Seawater Culture Increases Omega-3 Long-Chain Polyunsaturated Fatty Acids (N-3 LC-PUFA) Levels in Japanese Sea Bass (Lateolabrax japonicus), Probably by Upregulating Elovl5

Abstract

The fatty acid compositions of the fish muscle and liver are substantially affected by rearing environment. However, the mechanisms underlying this effect have not been thoroughly described. In this study, we investigated the effects of different culture patterns, i.e., marine cage culture and freshwater pond culture, on long-chain polyunsaturated fatty acids (LC-PUFA) biosynthesis in an aquaculturally important fish, the Japanese sea bass (Lateolabrax japonicus). Fish were obtained from two commercial farms in the Guangdong province, one of which raises Japanese sea bass in freshwater, while the other cultures sea bass in marine cages. Fish were fed the same commercial diet. We found that omega-3 long-chain polyunsaturated fatty acids (n-3 LC-PUFA) levels in the livers and muscles of the marine cage cultured fish were significantly higher than those in the livers and muscles of the freshwater pond cultured fish. Quantitative real-time PCRs indicated that fatty acid desaturase 2 (FADS2) transcript abundance was significantly lower in the livers of the marine cage reared fish as compared to the freshwater pond reared fish, but that fatty acid elongase 5 (Elovl5) transcript abundance was significantly higher. Consistent with this, two of the 28 CpG loci in the FADS2 promoter region were heavily methylated in the marine cage cultured fish, but were only slightly methylated in freshwater pond cultured fish (n = 5 per group). Although the Elovl5 promoter was less methylated in the marine cage reared fish as compared to the freshwater pond reared fish, this difference was not significant. Thus, our results might indicate that Elovl5, not FADS2, plays an important role in the enhancing LC-PUFA synthesis in marine cage cultures.

The Impact of Rearing Salinity on Flesh Texture, Taste, and Fatty Acid Composition in Largemouth Bass Micropterus salmoides

“…Inspired by this, we compared myofibril diameter and density in the samples, and revealed that high salinity significantly decreased myofibril diameter, but significantly increased myofibril density. Combined with the finding in our previous studies that salinity (or marine cage culture as compared with freshwater pond culture) significantly affects fish crude body composition [ 5 , 26 ], we conclude here that ambient salinity may change fish flesh texture through comprehensive effects on muscle composition and myofibril structure.…”

“…Shear value test revealed that salinity of 0.9% significantly decreased muscle tenderness compared with S 0 group ( p < 0.05, Table 1 ), which was consistent with the significantly decreased moisture content in 0.9% group in our previous study [ 26 ]. Similar results were also obtained in Japanese sea bass, in which marine cage culture led to a significant decrease in muscle moisture content and tenderness compared with freshwater pond culture [ 5 ]. Texture parameters, including hardness, chewiness, gumminess, and adhesiveness significantly increased with water salinity ( p < 0.05, Figure 1 ) while springiness decreased ( p < 0.05).…”

“…Flesh quality can also be affected by the microbiological changes in fish during storage and processing [ 2 ]. To date, most studies focusing on the effects of dietary formulation and rearing conditions upon flesh quality have placed their emphasis on the contents of critical nutrients, for example, the content of polyunsaturated fatty acid (PUFA) [ 3 , 4 , 5 ].…”

“…In rainbow trout, for example, salinity (0.17%) showed a significant effect upon the content of total monounsaturated fatty acid (MUFA) and total n-3 polyunsaturated fatty acid (n-3 PUFA) in gonad and liver tissues [ 8 ]. Moreover, recent studies in Nile tilapia and Japanese sea bass also showed that water salinity significantly improved the contents of free amino acids and PUFA, such as EPA and DHA, in the muscle tissue [ 1 , 5 , 9 , 10 ]. Moreover, an experiment in marine euryhaline crab Scylla paramamosain showed that salinity had an impact on flesh hardness, chewiness, and gumminess, and the contents of flavor compounds in flesh [ 11 ].…”

Recent Advances in Fish Nutrition: Insights on the Nutritional Implications of Modern Formulations

“…However, studies testing Apelin in fish species are scarce. Experiments were conducted to test the effects of Pyr-apelin-13 (an active form of apelin) on common carp in vitro (hypothalamus) and in vivo [12]. The results in vitro and in vivo displayed an upregulation of appetite-and growth-related genes, such as growth hormone receptor (GHR) and insulin-like growth factors 1 and 2 (IGF1 and IGF2, respectively), supporting the hypothesis that this orexigenic peptide might regulate the feeding and growth of this important commercial species.…”