Oncogenic and tumor suppressor pathways in subchronic aflatoxicosis in rats: Association with serum and urinary aflatoxin exposure biomarkers

In this study, the changes in oncogenic and tumor suppressor signaling pathways in liver and their association with serum and urinary biomarkers of aflatoxin exposure were evaluated in Wistar rats fed diets containing aflatoxin B1 (AFB1) for 90 days. Rats were divided into four groups (n = 15 per group) and assigned to dietary treatments containing 0 (control), 50 (AFB50), 100 (AFB100) and 200 μg AFB1 kg-1 diet (AFB200). Multiple preneoplastic foci of hepatocytes marked with glutathione-S-transferase-placental form (GST-P) were identified in AFB100 and AFB200 groups. Hepatocellular damage induced by AFB1 resulted in overexpression of cyclin D1 and β-catenin. The liver expression of retinoblastoma (Rb) and p27Kip1 decreased in AFB100 and AFB200 groups, confirming the favorable conditions for neoplastic progression to hepatocellular carcinoma. All samples from rats fed AFB1-contaminated diets had quantifiable AFB1-lysine in serum or urinary AFM1 and AFB1-N7-guanine, with mean levels of 20.42-50.34 ng mL-1, 5.31-37.68 and 39.15-126.37 ng mg-1 creatinine, respectively. Positive correlations were found between AFB1-lysine, AFM1 or AFB1-N7-guanine and GST-P+, β-catenin+ and cyclin D1+ hepatocytes, while Rb + cells negatively correlated with those AFB1 exposure biomarkers. The pathways evaluated are critical molecular mechanisms of AFB1-induced hepatocarcinogenesis in rats.

Determination of aflatoxin M1 and deoxynivalenol biomarkers in infants and children urines from Bangladesh

The mycotoxins aflatoxin B1 (AFB1) and deoxynivalenol (DON) are found worldwide in crops and dietary staples. The prevalence and levels of these contaminants can vary greatly, and data in Bangladeshi food commodities are scarce. To characterize human exposure, we have conducted biomonitoring, analyzing AFM1 (a metabolite of AFB1) and DON levels in urines of adult cohorts in Bangladesh. Yet, AFM1 and DON occurrence has not been studied in the very young population of this country. Thus, the same methods, HPLC-FD for AFM1 and LC-MS/MS for DON analysis, were now applied to determine these biomarkers in urines of infants (n = 49) and young children (n = 105) in Rajshahi and Dhaka district. Overall, AFM1 and DON detection frequency was 43.5% and 33.4%, with 34.7% and 11.5% in infant and 47.6% and 39.4% in children urines, respectively. The mean AFM1 levels in all infants (9.1 ± 14.3, max 55.6 pg/mL) and children (8.8 ± 12.9, max 75.3 pg/mL) were not significantly different. The AFM1 mean level was slightly higher in Dhaka (9.4 ± 12.4) compared to Rajshahi (8.5 ± 13.9 pg/mL) district. The average DON level was about 2-fold higher in infant (3.8 ± 2.9, max 6.8 ng/mL) than children urines (1.6 ± 1.8, max 8.6 ng/mL), and higher in Rajshahi (2.1 ± 2.3 ng/mL) than Dhaka (1.4 ± 1.6 ng/mL) district. The biomarker-based estimated average daily DON intake (29.6 ± 108.3 ng/kg bw in infants and 36.4 ± 81.8 ng/kg bw in children) or the maximum exposure (560 ng/kg bw) do not exceed the current maximum provisional tolerable daily intake value of 1 µg/kg bw for DON, although DON exposure in infants and children is higher than that of Bangladeshi adults. The AFM1 urine levels in young children are somewhat lower than those found previously in adult cohorts in Bangladesh, but the frequent detection of this biomarker for AFB1 exposure raises further concerns, also for this vulnerable part of the population. Therefore, continuous surveillance for aflatoxins in Bangladeshi food commodities is clearly required, first to identify major sources of intake and then to reduce exposure.

Biomonitoring of Aflatoxin B1 and Deoxynivalenol in a Rural Pakistan Population Using Ultra-Sensitive LC-MS/MS Method

There are limited data on exposure to mycotoxins in Pakistan. Here, we measured exposure to deoxynivalenol (DON), a common contaminant of wheat, and aflatoxin B1 (AFB1), a known contaminant of rice, using biomarkers of exposure. Wheat (n = 195) and rice (n = 62) samples were analyzed for AFB1 and DON levels, and the corresponding urinary biomarkers were analyzed in urine samples from a rural population (n = 264, aged 4-80 years, male 58%) using ultra-sensitive liquid chromatography-tandem mass spectrometry. AFB1 was detected in 66% of rice (5.04 ± 11.94 µg/kg) and 3% of wheat samples. AFM1 (hydroxylated form of AFB1)was detected in 69% of urine samples, mean 0.023 ± 0.048 ng/mL and DON was detected in 20% of urine samples, mean 0.170 ± 0.129 ng/mL. The maximum probable daily intake for DON derived from the urinary biomarker was 59.8 ng/kg b.w./day, which is below the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives' tolerable daily intake (1000 ng/kg b.w./day). However, for aflatoxin, the derived margin of exposure (MoE) of (13.2) was well below the safe MoE (10,000) suggested by the European Food Safety Authority. The calculated aflatoxin-associated cancer risk of 0.514/105 individuals/year suggests that measures should be taken to reduce the AFB1 contamination in food, particularly rice, in Pakistan.

Association between Urinary Levels of Aflatoxin and Consumption of Food Linked to Maize or Cow Milk or Dairy Products

The aim of this analysis was to assess the association between consumption of maize and dairy products and urine and serum levels of aflatoxin FM1 (AFM1) in a sample of 59 males occupationally exposed (29) and non-exposed (30) to aflatoxins. Two urine samples were collected for each person; each sample was accompanied by a questionnaire on food consumption in the preceding 96 h. Given the similar levels of contamination found in exposed and non-exposed workers, the association between food consumption and AFM1 levels was analyzed by pooling samples from exposed and non-exposed workers. No serum sample was found to be positive for AFM1, whereas 74% of the urine samples were positive; the average concentration of positive samples was 0.042 ng/mL (range < limit of detection (LoD) (0.002)-0.399 ng/mL). Of the 21 samples from maize consumers, 13 were positive for AFM1 (62%), with a mean concentration of 0.026 ng/mL (range 0.006-0.088 ng/mL), while 76% (74/94) of the samples from maize non-consumers were positive (mean 0.045, range < LoD (0.002)-0.399 ng/mL). No association was found with milk or dairy products. The high urine level of aflatoxins found in both exposed and non-exposed workers was not associated with the consumption of maize or cow milk products.

Frequency and levels of aflatoxin M1 in urine of children in Bogota, Colombia

A study was conducted to investigate the frequency and levels of AFM₁ and AFM₂ in urine from children who attended the emergency service of a pediatric referral hospital in Bogota, Colombia. A survey on the consumption of foods likely to be a source of aflatoxins and on sociodemographic variables was conducted as well. The frequency of AFM₁ in urine was found to be 41.7% with an average concentration in positive samples of 16 pg mL^-1 ± 10.7 pg mL^-1 (range > LOD-48.5 pg mL^-1). The presence of AFM₁ in the urine was related to the consumption of cereals likely to be contaminated with AFB₁, especially corn and rice. No detectable levels of AFM₂ were found in any sample. The results show that children's exposure to aflatoxins in Colombia is indeed a problem and should be one of the priorities of the health authorities. Continuous monitoring of aflatoxins in foods should be carried out, in compliance with Colombian regulations, using analytical methods that allow determination and quantification of aflatoxins in different biological and non-biological matrices at trace levels.

Association between Urinary Aflatoxin (AFM₁) and Dietary Intake among Adults in Hulu Langat District, Selangor, Malaysia

Aflatoxin is a food contaminant and its exposure through the diet is frequent and ubiquitous. A long-term dietary aflatoxin exposure has been linked to the development of liver cancer in populations with high prevalence of aflatoxin contamination in foods. Therefore, this study was conducted to identify the association between urinary aflatoxin M₁ (AFM₁), a biomarker of aflatoxin exposure, with the dietary intake among adults in Hulu Langat district, Selangor, Malaysia. Certain food products have higher potential for aflatoxin contamination and these were listed in a Food Frequency Questionnaire, which was given to all study participants. This allowed us to record consumption rates for each food product listed. Concomitantly, urine samples were collected, from adults in selected areas in Hulu Langat district, for the measurement of AFM₁ levels using an ELISA kit. Of the 444 urine samples collected and tested, 199 were positive for AFM₁, with 37 of them exceeding the limit of detection (LOD) of 0.64 ng/mL. Cereal products showed the highest consumption level among all food groups, with an average intake of 512.54 g per day. Chi-square analysis showed that consumption of eggs (X² = 4.77, p = 0.03) and dairy products (X² = 19.36, p < 0.01) had significant associations with urinary AFM₁ but both food groups were having a phi and Cramer’s V value that less than 0.3, which indicated that the association between these food groups’ consumption and AFM₁ level in urine was weak.

An investigation into aflatoxin M 1 in slaughtered fattening pigs and awareness of aflatoxins in Vietnam

BACKGROUND

Aflatoxin M1 (AFM1) is a hydroxylated metabolite formed after aflatoxin B1 (AFB1) is consumed by humans and animals; it can be detected in urine, milk and blood. It is well recognized that AFB1 is toxic to humans and other animals. The International Agency for Research on Cancer (IARC) classifies aflatoxins as group 1 carcinogens and AFM1 as group 2B carcinogen. The main objective of this study was to evaluate the exposure of pigs to aflatoxins as well as to assess the public awareness of aflatoxins among people in five provinces in Vietnam.

RESULTS

A total of 1920 urine samples were collected from slaughterhouses located in five provinces. Overall, the positive rate of AFM1 was 53.90% (95% confidence interval 51.64-56.15) using a cut-off of 0.15 μg/kg (range: limit of detection to 13.66 μg/kg, median: 0.2 μg/kg and mean: 0.63 μg/kg). A total of 252 people from the general population were interviewed from 5 provinces, and overall 67.86% reported being aware of aflatoxins. We also found that men and more highly educated had significantly increased awareness of aflatoxins compared to the females and primary/secondary school group. The respective odds ratios (ORs) were as follows: "male" group (OR: 2.64), "high school educated" group (OR: 3.40) and "college/university or more educated" group (OR: 10.20).

CONCLUSIONS

We can conclude that pigs in Vietnam are exposed to aflatoxins to varying degrees, and there may be a risk that pork products could contain AFM1. Further investigation is needed into the possible health impacts as well as to aid in establishing regulations for animal feed to reduce the health impacts in humans and animals.

Association between Aflatoxin M₁ and Liver Disease in HBV/HCV Infected Persons in Ghana

Aflatoxins are produced by the fungi Aspergillus flavus and Aspergillus parasiticus and are common food contaminants in tropical developing countries. Extensive aflatoxin consumption has been shown to be highly associated with liver disease. A case-control study was conducted to determine the association between aflatoxin and liver disease in Kumasi, Ghana. A questionnaire was administered to examine socio-demographic characteristics and food storage and consumption practices, and urine samples were collected to measure levels of the aflatoxin metabolite (AFM₁). Two hundred and seventy-six people participated in the study; 38 had liver disease (cases), 136 had neither hepatitis B/C nor liver disease (negative controls), and 102 were hepatitis B/C positive without liver cancer (positive controls). A much higher percent of participants in each group was male (76% of cases, 88% of negative controls and 65% of positive controls). Multivariate analysis showed that age was a significant predictor for being a case when cases were compared to negative controls. The odds of being a case was 70% less for participants aged 25-34 years (odds ratios (OR) 0.30; 95% confidence interval (CI) 0.10-0.88) compared to those ≥45 years. For cases; Akans were seven times more likely to have AFM₁ levels below the median when compared to other ethnic groups (OR 7; CI 1.41-34.68). When cases were compared to positive controls, they were 2.29 times more likely to report awareness of aflatoxin contamination of groundnuts (95% CI 1.06-4.91). Cases were also two times more likely to report awareness of aflatoxin contamination of maize than all controls combined (95% CI 1.02-4.11). However, most cases reported that aflatoxin contamination does not cause sickness in humans. This shows that there is awareness of aflatoxin contamination without proper understanding of the serious potential adverse health impacts among these study participants. These findings indicate that educational interventions that stress the harmful health effects of aflatoxin in food, with an emphasis on the higher risk for males, are urgently needed. The reasons for lower aflatoxin levels among Akans need to be determined, and the findings used to design interventions that benefit other ethnic groups in the society.

Multimycotoxin analysis in urines to assess infant exposure: a case study in Cameroon

This study was conducted to investigate mycotoxin exposure in children (n=220, aged 1.5-4.5years) from high mycotoxin contamination regions of Cameroon and to examine the association between the mycotoxin levels (in total 18 analytes) and several socio-demographic factors and anthropometric characteristics. A cross-sectional study was conducted in six villages in Cameroon with 220 children. Mycotoxins and their metabolites were detected in 160/220 (73%) urine samples. There were significant differences in the mean contamination levels of ochratoxin A (p=0.01) and β-zearalenol (p=0.017) between the two agro-ecological zones investigated. Likewise significant differences were observed in the mean levels of aflatoxin M1 (p=0.001) across the weaning categories of these children. The mean concentration of aflatoxin M1 detected in the urine of the partially breastfed children (1.43ng/mL) was significantly higher (p=0.001) than those of the fully weaned children (0.282ng/mL). Meanwhile, the mean concentrations of deoxynivalenol (3.0ng/mL) and fumonisin B1 (0.59ng/mL) detected in the urine of the male children was significantly (p value 0.021 for deoxynivalenol and 0.004 for fumonisin B1) different from the levels detected in the urine of female children; 0.71ng/mL and 0.01ng/mL for deoxynivalenol and fumonisin B1 respectively. In this study, there was no association between the different malnutrition categories (stunted, wasting and underweight) and the mycotoxin concentrations detected in the urine of these children. However, there is sufficient evidence to suggest that children in Cameroon under the age 5 are exposed to high levels of carcinogenic substances such as fumonisin B1, aflatoxin M1 and ochratoxin A through breastfeeding. To the best of our knowledge, this is the first report of its kind carried out in West Africa to determine multi-mycotoxin exposure in infants.

Association between aflatoxin M1 excreted in human urine samples with the consumption of milk and dairy products

This study aimed to find the association between urinary aflatoxin M(1) level and milk and dairy products consumption. Of 160 morning urine samples collected, aflatoxin M(1) was detected in 61.3 % samples (n = 98) [mean ± SD = 0.0234 ± 0.0177 ng/mL; range = 0-0.0747 ng/mL]. Of these positive samples, 67.3 % (n = 66) had levels above the limit of detection. Respondents with intake of milk and dairy products above median (67.79 g/day) had significantly high level of AFM(1) compared to those with low intake. A significant and positive association (φ = 0.286) was found between milk and dairy products consumption and urinary aflatoxin M(1) level.

Aflatoxin B1 albumin adducts in plasma and aflatoxin M1 in urine are associated with plasma concentrations of vitamins A and E

BACKGROUND

Although aflatoxin exposure has been associated with micronutrient deficiency in animals, there are few investigations on the effects of aflatoxin exposure on micronutrient metabolism in humans.

OBJECTIVE

To examine the relationship between aflatoxin B1 (AFB1) albumin adducts (AF-ALB) in plasma and the aflatoxin M1 (AFM1) metabolite in urine and plasma concentrations of retinol (vitamin A) and alpha-tocopherol (vitamin E) in Ghanaians.

METHODS

A cross-sectional study of 147 adult participants was conducted. Blood and urine samples were tested for aflatoxin and vitamins A and E levels.

RESULTS

Multivariable analysis showed that participants with high AF-ALB (>or=0.80 pmol/mg albumin) had increased odds of having vitamin A deficiency compared to those with lower AF-ALB [Odds Ratio (OR)=2.61; CI=1.03-6.58; p=0.04]. Participants with high AF-ALB also showed increased odds of having vitamin E deficiency but this was not statistically significant (OR=2.4; CI=0.96-6.05; p=0.06). Conversely, those with higher AFM1 values had a statistically nonsignificant reduced odds of having vitamin A deficiency (OR=0.31; CI=0.09-1.02; p=0.05) and a statistically significant reduced odds of having vitamin E deficiency (OR=0.31; CI=0.10-0.97; p=0.04). Participants with high AF-ALB or high AFM1 (>or=437.95 pg/dL creatinine) were almost 6 times more likely to be hepatitis B virus surface antigen (HBsAg)-positive (OR=5.88; CI=1.71-20.14; p=0.005) and (OR=5.84; CI=1.15-29.54; p=0.03) respectively.

CONCLUSIONS

These data indicate that aflatoxin may modify plasma micronutrient status. Thus, preventing aflatoxin exposure may reduce vitamin A and E deficiencies.

Detection of aflatoxin among hepatocellular carcinoma patients in Egypt

The present research were tempted to investigate whether Aflatoxin is an additive factor in development of HCC through detecting its metabolite Aflatoxin Ml1 in serum and urine of HCC and cirrhotics in Egypt. Present study comprised (46) Hepatocellular Carcinoma (HCC) patients with mean age (56.28 +/- 8.08), 30 males and 16 females, (12) cirrhotic patients with mean age (47.83 +/- 18.20), 7 males and 5 females and (12) sex and age matched healthy controls. All were exposed to, liver function tests, abdominal ultrasonography and detection of Aflatoxin metabolite M1 in serum and urine by means of the reverse phase HPLC device. Aflatoxin M1 was detected in sera of HCC group, cirrhotics and controls (57.8%) (5.61 +/- 17.21 ng mL(-1)), (91.7%) (19.23 +/- 20.42 ng mL(-1)) and (50%) (0.66 +/- 0.84 ng mL(-1)), respectively and in urine (41.3%) (3.82 +/- 8.03 ng mL(-1)) (91.7%) (43.22 +/- 45.02 ng mL(-1)) and (50%) (0.98 +/- 1.4 ng mL(-1)), respectively representing significant increase in the serum of the cirrhotic group (p < 0.02) and a high significant increase in urine of the cirrhotic group (p < 0.0001). Among HCC group patients, there is high significant value of M1 concentration in urine of upper Egypt residents compared to those of lower Egypt (p < 0.002). The mean value of Aflatoxin M1 concentration among females of the HCC group was significantly higher than that among males (p = 0.006). There is higher statistical significance of aflatoxin prevalence and concentration in serum and urine ofcirrhotics than HCC patients and controls and in concentration in urine of HCC patients from upper than lower Egypt.

Measurement of Aflatoxin and Aflatoxin Metabolites in Urine by Liquid Chromatography-Tandem Mass Spectrometry

Automated immunoaffinity solid-phase extraction followed by liquid chromatography-tandem mass spectrometry and chemical analogue internal standardization is employed to detect and quantify the aflatoxins AFB(1), AFB(2), AFG(1), AFG(2), and the metabolites AFM(1) and AFP(1) in urine. The dynamic range of the method is nearly three orders of magnitude with limits of detection in the low femtogram on column range. The method was validated over a 12-day period by eight analysts. This method is suitable for agricultural, forensic, and public health laboratories during an accidental outbreak or a chemical terrorism event where a rapid and accurate diagnosis of aflatoxicosis is needed.

Sample size and statistical power assessing the effect of interventions in the context of mixture distributions with detection limits

Often in randomized clinical trials and observational cohort studies, a non-negative continuously distributed response variable is measured in treatment and control groups. In the presence of true zeros for the response variable, a two-part zero-inflated log-normal model (which assumes that the data has a probability mass at zero and a continuous response for values greater than zero) is usually recommended. However, in some environmental health and human immunodeficiency virus (HIV) studies, quantitative assays for metabolites of toxicants, or quantitative HIV RNA measurements are subject to left-censoring due to values falling below the limit of detection (LD). Here, a zero-inflated log-normal mixture model is often suggested since true zeros are indistinguishable from left-censored values due to the LD. When the probabilities of true zeros in the two groups are not restricted to be equal, the information contributed by values falling below LD is used only to estimate the probability of true zeros in the context of mixture distributions. We derived the required sample size to assess the effect of a treatment in the context of mixture models with equal and unequal variances based on the left-truncated log-normal distribution. Methods for calculation of statistical power are also presented. We calculate the required sample size and power for a recent study estimating the effect of oltipraz on reducing urinary levels of the hydroxylated metabolite aflatoxin M(1) (AFM(1)) in a randomized, placebo-controlled, double-blind phase IIa chemoprevention trial in Qidong, China. A Monte Carlo simulation study is conducted to investigate the performance of the proposed methods.

Monitoring the mycotoxins in food and their biomarkers in the Czech Republic

Testing of the presence of toxigenic microfungi and mycotoxins in foodstuffs in the food chain is an important part of the food safety strategy in The Czech Republic. At the national level, control of their presence in the entire food chain is assured by Public Health Protection Agencies, by the Veterinary Administration and by the Czech Agriculture and Food Inspection Authority. This article summarizes surveillance activities of Public Health Protection Agencies and mycotoxins findings in dietary raw materials and foodstuffs from the 1990s to 2004 in the Czech Republic. At present, the health risk from the mycotoxins exposure from foodstuffs is assessed to be relatively low in the Czech Republic, especially as far as the foodstuffs of the Czech origin are concerned. It may result in late toxic effects (e. g., carcinogenic risk) following a single or repeated ingestion of low mycotoxins doses from foodstuffs. Nevertheless, the overall situation may change due to the globalization of the food market. In order to minimize the risk associated with mycotoxins and eliminate their impact on Czech public health, continuous monitoring of the presence of toxigenic moulds, mycotoxins, and their biomarkers is necessary, in conjunction with strict respect to European Union legislation.

Determinants of aflatoxin levels in Ghanaians: sociodemographic factors, knowledge of aflatoxin and food handling and consumption practices

Aflatoxins are among the most potent of carcinogens found in staple foods such as groundnuts, maize and other oil seeds. This study was conducted to measure the levels of aflatoxin B(1) (AFB(1)) albumin adducts in blood and aflatoxin M(1) (AFM(1)) metabolite in urine of people in a heavy peanut and maize consuming region of Ghana and to examine the association between aflatoxin levels and several socio-demographic factors and food handling and consumption practices. A cross-sectional study was conducted in four villages in the Ejura Sekyedumase district of Ghana. A socio-demographic survey was administered to 162 participants. Blood samples were collected from 140 and urine samples from 91 of the participants and AFB(1) albumin-adduct levels in blood and AFM(1) levels in urine were measured. High AFB(1) albumin-adduct levels were found in the plasma (mean+/-SD=0.89+/-0.46pmol/mg albumin; range=0.12-3.00pmol/mg; median=0.80pmol/mg) and high AFM(1) levels in the urine (mean+/-SD=1,800.14+/-2602.01pg/mg creatinine; range=non-detectable to 11,562.36pg/mg; median=472.67pg/mg) of most of the participants. There was a statistically significant correlation (r=0.35; p=0.007) between AFB(1)-albumin adduct levels in plasma and AFM(1) levels in urine. Several socio-demographic factors, namely, educational level, ethnic group, the village in which participants lived, number of individuals in the household, and number of children in the household attending secondary school, were found to be significantly associated with AFB(1) albumin-adduct levels by bivariate analysis. By multivariate analyses, ethnic group (p=0.04), the village in which participants live (p=0.02), and the number of individuals in the household (p=0.01), were significant predictors of high AFB(1) albumin-adducts. These findings indicate strongly that there is need for specifically targeted post-harvest and food handling and preparation interventions designed to reduce aflatoxin exposure among the different ethnic groups in this region of Ghana.

Fecal and urinary excretion of aflatoxin B1 metabolites (AFQ1, AFM1 and AFB-N7-guanine) in young Chinese males

Our study was designed to assess the fecal and urinary excretion of 3 aflatoxin B1 (AFB1) metabolites, aflatoxins M1 (AFM1) and Q1 (AFQ1) and aflatoxin B1-N7-guanine (AFB-N7-guanine) that are produced by the predominant forms of cytochrome P450 enzymes responsible for the biotransformation of AFB1. Fecal and urinary AFM1, AFQ1 and urinary AFB-N7-guanine were assessed in 83 young Chinese males selected from a larger population (n = 300) based on detectable urinary AFM1. The concentration of fecal AFQ1 (median 137 ng/g fresh weight, IQR 9.1 to 450) was approximately 60 times higher than that of AFM1 (2.3 ng/g, IQR 0.0 to 7.3). In urine, the median AFQ1 was 10.4 ng/ml (IQR 3.4 to 23.3), and the median AFM1 and AFB-N7-guanine 0.04 ng/ml (IQR 0.01 to 0.33) and 0.38 ng/ml (IQR 0.0 to 2.15), respectively. A subgroup (n = 14) with hepatitis B virus (HBV) infection had significantly higher fecal concentrations of AFQ1 (p = 0.043) and AFM1 (p = 0.001) than those who were hepatitis B-virus antigen (HBsAg) negative, and the respective differences in urinary AFQ1 and AFM1 concentrations approached statistical significance (p = 0.054, p = 0.138). Our study demonstrates that AFQ1 is excreted in urine and feces at higher levels than AFM1, and feces are an important route of excretion of these AFB1 metabolites. AFQ1 should be further assessed for its predictive value as a marker for exposure and risk of dietary aflatoxins.

Identification of aflatoxin M1-N7-guanine in liver and urine of tree shrews and rats following administration of aflatoxin B1

Epidemiological studies have shown that exposure to aflatoxin B(1) (AFB(1)) and concurrent infection with hepatitis B lead to a multiplicative risk of developing liver cancer. This chemical-viral interaction can be recapitulated in the tree shrew (Tupia belangeri chinensis). As an initial characterization of this model, the metabolism of AFB(1) in tree shrews has been examined and compared to a sensitive bioassay species, the rat. Utilizing LC/MS/MS, an unreported product, aflatoxin M(1)-N(7)-guanine (AFM(1)-N(7)-guanine), was detected in urine and hepatic DNA samples 24 h after administration of 400 microg/kg AFB(1). In hepatic DNA isolated from tree shrews, AFM(1)-N(7)-guanine was the predominant adduct, 0.74 +/- 0.14 pmol/mg DNA, as compared to 0.37 +/- 0.07 pmol/mg DNA of AFB(1)-N(7)-guanine. Conversely, in rat liver, 6.56 +/- 2.41 pmol/mg DNA of AFB(1)-N(7)-guanine and 0.42 +/- 0.13 pmol/mg DNA of AFM(1)-N(7)-guanine were detected. Rats excreted 1.00 +/- 0.21 pmol AFB(1)-N(7)-guanine/mg creatinine and 0.29 +/- 0.10 pmol AFM(1)-N(7)-guanine/mg creatinine as compared to 0.60 +/- 0.12 pmol AFB(1)-N(7)-guanine/mg creatinine and 0.69 +/- 0.16 pmol AFM(1)-N(7)-guanine/mg creatinine excreted by the tree shrew. Furthermore, tree shrew urine contained 40 times more of the hydroxylated metabolite, AFM(1), than was excreted by rats. In vitro experiments confirmed this difference in oxidative metabolism. Hepatic microsomes isolated from tree shrews failed to produce aflatoxin Q(1) or aflatoxin P(1) but formed a significantly greater amount of AFM(1) than rat microsomes. Bioassays indicated that the tree shrew was considerably more resistant than the rat to AFB(1) hepatocarcinogenesis, which may reflect the significant differences in metabolic profiles of the two species.

Increased risk of hepatocellular carcinoma in male hepatitis B surface antigen carriers with chronic hepatitis who have detectable urinary aflatoxin metabolite M1

We followed 145 men with chronic hepatitis B virus (HBV) hepatitis for 10 years to determine whether exposure to aflatoxin, or concomitant exposure to hepatitis C virus (HCV), or family history of hepatocellular carcinoma (HCC) increased the risk of developing HCC. We collected 8 monthly urine samples before beginning follow-up and pooled them to detect aflatoxin metabolite M1 (AFM1). AFM1 was detected in 78 (54%) of the subjects. The risk of HCC was increased 3.3-fold (with a 95% confidence interval of 1.2-8.7) in those with detectable AFM1 (above 3.6 ng/L). This relative risk was adjusted for age and for HCV status. The attributable risk from exposure to detectable AFM1 was 0.553 (0.087, 0.94). The relative risk of fatal cirrhosis for those with elevated AFM1 was 2.8 (0.6, 14.3), and the odds of having a persistently elevated alanine transaminase (ALT) were 2.5-fold greater in those with detectable AFM1 (P =.007). Concomitant infection with HCV increased the risk of HCC 5.8-fold (2. 0-17), adjusted for age and AFM1 status. A family history of HCC increased the risk of HCC 5.6-fold, adjusted for age and AFM1. Four men with detectable AFM1 and HCC all had missense mutation in codon 249 of the p53 gene in cancer tissues. This study shows that exposure to AFM1 can account for a substantial part of the risk of HCC in men with chronic HBV hepatitis and adds importantly to the evidence that HCV and family history of HCC increase the risk of HCC in men with chronic HBV hepatitis.

Automated column-switching high-performance liquid chromatography for the determination of aflatoxin M1

An extractionless method for determining aflatoxin M1 (AFM1), a major metabolite of aflatoxin B1 (AFB1), in human urine was developed. The biological fluid is injected directly into the chromatographic system after simple dilution and centrifugation. A pre-column, packed with a cation-exchange phase and coupled on-line to a column-switching liquid chromatography (LC) system, is used for sample pre-treatment and concentration. The analytes are non-selectively desorbed with the LC eluent and cleaned by means of a column-switching procedure. Pre-treatment and analysis were performed within 40 min. Average AFMI recovery reached 97% in the 10-100 ng/l range of urine. The detection limit of AFM1 in urine and milk was 2.5 ng/l for 1 ml of injected sample. A comparison with an immunoaffinity column clean-up and LC method was performed. The method was applied to determine AFM1 in the urine of AFB1 gavaged rats, and in the urine of both potentially exposed and supposedly unexposed workers. The method was also extended to milk.

Hydrated sodium calcium aluminosilicate (HSCAS), acidic HSCAS, and activated charcoal reduce urinary excretion of aflatoxin M1 in turkey poults. Lack of effect by activated charcoal on aflatoxicosis

In one experiment, the effect of inorganic sorbents on the metabolic fate of aflatoxin B1 (AFB1) was studied in turkey poults. At 5 weeks of age, female poults were surgically colostomized and 9 days later orally dosed with 0.75 mg AFB1/kg BW. Hydrated sodium calcium aluminosilicate (HSCAS), acidic HSCAS, and activated charcoal (AC) were tested, by concomitant administration with AFB1. Urine was collected up to 48 h post-dosing and analyzed for aflatoxin M1 (AFM1) which was the major metabolite found in all treatment groups. Hydrated sodium calcium aluminosilicate, previously proven beneficial in alleviating aflatoxicosis in farm animals, reduced urinary AFM1 output when orally dosed simultaneous with AFB1. Also, acidic HSCAS and AC significantly decreased AFM1 excretion when administered concomitantly with AFB1. A second experiment was conducted to evaluate the ability of two types of AC to modify aflatoxicosis when added to aflatoxin (AF)-contaminated (from culture material) diets of turkey poults. Although AC was able to decrease AFM1 excretion in the first experiment, no protective effects from AF toxicity were observed in the feeding study.

Inhibition of aflatoxin Ml excretion in rat urine during dietary intervention with oltipraz

4-Methyl-5-(2-pyrazinyl)-1,2-dithiole-3-thione (oltipraz) is an effective chemopreventive agent against several classes of carcinogens in many target organs. Induction of carcinogen detoxication enzymes, particularly glutathione S-transferases, appears to be an important component of the protective actions of oltipraz. It has recently been observed that addition of oltipraz to rat liver microsomes or to cultured human hepatocytes blocks the oxidative metabolism of aflatoxin B1 (AFB1) to its 8,9-oxide and the hydroxylated derivative aflatoxin Ml (AFM1). 0ltipraz is a competitive and perhaps irreversible inhibitor of cytochromes P450 1A2 and 3A4. To determine whether oltipraz can affect cytochrome P450-dependent metabolism of AFB1 in vivo we have assessed the effect of oltipraz on the urinary excretion of oxidative metabolites of AFB1 before, during and after a transient intervention. Male F344 rats, housed individually in glass metabolism cages, were gavaged daily with 25 microg [3H]AFB1 for 28 consecutive days. Starting on day 6 and extending to day 16 half of the rats were fed a diet supplemented with 0.075% oltipraz. Sequential 24 h urine samples were collected and a subset analyzed for AFB1 metabolites. AFM1 was the major metabolite detected in all urine samples, accounting for 2-6% of the administered dose. The excretion of AFM1 was greatly reduced (77%) during the active phase of the intervention, when oltipraz was added to the diet, but rapidly returned to control levels after cessation of oltipraz administration. This inhibition of AFM1 excretion was not seen in animals receiving oltipraz by gavage 24 h prior to dosing with AFB1. Collectively these data are consistent with the view that oltipraz or a short-lived metabolite inhibits cytochrome P450 1A2 in vivo.

Immunoaffinity column clean-up for the high-performance liquid chromatographic determination of aflatoxins B1, B2, G1, G2, M1 and Q1 in urine

A method for the determination of aflatoxins B1, B2, G1, G2, M1 and Q1 in human urine has been developed. The 10-ml urine samples were automatically cleaned up on immunoaffinity columns and analysed by high-performance liquid chromatography (HPLC), including post-column derivatization with bromine and fluorescence detection. Average aflatoxin recoveries were: B1 103%, B2 106%, G1 98% and G2 96% in the range 6.8-73 pg/ml of urine and M1 103% and Q1 100% in the range 18-97 pg/ml of urine. The relative standard deviations were all between 1% and 21%. The determination limits of aflatoxins in urine were 6.8 pg/ml for B1, B2, G1 and G2 and 18 pg/ml for M1 and Q1.

Aflatoxins B1, M1 and aflatoxicol in tissues and urine of calves receiving aflatoxin

Liver and kidney tissues and urine from calves chronically or acutely intoxicated by aflatoxin were surveyed to detect the presence of aflatoxins B1, M1 (AFB1, AFM1) and aflatoxicol (AFL). Aflatoxins B1, M1, and aflatoxicol were not found in the liver, kidney or urine from animals intoxicated by chronic forms. However in a calf that received a single dose of 0.8 mg of AFB1/kg of live weight and one submitted to a single dose of 1.8 mg of AFB1/kg of live weight detectable levels of aflatoxins occurred in tissues and urine.

[Study on the relationship between dietary aflatoxin B1 levels in foods and aflatoxin M1 excretion levels in children's urine in Guangxi]

617 children in high and low liver cancer incidence areas of Guangxi were observed for a study on the relationship between the dietary Aflatoxin B1 (AFB1) levels and Aflatoxin M1 (AFM1) excretion amounts in urine. The average amount of Aflatoxin B1 absorbed by children within 24 hours was 0.0883 x 10(-9) micrograms, (0.1232 x 10(-9)) in high liver cancer incidence area (LCIA), and 0.0306 x 10(-9) in low LCIA (P < 0.001). The average amount of AFM1 excreted in the children's urine within 24 hours was 0.0020 x 10(-9) micrograms, (0.0027 x 10(-9) in high LCIA, and 0.0010 x 10(-9) in low LCIA (P < 0.001). The conversion ratio from AFB1 to AFM1 excreted from urine was 2.27% in 24 hours after the children consumed AFB1 from foods. The ratio of conversion was 2.19% and 3.27% for the children who life in high and low LCIA respectively, it was 1.75% for the boys, 2.97% for the girls.

[Aflatoxins and primary liver cancer--a population based case-control study]

A case-control study of primary liver cancer (PLC) was conducted in 1989 at Fusui County, Guangxi Province. There were 99 PLC cases and 99 age-sex-residence matched controls. There were no difference of age, sex, race, cultural, level, marital status and annual income distribution (P > 0.05). The mean dietary AFB1 intakes of cases and controls were 117.72 + 105.68 mg/d, the mean outputs of AFM1 were 22.56 and 21.62 ng per morning urine respectively. The mean sera aflatoxin-albumin adducts in both groups were 24.96 and 18.72 pg per mg albumin respectively. These indicators were of no statistical significance. Conditional Logistic regression showed that HBV infection (OR = 5.33), drinking pond-ditch water (OR = 3.70), family history of PLC (OR = 2.88), and total alcohol intakes (OR = 1.002) were statistically significant as risk factors (P > 0.05) rather than aflatoxins. This may be due to the fact that the samples selected in hyperendemic area both took high quantities of aflatoxin.

[The aflatoxins and liver cancer in Guangxi, China]

The AFB1 intake and the AFM1 excretion of 81 households in 10 villages, Guanxi were investigated using the ELISA method. The results showed that there was positive correlation between PLC mortality and AFB1 intake from corn and peanut oil, but not from rice. The results of stepwise regression showed that main factors were AFB1 intake of males, AFM1 excretion of females and consumption of corn. The results showed that aflatoxins were correlated with mortality rates of liver cancer. Further investigation needs to be carried out in case-control and cohort studies.

Molecular dosimetry of urinary aflatoxin-DNA adducts in people living in Guangxi Autonomous Region, People's Republic of China

Hepatocellular carcinoma is one of the five leading human cancers causing at least 250,000 deaths each year. One of the major risk factors for this disease is exposure to dietary aflatoxins, and the development of appropriate molecular dosimetry biomarkers would facilitate the identification of individuals at risk. This study was undertaken to explore the relationship between dietary intake of aflatoxins and the excretion of the major aflatoxin-DNA adduct and other metabolites into the urine of chronically exposed people. The following protocol was developed for this investigation in Guangxi Autonomous Region, People's Republic of China, where the diets of 30 males and 12 females (ages, 25-64 years) were monitored for 1 week and aflatoxin intake levels determined each day. Starting on the fourth day, total urine volumes were obtained in consecutive 12-h fractions for 3 or 4 days. High performance liquid chromatography and competitive radioimmunoassay analyses were done on each of the urine samples, and the relationships between excretion of total aflatoxin metabolites, aflatoxin-N7-guanine, aflatoxin M1, aflatoxin P1, and aflatoxin B1, and aflatoxin B1 intake values were determined. The average intake of aflatoxin B1 by men was 48.4 micrograms/day, giving a total mean exposure during the study period of 276.8 micrograms. The average daily intake by women was 77.4 micrograms/day, resulting in a total average exposure during the 7-day period of 542.6 micrograms aflatoxin B1. Initial efforts to characterize aflatoxin metabolites in urine samples were with an analysis by competitive radioimmunoassay. The analysis by linear regression of the association between aflatoxin B1 intake/day and total aflatoxin metabolite excretion/day showed a correlation coefficient of only 0.26. These findings stimulated the immunoaffinity/analytical high performance liquid chromatography analysis for individual metabolites. When the data were analyzed by linear regression analysis, the aflatoxin N7-guanine excretion and aflatoxin B1 intake from the previous day showed a correlation coefficient of 0.65 and P less than 0.000001. Similar analysis for aflatoxin M1 resulted in a correlation coefficient of 0.55 and P less than 0.00001, whereas there was no positive statistical association between exposure in the diet and aflatoxin P1 excretion, despite aflatoxin P1 being quantitatively a major metabolite. Analysis of the total aflatoxin-N7-guanine excretion in the urine during the complete collection period plotted against the total aflatoxin B1 exposure in the diet for each of the individuals, smoothing the day to day variations, revealed a correlation coefficient of 0.80 and P less than 0.0000001.(ABSTRACT TRUNCATED AT 400 WORDS)