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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Publications at this Location » Publication #308886
Title: Expression of genes associated with fatty acid metabolism during maturation in diploid and triploid female rainbow trout

Author
item MANOR, MEGHAN - West Virginia University
item Weber, Gregory - Greg
item Cleveland, Beth
item YAO, JIANBO - West Virginia University
item KENNEY, P. BRETT - West Virginia University

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2014
Publication Date: 1/1/2015
Citation: Manor, M.L., Weber, G.M., Cleveland, B.M., Yao, J., Kenney, P. 2015. Expression of genes associated with fatty acid metabolism during maturation in diploid and triploid female rainbow trout. Aquaculture. 435:178-186.

Interpretive Summary: Fatty acid concentrations are important for fillet and egg quality in fishes. In many cultured fish species, such as salmonids, gonadal development occurs at the expense of stored energy and nutrients, including lipids. As a part of this repartitioning of nutrients, the quality of the fillet is decreased so that nutrients including omega-3 fatty acids, can be deposited into the eggs. Thus, these events are important to hatcheries interested in producing high quality eggs, and producers of large fish who are interested in the production of high quality fillets. We have previously shown ration can affect the quality of the fillet during sexual maturation. To characterize effects of sexual maturation on fatty acid metabolism in fish on a high nutritional plane, expression of thirty-five genes involved in fatty acid metabolism was determined in sexually maturing diploid and triploid female rainbow trout. Diploids are normal fish with the normal two sets of chromosomes whereas triploids are treated to have three sets of chromosomes which makes them sterile and prevents them from growing large gonads. The rainbow trout industry grows both diploid and triploid fish. Gene expression was assessed in liver, white muscle, and visceral adipose tissues for fish that were 16 to 24 months of age which is just before spawning and when most of egg growth takes place. Previously, we reported minimal differences in most growth measurements between maturing diploid and triploid fish, but there were disparate changes in muscle proximate composition, visceral fat stores, and fatty acid contents of energy stores at 21 months with triploid females having greater lipid or fatty acid stores. Here, we report that gene expression profiles of liver and white muscle provides a greater understanding of how these changes are regulated. Overall, this study suggests triploid females are undergoing higher levels of fatty acid synthesis while diploid females have higher levels of lipid utilization during sexual maturation. Accordingly, diploid females showed decreasing fatty acid stores during this time period. This information can be used by rainbow trout producers to determine when to harvest large food-fish before maturation affects fillet quality, and provides information that can assist development of diet formulations or feeding strategies to maximize fillet or egg quality.

Technical Abstract: To study effects of sexual maturation on fatty acid metabolism in fish on a high nutritional plane, expression of thirty-five genes involved in fatty acid metabolism was determined in sexually maturing diploid (2N; fertile) and triploid (3N; sterile) female rainbow trout. Gene expression was assessed in liver, white muscle, and visceral adipose tissues for fish that were 16 to 24 months of age. Previously, we reported minimal differences in most growth measurements between maturing 2N and 3N fish, but there were disparate changes in muscle proximate composition, visceral fat stores, and fatty acid contents of energy stores at 21 months with 3N females having greater lipid stores. Here, we report that gene expression profiles of liver and white muscle corresponded to the phenotypes with significant differences in expression at 20 months. Triploid females had increased expression of genes involved in fatty acid synthesis; including gpat, srebp1, acyl, acc, fas, and scd1 in liver and fas in muscle. Conversely, 2N muscle had increased expression of beta-oxidation genes cpt1b, cpt2, ehhadh, and acat2 and TORC1 inhibitors redd1, erk, mo25, and pras40. Diploid muscle also had increased expression of ppar-beta along with increased expression of the fatty acid transporter gene cd36, and beta-oxidation genes cpt1a, cpt1c, aco, and acdhvl at 20 months. Additionally, 2N visceral adipose tissue had increased cpt1a expression at 21 months. Overall, data suggest 3N females are undergoing higher levels of fatty acid synthesis while 2N females have higher levels of beta-oxidation during sexual maturation. Phenotypic data supports these findings with decreasing fatty acid stores in 2N females during this time period. Additionally, changes in gene expression are associated with altered expression within the mTOR and PPAR-beta signaling pathways.