Expression of genes associated with fatty acid metabolism during maturation in diploid and triploid female rainbow trout

To study the effects of sexual maturation on fatty acid metabolism in fish fed to satiation daily, 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 M 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 M 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 M. 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 β-oxidation genes cpt1b, cpt2, ehhadh, and acat2 and TORC1 inhibitors redd1, erk, mo25, and pras40. Diploid muscle also had increased expression of pparβ along with increased expression of the fatty acid transporter gene cd36, and β-oxidation genes cpt1a, cpt1c, aco, and acdhvl at 20 M. Additionally, 2N visceral adipose tissue had increased cpt1a expression at 21 M. Overall, data suggest that 3N females are undergoing higher levels of fatty acid synthesis while 2N females have higher levels of β-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 PPARβ signaling pathways.