INIBIOLP   05426
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE LA PLATA "PROF. DR. RODOLFO R. BRENNER"
Unidad Ejecutora - UE
capítulos de libros
Título:
Lipid Synthesis and Transport in Shrimps
Autor/es:
GARCIA CF.,; GONZALEZ-BARÓ M
Libro:
Crustaceans: Structure, Ecology and Life Cycle. Distribution
Editorial:
Nova Science Publishers
Referencias:
Lugar: Hauppauge, NY; Año: 2013; p. 71 - 94
Resumen:
In aquatic invertebrates, lipids represent an important source of stored energy, as well as structural components of cellular membranes and other lipoprotein complexes. In the freshwater shrimp Macrobrachium borellii, we demonstrated that the hepatopancreas, also known as midgut gland, has a high capacity for triacylglycerol biosynthesis, storage and breakdown. When radioactive palmitic acid was injected in vivo, most of the label was transported to the hepatopancreas, where triacylglycerol were actively synthesized. The enzymatic activity that initiates glycerolipid synthesis, glycerol-3-phosphate acyltransferase, is located in the mitochondria. In contrast, triacylglycerol synthesis in hepatopancreas microsomal fraction follows the monoacylglycerol pathway. Even though triacylglycerol count for the major lipid class (up to 80% of the total lipids), phosphatidylcholine is exported from the hepatopancreas to other tissues and transported in hemolymph as a high-density lipoprotein (HDL), suggesting that triacylglycerol are stored in the hepatopancreas for energy supply or lipid remodeling. M. borellii?s HDL lipid moiety is composed mainly of phosphatidylcholine with minor quantities of cholesterol and triacylglycerol. Lipid transference between hepatopancreas and HDL was studied in vitro, confirming that HDL releases free fatty acids to the hepatopancreas, whereas phosphatidylcholine and other phospholipids are liberated from the hepatopancreas to HDL. Proteins, lipids and carbohydrates present in the vitellus of eggs are important energy and building block sources for the embryo development in ovipara. In aquatic invertebrates, these compounds are usually associated forming lipoproteins called lipovitellins (LV) that function as nutrient sources for the development of the embryo and also satisfy the metabolic larvae needs from their birth to the moment they start feeding on external sources. In M. borellii and other crustaceans, LVs are high-density lipoproteins with phosphatidylcholine as the major lipid and minor quantities of other lipids like triacylglycerol and phosphatidylethanolamine. LVs are originated from a plasma lipoprotein restricted to ovogenic females: vtellogenin (VG). M. borellii?s VG lipids are similar quantities of phosphatidylcholine, sphingomyelin, triacylglycerol and phosphatidylethanolamine. During vitellogenesis, VG is endocyted into the ovary, where it is processed and changed into LV. Compared to VG, LV has twice as much phosphatidylcholine as the other lipid classes and less sphingomyelin, suggesting that the lipoprotein processing in the ovary provides LV with different lipid domains specific for its biological function. Due to the fact that some of LV apolipoproteins have been detected inside the developing embryo, it was concluded that LV was consumed. LV transfers to the embryo mainly the lipids loaded inside the ovary (mostly phosphatidylcholine), together with proteins to feed the embryos. Further studies are needed to determine the lipid transference mechanisms involving the lipoproteins with lipid donor and receptor organs. However, our knowledge about lipid transport and metabolism in crustaceans has evolved in the last few years regarding both plasma and yolk lipoproteins; it sets ground for understanding the lipoprotein function in reproduction and embryo development.