Nutrigenomic and nutriepigenomic effect of plant protein-based aquafeeds on fish

For the sustainable growth of Norwegian aquaculture industry, exploration of novel protein sources for fish feed is a necessity due to the limitation of marine fish meal resources. The last decade has seen a significant transition from fish meal to up to 70% plant ingredients in salmon feeds. This change into green diets for farmed salmon has led to new challenges in fish health and welfare, as well as product quality. Plant-based proteins have shown to affect the growth and health of the farmed fish depending on the percentage of plant proteins, fish species and various other factors. However, the molecular basis of these effects is not well understood. Very little is known about the effect of plant ingredients on epigenome of fishes. Therefore, EpiGreen aimed to study the effect of plant protein-based aquafeeds on fish growth and health at the molecular level by exploring global transcriptome and epigenome changes using zebrafish as a model. This knowledge has been also extended to a commercially important species for Norwegian aquaculture industry, by testing selected nutrigenomic markers from the zebrafish model, as well as analyzing nutriepigenomic effect, on on-growing Atlantic salmon fed with green diets. Diets containing 30% of typical plant proteins that are frequently used in salmon feeds, i.e. wheat, soy or pea, were evaluated in comparison with a control diet with marine proteins. RNASeq technology was used to identify differentially expressed transcripts at a global scale in key organs related to health (spleen) and growth performance (muscle). Whereas genome-wide analysis of DNA methylation patterns was performed by reduced representation bisulfite sequencing to examine the global epigenetic alterations in the mid intestine and liver. The findings of the EpiGreen project indicated that partial inclusions of soy or pea protein concentrate or wheat gluten in the diets caused significant alterations in transcript levels associated with health (spleen) and growth performance (muscle) in zebrafish. Further this project showed that plant ingredients could induce epigenetic modifications in the intestine of zebrafish. Supporting that histological analysis of the intestine also revealed some diet specific changes. EpiGreen also found that some of the differentially expressed genes in the muscle of zebrafish fed soy protein diet, could potentially use as biomarkers in the muscle of Atlantic salmon fed similar diet. Further, this study reported that wheat gluten diet could induce epigenetic changes in the liver of Atlantic salmon. In conclusion, EpiGreen project revealed that partial inclusion of plant based protein induce both nutrigenomic and nutriepigenomic effect on model species zebrafish as well as commercially important species Atlantic salmon. Ultimately, this project has addressed fish welfare concerns over forcing fish into a vegetarian diet.

EpiGreen project revealed for the first time that partial inclusions (30%) of soy or pea protein concentrate or wheat gluten in the diets could induce global epigenetic alterations in the intestine of zebrafish and liver of Atlantic salmon. It also reported that the same diets could cause changes in global gene expressions in the key organs related to immunity (spleen) and growth performance (muscle) of zebrafish. In conclusion, EpiGreen revealed that plant-based protein could induce both nutriepigenomics and nutrigenomics effects on fish. This postdoctoral fellowship enabled grant recipient to improve her skills and gain knowledge and competence in the fields of nutriepigenomics and nutrigenomics. It has supported her to participate in internationally recognized scientific conferences and research environments. It also helped her to improve her management and administrative skills. Ultimately, this project has contributed to a major advance in the grant recipient's academic career.

For the sustainable growth of Norwegian aquaculture industry, exploration of novel protein sources for fish feed is a necessity due to the limitation of marine fishmeal resources. Last decade, it showed a significant transition from fishmeal to up to 70% plant ingredients in salmon feeds. This complete change into green diets for farmed salmon has led to new challenges in fish health and welfare, and product quality. Some of these issues have been addressed by extensive research, but many challenges remain. The Norwegian Scientific Committee for Food Safety has identified data gaps in changes in fish feed formulations, pointing out that plant ingredients may introduce new contaminants that might transfer from feed to fish fillet risking consumer safety. Therefore, as a first step, EpiGreen aims to study the effect of plant protein-based aquafeeds on fish growth and health at molecular level by exploring global transcriptome and epigenome changes using zebrafish as a model. This knowledge will be extended to commercially important species for Norwegian aquaculture industry by testing selected nutrigenomic and nutriepigenomic markers from zebrafish model on on-growing Atlantic salmon fed with green diets. EpiGreen will evaluate the effect of diets with high ratios of commonly used plant proteins, wheat, soy or pea, in comparison with a control diet with marine proteins. It will adopt RNA-seq coupled with reduced representation bisulfite sequencing to examine transcriptomic and global epigenetic alterations in key organs related to growth performance and immunity. The findings will provide the first evidence that plant ingredients may induce epigenetic modifications leading to alterations in transcript levels associated with fish growth and health. EpiGreen will help to build up the project applicant's career in the research and academic field. It will create a research network with both national and international partners.