Metabolomics,Unknown,Transcriptomics,Genomics,Proteomics

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Microarray analysis of the white muscle transcriptome in feed deprived rainbow trout treated with insulin-like growth factor-I

ABSTRACT: Treatment with insulin-like growth factor-I (IGF-I) during feed deprivation attenuates the weight loss response in both mammals and fish, therefore the reduction in plasma IGF-I concentrations during fasting likely serves as a signal that contributes to the catabolic response. To better understand the physiological mechanisms responsible for this effect rainbow trout were administered IGF-I during a 2 wk period of feed deprivation and changes in gene expression in white muscle were determined using microarray analysis. Weight loss was reduced by 15% (P<0.05) in IGF-I treated fish. A total of 440 transcripts were identified as differentially regulated (P<0.05) between saline and IGF-I treated fish. Genes related to protein degradation were down-regulated and included protease and peptidase genes and genes involved in ubiquitin-proteasome and cathepsin-mediated proteolytic pathways. IGF-I increased expression of myosin binding protein H and coronin-1C, while decreasing expression of other myofibrillar and cytoskeleton-associated genes like troponin-C and parvalbumin-2. Polyadenylate-binding protein 2, a transcription factor that positively regulates myoD and myogenin expression, was upregulated with IGF-I treatment. Additional genes that were differentially regulated are associated with lipid and carbohydrate metabolism, mitochondrial biogenesis and electron transport, gene transcription, signal transduction and regulation of apoptosis. In summary, these data suggest that IGF-I plays a central role in regulating protein degradation, especially via the ubiquitin-proteasomal pathway, and that reductions in protein degradation and the subsequent effects on other physiological systems are largely responsible for the IGF-I-induced reduction in weight loss. Eight approximately 1-year old full-sibling rainbow trout families were housed in individual tanks, according to family, at the National Center for Cool and Cold Water. Each fish was pit-tagged at 7-months of age. At the beginning of the study, fish were anesthetized with tricaine methanesulfonate (MS-222), weighed, and an osmotic pump was surgically inserted into the peritoneal cavity of each fish (n=4 fish/family/treatment, N=16 fish). The osmotic pump contained either recombinant human IGF-I, which released hormone at 25 ug/kg/day, or saline, which was the vehicle used to resuspend IGF-I. Feed was withheld 2-days prior to surgery and for the experimental 2 week period. Fish were harvested using as overdose of MS-222, weighed, and white muscle samples were removed, frozen in liquid N, and stored at -80 C until analysis. Muscle RNA was isolated from muscle of the two families that exhibited the greatest difference in weight loss between IGF-I and saline treatments; families 64 and 107. Hybridizations were performed using a dye-swap design with an IGF-I and saline treated fish within the same family, therefore a total of 16 slides were hybridized using Alexa 647 and Alexa 555 dyes.

ORGANISM(S): Oncorhynchus mykiss

SUBMITTER: Beth Cleveland

PROVIDER: E-GEOD-31765 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:When puberty starts before males reach harvest size, animal welfare and sustainability issues occur in Atlantic salmon (Salmo salar) aquaculture. Hallmarks of male puberty are an increased proliferation activity in the testis and elevated androgen production. Examining transcriptional changes in salmon testis during the transition from immature to maturing testes may help understanding the regulation of puberty, potentially leading to procedures to modulate its start. Since differences in body weight influence, via unknown mechanisms, the chances for entering puberty, we used two feed rations to create body weight differences. Maturing testes were characterized by an elevated proliferation activity of Sertoli cells and of single undifferentiated spermatogonia. Pituitary gene expression data suggest increased Gnrh receptor and gonadotropin gene expression, potentially responsible for the elevated circulating androgen levels in maturing fish. Transcriptional changes in maturing testes included a broad variety of signaling systems (e.g. Tgfβ, Wnt, insulin/Igf, nuclear receptors), but also, activation of metabolic pathways such as anaerobic metabolism and protection against ROS. Feed restriction lowered the incidence of puberty. In males maturing despite feed restriction, plasma androgen levels were higher than in maturing fish receiving the full ration. A group of 449 genes that was up-regulated in maturing fully fed fish, was up-regulated more prominently in testis from fish maturing under caloric restriction. Moreover, 421 genes were specifically up-regulated in testes from fish maturing under caloric restriction, including carbon metabolism genes, a pathway relevant for nucleotide biosynthesis and for placing epigenetic marks. Undifferentiated spermatogonia and Sertoli cell populations increased at the beginning of puberty, which was associated with the up-regulation of metabolic pathways (e.g. anaerobic and ROS pathways) known from other stem cell systems. The higher androgen levels in males maturing under caloric restriction may be responsible for the stronger up-regulation of a common set of (449) maturation-associated genes, and the specific up-regulation of another set of (421) genes. The latter opened regulatory and/or metabolic options for initiating puberty despite feed restriction. As a means to reduce the incidence of male puberty in salmon, however, caloric restriction seems unsuitable.

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Microarray analysis of the white muscle transcriptome in feed deprived rainbow trout treated with insulin-like growth factor-I

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