INVESTIGADORES
GONZALEZ BARO Maria Del Rosario
capítulos de libros
Título:
Lipid Synthesis and Transport in Shrimps
Autor/es:
GARCIA, C.F.; GONZALEZ BARO, M.R.
Libro:
''Crustaceans: Structure, Ecology and Life Cycle
Editorial:
Nova 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.