Effect of a 12-Week Walking Program Monitored by Global Physical Capacity Score (GPCS) on Circulating Cell-Free mtDNA and DNase Activity in Patients with Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) involves low-grade mucosal inflammation. Among the various approaches capable of managing the symptoms, physical activity is still under investigation. Despite its benefits, it promotes oxidative stress and inflammation. Mitochondria impacts gut disorders by releasing damage-associated molecular patterns, such as cell-free mtDNA (cf-mtDNA), which support inflammation. This study evaluated the effects of a 12-week walking program on the cf-mtDNA and DNase in 26 IBS and 17 non-IBS subjects. Pro- and anti-inflammatory cytokines were evaluated by ELISA. Digital droplet PCR was used to quantify cf-mtDNA; DNase activity was assessed using a single radial enzyme diffusion assay. PCR-RFLP was used to genotype DNASE1 rs1053874 SNP. Significantly lower IL-10 levels were found in IBS than in non-IBS individuals. Exercise reduced cf-mtDNA in non-IBS subjects but not in IBS patients. DNase activity did not correlate with the cf-mtDNA levels in IBS patients post-exercise, indicating imbalanced cf-mtDNA clearance. Different rs1053874 SNP frequencies were not found between groups. The study confirms the positive effects of regular moderate-intensity physical activity in healthy subjects and its role in cf-mtDNA release and clearance. Walking alone might not sufficiently reduce subclinical inflammation in IBS, based on imbalanced pro- and anti-inflammatory molecules. Prolonged programs are necessary to investigate their effects on inflammatory markers in IBS.

cf-nDNA in the Follicular Fluid of Women Undergoing IVF Is Positively Correlated with Age

Age-related mitochondrial markers may facilitate the prognosis of artificial reproductive technology outcomes. In this report, we present our study concerning the ratio of cf-mtDNA/cf-nDNA, namely the amount of cell-free mitochondrial DNA relative to cell-free nuclear DNA, in the follicular fluid (FF) of women undergoing IVF, aiming to generate a molecular fingerprint of oocyte quality. The values of this ratio were measured and compared among three groups of women (101 in total): (A) 31 women with polycystic ovary syndrome (PCOS), (B) 34 women younger than 36 years, and (C) 36 women older than 35 years of age. Real-time quantitative PCR (qPCR) was performed to quantify the ratio by using nuclear- and mitochondrial-specific primers and analyzed for potential correlation with age and pregnancy rate. Our analysis showed that the level of FF-cf-mtDNA was lower in the group of advanced-age women than in the groups of PCOS and non-PCOS women. Moreover, a significant positive correlation between FF-cf-mtDNA and the number of mature (MII) oocytes was observed. Collectively, the data show that the relative ratio of cf- mtDNA to cf-nDNA content in human FF can be an effective predictor for assessing the corresponding oocyte's age-related performance in IVF.

Circulating Cell-Free DNA Levels in Psychiatric Diseases: A Systematic Review and Meta-Analysis

The cell-free DNA (cfDNA) levels are known to increase in biological fluids in various pathological conditions. However, the data on circulating cfDNA in severe psychiatric disorders, including schizophrenia, bipolar disorder (BD), and depressive disorders (DDs), is contradictory. This meta-analysis aimed to analyze the concentrations of different cfDNA types in schizophrenia, BD, and DDs compared with healthy donors. The mitochondrial (cf-mtDNA), genomic (cf-gDNA), and total cfDNA concentrations were analyzed separately. The effect size was estimated using the standardized mean difference (SMD). Eight reports for schizophrenia, four for BD, and five for DDs were included in the meta-analysis. However, there were only enough data to analyze the total cfDNA and cf-gDNA in schizophrenia and cf-mtDNA in BD and DDs. It has been shown that the levels of total cfDNA and cf-gDNA in patients with schizophrenia are significantly higher than in healthy donors (SMD values of 0.61 and 0.6, respectively; p < 0.00001). Conversely, the levels of cf-mtDNA in BD and DDs do not differ compared with healthy individuals. Nevertheless, further research is needed in the case of BD and DDs due to the small sample sizes in the BD studies and the significant data heterogeneity in the DD studies. Additionally, further studies are needed on cf-mtDNA in schizophrenia or cf-gDNA and total cfDNA in BD and DDs due to insufficient data. In conclusion, this meta-analysis provides the first evidence of increases in total cfDNA and cf-gDNA in schizophrenia but shows no changes in cf-mtDNA in BD and DDs. Increased circulating cfDNA in schizophrenia may be associated with chronic systemic inflammation, as cfDNA has been found to trigger inflammatory responses.

Analysis of cf-mtDNA and cf-nDNA fragment size distribution using different isolation methods in BV-2 cell supernatant of starvation-induced autophagy

Fragment size distribution, the important biological properties of cell-free DNA (cfDNA), provides useful information required for diagnostic assay development. However, besides methodological discrepancies, it varies due to the complicated origins and occurrences of in vivo cfDNA. In addition, limited data are available concerning the cfDNA associated with autophagy and distributional difference between cf-mitochondrial DNA (cf-mtDNA) and cf-nuclear DNA (cf-nDNA) fragments. Here we developed an in vitro model of mouse microglial cell (BV-2) with starvation-induced autophagy, in which cfDNA was isolated from the cell supernatant by ultrafiltration (UF) and column-based commercial kit (CC), respectively. Using Agilent 2100 Bioanalyzer, a DNA ladder pattern as the presence of peaks corresponding to mono-, di- and tri-nucleosomes was clearly visualized both in isolation products of UF and CC. However, we also detected shorter fragments than mono-nucleosome by UF. In comparing the UF and CC, we found that the former produced the higher recovery efficiency for spiked-in DNA of shorter fragments than mono-nucleosome in both water and medium, but the latter was superior for spiked-in DNA fragments which were longer than or equal to mono-nucleosome in medium. Combined with these two isolation methods, we have observed that autophagy-associated cf-mtDNA and cf-nDNA were both highly enriched in <mono-nucleosomes fragments more than 71%, and showed no significant differences in the relative percentages for these four fragment sizes. These results have improved our understanding of the fragment size distribution of autophagy-derived cf-mtDNA and cf-nDNA in vitro, and might further develop application of cfDNA as a diagnostic tool.

Mitochondrial DNA and Exercise: Implications for Health and Injuries in Sports

Recently, several studies have highlighted the tight connection between mitochondria and physical activity. Mitochondrial functions are important in high-demanding metabolic activities, such as endurance sports. Moreover, regular training positively affects metabolic health by increasing mitochondrial oxidative capacity and regulating glucose metabolism. Exercise could have multiple effects, also on the mitochondrial DNA (mtDNA) and vice versa; some studies have investigated how mtDNA polymorphisms can affect the performance of general athletes and mtDNA haplogroups seem to be related to the performance of elite endurance athletes. Along with several stimuli, including pathogens, stress, trauma, and reactive oxygen species, acute and intense exercise also seem to be responsible for mtDNA release into the cytoplasm and extracellular space, leading to the activation of the innate immune response. In addition, several sports are characterized by a higher frequency of injuries, including cranial trauma, associated with neurological consequences. However, with regular exercise, circulating cell-free mtDNA levels are kept low, perhaps promoting cf-mtDNA removal, acting as a protective factor against inflammation.