Accurate prediction of the unbound drug concentration-time profile at the CNS target site is crucial for the assessment of the right drug concentration-effect relationship. PBPK models have... Show moreAccurate prediction of the unbound drug concentration-time profile at the CNS target site is crucial for the assessment of the right drug concentration-effect relationship. PBPK models have supported the PK prediction of the CNS target sites and the translation of PK data between species and between populations, given their mechanistic, physiology-based structure. In this thesis, we have developed a CNS PBPK model which could predict adequately the brainECF, brainICF, and CSF unbound PK profiles and provide important insights into the brain unbound pharmacokinetics of patients with CNS diseases. Early prediction of the brain target site pharmacokinetics of the right patient population can prioritize drugs with the favored brain PK profiles, which might optimize and accelerate the CNS drug development process. Show less
This thesis describes studies of individuals with systemic lupus erythematosus (SLE) presenting with neuropsychiatric (NP) symptoms at the Leiden NPSLE clinic. A diverse range of studies, including... Show moreThis thesis describes studies of individuals with systemic lupus erythematosus (SLE) presenting with neuropsychiatric (NP) symptoms at the Leiden NPSLE clinic. A diverse range of studies, including laboratory, radiological, clinical and patient´s reported outcomes are presented.The Leiden NPSLE clinic is a tertiary referral center for patients with SLE and neuropsychiatric (NP) symptoms. In the NPSLE clinic, patients are assessed by a multidisciplinary team. Thereafter, clinical, radiological and laboratory measures are weighed in a consensus meeting to correctly attribute the NP symptoms: related to lupus activity (NPSLE) or not. This extensive and standardized assessment of NPSLE, a rare and heterogenous disease lacking a gold standard, is unique and creates the opportunity to explore many aspects of NPSLE in well-defined phenotypes.In the first part of this thesis, we evaluate both classification and treatment of patients withSLE and NP symptoms. The second part of this thesis focuses on a diverse range of clinicaloutcomes of NPSLE, including both morbidity and mortality. The last part of this thesisassesses potential biomarkers for (specific manifestations of) NPSLE. Show less
The general aim of this thesis was to study the frequency, causes and consequences of pathologic brain aging specifically focusing on sub-clinical and clinical MRI manifestations of vascular (small... Show moreThe general aim of this thesis was to study the frequency, causes and consequences of pathologic brain aging specifically focusing on sub-clinical and clinical MRI manifestations of vascular (small vessel disease) and neurodegenerative (brain atrophy) disease. A second aim was to improve the accuracy of the tools to quantify brain tissue so to better reflect the imaging characteristics of older people. All data presented in this thesis are from the AGES-Reykjavik Study including 5764 elderly men and women. The data is based on cross-sectional and longitudinal assessments of the brain with MRI measures. Show less
More than 45 years of research on the effects of glucocorticoids on brain function has yielded many insights, but also left a number of longstanding questions. One conundrum has been how activation... Show moreMore than 45 years of research on the effects of glucocorticoids on brain function has yielded many insights, but also left a number of longstanding questions. One conundrum has been how activation of the structurally comparable mineralocorticoid receptor (MR) and glucocorticoid receptor (GR) can lead to very different, or even opposite effects. It also remained unclear how the consequence of activation of a single receptor, GR, can differ from cell to cell and from situation to situation. In this thesis we have investigated two aspects of transcriptional regulation in response to glucocorticoids: the cause of MR/GR specificity, and the role of crosstalk with other transcription factors. Within the hippocampus, we found NeuroD factors to drive the specificity in corticosteroid receptor DNA binding and subsequent gene regulation, i.e. by stimulating MR signaling. We identified Jun dimerization protein 2 (Jdp2) as a stress-responsive MR-specific target gene. In a stress hormone relevant memory task, GR was suggested to act context-dependently and several novel GR target genes were detected. Further elucidation of distinct MR/GR downstream pathways will enable us to better understand the stress physiology and more specifically target aspects of glucocorticoid signaling for treatment of stress-related disorders. Show less
In this thesis we have analyzed an important number of laboratory, radiological, clinical and patient´s reported outcomes in systemic lupus erythematosus (SLE) patients presenting with... Show moreIn this thesis we have analyzed an important number of laboratory, radiological, clinical and patient´s reported outcomes in systemic lupus erythematosus (SLE) patients presenting with neuropsychiatric (NP) manifestations. Our studies are among the most robust to date in this field due to the large number of patients included, the prospective character and the standard assessment followed by a multidisciplinary expert consensus.Furthermore our studies include the novelty of a phenotypic characterization of all NP manifestations according to the suspected underlying pathophysiological mechanism (inflammation or immune-mediated vs. ischemic or thrombotic). These studies give more light to the understanding of the underlying pathophysiological mechanisms of nervous involvement in SLE. Show less
This thesis describes the longitudinal population-based CAMERA-study on the association between migraine and brain changes (e.g. white matter hyperintensities, infarct-like and other lesions) and... Show moreThis thesis describes the longitudinal population-based CAMERA-study on the association between migraine and brain changes (e.g. white matter hyperintensities, infarct-like and other lesions) and possible causes and consequences of those brain changes. Women with migraine showed higher incidence of deep white matter hyperintensities after nine years of follow-up. Infratentorial hyperintensities were also found more often among migraine women compared to controls. Migraine severity characteristics were not associated with progression of lesions. By using voxel based morphometry region-of-interest analyses, migraineurs showed decreased grey matter volume in visual areas of the right occipital cortex compared to controls. The occurrence of ischemia during attacks seems a logical explanation for the development of lesions. One other possible explanation for brain lesions is recurrent paradoxical (micro-)emboli as a result of right-to-left shunting (RLS). In our study, RLS are also more prevalent among migraineurs than among controls. As for the possible consequences: migraine patients and controls showed similar performance on all cerebellar functioning tests. In addition, cognitive functioning was similar for migraine patients and controls, deep white matter hyperintensities were not related to impaired cognitive performance, and migraine had no influence on this association. Our findings are reassuring for migraine patients and their doctors. Show less
The prevalence of obesity, defined as a body mass index (BMI) > 30 kg/m2, is increasing to epidemic proportions. In 2014, 11% of men and 15% of women worldwide were obese. Thus, more than... Show moreThe prevalence of obesity, defined as a body mass index (BMI) > 30 kg/m2, is increasing to epidemic proportions. In 2014, 11% of men and 15% of women worldwide were obese. Thus, more than half a billion adults worldwide are classed as obese. The fundamental cause of obesity is an imbalance between energy intake (excessive intake of energy-dense foods) and energy expenditure (reduced physical activity). People with obesity are at risk for a range of chronic conditions including cardiovascular disease (CVD) and nonalcoholic fatty liver disease (NAFLD). Furthermore, obesity is a major risk factor for the development of type 2 diabetes, which is one of the most common chronic diseases in nearly all countries. According to the World Health Organization, the global prevalence of diabetes in 2014 was estimated to be 9%, of which 90% was comprised of type 2 diabetes. This thesis focuses on cardiovascular and cerebral dimensions and function in people with obesity and type 2 diabetes. State-of-the-art imaging techniques are used to investigate links between the heart, liver, abdominal fat, and brain to elucidate parts of the complex relationships between these organs. Show less
Duchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness caused by DMD gene mutations leading to absence of the full-length dystrophin protein in muscle. Multiple... Show moreDuchenne muscular dystrophy (DMD) is characterized by progressive muscle weakness caused by DMD gene mutations leading to absence of the full-length dystrophin protein in muscle. Multiple dystrophin isoforms are expressed in brain, but little is known about their function. DMD is associated with specific learning and behavioral disabilities which are more prominent in patients with mutations in the distal part of the DMD gene, predicted to affect expression of shorter protein isoforms. The aim of this thesis was to provide a detailed description of the structural, perfusion and metabolic differences in the brain between patients with DMD and healthy age-matched controls and to assess the role of dystrophin isoforms. Show less
In this thesis I have described the introduction and validation of a new spatially non-selective arterial spin labeling (SNS-ASL) method in healthy subjects. Acceleration selective ASL (AccASL... Show moreIn this thesis I have described the introduction and validation of a new spatially non-selective arterial spin labeling (SNS-ASL) method in healthy subjects. Acceleration selective ASL (AccASL) was compared with pseudo continuous ASL (pCASL), a traditional ASL method, as well as other spatially non-selective ASL methods (velocity selective ASL, as introduced by Wong et al with two velocity-selective blocks, and using only a single labeling module), and with [15O]-H2O PET as the gold standard for brain perfusion imaging. By combining an AccASL with VSASL labeling module, the location of label origin in the vascular tree was assessed. Furthermore, time-encoded pCASL was explored in combination with SNS-ASL labeling modules to obtain insight into labeling at multiple post labeling delays (PLD). Finally, te-pCASL was combined with T2-Relaxation-under-Spin-Tagging (TRUST) to provide a time efficient method to distinguish spin compartments based on their T2-values. Show less
The focus of this thesis was to evaluate biomarkers of cardiovascular end organ damage in the metabolic syndrome and diabetes mellitus. We performed cross-sectional studies with biochemical and... Show moreThe focus of this thesis was to evaluate biomarkers of cardiovascular end organ damage in the metabolic syndrome and diabetes mellitus. We performed cross-sectional studies with biochemical and magnetic resonance imaging (MRI) techniques. We have demonstrated that insulin resistance is a strong risk predictor for CVD and we provided a novel link between inflammation and angiopoietin-like protein 4 (ANGPTL4) expression by showing that ANGPTL4 levels in humans are related to systemic inflammation and inflammatory stimuli increased ANGPTL4 expression using human macrophages in vitro. The imaging studies described in this thesis extend the knowledge of end organ damage and explored the relation with aortic stiffness. The impact of type 1 diabetes mellitus (T1DM) on regional grey matter was investigated and showed atrophy of all subcortical grey matter structures but the amygdala. By showing an association of aortic stiffness with subtle microstructural deficits in T1DM and kidney function in patients with hypertension the close link between aortic stiffness and the microcirculation is demonstrated. Furthermore regional and individual differences in response to an oral glucose load in MR assessed aortic stiffness were observed, which may open new future research paths possibly linking inter-individual variation in regional vascular response and CVD. Show less
This dissertation examines what network in the human brain is involved in the perception of prosody and whether activity within this network is modulated by the personality trait alexithymia. The... Show moreThis dissertation examines what network in the human brain is involved in the perception of prosody and whether activity within this network is modulated by the personality trait alexithymia. The first four chapters of this dissertation reveal that a bihemispheric network consisting of Heschl__s gyrus, the middle superior temporal gyrus, the posterior superior temporal gyrus and the pars opercularis of the inferior frontal gyrus is involved in the perception of emotional prosody. Furthermore, relative right hemispheric specialization for emotional prosody perception can be demonstrated but no hemispheric specialization can be found for linguistic prosody perception. Moreover, hemispheric specialization for emotional prosody perception seems to be driven by hemispheric specialization for non-prosody-specific acoustic dimensions of the speech signal, and not for abstract emotional processing. Additionally, automaticity of processing can be demonstrated for emotional prosody, particularly for anger, but not for emotional music. Last, alexithymia can indeed be demonstrated to modulate activity within the emotional prosody perception network, particularly at relatively early components of the emotional prosody perception pathway. This dissertation is of interest to neurolinguists, (neuro-)phoneticians, psychologists, cognitive neuroscientists, comparative biologists and neurologists specialized in aphasia Show less
The results in this thesis showed for the first time doublecortin-like (DCL)-specific expression in the adult mouse brain. Besides the expected regions with the capacity to generate new neurons ... Show moreThe results in this thesis showed for the first time doublecortin-like (DCL)-specific expression in the adult mouse brain. Besides the expected regions with the capacity to generate new neurons (hippocampus and olfactory forebrain), DCL expression was found in three novel brain areas namely hypothalamic tanycytes, suprachiasmatic nucleus and Islands of Calleja. A state of the art conditional shRNA expressing mouse model was used to target DCL mRNA. The analysis of these DCL knockdown animals using qPCR and Western blot revealed strong reduction of DCL protein expression. Subsequent stereological analysis using BrdU and several stem cell and neuronal markers revealed increased progenitor proliferation, but impaired neurogenesis in the hippocampus. This impaired neurogenesis was associated, however, with an apparent normal spatial and contextual fear memory formation in circular hole board and in a contextual fear conditioning paradigm. Therefore, DCL-regulated adult neurogenesis seems not crucial for hippocampus-dependent learning. However, more subtle functions like pattern separation and context distinction might be regulated by DCL. DCL knockdown also increased D2 activity within the hypothalamus. Altogether, the DCL-KD mouse seems a good working model to study adult neurogenesis and the role of DCL in this process. Show less
When a child is often scolded or threatened by his parents (emotional abuse) and /or when a child is structurally ignored or isolated by his parents (emotional neglect) we call this childhood... Show moreWhen a child is often scolded or threatened by his parents (emotional abuse) and /or when a child is structurally ignored or isolated by his parents (emotional neglect) we call this childhood emotional maltreatment (CEM). CEM is the most common form of child abuse, however, CEM is also the most hidden, underreported and least studied form of child abuse. An important reason for this may be because that the consequences of CEM are underestimated (e.g. __Sticks and Stones may break bones, but words will never hurt me__). However, this thesis shows that CEM is related with a persistent negative impact on cognition and the brain. We discovered that individuals that report CEM show differential structure and function of a brain area (the medial prefrontal cortex) that is crucial for role in responding to stress and thinking about yourself. Individuals with CEM also showed more activity in an area that signals threat (the amygdala) which may represent a persistent vigilance towards the detection of threat from others. These brain changes may underlie our other findings that individuals with CEM think more negatively about themselves and others. Negative thoughts can evoke negative thoughts and in new situations, which reinforces more negative memories. Due to this process, emotionally abused individuals may be more vulnerable to develop a depressive and/or anxiety disorder. Our findings warrant scientific and policital investments to increase societal awareness about the detrimental impact of CEM on cognition and the brain. Increased societal knowledge will hopefully lead to better awareness, reports, and subsequent interventions for individuals with CEM. Show less
The aims of this thesis were to gain insight into specific disease processes in Huntington__s Disease (HD) and to identify biomarkers. To achieve these aims, cognitive functioning, structural brain... Show moreThe aims of this thesis were to gain insight into specific disease processes in Huntington__s Disease (HD) and to identify biomarkers. To achieve these aims, cognitive functioning, structural brain characteristics and intrinstic functional brain connectivity of premanifest and early HD subjects were examined. Cortical, subcortical and the intermediate white matter brain tissue shows evidence of structural and functional decline. We found evidence that disease processes, such as altered metabolism, excessive iron accumulation and cell loss, play a role in the changes. We conclude that changes occur throughout the brain from the earliest disease phase onwards. Hence, both premanifest and manifest HD should not be regarded as a disorder of the basal ganglia, but as a disease affecting the whole brain. Candidate biomarkers that have the potential to objectively reflect the early changes and the progressive nature of the disease are measures of subcortical atrophy, integrity of white matter pathways and of intrinsic functional brain connectivity. Iron, creatine, and N-acetylaspartate concentrations in the caudate nucleus and putamen may prove to be useful as markers of disease state for objectifying transitional disease processes from premanifest to manifest HD. Visuospatial working memory could be applied as a state marker for stage two HD. Show less
The aim of this thesis was to find potential MRI biomarkers for Huntington__s disease (HD). Therefore, after an overview of the current literature on MRI biomarkers, followed by examinations of... Show moreThe aim of this thesis was to find potential MRI biomarkers for Huntington__s disease (HD). Therefore, after an overview of the current literature on MRI biomarkers, followed by examinations of volumetric MRI, magnetization transfer imaging (MTI), diffusion tensor imaging (DTI) and magnetic resonance spectroscopy (MRS) were applied in patients in different disease stages of HD. The main conclusions demonstrate that choosing the optimal biomarker for evaluating therapeutic effects is dependent on the disease stage and therapeutic compound. To evaluate the premanifest stages of the disease volumetric MRI and DTI are most suitable. When the transition period is the desired timeframe for evaluation, also MRS can be very useful, especially if the compound in question has a direct potential influence on certain pathogenic pathways which in turn have an impact on specific metabolites. Future research should focus on combining multiple imaging techniques; __multimodal imaging__. A composite MRI biomarker has the potential to distinguish between disease groups more accurately than a single biomarker and in this way improve the evaluation of therapeutic compounds. Show less
Synthetic glucocorticoids such as dexamethasone are frequently used to enhance pulmonary development in preterm ventilator-dependent infants. In contrast to the short-term benefit on survival and... Show moreSynthetic glucocorticoids such as dexamethasone are frequently used to enhance pulmonary development in preterm ventilator-dependent infants. In contrast to the short-term benefit on survival and lung maturation, early glucocorticoid exposure has been shown to adversely affect neurodevelopmental processes. Both human and animal studies have reported acute and long-lasting impairments, including shortening of the lifespan in rodents. Therefore, the objective of the studies described in this thesis was to investigate, using an animal model: 1) the short- and long-term consequences of neonatal dexamethasone treatment and 2) the possibility to prevent these effects using pharmacological and behavioural intervention strategies. We reported that systemic dexamethasone treatment acutely affects brain development by suppressing cell proliferation and glial activity. These acute effects on the brain can be partially prevented by central glucocorticoid receptor antagonist pre-treatment, which might serve as a protective strategy against the adverse effects of dexamethasone treatment on the developing brain. Although neonatal dexamethasone exposure clearly affects the developmental trajectory, we did not observe the frequently described detrimental long-lasting consequences of this treatment. We showed that daily handling of the neonate, which was an inevitable component of our experimental design and leads to enhanced levels of maternal care towards the offspring, may compensate for some of the adverse effects of dexamethasone treatment. We conclude that the impact of neonatal glucocorticoid exposure highly depends on interactions with other components of the early environment and is therefore susceptible to pharmacological and behavioural intervention strategies. Show less
Infants born very prematurely (gestational age <32 weeks) are at risk of brain injury and neurodevelopmental problems. Imaging the preterm infant__s brain during the neonatal period, using... Show moreInfants born very prematurely (gestational age <32 weeks) are at risk of brain injury and neurodevelopmental problems. Imaging the preterm infant__s brain during the neonatal period, using cranial ultrasonography (cUS) and magnetic resonance imaging (MRI), is important. Our aim was to study and describe brain findings in very preterm infants using modern, high-quality imaging techniques. Part I reviews brain maturation and injury, and imaging thereof, in very preterm infants. Part II discusses our experience on neonatal cUS (Chapters 2-3) and MRI (Chapter 4), and addresses indications, technical aspects, protocols and safety. Part III gives an overview of findings (incidence and evolution) on frequent, sequential neonatal cUS and term-equivalent MRI (Chapter 5), and their relation with perinatal factors (Chapter 6). Part IV focuses on imaging of white matter (Chapters 7-9), describing both normal maturational phenomena and pathological changes and assessing the accuracy of cUS and MRI for these changes. Part V focuses on imaging of deep grey matter (Chapters 10-12), describing both normal maturational phenomena and pathological changes on cUS and assessing their relation with clinical and MRI findings. Part VI reviews the main findings and conclusions of this thesis, and discusses future perspectives and proposals for further research (Chapter 13). Show less
The thesis describes the application of several different magnetic resonance (MR) techniques to study the effects of the progression of disease in a transgenic mouse model of Alzheimer's. Using MR... Show moreThe thesis describes the application of several different magnetic resonance (MR) techniques to study the effects of the progression of disease in a transgenic mouse model of Alzheimer's. Using MR imaging, the amyloid plaque deposition was visualized and the plaque load quantified in the same mice as they aged. Concurrently the transverse relaxation time (T2) was measured in affected brain regions and shown to decrease over time as plaque-load increased. To study the neurochemical profile in the mouse brain brain both one- (1D) and two-dimensional (2D) MR spectroscopic techniques were employed. 1D MRS is widely used in similar research, but has limited spectral resolution. To overcome this limitation, a 2D MRS technique was implemented and optimized for use in mouse brain. This technique, L-COSY, allowed the detection of several metabolites which were not visible using standard 1D MRS techniques. This technique was subsequently used to study the effects of Alzheimer's on the neurochemical profile. Observed changes were correlated with plaque deposition. Show less
Currently, the raising awareness of the role of glucocorticoids in the onset of numerous (neuro)-pathologies constitutes the increasing necessity of understanding the mechanisms of action of... Show moreCurrently, the raising awareness of the role of glucocorticoids in the onset of numerous (neuro)-pathologies constitutes the increasing necessity of understanding the mechanisms of action of glucocorticoids in bodily processes and brain functioning. Glucocorticoids mediate their effects by binding to intracellular receptors which act as transcription factors. A remarkable and yet unexplained phenomenon described more than two decades ago, is the cell-specific effects glucocorticoids bring about on gene expression in brain. For example, while glucocorticoids suppress corticotrophin-releasing hormone (CRH) synthesis in the hypothalamus, production of CRH in the central nucleus of the amygdala (CeA) is stimulated by increased hormone levels. Inasmuch as the neuroanatomical distribution of the corticosteroid receptors does not satisfactorily explain these effects, it is of interest to decipher the role of recently discovered coregu lator proteins that modulate the direction and the magnitude of steroid receptor-driven transcription. Therefore, in the current thesis the expression and function of central coregulators was studied: the coactivators SRC1a and SRC1e along with the corepressors N-CoR and SMRT were found to be expressed in brain and involved in regulation of CRH gene expression. Finally, a method that allows detection of coregulator recruitment by steroid receptors in brain tissue was developed. Show less
Not everyone who experiments with cocaine acquires compulsive drug use. The mechanism underlying this individual difference in susceptibility to addiction is poorly understood. Recent studies have... Show moreNot everyone who experiments with cocaine acquires compulsive drug use. The mechanism underlying this individual difference in susceptibility to addiction is poorly understood. Recent studies have identified genes and adverse life events (stress) as risk factors. The objective of this thesis is to investigate the contribution of the adrenal stress hormones glucocorticoids and epinephrine to the psychostimulant effects of cocaine in the inbred DBA/2 and C57BL/6 mouse strains. Behavioural sensitisation, measured as an enhanced locomotor response to repeated cocaine exposure, was used as a model for the long-term neural adaptations underlying aspects of drug addiction. The results demonstrate that adrenal hormones play a critical role in cocaine sensitivity, which depends on genetic background because surgical removal of the adrenals (__adrenalectomy__) prevented cocaine sensitisation in DBA/2, but not C57BL/6 mice. The impact of genetic background was further emphasised by strain-specific changes in the midbrain dopamine system that mediates the rewarding effects of drugs. The effects of adrenalectomy could only be fully reversed by co-administration of glucocorticoids and epinephrine. These findings show that, depending on genetic background, adrenal stress hormones are important risk factors for vulnerability to cocaine, suggesting that pharmacological intervention in stress hormone action has therapeutic potential in drug addiction. Show less
