Publications of A Illes

Positive association and future perspectives of mitochondrial DNA copy number and telomere length – a pilot twin study

Introduction Recent experimental and population studies have highlighted the existence of telomere-mitochondria interplay. Besides studies revealing the molecular mechanisms underlying the associations of telomere defects and mitochondrial functions, investigations of mitochondrial DNA copy number (mtDNAcn) and telomere length (TL) in healthy and disease phenotypes have likewise begun, with the aim of gaining more insights about their relationship in humans. Material and methods A total of 142 asymptomatic adult twins, comprising 96 monozygotic (MZ) and 46 dizygotic (DZ) twins (mean age: 50.54 ±15.43 years), members of the Hungarian Twin Registry, were included in the analysis. Applying the qPCR standard curve method, we investigated the relationship of mtDNA copy number, telomere length and clinical data, besides assessing co-twin similarities of MZ and DZ twins for their mtDNAcn and TL measures. Results We found that twins were similar in their intraclass correlation coefficients irrespective of zygosity, suggesting a possibly more important role of common (shared) environmental factors compared to non-shared (unique) environmental and to a smaller degree also individual genetic influences. We confirmed a significant positive association between mtDNAcn and TL (r = 0.28, p < 0.01) in age- and sex-corrected analysis. Following bivariate estimates and correction with significant predictors, the independent positive associations were further verified. Conclusions Our results extend the until now modest number of studies investigating mtDNAcn and TL simultaneously in humans. In addition, we are the first to examine the relationship between mtDNAcn and telomere length in MZ and DZ twin subjects.

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.