Extrusion cooking with glucose supplementation of fumonsin- contaminated corn grits protects against nephrotoxicity and disrupted sphingolipid metabolism in rats

Authors: Voss, Kenneth; Riley, Ronald; JACKSON, LAUREN - Us Food & Drug Administration (FDA); JABLOSKI, JOSEPH - Us Food & Drug Administration (FDA); BIANCHINI, ANDREIA - University Of Nebraska; BULLERMAN, LLOYD - University Of Nebraska; HANNA, MILFORD - University Of Nebraska; RYU, DOJIN - Texas Woman'S University

Submitted to: Molecular Nutrition and Food Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/2011
Publication Date: 9/20/2011
Citation: Voss, K.A., Riley, R.T., Jackson, L.S., Jabloski, J.E., Bianchini, A., Bullerman, L.B., Hanna, M.A., Ryu, D. 2011. Extrusion cooking with glucose supplementation of fumonsin-contaminated corn grits protects against nephrotoxicity and disrupted sphingolipid metabolism in rats. Molecular Nutrition and Food Research. 55:S312-S320. DOI: 10.1002/mnfr.201100067.

Interpretive Summary: Fumonisins are toxins produced by molds found in corn. Fumonisin B1 (FB1) is the most common. It causes animal diseases and, although its impact on human health is unclear, evidence suggests that FB1 increases the risk of certain cancers and birth defects. Therefore, minimizing exposure to fumonisins, especially FB1, is desirable. Extrusion cooking, which combines high heat and high pressure, reduces FB1 concentrations in corn and greater reductions have been achieved if glucose is added to the recipe. In an earlier bioassay, extrusion cooking with glucose supplementation partially reversed the kidney toxicity of FB1 contaminated (33 ppm FB1) corn grits that were fed to rats. To further evaluate the effectiveness of extrusion and extrusion with glucose to prevent FB1 toxicity, two additional batches of contaminated grits were prepared: Batch 1 contained 9.7 ppm and the Batch 2 contained 50 ppm FB1. Extrusion reduced FB1 concentrations in the grits by 64 to 72% and addition of glucose improved reductions to 89-94%. The uncooked, extruded and extruded, glucose supplemented grits were mixed (50%) with a standard rodent diet and fed to groups of rats for up to eight weeks to assess their toxic potential. Both batches of uncooked grits caused kidney toxicity as shown by the presence of microscopic lesions and disrupted lipid metabolism effects that are typically associated with FB1 exposure. Less severe effects were found in groups fed the extruded grits. Extrusion with glucose supplementation most effectively reduced toxicity and prevented the development of lesions or lipid metabolic effects in rats fed the less contaminated Batch-1 grits processed by this method. The bioassay results show for the first time that extrusion with glucose supplementation is a cooking method that can effectively prevent FB1 toxicity.

Technical Abstract: Fumonisins are mycotoxins produced by Fusarium verticillioides and F. proliferatum. They are found in corn and in corn-based foods. Fumonisin B1 (FB1), the most common fumonisin, causes animal diseases and, although its impact on human health is unclear, evidence suggests that it is a risk factor for cancers and birth (neural tube) defects. Extrusion cooking reduces FB1 concentrations in corn and greater reductions are achieved with glucose supplementation. Extrusion cooking with glucose supplementation using a single-screw extruder only partially reversed the nephrotoxicity of FB1 contaminated (33 ppm FB1) corn grits to rats. The efficacy of the extrusion using a twin-screw configuration for reducing fumonisin toxicity has not been evaluated. To do so, two batches of Fusarium verticillioides-fermented corn grits (Batch-1 contained 9.7 ppm FB1; Batch-2 contained 50 ppm FB1) were cooked without (Batch-1E; Batch-2E) or with 10% w/w glucose supplementation (Batch-1EG; Batch-2EG) by twin-screw extrusion. FB1 concentrations after cooking were: Batch-1E = 2.7 ppm; Batch-1EG = 0.6 ppm; Batch-2E = 18 ppm; and Batch-2EG = 5.7 ppm. These values corresponded to reductions of 72% (Batch-1E), 94% (Batch-1EG), 64% (Batch-2E) and 89% (Batch-2EG). Batch-1, Batch-1E, Batch-1EG, Batch-2, Batch-2E, Batch-2EG were mixed (1:1) with rodent chow and fed to male rats for 3 (n=5/group) or 8 (n=5/group) weeks. Control groups were fed uncooked (control) or extruded (extrusion control) uncontaminated (<0.2 ppm FB1) grits. General appearance, body weights and hematology and serum chemistry profiles of all groups were similar. Daily intakes of FB1 over the 8 week period averaged 354, 103, and 25.1 µg/kg body weight for Batch-1, Batch-1E and Batch-1EG, respectively and 1804, 698, and 222 µg/kg body weight Batch-2, Batch-2E and Batch-2EG, respectively. Apoptotic tubule lesions and elevated concentrations of sphinganine (Sa), sphingosine (So) and their 1- phosphate metabolites (biomarkers for fumonisin exposure) were found in the kidneys of animals fed Batch-1, Batch-1E, Batch-2, Batch-2E, or Batch-2EG grits. The effects were dose-dependent and greatest in the groups fed Batch-1 (diet concentration = 4.9 ppm), Batch-2 (25 ppm) and Batch-2E (9.0 ppm). Intermediate histopathological and sphingolipid effects were found in rats fed Batch-1E (1.4 ppm) or Batch-2EG (2.9 ppm). However, lesions and elevated Sa, So, Sa 1-P or So 1-P concentrations were absent in the Batch-1EG (0.3 ppm) fed group indicating prevention of toxicity by extrusion with glucose supplementation of the less contaminated grits. In summary, chemical analyses together with a bioassay which included tissue histopathology and sphingolipid evaluations demonstrated that extrusion with glucose supplementation using a twin-screw apparatus can be used to reduce FB1 concentrations in contaminated corn grits to levels that do not induce in vivo toxicity.