Nutrigenomic Biomarkers for dietary soybean meal utilization in rainbow trout  

Rainbow trout have been well studied for their intolerance to dietary soybean meal (SBM) and gene expression has been assessed in several tissues. Despite this, elucidation of biomarkers which can serves as surrogates for a quantifiable endpoint (e.g., distal enteritis) and serve as prognostic tools for selection programs (e.g., for soy tolerance), dietary formulations and experimental designs have been elusive.  In this study we assessed the physiological and metabolic response of rainbow trout to graded dietary SBM inclusion (0, 10, 20 and 40%) and correlated conventional growth performance response variables with molecular approaches to assess candidate genes for their utility as biomarkers to quantify soy intolerance. Results indicate several genes are correlated to SBM inclusion. However, transcriptional response of the same gene in different tissues can vary.  Heat shock proteins (Hsp70) display an "all or nothing response" in hepatic tissue (Figure 1) but show a graded response in intestinal cells.  Conversely, the oxidative stress gene, super oxide dismutase (SOD) shows a dose response in intestinal tissues which correlates with SBM inclusion (Figure 2).