Abstract
With increasing levels of fish meal (FM) protein in aquafeeds being replaced with soybean meal (SBM) protein, understanding the molecular mechanisms involved in response to alternative diets has become a critical concern. Thus, the goal of this study was to examine transcriptional differences in the intestine of juvenile yellow perch through RNA-sequencing (RNA-seq), after their initial introduction to a formulated diet with 75% SBM protein inclusion for 61 days, compared to those fed a traditional FM-based diet. Transcriptomic analysis revealed a concise set of differentially expressed genes in juveniles fed the SBM-based diet, the majority of which were intrinsic to the cholesterol biosynthesis pathway. Analysis of total body lipid and cholesterol levels were also investigated, with no between-treatment differences detected. Results of this study demonstrate that in response to SBM-based diets, yellow perch juveniles up-regulate the cholesterol biosynthesis pathway in order to maintain homeostasis. These findings suggest that the upregulation of the cholesterol biosynthesis pathway may negatively impact fish growth due to its large energy expenditure, and future studies are warranted.
Highlights
With increasing levels of fish meal (FM) protein in aquafeeds being replaced with soybean meal (SBM) protein, understanding the molecular mechanisms involved in response to alternative diets has become a critical concern
We reported that juvenile yellow perch fed a diet with 75% FM protein replacement with soybean meal protein displayed significantly reduced growth compared with those fed FM-based diets, yet adults fed the same diets had similar growth between the two groups[10]
Results from the present study reveal that juvenile fish fed SBM-based diets up-regulate genes involved in the cholesterol biosynthesis pathway and fatty acid transport in the mid intestinal region, compared to fish fed FM-based diets
Summary
With increasing levels of fish meal (FM) protein in aquafeeds being replaced with soybean meal (SBM) protein, understanding the molecular mechanisms involved in response to alternative diets has become a critical concern. Results of this study demonstrate that in response to SBM-based diets, yellow perch juveniles up-regulate the cholesterol biosynthesis pathway in order to maintain homeostasis. While soybean meal is an inexpensive alternative to fishmeal, it contains certain undesirable nutritional characteristics These include high carbohydrate levels, the presence of isoflavones, low methionine levels and anti-nutritional factors (lectins, oligosaccharides, saponins and trypsin inhibitors) that are reported to impede protein digestion, impair immune responses, and cause intestinal inflammation that hinders fish growth[2,3,4]. We reported that juvenile yellow perch fed a diet with 75% FM protein replacement with soybean meal protein displayed significantly reduced growth compared with those fed FM-based diets, yet adults fed the same diets had similar growth between the two groups[10] This suggests that juvenile fish are more susceptible to adverse growth performance, and that further investigation into the molecular mechanisms by which diet composition regulates growth is needed. The authors were unsure if down regulation of these processes were caused by tissue damage, or the presence of anti-nutritional factors in SBM that interfere with normal absorption of nutrients and are known to cause hypocholesterolemia[15,24]
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