Aims/hypothesis Characterisation of genetic variation that influences the response to glucose-lowering medications is instrumental to precision medicine for treatment of type 2 diabetes. The Study... Show moreAims/hypothesis Characterisation of genetic variation that influences the response to glucose-lowering medications is instrumental to precision medicine for treatment of type 2 diabetes. The Study to Understand the Genetics of the Acute Response to Metformin and Glipizide in Humans (SUGAR-MGH) examined the acute response to metformin and glipizide in order to identify new pharmacogenetic associations for the response to common glucose-lowering medications in individuals at risk of type 2 diabetes.Methods One thousand participants at risk for type 2 diabetes from diverse ancestries underwent sequential glipizide and metformin challenges. A genome-wide association study was performed using the Illumina Multi-Ethnic Genotyping Array. Imputation was performed with the TOPMed reference panel. Multiple linear regression using an additive model tested for association between genetic variants and primary endpoints of drug response. In a more focused analysis, we evaluated the influence of 804 unique type 2 diabetes- and glycaemic trait-associated variants on SUGAR-MGH outcomes and performed colocalisation analyses to identify shared genetic signals.Results Five genome-wide significant variants were associated with metformin or glipizide response. The strongest association was between an African ancestry-specific variant (minor allele frequency [MAF(Afr)]=0.0283) at rs149403252 and lower fasting glucose at Visit 2 following metformin (p=1.9x10(-9)); carriers were found to have a 0.94 mmol/l larger decrease in fasting glucose. rs111770298, another African ancestry-specific variant (MAF(Afr)=0.0536), was associated with a reduced response to metformin (p=2.4x10(-8)), where carriers had a 0.29 mmol/l increase in fasting glucose compared with non-carriers, who experienced a 0.15 mmol/l decrease. This finding was validated in the Diabetes Prevention Program, where rs111770298 was associated with a worse glycaemic response to metformin: heterozygous carriers had an increase in HbA(1c) of 0.08% and non-carriers had an HbA(1c) increase of 0.01% after 1 year of treatment (p=3.3x10(-3)). We also identified associations between type 2 diabetes-associated variants and glycaemic response, including the type 2 diabetes-protective C allele of rs703972 near ZMIZ1 and increased levels of active glucagon-like peptide 1 (GLP-1) (p=1.6x10(-5)), supporting the role of alterations in incretin levels in type 2 diabetes pathophysiology.Conclusions/interpretation We present a well-phenotyped, densely genotyped, multi-ancestry resource to study gene-drug interactions, uncover novel variation associated with response to common glucose-lowering medications and provide insight into mechanisms of action of type 2 diabetes-related variation. Show less
Stroke is one of the leading causes of disability and death worldwide. Prevention of stroke is therefore essential. Effective prevention should be tailored to the clinical characteristics,... Show moreStroke is one of the leading causes of disability and death worldwide. Prevention of stroke is therefore essential. Effective prevention should be tailored to the clinical characteristics, lifestyle, and environment of the individual, among others. This is also known as precision prevention. An important example illustrating the need for precision prevention is the existence of sex differences in stroke occurrence. In practice, for predicting stroke risk, only traditional risk factors (such as smoking and hypertension) are included, and women-specific risk factors are not yet routinely included. As a result, women with an increased risk of stroke may be missed, which also prevents timely initiation of preventive treatments. In this thesis, I tried to lay the foundation for precision prevention of stroke in women.Part I discussed the pathophysiology underlying women-specific risk factors for stroke, and gender differences in the clinical presentation of stroke. I found that the mechanisms underlying the relationship between women-specific risk factors and stroke, in particular the relationship between migraine and cerebral infarctions, seem to be particularly significant in the childbearing phase of life.In Part II, I described how health data from the EHR can be used to develop prediction models for the risk of myocardial infarction or stroke specifically for women under 50 years of age, and found that women-specific risk factors can add value in the predictions. However, there is still a long way to go to actually implement these models in practice, such as testing them on new datasets, and complying with current laws and regulations for safe application. Show less
Myasthenia Gravis (MG) is a chronic autoimmune disease affecting the neuromuscular junction. Although a hallmark of MG is muscle fatigability due to dysfunction of the neuromuscular junction ... Show moreMyasthenia Gravis (MG) is a chronic autoimmune disease affecting the neuromuscular junction. Although a hallmark of MG is muscle fatigability due to dysfunction of the neuromuscular junction (peripheral fatigue), a large number of MG patients also report symptoms of central fatigue, defined as an experienced lack of energy, physically and/or mentally. We systematically reviewed the literature on all aspects of central fatigue in MG. Results were categorized in 5 domains: prevalence, diagnosis, pathophysiology, treatment or impact. The prevalence of patient-reported fatigue varies between 42 and 82%, which is significantly higher than in control subjects. Fatigue severity is usually assessed with standardized questionnaires, but the choice of questionnaire varies widely between studies. The pathophysiology of fatigue is unknown, but it is strongly associated with depressive symptoms, female gender and disease severity. Fatigue is also highly prevalent in ocular MG and patients in remission, suggesting a multifactorial origin. Fatigued MG patients have a lower quality of life. Pharmacological treatment of MG is associated with improvement of fatigue and promising results have been found with physical and psychological training programs. Fatigue is a highly prevalent symptom of MG with a severe negative impact on quality of life. Physicians treating patients with MG should be aware of this symptom, as it may be treatable with physical or psychological training programs. (c) 2020 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license. ( http://creativecommons.org/licenses/by/4.0/ ) Show less
Muscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disease that is hallmarked by fatigable muscle weakness of in particular the cranial and bulbar muscles. The... Show moreMuscle-specific kinase (MuSK) myasthenia gravis (MG) is a neuromuscular autoimmune disease that is hallmarked by fatigable muscle weakness of in particular the cranial and bulbar muscles. The disease is caused by auto-antibodies binding MuSK on the post-synaptic muscle membrane. MuSK orchestrates formation, differentiation and maintenance of neuromuscular synapses. The research outlined in this thesis aimed at identifying the pathomechanism of MuSK MG. In passive transfer studies with immune incompetent mice we showed that IgG4 subclass antibodies from these patients exclusively induced myasthenia. We furthermore showed that anti-MuSK IgG4 causes the disease by inhibiting MuSK-Lrp4 interaction which results in loss of acetylcholine receptor clustering and synaptic disassembly. Our retrospective longitudinal study in 53 patients from three different cohorts identified the N-terminal Ig-like domain of MuSK as the main immunogenic region of the protein and showed that titers against this domain correlate with disease severity. Epitope patterns did not correlate with sensitivity to acetylcholine esterase inhibitors. Lastly we observed that, next to MuSK MG, 12 other antibody-mediated autoimmune diseases are hallmarked by predominant involvement of IgG4 antibodies. As IgG4 antibody-mediated autoimmune diseases differ in several aspects from other autoimmune disease they might form a new niche in antibody-mediated autoimmune diseases Show less
Preeclampsia is a complication of pregnancy which can suddenly change from a relatively mild phenotype into a life-threatening situation. One of the organs that is always involved during... Show morePreeclampsia is a complication of pregnancy which can suddenly change from a relatively mild phenotype into a life-threatening situation. One of the organs that is always involved during preeclampsia is the kidney. The placenta plays an important role in the renal pathophysiology of preeclampsia. The placenta produces excessive amounts of anti-angiogenic factors which are associated with systemic endothelial dysfunction. Although the underlying mechanisms of renal injury during preeclampsia remain unclear, women with preeclampsia have an increased risk of developing renal disease later in life. This observation suggests that preeclampsia __marks__ the mother__putatively in combination with pre-existent conditions__which might contribute to serious sequel throughout her life. Show less
Thrombotic thrombocytopenic purpura (TTP) is a rare, life-threatening disease characterized by acute episodes of widespread thrombosis in capillaries and small arteries. The discovery that the... Show moreThrombotic thrombocytopenic purpura (TTP) is a rare, life-threatening disease characterized by acute episodes of widespread thrombosis in capillaries and small arteries. The discovery that the plasmatic activity of the von Willebrand factor cleaving protease, ADAMTS13, is severely deficient in patients with TTP represented a turning point in the understanding of the pathophysiology of the disease. In spite of recent advances, the clinical course of TTP is characterized by considerable heterogeneity, the causes of which are largely unknown. Herein, we present a number of studies investigating the determinants of clinical heterogeneity in patients with both congenital and acquired forms of TTP. A __two-hit__ model of the pathophysiology of TTP is presented. Show less
This thesis investigated the association between several genetic factors and autoantibodies and the development of undifferentiated arthritis (UA) and rheumatoid arthritits (RA). Second, this... Show moreThis thesis investigated the association between several genetic factors and autoantibodies and the development of undifferentiated arthritis (UA) and rheumatoid arthritits (RA). Second, this thesis described a prediction model that estimates the chance to progress from UA to RA. The most important genetic risk factor for RA are the HLA-Class II alleles that encode for a common amino acid sequence, called the ‘Shared Epitope’. Investigating the progression to RA from UA revealed that the HLA-Shared Epitope alleles are not primarily a risk factor for RA but for the presence of anti-CCP antibodies, that are known to be specific for RA. Smoking in the presence of HLA-Shared Epitope alleles particularly increased the risk on anti-CCP-positive RA.. The HLA-DR3 alleles were associated with anti-CCP-negative RA. The presence of HLA-alleles encoding for D70ERAA correlated with a lower risk on RA and a less severe disease course. The presence of the PTPTN22 T-allele conferred an increased risk for both UA and RA. The knowledge on risk factors for RA-development was translated in a model that estimates the chance to progress to RA in patients that present with UA by using 9 clinical variables. The discriminative ability was high and this model allows individualized treatment decisions in UA. Show less
