A New Insight Into the Underlying Adaptive Strategies of Euryhaline Marine Fish to Low Salinity Environment: Through Cholesterol Nutrition to Regulate Physiological Responses

Abstract

Salinity is an important environmental factor that can affect the metabolism of aquatic organisms, while cholesterol can influence cellular membrane fluidity which are vital in adaption to salinity changes. Hence, a 4-week feeding trial was conducted to evaluate the effects of water salinity (normal 23 psu and low 5 psu) and three dietary cholesterol levels (CH0.16, 0.16%, CH1.0, 1.0% and CH1.6, 1.6%) on osmoregulation, cholesterol metabolism, fatty acid composition, long-chain polyunsaturated fatty acid (LC-PUFA) biosynthesis, oxidative stress (OS), and endoplasmic reticulum stress (ERS) of the euryhaline fish black seabream (Acanthopagrus schlegelii). The results indicated that in low salinity, fish fed with the CH1.0 diet improved ion reabsorption and osmoregulation by increased Na+ concentration in serum as well as expression levels of osmoregulation-related gene expression levels in gills. Both dietary cholesterol level and water salinity significantly affected most cholesterol metabolic parameters in the serum and tissues, and the results showed that low salinity promoted cholesterol synthesis but inhibited cholesterol catabolism. Besides, in low salinity, hepatic expression levels of LC-PUFA biosynthesis genes were upregulated by fed dietary cholesterol supplementation with contents of LC-PUFAs, including EPA and DHA being increased. Malondialdehyde (MDA) was significantly increased in low-salinity environment, whereas MDA content was decreased in fish fed with dietary CH1.0 by activating related antioxidant enzyme activity and gene expression levels. A similar pattern was recorded for ERS, which stimulated the expression of nuclear factor kappa B (nf-κb), triggering inflammation. Nevertheless, fish reared in low salinity and fed with dietary CH1.0 had markedly alleviated ERS and downregulated gene expression levels of pro-inflammatory cytokines. Overall, these findings demonstrate that cholesterol, as an important nutrient, plays vital roles in the process of adaptation to low salinity of A. schlegelii, and provides a new insight into underlying adaptive strategies of euryhaline marine fish reared in low salinity.

Cholesterol Modifies Nutritional Values and Flavor Qualities in Female Swimming Crab (Portunus trituberculatus)

“…In this study, dietary CHO levels increased the contents of ARA, EPA, n-3 LC-PUFA, and n-6 LC-PUFA in hepatopancreas or ARA, DHA, n-3 LC-PUFA, and n-6 LC-PUFA in muscle. This was in accordance with a previous study in black seabream (Acanthopagrus schlegelii) fed diet with 1.0% CHO [48]. Different with crustaceans, the need for exogenous CHO is still being debated, as bony fish have the ability to synthesize CHO [37].…”

Unraveling stress resilience: Insights from adaptations to extreme environments by Astyanax mexicanus cavefish

“…For instance, in the Micos cave, salinity reaches only 10% of the salinity found in the nearby river environments (Ornelas-García et al, 2018). Studies have shown that the gills play a crucial role in regulating the balance of osmotic pressure across various systems (Bao et al, 2022;Guh et al, 2015). Although there is limited knowledge of osmoregulation in A. mexicanus, cavefish populations have been shown to have larger gills with increased surface area compared to surface fish gills (Moran et al, 2015).…”

The Benefit of Optimal Dietary Lipid Level for Black Seabream Acanthopagrus schlegelii Juveniles under Low-Salinity Environment

“…Serum Biochemical Parameters, Biometric Indices, and Hepatic Histological Assay. Serum biochemical analysis showed that the contents of HDL-C, LDL-C, TG, and TC were significantly increased with the increase of dietary ostf1: osmotic stress transcription factor 1; 2 ncc: Na +/ Clcotransporter; 3 aqp1: aquaporin; 4 nkaα: Na + /K + -ATPase; 5 elovl4a: elongase 4a; 6 elovl4b: elongase 4b; 7 fads2: fatty acid desaturase 2; 8 sirt1: silent regulator 1; 9 pparα: peroxisome proliferator activated receptors alpha; 10 srebp-1: sterol regulatory element-binding protein 1; 11 Cu/Zn sod: Cu/Zn superoxide dismutase; 12 Mn sod: Mn superoxide dismutase; 13 cat: catalase; 14 foxO1: forkhead box 1; 15 grp78: glucose regulated protein 78; 16 atf6: activating transcription factor 6; 17 xbp1: X-box binding protein 1; 18 ire1α: inositol requiring enzyme-1; 19 nf-κb: nuclear factor kappa b; 20 tnfα: tumor necrosis factor alpha; 21 tgf-β1: transforming growth factor β1; 22 il-10: interleukin-10; 23 il-1β: interleukin-1 beta; 24 jnk: c-Jun N-terminal kinase; 25 bcl-2: B cell leukemia2; 26 bax: bcl 2-associated X. 7 Aquaculture Nutrition lipid levels under low-salinity environment (P < 0:05) (Figure 4(a)).…”

“…Many previous studies have reported that A. schlegelii has strong disease resistance and has the ability to tolerate a wide range of environmental conditions, which is becoming a very popular and commercially important marine fish species cultured in China, Japan, Korea, and other countries in Southeast Asia [22][23][24][25]. Seabream production in China reached almost 123,000 tons in 2020 [26].…”

“…Moreover, as a euryhaline fish, A. schlegelii is widely farmed under both normal/ambient salinity in seawater cages and low-salinity conditions in pond culture in China [ 23 ]. So it could be a good model to study the effects of low-salinity environment on physiological and biochemical responses of marine fish [ 22 , 27 ]. Until now, the nutritional requirement of A. schlegelii under low-salinity environment remains unknown.…”