Zebrafish Brain Research Articles

Identification of a neuropeptide in suppressing food intake in zebrafish

Neuropeptides play crucial roles in regulating various physiological processes in vertebrates. In this study, we identified a novel neuropeptide-encoding gene, nwk, in the genomes of some vertebrate species. The nwk cDNA was subsequently cloned from the brain of zebrafish. The Nwk precursor comprises 88 amino acids, with a putative mature peptide (Nwk-22) of 22 amino acids. Sequence analysis revealed that Nwk-22 is relatively conserved across vertebrate species. Nwk is predominantly expressed in the brain, with positive mRNA cells identified in the TPp and preoptic area. Intraperitoneal injection of Nwk-22 suppressed food intake and downregulated the mRNA expression of the orexigenic factor agouti-related peptide (agrp) in zebrafish. Additionally, a CRISPR/Cas9 approach was used to generate nwk mutant zebrafish. The nwk−/− zebrafish exhibited increased food consumption compared to wild-type controls. Furthermore, Nwk-22a injection in nwk−/− fish also suppressed agrp expression while stimulating the expression of the anorexigenic gene pomca, further supporting the anorexigenic role of Nwk. Taken together, these findings suggest that Nwk functions as an anorexigenic factor, reducing food intake by downregulating orexigenic genes like agrp and upregulating anorexigenic genes like pomc in zebrafish.

Spontaneous Brain Activity Emerges from Pairwise Interactions in the Larval Zebrafish Brain

Brain activity is characterized by brainwide spatiotemporal patterns that emerge from synapse-mediated interactions between individual neurons. Calcium imaging provides access to recordings of whole-brain activity at single-neuron resolution and, therefore, allows the study of how large-scale brain dynamics emerge from local activity. In this study, we use a statistical mechanics approach—the pairwise maximum entropy model—to infer microscopic network features from collective patterns of activity in the larval zebrafish brain and relate these features to the emergence of observed whole-brain dynamics. Our findings indicate that the pairwise interactions between neural populations and their intrinsic activity states are sufficient to explain observed whole-brain dynamics. In fact, the pairwise relationships between neuronal populations estimated with the maximum entropy model strongly correspond to observed structural connectivity patterns. Model simulations also demonstrated how tuning pairwise neuronal interactions drives transitions between observed physiological regimes and pathologically hyperexcitable whole-brain regimes. Finally, we use virtual resection to identify the brain structures that are important for maintaining the brain in a physiological dynamic regime. Together, our results indicate that whole-brain activity emerges from a complex dynamical system that transitions between basins of attraction whose strength and topology depend on the connectivity between brain areas. Published by the American Physical Society 2024

Protective effect of nanoemulsions containing CdTe quantum dots with potential application as a diagnostic agent.

A nanoemulsion containing CdTe quantum dots (NE-CdTe-QD) was developed to shield cells from cadmium toxicity and shown to be a promising candidate for brain tumor diagnosis. CdTe-QD was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. CdTe-QD exhibited high luminescence emission at 700nm, and their stability was maintained when encapsulated in lipidic/polymeric nanoemulsions (198 ± 2.0nm; PDI = 0.174; - 49.0mV). The biological effects of free and nanoemulsified CdTe-QD were tested in normal cells (NHF) and glioblastoma cell lines (U87-MG and T98G). Membrane colocalization of NE-CdTe-QD by T98G cells was observed. Instead, intracellular endoplasmic reticulum localization of NE-CdTe-QD was verified in U87-MG cells. Cell viability was reduced only when NE-CdTe-QD permeated the membrane of GBM cells, as observed in U87-MG cells, whereas no cytotoxic effects were observed in normal fibroblasts. Incorporating quantum dots directly into the brain cells is difficult. However, the nanoemulsions reduced the toxicity of CdTe-QD in zebrafish larvae and increased their circulation time, and direct injection into the zebrafish brain did not affect neural cell viability. This validates the potential application of these nanomaterials as diagnostic agents and satisfies the necessary criteria for their use as photosensitizers in photodynamic therapy.

Emoxypine succinate modulates behavioral and molecular responses in zebrafish model of iron Overload-Induced neuroinflammation via CDK5/GSK3- β and NLRP3 inflammasome pathway

Excessive iron accumulation in the brain plays a significant role in neurodegenerative processes, contributing to the pathogenesis of Alzheimer’s disease (AD). AD, a prominent neurological disorder affecting the central nervous system, is characterized by the accumulation of beta-amyloid (Aβ) and tau phosphorylation. This accumulation leads to the subsequent development of cognitive impairments, particularly in learning and memory functions. This study investigates the neuroprotective effects of emoxypine succinate in a zebrafish model of iron overload-induced neurodegeneration. Iron was administered to the zebrafish for 28 days to induce neurodegeneration. Following induction, Emoxypine succinate was employed as a treatment intervention for 14 days (concentrations of 4 mg/L, 8 mg/L, and 12 mg/L). Following the end of the treatment, behavioral tests (Y maze test, Novel tank test) were conducted on the zebrafish, and the biochemical (MDA, Catalase, SOD, GSH) and molecular parameters (AchE, Iron levels, IL-1β, TNF-α, CDK-5, GSK-3β, and NLRP3) of the zebrafish brain were also assessed. In the novel tank test, emoxypine succinate-treated groups exhibited significantly increased time in the upper zone (p < 0.001), higher distance travelled (p < 0.001), and shorter latency to the top (p < 0.001) compared to the negative control. Similarly, the Y-maze test revealed improved time in the novel arm (p < 0.001) and total distance travelled (p < 0.001) in treated groups versus the negative control. Assessment of oxidative stress parameters demonstrated significant reductions in oxidative stress in emoxypine succinate-treated groups. Furthermore, AChE activity decreased significantly (p < 0.001), and brain iron levels decreased substantially (p < 0.001) in treated groups, indicating positive therapeutic outcomes. Molecular analysis showed a significant reduction in pro-inflammatory markers like IL-1β, TNF-α, CDK-5, GSK-3β, and NLRP3 (p < 0.001). This comprehensive study highlights the potential efficacy of emoxypine succinate in mitigating neurodegeneration associated with iron dysregulation.

Mapping the cellular expression patterns of vascular endothelial growth factor aa and bb genes and their receptors in the adult zebrafish brain during constitutive and regenerative neurogenesis

The complex interplay between vascular signaling and neurogenesis in the adult brain remains a subject of intense research. By exploiting the unique advantages of the zebrafish model, in particular the persistent activity of neural stem cells (NSCs) and the remarkable ability to repair brain lesions, we investigated the links between NSCs and cerebral blood vessels. In this study, we first examined the gene expression profiles of vascular endothelial growth factors aa and bb (vegfaa and vegfbb), under physiological and regenerative conditions. Employing fluorescence in situ hybridization combined with immunostaining and histology techniques, we demonstrated the widespread expression of vegfaa and vegfbb across the brain, and showed their presence in neurons, microglia/immune cells, endothelial cells and NSCs. At 1 day post-lesion (dpl), both vegfaa and vegfbb were up-regulated in neurons and microglia/peripheral immune cells (macrophages). Analysis of vegf receptors (vegfr) revealed high expression throughout the brain under homeostatic conditions, with vegfr predominantly expressed in neurons and NSCs and to a lower extent in microglia/immune cells and endothelial cells. These findings were further validated by Vegfr3 and Vegfr4 immunostainings, which showed significant expression in neurogenic radial glial cells.Following brain lesion (1 dpl), while vegfr gene expression remained stable, vegfr transcripts were detected in proliferative cells within the injured parenchyma. Collectively, our results provide a first overview of Vegf/Vegfr signaling in the brain and suggest important roles for Vegf in neurogenesis and regenerative processes.

Positively charged mesoporous silica nanocarriers loaded with arbidol: A novel effective nano antiviral system against nervous necrosis virus

Viral nervous necrosis (VNN) caused by nervous necrosis virus (NNV) poses a significant threat to the global aquaculture industry, leading to substantial economic losses. In this study, we evaluated the anti-NNV activity of arbidol both in vitro and in vivo. Treatment with arbidol at a concentration of 10.48 μM effectively inhibited NNV-induced cytopathic effects in GF-1 cells, and the half-maximal inhibitory concentration (IC50) of arbidol against NNV was determined to be 7.915 μM. To improve drug delivery to the central nervous system, the primary site of NNV infection, we developed positively charged mesoporous silica nanocarriers (CMSNs) loaded with arbidol (CMSNs-ARB). Compared to unmodified mesoporous silica nanocarriers, CMSNs exhibited significantly higher uptake in GF-1 cells and zebrafish brains, indicating their potential to cross the blood-brain barrier (BBB) and deliver drugs more efficiently. In vivo experiments revealed that arbidol administration improved the survival rate of juvenile fish infected with NNV. Additionally, the use of CMSNs as a drug carrier further enhanced the larval survival rate by 13 % compared to the arbidol-only treatment group. These results demonstrate the potent anti-NNV activity of arbidol and highlight the potential of CMSNs as an effective drug delivery system to control fish viral diseases in aquaculture.

Identification of gene co-expression modules from zebrafish brain data: Applications in psychiatry illustrated through alcohol-related traits

Cumulative evidence suggests that zebrafish is a useful model in psychiatric research. Weighted Gene Co-expression Network Analysis (WGCNA) enables the reduction of genome-wide expression data to modules of highly co-expressed genes, which are hypothesized to interact within molecular networks. In this study, we first applied WGCNA to zebrafish brain expression data across different experimental conditions. Then, we characterized the different co-expression modules by gene-set enrichment analysis and hub gene-phenotype association. Finally, we analyzed association of polygenic risk scores (PRSs) based on genes of some interesting co-expression modules with alcohol dependence in 524 patients and 729 controls from Galicia, using competitive tests. Our approach revealed 34 co-expression modules in the zebrafish brain, with some showing enrichment in human synaptic genes, brain tissues, or brain developmental stages. Moreover, certain co-expression modules were enriched in psychiatry-related GWAS and comprised hub genes associated with psychiatry-related traits in both human GWAS and zebrafish models. Expression patterns of some co-expression modules were associated with the tested experimental conditions, mainly with substance withdrawal and cold stress. Notably, a PRS based on genes from co-expression modules exclusively associated with substance withdrawal in zebrafish showed a stronger association with human alcohol dependence than PRSs based on randomly selected brain-expressed genes. In conclusion, our analysis led to the identification of co-expressed gene modules that may model human brain gene networks involved in psychiatry-related traits. Specifically, we detected a cluster of co-expressed genes whose expression was exclusively associated with substance withdrawal in zebrafish, which significantly contributed to alcohol dependence susceptibility in humans.

The embryonic zebrafish brain is exclusively colonized by pu.1-dependent and lymphatic-independent population of microglia.

Microglia, the crucial immune cells inhabiting the central nervous system (CNS), perform a range of vital functions, encompassing immune defense and neuronal regulation. Microglia subsets with diverse functions and distinct developmental regulations have been identified recently. It is generally accepted that all microglia originate from hematopoiesis and depend on the myeloid transcription factor PU.1. However, a recent study reported the existence of mrc1+ microglia in zebrafish embryos, which are seemingly independent of Pu.1 and reliant on lymphatic vessels, sparking great interest in the possibility of lymphatic-originated microglia. To address this, we took advantage of a pu.1 knock-in zebrafish allele for a detailed investigation. Our results conclusively showed that almost all zebrafish embryonic microglia (~95% on average) express pu.1. Further, lineage tracing and mutant analysis revealed that these microglia neither emerged from nor depended on lymphatic vessels. In essence, our study refutes the presence of pu.1-independent but lymphatic-dependent microglia.

Microglia cannibalism and efferocytosis leads to shorter lifespans of developmental microglia.

The overproduction of cells and subsequent production of debris is a universal principle of neurodevelopment. Here we show an additional feature of the developing nervous system that causes neural debris - promoted by the sacrificial nature of embryonic microglia that irreversibly become phagocytic after clearing other neural debris. Described as long-lived, microglia colonize the embryonic brain and persist into adulthood. Using transgenic zebrafish to investigate the microglia debris during brain construction, we identified that unlike other neural cell-types that die in developmental stages after they have expanded, necroptosis-dependent microglial debris is prevalent when microglia are expanding in the zebrafish brain. Time-lapse imaging of microglia demonstrates that this debris is cannibalized by other microglia. To investigate features that promote microglia death and cannibalism, we used time-lapse imaging and fate-mapping strategies to track the lifespan of individual developmental microglia. These approaches revealed that instead of embryonic microglia being long-lived cells that completely digest their phagocytic debris, once most developmental microglia in zebrafish become phagocytic they eventually die, including ones that are cannibalistic. These results establish a paradox -- which we tested by increasing neural debris and manipulating phagocytosis -- that once most microglia in the embryo become phagocytic, they die, create debris and then are cannibalized by other microglia, resulting in more phagocytic microglia that are destined to die.

A Potential Neurotoxic Mechanism: Bisphenol S-Induced Inhibition of Glucose Transporter 1 Leads to ATP Excitotoxicity in the Zebrafish Brain.

Many environmental pollutants have neurotoxic effects, but the initial molecular events involved in these effects are unclear. Here, zebrafish were exposed to the neurotoxicant bisphenol S (BPS, 1, 10, or 100 μg/L) from the embryonic stage to the larval stage to explore the ability of BPS to interfere with energy metabolism in the brain. BPS, which is similar to a glucose transporter 1 (GLUT1) inhibitor, inhibited GLUT1 function but increased mitochondrial activity in the brains of larval zebrafish. Interestingly, GLUT1 inhibitor treatment and BPS exposure did not reduce energy production in the brain; instead, they increased ATP production by inducing the preferential use of ketone bodies. Moreover, BPS promoted the protein expression of the purinergic 2X receptor but inhibited the purinergic 2Y-mediated phosphatidylinositol signaling pathway, indicating that excess ATP acts as a neurotransmitter to activate the purinergic 2X receptor under the BPS-induced restriction of GLUT1 function. BPS-induced inhibition of GLUT1 increased the number of neurons but promoted apoptosis by activating ATP-purinergic 2X receptors in the brain, causing ATP excitatory neurotoxicity. Our data reveal a potential neurotoxic mechanism induced by BPS that may represent a new adverse outcome pathway.

Investigating the modulation of the endocannabinoid system by probiotic Lactiplantibacillus plantarum IMC513 in a zebrafish model of di-n-hexyl phthalate exposure

Environmental pollutants used as plasticizers in food packaging and in thousands of everyday products have become harmful for their impact on human health. Among them, phthalates, recognized as emerging endocrine disruptors (EDs) can induce toxic effects leading to different health disorders. Only few studies evaluated the effects of di-n-hexyl phthalate (DnHP) in in vivo models and no studies have been conducted to investigate the effect of DnHP on the endocannabinoid system (ECS), one of the majors signaling pathways involved in the microbiota–gut–brain axis. Due to the current relevance of probiotic bacteria as beneficial dietary interventions, the present study was aimed at evaluating the potential neuroprotective impact of daily administration of Lactiplantibacillus (Lpb.) plantarum IMC513 on zebrafish adults exposed to DnHP, with a focus on ECS modulation. Gene expression analysis revealed a promising protective role of probiotic through the restoration of ECS genes expression to the control level, in the brain of zebrafish daily exposed to DnHP. In addition, the levels of main endocannabinoids were also modulated. These findings confirm the potential ability of probiotics to interact at central level by modulating the ECS, suggesting the use of probiotics as innovative dietary strategy to counteract alterations by EDs exposure.

Whole-brain mapping in adult zebrafish and identification of a novel tank test functional connectome.

Identifying general principles of brain function requires the study of structure-function relationships in a variety of species. Zebrafish have recently gained prominence as a model organism in neuroscience, yielding important insights into vertebrate brain function. Although methods have been developed for mapping neural activity in larval animals, we lack similar techniques for adult zebrafish that have the advantage of a fully developed neuroanatomy and larger behavioral repertoire. Here, we describe a pipeline built around open-source tools for whole-brain activity mapping in freely swimming adult zebrafish. Our pipeline combines recent advances in histology, microscopy, and machine learning to capture cfos activity across the entirety of the adult brain. Images captured using light-sheet microscopy are registered to the recently created adult zebrafish brain atlas (AZBA) for automated segmentation using advanced normalization tools (ANTs). We used our pipeline to measure brain activity after zebrafish were subject to the novel tank test. We found that cfos levels peaked 15 minutes following behavior and that several regions containing serotoninergic, dopaminergic, noradrenergic, and cholinergic neurons were active during exploration. Finally, we generated a novel tank test functional connectome. Functional network analysis revealed that several regions of the medial ventral telencephalon form a cohesive sub-network during exploration. We also found that the anterior portion of the parvocellular preoptic nucleus (PPa) serves as a key connection between the ventral telencephalon and many other parts of the brain. Taken together, our work enables whole-brain activity mapping in adult zebrafish for the first time while providing insight into neural basis for the novel tank test.

11β-Hydroxysteroid dehydrogenase type 2 may mediate the stress-specific effects of cortisol on brain cell proliferation in adult zebrafish (Danio rerio).

Stress-induced increases in cortisol can stimulate or inhibit brain cell proliferation, but the mechanisms behind these opposing effects are unknown. We tested the hypothesis that 11β-hydroxysteroid dehydrogenase type 2 (Hsd11b2), a glucocorticoid-inactivating enzyme expressed in neurogenic regions of the adult zebrafish brain, mitigates cortisol-induced changes to brain cell proliferation, using one of three stress regimes: a single 1min air exposure (acute stress), two air exposures spaced 24 h apart (repeat acute stress) or social subordination (chronic stress). Plasma cortisol was significantly elevated 15 min after air exposure and recovered within 24 h after acute and repeat acute stress, whereas subordinate fish exhibited significant and sustained elevations relative to dominant fish for 24 h. Following acute stress, brain hsd11b2 transcript abundance was elevated up to 6 h after a single air exposure but was unchanged by repeat acute stress or social subordination. A sustained increase in brain Hsd11b2 protein levels occurred after acute stress, but not after repeat or chronic stress. Following acute and repeat acute stress, brain pcna transcript abundance (a marker of cell proliferation) exhibited a prolonged elevation, but was unaffected by social subordination. Interestingly, the number of telencephalic BrdU+ cells increased in fish after a single air exposure but was unchanged by repeat acute stress. Following acute and repeat acute stress, fish expressed lower brain glucocorticoid and mineralocorticoid receptor (gr and mr) transcript abundance while subordinate fish exhibited no changes. Taken together, these results demonstrate stressor-specific regulation of Hsd11b2 in the zebrafish brain that could modulate rates of cortisol catabolism contributing to observed differences in brain cell proliferation.

A nuclear jamming transition in vertebrate organogenesis.

Jamming of cell collectives and associated rigidity transitions have been shown to play a key role in tissue dynamics, structure and morphogenesis. Cellular jamming is controlled by cellular density and the mechanics of cell-cell contacts. However, the contribution of subcellular organelles to the physical state of the emergent tissue is unclear. Here we report a nuclear jamming transition in zebrafish retina and brain tissues, where physical interactions between highly packed nuclei restrict cellular movements and control tissue mechanics and architecture. Computational modelling suggests that the nuclear volume fraction and anisotropy of cells control the emerging tissue physical state. Analysis of tissue architecture, mechanics and nuclear movements during eye development show that retina tissues undergo a nuclear jamming transition as they form, with increasing nuclear packing leading to more ordered cellular arrangements, reminiscent of the crystalline cellular packings in the functional adult eye. Our results reveal an important role of the cell nucleus in tissue mechanics and architecture.

Morpho-Anatomical Degeneration of Dopaminergic Neurons in Adult Zebrafish Brain after Exposure to Nickel

Chronic exposure to heavy metals has been widely demonstrated to induce pathological features in different tissues and, in particular, in the central nervous system. Specific neurons, including dopaminergic neurons, were observed to be more susceptible to toxic agents. Several previous studies performed on zebrafish (Danio rerio) models observed that exposure to nickel (one of the most abundant heavy metals) induces impairment of memory and anxious-like behaviors. Nevertheless, this phenotypical evidence has not been associated with dopaminergic system damage, and no reports showing the effects of nickel on dopaminergic neurons are available. In this study, we aim to analyze the precise distribution and variation in dopaminergic neurons in adult zebrafish after chronic (96 h) exposure to nickel ions dissolved in water at different sub-lethal doses (0.4 mg L−1; 2 mg L−1 and 4 mg L−1). The effects of treatment on dopaminergic neurons were evaluated by measuring transcript and protein levels of tyrosine hydroxylase (TH), described as a dopaminergic neuron marker. As shown, the expression of the th1 and th2 genes was reduced in the entire brain of zebrafish treated with nickel. Immunostaining analysis allowed us to localize TH-expressing neurons mainly in the posterior tuberculum, where they were observed to be reduced after nickel treatment in a dose-dependent fashion. Consistently, the TUNEL assay revealed a significant increase in apoptosis of TH-expressing cells after treatment with 2 mg L−1 and 4 mg L−1 of nickel. Our findings represent the first evidence of the effect of nickel on the dopaminergic system.

Neural Stem Cell Regulation in Zebrafish.

Neural stem cells (NSCs) are progenitor cell populations generating glial cells and neurons and endowed with long-lasting self-renewal and differentiation potential. While some neural progenitors (NPs) in the embryonic nervous system are also long-lived and match this definition, the term NSC classically refers to such progenitor types in the adult. With the discovery of extensive NSC populations in the adult brain of Danio rerio (zebrafish) and of their high neurogenic activity, including for neuronal regeneration, this model organism has become a powerful tool to characterize and mechanistically dissect NSC properties. On these bases, this article will consider NSCs in the adult zebrafish brain, with a focus on its most extensively characterized domain, the telencephalon (notably its dorsal part, the pallium). Whenever necessary, we will also refer to other brain subdivisions, embryonic processes, and the mouse adult brain, whether for comparative purposes or because more information is available in these other systems.

Mirror-assisted light-sheet microscopy: a simple upgrade to enable bi-directional sample excitation.

Light-sheet microscopy is a powerful imaging technique that achieves optical sectioning via selective illumination of individual sample planes. However, when the sample contains opaque or scattering tissues, the incident light sheet may not be able to uniformly excite the entire sample. For example, in the context of larval zebrafish whole-brain imaging, occlusion by the eyes prevents access to a significant portion of the brain during common implementations using unidirectional illumination. We introduce mirror-assisted light-sheet microscopy (mLSM), a simple inexpensive method that can be implemented on existing digitally scanned light-sheet setups by adding a single optical element-a mirrored micro-prism. The prism is placed near the sample to generate a second excitation path for accessing previously obstructed regions. Scanning the laser beam onto the mirror generates a second, reflected illumination path that circumvents the occlusion. Online tuning of the scanning and laser power waveforms enables near uniform sample excitation with dual illumination. mLSM produces cellular-resolution images of zebrafish brain regions inaccessible to unidirectional illumination. The imaging quality in regions illuminated by the direct or reflected sheet is adjustable by translating the excitation objective. The prism does not interfere with visually guided behavior. mLSM presents an easy-to-implement, cost-effective way to upgrade an existing light-sheet system to obtain more imaging data from a biological sample.

Comparative insight into the regenerative mechanisms of the adult brain in zebrafish and mouse: highlighting the importance of the immune system and inflammation in successful regeneration.

Regeneration, the complex process of restoring damaged or absent cells, tissues, and organs, varies considerably between species. The zebrafish is a remarkable model organism for its impressive regenerative abilities, particularly in organs such as the heart, fin, retina, spinal cord, and brain. Unlike mammals, zebrafish can regenerate with limited or absent scarring, a phenomenon closely linked to the activation of stem cells and immune cells. This review examines the unique roles played by the immune response and inflammation in zebrafish and mouse during regeneration, highlighting the cellular and molecular mechanisms behind their divergent regenerative capacities. By focusing on zebrafish telencephalic regeneration and comparing it to that of the rodents, this review highlights the importance of a well-controlled, acute, and non-persistent immune response in zebrafish, which promotes an environment conducive to regeneration. The knowledge gained from understanding the mechanisms of zebrafish regeneration holds great promises for the treatment of human neurodegenerative diseases and brain damage (stroke and traumatic brain injuries), as well as for the advancement of regenerative medicine approaches.

Okra (Abelmoschus esculentus L. moench) fruit powder standardized in flavonoids improves glycemic control and metabolic memory in acute and chronic hyperglycemia

Type 2 diabetes mellitus (T2DM) is a chronic disease with high global prevalence characterized by persistent hyperglycemia. Elevated blood glucose levels are associated with constant oxidative stress and increased protein glycation, establishing a metabolic memory state. Therefore, the efficacy of the Okra (Abelmoschus esculentus L. moench) Fruit Powder Standardized in Flavonoids (OFP-SF) was evaluated in glucose homeostasis, oxidative stress, and metabolic memory, using zebrafish models of acute and chronic hyperglycemia. The OFP-SF was produced from dried fresh fruits and subsequently subjected to characterization regarding its antioxidant potential and chemical composition. Finally, the product was standardized to contain 1.6% flavonoids. In acute hyperglycemia, OFP-SF at doses of 125 μg and 250 μg demonstrated the ability to normalize blood glucose levels, reaching levels of 94.56 ± 5.9 mg/dL and 76.88 ± 8.9 mg/dL, respectively, when administered prior to glucose overload. The same doses were tested in a chronic hyperglycemia model, where after a seven-day treatment, animals receiving 125 and 250 μg of OFP-SF exhibited glycemic values of 73.45 ± 15.67 mg/dL and 33.96 ± 5.31 mg/dL, respectively, comparable to those observed in the Control group (49.48 ± 2.77 mg/dL). Furthermore, OFP-SF was able to mitigate metabolic memory by reducing oxidative stress and protein glycation in the brain, liver, and eye tissues of hyperglycemic zebrafish. These findings provide a basis for developing new products that utilize the phytochemical potential of A. esculentus fruits for the prevention and adjunctive treatment of T2DM.

Light-Dependent Circadian Rhythm Governs O-GlcNAc Cycling to Influence Cognitive Function in Adult Zebrafish.

This study explores the 24-h rhythmic cycle of protein O-GlcNAcylation within the brain and highlights its crucial role in regulating the circadian cycle and neuronal function based on zebrafish as an animal model. In our experiments, disruption of the circadian rhythm, achieved through inversion of the light-dark cycle or daytime melatonin treatment, not only impaired the rhythmic changes of O-GlcNAcylation along with altering expression patterns of O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) in zebrafish brain but also significantly impeded learning and memory function. In particular, circadian disruption affected rhythmic expression of protein O-GlcNAcylation and OGT in the nuclear fraction. Notably, the circadian cycle induces rhythmic alterations in O-GlcNAcylation of H2B histone protein that correspond to changes in H3 trimethylation. Disruption of the cycle interfered with these periodic histone code alterations. Pharmacological inhibition of OGT with OSMI-1 disrupted the wake-sleep patterns of zebrafish without affecting expression of circadian rhythm-regulating genes. OSMI-1 inhibited the expression of c-fos, bdnf, and calm1, key genes associated with brain function and synaptic plasticity, and decreased the binding of O-GlcNAcylated H2B and OGT to promoter regions of these genes. The collective findings support the potential involvement of circadian cycling of the O-GlcNAc histone code in regulating synaptic plasticity and brain function. Overall, data from this study provide evidence that protein O-GlcNAcylation serves as a pivotal posttranslational mechanism integrating circadian signals and neuronal function to regulate rhythmic physiology.