Robinson, Abraham (2012-07). Development of a Biomarker and Clay Based Remediation Strategy for Populations at Risk for Fumonisin Toxicosis. Doctoral Dissertation.
Thesis
Fumonisin B1 is the most prevalent congener of the fumonisin mycotoxins produced by Fusarium verticilliodies and is considered by many to be the most toxic. Fumonisin B1 has been classified by IARC as a class 2B carcinogen. This is primarily due to evidence suggesting increased exposure to FB1 through contaminated foodstuffs is responsible for increased incidence of esophageal cancer in regions of China and South Africa. Fumonisin B1 exposure has also been implicated in the increased incidence of neural tube defects along the Texas/Mexico border. Therefore the principal goals of this research were to 1) Identify sorbent materials that would be compatible with the chemical characteristics of fumonisin B1 and evaluate their ability to sequester the toxin using established in vitro techniques; 2) evaluate urinary FB1 as a biomarker of exposure from a fumonisin contaminated diet; 3) utilize urinary FB1 as a diagnostic tool to evaluate the efficacy of NS in reducing biomarkers of FB1 bioavailability in a Ghanaian population suspected to be co-exposed to aflatoxins and fumonisins. Isothermal analysis and an alternative animal model were examined and compared to previously published results to determine the sorbent toxin interaction activity in vitro as a predictor of in vivo efficacy. An HPLC method for detection and quantitation of urinary FB1 was developed based on methods previously adapted for primary amine and biomarker analysis. Urinary FB1 was evaluated as an HPLC detectable biomarker using a rodent model. Calcium and sodium montmorillonite clays were selected to interact with the positive charge on FB1 at low pH and sorb the molecule. Ferrihydrite was selected to interact with the negative charge on the FB1 molecule at neutral to high pH. While both polarities of sorbent were effective, montmorillonite clays demonstrated a higher capacity for sorption of FB1 than ferrihydrite. These in vitro results were confirmed in a rodent model where urinary FB1 was reduced 27% in NovaSil treated rats vs. controls. Finally, in a Ghanaian population co-exposed to aflatoxins and fumonisins, urinary FB1 was significantly reduced at 2 time points when the NovaSil treatment was compared to placebo.
