Ochratoxin A and its metabolites in urines of German adults-An assessment of variables in biomarker analysis

- OTA and OT-alpha levels in plasma and urine of two volunteers reflect their dietary habits.
- Urine biomarker analysis in a German cohort indicates frequent and variable exposure.
- Enzymatic hydrolysis of conjugated OTA metabolites in urine is recommended.

Ochratoxin A (OTA), a mycotoxin known for its nephrotoxic and carcinogenic properties, is a worldwide occurring contaminant in a variety of food commodities. Biomonitoring (i.e. analysis in biological fluids) can serve to assess human internal exposure from all consumed foods and beverages. We now determined the concentration of OTA and its metabolite ochratoxin alpha (OTα) in plasma and in urine of two male volunteers with different food habits, in order to assess intra-individual temporal fluctuations and inter-individual differences in their biomarker levels. Moreover, the urinary levels of both OTA and OTα were analyzed in a cohort of German adults (23 males, 27 females) on their regular diet. All samples were subjected to an enzymatic hydrolysis of biomarker conjugates prior to clean-up by liquid-liquid extraction and HPLC-FD analysis. The profile in the first individual showed small fluctuations over time: mean levels in plasma were 0.42 and 0.45 ng/mL for OTA and OTα, respectively, and in urine means of 0.06 ng/mL for both analytes. The other individual had mean levels of 1.64 and 0.20 ng/mL for OTA and OTα in plasma, and 0.24 and 2.22 ng/mL for these analytes in urine. It is concluded that inter-individual differences in biomarker levels reflect dissimilar dietary exposure and/or disposition of ingested mycotoxin, with an apparently more efficient detoxification of OTA to OTα in the second individual. In the German cohort (n = 50), analytes were detected in 100% (OTA: range 0.02-1.82 ng/mL mean level 0.21 ± 0.31 ng/mL) and 78% (OTα: range 0.01-14.25 ng/mL, mean level 1.33 ± 2.63 ng/mL) of all urines. Parameters such as gender, age and body mass index did not show a significant association with urine biomarker levels. This study indicates frequent exposure to OTA among German adults. The new results are discussed in the context of biomarker data from other countries and some methodological issues.