UMR Nutrition Aquaculture et Génomique
Nutrition Métabolisme et Aquaculture
64310 St Pée-sur-Nivelle France
Tel : +33 (0)5 59 51 59 93
Fax: +33 (0)5 59 54 51 52
Mail : first email@example.com
Cursus and training
Ingénieur Agronome graduate of the "Ecole Nationale Supérieure Agronomique de Rennes".
Attaché Scientifique Contractuelle, INRA, PhD, graduate of the University Claude Bernard, Lyon 1.
Recruitment as Chargée de Recherche, Station de Recherches Avicoles, INRA Nouzilly, in 1999.
A major objective in aquaculture is to optimise nutrient utilisation by farmed fish supplied through feeds containing different ingredients. A better knowledge of the mechanisms involved in the regulation nutrients use by fish remains crucial to bring solutions to these problems.
The mechanisms involved in the regulation of metabolism also depend on the interactions between hormonal factors and the nutrients. Most of the nutrients control target gene expression thus modifying the secretion or the intracellular signal transduction pathways of various hormones such as insulin, glucagon or glucocorticoïdes. My work focuses on the interactions between insulin and amino acids in fish, using rainbow trout as a model animal. Indeed, unlike most terrestrial farm animals, fish are characterized by very high protein requirements. In fish, proteins are also predominantly used for the production of energy through an oxidation pathway and are also used as precursors for endogenous glucose production. We suspect that amino acids are also involved in a negative feedback loop to suppress insulin signalling. Rainbow trout is known to use high levels of dietary carbohydrates rather poorly, with prolonged postprandial hyperglycemia after oral administration of glucose or a carbohydrate-rich meal despite normal insulin secretion. A reduced used of glucose by peripheral tissues and an absence of inhibition of hepatic gluconeogenesis have been also observed in rainbow trout fed with enriched-carbohydrates diets. However, hepatic gluconeogenic gene expression is diminished with low protein intake. Since insulin is considered as a key regulator of gluconeogenesis, we suspect that high amino acid intake restrains insulin activities.
Even in humans, recent data suggest that high-protein diets leads to insulin resistance. The effects of amino acids on the development of insulin resistance seem to be linked to a negative feedback loop of the S6K1 protein on the activity of the insulin receptor substrate 1 (IRS1). Such mechanisms can explain the metabolic features of the rainbow trout.
Negative amino acids feedback loop on insulin signalling pathway
We are currently trying to determine the effects of insulin on the expression of genes related to metabolism. The determination of the intracellular signalling pathway activated by insulin to regulate gene expression is also under investigation. For this purpose, we have undertaken studies on the effects of intraperitoneal administration of insulin in rainbow trout and developed primary hepatocyte cell culture.
Rainbow trout(Oncorhynchus mykiss)
Glucokinase, Glucose-6-Phosphatase, Phosphoenolpyruvate carboxykinase
Fatty acid synthase, Carnitine Palmitoyltransferase 1
Ubiquitin conjugating enzyme (E2), Atrogin-1, Muscle-specific RING Finger protein 1
C/EBP alpha , PGC1 alpha
Hepatocytes primary cell culture
Imminent studies will focus on determining both in vivo and in vitro, using primary hepatocytes, the potential interactions between the respective transduction pathways of insulin and amino acids and their consequences on the regulation of gene expression. We think that amino acids through their “signal effect” modify the intracellular signalling pathway of insulin. From this perspective we will analyse the serine phosphorylation of IRS1. Actually in mammals, IRS1 serine phosphorylation disrupts its association with the insulin receptor leading to its degradation which would lead to decreased insulin signalling.
These basic research should eventually allow us to better comprehend the potential consequences of changes in dietary amino acid profiles on trout metabolism.
Financial support: Conseil Régional Aquitaine.
This research project is developed in collaboration with Dr S. Tesseraud (Station de Recherches Avicoles, INRA, Nouzilly) and Professor J. Guttierrez (Département of Physiology, Faculty of Biology, University of Barcelona, Spain).
Lecture : MASTER Biology ; Speciality Biology, Animal productions and Quality, University of Rennes 1; Agrocampus Rennes.
Conférence dans le cadre de la deuxième année du MASTER Biologie ; Spécialité Biologie, Productions Animales et Qualité de l'université de Rennes 1 Agrocampus Rennes.
- Cassy, S., Metayer, S., Crochet, S., Rideau, N., Collin, A., Tesseraud, S., 2004. Leptin receptor in the chicken ovary: potential involvement in ovarian dysfunction of ad libitum-fed broiler breeder hens. Reprod Biol Endocrinol 2, 72.
- Cassy, S., Picard, M., Crochet, S., Derouet, M., Keisler, D.H., Taouis, M., 2004. Peripheral leptin effect on food intake in young chickens is influenced by age and strain. Domest. Anim. Endocrinol. 27, 51-61.
- Cassy, S., Derouet, M., Crochet, S., Dridi, S., Taouis, M., 2003. Leptin and insulin downregulate leptin receptor gene expression in chicken-derived leghorn male hepatoma cells. Poult. Sci. 82, 1573-1579.