Phosphate Metabolites Research Articles

ATP-free biosynthesis of a high-energy phosphate metabolite fructose 1,6-diphosphate by in vitro metabolic engineering

Fructose 1,6-diphosphate (FDP) is a widely used medicine and is also a precursor of two important three-carbon phosphates – glyceraldehyde 3-phosphate (GA3P) and dihydroxyacetone phosphate (DHAP) for the biosynthesis of numerous fine chemicals. An in vitro synthetic cofactor-free enzymatic pathway comprised of four hyperthermophilic enzymes was designed to produce FDP from starch and pyrophosphate. All of four hyperthermophilic enzymes (i.e., alpha-glucan phosphorylase from Thermotaga maritima, phosphoglucomutase from Thermococcus kodakarensis, glucose 6-phosphate isomerase from Thermus thermophilus, and pyrophosphate phosphofructokinase from T. maritima) were overexpressed in E. coli BL21(DE3) and purified by simple heat precipitation. The optimal pH and temperature of one-pot biosynthesis were 7.2 and 70°C, respectively. The optimal enzyme ratios of αGP, PGM, PGI and PFK were 2:2:1:2 in terms of units. Via step-wise addition of new substrates, up to 125 ± 4.6mM FDP was synthesized after 7-h reaction. This de novo ATP-free enzymatic pathway comprised of all hyperthermophilic enzymes could drastically decrease the manufacturing costs of FDP and its derivatives GA3P and DHAP, better than those catalyzed by ATP-regeneration cascade biocatalysis, the use of mesophilic enzymes, whole cell lysates, and microbial cell factories.

GENETIC POLYMORPHISMS OF GLUTATHIONE STRANSFERASE (M1 AND T1) AND PARAOXONASE 1 (PON1) AND SUSCEPTIBILITY TO CHRONIC KIDNEY DISEASE OF UNKNOWN ETIOLOGY IN PESTICIDE EXPOSED PATIENTS AT ZAGAZIG UNIVERSITY HOSPITALS

Background: Pesticide compounds are commonly used worldwide and in Egypt. Chronic low level exposure of humans to these compounds has resulted in many health adverse effects. There are many reports relating chronic kidney disease of unknown etiology (CKDu) epidemic to pesticide exposure including organophosphates (OP). Glutathione-S-transferase mu (GSTM1) and glutathione-S-transferase theta (GSTT1) are phase II xenobiotic metabolizing enzymes. Paraxonase 1 (PON1) is an enzyme linked to high-density lipoprotein. It can prevent oxidation of low-density lipoproteins and participates in organophosphate detoxification. Objective: To investigate the association of genetic polymorphism of GST (M1, T1) and PON1 Q192R with CKDu in pesticide exposed patients presented to Nephrology Unit, Internal Medicine Department, Zagazig University Hospitals, Sharkia Governorate. Methods: Gas chromatography- mass spectrometry (GC-MS) was used for detection of dialkyl phosphate metabolites in urine samples of subjects included in the study then genomic DNA isolated from the blood samples of 48 CKDu patient chronically exposed to pesticides giving positive result for dialkyl phosphate metabolites and matched control group was used to detect the presence or absence of the GSTM1 and GSTT1 genes (gene deletion) by multiplex polymerase chain reaction technique (multiplex PCR) and PON1 polymorphisms using polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) method. Conclusion: This study suggested that there is a correlation between chronic exposure to organophosphates and the risk of CKDu due to GSTM1 and GSTT1 genes deletions and PON1 gene polymorphisms.

Prenatal Residential Proximity to Agricultural Pesticide Use and IQ in 7-Year-Old Children.

Background:Residential proximity to agricultural pesticide use has been associated with neural tube defects and autism, but more subtle outcomes such as cognition have not been studied.Objectives:We evaluated the relationship between prenatal residential proximity to agricultural use of potentially neurotoxic pesticides and neurodevelopment in 7-year-old children.Methods:Participants included mothers and children () living in the agricultural Salinas Valley of California enrolled in the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study. We estimated agricultural pesticide use within 1 km of maternal residences during pregnancy using a geographic information system, residential location, and California’s comprehensive agricultural Pesticide Use Report data. We used regression models to evaluate prenatal residential proximity to agricultural use of five potentially neurotoxic pesticide groups (organophosphates, carbamates, pyrethroids, neonicotinoids, and manganese fungicides) and five individual organophosphates (acephate, chlorpyrifos, diazinon, malathion, and oxydemeton-methyl) and cognition in 7-year-old children. All models included prenatal urinary dialkyl phosphate metabolite concentrations.Results:We observed a decrease of 2.2 points [95% confidence interval (CI): , ] in Full-Scale IQ and 2.9 points (95% CI: , ) in Verbal Comprehension for each standard deviation increase in toxicity-weighted use of organophosphate pesticides. In separate models, we observed similar decrements in Full-Scale IQ with each standard deviation increase of use for two organophosphates (acephate and oxydemeton-methyl) and three neurotoxic pesticide groups (pyrethroids, neonicotinoids, and manganese fungicides).Conclusions:This study identified potential relationships between maternal residential proximity to agricultural use of neurotoxic pesticides and poorer neurodevelopment in children. https://doi.org/10.1289/EHP504

Urinary organophosphate insecticide metabolite concentrations during pregnancy and children's interpersonal, communication, repetitive, and stereotypic behaviors at 8 years of age: The home study

BackgroundPrenatal exposure to organophosphate insecticides may be associated with autism spectrum disorders and related behaviors. This association may be modified by single nucleotide polymorphisms in the paraoxonase (PON1) enzyme. ObjectiveWe examined the relationship of prenatal organophosphate insecticide biomarkers with reciprocal social, repetitive, and stereotypic behaviors in 8-year old children, and modification of this relationship by child PON1 polymorphisms. MethodsAmong 224 pregnant women, we quantified concentrations of six nonspecific dialkyl phosphate (DAP) metabolites of organophosphate insecticides in two urine samples collected at ~16 and ~26 weeks gestation. When children were eight years old, we administered the Social Responsiveness Scale (SRS), a continuous measure of various dimensions of interpersonal behavior, communication, and repetitive/stereotypic behaviors. We estimated the association between a 10-fold increase in the sum of six DAP concentrations (ΣDAP) and SRS scores. We examined whether child PON1192 and PON1–108 genotypes modified this association. ResultsAfter covariate adjustment, ΣDAP concentrations were not associated with SRS scores[β=–1.2; 95% confidence interval (CI): –4.0, 1.6]. Among children with the PON1–108TT genotype, ΣDAP concentrations were associated with 2.5-point higher (95% CI: −4.9, 9.8) SRS scores; however, the association was not different from the 1.8-point decrease (95% CI: −5.8, 2.2) among children with PON1–108CT/CC genotypes (ΣDAP × PON1–108 p-value =0.54). The association between ΣDAP concentrations and SRS scores was not modified by PON1192 (ΣDAP × PON1192 p-value =0.89). ConclusionsIn this cohort, prenatal urinary DAP concentrations were not associated with children's social behaviors; these associations were not modified by child PON1 genotype.

Persistent blood glucose reduction upon repeated transcranial electric stimulation in men

BackgroundTranscranial direct current stimulation (tDCS) of the human brain increases systemic glucose tolerance. Objective/HypothesisTo investigate whether this effect persists after one week of repeated stimulation. Because systemic glucose uptake relates to brain energy homeostasis, we concomitantly measured cerebral high-energy phosphate metabolites. MethodsIn a sham-controlled crossover design, 14 healthy men were tested under daily anodal tDCS vs. sham for 8 days. Systemic glucose metabolism was examined by concentrations of circulating glucose and insulin. Cerebral energy metabolism – i.e. adenosine triphosphate (ATP) and phosphocreatine (PCr) levels – was assessed by 31phosphorous magnetic resonance spectroscopy. ResultsBlood glucose concentrations were distinctly lower upon tDCS compared with sham stimulation on day 1. This effect persisted on day 8, while serum insulin levels remained persistently unchanged. Transcranial stimulation increased mean levels of ATP and PCr compared with sham on day 1 only. Blood glucose concentrations negatively correlated with PCr content after repeated daily stimulation. ConclusionsOur data confirm that tDCS reduces blood glucose through an insulin-independent mechanism. This effect persists after 8 days of repeated stimulation and relates to brain energy metabolism. Therefore, transcranial electric stimulation may be a promising non-pharmacological adjuvant option to treat systemic disorders such as glucose intolerance or type 2 diabetes mellitus with a low side-effect profile.

Predictors of Detected Organophosphorus Pesticides Among Orang Asli Children Living in Malaysia

BackgroundIncreasing use of pesticides in agriculture to control pest may result in permanent damage to the environment and consequently cause harmful health problems especially among infant and children. Due to pesticide's natural toxicity and its widespread use, it causes a serious threat to public health especially to this vulnerable group. ObjectiveThe purpose of this study was to determine the organophosphorus pesticide urinary metabolite levels and its predictors among Orang Asli children of the Mah Meri tribe living in an agricultural island in Kuala Langat, Selangor. MethodsData collection was carried out at an island in Kuala Langat, Selangor, where a total of 180 Orang Asli children of the Mah Meri tribe voluntarily participated in the study. Data were collected via a validated, modified questionnaire. Urinary organophosphate metabolites, namely dimethylphosphate, diethylphosphate, dimethylthiophosphate, dimethyldithiophosphate, diethylthiophosphate, and diethyldithiophosphate were measured to assess organophosphate pesticide exposure in children. FindingsEighty-four (46.7%) of the respondents were positive for urine dialkyl phosphate metabolites. In multivariable analysis, children who frequently consumed apples had 4 times higher risk of pesticide detection than those who consumed apple less frequently. In addition, those who frequently ate cucumbers had 4 times higher risk for pesticide detection than those who ate cucumbers less frequently. Children with a father whose occupation involved high exposure to pesticides (agriculture) had 3 times higher risk of pesticide detection than those with a father in a low-risk occupation (nonagriculture). ConclusionsAlmost half of the children (46.7%) in the study area tested positive for urinary dialkyl phosphate metabolite levels. Most of the metabolite levels were equal to or higher than that reported in other previous studies. Major factors associated with pesticide detection in children in this study were frequent intake of apple and cucumber and fathers who are working in an agricultural area.

Pre-transplantation 31P-magnetic resonance spectroscopy for quality assessment of human pancreatic grafts – A feasibility study

ObjectiveTo investigate the feasibility of using 31P-MRS for objective non-invasive quality assessment of human pancreas grafts prior to transplantation or islet isolation. Materials and methodsPancreata from 5 human donors, 3 males and 2 females, aged 49–78years, with body mass index (BMI) 22–31kg/m2, were included. Pancreata were perfused with histidine-tryptophan-ketoglutarate solution during procurement and stored in hypothermic condition (4°C) for 21–44h. During the period of hypothermic storage repeated spectra were obtained for each graft by 31P-MRS (1.5Tesla) to measure the cold ischemia time (CIT) dependent changes of the phosphorous metabolites adenosine triphosphate (ATP), phosphomonoesters (PME), phosphodiesters (PDE) and inorganic phosphate (Pi), in the grafts. Graft temperature was measured immediately before and after MR-examination. Reference spectrum for non-viable tissue was obtained after graft exposure to room temperature. ResultsPME/Pi, PDE/Pi and ATP/Pi spectral intensities ratios decreased with increasing CIT, reflecting the decreased viability of the grafts. PME/Pi ratio was the most discriminatory variable at prolonged CIT. 31P-MRS could be performed without significantly increasing graft temperature. Conclusions31P-MRS may provide quantitative parameters for evaluating graft viability ex vivo, and is a promising tool for objective non-invasive assessment of the quality of human pancreas grafts prior to transplantation or islet isolation.

Identification of potent tricyclic prodrug S1P1 receptor modulators.

Recently, our research group reported the identification of prodrug amino-alcohol 2 as a potent and efficacious S1P1 receptor modulator. This molecule is differentiated preclinically over the marketed drug fingolimod (Gilenya 1), whose active phosphate metabolite is an S1P1 full agonist, in terms of pulmonary and cardiovascular safety. S1P1 partial agonist 2, however, has a long half-life in rodents and was projected to have a long half-life in humans. The purpose of this communication is to disclose highly potent partial agonists of S1P1 with shorter half-lives relative to the clinical compound 2. PK/PD relationships as well as their preclinical pulmonary and cardiovascular safety assessment are discussed.

Investigation of the “true” extraction recovery of analytes from multiple types of tissues and its impact on tissue bioanalysis using two model compounds

LC-MS/MS has been widely applied to the quantitative analysis of tissue samples. However, one key remaining issue is that the extraction recovery of analyte from spiked tissue calibration standard and quality control samples (QCs) may not accurately represent the “true” recovery of analyte from incurred tissue samples. This may affect the accuracy of LC-MS/MS tissue bioanalysis. Here, we investigated whether the recovery determined using tissue QCs by LC-MS/MS can accurately represent the “true” recovery from incurred tissue samples using two model compounds: BMS-986104, a S1P1 receptor modulator drug candidate, and its phosphate metabolite, BMS-986104-P. We first developed a novel acid and surfactant assisted protein precipitation method for the extraction of BMS-986104 and BMS-986104-P from rat tissues, and determined their recoveries using tissue QCs by LC-MS/MS. We then used radioactive incurred samples from rats dosed with 3H-labeled BMS-986104 to determine the absolute total radioactivity recovery in six different tissues. The recoveries determined using tissue QCs and incurred samples matched with each other very well. The results demonstrated that, in this assay, tissue QCs accurately represented the incurred tissue samples to determine the “true” recovery, and LC-MS/MS assay was accurate for tissue bioanalysis. Another aspect we investigated is how the tissue QCs should be prepared to better represent the incurred tissue samples. We compared two different QC preparation methods (analyte spiked in tissue homogenates or in intact tissues) and demonstrated that the two methods had no significant difference when a good sample preparation was in place. The developed assay showed excellent accuracy and precision, and was successfully applied to the quantitative determination of BMS-986104 and BMS-986104-P in tissues in a rat toxicology study.

Growth-related changes of phosphorus metabolites in VX-2 carcinoma implanted into rabbit thigh muscle: in vivo 31P MR spectroscopy

The purpose of this study was to evaluate the usefulness of in vivo 31P magnetic resonance spectroscopy (MRS) for monitoring changes in growth-related phosphate metabolite concentration and intracellular pH value in rabbit thigh muscle implanted with VX-2 carcinoma. The time-course magnetic resonance imaging (MRI) and in vivo 31P MRS were examined weekly in the course of 10 weeks following the onset of a VX-2 carcinoma implantation. The spectra were quantitatively analyzed to obtain vital information on the time course variation of the phosphorus metabolites and intracellular pH value according to the tumor growth. Elevation in the concentrations of phosphormonoesters (PME), inorganic phosphate (Pi), and phosphodiesters (PDE) was observed over the time course of 3-4 weeks after the implantation of VX2 carcinoma, while the rest of the metabolites, PCr and ATP tended to be constant. The concentration changes of PME, Pi, and PDE were positively correlated with the volumes of tumor necrosis. The intracellular pH values decreased with the time course of tumor growth and the volumes of tumor necrosis. In vivo 31P MRS is capable of non-invasive monitoring of intracellular pH values as well as the concentration changes of phosphate metabolites during tumor growth.

Mitochondrial function assessed by 31P MRS and BOLD MRI in non-obese type 2 diabetic rats.

The study aims to characterize age‐associated changes in skeletal muscle bioenergetics by evaluating the response to ischemia‐reperfusion in the skeletal muscle of the Goto‐Kakizaki (GK) rats, a rat model of non‐obese type 2 diabetes (T2D). 31P magnetic resonance spectroscopy (MRS) and blood oxygen level‐dependent (BOLD) MRI was performed on the hindlimb of young (12 weeks) and adult (20 weeks) GK and Wistar (control) rats. 31P‐MRS and BOLD‐MRI data were acquired continuously during an ischemia and reperfusion protocol to quantify changes in phosphate metabolites and muscle oxygenation. The time constant of phosphocreatine recovery, an index of mitochondrial oxidative capacity, was not statistically different between GK rats (60.8 ± 13.9 sec in young group, 83.7 ± 13.0 sec in adult group) and their age‐matched controls (62.4 ± 11.6 sec in young group, 77.5 ± 7.1 sec in adult group). During ischemia, baseline‐normalized BOLD‐MRI signal was significantly lower in GK rats than in their age‐matched controls. These results suggest that insulin resistance leads to alterations in tissue metabolism without impaired mitochondrial oxidative capacity in GK rats.

Early childhood adversity potentiates the adverse association between prenatal organophosphate pesticide exposure and child IQ: The CHAMACOS cohort

BackgroundPrevious studies have observed an adverse association between prenatal exposure to organophosphate pesticide (OPs) and child cognition, but few studies consider the potential role of social stressors in modifying this relationship. ObjectiveWe seek to explore the potential role of early social adversities in modifying the relationship between OPs and child IQ in an agricultural Mexican American population. MethodsParticipants from the Center for the Health Assessment of Mothers and Children of Salinas (CHAMACOS) study, a prospective longitudinal pre-birth cohort study, include 329 singleton infants and their mothers followed from pregnancy through age 7. Dialkyl phosphate metabolite concentrations (DAPs), a biomarker of organophosphate pesticide exposure, were measured in maternal urine collected twice during pregnancy and averaged. Child cognitive ability was assessed at 7 years using the Wechsler Intelligence Scale for Children ⿿ Fourth Edition. Demographic characteristics and adversity information were collected during interviews and home visits at numerous time points from pregnancy until age 7. ResultsAmong low-income Latina mothers and their children in the Salinas Valley, total adversity and specific domains of adversity including poor learning environment and adverse parent-child relationships were negatively associated with child cognition. Adverse associations between DAP concentrations and IQ were stronger in children experiencing greater adversity; these associations varied by child sex. For example, the association between prenatal OP exposure and Full-Scale IQ is potentiated among boys who experienced high adversity in the learning environment (β=⿿13.3; p-value <0.01). ConclusionsGreater total and domain-specific adversity modifies negative relationships between prenatal OP exposure and child IQ differently among male and female children. These findings emphasize the need to consider plausible interactive pathways between social adversities and environmental exposures.

Non-invasive assessment of phosphate metabolism and oxidative capacity in working skeletal muscle in healthy young Chinese volunteers using (31)P Magnetic Resonance Spectroscopy.

Background. Generally, males display greater strength and muscle capacity than females while performing a task. Muscle biopsy is regarded as the reference method of evaluating muscle functions; however, it is invasive and has sampling errors, and is not practical for longitudinal studies and dynamic measurement during excise. In this study, we built an in-house force control and gauge system for quantitatively applying force to quadriceps while the subjects underwent 31P Magnetic Resonance Spectroscopy (31P-MRS); our aim was to investigate if there is a sex difference of phosphate metabolite change in working muscles in young heathy Chinese volunteers.Methods. Volunteers performed knee-extending excises using a force control and gauge system while lying prone in a Philips 3T Magnetic Resonance (MR) scanner. The 31P-MRS coil was firmly placed under the middle of the quadriceps . 31P-MRS measurements of inorganic phosphate (Pi), phosphocreatine (PCr) and adenosine triphosphate (ATP) were acquired from quadriceps while subjects were in a state of pre-, during- and post-exercise. The PCr, Pi, PCr/Pi, PCr/ATP, pH, work/energy cost ratio (WE), kPCr and oxidative capacity were compared between males and females.Results. A total of 17 volunteers underwent the study. Males: N = 10, age = 23.30 ± 1.25years; females: N = 7, age = 23.57 ± 0.79 years. In this study, males had significantly greater WE (16.33 ± 6.46 vs. 7.82 ± 2.16, p = 0.002) than females. Among PCr, Pi, PCr/Pi, PCr/ATP, pH, kPCr and oxidative capacity at different exercise status, only PCr/Pi (during-exercise, males = 5.630 ± 1.647, females = 4.014 ± 1.298, p = 0.047), PCr/ATP (during-exercise, males =1.273 ± 0.219, females = 1.523 ± 0.167, p = 0.025), and ATP (post-exercise, males = 24.469 ± 3.911 mmol/kg, females = 18.353 ± 4.818 mmol/kg, p = 0.035) had significant sex differences. Males had significantly greater PCr/Pi, but less PCr/ATP than females during exercise, suggesting males had higher energy transfer efficiency than females. At the post-exercise status, the recovery of PCr did not show sex difference.Conclusions. Our in-house force control and gauge system quantitatively applied force during the exercise for 31P-MRS experiments, and a sex difference of higher energy transfer efficiency and WE was detected in males with mild loaded exercising quadriceps. This noninvasive technology allows us to further study and understand the sex difference of high energy phosphate metabolism in the future.

Determinants of urinary concentrations of dialkyl phosphates among pregnant women in Canada — Results from the MIREC study

Organophosphate (OP) insecticides are commonly used in agriculture. Their use decreased in recent years as they were gradually replaced by other pesticides, but some OPs are still among the insecticides most used in Canada. Exposure to elevated levels of OPs during pregnancy has been associated with adverse birth outcomes and poorer neurodevelopment in children. The objective of the present study was to examine the relationship between the concentrations of OP pesticides urinary dialkyl phosphate (DAP) metabolites and various factors that are potential sources of exposure or determinants of DAP levels. In the Maternal-Infant Research on Environmental Chemicals (MIREC) Study, six DAPs were measured in 1st trimester urine samples of 1884 pregnant women living in Canada. They were grouped into sums of dimethyl alkyl phosphates (DMAP) and diethyl alkyl phosphates (DEAP) for statistical analysis. We found that 93% of women had at least one DAP detected in their urine. Geometric means (GM) of specific gravity-corrected levels for urine dilution were 59 (95% CI 56–62) and 21 (95% CI 20–22) nmol/L for DMAP and DEAP, respectively. The following characteristics were significantly associated with higher urinary concentrations of DMAP or DEAP: higher education, nulliparous, normal pre-pregnancy body mass index, non-smoker, not fasting at sampling, winter season at sampling, and early and late day collection times. Dietary items that were significantly related with higher urinary concentrations included higher intake of citrus fruits, apple juice, sweet peppers, tomatoes, beans and dry peas, soy and rice beverages, whole grain bread, white wine and green and herbal teas. This study indicates that exposure to these compounds is quasi-ubiquitous. The factors associated with greater DAP levels identified here could be useful to regulatory agencies for risk analysis and management. However, some exposure misclassification might occur due to the single DAP measurement available, and to the presence of preformed DAPs in the environment.

Tumor Lysis Syndrome: An Emergency in Pediatric Oncology

The tumor lysis syndrome (TLS) is an oncology emergency triggered by a massive and abrupt release of intracellular substances (potassium, phosphate, and purine metabolites) into the bloodstream. It may occur spontaneously or, more frequently, as a consequence of chemotherapy or radiation therapy. When the accumulation of these metabolites overwhelms the normal homeostatic mechanism, the TLS develops and leads to hyperkalemia, hyperphosphatemia, hyperuricemia, and hypocalcaemia. These metabolic derangements can progress to clinical manifestations including acute renal failure, cardiac arrhythmias, central nervous system toxicity, and even death. The key to prevent and manage TLS is the identification of high-risk patients to give them appropriate treatment measures when necessary.

Brain levels of high-energy phosphate metabolites and executive function in geriatric depression.

Depression in late life has been associated with difficulties in cognitive processing, particularly in the domains of executive function, processing speed and memory, and increases the risk of developing dementia suggesting a neurodegenerative phenotype. Mitochondrial dysfunction is frequently an early event in neurodegenerative illnesses and may be operative in patients with late life depression. Phosphorus magnetic resonance spectroscopy (31P MRS) allows for the quantification of bioenergetic molecules produced by mitochondria. Ten patients with late life depression and eight normal elderly controls were studied with Stroop color and interference tests, which are widely used measures of processing speed and executive function, respectively, followed by (31P) MRS 3-dimensional chemical-shift imaging measuring levels of adenosine triphosphate, phosphocreatine, inorganic phosphate, and pH over the whole brain. In all subjects, gray matter phosphocreatine was positively associated with Stroop interference. Levels of white matter adenosine triphosphate were associated with Stroop interference in subjects with late life depression but not normal elderly. There was also a complementary association between white matter inorganic phosphate and Stroop interference in late life depression patients. These findings suggest two independent sources of executive function dependence on bioenergetic state in the aging brain. The dependence of executive function performance in subjects with late life depression on ATP in white matter may be associated with mitochondrial impairment and is consistent with predictions of the vascular depression hypothesis. Further research with wider neuropsychological testing targeting bioenergetic markers could help clarify the scope of these effects. Copyright © 2016 John Wiley & Sons, Ltd.

Determination of glucuronide conjugates of hydroxyl triphenyl phosphate (OH-TPHP) metabolites in human urine and its use as a biomarker of TPHP exposure

In vitro studies using avian hepatocytes or human liver microsomes suggest that hydroxylation is an important pathway in the metabolism of triphenyl phosphate (TPHP), a chemical used as a flame retardant and plasticizer. TPHP metabolism can lead to the formation of para(p)- and meta(m)-hydroxyl-(OH-)TPHP products as well as their glucuronide conjugates. To determine whether the TPHP hydroxylation and depuration pathway also occurs in vivo in humans, the present study developed a sensitive method for quantification of p- and m-OH-TPHP glucuronides in human urine samples. In n = 1 pooled urine sample and n = 12 individual urine samples collected from four human volunteers from Ottawa (ON, Canada), p- and m-OH-TPHP glucuronides were detectable in 13 and 9 of the 13 analyzed samples and at concentrations ranging from <MLOQ-25 pg/mL and nd-4 pg/mL, respectively. A strong, positive correlation (p = 0.02, r = 0.6569) was observed between p-OH-TPHP glucuronide and diphenyl phosphate concentrations (DPHP, a known dealkylated metabolite of TPHP). To our knowledge, this is the first report demonstrating that TPHP hydroxylation and conjugation occurs in vivo in humans, and further suggests that p-OH-TPHP glucuronide can be used as a specific biomarker of TPHP exposure in humans.

Quantitative determination of nine urinary metabolites of organophosphate flame retardants using solid phase extraction and ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS).

Over the last few years, the use of organophosphate flame retardants (OPFRs) has been on the rise; however, there are knowledge gaps in both the human health effects of OPFRs and levels of human exposure. Currently, human biomonitoring data on the levels of OPFR metabolites in the Canadian population are still non-existent. Herein we describe a novel method to measure nine urinary OPFR metabolites using solid phase extraction and ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). The method detection limits were between 0.08 and 0.25ng/mL for target metabolites. The newly developed and validated method was applied to the analysis of 24 urine samples collected in 2010-12 from pregnant Canadian women. The most frequently detected OPFR metabolite in urine of study participants (detection frequency: 97%) was diphenyl phosphate (DPHP), with concentrations ranging between <0.13-25.2ng/mL, followed (75%) by the sum of two metabolites (DoCP: Di-o-cresyl phosphate and DpCP: Di-p- cresyl phosphate) of tricresyl phosphate, with concentrations between <0.13-4.38ng/mL. With the exception of desbutyl-tris-(2-butoxy-ethyl) phosphate which was not detected in any of the samples, all other OPFR metabolites measured were found among study participants with variable detection frequency, suggesting pregnant Canadian women may be exposed to OPFRs.

Exposure of Preschool-Age Greek Children (RHEA Cohort) to Bisphenol A, Parabens, Phthalates, and Organophosphates.

Phthalate esters (PEs), bisphenol A (BPA), and parabens (PBs), which are used in numerous consumer products, are known for their endocrine disrupting properties. Organophosphate chemicals (OPs), which form the basis of the majority of pesticides, are known for their neurotoxic activity in humans. All of these chemicals are associated with health problems to which children are more susceptible. Once they enter the human body, PEs, BPA, PBs, and OPs are metabolized and/or conjugated and finally excreted via urine. Hence, human exposure to these substances is examined through a determination of the urinary concentrations of their metabolites. This study assessed the exposure of Greek preschool-age children to PEs, BPA, PBs, and OPs by investigating the urinary levels of seven PEs metabolites, six PBs, BPA, and six dialkyl phosphate metabolites in five-hundred samples collected from 4-year-old children, subjects of the "RHEA" mother-child cohort in Crete, Greece. Daily intake of endocrine disruptors, calculated for 4 year old children, was lower than the corresponding daily intake for 2.5 year old children, which were determined in an earlier study of the same cohort. In some cases the daily intake levels exceeded the U.S. Environmental Protection Agency Tolerable Daily Intake (TDI) values and the EFSA Reference Doses (RfD) (e.g., for di-2-ethyl-hexyl phthalate, 3.6% and 1% of the children exceeded RfD and TDi, respectively). Exposure was linked to three main sources: PEs-BPA to plastic, PBs-diethyl phthalate to personal hygiene products, and OPs to food.

Prenatal Exposure to Organophosphorous Pesticides and Fetal Growth: Pooled Results from Four Longitudinal Birth Cohort Studies.

Background:Organophosphorous (OP) pesticides are associated with reduced fetal growth in animals, but human studies are inconsistent.Objectives:We pooled data from four cohorts to examine associations of prenatal OP exposure with birth weight (n = 1,169), length (n = 1,152), and head circumference (n = 1,143).Methods:Data were from the CHAMACOS, HOME, Columbia, and Mount Sinai birth cohorts. Concentrations of three diethyl phosphate (ΣDEP) and three dimethyl phosphate (ΣDMP) metabolites of OP pesticides [summed to six dialkyl phosphates (ΣDAPs)] were measured in maternal urine. Linear regression and mixed-effects models were used to examine associations with birth outcomes.Results:We found no significant associations of ΣDEP, ΣDMP, or ΣDAPs with birth weight, length, or head circumference overall. However, among non-Hispanic black women, increasing urinary ΣDAP and ΣDMP concentrations were associated with decreased birth length (β = –0.4 cm; 95% CI: –0.9, 0.0 and β = –0.4 cm; 95% CI: –0.8, 0.0, respectively, for each 10-fold increase in metabolite concentration). Among infants with the PON1192RR genotype, ΣDAP and ΣDMP were negatively associated with length (β = –0.4 cm; 95% CI: –0.9, 0.0 and β = –0.5 cm; 95% CI: –0.9, –0.1).Conclusions:This study confirms previously reported associations of prenatal OP exposure among black women with decreased infant size at birth, but finds no evidence of smaller birth weight, length, or head circumference among whites or Hispanics. Contrary to our hypothesis, we found stronger inverse associations of DAPs and birth outcome in infants with the less susceptible PON1192RR genotype. The large pooled data set facilitated exploration of interactions by race/ethnicity and PON1 genotype, but was limited by differences in study populations.Citation:Harley KG, Engel SM, Vedar MG, Eskenazi B, Whyatt RM, Lanphear BP, Bradman A, Rauh VA, Yolton K, Hornung RW, Wetmur JG, Chen J, Holland NT, Barr DB, Perera FP, Wolff MS. 2016. Prenatal exposure to organophosphorous pesticides and fetal growth: pooled results from four longitudinal birth cohort studies. Environ Health Perspect 124:1084–1092; http://dx.doi.org/10.1289/ehp.1409362