Identification of a novel crustacean vascular endothelial growth factor b-like in the mud crab Scylla paramamosain, and examination of its role in lipid accumulation

Vascular endothelial growth factor B (VEGFB), unlike other members of the VEGF family such as VEGFA, shows only limited potential in angiogenesis in mammals, but is involved in lipid metabolism, especially in transporting dietary lipids present in circulation through the vascular endothelium to peripheral tissues. However, the role of Vegfb in invertebrates such as decapod crustaceans with an open circulatory system is still poorly understood. Here, cDNA of a vegfb-like gene was cloned and characterized for the first time from a decapod crustacean, mud crab Scylla paramamosain. The mud crab vegfb-like gene encoded a polypeptide of 386 amino acids that possessed all the typical features of the Vegf family, and shared high homology with other crustacean Vegf orthologs. Relative expression levels of the vegfb-like gene were higher in metabolically active tissues such as gill, heart and muscle, and increased in ovary of female crabs as ovary matured. Knockdown of the vegfb-like gene in vivo reduced the contents of triglyceride in hemolymph and hepatopancreas, as well as total lipid in hepatopancreas. In addition, knockdown of the vegfb-like gene increased tissue expression levels of genes related to fatty acid transportation, allocation and hydrolysis, such as long-chain acyl-CoA synthetase 3/4 (acsl3/4), fatty acid transport protein 1 (fatp1), and hormone-sensitive lipase (hsl), and decreased the expression levels of the genes related to fatty acid synthesis like acetyl-CoA carboxylase (acc). These results in mud crab suggest that Vegfb might play important roles in regulating fatty acid absorption, utilization and allocation in crustaceans.