Antidepressant-like Effects of Representative Types of Food and Their Possible Mechanisms

Depression is a mental disorder characterized by low mood, lack of motivation, negative cognitive outlook, and sleep problems. Suicide may occur in severe cases, although suicidal thoughts are not seen in all cases. Globally, an estimated 350 million individuals grapple with depression, as reported by the World Health Organization. At present, drug and psychological treatments are the main treatments, but they produce insufficient responses in many patients and fail to work at all in many others. Consequently, treating depression has long been an important topic in society. Given the escalating prevalence of depression, a comprehensive strategy for managing its symptoms and impacts has garnered significant attention. In this context, nutritional psychiatry emerges as a promising avenue. Extensive research has underscored the potential benefits of a well-rounded diet rich in fruits, vegetables, fish, and meat in alleviating depressive symptoms. However, the intricate mechanisms linking dietary interventions to brain function alterations remain largely unexplored. This review delves into the intricate relationship between dietary patterns and depression, while exploring the plausible mechanisms underlying the impact of dietary interventions on depression management. As we endeavor to unveil the pathways through which nutrition influences mental well-being, a holistic perspective that encompasses multidisciplinary strategies gains prominence, potentially reshaping how we approach and address depression.

Insights into the cellular, molecular, and epigenetic targets of gamma-aminobutyric acid against diabetes: a comprehensive review on its mechanisms

Diabetes is a metabolic disease due to impaired or defective insulin secretion and is considered one of the most serious chronic diseases worldwide. Gamma-aminobutyric acid (GABA) is a naturally occurring non-protein amino acid commonly present in a wide range of foods. A number of studies documented that GABA has good anti-diabetic potential. This review summarized the available dietary sources of GABA as well as animal and human studies on the anti-diabetic properties of GABA, while also discussing the underlying mechanisms. GABA may modulate diabetes through various pathways such as inhibiting the activities of α-amylase and α-glucosidase, promoting β-cell proliferation, stimulating insulin secretion from β-cells, inhibiting glucagon secretion from α-cells, improving insulin resistance and glucose tolerance, and increasing antioxidant and anti-inflammatory activities. However, further mechanistic studies on animals and human are needed to confirm the therapeutic effects of GABA against diabetes.

Recent advances in physiochemical changes, nutritional value, bioactivities, and food applications of germinated quinoa: A comprehensive review

The production and consumption of functional foods has become an essential food industry trend. Due to its high nutritional content, quinoa is regarded as a super pseudocereal for the development of nutritious foods. However, the presence of antinutritional factors and quinoa's distinctive grassy flavor limit its food applications. Due to its benefits in enhancing the nutritional bioavailability and organoleptic quality of quinoa, germination has garnered significant interest. To date, there is no systematic review of quinoa germination and the health benefits of germinated quinoa. This review details the nutritional components and bioactivities of germinated quinoa, as well as the potential mechanisms for the accumulation of bioactive compounds during the germination process. Additionally, evidence supporting the health benefits of germinated quinoa, the current status of related product development, and perspectives for future research are presented. Thus, our research is likely to provide theoretical support for the use of germinated quinoa resources.

Gamma-aminobutyric acid (GABA): a comprehensive review of dietary sources, enrichment technologies, processing effects, health benefits, and its applications

Gamma-aminobutyric acid (GABA) is a naturally occurring potential bioactive compound present in plants, microorganisms, animals, and humans. Especially, as a main inhibitory neurotransmitter in the central nervous system, GABA possesses a broad spectrum of promising bioactivities. Thus, functional foods enriched with GABA have been widely sought after by consumers. However, the GABA levels in natural foods are usually low, which cannot meet people's demand for health effects. With the increasing public awareness on the food securities and naturally occurring processes, using enrichment technologies to elevate the GABA contents in foods instead of exogenous addition can enhance the acceptability of health-conscious consumers. Herein, this review provides a comprehensive insight on the dietary sources, enrichment technologies, processing effects of GABA, and its applications in food industry. Furthermore, the various health benefits of GABA-enriched foods, mainly including neuroprotection, anti-insomnia, anti-depression, anti-hypertensive, anti-diabetes, and anti-inflammatory are also summarized. The main challenges for future research on GABA are related to exploring high GABA producing strains, enhancing the stability of GABA during storage, and developing emerging enrichment technologies without affecting food quality and other active ingredients. A better understanding of GABA may introduce new windows for its application in developing functional foods.

Special tea products featuring functional components: Health benefits and processing strategies

The functional components in tea confer various potential health benefits to humans. To date, several special tea products featuring functional components (STPFCs) have been successfully developed, such as O-methylated catechin-rich tea, γ-aminobutyric acid-rich tea, low-caffeine tea, and selenium-rich tea products. STPFCs have some unique and enhanced health benefits when compared with conventional tea products, which can meet the specific needs and preferences of different groups and have huge market potential. The processing strategies to improve the health benefits of tea products by regulating the functional component content have been an active area of research in food science. The fresh leaves of some specific tea varieties rich in functional components are used as raw materials, and special processing technologies are employed to prepare STPFCs. Huge progress has been achieved in the research and development of these STPFCs. However, the current status of these STPFCs has not yet been systematically reviewed. Here, studies on STPFCs have been comprehensively reviewed with a focus on their potential health benefits and processing strategies. Additionally, other chemical components with the potential to be developed into special teas and the application of tea functional components in the food industry have been discussed. Finally, suggestions on the promises and challenges for the future study of these STPFCs have been provided. This paper might shed light on the current status of the research and development of these STPFCs. Future studies on STPFCs should focus on screening specific tea varieties, identifying new functional components, evaluating health-promoting effects, improving flavor quality, and elucidating the interactions between functional components.

A role of GABAA receptor α1 subunit in the hippocampus for rapid-acting antidepressant-like effects of ketamine

Ketamine can produce rapid-acting antidepressant effects in treatment-resistant patients with depression. Although alterations in glutamatergic and GABAergic neurotransmission in the brain play a role in depression, the precise molecular mechanisms in these neurotransmission underlying ketamine's antidepressant actions remain largely unknown. Mice exposed to FSS (forced swimming stress) showed depression-like behavior and decreased levels of GABA (γ-aminobutyric acid), but not glutamate, in the hippocampus. Ketamine increased GABA levels and decreased glutamate levels in the hippocampus of mice exposed to FSS. There was a correlation between GABA levels and depression-like behavior. Furthermore, ketamine increased the levels of enzymes and transporters on the GABAergic neurons (SAT1, GAD67, GAD65, VGAT and GAT1) and astrocytes (EAAT2 and GAT3), without affecting the levels of enzymes and transporters (SAT2, VGluT1 and GABA_AR γ2) on glutamatergic neurons. Moreover, ketamine caused a decreased expression of GABA_AR α1 subunit, which was specifically expressed on GABAergic neurons and astrocytes, an increased GABA synthesis and metabolism in GABAergic neurons, a plasticity change in astrocytes, and an increase in ATP (adenosine triphosphate) contents. Finally, GABA_AR antagonist bicuculline or ATP exerted a rapid antidepressant-like effect whereas pretreatment with GABA_AR agonist muscimol blocked the antidepressant-like effects of ketamine. In addition, pharmacological activation and inhibition of GABA_AR modulated the synthesis and metabolism of GABA, and the plasticity of astrocytes in the hippocampus. The present data suggest that ketamine could increase GABA synthesis and astrocyte plasticity through downregulation of GABA_AR α1, increases in GABA, and conversion of GABA into ATP, resulting in a rapid-acting antidepressant-like action. This article is part of the Special Issue on 'Ketamine and its Metabolites'.

Characterization of a novel flavored yogurt enriched in γ-aminobutyric acid fermented by Levilactobacillus brevis CGMCC1.5954

This study developed and characterized a γ-aminobutyric acid (GABA)-enriched yogurt fermented by Levilactobacillus brevis CGMCC1.5954. The GABA content in the yogurt was 147.36 mg/100 mL, which was 317.06% higher than that of the control group. Furthermore, there was a significant improvement in the aroma, hardness, adhesion, cohesiveness, and gelatinousness of yogurt. The chromatography and metabolomics analyses further confirmed the high GABA content in yogurt and its nutritional value, and the metabolic pathway for GABA production by L. brevis 54 was identified. A total of 58 volatile flavor compounds were identified using headspace solid-phase microextraction-gas chromatography-mass spectrometry, of which 2-nonanone and 2-heptanone may be responsible for the high odor score of GABA-enriched yogurt. This study developed a nutritious and unique GABA-enriched flavored yogurt, summarized the metabolic pathway of GABA, and provided a flavor fingerprint that could guide the production of specifically flavored yogurts.

Moringa oleifera seed ethanol extract and its active component kaempferol potentiate pentobarbital-induced sleeping behaviours in mice via a GABAergic mechanism

CONTEXT

Moringa oleifera Lam. (Moringaceae) (MO) is an important food plant that has high nutritional and medical value. However, there is limited information on whether its seeds can improve sleep.

OBJECTIVE

This study investigated the effects of MO seed ethanol extracts (EEMOS) on sleep activity improvement and examined the underlying mechanisms.

MATERIALS AND METHODS

Male ICR mice were placed into six groups (n = 12) and treated as follows: Control (sodium carboxymethyl cellulose, 20 mL/kg), estazolam tablets (2 mg/kg), EEMOS (1, 2 g/kg) and kaempferol (1, 2 mg/kg). These samples were successively given intragastric for 14 d. Locomotor activity assay, pentobarbital-induced sleeping and pentetrazol-induced seizures tests were utilized to examine the sedative-hypnotic effects (SHE) of EEMOS.

RESULTS

Compared with the control group, the results revealed that EEMOS (2 g/kg) and KA (2 mg/kg) possessed good SHE and could significantly elevate the levels of γ-aminobutyric acid and reduce the levels of glutamic acid in the mouse hypothalamus (p < 0.05). Moreover, SHE was blocked by picrotoxin, flumazenil and bicuculline (p < 0.05). EEMOS (2 g/kg) and KA (2 mg/kg) significantly upregulated the protein expression levels of glutamic acid decarboxylase-65 (GAD₆₅) and α₁-subunit of GABA_A receptors in the hypothalamus of mice (p < 0.05), not affecting glutamic acid decarboxylase-67 (GAD₆₇) and γ₂-subunit expression levels (p > 0.05). Additionally, they cause a significant increase in Cl^- influx in human cerebellar granule cells at a concentration of 8 µg/mL (p  <  0.05).

DISCUSSION AND CONCLUSIONS

These findings demonstrated that EEMOS could improve sleep by regulating GABA_A-ergic systems, and encourage further clinical trials to treat insomnia.

Effective Components and Molecular Mechanism of Agarwood Essential Oil Inhalation and the Sedative and Hypnotic Effects Based on GC-MS-Qtof and Molecular Docking

Agarwood has been used for the administration of hypnotic therapy. Its aromatic scent induces a relaxed state. However, its aromatic constituents and the underlying molecular effect are still unclear. This study aims to determine the active substance and molecular mechanism of the hypnotic effect of agarwood essential oil (AEO) incense inhalation in insomniac mice. Insomnia models were induced by para-chlorophenylalanine (PCPA, 300 mg/kg) in mice. The sleep-promoting effect was evaluated. Neurotransmitter levels and its receptor were detected to explore the molecular mechanism. The effective components were analyzed by GC-Q/TOF-MS of AEO. The binding mechanisms of the core compounds and core targets were verified by molecular docking. These results showed that AEO inhalation could significantly shorten sleep latency and prolong sleep time, inhibit autonomous activity and exert good sedative and sleep-promoting effects. A mechanistic study showed that AEO inhalation increased the levels of γ-aminobutyric acid (GABA_A), the GABA_A/glutamic acid (Glu) ratio, 5-hydroxytryptamine (5-HT) and adenosine (AD), upregulated the expression levels of GluR1, VGluT1 and 5-HT1A and downregulated 5-HT2A levels. Component analysis showed that the most abundant medicinal compounds were eremophilanes, cadinanes and eudesmanes. Moreover, the docking results showed that the core components stably bind to various receptors. The study demonstrated the bioactive constituents and mechanisms of AEO in its sedative and hypnotic effects and its multicomponent, multitarget and multipathway treatment characteristics in PCPA-induced insomniac mice. These results provide theoretical evidence for insomnia treatment and pharmaceutical product development with AEO.

Analysis of protein association networks regulating the neuroactive metabolites production in Lactobacillus species

Human population is intensively suffering from mental disorders and stress. Microbial metabolites may alter the brain activity, which seems to be an effective approach in the treatment of psychological distress. Earlier, microbial neuroactive metabolites such as trimethylamine, imidazolone propionate and taurine have been shown to alter the brain activity. In the present study proteins regulating their production and activity were explored in Lactobacillus species with the help of STRING (11.5) as a bioinformatic tool. Dataset network of urocanate hydratase, glycine radical enzyme and taurine ABC transporter protein (ATP-dependent transporter) have been identified in Lactobacillus nodensis, Lactobacillus vini and Lactobacillus paraplantarum strains. Further, cluster analysis of network resulted with groups of homologous proteins that most likely related to reductive monocarboxylic acid cycle, pyruvate fermentation to acetate IV and L-histidine degradation I pathway. The findings emphasize on the use and evaluation of selected Lactobacillus strains as psychoactive bacteria for the prevention and treatment of certain neurological and neurophysiological conditions.

Medicinal Plants in the Treatment of Depression: Evidence from Preclinical Studies

Medicinal plants and their extracts are natural remedies with enormous potential for treating various diseases, including depression and anxiety. In the case of depression, hundreds of plants have traditionally been used in folk medicine for generations. Different plant extracts and natural products have been analyzed as potential antidepressant agents with validated models to test for antidepressant-like effects in animals, although other complementary studies have also been employed. Most of these studies focus on the possible mediators implicated in these potential effects, with dopamine, serotonin, and noradrenaline being the principal neurotransmitters implicated, both through interference with receptors and with their metabolism by monoamino oxidases, as well as through neuro-endocrine and neuroprotective effects. There are approximately 650 reports of antidepressant-like medicinal plants in PubMed; 155 of them have been compiled in this review, with a relevant group yielding positive results. Saffron and turmeric are the most relevant species studied in both preclinical and clinical studies; St. John's wort or kava have also been tested extensively. To the best of our knowledge, no review to date has provided a comprehensive understanding of the biomolecular mechanisms of action of these herbs or of whether their potential effects could have real benefits. The purpose of this narrative review is to provide an update regarding medicinal plants from the year 2000 to the present to examine the therapeutic potential of these antidepressant-like plants in order to contribute to the development of new therapeutic methods to alleviate the tremendous burden that depression causes worldwide.

Flavor Characteristics of Ganpu Tea Formed During the Sun-Drying Processing and Its Antidepressant-Like Effects

Ganpu tea is a novel type of tea beverage with unique and pleasant flavor that encases Pu-erh tea leaves within an intact mandarin peel. However, to date, no holistic and detail studies on its chemical composition and biological activities have been reported yet. In the present study, by applying UPLC-Q-TOF and UPLC-MS technology, we systematically identified and analyzed 104 water-soluble compounds of Ganpu tea and their variation trend during the sun-drying processing. The results showed that the generation of pigments and gallic acid coincided with a dramatic decrease in catechin content, and a significant increase in alkaloid and flavonoid contents. The conversion of these compounds can contribute to the improvement of sensory attributes of Ganpu tea and maybe indispensable to its unique flavor. Moreover, the mice given orally with high dose of Ganpu tea (0.4 g/kg) showed a significantly reduced immobility duration as compared to that of the negative control group (p < 0.01) both in the forced swimming test and tail suspension test. Together, these results indicate that the sun-drying processing was indispensable to the formation of the unique flavor for Ganpu tea. Multiple types of compounds of Ganpu tea may collectively provide the synergistic attributes to its antidepressant-like properties.

Ginsenoside Rg5/Rk1 ameliorated sleep via regulating the GABAergic/serotoninergic signaling pathway in a rodent model

As the most common sleep disorder, insomnia seriously affects people's everyday lives. Phytochemicals have been shown to have excellent sleep-promoting effects. Therefore, this study was designed to investigate whether Rg5 and Rk1 extracted from ginseng had sleep-promoting effects and to explore their potential mechanisms. The results showed that Rg5 and Rk1 could significantly lessen the locomotor activity of mice and promote the sleep quality index, including increasing the amount of sleep in a pentobarbital sodium experiment with a threshold dose. In parallel, Rg5 and Rk1 could significantly shorten the sleep latency of mice and prolong the sleep time of mice. Furthermore, Rg5 and Rk1 augmented the GABA/Glu ratio, up-regulating the expression of the GABAA receptor and the GABAB receptor, whereas the GABAA receptor antagonist picrotoxin could antagonize the sleep quality of Rg5/Rk1. In addition, 5-HTP, the precursor of 5-HT, could enhance the sleep effect of Rg5 and Rk1 in mice, and both Rg5 and Rk1 could up-regulate the expression of 5-HT1A. These results were also confirmed by the detection of GABA and 5-HT in mouse cecum content. In conclusion, ginsenoside Rg5/Rk1 can exert sedative and hypnotic effects by affecting the GABA nervous system and the serotonin nervous system.

GABA-enriched teas as neuro-nutraceuticals

Teas enriched in GABA are consumed for their beneficial effects on blood pressure, stress and anxiety. These effects may involve actions of GABA on the central and peripheral nervous systems. The anaerobic procedures for the production of GABA-enriched teas increase GABA levels by 10-20 times. They also significantly alter the levels of other constituents that may interact with the actions of GABA. These include epigallocatechin gallate, caffeine and theanine. The possible interactions of these active constituents make the understanding of the effects of GABA-enriched teas complex. More data is needed to establish where and how GABA is acting following consumption of GABA-enriched teas. While there is considerable evidence that such GABA is acting on GABA receptors in the periphery, there is rather less evidence that is acting directly in the brain. Certainly, there is more to the action of GABA-enriched teas than GABA itself.

Some Reasons Why Preclinical Studies of Psychiatric Disorders Fail to Translate: What Can Be Rescued from the Misunderstanding and Misuse of Animal 'Models'?

The repeated failure of animal models to yield findings that translate into humans is a serious threat to the credibility of preclinical biomedical research. The use of animals in research that lacks translational validity is unacceptable in any ethical environment, and so this problem needs urgent attention. To reproduce any human illness in animals is a serious challenge, but this is especially the case for psychiatric disorders. Yet, many authors do not hesitate to describe their findings as a 'model' of such a disorder. More cautious scientists describe the behavioural phenotype as 'disorder-like', without specifying the way(s) in which the abnormal behaviour could be regarded as being analogous to any of the diagnostic features of the disorder in question. By way of discussing these problems, this article focuses on common, but flawed, assumptions that pervade preclinical research of depression and antidepressants. Particular attention is given to the difference between putative 'models' of this illness and predictive screens for candidate drug treatments, which is evidently widely misunderstood. However, the problems highlighted in this article are generic and afflict research of all psychiatric disorders. This dire situation will be resolved only when funders and journal editors take action to ensure that researchers interpret their findings in a less ambitious, but more realistic, evidence-based way that would parallel changes in research of the cause(s), diagnosis and treatment of psychiatric problems in humans.

Anti-stress effects of polyphenols: animal models and human trials

Polyphenols, a category of plant compounds that contain multiple phenol structural units, are widely distributed throughout the plant kingdom and have multiple benefits for human health including anti-obesity, anti-hyperglycemic, and anti-hyperlipidemic effects. Additionally, polyphenols have recently gained attention for their anti-stress effects. In this review article, we summarize physiological responses against exposure to stressors and discuss biomarkers for exposure to stressors that are widely used in animal studies and human trials. We also review commonly used animal models for evaluating anti-stress effects. Finally, we discuss recent findings related to the anti-stress effects of polyphenols evaluated in animal models and human trials, and their putative mechanisms. These emerging data require further investigation in scientific studies and human trials to evaluate the anti-stress effects of polyphenols and their potential use for the prevention of stress-related health problems.

Exploring plant metabolic genomics: chemical diversity, metabolic complexity in the biosynthesis and transport of specialized metabolites with the tea plant as a model

The diversity and complexity of secondary metabolites in tea plants contribute substantially to the popularity of tea, by determining tea flavors and their numerous health benefits. The most significant characteristics of tea plants are that they concentrate the complex plant secondary metabolites into one leaf: flavonoids, alkaloids, theanine, volatiles, and saponins. Many fundamental questions regarding tea plant secondary metabolism remain unanswered. This includes how tea plants accumulate high levels of monomeric galloylated catechins, unlike the polymerized flavan-3-ols in most other plants, as well as how they are evolved to selectively synthesize theanine and caffeine, and how tea plants properly transport and store these cytotoxic products and then reuse them in defense. Tea plants coordinate many metabolic pathways that simultaneously take place in young tea leaves in response to both developmental and environmental cues. With the available genome sequences of tea plants and high-throughput metabolomic tools as great platforms, it is of particular interest to launch metabolic genomics studies using tea plants as a model system. Plant metabolic genomics are to investigate all aspects of plant secondary metabolism at the genetic, genome, and molecular levels. This includes plant domestication and adaptation, divergence and convergence of secondary metaboloic pathways. The biosynthesis, transport, storage, and transcriptional regulation mechanisms of all metabolites are of core interest in the plant as a whole. This review highlights relevant contexts of metabolic genomics, outstanding questions, and strategies for answering them, with aim to guide future research for genetic improvement of nutrition quality for healthier plant foods.

Health Functions and Related Molecular Mechanisms of Tea Components: An Update Review

Tea is widely consumed all over the world. Generally, tea is divided into six categories: White, green, yellow, oolong, black, and dark teas, based on the fermentation degree. Tea contains abundant phytochemicals, such as polyphenols, pigments, polysaccharides, alkaloids, free amino acids, and saponins. However, the bioavailability of tea phytochemicals is relatively low. Thus, some novel technologies like nanotechnology have been developed to improve the bioavailability of tea bioactive components and consequently enhance the bioactivity. So far, many studies have demonstrated that tea shows various health functions, such as antioxidant, anti-inflammatory, immuno-regulatory, anticancer, cardiovascular-protective, anti-diabetic, anti-obesity, and hepato-protective effects. Moreover, it is also considered that drinking tea is safe to humans, since reports about the severe adverse effects of tea consumption are rare. In order to provide a better understanding of tea and its health potential, this review summarizes and discusses recent literature on the bioactive components, bioavailability, health functions, and safety issues of tea, with special attention paid to the related molecular mechanisms of tea health functions.

Neuroactive compounds in foods: Occurrence, mechanism and potential health effects

Neuroactive compounds are synthesized by certain plants and microorganisms by undertaking different tasks, especially as a stress response. Most common neuroactive compounds in foods are gamma-aminobutyric acid (GABA), serotonin, melatonin, kynurenine, kynurenic acid, dopamine, norepinephrine, histamine, tryptamine, tyramine and β-phenylethylamine. Fermented foods contain some of these compounds, which can affect human health and mood. Moreover, food processing such as roasting and malting alter amount and profile of neuroactive compounds in foods. In addition to plant-origin and microbially-formed neuroactive compounds in foods, these substances are also formed by gut microbiota, which is the most attractive subject to assess the interaction between gut microbiota and mental health. The discovery of microbiota-gut-brain axis calls for the investigation of the effects of diet on the formation of neuroactive compounds in the gut. Furthermore, probiotics and prebiotics are indispensable elements for the understanding of the food-mood relationship. The focus of this comprehensive review is to investigate the neuroactive compounds found naturally in foods or formed during fermentation. Their formation pathways in humans, plants and microorganisms, potential health effects, effects of diet on the formation of microbial metabolites including neuroactive compounds in the gut are discussed throughout this review. Furthermore, the importance of gut-brain axis, probiotics and prebiotics are discussed.

Supplementation with Lactobacillus kefiranofaciens ZW3 from Tibetan Kefir improves depression-like behavior in stressed mice by modulating the gut microbiota

Increasing evidence indicates that probiotics can effectively improve depression-like behavior. However, the underlying mechanism is still unclear. In this study, the antidepressant effect of Lactobacillus kefiranofaciens CGMCC2809 (ZW3) isolated from Tibetan Kefir grains was investigated using a mouse model of chronic unpredictable mild stress (CUMS). ZW3 improved depression-like behavior and independent exploration ability in the CUMS group. Moreover, ZW3 regulated biochemical disorders in the hypothalamic-pituitary-adrenal axis, immune system and tryptophan metabolism caused by stress. Furthermore, ZW3 could modulate the composition of the gut microbiota, and alleviate constipation by improving the fecal water content in stressed mice. We found that the probiotic strain was present in the whole intestine, even 7 days after its administration was stopped. These results suggest that L. kefiranofaciens ZW3 might improve depression by regulating the gut microbiota as a probiotic food.

Mechanisms Underlying the Anti-Depressive Effects of Regular Tea Consumption

This article is a comprehensive review of the literature pertaining to the antidepressant effects and mechanisms of regular tea consumption. Meta-data supplemented with recent observational studies were first analyzed to assess the association between tea consumption and depression risk. The literature reported risk ratios (RR) were 0.69 with 95% confidence intervals of 0.62-0.77. Next, we thoroughly reviewed human trials, mouse models, and in vitro experiments to determine the predominant mechanisms underlying the observed linear relationship between tea consumption and reduced risk of depression. Current theories on the neurobiology of depression were utilized to map tea-mediated mechanisms of antidepressant activity onto an integrated framework of depression pathology. The major nodes within the network framework of depression included hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, inflammation, weakened monoaminergic systems, reduced neurogenesis/neuroplasticity, and poor microbiome diversity affecting the gut-brain axis. We detailed how each node has subsystems within them, including signaling pathways, specific target proteins, or transporters that interface with compounds in tea, mediating their antidepressant effects. A major pathway was found to be the ERK/CREB/BDNF signaling pathway, up-regulated by a number of compounds in tea including teasaponin, L-theanine, EGCG and combinations of tea catechins and their metabolites. Black tea theaflavins and EGCG are potent anti-inflammatory agents via down-regulation of NF-κB signaling. Multiple compounds in tea are effective modulators of dopaminergic activity and the gut-brain axis. Taken together, our findings show that constituents found in all major tea types, predominantly L-theanine, polyphenols and polyphenol metabolites, are capable of functioning through multiple pathways simultaneously to collectively reduce the risk of depression.

The Association between Green and Black Tea Consumption on Successful Aging: A Combined Analysis of the ATTICA and MEDiterranean ISlands (MEDIS) Epidemiological Studies

Tea is one of the most-widely consumed beverages in the world with a number of different beneficial health effects, mainly ascribed to the polyphenolic content of the tea catechins. The aim of this study was to examine the consumption of green, black, or no tea, in relation to the previously validated successful ageing index (SAI; higher values "healthier" ageing) in a combined analysis of adults aged >50 years old from the ATTICA (n = 1128 adults from Athens, Greece metropolitan area) and the MEDiterranean Islands Study (MEDIS) (n = 2221 adults from various Greek island and Mani) studies. After adjusting for age, sex, smoking, and coffee consumption, green tea was positively associated with SAI (b ± SE: 0.225 ± 0.055, p < 0.001), while black tea was negatively associated with SAI (unstandardized b coefficient ± Standard error: -0.807 ± 0.054, p < 0.001). Green tea (vs black tea) consumption, had higher odds of a SAI of over 3.58 out of 10 (OR: 1.77, 95% CI: 1.38-2.28). Green tea consumption was also associated with higher levels of physical activity (p < 0.001) and reduced likelihood of hypertension (p = 0.006) compared with black tea. Two possible mechanisms are that green tea possesses high levels of catechins such as (-)-epigallocatechin 3-gallate and l-theanine compared with black tea. Therefore, the present analysis supports both the role of green tea constituents in successful ageing, as well as its role as an important component of an overall healthy diet in adults aged 50 years and over from these two epidemiological studies.

Effect of GABA-Fortified Oolong Tea on Reducing Stress in a University Student Cohort

GABA-containing tea has gained popularity as an accessible intervention to reduce the impact of chronic stress-induced autonomic imbalance and increased risk for cardiovascular disease despite a lack of evidence concerning the γ-aminobutyric acid (GABA) content in a cup of the tea and its effects on physiological and psychological stress as measures of cognitive function. We aimed to measure the effects of GABA-fortified tea consumption on heart rate variability (HRV) and stress in 30 participants using a pre-post cohort study design. Ten minute lead II ECG recordings were analyzed with Kubios software. Frequency domain parameters including total power, high and low frequency power, along with heart rate, were determined. A control group that consumed a non-fortified tea was included in the research. Statistical analysis was by two-way ANOVA for two-group comparison with time as an interaction and a significance level of p < 0.05. Oolong tea consumption led to a significant decrease in the immediate stress score and a significant improvement in HRV. We conclude that autonomic imbalance and HRV in people with acute stress is significantly reduced following a cup of GABA fortified oolong tea and highlights the complex interaction between autonomic nervous system function and mood.

Black tea affects obesity by reducing nutrient intake and activating AMP-activated protein kinase in mice

The effects of certain tea components on the prevention of obesity in humans have been reported recently. However, whether Yinghong NO. 9 black tea consumption has beneficial effects on obesity are not known. Here, we obtained a Yinghong NO. 9 black tea infusion (Y9 BTI) and examined the anti-obesity effects of its oral administration. ICR mice were fed a standard diet supplemented with Y9 BTI at 0.5, 1.0, or 2.0 g/kg body weight for two weeks, and the body weight were recorded. HE staining was used to evaluate the effect of Y9 BTI on mice liver. Western blot analysis was used to detect the expression levels of related proteins in the mice liver and adipose. We found that the body weights of the mice in the control group were significantly higher than those of the mice in the middle and high dose groups. The results of western blot showed that Y9 BTI up-regulated the expression of liver kinase B1 (LKB1) and adenosine monophosphate-activated protein kinase (AMPK) and also increased in AMPK phosphorylation (p-AMPK) and LKB1 phosphorylation (p-LKB1). Y9 BTI significantly down-regulated Fas Cell Surface Death Receptor(FAS) and activated the phosphorylation of acetyl-CoA carboxylase (ACC). Furthermore, Y9 BTI (2.0 g/kg BW) down-regulated the expression of three factors (IL-1β, Cox-2, and iNOS). Altogether, Y9 BTI supplementation reduced the feed intake of mice and may prevent obesity by inhibiting lipid absorption. These results suggest that Y9 BTI may regulate adipogenic processes through the LKB1/AMPK pathway.