Assessing Urinary Metabolomics in Giant Pandas Using Chromatography/Mass Spectrometry: Pregnancy-Related Changes in the Metabolome

Dietary areca nut extract supplementation modulates the growth performance and immunity of Jiaji ducks (Cairina moschata)

Areca nut extract (ANE) has a variety of pharmacological effects on animals. Here, we investigated the influence of ANE on the slaughter performance and immune function of Jiaji ducks. One hundred and fifty 42-day-old healthy Jiaji ducks were randomly divided into 2 groups (5 replicates of 15 ducks each), named DCK group (control) and DNT group (treatment), respectively. Ducks in the DCK group were fed a basal diet and ducks in the DNT group were fed a basal food supplemented with 0.08 g ANE per kg of basal diet. Additionally, using proteomics, untargeted metabolomics, and metagenomics, we analyzed the impact of ANE on the protein profile of the spleen, the composition of plasma metabolites, and the structure of the cecal microbiota. The results showed that the dietary inclusion of ANE significantly increased the slaughter rate of Jiaji ducks. Proteomic analysis revealed 78 differentially expressed proteins in the spleens of ANE-treated birds, including 54 proteins up-regulated and 24 proteins down-regulated in the DNT group, mainly enriched in cell adhesion molecules and glutathione metabolic pathways. Untargeted metabolomic analysis revealed that 117 serum metabolites were differentially regulated between the ANE and DCK groups; meanwhile, KEGG pathway analysis indicated that these metabolites were mainly involved in arachidonic acid metabolism, phospholipase D signaling pathway and eicosanoids. Furthermore, a metagenomic analysis showed that the genus Methanobrevibacter was significantly downregulated in the ANE supplementation group. Combined, the results of the metagenomic and metabolomic analyses showed that the relative abundance of Prevotella was significantly lower in the ANE group than in the DCK group and that Prevotella was negatively correlated with the levels of the anti-inflammatory compound hydrocinnamic acid and the lipid metabolism regulator ganoderic acid A. This study provides a reference for the application of ANE as a supplement in the diet of Jiaji ducks.

Biochemical Characteristics of Urine Metabolomics in Female Giant Pandas at Different Estrous Stages

The composition of urinary metabolites can reflect the physiological state of animals. Investigating the alterations in urine metabolomics during the estrus stage can provide valuable insights for enhancing the efficacy of estrus monitoring. This study aimed to perform an analysis of urinary metabolomics in female giant pandas, specifically examining the variations in specific metabolites across different estrous stages, namely, diestrus, proestrus, estrus, and metestrus. A total of 1234 metabolites were identified in positive ion mode from 76 samples of 19 individuals, with 643 metabolites identified in negative ion mode. The content of urine metabolites exhibited significant variation throughout different stages of estrus. During the peak of estrus, the metabolic pathways primarily enriched by significantly differential metabolites were the AMPK signaling pathway, vitamin digestion and absorption, galactose metabolism, and cysteine and methionine metabolism, as well as taurine and hypotaurine metabolism. By comparing the content of specific metabolites in distinct pathways across the four distinct estrous stages, higher levels of acetylcholine, D-fructose1,6-bisphosphate, L-homocystine, dulcitol, inositol, and S-sulfo-L-cysteine and lower levels of phosphoethanolamine, vitamin A, vitamin B12, and maleic acid were detected at estrus. This study offers a novel comparative analysis of urine metabolomics across different estrus stages in female giant pandas, identifying several potential perspectives for estrus monitoring and contributing to the breeding management of captive giant panda populations.

MicroRNA expression profiles in plasma exosomes of late pregnant giant pandas

BACKGROUND

MicroRNAs can regulate various biological functions including cell proliferation, differentiation, embryo formation, and implantation. The giant panda exhibits embryonic diapause, with embryo development resuming in late pregnancy. However, the changes in microRNAs during late pregnancy remain poorly understand.

METHODS AND RESULTS

After mating, plasma samples were collected on day 40 of early pregnancy (EP; n = 3) and 30 days before delivery of late pregnancy (LP; n = 3). Following microRNAs screening, a total of 120 microRNAs were detected in the plasma exosomes of pregnant pandas. Nine differentially expressed microRNAs (DEmicroRNAs) were identified in LP compared to EP, including three that were upregulated and six that were downregulated. Notably, miR-25b and miR-47 were significantly downregulated in LP group. All DEmicroRNAs were predicted to target a total of 2,675 genes. Pathway enrichment analysis of these target genes revealed significant enrichment in the MAPK and Rap1 signaling pathways, which are closely related to cell proliferation, differentiation, and cell-cell and cell-matrix interactions. Analysis of protein-protein interaction networks showed that most of the hub genes (five out of eight), including Fgfr1, Fgf2, Fgf18, Erbb4, and Kras within the MAPK and Rap1 pathways are associated with the cell proliferation and differentiation. Significantly, Erbb4 was regulated by significantly differentially expressed miRNA-47.

CONCLUSIONS

We suggest that plasma exosomal microRNAs are involved in cell proliferation and differentiation during embryonic development by regulating key hub genes within MAPK and Rap1 pathways. These findings provided new insights into the development of giant panda embryos.

Proteomic analysis of giant panda testicular tissue of different age groups

Background

The reproductive ability of male giant pandas has been a major complicating factor in the ex-situ conservation of the species. While it is well known that the testis produces sperm and secretes androgens, a process that requires precise regulation of various proteins, at present, there has been no systematic study on the composition of proteins in the testis of the giant pandas. Therefore, this study aims to apply proteomics to explore the regulation of proteins in the testes of giant pandas.

Methods

Samples from the testes of three giant pandas (22 years, 18 years, 8 days) were studied to assess the protein's function. A label-free quantitative method was used to isolate testicular proteins from each male, 139,039 peptides and 11,435 proteins were obtained.

Results

Gene Ontology (GO) annotates most of the proteins involved in the processes of protein phosphorylation, oxidation-reduction, proteolysis, and signal transduction. KEGG pathway indicated that most of the proteins were involved in the pathway of signal transduction, transport, and catabolism. The protein kinase and WD40 repeats were involved in protein-protein interaction, which in turn regulates gene expression in the testicular tissue of giant pandas.

Conclusions

This study is the first to conduct an in-depth proteomic analysis of testicular tissue in giant pandas. The results revealed the important role of proteins in testicular tissue on spermatogenesis, testosterone production, and testicular microenvironment, providing clues for further research on male giant panda reproduction.

Integrated transcriptome and metabolomic analyses uncover the mechanism of cadmium-caused mouse spermatogonia apoptosis via inducing endoplasmic reticulum stress

Cadmium (Cd) is a well-recognized male reproductive toxicant that can cause testicular germ cell apoptosis. However, the underlying mechanism needs investigation. CG-1 mouse spermatogonia (spg) cells were treated with 20 μM cadmium chloride (CdCl2) for 24 h. Cell apoptosis was measured, and the expressions of key genes and protein biomarkers involved in endoplasmic reticulum (ER) stress were detected, respectively. Untargeted metabolomics was performed to identify different metabolites, and transcriptome analysis was conducted to screen differentially expressed genes (DEGs). Our results indicated that CdCl2 exposure caused cell apoptosis, and DEGs were involved in several apoptosis-related pathways. Moreover, CdCl2 exposure apparently increased the mRNA and protein expressions levels of both GRP78 and ATF6α, disrupting the expression of various metabolites, particularly amino acids. Conclusively, our study reveals the pathway of CdCl2 toxicity on mouse spg, providing a deep understanding of CdCl2-induced testicular toxicity.

Abnormal expression of natural mating behaviour of captive adult giant pandas is related to physiological stress

During ex situ conservation, the adaptability of giant pandas to environmental changes is greatly challenged. The issue of natural reproduction in captive giant pandas remains unresolved both domestically and internationally. It hypothesized that the restricted natural reproductive capacity may be linked to abnormal mating behavior expression due to physiological stress resulting from incompatible pairings in confined environments. To test this hypothesis, we utilized ultra-high performance liquid chromatographytandem quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS) to analyse urine metabolites in captive adult giant pandas during their breeding period. Simultaneously, enzyme-linked immunosorbent assay was employed to measure the levels of cortisol and epinephrine in urine, providing insight into the psychological state of captive giant pandas during mate selection by examining all metabolites and related biochemical pathways. This comprehensive approach aims to fully elucidate the physiological mechanisms underlying the decline in natural reproductive capacity. The metabolomics findings indicate that the aberrant expression of natural mating behaviour in captive adult male and female giant pandas may be associated with dysfunction in amino acid metabolic pathways. The activation of these metabolic pathways is linked to psychological stress, such as the tryptophan metabolic pathway and GABAergic synapse pathway. The results of physiological indicators indicate a significant correlation between the expression of natural mating behaviour in captive adult pandas and the hormone urine cortisol, which is associated with physiological stress. These findings indicate that the atypical manifestation of natural mating behaviour in captive adult giant pandas may be associated with physiological stress induced by incompatible pairings within confined environments.

Biological characteristics of pregnancy in captive Yangtze finless porpoises revealed by urinary metabolomics†

The Yangtze finless porpoises (Neophocaena asiaeorientalis a.) are an endemic and critically endangered species in China. Intensive captive breeding is essential for understanding the biology of critically endangered species, especially their pregnancy characteristics, knowledge of which is crucial for effective breeding management. Urine metabolomics can reveal metabolic differences, arising from physiological changes across pregnancy stages. Therefore, we used the urinary metabolomic technology, to explore urinary metabolite changes in pregnant Yangtze finless porpoises. A total of 2281 metabolites were identified in all samples, which including organic acids and derivatives (24.45%), organoheterocyclic compounds (20.23%), benzenoids (18.05%), organic oxygen compounds (7.73%), and phenylpropanoids and polyketides (6.48%). There were 164, 387, and 522 metabolites demonstrating differential abundance during early pregnancy, mid pregnancy, and late pregnancy, respectively, from the levels observed in nonpregnancy. The levels of pregnenolone, 17α-hydroxyprogesterone, and tetrahydrocortisone were significantly higher during all pregnancy stages, indicating their important roles in fetal development. The differential metabolites between nonpregnancy and pregnancy were mainly associated with amino acid and carbohydrate metabolism. Moreover, metabolic activity varied across pregnancy stages; steroid hormone biosynthesis was predominant in early pregnancy, and amino acid biosynthesis and carbohydrate metabolism were predominant in mid pregnancy and late pregnancy, respectively. Our results provide new insights into metabolic characteristics in the Yangtze finless porpoises' urine during pregnancy, and indicate that the differential levels of urine metabolites can determine pregnancy in Yangtze finless porpoises, providing valuable information for the husbandry and management of pregnant Yangtze finless porpoises in captivity.

Altered rumen microbiome and correlations of the metabolome in heat-stressed dairy cows at different growth stages

IMPORTANCE

Heat stress is one of the main causes of economic losses in the dairy industry worldwide; however, the mechanisms associated with the metabolic and microbial changes in heat stress remain unclear. Here, we characterized both the changes in metabolites, rumen microbial communities, and their functional potential indices derived from rumen fluid and serum samples from cows at different growth stages and under different climates. This study highlights that the rumen microbe may be involved in the regulation of lipid metabolism by modulating the fatty acyl metabolites. Under heat stress, the changes in the metabolic status of growing heifers, heifers, and lactating cows were closely related to arachidonic acid metabolism, fatty acid biosynthesis, and energy metabolism. Moreover, this study provides new markers for further research to understand the effects of heat stress on the physiological metabolism of Holstein cows and the time-dependent changes associated with growth stages.

Age-related alterations in metabolome and microbiome provide insights in dietary transition in giant pandas

We conducted UPLC-MS-based metabolomics, 16S rRNA, and metagenome sequencing on the fecal samples of 44 captive giant pandas (Ailuropoda melanoleuca) from four age groups (i.e., Cub, Young, Adult, and Old) to comprehensively understand age-related changes in the metabolism and gut microbiota of giant pandas. We characterized the metabolite profiles of giant pandas based on 1,376 identified metabolites, with 152 significantly differential metabolites (SDMs) found across the age groups. We found that the metabolites and the composition/function of the gut microbiota changed in response to the transition from a milk-dominant diet in panda cubs to a bamboo-specific diet in young and adult pandas. Lipid metabolites such as choline and hippuric acid were enriched in the Cub group, and many plant secondary metabolites were significantly higher in the Young and Adult groups, while oxidative stress and inflammatory related metabolites were only found in the Old group. However, there was a decrease in the α-diversity of gut microbiota in adult and old pandas, who exclusively consume bamboo. The abundance of bacteria related to the digestion of cellulose-rich food, such as Firmicutes, Streptococcus, and Clostridium, significantly increased from the Cub to the Adult group, while the abundance of beneficial bacteria such as Faecalibacterium, Sarcina, and Blautia significantly decreased. Notably, several potential pathogenic bacteria had relatively high abundances, especially in the Young group. Metagenomic analysis identified 277 CAZyme genes including cellulose degrading genes, and seven of the CAZymes had abundances that significantly differed between age groups. We also identified 237 antibiotic resistance genes (ARGs) whose number and diversity increased with age. We also found a significant positive correlation between the abundance of bile acids and gut bacteria, especially Lactobacillus and Bifidobacterium. Our results from metabolome, 16S rRNA, and metagenome data highlight the important role of the gut microbiota-bile acid axis in the regulation of age-related metabolism and provide new insights into the lipid metabolism of giant pandas. IMPORTANCE The giant panda is a member of the order Carnivora but is entirely herbivorous. The giant panda's specialized diet and related metabolic mechanisms have not been fully understood. It is therefore crucial to investigate the dynamic changes in metabolites as giant pandas grow and physiologically adapt to their herbivorous diet. This study conducted UPLC-MS-based metabolomics 16S rRNA, and metagenome sequencing on the fecal samples of captive giant pandas from four age groups. We found that metabolites and the composition/function of gut microbiota changed in response to the transition from a milk-dominant diet in cubs to a bamboo-specific diet in young and adult pandas. The metabolome, 16S rRNA, and metagenome results highlight that the gut microbiota-bile acid axis has an important role in the regulation of age-related metabolism, and our study provides new insights into the lipid metabolism of giant pandas.

Multi-omics analysis revealed the brain dysfunction induced by energy metabolism in Pelteobagrus vachelli under hypoxia stress

Hypoxia in water environment has become increasingly frequent and serious due to global warming and environmental pollution. Revealing the molecular mechanism of fish hypoxia adaptation will help to develop markers of environmental pollution caused by hypoxia. Here, we used a multi-omics method to identify the hypoxia-associated mRNA, miRNA, protein, and metabolite involved in various biological processes in Pelteobagrus vachelli brain. The results showed that hypoxia stress caused brain dysfunction by inhibiting energy metabolism. Specifically, the biological processes involved in energy synthesis and energy consumption are inhibited in P. vachelli brain under hypoxia, such as oxidative phosphorylation, carbohydrate metabolism and protein metabolism. Brain dysfunction is mainly manifested as blood-brain barrier injury accompanied by neurodegenerative diseases and autoimmune diseases. In addition, compared with previous studies, we found that P. vachelli has tissue specificity in response to hypoxia stress and the muscle suffers more damage than the brain. This is the first report to the integrated analysis of the transcriptome, miRNAome, proteome, and metabolome in fish brain. Our findings could provide insights into the molecular mechanisms of hypoxia, and the approach could also be applied to other fish species. DATA AVAILABILITY: The raw data of transcriptome has been uploaded to NCBI database (ID: SUB7714154 and SUB7765255). The raw data of proteome has been uploaded to ProteomeXchange database (PXD020425). The raw data of metabolome has been uploaded to Metabolight (ID: MTBLS1888).

Untargeted metabolomics of the cochleae from two laryngeally echolocating bats

High-frequency hearing is regarded as one of the most functionally important traits in laryngeally echolocating bats. Abundant candidate hearing-related genes have been identified to be the important genetic bases underlying high-frequency hearing for laryngeally echolocating bats, however, extensive metabolites presented in the cochleae have not been studied. In this study, we identified 4,717 annotated metabolites in the cochleae of two typical laryngeally echolocating bats using the liquid chromatography-mass spectroscopy technology, metabolites classified as amino acids, peptides, and fatty acid esters were identified as the most abundant in the cochleae of these two echolocating bat species, Rhinolophus sinicus and Vespertilio sinensis. Furthermore, 357 metabolites were identified as significant differentially accumulated (adjusted p-value <0.05) in the cochleae of these two bat species with distinct echolocating dominant frequencies. Downstream KEGG enrichment analyses indicated that multiple biological processes, including signaling pathways, nervous system, and metabolic process, were putatively different in the cochleae of R. sinicus and V. sinensis. For the first time, this study investigated the extensive metabolites and associated biological pathways in the cochleae of two laryngeal echolocating bats and expanded our knowledge of the metabolic molecular bases underlying high-frequency hearing in the cochleae of echolocating bats.

Integrated omics analysis reveals differences in gut microbiota and gut-host metabolite profiles between obese and lean chickens

Abdominal fat is the major adipose tissue in chickens. In chicken, the deposition of abdominal fat affects meat yield and quality. Previous reports suggest that gut microbiota composition and function are associated with lipid metabolism. In this study, we used comparative metagenomics and metabolomics analysis to determine the gut microbiota and gut-host metabolite profiles in Shouguang (SG; a Chinese chicken breed with low-fat deposition) and Luqin (LQ; a fatty-type chicken breed with a fast growth rate) chickens. The results showed that LQ chickens had higher body weight, eviscerated yield, abdominal fat yield, abdominal fat ratio, and triglyceride (TG) content in the breast muscle than SG chickens. Untargeted metabolomics analyses showed a total of 11 liver metabolites, 19 plasma metabolites, and 30 cecal metabolites differentially enriched in LQ and SG chickens based on variable importance in the projection (VIP) ≥ 1 and P ≤ 0.05. These metabolites are involved in lipid and amino acid metabolism. The relative abundance of bacteria in the microbiota differed significantly between the 2 chicken breeds. The functional prediction of microbiota abundant in LQ chickens was starch and lactose degradation. Erysipelatoclostridium was abundant in LQ chickens and significantly positively correlated to palmitoyl ethanolamide (PEA), a key regulator of lipid metabolism. Our findings revealed differences in liver and plasma metabolites between chicken breeds with different adipose deposition capacities. Long-chain acylcarnitines might be important markers of adipose deposition differences in chickens. The cecum's microbial communities and metabolome profiles significantly differed between LQ and SG chickens. However, the relationship between cecal microbiota and their metabolites and liver and plasma metabolites is not thoroughly understood. Future research will focus on relating tissue metabolite changes to intestinal microbiota and their effects on body fat deposition.

Correlation analysis of serum reproductive hormones and metabolites during multiple ovulation in sheep

BACKGROUND

The establishment of non-invasive diagnostic method for multiple ovulation prediction is helpful to improve the efficiency of multiple ovulation. The blood hormones and metabolites would be suitable indexes for this subject.

METHODS

In this study, 86 estrus ewes (65 of induced estrus (IE) and 21 of spontaneous estrus (SE)) were selected and the blood samples were collected at the day before follicle-stimulating hormone (FSH) injection (1^st) and before artificial insemination (2^nd). The serum reproductive hormones ofFSH, luteinizing hormone (LH), 17β-Estradiol (E2), progesterone (P4) and anti-Mullerian hormone (AMH) were measured through enzyme linked immunosorbent assay (ELISA) and the untargeted metabolomics analysis was processed through LC-MS/MS. The embryos were collected after 6.5 days of artificial insemination.

RESULTS

In total, 975 and 406 embryos were collected in IE and SE group, respectively. The analysis of reproductive hormones showed that concentrations of FSH, E2 and AMH were positive correlated with the embryo yield while concentrations of LH and P4 were negative correlated in both group at 1^st detection. At 2^nd detection, the trends of reproductive hormones were similar with 1^st except P4, which was positive correlated with embryo yield. The metabolomics analysis showed that 1158 metabolites (721 in positive iron mode and 437 in negative iron mode) were detected and 617 were annotated. In 1^st comparation of high and low embryonic yield populations, 56 and 53 differential metabolites were identified in IE and SE group, respectively. The phosphatidyl choline (PC) (19:0/20:5) and PC (18:2/18:3) were shared in two groups. In 2^nd comparation, 48 and 49 differential metabolites were identified in IE and SE group, respectively. The PC (18:1/18:2) and pentadecanoic acid were shared. Most differential metabolites were significantly enriched in amino acid, fatty acid metabolism, digestive system secretion and ovarian steroidogenesis pathways.

CONCLUSIONS

This study showed that FSH, P4, AMH, the PC relevant metabolites and some anomic acids could be potential biomarkers for embryonic yield prediction in ovine multiple ovulation. The results would help to explain the relation between blood material and ovarian function and provide a theoretical basis for the multiple ovulation prediction.

Integrated application of multi-omics strategies provides insights into the environmental hypoxia response in Pelteobagrus vachelli muscle

Increasing pressures on aquatic ecosystems because of pollutants, nutrient enrichment, and global warming have severely depleted oxygen concentrations. This sudden and significant lack of oxygen has resulted in persistent increases in fish mortality rates. Revealing the molecular mechanism of fish hypoxia adaptation will help researchers to find markers for hypoxia induced by environmental stress. Here, we used a multiomics approach to identify several hypoxia-associated miRNAs, mRNAs, proteins, and metabolites involved in diverse biological pathways in the muscles of Pelteobagrus vachelli. Our findings revealed significant hypoxia-associated changes in muscles over 4 h of hypoxia exposure and discrete tissue-specific patterns. We have previously reported that P. vachelli livers exhibit increased anaerobic glycolysis, heme synthesis, erythropoiesis, and inhibit apoptosis when exposed to hypoxia for 4 h. However, the opposite was observed in muscles. According to our comprehensive analysis, fishes show an acute response to hypoxia, including activation of catabolic pathways to generate more energy, reduction of biosynthesis to decrease energy consumption, and shifting from aerobic to anaerobic metabolic contributions. Also, we found that hypoxia induced muscle dysfunction by impairing mitochondrial function, activating inflammasomes, and apoptosis. The hypoxia-induced mitochondrial dysfunction enhanced oxidative stress, apoptosis, and further triggered interleukin-1β production via inflammasome activation. In turn, interleukin-1β further impaired mitochondrial function or apoptosis by suppressing downstream mitochondrial biosynthesis–related proteins, thus resulting in a vicious cycle of inflammasome activation and mitochondrial dysfunction. Our findings contribute meaningful insights into the molecular mechanisms of hypoxia, and the methods and study design can be utilized across different fish species.

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First multiomics analysis of mRNA, miRNA, protein, and metabolite in fishes.

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Liver and muscle were tissue-specific induced by hypoxia.

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About 70 genes and 16 miRNAs related to hypoxia adaptation were detected.

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Hypoxia affects muscle function by mediating energy metabolism via HIF pathway.

LC-MS/MS targeting analysis of terpenoid metabolism in Carya cathayensis at different developmental stages

Terpenoid metabolism at different developmental stages of Carya cathayensis was elucidated based on LC-MS/MS analysis and multi-omics. Terpenoid metabolites 2-hydroxy-1,4-naphoquinone and 3-hydroxybenzoic acid reached the maximum at 105 days after pollination (DAP) (P2 stage). To reveal the complex mechanism of C. cathayensis embryogenesis in relation to terpenoid metabolites (90-165 DAP), a metabolomic and transcriptional co-expression analysis was conducted. Based on RNA-Seq analysis, 679 genes of 1144 terpenoid biosynthesis were differentially expressed. Six terpenoid metabolites and 86 differentially expressed genes related to terpenoquinone metabolism were identified. Comprehensive analysis of metabolome and transcriptional data revealed that terpenoquinone accumulated in the early phase was active in the later phase. Overall, we profiled the transcriptome and metabolome changes in C. cathayensis during the developmental phase to investigate the metabolic pathways and candidate genes underlying the changes at different growth stages.

Multi-omics analysis reveals the glycolipid metabolism response mechanism in the liver of genetically improved farmed Tilapia (GIFT, Oreochromis niloticus) under hypoxia stress

BACKGROUND

Dissolved oxygen (DO) in the water is a vital abiotic factor in aquatic animal farming. A hypoxic environment affects the growth, metabolism, and immune system of fish. Glycolipid metabolism is a vital energy pathway under acute hypoxic stress, and it plays a significant role in the adaptation of fish to stressful environments. In this study, we used multi-omics integrative analyses to explore the mechanisms of hypoxia adaptation in Genetically Improved Farmed Tilapia (GIFT, Oreochromis niloticus).

RESULTS

The 96 h median lethal hypoxia (96 h-LH50) for GIFT was determined by linear interpolation. We established control (DO: 5.00 mg/L) groups (CG) and hypoxic stress (96 h-LH50: 0.55 mg/L) groups (HG) and extracted liver tissues for high-throughput transcriptome and metabolome sequencing. A total of 581 differentially expressed (DE) genes and 93 DE metabolites were detected between the CG and the HG. Combined analyses of the transcriptome and metabolome revealed that glycolysis/gluconeogenesis and the insulin signaling pathway were down-regulated, the pentose phosphate pathway was activated, and the biosynthesis of unsaturated fatty acids and fatty acid metabolism were up-regulated in GIFT under hypoxia stress.

CONCLUSIONS

The results show that lipid metabolism became the primary pathway in GIFT under acute hypoxia stress. Our findings reveal the changes in metabolites and gene expression that occur under hypoxia stress, and shed light on the regulatory pathways that function under such conditions. Ultimately, this information will be useful to devise strategies to decrease the damage caused by hypoxia stress in farmed fish.