Comprimento do telômero e curso de vida: relações com condições de saúde, marcadores inflamatórios e desempenho físico em idosas da comunidade
Introduction: Telomere length (TL) has been pointed out as a possible biomarker of cellular aging, as its physiological size progressively shortens with the course of cellular replications. In addition to this physiological shortening, TL dysfunction is also stimulated by exposure to oxidative stres...
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| Formato: | doctoralThesis |
| Idioma: | por |
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| Acesso em linha: | https://repositorio.ufrn.br/jspui/handle/123456789/22717 |
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| Resumo: | Introduction: Telomere length (TL) has been pointed out as a possible biomarker of cellular aging, as its physiological size progressively shortens with the course of cellular replications. In addition to this physiological shortening, TL dysfunction is also stimulated by exposure to oxidative stress, inflammation and after chronic psychosocial stress. There is also a lack of knowledge about TL changes during the course of life in populations of older Brazilian women, and there is a need for studies which foster a better understanding of the influence of social contrasts, unfavorable socioeconomic conditions, as well as exposure to chronic social stress in TL. Objectives: 1) To develop a systematic review to explore the evidence on associations between chronic stress over the life course and TL; 2) To investigate possible associations between TL and childhood adversities (social and economic) in older women with different levels of education; 3) To evaluate whether TL is related to chronic diseases and inflammatory biomarkers in older women; and 4) To verify whether shorter telomeres are associated with poorer physical performance and higher self-reported functional limitations in older adults. Materials and methods: A systematic review was developed following a protocol published in 2014. An observational cross-sectional analytical study was concomitantly carried out with a sample of women (n = 106) with different levels of education (incomplete secondary education and complete secondary education) in the age group of 64-74 years residing in the municipality of Natal (Rio Grande do Norte). Data were collected from May 2014 to March 2015. The relative quantification of leukocyte telomere size (T/S) was performed by real-time qPCR in 83 women. The standardized questionnaire included sociodemographic information, childhood adversities, anthropometric measures, self-reported health, cognitive function, life habits, chronic health conditions, functional capacity and physical performance (short physical performance battery, gait speed and manual grip strength). Inflammatory biomarkers (interleukin-6 and c-reactive protein) were also analyzed. For statistical analysis, p<0.05 and 95% confidence intervals were used. The normality of the data was verified by the Kolmogorov-Smirnov test. Since TL presented non-normal distribution, the transformation of the measure into natural logarithm was performed for subsequent analyzes. Student's t-tests were applied for independent samples, and Chi-square and multiple linear regression models were adjusted for potential confounding factors. Results: The results of the systematic review were reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Considering the eighteen studies included in the review, we generally observed that individuals exposed to chronic stress, characterized by poverty, exposed to violence and/or caring for a sick relative had shorter telomeres compared to individuals who were not exposed to adversity. Analyzes of the cross-sectional study on TL and life course showed that the older adults with incomplete secondary education presented higher TL compared to the group of complete secondary education (2.8 ± 0.9 and 2.0 ± 0.9, respectively; p = 0.0001). Women who did not complete high school were exposed to more adversity in childhood, and among them, those who suffered two or more adversities had longer TL than women exposed to ≤1 adversity (p = 0.03); among women with at least complete secondary education, this difference was not significant (p = 0.49). In analyzes adjusted for age, educational level and parental alcohol abuse, a linear trend of higher TL for greater number of adversities (p = 0.02) was observed, and the difference in TL between education levels remained significant (p = 0.002). No difference between the education groups was observed for the following variables: cholesterol, triglycerides, fasting glycemia, glycated hemoglobin, c-reactive protein and interleukin-6 (p>0.05). Chronic health conditions, anthropometric measures, cardiovascular risk factors and inflammatory markers were not associated with TL, even after adjusting for age, schooling and childhood adversities (p>0.05). Similarly, TL was not related to any of the variables used to assess physical performance or functional capacity (p>0.05). Conclusions: The unexpected positive relationship between TL and lower education level and childhood adversities suggests that participants survived harsh living conditions and that these women probably have longer TL in relation to others among their birth cohort. The lack of relationship between TL and chronic diseases, cardiovascular risk, inflammation and physical performance did not support the hypothesis that TL is an aging biomarker in the population under study, but corroborates other studies that have shown TL to be considered as a marker of longevity, regardless of health conditions and physical performance. |
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