To determine the effect of vitamins C and E on lipid metabolism and interactions between them, L‐ascorbyl‐2‐monophosphate‐Mg (APM) and α‐tocopherol acetate (TA) were fortified to a commercially based diet and fed to 0‐year red sea bream Pagrus major and 1‐year black sea bream Acanthopagrus schlegeli. Fortification of APM and TA, respectively, increased ascorbate (ASC) and α‐tocopherol (α‐Toc) contents in the organs. In addition, APM fortification increased α‐Toc accumulation in both fishes, although TA fortification did not significantly affect the ASC content. Fortification of APM caused a depression in lipid accumulation in the intraperitoneal fat body and liver in red sea bream. Furthermore, a decrease in the serum thiobarbituric acid value in black sea bream and a reduction of the adipocyte diameter in the APM‐fortified groups of both fishes were observed. However, fortification of TA did not affect these parameters as significantly as did fortification of APM. The shortest recovery time to air‐dipping was found in the APM + TA‐fortified group, followed by the APM‐fortified group in red sea bream. The results implied an effect of vitamin C on lipid metabolism, and acceleration of vitamin E absorption and/or suppression of vitamin E degradation.

Hatchery‐reared black sea bream Acanthopagrus schlegeli juveniles averaging 0.05 g in body weight were fed either a control diet (commercial diet) or an experimental diet in which the commercial diet was fortified with 50 mg l‐ascorbyl 2‐monophosphate Mg (APM)/100 g diet for 50 days. Calcium ascorbate supplemented as a vitamin mixture in the control diet was completely destroyed during storage. Fortification with APM significantly increased the ascorbic acid levels in the muscle, liver, brain and eye. Although APM fortification did not influence growth, survival or fish body composition, adipocyte diameter in the intraperitoneal fat body (IPF) was significantly reduced. After the feeding experiment, the fish were kept for 39 days without feeding. Fortification with APM resulted in high survival, high muscle protein retention and low body weight loss. The results suggested the necessity of fortification with an adequate amount of ascorbate in the diet. While fatty acid compositions of the IPF, muscle and liver were not significantly influenced by APM fortification, characteristic changes in the fatty acid profile were found after starvation. Vitamin C and highly unsaturated fatty acids seemed crossly interactive in relation to lipolysis activity in black sea bream juveniles.

A new proteomics technology has been implemented to study the protein repertoires of developing oocytes of giant grouper (Epinephelus lanceolatus). Knowledge of the chemical composition and physiochemical properties of vitellogenin (Vtg) is necessary to interpret the functional and biological properties attributed during ovulation. Vtg, as a biomarker indicator in sex determination, has been analyzed to determine the sex and maturational status of fish in the absence of the gonad tissue. A male giant grouper was induced by 2 mg/kg of 17ß-estradiol (E2), and blood was sampled at days 0, 1, 3, 5, and 10. SDS-PAGE 1D electrophoresis was used to analyze Vtg protein, and Vtg identification was done with 4800 Plus MALDI TOF/TOF™ mass spectrophotometer (Applied Biosystems/MDS SCIEX, USA). Meanwhile, MS/MS de novo sequencing identified the proteins by matching sequences of tryptic peptides to the known sequences of other species. Vtg was confirmed by MASCOT at 95% significant level, and molecular mass was 187 kDa. Protein resolved on SDS-PAGE as a double band of approximately the same mass as determined with MALDI-TOF. The N-terminal sequences and identification of Vtg were also determined. The potential of using MS methods to understand the structure and function of Vtg is discussed.

Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were fortified at a level of 1.5% in a composed diet. The effects were confirmed in 0-year black sea bream Acanthopagrus schlegeli in terms of lipid metabolism and physiological activity. The EPA group was high in EPA in muscle, liver, intraperitoneal fat body (IPF), eye and brain. The levels of DHA in liver, eye, brain and heart were also high in the EPA group, suggesting that conversion of EPA to DHA occurred in those organs. Fortification of DHA increased the levels of DHA in organs except the eye, but did not affect EPA levels. Both the EPA and DHA groups showed smaller adipocytes or lower levels of lipid content than the control group. The starvation followed by feeding experiment caused marked body weight loss in the control group by consumption of muscle protein and lipids in IPF. Fortifications of EPA and DHA induced less mobilization of muscle protein and IPF lipids as energy. Liver function and resistance to air-dipping were improved by both EPA and DHA fortifications. The present results implied conversion of EPA to DHA in the fish with regard to parameters, such as lipid metabolism and physiological vitality.