Roles of leptin in initiation of acquired growth hormone resistance and control of metabolism in rainbow trout.

Catabolic conditions often induce concomitant changes in plasma leptin (Lep), growth hormone (GH), and insulin growth factor I (IGF-I) levels in teleost fish, but it is unclear whether these parts of the endocrine system are responding independently or functionally linked. In this study, fasted rainbow trout was used to study the effects of Lep on the GH-IGF-I system and metabolism. Fish were implanted intraperitoneally with recombinant rainbow trout Lep pellets and remained unfed. After 4 days, plasma GH levels were elevated in the Lep-treated fish in a dose-dependent manner; the expression of hepatic igf1 and plasma IGF-I levels were suppressed accordingly. In vitro Lep treatment reversed ovine GH (oGH)-stimulated expression of igf1 and igf2 in hepatocytes isolated from fasted fish, similar to the inhibitory effects of the MEK1/2 inhibitor U0126 treatment. However, Lep treatment alone had no effect on the expression of igfs or oGH-stimulated ghr2a expression in the hepatocytes. These results demonstrate an additive effect of Lep on suppression of IGF-I under catabolic conditions, indicating that Lep is likely involved in initiation of acquired GH resistance. Although the Lep-implant treatment had no effect on standard metabolic rate, it significantly suppressed gene expression of hepatic hydroxyacyl-CoA dehydrogenase, phosphoenolpyruvate carboxykinase, and glucose 6-phosphatase, which are key enzymes in lipid utilization and gluconeogenesis, in different patterns. Overall, this study indicates that the Lep increase in fasting salmonids is an important regulatory component for physiological adaptation during periods of food deprivation, involved in suppressing growth and hepatic metabolism to spare energy expenditure.

Assessing the effects of textile leachates in fish using multiple testing methods: From gene expression to behavior.

The textile industry, while of major importance in the world economy, is a toxic industry utilizing and emitting thousands of chemical substances into the aquatic environment. The aim of this project was to study the potentially harmful effects associated with the leaching of chemical residues from three different types of textiles: sportswear, children's bath towels, and denim using different fish models (cell lines, fish larvae and juvenile fish). A combination of in vitro and in vivo test systems was used. Numerous biomarkers, ranging from gene expression, cytotoxicity and biochemical analysis to behavior, were measured to detect effects of leached chemicals. Principle findings indicate that leachates from all three types of textiles induced cytotoxicity on fish cell lines (RTgill-W1). Leachates from sportswear and towels induced mortality in zebrafish embryos, and chemical residues from sportswear reduced locomotion responses in developing larval fish. Sportswear leachate increased Cyp1a mRNA expression and EROD activity in liver of exposed brown trout. Leachates from towels induced EROD activity and VTG in rainbow trout, and these effects were mitigated by the temperature of the extraction process. All indicators of toxicity tested showed that exposure to textile leachate can cause adverse reactions in fish. These findings suggested that chemical leaching from textiles from domestic households could pose an ecotoxicological threat to the health of the aquatic environment.