Feasibility of using urinary TDGA as a biomarker for VCM exposures.

Thiodiglycolic acid (TDGA) is a major metabolite of vinyl chloride monomer (VCM), and it has been suggested as an exposure biomarker for VCM. The validity of this biomarker when the level of VCM is less than 5 ppm, however, is questionable. The objective of this article is to evaluate the feasibility of using urinary TDGA as a biomarker of VCM exposure in a community health risk assessment setting where the concentration of VCM in air is typically very low (likely below 1 ppm). To achieve this objective, we examine the fraction of urinary TDGA associated with different levels of VCM exposures of three studies from different countries, using estimations of the TDGA metabolite predicted by a PBPK model. It is demonstrated that differences in background TDGA have considerable effect on the adequacy of TDGA as a biomarker of VCM. We conclude that, in a community health assessment setting, TDGA should not be used as an exposure biomarker for VCM without having a proper control group, and a PBPK model can be used first to determine whether or not the amount of TDGA in urine is of concern.

A Luminescent 3d-4f-4d MOF Nanoprobe as a Diagnosis Platform for Human Occupational Exposure to Vinyl Chloride Carcinogen.

A luminescent nanoprobe based on a lanthanide-transition heterometallic metal-organic framework (MOF) is first designed for specific detection of urinary thiodiglycolic acid (TDGA) which is the biomarker of carcinogenic vinyl chloride monomer (VCM) and represents the internal dose of human exposure to VCM. The nanoprobe demonstrates high selectivity to TDGA with about 27.5-fold luminescence enhancement. It also displays excellent sensitivity with a detection limit as low as 89 ng·mL-1 and fast response to TDGA within 4 min, while refraining from the interference of other coexisting species in urine. Such good sensing performance enables the nanoprobe to practically monitor TDGA levels in human urine. Moreover, a portable urine dipstick based on the sensor is developed to conveniently evaluate individuals' intoxication degree of VCM. This fast, sensitive, and selective nanoprobe has promising potential to be a useful tool for point-of-care diagnosis of disease associated with VCM exposure.

[Biologic monitoring of chlorine organic hydrocarbons in vinyl chloride and polyvinyl chloride production].

The authors presented data of chemical analytic control of chlorine compounds level in workplace air of vinyl chloride and polyvinyl chloride production, and biomonitoring results of vinyl chloride and 1.2-dichloroethane metabolite - thiodiacetic acid urinary level in workers of this production. Findings are exceeded hygienic norms on maximal concentrations of 1.2-dichloroethane in a workshop for vinyl chloride production from 1.0 to 2.85 MACs and of vinyl chloride in a workshop for polyvinyl chloride production from 2.06 to 5.52 MACs. Urinary levels of thiodiacetic acid were assessed in workers of vinyl chloride and polyvinyl chloride production in dependence on occupation, length of service and post-contact time.

Assessment of urinary thiodiglycolic acid exposure in school-aged children in the vicinity of a petrochemical complex in central Taiwan.

BACKGROUND: School-aged children living in the vicinity of vinyl chloride (VCM)/polyvinyl chloride (PVC) factories may have an increased risk of exposure to hazardous air pollutants. OBJECTIVES: We aimed to evaluate the urinary thiodiglycolic acid (TDGA) level, as TDGA is a major metabolite of VCM, for students at elementary schools near a petrochemical complex in central Taiwan. METHODS: We recruited 343 students from 5 elementary schools based on distance to the VCM/PVC factory. First-morning urine and blood samples were obtained from our subjects from October 2013 to September 2014. Urine samples were analyzed for urinary creatinine and TDGA using LC/MS-MS. Hepatitis virus infection were assessed using blood samples. We determined their vitamin consumption, resident location, parent's employment, and other demographic or lifestyle characteristics using a questionnaire. RESULTS: Median urinary TDGA levels for 316 students at 5 elementary schools from the closest (<.9km) to the farthest (∼8.6km) with respect to the petrochemical complex were 147.6, 95.5, 115.5, 86.8, and 17.3µg/g creatinine, respectively. After adjusting for age, gender, hepatitis virus infection, vitamin B consumption, passive smoking, and home to source distance, we found that urinary TDGA levels for the closest students was significantly higher than those at other schools. Further, median urinary TDGA levels for students during school time were 4.1-fold higher than those during summer vacation. CONCLUSIONS: After adjusting for confounders, urinary TDGA levels for the school-aged children decreased with increasing distances between the elementary schools and the petrochemical complex.

[Determination of thiodiglycolic acid in urine by ion chromatography with solidphase extraction].

OBJECTIVE: To establish a SPE-IC method to determine the thiodiglycolic acid in the urine of workers who were exposed to vinyl chloride monomer. METHODS: The samples were prepared by the process of being centrifuged and purified by C18 SPE column before separated by AS19 anion exchange column and detected by conductivity detector. The thiodiglycolic acid were characterized by the retention time and quantified by peak area and external standard method. RESULTS: The range of linearity was 0.05~50.00 µg/ml, and the correlation coefficient was 0.999 9. The method detection limit was 0.1 µg/ml and the method quantitative limit was 0.3 µg/ml. The within-run precision was 1.26%~5.03% and the betweenrun precision was 0.50%~8.78%. The spiked recoveries were 80.10%~104.20%. Samples could bestored at-20 ℃ for at least 2 weeks. The determination of thiodiglycolic acid could not be interfered by chloroacetic acid, dichloroacetic acid, trichloroacetic acid and other endogenous ionic compounds. CONCLUSION: This method is feasible for determination of thiodiglycolic acid in the urine of workers who were exposed to vinyl chloride monomer.

"Dilute-and-shoot" rapid-separation liquid chromatography tandem mass spectrometry method for fast detection of thiodiglycolic acid in urine.

A new sensitive rapid-separation liquid chromatography tandem mass spectrometry approach for the determination of thiodiglycolic acid (TDGA) in urine has been developed. The use of the "dilute-and-shoot" method helps to shorten the sample preparation stage and provides a sensitive and direct approach for TDGA determination in urine. Chromatographic separation of the analyte and other urine compounds was achieved using a reverse-phase liquid chromatography column with mobile phases consisting of 0.1% formic acid in water and acetonitrile in a gradient elution mode. For the identification and quantification of TDGA electrospray ionization-tandem mass spectrometry monitoring, two precursor-to-product ion transitions were used. The method demonstrates good linearity and has a detection limit of 50 ng mL⁻¹ in urine.

[Determination of thiodiglycolic acid in urine with gas chromatography-mass spectrometer].

OBJECTIVE: To establish a rapid determination method with gas chromatography-mass spectrometer (GC-MS) for thiodiglycolic acid (TDGA), a vinyl chloride (VCM) biomarker. METHODS: A high- sensitivity determination method was established using a moderate methyl esterification instead of methyl esterification of highly toxic diazo reaction. RESULTS: The standard curve regression linear equation of the method was: y=8460.5x-4758.2, the linear coefficient was 0.999 7, the minimum quantity concentration was 2.0 µg/L, the range of precision value was 0.81%-2.38%, and the average recovery of standard addition was 99.0%-102.9%. CONCLUSION: This method reduces the risk of traditional methyl esterification, improves the determination sensitivity compared with the GC-FPD method, and meets the determination requirement of TDGA.

Surface-activated chemical ionization-electrospray mass spectrometry in the analysis of urinary thiodiglycolic acid.

RATIONALE: Thiodiglycolic acid (TDGA) is a urinary metabolite of the oxazaphosphorine class of chemotherapeutics, in particular of ifosfamide. Ifosfamide metabolism generates chloroacetaldehyde (CAA), a toxic compound associated with neurotoxicity, nephrotoxicity, urotoxicity and cardiotoxicity. CAA, in turn, interacts with cellular thiol groups leading to GSH depletion, cell death and generation of thiodiglycolic acid (TDGA), as a final product. TDGA is mainly excreted in the urine. The ability to accurately measure TDGA in urine, therefore, will be a useful way of monitoring exposure to ifosfamide during chemotherapy. METHODS: TDGA in urine samples was measured with liquid chromatography coupled to mass spectrometry (LC/MS) by means of a novel Surface-Activated Chemical Ionization-Electrospray (SACI-ESI) or a classical ESI ion source alone. RESULTS: The SACI-ESI and ESI alone based methods for analysis of urinary TDGA were optimized and compared. A strong reduction in matrix effect together with enhanced quantification performances was obtained with the SACI-ESI when compared with ESI. In particular, an increase in quantification precision (from 85 to 95%) and accuracy (from 59 to 90%) were observed, which allowed for optimal detection of TDGA. CONCLUSIONS: The LC/SACI-ESI-MS approach provides a very sensitive and quantitative method for the analysis of TDGA. Thanks to the enhancement in sensitivity and matrix effect reduction, the SACI-ESI source enables the use of a relatively low-cost ion-trap mass spectrometer in the analysis of this toxicity biomarker in urine. Due to these characteristics, this approach would constitute an invaluable tool in the clinical laboratory, for measuring TDGA and other toxicity related biomarkers of chemotherapy with proper sensitivity and accuracy.

Supplemented creatine induces changes in human metabolism of thiocompounds and one- and two-carbon units.

The administration of creatine (5 g/day for one month) to 11 young active sportsmen affected their urinary excretion of creatine, creatinine, and thiodiglycolic acid (TDGA) as well as blood levels of homocysteine, vitamin B12 and folates. The probands were divided into four groups, according to the amount of creatine found in urine, and of folates and vitamin B12 determined in blood. The changes of folates and vitamin B12 were mutually reciprocal. Each group utilized CR as donor of one- and two-carbon (1C and 2C) units by means of homocysteine (HoCySH), folates, and vitamin B12, in different metabolic pathways. In 10 men the creatine administration was accompanied by an increase of HoCySH level in blood, while in the last man, with accidentally discovered hyperhomocysteinemia, the HoCySH level dropped by 50%. Differences between initial and terminal TDGA levels indicate that creatine affects equilibria of redox processes. Creatinine excretion into urine changed in the dependence on the extent of metabolic disturbances.

Dynamics of Excretion of Thiodiacetic Acid into Urine in Polyvinyl Chloride Production Workers.

BACKGROUND: Thiodiacetic acid (TDAA) is the main metabolite of vinyl chloride (VC) and 1,2-dichloroethane (EDC) and its urinary level is correlated with the level of exposure to these chemicals. OBJECTIVE: To study dynamics of the excretion of TDAA into urine of polyvinyl chloride (PVC) production workers. METHODS: The study sample consisted of 65 workers of VC and PVC divisions with various time intervals following exposure to the chemicals, 10 shift workers from PVC division, and 34 workers not exposed to the chemicals (control group). Analysis of urinary TDAA was carried out with gas chromatography with mass-selective detector. RESULTS: The concentrations of TDAA in the urine of workers of the VC division and in group of primary occupations who had a high level of exposure to the chemicals, were significantly (p<0.05) higher than that of workers of the PVC production division and group of auxiliary professions. The highest levels of TDAA in the urine of workers were found at the beginning of the next shift and during a long break, 24-48 hours after the cessation of the exposure. CONCLUSION: When conducting biomonitoring studies in PVC production workers, the optimal time for collecting urine samples is at the beginning of the next shift or during a long rest, 24-48 hours after the exposure.

Urinary thiodiglycolic acid is associated with increased risk of non-alcoholic fatty liver disease in children living near a petrochemical complex.

BACKGROUND: Occupational and experimental studies have revealed that high vinyl chloride monomer (VCM) exposure is associated with non-alcoholic fatty liver disease (NAFLD). Epidemiological study reported that children living near a petrochemical complex have elevated exposure levels of urinary thiodiglycolic acid (TDGA), a potential VCM biomarker. However, no studies on the association of urinary TDGA exposure with NAFLD in children are available. AIM: To assess the association of pediatric NAFLD with urinary TDGA exposure in school-aged children living near a petrochemical complex. MATERIALS AND METHODS: In total, 261 school-aged children (aged 6-13 years) living near a petrochemical complex were recruited during October 2013 to September 2014. First morning spot urine was sampled for analyzing urinary TDGA through liquid chromatography-tandem mass spectrometry. Ultrasonography and serum alanine aminotransferase (ALT) were examined in each participant. NAFLD was diagnosed as recommended by the North American and European Society of Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN and ESPGHAN). Risk for NAFLD with urinary TDGA exposure in children was evaluated using a multivariate logistic regression model. RESULTS: The percentage of children with NAFLDNASPGHAN and NAFLDESPGHAN were 9.6% and 11.5%, respectively. Median levels (µg/g creatinine) of urinary TDGA of children with NAFLDNASPGHAN (vs non-NAFLDNASPGHAN) and NAFLDESPGHAN (vs non-NAFLDESPGHAN) were 118.0 (vs 96.6) and 113.1 (vs 96.5), respectively. Participants in the highest urinary TDGA quartile (Q4: ≥160.0 µg/g creatinine) had a significantly increased risk (odds ratio [OR] = 4.95; 95% confidence interval [CI] = 1.15-21.38; P = 0.032) and dose-response trend (Ptrend = 0.045) for NAFLDNASPGHAN compared with those in the lowest urinary TDGA quartile (Q1: <35.4 µg/g creatinine) after adjustment for age, gender, BMI, triglycerides, HOMA-IR and distance of elementary schools from the petrochemical complex. Participants in the Q4 had borderline significantly increased risk (OR = 3.45; 95% CI = 0.89-13.42; P = 0.074) correlated with NAFLDESPGHAN compared with those in the Q1 after adjustment for confounders. CONCLUSION: Our findings support the hypothesis that children exposed to higher urinary TDGA levels significantly increased pediatric NAFLD risk. Serum ALT levels can be a useful predictor for screening children's NAFLD in field studies. Large and longitudinal studies are warranted to elucidate the association.

Association between urinary thiodiglycolic acid level and hepatic function or fibrosis index in school-aged children living near a petrochemical complex.

The effect of exposure to vinyl chloride monomer (VCM) on susceptibility to hepatotoxicity in children is unknown, although experimental studies have demonstrated a significantly increased risk of hepatocellular carcinoma in rodents exposed to VCM in early life. Epidemiological studies have revealed a high prevalence of liver fibrosis and abnormal liver function in workers exposed to high VCM levels. We aimed to assess the association among urinary thiodiglycolic acid (TDGA) level, abnormal liver function, and hepatic fibrosis in school-aged children living near a petrochemical complex. A total of 303 school-aged (6-13 years) children within 10 km nearly a petrochemical complex was recruited in central Taiwan. First-morning urine and blood samples were collected from each subject, and urinary TDGA level was analyzed through liquid chromatography-tandem mass spectrometry. Liver function was determined by serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels. Hepatic fibrosis was assessed using the AST to platelet ratio index (APRI) and fibrosis-4 score (FIB-4). Risk of hepatotoxicity induced by TDGA exposure was estimated using multivariate logistic regression. The median (range, subclinically abnormal %) AST and ALT levels of all subjects were 26.0 (17.0-99.0, 25.7%) and 15.0 (7.0-211.0, 5.9%) IU/L, respectively. Children in the highest urinary TDGA quartile (≥160.0 µg/g creatinine) exhibited significantly elevated median AST levels compared with those in the lowest quartiles (<35.4 µg/g creatinine, p = 0.033). After adjustment for potential confounding factors, children in the highest quartiles (Q4) of TDGA level had significantly increased odds ratio (OR) of subclinically abnormal AST (OR = 3.86; 95% confidence interval: 1.54-9.67) compared with those in the lowest quartile. A dose-response trend (p = 0.004) was observed. Our findings support the hypothesis that elevated urinary TDGA level in children living near petrochemical complex is associated with susceptibility to hepatotoxicity.

Effects of Food and Antacids on Pharmacokinetics and Pharmacodynamics of Lesinurad, a Selective Urate Reabsorption Inhibitor.

Two clinical studies were performed in healthy volunteers to investigate food and antacid effects on lesinurad, a novel selective uric acid reabsorption inhibitor approved for treatment of hyperuricemia associated with gout in combination with xanthine oxidase inhibitors. Study 1 evaluated a high-fat, high-calorie meal or high doses of antacids (3000 mg calcium carbonate or 1600 mg magnesium hydroxide/1600 mg aluminum hydroxide) on the pharmacokinetics (PK) and pharmacodynamics (PD) of 400 mg oral lesinurad. Study 2 evaluated low doses of antacids (1250 mg calcium carbonate or 800 mg magnesium hydroxide/800 mg aluminum hydroxide) on the PK and PD of 400 mg lesinurad. Food did not alter the plasma AUC of lesinurad and only reduced its Cmax by 18%. In the fasted conditions, high-dose calcium carbonate reduced the Cmax and AUC of lesinurad by 54% and 38%, respectively, whereas high-dose magnesium hydroxide/aluminum hydroxide reduced Cmax and AUC by 36% and 31%, respectively. Food enhanced the maximum serum urate (sUA)-lowering effect of lesinurad by approximately 20% despite reducing the Cmax of lesinurad. High-dose calcium carbonate decreased the urate-lowering effect approximately 20% in the first 6 hours, whereas high-dose magnesium hydroxide/aluminum hydroxide reduced the effect by 26%. Low-dose calcium carbonate or magnesium hydroxide/aluminum hydroxide in the presence of food did not significantly affect plasma lesinurad Cmax and AUC or the sUA lowering and renal handling of uric acid. In summary, study results suggest food did not meaningfully alter lesinurad PK and PD. High doses of antacids reduced lesinurad AUC up to 40% and reduced the lesinurad uric acid-lowering effect.

Diagnostic significance of urinary thiodiglycolic acid as a possible tool for studying the role of vitamins B12 and folates in the metabolism of thiolic substances.

We have found that the determination of thiodiglycolic acid (TDGA) in urine may help to characterize metabolic imbalance of substances participating in methionine synthesis, which leads to hyperhomocystinuria. From the metabolic scheme, based on a proper combination of known facts, we attempted to theoretically explain and to demonstrate the possibilities of TDGA formation via different ways of homocysteine transformation. This scheme was used in evaluating the results obtained by testing urine of a woman suffering from impaired function of methionine synthase reductase (CblE type of homocystinuria). The amount of TDGA excreted in her morning urine was very sensitive to the changes in her treatment based upon a combination of N5-formyl tetrahydrofolate, betaine and vitamin B12. Vitamin B12 given in the evening either alone or together with betaine increased the TDGA excretion in the morning urine up to ten times. On the other hand, in the absence of vitamin B12, betaine in combination with N5-formyl tetrahydrofolate hindered the appearance of TDGA in the morning urine. Generally, the determination of TDGA in urine of an appropriately pretreated patient may indicate the degree of success of the treatment.

Disposition and metabolism in 1-(2-chloroethyl)-3-(2',3',4'-tri-o-acetyl, ribopyranosyl)-1-nitrosourea in rats.

The antineoplastic activity in animals of 1-(2-chloroethyl)-3-(2',3',4'-tri-O-acetyl, ribopyranosyl)-1-nitrosourea (RPCNU) has been widely demonstrated. The present study deals with the disposition and the metabolism of three 14C-labeled species of RPCNU. The chemical plasma half-life of the drug was less than 5 min. Within the first min after injections, most of the radioactivity derived from ethyl-14C groups were recovered as volatile products. Among these, 2-chloroethanol was identified as a main component. Analysis of labeled species in urine after administration of [ethyl-14C]RPCNU showed that thiodiacetic acid and its sulfoxide were major metabolites of RPCNU (62% of the urinary radioactivity). Traces of N-acetylcarboxymethyl- and N-acetylhydroxyethylcysteine) were also detected. The only labeled species concentrating in particular tissues was that carrying the chloroethyl moiety. Uptake to high levels of [ethyl-14C]RPCNU did occur in liver, kidney, pancreas, thymus, and Harder's gland.

Identification of S-(carboxymethyl)-L-cysteine and thiodiglycolic acid, urinary metabolites of 2,2'-bis-(chloroethyl)-ether in the rat.

S-(carboxymethyl)-L-cysteine (CMC) and thiodiglycollic acid (TGA) were identified by gas chromatographic-mass spectrometric measurements in the urine of rats after intraperitoneal injections of 2,2'-bis-(chloroethyl)-ether (BCEE). It is therefore probable that BCEE is O-dealkylated by a mixed-function oxidation. The hepatocarcinogenic effect of BCEE may be explained by the liberation of chloroacetaldehyde in vivo.

Investigations on metabolism and carcinogenicity of 1,1,2-trichloroethane.

Two groups of male and female Sprague-Dawley rats (50 animals/group per sex) were treated with either 15.37 or 46.77 mumole of 1,1,2-TCE in DMSO/rat for 2 years. The animals were treated once a week by s.c. injection of test compound in the skin of neck. Two groups of controls received either DMSO or no treatment at all. The incidence of benign mesenchymal and epithelial tumors was not significant when compared with either DMSO-treated or untreated controls. The animals treated with 46.77 mumole 1,1,2-TCE significantly developed sarcomas when compared with the untreated controls. In a further experiment, either 40 mumole or 160 mumole 1,1,2-TCE was injected into male Wistar rats and the metabolites, TdGA and HEMA, were determined in 24-h urine samples. Comparative studies were carried out giving equimolar amounts of chloroethanol and 2-chloroacetaldehyde diethyl acetal. Analysis of the metabolites showed that no detectable HEMA was excreted in urine after treatment of rats with 1,1,2-TCE or chloroethanol. TdGA was excreted in urine much more among chloroacetaldehyde-treated animals than among 1,1,2-TCE- or chloroethanol-treated rats.

The analysis of thiodiglycollic acid by selected ion monitoring.

A selected ion monitoring assay for thiodiglycollic acid in urine is described. Urine samples are analysed by combined gas chromatography-mass spectrometry as their dibutyl esters using pimelic acid as an internal standard. Rapid analysis was achieved by the simplification of sample preparation. The assay has proved to be reliable, with a detection limit of less than 0.5 mumol/l. The excretion of large amounts of thiodiglycollic acid in premature babies urine has been confirmed, with the greatest excretion occurring from those neonates born with a gestational age of 30 wk or less.

Determination of 3-mercaptolactate, mercaptoacetate and N-acetylcysteine in urine by gas chromatography.

A method is described for the determination of 3-mercaptolactate, mercaptoacetate (thioglycolate) and N-acetylcysteine in urine. As these compounds are mainly excreted as their mixed disulfides with cysteine, they are first reduced to the free thiols by an insoluble polymer containing thiol groups. After purification by chromatography on an organomercurial adsorbent, the compounds are converted to benzyl derivatives by extractive alkylation and determined by gas chromatography. The identity of the compounds analyzed was verified by mass spectrometry. It was demonstrated that mercaptolactate and mercaptoacetate are almost entirely excreted as their mixed disulfides with cysteine, whereas appreciable amounts of N-acetylcyteine are present as the symmetrical disulfide and the free thiol. The urinary excretion of the compounds from healthy human beings was also studied.

Determination of thiodiglycolic acid in urine by capillary electrophoresis.

A sensitive capillary electrophoretic method was developed for the determination of thiodiglycolic acid (TDA) in urine which avoids the pretreatment of the urine sample. Several carrier electrolytes were examined. The most suitable carrier electrolyte system consisted of potassium hydrogen phthalate (5 mM), 2-(N-morpholino)ethanesulfonic acid (50 mM) and tetradecyltrimethylammonium bromide (0.5 mM), pH 5.2. Ten times diluted fresh midstream void urine was used for the determination. In this way, the concentrations of TDA between 5 and 50 mg/l in undiluted urine samples can be determined.