Starvation alters lipid and glycogen metabolism in clam Cyclina sinensis

This study investigates the effect of normal feeding (starvation for 0 days, control), starvation for 3 (S3), 9 (S9), 15 days (S15) and refeeding for 3 (S9R3), 9 (S9R9), 15 days (S15R15) on the expression of genes related to lipid and glycogen metabolism, the content of biochemical molecules, the activities of enzymes and the morphological structure of the hepatopancreas of C. sinensis. Results showed that the expression levels of cpt-I, acox, gdh, tre and pepck in hepatopancreas, cpt-I and acc in gonads, and tre and pepck in mantle initially increased and then decreased during starvation. the expression levels of gdh and pkm gradually increased with the duration of starvation. the mRNA level of cpt-I, dgat1 and acc reached a peak level in the S15R15 group, while the expression levels of gdh and pepck in mantle increased in the S9R3 and S9R9 groups. The hepatopancreatic LPS, LPL, and HK activity in the hepatopancreas and mantle of C. sinensis increased during starvation. Moreover, the TG content in the hepatopancreas and GN content in the mantle decreased with the prolongation of starvation. After refeeding, TG levels in the hepatopancreas increased slightly but remained significantly lower than in controls. The GN content in the hepatopancreas and mantle of the S9R9 and S15R15 groups was higher than those of the control group. The number of lipid droplets in the hepatopancreatic tubular decreased with prolonged starvation, but the content of lipid droplets in the hepatopancreatic tubular increased slightly after refeeding. However, with the increase in the duration of starvation, the wall of the hepatopancreatic tubular becomes thin and the number of vacuoles increases. These results indicate that lipid and glycogen metabolism are involved in this clam's physiological regulation in response to starvation stress.