Hyperglycemia elicits anxiety-like behaviors in zebrafish: Protective role of dietary diphenyl diselenide

Assessing the Influence of Low Doses of Sucrose on Memory Deficits in Fish Exposed to Common Insecticide Based on Fipronil and Pyriproxyfen

Although pesticides have been a constant concern for decades, in the last ten years, public discussions and scientific research have emphasized their impact on human health and the environment, drawing increased attention to the problems associated with their use. The association of environmental stressors such as pesticides with a sugar-rich diet can contribute to the growing global metabolic disease epidemic through overlapping mechanisms of insulin resistance, inflammation, and metabolic dysregulation. The main aim of this study was to evaluate the behavioral effects of the exposure of Silver crucian carp (Carassius auratus gibelio) to a commercial insecticide formulation containing fipronil, pyriproxyfen, and other additives, as well as sucrose and their mixtures. The behavioral responses in the T-test showed significant abnormalities in the exploratory activity evocative of memory deficits and an increased degree of anxiety in the groups of fish treated with the insecticide formulation and the mixture of the insecticide with sucrose. Aggression, quantified in the mirror-biting test, as biting and the frequency of approaches to the mirror contact zone, was significantly decreased only in the insecticide and sucrose group. All three groups showed behavioral changes reflective of toxicity, but only the combination of the two stress factors, environmental (insecticide) and metabolic (sucrose intake), resulted in pronounced memory alterations.

Microfiltered red-purple pitaya concentrate: A promising multifunctional food-derived colorant

Red pitaya fruit has become a source of natural colorant, because it is rich in betalains, a pigment that imparts a red-purple color that interests the food and cosmetics industries. This fruit also possesses high nutritional value, with a range of bioactive compounds known to confer potential health benefits and prevent chronic diseases, such as diabetes, which makes it useful for use as pharmaceutical agents and dietary supplements. In order to improve its technological and biological effects, a concentration will be required. Thus, the microfiltration, followed by vacuum concentration, can be an interesting strategy for this purpose. This study aimed to explore tangential microfiltration to produce microfiltered material, which is an important step to obtain the microfiltered red-purple pitaya concentrate. Therefore, physicochemical and chemical characterization (including 1H NMR analysis) and biological properties (toxicity and diabetes) of this concentrate were assessed, using adult zebrafish as a model. The results show that microfiltration was carried out efficiently, with an average consumption of 95.75 ± 3.13 and 74.12 ± 3.58 kW h m-3, varying according to the material used ("unpeeled pitaya pulp" or "pitaya pulp with peel," respectively). The in vivo tests indicated non-toxicity and hypoglycemic effect of the concentrate, since the blood glucose levels were significantly lower in the zebrafish groups treated with this concentrate in comparison with that of control group. Thus, this study suggests the potential of microfiltered red-purple pitaya concentrate as a promising multifunctional food-derived colorant, exhibiting beneficial biological effects far beyond its attractive color. PRACTICAL APPLICATION: Hylocereus polyrhizus (F.A.C. Weber) Britton & Rose has attracted attention as a potential source of natural colorants because of its red-purple skin and flesh color. In addition, this fruit has a range of bioactive compounds, which make it a valuable resource for providing potential health benefits and preventing chronic diseases such as diabetes. In this paper, the microfiltered red-purple pitaya concentrate showed beneficial biological effects far beyond its attractive color. Thus, this product can be considered a promising multifunctional food-derived colorant to use in the food, pharmaceutical, or cosmetics industries.

The effects of isocaloric diets derived from different lipid sources on zebrafish

Characterizing the effects of saturated fat intake on metabolic health and its changes remains a major challenge. Lipid diets, from different sources, vary widely in their physiological effects on health; therefore, it is important to consider the specific lipid source consumed. The objective of the study was to evaluate the effect of the imposition of isocaloric diets with different lipid sources in zebrafish (fish oil/pork lard). Depicting how metabolic, morphological and behavioral parameters might express themselves in these fishes. Forty adult female fishes were used for the experiment. The animals were divided into a control group (C), fed with unsaturated fatty acid diet, and a saturated fatty acid group (Sat). They received food three times a day, during the 11-week period. The results showed that animals in the Sat group had increased body weight, with a difference relative to the C group, from the third week of diet until the end of the experiment. At the end of the last week, the Sat group had a body weight 32% higher (P=0.0182) than the body weight of the control group. The consumption of a diet rich in saturated fatty acids did not generate signs related to stress and anxiety in zebrafish. There was an increase in glycemia at T60 and T120, with a statistically significant difference between the two moments. Animals in the Sat group showed an increase (P=0.0086) in hepatic steatosis compared to animals in the control group. The results obtained on the relationship between diet and metabolic changes are fundamental to ensure the understanding and appropriate treatment of these problems.

Simultaneous induction of systemic hyperglycaemia and stress impairs brain redox homeostasis in the adult zebrafish

For diabetic patients it is crucial to constantly monitor blood glucose levels to mitigate complications due to hyperglycaemia, including neurological issues and cognitive impairments. This activity leads to psychological stress, called "diabetes distress," a problem for most patients living with diabetes. Diabetes distress can exacerbate the hyperglycaemia effects on brain and negatively impact the quality of life, but the underlying mechanisms remain poorly explored. We simulated diabetes distress in adult zebrafish by modelling hyperglycaemia, through exposure to dextrose solution, along with chronic unpredictable mild stress (CUMS), and evaluated brain redox homeostasis by assessing reactive oxygen species (ROS) content, the antioxidant system, and effects on mitochondrial biogenesis and fission/fusion processes. We also evaluated the total, cytosolic and nuclear content of nuclear factor erythroid 2-related factor 2 (NRF2), a critical regulator of redox balance, in the whole brain and total NRF2 in specific brain emotional areas. The combined CUMS + Dextrose challenge, but not the individual treatments, reduced total NRF2 levels in the entire brain, but strongly increased its levels in the nuclear fraction. Compensatory upregulation of antioxidant genes appeared inadequate to combat elevated levels of ROS, leading to lowering of the reduced glutathione content and total antioxidant capacity. CUMS + Dextrose treatment also upregulated transcription factors implicated in mitochondrial biogenesis and dynamics with a predominance of fission, which is consistent with increased oxidative stress. In conclusion, this study highlights the close interplay between hyperglycaemia and psychological distress causing overriding oxidative stress in the brain, rendering the organism vulnerable to the development of disease complications.

Prophylactic zinc and therapeutic selenium administration in adult rats prevents long-term cognitive and behavioral sequelae by a transient ischemic attack

The transient hypoxic-ischemic attack, also known as a minor stroke, can result in long-term neurological issues such as memory loss, depression, and anxiety due to an increase in nitrosative stress. The individual or combined administration of chronic prophylactic zinc and therapeutic selenium is known to reduce nitrosative stress in the first seven days post-reperfusion and, due to an antioxidant effect, prevent cell death. Besides, zinc or selenium, individually administered, also causes antidepressant and anxiolytic effects. Therefore, this work evaluated whether combining zinc and selenium could prevent stroke-elicited cognition and behavior deficits after 30 days post-reperfusion. Accordingly, we assessed the expression of growth factors at 7 days post-reperfusion, a four-time course of memory (from 7 to 28 days post-learning test), and cell proliferation, depression, and anxiety-like behavior at 30 days post-reperfusion. Male Wistar rats with a weight between 190 and 240 g) were treated with chronic prophylactic zinc administration with a concentration of 0.2 mg/kg for 15 days before common carotid artery occlusion (10 min) and then with therapeutic selenium (6 μg/kg) for 7 days post-reperfusion. Compared with individual administrations, the administration combined of prophylactic zinc and therapeutic selenium decreased astrogliosis, increased growth factor expression, and improved cell proliferation and survival in two regions, the hippocampus, and cerebral cortex. These effects prevented memory loss, depression, and anxiety-like behaviors. In conclusion, these results demonstrate that the prophylactic zinc administration combined with therapeutic selenium can reduce the long-term sequelae caused by the transient ischemic attack. Significance statement. A minor stroke caused by a transient ischemic attack can result in psychomotor sequelae that affect not only the living conditions of patients and their families but also the economy. The incidence of these micro-events among young people has increased in the world. Nonetheless, there is no deep understanding of how this population group responds to regular treatments (Ekker and et al., 2018) [1]. On the basis that zinc and selenium have antioxidant, anti-inflammatory, and regenerative properties in stroke animal models, our work explored whether the chronic combined administration of prophylactic zinc and therapeutic selenium could prevent neurological sequelae in the long term in a stroke rat model of unilateral common carotid artery occlusion (CCAO) by 10-min. Our results showed that this combined treatment provided a long-term neuroprotective effect by decreasing astrogliosis, memory loss, anxiety, and depression-like behavior.

Diphenyl Diselenide Through Reduction of Inflammation, Oxidative Injury and Caspase-3 Activation Abates Doxorubicin-Induced Neurotoxicity in Rats

Neurotoxicity associated with chemotherapy is a debilitating side effect of cancer management in humans which reportedly involves inflammatory and oxidative stress responses. Diphenyl diselenide (DPDS) is an organoselenium compound which exhibits its anti-tumoral, anti-oxidant, anti-inflammatory and anti-mutagenic effects. Nevertheless, its possible effect on chemotherapy-induced neurotoxicity is not known. Using rat model, we probed the behavioral and biochemical effects accompanying administration of antineoplastic agent doxorubicin (7.5 mg/kg) and DPDS (5 and 10 mg/kg). Anxiogenic-like behavior, motor and locomotor insufficiencies associated with doxorubicin were considerably abated by both DPDS doses with concomitant enhancement in exploratory behavior as demonstrated by reduced heat maps intensity and enhanced track plot densities. Moreover, with exception of cerebral glutathione (GSH) level, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, biochemical data demonstrated reversal of doxorubicin-mediated decline in cerebral and cerebellar antioxidant status indices and the increase in acetylcholinesterase (AChE) activity by both doses of DPDS. Also, cerebellar and cerebral lipid peroxidation, hydrogen peroxide as well as reactive oxygen and nitrogen species levels were considerably diminished in rats administered doxorubicin and DPDS. In addition, DPDS administration abated myeloperoxidase activity, tumour necrosis factor alpha and nitric oxide levels along with caspase-3 activity in doxorubicin-administered rats. Chemoprotection of doxorubicin-associated neurotoxicity by DPDS was further validated by histomorphometry and histochemical staining. Taken together, DPDS through offsetting of oxido-inflammatory stress and caspase-3 activation elicited neuroprotection in doxorubicin-treated rats.

JM-20 potently prevents the onset of caffeine-induced anxiogenic phenotypes in zebrafish (Danio rerio)

Anxiety is among the most prevalent mental disorders present in the general population. Benzodiazepines are the most commonly prescribed drugs for the treatment of anxiety. Using zebrafish as a model organism, we investigated the anxiolytic activity of JM-20, a novel hybrid molecule with a 1,5-benzodiazepine ring fused to a dihydropyridine moiety. Firstly, we carried out some assays to analyze the possible toxicity mediated by JM-20. For this, zebrafish were exposed to different JM-20 concentrations (0-5 μM) for 96 h. Then, using the novel tank test, we evaluated both locomotor and anxiety-like behavior of the animals. Furthermore, brain, liver and plasma were removed to assess toxicity parameters. JM-20 exposure did not cause changes on novel tank, and also did not alter brain viability, hepatic LDH and plasma ALT levels. Afterward, we investigated whether a pre-exposure to JM-20 would prevent the anxiogenic effect evoked by caffeine. In the novel tank test, caffeine significantly decreased the time spent at the top, as well as the number of transitions to the top area. Moreover, caffeine decreased both the total and average time spent in the lit area, as well as increased the number of risk episodes evaluated by the light-dark test. Whole-body cortisol levels were also increased by caffeine exposure. Interestingly, pre-treatment with JM-20 abolished all alterations induced by caffeine. The anxiolytic effect profile of JM-20 was similar to those found for diazepam (positive control). Our findings show, for the first time, the anxiolytic effect of JM-20 in zebrafish, and its relationship with cortisol regulation.

Ebselen and Diphenyl Diselenide Inhibit SARS-CoV-2 Replication at Non-Toxic Concentrations to Human Cell Lines

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) was the causative agent of the COVID-19 pandemic, a global public health problem. Despite the numerous studies for drug repurposing, there are only two FDA-approved antiviral agents (Remdesivir and Nirmatrelvir) for non-hospitalized patients with mild-to-moderate COVID-19 symptoms. Consequently, it is pivotal to search for new molecules with anti-SARS-CoV-2 activity and to study their effects in the human immune system. Ebselen (Eb) is an organoselenium compound that is safe for humans and has antioxidant, anti-inflammatory, and antimicrobial properties. Diphenyl diselenide ((PhSe)₂) shares several pharmacological properties with Eb and is of low toxicity to mammals. Herein, we investigated Eb and (PhSe)₂ anti-SARS-CoV-2 activity in a human pneumocytes cell model (Calu-3) and analyzed their toxic effects on human peripheral blood mononuclear cells (PBMCs). Both compounds significantly inhibited the SARS-CoV-2 replication in Calu-3 cells. The EC₅₀ values for Eb and (PhSe)₂ after 24 h post-infection (hpi) were 3.8 µM and 3.9 µM, respectively, and after 48 hpi were 2.6 µM and 3.4 µM. These concentrations are safe for non-infected cells, since the CC₅₀ values found for Eb and (PhSe)₂ on Calu-3 were greater than 200 µM. Importantly, the concentration rates tested on viral replication were not toxic to human PBMCs. Therefore, our findings reinforce the efficacy of Eb and demonstrate (PhSe)₂ as a new candidate to be tested in future trials against SARS-CoV-2 infection/inflammation conditions.

Vitamin D Mitigates Hyperglycemia-Induced Cognition Decline in Danio rerio (Zebrafish) through the Activation of Antioxidant Mechanisms

Hyperglycemia contributes to the development of cognition impairment and related disorders, induces oxidative stress in neuronal cells; thereby, impairs normal signaling mechanisms involved in cognition processes. Studies have shown a significant decrease in the vitamin D in individuals with hyperglycemia and cognition impairment. But whether supplementing vitamin D has any beneficiary impact on mitigating hyperglycemia-induced cognition impairment is unknown. We have first tested the impact of hyperglycemia on the induction of cognition deficiency in a zebrafish model. Next, the molecular mechanisms related to oxidative stress, which are deregulated in hyperglycemic zebrafish brains, have been explored. Subsequently, the impact of supplementing the water with vitamin D and a known activator of nuclear factor erythroid-2 related factor 2 (Nrf2) i.e., sulforaphane (SFN) on learning and memory functions were assessed. We showed a significant increase in the oxidative stress in the brain tissue of zebrafish residing in hyperglycemic water (111 mM glucose). Addition of vitamin D and SFN increased Nrf2, but differentially modulated its target genes (NQO1, SOD, GPx etc) activity in zebrafish and neuronal cell lines thereby improved the hyperglycemia-induced decline of cognition impairment. Mechanistically, vitamin D binds to the Keap1 protein; thereby, interfering with its binding to Nrf2, which leads to the activation of antioxidant mechanisms in the cells. In summary, reducing the oxidative stress through vitamin D treatment is a possible option for controlling the cognition impairment in diabetic population, but studies testing this possibility in clinical trials are currently needed.

Zebrafish: A New Promise to Study the Impact of Metabolic Disorders on the Brain

Zebrafish has become a popular model to study many physiological and pathophysiological processes in humans. In recent years, it has rapidly emerged in the study of metabolic disorders, namely, obesity and diabetes, as the regulatory mechanisms and metabolic pathways of glucose and lipid homeostasis are highly conserved between fish and mammals. Zebrafish is also widely used in the field of neurosciences to study brain plasticity and regenerative mechanisms due to the high maintenance and activity of neural stem cells during adulthood. Recently, a large body of evidence has established that metabolic disorders can alter brain homeostasis, leading to neuro-inflammation and oxidative stress and causing decreased neurogenesis. To date, these pathological metabolic conditions are also risk factors for the development of cognitive dysfunctions and neurodegenerative diseases. In this review, we first aim to describe the main metabolic models established in zebrafish to demonstrate their similarities with their respective mammalian/human counterparts. Then, in the second part, we report the impact of metabolic disorders (obesity and diabetes) on brain homeostasis with a particular focus on the blood-brain barrier, neuro-inflammation, oxidative stress, cognitive functions and brain plasticity. Finally, we propose interesting signaling pathways and regulatory mechanisms to be explored in order to better understand how metabolic disorders can negatively impact neural stem cell activity.

Methylglyoxal disrupts the functionality of rat liver mitochondria

Methylglyoxal (MG) is a reactive metabolite derived from different physiological pathways. Its production can be harmful to cells via glycation reactions of lipids, DNA, and proteins. But, the effects of MG on mitochondrial functioning and bioenergetic responses are still elusive. Then, the effects of MG on key parameters of mitochondrial functionality were examined here. Isolated rat liver mitochondria were exposed to 0.1-10 mM of MG to determine its toxicity in the mitochondrial viability, membrane potential (Δψm), swelling and the superoxide (O2•-) production. Besides, mitochondrial oxidative phosphorylation parameters were analyzed by high-resolution respiratory (HRR) assay. In this set of experiments, routine state, PM state (pyruvate/malate), oxidative phosphorylation (OXPHOS), LEAK respiration, electron transport system (ETS) and oxygen residual (ROX) states were evaluated. HRR showed that PM state, OXPHOS CI-Linked, LEAK respiration, ETS CI/CII-Linked and ETS CII-Linked/ROX were significantly inhibited by MG exposure. MG also inhibited the complex II activity, and decreased Δψm and the viability of mitochondria. Taken together, our data indicates that MG is an inductor of mitochondrial dysfunctions and impairs important steps of respiratory chain, effects that can alter bioenergetics responses.

Short-term high-fat diet induces cognitive decline, aggression, and anxiety-like behavior in adult zebrafish

Obesity is a global health problem with high prevalence and defined by a high body mass index (BMI). Several comorbidities affecting the central nervous system (CNS) are associated with obesity (e.g., neurodegenerative diseases, cognitive deficit, and psychobehavioral disturbs). The zebrafish (Danio rerio) has been considered a suitable model organism to investigate the neurobehavioral features of various human diseases. Here, we verify the impact of a high-fat diet (HFD) on the CNS by specifically assessing the effects of short-term HFD on anxiety-like responses, aggression, social preference, and memory, which are essential behaviors for survival and reproduction. Animals were separated in three experimental groups. The standard diet group (SD) received 7.5 mg/fish of dry food, while HFD groups received 5 mg/fish dry food plus 7.5 (HFD-7.5) or 15 mg/fish (HFD-15) of chicken egg yolk daily. Dietary fat content (w/w) was approximately 6.5%, 16.9%, and 21.1%, respectively. We performed behavioral tests and morphometric analyses after two weeks of HFD. In comparison to SD animals, HFD groups showed typical obesogenic responses with increases in BMI, abdominal length, and body weight. HFD individuals also showed increased aggression and anxiety-like behaviors in the mirror-induced aggression and novel tank diving tests, respectively. Interestingly, HFD did not change the social preference behavior, mean swimming speed or spontaneous activity levels, while the HFD-15 group showed cognitive deficits in the inhibitory avoidance test. Collectively, this "proof-of-concept" study is the first report to characterize the effects of short-term HFD on different behavioral domains of zebrafish with high degree of face validity. Moreover, our data reinforce the growing utility of zebrafish to explore the neurobehavioral basis of obesity, providing clinically translatable data, complementing the existing rodent models and supporting future mechanistic studies.

Toxicology and pharmacology of synthetic organoselenium compounds: an update

Here, we addressed the pharmacology and toxicology of synthetic organoselenium compounds and some naturally occurring organoselenium amino acids. The use of selenium as a tool in organic synthesis and as a pharmacological agent goes back to the middle of the nineteenth and the beginning of the twentieth centuries. The rediscovery of ebselen and its investigation in clinical trials have motivated the search for new organoselenium molecules with pharmacological properties. Although ebselen and diselenides have some overlapping pharmacological properties, their molecular targets are not identical. However, they have similar anti-inflammatory and antioxidant activities, possibly, via activation of transcription factors, regulating the expression of antioxidant genes. In short, our knowledge about the pharmacological properties of simple organoselenium compounds is still elusive. However, contrary to our early expectations that they could imitate selenoproteins, organoselenium compounds seem to have non-specific modulatory activation of antioxidant pathways and specific inhibitory effects in some thiol-containing proteins. The thiol-oxidizing properties of organoselenium compounds are considered the molecular basis of their chronic toxicity; however, the acute use of organoselenium compounds as inhibitors of specific thiol-containing enzymes can be of therapeutic significance. In summary, the outcomes of the clinical trials of ebselen as a mimetic of lithium or as an inhibitor of SARS-CoV-2 proteases will be important to the field of organoselenium synthesis. The development of computational techniques that could predict rational modifications in the structure of organoselenium compounds to increase their specificity is required to construct a library of thiol-modifying agents with selectivity toward specific target proteins.

The pharmaceutical prednisone affects sheepshead minnow (Cyprinodon variegatus) metabolism and swimming performance

High usage of the synthetic glucocorticoids (GCs) has led to significant presence of this pharmaceutical group in surface waters where it can affect non-target organisms such as fish. Assessment of a fish's metabolism and swimming performance provide reliable sub-lethal measures of effects of GCs on oxygen-requiring processes and ability to swim. In this study, we determined time-dependent (7, 14 and 21 days) effects of the synthetic GC prednisone (1 μg L^-1) on sheepshead minnow (SHM) (Cyprinodon variegatus). Standard (SMR), routine (RMR) and maximum (MMR) metabolic rate, metabolic scope (MS), excess post-exercise oxygen consumption (EPOC), cost of transport (COT) and critical swimming speed (U_crit) were determined. Twenty-one days exposure to prednisone resulted in significantly higher SMR, RMR, MMR, MS, EPOC and COT compared with 7d and 14d prednisone fish. However, U_crit was not significantly different between prednisone and solvent control exposed fish (within 7d, 14d, 21d groups). SMR, RMR and MMR were lower in the 7d and 14d prednisone exposed fish compared with their solvent control groups. In contrast, SMR, RMR and MMR were all significantly higher in the 21d prednisone exposed fish compared with solvent control. EPOC was significantly higher in 14d prednisone exposed fish and trending higher in 21d and 7d prednisone exposed fish compared with their solvent controls. EPOC was significantly higher in 21d compared with 7d prednisone exposed fish. A significantly higher COT was seen in the 21d compared with 7d and 14d prednisone fish. Collectively, this study showed time-dependent effects of prednisone on SHM metabolism and swimming performance.

Methylglyoxal disturbs DNA repair and glyoxalase I system in Saccharomyces cerevisiae

Methylglyoxal (MG) is a highly reactive aldehyde able to form covalent adducts with proteins and nucleic acids, disrupting cellular functions. In this study, we performed a screening of Saccharomyces cerevisiae (S. cerevisiae) strains to find out which genes of cells are responsive to MG, emphasizing genes against oxidative stress and DNA repair. Yeast strains were grown in the YPD-Galactose medium containing MG (0.5 to 12 mM). The tolerance to MG was evaluated by determining cellular growth and cell viability. The toxicity of MG was more pronounced in the strains with deletion in genes engaged with DNA repair checkpoint proteins, namely Rad23 and Rad50. MG also impaired the growth and viability of S. cerevisiae mutant strains Glo1 and Gsh1, both components of the glyoxalase I system. Differently, the strains with deletion in genes encoding for antioxidant enzymes were apparently resistant to MG. In summary, our data indicate that DNA repair and MG detoxification pathways are keys in the control of MG toxicity in S. cerevisiae.

Modulation of redox and insulin signaling underlie the anti-hyperglycemic and antioxidant effects of diphenyl diselenide in zebrafish

The organic selenium compound diphenyl diselenide (DD) has been recognized as an antioxidant and neuroprotective agent, exerting an anti-hyperglycemic effect in experimental models of diabetes. However, the precise mechanisms involved in the protection are unclear. Using the zebrafish (Danio rerio) as a model organism, here we investigated biomarkers underlying the protective effects of DD against hyperglycemia, targeting in a transcriptional approach the redox and insulin-signaling pathway. Fish were fed on a diet containing DD (3 mg/kg) for 74 days. In the last 14 days, they were exposed to a 111 mM glucose solution to induce a hyperglycemic state. DD reduced blood glucose levels as well as normalized the brain mRNA transcription of four insulin receptors-coding genes (Insra1, Insra2, Insrb1, Insrb2), which were down-regulated by glucose. DD alone caused an up-regulation of relative mRNA transcription in both Insra receptors and glucose transporter 3 genes. DD counteracted hyperglycemia-induced lipid peroxidation, protein and thiol depletion. Along with the decreased activity of antioxidant enzymes SOD and GPx, the brain of hyperglycemic fish presented a reduction in mRNA transcription of FoxO3A, FoxO3B, Nrf2, GPx3A, SOD1, and SOD2 genes. Besides normalizing the transcriptional levels, DD caused an up-regulation of relative mRNAs that encode Nrf2, FoxO1A, FOXO3A, GPx4A, PTP1B, AKT and SelP. Collectively, our findings suggest that the antioxidant and anti-hyperglycemic actions of DD in a zebrafish diabetes model are likely associated with the regulation of the oxidative stress resistance and the insulin-signaling pathway and that could be related to the modulation at mRNA level of two important transcription factors, Nrf2 and FoxO.

Diphenyl diselenide dietary supplementation protects against fumonisin B1-induced oxidative stress in brains of the silver catfish Rhamdia quelen

The trend toward using plant-based ingredients in aquafeeds has raised important concerns for aquaculture owing to the negative impacts of mycotoxins on fish health; with emphasis for contamination by fumonisin B₁ (FB₁). The brain is an important target of FB₁; however, study of the pathways linked to brain damage is limited to an analysis of histopathological alterations. Reports have demonstrated the protective effects of dietary supplementation with diphenyl diselenide (Ph₂Se₂) in the brains of fish subjected to several environmental insults; nevertheless, its neuroprotective effects in fish fed with diets contaminated with FB₁ remain unknown. Therefore, the aim of this study was to evaluate whether oxidative damage may be a pathway associated with FB₁-induced neurotoxicity, as well as to evaluate whether dietary supplementation with Ph₂Se₂ prevents or reduces FB₁-mediated brain oxidative damage in silver catfish. Brain reactive oxygen species (ROS), lipid peroxidation (LOOH) and protein carbonylation increased on day 30 post-feeding in animals that received FB₁-contaminated diets compared to the control group, while brain antioxidant capacity against peroxyl radicals (ACAP) levels and catalase (CAT), glutathione peroxidase (GPx) and glutathione S-transferase (GST) activities were lower. Diphenyl diselenide dietary supplementation avoid increases in brain ROS levels, as well minimizing the augmentation of LOOH levels. Furthermore, Ph₂Se₂ prevented impairment of brain ACAP levels, as well as GPx and GST activities elicited by FB₁-contaminated diets. These data suggest that dietary supplementation with 3 mg/kg Ph₂Se₂ prevented FB₁-induced brain damage in silver catfish, and this protective effect occurred through avoided of excessive ROS production, as well as via prevention of brain lipid damage. Furthermore, Ph₂Se₂ exerted its neuroprotective effects via ameliorative effects on the enzymatic and non-enzymatic antioxidant defense systems, and may be an approach to prevent FB₁-induced brain oxidative stress; however, is not an alternative to prevent the impairment on performance caused by FB₁.

Protective role of diosgenin against hyperglycaemia-mediated cerebral ischemic brain injury in zebrafish model of type II diabetes mellitus

Impairment in glucose regulation is an indicatory effect capable of mediating multiple dysfunction such as cerebrovascular disorder with ischemia and brain damage inclusive. This study aims at investigating the glucose-lowering and neuroprotective capability of Diosgenin (DG) towards hyperglycemia-induced cerebral injury in a developed type 2 diabetes mellitus (T2DM) Zebrafish (ZF) model. T2DM was developed in ZF with 20 mg/kg body weight (b.w) multiple-low dose (MLD) Streptozotocin (STZ) for 28 days. Different doses of 20 mg/kg b.w (DG1) and 40 mg/kg b.w (DG2) DG was intraperitoneally administered twice in 7 days for a period of 28 days after T2DM was completely developed. Weight and behavioral changes were monitored and the catalytic activity including the plasma glucose level of diseased and treated ZF was spectrometrically estimated. Histopathological studies were employed to image the brain pathological condition during disease and treatment. SPSS was used as the statistical tool for result analysis and comparison of data obtained. STZ significantly (^###p < 0.001) induced hyperglycemia when compared to control as plasma glucose increases from 101.56 ± 4.52 mgdL⁻¹ to 175.87 ± 6.00 mg/dL. Our results have indicated a marked reduction in glucose concentration from a mean average of 175.87 ± 6.00 mgdL⁻¹ to 105.68 ± 4.48 mgdL⁻¹ and 82.06 ± 7.27 mgdL⁻¹ in DG 1 and DG 2 respectively. Catalytic activity significantly decreases (p < 0.05) from 206.42 ± 30.77 unit/mL to 123.85 ± 29.99 unit/mL at a minimum and maximum value of 103.21 and 275.23 in diseased ZF respectively. On DG treatment, catalytic activity significantly (p < 0.01) rise from 101.58 ± 11.29 and 130.73 ± 27.52 to 130.98 ± 17.13 and 255.96 ± 30.34 with DG1 and DG2 treatment respectively. Studies on the behavioral pattern of STZ-induced anxiolytic effect on ZF confirmed changes in the number of transitions and time spent in both Novel tank test (NTT) and Dark/light test (LDT). Histopathological analysis confirmed the cerebral cortex with inflammatory brain cells in the diseased condition and an attenuation of damage posed revealed in diseased state was largely reversed with DG. As compared to the normal control, a significant (^#p < 0.05 and ^###p < 0.001) changes in weight of fishes were recorded and DG1 and DG2 significantly promotes (***p < 0.001) body weight and improves the irregularities in weight of ZF during disease progression. Our study confirms that the potential of DG towards the management of hyperglycemia and hyperglycemia–mediated cerebral ischemic injury is through its blood glucose-lowering properties, anti-inflammatory activity, antioxidant effect, and anxiolytic capabilities.

High-glucose/high-cholesterol diet in zebrafish evokes diabetic and affective pathogenesis: The role of peripheral and central inflammation, microglia and apoptosis

Neuroinflammation and metabolic deficits contribute to the etiology of human affective disorders, such as anxiety and depression. The zebrafish (Danio rerio) has recently emerged as a powerful new model organism in CNS disease modeling. Here, we exposed zebrafish to 2% glucose and 10% cholesterol for 19 days to experimentally induce type 2 diabetes (DM) and to assess stress responses, microglia, inflammation and apoptosis. We analyzed zebrafish anxiety-like behavior in the novel tank and light-dark box (Days 15-16) tests, as well as examined their biochemical and genomic biomarkers (Day 19). Confirming DM-like state in zebrafish, we found higher whole-body glucose, triglyceride, total cholesterol, low-density lipoprotein levels and glucagon mRNA expression, and lower high-density lipoprotein levels. DM zebrafish also showed anxiety-like behavior, elevated whole-body cortisol and cytokines IFN-γ and IL-4, as well as higher brain mRNA expression of the glucocorticoid receptor, CD11b (a microglial biomarker), pro-inflammatory cytokines IL-6 and TNF-α (but not IL-1β or anti-inflammatory cytokines IL-4 and IL-10), GFAP (an astrocytal biomarker), neurotrophin BDNF, its receptors p75 and TrkB, as well as apoptotic Bax and Caspase-3 (but not BCl-2) genes. Collectively, this supports the overlapping nature of DM-related affective pathogenesis and emphasizes the role of peripheral and central inflammation and apoptosis in DM-related affective and neuroendocrine deficits in zebrafish.

Diphenyl diselenide modulates splenic purinergic signaling in silver catfish fed diets contaminated with fumonisin B1: An attempt to improve immune and hemostatic responses

The aim of this study was to determine whether purinergic signaling is a pathway associated with fumonisin B₁ (FB₁)-induced impairment of immune and hemostatic responses. We also determined whether dietary supplementation with diphenyl diselenide (Ph₂Se₂) prevents or reduces these effects. Splenic nucleoside triphosphate diphosphohydrolase (NTPDase) activity for adenosine triphosphate (ATP) and adenosine diphosphate (ADP) as substrates and total blood thrombocytes counts were significant lower in silver catfish fed with FB1-contaminated diets than in fish fed with a basal diet, while splenic adenosine deaminase (ADA) activity and metabolites of nitric oxide (NOx) levels were significant higher. Also, glutathione peroxidase (GPx) and superoxide dismutase (SOD) activities were significant lower in silver catfish fed with FB₁-contaminated diets than in fish fed with a basal diet. Dietary supplementation with 3 mg Ph₂Se₂/kg of feed effectively modulated splenic NTPDase (ATP as substrate), ADA, GPx and SOD activities, as well as NOx levels, and was partially effective in the modulation of spleen NTPDase activity (ADP as substrate) and total blood thrombocytes count. These data suggest that splenic purinergic signaling of silver catfish fed with FB₁-contaminated diets generates a pro-inflammatory profile that contributes to impairment of immune and inflammatory responses, via reduction of splenic ATP hydrolysis followed possible ATP accumulation in the extracellular environment. Reduction of ADP hydrolysis associated with possible accumulation in the extracellular environment can be a pathophysiological response that restricts the hemorrhagic process elicited by FB₁ intoxication. Supplementation with Ph₂Se₂ effectively modulated splenic enzymes associated with control of extracellular nucleotides (except ADP; that was partially modulated) and nucleosides, thereby limiting inflammatory and hemorrhagic processes.

Zebrafish models of diabetes-related CNS pathogenesis

Diabetes mellitus (DM) is a common metabolic disorder that affects multiple organ systems. DM also affects brain processes, contributing to various CNS disorders, including depression, anxiety and Alzheimer's disease. Despite active research in humans, rodent models and in-vitro systems, the pathogenetic link between DM and brain disorders remains poorly understood. Novel translational models and new model organisms are therefore essential to more fully study the impact of DM on CNS. The zebrafish (Danio rerio) is a powerful novel model species to study metabolic and CNS disorders. Here, we discuss how DM alters brain functions and behavior in zebrafish, and summarize their translational relevance to studying DM-related CNS pathogenesis in humans. We recognize the growing utility of zebrafish models in translational DM research, as they continue to improve our understanding of different brain pathologies associated with DM, and may foster the discovery of drugs that prevent or treat these diseases.

Animal models of major depressive disorder and the implications for drug discovery and development

INTRODUCTION

Depression is a highly debilitating psychiatric disorder that affects the global population and causes severe disabilities and suicide. Depression pathogenesis remains poorly understood, and the disorder is often treatment-resistant and recurrent, necessitating the development of novel therapies, models and concepts in this field. Areas covered: Animal models are indispensable for translational biological psychiatry, and markedly advance the study of depression. Novel approaches continuously emerge that may help untangle the disorder heterogeneity and unclear categories of disease classification systems. Some of these approaches include widening the spectrum of model species used for translational research, using a broader range of test paradigms, exploring new pathogenic pathways and biomarkers, and focusing more closely on processes beyond neural cells (e.g. glial, inflammatory and metabolic deficits). Expert opinion: Dividing the core symptoms into easily translatable, evolutionarily conserved phenotypes is an effective way to reevaluate current depression modeling. Conceptually novel approaches based on the endophenotype paradigm, cross-species trait genetics and 'domain interplay concept', as well as using a wider spectrum of model organisms and target systems will enhance experimental modeling of depression and antidepressant drug discovery.