Differential immune and metabolic responses underlie differences in the resistance of Siganus oramin and Trachinotus blochii to Cryptocaryon irritans infection

Chronic intermittent hypoxia modulates energy metabolic pathways and improves hypoxia tolerance capacity in golden pompano, Trachinotus blochii

Hypoxia is one of the most significant abiotic stresses affecting organisms in aquatic environments. However, dissolved oxygen in water is not always at the low concentrations that cause hypoxia, but their levels often fluctuate. Here, golden pompano (Trachinotus blochii) was subjected to low oxygen concentrations for 28 days (intermittent hypoxia, 2 h per day), and their metabolic indexes were systematically evaluated. RNA-seq was used to construct a regulatory network to elucidate the transcriptional regulation of golden pompano metabolism under intermittent hypoxia. We found that the liver lactic acid content, as well as hexokinase and phosphofructokinase activities, were elevated during the first 7 days, suggesting that anaerobic glycolysis was enhanced during the preceding period. In addition, triglyceride, lipoprotein lipase, and carnitine palmitoyltransferase-1 levels were elevated in the liver after 14 days, suggesting that lipid utilization was activated after 14 days. Intermittent hypoxia increased the activity of aspartate aminotransferase and alanine aminotransferase in the liver, decreased total plasma protein and amino acid levels, and enhanced the metabolism of proteins and amino acids. Decreased levels of oxidative stress and LOEcrit (the O2 tension for loss of equilibrium) were observed in golden pompano after 28 days of intermittent hypoxia. Transcriptome analysis showed that the fatty acid metabolism, PPAR signaling pathway, fatty acid degradation, D-amino acid metabolism, and cholesterol metabolism pathway were activated. These results suggest that intermittent hypoxia improves the metabolic activities of golden pompano, increases its hypoxia tolerance, and promotes its adaptation to hypoxic environments.

Proteins and Peptides Studied In Silico and In Vivo for the Treatment of Diabetes Mellitus: A Systematic Review

Bioinformatics has expedited the screening of new efficient therapeutic agents for diseases such as diabetes mellitus (DM). The objective of this systematic review (SR) was to understand naturally occurring proteins and peptides studied in silico and subsequently reevaluated in vivo for treating DM, guided by the question: which peptides or proteins have been studied in silico for the treatment of diabetes mellitus? The RS protocol was registered in the International Prospective Register of Systematic Reviews database. Articles meeting the eligibility criteria were selected from the PubMed, ScienceDirect, Scopus, Web of Science, Virtual Health Library (VHL), and EMBASE databases. Five studies that investigated peptides or proteins analyzed in silico and in vivo were selected. Risk of bias assessment was conducted using the adapted Strengthening the Reporting of Empirical Simulation Studies (STRESS) tool. A diverse range of assessed proteins and/or peptides that had a natural origin were investigated in silico and corresponding in vivo reevaluation demonstrated reductions in glycemia and/or insulin, morphological enhancements in pancreatic β cells, and alterations in the gene expression of markers associated with DM. The in silico studies outlined offer crucial insights into therapeutic strategies for DM, along with promising leads for screening novel therapeutic agents in future trials.

Expression of genes related to gonadal development and construction of gonadal DNA methylation maps of Trachinotus blochii under hypoxia

Chronic hypoxia can affect the growth and metabolism of fish and potentially impact gonadal development through epigenetic regulation. Trachinotus blochii (Golden pompano) is widely cultured near the coast and is sensitive to low oxygen conditions. We found that hypoxia and reoxygenation processes acted on multiple targets on the HPG axis, leading to endocrine disorders. Changes in the expression of key genes in the brain (gnrh), pituitary (fsh and lh), ovaries (cyp19a1a, foxl2, and er), and testes (dmrt1, ar, sox9, and gsdf) were associated with significant decreases in estrogen and testosterone levels. Hypoxia and reoxygenation lead to changes in DNA methylation levels in the gonads. Hypoxia upregulated the expression of dnmt1, dnmt3a, dnmt3b, tet1, and tet2 in females and dnmt3a and dnmt3b in males, while reoxygenation down-regulated the expression of dnmt1, dnmt3a, dnmt3b, tet1, and tet2 in males. Whole genome methylation sequencing showed that the number of differentially methylated regions was highest on chromosome 10 (5192) and lowest on chromosome 24 (275). Differentially methylated genes in females and males, as well as between males and females, were enriched in the oxytocin signaling pathway, fatty acid metabolism pathway, and HIF-1a pathway. In summary, hypoxia and reoxygenation can induce endocrine disorders, affect the expression of HPG axis genes, change the methylation pattern and modification pattern of gonad DNA, and then have potential effects on gonad development.

Transcriptomic Analysis Reveals Functional Interaction of mRNA-lncRNA-miRNA in Trachinotus ovatus Infected by Cryptocaryon irritans

The skin of Trachinotus ovatus is a crucial component of the mucosal immune system and serves as the primary site of infection by Cryptocaryon irritans. In order to investigate the significant role of skin in C. irritans infection, a comprehensive transcriptome analysis was conducted on skin tissues from the infection group, infection-adjacent group, and infection group compared with the infection-adjacent group (ATT_vs_PER, ADJ_vs_PER, ATT_vs_ADJ). This study identified differentially expressed long non-coding RNAs (DE lncRNAs), microRNAs (DE miRNAs), and differentially expressed genes (DEGs). The prediction of lncRNA target genes was accomplished by utilizing positional relationship (co-location) and expression correlation (co-expression) with protein-coding genes. Subsequently, functional enrichment analysis was conducted on the target genes of differentially expressed lncRNAs, revealing their involvement in signaling pathways such as tight junction, MAPK, and cell adhesion molecules. This study describes the regulatory network of lncRNA-miRNA-mRNA in T. ovatus skin tissue infected with C. irritans. Functional prediction analysis showed that differentially expressed lncRNA and miRNA may regulate the expression of immune genes such as interleukin-8 (il8) to resist the infection of C. irritans. Conducting additional research on these non-coding RNAs will facilitate a deeper understanding of their immune regulatory function in T. ovatus during C. irritans infection. The study of non-coding RNA in this study laid a foundation for revealing the molecular mechanism of the immune system of T. ovatus to respond to the infection of C. irritans. It provided a choice for the molecular breeding of Trachinotus ovatus against C. irritans.

Antidiabetic effects of protein hydrolysates from Trachinotus ovatus and identification and screening of peptides with α-amylase and DPP-IV inhibitory activities

In the present study, the antidiabetic properties of Trachinotus ovatus protein hydrolysates (TOH) in streptozotocin-induced diabetic mice were investigated, and peptides with α-amylase (AAM) and dipeptidyl peptidase IV (DPP-IV) inhibitory activities were identified and screened. The results showed that TOH alleviated body weight loss, polyphagia, blood glucose elevation and insulin secretion decline in diabetic mice. After 4 weeks of TOH administration, random blood glucose (RBG) decreased significantly. The TOH groups showed a dose-dependent reduction in fasting blood glucose (FBG), especially in the high-dose TOH group, which reduced FBG by 58% versus the effect of metformin. Moreover, TOH exerted a remarkable protective effect on hepatorenal function, as evidenced by increased superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) and decreased serum urea levels. Histopathological studies confirmed that TOH can significantly protect the kidney and pancreas from histological changes, which was of great benefit for ensuring the normal secretion of insulin and preventing the occurrence of complications such as diabetic nephropathy. Two fractions with higher inhibitory activity against AAM and DPP-IV, F4 and F6, were obtained from the ultrafiltration of TOH-2 (≤3 kDa). A total of 19 potentially active peptides from F4 and 3 potentially active peptides from F6 were screened by LC‒MS/MS combined with bioinformatic analysis. These peptides are small molecular peptides composed of 2-6 amino acids, rich in characteristic amino acids such as proline, arginine, phenylalanine and asparagine, and contain high proportions of peptides (68% for F4, 67% for F6) with hydrophobicity ≥50%. They offer potent antidiabetic potential and could potentially bind to the active sites in the internal cavities of the target enzymes AAM and DPP-IV. In summary, this study revealed for the first time the antidiabetic effects of protein hydrolysates of Trachinotus ovatus and their derived peptides, which are promising natural ingredients with the potential to be used for the treatment or prevention of diabetes.