Jan Lindemans

Genetic polymorphisms of the CYP3A4, CYP3A5, and MDR‐1 genes and pharmacokinetics of the calcineurin inhibitors cyclosporine and tacrolimus

The calcineurin inhibitors cyclosporine (INN, ciclosporin) and tacrolimus have a narrow therapeutic index and show considerable interindividual variability in their pharmacokinetics. The low oral bioavailability of calcineurin inhibitors is thought to result from the actions of the metabolizing enzymes cytochrome P450 (CYP) 3A4 and CYP3A5 and the multidrug efflux pump P‐glycoprotein, encoded by MDR‐1.

Periconceptional Maternal Folic Acid Use of 400 µg per Day Is Related to Increased Methylation of the IGF2 Gene in the Very Young Child

Background Countries worldwide recommend women planning pregnancy to use daily 400 µg of synthetic folic acid in the periconceptional period to prevent birth defects in children. The underlying mechanisms of this preventive effect are not clear, however, epigenetic modulation of growth processes by folic acid is hypothesized. Here, we investigated whether periconceptional maternal folic acid use and markers of global DNA methylation potential (S-adenosylmethionine and S-adenosylhomocysteine blood levels) in mothers and children affect methylation of the insulin-like growth factor 2 gene differentially methylation region (IGF2 DMR) in the child. Moreover, we tested whether the methylation of the IGF2 DMR was independently associated with birth weight. Methodology/Principal Findings IGF2 DMR methylation in 120 children aged 17 months (SD 0.3) of whom 86 mothers had used and 34 had not used folic acid periconceptionally were studied. Methylation was measured of 5 CpG dinucleotides covering the DMR using a mass spectrometry-based method. Children of mother who used folic acid had a 4.5% higher methylation of the IGF2 DMR than children who were not exposed to folic acid (49.5% vs. 47.4%; p = 0.014). IGF2 DMR methylation of the children also was associated with the S-adenosylmethionine blood level of the mother but not of the child (+1.7% methylation per SD S-adenosylmethionine; p = 0.037). Finally, we observed an inverse independent association between IGF2 DMR methylation and birth weight (−1.7% methylation per SD birthweight; p = 0.034). Conclusions Periconceptional folic acid use is associated with epigenetic changes in IGF2 in the child that may affect intrauterine programming of growth and development with consequences for health and disease throughout life. These results indicate plasticity of IGF2 methylation by periconceptional folic acid use.

Evaluation of newer risk markers for coronary heart disease risk classification: a cohort study.

BACKGROUND Whether newer risk markers for coronary heart disease (CHD) improve CHD risk prediction remains unclear. OBJECTIVE To assess whether newer risk markers for CHD risk prediction and stratification improve Framingham risk score (FRS) predictions. DESIGN Prospective population-based study. SETTING The Rotterdam Study, Rotterdam, the Netherlands. PARTICIPANTS 5933 asymptomatic, community-dwelling participants (mean age, 69.1 years [SD, 8.5]). MEASUREMENTS Traditional CHD risk factors used in the FRS (age, sex, systolic blood pressure, treatment of hypertension, total and high-density lipoprotein cholesterol levels, smoking, and diabetes) and newer CHD risk factors (N-terminal fragment of prohormone B-type natriuretic peptide levels, von Willebrand factor antigen levels, fibrinogen levels, chronic kidney disease, leukocyte count, C-reactive protein levels, homocysteine levels, uric acid levels, coronary artery calcium [CAC] scores, carotid intima-media thickness, peripheral arterial disease, and pulse wave velocity). RESULTS Adding CAC scores to the FRS improved the accuracy of risk predictions (c-statistic increase, 0.05 [95% CI, 0.02 to 0.06]; net reclassification index, 19.3% overall [39.3% in those at intermediate risk, by FRS]). Levels of N-terminal fragment of prohormone B-type natriuretic peptide also improved risk predictions but to a lesser extent (c-statistic increase, 0.02 [CI, 0.01 to 0.04]; net reclassification index, 7.6% overall [33.0% in those at intermediate risk, by FRS]). Improvements in predictions with other newer markers were marginal. LIMITATION The findings may not be generalizable to younger or nonwhite populations. CONCLUSION Among 12 CHD risk markers, improvements in FRS predictions were most statistically and clinically significant with the addition of CAC scores. Further investigation is needed to assess whether risk refinements using CAC scores lead to a meaningful change in clinical outcome. Whether to use CAC score screening as a more routine test for risk prediction requires full consideration of the financial and clinical costs of performing versus not performing the test for both persons and health systems. PRIMARY FUNDING SOURCE Netherlands Organization for Health Research and Development (ZonMw).

The Generation R Study Biobank: a resource for epidemiological studies in children and their parents

The Generation R Study is a population-based prospective cohort study from fetal life until young adulthood. The study is designed to identify early environmental and genetic causes of normal and abnormal growth, development and health from fetal life until young adulthood. In total, 9,778 mothers were enrolled in the study. Prenatal and postnatal data collection is conducted by physical examinations, questionnaires, interviews, ultrasound examinations and biological samples. Major efforts have been conducted for collecting biological specimens including DNA, blood for phenotypes and urine samples. In this paper, the collection, processing and storage of these biological specimens are described. Together with detailed phenotype measurements, these biological specimens form a unique resource for epidemiological studies focused on environmental exposures, genetic determinants and their interactions in relation to growth, health and development from fetal life onwards.

Polymorphisms in folate-related genes and risk of pediatric acute lymphoblastic leukemia

Polymorphisms in folate pathway genes may influence the susceptibility to acute lymphoblastic leukemia (ALL). DNA was isolated from 245 pediatric ALL patients (cases) and from 500 blood bank donors (controls). Polymorphisms in methylene-tetrahydrofolate reductase (MTHFR 677C>T, 1298A>C), methionine synthase (MTR 2756A>G), methionine synthase reductase (MTRR 66A>G), methylenetetrahydrofolate dehydrogenase (MTHFD1 1958G>A), nicotinamide N-methyltransferase (NNMT IVS -151C>T), serine hydroxymethyl transferase (SHMT1 1420C>T), thymidylate synthase (TS 2R3R), and the reduced folate carrier (RFC1 80G>A) were detected. In ALL patients, an increased occurrence was observed of the RFC1 80AA variant (odds ratio [OR] = 2.1; 95% confidence interval [CI] = 1.3-3.2; P = .002) and the RFC1 80A allele (OR = 1.5; 95% CI, 1.1-2.1; P = .02). Likewise, the NNMT IVS -151TT genotype showed a 2.2-fold increased ALL risk (OR = 2.2; 95% CI, 1.1-4.6; P = .04). A 1.4-fold reduction in ALL risk was observed for (heterozygous or homozygous) carriers of the TS 2R allele and the MTHFR 677T allele (OR = 0.7; 95% CI, 0.5-1.0; P < .05). Furthermore, interactions between NNMT and MTHFR 677C>T and RFC1 were observed. NNMT IVS -151CC/MTHFR 677CT + TT patients exhibited a 2-fold reduction in ALL risk whereas RFC1 80AA/NNMT IVS -151CT + TT subjects had a 4.2-fold increase in ALL risk (P = .001). For the first time, we associate the RFC1 80G>A and NNMT IVS -151C>T variants to an increased ALL susceptibility.

Homocysteine and folate concentrations in early pregnancy and the risk of adverse pregnancy outcomes: The generation R study

Please cite this paper as: Bergen N, Jaddoe V, Timmermans S, Hofman A, Lindemans J, Russcher H, Raat H, Steegers‐Theunissen R, Steegers E. Homocysteine and folate concentrations in early pregnancy and the risk of adverse pregnancy outcomes: the Generation R Study. BJOG 2012;119:739–751.

Validation of the assessment of folate and vitamin B12 intake in women of reproductive age: The method of triads

Objective:To validate the folate and vitamin B12 intakes estimated by a food-frequency questionnaire (FFQ) designed to be used in a case-control study on the association between maternal dietary intake and the risk of having a child with a congenital heart defect.Design and subjects:The FFQ was filled out by 53 women of reproductive age. Immediately thereafter, blood samples were taken to determine serum folate, red blood cell (RBC) folate and serum vitamin B12 concentrations. Subsequently, three dietary 24-h recalls (24HR) were completed during a period of three successive weeks and used as a reference method. The recalls comprised two weekdays and one weekend day. Using the method of triads, validity coefficients were calculated by comparing nutrient intakes derived from the FFQ and 24HR with the corresponding nutritional biomarkers in blood. The validity coefficient is the correlation between the dietary intake reported by the FFQ and the unknown ‘true’ dietary intake.Results:The comparison of B-vitamin intakes reported by the FFQ and the mean of the 24HR revealed deattenuated correlation coefficients of 0.98 for folate and 0.66 for vitamin B12. The correlation coefficients between the B-vitamin intakes estimated by the FFQ and concentrations of serum folate, RBC folate and serum vitamin B12 were 0.20, 0.28 and 0.21, respectively. The validity coefficients for serum folate, RBC folate and serum vitamin B12 were 0.94, 0.75 and 1.00, respectively. The estimated folate and vitamin B12 intakes were comparable with the results of the most recent Dutch food consumption survey.Conclusions:The adapted FFQ is a reliable tool to estimate the dietary intake of energy, macronutrients, folate and vitamin B12 in women of reproductive age. Therefore, this FFQ is suitable for the investigation of nutrient-disease associations in future.Sponsorship:Funding was provided by the Netherlands Heart Foundation (Grant 2002.B027).

Folic acid and homocysteine affect neural crest and neuroepithelial cell outgrowth and differentiation in vitro.

The beneficial effect of additional folic acid in the periconceptional period to prevent neural tube defects, orofacial clefts, and conotruncal heart defects in the offspring has been shown. Folate shortage results in homocysteine accumulation. Elevated levels of homocysteine have been related to neural tube defects. We studied the behavior of neuroepithelial cells and cranial and cardiac neural crest cells in vitro. Neural tube explants were cultured for 24 and 48 hr in medium after addition of folic acid and/or homocysteine. Folic acid addition increased neuroepithelial cell outgrowth and increased neural crest cell differentiation into nerve and smooth muscle cells. Addition of homocysteine increased neural crest cell outgrowth and migration from the neural tube and inhibited neural crest cell differentiation. Our findings suggest that neural tube defects caused by folate deficiency and hyperhomocysteinemia develop due to increased neuroepithelial to neural crest cell transformation. This increased transformation leads to a shortage of neuroepithelial cells in the neural tube. Defects in orofacial and conotruncal development are explained by abnormal differentiation of neural crest cells in the presence of high homocysteine concentrations. Our findings supports a critical role for folic acid and homocysteine in the development of neural tube defects and neural crest related heart malformations. Developmental Dynamics 227:301–308, 2003.

Low folate in seminal plasma is associated with increased sperm DNA damage

OBJECTIVE To determine associations between vitamin B status, homocysteine (tHcy), semen parameters, and sperm DNA damage. DESIGN Observational study. SETTING A tertiary referral fertility clinic. PATIENT(S) Two hundred fifty-one men of couples undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment, with subgroups of fertile (n = 70) and subfertile men (n = 63) defined according to semen concentration and proven fertility. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) The DNA fragmentation index (DFI) as marker of sperm DNA damage determined using the sperm chromatin structure assay (SCSA), and semen parameters assessed according to World Health Organization criteria; tHcy, folate, cobalamin, and pyridoxine concentrations determined in seminal plasma and blood. RESULT(S) In the total group of fertile and subfertile men, all biomarkers in blood were statistically significantly correlated with those in seminal plasma. No correlation was found between the biomarkers in blood and the semen parameters. In seminal plasma, both tHcy and cobalamin positively correlated with sperm count. Folate, cobalamin, and pyridoxine were inversely correlated with ejaculate volume. In fertile men, seminal plasma folate showed an inverse correlation with the DNA fragmentation index. CONCLUSION(S) Low concentrations of folate in seminal plasma may be detrimental for sperm DNA stability.

Maternal hyperhomocysteinaemia is a risk factor for congenital heart disease

Objective  To investigate the inter‐relation between mother and infant homocysteine, folate and vitamin B12 status and the risk of a child with congenital heart disease (CHD).