Grape-Derived Polyphenols Ameliorate Stress-Induced Depression by Regulating Synaptic Plasticity

Influence of human gut microbiome on the healthy and the neurodegenerative aging

The gut microbiome plays a crucial role in host health throughout the lifespan by influencing brain function during aging. The microbial diversity of the human gut microbiome decreases during the aging process and, as a consequence, several mechanisms increase, such as oxidative stress, mitochondrial dysfunction, inflammatory response, and microbial gut dysbiosis. Moreover, evidence indicates that aging and neurodegeneration are closely related; consequently, the gut microbiome may serve as a novel marker of lifespan in the elderly. In this narrative study, we investigated how the changes in the composition of the gut microbiome that occur in aging influence to various neuropathological disorders, such as mild cognitive impairment (MCI), dementia, Alzheimer's disease (AD), and Parkinson's disease (PD); and which are the possible mechanisms that govern the relationship between the gut microbiome and cognitive impairment. In addition, several studies suggest that the gut microbiome may be a potential novel target to improve hallmarks of brain aging and to promote healthy cognition; therefore, current and future therapeutic interventions have been also reviewed.

Comparison of the Protective Effects of Casein Hydrolysate Containing Tyr-Pro-Val-Glu-Pro-Phe and Casein on the Behaviors and Peripheral and Brain Functions in Mice with Chronic-Stress-Induced Anxiety and Insomnia

Chronic stress is a major inducer of anxiety and insomnia. Milk casein has been studied for its stress-relieving effects. We previously prepared a casein hydrolysate (CP) rich in the sleep-enhancing peptide YPVEPF, and this study aims to systemically investigate the different protective effects of CP and casein on dysfunction and anxiety/insomnia behavior and its underlying mechanisms in chronically stressed mice. Behavioral results showed that CP ameliorated stress-induced insomnia and anxiety more effectively than milk casein, and this difference in amelioration was highly correlated with an increase in GABA, 5-HT, GABAA, 5-HT1A receptors, and BDNF and a decrease in IL-6 and NMDA receptors in stressed mice. Furthermore, CP restored these dysfunctions in the brain and colon by activating the HPA response, modulating the ERK/CREB-BDNF-TrκB signaling pathway, and alleviating inflammation. The abundant YPVEPF (1.20 ± 0.04%) and Tyr-based/Trp-containing peptides of CP may be the key reasons for its different effects compared to casein. Thus, this work revealed the main active structures of CP and provided a novel dietary intervention strategy for the prevention and treatment of chronic-stress-induced dysfunction and anxiety/insomnia behaviors.

Apple polyphenol extract ameliorates sugary-diet-induced depression-like behaviors in male C57BL/6 mice by inhibiting the inflammation of the gut-brain axis

To explore whether apple polyphenol extract (APE) ameliorates sugary-diet-induced depression-like behaviors, thirty male C57BL/6 mice (3-4 weeks old) were assigned to three groups randomly to receive different treatments for 8 consecutive weeks: (1) control group (CON), (2) S-HSD group (60% high sucrose diet feeding with 0.1 mg mL-1 sucralose solution as drinking water), and (3) S-APE group (S-HSD feeding with 500 mg per (kg bw day) APE solution gavage). The S-HSD group showed significant depression-like behaviors compared with the CON group, which was manifested by an increased number of buried marbles in the marble burying test, prolonged immobility time in both the tail suspension test and forced swimming test, and cognitive impairment based on the Morris water maze test. However, APE intervention significantly improved the depression-like behaviors by reducing serum levels of corticosterone and adrenocorticotropic hormone, and increasing the serum level of IL-10. Moreover, APE intervention inhibited the activation of the NF-κB inflammatory pathway, elevated colonic MUC-2 protein expression, and elevated the colonic and hippocampal tight junction proteins of occludin and ZO-1. Furthermore, APE intervention increased the richness and diversity of gut microbiota by regulating the composition of microbiota, with increased relative abundance of Firmicutes and Bacteroidota, decreased relative abundance of Verrucomicrobiota at the phylum level, significantly lowered relative abundance of Akkermansia at the genus level, and rebalanced abnormal relative abundance of Muribaculaceae_unclassified, Coriobacteriaceae_UCG-002, and Lachnoclostridium induced by S-HSD feeding. Thus, our study supports the potential application of APE as a dietary intervention for ameliorating depression-like behavioral disorders.

Increased fruit intake is associated with reduced risk of depression: evidence from cross-sectional and Mendelian randomization analyses

Background

The association between dietary patterns and depression has gained significant attention, but the relationship between fruit intake and depression remains unclear. This study aimed to investigate the role of fruit intake in the risk of depression using data from the National Health and Nutrition Examination Survey (NHANES) and Mendelian randomization (MR) analysis, and further explore the causal relationship between them.

Materials and methods

Cross-sectional analysis was conducted using the 2005-2018 NHANES data. Specialized weighted complex survey design analysis software was used for multivariate logistic analysis. Additionally, genetic variants for fruit intake and depression, as well as its related neuroticism traits, from the GWAS were used as instrumental variables in MR analysis. The inverse variance weighted (IVW) method was employed as the primary analysis method to evaluate the causal relationship between them. MR-Egger regression, MR-PRESSO test, and leave-one-out analysis were conducted to assess heterogeneity and pleiotropy.

Results

In NHANES, compared to the lowest quartile (Q1, <0.12 cup], the highest quartile (Q4, >1.49 cups) of fruit intake showed a significant reduction in the risk of depression after adjusting for relevant covariates. Model 3, after rigorous adjustment for multiple covariates, demonstrated improved predictive performance in both Receiver operating characteristic (ROC) curve and Decision curve analysis (DCA). In Model 3, the proportion of reduced depression risk associated with fruit intake reached 31% (OR = 0.69, 95% CI: 0.50-0.95). This association remained significant in the MR analysis (OR = 0.92, 95% CI = 0.87-0.96; p = 5.09E-04). Fruit intake was also associated with a decreased risk of neuroticism traits related to depression, including feeling lonely (OR = 0.82, 95% CI = 0.74-0.90; p = 2.91E-05), feeling miserable (OR = 0.79, 95% CI = 0.72-0.87; p = 2.35E-06), feeling fed-up (OR = 0.75, 95% CI = 0.68-0.83; p = 2.78E-08), irritable mood (OR = 0.89, 95% CI = 0.79-0.99; p = 0.03), and neuroticism (OR = 0.85, 95% CI = 0.76-0.96; p = 9.94E-03). The causal relationship between feeling lonely and fruit intake was bidirectional.

Conclusion

Increased fruit intake has a causal effect in reducing the risk of depression and is beneficial for related psychological well-being.

Neurotoxicity of melittin: Role of mitochondrial oxidative phosphorylation system in synaptic plasticity dysfunction

Melittin (Mel), a main active peptide component of bee venom, has been proven to possess strong antitumor activity. Previous studies have shown that Mel caused severe cell membrane lysis and acted on the central nervous system (CNS). Here, this study was designed to investigate the effects of Mel on CNS and explore the potential mechanism. We confirmed the neurotoxic effect of melittin by in vivo and in vitro experiments. After subcutaneous administration of Mel (4 mg/kg, 8 mg/kg) for 14 days, the mice exhibited obvious depression-like behavior in a dose dependent manner. Besides, RNA-sequencing analysis revealed that oxidative phosphorylation (OXPHOS) signaling pathway was mostly enriched in hippocampus. Consistently, we found that Mel distinctly inhibited the activity of OXPHOS complex I and induced oxidative stress injury. Moreover, Mel significantly induced synaptic plasticity dysfunction in hippocampus via BDNF/TrkB/CREB signaling pathway. Taken together, the neurotoxic effect of Mel was involved in impairing OXPHOS system and hippocampal synaptic plasticity. These novel findings provide new insights into fully understanding the health risks of Mel and are conducive to the development of Mel related drugs.

Effects of Flavonoid-Rich Orange Juice Intervention on Major Depressive Disorder in Young Adults: A Randomized Controlled Trial

Many individuals are suffering from depression, and various improvements are being proposed. This study was conducted on young people diagnosed with depression and aimed to assess the effects of flavonoid-rich orange juice on the major depressive disorder (MDD) using a randomized controlled trial. In all, 40 young men and women with MDD aged 18−29 years were randomly assigned to a flavonoid-rich orange juice group (FR group) and a flavonoid-low orange cordial group (FL group). The subjects drank the corresponding juice three times a day (190 mL per bottle) for 8 weeks. The blood BDNF, zonulin, and claudin-5 levels significantly increased (p < 0.0001, p < 0.01, and p < 0.05, respectively) in the FR group, and the fatty acid binding protein 2 (FABP2) level was significantly decreased (p < 0.0001) in the FR group after the juice intervention. The FABP2, LPS, and valeric acid levels were negatively correlated with the abundance of Butyricicoccus pullicaecorum, which was higher in the FR group. Orange juice intake improved depressive symptoms in young adults with MDD in the FR group. This B. pullicaecorum can be a potential biomarker for clinical improvement in young adults with MDD patients.

The Interaction of Polyphenols and the Gut Microbiota in Neurodegenerative Diseases

Polyphenols are secondary metabolites of plants and play a potential role in the prevention and treatment of neurodegenerative diseases (NND) such as Alzheimer's disease (AD) and Parkinson's disease (PD) due to their unique physiological functions such as acting as antioxidants, being anti-inflammatory, being neuroprotective, and promoting intestinal health. Since dietary polyphenols exist in plant foods in the form of glycosylation or esterification or are combined with polymers, they need to undergo extensive metabolism through phase I and phase II biotransformations by various intestinal enzymes, as well as metabolism by the intestinal microbiota before they can be fully absorbed. Polyphenols improve intestinal microbiota disorders by influencing the structure and function of intestinal microbiota, inducing beneficial bacteria to produce a variety of metabolites such as short-chain fatty acids (SCFAs), promoting the secretion of hormones and neurotransmitters, and playing an important role in the prevention and treatment of NND by affecting the microbe-gut-brain axis. We review the ways in which some polyphenols can change the composition of the intestinal microbiota and their metabolites in AD or PD animal models to exert the role of slowing down the progression of NND, aiming to provide evidence for the role of polyphenols in slowing the progression of NND via the microbiota-gut-brain (MGB) axis.

Potential of Probiotics as an Adjunct for Patients with Major Depressive Disorder

Major depressive disorder (MDD) is an enfeebling disease with a lifetime incidence of 20%. While accumulating studies implicate a correlation between the disease and gut microbiota, data show that not every patient responded to probiotic treatments. To comprehensively assess the potential role of probiotics in MDD, this study first summarizes the current pathological hypothesis of the disease from a life-stage perspective, focuses on the potential role of "depression gut microbiota." Currently available managements are then briefly summarized and novel bio-materials having potential therapeutic effects on MDD are also evaluated. To harness the positive effect of probiotics, prebiotics, and postbiotics, clinical evidence and their applications on MDD patients are listed. Factors that may counteract the pre/probiotic applications, such as diet, physiology, gender difference, and use of antibiotics and antidepressants are also discussed. The endocannabinoid (eCBs) system may be promising targets for probiotic therapy. More evidence is needed to demonstrate the hierarchical factors in the complex network driving the disease, and probiotic can be one promising adjunct for patients with MDD.

Natural products for the treatment of stress-induced depression: Pharmacology, mechanism and traditional use

ETHNOPHARMACOLOGICAL RELEVANCE

Depression, one of the most common psychiatric disorders, is the fourth leading cause of long-term disability worldwide. A series of causes triggered depression, including psychological stress and conflict, as well as biological derangement, among which stress has a pivotal role in the development of depression. Traditional herbal medicine has been used for the treatment of various disorders including depression for a long history with multi-targets, multi-levels and multi-ways, attracting great attention from scholars. Recently, natural products have been commercialized as antidepressants which have become increasingly popular in the world health drug markets. Major research contributions in ethnopharmacology have generated and updated vast amount of data associated with natural products in antidepressant-like activity.

AIMS OF THE REVIEW

This review aims to briefly discuss the pathological mechanism, animal models of stress-induced depression, traditional use of herbal medicines and especially recapitulate the natural products with antidepressant activity and their pharmacological functions and mechanism of action, which may contribute to a better understanding of potential therapeutic effects of natural products and the development of promising drugs with high efficacy and low toxicity for the treatment of stress-induced depression.

MATERIALS AND METHODS

The contents of this review were sourced from electronic databases including PubMed, Sci Finder, Web of Science, Science Direct, Elsevier, Google Scholar, Chinese Knowledge On frastructure (CNKI), Wan Fang, Chinese Scientific and Technological Periodical Database (VIP) and Chinese Biomedical Database (CBM). Additional information was collected from Yao Zhi website (https://db.yaozh.com/). Data were obtained from April 1992 to June 2021. Only English language was applied to the search. The search terms were 'stress-induced depression', 'pathological mechanism' in the title and 'stress', 'depression', 'animal model' and 'natural products' in the whole text.

RESULTS

Stress-induced depression is related to the monoaminergic system, hypothalamic-pituitary-adrenal (HPA) axis, neuronal plasticity and a series of inflammatory factors. Four main types of animal models of stress-induced depression were represented. Fifty-eight bioactive phytochemical compounds, fifty-six herb medicines and five formulas from traditional Chinese medicine were highlighted, which exert antidepressant effects by inhibiting monoamine oxidase (MAO) reaction, alleviating dysfunction of the HPA axis and nerve injury, and possessing anti-inflammatory activities.

CONCLUSIONS

Natural products provide a large number of compounds with antidepressant-like effects, and their therapeutic impacts has been highlighted for a long time. This review summarized the pathological mechanism and animal models of stress-induced depression, and the natural products with antidepressant activity in particular, which will shed light on the action mechanism and clinical potential of these compounds. Natural products also have been a vital and promising source for future antidepressant drug discovery.

The Effects of Stress and Diet on the "Brain-Gut" and "Gut-Brain" Pathways in Animal Models of Stress and Depression

Compelling evidence is building for the involvement of the complex, bidirectional communication axis between the gastrointestinal tract and the brain in neuropsychiatric disorders such as depression. With depression projected to be the number one health concern by 2030 and its pathophysiology yet to be fully elucidated, a comprehensive understanding of the interactions between environmental factors, such as stress and diet, with the neurobiology of depression is needed. In this review, the latest research on the effects of stress on the bidirectional connections between the brain and the gut across the most widely used animal models of stress and depression is summarised, followed by comparisons of the diversity and composition of the gut microbiota across animal models of stress and depression with possible implications for the gut–brain axis and the impact of dietary changes on these. The composition of the gut microbiota was consistently altered across the animal models investigated, although differences between each of the studies and models existed. Chronic stressors appeared to have negative effects on both brain and gut health, while supplementation with prebiotics and/or probiotics show promise in alleviating depression pathophysiology.

Ancestral Food Sources Rich in Polyphenols, Their Metabolism, and the Potential Influence of Gut Microbiota in the Management of Depression and Anxiety

The relationship between a population's diet and the risk of suffering from mental disorders has gained importance in recent years, becoming exacerbated due to the COVID-19 lockdown. This review concentrates relevant literature from Scopus, PubMed, and Google Scholar analyzed with the aim of rescuing knowledge that promotes mental health. In this context, it is important to highlight those flowers, seeds, herbaceous plants, fungi, leaves, and tree barks, among other ancestral matrices, that have been historically part of the eating habits of human beings and have also been a consequence of the adaptation of collectors, consuming the ethnoflora present in different ecosystems. Likewise, it is important to note that this knowledge has been progressively lost in the new generations. Therefore, this review concentrates an important number of matrices used particularly for food and medicinal purposes, recognized for their anxiolytic and antidepressant effects, establishing the importance of metabolism and biotransformation mainly of bioactive compounds such as polyphenols by the action of the gut microbiota.

Mechanism of Dopaminergic Nerve Transmission in Different Doses of Morphine Addiction and Stress-Induced Depression

Depression not only threatens the health and quality of life of patients but also brings a huge mental and economic burden to the patients' families. This paper mainly studies the mechanism of dopaminergic neurotransmission in different doses of morphine addiction and stress-induced depression. In the experiment, 40 male SD rats were selected. The experiment established a rat model of chronic stress depression. The rats used in this model are all raised in a single cage, and there will be various stimuli every day for 21 days, but high-intensity continuous stimuli must be avoided, and the same stimuli will not appear continuously. The experiment established a depression animal model through chronic unpredictable mild stress (CUMS), combined with the conditioned position preference (CPP) model of morphine addiction to detect the establishment of CPP in such animals, so as to explore certain stress stimuli or depression, the influence on morphine addiction, and the relationship between them. The second or third branches of pyramidal neurons were selected to analyze the PL and CA3 regions. When analyzing the density of dendrites, each animal selected at least 8 dendrites in order to count the number of dendrites and selected a length of 20 μm on each branch to record the number of dendrites. All measured values are expressed as average ± standard deviation and analyzed by SPSS17.0 statistical software, and Levene test is used in the scattered consistency test. The average NIV of PEN before injection was 11.92 ± 2.90 Hz, and the average latency was 0.16 ± 0.03 s. The results indicate that CUMS may reduce the conditioned learning and memory ability by damaging the learning loop, rather than affecting the reward loop to weaken the establishment of morphine-dependent CPP.

Neurophysiological Effects of Whole Coffee Cherry Extract in Older Adults with Subjective Cognitive Impairment: A Randomized, Double-Blind, Placebo-Controlled, Cross-Over Pilot Study

Bioactive plant-based compounds have shown promise as protective agents across multiple domains including improvements in neurological and psychological measures. Methodological challenges have limited our understanding of the neurophysiological changes associated with polyphenol-rich supplements such as whole coffee cherry extract (WCCE). In the current study, we (1) compared 100 mg of WCCE to a placebo using an acute, randomized, double-blind, within-subject, cross-over design, and we (2) conducted a phytochemical analysis of WCCE. The primary objective of the study was to determine the neurophysiological and behavioral changes that resulted from the acute administration of WCCE. We hypothesized that WCCE would increase brain-derived neurotrophic factor (BDNF) and glutamate levels while also increasing neurofunctional measures in cognitive brain regions. Furthermore, we expected there to be increased behavioral performance associated with WCCE, as measured by reaction time and accuracy. Participants underwent four neuroimaging scans (pre- and post-WCCE and placebo) to assess neurofunctional/metabolic outcomes using functional magnetic resonance imaging and magnetic resonance spectroscopy. The results suggest that polyphenol-rich WCCE is associated with decreased reaction time and may protect against cognitive errors on tasks of working memory and response inhibition. Behavioral findings were concomitant with neurofunctional changes in structures involved in decision-making and attention. Specifically, we found increased functional connectivity between the anterior cingulate and regions involved in sensory and decision-making networks. Additionally, we observed increased BDNF and an increased glutamate/gamma-aminobutyric acid (GABA) ratio following WCCE administration. These results suggest that WCCE is associated with acute neurophysiological changes supportive of faster reaction times and increased, sustained attention.

Grapevine as a Rich Source of Polyphenolic Compounds

Grapes are rich in primary and secondary metabolites. Among the secondary metabolites, polyphenolic compounds are the most abundant in grape berries. Besides their important impacts on grape and wine quality, this class of compounds has beneficial effects on human health. Due to their antioxidant activity, polyphenols and phenolic acids can act as anti-inflammatory and anticancerogenic agents, and can modulate the immune system. In grape berries, polyphenols and phenolic acids can be located in the pericarp and seeds, but distribution differs considerably among these tissues. Although some classes of polyphenols and phenolic acids are under strict genetic control, the final content is highly influenced by environmental factors, such as climate, soil, vineyard, and management. This review aims to present the main classes of polyphenolic compounds and phenolic acids in different berry tissues and grape varieties and special emphasis on their beneficial effect on human health.

Relationship between Wine Consumption, Diet and Microbiome Modulation in Alzheimer's Disease

Alzheimer's disease (AD) is a progressive neurodegenerative disorder leading to the most common form of dementia in elderly people. Modifiable dietary and lifestyle factors could either accelerate or ameliorate the aging process and the risk of developing AD and other age-related morbidities. Emerging evidence also reports a potential link between oral and gut microbiota alterations and AD. Dietary polyphenols, in particular wine polyphenols, are a major diver of oral and gut microbiota composition and function. Consequently, wine polyphenols health effects, mediated as a function of the individual's oral and gut microbiome are considered one of the recent greatest challenges in the field of neurodegenerative diseases as a promising strategy to prevent or slow down AD progression. This review highlights current knowledge on the link of oral and intestinal microbiome and the interaction between wine polyphenols and microbiota in the context of AD. Furthermore, the extent to which mechanisms bacteria and polyphenols and its microbial metabolites exert their action on communication pathways between the brain and the microbiota, as well as the impact of the molecular mediators to these interactions on AD patients, are described.

The dichotomous role of the gut microbiome in exacerbating and ameliorating neurodegenerative disorders

INTRODUCTION

Age related neurodegenerative disorders affect millions of people around the world. The role of the gut microbiome (GM) in neurodegenerative disorders has been elucidated over the past few years. Dysbiosis of the gut microbiome ultimately results in neurodegeneration. However, the gut microbiome can be modulated to promote neuro-resilience.

AREAS COVERED

This review is focused on demonstrating the role of the gut microbiome in host physiology in Parkinson's disease (PD) and other neurodegenerative disorders. We will discuss how the microbiome will impact neurodegeneration in PD, Alzheimer's Disease (AD), Multiple sclerosis (MS), Amyotrophic Lateral Sclerosis (ALS), and finally discuss how the gut microbiome can be influenced through diet and lifestyle.

EXPERT OPINION

Currently, much of the focus has been to study the mechanisms by which the microbiome induces neuroinflammation and neurodegeneration in PD, AD, MS, ALS. In particular, the role of certain dietary flavonoids in regulation of gut microbiome to promote neuro-resilience. Polyphenol prebiotics delivered in combination with probiotics (synbiotics) present an exciting new avenue to harness the microbiome to attenuate immune inflammatory responses which ultimately may influence brain cascades associated with promotion of neurodegeneration across the lifespan.

Gut Microbiota: A Pivotal Hub for Polyphenols as Antidepressants

Polyphenols, present in a broad range of plants, have been thought to be responsible for many beneficial health effects, such as an antidepressant. Despite that polyphenols can be absorbed in the small intestine directly, most of them have low bioavailability and reach the large intestine without any modifications due to their complex structures. The interaction between microbial communities and polyphenols in the intestine is important for the latter to exert antidepressant effects. Gut microbiota can improve the bioavailability of polyphenols; in turn, polyphenols can maintain the intestinal barrier as well as the community of the gut microbiota in normal status. Furthermore, gut microbita catabolize polyphenols to more active, better-absorbed metabolites, further ameliorating depression through the microbial-gut-brain (MGB) axis. Based on this evidence, the review illustrates the potential role of gut microbiota in the processes of polyphenols or their metabolites acting as antidepressants and further envisions the gut microbiota as therapeutic targets for depression.