Cold stress regulates lipid metabolism via AMPK signalling in Cherax quadricarinatus

Lipids play an important role in protecting poikilotherms from cold stress, but relatively little is known about the regulation of lipid metabolism under cold stress, especially in crustaceans. In the present study, red-clawed crayfish Cherax quadricarinatus was employed as a model organism. Animals were divided into four temperature groups (25, 20, 15 and 9 degrees C) and treated for 4 weeks, with the 25 degrees C group serving as a control. The total lipid content in the hepatopancreas as well as the triglyceride, cholesterol and free fatty acid levels in the hemolymph were determined. Lipids stored in the hepatopancreas and hemolymph decreased with decreasing temperature, with changes in the 9 degrees C group most pronounced, indicating that lipids are the main energy source for crayfish at low temperatures. Furthermore, enzyme activity of lipase, fatty acid synthase, acetyl-CoA carboxylase, and lipoprotein esterase, and gene expression analysis of fatty acid synthase gene, acetyl-CoA carboxylase gene and carnitine palmitoyltransferase gene showed that the digestion, synthesis and oxidation of lipids in the hepatopancreas were inhibited under low temperature stress, but expression of sphingolipid delta-4 desaturase (DEGS) was increased, indicating an increase in the demand for highly unsaturated fatty acids at low temperatures. Analysis of the expression of genes related to the AMP-activated protein kinase (AMPK) signalling pathway revealed that the adiponectin receptor gene was rapidly upregulated at low temperatures, which may in turn activate the expression of the downstream AMPK alpha gene, thereby inhibiting lipid anabolism.