Creatine Prevents Corticosterone-Induced Reduction in Hippocampal Proliferation and Differentiation: Possible Implication for Its Antidepressant Effect

Chronic Corticosterone Administration-Induced Mood Disorders in Laboratory Rodents: Features, Mechanisms, and Research Perspectives

Mood disorders mainly affect the patient's daily life, lead to suffering and disability, increase the incidence rate of many medical illnesses, and even cause a trend of suicide. The glucocorticoid (GC)-mediated hypothalamus-pituitary-adrenal (HPA) negative feedback regulation plays a key role in neuropsychiatric disorders. The balance of the mineralocorticoid receptor (MR)/glucocorticoid receptor (GR) level contributes to maintaining the homeostasis of the neuroendocrine system. Consistently, a chronic excess of GC can also lead to HPA axis dysfunction, triggering anxiety, depression, memory loss, and cognitive impairment. The animal model induced by chronic corticosterone (CORT) administration has been widely adopted because of its simple replication and strong stability. This review summarizes the behavioral changes and underlying mechanisms of chronic CORT administration-induced animal models, including neuroinflammatory response, pyroptosis, oxidative stress, neuroplasticity, and apoptosis. Notably, CORT administration at different doses and cycles can destroy the balance of the MR/GR ratio to make dose-dependent effects of CORT on the central nervous system (CNS). This work aims to offer an overview of the topic and recommendations for future cognitive function research.

Psidium Exotic and Native Species from Brazil Abolish Depression-like Behavior and Oxidative Stress induced by Corticosterone in Mice

Depression is a highly prevalent neuropsychiatric disorder worldwide. One currently accepted hypothesis of this pathogenesis is the hypothalamic-pituitary-adrenal axis dysfunction, which involves oxidative stress and brain damage. Therefore, antioxidants, such as phenolic compounds, could be used in depression. In this study, we investigated the antidepressant-like and antioxidant effects of an aqueous extract of the leaves of three species of the genus Psidium, Myrtaceae family, in mice. The exotic Psidium guajava L. and the natives Psidium guineense Sw. and Psidium cattleianum Sabine (10, 1, and 0.1 mg/kg, respectively) and fluoxetine (10 mg/kg) were administered orally (p. o.) once daily for 21 days, with or without corticosterone (20 mg/kg). After behavioral assessments (tail suspension, splash, and open-field tests), the hippocampus, prefrontal cortex, liver, kidneys, and plasma were examined to determine the oxidative stress status. The three extracts and fluoxetine treatment decreased the immobility time and counteracted the oxidative stress induced by corticosterone administration. The phenolic compounds identified as major components of the extracts, quercetin in P. guajava and P. guineense and o-coumaric acid in P. cattleianum, may be involved in the biological activities. Therefore, the aqueous leaf extracts of P. guajava, P. cattleianum, and P. guineense could be potential antidepressants helpful in treating depression and other diseases with elevated nitro-oxidative stress.

Lung-brain crosstalk: Behavioral disorders and neuroinflammation in septic survivor mice

Although studies have suggested an association between lung infections and increased risk of neuronal disorders (e.g., dementia, cognitive impairment, and depressive and anxious behaviors), its mechanisms remain unclear. Thus, an experimental mice model of pulmonary sepsis was developed to investigate the relationship between lung and brain inflammation. Male Swiss mice were randomly assigned to either pneumosepsis or control groups. Pneumosepsis was induced by intratracheal instillation of Klebsiella pneumoniae, while the control group received a buffer solution. The model's validation included assessing systemic markers, as well as tissue vascular permeability. Depression- and anxiety-like behaviors and cognitive function were assessed for 30 days in sepsis survivor mice, inflammatory profiles, including cytokine levels (lungs, hippocampus, and prefrontal cortex) and microglial activation (hippocampus), were examined. Pulmonary sepsis damaged distal organs, caused peripheral inflammation, and increased vascular permeability in the lung and brain, impairing the blood-brain barrier and resulting in bacterial dissemination. After sepsis induction, we observed an increase in myeloperoxidase activity in the lungs (up to seven days) and prefrontal cortex (up to 24 h), proinflammatory cytokines in the hippocampus and prefrontal cortex, and percentage of areas with cells positive for ionized calcium-binding adaptor molecule 1 (IBA-1) in the hippocampus. Also, depression- and anxiety-like behaviors and changes in short-term memory were observed even 30 days after sepsis induction, suggesting a crosstalk between inflammatory responses of lungs and brain.

The major biogenic amine metabolites in mood disorders

Mood disorders, including major depressive disorder and bipolar disorder, have a profound impact on more than 300 million people worldwide. It has been demonstrated mood disorders were closely associated with deviations in biogenic amine metabolites, which are involved in numerous critical physiological processes. The peripheral and central alteration of biogenic amine metabolites in patients may be one of the potential pathogeneses of mood disorders. This review provides a concise overview of the latest research on biogenic amine metabolites in mood disorders, such as histamine, kynurenine, and creatine. Further studies need larger sample sizes and multi-center collaboration. Investigating the changes of biogenic amine metabolites in mood disorders can provide biological foundation for diagnosis, offer guidance for more potent treatments, and aid in elucidating the biological mechanisms underlying mood disorders.

Molecular, Pathophysiological, and Clinical Aspects of Corticosteroid-Induced Neuropsychiatric Effects: From Bench to Bedside

Corticosteroids are frequently prescribed across medical disciplines, yet they are associated with various adverse effects, including neuropsychiatric symptoms, documented since their introduction over 60 years ago. The cellular mechanisms underlying neuropsychiatric symptoms are complex and somewhat obscure, involving multiple pathways. Notably, they include changes in excitability, cellular death of hippocampal and striatal neurons, and increased inflammation and oxidative stress. Clinical presentation varies, encompassing affective disorders (anxiety, euphoria, depression), psychotic episodes, and cognitive deficits. It is crucial to note that these manifestations often go unnoticed by treating physicians, leading to delayed detection of severe symptoms, complications, and underreporting. Discontinuation of corticosteroids constitutes the cornerstone of treatment, resolving symptoms in up to 80% of cases. Although the literature on this topic is scant, isolated cases and limited studies have explored the efficacy of psychotropic medications for symptomatic control and prophylaxis. Pharmacological intervention may be warranted in situations where corticosteroid reduction or withdrawal is not feasible or beneficial for the patient.

ACE gene polymorphisms (rs4340) II and DI are more responsive to the ergogenic effect of caffeine than DD on aerobic power, heart rate, and perceived exertion in a homogeneous Brazilian group of adolescent athletes

The purpose of this study was to verify the association between angiotensin-converting enzyme (ACE) genotypes DD, DI, and II and caffeine (CAF) ingestion on endurance performance, heart rate, ratio of perceived exertion (RPE), and habitual caffeine intake (HCI) of adolescent athletes. Seventy-four male adolescent athletes (age: DD=16±1.7; DI=16±2.0; II=15±1.7 years) ingested CAF (6 mg/kg) or placebo (PLA) one hour before performing the Yo-Yo Intermittent Recovery level 1 (Yo-Yo IR1) test. No difference was found among groups for HCI. However, CAF increased the maximal distance covered and VO2max in DI and II genotype carriers compared to PLA (DD: Δ=31 m and 0.3 mL·kg-1·min-1; DI: Δ=286 m and 1.1 mL·kg-1·min-1; II: Δ=160 m and 1.4 mL·kg-1·min-1). Heart rate of DI and II genotype carriers increased with CAF compared to PLA, while RPE was higher in the II and lower in the DD genotypes. The correlations between HCI and maximal distance covered or VO2max were significant in the II genotype carriers with CAF. CAF increased endurance capacity, heart rate, and RPE in adolescent athletes with allele I, while endurance performance and aerobic power had a positive correlation to HCI in the II genotype group. These findings suggested that DD genotype were less responsive to CAF and that genetic variations should be taken into account when using CAF supplementation to enhance exercise performance.

20(S)-Protopanaxadiol Exerts Antidepressive Effects in Chronic Corticosterone-Induced Rodent Animal Models as an Activator of Brain-Type Creatine Kinase

20(S)-Protopanaxadiol (PPD) is one of the bioactive ingredients in ginseng and possesses neuroprotective properties. Brain-type creatine kinase (CK-BB) is an enzyme involved in brain energy homeostasis via the phosphocreatine-creatine kinase system. We previously identified PPD as directly bound to CK-BB and activated its activity in vitro. In this study, we explored the antidepressive effects of PPD that target CK-BB. First, we conducted time course studies on brain CK-BB, behaviors, and hippocampal structural plasticity responses to corticosterone (CORT) administration. Five weeks of CORT injection reduced CK-BB activity and protein levels and induced depression-like behaviors and hippocampal structural plasticity impairment. Next, a CK inhibitor and an adeno-associated virus-targeting CKB were used to diminish CK-BB activity or its expression in the brain. The loss of CK-BB in the brain led to depressive behaviors and morphological damage to spines in the hippocampus. Then, a polyclonal antibody against PPD was used to determine the distribution of PPD in the brain tissues. PPD was detected in the hippocampus and cortex and observed in astrocytes, neurons, and vascular endotheliocytes. Finally, different PPD doses were used in the chronic CORT-induced depression model. Treatment with a high dose of PPD significantly increased the activity and expression of CK-BB after long-term CORT injection. In addition, PPD alleviated the damage to depressive-like behaviors and structural plasticity induced by repeated CORT injection. Overall, our study revealed the critical role of CK-BB in mediating structural plasticity in CORT-induced depression and identified CK-BB as a therapeutic target for PPD, allowing us to treat stress-related mood disorders.

Exploring the pathophysiological influence of heme oxygenase-1 on neuroinflammation and depression: A study of phytotherapeutic-based modulation

BACKGROUND

The heme oxygenase (HO) system plays a significant role in neuroprotection and reduction of neuroinflammation and neurodegeneration. The system, via isoforms HO-1 and HO-2, regulates cellular redox balance. HO-1, an antioxidant defense enzyme, is highlighted due to its association with depression, characterized by heightened neuroinflammation and impaired oxidative stress responses.

METHODOLOGY

We observed the pathophysiology of HO-1 and phytochemicals as its modulator. We explored Science Direct, Scopus, and PubMed for a comprehensive literature review. Bibliometric and temporal trend analysis were done using VOSviewer.

RESULTS

Several phytochemicals can potentially alleviate neuroinflammation and oxidative stress-induced depressive symptoms. These effects result from inhibiting the MAPK and NK-κB pathways - both implicated in the overproduction of pro-inflammatory factors - and from the upregulation of HO-1 expression mediated by Nrf2. Bibliometric and temporal trend analysis further validates these associations.

CONCLUSION

In summary, our findings suggest that antidepressant agents can mitigate neuroinflammation and depressive disorder pathogenesis via the upregulation of HO-1 expression. These agents suppress pro-inflammatory mediators and depressive-like symptoms, demonstrating that HO-1 plays a significant role in the neuroinflammatory process and the development of depression.

The effect of scutellaria baicalensis and its active ingredients on major depressive disorder: a systematic review and meta-analysis of literature in pre-clinical research

Background: Scutellaria baicalensis, the dry root of scutellaria baicalensis georgi, is a traditional Chinese medicine with long. In clinic, scutellaria baicalensis is commonly used in prescription for the treatment of depression. Additionally, numerous pre-clinical studies have shown that Scutellaria baicalensis and its active constituents are effective for depression. In this study, we aims to systematically review the roles of scutellaria baicalensis in depression and summarize the possible mechanism. Methods: A systematic review and meta-analysis were conducted to analyze the existing studies on the effects of scutellaria baicalensis on depression in animal models. Briefly, we searched electronic databases including Pubmed and Embase for preclinical trial studies from inception to September 2023. The items in each study were evaluated by two independent reviewers, and meta-analyses were performed on scutellaria baicalensis-induced behavioral changes in the study. Finally, random effects model is used to collect data. Results: A total of 49 studies were identified, and 13 studies were included in the final analysis. They all reported the different antidepressant effects of scutellaria baicalensis and the underlying biological mechanisms. Among the included 13 studies, the results of eight articles SPT[SMD = -2.80, 95%CI(-4.03, -1.57), p < 0.01], the results of the nine articles OFT[SMD = -2.38, 95%CI(-3.53, -1.23), p < 0.01], and the results of two articles NSFT[SMD = -2.98, 95%CI(-3.94, -2.02), p < 0.01] were significantly different from the control group. The risk of bias was moderate in all studies, however, there was a significant heterogeneity among studies. Conclusion: These results preliminarily suggest that scutellaria baicalensis can alleviate depressive behaviors and modulate underlying mechanisms, which is expected to be a promising antidepressant.

Effects of Creatine Supplementation on Brain Function and Health

While the vast majority of research involving creatine supplementation has focused on skeletal muscle, there is a small body of accumulating research that has focused on creatine and the brain. Preliminary studies indicate that creatine supplementation (and guanidinoacetic acid; GAA) has the ability to increase brain creatine content in humans. Furthermore, creatine has shown some promise for attenuating symptoms of concussion, mild traumatic brain injury and depression but its effect on neurodegenerative diseases appears to be lacking. The purpose of this narrative review is to summarize the current body of research pertaining to creatine supplementation on total creatine and phophorylcreatine (PCr) content, explore GAA as an alternative or adjunct to creatine supplementation on brain creatine uptake, assess the impact of creatine on cognition with a focus on sleep deprivation, discuss the effects of creatine supplementation on a variety of neurological and mental health conditions, and outline recent advances on creatine supplementation as a neuroprotective supplement following traumatic brain injury or concussion.

Ketamine, but not fluoxetine, rapidly rescues corticosterone-induced impairments on glucocorticoid receptor and dendritic branching in the hippocampus of mice

Although numerous studies have investigated the mechanisms underlying the fast and sustained antidepressant-like effects of ketamine, the contribution of the glucocorticoid receptor (GR) and dendritic branching remodeling to its responses remain to be fully established. This study investigated the ability of a single administration of ketamine to modulate the GR and dendritic branching remodeling and complexity in the hippocampus of mice subjected to chronic corticosterone (CORT) administration. CORT was administered for 21 days, followed by a single administration of ketamine (1 mg ∕kg, i.p.) or fluoxetine (10 mg ∕kg, p.o., conventional antidepressant) in mice. On 22^nd, 24 h after the treatments, GR immunocontent in the hippocampus was analyzed by western blotting, while the dendritic arborization and dendrite length in the ventral and dorsal dentate gyrus (DG) of the hippocampus was analyzed by Sholl analysis. Chronic CORT administration downregulated hippocampal GR immunocontent, but this alteration was completely reversed by a single administration of ketamine, but not fluoxetine. Moreover, CORT administration significantly decreased dendritic branching in the dorsal and ventral DG areas and caused a mild decrease in dendrite length in both regions. Ketamine, but not fluoxetine, reversed CORT-induced dendritic branching loss in the ventral and dorsal DG areas, regions associated with mood regulation and cognitive functions, respectively. This study provides novel evidence that a single administration of ketamine, but not fluoxetine, rescued the impairments on GR and dendritic branching in the hippocampus of mice subjected to chronic CORT administration, effects that may be associated with its rapid antidepressant response.

The Association Between Antidepressant Effect of SSRIs and Astrocytes: Conceptual Overview and Meta-analysis of the Literature

Major depressive disorders (MDD) a worldwide psychiatric disease, is yet to be adequately controlled by therapies; while the mechanisms of action of antidepressants are yet to be fully characterised. In the last two decades, an increasing number of studies have demonstrated the role of astrocytes in the pathophysiology and therapy of MDD. Selective serotonin reuptake inhibitors (SSRIs) are the most widely used antidepressants. It is generally acknowledged that SSRIs increase serotonin levels in the central nervous system by inhibiting serotonin transporters, although the SSRIs action is not ideal. The SSRIs antidepressant effect develops with considerable delay; their efficacy is low and frequent relapses are common. Neither cellular nor molecular pharmacological mechanisms of SSRIs are fully characterised; in particular their action on astrocytes remain underappreciated. In this paper we overview potential therapeutic mechanisms of SSRIs associated with astroglia and report the results of meta-analysis of studies dedicated to MDD, SSRIs and astrocytes. In particular, we argue that fluoxetine, the representative SSRI, improves depressive-like behaviours in animals treated with chronic mild stress and reverses depression-associated decrease in astrocytic glial fibrillary acidic protein (GFAP) expression. In addition, fluoxetine upregulates astrocytic mRNA expression of 5-hydroxytriptamin/serotonin2B receptors (5-HT2BR). In summary, we infer that SSRIs exert their anti-depressant effect by regulating several molecular and signalling pathways in astrocytes.

Dopaminergic Receptors as Neuroimmune Mediators in Experimental Autoimmune Encephalomyelitis

The dopaminergic system plays an essential role in maintaining homeostasis between the central nervous system (CNS) and the immune system. Previous studies have associated imbalances in the dopaminergic system to the pathogenesis of multiple sclerosis (MS). Here, we examined the protein levels of dopaminergic receptors (D1R and D2R) in different phases of the experimental autoimmune encephalomyelitis (EAE) model. We also investigated if the treatment with pramipexole (PPX)-a dopamine D2/D3 receptor-preferring agonist-would be able to prevent EAE-induced motor and mood dysfunction, as well as its underlying mechanisms of action. We report that D2R immunocontent is upregulated in the spinal cord of EAE mice 14 days post-induction. Moreover, D1R and D2R immunocontents in lymph nodes and the oxidative damage in the spinal cord and striatum of EAE animals were significantly increased during the chronic phase. Also, during the pre-symptomatic phase, axonal damage in the spinal cord of EAE mice could already be found. Surprisingly, therapeutic treatment with PPX failed to inhibit the progression of EAE. Of note, PPX treatment inhibited EAE-induced depressive-like while failed to inhibit anhedonic-like behaviors. We observed that PPX treatment downregulated IL-1β levels and increased BNDF content in the spinal cord after EAE induction. Herein, we show that a D2/D3 receptor-preferred agonist mitigated EAE-induced depressive-like behavior, which could serve as a new possibility for further clinical trials on treating depressive symptoms in MS patients. Thus, we infer that D2R participates in the crosstalk between CNS and immune system during autoimmune and neuroinflammatory response induced by EAE, mainly in the acute and chronic phase of the disease.

Stress-Related Dysfunction of Adult Hippocampal Neurogenesis-An Attempt for Understanding Resilience?

Newborn neurons in the adult hippocampus are regulated by many intrinsic and extrinsic cues. It is well accepted that elevated glucocorticoid levels lead to downregulation of adult neurogenesis, which this review discusses as one reason why psychiatric diseases, such as major depression, develop after long-term stress exposure. In reverse, adult neurogenesis has been suggested to protect against stress-induced major depression, and hence, could serve as a resilience mechanism. In this review, we will summarize current knowledge about the functional relation of adult neurogenesis and stress in health and disease. A special focus will lie on the mechanisms underlying the cascades of events from prolonged high glucocorticoid concentrations to reduced numbers of newborn neurons. In addition to neurotransmitter and neurotrophic factor dysregulation, these mechanisms include immunomodulatory pathways, as well as microbiota changes influencing the gut-brain axis. Finally, we discuss recent findings delineating the role of adult neurogenesis in stress resilience.

Creatine in Health and Disease

Although creatine has been mostly studied as an ergogenic aid for exercise, training, and sport, several health and potential therapeutic benefits have been reported. This is because creatine plays a critical role in cellular metabolism, particularly during metabolically stressed states, and limitations in the ability to transport and/or store creatine can impair metabolism. Moreover, increasing availability of creatine in tissue may enhance cellular metabolism and thereby lessen the severity of injury and/or disease conditions, particularly when oxygen availability is compromised. This systematic review assesses the peer-reviewed scientific and medical evidence related to creatine's role in promoting general health as we age and how creatine supplementation has been used as a nutritional strategy to help individuals recover from injury and/or manage chronic disease. Additionally, it provides reasonable conclusions about the role of creatine on health and disease based on current scientific evidence. Based on this analysis, it can be concluded that creatine supplementation has several health and therapeutic benefits throughout the lifespan.

Role of adult hippocampal neurogenesis in the antidepressant actions of lactate

In addition to its role as a neuronal energy substrate and signaling molecule involved in synaptic plasticity and memory consolidation, recent evidence shows that lactate produces antidepressant effects in animal models. However, the mechanisms underpinning lactate's antidepressant actions remain largely unknown. In this study, we report that lactate reverses the effects of corticosterone on depressive-like behavior, as well as on the inhibition of both the survival and proliferation of new neurons in the adult hippocampus. Furthermore, the inhibition of adult hippocampal neurogenesis prevents the antidepressant-like effects of lactate. Pyruvate, the oxidized form of lactate, did not mimic the effects of lactate on adult hippocampal neurogenesis and depression-like behavior. Finally, our data suggest that conversion of lactate to pyruvate with the concomitant production of NADH is necessary for the neurogenic and antidepressant effects of lactate.

Physical exercise stimulates hippocampal mTORC1 and FNDC5/irisin signaling pathway in mice: Possible implication for its antidepressant effect

Several lines of evidence have consistently indicated that physical exercise has antidepressant effects by improving hippocampal function, although the signaling pathways underpinning these responses are not well established. Therefore, this study investigated the role of mechanistic target of rapamycin complex 1 (mTORC1) and fibronectin type III domain-containing protein 5 (FNDC5)/irisin signaling in the antidepressant-like effect of physical exercise. We showed that physical exercise (treadmill running - 45 min/day/5 days/week for 4 weeks) produced an antidepressant-like effect as indicated by a reduction on the immobility time in mice subjected to the forced swimming test (FST) without altering locomotor activity in the open field test (OFT). Rapamycin (a selective mTORC1 inhibitor, 0.2 nmol/site, i.c.v.) administration completely abolished the antidepressant-like effect of physical exercise in the FST, suggesting that mTORC1 activation plays a role for its behavioral effect. Accordingly, physical exercise increased the number of phosphorylated mTORC1 (Ser2448)-positive cells in the entire and ventral subgranular zone of the hippocampal dentate gyrus. Physical exercise was also effective in augmenting the hippocampal FNDC5/irisin immunocontent, but rapamycin administration did not alter this effect. Our results reinforce the notion that physical exercise exerts an antidepressant-like effect and identifies the mTORC1-mediated signaling pathway as a target for its behavioral effects. This study provides additional evidence that physical exercise increases hippocampal FNDC5/irisin immunocontent, but this effect seems to be independent on hippocampal mTORC1 activation. Altogether the results contribute to elucidate possible molecular targets implicated in the antidepressant effects of physical exercise and highlight the role of mTORC1 signaling for its behavioral response.

Enriched environment ameliorates dexamethasone effects on emotional reactivity and metabolic parameters in mice

Convincing evidence shows that stress is associated with the development and course of psychiatric and metabolic disorders. The hypothalamic-pituitary-adrenal (HPA) axis mediates the stress response, a cascade of events that culminate in the release of glucocorticoids from the adrenal cortex. Chronic hypercortisolism typically characterizes stress-related illnesses, such as depression, anxiety, and metabolic syndrome. Considering previous studies pointing that environmental enrichment (EE) mitigates the deleterious effects of stress on neurobiological systems, we hypothesized that EE can confer resiliency against prolonged glucocorticoid administration-induced behavioral and metabolic alterations in mice. In this regard, three-month-old male Swiss mice were exposed to a four-week period of standard environment (SE) or EE. After this period, still in the respective environments, dexamethasone was administered intraperitoneally (i.p.) at a dose of 4 mg/kg, for 21 consecutive days, in order to generate the emotional-related behavioral outcomes, as previously described. It is demonstrated herein that EE prevents the dexamethasone-induced anxiety-like and passive stress-coping behaviors, as observed in the open field and tail suspension tests. Moreover, EE mitigated the hyperproteinemia and body weight loss induced by excess dexamethasone and decreased basal glucose levels. Taken together, these results support the hypothesis that EE attenuates the effects of chronic administration of synthetic glucocorticoids in mice, a strategy that may be translated to the clinical perspective.

Prophylactic effect of physical exercise on Aβ1-40-induced depressive-like behavior: Role of BDNF, mTOR signaling, cell proliferation and survival in the hippocampus

Alzheimer's disease (AD) is characterized by progressive cognitive impairments as well as non-cognitive symptoms such as depressed mood. Physical exercise has been proposed as a preventive strategy against AD and depression, an effect that may be related, at least partially, to its ability to prevent impairments on cell proliferation and neuronal survival in the hippocampus, a structure implicated in both cognition and affective behavior. Here, we investigated the ability of treadmill exercise (4 weeks) to counteract amyloid β_1-40 peptide-induced depressive-like and anxiety-like behavior in mice. Moreover, we addressed the role of the BDNF/mTOR intracellular signaling pathway as well as hippocampal cell proliferation and survival in the effects of physical exercise and/or Aβ_1-40. Aβ_1-40 administration (400 pmol/mouse, i.c.v.) increased immobility time and reduced the latency to immobility in the forced swim test, a finding indicative of depressive-like behavior. In addition, Aβ_1-40 administration also decreased time spent in the center of the open field and increased grooming and defecation, alterations indicative of anxiety-like behavior. These behavioral alterations were accompanied by a reduction in the levels of mature BDNF and mTOR (Ser²⁴⁴⁸) phosphorylation in the hippocampus. In addition, Aß_1-40 administration reduced cell proliferation and survival in the ventral, dorsal and entire dentate gyrus of the hippocampus. Importantly, most of these behavioral, neurochemical and structural impairments induced by Aβ_1-40 were not observed in mice subjected to 4 weeks of treadmill exercise. These findings indicate that physical exercise has the potential to prevent the occurrence of early emotional disturbances associated with AD and this appears to be mediated, at least in part, by modulation of hippocampal BDNF and mTOR signaling as well as through promotion of cell proliferation and survival in the hippocampal DG.

Impaired Mitochondrial ATP Production Downregulates Wnt Signaling via ER Stress Induction

Wnt signaling affects fundamental development pathways and, if aberrantly activated, promotes the development of cancers. Wnt signaling is modulated by different factors, but whether the mitochondrial energetic state affects Wnt signaling is unknown. Here, we show that sublethal concentrations of different compounds that decrease mitochondrial ATP production specifically downregulate Wnt/β-catenin signaling in vitro in colon cancer cells and in vivo in zebrafish reporter lines. Accordingly, fibroblasts from a GRACILE syndrome patient and a generated zebrafish model lead to reduced Wnt signaling. We identify a mitochondria-Wnt signaling axis whereby a decrease in mitochondrial ATP reduces calcium uptake into the endoplasmic reticulum (ER), leading to endoplasmic reticulum stress and to impaired Wnt signaling. In turn, the recovery of the ATP level or the inhibition of endoplasmic reticulum stress restores Wnt activity. These findings reveal a mechanism that links mitochondrial energetic metabolism to the control of the Wnt pathway that may be beneficial against several pathologies.

Beyond sports: Efficacy and safety of creatine supplementation in pathological or paraphysiological conditions of brain and muscle

Creatine is pivotal in energy metabolism of muscle and brain cells, both in physiological and in pathological conditions. Additionally, creatine facilitates the differentiation of muscle and neuronal cells. Evidence of effectiveness of creatine supplementation in improving several clinical conditions is now substantial, and we review it in this paper. In hereditary diseases where its synthesis is impaired, creatine has a disease-modifying capacity, especially when started soon after birth. Strong evidence, including a Cochrane meta-analysis, shows that it improves muscular strength and general well-being in muscular dystrophies. Significant evidence exists also of its effectiveness in secondary prevention of statin myopathy and of treatment-resistant depression in women. Vegetarians and vegans do not consume any dietary creatine and must synthesize all they need, spending most of their methylation capacity. Nevertheless, they have a lower muscular concentration of creatine. Creatine supplementation has proved effective in increasing muscular and neuropsychological performance in vegetarians or vegans and should, therefore, be recommended especially in those of them who are athletes, heavy-duty laborers or who undergo intense mental effort. Convincing evidence also exists of creatine effectiveness in muscular atrophy and sarcopenia in the elderly, and in brain energy shortage (mental fatigue, sleep deprivation, environmental hypoxia as in mountain climbing, and advanced age). Furthermore, we review more randomized, placebo-controlled trials showing that creatine supplementation is safe up to 20 g/d, with a possible caveat only in people with kidney disease. We trust that the evidence we review will be translated into clinical practice and will spur more research on these subjects.

The possible beneficial effects of creatine for the management of depression

Depression, a highly prevalent neuropsychiatric disorder worldwide, causes a heavy burden for the society and is associated with suicide risk. The treatment of this disorder remains a challenge, since currently available antidepressants provide a slow and, often, incomplete response and cause several side effects that contribute to diminish the adhesion of patients to treatment. In this context, several nutraceuticals have been investigated regarding their possible beneficial effects for the management of this neuropsychiatric disorder. Creatine stands out as a supplement frequently used for ergogenic purpose, but it also is a neuroprotective compound with potential to treat or mitigate a broad range of central nervous systems diseases, including depression. This review presents preclinical and clinical evidence that creatine may exhibit antidepressant properties. The focus is given on the possible molecular mechanisms underlying its effects based on the results obtained with different animal models of depression. Finally, evidence obtained in animal models of depression addressing the possibility that creatine may produce rapid antidepressant effect, similar to ketamine, are also presented and discussed.

Regulation of Tau Protein on the Antidepressant Effects of Ketamine in the Chronic Unpredictable Mild Stress Model

Tau protein is known to play an important role in maintaining microtubule assembly and stabilization, and maintaining the normal morphology of neurons, but several studies have found that chronic stress leads to Tau hyperphosphorylation. A large number of clinical trials have found that ketamine, which is an N-methyl-D-aspartate receptor antagonist, produces a rapid, long-lasting, and potent antidepressant effect in patients suffering from major depression. This rapid antidepressant effect of ketamine, which involves many mechanisms, has attracted wide attention. However, the relationship between ketamine's antidepressant effects and Tau protein has rarely been examined. We used C57BL/6 and Tau KO mice exposed to 42 days of chronic unpredictable mild stress (the CUMS model) to investigate the effect of ketamine on behavioral changes and synaptic functioning of the hippocampus. The results showed that a single treatment of ketamine rapidly relieved the CUMS-induced anhedonia, depression-like, and anxious behaviors of the C57BL/6 mice. The abnormal behaviors were accompanied by increased levels of specific alterations of hyperphosphorylated Tau protein in cytoplasm and synapse in the hippocampus of the C57BL/6 mice, but ketamine reduced the aggregation of hyperphosphorylated Tau protein only in the synapse. We also found that CUMS exposure reduced the levels of GluA1 and PSD95 in the hippocampus of the C57BL/6 mice and that these deficits were reversed by ketamine. However, the Tau KO mice did not develop any stress-induced depressive behaviors or deficits of hippocampal function. The antidepressant effect of ketamine may decrease the levels of hyperphosphorylated Tau protein in synapse of C57BL/6 mice.

Subchronic administration of creatine produces antidepressant-like effect by modulating hippocampal signaling pathway mediated by FNDC5/BDNF/Akt in mice

Creatine has been shown to play a significant role in the pathophysiology and treatment of major depressive disorder (MDD) in preclinical and clinical studies. However, the biological mechanisms underlying its antidepressant effect is still not fully elucidated. This study investigated the effect of creatine (p.o.) administered for 21 days in the behavior of mice submitted to tail suspension test (TST), a predictive test of antidepressant activity. Creatine reduced the immobility time in the TST (1-10 mg/kg), without affecting locomotor activity, a finding consistent with an antidepressant profile. Creatine administration increased the ubiquitous creatine kinase (uCK) and creatine kinase brain isoform (CK-B) mRNA in the hippocampus of mice. Taking into account that PGC-1α induces FNDC5/irisin expression mediating BDNF-dependent neuroplasticity, the effect of creatine administration (1 mg/kg, p. o.) on the hippocampal PGC-1α, FNDC5 and BDNF gene expression was investigated. Creatine treatment increased PGC-1α, FNDC5 and BDNF mRNA in the hippocampus as well as BDNF immunocontent. The involvement of BDNF downstream intracellular signaling pathway mediated by Akt, proapoptotic proteins BAX and BAD and antiapoptotic proteins Bcl2 and Bcl-xL was also investigated following creatine treatment. Creatine increased Akt phosphorylation (Ser 473), and Bcl2 mRNA and protein levels, and Bcl-xL mRNA, whereas BAD mRNA was decreased following creatine administration in the hippocampus. Altogether these results indicate that creatine antidepressant-like effect may be dependent on Akt activation and increased expression of the neuroprotective proteins in the hippocampus of mice. The obtained data reinforce the antidepressant property of creatine and highlight the role of these molecular targets in the pathophysiology of MDD.

Antidepressant effects of creatine on amyloid β1-40-treated mice: The role of GSK-3β/Nrf2 pathway

Alzheimer's disease (AD) is characterized by progressive synaptic dysfunction and neuronal lost in specific brain areas including hippocampus, resulting in memory/learning deficits and cognitive impairments. In addition, non-cognitive symptoms are reported in AD patients, such as anxiety, apathy and depressed mood. The current antidepressant drugs present reduced efficacy to improve depressive symptoms in AD patients. Here, we investigated the ability of creatine, a compound with neuroprotective and antidepressant properties, to counteract amyloid β_1-40 peptide-induced depressive-like behavior in mice. Moreover, we addressed the participation of the intracellular signaling pathway mediated by glycogen synthase kinase-3β (GSK-3β)/nuclear factor erythroid-2-related factor 2 (Nrf₂) in the creatine effects. Aß_1-40 administration (400 pmol/mouse, i.c.v.) increased the immobility time in the tail suspension test and decreased the grooming time and increased latency to grooming in the splash test, indicative of depressive-like behavior. These impairments were attenuated by creatine (0.01 and 10 mg/kg, p.o.) and fluoxetine (10 mg/kg, p.o., positive control). No significant alterations on locomotor performance were observed in the open field. Aß_1-40 administration did not alter hippocampal phospho-GSK-3β (Ser⁹)/total GSK-3β, total GSK-3β and heme oxygenase-1 (HO-1) immunocontents. However, Aß_1-40-infused mice treated with creatine (0.01 mg/kg) presented increased phosphorylation of GSK-3β(Ser⁹) and HO-1 immunocontent in the hippocampus. Fluoxetine per se increased GSK-3β(Ser⁹) phosphorylation, but did not alter HO-1 levels. In addition, Aß_1-40 administration increased hippocampal glutathione (GSH) levels as well as glutathione reductase (GR) and thioredoxin reductase (TrxR) activities, and these effects were abolished by creatine and fluoxetine. This study provides the first evidence of the antidepressive-like effects of creatine in Aß_1-40-treated mice, which were accompanied by hippocampal inhibition of GSK-3β and modulation of antioxidant defenses. These findings indicate the potential of creatine for the treatment of depression associated with AD.