Biomarker monitoring of controlled dietary acrylamide exposure indicates consistent human endogenous background

Abstract

The aim of the present study was to explore the relation of controlled dietary acrylamide (AA) intake with the excretion of AA-related urinary mercapturic acids (MA), N-acetyl-S-(carbamoylethyl)-l-cysteine (AAMA) and N-acetyl-S-(1-carbamoyl-2-hydroxyethyl)-l-cysteine (GAMA). Excretion kinetics of these short-term exposure biomarkers were monitored under strictly controlled conditions within a duplicate diet human intervention study. One study arm (group A, n = 6) ingested AA via coffee (0.15–0.17 µg/kg bw) on day 6 and in a meal containing an upper exposure level of AA (14.1–15.9 μg/kg bw) on day 10. The other arm (group B) was on AA minimized diet (washout, 0.05–0.06 µg/kg bw) throughout the whole 13-day study period. On day 6, these volunteers ingested 13C3D3-AA (1 μg/kg bw). In both arms, urinary MA excretion was continuously monitored and blood samples were taken to determine hemoglobin adducts. Ingestion of four cups of coffee resulted in a slightly enhanced short-term biomarker response within the background range of group B. At the end of the 13-day washout period, group B excreted an AAMA baseline level of 0.14 ± 0.10 µmol/d although AA intake was only about 0.06 µmol/d. This sustained over-proportional AAMA background suggested an endogenous AA baseline exposure level of 0.3–0.4 µg/kg bw/d. The excretion of 13C3D3-AA was practically complete within 72–96 h which rules out delayed release of AA (or any other MA precursor) from deep body compartments. The results provide compelling support for the hypothesis of a sustained endogenous AA formation in the human body.

Biomonitoring of nutritional acrylamide intake by consumers without dietary preferences as compared to vegans

“…As case in point, vegan-female-3 excreted within 72 h about 64% of the respective dietary AA intake (546 nmol) on day 2 as AAMA. Under strictly controlled conditions, a sustained endogenous background exposure to AA had compellingly been demonstrated in the above studies (Goempel et al 2017;Ruenz et al 2016). The present study also supports the premise of a steady background, as exemplified for vegan-female-3.…”

“…2b) showed excretion kinetics obviously undisturbed by smoke exposure, comparable to those also observed previously in human intervention studies under strictly controlled conditions. These have indicated that an AA intake of 1.3-1.8 µg/kg bw resulted in a mean of 58% of the ingested AA being excreted as AAMA (7% as GAMA) within 72 h. (Goempel et al 2017;Ruenz et al 2016) In the present study in free-living individuals, about similar excretion kinetics were seen. AAMA was excreted in less than 72 h with a maximum value already reached within 12 h after the reported dietary intake.…”

“…Acrylamide contents of relevant food samples were determined in duplicate by a stable isotope dilution method (SIDA) as recently described (Goempel et al 2017). In short, food samples were extracted with water using 250 ng D 3 -AA as internal standard for all food samples, then purified via solid phase extraction (SPE) using Isolute ® ENV+ columns (Biotage, Uppsala, Sweden), concentrated and measured via high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) (Agilent 1290 Infinity Series HPLC, Waldbronn, Germany, coupled to an AB Sciex QTrap 5500, Darmstadt, Germany) using positive electrospray ionization and the multiple reaction monitoring (MRM) mode.…”

“…Urinary MA were expressed as amounts per excreted total urine volume and normalized to ucr. Determination of AAMA and GAMA followed the SIDA method as published before (Goempel et al 2017). In brief, urine samples (1 mL each) were purified via SPE using Isolute ® ENV+ columns (Biotage, Uppsala, Sweden) and diluted 1:4 for analysis via UHPLC-ESI-MS/ MS (Agilent 1290 Infinity Series HPLC + AB Sciex QTrap 5500).…”

“…Both, AA and GA, are predominantly conjugated with glutathione (GSH) and further metabolized to mercapturic acids (MA) like N-acetyl-S-(2-carbamoylethyl)-l-cysteine (AAMA), derived from AA, and N-acetyl-S-(2-hydroxy-2-carbamoylethyl)-l-cysteine (GAMA), derived from GA (Fennell et al 2005;Watzek et al 2012b;Boettcher et al 2006). AAMA and GAMA are widely utilized as short-term biomarkers of exposure, because they are excreted within about 3 days following exposure (Goempel et al 2017). In contrast, adducts to the N-terminal valine of hemoglobin (Hb) are conceived as biomarkers reflecting cumulative exposure over the lifetime of red blood cells, known to be completely replaced within about 4 months in humans (Vikström et al 2012).…”