This thesis describes the effects of shortterm fasting on chemotherapy outcome in patients with breast cancer and the IGF-1 and insulin pathway as a target for cancer therapy and as a biomarker for... Show moreThis thesis describes the effects of shortterm fasting on chemotherapy outcome in patients with breast cancer and the IGF-1 and insulin pathway as a target for cancer therapy and as a biomarker for chemotherapy outcome.Preclinical research is evaluated, which shows that short-term fasting during chemotherapy is effective. The effects of short-term fasting in humans is not evident yet. Although the first small clinical studies of short-term fasting as adjunct to chemotherapy are promising in terms of decreased toxicity and enhanced efficacy, the exact mechanism and effects are not established yet. More studies and a longer follow-up are needed to prove this.Insulin-like growth factor 1 (IGF-1) and insulin are members of the IGF-1 pathway, which is involved in cell growth and proliferation. The effects of the IGF-1 pathway on chemotherapy outcome and the pathway itself as target for cancer therapy are described. The disappointing results of clinical studies of IGF-1R inhibitors may be caused by the complexity of the IGF-1R pathway. Lowering both insulin and IGF-1, perhaps with a short-term fasting intervention, serves as a possible target in cancer therapy. Show less
Type 1 diabetes (T1D) results from the immune-mediated destruction of the insulin-producing beta cells. Genetic predisposition, impaired immune regulation, and beta cell (dys)function all... Show moreType 1 diabetes (T1D) results from the immune-mediated destruction of the insulin-producing beta cells. Genetic predisposition, impaired immune regulation, and beta cell (dys)function all contribute to disease initiation and progression. A critical gap in our knowledge is what causes the break in peripheral tolerance that eventually leads to beta cell destruction. We propose that neoepitopes generated by dysfunctional beta cells activate immune surveillance, causing beta cell autoimmunity. ER stress imposed both by intrinsic beta cell physiology and by external secondary triggers seems to be a crucial component in this process. Understanding the molecular mechanisms underlying beta cell dysfunction and neoantigen generation is critical to identify clinically relevant neoepitopes. This subsequently provides more insight in the disease dynamics as well as contribute to translational research in the development of biomarker assays and development of therapeutic strategies targeting autoreactive T-cells and beta cell function. Our task will be to restore the balance between immune reactivity and beta cell function, in order to prevent, treat, or cure type 1 diabetes. Show less
Metabolic disease has become pandemic in the developed world. Given our lack of understanding of its molecular pathology, we are often unable to diagnose patients before they reach an... Show moreMetabolic disease has become pandemic in the developed world. Given our lack of understanding of its molecular pathology, we are often unable to diagnose patients before they reach an irreversible state of diabetes or cardiovascular disease. Much research has been done on the role of insulin signaling in metabolic disease, as well as the resultant disturbed lipid homeostasis present in cardiovascular disease and atherosclerosis. Here we add to existing work by developing new tools and sketching out the pathology of dysregulated adipose insulin signaling. We discuss the mechanism of lipodystrophy by using adipocytes differentiated from patient-derived iPSCs. These cells mimic the clinical phenotype and hint at mechanism that reduced patients’ adipose tissue mass. In mice we find that if we knock out the adipose insulin receptor, there is disrupted adipose and liver metabolism. There is a protection from diet-induced obesity, but a dramatically reduced lifespan. We also establish a relationship between obesity and inflammation by transcriptomically assessing obese human adipocytes. We find that an immune factor is responsible for lipid droplet formation and content. Lastly, we develop a new differentiation and purification strategy for iPSC-derived hepatocytes, which we employ to in vitro model a SNP that protects against cardiovascular disease. Show less
Weighing the strengths and limitations of our studies, we believe our results contribute to the unraveling of causal pathways between obesity and lung function impairment. The main conclusion of... Show moreWeighing the strengths and limitations of our studies, we believe our results contribute to the unraveling of causal pathways between obesity and lung function impairment. The main conclusion of the first part of this thesis is that visceral fat is associated with lung function impairment in men with the metabolic syndrome. Furthermore, we conclude that in the general population there is no causal association between insulin resistance and lung function, nor an association between visceral fat and exhaled nitric oxide. In the second part of this thesis we showed that vitamin D is associated with lung function and nitric oxide in obese participants.In the study presented in this thesis antimicrobial peptides levels were lower in allergic asthmatics than in healthy controls. Unfortunately, we were not able to conclude if vitamin D supplementation influences these antimicrobial peptide levels. Larger studies are needed to investigate whether vitamin D also increases antimicrobial peptides in the lung.In summary, obesity is a global burden that influences lung function. Future research should reveal if obesity, and in particular visceral fat, causes lung inflammation and thereby impairs lung function.Large randomized trials are necessary to establish the effect of vitamin D therapy on infections in vitamin deficient patients. Show less
Although mortality in old age has significantly decreased over the last fifty years in the developed world, there still remains a large inter-individual variability in ageing trajectories,... Show more Although mortality in old age has significantly decreased over the last fifty years in the developed world, there still remains a large inter-individual variability in ageing trajectories, morbidity and mortality. In the three parts of this thesis, we examined three interacting systems that have been identified as contributing to a slower pace of ageing, namely glucose/insulin metabolism (part I), the thyroid axis (part II), and the autonomic nervous system (part III). We found that familial longevity is associated with a stronger association of insulin parameters with microstructural brain parameters, and by higher TSH secretion, in the absence of differences in basal energy metabolism or differences in heart rate and its variability. Using specialized MRI techniques, we showed that subtle changes in microstructural brain parenchymal homogeneity in relation to insulin can be detected, even in brain tissue that appears normal on conventional MR imaging sequences. Insulin (rather than glucose), seemed to be a stronger indicator of micro- structural brain integrity in normo-glycemic older adults. Furthermore, intranasal application of insulin improved brain perfusion in parietal and occipital gray matter and in the thalamus of older adults. These results deepen our understanding of the physiological mechanisms and processes that underlie the ageing process. Show less
The aim of this thesis was to gain further insight into the role of glucagon in glucose homeostasis in healthy volunteers and type 2 diabetes mellitus (T2DM) patients, and to explore the novel... Show moreThe aim of this thesis was to gain further insight into the role of glucagon in glucose homeostasis in healthy volunteers and type 2 diabetes mellitus (T2DM) patients, and to explore the novel antisense glucagon receptor antagonist. Chapter 2 showed that the effect of meal replacers containing protein hydrolysate on plasma glucose lowering is limited in T2DM patients due to a collective increase of both insulin and glucagon levels. In chapter 3 and 4 a glucagon challenge test in healthy volunteers and T2DM was studied and showed a good reproducibility and no confounding changes in autonomic nervous system tone. T2DM patients respond profoundly different to a glucagon challenge test compared to healthy volunteers and the response to a glucagon challenge test in T2DM subjects is influenced by the type of therapy. Chapter 5 provided the first proof of pharmacology of a novel antisense glucagon receptor antagonist in humans, ISIS 325568, as reflected by a reduction in glucagon-induced glucose excursion by using a well-characterized glucagon challenge test. In chapter 6 we designed a semi-mechanistic model which simultaneously describes glucagon, plasma glucose, insulin and glucagon receptor internalization using data from glucagon challenges in healthy volunteers. Show less
Neonatal health care is provided with medication and protocols for almost all morbidities. Before the use of these medicines is allowed, they are extensively studied and tested for efficacy and... Show moreNeonatal health care is provided with medication and protocols for almost all morbidities. Before the use of these medicines is allowed, they are extensively studied and tested for efficacy and safety. As patient population and knowledge on specific diseases changes with time, repeated evaluation of efficacy and safety of current used policies is of paramount importance. In this thesis six __Neonatal Pearls__ are presented: six relatively rare clinical conditions, of which a retrospective study evaluates the efficacy, safety and/or long term consequences of the current protocol. Despite their retrospective design and relatively small sample size, they are all of significant value and may serve as potential foundations for future protocol adjustments and randomized controlled trials. The evaluated clinical conditions and policies include: -Fetal, neonatal and developmental outcomes of lithium exposed pregnancies -Neonatal outcome in allo-immune thrombocytopenia after maternal treatment with antenatal intravenous immunoglobulin - Repeated courses of ibuprofen for closure of a patent ductus arteriosus - Use of rifampin in persistent coagulase negative staphylococcal bacteremia in neonates - Outcome and management in neonatal thrombocytopenia due to maternal idiopathic thrombocytopenic purpura - Short and long term outcome of neonatal hyperglycemia in very preterm infants Show less
This thesis describes the role of the brain in the regulation of peripheral triglyceride metabolism, in the context of the metabolic syndrome. Based on various pharmacological studies we described... Show moreThis thesis describes the role of the brain in the regulation of peripheral triglyceride metabolism, in the context of the metabolic syndrome. Based on various pharmacological studies we described the role of two hormones, insulin and glucagon-like peptide-1, in the production and clearance of triglycerides. We showed that insulin stimulates the uptake of (triglyceride-derived) fatty acids and that the brain plays an essential role in this process. Additionally, we showed that the glucagon-like peptide-1 receptor analogue exendin-4 decreases triglyceride production by the liver, albeit that the brain does not seem to be involved in this effect. Furthermore, we unraveled the mechanism underlying the effects of metformin, the first-line drug used to treat Type 2 Diabetes, on triglyceride metabolism. We showed that metformin lowers plasma triglyceride levels by stimulating the uptake and subsequent oxidation of triglycerides by the brown adipose tissue, and herewith provided new therapeutical opportunities for this drug. Finally, we showed that apolipoprotein A5, a stimulator of triglyceride hydrolysis and subsequent clearance from the plasma, plays a role in the central regulation of food intake, and herewith described a novel function for this apolipoprotein. Show less
The studies in this thesis contribute to the understanding of the role of the brain in insulin sensitivity. We demonstrate that disturbances in circadian rhythm resulting in alterations in SCN... Show moreThe studies in this thesis contribute to the understanding of the role of the brain in insulin sensitivity. We demonstrate that disturbances in circadian rhythm resulting in alterations in SCN output, can contribute to the development of insulin resistance. We also shown that insulin-stimulated glucose uptake by muscle and insulin-stimulated FA uptake by WAT is in part dependent on insulin action in the brain. These effects of circulating insulin on peripheral organs via the brain are abrogated by high-fat diet. These brain-dependent effects of insulin could reflect a similar situation for other hormones, for instance thyroid hormones. Furthermore, we demonstrate that topiramate improves insulin resistance by restoring insulin sensitivity in the brain, suggesting that therapeutical targets in the brain may offer challenging new approaches to treat insulin resistance of peripheral organs in T2DM. Show less
This thesis discusses the metabolic and endocrine characteristics of long-lived Dutch families. We found that familial longevity is marked by low thyroid function and preserved insulin senitivity.... Show moreThis thesis discusses the metabolic and endocrine characteristics of long-lived Dutch families. We found that familial longevity is marked by low thyroid function and preserved insulin senitivity. The second part of this thesis adresses the Gompertz law of mortality as an estimate of the rate of senescence Show less
The research on 3T3-L1 adipocytes described in this thesis demonstrates how two different types of cellular stress inducing agents, namely the vicinal thiol binding agent arsenite and the... Show moreThe research on 3T3-L1 adipocytes described in this thesis demonstrates how two different types of cellular stress inducing agents, namely the vicinal thiol binding agent arsenite and the conventional PKC-binding and -activating agent PMA act to increase glucose uptake in these cells. Whereas arsenite uses mainly the insulin-responsive GLUT4 transporter, PMA increases basal glucose transport through the GLUT1 transporter. As described in Chapter 3, arsenite-induced glucose uptake illustrates several requirements needed by any agent acting through GLUT4. These are, a tyrosine kinase activity, p38 MAPK activation and PKC-\lambda activity. Though PI-3' kinase activation is an essential step in insulin-signalling, this step is not required for arsenite-induced glucose uptake. Apparently, the need for tyrosine-kinase activity in arsenite induced glucose uptake resides in the ability to tyrosine-phosphorylate Cbl (see Chapter 3 Fig. 5). A further illustration of the importance of Cbl-tyrosine phosphorylation comes from our studies on rottlerin (Chapter 4). The ATP-depletion mediated by this pharmacological compound does not seem to be responsible for the observed inhibition of GLUT4 translocation (as was postulated by Kayali et al.[1]). Rather, aside from acting as an uncompetitive inhibitor of GLUT4, rottlerin hampers Cbl tyrosine phosphorylation, which leads to a 75% reduction in GLUT4 translocation (see Chapter 4, Fig. 3 and 4). Regrettably, the nature of the arsenite-induced tyrosine-kinase activity remains as of yet unidentified. Though the specific ability of arsenite to induce STAT5a tyrosine-phosphorylation in the mature adipocyte, should provide a straightforward tool to enable its identification (J.L Gonz_lez-Galindo, unpublished observations) Previously it had been demonstrated that insulin-induced p38 MAPK was involved in regulating the amount of glucose taken up by the cell without affecting GLUT4 translocation, suggesting some kind of intrinsic effect on the GLUT4 transporter itself [2]. Our observations on arsenite, a potent activator of p38 MAPK, illustrate a similar phenomenon in GLUT4-mediated stress-induced glucose uptake (see Chapter 3, Fig. 6). Subsequent research, described in a recently submitted manuscript, provides a detailed analysis of the involvement of p38 MAPK. These data demonstrate that p38 MAPK is involved in fine-tuning glucose uptake by regulating the turnover capacity of the GLUT4 transporter. A further note on the fine tuning of GLUT4-mediated glucose uptake comes from the observations on genistein, described in Chapter 5. This research suggests that in GLUT4 the turnover capacity for glucose can also be regulated through an intracellular ATP-binding Walker B motif akin to that described for GLUT1 [3]. Though further research is required to elucidate this mechanism, this theoretical resolution constitutes a significant step forwards towards understanding mechanisms in action after GLUT4 membrane translocation. If these observations are mechanistically linked in the cell remains to be elucidated. Aside from leading to enquiries into the mechanisms of insulin-induced glucose uptake, arsenite also opened up an avenue of more physiological research. We observed that arsenite-induced glucose uptake was sensitive to treatment with the insulin-resistance inducing agent dexamethasone. Subsequent analysis (described in Chapter 7) learned that although PI-3' kinase signalling is affected, in 3T3-L1 adipocytes the signalling pathway downstream is able to absorb this impediment. Rather, MKP-1 and -4 are upregulated in response to dexamethasone. Consequentially p38 MAPK activity is lost, leading to a reduction in glucose uptake. Given that MKP-4 is also upregulated in db/db- and ob/ob-mice [4], and that treatment of db/db mice with a glucocorticoid-receptor antagonist improves blood glucose levels [5;6], attenuation of p38 MAPK-signalling could be an important factor in type II diabetes. To enable the studies described in this chapter, a novel tool had to be developed. 3T3-L1 adipocytes have for long been inaccessible to ectopic expression of DNA. By the application of Lentivirus as described in Chapter 6, a large number of cells can be efficiently and reliably transduced. This novel tool will make the 3T3-L1 adipocyte readily amendable to routine molecular biological techniques, which will be of great benefit to the research field. In contrast to arsenite, PMA does not induce GLUT4 translocation, but acts solely through GLUT1. As illustrated in Chapter 8 of this thesis, in 3T3-L1 adipocytes the earliest and most PMA-sensitive PKC isoform is PKC-\betaII. But rather than activation, it is the concomitant degradation of this isoform which induces GLUT1 translocation. Further research (described in Chapter 9) highlighted the processes involved : First transcription of GLUT1, operating through the classical PKC-ERK-GLUT1 pathway. Second, translocation of GLUT1. This translocation is mediated by PKC-\lambda which is found associated with PKC-\betaII in the basal state. Thus upon degradation of the \betaII-isoform (or disruption of this complex by treatment with myristoylated pseudo-substrate peptides against \betaII) PKC-\lambda is released and free to act as a positional queue inducing translocation of the GLUT1 containing vesicles. Show less
