Michael S. Bloom

DNA methylation changes in whole blood is associated with exposure to the environmental contaminants, mercury, lead, cadmium and bisphenol A, in women undergoing ovarian stimulation for IVF

BACKGROUND Changes in DNA methylation may play an important role in the deleterious reproductive effects reported in association with exposure to environmental pollutants. In this pilot study, we identify candidate methylation changes associated with exposure to pollutants in women undergoing in vitro fertilization (IVF). METHODS Blood and urine were collected from women on the day of oocyte retrieval. Whole blood was analyzed for mercury and lead, and urine for cadmium using inductively coupled plasma mass spectrometry. Unconjugated bisphenol A (BPA) was analyzed in serum using high-performance liquid chromatography with Coularray detection. Participants were dichotomized as higher or lower exposure groups by median concentrations. Using the Illumina GoldenGate Methylation Cancer Panel I, DNA methylation in whole blood from 43 women was assessed at 1505 CpG sites for association with exposure levels of each pollutant. Candidate CpG sites were identified using a Diff Score >|13| (P< 0.05) and an absolute difference >10% which were confirmed using bisulfite pyrosequencing. RESULTS Methylation of the GSTM1/5 promoter was increased for women with higher mercury exposure (P= 0.04); however, no correlation was observed (r= 0.17, P= 0.27). Reduced methylation was detected in the COL1A2 promoter in women with higher exposure to lead (P= 0.004), and an inverse correlation was observed (r = - 0.45, P= 0.03). Lower methylation of a promoter CpG site at the TSP50 gene was detected in women with higher BPA exposure (P= 0.005), and again an inverse correlation was identified (r = - 0.51, P= 0.001). CONCLUSIONS Altered DNA methylation at various CpG sites was associated with exposure to mercury, lead or BPA, providing candidates to be investigated using a larger study sample, as the results may reflect an independently associated predictor (e.g. socioeconomic status, diet, genetic variants, altered blood cell composition). Further studies accommodating variations in these factors will be needed to confirm these associations and identify their underlying causes.

Blood pressure and hypertension in relation to levels of serum polychlorinated biphenyls in residents of Anniston, Alabama.

Objective To determine risk factors for elevated blood pressure and hypertension in residents of Anniston, Alabama who live near a plant that manufactured polychlorinated biphenyls (PCBs). Methods A total of 758 Anniston residents had multiple measurements of blood pressure, provided information on demographic factors, medications, smoking, and exercise, and provided blood samples for determination of PCBs and total serum lipid. Results Rates of hypertension increased significantly (P < 0.05) with age and concentration of serum PCBs and were higher in African–Americans (n = 351) than in whites (n = 407). Hypertension also increased with BMI, but was not related to total serum lipid, sex, smoking, or exercise. Among 394 persons not on antihypertensive medication, linear regression analysis demonstrated a significant positive relation between serum PCB level and both systolic and diastolic blood pressure. After adjustment for potentially confounding variables, logistic regression gave odds ratios for the highest to lowest tertiles of total serum PCBs that exceeded 3.5 for both systolic and diastolic hypertension. When analyzed by quintiles of PCBs, the highest odds ratio was in the third quintile, suggesting a low dose effect. Conclusion In individuals not on antihypertensive medication, serum PCB levels were significantly associated with prevalence of hypertension. Significant positive associations were also observed between PCB concentrations and systolic and diastolic blood pressure even in normotensive ranges. The strength of the relationships between PCB exposure and both hypertension and blood pressure suggests that PCB exposure may be an important contributing factor in regulation of blood pressure.

Thyroid Function and Perfluoroalkyl Acids in Children Living Near a Chemical Plant

Background: Animal studies suggest that some perfluoroalkyl acids (PFAAs), including perfluorooctanoate (PFOA), perfluorooctane sulfonate (PFOS), and perfluorononanoic acid (PFNA) may impair thyroid function. Epidemiological findings, mostly related to adults, are inconsistent. Objectives: We investigated whether concentrations of PFAAs were associated with thyroid function among 10,725 children (1–17 years of age) living near a Teflon manufacturing facility in the Mid-Ohio Valley (USA). Methods: Serum levels of thyroid-stimulating hormone (TSH), total thyroxine (TT4), and PFAAs were measured during 2005–2006, and information on diagnosed thyroid disease was collected by questionnaire. Modeled in utero PFOA concentrations were based on historical information on PFOA releases, environmental distribution, pharmacokinetic modeling, and residential histories. We performed multivariate regression analyses. Results: Median concentrations of modeled in utero PFOA and measured serum PFOA, PFOS, and PFNA were 12, 29, 20, and 1.5 ng/mL, respectively. The odds ratio for hypothyroidism (n = 39) was 1.54 [95% confidence interval (CI): 1.00, 2.37] for an interquartile range (IQR) contrast of 13 to 68 ng/mL in serum PFOA measured in 2005–2006. However, an IQR shift in serum PFOA was not associated with TSH or TT4 levels in all children combined. IQR shifts in serum PFOS (15 to 28 ng/mL) and serum PFNA (1.2 to 2.0 ng/mL) were both associated with a 1.1% increase in TT4 in children 1–17 years old (95% CIs: 0.6, 1.5 and 0.7, 1.5 respectively). Conclusions: This is the first large-scale report in children suggesting associations of serum PFOS and PFNA with thyroid hormone levels and of serum PFOA and hypothyroidism.

Serum unconjugated bisphenol A concentrations in women may adversely influence oocyte quality during in vitro fertilization

Bisphenol A (BPA) is an endocrine disruptor with estrogenic properties that can adversely affect meiotic spindle assemblies. Our data indicate that BPA exposure in female patients may interfere with oocyte quality during IVF, as suggested by the inverse association between serum unconjugated BPA concentration and normal fertilization.

Bisphenol A exposure reduces the estradiol response to gonadotropin stimulation during in vitro fertilization

OBJECTIVE To investigate associations between serum bisphenol A (BPA) concentrations and follicular response to exogenous ovary stimulation. DESIGN Fasting serum was prospectively collected on the day of oocyte retrieval and assessed for unconjugated BPA using high-performance liquid chromatography with Coularray detection. Multivariable linear regression and negative binomial regression were used to assess associations between concentrations of BPA and outcome measures. Models were adjusted for race/ethnicity, antral follicle count at baseline, and cigarette smoking. SETTING A reproductive health center. PATIENT(S) Forty-four women undergoing IVF. INTERVENTION(S) None. MAIN OUTCOME MEASURE(S) Peak E(2) level and the number of oocytes retrieved during IVF. RESULT(S) The median unconjugated serum BPA concentration is 2.53 ng/mL (range = 0.3-67.36 ng/mL). Bisphenol A is inversely associated with E(2) (β = -0.16; 95% confidence interval = -0.32, 0.01), as well as with E(2) normalized to the number of mature-sized follicles at the hCG trigger (β = -0.14; 95% confidence interval = -0.24, -0.03). No association is observed for BPA and the number of oocytes retrieved (adjusted risk ratio = 0.95; 95% confidence interval = 0.82, 1.10). CONCLUSION(S) Bisphenol A is associated with a reduced E(2) response during IVF. Although limited by the preliminary nature of this study, these results merit confirmation in a future comprehensive investigation.

Exploratory assessment of perfluorinated compounds and human thyroid function.

Thyroid hormones play critical roles in human neurodevelopment and adult neurocognitive function. Persistent organohalogen pollutants, such as perfluorinated compounds (PFCs), may interfere with thyroid homeostasis and thus exposures to these compounds might represent risk factors for neurologic and cognitive abnormalities. In this study, serum specimens collected from thirty-one licensed anglers in New York State were analyzed for levels of thyroid stimulating hormone (TSH), free thyroxine (FT(4)), perfluorodecanoic acid (PFDA), perfluorononanoic acid (PFNA), perfluoroheptanoic acid (PFHpA), perfluorohexanesulfonate (PFHxS), perfluorooctanoic acid (PFOA), perfluorooctanesulfonate (PFOS), perfluorooctanesulfonamide (PFOSA), and perfluoroundecanoic acid (PFUnDA). PFOS and PFOA occurred in the highest concentrations with geometric means of 19.6 ng/mL (95% CI 16.3-23.5) and 1.3 ng/mL (95% CI 1.2-1.5), respectively. In a cross-sectional analysis, no statistically significant associations were detected for PFCs, or their sum, with TSH or FT(4) at alpha=0.05. However, post hoc power analyses, though limited, suggested that moderate increases in sample size, to 86 and 129 subjects, might facilitate 80% power to detect statistically significant associations for FT(4) and PFDA (beta=0.09) and PFUnDA (beta=0.08), respectively. The consumption of sportfish may have contributed to PFDA (r=0.52, P=0.003) and PFUnDA (r=0.40, P=0.025) levels. This preliminary study does not indicate associations between non-occupational PFCs exposures and thyroid function. However, the possibility for weak associations for FT(4) with PFDA and PFUnDA, PFCs measured in low concentrations, is raised. Given the ubiquity of PFCs in the environment and the importance of thyroid function to neurodevelopmental and neurocognitive endpoints, a confirmatory study is warranted.

Environmental exposure to PBDEs and thyroid function among New York anglers

Experimental studies suggest that polybrominated diphenyl ethers (PBDEs) can influence thyroid function, although the few human studies reported provide little support for this premise. Great Lakes sportfish anglers represent a population with potentially elevated dietary exposure to PBDEs due to the lipophilic nature of these compounds. Thirty-six licensed anglers who participated in the New York State Angler Cohort Study donated blood and completed questionnaires regarding demographic, clinical and sportfish consumption information. Archived blood specimens were analyzed for thyroid stimulating hormone, total and free thyroxine, total triiodothyronine, total serum lipids and nine PBDE congeners. PBDE congener profiles were dominated by BDE-47 (median=7.9ng/g lipids), BDE-153, and BDE-99 (medians=1.8ng/g lipids). No significant associations were observed between congeners, or their sum (ΣPBDEs), and thyroid function. However, the possibility of a positive association between ΣPBDEs and fT(4), detectable with an approximate ninefold increase in sample size, suggests that additional studies are needed.

Associations between urinary phthalate concentrations and semen quality parameters in a general population

STUDY QUESTION Are urinary phthalate concentrations associated with altered semen quality parameters among males recruited from the general population? SUMMARY ANSWER Urinary levels of metabolites of phthalate diesters are associated with lower total sperm counts, larger sperm head sizes, and higher percentages of morphologically abnormal sperm. WHAT IS KNOWN ALREADY High dose experiments in rats implicate phthalates as anti-androgens. Studies involving infertile men seeking care suggest that phthalates influence measures of semen quality raising concern about the implications for men in the general population. STUDY DESIGN, SIZE, DURATION This prospective cohort study comprised 501 male partners in couples discontinuing contraception to become pregnant, who were recruited from 16 US counties using population-based sampling frameworks from 2005 to 2009. PARTICIPANTS/MATERIALS, SETTING, METHODS Urine and semen samples were obtained at baseline from 473 (94%) men, of whom 378 (80%) men provided a second sample the following month. Urine was analyzed for 14 monoester metabolites of phthalate diesters by high-performance liquid chromatography coupled to tandem mass spectrometry. Semen samples were analyzed for 34 quality parameters categorized as general, motility, morphology, sperm head and sperm chromatin structure. MAIN RESULTS AND THE ROLE OF CHANCE Urinary mono-[2-(carboxymethyl) hexyl] phthalate (MCMHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP), mono-benzyl phthalate (MBzP), and mono-isononyl phthalate (MNP) were significantly associated with lower total sperm counts and concentrations, larger sperm head sizes, higher proportions of megalo head sperm morphology, and/or other morphological changes. Urinary mono-methyl phthalate (MMP) and mono-cyclohexyl phthalate (MCPP) were significantly associated with lower sperm motility, and urine mono-2-ethylhexyl phthalate (MEHP) was significantly associated with higher sperm motility. LIMITATIONS, REASONS FOR CAUTION While adverse associations were observed, the implications of the findings for couple fecundity and fertility remain to be established. Cautious interpretation is needed in light of reliance on a single measurement of phthalate measure and no correction for multiple comparisons.

High-density lipoprotein metabolism and the human embryo

BACKGROUND High-density lipoprotein (HDL) appears to be the dominant lipoprotein particle in human follicular fluid (FF). The reported anti-atherogenic properties of HDL have been attributed in part to reverse cholesterol transport. The discoveries of the scavenger receptor class B type I (SR-BI) and the ATP-binding cassette A1 lipid (ABCA1) transporter have generated studies aimed at unraveling the pathways of HDL biogenesis, remodeling and catabolism. The production of SR-BI and ABCA1 knockout mice as well as other lipoprotein metabolism-associated mutants has resulted in reduced or absent fertility, leading us to postulate the existence of a human hepatic-ovarian HDL-associated axis of fertility. Here, we review an evolving literature on the role of HDL metabolism on mammalian fertility and oocyte development. METHODS An extensive online search was conducted of published articles relevant to the section topics discussed. All relevant English language articles contained in Pubmed/Medline, with no specific time frame for publication, were considered for this narrative review. Cardiovascular literature was highly cited due to the wealth of relevant knowledge on HDL metabolism, and the dearth thereof in the reproductive field. RESULTS Various vertebrate models demonstrate a role for HDL in embryo development and fertility. In our clinical studies, FF levels of HDL cholesterol and apolipoprotein AI levels were negatively associated with embryo fragmentation, but not with embryo cell cleavage rate. However, the HDL component, paraoxonase 1 arylesterase activity, was positively associated with embryo cell cleavage rate. CONCLUSIONS HDL contributes to intra-follicular cholesterol homeostasis which appears to be important for successful oocyte and embryo development.

Spontaneous pregnancy loss in humans and exposure to arsenic in drinking water.

Maternal exposure to high concentrations of inorganic arsenic (iAs) in naturally contaminated drinking groundwater sources has been associated with an increased risk for the spontaneous loss of clinically recognized pregnancies in several epidemiologic studies. Whereas a large worldwide population depends on drinking groundwater sources with high levels of iAs contamination, in quantities exceeding 10 parts per billion (ppb), an even larger population is likely to be exposed to mild-moderate drinking groundwater iAs contamination, in quantities <10ppb. Only a single epidemiologic study to date has considered spontaneous pregnancy loss in association with consumption of drinking water with mild-moderate iAs contamination; the vast majority of published studies of spontaneous loss addressed populations with substantial exposure. The aim of this review is to evaluate the published literature to assess the plausibility for a causal association between exposure to iAs-contaminated drinking water and the spontaneous loss of clinically recognized pregnancy. In spite of numerous methodologic limitations resulting from circumstance or design, a consistent pattern of increased risk for loss is suggested by the epidemiologic literature. Moreover, these study results are corroborated by a large number of experimental studies, albeit usually conducted at concentrations exceeding that to which humans are exposed via contaminated drinking water. In this review, we discuss sources of human iAs exposure, highlight several experimental studies pertinent to a possible causal link between iAs and spontaneous pregnancy loss in humans, and provide a critical review of published epidemiologic studies of pregnancy loss and drinking water iAs exposures, and their limitations. Based on a review of the published literature, we recommend the future conduct of a two-stage comprehensive prospective study of low-moderate iAs drinking water exposure and spontaneous pregnancy loss.