Periodic Report Summary 3 - SWITCHBOX (Switchbox: Maintaining health in old age through homeostasis) Project Context and Objectives:The overall objective of Switchbox is to facilitate maintenance of health in aging through better understanding and exploitation of homeostatic mechanisms. Focus has been placed on metabolic homeostasis, integrated by the hypothalamus, which via its projections to other brain regions and the periphery regulates both metabolic and mental health. Switchbox has emphasised maintaining brain function as age-related brain disorders and impairments represent a major socioeconomic burden. Current consensus holds that brain and metabolic/endocrine processes are bi-directionally linked and that dysregulation of homeostatic mechanisms during aging is associated with increased morbidity and impairments in brain function.Two main tenets frame our work. The first concerns the links between three main endocrine signalling axes and metabolic and cognitive aging. Much current thinking holds IGF signalling to be a key factor driving the aging process. Our hypothesis, derived from epidemiological data and animal studies is that 3 interacting systems namely Insulin signalling (IS) and the hypothalamic/pituitary / adrenal (HPA) and thyroid (HPT) axes are significant modifiers of the aging process. Both the HPA and HPT transduce internal and external environmental signals to the central homeostatic switchbox and over-activity of either system accelerates ageing. Cross-talk among the three systems governs the interlinked functions of metabolic control and cognitive performance. Switchbox is obtaining large sets of functional data on processes and mechanisms underlying how these systems interact in the hypothalamus and periphery to regulate homeostasis during development and aging. The second idea is that there is a vital need to better understand the physiological inks between metabolic factors and cognitive function to generate useful strategies to improve health during aging. Recent technological strides in brain imaging in humans and rodents now permit study of how metabolic factors induce signalling changes in distinct brain areas. We are exploiting the immense potential of these techniques to amplify knowledge of the links between peripheral homeostatic responses to challenge central, hypothalamic controls during aging.To reach these objectives Switchbox has designed an overall strategy that will go beyond the focus of many current aging studies in humans and in animals concentrating on the establishment of specific, one-to-one, correlations, based on a priori hypotheses. We consider it important to identify robust predictive variables through analysis of multimodal endpoints across populations clustered according to distinct criteria. Thus, in Switchbox, the “wet biomarker” analysis will be complemented by neuro-functional (patterns of brain activation using fMRI) and neuro-structural (whole-brain network) analyses. The data from these studies will be analysed using appropriate statistical tools for complex data, followed by principal component analysis, and we will seek co-variances that can be expected to improve prediction of cognitive performance and/or healthy aging in individuals.Project Results:First 18 months: the main achievements were finalisation of consortium-standard protocols for both the human and rodent studies in order to ensure that downstream data uploading to the shared databases would be facilitated. This work is having positive flow on effects on the capacity to fully exploit the data and ensure optimisation of cross partner comparisons (of human and rodent data). The analysis of the baseline data has already yielded numerous insights into the complex relationships between cognitive function, lifestyle factors, age and parameters of health and metabolism in both the rodent groups and human cohorts.Second 18 months: the baseline data aspects have been largely completed (despite some unavoidable technical issues – such as requirements for increased sampling and manual processing of samples, incurring delays) and paved the way to deploy both the stress and intervention studies (undertaken in parallel in humans and rodents in WP 3 & 4). Another noteworthy aspect of the work has been the comparison of different multiple factor analysis methodologies in order to determine best practices, notably concerning neurocognitive tests, so that recommendations are extended to all partners working on humans. Baseline studies in humans have confirmed some of the preliminary hypotheses (eg that offspring of the Leiden Longevity Study (LLS) cohort perform better in certain cognitive tests than their partners, perhaps due to differences in sub-clinicial vascular pathology. Other results have been more surprising, such as the fact that inter-individual differences in cognitive reserve a capacity to cope with challenging conditions) are possibly age-independent. Neuroimaging studies and the structural analysis of brain white matter are elucidating the interplay between stress and healthy ageing, as well as the link between stress and addiction. Other studies have explored the relation between depression and / or stressed mood with body composition and confirming that preventing malnutrition or adiposity is a strategy to prevent against depressive mood throughout ageing and further maintaining perceived stress levels low. Another major result arising from the LLS cohort was confirmation of the hypothesised adaptations in the hypothalamus/ pituitary/ thyroid axis with distinct features seen in offspring of the LLS cohort and not in their partner.Parallel studies of stress in rodents have also yielded surprising results with some ‘very old mice’ performing better in some cognitive /behavioural tests than their younger counterparts, probably due to other health determining factors than cognition and metabolic regulation, indicating the potential confounds when seeking metabolic correlates of cognitive ageing in mice. Sleep studies on mice indicate that sleep integrity declines progressively with ageing and that a history of peripubertal-induced obesity accelerates this decline. In terms of hypothalamus/ pituitary/ thyroid axis, as in humans distinct differences were seen in long-lived versus control mice strains.As full deployment of the second stage of the project gained momentum, further insights were gleaned from the assessment and analysis of the baseline (normal ageing) data and longitudinal assessments (benefitting from the consortium’s activities with respect to the Consortium established best practices). In the final 18 Months: In WP2 progress was made in adapting protocols for the longitudinal studies (rodents) and the elderly human volunteers. These methodological developments enabled multiple publications from all teams. A significant outcome is that the work will continue in another EU projet, Thyrage, financed in the latest round of H2020 funding.In WP3 many findings in both rodent and human models showed significant associations between thyroid and glucocorticoid axes with healthier ageing, both in terms of brain function and peripheral metabolism.In WP4, work was designed to assess the impact of neuropeptide delivery to the brain (nasal inhalation in humans, hypothalamic injection in rodents). An insulin inhalation was adapted for elderly participants and rodent work was focused on modulating thyroid axis.In WP2 many results converged pointing to roles of the thyroid and glucocorticoid axes in better ageing. - Another link between endocrine and metabolic homeostasis and brain function was revealed with the finding that magnetization transfer ratio (MTR) histogram peak height is a sensitive measure to detect microstructural brain changes related to visceral adiposity. - Yet another link between endocrine function and brain activity revealed was that thyroid hormone (TH) levels are significantly associated with brain resting state networks (RSNs) activity, mainly in males. Thus, THs may have a role in RSNs activity, with potentially different implications between genders. Results demonstrate that TH levels allied with neuroimaging can be a relevant strategy in the understanding of RSNs in healthy ageing brains. - Notably, a joint publication by Partners 2, 5 and 1 (Jansen et al., Sci Rep 2015;5:11525), reported that familial longevity was characterized by higher thyroid stimulating hormone (TSH) secretion, in the absence of differences in thyroid hormone (TH) levels. -Similarly, Partner 6 showed that only TSH proved to have a significant positive relationship with cognitive architecture, indicating that processing speed and verbal memory were higher in subjects with higher TSH.In WP3, which investigated resetting of homeostatic responses to stress, a key discovery was that offspring from long-lived families may tend to worry less prior to stressful events, which together with a lower starting point in physiological responses, and a lower peak when confronted with an actual stressor, might limit damage due to stress over a lifetime. This finding could have clinical relevance. -Similarly, using sleep-wake behaviour (SWB) in rodent models as a homeostatic readout and an indicator for judging ‘quality of life’, we found that mice subjected to peri-pubertal diet-induced obesity showed fragmented sleep patterns that could be partially corrected with injected of peptidePYY3-36. Given that obese individuals suffer from frequent awakenings during the night, these findings can have translational impacts.In WP4, an insulin inhalation protocol was adapted for elderly participants and rodent work was focused on modulating thyroid axis. Key publications are currently being submitted on each of these aspects. Notable findings include that altering thyroid signalling in the rodent hypothalamus abrogates the favourable metabolic phenotype of long-lived mice with low TH, confirming our initial hypothesis that hypothalamic control of metabolism is an essential component of brain and body homeostasis during ageing.Potential Impact:Switchbox aims to generate translatable results with short and longer-term impacts across fields by establishing a central repository for multiple data sets on human and rodent aging that will be used to derive algorithms for healthy aging and to inform different stakeholder groups and healthy ageing networks. The Switchbox consortium of six partners has produced over 60 project-related accepted peer reviewed publications* (as of end of Reporting Period 3 and including publications in press) and 1 book chapter. At the time of writing: 18 in 2015, 14 in 2014, 13 in 2013, 6 in 2012 (and 1 in 2011).- This makes an average of more than 8 project related publications per partner in the four years of the project.- A number of publications are on-going.- The quality of the publications is attested by the impact factors of the journals publishing the work, notably Nature Communications, Science Reports, Endocrine Reviews, etc.- A major result was the publication of a popular science book by one of the partners, Prof R Westendorp: https://www.penguin.com.au/products/9781925106916/growing-older-without-growing-old-vitality-and-ageingThe Switchbox project consortium partners, due to the importance of the comparative (between rodent and human studies) and collaborative components of its experimental plan, spent a significant part of the initial phase of the project establishing and improving standardised protocols applicable in each laboratory. Together with the technical difficulties related to generating, depositing in a central repository and assessments on how best to handle the data generated, this has led to several publications reviewing the methodologies and instruments. This is contributing to advancing knowledge and continual improvement of best practice for a wide range of disciplines. For example:High-resolution spatiotemporal mapping of the complete neural circuitry and identification of the cellular processes impacted by stress will help to advance discovery of strategies to reduce or reverse the burden of stress-related neuropsychiatric disorders (see Sousa & Almeida 2012).Insights into the neuropathology of stress by comparing structural consequences of stress exposure of different parts of the human and rodent brain via the assessment and fine-tuning of recent neuroimaging techniques that allow direct monitoring of the spatio-temporal effects of stress and the role of different structures of the central nervous system in regulating the HPT axis of the human brain (see Lucassen et al. 2014)In addition, the consortium has also already produced a large body of work elucidating the factors underlying healthy ageing. For example: The decline of cognitive function in old age is a great challenge for modern society. Switchbox is providing a better understanding of the differences and similarities in the capacity to cope with challenging conditions in young and healthy aged subjects, suggesting that inter-individual differences in cognitive reserve are age-independent (see Zihl et al. 2014).The project provides supporting evidence that physiological and behavioral functions are particularly sensitive to the programming effects of environmental factors such as stress and nutrition during early life, and perhaps at later stages of life. Data suggests gender and educational level are early determinants of cognitive performance in later life and that social-inclusion/engagement and education have a protective effect on mental ageing (see Santos et al. 2012, 2013)Individuals with a high cortisol response to stress might on one hand be protected against reductions in reward sensitivity, which has been linked to anhedonia and depression, but they may ultimately be more vulnerable to increased reward sensitivity, and addictions (see Oei et al. 2014).Further to studies in humans, work on animal models show that modification of the hypothalamus/ pituitary/ thyroid axis are associated with longevity. In mice, negative correlations between thyroid hormone (TH) levels and longevity are observed, leading to the hypothesis that dysregulation of TH availability in defined tissues and cell populations, either too much or too little, will either exhaust the stem cell population precociously or contribute to pathological amplification (see Bowers et al. 2013).Four main results with translational perspectives result from the work :- (i) Two new protocols for either giving drugs to or taking 24h blood samples in elderly subjects were developed. In the first case, an insulin inhalation protocol was adapted for elderly participants. The proof of principle that drugs targeting the brain can be used in elderly patients can open therapeutic perspectives in gerontology. In the second case several adaptations to existing protocols were needed. The optimised protocol has been published to make it available to other members of the community confronted with similar challenges.- (ii) A new reporter mouse was created for increased sensitivity for analysing tissue reponses to thyroid hormone signalling. Applications include novel drug design. - (iii) The consolidation of the Mind data base that now includes human and rodent data on brain imaging, behaviour, endocrine and metabolic parameters during ageing, will be opened to external collaborators on request. Notably, this central repository houses multiple data sets on human ageing (gender, physiological, brain imaging, cognitive and socio-cultural parameters).- (iv) An assay was set up to measure TSH bioactivity in human serum samples. Current assays use an indirect cAMP radioimmunoassay method. We measured TSH bioactivity in 40 anonymized samples from the Leiden Longevity Study. Due to the very high cost of the radioimmunoassay and the rapid decay of the used isotope, this assay is not suitable to measure the TSH bioactivity from large cohorts. Therefore, an alpha screen (PerkinElmer) was set up based on a novel cAMP assay. With this technology the throughput of the assay is increased and the TSH bioactivity can be determined even in samples of large cohorts.List of Websites:www.switchbox-online.eu Other report summaries Periodic Report Summary 2 - SWITCHBOX (Switchbox: Maintaining health in old age through homeostasis) Periodic Report Summary - SWITCHBOX (Switchbox: Maintaining health in old age through homeostasis)
