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ARS Home » Northeast Area » Leetown, West Virginia » Cool and Cold Water Aquaculture Research » Research » Publications at this Location » Publication #329423
Research Project: Integrated Research Approaches for Improving Production Efficiency in Salmonids

Location: Cool and Cold Water Aquaculture Research

Title: Specific Roles for 17ß-Estradiol versus Gonad Development in Nutrient Partitioning and Regulation of Nutrient- and Growth-Related Mechanisms During Sexual Maturation in Rainbow Trout

Author
item Cleveland, Beth
item Weber, Gregory - Greg

Submitted to: International Symposium on Fish Endocrinology
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2016
Publication Date: 6/27/2016
Citation: Cleveland, B.M., Weber, G.M. 2016. Specific Roles for 17ß-Estradiol versus Gonad Development in Nutrient Partitioning and Regulation of Nutrient- and Growth-Related Mechanisms During Sexual Maturation in Rainbow Trout. International Symposium on Fish Endocrinology. P6 OR-08.

Interpretive Summary:

Technical Abstract: The contribution of sex steroids to nutrient partitioning and energy balance during gonad development was studied in rainbow trout (Oncorhynchus mykiss). Nineteen month old triploid (3N) female rainbow trout were fed a diet supplemented with 17ß-estradiol (E2) at 30 mg steroid/kg diet for a 1 month period. Growth performance, nutrient partitioning, and expression of genes central to growth and nutrient metabolism were compared to 3N and age-matched diploid (2N) female fish consuming a control diet. Only 2N fish exhibited active gonad development, with gonad weights (GSI) increasing from 3.7% to 5.5% of body weight throughout the study while GSI in 3N fish remained at 0.03%. Consumption of E2 in 3N fish reduced fillet growth and caused lower fillet yield compared to 2N and 3N controls (P less than 0.05). In contrast, viscera fat somatic index was least in maturing 2N (P less than 0.05) but was not affected by E2 in 3N. Gene transcripts associated with physiological pathways were identified in maturing 2N and E2-treated 3N fish that differed in abundance from 3N control fish (P less than 0.05). In liver these mechanisms included the growth hormone/insulin-like growth factor (IGF) axis (igf1, igf2), IGF binding proteins (igfbp1b1, igfbp2b1, igfbp5b1, igfbp6b1), and genes associated with fatty acid binding (fabp3, fabp4), synthesis (acc), fatty acid oxidation (cpt1a), and the pparg transcription factor. In muscle these mechanisms included reductions in myogenic gene expression (fst, myog) and the proteolysis-related genes, ctsl and gabarapl1, suggesting an E2-induced reduction in the capacity for muscle growth. These findings suggest that increased E2 signaling in the sexually maturing female rainbow trout alters physiological pathways in liver, particularly those related to IGF signaling and lipid metabolism, to reduce de novo fatty acid synthesis, increase lipid oxidation, and partition nutrients away from muscle growth towards support of maturation-related processes. In contrast, the mobilization of viscera lipid stores appear to be predominantly driven by energy demands associated with gonad development.