Analysis of urinary N-acetyl-S-(propionamide)-cysteine as a biomarker for the assessment of acrylamide exposure in smokers

Determinants of exposure to acrylamide in European children and adults based on urinary biomarkers: results from the "European Human Biomonitoring Initiative" HBM4EU participating studies

Little is known about exposure determinants of acrylamide (AA), a genotoxic food-processing contaminant, in Europe. We assessed determinants of AA exposure, measured by urinary mercapturic acids of AA (AAMA) and glycidamide (GAMA), its main metabolite, in 3157 children/adolescents and 1297 adults in the European Human Biomonitoring Initiative. Harmonized individual-level questionnaires data and quality assured measurements of AAMA and GAMA (urine collection: 2014-2021), the short-term validated biomarkers of AA exposure, were obtained from four studies (Italy, France, Germany, and Norway) in children/adolescents (age range: 3-18 years) and six studies (Portugal, Spain, France, Germany, Luxembourg, and Iceland) in adults (age range: 20-45 years). Multivariable-adjusted pooled quantile regressions were employed to assess median differences (β coefficients) with 95% confidence intervals (95% CI) in AAMA and GAMA (µg/g creatinine) in relation to exposure determinants. Southern European studies had higher AAMA than Northern studies. In children/adolescents, we observed significant lower AA associated with high socioeconomic status (AAMA:β =  - 9.1 µg/g creatinine, 95% CI - 15.8, - 2.4; GAMA: β =  - 3.4 µg/g creatinine, 95% CI - 4.7, - 2.2), living in rural areas (AAMA:β =  - 4.7 µg/g creatinine, 95% CI - 8.6, - 0.8; GAMA:β =  - 1.1 µg/g creatinine, 95% CI - 1.9, - 0.4) and increasing age (AAMA:β =  - 1.9 µg/g creatinine, 95% CI - 2.4, - 1.4; GAMA:β =  - 0.7 µg/g creatinine, 95% CI - 0.8, - 0.6). In adults, higher AAMA was also associated with high consumption of fried potatoes whereas lower AAMA was associated with higher body-mass-index. Based on this large-scale study, several potential determinants of AA exposure were identified in children/adolescents and adults in European countries.

A systematic review: on the mercaptoacid metabolites of acrylamide, N-acetyl-S-(2-carbamoylethyl)-L-cysteine

Acrylamide is widely found in a variety of fried foods and cigarettes and is not only neurotoxic and carcinogenic, but also has many potential toxic effects. The current assessment of acrylamide intake through dietary questionnaires is confounded by a variety of factors, which poses limitations to safety assessment. In this review, we focus on the levels of AAMA, the urinary metabolite of acrylamide in humans, and its association with other diseases, and discuss the current research gaps in AAMA and the future needs. We reviewed a total of 25 studies from eight countries. In the general population, urinary AAMA levels were higher in smokers than in non-smokers, and higher in children than in adults; the highest levels of AAMA were found in the population from Spain, compared with the general population from other countries. In addition, AAMA is associated with several diseases, especially cardiovascular system diseases. Therefore, AAMA, as a biomarker of internal human exposure, can reflect acrylamide intake in the short term, which is of great significance for tracing acrylamide-containing foods and setting the allowable intake of acrylamide in foods.

Investigation of exposure biomarkers in human plasma following differing levels of tobacco-specific N-nitrosamines and nicotine in cigarette smoke

Tobacco-specific N-nitrosamines (TSNAs) are strong carcinogens widely found in tobacco products, environmental tobacco smoke, lake, and wastewater. The main objective of this study was to investigate the effects of cigarette smoke with different yields of TSNAs (NNK, NNN, NAT, NAB) and nicotine on the levels of biomarkers of exposure in smokers' plasma. Three hundred healthy volunteers were recruited comprising 60 smokers of each of 3 mg, 8 mg and 10 mg ISO tar yield cigarettes and 60 smokers who smoked 10 mg, 8 mg, and 3 mg for 14 days sequentially and 60 non-smokers. All study participants were male, aged from 21 to 45 years old, and were recruited from a same unit in Hebei, China. We measured the levels of NNAL, NAT, NNN, NAB and cotinine in plasma from 240 smokers and 60 non-smokers using a novel method established by online two-dimensional solid phase extraction-liquid chromatography-tandem mass spectrometry. The results showed that NNAL, NAT, NNN, NAB and cotinine in the plasma of smokers smoking cigarette with low TSNAs and nicotine were lower than that with high TSNAs and nicotine. When smokers switched from higher to lower TSNA yields of cigarettes, their plasma NNAL, NAT, NNN, NAB levels significantly decreased. The plasma concentrations of NNAL were significantly correlated with those of cotinine, NNN, NAT and NAB for smokers (p < 0.001). Similarly, the plasma concentrations of cotinine were significantly correlated with those of NNN, NAT and NAB for smokers (p < 0.001). The plasma NNAL, NAT, NNN, NAB and cotinine levels for smokers were significantly higher than those for non-smokers. These findings suggested that the total NNAL, NNN, NAT, NAB and cotinine in plasma were valid and reliable biomarkers for human exposure to TSNAs and nicotine.

Cigarette smoking is associated with acrylamide exposure among the U.S. population: NHANES 2011-2016

2-carbamoylethyl mercapturic acid (2CaEMA, N-Acetyl-S-carbamoylethyl-L-cysteine) is a urinary metabolite and exposure biomarker of acrylamide, which is a harmful volatile organic compound found in cigarette smoke and in some foods. The goal of this study was to determine the association between cigarette smoking and urinary 2CaEMA concentrations among the U.S. population while considering potential dietary sources of acrylamide intake and demographics. We measured 2CaEMA concentrations in urine specimens collected during the National Health and Nutrition Examination Survey 2011-2012, 2013-2014, and 2015-2016 cycles from eligible participants 18 years and older (n = 5443) using liquid chromatography/tandem mass spectrometry. We developed multiple regression models with urinary 2CaEMA concentrations as the dependent variable and sex, age, race/Hispanic origin, reported primary sources of dietary acrylamide intake, and cigarette smoke exposure as independent variables. This study demonstrates that cigarette smoking is strongly associated with urinary 2CaEMA, suggests that cigarette smoking is likely a primary source of acrylamide exposure, and provides a baseline measure for 2CaEMA in the U.S. population.

Review of the state of the art of acrylamide human biomonitoring

Human biomonitoring (HBM) is a very useful tool for assessing human exposure to acrylamide (AA). In the framework of the Human Biomonitoring Initiative (HBM4EU) AA was included in its second list of priority substances due to the potential threat to human health. HBM data on AA are scarce, but the use of specific and sensitive biomarkers represents a reliable indicator of exposure. In this review an overview of available knowledge on HBM of AA is provided in terms of: i) preferred exposure biomarkers and matrices for the HBM of AA; ii) analytical methods for determining its biomarkers of exposure in the most used specimens; iii) current HBM data available; and iv) tools for interpreting HBM data for AA in relation to risk assessment. Finally, future trends in this field are discussed.

Exposure assessment of Spanish lactating mothers to acrylamide via human biomonitoring

Acrylamide (AA) is an organic compound classified as "Probably carcinogenic to humans" (Group 2 A) that can be found principally in processed carbohydrate-rich foods and tobacco smoke. In humans, after exposure, AA is rapidly metabolized and excreted in urine, predominantly as N-acetyl-S-(2-carbamoylethyl)-l-cysteine (AAMA), N-acetyl-S-(2-carbamoyl-2-hydroxyethyl)-l-cysteine (GAMA3) and N-Acetyl-3-[(3-amino-3-oxopropyl)sulfinyl]-L-alanine (AAMA-Sul), which can be used as short-term biomarkers of exposure to AA. In this study, the presence of AA metabolites in urine samples of lactating mothers living in Spain (n = 114) was analyzed by "dilute and shoot" and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). All urinary metabolites were detected in 100% of the analyzed samples, with geometric means of 70, 33 and 15 ng ml^-1, for AAMA, AAMA-Sul and GAMA3, respectively. The consumption of coffee, bread and precooked food products were found to be significant predictors of internal exposure to AA. An estimated daily intake (EDI) of AA based on its urinary metabolites was calculated, obtaining mean values between 1.2 and 1.9 μg AA·kg bw^-1·day^-1 in the target population. The risk assessment was evaluated using both reverse and forward dosimetry, showing an average margin of exposure (MOE) of 349 and a hazard quotient (HQ) of 5.5. Therefore, AA exposure should be considered a medium priority for risk assessment follow-up in the Spanish population, since a health concern with respect to non-neoplastic toxicity could not be discarded.

Are AAMA and GAMA Levels in Urine after Childbirth a Suitable Marker to Assess Exposure to Acrylamide from Passive Smoking during Pregnancy?-A Pilot Study

Introduction: Acrylamide (AA) is a “probably carcinogenic to humans” monomer that can form in heated starchy food and in tobacco smoke. N-Acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-Acetyl-S-(2-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA), acrylamide metabolites in urine, are recognized as good markers of exposure to acrylamide. Aim: The aim of the study is a preliminary assessment whether the levels of AAMA and GAMA in urine after childbirth are good markers of acrylamide exposure due to passive smoking during pregnancy. Material and method: The study group consisted 67 non-smokers and 10 passive-smoker women during pregnancy. AAMA and GAMA levels in urine samples were determined using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Results: The median AAMA levels in urine of non-smoking and passively smoking women were 30.7 μg/g creatinine and 25.2 μg/g creatinine, respectively. Much lower values were determined for GAMA: 11.4 μg/g creatinine and 10.3 μg/g creatinine, respectively. There is no significant difference between AAMA and GAMA content in urine samples between both groups of women as well as in the anthropometric parameters of newborns between those two groups of mothers. Conclusion: Our pilot study did not confirm that postpartum AAMA and GAMA concentrations in urine are good markers of exposure to acrylamide from passive smoking during pregnancy. It is probably due to the different ways of acrylamide absorption from tobacco smoke by active and passive smokers. Exposure of pregnant women to acrylamide from passive smoking requires further research.

Feasibility of using urinary N7-(2-carbamoyl-2-hydroxyethyl) Guanine as a biomarker for acrylamide exposed workers

Acrylamide (AA), a probable human carcinogen, is a widely-used industrial chemical but is also present in tobacco smoke and carbohydrate-rich foods processed at high temperatures. AA is metabolized to glycidamide (GA) to cause the formation of DNA adducts. N7-(2-carbamoyl-2-hydroxyethyl) guanine (N7-GAG), the most abundant DNA adduct induced by GA, was recently detected in urine of smokers and non-smokers. In this study, we assessed the variability of AA exposure and biomarkers of AA exposure in urine samples repeatedly collected from AA-exposed workers and explored the half-life of N7-GAG. A total of 8 AA-exposed workers and 36 non-exposed workers were recruited. Pre-shift and post-shift urine samples were collected from the exposed group in parallel with personal sampling for eight consecutive days and from the control group on day 1 of the study. Urinary N7-GAG and the mercapturic acids of AA and GA, namely N-acetyl-S-(2-carbamoylethyl)-L-cysteine (AAMA) and N-(R,S)-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-L-cysteine (GAMA) were analyzed using on-line solid phase extraction-liquid chromatography-electrospray ionization/tandem mass spectrometry methods. We found that N7-GAG levels in urine were significantly higher in exposed workers than in controls and that N7-GAG level correlated positively with AAMA and GAMA levels. Results from this study showed that AAMA and GAMA possibly remain the more preferred biomarkers of AA exposure and that N7-GAG levels could be elevated by occupational exposures to AA and serve as a biomarker of AA-induced genotoxicity for epidemiological studies.

Metabolomics analysis of serum from subjects after occupational exposure to acrylamide using UPLC-MS

Since occupational exposure to acrylamide (ACR) may cause nerve damage, sensitive biomarkers to evaluate the early effects of ACR on human health are needed. In the present study, we have compared a group of individuals with occupational exposure to ACR (contact group, n = 65) with a group of individuals with no exposure (non-contact group, n = 60). Serum metabolomics analysis of the contact and non-contact groups was carried out using ultra performance liquid chromatograph/time of flight mass spectrometry, combined with multivariate analysis, to identify potential metabolites. Serum biochemical indexes of the contact and non-contact groups were also determined using an automatic biochemistry analyzer. There was a clear separation between the contact group and the non-contact group; receiver operator characteristic curve analysis suggested that phytosphingosine, 4E,15Z-bilirubin IXa and tryptophan were the best metabolites to use as biomarkers. Liver function was also found to be abnormal in the contact group. Important, ACR-related, metabolic changes were seen in the contact group and new biomarkers for assessing the toxicity of ACR on the central nervous system have been proposed. This study will provide a sound basis for exploring the toxic mechanisms and metabolic pathways of ACR.

A urinary metabolomics study of rats after the exposure to acrylamide by ultra performance liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry

Acrylamide (ACR) is known to induce neurotoxicity in humans and occupational exposure to ACR has an effect on human health. Since some animal experiments indicate the metabolic change caused by the ACR based on the metabolomics, increasing concern is the change of metabolite profiles by the low-dose ACR. In the present study, a low-dose of ACR (18 mg kg(-1)) was administered to male Wistar rats for 40 days. Ultra performance liquid chromatography/time of flight mass spectrometry (UPLC-Q-TOF MS) was used to examine urine samples from ACR-dosed and control animals. Multiple statistical analyses with principal component analysis (PCA) were used to investigate metabolite profile changes in urine samples, and to screen for potential neurotoxicity biomarkers. PCA showed differences between the ACR-dosed and control groups 20 days after the start of dosing; a bigger separation between the two groups was seen after dosing for 40 days. Levels of 4-guanidinobutanoic acid and 2-oxoarginine were significantly higher in urine from the ACR-dosed group than in urine from the control group after 10 days (p < 0.05). Receiver operator characteristic (ROC) curve analysis suggested that 4-guanidinobutanoic acid and 2-oxoarginine were the major metabolites. Our results suggest that high levels of 4-guanidinobutanoic acid and 2-oxoarginine may be related to ACR neurotoxicity. These metabolites could, therefore, act as sensitive biomarkers for ACR exposure and be useful for investigating toxic mechanisms. They may also provide a scientific foundation for assessing the effects of chronic low-dose ACR exposure on human health.

Study of urinary 2-{[2-(acetylamino-2-carboxyethyl]sulfanyl}butanedioic acid, a mercapturic acid of rats treated with maleic acid

Maleic anhydride was reported illegally adulterated into starch to prepare traditional foods for decades in Taiwan. Maleic acid (MA), hydrolyzed from maleic anhydride, could cause kidney damages to animals. The potential health effects due to long-term MA exposures through food consumption have been of great concerns. Assessment of the dietary MA exposures could be very difficult and complicated. One of the alternatives is to analyze an MA-specific biomarker to assess the daily total MA intake. Therefore, this paper aimed to study the mercapturic acid of MA, 2-{[2-(acetylamino)-2-carboxyethyl]sulfanyl}butanedioic acid (MAMA), with our newly-developed isotope-dilution online solid-phase extraction liquid chromatography tandem mass spectrometry (ID-SPE-LC-MS/MS) method. MAMA was first synthesized, purified, and characterized with NMR to reveal two diastereomers and used for developing the analytical method. The method was validated to reveal excellent sensitivity with a LOD at 16.3ng/mL and a LOQ at 20.6ng/mL and used to analyze MAMA in urine samples collected from Sprague-Dawley rats treated with a single dose of 0mg/kg, 6mg/kg, and 60mg/kg (n=5) of MA through gavage. Our results show dose-dependent increases in urinary MAMA contents, and 70% MAMA was excreted within 12h with no gender differences (p>0.05). A half life of urinary MAMA was estimated at 6.8h for rat. The formation of urinary MAMA validates it as a chemically-specific biomarker for current MA exposure. Future study of MA metabolism in vivo will elucidate mechanisms of MAMA formation, and analysis of this marker in epidemiology studies could help to shed light on the causal effects of MA on human.

Association between measurements of thyroid function and the acrylamide metabolite N-Acetyl-S-(propionamide)-cysteine in adolescents and young adults

Acrylamide is present in mainstream cigarette smoke and in some foods prepared at high temperatures. Animal studies have shown that acrylamide exposure alters thyroid function; however, it is not known if this also occurs in humans. The study examined the association between the urinary levels of the acrylamide metabolite and serum thyroid measures in adolescents and young adults. We recruited 793 subjects (mean age, 21.3 years; range, 12-30 years) from a population-based sample of Taiwanese adolescents and young adults to determine if the urinary levels of the acrylamide metabolite N-acetyl-S-(propionamide)-cysteine (AAMA) and the 6 serum thyroid measures are associated. The mean (SD) AAMA were 76.54 (76.42) µg/L. Linear regression analyzes showed a 1-unit increase in natural log AAMA was significantly associated with a decrease in serum free thyroxine (T4) (ng/dL) (β=-0.041, SE=0.013, p=0.001) after controlling for covariates. Subpopulation analyzes showed AAMA and free T4 were significantly associated with females, age 20-30 years, non-current smokers, and non-alcohol consumers. In conclusion, higher urinary AAMA concentrations were associated with decreased levels of free T4 in this cohort. Further studies are warranted to determine if there is a causal relationship between acrylamide exposure and thyroid function.

Probabilistic risk assessment of exposure to leucomalachite green residues from fish products

To assess the potential risk of human exposure to carcinogenic leucomalachite green (LMG) due to fish consumption, the probabilistic risk assessment was conducted for adolescent, adult and senior adult consumers in Taiwan. The residues of LMG with the mean concentration of 13.378±20.56 μg kg(-1) (BFDA, 2009) in fish was converted into dose, considering fish intake reported for three consumer groups by NAHSIT (1993-1996) and body weight of an average individual of the group. The lifetime average and high 95th percentile dietary intakes of LMG from fish consumption for Taiwanese consumers were estimated at up to 0.0135 and 0.0451 μg kg-bw(-1) day(-1), respectively. Human equivalent dose (HED) of 2.875 mg kg-bw(-1) day(-1) obtained from a lower-bound benchmark dose (BMDL10) in mice by interspecies extrapolation was linearly extrapolated to oral cancer slope factor (CSF) of 0.035 (mgkg-bw(-1)day(-1))(-1) for humans. Although, the assumptions and methods are different, the results of lifetime cancer risk varying from 3×10(-7) to 1.6×10(-6) were comparable to those of margin of exposures (MOEs) varying from 410,000 to 4,800,000. In conclusions, Taiwanese fish consumers with the 95th percentile LADD of LMG have greater risk of liver cancer and need to an action of risk management in Taiwan.

Positive association between urinary levels of 8-hydroxydeoxyguanosine and the acrylamide metabolite N-acetyl-S-(propionamide)-cysteine in adolescents and young adults

Acrylamide is present in mainstream cigarette smoke and in some foods prepared at high temperatures. Animal studies have shown that acrylamide exposure increases oxidative stress; however, it is not known if this also occurs in humans. We recruited 800 subjects (mean age, 21.3 years, range, 12-30 years) from a population-based sample of Taiwanese adolescents and young adults to determine if urinary levels of the acrylamide metabolite N-acetyl-S-(propionamide)-cysteine (AAMA) and the oxidative stress product 8-hydroxydeoxyguanosine (8-OHdG) are associated. The mean (SD) AAMA and 8-OHdG were 76.54 (76.42)μg/L and 3.48 (2.37)μg/L, respectively. In linear regression analyses, a 1-unit increase in natural log AAMA was significantly associated with an increase in natural log 8-OHdG (μg/g creatinine) (β=0.044, SE=0.019, P=0.020) after controlling for covariates. Subpopulation analyses showed AAMA and 8-OHdG were significantly associated with males, adolescents, non-current smokers, without alcohol consumption, subjects, body mass index ≥ 24, and homeostasis model assessment of insulin resistance score ≥ 0.9. In conclusion, higher urinary AAMA concentrations were associated with increased levels of urinary 8-OHdG in this cohort. Further studies are warranted to determine if there is a causal relationship between acrylamide exposure and oxidative stress.

Review of methods for the reduction of dietary content and toxicity of acrylamide

Potentially toxic acrylamide is largely derived from heat-induced reactions between the amino group of the free amino acid asparagine and carbonyl groups of glucose and fructose in cereals, potatoes, and other plant-derived foods. This overview surveys and consolidates the following dietary aspects of acrylamide: distribution in food originating from different sources; consumption by diverse populations; reduction of the acrylamide content in the diet; and suppression of adverse effects in vivo. Methods to reduce adverse effects of dietary acrylamide include (a) selecting potato, cereal, and other plant varieties for dietary use that contain low levels of the acrylamide precursors, namely, asparagine and glucose; (b) removing precursors before processing; (c) using the enzyme asparaginase to hydrolyze asparagine to aspartic acid; (d) selecting processing conditions (pH, temperature, time, processing and storage atmosphere) that minimize acrylamide formation; (e) adding food ingredients (acidulants, amino acids, antioxidants, nonreducing carbohydrates, chitosan, garlic compounds, protein hydrolysates, proteins, metal salts) that have been reported to prevent acrylamide formation; (f) removing/trapping acrylamide after it is formed with the aid of chromatography, evaporation, polymerization, or reaction with other food ingredients; and (g) reducing in vivo toxicity. Research needs are suggested that may further facilitate reducing the acrylamide burden of the diet. Researchers are challenged to (a) apply the available methods and to minimize the acrylamide content of the diet without adversely affecting the nutritional quality, safety, and sensory attributes, including color and flavor, while maintaining consumer acceptance; and (b) educate commercial and home food processors and the public about available approaches to mitigating undesirable effects of dietary acrylamide.