Long-term stability of human aflatoxin B1 albumin adducts assessed by isotope dilution mass spectrometry and high-performance liquid chromatography-fluorescence

Association of aflatoxin with gallbladder cancer in a case-control study nested within a Chinese cohort

We evaluated whether aflatoxin B1 (AFB1 ) exposure was associated with later risk of developing gallbladder cancer (GBC). We measured AFB1 -lysine albumin adducts in baseline samples from the Shanghai Cohort Study of 18 244 men aged 45 to 64 years (recruited 1986-1989). We included 84 GBC cases with sufficient serum and 168 controls matched on age at sample collection, date of blood draw and residence. We calculated adjusted odds ratios (ORs) and 95% confidence intervals (95% CIs) for detectable vs non-detectable AFB1 -lysine albumin adducts and gallbladder cancer. AFB1 -lysine albumin adducts were detected in 50.0% of GBC cases, and risk of GBC was twice as high in those with detectable vs undetectable levels (OR = 2.0, 95% CI = 1.0-3.9). ORs ranged from 1.8 (95% CI = 0.75-4.3) for 0.5 to <1.75 pg/mg vs undetectable adduct levels to 2.2 (95% CI = 0.91-5.6) for >3.36 pg/mg vs undetectable, suggesting a dose-response (Ptrend  = .05). When restricted to cases diagnosed before the median time to diagnosis after blood draw (18.4 years), results were similar (OR = 2.2, 95% CI = 0.80-5.8) to those for the entire follow-up duration. The OR was 9.4 (95% CI = 1.7-51.1) for individuals with detectable AFB1 -lysine albumin adducts and self-reported gallstones compared to individuals with neither. Participants with detectable AFB1 -lysine albumin adducts at baseline had increased risk of developing GBC, replicating the previously observed association between AFB1 exposure and providing the first evidence of temporality.

Child Aflatoxin Exposure is Associated with Poor Child Growth Outcomes: A Prospective Cohort Study in Rural Malawi

Background

Aflatoxin (AF) exposure is associated with child growth faltering in cross-sectional studies, with limited findings from longitudinal studies.

Objectives

To evaluate the relationship between maternal AF B₁-lysine adduct concentration, child AF B₁-lysine adduct concentration, and child growth in the first 30 mo of life.

Methods

AF B₁-lysine adduct was measured in mother-child dyad plasma samples using isotope dilution mass spectrometry. Using linear regression, we assessed the relationship between AF B₁-lysine adduct concentration and child weight, height, and head and mid-upper arm circumferences at 1 wk, 6, 12, 18, 24, and 30 mo of age.

Results

In adjusted models, maternal prenatal AF B₁-lysine adduct (pg/μL) was positively associated with newborn anthropometric outcomes; largest beta coefficients for associations between standardized values were for newborn weight-for-age z-score [β = 0.13; 95% confidence interval (CI): 0.02, 0.24; P < 0.05 and β = 0.11; 95% CI: 0.00, 0.22; P < 0.05 for second and third trimester AF, respectively]. Child AF B₁-lysine adduct (pg/μL) at 6 mo was negatively associated with head circumference-for-age z-score at 6, 18, 24, and 30 mo, with beta coefficients ranging from β = -0.15; 95% CI: -0.28, -0.02 to β = -0.17; 95% CI: -0.31, -0.03; P < 0.05); 18-mo AF was negatively associated with anthropometric outcomes at 18, 24, and 30 mo, most consistently with length-for-age z-score (β = -0.18; 95% CI: -0.32, -0.04, β = -0.21; 95% CI: -0.35, -0.07, β = -0.18; 95% CI: -0.32, -0.03 at 18, 24 and 30 mo, respectively).

Conclusions

Child AF exposure was associated with impaired child growth, but maternal AF exposure was not. Exposure during infancy was linked to persistent deficit in head circumference, implying reduced brain size lasting beyond the age of 2 years. Exposure at 18 mo was linked to persistent linear growth deficit. Further research should elucidate mechanisms through which AF affects child growth.

Assessing the Impacts of Preanalytical Field Sampling Challenges on the Reliability of Serum Aflatoxin B1-Lysine Measurements by Use of LC-MS/MS

Aflatoxin exposure is endemic in developing countries with warm, humid climates that promote toxigenic mold growth on crops and foodstuffs. Estimating human aflatoxin exposure is key to identifying and abating contamination sources. Serum aflatoxin B1 bound to albumin lysine (AFB1-lys) is a preferred exposure biomarker, but field sample collection, processing, transportation, and storage logistics are challenging. We validated an improved LC-MS/MS method for serum AFB1-lys and applied it to three field sampling challenges: transportation/storage (elevated temperature); collection/processing (hemolysis); and sample type substitution (heparinized plasma). Our new LC-MS/MS method had a LOD of 0.03 ng/mL, accuracy (mean spike recovery) of 112%, total imprecision (replicate pool measurements) ≤5% at ≥0.2 ng/mL, and results that were 95.1% similar (mean percentage similarity) to an established method. AFB1-lys in human serum spiked with serum from aflatoxin-dosed rats was stable for 14 days at both ambient (22.5 °C) and elevated (38 °C) temperatures. Simulated hemolysis (adding 0.25–3 mg hemoglobin) did not affect AFB1-lys accuracy at ≥0.5 ng/mL but caused 10–25% signal suppression. Heparinized plasma AFB1-lys was 99.0% similar to serum but interfered with albumin measurements (bromocresol green) causing spurious low bias. Further investigation is warranted, but our findings suggest that AFB1-lys is pre-analytically robust.

Environmental and Lifestyle Risk Factors in the Carcinogenesis of Gallbladder Cancer

Gallbladder cancer (GBC) is an aggressive neoplasm that in an early stage is generally asymptomatic and, in most cases, is diagnosed in advanced stages with a very low life expectancy because there is no curative treatment. Therefore, understanding the early carcinogenic mechanisms of this pathology is crucial to proposing preventive strategies for this cancer. The main risk factor is the presence of gallstones, which are associated with some environmental factors such as a sedentary lifestyle and a high-fat diet. Other risk factors such as autoimmune disorders and bacterial, parasitic and fungal infections have also been described. All these factors can generate a long-term inflammatory state characterized by the persistent activation of the immune system, the frequent release of pro-inflammatory cytokines, and the constant production of reactive oxygen species that result in a chronic damage/repair cycle, subsequently inducing the loss of the normal architecture of the gallbladder mucosa that leads to the development of GBC. This review addresses how the different risk factors could promote a chronic inflammatory state essential to the development of gallbladder carcinogenesis, which will make it possible to define some strategies such as anti-inflammatory drugs or public health proposals in the prevention of GBC.

Environmental Pollutants, Mucosal Barriers, and Pathogen Susceptibility; The Case for Aflatoxin B1 as a Risk Factor for HIV Transmission and Pathogenesis

HIV transmission risk is dependent on the infectivity of the HIV+ partner and personal susceptibility risk factors of the HIV- partner. The mucosal barrier, as the internal gatekeeper between environment and self, concentrates and modulates the internalization of ingested pathogens and pollutants. In this review, we summarize the localized effects of HIV and dietary toxin aflatoxin B1 (AFB1), a common pollutant in high HIV burden regions, e.g., at the mucosal barrier, and evidence for pollutant-viral interactions. We compiled literature on HIV and AFB1 geographic occurrences, mechanisms of action, related co-exposures, personal risk factors, and HIV key determinants of health. AFB1 exposure and HIV sexual transmission hotspots geographically co-localize in many low-income countries. AFB1 distributes to sexual mucosal tissues generating inflammation, microbiome changes and a reduction of mucosal barrier integrity, effects that are risk factors for increasing HIV susceptibility. AFB1 exposure has a positive correlation to HIV viral load, a risk factor for increasing the infectivity of the HIV+ partner. The AFB1 exposure and metabolism generates inflammation that recruits HIV susceptible cells and generates chemokine/cytokine activation in tissues exposed to HIV. Although circumstantial, the available evidence makes a compelling case for studies of AFB1 exposure as a risk factor for HIV transmission, and a modifiable new component for combination HIV prevention efforts.

Mycotoxins Affecting Animals, Foods, Humans, and Plants: Types, Occurrence, Toxicities, Action Mechanisms, Prevention, and Detoxification Strategies-A Revisit

Mycotoxins are produced by fungi and are known to be toxic to humans and animals. Common mycotoxins include aflatoxins, ochratoxins, zearalenone, patulin, sterigmatocystin, citrinin, ergot alkaloids, deoxynivalenol, fumonisins, trichothecenes, Alternaria toxins, tremorgenic mycotoxins, fusarins, 3-nitropropionic acid, cyclochlorotine, sporidesmin, etc. These mycotoxins can pose several health risks to both animals and humans, including death. As several mycotoxins simultaneously occur in nature, especially in foods and feeds, the detoxification and/or total removal of mycotoxins remains challenging. Moreover, given that the volume of scientific literature regarding mycotoxins is steadily on the rise, there is need for continuous synthesis of the body of knowledge. To supplement existing information, knowledge of mycotoxins affecting animals, foods, humans, and plants, with more focus on types, toxicity, and prevention measures, including strategies employed in detoxification and removal, were revisited in this work. Our synthesis revealed that mycotoxin decontamination, control, and detoxification strategies cut across pre-and post-harvest preventive measures. In particular, pre-harvest measures can include good agricultural practices, fertilization/irrigation, crop rotation, using resistant varieties of crops, avoiding insect damage, early harvesting, maintaining adequate humidity, and removing debris from the preceding harvests. On the other hand, post-harvest measures can include processing, chemical, biological, and physical measures. Additionally, chemical-based methods and other emerging strategies for mycotoxin detoxification can involve the usage of chitosan, ozone, nanoparticles, and plant extracts.

Aflatoxins in randomly selected groundnuts (Arachis hypogaea) and its products from some local markets across Ghana: Human risk assessment and monitoring

A random assessment and human risk analysis were conducted on 80 groundnut pastes and raw groundnuts from some local markets across the different agroecological zones of Ghana. Total aflatoxins (AFtotal) and aflatoxins (AFB₁, AFB₂, AFG₁, and AFG₂) were analyzed using the High-Performance Liquid Chromatography (HPLC) method. Out of 80 samples investigated, 49 (61.25 %) tested positive for AFB₁ and ranged from 0.38 ± 0.04-230.21 ± 22.14 μg/kg. The same proportion was recorded for total aflatoxins (AF_total) and ranged between 0.38 ± 0.02-270.51 ± 23.14 μg/kg. Limits of AFB₁ and total aflatoxins (AFtotal) for the Ghana Standards Authority (GSA) (5 and 10 μg/kg) and the European Food Safety Authority (EFSA) (2 and 4 μg/kg), were used as checks. A total of 33 (41.25 %) samples were above the limits for both. Risk assessments recorded for Estimated Daily Intake (EDI), Margin of Exposure (MOE), potency, cancer risk, and population risks ranged 0.087-0.380 μg/Kg.bw/day, 1052.630-4597.700, 0-0.00396 ng Aflatoxins kg^-1bwday^-1 and, 1.5 × 10^-3 - 7.9 × 10^-4 respectively for total aflatoxins. While for aflatoxins B₁ (AFB₁), ranges of values of 0.068-0.300 μg/Kg.bw/day, 1333.33-5882.35, 0-0.00396 ng aflatoxins kg/bw/day and, 1.19 × 10^-3 - 6.34 × 10^-4 corresponded for Estimated Daily Intake (EDI), Margin of Exposure (MOE), potency, cancer risk, and population risk respectively. There were risks of adverse health effects involved in the consumption of groundnuts for all age groups investigated since MOE values were all below 10,000.

Increase in aflatoxin exposure in two populations residing in East and West Texas, United States

Although aflatoxin (AF) exposure has not been recognized as a major problem in the United States and other developed nations, recent global climate change may have a profound impact on distribution of toxigenic fungi growth and production of AFs in grain and groundnuts. Alterations in the contamination pattern can increase human dietary exposure, and further invoke public health concerns and associated disease risks. In this study, two populations from East and West Texas, known for their high risk of liver cancer, were examined for their AF exposure at three different time periods from 2004 to 2014. Serum samples (n = 1124) were collected from participants recruited for various studies from Bexar County and Lubbock County, TX, over the span of 2004 through 2014. The exposure biomarker, serum AFB₁-lysine adduct, was analyzed by HPLC-FLD and confirmed by LC-MS. Both populations showed a significant increase in detection rate, as well as median levels of serum AFB₁-lysine adduct over time, from 2.35 to 4.34 pg/mg albumin in East Texas (2007-2014), and 0.63-3.98 pg/mg albumin in West Texas (2004-2010). This observed shift in exposure likely represents a shift in the AF contamination pattern in the State of Texas, and may warrant further studies on risk assessment for the potential etiological effects of such increased exposures.

Time-Resolved Fluorescence Immunochromatography Assay (TRFICA) for Aflatoxin: Aiming at Increasing Strip Method Sensitivity

Aflatoxin is the most harmful mycotoxin that is ubiquitous in foods and agro-products. Because of its high toxicity, maximum admissible levels of aflatoxins (AF) is regulated worldwide, and monitoring of their occurrence in several commodities is mandatory for assuring food safety and consumers' health. Considering that the strip method is very simple and convenient for users, in order to enhance strip assay's sensitivity, a lot of time-resolved fluorescence immunochromatography assays (TRFICAs) were developed recently with increasing several times of assay sensitivity compared with traditional gold nanoparticle-based strip assay (GNP-SA). This review briefly describes the newly developed TRFICA for aflatoxin determination, including TRFICA for aflatoxin B1 (AFB1) detection, TRFICA for aflatoxin M1 (AFM1) detection, TRFICA for total aflatoxins (AFB1 + B2 + G1 + G2) detection and the latest identification-nanobody-based TRFICA for aflatoxin detection. The application of TRFICA for aflatoxin detection in different agro-products is also concluded in this review. Reasonably, TRFICA has been becoming one of the most important tool for monitoring aflatoxin in foods and agro-products.

Corn Flour Intake, Aflatoxin B1 Exposure, and Risk of Esophageal Precancerous Lesions in a High-Risk Area of Huai'an, China: A Case-Control Study

Aflatoxin B₁ (AFB₁), which has potent toxicity and carcinogenicity, is a common contaminant of important agricultural commodities. This study aimed to investigate the frequency of corn flour intake and assess the exposure to AFB₁ via direct detection of AFB₁ in the diet and serum AFB₁ exposure biomarker, so as to evaluate their associations with the risk of esophageal precancerous lesions (EPL). A case-control study based on three-day duplicate diet samples was performed in Huai'an District. One hundred EPL cases and 100 healthy controls were enrolled and required to be age- (±2 years) and gender-matched. The concentration of AFB₁ in food samples and the level of serum AFB₁-albumin (AFB₁-Alb) adduct were quantitatively analyzed. Results showed that corn flour intake was positively associated with serum AFB₁-Alb adduct level (p for trend = 0.003), dietary AFB₁ exposure (p for trend < 0.001), and the risk of EPL (p for trend = 0.017). Increased serum AFB₁-Alb adduct level was associated with an increased risk of EPL as well (p for trend < 0.001). In conclusion, corn flour may be an essential source of AFB₁ in Huai'an District, whereas high exposure to AFB₁ is likely to be an important risk factor contributing to the progression of EPL.

Aflatoxin exposure in utero and birth and growth outcomes in Tanzania

Some evidence suggests that aflatoxin may contribute to the high prevalence of stunting observed in low-income countries. Whereas several studies have been conducted in West Africa, fewer exist in East Africa and even fewer in nonagricultural contexts. We analyzed serum samples from 400 iron-replete, nonanemic pregnant women from a cohort in Dar es Salaam, Tanzania to determine the extent and magnitude of exposure to aflatoxin and to study the relationship between levels of aflatoxin exposure in utero and infant birth and growth outcomes. Ninety-nine percent of women had detectable concentrations of aflatoxin B1-lysine (AFB1-lysine), with a median level of 1.4-pg/mg albumin, indicating a much lower level compared to studies of rural populations in sub-Saharan Africa. Our results do not show a statistically significant relationship between AFB1-lysine levels and birth weight, small for gestational age, or prematurity. We observe a small statistically significant reduction in gestational age at delivery (0.47 weeks; 95% CI: -0.86, -0.07) as the natural log of AFB1-lysine levels increases by 1 unit of pg/mg of albumin, after controlling for potential confounders. Among a nonrandom set of infants who had measurements for placental weight, haemoglobin at delivery, and follow-up z-score measurements, we find no association between aflatoxin plasma concentrations and these variables. These findings suggest a high prevalence of chronic low-level exposure to aflatoxin, though its effect on birth outcomes in this population remains unclear. Our research adds to a growing body of literature finding mixed associations between aflatoxins on pregnancy outcomes and child growth.

Human Biomonitoring of Mycotoxins in Blood, Plasma and Serum in Recent Years: A Review

This manuscript reviews the state-of-the-art regarding human biological monitoring (HBM) of mycotoxins in plasma serum and blood samples. After a comprehensive and systematic literature review, with a focus on the last five years, several aspects were analyzed and summarized: a) the biomarkers analyzed and their encountered levels, b) the analytical methodologies developed and c) the relationship between biomarker levels and some illnesses. In the literature reviewed, aflatoxin B1-lysine (AFB1-lys) and ochratoxin A (OTA) in plasma and serum were the most widely studied mycotoxin biomarkers for HBM. Regarding analytical methodologies, a clear increase in the development of methods for the simultaneous determination of multiple mycotoxins has been observed. For this purpose, the use of liquid chromatography (LC) methodologies, especially when coupled with tandem mass spectrometry (MS/MS) or high resolution mass spectrometry (HRMS), has grown. A high percentage of the samples analyzed for OTA or aflatoxin B1 (mostly as AFB1-lys) in the reviewed papers were positive, demonstrating human exposure to mycotoxins. This review confirms the importance of mycotoxin human biomonitoring and highlights the important challenges that should be faced, such as the inclusion of other mycotoxins in HBM programs, the need to increase knowledge of mycotoxin metabolism and toxicokinetics, and the need for reference materials and new methodologies for treating samples. In addition, guidelines are required for analytical method validation, as well as equations to establish the relationship between human fluid levels and mycotoxin intake.

A semiconductor quantum dot-based ratiometric electrochemical aptasensor for the selective and reliable determination of aflatoxin B1

In recent years, a ratiometric electrochemical method has been investigated due to its ability to effectively reduce the background electrical signals via the introduction of an internal calibration mechanism, which has great practical significance in the detection of mycotoxins in foods. Herein, we report a ratiometric electrochemical aptasensor based on two semiconductor quantum dots (i.e. CdTe and PbS QDs) for the detection of aflatoxin B1 (AFB1). The aptasensor was fabricated by immobilizing PbS QD-coated silica hybrid spheres (SiO2@PbS) onto CdTe QD-modified Fe3O4@SiO2 (Fe3O4@SiO2/CdTe) surface through biorecognition between the aptamer and complementary DNAs, where PbS QDs acted as external signal labels and CdTe QDs acted as internal reference labels. In the presence of AFB1, the aptamer connected to SiO2@PbS preferred to form an aptamer/AFB1 complex, which brought about the separation of SiO2@PbS linked with the CdTe QDs; with the addition of more AFB1 to the solution, the amount of SiO2@PbS present on the Fe3O4@SiO2/CdTe surface reduced. After several steps of endonuclease cleavage, magnetic separation, and dissolution with acid, the square wave voltammetry signals of Pb2+ and Cd2+ maintained an inverse relationship with the target content based on the SWV stripping measurements; the proposed method had the wide linear range of 5 pg mL-1-50 ng mL-1 and the determination limit of 4.5 pg mL-1 (S/N = 3) and was applied for the detection of AFB1 in peanuts. The proposed aptasensor has an important practical significance for the development of food safety.

Assessment of aflatoxin B1-lysine adduct in serum of infant population of the Huasteca Potosina, México – a pilot study

Aflatoxins are mycotoxins considered to be highly toxic and produce adverse effects on human health. These compounds, mainly aflatoxin B1 (AFB1), have been classified as human carcinogens, due to its association with the development of hepatocellular carcinoma. In Mexico, the study of aflatoxins has been focused on the evaluation of products of the basic basket, particularly on maize, which is the basis of the Mexican diet. On the other hand, most of these studies have been conducted in urban areas. Indigenous populations may be exposed to a higher risk than urban ones due to the high consumption of tortillas, the harvest and the storage conditions of their food; hence, AFB1 is frequently found contaminating maize, which is the main food source for Mexicans. There is scarce evidence of exposure in vulnerable populations, such as children. Therefore, the main objective of this research was to conduct a pilot study for the evaluation of exposure to AFB1 through the AFB1-lys adduct in 31 serum samples of children from indigenous communities in Mexico. AFB1-lys was measured by High Pressure Liquid Chromatography with fluorescence detector (HPLC-FLD), with limits of detection and quantification of 3.5 and 4.7 pg/ml, respectively. Results from this pilot study revealed that 13% of children were of short stature, 9.7% presented overweight and 6.5% obesity. 45% of the children presented detectable concentrations of AFB1-lys adduct, with a median (minimum-maximum) of 5.6 (4.8-6.5) pg of AFB1-lys adduct/mg of albumin. The AFB1-lysine exposure biomarker is an important tool for the surveillance of aflatoxins and their effects on health, so, following this intervention, it would be necessary to monitor the exposure of vulnerable populations to aflatoxins, especially in rural areas where foods are more contaminated.

Evaluation of emerging biomarkers of renal damage and exposure to aflatoxin-B1 in Mexican indigenous women: a pilot study

Aflatoxins (AFs) are mycotoxins produced by Aspergillus parasiticus and Aspergillus flavus which frequently contaminate maize. These compounds are considered toxic, especially AFB1 which has been classified as a human carcinogen, due to its relationship with the generation of hepatocellular carcinoma. Studies in vivo, in animal models, prove that chronic consumption of AFB1 has an association with renal adverse effects, but evidence in humans is scarce. Therefore, the main objective of this research was to conduct a pilot study to evaluate the correlation between exposure to AFB1 and early-stage renal damage in indigenous women of San Luis Potosí, Mexico. Exposure to AFB1 was measured through the biomarker AFB1-lysine and renal damage through kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and cystatin-C (Cys-C). AFB1-Lys was measured by HPLC-FLD. The method was validated with a correlation coefficient of 0.99 and limit of detection and quantification of 3.5 and 4.7 pg mL-1, respectively. Levels of NGAL, KIM-1, and Cys-C were determined (median (P25-P75), 5.96 (3.16-15.91), 0.137 (0.137-0.281), and 18.49 (5.76-29.57) ng mL-1, respectively). Additionally, glomerular filtration rate (GFR) (83.3 (59.8-107.4) mL/min/1.73 m2) and serum creatinine (SCr) (0.88 (0.72-1.22) mg dL-1) were obtained. The median concentrations for AFB1-Lys were 2.08 (1.89-5.8) pg mg-1 of albumin. Statistically significant correlations between AFB1-Lys/KIM-1 (Rho = 0.498, p = 0.007) and AFB1/Cys-C (Rho = 0.431, p = 0.014) were found. Our results indicate that women are exposed to AFB1, due to the fact that the AFB1-Lys biomarker was found in a high percentage of the study population (83%). In addition, the results of exposure to AFB1 show a strong significant correlation between KIM-1 and Cys-C that may indicate the toxic renal effect. These results are alarming because of the high toxicity of this compound and require adequate intervention to reduce AFB1 exposure in these populations.

Epigenetic alterations caused by aflatoxin b1: a public health risk in the induction of hepatocellular carcinoma

Aflatoxin B1 (AFB1) is currently the most commonly studied mycotoxin due to its great toxicity, its distribution in a wide variety of foods such as grains and cereals and its involvement in the development of + (hepatocellular carcinoma; HCC). HCC is one of the main types of liver cancer, and has become a serious public health problem, due to its high incidence mainly in Southeast Asia and Africa. Studies show that AFB1 acts in synergy with other risk factors such as hepatitis B and C virus leading to the development of HCC through genetic and epigenetic modifications. The genetic modifications begin in the liver through the biomorphic AFB1, the AFB1-exo-8.9-Epoxy active, which interacts with DNA to form adducts of AFB1-DNA. These adducts induce mutation in codon 249, mediated by a transversion of G-T in the p53 tumor suppressor gene, causing HCC. Thus, this review provides an overview of the evidence for AFB1-induced epigenetic alterations and the potential mechanisms involved in the development of HCC, focusing on a critical analysis of the importance of severe legislation in the detection of aflatoxins.

Fabrication of magnetically assembled aptasensing device for label-free determination of aflatoxin B1 based on EIS

Aflatoxin B1 (AFB1), one of the most common mycotoxins in food matrixes, has been identified as the most toxic contaminant with mutagenic, teratogenic, immunosuppressive, and carcinogenic effects. In this work, a magnetically assembled aptasensing device has been designed for label-free determination of AFB1 by employing a disposable screen-printed carbon electrode (SPCE) covered with a designed polydimethylsiloxane (PDMS) film as the micro electrolytic cell. The magnetically controlled bio-probes were firstly prepared by immobilization of the thiolated aptamers on the Fe₃O₄@Au magnetic beads, which was rapidly assembled on the working electrode of SPCE within 10 s, by using a magnet placed at the opposite side. The PDMS film with a centered hole was covered on the SPCE surface to achieve a more practicable and flexible electrochemical measurement. In this effort, a label-free aptasensor for the sensitive and selective determination of AFB1 has been developed using electrochemical impedance spectroscopy upon the biorecognition between aptamers and the targets. The developed method had a wide linear range of 20 pg mL^-1-50 ng mL^-1 with a detection limit of 15 pg mL^-1 (S/N = 3) and succeeded in spiked samples of peanuts. The developed aptasensing device shows fantastic application prospect with simple design, easy operation, low cost, and high sensitivity and selectivity characteristics. This sensing strategy represents a promising path toward routine quality control of food safety and creates the opportunity to develop facile aptasensing device for other targets.

Aflatoxin B1 exposure increases the risk of hepatocellular carcinoma associated with hepatitis C virus infection or alcohol consumption

BACKGROUND

Hepatocarcinogenicity of aflatoxin B₁ (AFB₁) has rarely been studied in populations with hepatitis C virus (HCV) infection and those without hepatitis B virus (HBV) and HCV infection (non-B-non-C). This case-control study nested in a community-based cohort aimed to investigate the HCC risk associated with AFB₁ in HCV-infected and non-B-non-C participants.

METHODS

Baseline serum AFB₁-albumin adduct levels were measured in 100 HCC cases and 1767 controls seronegative for anti-HCV and HBsAg (non-B-non-C), and another 103 HCC cases and 176 controls who were anti-HCV-seropositive and HBsAg-seronegative. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated using logistic regression.

RESULTS

In 20 years of follow-up, the follow-up time to newly developed HCC was significantly shorter in participants with higher serum AFB₁-albumin adduct levels in non-B-non-C (p = 0.0162) and HCV-infected participants (p < 0.0001). Within 8 years of follow-up, HCV infection and AFB₁ exposure were independent risk factors for HCC. Elevated serum AFB₁-albumin adduct levels were significantly associated with an increased risk of HCC newly developed within 8 years of follow-up in non-B-non-C participants with habitual alcohol consumption [crude OR (95% CI) for high vs. low/undetectable levels, 4.22 (1.16-15.37)] and HCV-infected participants [3.39 (1.31-8.77)], but not in non-B-non-C participants without alcohol drinking habit. AFB₁ exposure remained an independent risk predictor for HCV-related HCC after adjustment for other HCC predictors (multivariate-adjusted OR [95% CI], 3.65 [1.32-10.10]).

CONCLUSIONS

AFB₁ exposure contributes to the development of HCC in participants with significant risk factors for cirrhosis including alcohol and HCV infection.

Aflatoxin exposure in Nigerian children with severe acute malnutrition

Aflatoxin exposure is an important public health concern in sub-Saharan Africa as well as parts of Latin America and Asia. In addition to hepatocellular carcinoma, chronic aflatoxin exposure is believed to play a role in childhood growth impairment. The most reliable biomarker of chronic aflatoxin exposure is the aflatoxin-albumin adduct, as measured by ELISA or isotope dilution mass spectrometry (IDMS). In this report, we have used high resolution LC-MS/MS with IDMS to quantitate AFB₁-lysine in an extremely vulnerable population of Nigerian children suffering from severe acute malnutrition. To increase the sensitivity and reliability of the analyses, a labelled AFB₁-¹³C₆¹⁵N₂-lysine internal standard was synthesized. AFB₁-lysine concentrations in this population ranged between 0.2 and 59.2 pg/mg albumin, with a median value of 2.6 pg/mg albumin. AFB₁-lysine concentrations were significantly higher in stunted children (median = 4.6 pg/mg) compared to non-stunted (1.2 pg/mg), as well as in children with severe acute malnutrition (4.3 pg/mg) compared to controls (0.8 pg/mg). The median concentrations were also higher in children with kwashiorkor (6.3 pg/mg) compared to those suffering from marasmus (0.9 pg/mg). This is the first report of the use of high-resolution mass spectrometry to quantitate AFB₁-lysine in humans.

A review of the current situation of aflatoxin M1 in cow's milk in Serbia: risk assessment and regulatory aspects

The aim of this systematic review is to provide information regarding the incidence and levels of aflatoxin M₁ (AFM₁) in raw and heat processed cow's milk in Serbia during 2015-16 and to compare these with collected data on the occurrence of AFM₁ in raw milk and dairy products during the last decade in our region. Estimation of dietary exposure (EDI) and hazard index (HI) calculations for different age groups of the population were also carried out, based on the AFM₁ content of milk samples and on available food consumption data in Serbia. AFM₁ was detected in 69.9% (984/1408) of raw milk samples in 2015 versus 84.9% (3094/3646) in 2016, while in heat-processed milk, AFM₁ was detected in 77.8% (364/468) in 2015 versus 98.5% (753/765) in 2016. On the basis of the obtained results, 450 (9%) of raw and 14 (1.1%) of heat-processed milk samples were contaminated with AFM₁ levels above the maximum permitted level in Serbia (0.25 μg kg^-1). However, a large percentage of raw and heat processed milk in Serbia (30.1% and 17.3%, respectively) was contaminated with AFM₁ levels above the maximum permitted level regulated in the European Union (0.05 μg kg^-1). Therefore, in order to protect consumer health, it is extremely important to further control the level of aflatoxins in milk, and this should be considered as a high priority for risk management actions.

Aflatoxin B1 exposure increases the risk of cirrhosis and hepatocellular carcinoma in chronic hepatitis B virus carriers

The relation between aflatoxin B1 (AFB1 ) and cirrhosis in chronic carriers of hepatitis B virus (HBV) remains inconclusive. This case-control study nested in a large community-based cohort aimed to assess the effect of AFB1 exposure on cirrhosis and HCC in chronic HBV carriers. Serum AFB1 -albumin adduct levels at study entry were measured in 232 cirrhosis cases, 262 HCC cases and 577 controls. Multivariate-adjusted odds ratios (aORs) and 95% confidence intervals (95% CIs) were estimated using logistic regression. Among all chronic HBV carriers, the time intervals between study entry and diagnosis of HCC, cirrhosis, cirrhotic HCC, and non-cirrhotic HCC were all significantly (p < 0.0001) shorter in participants with high serum levels of AFB1 -albumin adducts than those with low/undetectable levels. There were significant dose-response relations with serum AFB1 -albumin adduct level at study entry for cirrhosis (p-trend = 0.0001) and cirrhotic HCC (p-trend < 0.0001) newly diagnosed within 9 years after entry as well as non-cirrhotic HCC (p-trend = 0.021) newly diagnosed within 4 years after entry. The aORs (95% CIs) for high versus undetectable serum AFB1 -albumin adduct levels were 2.45 (1.51-3.98) for cirrhosis (p = 0.0003), 5.47 (2.20-13.63) for cirrhotic HCC (p = 0.0003), and 5.39 (1.11-26.18) for non-cirrhotic (p = 0.0368) HCC, respectively. There remained a significant dose-response relation between serum AFB1 -albumin adduct level and HCC risk (p-trend = 0.0291) in cirrhosis patients, showing an aOR (95% CI) of 3.04 (1.11-8.30) for high versus undetectable serum levels (p = 0.0299). It is concluded that AFB1 exposure may increase the risk of cirrhosis and HCC in a dose-response manner among chronic HBV carriers.

Association of Aflatoxin and Gallbladder Cancer

BACKGROUND & AIMS

Aflatoxin, which causes hepatocellular carcinoma, may also cause gallbladder cancer. We investigated whether patients with gallbladder cancer have higher exposure to aflatoxin than patients with gallstones.

METHODS

We measured aflatoxin B1 (AFB1)-lysine adducts in plasma samples from the Shanghai Biliary Tract Cancer case-control study, conducted from 1997 through 2001. We calculated age- and sex-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) and the population-attributable fraction for 209 patients with gallbladder cancer and gallstones vs 250 patients with gallstones without cancer (controls). In 54 patients with gallbladder cancer, tumor tissue was examined for the R249S mutation in TP53, associated with aflatoxin exposure, through targeted sequencing.

RESULTS

The AFB1-lysine adduct was detected in 67 (32%) of 209 patients with gallbladder cancer and 37 (15%) of the 250 controls (χ2 P < .0001), almost threefold more patients with gallbladder cancer than controls (OR, 2.71; 95% CI, 1.70-4.33). Among participants with detectable levels of AFB1-lysine, the median level of AFB1-lysine was 5.4 pg/mg in those with gallbladder cancer, compared with 1.2 pg/mg in controls. For patients in the fourth quartile of AFB1-lysine level vs the first quartile, the OR for gallbladder cancer was 7.61 (95% CI, 2.01-28.84). None of the 54 gallbladder tumors sequenced were found to have the R249S mutation in TP53. The population-attributable fraction for cancer related to aflatoxin was 20% (95% CI, 15%-25%).

CONCLUSIONS

In a case-control study of patients with gallbladder cancer and gallstones vs patients with gallstones without cancer, we associated exposure to aflatoxin (based on plasma level of AFB1-lysine) with gallbladder cancer. Gallbladder cancer does not appear associate with the R249S mutation in TP53. If aflatoxin is a cause of gallbladder cancer, it may have accounted for up to 20% of the gallbladder cancers in Shanghai, China, during the study period, and could account for an even higher proportion in high-risk areas. If our findings are verified, reducing aflatoxin exposure might reduce the incidence of gallbladder cancer.

Comparison of biological effects with albumin adducts of 4,4'-methylenediphenyl diisocyanate in workers

Lung sensitization and asthma are the main health effects of 4,4'-methylenediphenyl diisocyanate (MDI). Albumin adducts (isocyanate-specific adducts) of MDI might be involved in the etiology of sensitization reactions. Albumin adducts of MDI were analyzed in sera of diisocyanate-exposed worker with and without diisocyanate occupational asthma (DA), as well as in exposed workers with and without diisocyanate-specific IgG antibodies. In DA-positive workers and IgG-positive workers, albumin adducts were significantly higher versus workers without DA and those who were specific IgG negative. The odds ratio to be DA-positive was 57 times larger for workers with adduct levels above 230 fmol/mg. The odds ratio to be IgG-positive was 10 times larger for workers with adduct levels above 113 fmol/mg. Therefore, albumin adducts appear to be a good predictor of the biological effects. The albumin-adduct levels in workers without biological effects were in the range of the adduct levels found in previous studies of healthy MDI-factory and construction site workers.

Determination of albumin adducts of 4,4'-methylenediphenyl diisocyanate after specific inhalative challenge tests in workers

4,4'-Methylenediphenyl diisocyanate (MDI) is the most important isocyanate used in the industry. Lung sensitization with bronchial asthma is the main disorder in exposed workers. Albumin adducts of MDI might be involved in specific immunological reactions. MDI adducts with lysine (MDI-Lys) of albumin have been found in MDI-workers and construction workers. MDI-Lys is an isocyanate-specific adduct of MDI with albumin. In the present study, we report MDI-adducts in workers undergoing diagnostic MDI challenge tests. The workers were exposed for 2h to 5ppb of MDI. The adduct levels increase significantly after the exposure to MDI in the challenge chamber. About 0.6% of the dose was bound to albumin. So far, only urinary metabolites of MDI were measured to monitor isocyanate workers. However, such urinary metabolites are not isocyanate specific. Therefore, we propose to measure albumin adducts for monitoring MDI exposed subjects.

Determination of albumin adducts of 4,4'-methylenediphenyl diisocyanate in workers of a 4,4'-methylenedianiline factory

Lung sensitization and asthma are the main health effects of 4,4'-methylenediphenyl diisocyanate (MDI). Albumin adducts (isocyanate specific adducts) of MDI might be involved in the etiology of sensitization reactions. Albumin adducts of MDI have been found in subjects classified as 4,4'-methylenedianiline (MDA) workers. The mean adduct levels in these MDA-workers were 1.5 times higher than in MDI-workers of the same company. MDA-specific hemoglobin adducts, were present ten times more in the MDA-workers than in the MDI-workers. MDA-workers with specific work task had significantly higher albumin adduct levels.

Longitudinal evaluation of aflatoxin exposure in two cohorts in south-western Uganda

Aflatoxins (AF) are a group of mycotoxins. AF exposure causes acute and chronic adverse health effects such as aflatoxicosis and hepatocellular carcinoma in human populations, especially in the developing world. In this study, AF exposure was evaluated using archived serum samples from human immunodeficiency virus (HIV)-seronegative participants from two cohort studies in south-western Uganda. AFB1-lysine (AFB-Lys) adduct levels were determined via HPLC fluorescence in a total of 713 serum samples from the General Population Cohort (GPC), covering eight time periods between 1989 and 2010. Overall, 90% (642/713) of the samples were positive for AFB-Lys and the median level was 1.58 pg mg(-1) albumin (range = 0.40-168 pg mg(-1) albumin). AFB-Lys adduct levels were also measured in a total of 374 serum samples from the Rakai Community Cohort Study (RCCS), across four time periods between 1999 and 2003. The averaged detection rate was 92.5% (346/374) and the median level was 1.18 pg mg(-1) albumin (range = 0.40-122.5 pg mg(-1) albumin). In the GPC study there were no statistically significant differences between demographic parameters, such as age, sex and level of education, and levels of serum AFB-Lys adduct. In the RCCS study, longitudinal analysis using generalised estimating equations revealed significant differences between the adduct levels and residential areas (p = 0.05) and occupations (p = 0.02). This study indicates that AF exposure in people in two populations in south-western Uganda is persistent and has not significantly changed over time. Data from one study, but not the other, indicated that agriculture workers and rural area residents had more AF exposure than those non-agricultural workers and non-rural area residents. These results suggest the need for further study of AF-induced human adverse health effects, especially the predominant diseases in the region.

Aflatoxin exposure during the first 1000 days of life in rural South Asia assessed by aflatoxin B₁-lysine albumin biomarkers

Aflatoxin B1 is a potent carcinogen, occurring from mold growth that contaminates staple grains in hot, humid environments. In this investigation, aflatoxin B1-lysine albumin biomarkers were measured by mass spectrometry in rural South Asian women, during the first and third trimester of pregnancy, and their children at birth and at two years of age. These subjects participated in randomized community trials of antenatal micronutrient supplementation in Sarlahi District, southern Nepal and Gaibandha District in northwestern Bangladesh. Findings from the Nepal samples demonstrated exposure to aflatoxin, with 94% detectable samples ranging from 0.45 to 2939.30 pg aflatoxin B1-lysine/mg albumin during pregnancy. In the Bangladesh samples the range was 1.56 to 63.22 pg aflatoxin B1-lysine/mg albumin in the first trimester, 3.37 to 72.8 pg aflatoxin B1-lysine/mg albumin in the third trimester, 4.62 to 76.69 pg aflatoxin B1-lysine/mg albumin at birth and 3.88 to 81.44 pg aflatoxin B1-lysine/mg albumin at age two years. Aflatoxin B1-lysine adducts in cord blood samples demonstrated that the fetus had the capacity to convert aflatoxin into toxicologically active compounds and the detection in the same 2-year-old children illustrates exposure over the first 1000 days of life.

Carcinogenic effects of aflatoxin B1 among wheat handlers

BACKGROUND

Epidemiological studies have demonstrated that serum aflatoxin B1 (AFB1) is a hepatocarcinogenic mycotoxin and contributor to the high rate of hepatocellular carcinoma (HCC). The prevalence of liver cancer in Egypt is particularly worrisome. In a registry-based analysis of occupational risk for HCC, significant excesses were observed especially for grain mill workers.

OBJECTIVE

The aim of this study was to assess the hepatic carcinogenicity of AFB1 in wheat handlers.

METHODS

Serum AFB1/albumin (AFB1/Alb), alpha-fetoprotein (AFP), alpha-l-fucosidase (AFU), and arginase were estimated in exposed wheat handlers including millers and bakers. The control group was composed of non-occupationally exposed workers.

RESULTS

AFB1/Alb and AFU were significantly higher among workers employed as bakers compared to mill workers and controls. Mill workers had higher levels of AFB1/Alb than the controls. AFB1/Alb, AFP, and AFU were all significantly higher and arginase was significantly lower among HCC cases compared to the other groups. There was a significant correlation between AFU and AFB1/Alb in bakers and between AFP and AFB1/Alb in HCC cases. Arginase was inversely correlated with AFB1/Alb in HCC cases. AFB1/Alb was significantly correlated with the duration of exposure in bakers.

CONCLUSION

Wheat handlers exposed to Aspergillus flavus have a high risk of elevated serum AFB1/Alb levels and AFU.

Carcinogenic effects of aflatoxin B1 among wheat handlers

BACKGROUND

Epidemiological studies have demonstrated that serum aflatoxin B1 (AFB1) is a hepatocarcinogenic mycotoxin and contributor to the high rate of hepatocellular carcinoma (HCC). The prevalence of liver cancer in Egypt is particularly worrisome. In a registry-based analysis of occupational risk for HCC, significant excesses were observed especially for grain mill workers.

OBJECTIVE

The aim of this study was to assess the hepatic carcinogenicity of AFB1 in wheat handlers.

METHODS

Serum AFB1/albumin (AFB1/Alb), alpha-fetoprotein (AFP), alpha-l-fucosidase (AFU), and arginase were estimated in exposed wheat handlers including millers and bakers. The control group was composed of non-occupationally exposed workers.

RESULTS

AFB1/Alb and AFU were significantly higher among workers employed as bakers compared to mill workers and controls. Mill workers had higher levels of AFB1/Alb than the controls. AFB1/Alb, AFP, and AFU were all significantly higher and arginase was significantly lower among HCC cases compared to the other groups. There was a significant correlation between AFU and AFB1/Alb in bakers and between AFP and AFB1/Alb in HCC cases. Arginase was inversely correlated with AFB1/Alb in HCC cases. AFB1/Alb was significantly correlated with the duration of exposure in bakers.

CONCLUSION

Wheat handlers exposed to Aspergillus flavus have a high risk of elevated serum AFB1/Alb levels and AFU.

Advanced hyphenated chromatographic-mass spectrometry in mycotoxin determination: current status and prospects

Mass spectrometric techniques are essential for advanced research in food safety and environmental monitoring. These fields are important for securing the health of humans and animals, and for ensuring environmental security. Mycotoxins, toxic secondary metabolites of filamentous fungi, are major contaminants of agricultural products, food and feed, biological samples, and the environment as a whole. Mycotoxins can cause cancers, nephritic and hepatic diseases, various hemorrhagic syndromes, and immune and neurological disorders. Mycotoxin-contaminated food and feed can provoke trade conflicts, resulting in massive economic losses. Risk assessment of mycotoxin contamination for humans and animals generally depends on clear identification and reliable quantitation in diversified matrices. Pioneering work on mycotoxin quantitation using mass spectrometry (MS) was performed in the early 1970s. Now, unambiguous confirmation and quantitation of mycotoxins can be readily achieved with a variety hyphenated techniques that combine chromatographic separation with MS, including liquid chromatography (LC) or gas chromatography (GC). With the advent of atmospheric pressure ionization, LC-MS has become a routine technique. Recently, the co-occurrence of multiple mycotoxins in the same sample has drawn an increasing amount of attention. Thus, modern analyses must be able to detect and quantitate multiple mycotoxins in a single run. Improvements in tandem MS techniques have been made to achieve this purpose. This review describes the advanced research that has been done regarding mycotoxin determination using hyphenated chromatographic-MS techniques, but is not a full-circle survey of all the literature published on this topic. The present work provides an overview of the various hyphenated chromatographic-MS-based strategies that have been applied to mycotoxin analysis, with a focus on recent developments. The use of chromatographic-MS to measure levels of mycotoxins, including aflatoxins, ochratoxins, patulin, trichothecenes, zearalenone, and fumonisins, is discussed in detail. Both free and masked mycotoxins are included in this review due to different methods of sample preparation. Techniques are described in terms of sample preparation, internal standards, LC/ultra performance LC (UPLC) optimization, and applications and survey. Several future hyphenated MS techniques are discussed as well, including multidimensional chromatography-MS, capillary electrophoresis-MS, and surface plasmon resonance array-MS.

Reduced aflatoxin exposure presages decline in liver cancer mortality in an endemic region of China

Primary liver cancer (PLC) is the third leading cause of cancer mortality globally. In endemic areas of sub-Saharan Africa and Asia, PLC largely arises from chronic infection with hepatitis B virus (HBV) and ingestion of aflatoxins. Although synergistic interactions between these two risk factors have been observed in cohort studies in China, here we determined the impact of agricultural reforms in the 1980s leading to diminished maize consumption and implementation of subsidized universal vaccination against HBV in the 2000s on PLC primary prevention. A population-based cancer registry was used to track PLC mortality in Qidong, China and was compared with the timeline of HBV immunization. Randomly selected serum samples from archived cohort collections from the 1980s to present were analyzed for aflatoxin biomarkers. More than 50% reductions in PLC mortality rates occurred across birth cohorts from the 1960s to the 1980s for Qidongese less than 35 years of age although all were born before universal vaccination of newborns. Median levels of the aflatoxin biomarker decreased from 19.3 pg/mg albumin in 1989 to undetectable (<0.5 pg/mg) by 2009. A population attributable benefit of 65% for reduced PLC mortality was estimated from a government-facilitated switch of dietary staple from maize to rice; 83% of this benefit was in those infected with HBV. Food policy reforms in China resulted in a dramatic decrease in aflatoxin exposure, which, independent of HBV vaccination, reduced liver cancer risk. The extensive HBV vaccine coverage now in place augurs even greater risk reductions in the future.

Global DNA methylation in a population with aflatoxin B1 exposure

We previously reported that global DNA hypomethylation, measured as Sat2 methylation in white blood cells (WBC), and aflatoxin B1 (AFB1) exposure were associated with increased hepatocellular carcinoma risk. In this study, we assessed the association between AFB1 exposure and global DNA methylation. We measured LINE-1 and Sat2 methylation in WBC DNA samples from 1140 cancer free participants of the Cancer Screening Program (CSP) cohort. Blood and urine samples were used to determine the level of AFB1-albumin (AFB1-Alb) adducts and urinary AFB1 metabolites. In continuous models, we found reverse associations of urinary AFB1 with LINE-1 and Sat2 methylation. The odds ratio (OR) per 1 unit decrease were 1.12 (95%CI = 1.03-1.22) for LINE-1 and 1.48 (95%CI = 1.10-2.00) for Sat2 methylation. When compared with subjects in the highest quartile of LINE-1, we found that individuals in the 2nd and 3rd quartiles were less likely to have detectable AFB1-Alb adducts, with ORs (95%CI) of 0.61 (0.40-0.93), 0.61 (0.40-.94), and 1.09 (0.69-1.72), respectively. The OR for detectable AFB1-Alb was 1.81 (95%CI = 1.15-2.85) for subjects in the lowest quartile of Sat2 methylation. The OR for detection of urinary AFB1 for those with LINE-1 methylation in the lowest quartile compared with those in the highest quartile was 1.87 (95%CI = 1.15-3.04). The corresponding OR was 1.75 (95%CI = 1.08-2.82) for subjects in the lowest quartile of Sat2 methylation. The association between AFB1 exposure and global DNA methylation may have implications for the epigenetic effect of AFB1 on hepatocellular carcinoma development and also suggests that changes in DNA methylation may represent an epigenetic biomarker of dietary AFB1 exposure.

Serum concentrations of an aflatoxin-albumin adduct in the National Health and Nutrition Examination Survey (NHANES) 1999-2000

BACKGROUND

During 1998, weather conditions in the United States favored the growth of Aspergillus species leading to widespread contamination of Midwestern and Southern corn with hepatotoxic and hepatocarcinogenic aflatoxins. We designed a study to provide the first national prevalence estimate of aflatoxin exposure using the National Health and Nutrition Examination Survey (NHANES), a representative cross-sectional survey of the noninstitutionalized civilian population of the US.

METHODS

Isotope dilution liquid chromatography-tandem mass spectrometry was used to quantitate serum concentrations of aflatoxin B1-lysine in a one-third random subset of participants from NHANES 1999-2000.

RESULTS

About 1% of the U.S. population had detectable levels (≥0.02μg/l) of aflatoxin B1-lysine. Of those with detectable levels, the geometric mean (95% confidence interval) was 0.038 (0.024-0.060) μg/l (equivalent to 0.842 (0.530-1.34) pg/mg albumin). The highest value was 0.2μg/l (4.43pg/mg albumin). Based on liver function biomarkers, there was no evidence of increased liver dysfunction in these persons.

CONCLUSIONS

During a time when exposure to aflatoxins in food products might have been expected to be increased, we identified few exposed persons. Although none of the subgroup analyses provided reliable estimates due to high relative standard errors, they suggested that additional targeted surveillance may be warranted.

The role of biomarkers in evaluating human health concerns from fungal contaminants in food

Mycotoxins are toxic secondary metabolites that globally contaminate an estimated 25 % of cereal crops and thus exposure is frequent in many populations. Aflatoxins, fumonisins and deoxynivalenol are amongst those mycotoxins of particular concern from a human health perspective. A number of risks to health are suggested including cancer, growth faltering, immune suppression and neural tube defects; though only the demonstrated role for aflatoxin in the aetiology of liver cancer is widely recognised. The heterogeneous distribution of mycotoxins in food restricts the usefulness of food sampling and intake estimates; instead biomarkers provide better tools for informing epidemiological investigations. Validated exposure biomarkers for aflatoxin (urinary aflatoxin M(1), aflatoxin-N7-guaunine, serum aflatoxin-albumin) were established almost 20 years ago and were critical in confirming aflatoxins as potent liver carcinogens. Validation has included demonstration of assay robustness, intake v. biomarker level, and stability of stored samples. More recently, aflatoxin exposure biomarkers are revealing concerns of growth faltering and immune suppression; importantly, they are being used to assess the effectiveness of intervention strategies. For fumonisins and deoxynivalenol these steps of development and validation have significantly advanced in recent years. Such biomarkers should better inform epidemiological studies and thus improve our understanding of their potential risk to human health.

Mass spectrometry of peptides and proteins from human blood

It is difficult to convey the accelerating rate and growing importance of mass spectrometry applications to human blood proteins and peptides. Mass spectrometry can rapidly detect and identify the ionizable peptides from the proteins in a simple mixture and reveal many of their post-translational modifications. However, blood is a complex mixture that may contain many proteins first expressed in cells and tissues. The complete analysis of blood proteins is a daunting task that will rely on a wide range of disciplines from physics, chemistry, biochemistry, genetics, electromagnetic instrumentation, mathematics and computation. Therefore the comprehensive discovery and analysis of blood proteins will rank among the great technical challenges and require the cumulative sum of many of mankind's scientific achievements together. A variety of methods have been used to fractionate, analyze and identify proteins from blood, each yielding a small piece of the whole and throwing the great size of the task into sharp relief. The approaches attempted to date clearly indicate that enumerating the proteins and peptides of blood can be accomplished. There is no doubt that the mass spectrometry of blood will be crucial to the discovery and analysis of proteins, enzyme activities, and post-translational processes that underlay the mechanisms of disease. At present both discovery and quantification of proteins from blood are commonly reaching sensitivities of ∼1 ng/mL.

Present and future directions of translational research on aflatoxin and hepatocellular carcinoma. A review

The aflatoxins were discovered in toxic peanut meal causing "turkey X" disease, which killed large numbers of turkey poults, ducklings and chicks in the UK in the early 1960s. Extracts of toxic feed induced the symptoms in experimental animals, and purified metabolites with properties identical to aflatoxins B(1) and G(1) (AFB(1) and AFG(1)) were isolated from Aspergillus flavus cultures. Structure elucidation of aflatoxin B(1) was accomplished and confirmed by total synthesis in 1963. AFB(1) is a potent liver carcinogen in rodents, non-human primates, fish and birds, operating through a genotoxic mechanism involving metabolic activation to an epoxide, formation of DNA adducts and, in humans, modification of the p53 gene. Aflatoxins are unique among environmental carcinogens, in that elucidation of their mechanisms of action combined with molecular epidemiology provides a foundation for quantitative risk assessment; extensive evidence confirms that contamination of the food supply by AFB(1) puts an exposed population at increased risk of developing hepatocellular carcinoma (HCC). Molecular biomarkers to quantify aflatoxin exposure in individuals were essential to link aflatoxin exposure with liver cancer risk. Biomarkers were validated in populations with high HCC incidence in China and The Gambia, West Africa; urinary AFB(1)-N (7)-Guanine excretion was linearly related to aflatoxin intake, and levels of aflatoxin-serum albumin adducts also reflected aflatoxin intake. Two major cohort studies employing aflatoxin biomarkers identified their causative role in HCC etiology. Results of a study in Shanghai men strongly support a causal relationship between HCC risk and the presence of biomarkers for aflatoxin and HBV infection, and also show that the two risk factors act synergistically. Subsequent cohort studies in Taiwan confirm these results. IARC classified aflatoxin as a Group 1 human carcinogen in 1993, based on sufficient evidence in humans and experimental animals indicating the carcinogenicity of naturally occurring mixtures of aflatoxins, aflatoxin B(1), G(1) and M(1). Aflatoxin biomarkers have also been used to show that primary prevention to reduce aflatoxin exposure can be achieved by low-technology approaches at the subsistence farm level in sub-Saharan Africa. Also, in residents of Qidong, China, oral dosing with chlorophyllin, a chlorophyll derivative, prior to each meal led to significant reduction in aflatoxin-DNA biomarker excretion, supporting the feasibility of preventive measures to reduce HCC risk in populations experiencing unavoidable aflatoxin exposure. The systematic, comprehensive approach used to create the total aflatoxin database justifies optimism for potential success of preventive interventions to ameliorate cancer risk attributable to aflatoxin exposure. This strategy could serve as a template for the development, validation and application of molecular and biochemical markers for other carcinogens and cancers as well as other chronic diseases resulting from environmental exposures.

Aflatoxin: a 50-year odyssey of mechanistic and translational toxicology

Since their discovery 50 years ago, the aflatoxins have become recognized as ubiquitous contaminants of the human food supply throughout the economically developing world. The adverse toxicological consequences of these compounds in populations are quite varied because of a wide range of exposures leading to acute effects, including rapid death, and chronic outcomes such as hepatocellular carcinoma. Furthermore, emerging studies describe a variety of general adverse health effects associated with aflatoxin, such as impaired growth in children. Aflatoxin exposures have also been demonstrated to multiplicatively increase the risk of liver cancer in people chronically infected with hepatitis B virus (HBV) illustrating the deleterious impact that even low toxin levels in the diet can pose for human health. The public health impact of aflatoxin exposure is pervasive. Aflatoxin biomarkers of internal and biologically effective doses have been integral to the establishment of the etiologic role of this toxin in human disease through better estimates of exposure, expanded knowledge of the mechanisms of disease pathogenesis, and as tools for implementing and evaluating preventive interventions.

Aflatoxin B1 exposure, hepatitis B virus infection, and hepatocellular carcinoma in Taiwan

To evaluate the role of aflatoxin B1 (AFB1) exposure on risk of hepatocellular carcinoma (HCC), a case-control study nested within a community-based cohort was conducted. Baseline blood and urine samples were used to determine the level of AFB1-albumin adducts and urinary AFB1 metabolites. Conditional logistic regression analysis was used to calculate odds ratios (OR) and 95% confidence intervals (95% CI) to assess the effect of AFB1 exposure on risk of HCC. The adjusted ORs (95% CIs) were 1.54 (1.01-2.36) and 1.76 (1.18-2.58), respectively, for those with AFB1-albumin adducts and urinary AFB1 metabolite levels above the mean compared with those with levels below the mean. When compared with subjects in the lowest quartile of urinary AFB1 metabolites, there was an increase in risk of HCC, with adjusted ORs (95% CIs) of 0.57 (0.14-2.43), 1.43 (0.32-6.42), and 4.91 (1.18-20.48; Ptrend=0.02), respectively, among noncarriers of hepatitis B virus (HBV) infection. The adjusted OR (95% CI) was 7.49 (5.13-10.93) for carriers of hepatitis B surface antigen compared with noncarriers, regardless of AFB1 status. The ORs (95% CI) were 10.38 (5.73-18.82) and 15.13 (7.83-29.25) for carriers of hepatitis B surface antigens with levels of AFB1-albumin adducts and urinary AFB1 metabolites above the mean, respectively. The combined effect of aflatoxin exposure and HBV infection did not differ by duration of follow-up. Consistent with our previous study with fewer subjects, these data show that AFB1 exposure is a risk factor for HCC risk. However, in this larger study, the effect of combined AFB1 exposure and HBV infection is more consistent with an additive than a multiplicative model.