Biomarkers of aging and survival kinetics

Circadian rhythms of body temperature and locomotor activity in aging BALB/c mice: early and late life span predictors

Impairment of one or more parameters of circadian rhythms (CR) of body temperature (BT) and locomotor activity (LMA) are considered among the hallmarks of mammalian aging. These alterations are frequently used as markers for imminent death in laboratory mice. However, there are still contradictory data for particular strains and it is also uncertain which changes might predict senescence changes later in life, including the force of mortality. In the present paper we use telemetry to study LMA and CR of BT during aging of BALB/c mice. At our knowledge this is the first time that CR of BT and LMA are investigated in this strain in a range of age covering the whole lifespan, from young adult up to very old age. CR of BT was analyzed with a cosine model using a cross sectional approach and follow-up measurements. The results show that BT, LMA, amplitude, goodness-of-fit (GoF) to circadian cycle of temperature decrease with different shapes during chronological age. Moreover, we found that the % change of amplitude and BT in early life (5-19 months) can predict the remaining lifespan of the mice. Later in life (22-32 months), best predictors are single measurements of LMA and GoF. The results of this study also offer potential measures to rapidly identifying freely unrestrained mice with the worst longitudinal outcome and against which existing or novel biomarkers and treatments may be assessed.

Health Differences in Advanced Old Age

The first part of this paper provides a general outline of objectives and methods of the Internal Medicine and Geriatrics Unit of the Berlin Aging Study (BASE). Based on a multi-dimensional conceptualization of health, objective and laboratory data collected about different organ systems, e.g. cardiovascular and musculoskeletal, and functional capacity are complemented by qualitative clinical diagnoses and judgements as well as self-reported health problems and functional limitations. Some of the central questions that can be addressed using these data relate to understanding the nature and processes of differential ageing. The second part of the paper includes initial analyses of inter-individual health differences in advanced old age (70 to 105 years). Initial findings indicated that heterogeneity in somatic morbidity and functional capacity was at least as large in old adults (70 to 84 years) as in very old adults (85 to 105 years), even though higher rates of somatic morbidity and lower levels of functional capacity were observed in the very old. Chronological age and morbidity as well as psychosocial and demographic factors were found to be independent predictors of functional capacity in advanced old age. Additionally, the relative importance of psychosocial factors was found to be a function of age with lower predictive ability among the very old. In conclusion, these initial findings support the hypothesis of significant health differences in advanced old age due to differential ageing.

Influence of age on circadian rhythms of adrenoceptors in brain cortex, heart and submandibular glands of BALB/c mice: when circadian studies are not only useful but necessary

In the present paper we study circadian rhythm variation of alpha1-adrenoceptors (alpha(1)ARs) and beta-adrenoceptors (betaARs) characteristics during aging. Experiments have been performed on mice's whole brain cortex, heart and submandibular glands, which have physiologically relevant regulatory functions at different ages. We used 36 young (4 months) and 36 old (26 months) mice; six animals from each group were sacrificed every 4h, starting at 8.00 a.m. Both the alpha(1)ARs and betaARs density in heart and brain and the betaARs of submandibular glands are significantly lower in old mice with respect to the young ones. The difference, however, if the comparison is performed only at a particular time, for example 8.00 a.m., is not always significant. The alpha(1)ARs density in submandibular glands does not show significant difference with aging, but opposite phases are observed. This study demonstrates that in dynamical systems such as receptors, single point analysis is not so suitable for a correct estimate of adrenoceptors density variation between young and old mice.

Use of mathematical models of survivorship in the study of biomarkers of aging: the role of heterogeneity

An ever increasing number of people have been engaging in aging research using various interventions aimed to modify aging processes, and/or life span, of experimental animals. Since this type of studies needs outcome parameters for assessing the efficacy of such interventions, research on biomarkers of aging (ABs) has received new stimuli. In the present paper, the problem of the occurrence of a vicious circle any time we study ABs and determinants of aging is addressed. In fact, while ABs would represent the standard reference to be used in the study of the main causes of processes of aging, these very determinants should already be known in order to get reliable ABs. A feasible way to overcome this impasse is proposed, using mathematical models of survivorship or mortality based on biological hypotheses and accounting for inter-individual heterogeneity, a necessary ingredient for a correct interpretation of survival results. Specific kinetics of experimental parameters that are candidates as ABs can be compared to the kinetics hypothesized for general biological functions entering the model. We have built a model of this type that can also be used to perform a reliable overall gross estimate of the rate of aging, R(a), in the population, a parameter useful when judging the success of interventions aimed to act on determinants of aging. The perspective that theory of complex systems can be of help in the search for ABs is also discussed.

Long-live euthymic BALB/c-nu mice. I. Survival study suggests body weight as a life span predictor

This paper is the first of a series aimed to show the main physiological and pathological characteristics of male euthymic BALB/c-nu mice, a long-live strain of BALB/c mice bred in our own Institute. In particular, the first two paired papers are respectively devoted to general survival information and disease characteristics, also taking into account very old animals that are of high interest for studies on successful aging. In this paper we report the analysis of survival kinetics, the time course of body weight and the correlation between body weight and time-at-death. The longitudinal study has been performed on 88 male mice, checking individually their body weight and date of death and analyzing survival data by a model built by our own. Survival analysis shows quite higher longevity (median age: about 29 months) in this population when compared with other BALB/c strains. The most relevant finding on body weight is its correlation with longevity until the age of 22 months: thinner subjects live longer and lose weight at a lower rate than their heavier mates. Results have formed the basis on which to plan the cross-sectional experiment to study pathologies and biological parameters at different ages, including a group of mice at very advanced ages (34 months).

Conceptualisation and measurement of frailty in elderly people

The use of the term 'frailty' has shown tremendous growth in the last 15 years, but this has not been accompanied by a widely accepted definition, let alone agreed-upon measures. In this paper, we review approaches to the definition and measurement of frailty and discuss the relationship between frailty, aging and disability. Two trends are evident in definitions, which often trade off comprehensiveness for precision: frailty can be seen as being synonymous with a single-system problem or as a multisystem problem. The essential feature of frailty is the notion of risk due to instability (itself suggesting a balance of many factors), and has been only poorly measured to date. Future models of frailty should incorporate more precise operationalisation of the probability of frailty and better explain the relationship between disease, disability and frailty.