suggest that selected built environment variables (e.g. population density and road/intersection ratio) may influence levels of mtDNA copy number in leukocytes in Mexican Americans.

Association Between Leukocyte Mitochondrial DNA Copy Number and Non-alcoholic Fatty Liver Disease in a Chinese Population Is Mediated by 8-Oxo-2'-Deoxyguanosine.

Background: Alterations in mitochondrial DNA are potentially associated with oxidative stress and may be involved in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). However, the association between mitochondrial DNA copy number (mtDNAcn) and NAFLD was not consistent. In addition, the association between inflammation and NAFLD has not been established yet. The present study, based on a Chinese population of individuals with different glucose statuses, aimed to explore the association between leukocyte mtDNAcn, markers of oxidative stress, and inflammation and NAFLD.Methods: A total of 318 participants from a diabetes project were included. NAFLD was diagnosed by ultrasonography. Leukocyte mtDNAcn was determined by PCR assay. The levels of the inflammation markers tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) and the oxidative stress markers glutathione reductase (GR), superoxide dismutase (SOD), and 8-oxo-2′-deoxyguanosine (8-oxo-dG) were also measured.Results: Participants with NAFLD (n = 105) exhibited significantly higher leukocyte mtDNAcn, IL-6, and 8-oxo-dG (all P < 0.05). Pearson correlation analysis indicated mtDNAcn was negatively associated with age, uric acid, SOD, and TNF-α, but was positively associated with 8-oxo-dG (all P < 0.05). Univariate logistic regression analysis revealed that mtDNAcn was positively associated with NAFLD [odds ratio (OR) = 1.617, 95% confidence interval (CI) = 1.036–2.525; P = 0.034]. However, after adjustment for 8-oxo-dG, this association was no longer statistically significant (OR = 1.534, 95% CI = 0.979–2.403, P = 0.062). Moreover, the stress marker 8-oxo-dG was independently associated with NAFLD after adjustment for mtDNAcn, IL-6, glucose tolerance status, and other conventional NAFLD risk factors (OR = 1.707, 95% CI =1.142–2.550, P = 0.009). Mediation analysis indicated that 8-oxo-dG fully mediated the effect of mtDNAcn on the incidence of NAFLD (direct effect β = 0.5221, 95% CI = −0.0648 to 1.2504; indirect effect β = 0.0946, 95% CI = 0.0049–0.2463).Conclusions: In a Chinese population, the association between leukocyte mtDNAcn and NAFLD was fully mediated by high levels of 8-oxo-dG. Thus, oxidative stress may be an important driver of NAFLD, and clinical interventions aimed at decreasing oxidative stress to improve NAFLD warrant further research.

Insulinemic Potential of Lifestyle Is Inversely Associated with Leukocyte Mitochondrial DNA Copy Number in US White Adults

Poor lifestyles have been linked to insulin insensitivity/hyperinsulinemia, which may contribute to downstream changes such as inflammation and oxidative damage and the development of chronic diseases. As a biomarker of intracellular oxidative stress, leukocyte mitochondrial DNA copy number (mtDNA-CN) has been related to lifestyle factors including diet and weight. No epidemiologic study has examined the relation between combined insulinemic potential of lifestyle and mtDNA-CN. Our aim was to examine the association between Empirical Lifestyle Index for Hyperinsulinemia (ELIH) and leukocyte mtDNA-CN in US men and women. This cross-sectional analysis included 2835 white adults without cancers, diabetes, or cardiovascular disease at blood collection, including 2160 women from the Nurses' Health Study and 675 men from the Health Professionals Follow-Up Study. ELIH is an index based on plasma C-peptide that characterizes the insulinemic potential of lifestyle (diet, body weight, and physical activity). Relative mtDNA-CN in peripheral blood leukocytes was measured by qPCR-based assay. We found a significant inverse association between ELIH and mtDNA-CN. In multivariable-adjusted linear models, absolute least squares means±SDs of mtDNA-CN z score across ELIH quintiles in women were as follows: Q1: 0.14±0.05; Q2: 0.04±0.06; Q3: 0.008±0.05; Q4: 0.01±0.05; and Q5: -0.06±0.05 (P-trend=0.006). Means±SDs in men were as follows: Q1: 0.25±0.09; Q2: 0.23±0.09; Q3: 0.07±0.09; Q4: 0.02±0.09; and Q5: -0.04±0.09 (P-trend=0.007). Means±SDs in all participants were as follows: Q1: 0.16±0.05; Q2: 0.07±0.05; Q3: 0.01±0.05; Q4: 0.01±0.05; and Q5: -0.05±0.05 (P-trend=0.0004). Hyperinsulinemic lifestyles (i.e., higher ELIH) were associated with lower leukocyte mtDNA-CN among subjects without major diseases, suggesting that the difference in lifestyle insulinemic potential may be related to excessive oxidative stress damage.

Association between pre-diagnostic leukocyte mitochondrial DNA copy number and survival among colorectal cancer patients

BackgroundMitochondrial DNA copy number (mtDNAcn) is considered a biomarker for mitochondrial function and oxidative stress. Although previous studies have suggested a potential relationship between mtDNAcn at the time of colorectal cancer (CRC) diagnosis and CRC prognosis, findings have been inconsistent, and no study has specifically investigated the association of pre-diagnostic mtDNAcn with CRC survival. MethodsWe examined the association of pre-diagnostic leukocyte mtDNAcn (measured by qPCR) with overall and CRC-specific survival among 587 patients in Nurses’ Health Study and Health Professionals Follow-Up Study. Cox models were constructed to estimate hazard ratios (HRs) and 95 % confidence intervals (95 % CIs). ResultsDuring a mean follow-up of 10.5 years, 395 deaths were identified; 180 were due to CRC. Overall, we did not observe significant associations between mtDNAcn and either overall or CRC-specific survival among all cases or by cancer location, grade, or stage. In an exploratory stratified analysis, a suggestive inverse association of mtDNAcn and overall death risk appeared among current smokers [HR (95 % CI) for 1 SD decrease in mtDNAcn = 1.50 (0.98, 2.32), P-trend = 0.06]. Reduced mtDNAcn and lower CRC-specific death risk was observed among patients aged ≤ 70.5 at diagnosis [HR (95 % CI) for 1 SD decrease of mtDNAcn = 0.71 (0.52, 0.97), P-trend = 0.03], ≤ 5 years from blood collection to diagnosis [HR (95 % CI) for 1 SD decrease in mtDNAcn = 0.65 (0.44, 0.96), P-trend = 0.03] and those consuming a low-inflammatory diet [HR (95 % CI) for 1 SD decrease in mtDNAcn = 0.61 (0.42, 0.88), P-trend = 0.009]. Conclusionno significant associations between pre-diagnostic leukocyte mtDNAcn and either overall or CRC-specific survival appeared but exploratory analysis identified potential sub-group associations.

Potential Protective Effect of Dietary Intake of Non-α-Tocopherols on Cellular Aging Markers Mediated by Tumor Necrosis Factor-α in Prediabetes: A Cross-Sectional Study of Chinese Adults.

It remains unknown how different glucose tolerance status affects the relationships between dietary intake of different tocopherol isoforms (α-, β-, γ-, and δ-tocopherol) and cellular aging, oxidative stress, and inflammatory markers. The authors conducted a cross-sectional study among 582 Chinese adults with different glucose tolerance status to explore the association between dietary intake of different tocopherol isoforms and cellular aging, oxidative stress, and inflammatory markers. The inverse correlations between non-α-tocopherols and tumor necrosis factor-alpha (TNF-α) varied substantially across different glucose tolerance status, with the strongest observed in prediabetes (r = −0.33 for β-/γ-tocopherol, r = −0.37 for δ-tocopherol, p < 0.01), followed by normal glucose tolerance (NGT). While such correlations were abolished in established diabetes. Furthermore, within prediabetes, the strongest inverse correlations between non-α-tocopherols and TNF-α were observed in impaired fasting glucose (IFG) (r = −0.42 for β-/γ-tocopherol, r = −0.55 for δ-tocopherol, p < 0.01), while such correlations were significantly attenuated in individuals with impaired glucose tolerance (IGT) and IFG+IGT. And mediation model analysis displayed that TNF-α mediated the protective effect of non-α-tocopherols on leukocyte telomere length and mitochondrial DNA copy number, which was uniquely observed in prediabetes, while such mediation effect was statistically nonsignificant in NGT and established diabetes. In conclusion, our findings indicate that dietary intake of non-α-tocopherols might protect against cellular aging markers mediated by TNF-α in prediabetes. Individuals with prediabetes, especially for IFG, might benefit from increasing dietary intake of non-α-tocopherol in alleviating inflammation and cellular aging, which might provide a new dietary avenue for delaying diabetes onset.