Joris Penders

Placental Mitochondrial DNA Content and Particulate Air Pollution during in Utero Life

Background: Studies emphasize the importance of particulate matter (PM) in the formation of reactive oxygen species and inflammation. We hypothesized that these processes can influence mitochondrial function of the placenta and fetus. Objective: We investigated the influence of PM10 exposure during pregnancy on the mitochondrial DNA content (mtDNA content) of the placenta and umbilical cord blood. Methods: DNA was extracted from placental tissue (n = 174) and umbilical cord leukocytes (n = 176). Relative mtDNA copy numbers (i.e., mtDNA content) were determined by real-time polymerase chain reaction. Multiple regression models were used to link mtDNA content and in utero exposure to PM10 over various time windows during pregnancy. Results: In multivariate-adjusted analysis, a 10-µg/m³ increase in PM10 exposure during the last month of pregnancy was associated with a 16.1% decrease [95% confidence interval (CI): –25.2, –6.0%, p = 0.003] in placental mtDNA content. The corresponding effect size for average PM10 exposure during the third trimester was 17.4% (95% CI: –31.8, –0.1%, p = 0.05). Furthermore, we found that each doubling in residential distance to major roads was associated with an increase in placental mtDNA content of 4.0% (95% CI: 0.4, 7.8%, p = 0.03). No association was found between cord blood mtDNA content and PM10 exposure. Conclusions: Prenatal PM10 exposure was associated with placental mitochondrial alterations, which may both reflect and intensify oxidative stress production. The potential health consequences of decreased placental mtDNA content in early life must be further elucidated.

Placental DNA hypomethylation in association with particulate air pollution in early life

BackgroundThere is evidence that altered DNA methylation is an important epigenetic mechanism in prenatal programming and that developmental periods are sensitive to environmental stressors. We hypothesized that exposure to fine particles (PM2.5) during pregnancy could influence DNA methylation patterns of the placenta.MethodsIn the ENVIRON AGE birth cohort, levels of 5’-methyl-deoxycytidine (5-mdC) and deoxycytidine (dC) were quantified in placental DNA from 240 newborns. Multiple regression models were used to study placental global DNA methylation and in utero exposure to PM2.5 over various time windows during pregnancy.ResultsPM2.5 exposure during pregnancy averaged (25th-75th percentile) 17.4 (15.4-19.3) μg/m3. Placental global DNA methylation was inversely associated with PM2.5 exposures during whole pregnancy and relatively decreased by 2.19% (95% confidence interval [CI]: -3.65, -0.73%, pu2009=u20090.004) for each 5xa0μg/m3 increase in exposure to PM2.5. In a multi-lag model in which all three trimester exposures were fitted as independent variables in the same regression model, only exposure to PM2.5 during trimester 1 was significantly associated with lower global DNA methylation (-2.13% per 5xa0μg/m3 increase, 95% CI: -3.71, -0.54%, pu2009=u20090.009). When we analyzed shorter time windows of exposure within trimester 1, we observed a lower placental DNA methylation at birth during all implantation stages but exposure during the implantation range (6-21d) was strongest associated (-1.08% per 5xa0μg/m3 increase, 95% CI: -1.80, -0.36%, pu2009=u20090.004).ConclusionsWe observed a lower degree of placental global DNA methylation in association with exposure to particulate air pollution in early pregnancy, including the critical stages of implantation. Future studies should elucidate genome-wide and gene-specific methylation patterns in placental tissue that could link particulate exposure during in utero life and early epigenetic modulations.

Bone resorption and environmental exposure to cadmium in children: a cross--sectional study.

BackgroundExposure to cadmium has been associated with osteoporosis and fracture risk in women and elderly, but studies in children are lacking. In the present study we investigate the association between markers of bone demineralization [urinary calcium (Ca) and deoxypyridinoline (DPD) excretion] and urinary cadmium (Cd) excretion (as an index of lifetime body burden).Methods155 schoolchildren from 2 elementary schools in Lahore, Pakistan were included. Urinary Cd was measured as an index of lifetime exposure. We assessed the multivariate-adjusted association of exposure with markers of bone resorption, urinary DPD as well as with Ca excretion.ResultsUrinary Cd averaged 0.50 nmol/mmol creatinine and was not influenced by age, height, weight and socio-economic status (SES). Independent of gender, age, height, weight and SES a doubling of urinary Cd was associated with a 1.72 times (p < 0.0001) increase in urinary DPD and, a 1.21 times (p = 0.02) increase in urinary Ca. Additional adjustment for urinary Ca revealed still significant associations between urinary Cd and urinary DPD. The shape of the association was linear without evidence of a threshold.ConclusionsEven in young children, low-level environmental exposure to cadmium is associated with evidence of bone resorption, suggesting a direct osteotoxic effect with increased calciuria. These findings might have clinical relevance at older age.

In Utero Fine Particle Air Pollution and Placental Expression of Genes in the Brain-Derived Neurotrophic Factor Signaling Pathway: An ENVIRONAGE Birth Cohort Study.

Background Developmental processes in the placenta and the fetal brain are shaped by the same biological signals. Recent evidence suggests that adaptive responses of the placenta to the maternal environment may influence central nervous system development. Objectives We studied the association between in utero exposure to fine particle air pollution with a diameter ≤ 2.5 μm (PM2.5) and placental expression of genes implicated in neural development. Methods Expression of 10 target genes in the brain-derived neurotrophic factor (BDNF) signaling pathway were quantified in placental tissue of 90 mother–infant pairs from the ENVIRONAGE birth cohort using quantitative real-time polymerase chain reaction. Trimester-specific PM2.5 exposure levels were estimated for each mother’s home address using a spatiotemporal model. Mixed-effects models were used to evaluate the association between the target genes and PM2.5 exposure measured in different time windows of pregnancy. Results A 5-μg/m3 increase in residential PM2.5 exposure during the first trimester of pregnancy was associated with a 15.9% decrease [95% confidence interval (CI): –28.7, –3.2%, p = 0.015] in expression of placental BDNF at birth. The corresponding estimate for synapsin 1 (SYN1) was a 24.3% decrease (95% CI: –42.8, –5.8%, p = 0.011). Conclusions Placental expression of BDNF and SYN1, two genes implicated in normal neurodevelopmental trajectories, decreased with increasing in utero exposure to PM2.5. Future studies are needed to confirm our findings and evaluate the potential relevance of associations between PM2.5 and placental expression of BDNF and SYN1 on neurodevelopment. We provide the first molecular epidemiological evidence concerning associations between in utero fine particle air pollution exposure and the expression of genes that may influence neurodevelopmental processes. Citation Saenen ND, Plusquin M, Bijnens E, Janssen BG, Gyselaers W, Cox B, Fierens F, Molenberghs G, Penders J, Vrijens K, De Boever P, Nawrot TS. 2015. In utero fine particle air pollution and placental expression of genes in the brain-derived neurotrophic factor signaling pathway: an ENVIRONAGE Birth Cohort Study. Environ Health Perspect 123:834–840; http://dx.doi.org/10.1289/ehp.1408549

Establishment of reference values for novel urinary biomarkers for renal damage in the healthy population: are age and gender an issue?

Abstract Background: Recently, a lot of research has focused on the discovery of novel renal biomarkers. Among others, the urinary kidney injury molecule 1 (KIM-1) and neutrophil gelatinase-associated lipocalin (NGAL) have been proven to be promising biomarkers in a wide variety of renal pathologies. However, little is known about the normal concentrations in urine of healthy subjects. Therefore, the goal of our study is to establish reference values for urinary KIM-1, NGAL, N-acetyl-β-D-glucosamidase (NAG), and cystatin C in a healthy population, taking into account possible effects of age and gender. Methods: We collected urine samples from 338 healthy, nonsmoking subjects between 0 and 95 years old. Subjects with elevated α1-microglobulin values were excluded. Next to the urinary concentrations of KIM-1, NGAL, NAG, and cystatin C, we measured urinary creatinine and specific gravity to correct for urinary dilution. The possible effect of age and gender on the four urinary biomarkers was investigated, and the reference values were established. Results: For the absolute urinary concentrations of the biomarkers, age had a significant effect on all the biomarkers, except for cystatin C, whereas gender significantly affected all four of them, except for NAG. The normalization of biomarkers for creatinine and specific gravity had an effect on the correlation between the biomarkers on one hand and age and gender on the other. Conclusions: In conclusion, age and gender had different effects on KIM-1, NGAL, NAG, and cystatin C. Based on this knowledge, age- and gender-specific reference values for KIM-1, NGAL, NAG, and cystatin C were established.

Urinary Composition During Decongestive Treatment in Heart Failure With Reduced Ejection Fraction

Background—The urinary composition, including sodium (Na+) and chloride (Cl−) concentrations, might provide useful information in addition to urine output during decongestive treatment in heart failure. Methods and Results—Consecutive patients with heart failure (n=61), ejection fraction ⩽45%, worsening symptoms, and scheduled treatment with intravenous loop diuretics were included. Patients received protocol-driven therapy until complete decongestion, assessed clinically and by echocardiography. Three consecutive 24-hour urinary collections were performed. With 2 mg (1–4 mg), 1 mg (0–2 mg), and 1 mg (0–1 mg) bumetanide administered in bolus during consecutive 24-hour intervals, in addition to combinational diuretic therapy in ≈70% and both oral spironolactone and vasodilators in ≈90%, euvolemia was reached, often within 24 hours. Urine output was higher during the first when compared with the second or third 24-hour interval (2700 versus 1550 or 1375 mL, respectively; P<0.001), but this was no longer significant after correction for diuretic dose (P=0.263), indicating preserved diuretic efficiency during the study. In contrast, urinary Na+ and Cl− excretion both decreased significantly, even after correction for diuretic dose (P=0.040 and 0.004, respectively), leading to decreasing urinary concentrations with progressive decongestion. After reaching euvolemia, lower urinary Na+/Cr and Cl−/Cr ratios were both associated with urine output ⩽1500 mL (area under the curve, 0.830 and 0.826, respectively; P<0.001 for both), in contrast to plasma N-terminal pro–B-type natriuretic peptide levels that were not (area under the curve, 0.515; P=0.735) Conclusions—The urinary composition during progressive decongestion in heart failure with reduced ejection fraction is characterized by a drop in urinary Na+ and Cl− concentrations. The urinary Na+/Cr or Cl−/Cr ratio might provide insightful information to titrate diuretic therapy.

The association between urinary kidney injury molecule 1 and urinary cadmium in elderly during long-term, low-dose cadmium exposure: a pilot study

BackgroundUrinary kidney injury molecule 1 is a recently discovered early biomarker for renal damage that has been proven to be correlated to urinary cadmium in rats. However, so far the association between urinary cadmium and kidney injury molecule 1 in humans after long-term, low-dose cadmium exposure has not been studied.MethodsWe collected urine and blood samples from 153 non-smoking men and women aged 60+, living in an area with moderate cadmium pollution from a non-ferrous metal plant for a significant period. Urinary cadmium and urinary kidney injury molecule 1 as well as other renal biomarkers (alpha1-microglobulin, beta2-microglobulin, blood urea nitrogen, urinary proteins and microalbumin) were assessed.ResultsBoth before (r = 0.20; p = 0.01) and after (partial r = 0.32; p < 0.0001) adjustment for creatinine, age, sex, past smoking, socio-economic status and body mass index, urinary kidney injury molecule 1 correlated with urinary cadmium concentrations. No significant association was found between the other studied renal biomarkers and urinary cadmium.ConclusionsWe showed that urinary kidney injury molecule 1 levels are positively correlated with urinary cadmium concentration in an elderly population after long-term, low-dose exposure to cadmium, while other classical markers do not show an association. Therefore, urinary kidney injury molecule 1 might be considered as a biomarker for early-stage metal-induced kidney injury by cadmium.

Blood pressure changes in association with black carbon exposure in a panel of healthy adults are independent of retinal microcirculation

Exposure to ambient particulate matter and elevated blood pressure are risk factors for cardiovascular morbidity and mortality. Microvascular changes might be an important pathway in explaining the association between air pollution and blood pressure. The objective of the study was to evaluate the role of the retinal microcirculation in the association between black carbon (BC) exposure and blood pressure. We estimated subchronic BC exposure based on 1-week personal measurements (μ-Aethalometer, AethLabs) in 55 healthy nurses. Blood pressure and retinal microvasculature were measured on four different days (range: 2-4) during this week. Subchronic BC exposure averaged (± SD) 1334±631ng/m(3) and ranged from 338ng/m(3) to 3889ng/m(3). An increased exposure of 631ng/m(3) BC was associated with a 2.77mmHg (95% CI: 0.39 to 5.15, p=0.027) increase in systolic blood pressure, a 2.35mmHg (95% CI: 0.52 to 4.19, p=0.016) increase in diastolic blood pressure and with 5.65μm (95% CI: 1.33 to 9.96, p=0.014) increase in central retinal venular equivalent. Mediation analysis failed to reveal an effect of retinal microvasculature in the association between blood pressure and subchronic BC exposure. In conclusion, we found a positive association between blood pressure and subchronic black carbon exposure in healthy adults. This finding adds evidence to the association between black carbon exposure and cardiovascular health effects, with elevated blood pressure as a plausible intermediate effector. Our results suggest that the changes in a persons blood pressure as a result of subchronic black carbon exposure operate independently of the retinal microcirculation.

Effect of pH on the stability of kidney injury molecule 1 (KIM-1) and on the accuracy of its measurement in human urine

BACKGROUNDnUrinary KIM-1 is a novel biomarker for tubular kidney damage, however little is known about its stability. The goal of this study is to examine the effect of urinary pH on the stability of KIM-1.nnnMETHODSnUrine samples were collected from 45 volunteers. Samples were aliquoted, adapted to different pH values (range 4 to 9) and stored at -80°C. After thawing, each aliquot was divided into two, of which one was used to measure KIM-1 (human tim-1/kim-1/Havcr Elisa kit; R&D systems) at the same pH at which it was stored, while the other was readapted to pH 7 before measurement.nnnRESULTSnKIM-1 values of aliquots of the same sample are stable when stored at pH 6, 7 and 8 whereas at lower and higher storage pH, KIM-1 levels decrease significantly. When samples are readjusted to a neutral pH just before KIM-1 measurement, there are no longer significant differences between KIM-1 in aliquots stored at different pH values.nnnCONCLUSIONSnNo effect of urinary pH on the stability of KIM-1 was seen. However, the only commercially available human tim-1/kim-1/Havcr Elisa kit of RD systems is pH dependent and we therefore suggest samples should be adjusted to neutral pH before measurement.

Collection and storage requirements for urinary kidney injury molecule-1 (KIM-1) measurements in humans

Abstract Background: Urinary kidney injury molecule-1 (KIM-1) is a recently discovered biomarker for early renal damage. However, little is known about the collection and storage requirements prior to its measurement in human urine. Methods: Samples of healthy volunteers were collected and aliquoted. The effect of pre-freezing time, thawing, addition of protease inhibitors, centrifugation, storage time (up to 1.5 years) and temperature (4°C, –20°C and –80°C) was tested. Results: Addition of protease inhibitors and centrifugation prior to freezing did not affect the KIM-1 measurements. When samples were kept at room temperature for longer than 3 h before freezing or defrosted more than 1 h before measurement, mean KIM-1 values differed significantly compared to aliquots with minimal pre-freezing and thawing time. Samples frozen at –80°C were stable for up to 1.5 years; however an increasing number of freeze-thaw cycles adversely affected KIM-1 measurements. When stored at 4°C and –20°C, samples were less stable compared to those stored at –80°C. Conclusions: This study recommends that urine samples collected for KIM-1 measurements are frozen within 3 h after voiding and only be defrosted immediately prior to measurement. Addition of protease inhibitor and centrifugation prior to measurement is not necessary. Samples are preferably stored at –80°C and freeze-thaw cycles should be avoided.