Regulació nutricional i endocrina de la lipòlisi i la lipoproteïna lipasa en la truita irisada ("Oncorhynchus mykiss") i l'orada ("Sparus aurata")

by Albalat Ribé, Amaya

Abstract (Summary)
SUMMARY: In the present work, we have established the conditions for obtaining adipocytes of rainbow trout (Oncorhynchus mykiss) and gilthead seabream (Sparus aurata). Lipolysis increased proportionally with cell concentration and incubation time. In rainbow trout, insulin decreased lipolysis while glucagon was lipolytic. Moreover, in both species, fasting and an "in vivo" injection of glucagon in rainbow trout increased lipolysis measured in adipocytes. In gilthead seabream, glucagon, growth hormone and diets rich in vegetal proteins were lipolytic. The next objective was to analyse the role of tumor necrosis factor alpha (TNF-alpha) on lipolysis of rainbow trout adipocytes. TNF-alpha?increased lipolysis in a dose and time dependent manner. Adipocytes incubated with supernatants of rainbow trout macrophages stimulated with lipopolisacarid (LPS) showed a higher lipolysis. The stimulatory effect of TNF-alpha was partially blocked using inhibitors of MEK1/2 and p38. Finally, adipocytes from LPS-injected rainbow trout showed higher lipolysis while lipoprotein lipase (LPL) activity in adipose tissue of LPS-injected fish was lower. The second part of this work was focused on the study of the regulation of lipoprotein lipase activity. In rainbow trout, LPL activity in adipose tissue increased in response to feeding, while in both species, fasting produced a down-regulation of LPL activity in adipose tissue, concomitant with low levels of insulin. Insulin administered "in vivo" produced an increase in LPL activity in adipose tissue in both species. In gilthead seabream, this increase in activity was acompanied by an increase in LPL mRNA while in vitro studies in rainbow trout, using fat pads, revealed that insulin stimulated the proportion of LPL in active conformation at extracellular level. Finally, we established the protocol for measuring glucose uptake in isolated adipocytes of rainbow trout. Glucose uptake increased with cell concentration and incubation time. Cytochalasin B inhibited glucose transport suggesting that glucose uptake is carried out by specific facilitative glucose transporters. Insulin and insulin growth factor-I stimulated glucose uptake in isolated adipocytes. This stimulatory effect of insulin was totally blocked by wortmanin suggesting that PI3K/Akt is the main intracellular signalling mechanism involved.
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Bibliographical Information:

Advisor:Navarro Álvarez, Isabel

School:Universitat de Barcelona

School Location:Spain

Source Type:Master's Thesis

Keywords:fisiologia fac biologia


Date of Publication:10/28/2005

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