In the young and healthy shoulder, cranially directed forces during abduction are counteracted by co-contraction of the rotator cuff muscles. In this way, it is prevented that the humerus moves... Show moreIn the young and healthy shoulder, cranially directed forces during abduction are counteracted by co-contraction of the rotator cuff muscles. In this way, it is prevented that the humerus moves cranially towards the acromion, thus entrapping subacromial tissues. During ageing however, shoulder tissues are subject to marked degeneration, which particularly concerns the rotator cuff muscles. This may have two consequences. First, due to reduced contribution of the upper parts of the rotator cuff to the abduction movement, the deltoid has to compensate, which results in a more cranially, instead of mediocranially directed force. Second, reduced stabilising force by the rotator cuff may jeopardise counteraction of cranial deltoid forces. These changes could lead to cranialisation of the humerus with painful compression of subacromial tissues, as observed in patients with Subacromial Pain Syndrome (SAPS). Previous studies have shown that by co-contraction of arm adductors, humeral-head depression may be accomplished, for the purpose of unloading subacromial tissues. In this thesis, we investigated the role of adductor co-contraction in the ageing asymptomatic population and in patients with SAPS. This has resulted in eight scientific publications with which the fundaments for evidence-based therapy in SAPS have been built, with as cornerstone training of adductor co-contraction. Show less
The shoulder joint is a frequent anatomic site of musculoskeletal pain. Most middle-aged adults with shoulder pain have been diagnosed with subacromial bursitis, or subacromial impingement syndrome... Show moreThe shoulder joint is a frequent anatomic site of musculoskeletal pain. Most middle-aged adults with shoulder pain have been diagnosed with subacromial bursitis, or subacromial impingement syndrome. Attrition underneath the acromion have been presumed to cause painful inflammation of subacromial tissues for years, but scientific evidence was limited. The real cause for subacromial pain is still unknown, which resulted in the diagnostic label “subacromial pain syndrome”. In this thesis, we focused on the effectiveness of acromioplasty in the treatment of patients with subacromial pain. We found no effect of acromioplasty over bursectomy alone on long-term shoulder pain and function. We also examined shoulder kinematics and muscle activation in patients with subacromial pain. We found an association between the size of rotator cuff tears as well as subacromial pain syndrome with shoulder kinematics, and described an increase in teres major muscle activity in subacromial pain syndrome. The project contributed to changed recommendations in guidelines regarding the treatment of subacromial pain syndrome. Our kinematic and biomechanical studies may create a biomechanical rationale for physiotherapeutic strategies targeted at the teres major muscle in the treatment of subacromial pain. Show less
Plant architecture has distinct forms in different plant species, but also within a species the finalarchitecture of a plant is determined by its gradual development and changes therein induced by... Show morePlant architecture has distinct forms in different plant species, but also within a species the finalarchitecture of a plant is determined by its gradual development and changes therein induced by environmental conditions during the plant’s life cycle. Higher plants have the ability tocontinually produce new organs and tissues during their lifetime. This unique ability is provided by pools of stem cells organized in so-called meristems. Primary meristems located at apices, of the plant body are involved in elongation of the main plant axes, whereas secondary meristems in lateral positions play a role in branching and axis thickening. First chapter is reviewing the current advances in our understanding of the molecular mechanisms that regulate plant meristems and their developmental phase transitions in Arabidopsis thaliana. AT-HOOK MOTIF NUCLEAR LOCALIZED (AHL) gene family is introduced in chapter 1,and that of family member AHL15 described and studied more in detail in chapter 2. In chapter 3 we identified a new branch of the ageing pathway in Arabidopsis, in which the longevity-promoting AHL15 protein represses ageing independent of miR156/157. Chapter 4 of this thesis focuses on AHL15's effect on Arabidopsis vascular cambium activity and secondary growth. Analysis showed that in an ahl15 loss-of-function mutant, interfascicular secondary growth is significantly reduced. Show less
Maintenance and repair is of key importance for the proper functioning of cells, tissues, and integrated physiology. We hypothesize that the balance between investments in growth, development, and... Show moreMaintenance and repair is of key importance for the proper functioning of cells, tissues, and integrated physiology. We hypothesize that the balance between investments in growth, development, and reproduction versus maintenance and repair is regulated by the brain. Specifically (the interplay of) hormones of the different hypothalamic-pituitary-target gland axes seem to be key regulators in constantly adjusting this balance to its optimal state. This thesis describes the associations between familial longevity and hormones of different hypothalamic-pituitary-target gland axes. In Chapter 2, the question is addressed whether circulating insulin-like growth factor 1 (IGF‐1) axis parameters associate with old age survival and functional status in nonagenarians from the LLS. In Chapter 3, we use growth hormone (GH) concentrations measured every 10 min over 24 h to derive and compare GH secretion parameters between offspring of long-lived families and their partners. In Chapter 4, we investigate the association between hypothalamic-pituitary-gonadal axis parameters and familial longevity. In Chapter 5, we use 24-h time series data of pituitary hormones to investigate how changes in the different hormonal axes are correlated with each other over time. In Chapter 6, we determine the circadian rhythm of bone turnover markers in healthy older subjects. Show less
In this thesis we aimed to get insight in how the methylome is established during development and subsequently degenerates during ageing using an integrative approach to the analysis of DNA... Show moreIn this thesis we aimed to get insight in how the methylome is established during development and subsequently degenerates during ageing using an integrative approach to the analysis of DNA methylation in conjunction with other levels of genomics data. The first two empirical chapters of this thesis describe the establishment and the maintenance of the epigenome during fetal development and in later life in multiple tissues. In the subsequent two chapters we investigated the loss of control over the methylome in blood and other tissues. Show less
Human ageing is characterized by a gradual decline in cognitive and physical performance strongly determining someone’s functional abilities and quality of life. In this thesis, insights into... Show moreHuman ageing is characterized by a gradual decline in cognitive and physical performance strongly determining someone’s functional abilities and quality of life. In this thesis, insights into these age-related changes and most importantly their interactions are given, which might be suggestive for potential causal mechanisms and is required for the development of preventive and therapeutic paradigms. We focused on global and domain specific measures of cognitive and physical performance and assessed the interactions across different populations of calendar and biological age (range 45 to 90 years). For the assessment of physical performance, instrumented measures were introduced to assess their additional value. Across the entire age range, interactions between cognitive and physical performance were consistently found. The temporal relationship differed across age and domains, suggesting a specific rather than a general relationship. Because age-related changes were already observed from middle age, these results encourage the early and repeated assessment of cognitive and physical performance across different domains and development of age and domain specific interventions. Instrumented measures can be used for the identification of age-related changes and show promising results in providing additional insights into potential underlying determinants. This will enable the development of even more refined and patient specific interventions. Show less
With the increase in life expectancy, the prevalence of cognitive disorders is expected to rise the coming years. In this thesis we studied the association between blood pressure, cardiac... Show moreWith the increase in life expectancy, the prevalence of cognitive disorders is expected to rise the coming years. In this thesis we studied the association between blood pressure, cardiac biomarkers and cognitive function in 5800 people with mean age of 75 years. Furthermore, we investigated the feasibility to use smartphone technology to measure home blood pressure in 151 people during a 6 months follow-up period. We show that higher variability in blood pressure is associated with increased microdamage of the brain and worse cognitive function, independent of average blood pressure and use of blood pressure lowering medication. Furthermore, increased levels of N-terminal pro-brain natriuretic peptide (NT-proBNP) and cardiac troponin T (cTnT), both markers of cardiac disease, are associated with worse cognitive function and steeper cognitive decline, independent of cardiovascular diseases or risks. Finally, we show that smartphone-based technology is a reliable and promising method with good adherence to measure blood pressure at home. This provides a possibility for implementation in large-scale studies and can potentially contribute to blood pressure reduction, eventually helping to prevent cognitive impairment. Show less
With increasing age, incidence and prevalence of cardiovascular disease increase. Many physicians face the dilemma whether or not to start preventive treatment in old age. To help physicians decide... Show moreWith increasing age, incidence and prevalence of cardiovascular disease increase. Many physicians face the dilemma whether or not to start preventive treatment in old age. To help physicians decide whether to advise preventive medication to their older patients, prediction of those at highest or lowest (relative) risk using (preferably) inexpensive and easy to use cardiovascular risk factors is important. However, in old age there is a lack of good cardiovascular risk predictors. This thesis shows that the use of multiple blood pressure measurements expressed in the variability (in diastolic blood pressure) or trends in blood pressure can identify older persons with high cardiovascular risk. It also shows that in the oldest old, the absence or presence of heart failure does not influence the prognostic value of low systolic blood pressure regarding risk of death. The serological biomarker N-terminal pro-B-type natriuretic peptide (NT-proBNP) is found to be an interesting candidate in cardiovascular risk prediction in old age, especially in secondary prevention. In the oldest old, an increase in NT-proBNP still reflects increased risk of (cardiovascular) death, independent of decreasing renal function and is associated with incident heart failure and atrial fibrillation. Show less
The evolution of ageing is a field flush with misconceptions, misunderstandings, and hiatuses. In this thesis I address the most important misunderstanding and misconceptions, and develop new... Show moreThe evolution of ageing is a field flush with misconceptions, misunderstandings, and hiatuses. In this thesis I address the most important misunderstanding and misconceptions, and develop new theory to fill the gaps. This work directly leads to the restatement of the central question in the evolutionary theory of ageing. Rather than evaluating evolutionary forces in models that are at best weakly rooted in (patho-) physiological mechanisms, usually phrased in terms of __age-specific genes__ that are not further specified, as is the current practice, the most pressing question becomes why an organism cannot, or does not, do in itself what it is perfectly capable of doing outside itself in the form of reproduction, namely producing a perfectly healthy __young__ organism. Evolutionary forces cannot answer this question. If anything, this is a mechanistic question. I suggest investigating __the evolution of unretainability__: why and how has our form of life evolved, in which it is mechanistically impossible to bring ageing to a halt, and what are the responsible mechanistic constraints? Show less
In this thesis I describe studies of life history traits under variation in nutrition focused on ageing. The predictive adaptive response is a type of plastic response which is advantageous later... Show moreIn this thesis I describe studies of life history traits under variation in nutrition focused on ageing. The predictive adaptive response is a type of plastic response which is advantageous later in life, rather than immediately. We tested with a resource allocation model whether for a relatively short-lived organism, Bicyclus anynana increasing allocation to dispersal capability would be advantageous as an adult, when the individual would be stressed as a larva. This was indeed the case. Using a similar model we tested whether increased lifespan under dietary restriction would be evolutionary conserved. This did not seem to be the case. Then we describe how traits and gene expression in fruit flies (Drosophila melanogaster) was affected by sustained cycles of low and high food, compared to constant food controls. Furthermore we compare predictions from a model, in which the relationship between fecundity and lifespan changes with the age of the flies measured. Lastly we test whether genetic variation in genes described in model organisms under laboratory conditions can be correlated to phenotypic variation in life history traits under natural conditions of the least killifish (Heterandria formosa). Indeed this was the case Show less
This thesis aims to describe the role of glucose metabolism in human longevity and to translate the results to an intervention aimed at improving health in older age in the general population. In... Show moreThis thesis aims to describe the role of glucose metabolism in human longevity and to translate the results to an intervention aimed at improving health in older age in the general population. In the first part, we describe evidence for enhanced glucose metabolism in long-lived families. Middle-aged individuals predisposed to longevity were characterized by enhande insulin action at the level of the skeletal muscle, lower accumulation of intramyocellular lipids and lower nocturnal glucose levels. These results have provided the biological basis upon which health-promoting intervention in older age may be funded. In the second part, we have shonw that an internet-based intervention is effective at increasing physical activity and improving health in an older population. Furthermore, increasing total daily physical activity in sedentary elderly was shown to lead to better metabolic health. Show less
The aim of this thesis was to identify in the human blood transcriptome, relevant pathways and potential biomarker profiles that associate with chronological age and discriminate between __healthy... Show moreThe aim of this thesis was to identify in the human blood transcriptome, relevant pathways and potential biomarker profiles that associate with chronological age and discriminate between __healthy agers__ from long-lived families and normative ageing controls. Such profiles may harbor determinants of the biological ageing rate. We studied genome-wide gene expression profiles in blood of members of the Leiden Longevity Study (LLS) and replicated our findings by extended sampling within the unique LLS cohort. The findings of the exploratory analysis prompted us to investigate multiple genes in the IL7R and MTOR pathways for association with familial longevity. The results obtained by examining mRNA from blood samples brought us to study mTOR protein levels and signalling in primary skin fibroblasts from the corresponding donors in the LLS. Finally, to discover robust, biologically relevant gene networks as markers of chronological ageing in larger sample sizes, we performed an explorative network-based meta-analysis on large publicly available transcriptomic datasets. We have identified several networks, pathways and candidate genes potentially marking the biological age and the rate of ageing Show less
Sarcopenia in old age has been associated with a higher mortality, poor physical functioning, poor outcome of surgery and higher drug toxicity. There is no general consensus on the definition of... Show moreSarcopenia in old age has been associated with a higher mortality, poor physical functioning, poor outcome of surgery and higher drug toxicity. There is no general consensus on the definition of sarcopenia. The aim of the research presented in this thesis was to assess the implications of the use of different diagnostic criteria for sarcopenia, and to define the most accurate criteria for sarcopenia. Currently used diagnostic criteria for sarcopenia can be divided into criteria based on (1) low muscle mass, (2) low muscle strength, and (3) low walking speed. This thesis describes how muscle mass can be further divided into relative muscle mass and absolute muscle mass. A higher body or fat mass is associated with a lower relative muscle mass and with a higher absolute muscle mass. Higher relative muscle mass at old age is associated with better physical performance and with less insulin resistance. It is suggested to reserve the term sarcopenia to describe a low muscle mass and dynapenia to describe a low muscle strength. Most importantly, this research illustrates that it is impossible to compare studies about sarcopenia in scientific literature due to the use of different diagnostic criteria for sarcopenia. Show less
Long-Lived Sociality is an ethnographic account of the lives of older persons in Kerala. Through its detailed account of these highly educated, middle and upper class individuals, it challenges... Show moreLong-Lived Sociality is an ethnographic account of the lives of older persons in Kerala. Through its detailed account of these highly educated, middle and upper class individuals, it challenges many popular and academic stereotypical notions of the old. Contrary to such preconceptions for instance, their lives turn out to be interdependent, not at all stagnant, extremely mobile and as far as possible actively shaped by the older persons themselves. Cultural notions about sociality are furthermore explored to understand how meaning is given to social and care relationships with others. These relations are informed by strong expectations and a discourse that stresses the importance of duties. This discourse makes it possible for older persons to explicitly demand care when needed. The investigation of the possibilities and limitations of this discourse provides insights into the older persons__ appreciation of their social lives and their overall wellbeing. Show less
Humans have a long post-reproductive life span. In this thesis we study this post-reproductive life span from an evolutionary perspective. Why did humans evolve such a long post-reproductive life... Show moreHumans have a long post-reproductive life span. In this thesis we study this post-reproductive life span from an evolutionary perspective. Why did humans evolve such a long post-reproductive life span? We tested the hypothesis that men and women after age 50 are able to contribute to their fitness either direct by continued reproduction or indirect through improving the reproductive success of subsequent generations. In a prospective full kin analysis in the Upper East Region in Ghana, we studied the effect of different kin members on offspring production, survival and early growth patterns in a polygamous population that lives in an environment that could reflect our recent evolutionary past. We were able to confirm that post-reproductive survival in females indeed has a selective advantage. However, in this population, the advantage was not through increased survival of offspring as found by others, but through increased reproduction of their household. Also, we found that grandfathers, through continued reproduction up to high age created a selective pressure for old age survival. This direct effect was larger than the indirect effect of post-reproductive survival in women which could point to a more important role of men in the evolution of longevity than previously thought. Show less
Human fitness is critically reliant on the immune system to provide protection against pathogens. We argue that a pro-inflammatory response is crucial for defense against pathogens and that it is... Show moreHuman fitness is critically reliant on the immune system to provide protection against pathogens. We argue that a pro-inflammatory response is crucial for defense against pathogens and that it is very likely that infectious pressure has resulted in selective survival for genetic variants encoding for higher pro-inflammatory responsiveness. In industrialized populations many chronic diseases have been associated with an imbalance in pro- and anti-inflammatory responsiveness. We argue that from an evolutionary perspective, these chronic diseases in later life could be explained by genetic adaptations to survive a harsh environment. In order to study the role of the innate immune response in life-history regulation in a pathogen-rich environment, we set out a study in Northern Ghana. In a population living under adverse conditions we studied the role of the inflammatory response in survival and fertility. In Chapter 1 a general introduction was given on the research hypotheses and an overview of aims and description of the study population and methods. The general frame-work of the study was explained in depth in Chapter 2. Here we hypothesized that human life-history regulation in our evolutionary past, or under adverse conditions can largely be explained by selections that operated in the innate immune response. We proposed that fertility is associated with an anti-inflammatory response, whereas survival in a pathogen-rich environment is dependent on a strong pro-inflammatory response. We hypothesize that populations living under adverse conditions have been selected for a pro-inflammatory innate immune response. Also we argue that fitness in itself is a conflict between pro- and anti-inflammatory responsiveness where concessions have to be made to allow reproduction as well as defense. Furthermore we argue that evolutionary programming of the inflammatory response might underlie age-related diseases as observed in populations living under affluent conditions. It is arbitrary how to measure an innate immune response ex vivo, that reflects a general response mode irrespective the type of pathogen involved. In Chapter 3 a method is described to test innate tendency of immune activation. The assay is also validated. Given the fact that bacteria and other pathogens normally use several TLRs together to induce an immune response, we argue that mixed stimulation of both TLR2 and TLR4 receptors gives a broader view of an immune response than with the usual assay on a single TLR-agonist. Compared to variability of cytokine production in the Netherlands, we show that ex vivo IL10 production is comparable. Therefore we suggest that in Ghana IL10 is highly genetically regulated. TNF_, on the other hand, is more prone to variation in general, but especially in Ghana and might be more dependent on environmental modulation. In Chapter 4 we compared age-related cytokine production in adverse and affluent conditions. When measured cross-sectionally, IL10 production decreases with age in the Netherlands and in Ghana. TNF_ production decreases with age in the Netherlands, but remained equal over all age-categories in Ghana or, dependent on the stimulation, increased with age. We conclude that the decline in innate cytokine responses is an intrinsic ageing phenomenon, while pathogen exposure and/or selective survival may drive pro-inflammatory responses under adverse living conditions. As TLR2 and TLR4 are important recognition receptors for a large set of pathogens, it might be that variation in these receptors results in different induction of innate immune responses and selective survival. In Chapter 5 we report that at the end of the TLR4 gene there was variation that associated with higher ex vivo LPS-induced IL10 production. None of the variants in TLR2 or TLR4 however were associated with P. falciparum infection or survival. As the prevalence of malaria was high in this area, we conclude that it is likely that in contrast to other studies, these genetic variants do not play a role in disease state and outcome of infection. Another pathogen receptor is PTX3. It is not only involved in recognition of pathogens, but also in the formation of the extracellular matrix of the oocyte. Therefore it might be crucial for female fertility. In Chapter 6 we assess whether genetic variation in PTX3 production is associated with life-time reproductive success. We found genetic variants in PTX3 that associated with higher PTX3 production capacity ex vivo and increased fertility and vice versa. We found no evidence for selective survival of genetic variants. We conclude that PTX3 is important for human fertility, whereas no concessions were made with regard to survival. In Chapter 7 we asses the role of IL10 in survival. We report on genetic variation in the IL10 gene that associated with lower IL10 and higher TNF_ production. Carriers of these genetic variants had a higher survival chance when living under adverse conditions. However, survival chances of these variants decreased when people had access to clean drinking water. We conclude to have found evidence that adverse environmental conditions favor selection for a pro-inflammatory response pattern. Show less
Replicative ageing of fibroblasts has often been used as a model for organismal ageing. The general assumption that the ageing process is mirrored by cellular senescence in vitro is based on lower... Show moreReplicative ageing of fibroblasts has often been used as a model for organismal ageing. The general assumption that the ageing process is mirrored by cellular senescence in vitro is based on lower replicative capacity of human fibroblasts from donors of higher chronological age, but these inverse relations have not been reported unequivocally. The relation between chronological age and fibroblast growth characteristics was assessed in nonagenarian subjects of the Leiden 85+ Study. A high remaining replicative capacity impressively showed that even in the very elderly a crucial number of cells with high mitotic capacity are left to give rise to fibroblast strains with the capacity for more than 100 population doublings. During the course of fibroblast growth in vitro, beta-galactosidase activity has been shown to be a reliable biomarker for replicative senescence. In myoblast cultures the relation between mixed cultures and clonal cultures was studied, showing marked heterogeneity between clonal cultures that all had a significantly lower replicative capacity when compared to mixed cultures, indicating heterogeneity of cells within one tissue compartment in their in vivo history. In a formal review on the replicative capacity of fibroblasts from patients suffering from accelerated ageing syndromes, age related diseases and donor age it was found that except for premature ageing syndromes, the replicative capacity of fibroblasts in vitro does not mirror key characteristics of human life histories. Show less
There is accumulating evidence that the evolutionary trade-off between body maintenance and fertility is also present in humans. Several studies have shown this trade-off in historic data sets.... Show moreThere is accumulating evidence that the evolutionary trade-off between body maintenance and fertility is also present in humans. Several studies have shown this trade-off in historic data sets. Other studies found no evidence for the trade-off. This could, in part, be explained by the fact that the populations under study resided in a modern affluent environment characterized by low mortality and fertility rates, i.e. having past the epidemiologic transition. Lycett et al for instance demonstrated that the trade-off was stronger under conditions of poverty. Accordingly, it has been shown, that the trade-off disappeared in the British aristocracy when environmental conditions markedly improved after 1700 and initiated a demographic transition. Similar trends over time were found in other studies. The objective of this thesis was to test the hypothesis that fertility trades off with early survival in a contemporary population that is still exposed to adverse environmental conditions. Therefore all the studies were performed in the upper east region of Ghana, Africa. The results can be divided into two parts. Part A, Chapters 2, 3 and 4, describes the research population analyzes whether or not the epidemiologic transition has taken place. Part B, Chapters 5, 6 and 7, describes the actual testing of the hypothesis. Show less
The lifespan of an organism is determined by a complex network of environmental-, genetic- and stochastic factors. Each of these components contributes to the wide variability in lifespan between... Show moreThe lifespan of an organism is determined by a complex network of environmental-, genetic- and stochastic factors. Each of these components contributes to the wide variability in lifespan between and within species. In recent years, it has been shown that 20-30 % of human lifespan is under genetic control. Furthermore, a number of longevity candidate genes have been identified. The majority of candidate genes have emerged from studies with model organisms, but also from the biology of human ageing. The objective of this thesis was to test the impact of the most prominent longevity candidate genes on the prevalence of age-related diseases and lifespan in humans. All studies presented in this thesis were performed within the Leiden 85-plus Study, which is a population-based prospective study of the oldest old. The results revealed that genetic variations in most of the candidate genes influence metabolism, prevalence of age-related diseases, cognitive functioning and lifespan. Therefore, the approach of analyzing the most prominent longevity candidate genes in humans, contributes to the identification of biological mechanisms that influence the prevalence of disease in old age and lifespan. Show less
The general aim of the work described in this thesis is to help explain the variation in ageing by using the life history framework of B. anynana. Each chapter focuses on a different aspect of the... Show moreThe general aim of the work described in this thesis is to help explain the variation in ageing by using the life history framework of B. anynana. Each chapter focuses on a different aspect of the life history, together giving a complete picture of the origins of variation in ageing in this species. A central theme to every chapter is the relative influence of genes, the environment, and how they related to plasticity. A summarising discussion of all chapters, and a perspective on how the ideas in this thesis will contribute to ageing research in the future is also included. Show less
