Evaluating primary (cry1Ab) and secondary effects (deoxynivalenol) of GM maize when fed to zebrafish (Danio rerio). Investigating growth, intestinal mRNA and white blood cell differentiation

Abstract

Several of the plants which are currently being used in fish feed in Norway today, are being genetically modified (GM) around the world. The use of GM plants is increasing worldwide, and whether these are safe to use in fish feed has been questioned. Deoxynivalenol (DON) is a highly prevalent mycotoxin contaminant found in crops. Previous findings suggest that GM maize has a higher level of this contaminant. This study aims to investigate whether GM maize (event MON 810) and low DON contamination affects performance, intestinal mRNA and white blood differentiation when fed to Zebrafish (Danio rerio). Two separate trials were run simultaneously; (1) zebrafish were fed either GM maize (event MON 810) or the conventional near-isogenic parental line for 45 days, (2) zebrafish were fed diets with increasing concentration of synthetic DON (0.0, 0.1, 0.5, 1.5, 2, 3 ppm DON) for 45 days. All fish were weight and measured when terminated. The intestine was analyzed for difference in gene expressions using Quantitative Real Time RT PCR (qPCR), and white blood cell differentiation was performed on blood samples. Feed acceptance was good for both trials. The fish fed GM maize had a higher growth than the non-GM group, although this increase was not significant. There fish feed 0.1 ppm DON had the highest growth for the DON trial, however there were no significant differences between the diets. No significant differences was observed for the mean normalized gene expressions (MNE) for the maize diets, although there was a trend towards increase of mitogen activated protein kinase (Mapk14) which could indicate ribotoxic stress. The MNE for the DON trial showed no significant difference or dose response to the increased DON concentrations in the diets. No effects were observed for the white blood cell differentiation for either of the trials. In conclusion, an inclusion level of 19 % GM maize does not significantly affect fish performance, intestinal mRNA or white blood cell differentiation in zebrafish. Low concentrations of naturally contaminated or synthetically DON do not seem to affect zebrafish growth, intestinal mRNA transcript levels or white blood cell differentiation. The lack of effects indicates, compared to other investigated animals, that zebrafish is not very sensitive to DON contamination if feed.