Many common disorders, including depression, dementia and obesity are for a large part heritable. Despite the fact that genome-wide association studies (GWAS) have contributed substantially to... Show moreMany common disorders, including depression, dementia and obesity are for a large part heritable. Despite the fact that genome-wide association studies (GWAS) have contributed substantially to unraveling the genetic architecture of these polygenetic disorders, a large amount of ‘missing heritability’ remains. A possible explanation is that GWAS, aside single-nucleotide polymorphisms cannot assess the contribution of other important genetic polymorphisms, especially tandem repeats. Tandem repeats constitute 3% of the human genome. Nine hereditary neurodegenerative diseases, known as polyglutamine diseases, including Huntington disease (HD), are the most prevalent disorders associated with tandem repeat variations. These diseases are caused by an elongated cytosine-adenine-guanine (CAG) repeat sequence in the respective polyglutamine disease-associated gene (PDAG). In this dissertation, we provide ample evidence that CAG repeat variations within the ‘normal’ range in PDAGs can affect various aspects of disease, including the age of onset in HD, cognitive function, depression and body mass index. Finally, we found a relatively large prevalence of intermediate and pathological PDAG alleles in the general population. Therefore, we provided support for the role of repetitive DNA polymorphisms in elucidating the ‘missing heritability’ of polygenetic disorders and emphasized the necessity to include these variations in future genetic research. Show less
Cerebrovascular changes, including reduced cerebral blood flow (CBF), occur early in the development of Alzheimer disease and may accelerate disease progression. This randomized, double-blind,... Show moreCerebrovascular changes, including reduced cerebral blood flow (CBF), occur early in the development of Alzheimer disease and may accelerate disease progression. This randomized, double-blind, placebo-controlled study investigated how 6 months of treatment with the calcium antagonist nilvadipine would affect CBF in patients with mild-to-moderate Alzheimer disease. CBF was measured with magnetic resonance arterial spin labeling in whole-brain gray matter and in a priori defined regions of interest including the hippocampus. Fifty-eight patients were randomly assigned (29 in each group), of whom 22 in both groups had no magnetic resonance exclusion criteria and were medication compliant over 6 months. Mean age was 72.8 +/- 6.2 years, mean mini-mental state examination was 20.4 +/- 3.4. Nilvadipine treatment lowered systolic blood pressure (Delta=-11.5 [95% CI, -19.7 to -3.2] mm Hg; P<0.01), while whole-brain gray-matter CBF remained stable (Delta=5.4 [95% CI, -6.4 to 17.2] mL/100 g per minute; P=0.36). CBF in the hippocampus increased (left: Delta=24.4 [95% CI, 4.3-44.5] mL/100 g per minute; P=0.02; right: Delta=20.1 [95% CI, -0.6 to 40.8] mL/100 g per minute; P=0.06). There was no significant change in CBF in the posterior cingulate cortex (Delta=5.2 [95% CI, -16.5 to 27.0] mL/100 g per minute; P=0.63) or other regions of interest. In conclusion, nilvadipine reduced blood pressure and increased CBF in the hippocampus, whereas other regions showed stable or small nonsignificant increases in CBF. These findings not only indicate preserved cerebral autoregulation in Alzheimer disease but also point toward beneficial cerebrovascular effects of antihypertensive treatment. Show less
Mahinrad, S.; Bulk, M.; Velpen, I. van der; Mahfouz, A.; Roon-Mom, W. van; Fedarko, N.; ... ; Weerd, L. van der 2018
