Astaxanthin supplementation enhances adult hippocampal neurogenesis and spatial memory in mice

A marine-derived antioxidant astaxanthin as a potential neuroprotective and neurotherapeutic agent: A review of its efficacy on neurodegenerative conditions

Astaxanthin is a potent lipid-soluble carotenoid produced by several different freshwater and marine microorganisms, including microalgae, bacteria, fungi, and yeast. The proven therapeutic effects of astaxanthin against different diseases have made this carotenoid popular in the nutraceutical market and among consumers. Recently, astaxanthin is also receiving attention for its effects in the co-adjuvant treatment or prevention of neurological pathologies. In this systematic review, studies evaluating the efficacy of astaxanthin against different neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, cerebrovascular diseases, and spinal cord injury are analyzed. Based on the current literature, astaxanthin shows potential biological activity in both in vitro and in vivo models. In addition, its preventive and therapeutic activities against the above-mentioned diseases have been emphasized in studies with different experimental designs. In contrast, none of the 59 studies reviewed reported any safety concerns or adverse health effects as a result of astaxanthin supplementation. The preventive or therapeutic role of astaxanthin may vary depending on the dosage and route of administration. Although there is a consensus in the literature regarding its effectiveness against the specified diseases, it is important to determine the safe intake levels of synthetic and natural forms and to determine the most effective forms for oral intake.

Effect of astaxanthin in type-2 diabetes -induced APPxhQC transgenic and NTG mice

OBJECTIVES

Aggregation and misfolding of amyloid beta (Aβ) and tau proteins, suggested to arise from post-translational modification processes, are thought to be the main cause of Alzheimer's disease (AD). Additionally, a plethora of evidence exists that links metabolic dysfunctions such as obesity, type 2 diabetes (T2D), and dyslipidemia to the pathogenesis of AD. We thus investigated the combinatory effect of T2D and human glutaminyl cyclase activity (pyroglutamylation), on the pathology of AD and whether astaxanthin (ASX) treatment ameliorates accompanying pathophysiological manifestations.

METHODS

Male transgenic AD mice, APPxhQC, expressing human APP751 with the Swedish and the London mutation and human glutaminyl cyclase (hQC) enzyme and their non-transgenic (NTG) littermates were used. Both APPxhQC and NTG mice were allocated to 3 groups, control, T2D-control, and T2D-ASX. Mice were fed control or high fat diet ± ASX for 13 weeks starting at an age of 11-12 months. High fat diet fed mice were further treated with streptozocin for T2D induction. Effects of genotype, T2D induction, and ASX treatment were evaluated by analysing glycemic readouts, lipid concentration, Aβ deposition, hippocampus-dependent cognitive function and nutrient sensing using immunosorbent assay, ELISA-based assays, western blotting, immunofluorescence staining, and behavioral testing via Morris water maze (MWM), respectively.

RESULTS

APPxhQC mice presented a higher glucose sensitivity compared to NTG mice. T2D-induced brain dysfunction was more severe in NTG compared to the APPxhQC mice. T2D induction impaired memory functions while increasing hepatic LC3B, ABCA1, and p65 levels in NTG mice. T2D induction resulted in a progressive shift of Aβ from the soluble to insoluble form in APPxhQC mice. ASX treatment reversed T2D-induced memory dysfunction in NTG mice and in parallel increased hepatic pAKT while decreasing p65 and increasing cerebral p-S6rp and p65 levels. ASX treatment reduced soluble Aβ38 and Aβ40 and insoluble Aβ40 levels in T2D-induced APPxhQC mice.

CONCLUSIONS

We demonstrate that T2D induction in APPxhQC mice poses additional risk for AD pathology as seen by increased Aβ deposition. Although ASX treatment reduced Aβ expression in T2D-induced APPxhQC mice and rescued T2D-induced memory impairment in NTG mice, ASX treatment alone may not be effective in cases of T2D comorbidity and AD.

The changes of neurogenesis in the hippocampal dentate gyrus of SAMP8 mice and the effects of acupuncture and moxibustion

BACKGROUND

Influenced by the global aging population, the incidence of Alzheimer's disease (AD) has increased sharply. In addition to increasing β-amyloid plaque deposition and tau tangle formation, neurogenesis dysfunction has recently been observed in AD. Therefore, promoting regeneration to improve neurogenesis and cognitive dysfunction can play an effective role in AD treatment. Acupuncture and moxibustion have been widely used in the clinical treatment of neurodegenerative diseases because of their outstanding advantages such as early, functional, and benign two-way adjustment. It is urgent to clarify the effectiveness, greenness, and safety of acupuncture and moxibustion in promoting neurogenesis in AD treatment.

METHODS

Senescence-accelerated mouse prone 8 (SAMP8) mice at various ages were used as experimental models to simulate the pathology and behaviors of AD mice. Behavioral experiments, immunohistochemistry, Western blot, and immunofluorescence experiments were used for comparison between different groups.

RESULTS

Acupuncture and moxibustion could increase the number of PCNA+ DCX+ cells, Nissl bodies, and mature neurons in the hippocampal Dentate gyrus (DG) of SAMP8 mice, restore the hippocampal neurogenesis, delay the AD-related pathological presentation, and improve the learning and memory abilities of SAMP8 mice.

CONCLUSION

The pathological process underlying AD and cognitive impairment were changed positively by improving the dysfunction of neurogenesis. This indicates the promising role of acupuncture and moxibustion in the prevention and treatment of AD.

Dietary Astaxanthin: A Promising Antioxidant and Anti-Inflammatory Agent for Brain Aging and Adult Neurogenesis

Decreased adult neurogenesis, or the gradual depletion of neural stem cells in adult neurogenic niches, is considered a hallmark of brain aging. This review provides a comprehensive overview of the intricate relationship between aging, adult neurogenesis, and the potential neuroregenerative properties of astaxanthin, a carotenoid principally extracted from the microalga Haematococcus pluvialis. The unique chemical structure of astaxanthin enables it to cross the blood-brain barrier and easily reach the brain, where it may positively influence adult neurogenesis. Astaxanthin can affect molecular pathways involved in the homeostasis, through the activation of FOXO3-related genetic pathways, growth, and regeneration of adult brain neurons, enhancing cell proliferation and the potency of stem cells in neural progenitor cells. Furthermore, astaxanthin appears to modulate neuroinflammation by suppressing the NF-κB pathway, reducing the production of pro-inflammatory cytokines, and limiting neuroinflammation associated with aging and chronic microglial activation. By modulating these pathways, along with its potent antioxidant properties, astaxanthin may contribute to the restoration of a healthy neurogenic microenvironment, thereby preserving the activity of neurogenic niches during both normal and pathological aging.

Effects of Walnut and Pumpkin on Selective Neurophenotypes of Autism Spectrum Disorders: A Case Study

Special diets or nutritional supplements are regularly given to treat children with autism spectrum disorder (ASD). The increased consumption of particular foods has been demonstrated in numerous trials to lessen autism-related symptoms and comorbidities. A case study on a boy with moderate autism who significantly improved after three years of following a healthy diet consisting of pumpkin and walnuts was examined in this review in connection to a few different neurophenotypes of ASD. We are able to suggest that a diet high in pumpkin and walnuts was useful in improving the clinical presentation of the ASD case evaluated by reducing oxidative stress, neuroinflammation, glutamate excitotoxicity, mitochondrial dysfunction, and altered gut microbiota, all of which are etiological variables. Using illustrated figures, a full description of the ways by which a diet high in pumpkin and nuts could assist the included case is offered.

Exercise-brain interaction of neuroplasticity: empirical evidence in the rodent adaptation

PURPOSE

Exercise is gradually being recognized as an essential component of brain plasticity at the molecular, functional, and structural changes levels. What are the causes of the observed exercise reimbursements in neuroscience? Several types of exercises have been studied in various doses in neurological, physiological, psychological, and biochemical experiments. More clarity is required to reveal exercise-brain interactions such as optimal exercise condition variables and neuroplasticity.

METHODS

This review briefly highlights the empirical evidence of the positive effects neuroprotective activity on neuroscientific advancement.

RESULTS

The key areas are as follows: (a) stress exercise model using rodents, (b) hippocampal activation and plasticity with exercise, (c) glycogen metabolism in the brain, and (d) adaptation as a high-intensity interval training model in animals involved in exercise-induced brain plasticity.

CONCLUSION

Overall, exercise-induced molecular, functional, and structural changes in the neuronal system may affect rodents' performance. This study emphasizes the significance of understanding exercise neuroscience and makes recommendations for future research.

Pharmaceutical and nutraceutical potential of natural bioactive pigment: astaxanthin

Astaxanthin (3,3'-dihydroxy-β,β-carotene-4,4'-dione) is an orange-red, lipophilic keto-carotenoid pigment. It is majorly found in marine ecosystems particularly in aquatic animals such as salmon, shrimp, trout, krill, crayfish, and so on. It is also synthesized in microalgae Heamatococcus pluvialis, Chlorococcum, Chlorella zofingiensis, red yeast Phaffia rhodozyma and bacterium Paracoccus carotinifaciens. Some aquatic and terrestrial creatures regarded as a primary and secondary sources of the astaxanthin producing and accumulating it through their metabolic pathways. Astaxanthin is the powerful antioxidant, nutritional supplement as well as promising therapeutic compound, observed to have activities against different ravaging diseases and disorders. Researchers have reported remarkable bioactivities of astaxanthin against major non-communicable chronic diseases such as cardiovascular diseases, cancer, diabetes, neurodegenerative, and immune disorders. The current review discusses some structural aspects of astaxanthin. It further elaborates its multiple potencies such as antioxidant, anti-inflammatory, anti-proliferative, anti-cancer, anti-obese, anti-diabetic, anti-ageing, anti-TB, anti-viral, anti-COVID 19, neuro-protective, nephro-protective, and fertility-enhancing properties. These potencies make it a more precious entity in the preventions as well as treatments of prevalent systematic diseases and/or disorders. Also, the review is acknowledging and documenting its powerful bioactivities in relation with the pharmaceutical as well as nutraceutical applicability.

Neurogenesis in aging and age-related neurodegenerative diseases

Adult neurogenesis, the process by which neurons are generated in certain areas of the adult brain, declines in an age-dependent manner and is one potential target for extending cognitive healthspan. Aging is a major risk factor for neurodegenerative diseases and, as lifespans are increasing, these health challenges are becoming more prevalent. An age-associated loss in neural stem cell number and/or activity could cause this decline in brain function, so interventions that reverse aging in stem cells might increase the human cognitive healthspan. In this review, we describe the involvement of adult neurogenesis in neurodegenerative diseases and address the molecular mechanistic aspects of neurogenesis that involve some of the key aggregation-prone proteins in the brain (i.e., tau, Aβ, α-synuclein, …). We summarize the research pertaining to interventions that increase neurogenesis and regulate known targets in aging research, such as mTOR and sirtuins. Lastly, we share our outlook on restoring the levels of neurogenesis to physiological levels in elderly individuals and those with neurodegeneration. We suggest that modulating neurogenesis represents a potential target for interventions that could help in the fight against neurodegeneration and cognitive decline.

Recent Advancements and Future Perspectives of Microalgae-Derived Pharmaceuticals

Microalgal cells serve as solar-powered factories that produce pharmaceuticals, recombinant proteins (vaccines and drugs), and valuable natural byproducts that possess medicinal properties. The main advantages of microalgae as cell factories can be summarized as follows: they are fueled by photosynthesis, are carbon dioxide-neutral, have rapid growth rates, are robust, have low-cost cultivation, are easily scalable, pose no risk of human pathogenic contamination, and their valuable natural byproducts can be further processed. Despite their potential, there are many technical hurdles that need to be overcome before the commercial production of microalgal pharmaceuticals, and extensive studies regarding their impact on human health must still be conducted and the results evaluated. Clearly, much work remains to be done before microalgae can be used in the large-scale commercial production of pharmaceuticals. This review focuses on recent advancements in microalgal biotechnology and its future perspectives.

Astaxanthin ameliorates damage to the cerebral cortex, hippocampus and cerebellar cortex caused by methotrexate

We investigated the ameliorating effects of astaxanthin (AXA) on methotrexate (MTX) induced damage to the cerebral cortex, hippocampus, cerebellar cortex and blood. We used 24 female Wistar albino rats divided into three groups of eight as follows: sham/control group, single dose of saline intraperitoneally (i.p.) and 7 days orally; MTX group, single dose of 20 mg/kg MTX (i.p.); MTX + AXA group, single dose of 20 mg/kg MTX i.p.+ 100 mg/kg AXA orally for 7 days. For all groups we measured total oxidant status (TOS) and total antioxidant status (TAS) in the cerebral cortex, hippocampus and blood. Histological sections of cerebral cortex, hippocampus and cerebellar cortex were inspected microscopically. Caspase-3 (cas-3), granulocyte colony-stimulating factor (GCSF), growth related oncogene (GRO), inducible nitric oxide synthase (iNOS) and myelin basic protein (MBP) were estimated immunohistochemically in the cerebral cortex, hippocampus and cerebellar cortex. In the MTX group, TAS was decreased significantly in the cerebral cortex, hippocampus and blood, while TOS was significantly increased. AXA significantly ameliorated oxidative stress parameters in the cerebral cortex and hippocampus. Histopathological examination revealed degeneration, edema and hyperemia in the cerebral cortex, hippocampus and cerebellar cortex in the MTX group. AXA treatment ameliorated histopathological changes. MTX decreased MBP expression in cerebral cortex. Although MBP expression was decreased in the cerebral cortex, hippocampus and cerebellar cortex stimulated with MTX, the expressions of cas-3, GCSF, GRO and iNOS were significantly increased. AXA ameliorated the expression of cas-3, GCSF, GRO, iNOS and MBP. AXA exhibits anti-inflammatory, antioxidant and anti-apoptotic effects on MTX induced toxicity in the cerebral cortex, hippocampus and cerebellar cortex by increasing MBP expression, regulating inflammatory cytokine release and reducing oxidative stress.

Benefits of Exercise and Astaxanthin Supplementation: Are There Additive or Synergistic Effects?

A healthy lifestyle is essential for maintaining physical and mental health. Health promotion, with a particular emphasis on regular exercise and a healthy diet, is one of the emerging trends in healthcare. However, the way in which exercise training and nutrients from dietary intake interact with each other to promote additive, synergistic, or antagonistic effects on physiological functions leading to health promotion, and the possible underlying biomolecular mechanisms of such interactions, remain poorly understood. A healthy diet is characterized by a high intake of various bioactive compounds usually found in natural, organic, and fresh foodstuffs. Among these bioactive compounds, astaxanthin (ASX), a red carotenoid pigment especially found in seafood, has been recognized in the scientific literature as a potential nutraceutical due to its antioxidant, anti-inflammatory, and neurotrophic properties. Therefore, scientists are currently exploring whether this promising nutrient can increase the well-known benefits of exercise on health and disease prevention. Hence, the present review aimed to compile and summarize the current scientific evidence for ASX supplementation in association with exercise regimes, and evaluate the additive or synergistic effects on physiological functions and health when both interventions are combined. The new insights into the combination paradigm of exercise and nutritional supplementation raise awareness of the importance of integrative studies, particularly for future research directions in the field of health and sports nutrition science.

Natural Antioxidants: A Novel Therapeutic Approach to Autism Spectrum Disorders?

Autism spectrum disorders (ASD) are a group of neurodevelopmental syndromes with both genetic and environmental origins. Several recent studies have shown that inflammation and oxidative stress may play a key role in supporting the pathogenesis and the severity of ASD. Thus, the administration of anti-inflammatory and antioxidant molecules may represent a promising strategy to counteract pathological behaviors in ASD patients. In the current review, results from recent literature showing how natural antioxidants may be beneficial in the context of ASD will be discussed. Interestingly, many antioxidant molecules available in nature show anti-inflammatory activity. Thus, after introducing ASD and the role of the vitamin E/vitamin C/glutathione network in scavenging intracellular reactive oxygen species (ROS) and the impairments observed with ASD, we discuss the concept of functional food and nutraceutical compounds. Furthermore, the effects of well-known nutraceutical compounds on ASD individuals and animal models of ASD are summarized. Finally, the importance of nutraceutical compounds as support therapy useful in reducing the symptoms in autistic people is discussed.

The protective effect of astaxanthin on the ganglion cell complex in glutamate/aspartate transporter deficient mice, a model of normal tension glaucoma, analyzed by spectral domain-optical coherence tomography

Astaxanthin (AST), a natural marine carotenoid, possess a wide variety of biological functions. In particular, as a strong antioxidant, AST effectively scavenges oxygen free radicals and reduces oxidative stress. In addition, recent in vitro studies have suggested that AST attenuates glutamate-induced apoptosis and cytotoxicity. The glutamate/aspartate transporter (GLAST) deficient (GLAST-/-) mouse is a mouse model of normal tension glaucoma (NTG) caused by both the glutamate neurotoxicity and oxidative stress in the retina. In the present study, we investigated the effects of AST on the ganglion cell complex, indicator of glaucomatous structural damage, using spectral domain-optical coherence tomography. As a result, AST significantly attenuated the thinning of ganglion cell complex in GLAST-/- mice in comparison to an AST-free control group. Our results suggest the possibility that AST has protective effects against glutamate neurotoxicity and oxidative stress in the retina. At present, the only treatment for NTG that is available in the clinical setting is to reduce the IOP as much as possible. Thus, our results suggest that AST supplementation may be effective for some types of NTG in which glutamate neurotoxicity and oxidative stress are involved.

Plant-Derived Antioxidants Protect the Nervous System From Aging by Inhibiting Oxidative Stress

Alzheimer's disease (AD) has become a major disease contributing to human death and is thought to be closely related to the aging process. The rich antioxidant substances in plants have been shown to play a role in delaying aging, and in recent years, significant research has focused on also examining their potential role in AD onset and progression. Many plant-derived antioxidant research studies have provided insights for the future treatment and prevention of AD. This article reviews various types of plant-derived antioxidants with anti-aging effects on neurons. Also it distinguishes the different types of active substances that exhibit different degrees of protection for the nervous system and summarizes the mechanism thereof. Plant-derived antioxidants with neuroprotective functions can protect various components of the nervous system in a variety of ways and can have a positive impact on interventions to prevent and alleviate AD. Furthermore, when considering neuroprotective agents, glial cells also contribute to the defense of the nervous system and should not be ignored.

Astaxanthin as a Putative Geroprotector: Molecular Basis and Focus on Brain Aging

In recent years, the scientific interest in natural compounds with geroprotective activities has grown exponentially. Among the various naturally derived molecules, astaxanthin (ASX) represents a highly promising candidate geroprotector. By virtue of the central polyene chain, ASX acts as a scavenger of free radicals in the internal membrane layer and simultaneously controls oxidation on the membrane surface. Moreover, several studies have highlighted ASX’s ability to modulate numerous biological mechanisms at the cellular level, including the modulation of transcription factors and genes directly linked to longevity-related pathways. One of the main relevant evolutionarily-conserved transcription factors modulated by astaxanthin is the forkhead box O3 gene (FOXO3), which has been recognized as a critical controller of cell fate and function. Moreover, FOXO3 is one of only two genes shown to robustly affect human longevity. Due to its tropism in the brain, ASX has recently been studied as a putative neuroprotective molecule capable of delaying or preventing brain aging in different experimental models of brain damage or neurodegenerative diseases. Astaxanthin has been observed to slow down brain aging by increasing brain-derived neurotrophic factor (BDNF) levels in the brain, attenuating oxidative damage to lipids, protein, and DNA and protecting mitochondrial functions. Emerging data now suggest that ASX can modulate Nrf2, FOXO3, Sirt1, and Klotho proteins that are linked to longevity. Together, these mechanisms provide support for a role of ASX as a potential geroneuroprotector.

Astaxanthin Ameliorated Parvalbumin-Positive Neuron Deficits and Alzheimer's Disease-Related Pathological Progression in the Hippocampus of AppNL-G-F/NL-G-F Mice

Growing evidence suggests that oxidative stress due to amyloid β (Aβ) accumulation is involved in Alzheimer's disease (AD) through the formation of amyloid plaque, which leads to hyperphosphorylation of tau, microglial activation, and cognitive deficits. The dysfunction or phenotypic loss of parvalbumin (PV)-positive neurons has been implicated in cognitive deficits. Astaxanthin is one of carotenoids and known as a highly potent antioxidant. We hypothesized that astaxanthin's antioxidant effects may prevent the onset of cognitive deficits in AD by preventing AD pathological processes associated with oxidative stress. In the present study, we investigated the effects of astaxanthin intake on the cognitive and pathological progression of AD in a mouse model of AD. The App^{NL-G-F/NL-G-F} mice were fed with or without astaxanthin from 5-to-6 weeks old, and cognitive functions were evaluated using a Barnes maze test at 6 months old. PV-positive neurons were investigated in the hippocampus. Aβ42 deposits, accumulation of microglia, and phosphorylated tau (pTau) were immunohistochemically analyzed in the hippocampus. The hippocampal anti-oxidant status was also investigated. The Barnes maze test indicated that astaxanthin significantly ameliorated memory deficits. Astaxanthin reduced Aβ42 deposition and pTau-positive areal fraction, while it increased PV-positive neuron density and microglial accumulation per unit fraction of Aβ42 deposition in the hippocampus. Furthermore, astaxanthin increased total glutathione (GSH) levels, although 4-hydroxy-2,3-trans-nonenal (4-HNE) protein adduct levels (oxidative stress marker) remained high in the astaxanthin supplemented mice. The results indicated that astaxanthin ameliorated memory deficits and significantly reversed AD pathological processes (Aβ42 deposition, pTau formation, GSH decrease, and PV-positive neuronal deficits). The elevated GSH levels and resultant recovery of PV-positive neuron density, as well as microglial activation, may prevent these pathological processes.

Effects of Astaxanthin from Shrimp Shell on Oxidative Stress and Behavior in Animal Model of Alzheimer's Disease

This study aimed to investigate the effect of astaxanthin (ASX) extracted and ASX powder from shrimp (Litopenaeus vannamei) shells on Wistar rats with Alzheimer's disease, induced by amyloid-β (1-42) peptides. In this task, the rats were divided into eight groups: (1) Control, (2) sham operate, (3) negative control (vehicle) + Aβ_1-42, (4) ASX extract+Aβ_1-42, (5) commercial ASX + Aβ_1-42, (6) ASX powder + Aβ_1-42, (7) blank powder + Aβ_1-42, and (8) vitamin E + Aβ_1-42. All treatments were orally administrated for 30 days. At 14- and 29-days post injection, animals were observed in behavioral tests. On the 31st day, animals were sacrificed; the hippocampus and cortex were collected. Those two brain areas were then homogenized and stored for biochemical and histological analysis. The results showed that the Aβ_1-42 infused group significantly reduced cognitive ability and increased memory loss, as assessed by the Morris water maze test, novel object recognition test, and novel object location test. Moreover, the Aβ_1-42 infused group exhibited a deterioration of oxidative markers, including glutathione peroxidase enzymes (GPx), lipid peroxidation (MDA), products of protein oxidation, and superoxide anion in the cortex and the hippocampus. Meanwhile, ASX powder (10 mg/kg body weight) showed a significant reduction in cognitive and memory impairments and oxidative stress which is greater than ASX extract in the same dose of compound or vitamin E (100 mg/kg body weight). Our study indicates the beneficial properties of ASX in alleviation of cognitive functions and reducing neurodegeneration in Wistar rats induced by amyloid-β (1-42) peptides.

Effects of Composite Supplement Containing Astaxanthin and Sesamin on Cognitive Functions in People with Mild Cognitive Impairment: A Randomized, Double-Blind, Placebo-Controlled Trial

Background:

Dementia and its first or transitional stage, mild cognitive impairment (MCI), is a major concern for the aging Japanese society. Thus, the use of dietary supplements to improve or maintain cognitive function has become a topic of public interest.

Objective:

In this study, we evaluated the effects of a composite supplement containing food-derived antioxidants, specifically astaxanthin and sesamin (AS), on cognitive function in people with MCI.

Method:

Twenty-one healthy participants with MCI were recruited in our double-blind placebo-controlled pilot study. They were assigned to either an AS group, who received ingestible capsules containing AS, or a placebo group, who received identical placebo capsules. To assess cognitive functions, we performed the Japanese version of the Central Nervous System Vital Signs (CNSVS) test and the Alzheimer’s Disease Assessment Scale-Cog test at baseline, after 6 weeks, and after 12 weeks of dietary supplementation.

Results:

The CNSVS test revealed significant improvements in psychomotor speed and processing speed in the AS group compared with the placebo group, suggesting that the daily supplementation of AS improved cognitive functions related to the ability to comprehend, and perform complex tasks quickly and accurately.

Conclusion:

Our results provide support for the use of AS as a dietary supplementation for improving cognitive functions.

Leptin in hippocampus mediates benefits of mild exercise by an antioxidant on neurogenesis and memory

Regular exercise and dietary supplements with antioxidants each have the potential to improve cognitive function and attenuate cognitive decline, and, in some cases, they enhance each other. Our current results reveal that low-intensity exercise (mild exercise, ME) and the natural antioxidant carotenoid astaxanthin (AX) each have equivalent beneficial effects on hippocampal neurogenesis and memory function. We found that the enhancement by ME combined with AX in potentiating hippocampus-based plasticity and cognition is mediated by leptin (LEP) made and acting in the hippocampus. In assessing the combined effects upon wild-type (WT) mice undergoing ME with or without an AX diet for four weeks, we found that, when administrated alone, ME and AX separately enhanced neurogenesis and spatial memory, and when combined they were at least additive in their effects. DNA microarray and bioinformatics analyses revealed not only the up-regulation of an antioxidant gene, ABHD3, but also that the up-regulation of LEP gene expression in the hippocampus of WT mice with ME alone is further enhanced by AX. Together, they also increased hippocampal LEP (h-LEP) protein levels and enhanced spatial memory mediated through AKT/STAT3 signaling. AX treatment also has direct action on human neuroblastoma cell lines to increase cell viability associated with increased LEP expression. In LEP-deficient mice (ob/ob), chronic infusion of LEP into the lateral ventricles restored the synergy. Collectively, our findings suggest that not only h-LEP but also exogenous LEP mediates effects of ME on neural functions underlying memory, which is further enhanced by the antioxidant AX.

Astaxanthin supplementation modulates cognitive function and synaptic plasticity in young and aged mice

The incidence of neurodegenerative disorders and cognitive impairment is increasing. Rising prevalence of age-related medical conditions is associated with a dramatic economic burden; therefore, developing strategies to manage these health concerns is of great public health interest. Nutritionally based interventions have shown promise in treatment of these age-associated conditions. Astaxanthin is a carotenoid with reputed neuroprotective properties in the context of disease and injury, while emerging evidence suggests that astaxanthin may also have additional biological activities relating to neurogenesis and synaptic plasticity. Here, we investigate the potential for astaxanthin to modulate cognitive function and neural plasticity in young and aged mice. We show that feeding astaxanthin to aged mice for 1 month improves performance on several hippocampal-dependent cognitive tasks and increases long-term potentiation. However, we did not observe an alteration in neurogenesis, nor did we observe a change in microglial-associated IBA1 immunostaining. This demonstrates the potential for astaxanthin to modulate neural plasticity and cognitive function in aging.

Dietary astaxanthin can accumulate in the brain of rats

We evaluated the distribution of astaxanthin in rat brains after a single dose administration and after feeding 0.1% astaxanthin diet for 5 days. Astaxanthin was detected in the hippocampus and cerebral cortex 4 and 8 h after a single dose. Astaxanthin concentration in rat brains was higher after consumption of astaxanthin diet for 5 days than after a single dose.

On the Neuroprotective Role of Astaxanthin: New Perspectives?

Astaxanthin is a carotenoid with powerful antioxidant and anti-inflammatory activity produced by several freshwater and marine microorganisms, including bacteria, yeast, fungi, and microalgae. Due to its deep red-orange color it confers a reddish hue to the flesh of salmon, shrimps, lobsters, and crayfish that feed on astaxanthin-producing organisms, which helps protect their immune system and increase their fertility. From the nutritional point of view, astaxanthin is considered one of the strongest antioxidants in nature, due to its high scavenging potential of free radicals in the human body. Recently, astaxanthin is also receiving attention for its effect on the prevention or co-treatment of neurological pathologies, including Alzheimer and Parkinson diseases. In this review, we focus on the neuroprotective properties of astaxanthin and explore the underlying mechanisms to counteract neurological diseases, mainly based on its capability to cross the blood-brain barrier and its oxidative, anti-inflammatory, and anti-apoptotic properties.

A Novel 2-Phenylamino-Quinazoline-Based Compound Expands the Neural Stem Cell Pool and Promotes the Hippocampal Neurogenesis and the Cognitive Ability of Adult Mice

The adult neurogenesis occurs throughout the life of the mammalian hippocampus and is found to be essential for learning and memory. Identifying new ways to manipulate the number of neural stem cells (NSCs) and enhance endogenous neurogenesis in adults is very important. Here we found that a novel compound, N2-(4-isopropylphenyl)-5-(3-methoxyphenoxy)quinazoline-2,4-diamine (code-named Yhhu-3792), enhanced the self-renewal capability of NSCs in vitro and in vivo. In vitro, Yhhu-3792 increased the ratio of 5-Bromo-2-deoxyuridine⁺ /4'-6-diamidino-2-phenylindole⁺ embryonic NSCs and accelerated the growth of neurospheres significantly. We demonstrated that Yhhu-3792 activated Notch signaling pathway and promoted the expression of Notch target genes, Hes3 and Hes5. And the Notch signaling inhibitor DAPT could inhibit its function. Thus, we concluded Yhhu-3792 increased the number of embryonic NSCs via activating the Notch signaling pathway. We measured the effect of Yhhu-3792 on epidermal growth factor receptor signaling, which demonstrated Yhhu-3792 act via a different mechanism with the quinazoline parent chemical group. In the eight-week-old male C57BL/6 mice, chronic Yhhu-3792 administration expanded the NSCs pool and promoted endogenous neurogenesis in the hippocampal dentate gyrus (DG). It also increased the spatial and episodic memory abilities of mice, when evaluated with the Morris water maze and Fear conditioning tests. In conclusion, Yhhu-3792 could be a novel drug candidate to promote the self-renew of NSCs and adult neurogenesis. And it may have therapeutic potential in the impairment of learning and memory associated DG dysfunction. Stem Cells 2018;36:1273-1285.

Astaxanthin protects against kainic acid-induced seizures and pathological consequences

Excitotoxic damage caused by increased glutamate levels is involved in the pathogenesis of neurodegenerative diseases. Astaxanthin, a natural carotenoid with multiple health benefits, inhibits glutamate release from the brain tissue; however, whether it possesses the ability to affect glutamate-induced brain injury is unknown. The present study investigated the neuroprotective effects of astaxanthin on kainic acid (KA)-induced excitotoxicity in rats and the possible underlying intracellular signaling pathway. The rats were orally administrated with astaxanthin (50 or 100 mg/kg) for 7 days (once a day), and KA (15 mg/kg) was administered intraperitoneally at 1 h after the final administration. The results revealed that KA induced seizures, increased the hippocampal glutamate levels, caused considerable neuronal death and microglial activation in the hippocampal CA3 regions, and increased the production of proinflammatory cytokines. Astaxanthin pretreatment prevented these changes. Furthermore, astaxanthin pretreatment increased the expression of neuronal cell survival-related factors, including phosphorylated Akt, phosphorylated glycogen synthase kinase-3β, and Bcl-2 in the hippocampus of KA-injected rats. These results suggested that astaxanthin can attenuate seizures, mitigate inflammation, augment survival signals, and prevent hippocampal neuronal damage in the animal model of KA-induced excitotoxicity.

Effect of astaxanthin-rich extract derived from Paracoccus carotinifaciens on cognitive function in middle-aged and older individuals

This study was conducted to investigate the effect of dietary supplement containing astaxanthin-rich extract derived from Paracoccus carotinifaciens (astaxanthin supplement) on cognitive function of subjects aged 45–64 years. Cognitive functions of 28 subjects orally administered 8 mg astaxanthin/day of astaxanthin supplement for 8 weeks (astaxanthin group) and 26 subjects given a placebo (placebo group) were compared by word memory test, verbal fluency test, and Stroop test. The astaxanthin group experienced significantly larger increase in blood astaxanthin level than the placebo group. However, there were no significant intergroup differences in the results of the tests. A subgroup analysis was performed after dividing subjects into the <55 years old and ≥55 years old age groups. The result of “words recalled after 5 minutes” in word memory test in <55 years old subjects showed significant improvement in the astaxanthin group than in the placebo group, which was not found in ≥55 years old subjects. Our results indicate that people aged 45–54 years may experience improved cognitive function after ingesting astaxanthin supplement for 8 weeks. On the basis of the parameters tested, administration of astaxanthin supplement was not associated with any problems related to safety.

Astaxanthin is neuroprotective in an aged mouse model of Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder and prevalence increases with age. Normal physiological changes that occur during the aging process reflect the pathological characteristics of Parkinson's disease. It is also recognized that age related changes significantly interact with the pathological mechanisms that underlie the neurodegeneration in PD and perpetuate the disease process. Despite the fact that aging is considered to be a primary risk factor for developing PD, the use of aged animal models are still under-utilized in pre-clinical research, thus reducing the translatability of experimental findings. Here, we use a natural compound astaxanthin (AXT) with multiple biological activities to attenuate neurotoxicity in a mouse model of Parkinson's disease in both young and aged mice. We observed that AXT preserved neurons in the substantia nigra of both young and aged mice that were exposed to the MPTP neurotoxin. However, AXT was less efficacious in the aged animals, as AXT was not able to protect against the MPTP induced loss of tyrosine hydroxylase (TH) throughout the aged nigro-striatal circuit. This disparity in the neuroprotective effect of AXT suggests that aging is a critical factor to consider during the development of novel therapeutics for neurodegenerative diseases and should be more rigorously evaluated in preclinical models.

Lobster processing by-products as valuable bioresource of marine functional ingredients, nutraceuticals, and pharmaceuticals

The worldwide annual production of lobster was 165,367 tons valued over $3.32 billion in 2004, but this figure rose up to 304,000 tons in 2012. Over half the volume of the worldwide lobster production has been processed to meet the rising global demand in diversified lobster products. Lobster processing generates a large amount of by-products (heads, shells, livers, and eggs) which account for 50-70% of the starting material. Continued production of these lobster processing by-products (LPBs) without corresponding process development for efficient utilization has led to disposal issues associated with costs and pollutions. This review presents the promising opportunities to maximize the utilization of LPBs by economic recovery of their valuable components to produce high value-added products. More than 50,000 tons of LPBs are globally generated, which costs lobster processing companies upward of about $7.5 million/year for disposal. This not only presents financial and environmental burdens to the lobster processors but also wastes a valuable bioresource. LPBs are rich in a range of high-value compounds such as proteins, chitin, lipids, minerals, and pigments. Extracts recovered from LPBs have been demonstrated to possess several functionalities and bioactivities, which are useful for numerous applications in water treatment, agriculture, food, nutraceutical, pharmaceutical products, and biomedicine. Although LPBs have been studied for recovery of valuable components, utilization of these materials for the large-scale production is still very limited. Extraction of lobster components using microwave, ultrasonic, and supercritical fluid extraction were found to be promising techniques that could be used for large-scale production. LPBs are rich in high-value compounds that are currently being underutilized. These compounds can be extracted for being used as functional ingredients, nutraceuticals, and pharmaceuticals in a wide range of commercial applications. The efficient utilization of LPBs would not only generate significant economic benefits but also reduce the problems of waste management associated with the lobster industry. This comprehensive review highlights the availability of the global LPBs, the key components in LPBs and their current applications, the limitations to the extraction techniques used, and the suggested emerging techniques which may be promising on an industrial scale for the maximized utilization of LPBs. Graphical abstractLobster processing by-product as bioresource of several functional and bioactive compounds used in various value-added products.

Neuroprotective mechanisms of astaxanthin: a potential therapeutic role in preserving cognitive function in age and neurodegeneration

Astaxanthin (AXT) is a carotenoid with multiple health benefits. It is currently marketed as a health supplement and is well known for its antioxidant capacity. Recent evidence has emerged to suggest a broad range of biological activities. The interest in this compound has increased dramatically over the last few years and many studies are now applying this molecule across many disease models. Results from the current research are beginning to come together to suggest neuroprotective properties including anti-inflammatory, anti-apoptotic, and antioxidant effects, as well as the potential to promote or maintain neural plasticity. These emergent mechanisms of actions implicate AXT as a promising therapeutic agent for neurodegenerative disease. This review will examine and extrapolate from the recent literature to build support for the use of AXT in mitigating neuropathy in normal aging and neurodegenerative disease.

Environmental enrichment and physical exercise revert behavioral and electrophysiological impairments caused by reduced adult neurogenesis

It is well known that adult neurogenesis occurs in two distinct regions, the subgranular zone of the dentate gyrus and the subventricular zone along the walls of the lateral ventricles. Until now, the contribution of these newly born neurons to behavior and cognition is still uncertain. The current study tested the functional impacts of diminished hippocampal neurogenesis on emotional and cognitive functions in transgenic Gfap-tk mice. Our results showed that anxiety-related behavior evaluated both in the elevated plus maze as well as in the open field, social interaction in the sociability test, and spatial working memory in the spontaneous alternation test were not affected. On the other hand, recognition and emotional memory in the object recognition test and contextual fear conditioning, and hippocampal long-term potentiation were impaired in transgenic mice. Furthermore, we evaluated whether environmental enrichment together with physical exercise could improve or even restore the level of adult neurogenesis, as well as the behavioral functions. Our results clearly demonstrated that environmental enrichment together with physical exercise successfully elevated the overall number of progenitor cells and young neurons in the dentate gyrus of transgenic mice. Furthermore, it led to a significant improvement in object recognition memory and contextual fear conditioning, and reverted impairments in hippocampal long-term potentiation. Thus, our results confirm the importance of adult neurogenesis for learning and memory processes and for hippocampal circuitry in general. Environmental enrichment and physical exercise beneficially influenced adult neurogenesis after it had been disrupted and most importantly recovered cognitive functions and long-term potentiation. © 2016 Wiley Periodicals, Inc.

The sphingosine-1-phosphate analogue, FTY-720, promotes the proliferation of embryonic neural stem cells, enhances hippocampal neurogenesis and learning and memory abilities in adult mice

BACKGROUND AND PURPOSE

Fingolimod (FTY-720) is the first oral therapeutic drug approved for the relapsing-remitting forms of multiple sclerosis. Neural stem cells (NSCs) are capable of continuous self-renewal and differentiation. The dentate gyrus of the hippocampus in the adult mammalian brain contains a population of NSCs and is one of the regions where neurogenesis takes place. FTY-720 has been shown to have neuroprotective effects in several model systems, so we investigated the direct effects of FTY-720 on NSCs and adult neurogenesis.

EXPERIMENTAL APPROACHES

We assessed the effects of FTY-720 on the proliferation and differentiation of cultured embryonic hippocampal NSCs using the 5-bromo-2-deoxyuridine incorporation assay, the neurosphere formation assay and western blot analysis. Receptor selective agonists and antagonists were used to identify the mechanisms involved. Neurogenesis in the hippocampus of C57BL/6 mice was also assessed by immunohistochemistry. The Morris water maze and fear conditioning tests were used to detect the learning and memory abilities of mice.

KEY RESULTS

FTY-720 promoted the proliferation of embryonic hippocampal NSCs probably via the activation of ERK signalling, Gi/o proteins and S1P1 receptors. However, FTY-720 did not affect the differentiation of cultured hippocampal NSCs. In vivo, chronic treatment with FTY-720 promoted hippocampal neurogenesis in adult C57BL/6 mice and enhanced their learning and memory abilities.

CONCLUSIONS AND IMPLICATIONS

Our results suggest a new target for the activation of NSCs and provide an insight into the therapeutic effects of FTY-720 in neuropsychiatric disorders, neurodegenerative diseases and age-related cognitive decline where hippocampal neurogenesis is compromised.