Jing Zhi Guan

Change in the telomere length distribution with age in the Japanese population

Telomeres play a role in cellular aging and they may also contribute to the genetic basis of human aging and longevity. A gradual loss of the telomeric repeat sequences has been reported in adult tissue specimens. This study determined the percentage of telomere restriction fragment in various molecular-sized regions in addition to measuring the average telomere length. Mean telomere restriction fragment (TRF) length was determined by Southern blot analysis using a longer telomeric repeat probe with higher sensitivity. A significant decrease in longer telomere fragments and a quick increase in the shortest fragments were observed, especially in male subjects. There was a tendency that the age-adjusted telomere length was longer in females than that observed in males, while males lose the telomeric sequence faster than females. These data indicated that the percentage of longer telomeres fragments decreased, while the shortest fragments increased quickly with age. In addition, the longest telomere fragments decreased and the short fragments increased with a relatively stable frequency with age. There was also a significant difference in the longest telomere fragment percentage between males and female in their 40s and 50s, whereas no difference was observed in the mean TRF length. Interestingly, the changing rate of the longest and the shortest range group of TRF percentage associated with aging seemed quite different between before and after 50-year old with a gender-related contrast. This contrast implies a drastic change around the age of 50 of unknown factors that affect telomere attrition.

Effect of vitamin E administration on the elevated oxygen stress and the telomeric and subtelomeric status in Alzheimer's disease.

Background: Oxidative stress (OS) may be involved in the neurodegenerative process in Alzheimer’s disease (AD). Telomeres, the repeated sequences that cap chromosome ends, undergo shortening with each cell division, are sensitive to OS, and serve as markers of a cell’s replicative history. Telomere length shortening has been reported to relate to OS with aging process and aging-associated diseases, but the telomeric changes were not always identical, especially in change of telomere length distribution and subtelomeric methylation. The involvement of an OS-associated telomere change in the pathogenesis of AD has been discussed for decades, and the telomere length and telomerase activity were analyzed. However, other telomeric factors, such as the telomere distribution and subtelomeric methylation status, have not yet been analyzed. Objective: The subtelomeric methylation status as well as the telomere length were studied in AD with an antioxidant vitamin in terms of OS. Methods: We measured urinary 8-iso-PGF2α, a lipid-peroxidation product as an OS marker, and methylated and non-methylated telomere lengths in the peripheral blood mononuclear cells by Southern blotting in AD patients before and after vitamin E treatment. Results: The level of urinary 8-iso-PGF2α was found to have increased in AD. Middle-ranged telomeres (4.4–9.4 kb) increased and the shortest telomeres (<4.4 kb) decreased in AD patients. Telomeres were more methylated in both long telomeres and in short telomeres in AD compared with the control. The oral administration of the antioxidant vitamin E in 400 mg/day for 6 months in AD patients partly reversed AD-associated alterations in OS marker levels. Conclusions: AD patients showed an elevated OS marker level, and vitamin E lowered the OS level. In comparison with controls, AD patients showed shorter telomere lengths. Cells with short and long telomeres bore relatively hypermethylated subtelomeres in AD patients. Aging-associated accumulation of cells bearing short telomeres was not observed in AD. These results imply that long telomeres with hypomethylation tend to shorten faster, and cells bearing short telomeres with hypomethylation tend to more easily enter into a senescent state under elevated OS stress in AD. However, no significant effect on the altered telomeric profiles in AD patients could be detected after a 6-month administration of vitamin E.

Patients with multiple sclerosis show increased oxidative stress markers and somatic telomere length shortening.

Lipid peroxidation due to oxidative stress (OS) may play an important role in the pathogenesis of chronic systemic inflammatory diseases such as multiple sclerosis (MS). Telomeres, repeated sequences that cap chromosome ends, undergo shortening with each cycle of cell division, resulting in cellular senescence. Research regarding telomere shortening has provided novel insight into the pathogenesis of various diseases. We hypothesized that OS damage leads to inflammatory reactions, which subsequently shortens the telomere length in MS. We enrolled 59 patients with MS, and age- and gender-matched 60 healthy controls. We divided MS subjects into three groups matched for age and gender according to the severity of disability: relatively benign course (BMS), secondary progressive MS, and primary progressive MS (PPMS). We analyzed the telomere length in peripheral blood mononuclear cells and the 8-iso-PGF2α concentration in urine, a reliable and stable marker of lipid peroxidation in vivo. The data showed significant higher levels of urinary 8-iso-PGF2α in MS subjects than in the controls. The lag-time, which represents the direct measurement of the resistance of low-density lipoprotein to oxidation, was shorter in the PPMS subjects than in the groups. Compared to that observed in the controls, the mean telomere length was significantly shorter in the PPMS group, whereas no significant telomere shortening was found between the controls and other subjects. Our data suggest that a decreased telomere length and enhanced lipid peroxidation reflects the severest stage of MS.

Age-Related Changes in Subtelomeric Methylation in the Normal Japanese Population

BACKGROUND The telomeres of somatic cells become shorter with individual aging. However, no significant change in subtelomeric methylation of somatic cells with aging has yet been reported. METHODS Telomere lengths of the peripheral blood cells of 148 normal Japanese were analyzed by Southern blotting using methylation-sensitive and -insensitive isoschizomers. RESULTS With aging, long telomeres decrease and short telomeres increase, and the contents of the telomeres with methylated subtelomere increase in long telomeres, thus leading us to postulate that telomeres with less methylated subtelomeres tend to become shortened faster. CONCLUSIONS A telomere length distribution analysis with methylation-sensitive and -insensitive isoschizomer seems to be a useful tool to assess the subtelomeric methylation status of the somatic cell population. The subtelomeric methylation of peripheral blood cells is also indicated to be an indicator for aging-associated genomic changes.

Aging-Related Alterations of Subtelomeric Methylation in Sarcoidosis Patients

Telomeres in somatic cells become shorter with aging, and the shortening is accelerated by pathophysiological conditions. Telomere shortening can be influenced by subtelomeric DNA methylation. The telomere length and subtelomeric methylation status in peripheral leukocytes were compared in healthy controls and sarcoidosis patients. The sarcoidosis patients revealed shorter telomeres and a faster attrition of telomere shortening in comparison with healthy controls. Both healthy controls and sarcoidosis patients showed that long telomeres (>9.4 kb) decrease and short telomeres (<4.4 kb) increase with aging, accompanying relative increases of long telomeres with subtelomeric hypermethylation and short telomeres with subtelomeric hypomethylation. This suggested that the aging-related telomere shortening is associated with the surrounding subtelomeric hypomethylation. Furthermore, sarcoidosis patients showed this alteration of the subtelomeric methylation earlier than controls (in their 60s or later). This altered subtelomeric hypomethylation may correspond to the accelerated telomere shortening in sarcoidosis. This also means that the subtelomeric hypomethylation can be also influenced by certain disease conditions.

Aging-associated alteration of telomere length and subtelomeric status in female patients with Parkinson's disease.

Abstract: A telomere is a repetitive DNA structure at chromosomal ends that stabilizes the chromosome structure and prevents harmful end-to-end recombinations. The telomere length of somatic cells becomes shorter with aging because of the “end replication problem.” This telomere shortening is accelerated by pathophysiological conditions including daily mental stress. Living with Parkinsons disease (PD) causes physical and mental stress; therefore, the authors hypothesized that the telomere length of somatic cells was shortened excessively in patients with PD. In order to detect PD-associated somatic telomeric alterations, the telomere length and subtelomeric methylation status of peripheral leukocytes of PD patients were assessed by Southern blotting, using methylation-sensitive and -insensitive isoschizomers. The results demonstrated that the peripheral leukocytes of Japanese female patients with PD bore fewer long telomeres and a proportional increase of hypomethylated subtelomeres in short telomeres in comparison with the healthy controls. This study indicates that with the neurodegeneration associated with PD, telomeric and subtelomeric structural alterations occur. These structural telomere altertions most likely occur secondary to the acceleration of aging-associated telomeric changes and the accelerated loss of cells bearing short telomeres.

Telomerase activity and telomere length distribution in vascular endothelial cells in a short‐term culture under the presence of hydrogen peroxide

Aim:  The aim of this study was to assess the biological effects of oxidative stress on human vascular endothelial cells.

Different levels of hypoxia regulate telomere length and telomerase activity

This study was designed to identify changes in telomere length and telomerase activity in human umbilical vein endothelial cells (HUVECs) exposed to various levels of hypoxia. Mild hypoxia (10%, 15% oxygen) increased telomere length, which did not appear to change under severe hypoxia (1% oxygen). Telomerase activity in HUVECs correlated inversely with oxygen concentration. Endothelial cell telomere elongation with telomerase activation in conditions of mild hypoxia was demonstrated in this study. High telomerase activity may contribute to hypoxia- related telomere elongation. The best cell growth and longest telomere length were observed at 10%O2, and this percentage may therefore be the optimal level for maintaining vascular endothelial cells. In addition, elevated telomerase activity maintains telomere length within normal range in conditions of severe hypoxia (1%O2). The telomere length distribution in HUVECs under hypoxia seems to be regulated by a balance between telomere attrition by hypoxia and telomere elongation by enhanced telomerase activity acting on telomeres, perhaps in a telomere-length dependent manner.

Alteration of Telomere Length and Subtelomeric Methylation in Human Endothelial Cell Under Different Levels of Hypoxia

BACKGROUND AND AIMS Hypoxia-associated changes of telomeric structure in cell cultures have been analyzed mainly in cancer cells, stem cells, or cells transduced with vectors containing the telomerase gene, but not in somatic cells. The stability of telomere structure has been reported to be associated with subtelomeric methylation status. However, there are no reports of epigenetic alterations of telomeric regions of human somatic cells under hypoxia. This study aims at detecting and analyzing the subtelomeric methylation status in human somatic cells cultured under hypoxia. METHODS Mean telomere length and telomerase activity of human umbilical vein endothelial cells (HUVECs) cultured in hypoxic conditions were measured. Subtelomeric methylation status of these cells was assessed by genomic Southern blot with telomere DNA probe using methylation-sensitive and -insensitive isoschizomers, MspI and HpaII. RESULTS The telomerase activity in HUVECs correlated inversely with the oxygen concentration. Mild hypoxia (10 or 15% oxygen) increased the telomere lengths, whereas the telomere lengths did not appear to change when <1% O(2). The subtelomere of the shortest telomere range was methylated the most at 1% O(2). CONCLUSIONS Subtelomeric hypermethylation of short telomeres at 1% O(2) compared to milder hypoxia implied that the subtelomeric hypermethylation may yield telomere stability and favor the cell survival of short telomere-bearing cells.