Telomere Length in Peripheral Blood Mononuclear Cells of Patients on Chronic Hemodialysis Is Related With Telomerase Activity and Treatment Duration

The influence of Klotho protein and prooxidant-antioxidant balance combination on the mortality of HD patients

PURPOSE

End-stage renal disease patients on chronic hemodialysis (HD) have a shortened life expectancy compared to the general population. The aim of this study was to evaluate a possible link between three new and emerging factors in renal pathophysiology: Klotho protein, telomere length in peripheral blood mononuclear cells (TL) and redox status parameters before HD (bHD) and after HD (aHD), and to test mortality prediction capability of these emerging parameters in a population of HD patients.

METHODS

The study included 130 adult patients with average age 66 (54-72), on HD (3 times per week; 4-5 h per session). Klotho level, TL, routine laboratory parameters, dialysis adequacy and redox status parameters: advanced oxidation protein products (AOPP), prooxidant-antioxidant balance (PAB), superoxide anion (O2.-), malondialdehyde (MDA), ischemia-modified albumin (IMA), total sulfhydryl group content (SHG), and superoxide dismutase (SOD) were determined.

RESULTS

Klotho concentration was significantly higher aHD; 68.2 (22.6-152.9) vs. bHD 64.2 (25.5-119.8) (p = 0.027). The observed increase in TL was not statistically significant. AOPP, PAB, SHG, and SOD activity were significantly increased aHD (p > 0.001). The patients with the highest mortality risk score (MRS) had significantly higher PAB bHD (p = 0.002). Significantly lower O2.- (p < 0.001), SHG content (p = 0.072), and IMA (p = 0.002) aHD were found in patients with the lowest MRS values. Principal component analysis revealed redox balance-Klotho factor as a significant predictor of high mortality risk (p = 0.014).

CONCLUSION

Decreased Klotho and TL attrition as well as redox status disturbance could be connected with higher mortality rate in HD patients.

Telomere Attrition in Chronic Kidney Diseases

Telomeres are dynamic DNA nucleoprotein structures located at the end of chromosomes where they maintain genomic stability. Due to the end replication problem, telomeres shorten with each cell division. Critically short telomeres trigger cellular senescence, which contributes to various degenerative and age-related diseases, including chronic kidney diseases (CKDs). Additionally, other factors such as oxidative stress may also contribute to accelerated telomere shortening. Indeed, telomeres are highly susceptible to oxidative damage due to their high guanine content. Here, we provide a comprehensive review of studies examining telomere length (TL) in CKDs to highlight the association between TL and the development and progression of CKDs in humans. We then focus on studies investigating TL in patients receiving kidney replacement therapy. The mechanisms of the relationship between TL and CKD are not fully understood, but a shorter TL has been associated with decreased kidney function and the progression of nephropathy. Interestingly, telomere lengthening has been observed in some patients in longitudinal studies. Hemodialysis has been shown to accelerate telomere erosion, whereas the uremic milieu is not reversed even in kidney transplantation patients. Overall, this review aims to provide insights into the biological significance of telomere attrition in the pathophysiology of kidney disease, which may contribute to the development of new strategies for the management of patients with CKDs.

Telomere therapy for chronic kidney disease

Chronic kidney disease (CKD) is estimated to affect almost 10% of individuals worldwide and is one of the leading causes of morbidity and mortality. Renal fibrosis, a central pathway in CKD progression (irrespective of etiology), is associated with shortened or dysfunctional telomeres in animal studies. Telomeres are specialized nucleoprotein structures located at the chromosome end that maintain genomic integrity. The mechanisms of associations between telomere length and CKD have not yet been fully elucidated, however, CKD patients with shorter telomere length may have decreased renal function and a higher mortality rate. A plethora of ongoing research has focused on possible therapeutic applications of telomeres with the overall goal to preserve telomere length as a therapy to treat CKD.

Telomere shortening in patients on long-term hemodialysis

Background

Leukocyte telomere length shortening is a characteristic of premature senescence, a process that can be accelerated by oxidative stress. In general, patients with end-stage renal disease undergoing regular hemodialysis (HD) are repeatedly exposed to oxidative stress. Patients undergoing HD tend to have cardiovascular diseases associated with oxidative stress and inflammation. Therefore, we assumed that telomere length is associated with HD vintage and the degree of vascular calcification.

Methods

A total of 144 patients undergoing regular HD before kidney transplantation and 62 patients on hemodialysis, but not undergoing kidney transplantation, were enrolled. We measured common laboratory values, such as calcium, phosphate, and hemoglobin levels, and assessed the degree of vascular calcification in the patients. The leukocyte telomere length was measured using reverse transcription polymerase chain reaction, and Spearman correlation was used for correlation analysis.

Results

The leukocyte telomere length was negatively associated with age (rho = −0.306, P＜0.01); it was shorter in middle-aged patients than in young patients (13.48 ± 4.80 vs. 15.86 ± 4.51, P < 0.01). The telomere length was significantly different among patients aged 52–74 years in groups with different HD vintages. Additionally, the telomere length was positively associated with serum hemoglobin (Hb) levels in all patients (rho = 0.290, P < 0.01). There was a significant difference among patients divided into three groups according to the degree of anemia (17.09 ± 5.64 vs. 14.40 ± 4.07 vs. 13.99 ± 3.95, P < 0.01). Further, a significant difference was observed in the telomere length among patients with different degrees of vascular calcification (16.79 ± 4.91 vs. 13.61 ± 2.82 vs. 14.62 ± 3.63 vs. 10.71 ± 3.74, P < 0.01). The telomere length was shorter in the patients on hemodialysis who did not receive a kidney transplant than in the surgical patients (8.12 ± 1.83 vs. 14.33 ± 4.63, P < 0.01).

Conclusion

This study demonstrated that the telomere length was significantly correlated with HD vintage in patients of a certain age group. The telomere length was shorter in patients on hemodialysis who matched for age and dialysis vintage with kidney transplant patients. It was also associated with vascular calcification and serum Hb levels in all patients undergoing HD.

Cost-Effective Trap qPCR Approach to Evaluate Telomerase Activity: an Important Tool for Aging, Cancer, and Chronic Disease Research

OBJECTIVES

Telomeres are a terminal "DNA cap" that prevent chromosomal fusion and degradation. However, aging is inherent to life, and so is the loss of terminal sequences. Telomerase is a specialized reverse transcriptase encoded by self-splicing introns that counteract chromosome erosion. Telomerase activity is observed during early embryonic development, but after the blastocyst stage, the expression of telomerase reduces. The consequences of either insufficient or unrestrained telomerase activity underscore the importance of ongoing studies aimed at elucidating the regulation of telomerase activity in humans. In the present study, we aimed to standardize a simplified telomerase repeat-amplification protocol (TRAP) assay to detect telomerase activity in unstimulated and PHA-stimulated mononuclear cells.

METHODS AND RESULTS

Our optimized qPCR-based can efficiently evaluate telomerase activity. Quantification of protein and DNA between unstimulated and PHA-stimulated peripheral blood mononuclear cells revealed cellular activation and cell-cycle entry. The assay also showed that relative telomerase activity is significantly different between these two conditions, supporting the applicability of the assay. Furthermore, our findings corroborated that telomerase activity decreases with age.

CONCLUSIONS

Telomeres and telomerase are implicated in aging and development of chronic diseases and cancer; however, difficulty in accessing commercial kits to investigate these aspects is a critical constraint in health surveillance studies. Our optimized assay was successfully used to differentiate telomerase activity between unstimulated and stimulated cells, clearly showing the reactivation of telomerase upon cell activation. This assay is affordable, reproducible, and can be executed in resource-limited settings.

Uraemia-induced immune senescence and clinical outcomes in chronic kidney disease patients

BACKGROUND

Patients with chronic kidney disease (CKD) are more prone to develop premature age-related diseases. Data on immune senescence are scarce in CKD populations, except in end-stage renal disease and dialysis. We designed a longitudinal prospective study to evaluate immune senescence at different CKD stages and its influence on CKD patient outcomes.

METHODS

Clinical and biological data collections were performed on 222 patients at different CKD stages [1-2 (n = 85), 4 (n = 53) and 5 (n = 84)]. Immune senescence biomarkers were measured by cytometry on T cells (CD28, CD57, CD45RA, CD31, γH2A.X) or by quantitative polymerase chain reaction [relative telomere length (RTL)] on peripheral blood mononuclear cells and analysed according to CKD stages and outcomes.

RESULTS

CKD was associated with an increase in immune senescence and inflammation biomarkers, as follows: low thymic output (197 ± 25 versus 88 ± 13 versus 73 ± 21 CD4+CD45RA+CD31+ T cells/mm3), an increased proportion of terminally differentiated T cells (CD8+CD28-CD57+) (24 ± 18 versus 32 ± 17 versus 35 ± 19%) restricted to cytomegalovirus-positive patients, telomere shortening (1.11 ± 0.36 versus 0.78 ± 0.24 versus 0.97 ± 0.21 telomere:single copy ratio) and an increase in C-reactive protein levels [median 2.9 (range 1.8-4.9) versus 5.1 (27-9.6) versus 6.2 (3.4-10.5) mg/L]. In multivariate analysis, shorter RTL was associated with death {hazard ratio [HR] 4.12 [95% confidence interval (CI) 1.44-11.75]}. Low thymic output was associated with infections [HR 1.79 (95% CI (1.34-9.58)] and terminally differentiated CD8+ T-cell expansion with a risk of cardiovascular events [CEs; HR 4.86 (95% CI 1.72-13.72)].

CONCLUSION

CKD was associated with premature immune ageing. Each of these alterations increased the risk of specific age-related diseases, such as RTL and death, thymic function and infections and terminally differentiated CD8+ T-cell expansion and CEs.

Effect of antioxidants, mitochondrial cofactors and omega-3 fatty acids on telomere length and kinematic joint mobility in young and old shepherd dogs - A randomized, blinded and placebo-controlled study

In dogs, decreasing telomere length is a biomarker for cellular aging. On a systemic level, aging affects the locomotor system in particular, leading to restricted joint mobility. As aging is thought to be related to oxidative stress, it may be counteracted by a diet enriched with antioxidants, mitochondrial cofactors and omega-3 fatty acids. This randomized, blinded and placebo-controlled study examined the influence of an accordingly enriched diet compared to a control diet on 36 young and 38 old shepherd dogs. At the outset, after 3 and after 6 months, mean and minimum telomere lengths were measured. Furthermore, minimum and maximum joint angles and range of motion of the shoulder, elbow, carpal, hip, stifle and tarsal joints were measured by computer-assisted gait analysis. A positive influence of the enriched diet on old dogs could be verified for minimum telomere length and all three parameters of the shoulder joint on the side with the higher vertical ground reaction force after 6 months. In the other joints there were less significant differences; in some cases they indicated a contrary influence of the enriched diet on young dogs, probably due to its reduced protein content. The greater effect of the enriched diet on minimum than on mean telomere length may be due to the higher preference of telomerase for short telomeres. The greater effect on shoulder joint mobility is explained by the greater influence of musculature and connective tissue in this joint. For elderly dogs it is advisable to feed these nutritional supplements.

Telomere length regulators are activated in young men after pediatric kidney transplantation compared to healthy controls and survivors of childhood cancer-A cross-sectional study

Chronic diseases are known to cause premature aging and frailty. Data about telomere length and telomere length-regulating proteins after pediatric KTx are scarce. Leukocyte telomere length and gene expression level of eight telomere-binding proteins were analyzed in 20 KTx recipients, eight childhood NBL survivors, and nine healthy controls. The influence of key clinical parameters on telomere length and on regulators of telomere length was evaluated. The telomere length in the KTx recipients tended to be shorter (0.53 AU) than in the healthy controls (0.64 AU) but longer than in the NBL survivors (0.38 AU). There was no significant difference in telomere length between the NBL survivors and the KTx recipients (P = .110). The gene expression level of telomere length-preserving protein RPA1 was significantly higher in the KTx recipients than among the NBL survivors or healthy controls, while the expression of TRF2 and the tumor suppressor gene p16 was significantly higher in the KTX recipients when compared to the controls. TRF2 and TIN2 correlated significantly with hsCRP; additionally, TRF2 showed significant correlation with plasma creatinine and eGFR. KTx recipients have near to normal telomere length, but they have significantly higher gene expression levels of telomere regulatory proteins compared with healthy controls, suggesting activation of mechanisms preserving telomere length among KTx recipients. Our results suggest that declined graft function and consequent inflammatory response may have influence on telomerase activity.

Peripheral Blood Leukocyte Telomere Length Is Associated with Age but Not Renal Function: A Cross-Sectional Follow-Up Study

OBJECTIVES

We aimed to evaluate the relationship between baseline renal function and changes in telomere length in Han Chinese.

METHODS

The telomere restriction fragment (TRF) length of leukocytes in the peripheral blood was measured in healthy volunteers recruited in 2014. The estimated glomerular filtration rate (eGFR) was calculated based on serum creatinine (Scr) and serum cystatin C (CysC)-eGFRcys and eGFRScr-cys through the Cockcroft-Gault formula (eGFRC-G) or the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI / eGFRCKD-EPI) equation. The correlation between telomere length changes over time and renal function was analyzed.

RESULTS

Leukocyte TRF lengths were negatively correlated to age (r = -0.393, p < 0.001) and serum CysC (r = -0.180, p < 0.01), while positively associated with eGFRCKD-EPI, eGFRC-G, eGFRcys, and eGFRScr-cys (r = 0.182, 0.122, 0.290, and 0.254 respectively, p < 0.01). The 3-year change of telomere length was 46 bp/years. When adjusted for age, the associations between telomere length changes and baseline, subsequent TRF lengths, and serum CysC were no longer present. No association was observed between TRF length changes and renal function.

CONCLUSION

The rate of telomere length changes was affected by age and baseline telomere length. The telomere length changes might be important markers for aging.

[Role of the mechanisms of replicative cellular senescence in structural and functional changes of the vascular wall in chronic kidney disease]

This review considers the mechanisms and risk factors for the development of replicative cellular senescence of the vascular wall in patients with CKD and discusses therapeutic approaches to slowing the accelerated vascular aging.

Artificial Organs 2015: A Year in Review

In this Editor's Review, articles published in 2015 are organized by category and briefly summarized. We aim to provide a brief reflection of the currently available worldwide knowledge that is intended to advance and better human life while providing insight for continued application of technologies and methods of organ Replacement, Recovery, and Regeneration. As the official journal of The International Federation for Artificial Organs, The International Faculty for Artificial Organs, the International Society for Rotary Blood Pumps, the International Society for Pediatric Mechanical Cardiopulmonary Support, and the Vienna International Workshop on Functional Electrical Stimulation, Artificial Organs continues in the original mission of its founders "to foster communications in the field of artificial organs on an international level." Artificial Organs continues to publish developments and clinical applications of artificial organ technologies in this broad and expanding field of organ Replacement, Recovery, and Regeneration from all over the world. We take this time also to express our gratitude to our authors for providing their work to this journal. We offer our very special thanks to our reviewers who give so generously of their time and expertise to review, critique, and especially provide meaningful suggestions to the author's work whether eventually accepted or rejected. Without these excellent and dedicated reviewers, the quality expected from such a journal could not be possible. We also express our special thanks to our Publisher, John Wiley & Sons for their expert attention and support in the production and marketing of Artificial Organs. We look forward to reporting further advances in the coming years.

The Telomere/Telomerase System in Chronic Inflammatory Diseases. Cause or Effect?

Telomeres are specialized nucleoprotein structures located at the end of linear chromosomes and telomerase is the enzyme responsible for telomere elongation. Telomerase activity is a key component of many cancer cells responsible for rapid cell division but it has also been found by many laboratories around the world that telomere/telomerase biology is dysfunctional in many other chronic conditions as well. These conditions are characterized by chronic inflammation, a situation mostly overlooked by physicians regarding patient treatment. Among others, these conditions include diabetes, renal failure, chronic obstructive pulmonary disease, etc. Since researchers have in many cases identified the association between telomerase and inflammation but there are still many missing links regarding this correlation, the latest findings about this phenomenon will be discussed by reviewing the literature. Our focus will be describing telomere/telomerase status in chronic diseases under the prism of inflammation, reporting molecular findings where available and proposing possible future approaches.