A 10‐week feeding experiment was conducted to evaluate the effects of supplemental betaine on growth performance, body composition and lipid deposition in allogynogenetic gibel carp. Four isoproteic (37% crude protein) and isolipidic (5% crude lipid) artificial diets with 0%, 0.08%, 0.4% and 2% betaine supplementation were formulated, and named VB0, VB0.08, VB0.4 and VB2, respectively. Each diet was fed in triplicate to fish about 10 g in weight. The results showed that 0.4% betaine supplementation significantly improved growth performance and reduced lipid content in the hepatopancreas, muscle and the whole body compared with the control group. Moreover, both fatty acid synthase and acetyl‐CoA carboxylase, two important lipogenic genes, showed significantly lower expression in the VB0.4 group than in the control group, and a strong correlation was detected between lipid content and mRNA expression levels for FAS and ACC in the hepatopancreas. Taken together, appropriate (0.4%) betaine supplementation in the diet not only improved growth, but also reduced lipid deposition in allogynogenetic gibel carp, probably by diminishing lipogenic gene expression.
This research aimed to investigate the role of dietary betaine in high-fat diet in cholesterol metabolism in gibel carp. Fish were randomly allocated to five groups and fed with basic diet, high-fat diet and high-fat diet with 1 g/kg, 4 g/kg and 16 g/kg betaine, respectively. The feeding trial lasted 10 weeks. The results showed that though betaine addition decreased fish final body weight, it alleviated lipid metabolism disorder caused by high-fat diet according to serum TC, TG, LDLC and HDLC levels. More importantly, betaine supplementation enhanced cholesterol synthesis as well as conversion of cholesterol to bile acid by promoting expression of HMGCR and CYP7A1 genes. Meanwhile, betaine supplementation not only promoted bile acid efflux and increased total bile acid level in the intestine but also improved intestinal lipase activity.Moreover, high-fat diet with betaine addition improved the hepatopancreas' antioxidant capacity, lessened hepatopancreas injury and increased fish survival during the feeding trial and under bacterial challenge. In summary, dietary betaine supplementation was beneficial to alleviate high-fat feeding-induced lipid metabolism disorder, promote cholesterol conversion to bile acid and enhance hepatopancreas function in gibel carp.
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.
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