Fumonisin exposure biomarkers in humans consuming maize staple diets

[摘要] ENGLISH ABSTRACT: Fumonisins are carcinogenic mycotoxins which occur world-wide in maize andmaize-based products intended for human consumption. Consumption of fumonisin contaminatedmaize as a staple diet has been associated with oesophageal and livercancer incidence as well as neural tube defects. This study has confirmed the Stateof Santa Catarina, Brazil as another region where the consumption of maizecontaminated with fumonisins and high oesophageal cancer incidence co-occur.Since fumonisins exert their main biochemical effect by disruption of the sphingolipidbiosynthetic pathway and are implicated in cancer, the role of fumonisin B1 (FB1) inFB1–induced rat hepatocyte nodules was investigated. The current study showedthat FB1 exposure activated sphingosine accumulation in the nodules which couldinduce the bio-active sphingosine 1-phosphate to provide a selective growth stimuluson subsequent FB1 exposure. Since the FB1-induced hepatocyte nodules were notresistant to the disruption of sphingolipid biosynthesis, it was not the mechanismwhereby the altered hepatocytes escaped the mitoinhibition of FB1 and selectivelyproliferated into hepatocyte nodules. A study in maize subsistence farmingcommunities investigated the sphingosine and sphinganine levels in blood and urineof participants. Fumonisin exposure was assessed in these communities based onfumonisin levels in maize that was concurrently collected from the areas where theparticipants resided. Subsequently fumonisin exposure was assessed in individualsbased on the fumonisin levels in maize collected from each household and byacquiring weighed food records for each member of the household. It was confirmedin both these studies that communities are chronically exposed to fumonisin levelswell above the provisional maximum tolerable daily intake determined by the Joint FAO/WHO Expert Committee on Food Additives. Since the sphinganine andsphingosine levels in blood and urine of the participants exposed to various levels offumonisin were not significantly different, the sphingoid bases and their ratios couldnot be established as a biomarker of fumonisin exposure. Therefore, an alternativebiomarker of exposure was investigated during studies into a practical cost effectivemethod to reduce fumonisin. The customary maize food preparation practices wereassessed in a maize subsistence farming community and subsequently optimised toreduce the fumonisin levels in the maize under laboratory-controlled conditions.Implementation of this optimised and culturally acceptable intervention method ofsorting and washing maize in a rural community reduced fumonisin contamination inhome-grown maize by 84%. The intervention study attained a 62% reduction infumonisin exposure based on fumonisin levels in maize-based food andconsumption as assessed by 24-h dietary recall questionnaires. The alternativebiomarker of fumonisin exposure, urinary FB1, was investigated during theintervention study. The FB1 urinary biomarker measured fumonisin intake at theindividual level and confirmed the reduction achieved as assessed by food analysisand food intake data. The biomarker was thus well correlated with fumonisinexposure and confirmed the efficacy of the simple and culturally acceptableintervention method. Utilisation of the urinary FB1 biomarker and the customisedhand-sorting and washing of maize to reduce fumonisin exposures has the potentialto improve food safety and health in subsistence maize farming communities.

[发布机构] Stellenbosch University