Mycotoxins in food for Tilapia: evaluation of the level of contamination and effect on parameters of oxidative damage in cells and lymphoid tissues of nilotic tilapia (Oreochromis niloticus).

Nile tilapia (Oreochromis spp.) culturing, Mexico’s most important fresh water fish by capture, is realized mainly on sub-tropical environments. Such conditions favor
commercial culturing and feed contamination by molds such as Aspergillus and Fusarium spp., producers of aflatoxins (AF) and fumonisins (FB) respectively. In the
present study, fish feed from 10 tilapia farms located in Nayarit, México were collected, during three seasons (spring, summer and winter) between 2009-2010.
Water activity (aw) and total aflatoxin (AF) and fumonisin (FB) concentrations by ELISA and HPLC were determined in each sample. Results showed no contamination
by AF; regarding to FB, 19 positive samples (60%) by ELISA and 14 positive samples (46%) by HPLC were detected, with levels ranging from 0.148 to 2.587 mg/kg which
are below permit limits according to the European Union 2006/576 Recommendation.
Two FB concentrations (1.0 and 2.5 ppm) were used based on contamination level registered, in order to evaluate oxidative damage (protein oxidation level and lipid
hydroperoxides concentration) and anti-oxidant enzymes activity glutathione S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD). In vitro
exposures were assessed during 24, 48 and 96 h using peripheral blood mononuclear cells (PBMC) while in vivo exposures were performed on PBMC, spleen
cells and liver tissue during 4, 14 and 21 days. Results showed that FB affects negatively on CAT activity in all cells and tissues exposed on both in vitro and in vivo
conditions. On the other hand, SOD activity was affected only in PBMC and spleen during in vivo FB exposure. Regarding oxidative damage, FB causes an increase on
protein oxidation level in all exposed cells and tissues, while lipid hydroperoxides increased only on PBMC. These results suggest that FB acute exposure modifies
oxidative stress parameters on exposed cells and tissues, which could affect the physiology and later growing and production of this organism.