Green tea extract enhances parieto-frontal connectivity during working memory processing

The Role of Dietary Ingredients in Mental Energy - A Scoping Review of Randomized Controlled Trials

Low mental energy can contribute to decreased productivity, altered life balance, decreased physical performance, and ultimately affect quality of life. As such, there is a great demand for food and beverage products that positively impact mental energy. Numerous products claim to alter mental energy making continued review of the scientific evidence critical. The objective of this study was to conduct a scoping review of randomized controlled trials to evaluate the effect of 18 dietary ingredients on mental energy outcomes in adults without severe disease. Methods: A literature search, completed using PubMed, resulted in the identification of 2261 articles, 190 of which met eligibility from initial abstract review. Full-text review was completed on the 190 studies which resulted in 101 articles that fully met eligibility for inclusion in this study. The search strategy for two ingredients did not yield any eligible studies, leaving studies for 16 ingredients that were extracted and summarized by reported significantly improved outcomes for cognition, mood and perceived feelings, and sleep assessments. The preliminary results for several dietary ingredients directionally suggested a mental energy benefit (≥20% of outcomes), including ashwagandha, chamomile, dark chocolate, ginseng, green tea, lavender, lion's mane mushroom, maca, tart cherries, turmeric, and valerian root. The results of this scoping review suggest that of the 16 dietary ingredients reviewed, 11 may be promising for further exploration on their potential benefits in supporting mental energy. Given consumer demand and market growth for food and beverage products that positively impact mental energy; continued efforts in assessment method alignment and additional evaluation in well-designed trials is warranted.KEY TEACHING POINTSOf the 16 dietary ingredients reviewed, 11 (ashwagandha, chamomile, dark chocolate, ginseng, green tea, lavender, lion's mane mushroom, maca, melatonin foods, turmeric, and valerian root) may be promising for further exploration on their potential mental energy benefits.Dark chocolate, ginseng, ashwagandha, and lion's mane mushroom were the most promising ingredients for further evaluation in the cognition domain of the ingredients evaluated.Turmeric, maca, lavendar, and ashwagandha were the most promising ingredients for further evaluation in the mood and perceived feelings domain of the ingredients evaluated.Ashwagandha, chamomile, green tea, melatonin foods, valerian root were the most promising ingredients for further evaluation in the sleep domain of the ingredients evaluated.Additional, well-designed, consistent, clinical trials and systematic reviews are warranted as the challenge of heterogeneity in mental energy study design remains.

Ingestion of taxifolin-rich foods affects brain activity, mental fatigue, and the whole blood transcriptome in healthy young adults: a randomized, double-blind, placebo-controlled, crossover study

The antioxidant properties of polyphenols, which are found in most plants, have been shown to be useful for maintaining health, including enhancing brain function and alleviating stress. We aimed to investigate the effect of a single intake of taxifolin-containing foods on cognitive task performance and whole blood gene expression in healthy young adults. This study was a randomized, placebo-controlled, double-blind, crossover trial in which healthy young adults were administered a single dose of either a placebo or food containing taxifolin. Cognitive tests (serial 3s, serial 7s, and rapid visual information processing) to examine brain activity and visual analog scale questionnaires to analyze mental fatigue were applied. The set of tests was repeated four times. The findings showed that taxifolin intake improved calculation abilities and reduced mental fatigue. An analysis of whole blood gene expression before and after the test revealed that the expression of foreign substance removal-related genes increased following the ingestion of taxifolin and that most differentially expressed genes were enriched in granulocytes. Taxifolin intake was shown to affect the brain activity of healthy young adults and demonstrated an antifatigue effect, thereby reducing subjective fatigue. A single intake of taxifolin may enhance the removal of foreign substances by strengthening the innate immune system and suppressing the occurrence of injury.

Mental Performance and Sport: Caffeine and Co-consumed Bioactive Ingredients

The plant defence compound caffeine is widely consumed as a performance enhancer in a sporting context, with potential benefits expected in both physiological and psychological terms. However, although caffeine modestly but consistently improves alertness and fatigue, its effects on mental performance are largely restricted to improved attention or concentration. It has no consistent effect within other cognitive domains that are important to sporting performance, including working memory, executive function and long-term memory. Although caffeine's central nervous system effects are often attributed to blockade of the receptors for the inhibitory neuromodulator adenosine, it also inhibits a number of enzymes involved both in neurotransmission and in cellular homeostasis and signal propagation. Furthermore, it modulates the pharmacokinetics of other endogenous and exogenous bioactive molecules, in part via interactions with shared cytochrome P450 enzymes. Caffeine therefore enjoys interactive relationships with a wide range of bioactive medicinal and dietary compounds, potentially broadening, increasing, decreasing, or modulating the time course of their functional effects, or vice versa. This narrative review explores the mechanisms of action and efficacy of caffeine and the potential for combinations of caffeine and other dietary compounds to exert psychological effects in excess of those expected following caffeine alone. The review focusses on, and indeed restricted its untargeted search to, the most commonly consumed sources of caffeine: products derived from caffeine-synthesising plants that give us tea (Camellia sinensis), coffee (Coffea genus), cocoa (Theabroma cacao) and guaraná (Paullinia cupana), plus multi-component energy drinks and shots. This literature suggests relevant benefits to mental performance that exceed those associated with caffeine for multi-ingredient energy drinks/shots and several low-caffeine extracts, including high-flavanol cocoa and guarana. However, there is a general lack of research conducted in such a way as to disentangle the relative contributions of the component parts of these products.

Can magnetic resonance imaging enhance the assessment of potential new treatments for cognitive impairment in mood disorders? A systematic review and position paper by the International Society for Bipolar Disorders Targeting Cognition Task Force

BACKGROUND

Developing treatments for cognitive impairment is key to improving the functioning of people with mood disorders. Neuroimaging may assist in identifying brain-based efficacy markers. This systematic review and position paper by the International Society for Bipolar Disorders Targeting Cognition Task Force examines the evidence from neuroimaging studies of pro-cognitive interventions.

METHODS

We included magnetic resonance imaging (MRI) studies of candidate interventions in people with mood disorders or healthy individuals, following the procedures of the Preferred Reporting Items for Systematic reviews and Meta-Analysis 2020 statement. Searches were conducted on PubMed/MEDLINE, PsycInfo, EMBASE, Cochrane Library, and Clinicaltrials.gov from inception to 30th April 2021. Two independent authors reviewed the studies using the National Heart, Lung, Blood Institutes of Health Quality Assessment Tool for Controlled Intervention Studies and the quality of neuroimaging methodology assessment checklist.

RESULTS

We identified 26 studies (N = 702). Six investigated cognitive remediation or pharmacological treatments in mood disorders (N = 190). In healthy individuals, 14 studies investigated pharmacological interventions (N = 319), 2 cognitive training (N = 73) and 4 neuromodulatory treatments (N = 120). Methodologies were mostly rated as 'fair'. 77% of studies investigated effects with task-based fMRI. Findings varied but most consistently involved treatment-associated cognitive control network (CCN) activity increases with cognitive improvements, or CCN activity decreases with no cognitive change, and increased functional connectivity. In mood disorders, treatment-related default mode network suppression occurred.

CONCLUSIONS

Modulation of CCN and DMN activity is a putative efficacy biomarker. Methodological recommendations are to pre-declare intended analyses and use task-based fMRI, paradigms probing the CCN, longitudinal assessments, mock scanning, and out-of-scanner tests.

Green tea improves cognitive function through reducing AD-pathology and improving anti-oxidative stress capacity in Chinese middle-aged and elderly people

Background: Numerous benefits of green tea have been reported. However, the effects of green tea on cognitive function remain disputable and the mechanism is still unclear.

Objective: To investigate the relationship of green tea consumption with cognitive function and related blood biomarkers among Chinese middle-aged and elderly people.

Methods: A total of 264 participants aged 50–70 years old were enrolled from Zhongnan Hospital of Wuhan University. They were interviewed about green tea consumption patterns and underwent neuropsychological tests covering five main cognitive domains to assess cognition including Montreal Cognitive Assessment (MoCA) and the other 10 scales. Then we detected serum oxidative stress biomarkers including Superoxide Dismutase (SOD), Malondialdehyde (MDA), Glutathione Peroxidase (GPx), Glutathione Reductase (GR), and Alzheimer’s disease (AD) markers including β-amyloid (Aβ)₄₀, Aβ₄₂, and phosphorylated tau-181 (pTau₁₈₁).

Results: In the tea-consuming group, the MoCA scores (P = 0.000), Hopkins Verbal Learning Test (HVLT) immediate recall (P = 0.012) and delayed recall (P = 0.013) were significantly higher while Trail Making Test-B (P = 0.005) and Victoria Stroop test interference (P = 0.000) were lower. In terms of oxidative stress markers, the tea-consuming group had lower serum MDA levels (P = 0.002) and higher serum SOD (P = 0.005) and GPx (P = 0.007) levels. In terms of AD markers, serum pTau₁₈₁ (P < 0.000), Aβ₄₂ (P = 0.019) and total Aβ levels (P = 0.034) but not serum Aβ₄₀ levels, were lower in the tea-consuming group. In the logistic regression analysis, there was a significant negative correlation between green tea consumption and cognitive impairment (OR = 0.26, 95 % CI 0.13 0.52 for high group).

Conclusion: Regular green tea consumption is associated with better cognitive function among Chinese middle-aged and elderly people, mainly reflected in memory and executive function. It may achieve protective effects by reducing AD-related pathology and improving anti-oxidative stress capacity and higher levels of tea consumption have a stronger protective effect.

Plant-derived nootropics and human cognition: A systematic review

Substances with modulatory capabilities on certain aspects of human cognition have been revered as nootropics from the dawn of time. The plant kingdom provides most of the currently available nootropics of natural origin. Here, in this systematic review, we aim to provide state-of-the-art information regarding proven and unproven effects of plant-derived nootropics (PDNs) on human cognition in conditions of health and disease. Six independent searches, one for each neurocognitive domain (NCD), were performed in parallel using three independent scientific library databases: PubMed, Cochrane and Scopus. Only scientific studies and systematic reviews with humans published between January 2000 and November 2021 were reviewed, and 256 papers were included. Ginkgo biloba was the most relevant nootropic regarding perceptual and motor functions. Bacopa monnieri improves language, learning and memory. Withania somnifera (Ashwagandha) modulates anxiety and social-related cognitions. Caffeine enhances attention and executive functions. Together, the results from the compiled studies highlight the nootropic effects and the inconsistencies regarding PDNs that require further research.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.2021137.

The beneficial effects of green tea on sleep deprivation-induced cognitive deficits in rats: the involvement of hippocampal antioxidant defense

BACKGROUND

The weight of evidence suggests that sleep is essential for the processes of memory consolidation and sleep deprivation (SD) impairs the retention of long-term memory in both humans and experimental animals, which is associated with oxidative stress damage within the brain. Green tea polyphenols have revealed carcinogenic, antioxidant, anti-, and anti-mutagenic properties. We aimed to investigate the possible protective effect of green tea extract (GTE) and its main active catechin, epigallocatechin-3-gallate (EGCG), on post-training total sleep deprivation (TSD) -induced spatial memory deficits and oxidative stress profile in the hippocampus of the rat.

METHODS

Male rats were treated with saline, GTE (100 and 200 mg/kg/day), and EGCG (50 mg/kg/day) intraperitoneally for 21 days and then trained in Morris water maze (MWM) in a single day protocol. Immediately after the end of MWM training, animals were sleep deprived for 6 h by the gentle handling method, and then evaluated for spatial memory. Hippocampal levels of malondialdehyde, (MDA), and thiol was assessed as oxidant and antioxidant markers.

RESULTS

Spatial memory was impaired in the TSD group and GTE at the dose of 200 mg/kg/day as well as EGCG at the dose of 50 mg/kg/day could reverse the impairment to the saline-treated levels. Despite the unchanged MDA levels, hippocampal total thiol was significantly decreased after TSD and EGCG increased it to the basal levels.

CONCLUSION

In conclusion, green tea and its main catechin, EGCG, could prevent memory impairments during 6 h of TSD; probably through normalizing the antioxidant thiol defense system which was impaired during TSD.

Increased functional interaction within frontoparietal network during working memory task in major depressive disorder

Abnormal fronto-parietal activation has been suggested as a neural underpinning of the working memory (WM) deficits in major depressive disorder (MDD). However, the potential interaction within the frontoparietal network during WM processing in MDD remains unclear. This study aimed to examine the role of abnormal functional interactions within frontoparietal network in the neuropathological mechanisms of WM deficits in MDD. A total of 40 MDD patients and 47 demographic matched healthy controls (HCs) were included. Functional magnetic resonance imaging and behavioral data were collected during numeric n-back tasks. The psychophysiological interaction and dynamic causal modelling methods were applied to investigate the connectivity within the frontoparietal network in MDD during n-back tasks. The psychophysiological interaction analysis revealed that MDD patients showed increased functional connectivity between the right inferior parietal lobule (IPL) and the right dorsolateral prefrontal cortex (dlPFC) compared with HCs during the 2-back task. The dynamic causal modelling analysis revealed that MDD patients had significantly increased forward modulation connectivity from the right IPL to the right dlPFC than HCs during the 2-back task. Partial correlation was used to calculate the relationship between connective parameters and psychological variables in the MDD group, which showed that the effective connectivity from right IPL to right dlPFC was correlated negatively with the sensitivity index d' of WM performances and positively with the depressive severity in MDD group. In conclusion, the abnormal functional and effective connectivity between frontal and parietal regions might contribute to explain the neuropathological mechanism of working memory deficits in major depressive disorder.

Configural learning memory can be transformed from intermediate-term to long-term in pond snail Lymnaea stagnalis

A lab bred W-strain of Lymnaea stagnalis exhibits configural learning (CL). CL is a form of higher order associative learning wherein when snails experience two contrasting stimuli together such as predatory odour (CE: crayfish effluent) and food odour (C: carrot odour) they learn and associate risk with food. The memory for CL has been shown to last 3 h. Here, we show that when only a single CL-training session is given only a 3 h memory is formed. Memory is not present 24 h after the training session. However, memory can be enhanced and snails show long term memory (24 h memory) when trained for a second time within a 7-day time period after the first CL-training. We further hypothesised that Green tea exposure will enhance memory persistence as catechins in green tea are shown to be cognitive enhancers. We thus subjected snails to CL training followed by green tea exposure which resulted in enhanced memory persistence and it occurred during memory consolidation phase. Thus, we show for the first time that CL intermediate-term memory can be transformed to long-term memory by green tea and multiple trainings in a lab bred strain of Lymnaea.

The effects of lutein and zeaxanthin on resting state functional connectivity in older Caucasian adults: a randomized controlled trial

The carotenoids lutein (L) and zeaxanthin (Z) accumulate in retinal regions of the eye and have long been shown to benefit visual health. A growing literature suggests cognitive benefits as well, particularly in older adults. The present randomized controlled trial sought to investigate the effects of L and Z on brain function using resting state functional magnetic resonance imaging (fMRI). It was hypothesized that L and Z supplementation would (1) improve intra-network integrity of default mode network (DMN) and (2) reduce inter-network connectivity between DMN and other resting state networks. 48 community-dwelling older adults (mean age = 72 years) were randomly assigned to receive a daily L (10 mg) and Z (2 mg) supplement or a placebo for 1 year. Resting state fMRI data were acquired at baseline and post-intervention. A dictionary learning and sparse coding computational framework, based on machine learning principles, was used to investigate intervention-related changes in functional connectivity. DMN integrity was evaluated by calculating spatial overlap rate with a well-established DMN template provided in the neuroscience literature. Inter-network connectivity was evaluated via time series correlations between DMN and nine other resting state networks. Contrary to expectation, results indicated that L and Z significantly increased rather than decreased inter-network connectivity (Cohen's d = 0.89). A significant intra-network effect on DMN integrity was not observed. Rather than restoring what has been described in the available literature as a "youth-like" pattern of intrinsic brain activity, L and Z may facilitate the aging brain's capacity for compensation by enhancing integration between networks that tend to be functionally segregated earlier in the lifespan.

SmFLS negatively regulates peel coloring of eggplant (Solanum melongena) under high temperature

The SmFLS gene was cloned from eggplant and has an ORF of 1014 bp encoding 337 amino acids. The deduced protein sequence of SmFLS was 88.07% and 84.94% identical to homologs encoded by StFLS in Solanum tuberosum and SlFLS in S. lycopersicum, respectively. SmFLS contains typical DIOX_N and 2OG-Fe (II)_Oxy functional domains, as well as five strictly conserved amino acid residues (H223, D225, H279, R289, and S291) related to FLS enzyme activity. Phylogenetic tree analysis showed that SmFLS had the closest genetic relationship with the FLS genes in potato and tomato. At a high temperature of 35 °C, the expression level of SmFLS was higher than that of the control in the same period, and it reached extremely significant levels on 15DAF and 20DAF, at which the eggplant peel color became lighter accordingly. Upon overexpression of SmFLS in eggplant, the flavonol content of transformed plants was significantly higher than that of untransformed plants, and the peel color was lighter than that of the control. The results indicate that SmFLS negatively regulates eggplant peel coloration under high temperature.

Effects of Matcha Green Tea Powder on Cognitive Functions of Community-Dwelling Elderly Individuals

Matcha Green Tea Powder contains a variety of active ingredients beneficial to health, such as tea catechins, lutein and vitamin K. It is also known that these ingredients confer benefits upon cognitive functions of elderly people. Therefore, we aimed to investigate the relationship between a daily supplementation of Matcha and the change in cognitive functions of community-dwelling elderly people. A randomized, double-blind, placebo-controlled 12-week trial was performed. Sixty-one participants were recruited and randomly assigned to receive test drink containing 3 g powder from fresh Matcha or placebo powder per day. Changes in cognitive function were assessed utilizing a psychometric test battery. Daily food intake was assessed by a Brief-type Self-administered Diet History Questionnaire (BDHQ). In the gender-specific analysis, a significant cognitive enhancement was observed in the Montreal Cognitive Assessment (MoCA) score in the active group of women. In dietary analysis, we found a significant inverse correlation between consumption of vitamin K in daily diet, excluding test drinks, and change in MoCA. The present study suggests that daily supplementation of Matcha Green Tea Powder has protective effects against cognitive decline in community-dwelling elderly women.

Central and Peripheral Metabolic Defects Contribute to the Pathogenesis of Alzheimer's Disease: Targeting Mitochondria for Diagnosis and Prevention

Significance: Epidemiological studies indicate that metabolic disorders are associated with an increased risk for Alzheimer's disease (AD). Metabolic remodeling occurs in the central nervous system (CNS) and periphery, even in the early stages of AD. Mitochondrial dysfunction has been widely accepted as a molecular mechanism underlying metabolic disorders. Therefore, focusing on early metabolic changes, especially from the perspective of mitochondria, could be of interest for early AD diagnosis and intervention. Recent Advances: We and others have identified that the levels of several metabolites are fluctuated in the periphery before their accumulation in the CNS, which plays an important role in the pathogenesis of AD. Mitochondrial remodeling is likely one of the earliest signs of AD, linking nutritional imbalance to cognitive deficits. Notably, by improving mitochondrial function, mitochondrial nutrients efficiently rescue cellular metabolic dysfunction in the CNS and periphery in individuals with AD. Critical Issues: Peripheral metabolic disorders should be intensively explored and evaluated for the early diagnosis of AD. The circulating metabolites derived from mitochondrial remodeling represent novel potential diagnostic biomarkers for AD that are more readily detected than CNS-oriented biomarkers. Moreover, mitochondrial nutrients provide a promising approach to preventing and delaying AD progression. Future Directions: Abnormal mitochondrial metabolism in the CNS and periphery is involved in AD pathogenesis. More clinical studies provide evidence for the suitability and reliability of circulating metabolites and cytokines for the early diagnosis of AD. Targeting mitochondria to rewire cellular metabolism is a promising approach to preventing AD and ameliorating AD-related metabolic disorders.

High-Frequency Repetitive Transcranial Magnetic Stimulation Could Improve Impaired Working Memory Induced by Sleep Deprivation

Objective

To investigate whether and how the working memory impairment induced by sleep deprivation (SD) could be recovered by using repetitive transcranial magnetic stimulation (rTMS), as well as to clarify the corresponding brain activity changes.

Methods

Seventeen healthy adults received one session of 5.0 Hz rTMS over the left dorsolateral prefrontal cortex (DLPFC) following 24 hours of SD. Resting state functional magnetic resonance imaging (fMRI) and working memory test were performed during a rested waking period, after SD and rTMS. The amplitude of low-frequency fluctuations (ALFF) was used to detect the spontaneous neural activity changes after both SD and rTMS. The relationship between ALFF and the performance of working memory was also assessed by using correlation analysis.

Results

After SD, the participants exhibited lower response accuracies and longer reaction times on the working memory tests of letters and numbers. The decreased response accuracy of numbers was significantly improved after rTMS similarly to the state of the rested waking period after a normal night of sleep. ALFF values decreased from the rested waking period state to the state of SD in the brain regions involving the frontal gyrus, precuneus, angular gyrus, and parietal lobe which showed significantly increased ALFF after rTMS. Furthermore, significantly positive correlations were observed between changes of response accuracy and the changes of ALFF value of the inferior frontal gyrus and supramarginal gyrus.

Conclusion

These results indicate that high-frequency rTMS applied over left DLPFC may contribute to the recovery of the impaired working memory after SD by modulating the neural activity of related brain regions.

MIND food and speed of processing training in older adults with low education, the MINDSpeed Alzheimer's disease prevention pilot trial

BACKGROUND

Multiple national organizations and leaders have called for increased attention to dementia prevention in those most vulnerable, for example persons with limited formal education. Prevention recommendations have included calls for multicomponent interventions that have the potential to improve both underlying neurobiological health and the ability to function despite neurobiological pathology, or what has been termed cognitive reserve.

OBJECTIVES

Test feasibility, treatment modifier, mechanism, and cognitive function effects of a multicomponent intervention consisting of foods high in polyphenols (i.e., MIND foods) to target neurobiological health, and speed of processing training to enhance cognitive reserve. We refer to this multicomponent intervention as MINDSpeed.

DESIGN

MINDSpeed is being evaluated in a 2 × 2 randomized factorial design with 180 participants residing independently in a large Midwestern city. Qualifying participants are 60 years of age or older with no evidence of dementia, and who have completed 12 years or less of education. All participants receive a study-issued iPad to access the custom study application that enables participants, depending on randomization, to select either control or MIND food, and to play online cognitive games, either speed of processing or control games.

METHODS

All participants complete informed consent and baseline assessment, including urine and blood samples. Additionally, up to 90 participants will complete neuroimaging. Assessments are repeated immediately following 12 weeks of active intervention, and at 24 weeks post-randomization. The primary outcome is an executive cognitive composite score. Secondary outcomes include oxidative stress, pro-inflammatory cytokines, and neuroimaging-captured structural and functional metrics of the hippocampus and cortical brain regions.

SUMMARY

MINDSpeed is the first study to evaluate the multicomponent intervention of high polyphenol intake and speed of processing training. It is also one of the first dementia prevention trials to target older adults with low education. The results of the study will guide future dementia prevention efforts and trials in high risk populations.

Dietary supplementation of a high-temperature-processed green tea extract attenuates cognitive impairment in PS2 and Tg2576 mice

Green tea intake is generally recognized as an effective supplement that promotes mental clarity and cognitive function. These health benefits of green tea have been attributed mainly to its effective component, epigallocatechin gallate (EGCG). Because various catechin derivatives potently enhance these health benefits, we manipulated the extraction process with a high-temperature intervention. High-temperature-processed green tea extract (HTP-GTE) showed an elevated proportion of gallocatechin gallate (GCG) content. To investigate the preventive effects of HTP-GTE on cognitive decline, we found its neuroprotective effects against amyloid β (Aβ)-induced neurotoxicity in neurons and clarified that GCG significantly inhibited Aβ aggregation in vitro. Moreover, we showed that HTP-GTE intake attenuated several cognitive-decline phenotypes in a model mouse of Alzheimer's disease. These beneficial effects of HTP-GTE against cognitive decline were due to the distinctive composition of the extract and suggest the possibility that HTP-GTE supplementation could attenuate cognitive decline of Alzheimer's disease.

Psychotropic effects of L-theanine and its clinical properties: From the management of anxiety and stress to a potential use in schizophrenia

Anxiety disorders are highly prevalent in modern societies, and are ranked the sixth most important contributor of non-fatal negative health outcomes. _L-theanine is an amino acid naturally found in green tea (Camellia sinensis) and some other plant extracts, and recent clinical studies have proposed promising adjuvant effects of _L-theanine for the negative impact of anxiety and psychological stress on health. In this integrative narrative review, we aimed to appraise and further discuss the effects of _L-theanine administration on anxiety disorders and psychological stress. Published data suggests that _L-theanine administered at daily doses ranging from 200 to 400 mg for up to 8 weeks are safe and induce anxiolytic and anti-stress effects in acute and chronic conditions. _L-theanine at doses lower and higher than these may also show promising therapeutic potential; however, a more thorough investigation through randomized double-blind placebo-controlled crossover clinical trials are necessary to elucidate its effects for longer periods, providing further insights for meta-analyses and the development of recommendation guidelines. Additionally, animal studies investigating a higher dosage, its combination with other pharmacological compounds and associated metabolic comorbidities are recommended, as cases of hepatotoxicity associated with the consumption of green tea extract have been reported.

Habitual tea drinking modulates brain efficiency: evidence from brain connectivity evaluation

The majority of tea studies have relied on neuropsychological measures, and much fewer on neuroimaging measures, especially for interregional connections. To date, there has been no exploration of the effect of tea on system-level brain networks. We recruited healthy older participants to two groups according to their history of tea drinking frequency and investigated both functional and structural networks to reveal the role of tea drinking on brain organization. The results showed that tea drinking gave rise to the more efficient structural organization, but had no significant beneficial effect on the global functional organization. The suppression of hemispheric asymmetry in the structural connectivity network was observed as a result of tea drinking. We did not observe any significant effects of tea drinking on the hemispheric asymmetry of the functional connectivity network. In addition, functional connectivity strength within the default mode network (DMN) was greater for the tea-drinking group, and coexistence of increasing and decreasing connective strengths was observed in the structural connectivity of the DMN. Our study offers the first evidence of the positive contribution of tea drinking to brain structure and suggests a protective effect on age-related decline in brain organisation.

Role of green tea catechins in prevention of age-related cognitive decline: Pharmacological targets and clinical perspective

Over the past decade, a wide range of scientific investigations have been performed to reveal neuropathological aspects of cognitive disorders; however, only limited therapeutic approaches currently exist. The failures of conventional therapeutic options as well as the predicted dramatic rise in the prevalence of cognitive decline in the coming future show the necessity for novel therapeutic agents. Recently, a wide range of research has focused on pharmacological activities of green tea catechins worldwide. Current investigations have clarified mechanistic effects of the catechins in inflammatory cascades, oxidative damages, different cellular transcription as well as transduction pathway in various body systems. It has been demonstrated that green tea polyphenols prevent age-related neurodegeneration through improvement of endogenous antioxidant defense mechanisms, modulation of neural growth factors, attenuation of neuroinflammatory pathway, and regulation of apoptosis. The catechins exhibited beneficial effects in cellular and animal models of neurodegenerative diseases including Alzheimer's disease, MS, and Parkinson's disease. The present review discusses the current pharmacological targets, which can be involved in the treatment of cognitive decline and addresses the action of catechin derivatives elicited from green tea on the multiple neural targets.

Diabetes and Alzheimer's Disease: Can Tea Phytochemicals Play a Role in Prevention?

Dementia and diabetes mellitus are prevalent disorders in the elderly population. While recognized as two distinct diseases, diabetes has more recently recognized as a significant contributor to risk for developing dementia, and some studies make reference to type 3 diabetes, a condition resulting from insulin resistance in the brain. Alzheimer's disease, the most common form of dementia, and diabetes, interestingly, share underlying pathological processes, commonality in risk factors, and, importantly, pathways for intervention. Tea has been suggested to possess potent antioxidant properties. It is rich in phytochemicals including, flavonoids, tannins, caffeine, polyphenols, boheic acid, theophylline, theobromine, anthocyanins, gallic acid, and finally epigallocatechin-3-gallate, which is considered to be the most potent active ingredient. Flavonoid phytochemicals, known as catechins, within tea offer potential benefits for reducing the risk of diabetes and Alzheimer's disease by targeting common risk factors, including obesity, hyperlipidemia, hypertension, cardiovascular disease, and stroke. Studies also show that catechins may prevent the formation of amyloid-β plaques and enhance cognitive functions, and thus may be useful in treating patients who have Alzheimer's disease or dementia. Furthermore, other phytochemicals found within tea offer important antioxidant properties along with innate properties capable of modulating intracellular neuronal signal transduction pathways and mitochondrial function.

A Combination of Essential Fatty Acids, Panax Ginseng Extract, and Green Tea Catechins Modifies Brain fMRI Signals in Healthy Older Adults

OBJECTIVES

To assess the effects of a combination of omega 3 essential fatty acids, green tea catechins, and ginsenosides on cognition and brain functioning in healthy older adults.

DESIGN

Double-blind, placebo-controlled, crossover design randomized controlled trial with 26-day intervention phases and a 30-day washout period.

SETTING

The Institute for Dementia Research and Prevention at the Pennington Biomedical Research Center.

PARTICIPANTS

Ten independently-living, cognitively-healthy older adults (mean age: 67.3 + 2.01 years).

INTERVENTION

Daily consumption of an investigational product (trade name "Cerbella TM") consisting of an emulsified liquid combination of standardized fish oil, panax ginseng extract, and green tea catechins in a flavored base of lecithin phospholipids optimized to maximize bioavailability of the active ingredients.

MEASUREMENTS

Before and after supplementation with the investigational product or placebo, participants completed cognitive tests including the Mini Mental State Exam (MMSE), Stroop test, Digit Symbol Substitution Test (DSST), and Immediate and Delayed Recall tests, as well as functional magnetic resonance imaging (fMRI) during a standard cognitive task switching paradigm.

RESULTS

Performance on the MMSE, Stroop test, and DSST increased significantly over one month of supplementation with the investigational product (one-sample t tests, p<.05) although differences between these changes and corresponding changes during supplementation with placebo were not significant (two-sample t tests, p>.05). During supplementation with the investigational product, brain activation during task performance increased significantly more than during supplementation with placebo in brain regions known to be activated by this task (anterior and posterior cingulate cortex). Functional connectivity during task execution between task regions (middle frontal gyrus and anterior cingulate cortex) increased significantly during supplementation with the investigational product, relative to placebo. Functional connectivity during rest between task regions (precentral gyrus and middle frontal gyrus) and default mode network regions (medial frontal gyrus and precuneus) decreased during supplementation with the investigational product relative to placebo, suggesting greater segregation of task and rest related brain activity.

CONCLUSION

One-month supplementation with a combination of omega 3 essential fatty acids, green tea catechins, and ginsenosides was associated with suggestive changes in cognitive functioning as well as modification of brain activation and brain functional connectivity in cognitively healthy older adults.

The Effects of Green Tea Extract on Working Memory in Healthy Women

OBJECTIVES

This study aimed to examine the effects of green tea extract on working memory in healthy younger (21 - 29 y) and older (50 - 63 y) women.

DESIGN

A single-blind, placebo-controlled, crossover design was used.

SETTING

A university laboratory.

PARTICIPANTS

Twenty non-smoking Caucasian women were recruited in the younger (10) and older (10) age group.

INTERVENTION

Subjects received 5.4 g green tea extract (at least 45% epigallocatechin-3-gallate) or placebo (cornstarch) within a 24-hour period.

MEASUREMENTS

Working memory was measured by reading span and N-back task paradigm. Blood sample (20 mL) was collected and measured for plasma malondialdehyde (MDA) and total antioxidant capacity (TEAC) concentration. A 24-hour recall was conducted for each treatment period to ensure similar dietary patterns.

RESULTS

Green tea extract significantly improved reading span performance in older women, indicated by higher absolute and partial scores of reading span. No significant changes were observed in the younger group. N-back latencies and accuracies were not significantly different after green tea treatment in either age group. Plasma concentration of MDA and TEAC were not different after green tea extract in either group.

CONCLUSION

Acute supplementation of decaffeinated green tea extract may enhance working memory capacity of women between 50 to 63 years of age. This study provides preliminary evidence that consumption of green tea extract may enhance the cognitive performance in older adults and thus provide potential chemopreventive benefits in this group. The mechanism should be explored in future research.

Green tea effects on cognition, mood and human brain function: A systematic review

BACKGROUND

Green tea (Camellia sinensis) is a beverage consumed for thousands of years. Numerous claims about the benefits of its consumption were stated and investigated. As green tea is experiencing a surge in popularity in Western culture and as millions of people all over the world drink it every day, it is relevant to understand its effects on the human brain.

PURPOSE

To assess the current state of knowledge in the literature regarding the effects of green tea or green tea extracts, l-theanine and epigallocatechin gallate both components of green tea-on general neuropsychology, on the sub-category cognition and on brain functions in humans.

METHODS

We systematically searched on PubMed database and selected studies by predefined eligibility criteria. We then assessed their quality and extracted data. We structured our effort according to the PRISMA statement.

OUTCOME

We reviewed and assessed 21 studies, 4 of which were randomised controlled trials, 12 cross-over studies (both assessed with an adapted version of the DELPHI-list), 4 were cross-sectional studies and one was a cohort study (both assessed with an adapted version of the Newcastle-Ottawa assessment scale). The average study quality as appraised by means of the DELPHI-list was good (8.06/9); the studies evaluated with the Newcastle-Ottawa-scale were also good (6.7/9).

CONCLUSIONS

The reviewed studies presented evidence that green tea influences psychopathological symptoms (e.g. reduction of anxiety), cognition (e.g. benefits in memory and attention) and brain function (e.g. activation of working memory seen in functional MRI). The effects of green tea cannot be attributed to a single constituent of the beverage. This is exemplified in the finding that beneficial green tea effects on cognition are observed under the combined influence of both caffeine and l-theanine, whereas separate administration of either substance was found to have a lesser impact.

The impact of gut hormones on the neural circuit of appetite and satiety: A systematic review

The brain-gut-axis is an interdependent system affecting neural functions and controlling our eating behaviour. In recent decades, neuroimaging techniques have facilitated its investigation. We systematically looked into functional and neurochemical brain imaging studies investigating how key molecules such as ghrelin, glucagon-like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY), cholecystokinin (CCK), leptin, glucose and insulin influence the function of brain regions regulating appetite and satiety. Of the 349 studies published before July 2016 identified in the database search, 40 were included (27 on healthy and 13 on obese subjects). Our systematic review suggests that the plasma level of ghrelin, the gut hormone promoting appetite, is positively correlated with activation in the pre-frontal cortex (PFC), amygdala and insula and negatively correlated with activation in subcortical areas such as the hypothalamus. In contrast, the plasma levels of glucose, insulin, leptin, PYY, GLP-1 affect the same brain regions conversely. Our study integrates previous investigations of the gut-brain matrix during food-intake and homeostatic regulation and may be of use for future meta-analyses of brain-gut interactions.

Amyloid β Protein Aggravates Neuronal Senescence and Cognitive Deficits in 5XFAD Mouse Model of Alzheimer's Disease

BACKGROUND

Amyloid β (Aβ) has been established as a key factor for the pathological changes in the brains of patients with Alzheimer's disease (AD), and cellular senescence is closely associated with aging and cognitive impairment. However, it remains blurred whether, in the AD brains, Aβ accelerates the neuronal senescence and whether this senescence, in turn, impairs the cognitive function. This study aimed to explore the expression of senescence-associated genes in the hippocampal tissue from young to aged 5XFAD mice and their age-matched wild type (WT) mice to determine whether senescent neurons are present in the transgenic AD mouse model.

METHODS

The 5XFAD mice and age-matched wild type mice, both raised from 1 to 18 months, were enrolled in the study. The senescence-associated genes in the hippocampus were analyzed and differentially expressed genes (DEGs) were screened by quantitative real-time polymerase chain reaction. Cognitive performance of the mice was evaluated by Y-maze and Morris water maze tests. Oligomeric Aβ (oAβ) (1-42) was applied to culture primary neurons to simulate the in vivo manifestation. Aging-related proteins were detected by Western blotting analysis and immunofluorescence.

RESULTS

In 5XFAD mice, of all the DEGs, the senescence-associated marker p16 was most significantly increased, even at the early age. It was mainly localized in neurons, with a marginal expression in astrocytes (labeled as glutamine synthetase), nil expression in activated microglia (labeled as Iba1), and negatively correlated with the spatial cognitive impairments of 5XFAD mice. oAβ (1-42) induced the production of senescence-related protein p16, but not p53 in vitro, which was in line with the in vivo manifestation.

CONCLUSIONS

oAβ-accelerated neuronal senescence may be associated with the cognitive impairment in 5XFAD mice. Senescence-associated marker p16 can serve as an indicator to estimate the cognitive prognosis for AD population.

Herbal Medicine for the Treatment of Vascular Dementia: An Overview of Scientific Evidence

Dementia is a leading cause of mental and physical disability. Vascular dementia (VaD) is the second most common cause of dementia after Alzheimer's disease (AD) constituting 10–15% of the dementia population. Currently there are no approved pharmaceutical options for VaD and the conventional anti-AD therapies provide only modest, short-term relief of symptoms associated with VaD. Herbal medicines have been used for the management of dementia-like symptoms for centuries and may provide viable therapies for VaD due to their multicomponent and multitarget approach. This review is designed to provide an updated overview on the current status of herbal medicine research, with an emphasis on Chinese herbal medicine, for the treatment of VaD or dementia. A case study is also provided to demonstrate the development process of a novel standardized complex herbal formulation for VaD. The article reveals some preliminary evidence to support the use of single and complex herbal preparations for VaD and dementia. Multiple issues in relation to clinical and preclinical research have been identified and future research directions are discussed.

Green Tea Consumption and the Risk of Incident Dementia in Elderly Japanese: The Ohsaki Cohort 2006 Study

OBJECTIVE

Biologic studies have shown that certain components of green tea may have protective effects on neurocognition. However, because of the lack of human epidemiologic studies, the impact of green tea consumption on the incidence of dementia has never been confirmed. The objective of this cohort study was to clarify the association between green tea consumption and incident dementia.

METHODS

In this 5.7-year prospective cohort study, using a questionnaire, information on daily green tea consumption and other lifestyle factors was collected from elderly Japanese individuals aged 65 years or more. Data on incident dementia were retrieved from the public Long-term Care Insurance Database.

RESULTS

Among 13,645 participants, the 5.7-year rate of incident dementia was 8.7%. More frequent green tea consumption was associated with a lower risk of incident dementia (hazard ratio for ≥5 cups/day versus <1 cup/day: 0.73; 95% confidence interval: 0.61-0.87). The lower risk of incident dementia was consistent even after selecting participants who did not have subjective memory complaints at the baseline.

CONCLUSION

Green tea consumption is significantly associated with a lower risk of incident dementia.

The Relieving Effects of BrainPower Advanced, a Dietary Supplement, in Older Adults with Subjective Memory Complaints: A Randomized, Double-Blind, Placebo-Controlled Trial

Subjective memory complaints (SMCs) are common in older adults that can often predict further cognitive impairment. No proven effective agents are available for SMCs. The effect of BrainPower Advanced, a dietary supplement consisting of herbal extracts, nutrients, and vitamins, was evaluated in 98 volunteers with SMCs, averaging 67 years of age (47-88), in a randomized, double-blind, placebo-controlled trial. Subjective hypomnesis/memory loss (SML) and attention/concentration deficits (SAD) were evaluated before and after 12-week supplementation of BrainPower Advanced capsules (n = 47) or placebo (n = 51), using a 5-point memory questionnaire (1 = no/slight, 5 = severe). Objective memory function was evaluated using 3 subtests of visual/audio memory, abstraction, and memory recall that gave a combined total score. The BrainPower Advanced group had more cases of severe SML (severity ⩾ 3) (44/47) and severe SAD (43/47) than the placebo group (39/51 and 37/51, < 0.05, < 0.05, resp.) before the treatment. BrainPower Advanced intervention, however, improved a greater proportion of the severe SML (29.5%)(13/44) (P < 0.01) and SAD (34.9%)(15/43)(P < 0.01) than placebo (5.1% (2/39) and 13.5% (5/37), resp.). Thus, 3-month BrainPower Advanced supplementation appears to be beneficial to older adults with SMCs.

Identification of UDP-glycosyltransferases involved in the biosynthesis of astringent taste compounds in tea (Camellia sinensis)

Galloylated catechins and flavonol 3-O-glycosides are characteristic astringent taste compounds in tea (Camellia sinensis). The mechanism involved in the formation of these metabolites remains unknown in tea plants. In this paper, 178 UGT genes (CsUGTs) were identified inC. sinensis based on an analysis of tea transcriptome data. Phylogenetic analysis revealed that 132 of these genes were clustered into 15 previously established phylogenetic groups (A to M, O and P) and a newly identified group R. Three of the 11 recombinant UGT proteins tested were found to be involved in the in vitro biosynthesis of β-glucogallin and glycosylated flavonols. CsUGT84A22 exhibited catalytic activity toward phenolic acids, in particular gallic acid, to produce β-glucogallin, which is the immediate precursor of galloylated catechin biosynthesis in tea plants. CsUGT78A14 and CsUGT78A15 were found to be responsible for the biosynthesis of flavonol 3-O-glucosides and flavonol 3-O-galactosides, respectively. Site-directed mutagenesis of the Q373H substitution for CsUGT78A14 indicated that the Q (Gln) residue played a catalytically crucial role for flavonoid 3-O-glucosyltransferase activity. The expression profiles of the CsUGT84A22, CsUGT78A14, and CsUGT78A15 genes were correlated with the accumulation patterns of β-glucogallin and the glycosylated flavonols which indicated that these three CsUGT genes were involved in the biosynthesis of astringent compounds inC. sinensis.

Predictors of Memory Deficits in Adolescents and Young Adults with Congenital Heart Disease Compared to Healthy Controls

INTRODUCTION

Adolescents and young adults with congenital heart disease (CHD) show a range of memory deficits, which can dramatically impact their clinical outcomes and quality of life. However, few studies have identified predictors of these memory changes. The purpose of this investigation was to identify predictors of memory deficits in adolescents and young adults with CHD after surgical palliation compared to healthy controls.

METHOD

One hundred fifty-six adolescents and young adults (80 CHD and 76 controls; age 14-21 years) were recruited and administered an instrument to assess memory [Wide Range Assessment of Memory and Learning Second Edition - general memory index (GMI) score] and completed questionnaires that measure anxiety, depression, sleepiness, health status, and self-efficacy. Descriptive and non-parametric statistics were used to assess group differences, and logistic regression to identify predictors of memory deficits.

RESULTS

CHD subjects consisted of 58% males, median age 17 years, 43% Hispanic, and medians of 2 previous heart surgeries and 14 years since last surgery. Memory deficits (GMI ≤ 85) were identified in 50% CHD compared to 4% healthy controls (median GMI 85 vs. 104, p < 0.001). Of GMI subscale medians, CHD subjects had significantly worse memory performance vs. healthy controls (verbal 88 vs. 105, p < 0.001; attention 88 vs. 109, p < 0.001; working memory 86 vs. 108, p < 0.001). No significant differences appeared between groups for visual memory. Multiple clinical and psychosocial factors were identified which were statistically different on bivariate analyses between the subjects with and without memory deficits. By multivariate analysis, male gender, number of surgeries, anxiety, and self-efficacy emerged as independent predictors of memory deficits.

CONCLUSION

Adolescents and young adults with CHD, more than a decade since their last surgery, show significant verbal, attention, and working memory deficits over controls. To enhance patient memory/self-care, clinicians should explore ways to reduce anxiety, improve self-efficacy, and increase use of visual patient education material, especially in CHD males.

Dissociable Behavioral, Physiological and Neural Effects of Acute Glucose and Fructose Ingestion: A Pilot Study

Previous research has revealed that glucose and fructose ingestion differentially modulate release of satiation hormones. Recent studies have begun to elucidate brain-gut interactions with neuroimaging approaches such as magnetic resonance imaging (MRI), but the neural mechanism underlying different behavioral and physiological effects of glucose and fructose are unclear. In this paper, we have used resting state functional MRI to explore whether acute glucose and fructose ingestion also induced dissociable effects in the neural system. Using a cross-over, double-blind, placebo-controlled design, we compared resting state functional connectivity (rsFC) strengths within the basal ganglia/limbic network in 12 healthy lean males. Each subject was administered fructose, glucose and placebo on three separate occasions. Subsequent correlation analysis was used to examine relations between rsFC findings and plasma concentrations of satiation hormones and subjective feelings of appetite. Glucose ingestion induced significantly greater elevations in plasma glucose, insulin, GLP-1 and GIP, while feelings of fullness increased and prospective food consumption decreased relative to fructose. Furthermore, glucose increased rsFC of the left caudatus and putamen, precuneus and lingual gyrus more than fructose, whereas within the basal ganglia/limbic network, fructose increased rsFC of the left amygdala, left hippocampus, right parahippocampus, orbitofrontal cortex and precentral gyrus more than glucose. Moreover, compared to fructose, the increased rsFC after glucose positively correlated with the glucose-induced increase in insulin. Our findings suggest that glucose and fructose induce dissociable effects on rsFC within the basal ganglia/limbic network, which are probably mediated by different insulin levels. A larger study would be recommended in order to confirm these findings.

Green tea consumption affects cognitive dysfunction in the elderly: a pilot study

Green tea is known to have various health benefits for humans. However, the effect of green tea consumption on cognitive dysfunction remains to be clinically verified. We conducted a clinical study to investigate the effects of green tea consumption on cognitive dysfunction. Twelve elderly nursing home residents with cognitive dysfunction (Mini-Mental State Examination Japanese version (MMSE-J) score: <28) participated in the study (2 men, 10 women; mean age, 88 years). The participants consumed green tea powder 2 g/day for 3 months. After three months of green tea consumption, the participants’ MMSE-J scores were significantly improved (before, 15.3 ± 7.7; after, 17.0 ± 8.2; p = 0.03). This result suggests that green tea consumption may be effective in improving cognitive function or reducing the progression of cognitive dysfunction; however, long-term large-scale controlled studies are needed to further clarify the effect.