Lipids from fat store in fish : Cellular, metabolic and hormonal control

Abstract

Specificities of cellular, metabolic, and hormonal control of fat accretion and mobilisation are reviewed in the light of personnal data. Very little information on adipose tissues of fish is available. According to mechanisms observed in mammals, the involvment of hyperplastic processes together with hypertrophic processes in the development of adipose tissues in fish is emphasized but has yet to be demonstrated. The characteristics of lipoproteins involved in the transport of dietary lipid and of lipid from fat stores seemed to be similar in fish and in mammals except for the appearance of vitellogenin during female gonadal development. Cholesterol transport seems to be different from that of mammals but the specificities of such a process remain to be clarified. Transport of lipids and mobilisation are controlled both by the apoprotein composition of lipoproteins and by the existence of enzymes which metabolize the lipoproteins. The main hormone involved directly in the control of fat accretion is insulin. The indirect control of fat accretion (through the interaction with insulin action) and the direct control of fat mobilisation is mediated through a multi-hormonal process which include hypohyseal, thyroid, pancreatic and corticosteroid hormones. Fish seem to be original in their dependancy of lipid accretion from the environment and in their high physiological potencies for lipid mobilization and redistribution within tissues.