Dietary zinc levels affects lipid and fatty acid metabolism in hepatopancreas of mud crab (Scylla paramamosain)

Abstract

This study investigated the influences of dietary zinc (Zn) on lipid and fatty acid metabolism of Scylla paramamosain. Three diets containing analyzed Zn levels including 44.5 (low Zn), 68.5 (medium Zn) and 254.7 (high Zn) mg/kg were prepared and fed to mud crab for 10 weeks, respectively. Medium dietary Zn levels improved the growth of mud crab than those fed the high Zn diet. The concentration of Zn in tissues was positively correlated with dietary Zn levels. Crabs fed with high Zn diet significantly decreased lipid content in hepatopancreas and muscle when compared to those fed the medium Zn diet. The lowest diameter, area and number of R cell in hepatopancreas histology were observed in those fed the high Zn diet. Furthermore, medium levels of dietary Zn significantly increased docosahexaenoic acid (DHA) and n-3 polyunsaturated fatty acid (PUFA) contents in hepatopancreas. Crabs fed high Zn diet dramatically down-regulated expression of acc, fas, g6pd, 6pgd and srebp, but up-regulated expression of aco3, cpt1 and fabp1 in hepatopancreas. Crabs fed with medium Zn diet significantly increased the mRNA levels of fad in hepatopancreas. In summary, the results of present study emphasized the adverse effects of excess dietary Zn (254.7 mg/kg) on suppress hepatopancreatic lipid and n-3 PUFA accumulation, dietary 68.5 mg/kg Zn level was recommended to maintain optimal lipid and fatty acid metabolism of mud crab.