Changes in lipid biology during ovarian development in farmed beluga sturgeon, Huso huso L.

This study was conducted in order to understand key biochemical, physiological and molecular changes associated with ovarian growth and with lipid transfer and/or accumulation into the ovary during oogenesis in captive beluga sturgeon. Plasma levels of triacylglycerides, cholesterol, phospholipid and sex steroid hormones were determined and found to all increase notably throughout development from the perinucleolar to the tertiary yolk stage. Using fast protein liquid chromatography, three major lipoprotein peaks were recognized in chromatograms from all samples. These peaks were characterised as containing very low density lipoprotein (Vldl), low density lipoprotein/ high density lipoprotein (Ldl/Hdl) and plasma proteins, respectively. While Ldl/Hdl represented the most abundant lipoprotein fraction, relative abundance of different lipoprotein classes did not change with stage of oogenesis. Eluted lipoproteins were separated using sodium dodecyl sulfate polyacrylamide gel electrophoresis and sequenced. The peptide sequence spectra for 66, 205, 29 and 70 kDa bands matched with albumin, vitellogenin (Vtg) AB2b, immunoglobulin light-chain precursor and immunoglobulin heavy-chain, respectively. The large amount of albumin in the plasma protein peak and the presence of Vtg AB2b to within Ldl/Hdl reinforce the lipoprotein classification. Lastly, transcript levels of ovarian lipoprotein lipase (lpl), apolipoprotein E (apoe) very low density lipoprotein receptors (vldlr), and low-density lipoprotein receptor-related protein 8-like (lrp8) were estimated using quantitative polymerase chain reaction. The high mRNA levels of lpl, apoe, and lipoprotein receptors vldlr and lrp8, in previtellogenic females suggest that sturgeon oocytes need to be prepared to accept and traffic Vtg and lipids internally, prior to the start of vitellogenesis.