Lipid deposition and mobilisation in atlantic salmon adipocytes

The present study aimed to elucidate how Atlantic salmon adipocytes pre-enriched with palmitic (16:0, PA), oleic (18:1n􀀀9, OA), or eicosapentaenoic (20:5n􀀀3, EPA) acid respond to a fasting condition mimicked by nutrient deprivation and glucagon. All experimental groups were supplemented with radiolabeled PAto trace secreted lipids and distribution of radioactivity in di_erent lipid classes. There was a higher content of intracellular lipid droplets in adipocytes pre-enriched with OAthan in adipocytes pre-enriched with PAor EPA. In the EPAgroup, the radiolabeled PAwas mainly esterified in phospholipids and triacylglycerols, whereas in the OA and PA groups, the radioactivity was mainly recovered in phospholipids and cholesterol-ester. By subjecting the experimental groups to nutrient-deprived media supplemented with glucagon, lipolysis occurred in all groups, although to a lower extent in the OA group. The lipids were mainly secreted as esterified lipids in triacylglycerols and phospholipids, indicating mobilization in lipoproteins. A significant proportion was secreted as free fatty acids and glycerol. Leptin secretion was reduced in all experimental groups in response to fasting, while the mitochondria area responded to changes in the energy supply and demand by increasing after 3 h of fasting. Overall, di_erent lipid classes in adipocytes influenced their mobilization during fasting.