Marine natural products: potential agents for depression treatment

Depression is a common psychiatric disorder. Due to the disadvantages of current clinical drugs, including poor efficacy and unnecessary side effects, research has shifted to novel natural products with minimal or no adverse effects as therapeutic alternatives. The ocean is a vast ecological home, with a wide variety of organisms that can produce a large number of natural products with unique structures, some of which have neuroprotective effects and are a valuable source for the development of new drugs for depression. In this review, we analyzed preclinical and clinical studies of natural products derived from marine organisms with antidepressant potential, including the effects on the pathophysiology of depression, and the underlying mechanisms of these effects. It is expected to provide a reference for the development of new antidepressant drugs.

Cannabidiol and brain function: current knowledge and future perspectives

Cannabidiol (CBD) is a naturally occurring non-psychoactive cannabinoid found in Cannabis sativa, commonly known as cannabis or hemp. Although currently available CBD products do not meet the safety standards of most food safety authorities to be approved as a dietary supplement or food additive, CBD has been gaining widespread attention in recent years due to its various potential health benefits. While primarily known for its therapeutic effects in managing epileptic seizures, psychosis, anxiety, (neuropathic) pain, and inflammation, CBD's influence on brain function has also piqued the interest of researchers and individuals seeking to enhance cognitive performance. The primary objective of this review is to gather, synthesize, and consolidate scientifically proven evidence on the impact of CBD on brain function and its therapeutic significance in treating neurological and mental disorders. First, basic background information on CBD, including its biomolecular properties and mechanisms of action is presented. Next, evidence for CBD effects in the human brain is provided followed by a discussion on the potential implications of CBD as a neurotherapeutic agent. The potential effectiveness of CBD in reducing chronic pain is considered but also in reducing the symptoms of various brain disorders such as epilepsy, Alzheimer's, Huntington's and Parkinson's disease. Additionally, the implications of using CBD to manage psychiatric conditions such as psychosis, anxiety and fear, depression, and substance use disorders are explored. An overview of the beneficial effects of CBD on aspects of human behavior, such as sleep, motor control, cognition and memory, is then provided. As CBD products remain largely unregulated, it is crucial to address the ethical concerns associated with their use, including product quality, consistency, and safety. Therefore, this review discusses the need for responsible research and regulation of CBD to ensure its safety and efficacy as a therapeutic agent for brain disorders or to stimulate behavioral and cognitive abilities of healthy individuals.

Plasma irisin and the brain-derived neurotrophic factor levels in sedentary subjects: effect of 8-weeks lifestyle intervention

Objectives. Sedentary lifestyle increasingly observed in the population contributes to the incremental incidence of obesity, cardiovascular diseases, mental disorders, type 2 diabetes, hyper-tension, dyslipidemia, and others. Physical inactivity together with an imbalance in caloric intake and expenditure leads to a loss of muscle mass, reduced insulin sensitivity, and accumulation of the visceral fat. Organokines (adipokines, myokines, hepatokines, etc.) serve in the organism for inter-organ communication. However, human studies focused on the exercise-related changes in plasma levels of certain myokines have produced contradictory results. In the present study, we verified a hypothesis that myokine irisin, which is expected to increase in response to physical activity, induces brain-derived neurotrophic factor (BDNF) production and by this way mediates the beneficial effect of exercise on several brain functions. Subjects and Methods. Women (n=27) and men (n=10) aged 44.5±12.0 years, who were sedentary and overweight/obese (men ≥25%, women ≥28% body fat), participated in the study. The effect of an 8-week intensive lifestyle intervention (150 minutes of moderate physical activity per week, diet modification, and reduction of caloric intake) on the selected organokines (irisin, BDNF) in the context of an expected improvement in cardiometabolic status was examined. Results. The 8-week lifestyle intervention resulted in a significant (p<0.05) reduction in body mass index, body fat, blood pressure, insulin resistance, lipid and liver parameters, and irisin levels (p<0.001). However, BDNF increase in the whole group did not reach statistical significance. After the improvement of cardiometabolic parameters, a significant decrease in irisin and increase in BDNF levels were also observed in the subgroup with unsatisfactory (≤5%) body weight reduction. Neither relationship between irisin and BDNF levels, nor effect of age or sex on their levels was observed. Conclusions. We cannot confirm the hypothesis that exercise-induced irisin may increase the BDNF levels, whereas, the organokine levels in the periphery may not completely reflect the processes in the brain compartments. The observed decrease in irisin levels after 8-week intensive lifestyle intervention program, which was in contrary to its supposed mechanisms of action and dynamics, suggests the presence of several yet undiscovered impacts on the secretion of irisin.

BDNF gene Val66Met polymorphisms as a predictor for clinical presentation in schizophrenia - recent findings

Schizophrenia is a highly heritable, severe psychiatric disorder that involves dysfunctions in thinking, emotions, and behavior, with a profound impact on a person's ability to function normally in their daily life. Research efforts continue to focus on elucidating possible genetic underlying mechanisms of the disorder. Although the genetic loci identified to date to be significantly associated with schizophrenia risk do not represent disease-causing factors, each one of them could be seen as a possible incremental contributor. Considering the importance of finding new and more efficient pharmacological approaches to target the complex symptomatology of this disorder, in this scoping review, we are focusing on the most recent findings in studies aiming to elucidate the contribution of one of the genetic factors involved - the BDNF gene Val66Met polymorphisms. Here we performed a systematic search in Pubmed, Embase, and Web of Science databases with the search terms: (BDNF gene polymorphism) AND (schizophrenia) for articles published in the last 5 years. To be selected for this review, articles had to report on studies where genotyping for the BDNF Val66Met polymorphism was performed in participants diagnosed with schizophrenia (or schizophrenia spectrum disorders or first-episode psychosis). The search provided 35 results from Pubmed, 134 results from Embase, and 118 results from the Web of Science database. Twenty-two articles were selected to be included in this review, all reporting on studies where an implication of the BDNF Val66Met polymorphisms in the disorder's pathophysiology was sought to be elucidated. These studies looked at BDNF gene Val66Met polymorphism variants, their interactions with other genes of interest, and different facets of the illness. The Met/Met genotype was found to be associated with higher PANSS positive scores. Furthermore, Met/Met homozygous individuals appear to present with worse cognitive function and lower levels of serum BDNF. In the Val/Val genotype carriers, increased BDNF levels were found to correlate with weight gain under Risperidone treatment. However, due to heterogeneous results, the diversity in study populations and studies' small sample sizes, generalizations cannot be made. Our findings emphasize the need for further research dedicated to clarifying the role of gene polymorphisms in antipsychotic treatment to enhance specificity and efficacy in the treatment of schizophrenia.

Exploring Rosiglitazone's Potential to Treat Alzheimer's Disease through the Modulation of Brain-Derived Neurotrophic Factor

Alzheimer's disease (AD) is a progressive neurodegenerative disorder that debilitates over 55 million individuals worldwide. Currently, treatments manage and alleviate its symptoms; however, there is still a need to find a therapy that prevents or halts disease progression. Since AD has been labeled as "type 3 diabetes" due to its similarity in pathological hallmarks, molecular pathways, and comorbidity with type 2 diabetes mellitus (T2DM), there is growing interest in using anti-diabetic drugs for its treatment. Rosiglitazone (RSG) is a peroxisome proliferator-activated receptor-gamma agonist that reduces hyperglycemia and hyperinsulinemia and improves insulin signaling. In cellular and rodent models of T2DM-associated cognitive decline and AD, RSG has been reported to improve cognitive impairment and reverse AD-like pathology; however, results from human clinical trials remain consistently unsuccessful. RSG has also been reported to modulate the expression of brain-derived neurotrophic factor (BDNF), a protein that regulates neuroplasticity and energy homeostasis and is implicated in both AD and T2DM. The present review investigates RSG's limitations and potential therapeutic benefits in pre-clinical models of AD through its modulation of BDNF expression.

Prolonged fluoride exposure induces spatial-memory deficit and hippocampal dysfunction by inhibiting small heat shock protein 22 in mice

Millions of residents in areas with high-fluoride drinking water supply ingest excessive levels of fluoride for long periods. This study investigated the mechanisms and impacts of lifelong exposure to naturally occurring moderate-high-fluoride drinking water on spatial-memory function by studying mice in controlled experiments. Spatial-memory deficits and disorders of hippocampal neuronal electrical activity were observed in mice exposed to 25-ppm or 50-ppm-fluoride drinking water for 56 weeks, but not in adult or old mice exposed to 50 ppm fluoride for 12 weeks. Ultrastructural analysis showed severely damaged hippocampal mitochondria, evidenced by reduced mitochondrial membrane potential and ATP content. Mitochondrial biogenesis was impaired in fluoride-exposed mice, manifesting as a significantly reduced mtDNA content, mtDNA-encoded subunits mtND6 and mtCO1, and respiratory complex activities. Fluoride reduced expression of Hsp22, a beneficial mediator of mitochondrial homeostasis, and decreased levels of signaling for the PGC-1α/TFAM pathway-which regulates mitochondrial biogenesis-and the NF-κβ/STAT3 pathway-which regulates mitochondrial respiratory chain enzyme activity. Hippocampus-specific Hsp22-overexpression improved fluoride-induced spatial-memory deficits by activating the PGC-1α/TFAM and STAT3 signaling pathways, while Hsp22-silencing aggravated the deficits by inhibiting both pathways. Downregulation of Hsp22 plays a vital role in fluoride-induced spatial-memory deficits by impacting mtDNA-encoding subsets and mitochondrial respiratory chain enzyme activity.

Serum brain-derived neurotrophic factor as diagnosis clue for Alzheimer's disease: A cross-sectional observational study in the elderly

Objective

Brain-derived neurotrophic factor (BDNF) has not been validated as a diagnostic marker for Alzheimer's disease (AD). To provide a different perspective, this study aimed to evaluate the relationship between serum levels of mature BDNF (mBDNF) and precursor BDNF (proBDNF) in AD and to investigate whether serum BDNF levels or the ratio of mBDNF levels to proBDNF levels (M/P) could be a valuable biomarker for determining the risk of AD in elderly individuals.

Method

A total of 126 subjects who met the inclusion criteria were assigned to either the AD group (n = 62) or the healthy control group (HC, n = 64) in this cross-sectional observationl study. Serum levels of mBDNF and proBDNF were measured using enzyme immunoassay kits. We analyzed the Mini-Mental State Examination (MMSE) scores from the two groups and examined the associations between AD and BDNF metabolism.

Results

The serum concentration of proBDNF was significantly higher in ADs (4140.937 pg/ml) than in HCs (2606.943 pg/ml; p &lt; 0.01). The MMSE significantly correlated with proBDNF (p &lt; 0.01, r = −0.686) and M/P (p &lt; 0.01, r = 0.595) in all subjects. To determine the risk for AD, the area under the receiver operating characteristic curve was calculated, which was 0.896 (95% confidence interval 0.844–0.949) for proBDNF and 0.901 (95% 0.850–0.953) for proBDNF and M/P combined.

Conclusion

We observed a correlation between low serum proBDNF levels and higher MMSE scores in AD. The most effective diagnostic strategy was the combination of proBDNF and M/P, whereas mBDNF levels performed poorly when we evaluated the predictive model.

Selective TLR4 Antagonism Prevents and Reverses Morphine-Induced Persistent Postoperative Cognitive Dysfunction, Dysregulation of Synaptic Elements, and Impaired BDNF Signaling in Aged Male Rats

Perioperative neurocognitive disorders (PNDs) are characterized by confusion, difficulty with executive function, and episodic memory impairment in the hours to months following a surgical procedure. Postoperative cognitive dysfunction (POCD) represents such impairments that last beyond 30 d postsurgery and is associated with increased risk of comorbidities, progression to dementia, and higher mortality. While it is clear that neuroinflammation plays a key role in PND development, what factors underlie shorter self-resolving versus persistent PNDs remains unclear. We have previously shown that postoperative morphine treatment extends POCD from 4 d (without morphine) to at least 8 weeks (with morphine) in aged male rats, and that this effect is likely dependent on the proinflammatory capabilities of morphine via activation of toll-like receptor 4 (TLR4). Here, we extend these findings to show that TLR4 blockade, using the selective TLR4 antagonist lipopolysaccharide from the bacterium Rhodobacter sphaeroides (LPS-RS Ultrapure), ameliorates morphine-induced POCD in aged male rats. Using either a single central preoperative treatment or a 1 week postoperative central treatment regimen, we demonstrate that TLR4 antagonism (1) prevents and reverses the long-term memory impairment associated with surgery and morphine treatment, (2) ameliorates morphine-induced dysregulation of the postsynaptic proteins postsynaptic density 95 and synaptopodin, (3) mitigates reductions in mature BDNF, and (4) prevents decreased activation of the BDNF receptor TrkB (tropomyosin-related kinase B), all at 4 weeks postsurgery. We also reveal that LPS-RS Ultrapure likely exerts its beneficial effects by preventing endogenous danger signal HMGB1 (high-mobility group box 1) from activating TLR4, rather than by blocking continuous activation by morphine or its metabolites. These findings suggest TLR4 as a promising therapeutic target to prevent or treat PNDs.SIGNIFICANCE STATEMENT With humans living longer than ever, it is crucial that we identify mechanisms that contribute to aging-related vulnerability to cognitive impairment. Here, we show that the innate immune receptor toll-like receptor 4 (TLR4) is a key mediator of cognitive dysfunction in aged rodents following surgery and postoperative morphine treatment. Inhibition of TLR4 both prevented and reversed surgery plus morphine-associated memory impairment, dysregulation of synaptic elements, and reduced BDNF signaling. Together, these findings implicate TLR4 in the development of postoperative cognitive dysfunction, providing mechanistic insight and novel therapeutic targets for the treatment of cognitive impairments following immune challenges such as surgery in older individuals.

The Role of Gut Dysbiosis in the Pathophysiology of Neuropsychiatric Disorders

Mounting evidence shows that the complex gut microbial ecosystem in the human gastrointestinal (GI) tract regulates the physiology of the central nervous system (CNS) via microbiota and the gut-brain (MGB) axis. The GI microbial ecosystem communicates with the brain through the neuroendocrine, immune, and autonomic nervous systems. Recent studies have bolstered the involvement of dysfunctional MGB axis signaling in the pathophysiology of several neurodegenerative, neurodevelopmental, and neuropsychiatric disorders (NPDs). Several investigations on the dynamic microbial system and genetic-environmental interactions with the gut microbiota (GM) have shown that changes in the composition, diversity and/or functions of gut microbes (termed "gut dysbiosis" (GD)) affect neuropsychiatric health by inducing alterations in the signaling pathways of the MGB axis. Interestingly, both preclinical and clinical evidence shows a positive correlation between GD and the pathogenesis and progression of NPDs. Long-term GD leads to overstimulation of hypothalamic-pituitary-adrenal (HPA) axis and the neuroimmune system, along with altered neurotransmitter levels, resulting in dysfunctional signal transduction, inflammation, increased oxidative stress (OS), mitochondrial dysfunction, and neuronal death. Further studies on the MGB axis have highlighted the significance of GM in the development of brain regions specific to stress-related behaviors, including depression and anxiety, and the immune system in the early life. GD-mediated deregulation of the MGB axis imbalances host homeostasis significantly by disrupting the integrity of the intestinal and blood-brain barrier (BBB), mucus secretion, and gut immune and brain immune functions. This review collates evidence on the potential interaction between GD and NPDs from preclinical and clinical data. Additionally, we summarize the use of non-therapeutic modulators such as pro-, pre-, syn- and post-biotics, and specific diets or fecal microbiota transplantation (FMT), which are promising targets for the management of NPDs.

Participation of the Serotonergic System and Brain-Derived Neurotrophic Factor in the Antidepressant-like Effect of Flavonoids

Depressive disorders are among the most disabling diseases experienced around the world, and their incidence has significantly increased over the last few decades due to multiple environmental, social, and biological factors. The search for new pharmacological alternatives to treat depression is a global priority. In preclinical research, molecules obtained from plants, such as flavonoids, have shown promising antidepressant-like properties through several mechanisms of action that have not been fully elucidated, including crossing of the blood brain barrier (BBB). This review will focus on discussing the main findings related to the participation of the serotonergic system and brain-derived neurotrophic factor (BDNF) on the antidepressant-like effect of some flavonoids reported by behavioral, neurochemical, and molecular studies. In this sense, evidence shows that depressive individuals have low levels of serotonin and BDNF, while flavonoids can reverse it. Finally, the elucidation of the mechanism used by flavonoids to modulate serotonin and BDNF will contribute to our understanding of the neurobiological bases underlying the antidepressant-like effects produced by these natural compounds.

Low VGF is associated with executive dysfunction in patients with major depressive disorder

OBJECTIVES

Executive dysfunction is considered to be one of the cognitive impairment dimensions that are easily observed in depression, but its underlying molecular mechanism is still unclear. Study have shown that the neuropeptide VGF (non-acronymic) plays an important role in the regulation of hippocampal neurogenesis and neuroplasticity. Previous studies have shown that VGF may be related to the psychopathology of depression and cognitive impairment. However, the correlation between VGF and executive dysfunction in MDD has not been investigated.

METHODS

A total of 35 MDD patients and 31 healthy control patients were enrolled in this study. The 17-item Hamilton Depression Rating Scale (HDRS) was used to measure the severity of depression, and the Wisconsin Card Sorting Test (WCST) was used to assess executive dysfunction. Double antibody sandwich enzyme-linked immunosorbent assay (ELISA) was used to determine serum VGF in peripheral blood.

RESULTS

The level of serum VGF in MDD patients was significantly lower compared to that in the healthy control group (p < 0.001). Moreover, Response Administered (RA) scores, Response preservative errors (RPE), and Non-response preservative errors (NRPE) were all higher in the MDD group (all p < 0.05). In contrast, Categories Completed (CC) and Response Correct (RC) scores were lower (all p < 0.05). Further results showed a significant correlation between serum VGF with RA (r = -0.372, p = 0.028) and RPE scores (r = 0.507, p = 0.002) in patients with depression, while serum VGF showed no correlation with the severity of depression in either group.

CONCLUSIONS

VGF may play an important role in executive function dysfunction in MDD patients, and VGF levels may become a new marker for predicting executive function dysfunction in depression.

Probiotics ameliorates LPS induced neuroinflammation injury on Aβ 1-42, APP, γ-β secretase and BDNF levels in maternal gut microbiota and fetal neurodevelopment processes

The gut microbiota influences brain development and functioning through the gut-brain axis. This is first study regulate maternal gut microbiota and fetal neurodevelopment processes by using probiotics such as Bifidobacterium bifidum (BIF) and Lactobacillus salivarius (LAC) in the prenatal period. In this study, Wistar Albino female rats were divided into five groups; Control, lipopolysaccharide (LPS, 100 µg/kg), LPS + LAC, LPS + BIF and LPS + LAC + BIF (4 × 10⁹ ml CFU). Maternal rats were given probiotics for 21 days. Inflammation was induced by lipopolysaccharide (LPS), on the 17th day of pregnancy. After birth, the brain tissues of the maternal and neonatal rats were removed and their blood was collected. Fecal calprotectin levels of pregnant rats were measured as an important biomarker in determining intestinal flora disruption. Calprotectin levels were high in LPS group (p < 0.05). Aβ 1-42, APP, γ secretase and β- secretase levels were higher in both maternal and neonatal LPS groups (p < 0.05). These levels were statistically decreased in the probiotic groups compared to the LPS group, as demonstrated in both biochemical and histological analyzes (p < 0.05). While BDNF mRNA expression decreased in LPS groups, APP level increased in the same group. The difference between groups in mRNA expressions in the neonatal brain tissues was similar to maternal brain tissues. What's more, BDNF/actin and APP/actin rates were proven by western blot and the damage caused by neuroinflammation in the brain tissue and the preservation of the intestinal microbiota were visualized histopathologically on the morphological structures in all groups. It will shed light on new therapeutic strategies for the impact of the use of probiotics on the neurodevelopmental processes of the neonatal against LPS-induced inflammatory responses and impaired gut microbiota in the prenatal period.

A Cross-Sectional Study on Associations Between BDNF, CRP, IL-6 and Clinical Symptoms, Cognitive and Personal Performance in Patients With Paranoid Schizophrenia

BACKGROUND

Cognitive impairment is among the core dimensions in schizophrenia and is a significant predictor of everyday functioning in people with schizophrenia. Given the enormous burden of schizophrenia, the search for its clinically relevant biomarkers is essential. Researchers have been trying to elucidate factors of cognitive impairment as well as personal performance, but the search is still ongoing. The aim of the study was to search for associations between BDNF, CRP, IL-6 and clinical symptoms, cognitive and personal performance in patients with paranoid schizophrenia.

METHODS

A total of 86 patients (53.5% women, mean age 31.1 ± 6.5) with paranoid schizophrenia (F20.0; ICD-10) in remission were examined. Clinical and neuropsychological examination included the Positive and Negative Syndrome Scale, Personal and Social Performance Scale, Calgary Depression Scale for Schizophrenia and the Brief Assessment of Cognitive Function in Schizophrenia. IL-6, BDNF, CRP levels were determined in the patients' blood serum.

RESULTS

Cognitive impairment was revealed in 79.1% of patients and was more profound in patients with higher number of hospitalizations (p = 0.006). The average BDNF levels were 13.38 ± 15.84 ng/ml, CRP concentration was 2.09 ± 2.54 mg/l, and IL-6 levels were 12.14 ± 5.88 pg/ml. There were no differences in biomarker levels or BACS results in patients that had different antipsychotic therapy or differed in the presence of anticholinergic therapy. CRP levels were higher in patients with longer disease duration, lower age of onset, more impaired personal social performance and processing speed. IL-6 was higher in individuals with lower working memory scores. PANSS negative subscale score negatively correlated and PSP score positively correlated with most cognitive domains. A linear regression established that the first episode vs. multiple episodes of schizophrenia could statistically significantly predict personal and social performance and cognition, including speech fluency and planning, as well as CRP levels.

CONCLUSIONS

This study continues the search for biomarkers of schizophrenia and cognitive impairment in schizophrenia to improve the reliability of diagnosing the disorder and find new treatment approaches. The role of the number of psychoses experienced (first episode vs. multiple episodes of schizophrenia) in cognition, personal and social performance and inflammation is shown.

The Gut Microbiome and Alzheimer's Disease: A Growing Relationship

Evidence that the gut microbiota plays a key role in the pathogenesis of Alzheimer's disease is already unravelling. The microbiota-gut-brain axis is a bidirectional communication system that is not fully understood but includes neural, immune, endocrine, and metabolic pathways. The progression of Alzheimer's disease is supported by mechanisms related to the imbalance in the gut microbiota and the development of amyloid plaques in the brain, which are at the origin of Alzheimer's disease. Alterations in the composition of the gut microbiome led to dysregulation in the pathways governing this system. This leads to neurodegeneration through neuroinflammation and neurotransmitter dysregulation. Neurodegeneration and disruption of the blood-brain barrier are frontiers at the origin of Alzheimer's disease. Furthermore, bacteria populating the gut microbiota can secrete large amounts of amyloid proteins and lipopolysaccharides, which modulate signaling pathways and alter the production of proinflammatory cytokines associated with the pathogenesis of Alzheimer's disease. Importantly, through molecular mimicry, bacterial amyloids may elicit cross-seeding of misfolding and induce microglial priming at different levels of the brain-gut-microbiota axis. The potential mechanisms of amyloid spreading include neuron-to-neuron or distal neuron spreading, direct blood-brain barrier crossing, or via other cells such as astrocytes, fibroblasts, microglia, and immune system cells. Gut microbiota metabolites, including short-chain fatty acids, pro-inflammatory factors, and neurotransmitters may also affect AD pathogenesis and associated cognitive decline. The purpose of this review is to summarize and discuss the current findings that may elucidate the role of gut microbiota in the development of Alzheimer's disease. Understanding the underlying mechanisms may provide new insights into novel therapeutic strategies for Alzheimer's disease, such as probiotics and targeted oligosaccharides.

Human Gut Microbiota in Health and Selected Cancers

The majority of the epithelial surfaces of our body, and the digestive tract, respiratory and urogenital systems, are colonized by a vast number of bacteria, archaea, fungi, protozoans, and viruses. These microbiota, particularly those of the intestines, play an important, beneficial role in digestion, metabolism, and the synthesis of vitamins. Their metabolites stimulate cytokine production by the human host, which are used against potential pathogens. The composition of the microbiota is influenced by several internal and external factors, including diet, age, disease, and lifestyle. Such changes, called dysbiosis, may be involved in the development of various conditions, such as metabolic diseases, including metabolic syndrome, type 2 diabetes mellitus, Hashimoto's thyroidis and Graves' disease; they can also play a role in nervous system disturbances, such as multiple sclerosis, Alzheimer's disease, Parkinson's disease, and depression. An association has also been found between gut microbiota dysbiosis and cancer. Our health is closely associated with the state of our microbiota, and their homeostasis. The aim of this review is to describe the associations between human gut microbiota and cancer, and examine the potential role of gut microbiota in anticancer therapy.

Vitamin A Deficiency Exacerbates Gut Microbiota Dysbiosis and Cognitive Deficits in Amyloid Precursor Protein/Presenilin 1 Transgenic Mice

Vitamin A deficiency (VAD) plays an essential role in the pathogenesis of Alzheimer’s disease (AD). However, the specific mechanism by which VAD aggravates cognitive impairment is still unknown. At the intersection of microbiology and neuroscience, the gut-brain axis is undoubtedly contributing to the formation and function of neurological systems, but most of the previous studies have ignored the influence of gut microbiota on the cognitive function in VAD. Therefore, we assessed the effect of VAD on AD pathology and the decline of cognitive function in AD model mice and determined the role played by the intestinal microbiota in the process. Twenty 8-week-old male C57BL/6J amyloid precursor protein/presenilin 1 (APP/PS1) transgenic mice were randomly assigned to either a vitamin A normal (VAN) or VAD diet for 45 weeks. Our results show that VAD aggravated the behavioral learning and memory deficits, reduced the retinol concentration in the liver and the serum, decreased the transcription of vitamin A (VA)-related receptors and VA-related enzymes in the cortex, increased amyloid-β peptides (Aβ40 and Aβ42) in the brain and gut, upregulate the translation of beta-site APP-cleaving enzyme 1 (BACE1) and phosphorylated Tau in the cortex, and downregulate the expression of brain-derived neurotrophic factor (BDNF) and γ-aminobutyric acid (GABA) receptors in the cortex. In addition, VAD altered the composition and functionality of the fecal microbiota as exemplified by a decreased abundance of Lactobacillus and significantly different α- and β-diversity. Of note, the functional metagenomic prediction (PICRUSt analysis) indicated that GABAergic synapse and retinol metabolism decreased remarkably after VAD intervention, which was in line with the decreased expression of GABA receptors and the decreased liver and serum retinol. In summary, the present study provided valuable facts that VAD exacerbated the morphological, histopathological, molecular biological, microbiological, and behavioral impairment in the APP/PS1 transgenic mice, and the intestinal microbiota may play a key mediator role in this mechanism.

Association Between Components of Cognitive Reserve and Serum BDNF in Healthy Older Adults

Background: The brain-derived neurotrophic factor (BDNF) protein has been shown to have a prominent role in neuron survival, growth, and function in experimental models, and the BDNF Val66Met polymorphism which regulates its expression has been linked to resilience toward the effects of aging on cognition. Cognitively stimulating activity is linked to both increased levels of BDNF in the brain, and protection against age-related cognitive decline. The aim of this study was to investigate the associations between serum BDNF levels, the BDNF Val66Met genotype, and components of cognitive reserve in early and mid-life, measured with the Lifetime of Experiences Questionnaire (LEQ). Methods: Serum BDNF levels were measured cross-sectionally in 156 participants from the Tasmanian Healthy Brain Project (THBP) cohort, a study examining the potential benefits of older adults engaging in a university-level education intervention. Multiple linear regression was used to estimate serum BDNF's association with age, education, gender, BDNF Val66Met genotype, later-life university-level study, and cognitively stimulating activities measured by the LEQ. Results: Serum BDNF in older adults was associated with early life education and training, increasing 0.007 log(pg/ml) [95%CI 0.001, 0.012] per unit on the LEQ subscale. Conversely, education and training in mid-life were associated with a -0.007 log(pg/ml) [-0.012, -0.001] decrease per unit on the LEQ subscale. Serum BDNF decreased with age (-0.008 log(pg/ml) [-0.015, -0.001] per year), and male gender (-0.109 log(pg/ml) [-0.203, -0.015]), but mean differences between the BDNF Val66Met polymorphisms were not significant (p = 0.066). All effect sizes were small, with mid-life education and training having the largest effect size ( η p 2 = 0.044). Conclusion: Education in both early and mid-life explained small but significant amounts of variance in serum BDNF levels, more than age or gender. These effects were opposed and independent, suggesting that education at different stages of life may be associated with different cognitive and neural demands. Education at different stages of life may be important covariates when estimating associations between other exposures and serum BDNF.

Brain-Derived Neurotrophic Factor Signaling in Depression and Antidepressant Action

Neurotrophic factors, particularly BDNF (brain-derived neurotrophic factor), have been associated with depression and antidepressant drug action. A variety of preclinical and clinical studies have implicated impaired BDNF signaling through its receptor TrkB (neurotrophic receptor tyrosine kinase 2) in the pathophysiology of mood disorders, but many of the initial findings have not been fully supported by more recent meta-analyses, and more both basic and clinical research is needed. In contrast, increased expression and signaling of BDNF has been repeatedly implicated in the mechanisms of both typical and rapid-acting antidepressant drugs, and recent findings have started to elucidate the mechanisms through which antidepressants regulate BDNF signaling. BDNF is a critical regulator of various types of neuronal plasticities in the brain, and plasticity has increasingly been connected with antidepressant action. Although some equivocal data exist, the hypothesis of a connection between neurotrophic factors and neuronal plasticity with mood disorders and antidepressant action has recently been further strengthened by converging evidence from a variety of more recent data reviewed here.

Early-life stress effects on BDNF DNA methylation in first-episode psychosis and in rats reared in isolation

Stressful events during early-life are risk factors for psychiatric disorders. Brain-derived neurotrophic factor (BDNF) is implicated in psychosis pathophysiology and deficits in BDNF mRNA in animal models of psychiatric disease are reported. DNA methylation can control gene expression and may be influenced by environmental factors such as early-life stress. We investigated BDNF methylation in first-episode psychosis (FEP) patients (n = 58), their unaffected siblings (n = 29) and community-based controls (n = 59), each of whom completed the Childhood Trauma Questionnaire (CTQ); BDNF methylation was also tested in male Wistar rats housed isolated or grouped from weaning. DNA was extracted from human blood and rat brain (prefrontal cortex and hippocampus), bisulphite-converted and the methylation of equivalent sequences within BDNF exon IV determined by pyrosequencing. BDNF methylation did not differ significantly between diagnostic groups; however, individuals who had experienced trauma presented higher levels of methylation. We found association between the mean BDNF methylation and total CTQ score in FEP, as well as between individual CpG sites and subtypes of trauma. No significant correlations were found for controls or siblings with child trauma. These results were independent of age, gender, body mass index, BDNF genotype or LINE-1, a measure of global methylation, which showed no significant association with trauma. Isolation rearing resulted in increased BDNF methylation in both brain regions compared to group-housed animals, a correlate of previously reported changes in gene expression. Our results suggest that childhood maltreatment may result in increased BDNF methylation, providing a mechanism underlying the association between early-life stress and psychosis.

Current Methodological Pitfalls and Caveats in the Assessment of Exercise-Induced Changes in Peripheral Brain-Derived Neurotrophic Factor: How Result Reproducibility Can Be Improved

Neural mechanisms, such as enhanced neuroplasticity within the motor system, underpin exercise-induced motor improvements. Being a key mediator of motor plasticity, brain-derived neurotrophic factor (BDNF) is likely to play an important role in mediating exercise positive effects on motor function. Difficulties in assessing brain BDNF levels in humans have drawn attention to quantification of blood BDNF and raise the question of whether peripheral BDNF contributes to exercise-related motor improvements. Methodological and non-methodological factors influence measurements of blood BDNF introducing a substantial variability that complicates result interpretation and leads to inconsistencies among studies. Here, we discuss methodology-related issues and approaches emerging from current findings to reduce variability and increase result reproducibility.

Emerging role of gut microbiota in modulation of neuroinflammation and neurodegeneration with emphasis on Alzheimer's disease

Alzheimer's disease (AD) is a complex multifactorial disease involving chronic neuroinflammation and neurodegeneration. It has been recently recognized that gut microbiota interacts with the brain, and it is termed as microbiota-gut-brain axis. Modulation of this axis has been recently reported to affect the pathogenesis of neurodegenerative diseases, such as AD. Gut microbiota has a pivotal role in regulating multiple neuro-chemical pathways through the highly interconnected gut-brain axis. Recent emerging evidences have highlighted that the intestinal microflora takes part in bidirectional communication between the gut and the brain. Due to this, the researchers have suggested that human gut microflora may even act as the "second brain" and may be responsible for neurodegenerative disorders like Alzheimer's disease. Dysbiosis of gut microbiota can induce increased intestinal permeability and systemic inflammation. This may lead to the development of AD pathologies and cognitive impairment via the neural, immune, endocrine, and metabolic pathways. Thus, the modulation of gut microbiota through personalized diet, oral bacteriotherapy may lead to alteration of gut microbiota their products including amyloid protein. It has been demonstrated that modulation of the gut microbiota induces beneficial effects on neuronal pathways consequently leading to delay the progression of Alzheimer's disease. Thus, this approach may provide a novel therapeutic option for treatment of AD.

Interplay of Good Bacteria and Central Nervous System: Cognitive Aspects and Mechanistic Considerations

The human gastrointestinal tract hosts trillions of microorganisms that is called “gut microbiota.” The gut microbiota is involved in a wide variety of physiological features and functions of the body. Thus, it is not surprising that any damage to the gut microbiota is associated with disorders in different body systems. Probiotics, defined as living microorganisms with health benefits for the host, can support or restore the composition of the gut microbiota. Numerous investigations have proved a relationship between the gut microbiota with normal brain function as well as many brain diseases, in which cognitive dysfunction is a common clinical problem. On the other hand, increasing evidence suggests that the existence of a healthy gut microbiota is crucial for normal cognitive processing. In this regard, interplay of the gut microbiota and cognition has been under focus of recent researches. In the present paper, I review findings of the studies considering beneficial effects of either gut microbiota or probiotic bacteria on the brain cognitive function in the healthy and disease statuses.

Gut-brain axis: A matter of concern in neuropsychiatric disorders…!

The gut microbiota is composed of a large number of microbes, usually regarded as commensal bacteria. It has become gradually clear that gastrointestinal microbiota affects gut pathophysiology and the central nervous system (CNS) function by modulating the signaling pathways of the microbiota-gut-brain (MGB) axis. This bidirectional MGB axis communication primarily acts through neuroendocrine, neuroimmune, and autonomic nervous systems (ANS) mechanisms. Accumulating evidence reveals that gut microbiota interacts with the host brain, and its modulation may play a critical role in the pathology of neuropsychiatric disorders. Recently, neuroscience research has established the significance of gut microbiota in the development of brain systems that are essential to stress-related behaviors, including depression and anxiety. Application of modulators of the MGB, such as psychobiotics (e.g., probiotics), prebiotics, and specific diets, may be a promising therapeutic approach for neuropsychiatric disorders. The present review article primarily focuses on the relevant features of the disturbances of the MGB axis in the pathophysiology of neuropsychiatric disorders and its potential mechanisms.

BDNF as a Biomarker of Cognition in Schizophrenia/Psychosis: An Updated Review

Brain Derived Neurotrophic Factor (BDNF) has been linked to cognitive symptoms of schizophrenia, which has been documented in previous reviews by several authors. However, a trend has recently emerged in this field moving from studying schizophrenia as a disease to studying psychosis as a group. This review article focuses on recent BDNF studies in relation to cognition in human subjects during different stages of the psychotic process, including subjects at high risk of developing psychosis, patients at their first episode of psychosis, and patients with chronic schizophrenia. We aim to provide an update of BDNF as a biomarker of cognitive function on human subjects with schizophrenia or earlier stages of psychosis, covering new trends, controversies, current research gaps, and suggest potential future developments in the field. We found that most of current research regarding BDNF and cognitive symptoms in psychosis is done around schizophrenia as a disease. Therefore, it is necessary to expand the study of the relationship between BDNF and cognitive symptoms to psychotic illnesses of different stages and origins.

Exploring the Impact of Modifiable Factors on Serum BDNF in Psychiatric Patients and Community Controls

BACKGROUND

Brain-derived neurotrophic factor (BDNF) has been a focus of psychiatric research for the past two decades. BDNF has been shown to impact neural function and development. Studies have investigated serum BDNF as a biomarker for psychiatric disorders such as depression and schizophrenia. In some studies, investigators attempt to control for variables such as smoking status, exercise, or diet. However, the relationship between these factors and BDNF is not clearly established. Furthermore, some studies have questioned whether a difference in the impact of BDNF exists between psychiatric and healthy populations.

PURPOSE

We aim to examine the association between serum BDNF levels and modifiable risk factors such as body mass index (BMI), smoking, exercise levels, and diet. Subsequently, we aim to examine whether the relationship between these risk factors and serum BDNF is different between psychiatric and control populations.

PATIENTS AND METHODS

We use cross-sectional data from an age- and sex-matched case-control study of participants with psychiatric inpatients and community controls without psychiatric diagnoses. Participants completed comprehensive assessments at study enrolment including sociodemographic information, smoking status, exercise, diet, and BMI. Serum BDNF levels were collected from participants. Linear regression analysis was performed to determine the association between modifiable factors and serum BDNF level.

RESULTS

A significant association was found between sedentary activity level and lower serum BDNF levels (Beta coefficient = -2.49, 95% confidence interval [CI] -4.70, -0.28, p = 0.028). Subgroup analysis demonstrated that this association held for psychiatric inpatients but not for community controls; it also held in females (Beta coefficient = -3.18, 95% CI -6.29, -0.07, p = 0.045) but not in males (Beta coefficient = -1.42, 95% CI -4.61, 1.78, p = 0.383). Antidepressant use had a significantly different association between male (Beta coefficient = 3.20, 95% CI 0.51, 5.88, p = 0.020) and female subgroups (Beta coefficient = -3.10, 95% CI -5.75, -0.46, p = 0.022). No significant association was found between other factors and serum BDNF.

CONCLUSION

Sedentary activity level may lead to lower serum BDNF levels in individuals with psychiatric diagnoses. Our findings support the notion that physical activity can provide a positive impact as part of treatment for psychiatric illness.

Extra-cranial factors in the development of Alzheimer's disease

The development of Alzheimer's Disease (AD) likely involves dysfunction in more than one extra-cranial organ system. AD appears to depend on several functional organ impairments that develops frequently during aging: lack of normal hepatic synthesis, defective detoxification of ammonia, gut microbiome dysbiosis, the development of insulin resistance, diminished adrenal production of dehydroepiandrosterone, nutrient depletion, impaired immune processes with persistent chronic neuro-inflammation, and persistent infectious processes are important components of this system-wide disorder. By reviewing these abnormalities in different organ systems, this review intends to suggest that clinical research into the prevention of dementia needs to take this interplay of organ system dysfunction into account. The design of therapeutic interventions needs to address dysfunction in more than one system at a time. We have singled out one aberrant signaling pathway, NF-kB, that seems common to several of the dysfunctional organ systems and suggest some potential interventions that may be effective when combined with others. Clinical research may need to shift from single factor interventions to studies that include multiple simultaneous interventions that restore health in multiple impaired organ systems in the aging human in order to avert future epidemics of AD.

Proteolytic cleavage of proBDNF to mBDNF in neuropsychiatric and neurodegenerative diseases

Brain-derived neurotrophic factor (BDNF) is involved in pathophysiological mechanisms in neuropsychiatric diseases, including depression, anxiety, and schizophrenia (SZ), as well as neurodegenerative diseases like Parkinson's disease (PD) and Alzheimer's disease (AD). An imbalance or insufficient pro-brain-derived neurotrophic factor (proBDNF) transformation into mature BDNF (mBDNF) is potentially critical to the disease pathogenesis by impairing neuronal plasticity as suggested by results from many studies. Thus, promoting proBDNF transformation into mBDNF is therefore hypothesized as beneficial for the treatment of neuropsychiatric and neurodegenerative diseases. ProBDNF is proteolytically cleaved into the mBDNF by intracellular furin/proprotein convertases and extracellular proteases (plasmin/matrix metallopeptidases). This article reviews the mechanisms of the conversion of proBDNF to mBDNF and the research status of intracellular/extracellular proteolytic proteases for neuropsychiatric and neurodegenerative disorders.

Spaceflight and brain plasticity: Spaceflight effects on regional expression of neurotransmitter systems and neurotrophic factors encoding genes

The critical problem of space exploration is the effect of long-term space travel on brain functioning. Current information concerning the effects of actual spaceflight on the brain was obtained on rats and mice flown on five missions of Soviet/Russian biosatellites, NASA Neurolab Mission STS90, and International Space Station (ISS). The review provides converging lines of evidence that: 1) long-term spaceflight affects both principle regulators of brain neuroplasticity - neurotransmitters (5-HT and DA) and neurotrophic factors (CDNF, GDNF but not BDNF); 2) 5-HT- (5-HT_2A receptor and MAO A) and especially DA-related genes (TH, MAO A, COMT, D1 receptor, CDNF and GDNF) belong to the risk neurogenes; 3) brain response to spaceflight is region-specific. Substantia nigra, striatum and hypothalamus are highly sensitive to the long-term spaceflight: in these brain areas spaceflight decreased the expression of both DA-related and neurotrophic factors genes. Since DA system is involved in the regulation of movement and cognition the data discussed in the review could explain dysfunction of locomotion and behavior of astronauts and direct further investigations to the DA system.

Depression and Anxiety in the Epilepsies: from Bench to Bedside

PURPOSE OF REVIEW

Depression and anxiety substantially contribute to interictal disability in patients with epilepsy (PWE). This review summarizes current studies that shed light on mechanisms of comorbidity.

RECENT FINDINGS

Mounting epidemiological data implicate shared risk factors for anxiety/depression and seizure propensity, but these remain largely elusive and probably vary by epilepsy type. Within PWE, these symptoms appear to be associated with unique genetic, neuropathological, and connectivity profiles. Temporal lobe epilepsy has received enormous emphasis particularly in preclinical studies of comorbidity, where candidate neurobiological mechanisms underlying bidirectionality have been tested without psychopharmacological confounds. Depression and anxiety in epilepsy reflect dysfunction within broadly distributed limbic networks that may be the cause or consequence of epileptogenesis. In refractory epilepsy, seizures and/or certain anticonvulsants may distort central emotional homeostatic mechanisms that perpetually raise seizure risk. Developing future safe and effective combined anticonvulsant-antidepressant treatments will require a detailed understanding of anatomical and molecular nodes that pleiotropically enhance seizure risk and negatively alter emotionality.

Serum 25-Hydroxyvitamin D Concentrations Are Associated with Mental Health and Psychosocial Stress in Young Adults

We aimed to test the hypothesis that serum 25-hydroxyvitamin D₃ (25(OH)D) concentration is associated with mental health and life stress measures in young adults and investigate gender and racial disparities in these associations. This study comprised 327 black and white participants. Depression, trait anxiety, perceived stress, and hostility were measured by the following validated instruments: Beck Depression Inventory (BDI), State-Trait Anxiety Inventory (STAI), Perceived Stress Scale (PSS), and Cook–Medley Hostility Scale (CMHS). Linear regression was used to estimate correlations between serum 25(OH)D concentration and mental health measurements in the total population and in subgroups stratified by gender and race. In this sample (28.2 ± 3.1 years, 52% female, 53% black), serum 25(OH)D concentration was negatively related to BDI, STAI, PSS, total CMHS score, and the majority of CMHS subscale scores (p-values < 0.05). Stratified by gender, most of these associations remained significant only in women (p-values < 0.05). Stratified by race, higher 25(OH)D concentrations in white participants were significantly related to lower BDI, STAI, PSS, and CMHS-cynicism subscales (p-values < 0.05); 25(OH)D concentrations in the black participants were only inversely associated with CMHS and most CMHS subscales (p-values < 0.05) but not with BDI, STAI, and PSS. We present novel findings of consistent inverse relationships between serum 25(OH)D concentration and various measures of mental health and life stress. Long-term interventional studies are warranted in order to investigate the roles of vitamin D supplementation in the prevention and mitigation of depression, anxiety, and psychological stress in young adults.

Gut Microbiota in Neurological Disorders

The incidence of neurological disorders such as multiple sclerosis (MS), Alzheimer's disease (AD) and Parkinson's disease (PD) is increasing throughout the world, but their pathogenesis remains unclear and successful treatment remains elusive. Bidirectional communications between the central nervous system and gut microbiota may play some role in the pathogenesis of the above disorders. Up to a thousand bacterial species reside in human intestine; they colonize the gut shortly after birth and remain for life. Numerous studies point to the role of microbiota composition in the development, course and treatment of MS, AD and PD.

Plasma and serum brain-derived neurotrophic factor (BDNF) levels and their association with neurocognition in at-risk mental state, first episode psychosis and chronic schizophrenia patients

Objectives: Brain-derived neurotrophic factor (BDNF) is involved in numerous cognitive processes. Since cognitive deficits are a core feature of psychotic disorders, the investigation of BDNF levels in psychosis and their correlation with cognition has received increased attention. However, there are no studies investigating BDNF levels in individuals with an at-risk mental state (ARMS) for psychosis. Hence, the aims of the present study were: (1) assessing peripheral BDNF levels across different (potential) stages of psychosis; (2) investigating their association with cognition.Methods: Plasma and serum BDNF levels and neuropsychological performance were assessed in 16 ARMS, six first-episode psychosis (FEP), and 11 chronic schizophrenia (CS) patients. Neuropsychological assessment covered intelligence, verbal memory, working memory, attention and executive functioning.Results: Both plasma and serum BDNF levels were highest in CS, intermediate in FEP and lowest in ARMS. Multiple regression analysis revealed a significant positive association of plasma BDNF levels with planning ability across all groups.Conclusions: The lower peripheral BDNF levels in ARMS compared to FEP and CS might point towards an important drop of this neurotrophin prior to the onset of frank psychosis. The associations of peripheral BDNF with planning-abilities match previous findings.

Hericium erinaceus Improves Mood and Sleep Disorders in Patients Affected by Overweight or Obesity: Could Circulating Pro-BDNF and BDNF Be Potential Biomarkers?

Epidemiological data indicate that subjects affected by obesity have an increased risk of developing mood disorders. The relationship between obesity and mood disorders is bidirectional. We assessed whether a Hericium erinaceus treatment improved depression, anxiety, sleep, and binge eating disorders after 8 weeks of supplementation in subjects affected by overweight or obesity under a low calorie diet regimen. Looking for a possible clinical biomarker, we assessed the serum balance between brain-derived neurotrophic factor (BDNF) and its precursor pro-BDNF before and after H. erinaceus supplementation. Seventy-seven volunteers affected by overweight or obesity were recruited at the offices of the Department of Preventive Medicine, Luigi Devoto Clinic of Work, Obesity Centre, at the IRCCS Foundation Policlinico Hospital of Milan (Italy). Patients were recruited only if they had a mood and/or sleep disorder and/or were binge eating as evaluated through self-assessment questionnaires. We used two different enzyme-linked immunosorbent assays kits to discriminate circulating levels of pro-BDNF and BDNF. Eight weeks of oral H. erinaceus supplementation decreased depression, anxiety, and sleep disorders. H. erinaceus supplementation improved mood disorders of a depressive-anxious nature and the quality of the nocturnal rest. H. erinaceus increased circulating pro-BDNF levels without any significant change in BDNF circulating levels.

Is Brain-Derived Neurotrophic Factor: A Common Link Between Neurodegenerative Disorders and Cancer?

BACKGROUND

Cancer is a common disease caused by the excessive proliferation of cells, and neurodegenerative diseases are the disorders caused due to the degeneration of neurons. Both can be considered as diseases caused by the dysregulation of cell cycle events. A recent data suggests that there is a strong inverse association between cancer and neurodegenerative disorders. There is indirect evidence to postulate Brain-derived Neurotrophic Factor (BDNF) as a potential molecular link in this association.

DISCUSSION

The BDNF levels are found to be downregulated in many neurodegenerative disorders and are found to be upregulated in various kinds of cancers. The lower level of BDNF in Alzheimer's and Parkinson's disease has been found to be related to cognitive and other neuropsychological impairments, whereas, its higher levels are associated with the tumour growth and metastasis and poor survival rate in the cancer patients.

CONCLUSION

In this review, we propose that variance in BDNF levels is critical in determining the course of cellular pathophysiology and the development of cancer or neurodegenerative disorder. We further propose that an alternative therapeutic strategy that can modulate BDNF expression, can rescue or prevent above said pathophysiological course. Larger studies that examine this link through animal studies are imperative to understand the putative biochemical and molecular link to wellness and disease.

The pharmacological perturbation of brain zinc impairs BDNF-related signaling and the cognitive performances of young mice

Zinc (Zn2+) is a pleiotropic modulator of the neuronal and brain activity. The disruption of intraneuronal Zn2+ levels triggers neurotoxic processes and affects neuronal functioning. In this study, we investigated how the pharmacological modulation of brain Zn2+ affects synaptic plasticity and cognition in wild-type mice. To manipulate brain Zn2+ levels, we employed the Zn2+ (and copper) chelator 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol, CQ). CQ was administered for two weeks to 2.5-month-old (m.o.) mice, and effects studied on BDNF-related signaling, metalloproteinase activity as well as learning and memory performances. CQ treatment was found to negatively affect short- and long-term memory performances. The CQ-driven perturbation of brain Zn2+ was found to reduce levels of BDNF, synaptic plasticity-related proteins and dendritic spine density in vivo. Our study highlights the importance of choosing "when", "where", and "how much" in the modulation of brain Zn2+ levels. Our findings confirm the importance of targeting Zn2+ as a therapeutic approach against neurodegenerative conditions but, at the same time, underscore the potential drawbacks of reducing brain Zn2+ availability upon the early stages of development.

Frailty and the gut

Frailty, which is a syndrome that encompasses losses in physical, psychological and social domains, is responsible for enhanced vulnerability to endogenous and/or exogenous stressors. Frailty is a public health problem for an ageing society; however, it is poorly understood and often under-recognised in clinical settings. In particular, the impact of frailty on either intestinal functions, i.e. immune response, permeability, and absorption, or gut microbiota composition is as yet mostly unexplored. A better comprehension of the intestinal dysfunction occurring in the elderly would help in clarifying the mechanisms predisposing frail patients to a higher risk of infectious or inflammatory events. Moreover, recent evidence suggests that senescence-induced perturbations of the gut-brain axis are involved in the neuroinflammation process, thus raising the hypothesis that preserving gut permeability and preventing frailty-related changes in the microbiota composition might reduce the susceptibility to develop neurodegenerative disorders. In this review, we highlight the current insights concerning the relationship between frailty, intestinal functions, microbiota, and gut-brain axis.

Cognitive impairments and low BDNF serum levels in first-episode drug-naive patients with schizophrenia

Evidence shows that BDNF may regulate activity-dependent forms of synaptic plasticity underlying learning and memory. Previous studies reported low BDNF levels and cognitive impairment in the early stage of schizophrenia. Our current study aimed to explore the association between serum BDNF and cognitive functions in first-episode drug-naïve (FEDN) patients with schizophrenia, which has been under-investigated. We recruited 80 FEDN patients and 80 healthy controls and examined the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and serum BDNF in both groups. Patient psychopathology was assessed using the Positive and Negative Syndrome Scale (PANSS). BDNF levels were significantly lower in patients compared to controls (p < 0.001). The RBANS total score and nearly all indexes (all p < 0.001) except for visuospatial/constructional index (p > 0.05) were significantly lower in patients than controls. No significant correlation was found between BDNF and any index or total scores of RBANS in either patients or healthy controls (all p > 0.05). However, the PANSS negative subscale score were negatively associated with both the immediate memory and language indexes (both p < 0.005). Our findings suggest that excessive cognitive impairments are present in the early stage of schizophrenia. Low BDNF may contribute to the pathogenesis of schizophrenia, but maybe not to its cognitive impairments.

The Gut Microbiota and Alzheimer's Disease

The gut microbiota comprises a complex community of microorganism species that resides in our gastrointestinal ecosystem and whose alterations influence not only various gut disorders but also central nervous system disorders such as Alzheimer's disease (AD). AD, the most common form of dementia, is a neurodegenerative disorder associated with impaired cognition and cerebral accumulation of amyloid-β peptides (Aβ). Most notably, the microbiota-gut-brain axis is a bidirectional communication system that is not fully understood, but includes neural, immune, endocrine, and metabolic pathways. Studies in germ-free animals and in animals exposed to pathogenic microbial infections, antibiotics, probiotics, or fecal microbiota transplantation suggest a role for the gut microbiota in host cognition or AD-related pathogenesis. The increased permeability of the gut and blood-brain barrier induced by microbiota dysbiosis may mediate or affect AD pathogenesis and other neurodegenerative disorders, especially those associated with aging. In addition, bacteria populating the gut microbiota can secrete large amounts of amyloids and lipopolysaccharides, which might contribute to the modulation of signaling pathways and the production of proinflammatory cytokines associated with the pathogenesis of AD. Moreover, imbalances in the gut microbiota can induce inflammation that is associated with the pathogenesis of obesity, type 2 diabetes mellitus, and AD. The purpose of this review is to summarize and discuss the current findings that may elucidate the role of the gut microbiota in the development of AD. Understanding the underlying mechanisms may provide new insights into novel therapeutic strategies for AD.

Immediate Early Genes Anchor a Biological Pathway of Proteins Required for Memory Formation, Long-Term Depression and Risk for Schizophrenia

While the causes of myriad medical and infectious illnesses have been identified, the etiologies of neuropsychiatric illnesses remain elusive. This is due to two major obstacles. First, the risk for neuropsychiatric disorders, such as schizophrenia, is determined by both genetic and environmental factors. Second, numerous genes influence susceptibility for these illnesses. Genome-wide association studies have identified at least 108 genomic loci for schizophrenia, and more are expected to be published shortly. In addition, numerous biological processes contribute to the neuropathology underlying schizophrenia. These include immune dysfunction, synaptic and myelination deficits, vascular abnormalities, growth factor disruption, and N-methyl-D-aspartate receptor (NMDAR) hypofunction. However, the field of psychiatric genetics lacks a unifying model to explain how environment may interact with numerous genes to influence these various biological processes and cause schizophrenia. Here we describe a biological cascade of proteins that are activated in response to environmental stimuli such as stress, a schizophrenia risk factor. The central proteins in this pathway are critical mediators of memory formation and a particular form of hippocampal synaptic plasticity, long-term depression (LTD). Each of these proteins is also implicated in schizophrenia risk. In fact, the pathway includes four genes that map to the 108 loci associated with schizophrenia: GRIN2A, nuclear factor of activated T-cells (NFATc3), early growth response 1 (EGR1) and NGFI-A Binding Protein 2 (NAB2); each of which contains the "Index single nucleotide polymorphism (SNP)" (most SNP) at its respective locus. Environmental stimuli activate this biological pathway in neurons, resulting in induction of EGR immediate early genes: EGR1, EGR3 and NAB2. We hypothesize that dysfunction in any of the genes in this pathway disrupts the normal activation of Egrs in response to stress. This may result in insufficient electrophysiologic, immunologic, and neuroprotective, processes that these genes normally mediate. Continued adverse environmental experiences, over time, may thereby result in neuropathology that gives rise to the symptoms of schizophrenia. By combining multiple genes associated with schizophrenia susceptibility, in a functional cascade triggered by neuronal activity, the proposed biological pathway provides an explanation for both the polygenic and environmental influences that determine the complex etiology of this mental illness.

Effect of Physical Activity on Cognitive Development: Protocol for a 15-Year Longitudinal Follow-Up Study

The aim of the study is to investigate the relationship between physical activity as assessed by accelerometers and cognitive development across the human age ranges (from children and adolescents to adults). Additionally, this study seeks to explore whether physical activity contributes to cognitive development via modification of plasma insulin-like growth factor 1 (IGF-1) and brain-derived neurotrophic factor (BDNF). In the study, 500 preschool children (3.5–5.5 years old) are taking part in 6 triennial assessment waves over the span of 15 years. At each wave, participant measures included (a) 7-day physical activity monitoring using ActiGraph's GT3X accelerometers, (b) the evaluation of cognitive development, (c) anthropometric and physical fitness assessments, (d) plasma IGF-1 and BDNF concentrations, and (e) retrospective questionnaires. Linear regression models are used to examine the effect of physical activity on cognitive development; plasma IGF-1 and BDNF concentrations are considered as mediators into data analyses. The results of the study may help to inform future health interventions that utilize physical activity as a means to improve cognitive development in children, adolescents, and adults. Additionally, the study may assist in determining whether the putative effects occur via modification of plasma IGF-1 or BDNF concentrations.

Multimodal physical activity increases brain-derived neurotrophic factor levels and improves cognition in institutionalized older women

Physical activity has been proposed as a promising intervention to improve cognition and decrease the risk of dementia in older adults. Brain-derived neurotrophic factor (BDNF) appears to mediate, at least partially, these effects of exercise. However, intervention studies of the effects of multimodal exercises on cognition and BDNF levels are scarce and composed by small samples. Thus, the generalization of the conclusions of these studies depends on the reproducibility of the results. In order to contribute to the knowledge on the field, the present study evaluated the effects of a physical activity intervention composed by muscle strengthening and aerobic conditioning on BDNF levels and cognition in older women. Independent and non-demented subjects (≥75 years) were assigned to a 3-month physical activity intervention (n = 22, 60 min exercise sessions three times a week) or to a control condition (n = 10, no exercise). Clinical (anxiety and depression symptoms), neuropsychological (Digit Span, Stroop, Trail Making, and Contextual Memory tests), physical (upper and lower limb strength, aerobic conditioning), and physiological (serum BDNF) parameters were evaluated immediately before, 1 month, and 3 months after starting intervention. Results indicated that controls had stable levels for all measured variables, whereas the intervention group improved on physical fitness, depressive symptoms, cognitive performance, and BDNF levels. Moreover, a linear regression identified an association between aerobic conditioning and BDNF levels. In conclusion, combined muscle strengthening and aerobic conditioning was able to improve cognitive performance and increase BDNF levels. Aerobic conditioning seems to be an important mediator of these outcomes.

Effects of gravity changes on gene expression of BDNF and serotonin receptors in the mouse brain

Spaceflight entails various stressful environmental factors including microgravity. The effects of gravity changes have been studied extensively on skeletal, muscular, cardiovascular, immune and vestibular systems, but those on the nervous system are not well studied. The alteration of gravity in ground-based animal experiments is one of the approaches taken to address this issue. Here we investigated the effects of centrifugation-induced gravity changes on gene expression of brain-derived neurotrophic factor (BDNF) and serotonin receptors (5-HTRs) in the mouse brain. Exposure to 2g hypergravity for 14 days showed differential modulation of gene expression depending on regions of the brain. BDNF expression was decreased in the ventral hippocampus and hypothalamus, whereas increased in the cerebellum. 5-HT1BR expression was decreased in the cerebellum, whereas increased in the ventral hippocampus and caudate putamen. In contrast, hypergravity did not affect gene expression of 5-HT1AR, 5-HT2AR, 5-HT2CR, 5-HT4R and 5-HT7R. In addition to hypergravity, decelerating gravity change from 2g hypergravity to 1g normal gravity affected gene expression of BDNF, 5-HT1AR, 5-HT1BR, and 5-HT2AR in various regions of the brain. We also examined involvement of the vestibular organ in the effects of hypergravity. Surgical lesions of the inner ear's vestibular organ removed the effects induced by hypergravity on gene expression, which suggests that the effects of hypergravity are mediated through the vestibular organ. In summary, we showed that gravity changes induced differential modulation of gene expression of BDNF and 5-HTRs (5-HT1AR, 5-HT1BR and 5-HT2AR) in some brain regions. The modulation of gene expression may constitute molecular bases that underlie behavioral alteration induced by gravity changes.

Cognitive impairment in first-episode drug-naïve patients with schizophrenia: Relationships with serum concentrations of brain-derived neurotrophic factor and glial cell line-derived neurotrophic factor

OBJECTIVES

Evidence suggests that brain-derived neurotrophic factor (BDNF) and glial cell line -derived neurotrophic factor (GDNF) are important in the regulation of synaptic plasticity, which plays a key role in the cognitive processes in psychiatric disorders. Our work aimed at exploring the associations between serum BDNF and GDNF levels and cognitive functions in first-episode drug-naïve (FEDN) patients with schizophrenia.

METHODS

The BDNF and GDNF levels of 58 FEDN patients and 55 age- and sex-matched healthy controls were measured and test subjects were examined using several neurocognitive tests including the verbal fluency test (VFT), the trail making test (TMT), the digit span test (DST), and the Stroop test.

RESULTS

Patients performed significantly worse than controls in nearly all neurocognitive performances except the forward subscale part of the DST. BDNF levels were inversely correlated to TMT-part B scores and positively correlated to VFT-action in the FEDN group. GDNF levels showed a positive correlation with VFT-action scores and a negative correlation with TMT-part B scores of these patients.

CONCLUSION

Current data suggests that cognitive dysfunction widely exists in the early stages of schizophrenia. BDNF and GDNF may be jointly contributed to the pathological mechanisms involved in cognitive impairment in FEDN patients with schizophrenia.

Microbiota-gut-brain axis and the central nervous system

The gut and brain form the gut-brain axis through bidirectional nervous, endocrine, and immune communications. Changes in one of the organs will affect the other organs. Disorders in the composition and quantity of gut microorganisms can affect both the enteric nervous system and the central nervous system (CNS), thereby indicating the existence of a microbiota-gut-brain axis. Due to the intricate interactions between the gut and the brain, gut symbiotic microorganisms are closely associated with various CNS diseases, such as Parkinson's disease, Alzheimer's disease, schizophrenia, and multiple sclerosis. In this paper, we will review the latest advances of studies on the correlation between gut microorganisms and CNS functions & diseases.