P. Meijer

The Netherlands twin register biobank: A resource for genetic epidemiological studies

In 2004 the Netherlands Twin Register (NTR) started a large scale biological sample collection in twin families to create a resource for genetic studies on health, lifestyle and personality. Between January 2004 and July 2008, adult participants from NTR research projects were invited into the study. During a home visit between 7:00 and 10:00 am, fasting blood and morning urine samples were collected. Fertile women were bled on day 2-4 of the menstrual cycle, or in their pill-free week. Biological samples were collected for DNA isolation, gene expression studies, creation of cell lines and for biomarker assessment. At the time of blood sampling, additional phenotypic information concerning health, medication use, body composition and smoking was collected. Of the participants contacted, 69% participated. Blood and urine samples were collected in 9,530 participants (63% female, average age 44.4 (SD 15.5) years) from 3,477 families. Lipid profile, glucose, insulin, HbA1c, haematology, CRP, fibrinogen, liver enzymes and creatinine have been assessed. Longitudinal survey data on health, personality and lifestyle are currently available for 90% of all participants. Genome-wide SNP data are available for 3,524 participants, with additional genotyping ongoing. The NTR biobank, combined with the extensive phenotypic information available within the NTR, provides a valuable resource for the study of genetic determinants of individual differences in mental and physical health. It offers opportunities for DNA-based and gene expression studies as well as for future metabolomic and proteomic projects.

Coagulation and Fibrinolysis Markers and Risk of Dementia

We performed a cross-sectional case-control study among 277 subjects with dementia and 298 control subjects drawn from participants of the Rotterdam Study, a population-based cohort study among subjects aged 55 years or over, and from participants of the Rotterdam Stroke Databank, a hospital-based stroke registry, with the objective to evaluate the association of indicators of coagulability, fibrinogen, prothrombin fragments 1+2, thrombin-antithrombin complex (TAT), and indicators of fibrinolysis, plasmin-inhibitor complex, D-dimer and tissue-type plasminogen activator (t-PA) with dementia. Increased levels of TAT, D-dimer and t-PA activity were associated with an increased risk of dementia. Additional stratified analyses indicated that an increased TAT level was the primary factor related to dementia. The present study provides evidence that predominantly increased thrombin generation is associated with dementia.

Genetics of dizygotic twinning. A feasibility study for a biobank.

To locate the genes that make a substantial contribution to variation in natural dizygotic twinning in humans, large-scale studies are needed. New studies should not stop at DNA genotyping, but collect material that allow gene-expression analysis, transcriptomics, proteomics and endocrinology. In this article we describe a pilot study to examine the feasibility, effectiveness and logistics of large-scale nationwide sample collection in Dutch families in which two or more sisters have given birth to spontaneous dizygotic twins. Pedigree data and addresses from family members of proband mothers were collected by telephone. Blood and urine samples were collected during a home visit, and handled in the afternoon. All participants were bled between 7 a.m. and 10 a.m. after overnight fasting. Blood samples of fertile women with a natural cycle were collected on the second, third or fourth day of their menstrual cycle. The effects of transportation and storage on blood quality, lipids, RNA with and without challenge, lymphocytes and other parameters were examined. Genomic DNA was isolated from blood and cells were immortalized using Epstein-Barr virus. In 78.6% of the women with a natural cycle blood samples were collected on the second, third or fourth day of the menstrual cycle. This percentage is likely to increase with the more dense geographical distribution of participants in the larger population. We conclude that the pilot study demonstrated the feasibility of this protocol to collect good quality of plasma, DNA, RNA and lymphocyte samples by home visits.

Response to Activated Protein C in Subjects with and without Dementia

We performed a cross-sectional case-control study among 295 subjects with dementia and 406 control subjects drawn from participants of the Rotterdam Study, a population-based cohort study among subjects aged 55 years or over, and from participants of the Rotterdam Stroke Databank, a hospital-based stroke registry, to evaluate the association of the factor V Leiden mutation and activated protein C (APC) response with dementia and its subtypes. The risk of dementia was 2.11-fold increased among carriers of factor V Leiden mutation relative to subjects lacking factor V Leiden mutation (95% confidence interval, CI, 0.93–4.77). The increased risks of vascular dementia and of Alzheimer’s disease were 4.28 (95% CI 1.26–14.5) and 2.15 (95% CI 0.82–5.63), respectively. No association was found for APC response. We showed a nonsignificant twofold increased risk of dementia among subjects with factor V Leiden. The association appeared to be stronger for vascular dementia.