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Submitted to: Aquaculture Conference Proceedings
Publication Type: Abstract Only Publication Acceptance Date: 9/28/2012 Publication Date: 2/25/2013 Citation: Cleveland, B.M., Weber, G.M. 2013. Effects of phytoestrogens on indices of protein turnover in rainbow trout (Oncorhynchus mykiss) primary myocytes. Aquaculture Conference Proceedings. P0315. Interpretive Summary: Technical Abstract: Soybeans and other legumes investigated as alternative ingredients in aquafeeds contain phytoestrogens that act as endocrine disruptors, capable of binding to and activating estrogen receptors, although at a much lower level of estrogenicity compared to estradiol. Estradiol has catabolic effects on protein retention in rainbow trout white muscle, as it both reduces rates of protein synthesis and increases rates of protein degradation. The objective of this study was to determine if phytoestrogens can mimic the effects of estradiol on indices of protein turnover in rainbow trout primary myocytes. Six day-old primary myocytes were isolated from juvenile rainbow trout (~4 – 10 grams) and exposed to increasing concentrations (10 nM – 100 µM) of phytoestrogens identified in plants that are of interest for aquafeeds. Cells were exposed to these compounds for 24 hrs, after which rates of protein synthesis and protein degradation and the expression of proteolysis-related genes were determined. All phytoestrogens, except biochanin A, decreased rates of protein synthesis, while only genistein and daidzein increased rates of protein degradation (figure 1). Genistein produced the greatest effects on proteolysis-related gene expression, increasing expression of ubiquitin ligase genes fbxo32 (atrogin-1) and fbxo25, cathepsin D and cathepsin L, autophagy-related genes atg12, lc3b, and gabarapl1, and caspase 8, while decreasing expression of caspase 3 (P < 0.05). Effects of other phytoestrogens, when significant, were primarily identified for autophagy-related genes. These results are consistent with a negative effect of dietary phytoestrogens, especially genistein, on the retention of protein in rainbow trout white muscle, largely via reductions in protein synthesis. Therefore, the presence of phytoestrogens in plant-derived aquafeeds may contribute to suboptimal growth performance and reduced protein retention in rainbow trout. |
