Liver Transcriptomic Analysis of the Effects of Dietary Fish Oil Revealed a Regulated Expression Pattern of Genes in Adult Female Spotted Scat (Scatophagus argus)

Abstract

Despite the significance of n-3 long-chain polyunsaturated fatty acid (n-3 LC-PUFA) in fish oil in promoting the maturation of female broodstocks, the detailed mechanism of the effect on the expression of hepatic reproduction-related genes is still unclear. In this study, transcriptome sequencing was used to analyze the effect of the higher dietary n-3 LC-PUFA level on gene expression in the liver of adult females spotted scat. Two-year-old female spotted scat (average weight, 242.83 ± 50.90 g) were fed with diets containing 8% fish oil (FO) or 8% soybean oil (SO) for 40 days. The fatty acid profile in the serum, liver, and ovary was analyzed, and high proportions of n-3 LC-PUFA were observed in the FO group. The final average fish body weight and gonadosomatic index were similar between the FO and SO groups. The serum vitellogenin (Vtg) and hepatosomatic index (HSI) of the FO group were significantly higher and lower than that of the SO group, respectively. Comparatively, the liver transcriptome analysis showed 497 upregulated and 267 downregulated genes in the FO group. Among them, the expression levels of three estrogen-regulated genes (i.e., Vtga, Vtgb, and Zp4) were significantly higher in the FO than in the SO group. This expression pattern could be related to the upregulation of Hsd17b7 (the key gene for the synthesis of liver steroid hormone) and the downregulation of the Hsp90 (the estrogen receptor chaperone). The expression levels of Foxo1a and Lep, which are involved in the lipid metabolism, decreased significantly in the FO group, which may be related to the lower level of HSI in the FO group. The genes related to liver LC-PUFA absorption and transport, Fabp2 and Mfsd2ab, were significantly upregulated in the FO group, indicating that fish actively adapt to high-fish-oil diets. In brief, high-fish-oil diets can influence the expression of genes related to liver n-3 LC-PUFA metabolism and reproduction, inhibit the accumulation of liver fat, and promote the liver health and gonad development. This study will contribute to clarifying the mechanism of dietary n-3 LC-PUFA on promoting reproductive development in teleost fish.

Transcriptomic analysis provides new insights into the secondary follicle growth in spotted scat (Scatophagus argus)

“…The fatty acids and PPAR agonists can up-regulate the regulation of fabp2, fabp3, and fabp6 genes in zebrafish tissues (Venkatachalam et al, 2013). Dietary fish oil supplementation increase fabp2 expression in the liver, indicating that fabp2 potentially participates in the metabolism of long-chain unsaturated fatty acids in S. argus (Wang et al, 2021b). Herein, ppara, ppard, and fabp3 were upregulated, while fabp1 and fabp4 were down-regulated in the stage IV ovary (Figure 7 and Supplementary Table S9), indicating that different fabps potentially have different functions.…”

Integrated transcriptomic and metabolomic analyses identify key factors in the vitellogenesis of juvenile Sichuan bream (Sinibrama taeniatus)

“…E 2 forms dimers with ERs and subsequently bind to the estrogen response elements in the promoter region of the Vtg gene, leading to transcription and translation through genomic effects (Gruber et al, 2004). To date, three estrogen receptor subtypes have been described for fish, including estrogen receptor 1 (esr1), estrogen receptor 2b (esr2b) and estrogen receptor 2a (esr2a) (Wang et al, 2021). Vtg synthesis in teleosts is generally thought to be mediated primarily by esr1 (Cerda et al, 2008).…”

“…The addition of 8% fish oil to the diet of spotted scat (Scatophagus argus) compared to 8% soybean oil can effectively promote the accumulation of yolk in the ovaries by regulating the expression of genes related to steroid hormones, glucose and lipid metabolic pathways, with an increased proportion of n-3 long chain polyunsaturated fatty acids, such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), in the ovaries (Wang et al, 2022). Meanwhile, dietary supplementation with fish oil increased the serum vitellogenin levels of female spotted scat and upregulated the expression of the reproduction-related genes vtga, vtgb, and zp4, as well as fabp2 and mfsd2ab, which are related to lipid absorption and transport in the liver (Wang et al, 2021).…”