Loss of the Association between Telomere Length and Mitochondrial DNA Copy Number Contribute to Colorectal Carcinogenesis

Exploring the Link Between Telomeres and Mitochondria: Mechanisms and Implications in Different Cell Types

Telomeres protect chromosome ends from damage, but they shorten with each cell division due to the limitations of DNA replication and are further affected by oxidative stress. This shortening is a key feature of aging, and telomerase, an enzyme that extends telomeres, helps mitigate this process. Aging is also associated with mitochondrial dysfunction, leading to increased reactive oxygen species (ROS) that exacerbate cellular damage and promote apoptosis. Elevated ROS levels can damage telomeres by oxidizing guanine and disrupting their regulation. Conversely, telomere damage impacts mitochondrial function, and activation of telomerase has been shown to reverse this decline. A critical link between telomere shortening and mitochondrial dysfunction is the DNA damage response, which activates the tumor suppressor protein p53, resulting in reduced mitochondrial biogenesis and metabolic disruptions. This highlights the bidirectional relationship between telomere maintenance and mitochondrial function. This review explores the complex interactions between telomeres and mitochondria across various cell types, from fibroblasts to sperm cells, shedding light on the interconnected mechanisms underlying aging and cellular function.

Mitochondrial DNA Copy Number Is Associated with the Severity of Irritable Bowel Syndrome

Background and Objectives: Irritable bowel syndrome (IBS), as a gastrointestinal disorder, presents with abdomen pain and alterations in the bowel habits. Its pathogenesis remains unclear. Here, we examined mitochondrial DNA copy number (mtCN) in IBS and its clinical value. Materials and Methods: mtCN was analyzed in 43 IBS patients using quantitative real-time polymerase chain reaction. Furthermore, data on the clinical characteristics of patients and symptom severity of IBS were collected, and their association with mtCN was analyzed. Results: mtCN was higher in patients with IBS (p = 0.008) and those with a drinking habit (p = 0.004). Smoking and the presence of a sleep partner showed a possible association with mtCN; however, it did not reach significance. The severity of IBS symptoms tended to positively correlate with mtCN (r = 0.279, p = 0.070). Conclusions: Overall, we demonstrated a potential association between mtCN and the clinicopathologic characteristics of patients with IBS. Further studies considering genetic and clinical factors are required.

Mitochondrial DNA copy number plays opposing roles in T-lymphocyte infiltration of colorectal cancer based on mismatch repair status: new directions for immunotherapy?

BACKGROUND

Researchers have previously reported that mitochondrial DNA copy number (mtDNA-CN) can play different roles in microsatellite instable/mismatch repair-deficient (MSI/dMMR) and microsatellite stable/mismatch repair-proficient (MSS/pMMR) colorectal cancer (CRC). To support malignancy, dMMR CRC relies on glycolysis, while pMMR CRC favors oxidative phosphorylation. However, it is unclear whether mtDNA-CN changes are related to T cell infiltration in CRC.

METHODS

The mtDNA-CN was detected by qRT-PCR in 532 patients, and the expression of CD3 and CD8 in 485 patients was detected by immunohistochemistry. The correlation between mtDNA-CN and the prognosis of CRC patients was further analyzed, and the correlation between mtDNA-CN and T lymphocyte infiltration was also analyzed. Biopsy specimens from the immune checkpoint inhibitors (ICIs) treatment cohort were obtained to verify the correlation between mtDNA-CN and the efficacy of ICIs. The effects of mtDNA-CN and MMR status on gene expression were analyzed by RNA-seq.

RESULTS

Our results show that mtDNA-CN has inverse relationships to CRC prognosis in cases with different MMR statuses, potentially inducing the U-shaped association in CRC. The opposing correlations between mtDNA-CN and T lymphocyte infiltration in cases of dMMR CRC and pMMR CRC further suggest that mtDNA-CN might play an important role in CRC development. More importantly, cases of pMMR CRC with lower mtDNA-CN and of dMMR CRC with higher mtDNA-CN can benefit more dramatically from ICIs. Furthermore, RNA-seq revealed a link between the level of mtDNA-CN and T lymphocyte infiltration in CRC cases with different MMR statuses.

CONCLUSION

Our study found a potential relationship between mtDNA-CN and CRC development that differs by MMR status, potentially providing a rationale for the use of mtDNA-CN as both a predictive biomarker and a therapeutic target for ICIs.

Association between the peripartum maternal and fetal telomere lengths and mitochondrial DNA copy numbers and preeclampsia: a prospective case-control study

Purpose

To explore changes in telomere length (TL) and mitochondrial copy number (mtDNA-CN) in preeclampsia (PE) and to evaluate the combined effect of maternal TL and mtDNA-CN on PE risk.

Methods

A case–control study of 471 subjects (130 PE cases and 341 age frequency matched controls with gestational age rank from 24 to 42 weeks) was conducted in Nanjing Drum Tower Hospital, Jiangsu Province of China. Relative telomere length (RTL) and mtDNA-CN were measured using quantitative polymerase chain reaction (qPCR), and PE risk was compared between groups by logistic regression analyses.

Results

PE patients displayed longer RTL (0.48 versus 0.30) and higher mtDNA-CN (3.02 versus 2.00) in maternal blood as well as longer RTL (0.61 versus 0.35) but lower mtDNA-CN (1.69 versus 5.49) in cord blood (all p < 0.001). Exercise during pregnancy exerted an obvious effect of maternal telomere length prolongation. Multiparous women with folic acid intake during early pregnancy and those who delivered vaginally showed longer telomere length, while those factors imposed no or opposite effect on RTL in PE cases. Furthermore, RTL and mtDNA-CN were positively correlated in controls (in maternal blood r = 0.18, p < 0.01; in cord blood r = 0.19, p < 0.001), but this correlation was disrupted in PE patients in both maternal blood and cord blood. Longer maternal RTL and higher mtDNA-CN were associated with a higher risk of PE, and the ROC curve of RTL and mtDNA-CN for predicting PE risk presented an AUC of 0.755 (95% CI: 0.698–0.812).

Conclusions

The interaction of TL and mtDNA-CN may play an important role in the pathogenesis of PE and could be a potential biomarker of PE risk.

Supplementary information

The online version contains supplementary material available at 10.1186/s12884-022-04801-0.

Telomere Length but Not Mitochondrial DNA Copy Number Is Altered in Both Young and Old COPD

Accelerated ageing is implicated in the pathogenesis of respiratory diseases as chronic obstructive pulmonary disease (COPD), but recent evidence indicates that the COPD can have roots early in life. Here we hypothesise that the accelerated ageing markers might have a role in the pathobiology of young COPD. The objective of this study was to compare two hallmarks of ageing, telomere length (TL), and mitochondrial DNA copy number (mtDNA-CN, as a surrogate marker of mitochondrial dysfunction) in young (≤ 50 years) and old (>50 years) smokers, with and without COPD. Both, TL and mtDNA-CN were measured in whole blood DNA by quantitative PCR [qPCR] in: (1) young ever smokers with (n = 81) or without (n = 166) COPD; and (2) old ever smokers with (n = 159) or without (n = 29) COPD. A multivariable linear regression was used to assess the association of TL and mtDNA-CN with lung function. We observed that in the entire study population, TL and mtDNA-CN decreased with age, and the former but not the latter related to FEV₁/FVC (%), FEV₁ (% ref.), and DLCO (% ref.). The short telomeres were found both in the young and old patients with severe COPD (FEV₁ <50% ref.). In addition, we found that TL and mtDNA-CN were significantly correlated, but their relationship was positive in younger while negative in the older patients with COPD, suggesting a mitochondrial dysfunction. We conclude that TL, but not mtDNA-CN, is associated with the lung function impairment. Both young and old patients with severe COPD have evidence of accelerated ageing (shorter TL) but differ in the direction of the correlation between TL and mtDNA-CN in relation to age.

Mitochondrial DNA Copy Number Variations in Gastrointestinal Tract Cancers: Potential Players

Alterations of mitochondria have been linked to several cancers. Also, the mitochondrial DNA copy number (mtDNA-CN) is altered in various cancers, including gastrointestinal tract (GIT) cancers, and several research groups have investigated its potential as a cancer biomarker. However, the exact causes of mtDNA-CN variations are not yet revealed. This review discussed the conceivable players in this scheme, including reactive oxygen species (ROS), mtDNA genetic variations, DNA methylation, telomere length, autophagy, immune system activation, aging, and infections, and discussed their possible impact in the initiation and progression of cancer. By further exploring such mechanisms, mtDNA-CN variations may be effectively utilized as cancer biomarkers and provide grounds for developing novel cancer therapeutic agents.

Benchmark dose analysis for PAHs hydroxyl metabolites in urine based on mitochondrial damage of peripheral blood leucocytes in coke oven workers in China

OBJECTIVES

The aim was to explore the dose-response relationship between occupational polycyclic aromatic hydrocarbons (PAHs) exposure and mitochondrial damage in coke oven plants workers.

METHODS

544 workers and 238 healthy people were recruited. The ultra-high performance liquid chromatography was used to determine the level of 1-hydroxypyrene, 1-hydroxynaphthalene, 2-hydroxynaphthalene and 3-hydroxyphenanthrene. The real-time fluorescence quantitative polymerase chain reaction was used to determine the mitochondrial DNA copy number (mtDNAcn). The benchmark dose software was used to analyze the benchmark dose.

RESULTS

The mtDNAcn in the exposure group was lower than that in the control group. The concentrations of 1-hydroxypyrene, 1-hydroxynaphthalene, 2-hydroxynaphthalene and 3-hydroxyphenanthrene in the exposure group were higher than those in the control group. There is a dose-response relationship between 1-hydroxypyrene, 3-hydroxyphenanthrene and mitochondrial DNA damage. The benchmark dose lower confidence limit (BMDL) of 1-hydroxypyrene were 0.045, 0.004, and 0.058 pg/μg creatinine in the total, male, and female population, respectively. The BMDL of 3-hydroxyphenanthrene were 5.142, 6.099, and 2.807 pg/μg creatinine in the total, male, and female population, respectively.

CONCLUSIONS

The BMDL of 1-hydroxypyrene and 3-hydroxyphenanthrene initially explored can provide a reference to establish occupational exposure biological limits.

Dynamic Changes of Mitochondrial DNA Copy Number in Gastrointestinal Tract Cancers: A Systematic Review and Meta-Analysis

We have performed a systematic review and meta-analysis for evaluation of mitochondrial DNA copy number (mtDNA-CN) alterations in peripheral blood leukocytes (PBL), and tumor tissues of gastrointestinal tract (GIT) cancers. Analysis of the PBL demonstrated a significant decrease [OR: 0.6 (0.5, 0.8)] and increase [OR: 1.4 (1.1, 1.9)] prior to and following GIT cancer development, respectively. This trend was more evident in CRC, and GC subgroups. Analysis of tissue yielded high levels of heterogeneity. However, the mean difference for the CRC subgroup was statistically significant [1.5 (1.0, 2.2)]. Our analysis suggests mtDNA-CN deserves further investigations as a GIT-cancer screening tool.

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

BACKGROUND

Mitochondrial 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.

METHODS

We 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).

RESULTS

During 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].

CONCLUSION

no significant associations between pre-diagnostic leukocyte mtDNAcn and either overall or CRC-specific survival appeared but exploratory analysis identified potential sub-group associations.

Tight co-twin similarity of monozygotic twins for hTERT protein level of T cell subsets, for telomere length and mitochondrial DNA copy number, but not for telomerase activity

Our study analyzed lymphocyte subpopulations of 32 monozygotic twins and compared the level of the catalytic reverse transcriptase protein subunit (hTERT) in T lymphocytes (Tly), helper- (Th), cytotoxic- (Tc) and regulatory T cell (Treg) subgroups. Four variables related to telomere and mitochondrial biology were simultaneously assessed, applying multi-parametric flow cytometry, TRAP-ELISA assay and qPCR standard curve method on peripheral blood mononuclear cell (PBMC) samples of genetically matched individuals. Twin data of telomerase activity (TA), hTERT protein level, telomere length (TL) and mitochondrial DNA copy number (mtDNAcn) were analyzed for co-twin similarity. The present study has provided novel information by demonstrating very high intraclass correlation (ICC) of hTERT protein level in T lymphocytes (0.891) and in both Th (0.896), Treg (0.885) and Tc (0.798) cell subgroups. When comparing results measured from PBMCs, intraclass correlation was also high for telomere length (0.815) and considerable for mtDNA copy number (0.524), and again exceptionally high for the rate-limiting telomerase subunit, hTERT protein level (0.946). In contrast, telomerase activity showed no co-twin similarity (ICC 0). By comparing relative amounts of hTERT protein levels in different lymphocyte subgroups of twin subjects, in Treg cells significantly higher level could be detected compared to Tly, Th or Tc cell subgroups. This is the first study that simultaneously analyzed co-twin similarity in MZ twins for the above four variables and alongside assessed their relationship, whereby positive association was found between TL and mtDNAcn.