International Journal of Molecular Sciences

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18 pages, 4356 KiB

Open AccessArticle

Rainbow Trout (Oncorhynchus mykiss) Pre-Smolts Treated with 11-Deoxycorticosterone Regulate Liver Carbohydrate Metabolism and Gill Osmoregulation

by Rodrigo Zuloaga, Luciano Ahumada-Langer, Jorge Eduardo Aedo, Katalina Llanos-Azócar, Alfredo Molina and Juan Antonio Valdés

Int. J. Mol. Sci. 2025, 26(8), 3725; https://doi.org/10.3390/ijms26083725 - 15 Apr 2025

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Abstract

Smoltification is stressful for salmonids, and cortisol is one of the central endocrine regulators for seawater adaptation. It has been established that cortisol plays both mineralocorticoid and glucocorticoid functions by MR and GR, respectively, since the aldosterone hormone is absent. Recently, investigations have [...] Read more.

Smoltification is stressful for salmonids, and cortisol is one of the central endocrine regulators for seawater adaptation. It has been established that cortisol plays both mineralocorticoid and glucocorticoid functions by MR and GR, respectively, since the aldosterone hormone is absent. Recently, investigations have proposed that the 11-deoxycorticosterone (DOC) mineralocorticoid precursor might support cortisol effects, but this mechanism remains unclear. Hence, we assessed the early effects of DOC on rainbow trout pre-smolts, the key smoltification stage, via metabolic and transcriptomic approaches. Thirty-six juveniles (~120 g) were treated for 3 h with DOC (1 mg/kg) and/or mineralocorticoid (eplerenone) or glucocorticoid (mifepristone) receptor antagonists (n = 6 for each group). DOC decreased plasma glucose and pyruvate and increased phosphate and liver glycogen. DOC also downregulated carbohydrate metabolism-related genes in the liver. Finally, gill RNA-seq analysis presented 1660 differentially expressed transcripts in DOC versus vehicle, 1022 for eplerenone + DOC versus DOC and 3324 for mifepristone + DOC versus DOC. The enrichment analysis mainly revealed the upregulation of ion transmembrane transport and carbohydrate metabolism and the downregulation of stress and innate immune responses. This suggests a significant role of DOC in liver carbohydrate metabolism and gill osmoregulation of pre-smolts through both receptors. Hence, this could contribute to improving animal welfare monitoring during smoltification by featuring novel and potential biomarkers. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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23 pages, 5532 KiB

Open AccessArticle

Characterization of Leptin and Leptin Receptor Gene in the Siberian Sturgeon (Acipenser baerii): Molecular Cloning, Tissue Distribution, and Its Involvement in Feeding Regulation

by Hongwei Wu, Jiamei Li, Kezhen Jiang, Yingzi Li, Zhaoxiong Yu, Bin Wang, Bo Zhou, Xin Zhang, Ni Tang and Zhiqiong Li

Int. J. Mol. Sci. 2025, 26(5), 1968; https://doi.org/10.3390/ijms26051968 - 25 Feb 2025

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Abstract

Leptin is an adipokine known as a regulator of feeding and metabolism in mammals. Previous studies on fish have revealed its role in food intake regulation in limited teleosts. However, its specific function in Siberian sturgeon, an ancient Chondrostei fish, remains poorly understood. [...] Read more.

Leptin is an adipokine known as a regulator of feeding and metabolism in mammals. Previous studies on fish have revealed its role in food intake regulation in limited teleosts. However, its specific function in Siberian sturgeon, an ancient Chondrostei fish, remains poorly understood. This study represents the first successful cloning of sequences for leptin and leptin receptors in Siberian sturgeon, achieved using RT-PCR. The predicted leptin sequence in this species consists of 168 amino acids that exhibit low identity with other fish species, except within the Acipenseriformes order. Tissue distribution analysis revealed a high expression of Siberian sturgeon leptin mRNA in the liver and lepr mRNA in the hypothalamus. Fasting differentially affected the expression of leptin and lepr mRNA, with decreased levels in the hypothalamus and increased levels in the liver (leptin: 3–15 days; lepr: 6–15 days). Recombinant Siberian sturgeon leptin (Ssleptin) was produced via E. coli expression, and intraperitoneal injection (100 ng/g BW) significantly inhibited food intake. The anorectic effect was correlated with changes in hypothalamic gene expression, including downregulation of orexigenic factors (agrp, orexin, npy, and ghrelin) and upregulation of anorexigenic factors (pomc, mch, and insulin). Meanwhile, the peripheral administration of Ssleptin promoted the expression of resistin in the liver and concurrently increased cck and pyy mRNA levels in the valvular intestine. Furthermore, Ssleptin injection stimulated the expression of hypothalamic lepr, jak2, akt, and ampkα2 mRNA. These findings suggest that leptin plays a significant role in the feeding control of Siberian sturgeon and provide new insights into the evolutionary function of leptin in fish. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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18 pages, 3424 KiB

Open AccessArticle

Exploration of Appetite Regulation in Yangtze Sturgeon (Acipenser dabryanus) During Weaning

by Bin Wang, Ni Tang, Shuhuang Chen, Xin Zhang, Defang Chen, Zhiqiong Li and Bo Zhou

Int. J. Mol. Sci. 2025, 26(3), 950; https://doi.org/10.3390/ijms26030950 - 23 Jan 2025

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Abstract

Yangtze sturgeon is an endangered fish species. After weaning, some Yangtze sturgeon fry refuse to consume any food, which causes a low survival rate during the artificial breeding period. This study showed that the body length and body weight of failed weaning Yangtze [...] Read more.

Yangtze sturgeon is an endangered fish species. After weaning, some Yangtze sturgeon fry refuse to consume any food, which causes a low survival rate during the artificial breeding period. This study showed that the body length and body weight of failed weaning Yangtze sturgeons were significantly lower than those of successful weaning sturgeons. Since the brain is the center of appetite regulation, RNA-seq of the brain was employed to analyze the differentially expressed genes and their biological functions in successfully and unsuccessfully weaned fry. After that, 82,151 unigenes and 3222 DEGs were obtained. Based on the results of RNA-seq, appetite factors, including POMC, CART, NPY and AgRP, were cloned, and then a weaning experiment was designed to explore the changes in appetite after feeding a microcapsule diet (weaning group). The results showed that, during the weaning period, the expression of CART was increased on the 1st and 3rd days but decreased on the 5th, 6th, 8th and 10th days. The expression of AgRP was downregulated on the 1st and 3rd days but upregulated on the 5th, 6th, 8th and 10th days. These findings indicate that appetite was suppressed in the early and middle periods but enhanced in the latter period of weaning and that CART may play an important role in the appetite-suppressing effect. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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19 pages, 862 KiB

Open AccessArticle

Effect of Dietary Lactobacillus plantarum Supplementation on the Growth Performance, Intestinal Health, Antioxidant Capacity, and mTOR Signaling Pathway of Juvenile Coho Salmon (Oncorhynchus kisutch)

by Qin Zhang, Lan Li, Rongxin Qin, Liuqing Meng, Dongsheng Liu, Tong Tong, Lixiao Xu, Yongqiang Liu and Weiguang Kong

Int. J. Mol. Sci. 2025, 26(3), 907; https://doi.org/10.3390/ijms26030907 - 22 Jan 2025

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Abstract

This study investigates the effect of dietary Lactobacillus plantarum supplementation on juvenile coho salmon (Oncorhynchus kisutch). Four groups of the juveniles (initial weight 103.87 ± 2.65 g) were fed for 10 weeks with four diets containing 0 (control diet), 10⁵ [...] Read more.

This study investigates the effect of dietary Lactobacillus plantarum supplementation on juvenile coho salmon (Oncorhynchus kisutch). Four groups of the juveniles (initial weight 103.87 ± 2.65 g) were fed for 10 weeks with four diets containing 0 (control diet), 10⁵ (T1), 10⁷ (T2), and 10⁹ (T3) cfu/g of L. plantarum. The main results are as follows: Compared with the control diet, the final weight, specific growth rate (SGR), and weight gain rate (WGR) of the juveniles fed the T1, T2, and T3 diet significantly (p < 0.05) increased, while the feed coefficient ratio (FCR) expressed an opposite trend. The activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) in the serum of the juveniles fed the T2 diet significantly (p < 0.05) increased, while the malondialdehyde (MDA) expressed an opposite trend. The expression of phosphatidylinositol 4,5-bisphosphate 3-kinase (pi3k), AKT-interacting protein (akt), mechanistic target of rapamycin kinase (mtor), glucose-6-phosphate dehydrogenase (g6pd), sod, cat, and gsh-px genes in the liver of the juveniles fed the T2 diet significantly (p < 0.05) increased. In conclusion, the T2 diet significantly improved the growth performance, antioxidant capacity, and upregulated key mTOR pathway genes in juvenile coho salmon. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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27 pages, 29104 KiB

Open AccessArticle

Metabonomics and Transcriptomics Analyses Reveal the Underlying HPA-Axis-Related Mechanisms of Lethality in Larimichthys polyactis Exposed to Underwater Noise Pollution

by Qinghua Jiang, Yu Zhang, Ting Ye, Xiao Liang and Bao Lou

Int. J. Mol. Sci. 2024, 25(23), 12610; https://doi.org/10.3390/ijms252312610 - 24 Nov 2024

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Abstract

The problem of marine noise pollution has a long history. Strong noise (>120 dB re 1 µPa) will affects the growth, development, physiological responses, and behaviors of fish, and also can induce the stress response, posing a mortal threat. Although many studies have [...] Read more.

The problem of marine noise pollution has a long history. Strong noise (>120 dB re 1 µPa) will affects the growth, development, physiological responses, and behaviors of fish, and also can induce the stress response, posing a mortal threat. Although many studies have reported that underwater noise may affect the survival of fish by disturbing their nervous system and endocrine system, the underlying causes of death due to noise stimulation remain unknown. Therefore, in this study, we used the underwater noise stress models to conduct underwater strong noise (50–125 dB re 1 µPa, 10–22,000 Hz) stress experiments on small yellow croaker for 10 min (short-term noise stress) and 6 days (long-term noise stress). A total of 150 fishes (body weight: 40–60 g; body length: 12–14 cm) were used in this study. Omics (metabolomics and transcriptomics) studies and quantitative analyses of important genes (HPA (hypothalamic–pituitary–adrenal)-axis functional genes) were performed to reveal genetic and metabolic changes in the important tissues associated with the HPA axis (brain, heart, and adrenal gland). Finally, we found that the strong noise pollution can significantly interfere with the expression of HPA-axis functional genes (including corticotropin releasing hormone (CRH), corticotropin releasing hormone receptor 2 (CRHR2), and arginine vasotocin (AVT)), and long-term stimulation can further induce metabolic disorders of the functional tissues (brain, heart, and adrenal gland), posing a lethal threat. Meanwhile, we also found that there were two kinds of death processes, direct death and chronic death, and both were closely related to the duration of stimulation and the regulation of the HPA axis. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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19 pages, 2697 KiB

Open AccessArticle

Synergistic Effects of Dietary Tryptophan and Dip Vaccination in the Immune Response of European Seabass Juveniles

by Diogo Peixoto, Inês Carvalho, André Cunha, Paulo Santos, Lourenço Ramos-Pinto, Marina Machado, Rita Azeredo and Benjamín Costas

Int. J. Mol. Sci. 2024, 25(22), 12200; https://doi.org/10.3390/ijms252212200 - 13 Nov 2024

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Abstract

Vaccination is an effective, cost-efficient method to preventing disease outbreaks. However, vaccine procedures can induce adverse reactions due to stress, increasing plasma cortisol in the short term. In this context, tryptophan may prove to be fundamental as it has been demonstrated to have [...] Read more.

Vaccination is an effective, cost-efficient method to preventing disease outbreaks. However, vaccine procedures can induce adverse reactions due to stress, increasing plasma cortisol in the short term. In this context, tryptophan may prove to be fundamental as it has been demonstrated to have various desirable neuroendocrine attributes in different fish species. Therefore, this study aimed to evaluate both short-term (3 days) and long-term (21 days) effects of dietary tryptophan supplementation on European seabass juveniles’ (26.23 ± 7.22 g) response to vaccination and disease resistance to Tenacibaculum maritimum. The short-term tryptophan-fed fish exhibited increased hepatic superoxide dismutase and plasma cortisol levels, along with the downregulation of immune-related genes. Despite these changes, disease resistance was unaffected. When fish were later dip vaccinated, tryptophan prevented the stress-induced plasma cortisol increase and upregulated the gene expression of igm, suggesting tryptophan’s role in enhancing vaccination efficiency by counteracting stress-associated effects. In the long term, the lowest supplementation dose counteracted vaccine-mediated reduced gene expression, and fish fed this diet showed a more modest molecular response. Overall, the findings suggest a complex interplay between tryptophan supplementation, immune responses, and vaccine efficiency in fish. Further research is necessary to clarify how tryptophan could consistently improve vaccine efficiency in aquaculture. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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16 pages, 8629 KiB

Open AccessArticle

The Identification of Proteomic Signatures Associated with Alkaline Tolerance in the Skin Mucus of Crucian Carp (Carassius auratus)

by Zhipeng Sun, Jing Huang, Xiaofeng Zhang, Yumei Chang and Guo Hu

Int. J. Mol. Sci. 2024, 25(21), 11618; https://doi.org/10.3390/ijms252111618 - 29 Oct 2024

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Abstract

The skin is covered by a protective mucus layer, which is essential to the innate defense mechanism of fish. Investigating the response of skin mucus to various toxic stresses is crucial for enhancing its ability to tackle environmental challenges and developing strategies to [...] Read more.

The skin is covered by a protective mucus layer, which is essential to the innate defense mechanism of fish. Investigating the response of skin mucus to various toxic stresses is crucial for enhancing its ability to tackle environmental challenges and developing strategies to mitigate toxic effects. Alkalinity stress assays (50 mmol/L NaHCO₃) were conducted on crucian carp (Carassius auratus) from Lake Dali Nur (pH = 9.6) and Ping Xiang red crucian carp from freshwater (pH = 7) over 7 days. The expression of skin mucous proteins was analyzed using the liquid chromatography (LC)-spectrometry (MS)/MS Analysis-Data-independent acquisition (DIA) mode. A total of 12,537 proteins were identified across 20 samples from four groups, with 12,025 quantified. In the alkaline water population, high alkali stress resulted in the up-regulation of 139 proteins and the down-regulation of 500 proteins. In contrast, the freshwater population showed an increase in 112 proteins and a decrease in 120; both populations had a total of 23 genes up-regulated and 21 down-regulated. The protein regulatory network for the alkaline water group included 3146 pairwise interactions among 464 nodes, with only 20 being differentially expressed proteins. Conversely, the freshwater group’s network comprised just 1027 specific interactions across 337 nodes, with 6 corresponding to differentially expressed proteins. A common protein regulatory network responding to high alkali stress was extracted and visualized for both populations. Based on their regulatory relationships and expression levels, these proteins are hypothesized to play similar roles under high alkali stress. Notably, the alpha-globin fragment and keratin type I cytoskeletal 13-like proteins showed markedly up-regulated expression, with the alpha-globin fragment increasing nearly a thousandfold from an extremely low level. This suggests it could serve as a potential biomarker for alkali tolerance, warranting further investigation. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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23 pages, 3098 KiB

Open AccessArticle

Exploring Multifunctional Markers of Biological Age in Farmed Gilthead Sea Bream (Sparus aurata): A Transcriptomic and Epigenetic Interplay for an Improved Fish Welfare Assessment Approach

by Álvaro Belenguer, Fernando Naya-Català, Josep Àlvar Calduch-Giner and Jaume Pérez-Sánchez

Int. J. Mol. Sci. 2024, 25(18), 9836; https://doi.org/10.3390/ijms25189836 - 11 Sep 2024

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Abstract

DNA methylation clocks provide information not only about chronological but also biological age, offering a high-resolution and precise understanding of age-related pathology and physiology. Attempts based on transcriptomic and epigenetic approaches arise as integrative biomarkers linking the quantification of stress responses with specific [...] Read more.

DNA methylation clocks provide information not only about chronological but also biological age, offering a high-resolution and precise understanding of age-related pathology and physiology. Attempts based on transcriptomic and epigenetic approaches arise as integrative biomarkers linking the quantification of stress responses with specific fitness traits and may help identify biological age markers, which are also considered welfare indicators. In gilthead sea bream, targeted gene expression and DNA methylation analyses in white skeletal muscle proved sirt1 as a reliable marker of age-mediated changes in energy metabolism. To complete the list of welfare auditing biomarkers, wide analyses of gene expression and DNA methylation in one- and three-year-old fish were combined. After discriminant analysis, 668 differentially expressed transcripts were matched with those containing differentially methylated (DM) regions (14,366), and 172 were overlapping. Through enrichment analyses and selection, two sets of genes were retained: 33 showing an opposite trend for DNA methylation and expression, and 57 down-regulated and hypo-methylated. The first set displayed an apparently more reproducible and reliable pattern and 10 multifunctional genes with DM CpG in regulatory regions (sirt1, smad1, ramp1, psmd2—up-regulated; col5a1, calcrl, bmp1, thrb, spred2, atp1a2—down-regulated) were deemed candidate biological age markers for improved welfare auditing in gilthead sea bream. Full article

(This article belongs to the Special Issue Fish Nutrition, Metabolism and Physiology)

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