RESUMEN
Background. Increased oxidative stress is a well described feature of patients in hemodialysis. Their need for multiple blood transfusions and supplemental iron causes a significant iron overload that has recently been associated with increased oxidation of polyunsaturated lipids and accelerated aging due to DNA damage caused by telomere shortening. Methods. A total of 70 patients were evaluated concomitantly, 35 volunteers with ferritin levels below 500 ng/mL (Group A) and 35 volunteers with ferritin levels higher than 500 ng/mL (Group B). A sample of venous blood was taken to extract DNA from leukocytes and to measure relative telomere length by real-time PCR. Results. Patients in Group B had significantly higher plasma TBARS (p = 0.008), carbonyls (p = 0.0004), and urea (p = 0.02) compared with those in Group A. Telomeres were significantly shorter in Group B, 0.66 (SD, 0.051), compared with 0.75 (SD, 0.155) in Group A (p = 0.0017). We observed a statistically significant association between relative telomere length and ferritin levels (r = -0.37, p = 0.001). Relative telomere length was inversely related to time on hemodialysis (r = -0.27, p = 0.02). Conclusions. Our findings demonstrate that iron overload was associated with increased levels of oxidative stress and shorter relative telomere length.
Asunto(s)
Sobrecarga de Hierro/etiología , Fallo Renal Crónico/complicaciones , Estrés Oxidativo , Adulto , Envejecimiento Prematuro , Ecocardiografía , Femenino , Ferritinas/análisis , Humanos , Sobrecarga de Hierro/metabolismo , Fallo Renal Crónico/metabolismo , Fallo Renal Crónico/patología , Leucocitos/citología , Leucocitos/metabolismo , Masculino , Malondialdehído/sangre , Persona de Mediana Edad , Carbonilación Proteica , Reacción en Cadena en Tiempo Real de la Polimerasa , Diálisis Renal , Telómero/genética , Acortamiento del Telómero , Urea/sangreRESUMEN
BACKGROUND: Recently, a direct correlation with telomere length, proliferative potential and telomerase activity has been found in the process of aging in peripheral blood cells. The objective of the study was to evaluate telomere length and proliferative potential in peripheral blood mononuclear cells (PBMCs) after stimulation with Concanavalin A (ConA) of young adults compared with older adults. METHODS: Blood samples were obtained from 20 healthy young males (20-25 years old) (group Y) and 20 males (60-65 years old) (group O). We compared PBMC proliferation before and after stimulation with ConA. DNA was isolated from cells separated before and after culture with ConA for telomeric measurement by real-time polymerase chain reaction. RESULTS: In vitro stimulation of PBMCs from young subjects induced an increase of telomere length as well as a higher replicative capacity of cell proliferation. Samples from older adults showed higher loss of telomeric DNA (p = 0.03) and higher levels of senescent (≤6.2 kb) telomeric DNA (p = 0.02) and displayed a marked decrease of proliferation capacity. Viability cell counts and CFSE tracking in 72-h-old cell cultures indicated that group O PBMCs (CD8+ and CD4+ T cells) underwent fewer mitotic cycles and had shorter telomeres than group Y (p = 0.04). CONCLUSIONS: Our findings confirm that telomere length in older-age adults is shorter than in younger subjects. After stimulation with ConA, cells are not restored to the previous telomere length and undergo replicative senescence. This is in sharp contrast to the response observed in young adults after ConA stimulation where cells increase in telomere length and replicative capacity. The mechanisms involved in this phenomenon are not yet clear and merit further investigation.