Young Zebrafish Research Articles

Aging in zebrafish is associated with reduced locomotor activity and strain dependent changes in bottom dwelling and thigmotaxis.

Aging is associated with a wide range of physiological and behavioral changes in many species. Zebrafish, like humans, rodents, and birds, exhibits gradual senescence, and thus may be a useful model organism for identifying evolutionarily conserved mechanisms related to aging. Here, we compared behavior in the novel tank test of young (6-month-old) and middle aged (12-month-old) zebrafish from two strains (TL and TU) and both sexes. We find that this modest age difference results in a reduction in locomotor activity in male fish. We also found that background strain modulated the effects of age on predator avoidance behaviors related to anxiety: older female TL fish increased bottom dwelling whereas older male TU fish decreased thigmotaxis. Although there were no consistent effects of age on either short-term (within session) or long-term (next day) habituation to the novel tank, strain affected the habituation response. TL fish tended to increase their distance from the bottom of the tank whereas TU fish had no changes in bottom distance but instead tended to increase thigmotaxis. Our findings support the use of zebrafish for the study of how age affects locomotion and how genetics interacts with age and sex to alter exploratory and emotional behaviors in response to novelty.

Scalable Neuroanatomical and Behavioral Phenotyping of Radio Frequency Radiation on Young Zebrafish

Scalable Neuroanatomical and Behavioral Phenotyping of Radio Frequency Radiation on Young Zebrafish

Angptl4 gene expression as a marker of adaptive homeostatic response to social isolation across the lifespan in zebrafish

Social isolation has detrimental health effects, but the underlying mechanisms are unclear. Here, we investigated the impact of 2 weeks of isolation on behavior and gene expression in the central nervous system at different life stages of zebrafish. Results showed that socially deprived young adult zebrafish experienced increased anxiety, accompanied by changes in gene expression. Most gene expression patterns returned to normal within 24 hours of reintroduction to a social environment, except angptl4, which was upregulated after reintroduction, suggesting an adaptive mechanism. Similarly, aging zebrafish displayed heightened anxiety and increased central nervous system expression of angptl4 during isolation, but effects were reversed upon reintroduction to a social group. The findings imply that angptl4 plays a homeostatic role in response to social isolation, which varies across the lifespan. The study emphasizes the importance of social interactions for psychological well-being and highlights the negative consequences of isolation, especially in older individuals. Further research may unravel how social isolation affects angptl4 expression and its developmental and aging effects.

Surface Electrical Impedance Myography Detects Skeletal Muscle Atrophy in Aged Wildtype Zebrafish and Aged gpr27 Knockout Zebrafish.

Throughout a vertebrate organism's lifespan, skeletal muscle mass and function progressively decline. This age-related condition is termed sarcopenia. In humans, sarcopenia is associated with risk of falling, cardiovascular disease, and all-cause mortality. As the world population ages, projected to reach 2 billion older adults worldwide in 2050, the economic burden on the healthcare system is also projected to increase considerably. Currently, there are no pharmacological treatments for sarcopenia, and given the long-term nature of aging studies, high-throughput chemical screens are impractical in mammalian models. Zebrafish is a promising, up-and-coming vertebrate model in the field of sarcopenia that could fill this gap. Here, we developed a surface electrical impedance myography (sEIM) platform to assess skeletal muscle health, quantitatively and noninvasively, in adult zebrafish (young, aged, and genetic mutant animals). In aged zebrafish (~85% lifespan) as compared to young zebrafish (~20% lifespan), sEIM parameters (2 kHz phase angle, 2 kHz reactance, and 2 kHz resistance) robustly detected muscle atrophy (p < 0.000001, q = 0.000002; p = 0.000004, q = 0.000006; p = 0.000867, q = 0.000683, respectively). Moreover, these same measurements exhibited strong correlations with an established morphometric parameter of muscle atrophy (myofiber cross-sectional area), as determined by histological-based morphometric analysis (r = 0.831, p = 2 × 10-12; r = 0.6959, p = 2 × 10-8; and r = 0.7220; p = 4 × 10-9, respectively). Finally, the genetic deletion of gpr27, an orphan G-protein coupled receptor (GPCR), exacerbated the atrophy of skeletal muscle in aged animals, as evidenced by both sEIM and histology. In conclusion, the data here show that surface EIM techniques can effectively discriminate between healthy young and sarcopenic aged muscle as well as the advanced atrophied muscle in the gpr27 KO animals. Moreover, these studies show how EIM values correlate with cell size across the animals, making it potentially possible to utilize sEIM as a "virtual biopsy" in zebrafish to noninvasively assess myofiber atrophy, a valuable measure for muscle and gerontology research.

Electrical impedance myography detects age-related skeletal muscle atrophy in adult zebrafish

Age-related deficits in skeletal muscle function, termed sarcopenia, are due to loss of muscle mass and changes in the intrinsic mechanisms underlying contraction. Sarcopenia is associated with falls, functional decline, and mortality. Electrical impedance myography (EIM)—a minimally invasive, rapid electrophysiological tool—can be applied to animals and humans to monitor muscle health, thereby serving as a biomarker in both preclinical and clinical studies. EIM has been successfully employed in several species; however, the application of EIM to the assessment of zebrafish—a model organism amenable to high-throughput experimentation—has not been reported. Here, we demonstrated differences in EIM measures between the skeletal muscles of young (6 months of age) and aged (33 months of age) zebrafish. For example, EIM phase angle and reactance at 2 kHz showed significantly decreased phase angle (5.3 ± 2.1 versus 10.7 ± 1.5°; p = 0.001) and reactance (89.0 ± 3.9 versus 172.2 ± 54.8 ohms; p = 0.007) in aged versus young animals. Total muscle area, in addition to other morphometric features, was also strongly correlated to EIM 2 kHz phase angle across both groups (r = 0.7133, p = 0.01). Moreover, there was a strong correlation between 2 kHz phase angle and established metrics of zebrafish swimming performance, including turn angle, angular velocity, and lateral motion (r = 0.7253, r = 0.7308, r = 0.7857, respectively, p < 0.01 for all). In addition, the technique was shown to have high reproducibility between repeated measurements with a mean percentage difference of 5.34 ± 1.17% for phase angle. These relationships were also confirmed in a separate replication cohort. Together, these findings establish EIM as a fast, sensitive method for quantifying zebrafish muscle function and quality. Moreover, identifying the abnormalities in the bioelectrical properties of sarcopenic zebrafish provides new opportunities to evaluate potential therapeutics for age-related neuromuscular disorders and to interrogate the disease mechanisms of muscle degeneration.

Beneficial Effect of Vitamin D on Non-Alcoholic Fatty Liver Disease (NAFLD) Progression in the Zebrafish Model

A major cause of chronic liver disease, cirrhosis, and hepatocellular carcinoma, non-alcoholic fatty liver disease (NAFLD) results from excessive liver fat accumulation. Vitamin D (VitD) plays multiple important roles in diverse physiologic processes. Here, we describe the role of VitD in the complex pathogenesis of NAFLD and explore the possible therapeutic role of VitD supplementation in NAFLD therapy. To compare the effect of VitD to other interventions such as low-calorie diet, we induced NAFLD in young adult zebrafish (Danio rerio, AB strain) and monitored the effects of VitD supplementation on the disease course. The zebrafish administered with high-dose VitD (1.25 μg) had significantly reduced liver fat compared to those that received low-dose VitD (0.049 μg) or caloric restriction. Gene expression analysis revealed that VitD downregulated several pathways that may play a role in NAFLD etiology, which affected fatty acid metabolism, vitamins and their cofactors, ethanol oxidation, and glycolysis. The pathway analysis revealed that the cholesterol biosynthesis pathway and the isoprenoid biosynthetic process pathway were significantly upregulated whereas the small molecule catabolic process pathway significantly downregulated following the exposure of NAFLD zebrafish model to high VitD dose. Therefore, our findings suggest the association of novel biochemical pathways with NAFLD and highlight the potential of VitD supplementation to reverse the severity of NAFLD, especially in younger people.

Zebrafish Sexual Behavior in Plain and Enriched Environments: Parameters in the Valproate Model of Autism

Autism is a complex alteration in children’s developing nervous system that manifests in behavioral patterns that do not match those of typical subjects. Moreover, starting at puberty, these children may encounter problems regarding social interaction related to sexual encounters. As studies are scarce, we used the valproate model of autism in the zebrafish to contribute to the knowledge related to sexual behavior in this disorder. Young zebrafish were reproduced, embryos collected, and organized in groups of control or treated with valproic acid, as the autism model. Sexual behavior was recorded in fish from these embryos as they became sexually active. The results show that the zebrafish’s sexual behavior is organized into appetitive, preconsummatory, and consummatory behaviors, as in other vertebrates. In the autism model, the patterns of sexual behavior are present but with significant modifications. The behavior of males was the most affected, while in females, the most affected parameter was oviposition. These results show that, in the autism model of zebrafish, sexual behavior is not suppressed, but it seems that critical changes occur in the neuroendocrine system that reduces reproductive success. Furthermore, the enriched environment was beneficial in maintaining the consummatory behaviors of females and males with autism-like behaviors.

Caloric restriction reinforces the stem cell pool in the aged brain without affecting overall proliferation status

Overfeeding (OF) and obesity increase the risk for brain aging and neurodegenerative diseases due to increased oxidative stress and neuroinflammation, which likely contribute to cellular dysfunction. In contrast, caloric restriction (CR) is an intervention known for its effects on extending both life- and health-span. In the current study, the effects on the aging brain of two short-term feeding regimens, OF and CR, were investigated. We applied these diets for 12 weeks to both young and aged zebrafish. We performed protein and mRNA level analysis to examine diet-mediated effects on any potential age-related alterations in the brain. Markers implicated in the regulation of brain aging, cell cycle, proliferation, inflammation, and cytoskeleton were analyzed. The most prominent result observed was a downregulation in the expression levels of the stem cell marker, Sox2, in CR-fed animals as compared to OF-fed fish. Furthermore, our data highlighted significant age-related downregulations in Tp53, Myca, and L-plastin levels. The multivariate analyses of all datasets suggested that as opposed to OF, the adaptive mechanisms increasing lifespan via CR are likely exerting their effects by reinforcing the stem cell pool and downregulating inflammation. The data reveal important therapeutic targets with respect to the state of nutrient uptake for the slowing down of the detrimental effects of aging, resulting in a healthy and extended lifespan, as well as lowering the risk for neurodegenerative disease.

Early life exposure to chronic unpredictable stress induces anxiety-like behaviors and increases the excitability of cerebellar neurons in zebrafish

Anxiety is a common emotional disorder in children. To understand its underlying mechanisms, chronic unpredictable stress (CUS) has been established as a stress model in zebrafish. By using the tall tank test, the stress response reliability could be improved in adult fish which has not been confirmed in larvae. In addition, the increasing evidences have shown that cerebellum plays important roles in anxiety. Whether CUS will affect cerebellar neuronal activity remains unknown. We found that CUS exposure to larvae (from 10 to 17 days post fertilization) induced anxiety-like behaviors and social cohesion impairments within 1–2 d after CUS, including a prolonged freezing time, an increased time spent at the bottom of tank, an increased thigmotaxis index, and an increased interindividual distance. Our results showed that the four behavioral tests were homogeneous, especially the tall tank test either anxiety-like behaviors or the basal locomotion. Furthermore, we found that CUS enhanced the excitability of cerebellar neurons, as the amplitude, frequency, time to peak and half-width of spontaneous firing significantly decreased, as well as the amplitude of excitatory post-synaptic current when compared with the control group. CUS also activated hyperpolarization-activated cyclic nucleotide-gated and potassium channels of cerebellar neurons. Multiple linear regression analysis showed that the total distance in bottom (tall tank test) was correlated positively with outward Na+-K+ currents (r = 0.848, P = 0.016), and the thigmotaxis index (open field test) correlated with action potential amplitude (r = 0.854, P = 0.030). Altogether, early life CUS transiently induced an anxiety-like behavior which could be more accurately assessed by combining the tall tank test with other behavior tests in young zebrafish. CUS increased the excitability of cerebellar neurons might provide new targets to treat emotional diseases such as anxiety.

A scalable assay for chemical preference of small freshwater fish.

Sensing the chemical world is of primary importance for aquatic organisms, and small freshwater fish are increasingly used in toxicology, ethology, and neuroscience by virtue of their ease of manipulation, tissue imaging amenability, and genetic tractability. However, precise behavioral analyses are generally challenging to perform due to the lack of knowledge of what chemical the fish are exposed to at any given moment. Here we developed a behavioral assay and a specific infrared dye to probe the preference of young zebrafish for virtually any compound. We found that the innate aversion of zebrafish to citric acid is not mediated by modulation of the swim but rather by immediate avoidance reactions when the product is sensed and that the preference of juvenile zebrafish for ATP changes from repulsion to attraction during successive exposures. We propose an information-based behavioral model for which an exploration index emerges as a relevant behavioral descriptor, complementary to the standard preference index. Our setup features a high versatility in protocols and is automatic and scalable, which paves the way for high-throughput preference compound screening at different ages.

Young fecal transplantation mitigates the toxicity of perfluorobutanesulfonate and potently refreshes the reproductive endocrine system in aged recipients

The aging process leads to the gradual impairment of physiological functions in the elderly, making them more susceptible to the toxicity of environmental pollutants. In this study, aged zebrafish were first transplanted with the feces from young donors and subsequently exposed to perfluorobutanesulfonate (PFBS), an emerging persistent toxic pollutant. The interaction between young fecal transplant and PFBS inherent toxicity was investigated, focusing on reproductive performance and the underlying endocrine mechanism. The results showed that PFBS single exposure increased the percentage of primary oocytes in aged ovaries, implying a blockage of oogenesis. However, transplantation of young feces completely abolished the effects of PFBS and promoted oocyte growth, as inferred by the obviously lower percentage of primary oocytes, accompanied by a higher percentage of cortical-alveolar oocytes. Measurement of sex hormones found that PFBS significantly increased the blood concentration of estradiol and disrupted the balance of sex hormones in the elderly, which were, however, efficiently ameliorated by young fecal transplantation. Based on gene transcription along the hypothalamic-pituitary-gonadal axis, hierarchical clustering analysis showed similar profiles of the reproductive endocrine system between young zebrafish and their aged counterparts transplanted with young feces, implying that young fecal transplantation might refresh the endocrine system of aged recipients, regardless of PFBS exposure. The increased transcription levels of mRNAs encoding vitellogenin, activinBA, and membrane bound progestin receptors would cooperatively enhance the growth and maturation of oocytes in the ovaries of aged zebrafish receiving young fecal transplantation. Overall, the findings highlighted the potent efficacy of young fecal transplantation to improve the reproductive function of the elderly and to mitigate the endocrine disruption of an environmental pollutant. These findings are expected to broaden our understanding of the efficacy, mechanisms, and application of fecal transplantation.

A subset of gut leukocytes has telomerase-dependent “hyper-long” telomeres and require telomerase for function in zebrafish

BackgroundTelomerase, the enzyme capable of elongating telomeres, is usually restricted in human somatic cells, which contributes to progressive telomere shortening with cell-division and ageing. T and B-cells cells are somatic cells that can break this rule and can modulate telomerase expression in a homeostatic manner. Whereas it seems intuitive that an immune cell type that depends on regular proliferation outbursts for function may have evolved to modulate telomerase expression it is less obvious why others may also do so, as has been suggested for macrophages and neutrophils in some chronic inflammation disease settings. The gut has been highlighted as a key modulator of systemic ageing and is a key tissue where inflammation must be carefully controlled to prevent dysfunction. How telomerase may play a role in innate immune subtypes in the context of natural ageing in the gut, however, remains to be determined.ResultsUsing the zebrafish model, we show that subsets of gut immune cells have telomerase-dependent”hyper-long” telomeres, which we identified as being predominantly macrophages and dendritics (mpeg1.1+ and cd45+mhcII+). Notably, mpeg1.1+ macrophages have much longer telomeres in the gut than in their haematopoietic tissue of origin, suggesting that there is modulation of telomerase in these cells, in the gut. Moreover, we show that a subset of gut mpeg1.1+ cells express telomerase (tert) in young WT zebrafish, but that the relative proportion of these cells decreases with ageing. Importantly, this is accompanied by telomere shortening and DNA damage responses with ageing and a telomerase-dependent decrease in expression of autophagy and immune activation markers. Finally, these telomerase-dependent molecular alterations are accompanied by impaired phagocytosis of E. coli and increased gut permeability in vivo.ConclusionsOur data show that limiting levels of telomerase lead to alterations in gut immunity, impacting on the ability to clear pathogens in vivo. These are accompanied by increased gut permeability, which, together, are likely contributors to local and systemic tissue degeneration and increased susceptibility to infection with ageing.Graphical

Variability in fecal metabolome depending on age, PFBS pollutant, and fecal transplantation in zebrafish: A non-invasive diagnosis of health

To protect the wellbeing of research animals, certain non-invasive measures are in increasing need to facilitate an early diagnosis of health and toxicity. In this study, feces specimen was collected from adult zebrafish to profile the metabolome fingerprint. Variability in fecal metabolite composition was also distinguished as a result of aging, perfluorobutanesulfonate (PFBS) toxicant, and fecal transplantation. The results showed that zebrafish feces was very rich in a diversity of metabolites that belonged to several major classes, including lipid, amino acid, carbohydrate, vitamin, steroid hormone, and neurotransmitter. Fecal metabolites had functional implications to multiple physiological activities, which were characterized by the enrichment of digestion, absorption, endocrine, and neurotransmission processes. The high richness and functional involvement of fecal metabolites pinpointed feces as an abundant source of diagnostic markers. By comparison between young and aged zebrafish, fundamental modifications of fecal metabolomes were caused by aging progression, centering on the neuroactive ligand-receptor interaction pathway. Exposure of aged zebrafish to PFBS pollutant also significantly disrupted the metabolomic structure in feces. Of special concern were the changes in fecal hormone intermediates after PFBS exposure, which was concordant with the in vivo endocrine disrupting effects of PFBS. Furthermore, it was intriguing that transplantation of young zebrafish feces efficiently mitigated the metabolic perturbation of PFBS in aged recipients, highlighting the health benefits of therapeutic strategies based on gut microbiota manipulation. In summary, the present study provides preliminary clues to evidence the non-invasive advantage of fecal metabolomics in the early diagnosis and prediction of physiology and toxicology.

Age-Dependent Effects of Chronic Stress on Zebrafish Behavior and Regeneration.

Stress can have a significant impact on many aspects of an organism’s physiology and behavior. However, the relationship between stress and regeneration, and how this relationship changes with age remains poorly understood. Here, we subjected young and old zebrafish to a chronic stress protocol and evaluated the impact of stress exposure on multiple measures of zebrafish behavior, specifically thigmotaxis (open field test) and scototaxis (light/dark preference test), and on regeneration ability after partial tail amputation. We found evidence that young and older adult fish are differentially impacted by stress. Only young fish showed a significant change in anxiety-like behaviors after being exposed to chronic stress, while their regeneration ability was not affected by the stress protocol. On the other hand, older fish regenerated their caudal fin significantly slower compared to young fish, but their behavior remained unaffected after being exposed to stress. We further investigated the expression of two candidate genes (nlgn1 and sam2) expressed in the central nervous system, and known to be associated with stress and anxiety-like behavior. The expression of stress-related gene candidate sam2 increased in the brain of older individuals exposed to stress. Our results suggest there is a close relationship between chronic stress, regeneration, and behavior in zebrafish (Danio rerio), and that the impact of stress is age-dependent.

Technologies bringing young Zebrafish from a niche field to the limelight

Fundamental life science and pharmaceutical research are continually striving to provide physiologically relevant context for their biological studies. Zebrafish present an opportunity for high-content screening (HCS) to bring a true in vivo model system to screening studies. Zebrafish embryos and young larvae are an economical, human-relevant model organism that are amenable to both genetic engineering and modification, and direct inspection via microscopy. The use of these organisms entails unique challenges that new technologies are overcoming, including artificial intelligence (AI). In this perspective article, we describe the state-of-the-art in terms of automated sample handling, imaging, and data analysis with zebrafish during early developmental stages. We highlight advances in orienting the embryos, including the use of robots, microfluidics, and creative multi-well plate solutions. Analyzing the micrographs in a fast, reliable fashion that maintains the anatomical context of the fluorescently labeled cells is a crucial step. Existing software solutions range from AI-driven commercial solutions to bespoke analysis algorithms. Deep learning appears to be a critical tool that researchers are only beginning to apply, but already facilitates many automated steps in the experimental workflow. Currently, such work has permitted the cellular quantification of multiple cell types in vivo, including stem cell responses to stress and drugs, neuronal myelination and macrophage behavior during inflammation and infection. We evaluate pro and cons of proprietary versus open-source methodologies for combining technologies into fully automated workflows of zebrafish studies. Zebrafish are poised to charge into HCS with ever-greater presence, bringing a new level of physiological context.

Analysis of transcribed sequences from young and mature zebrafish thrombocytes.

The zebrafish is an excellent model system to study thrombocyte function and development. Due to the difficulties in separating young and mature thrombocytes, comparative transcriptomics between these two cell types has not been performed. It is important to study these differences in order to understand the mechanism of thrombocyte maturation. Here, we performed single-cell RNA sequencing of the young and mature zebrafish thrombocytes and compared the two datasets for young and mature thrombocyte transcripts. We found a total of 9143 genes expressed cumulatively in both young and mature thrombocytes, and among these, 72% of zebrafish thrombocyte-expressed genes have human orthologs according to the Ensembl human genome annotation. We also found 397 uniquely expressed genes in young and 2153 uniquely expressed genes in mature thrombocytes. Of these 397 and 2153 genes, 272 and 1620 corresponded to human orthologous genes, respectively. Of all genes expressed in both young and mature thrombocytes, 4224 have been reported to be expressed in human megakaryocytes, and 1603 were found in platelets. Among these orthologs, 156 transcription factor transcripts in thrombocytes were found in megakaryocytes and 60 transcription factor transcripts were found in platelets including a few already known factors such as Nfe2 and Nfe212a (related to Nfe2) that are present in both megakaryocytes, and platelets. These results indicate that thrombocytes have more megakaryocyte features and since platelets are megakaryocyte fragments, platelets also appear to be thrombocyte equivalents. In conclusion, our study delineates the differential gene expression patterns of young and mature thrombocytes, highlighting the processes regulating thrombocyte maturation. Future knockdown studies of these young and mature thrombocyte-specific genes are feasible and will provide the basis for understanding megakaryocyte maturation.

The psychoactive effects of Bryophyllum pinnatum (Lam.) Oken leaves in young zebrafish.

Bryophyllum pinnatum (Lam.) Oken (BP) is a plant that is used worldwide to treat inflammation, infections, anxiety, restlessness, and sleep disorders. While it is known that BP leaves are rich in flavonoids, the extent of the beneficial and toxic effects of its crude extracts remains unclear. Although some neurobehavioral studies using leaf extracts have been conducted, none has examined the effects of water-extracted leaf samples. The zebrafish is a powerful animal model used to gain insights into the efficacy and toxicity profiles of this plant due to its high fecundity, external development, and ease of performing behavioral assays. In this study, we performed behavioral testing after acute exposure to different concentrations of aqueous extract from leaves of B. pinnatum (LABP) on larval zebrafish, investigating light/dark preference, thigmotaxis, and locomotor activity parameters under both normal and stressed conditions. LABP demonstrated dose-and time-dependent biphasic effects on larval behavior. Acute exposure (25 min) to 500 mg/L LABP resulted in decreased locomotor activity. Exposure to 300 mg/L LABP during the sleep cycle decreased dark avoidance and thigmotaxis while increasing swimming velocity. After sleep deprivation, the group treated with 100 mg/L LABP showed decreased dark avoidance and increased velocity. After a heating stressor, the 30 mg/L and 300 mg/L LABP-treated groups showed decreased dark avoidance. These results suggest both anxiolytic and psychoactive effects of LABP in a dose-dependent manner in a larval zebrafish model. These findings provide a better understanding of the mechanisms underlying relevant behavioral effects, consequently supporting the safe and effective use of LABP for the treatment of mood disorders.

Nanoscale Structural Characterization and Impact on Long-term memory of Amyloid-β42 Oligomeric forms in Zebrafish

The contribution of amyloid-β (Aβ) soluble forms to Alzheimer's Disease (AD) is undergoing revision and the characterization of monomeric, oligomeric and protofibrillar Aβ forms used in vivo to model AD is a critical step to ensure data interpretation. Atomic force microscopy (AFM) was used to characterize the nanoscale morphology of different Aβ42 forms also used for cerebroventricular injection (cvi) in young (6mo) and aged (36mo) adult zebrafish behavioral and cognitive tests. On the AFM, monomeric solution deposited onto mica resulted mostly in thin filamentous structures and shorter monomeric agglomerates with heights around or below 1.5 nm, as expected for single Aβ42. The oligomeric form was dominated by particles with globular morphology and a few short aggregates around 1 nm high and 8–12 nm long. The protofibrillar form had micrometer-long twisted fibrils of varying diameters (4.5–10 nm) and large entangled clusters with sizes of up to several tens of micrometers. On the Open Tank used to test exploratory parameters, no differences were observed between injected animals and their age-matched controls, except for a reduced distance travelled by aged individuals that received the Aβ42 oligomeric form. Long-term memory (LTM) for the inhibitory avoidance task was not influenced by monomers cvi, whilst oligomeric and fibrillar Aβ42 hindered LTM formation in young and aged groups. Our findings support current views of deleterious effects of Aβ42 soluble forms on cognition and ensures that preparations were structurally unique and within expected morphologies and dimensions.

Zebrafish obesogenic test identifies anti-adipogenic fraction in Moringa oreifera leaf extracts.

The zebrafish obesogenic test (ZOT) is a powerful tool for identifying anti‐adipogenic compounds for in vivo screening. In our previous study, we found that Moringa oleifera (MO) leaf powder suppressed the accumulation of visceral adipose tissue (VAT) in ZOT. MO demonstrates a wide range of pharmacological effects; however, little is known about its functional constituents. To identify the anti‐adipogenic components of MO leaves, we prepared extracts using different extraction methods and tested the obtained extracts and fractions using ZOT. We found that the dichloromethane extract and its hexane:EtOAc = 8:2 fraction reduced VAT accumulation in young zebrafish fed a high‐fat diet. We also performed gene expression analysis in the zebrafish VAT and found that CCAAT/enhancer‐binding protein beta and CCAAT/enhancer‐binding protein delta (associated with early stages of adipogenesis) gene expression was downregulated after fraction 2 administration. We identified a new MO fraction that suppressed VAT accumulation by inhibiting early adipogenesis using the ZOT. Phenotype‐driven zebrafish screening is a reasonable strategy for identifying bioactive components in natural products.

Fecal transplantation from young zebrafish donors efficiently ameliorates the lipid metabolism disorder of aged recipients exposed to perfluorobutanesulfonate

Aging is a biological process that is accompanied by the gradual loss of physiological functions. Under the context of ubiquitous and persistent environmental pollution, the elderly will be more vulnerable to the detrimental effects of toxic pollutants than the young. With objectives to explore effective measures to ameliorate the double stress of aging and toxicants, the present study transplanted the feces from young zebrafish donors to aged recipients, which were concurrently exposed to perfluorobutanesulfonate (PFBS), an emerging environmental pollutant of international concern. After exposure, growth, hepatic structural organization, and lipid metabolism were examined. The results showed that, irrespective of PFBS toxicity, transplantation of young feces significantly enhanced the growth of the aged. In the livers of aged and PFBS-exposed zebrafish, vacuolization symptom was prevalently observed, while young fecal transplantation alleviated the structural defects in aged livers. In the gut of the elderly, digestive activity of lipids was promoted after the transplantation of young feces. The blood of the aged females accumulated significantly higher concentration of triglyceride (TG) than the young counterparts (2.6-fold), implying that the elderly were at high risk of cardiovascular diseases. PFBS treatment of the aged further increased blood TG levels by 2.0-fold relative to the aged control group, pointing to the aggravation of the health of the elderly by environmental pollution. However, it is intriguing that young fecal transplantation efficiently inhibited the metabolic toxicity of PFBS and restored the normal level of blood TG, which provided more evidence about the benefit of young fecal transplant to improve the health of the aged individuals. In the aged livers transplanted with young feces, mitochondrial β-oxidation of fatty acids was consistently activated. Overall, the present study verified the efficacy of young fecal transplantation to mitigate the metabolic disorders resulting from aging and an environmental pollutant.