Long-term Stability of Human Aflatoxin B1 Albumin Adducts Assessed by Isotope Dilution Mass Spectrometry and High-Performance Liquid Chromatography–Fluorescence

Abstract

The measurement of the aflatoxin B 1 -lysine serum albumin adduct in human blood samples is the most facile biomarker for the assessment of chronic exposure to aflatoxin B 1 . Many technologies have been developed for the measurement of this protein adduct including immunoassays, high-performance liquid chromatography (HPLC) with fluorescence detection, and a newly developed isotope-dilution mass spectrometry method. Irrespective of the technology used to determine this adduct level, an important question remains about the long-term stability of this damage product in stored samples. To address this issue, 19 human serum samples that had been previously analyzed for the aflatoxin B 1 -lysine adduct by highperformance liquid chromatography -fluorescence in 1989 were re-analyzed by isotope dilution mass spectrometry after storage at À80°C. The adduct concentrations measured by these two techniques were identical within 4% over the range 5 to 100 pg of aflatoxin B 1 -lysine/mg albumin. In addition, the specific chemical structure of the aflatoxin B 1 -lysine adduct in human samples was confirmed for the first time by collision-induced dissociation full scan mass spectrometry analysis of the protonated adduct molecular ion. These results illustrate that the aflatoxin B 1 -lysine serum albumin adduct can be stable in human serum stored at À80°C since 1989, and this provides confidence for the measurement of this biomarker in repository samples from epidemiologic investigations. (Cancer Epidemiol Biomarkers Prev 2008;17(6):1436 -9)

Global DNA methylation in a population with aflatoxin B1exposure

“…confirmed, 52 as well as their significant correlation with AFB 1 intake. 53 Measurement of the adduct levels in urine, however, provides a noninvasive means of estimating the levels of AFB 1 exposure, with a correlation of 0.65 found between total dietary AFB 1 intake and urinary AFB 1 extraction.…”

Carcinogenic effects of aflatoxin B1 among wheat handlers

“…23 The authors have previously found that airborne ) in the Helwan district in Cairo, Egypt, and the concentration of Aspergillus flavus in the two workplaces was higher compared to that in the control area (11.5¡1.41 cfu/m 3 ). 8 Chronic occupational exposure to high concentrations of Aspergillus flavus was found to cause significant elevation in the serum AFB1/Alb of bakers and flourmill workers compared to the normal controls.…”

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

“…As a result of its longer in vivo half-life as compared with other urinary AFB 1 metabolites, such as AFM 1 and AFB-N 7 -guanine, the AFB-Lys adduct can reflect integrated exposures over 2-3m o n t h s . The long-term stability (up to 20 years) in frozen serum or plasma made this adduct a first choice of biomarkers to study human AF exposure and its link to diseases (Wang et al 1996;Wang, Abubaker, et al 2001;Scholl & Groopman 2008). Highly significant associations between AFB-Lys adduct level and dietary AFB 1 exposure have been found in human populations from several regions of the world.…”

“…Additionally, our study used archived serum samples in both cohorts. Even though the AFB-Lys adduct has been shown to have a long-term stability over 20 years under proper storage conditions (Wang et al 1996;Wang, Abubaker, et al 2001;Scholl & Groopman 2008), the repeated thaw and freeze cycle of these samples may degrade the adduct level in the original samples. Nevertheless, by using longitudinal study design and a more accurate detection method for AFB-Lys measurement, our study shows the constant AF exposure over 21 years and provides better estimates of AF exposure in central and south-western Ugandan populations.…”