l-Theanine, an amino acid in green tea, attenuates beta-amyloid-induced cognitive dysfunction and neurotoxicity: reduction in oxidative damage and inactivation of ERK/p38 kinase and NF-kappaB pathways

The P38MAPK Pathway Mediates the Destruction of the Blood-Brain Barrier in Anti-NMDAR Encephalitis Mice

The clinical manifestations of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis may be closely related to the integrity of the blood-brain barrier (BBB). The P38 mitogen-activated protein kinase (P38MAPK) pathway plays a protective role in neurodegenerative diseases. However, whether the P38MAPK pathway is involved in the underlying mechanism of tight junction (TJ) protein disruption and neuronal damage has not been elucidated. Therefore, in this study, a mouse model of anti-NMDAR encephalitis was established by active immunization with NMDAR NR1356-385 peptides. The critical pathways of P38MAPK were screened by interaction network and co-enrichment analysis. The role of P38MAPK pathways was investigated by the injection of P38MAPK inhibitor SB203580 (10 mg/kg, i.p.). Compared with the control group, the expression of occludin and zonula occludens (ZO)-1 in NMDAR NR1356-385 group mice was downregulated, and the structure and function of BBB were damaged. However, after the intervention of SB203580, the activation of the P38MAPK was inhibited, the expression of matrix metalloproteinase 9 (MMP9) was reduced, and the function of BBB was improved. Meanwhile, inhibiting the P38MAPK pathway reversed the degradation of NMDAR NR1, while reducing the expression of the glial fibrillary acidic protein (GFAP) and pro-inflammatory factor tumor necrosis factor (TNF-α). It also relieved the damage of neuron-specific nucleus (NeuN), thus alleviating psychobehavioral symptoms. In conclusion, our results suggested that the P38MAPK pathway is involved in BBB destruction and neurobehavioral change in mice with anti-NMDAR encephalitis. Targeting the P38MAPK pathway may be a promising option for the treatment of anti-NMDAR encephalitis.

An insight into the concept of neuroinflammation and neurodegeneration in Alzheimer's disease: targeting molecular approach Nrf2, NF-κB, and CREB

Alzheimer's disease (AD) is a most prevalent neurologic disorder characterized by cognitive dysfunction, amyloid-β (Aβ) protein accumulation, and excessive neuroinflammation. It affects various life tasks and reduces thinking, memory, capability, reasoning and orientation ability, decision, and language. The major parts responsible for these abnormalities are the cerebral cortex, amygdala, and hippocampus. Excessive inflammatory markers release, and microglial activation affect post-synaptic neurotransmission. Various mechanisms of AD pathogenesis have been explored, but still, there is a need to debate the role of NF-κB, Nrf2, inflammatory markers, CREB signaling, etc. In this review, we have briefly discussed the signaling mechanisms and function of the NF-ĸB signaling pathway, inflammatory mediators, microglia activation, and alteration of autophagy. NF-κB inhibition is a current strategy to counter neuroinflammation and neurodegeneration in the brain of individuals with AD. In clinical trials, numbers of NF-κB modulators are being examined. Recent reports revealed that molecular and cellular pathways initiate complex pathological competencies that cause AD. Moreover, this review will provide extensive knowledge of the cAMP response element binding protein (CREB) and how these nuclear proteins affect neuronal plasticity.

Downregulation of ATF-4 Attenuates the Endoplasmic Reticulum Stress-Mediated Neuroinflammation and Cognitive Impairment in Experimentally Induced Alzheimer's Disease Model

Protein aggregation is invariably associated with the inflammation as a factor in Alzheimer's disease (AD). We investigated the interaction between downstream factors of endoplasmic reticulum (ER) stress pathway and inflammation, with implications in cognitive impairment in AD. Amyloid-β (Aβ)(1-42) was administered by bilateral intracerebroventricular (icv) injection in the brain of adult male Wistar rats to experimentally develop AD. The cognitive impairment was assessed by measuring behavioral parameters such as Morris water maze and novel object recognition tests. Levels of pro-inflammatory cytokines such as interleukin (IL)-1β and tumor necrosis factor (TNF)-α and anti-inflammatory cytokines IL-4 and IL-10 were measured by the enzyme-linked immunosorbent assay (ELISA) in different rat brain regions. Inflammatory marker proteins such as cyclo-oxygenase (COX)-2 and phosphorylation of nuclear factor kappa B (NF-КB) (p65) were measured by the western blotting. Gene expression of ER stress downstream factors such as ATF-4, CHOP, and GADD-34 was analyzed by qRT-PCR. Histological studies were performed to check Aβ accumulation and neuronal degeneration. Integrated stress response inhibitor (ISRIB) was used to confirm the specific role of ER stress-mediated inflammation in cognitive impairment. Administration of Aβ(1-42) resulted in alteration in levels of inflammatory cytokines, inflammatory proteins, and mRNA levels of ER stress downstream factors. ISRIB treatment resulted in attenuation of Aβ(1-42)-induced ER stress, inflammation, neurodegeneration, and cognitive impairment in rats. These results indicate that ER stress-mediated inflammation potentiates the cognitive impairment in AD. An understanding of cascade of events, interaction of ER stress which was a hallmark of the present investigation together with inflammation and modulation of downstream signalling factors could serve as potent biomarkers to study AD progression.

Pomegranate polyphenol punicalin ameliorates lipopolysaccharide-induced memory impairment, behavioral disorders, oxidative stress, and neuroinflammation via inhibition of TLR4-NF-кB pathway

Neuroinflammation may play an important role in the development of Alzheimer's disease (AD). Previous studies have reported that lipopolysaccharide (LPS)-induced neuroinflammation causes memory impairments and behavioral disorders. We investigated the potential preventive effects of punicalin (PUN), a polyphenolic component of pomegranate, on LPS-induced memory deficiency and anxiety- and depression-like behaviors, along with the underlying mechanisms. LPS-treated cultured microglial BV2 cells and BV2 cell/Neuro-2a (N2a) cell coculture system were investigated for anti-neuroinflammatory effects of PUN in vitro. The in vivo experiments involved mice administered a 4-week course of oral gavage with 1500 mg/kg/d PUN before intraperitoneal LPS (250 mg/kg daily 7 times) injections. The in vitro results demonstrated that PUN inhibited the LPS-induced inflammatory cytokine (IL-18, IL-1β, TNF-ɑ, and IL-6) production in BV2 cells and protected N2a cells from synaptic damage mediated by BV2 microglia-induced neuroinflammation. In in vivo studies, it was observed that PUN improved memory impairment and anxiety- and depression-like behaviors caused by LPS and reduced the expression of inflammatory proteins such as iNOS, COX-2, IL-1β, IL-2, IL-6, and TNF-α. Furthermore, PUN inhibited the LPS-induced production of MDA; increased the activities of CAT, SOD, and GSH-Px, and inhibited LPS-induced Aβ1-42 generation through down-regulation of APP and BACE1 expression. Moreover, PUN also suppressed the expression of TLR4, IRAK4, TRAF6, IKK-β, NF-κB, p65, and HMGB1 in LPS-treated mouse brain and cultured microglial BV-2 cells. These results suggest that PUN inhibits LPS-induced memory impairment via anti-inflammatory and anti-amylogenic mechanisms through inhibition of TLR4-NF-kB activation.

Trends and hotspots in tea and Alzheimer's disease research from 2014 to 2023: A bibliometric and visual analysis

Objectives

The positive effects of tea on Alzheimer's disease (AD) have increasingly captured researchers' attention. Nevertheless, the quantitative comprehensive analysis in the relevant literatur is lack. This paper aims to thoroughly examine the current research status and hotspots from 2014 to 2023, providing a valuable reference for subsequent research.

Methods

Documents spanning from 2014 to 2023 were searched from the Web of Science, and the R software, VOSviewer, and Citespace software were used for analysis and visualization.

Results

A total of 374 documents were contained in the study. The rate of article publications exhibited a consistent increase each year from 2014 to 2023. Notably, China emerged as the leading country in terms of published articles, followed by the United States and India. Simultaneously, China is also in a leading position in cooperation with other countries. Molecules emerged as the most frequently published journal, while the Journal of Alzheimer's Disease secured the top spot in terms of citations. The identified main keywords included oxidative stress, amyloid, epigallocatechin gallate, and green tea polyphenol, among others. These focal areas delved into the antioxidative and anti-amyloid aggregation actions of tea's polyphenolic components. Furthermore, the particularly way in which epigallocatechin gallate delivers neuroprotective outcomes by influencing molecules related to AD represents a focal point of research.

Conclusion

The increasing attention from researchers on the role of tea in ameliorating AD positions it as a hot spot in the development of anti-AD drugs in the development of future. Through our generalized analysis of the current landscape and hotspots regarding tea's application in AD, this study provides an estimable reference for future research endeavors.

Moderate coffee or tea consumption decreased the risk of cognitive disorders: an updated dose-response meta-analysis

CONTEXT

Although several epidemiological studies have examined the association between coffee or tea intake and the risk of cognitive disorders, the results to date are inconsistent.

OBJECTIVE

An updated systematic review and dose-response meta-analysis was conducted to confirm the association between coffee, tea, and caffeine consumption and the risk of cognitive disorders.

DATA SOURCES

PubMed, Embase, and Web of Science were searched from inception to January 2022 for relevant studies, including dementia, Alzheimer disease (AD), and cognitive impairment or decline.

DATA EXTRACTION

Two reviewers independently performed data extraction and assessed the study quality.

DATA ANALYSIS

Restricted cubic splines were used to conduct the dose-response meta-analysis for coffee and tea intake.

RESULTS

Twenty-two prospective studies and 11 case-control studies involving 389 505 participants were eligible for this meta-analysis. Coffee and tea consumption was linked to a lower risk of cognitive disorders, with an overall relative risk (RR) of 0.73 (95% CI: 0.60-0.86) and 0.68 (95% CI: 0.56-0.80), respectively. The subgroup analysis revealed that ethnicity, sex, and outcomes had significant effects on this association. Protection was stronger for men than that for women in both coffee and tea consumption. A nonlinear relationship was found between coffee consumption and AD risk, and the strength of protection peaked at approximately 2.5 cups/day (RR: 0.74; 95% CI: 0.59-0.93). A linear relationship was found between tea consumption and cognitive disorders, and the risk decreased by 11% for every 1-cup/day increment.

CONCLUSION

This meta-analysis demonstrated that the consumption of 2.5 cups coffee/day minimizes the risk of AD, and 1 cup/day of tea intake leads to an 11% reduction in cognitive deficits. Effective interventions involving coffee and tea intake might prevent the occurrence of dementia.

Comprehensive Review of Nutraceuticals against Cognitive Decline Associated with Alzheimer's Disease

Nowadays, nutraceuticals are being incorporated into functional foods or used as supplements with nonpharmacological approaches in the prevention and management of several illnesses, including age-related conditions and chronic neurodegenerative diseases. Nutraceuticals are apt for preventing and treating such disorders because of their nontoxic, non-habit-forming, and efficient bioactivities for promoting neurological well-being due to their ability to influence cellular processes such as neurogenesis, synaptogenesis, synaptic transmission, neuro-inflammation, oxidative stress, cell death modulation, and neuronal survival. The capacity of nutraceuticals to modify all of these processes reveals the potential to develop food-based strategies to aid brain development and enhance brain function, prevent and ameliorate neurodegeneration, and possibly reverse the cognitive impairment observed in Alzheimer's disease, the most predominant form of dementia in the elderly. The current review summarizes the experimental evidence of the neuroprotective capacity of nutraceuticals against Alzheimer's disease, describing their mechanisms of action and the in vitro and in vivo models applied to evaluate their neuroprotective potential.

Tea intake or consumption and the risk of dementia: a meta-analysis of prospective cohort studies

Purpose

Dementia affects as many as 130 million people, which presents a significant and growing medical burden globally. This meta-analysis aims to assess whether tea intake, tea consumption can reduce the risk of dementia, Alzheimer's disease (AD) and Vascular dementia (VD).

Patients and methods

Cochrane Library, PubMed and Embase were searched for cohort studies from inception to November 1, 2022. The Newcastle Ottawa Quality Assessment Scale (NOS) was applied to evaluate the risk of bias of the included studies. We extracted the data as the relative risks (RRs) for the outcome of the interest, and conducted the meta-analysis utilizing the random effect model due to the certain heterogeneity. Sensitivity analysis were performed by moving one study at a time, Subgroup-analysis was carried out according to different ages and dementia types. And the funnel plots based on Egger's and Begger's regression tests were used to evaluate publication bias. All statistical analyses were performed using Stata statistical software version 14.0 and R studio version 4.2.0.

Results

Seven prospective cohort studies covering 410,951 individuals, which were published from 2009 and 2022 were included in this meta-analysis. The methodological quality of these studies was relatively with five out of seven being of high quality and the remaining being of moderate. The pooling analysis shows that the relationship between tea intake or consumption is associated with a reduced risk of all-cause dementia (RR = 0.71, 95% CI [0.57-0.88], I² = 79.0%, p < 0.01). Further, the subgroup-analysis revealed that tea intake or consumption is associated with a reduced risk of AD (RR = 0.88, 95% CI [0.79-0.99], I² = 52.6%, p = 0.024) and VD (RR = 0.75, 95% CI [0.66-0.85], I = 0.00%, p < 0.001). Lastly, tea intake or consumption could reduce the risk of all-cause dementia to a greater degree among populations with less physical activity, older age, APOE carriers, and smokers.

Conclusion

Our meta-analysis demonstrated that tea (green tea or black tea) intake or consumption is associated with a significant reduction in the risk of dementia, AD or VD. These findings provide evidence that tea intake or consumption should be recognized as an independent protective factor against the onset of dementia, AD or VD.

Flavor perception and health benefits of tea

As one of the most consumed non-alcoholic beverages in the world, tea is acclaimed for its pleasant flavor and various health benefits. Different types of tea present a distinctive flavor and bioactivity due to the changes in the composition and proportion of respective compounds. This article aimed to provide a more comprehensive understanding of tea flavor (including aroma and taste) and the character of tea in preventing and alleviating diseases. The recent advanced modern analytical techniques for revealing flavor components in tea, including enrichment, identification, quantitation, statistics, and sensory evaluation methodologies, were summarized in the following content. Besides, the role of tea in anti-cancer, preventing cardiovascular disease and metabolic syndrome, anti-aging and neuroprotection, and regulating gut microbiota was also listed in this article. Moreover, questions and outlooks were mentioned to objectify tea products' flavor quality and health benefits on a molecular level and significantly promote our understanding of the comprehensive value of tea as a satisfactory health beverage in the future.

L-theanine attenuates LPS-induced motor deficit in experimental rat model of Parkinson's disease: emphasis on mitochondrial activity, neuroinflammation, and neurotransmitters

RATIONALE

Parkinson's disease (PD) is a neurodegenerative disorder characterized by loss of dopaminergic neurons. The pathogenesis of PD includes oxidative stress, mitochondrial dysfunction, neuroinflammation, and neurotransmitter dysregulation. L-theanine is found in green tea and has antioxidant, anti-inflammatory, and neuroprotective effects with a high blood brain barrier permeability.

OBJECTIVE

The objective of this study was to investigate the possible neuroprotective effect of L-theanine in lipopolysaccharide (LPS) induced motor deficits and striatal neurotoxicity in a rat model of PD.

METHODS

LPS was infused at a dose of 5 μg/5 μl PBS stereotaxically into SNpc of rats. Treatment with L-theanine (50 and 100 mg/kg; po) and Sinemet (36 mg/kg; po) was given from day 7 to 21 in of LPS injected rat. On a weekly basis all behavioral parameters were assessed, and animals were sacrificed on day 22. The striatum tissue of brain was isolated for biochemicals (Nitrite, GSH, catalase, SOD, mitochondrial complexes I and IV), neuroinflammatory markers, and neurotransmitters (serotonin, dopamine, norepinephrine, GABA, and glutamate) estimations.

RESULTS

Results revealed that L-theanine dose-dependently and significantly reversed motor deficits, assessed through locomotor and rotarod activity. Moreover, L-theanine attenuated biochemical markers, reduced oxidative stress, and neurotransmitters dysbalance in the brain. L-theanine treatment at 100 mg/kg; po substantially reduced these pathogenic events by increasing mitochondrial activity, restoring neurotransmitter levels, and inhibiting neuroinflammation.

CONCLUSIONS

These data suggest that the positive effects of L-theanine on motor coordination may be mediated by the suppression of NF-κB induced by LPS. Therefore, L-theanine would have a new therapeutic potential for PD.

Neobaicalein prevents isoflurane anesthesia-induced cognitive impairment in neonatal mice via regulating CREB1

OBJECTIVES

Isoflurane (ISO) is widely used in the clinic and research. The authors aimed to explore whether Neobaicalein (Neob) could protect neonatal mice from ISO-induced cognitive damage.

METHOD

The open field test, Morris water maze test, and tail suspension test was performed to assess the cognitive function in mice. Enzyme-linked immunosorbent assay was used to evaluate inflammatory-related protein concentrations. Immunohistochemistry was used to assess Ionized calcium-Binding Adapter molecule-1 (IBA-1) expression. Hippocampal neuron viability was detected using the Cell Counting Kit-8 assay. Double immunofluorescence staining was employed to confirm the interaction between proteins. Western blotting was used to assess protein expression levels.

RESULTS

Neob notably improved cognitive function and exhibited anti-inflammatory effects; moreover, under iso-treatment, it exhibited neuroprotective effects. Furthermore, Neob suppressed interleukin-1β, tumor necrosis factor-α, and interleukin-6 levels and upregulated interleukin-10 levels in ISO-treated mice. Neob significantly mitigated iso-induced increases in IBA-1-positive cell numbers of the hippocampus in neonatal mice. Furthermore, it inhibited ISO-induced neuronal apoptosis. Mechanistically, Neob was observed to upregulate cAMP Response Element Binding protein (CREB1) phosphorylation and protected hippocampal neurons from ISO-mediated apoptosis. Moreover, it rescued ISO-induced abnormalities of synaptic protein.

CONCLUSIONS

Neob prevented ISO anesthesia-induced cognitive impairment by suppressing apoptosis and inflammation through upregulating CREB1.

Current Naturopathy to Combat Alzheimer's Disease

Neurodegeneration is the progressive loss of structure or function of neurons, which may ultimately involve cell death. The most common neurodegenerative disorder in the brain happens with Alzheimer's disease (AD), the most common cause of dementia. It ultimately leads to neuronal death, thereby impairing the normal functionality of the central or peripheral nervous system. The onset and prevalence of AD involve heterogeneous etiology, either in terms of genetic predisposition, neurometabolomic malfunctioning, or lifestyle. The worldwide relevancies are estimated to be over 45 million people. The rapid increase in AD has led to a concomitant increase in the research work directed towards discovering a lucrative cure for AD. The neuropathology of AD comprises the deficiency in the availability of neurotransmitters and important neurotrophic factors in the brain, extracellular betaamyloid plaque depositions, and intracellular neurofibrillary tangles of hyperphosphorylated tau protein. Current pharmaceutical interventions utilizing synthetic drugs have manifested resistance and toxicity problems. This has led to the quest for new pharmacotherapeutic candidates naturally prevalent in phytochemicals. This review aims to provide an elaborative description of promising Phyto component entities having activities against various potential AD targets. Therefore, naturopathy may combine with synthetic chemotherapeutics to longer the survival of the patients.

Can habitual tea drinking be an effective approach against age-related neurodegenerative cognitive disorders: A systematic review and meta-analysis of epidemiological evidence

Our present knowledge about the efficacy of tea consumption in improving age-related cognitive disorders is incomplete since previous epidemiological studies provide inconsistent evidence. This unified systematic review and meta-analysis based on updated epidemiological cohort studies and randomized controlled trials (RCTs) evidence aimed to overcome the limitations of previous reviews by examining the efficacy of distinct types of tea consumption. PubMed, Embase, and MEDLINE were searched up to May 20, 2022, and 23 cohorts and 12 cross-sectional studies were included. Random-effects meta-analyses were conducted to obtain pooled RRs or mean differences with 95% CIs. The pooled RRs of the highest versus lowest tea consumption categories were 0.81 (95% CIs: 0.75-0.88) and 0.69 (95% CIs: 0.61-0.77), respectively. The pooled mean difference of four included RCTs revealed a beneficial effect of tea on cognitive dysfunction (MMSE ES: 1.03; 95% CI, 0.14-1.92). Subgroup analyses further demonstrated that green and black tea intake was associated with a lower risk of cognitive disorders in eastern countries, especially in women. The evidence quality was generally low to moderate. The present review provides insight into whether habitual tea consumption can be an effective approach against age-related neurodegenerative cognitive disorders and summarizes potential mechanisms based on currently published literature.

Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases

Nuclear Factor-Erythroid Factor 2 (Nrf2) is an important transcription factor that regulates the expression of large number of genes in healthy and disease states. Nrf2 is made up of 605 amino acids and contains 7 conserved regions known as Nrf2-ECH homology domains. Nrf2 regulates the expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy and mitochondrial function in all organs of the human body, in the peripheral and central nervous systems. Mounting evidence also suggests that altered expression of Nrf2 is largely involved in aging, neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's diseases, Amyotrophic lateral sclerosis, Stroke, Multiple sclerosis and others. The purpose of this article is to detail the essential role of Nrf2 in oxidative stress, antioxidative defense, detoxification, inflammatory responses, transcription factors, proteasomal and autophagic/mitophagic degradation, and metabolism in aging and neurodegenerative diseases. This article also highlights the Nrf2 structural and functional activities in healthy and disease states, and also discusses the current status of Nrf2 research and therapeutic strategies to treat aging and neurodegenerative diseases.

Transcription Factors as Targets of Natural Compounds in Age-Related Diseases and Cancer: Potential Therapeutic Applications

Inflammation exacerbates systemic pathophysiological conditions and chronic inflammation is a sustained and systemic phenomenon that aggravates aging that can lead to chronic age-related diseases. These inflammatory phenomena have recently been redefined and delineated at the molecular, cellular, and systemic levels. Many transcription factors that are activated in response to tumor metabolic state have been reported to be regulated by a class of histone deacetylase called sirtuins (SIRTs). Sirtuins play a pivotal role in the regulation of tumor cell metabolism, proliferation, and angiogenesis, including oxidative stress and inflammation. The SIRT1-mediated signaling pathway in diabetes and cancer is the SIRT1/forkhead-box class O (FoxO)/nuclear factor-kappa B (NF-κB) pathway. In this review, we describe the accumulation of SIRT1-, NF-κB-, and FoxO-mediated inflammatory processes and cellular proinflammatory signaling pathways. We also describe the proinflammatory mechanisms underlying metabolic molecular pathways in various diseases such as liver cancer and diabetes. Finally, the regulation of cancer and diabetes through the anti-inflammatory effects of natural compounds is highlighted. Evidence from inflammation studies strongly suggests that cells may be a major source of cytokines secreted during various diseases. A better understanding of the mechanisms that underpin the inflammatory response and palliative role of natural compounds will provide insights into the molecular mechanisms of inflammation and various diseases for potential intervention.

Antarctic krill oil exhibited synergistic effects with nobiletin and theanine in ameliorating memory and cognitive deficiency in SAMP8 mice: Applying the perspective of the sea–land combination to retard brain aging

The complex pathogenesis of Alzheimer's disease (AD) leads to a limited therapeutic effect; therefore, the combination of multiple bioactive ingredients may be more effective in improving AD due to synergistic effects. Based on the perspective of the sea–land combination, the effects of sea-derived Antarctic krill oil (AKO) combined with land-derived nobiletin (Nob) and L-theanine (The) on memory loss and cognitive deficiency were studied in senescence-accelerated prone 8 mice (SAMP8). The results demonstrated that AKO combined with The significantly increased the number of platform crossings in the Morris water maze test by 1.6-fold, and AKO combined with Nob significantly increased the preference index in a novel object recognition test. AKO exhibited synergistic effects with Nob and The in ameliorating recognition memory and spatial memory deficiency in SAMP8 mice, respectively. Further research of the mechanism indicated that AKO exhibited synergistic effects with Nob in suppressing β-amyloid (Aβ) aggregation, neurofibrillary tangles, and apoptosis and neuroinflammation, while the synergistic effects of AKO and The involved in synaptic plasticity and anti-neuroinflammation, which revealed that the combination was complex, not a mechanical addition. These findings revealed that the sea–land combination may be an effective strategy to treat and alleviate AD.

Tea Consumption Is Associated with Reduced Cognitive Decline and Interacts with Iron Intake: A Population-Based Longitudinal Study on 4,820 Old Adults

Background: Previous studies suggest a positive effect of tea intake on cognition. Additional micronutrients that may moderate this association was not previously examined. Objective: To examine the association between tea consumption and cognition and explore the interaction between tea consumption and iron intake. Methods: Data from the China Health and Nutrition Survey between 1997 and 2011 was used. 4,820 individuals (≥55 years) were included in the analyses. Measurement of cognitive function was conducted in 1997, 2000, 2004, and 2006. Tea consumption was self-reported. Food intake was assessed by 24-hour dietary recalls of three consecutive days during home visits between 1997 and 2011. Multivariable mixed linear regression and logistic regression was used to assess the association. Results: Tea consumption was associated with reduced global cognitive function decline. In fully adjusted models, regression coefficients (95% CIs) for those who consumed 0 cups/day,<2 cups/day, 2–3.9 cups/day, and≥4 cups/day of tea were 0, –0.09 (–0.55–0.37), 0.05 (–0.34–0.45), and 0.87 (0.46–1.29), respectively. This effect was stronger in adults > 60 years. Tea consumption of≥4 cups/day was inversely associated with self-reported poor memory (OR 0.70 (95% CI 0.56–0.86)) and memory decline (OR, 0.73 (95% CI 0.62–0.87)). There was a significant interaction between tea consumption and iron intake in relation to cognition. High iron intake was inversely associated with cognition in non-consumers of tea but not in tea consumers. Conclusion: Higher tea intake is associated with reduced cognitive decline in adults and inhibits the adverse effect of high iron intake.

Hormonal regulation of health-promoting compounds in tea (Camellia sinensis L.)

Tea is the most frequently consumed natural beverage across the world produced with the young leaves and shoots of the evergreen perennial plant Camellia sinensis (L.) O. Kuntze. The expanding global appeal of tea is partly attributed to its health-promoting benefits such as anti-inflammation, anti-cancer, anti-allergy, anti-hypertension, anti-obesity, and anti- SARS-CoV-2 activity. The many advantages of healthy tea intake are linked to its bioactive substances such as tea polyphenols, flavonoids (catechins), amino acids (theanine), alkaloids (caffeine), anthocyanins, proanthocyanidins, etc. that are produced through secondary metabolic pathways. Phytohormones regulate secondary metabolite biosynthesis in a variety of plants, including tea. There is a strong hormonal response in the biosynthesis of polyphenols, catechins, theanine and caffeine in tea under control and perturbed environmental conditions. In addition to the impact of preharvest plant hormone manipulation on green tea quality, changes in hormones of postharvest tea also regulate quality-related metabolites in tea. In this review, we discuss the health benefits of major tea constituents and the role of various plant hormones in improving the endogenous levels of these compounds for human health benefits. The fact that the ratio of tea polyphenols to amino acids and the concentrations of tea components are changed by environmental conditions, most notably by climate change-associated variables, the selection and usage of optimal hormone combinations may aid in sustaining tea quality, and thus can be beneficial to both consumers and producers.

Evaluation of the Brewing Characteristics, Digestion Profiles, and Neuroprotective Effects of Two Typical Se-Enriched Green Teas

As a functional beverage, selenium (Se)-enriched green tea (Se-GT) has gained increasing popularity for its superior properties in promoting health. In this study, we compared the brewing characteristics, in vitro digestion profiles, and protective effects on neurotoxicity induced through the amyloid-beta (Aβ) peptide of two typical Se-GTs (Enshi Yulu (ESYL) and Ziyang Maojian (ZYMJ), representing the typical low-Se green tea and high-Se green tea, respectively). ESYL and ZYMJ showed similar chemical component leaching properties with the different brewing methods, and the optimized brewing conditions were 5 min, 90 °C, 50 mL/g, and first brewing. The antioxidant activities of the tea infusions had the strongest positive correlation with the tea polyphenols among all of the leaching substances. The tea infusions of ESYL and ZYMJ showed similar digestive behaviors, and the tea polyphenols in the tea infusions were almost totally degraded or transferred after 150 min of dynamic digestion. Studies conducted in a cell model of Alzheimer’s disease (AD) showed that the extract from the high-Se green tea was more effective for neuroprotection compared with the low-Se green tea. Overall, our results revealed the best brewing conditions and digestion behaviors of Se-GT and the great potential of Se-GT or Se-enriched green extract (Se-GTE) to be used as promising AD-preventive beverages or food ingredients.

A comprehensive review on the prevention and regulation of Alzheimer's disease by tea and its active ingredients

Alzheimer's disease (AD) has brought a heavy burden to society as a representative neurodegenerative disease. The etiology of AD combines multiple factors, concluding family, gender, head trauma, diseases and social psychology. There are multiple hypotheses explaining the pathogenesis of AD such as β-amyloid (Aβ) deposition and tau hyperphosphorylation, which lead to extracellular amyloid plaques and neurofibrillary tangles in neurons. The existing therapeutic drugs have several disadvantages including single target, poor curative effect, and obvious side effects. Tea contains many bioactive components, such as tea polyphenols (TPP), L-theanine (L-TH), tea pigment, tea polysaccharides and caffeine. The epidemiological investigations have shown that drinking tea can reduce the risk of AD. The mechanisms of tea active ingredients in the prevention and regulation of AD includes reducing the generation and aggregation of Aβ; inhibiting tau aggregation and hyperphosphorylation; inhibiting neuronal apoptosis and regulate neurotransmitters; relieving oxidative stress and neuroinflammation as well as the regulation of intestinal flora. This review summarizes the different signaling pathways that tea active ingredients regulate AD. Furthermore, we propose the main limitations of current research and future research directions, hoping to contribute to the development of natural functional foods based on tea active ingredients in the prevention and treatment of AD.

Metabolomics Study Suggests the Mechanism of Different Types of Tieguanyin (Oolong) Tea in Alleviating Alzheimer’s Disease in APP/PS1 Transgenic Mice

Previously, we found that three types of Tieguanyin tea (Tgy-Q, Tgy-N and Tgy-C) extracts could alleviate Alzheimer’s disease (AD) in a mouse model among which Tgy-C was more effective. In this study, APP/PS1 transgenic mice were used to investigate the metabolomic changes in the feces of mice treated with Tieguanyin tea extracts. Results showed that the profile of fecal metabolites was obviously changed in AD mice. Metabolomics analysis found the effects of Tgy-C, especially its decreasing effect on the fecal metabolites in AD mice—132 of the 155 differential metabolites were decreased. KEGG enrichment revealed that differential metabolites could participate in functional pathways including protein digestion and absorption, biosynthesis of amino acids and ABC transporters. Further comparisons of the metabolites between groups showed that although Tgy-N and Tgy-Q exerted a decreasing effect on the fecal metabolites, Tgy-C was more effective. Moreover, correlation analysis found that the levels of the fecal metabolites were highly correlated with the contents of functional components in tea extracts. Finally, 16S rDNA sequencing presented that Tieguanyin extracts modified the gut microbiota by targeting diverse bacteria. In this study, we investigated the differences of three types of Tieguanyin tea extracts on the fecal metabolites as well as the bacterial community of the gut microbiota in AD mice. The identified differential metabolites and the changed intestinal bacteria might provide potential diagnostic biomarkers for the occurrence and progression of AD.

Association Between Tea Drinking and Cognitive Disorders in Older Adults: A Meta-Analysis of Observational Studies

Introduction

Previous research has shown that tea drinking has a bearing on Cognitive Disorders, but the conclusions are inconsistent. The purpose of this research was to systematically assess the published evidence pertaining to tea drinking and the risk of cognitive disorders in older adults using a meta-analysis, and to concurrently evaluate the dose-response association.

Design

A meta-analysis.

Setting and Participants

We used the PubMed and Web of Science databases for a literature search until 30 May 2021. We initially retrieved 20,908 studies (14,884 from PubMed and 6,024 from the Web of Science), Thirty-six studies met the inclusion criteria (7 case-control, 16 cohort, and 13 cross-sectional studies), involved 224,980 participants.

Methods

Pooled odd ratios (ORs) with their corresponding 95% confidence intervals (CIs) were used to evaluate the strength of the association under a fixed- or random-effect model according to heterogeneity test results.

Results

The results showed that drinking tea was negatively associated with cognitive disorders (OR: 0.76, 95% CI: 0.70–0.82). Moreover, dose-response associations were found between tea drinking and cognitive disorders (1 time/day: OR, 0.81; 95% CI, 0.70–0.95; 1 cup/day: OR, 0.86; 95% CI, 0.78–0.94). In addition, subgroup analyses were performed according to study designs, study population, types of tea drinking, outcomes and methods used to assess outcomes. Most of the results in the subgroup analyses were consistent with the main results.

Conclusion

The results of the present study provided abundant evidence that tea drinking is inversely proportional with the occurrence of cognitive disorders in older adults. A linear dose-response association between tea drinking and decreased prevalence of cognitive disorders was found.

L-theanine prevents progression of nonalcoholic hepatic steatosis by regulating hepatocyte lipid metabolic pathways via the CaMKKβ-AMPK signaling pathway

Background

L-theanine, a non-protein amino acid was found principally in the green tea, has been previously shown to exhibit potent anti-obesity property and hepatoprotective effect. Herein, we investigated the effects of L-theanine on alleviating nonalcoholic hepatic steatosis in vitro and in vivo, and explored the underlying molecular mechanism.

Methods

In vitro, HepG2 and AML12 cells were treated with 500 μM oleic acid (OA) or treated with OA accompanied by L-theanine. In vivo, C57BL/6J mice were fed with normal control diet (NCD), high‐fat diet (HFD), or HFD along with L-theanine for 16 weeks. The levels of triglycerides (TG), accumulation of lipid droplets and the expression of genes related to hepatocyte lipid metabolic pathways were detected in vitro and in vivo.

Results

Our data indicated that, in vivo, L-theanine significantly reduced body weight, hepatic steatosis, serum levels of alanine transaminase (ALT), aspartate transaminase (AST), TG and LDL cholesterol (LDL-C) in HFD-induced nonalcoholic fatty liver disease (NAFLD) mice. In vitro, L-theanine also significantly alleviated OA induced hepatocytes steatosis. Mechanic studies showed that L-theanine significantly inhibited the nucleus translocation of sterol regulatory element binding protein 1c (SREBP-1c) through AMPK-mTOR signaling pathway, thereby contributing to the reduction of fatty acid synthesis. We also identified that L-theanine enhanced fatty acid β-oxidation by increasing the expression of peroxisome proliferator–activated receptor α (PPARα) and carnitine palmitoyltransferase-1 A (CPT1A) through AMP-activated protein kinase (AMPK). Furthermore, our study indicated that L-theanine can active AMPK through its upstream kinase Calmodulin-dependent protein kinase kinase-β (CaMKKβ).

Conclusions

Taken together, our findings suggested that L-theanine alleviates nonalcoholic hepatic steatosis by regulating hepatocyte lipid metabolic pathways via the CaMKKβ-AMPK signaling pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12986-022-00664-6.

History in Perspective: The Prime Pathological Players and Role of Phytochemicals in Alzheimer’s Disease

Alzheimer's disease is a steadily progressive, irreversible neurological disorder that is most frequently categorized under the umbrella term "neurodegeneration". Several attempts are underway to clarify the pathogenic mechanisms, identify the aetiologies, and determine a pathway by which the therapeutic steps can be implemented. Oxidative stress is one of the pathogenic processes, which is commonly believed to be associated with neurodegenerative diseases. Accumulation of extracellular amyloid-β protein (Aβ), hyperphosphorylation of tau, initiation of neurometabolic reactions characterized by the loss of neuronal function and synaptic failure, and decreased or lost learning capability and memory function are the most central neuropathological characteristics of AD. According to the amyloid cascade hypothesis, the enhanced deposition of Aβ deposits and neurofibrillary tangles due to hyperphosphorylation of Tau activates the cascade reactions in the brain. These reactions affect the synaptic activity and activation of microglia, which results in neuroinflammation due to enhanced immune function. Plant-based phytochemicals have also been used long ago against several diseases. Phytoconstituents play a significant neuroprotective property by preventing the pathophysiology of the disease. In this review, we have discussed the formation and crosstalk between amyloid and tau pathologies as well as the effect of neuroinflammation on the progression of AD. We have specifically focused on the formation of NFT, β-amyloids, inflammation, and pathophysiology of AD and the role of phytochemicals in the prevention of AD.

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AD is an insidious, slowly progressive, and neurodegenerative disorder.

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Common symptoms are memory loss, difficulty in recalling, and understanding.

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β-amyloids and Neurofibrillary tangles are the main factors in AD pathogenesis.

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Activated microglia and oxidative stress have different effects on AD progression.

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Phytochemicals show a key role against AD by inhibiting several pathways.

Green Tea Suppresses Amyloid β Levels and Alleviates Cognitive Impairment by Inhibiting APP Cleavage and Preventing Neurotoxicity in 5XFAD Mice

SCOPE

The consumption of green tea is considered to be associated with a lower incidence of neurodegenerative diseases. In the present study, it is investigated the role of amyloid precursor protein cleavage, glial cell activation, neuroinflammation, and synaptic alterations in the protective effects of green tea against the amyloid β (Aβ) accumulation and cognitive impairment.

METHODS AND RESULTS

5XFAD mice are treated with green tea extract (GTE) for 8 or 16 weeks. Barnes maze and Y maze testing demonstrated that spatial learning and memory ability are markedly improved by GTE treatment. Immunofluorescence staining, ELISA, and western blot showed GTE significantly alleviate the formation of Aβ and reduce the levels of sAPPβ and C99, as well as sAPPα and C83. Meanwhile, GTE suppressed GFAP and Iba1 levels in the glial cells, increased PSD95 and synaptophysin levels in synaptic cells. Further, the IL-1β level is decreased, RNA sequencing reveals the genes annotated in response to stimulus and immune response are regulated.

CONCLUSION

Our findings indicate GTE suppresses Aβ levels and alleviate cognitive impairment in 5XFAD mice. These beneficial effects are accompanied by inhibition of APP cleavage pathways, suppression of glial cell activation and pro-inflammatory responses, and a reduction of synapse loss.

l-Theanine Ameliorates d-Galactose-Induced Brain Damage in Rats via Inhibiting AGE Formation and Regulating Sirtuin1 and BDNF Signaling Pathways

The maintenance of homeostasis is essential for mitigating stress and delaying degenerative diseases such as Alzheimer's disease (AD). AD is generally defined as the abnormal production of β-amyloid (Aβ) and advanced glycation end products (AGEs). The effects of l-theanine on Aβ and AGE generation were investigated in this study. Decreased AGEs and Aβ_1-42 levels were reflected by increased acetylcholine (ACh) concentration and acetylcholinesterase (AChE) activity inhibition compared to model rats. l-Theanine also inhibited nuclear factor-κB (p65) protein expression by activating sirtuin1 (SIRT1), reducing inflammatory factor expression, and downregulating the mRNA and protein expression of AGE receptors (RAGE). Superoxide dismutase 2 and catalase protein expressions were markedly upregulated by l-theanine, whereas oxidative stress-related injury was alleviated. The expression of peroxisome proliferator-activated receptor-γ coactivator 1α (PGC-1α) was also found to be increased. H&E staining showed that the apoptosis of hippocampal neurons was mitigated by decreased Bax and cleaved-caspase-3 protein expression and the increase of Bcl-2 protein expression. Moreover, l-theanine increased the gene and protein expression of brain-derived neurotrophic factor (BDNF). These findings suggest that the potential preventive effects of l-theanine against AD may be attributed to its regulation of SIRT1 and BDNF proteins and its mitigation of AGEs/RAGE signaling pathways in the brain tissue of AD model rats.

Anti-Neuroinflammatory Potential of Polyphenols by Inhibiting NF-κB to Halt Alzheimer's Disease

Alzheimer's disease (AD) is an irrevocable chronic brain disorder featured by neuronal loss, microglial accumulation, and progressive cognitive impairment. The proper pathophysiology of this life-threatening disorder is not completely understood and no exact remedies have been found yet. Over the last few decades, research on AD has mainly highlighted pathomechanisms linked to a couple of the major pathological hallmarks, including extracellular senile plaques made of amyloid-β (Aβ) peptides, and intracellular neurofibrillary tangles (NFTs) made of tau proteins. Aβ can induce apoptosis, trigger an inflammatory response, and inhibit the synaptic plasticity of the hippocampus, which ultimately contributes to reducing cognitive functions and memory impairment. Recently, a third disease hallmark, the neuroinflammatory reaction that is mediated by cerebral innate immune cells, has become a spotlight in the current research area, assured by pre-clinical, clinical, and genetic investigations. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), a cytokine producer, is significantly associated with physiological inflammatory proceedings and thus shows a promising candidate for inflammation- based AD therapy. Recent data reveal that phytochemicals, mainly polyphenol compounds, exhibit potential neuroprotective functions and these may be considered as a vital resource for discovering several drug candidates against AD. Interestingly, phytochemicals can easily interfere with the signaling pathway of NF-κB. This review represents the anti-neuroinflammatory potential of polyphenols as inhibitors of NF-κB to combat AD pathogenesis.

Bioactive Compounds and Traditional Herbal Medicine: Promising Approaches for the Treatment of Dementia

Dementia is a term that encompasses a group of clinical symptoms affecting memory, thinking and social abilities, characterized by progressive impairment of memory performance and cognitive functions. There are several factors involved in the pathogenesis and progression of dementia, such as old age, brain ischemia, toxin exposure, and oxidative stress. There are extensive similarities between dementia and Alzheimer's disease (AD) either in clinical manifestations or experimental animal models. AD is the most dominant form of dementia, characterized by the accumulation of beta-amyloid protein and cholinergic neurotransmission deficits in the brain. Currently available medications for the treatment of dementia, such as choline esterase inhibitors, N-methyl-D-aspartate (NMDA) antagonists (memantine), have short-term efficacy and only relieve symptoms rather than targeting the main underlying pathogenesis. Several animal studies and clinical trials are being conducted to provide a rational approach to these medicinal plants in the prevention or treatment of memory deficits. This review highlights the potential effects of medicinal plants and their derived lead molecules, and explains the related mechanisms and effects reviewed from published literature as major thrust aspects and hopeful strategies in the prevention or treatment of dementia.

Biochemical characterization of specific Alanine Decarboxylase (AlaDC) and its ancestral enzyme Serine Decarboxylase (SDC) in tea plants (Camellia sinensis)

Background

Alanine decarboxylase (AlaDC), specifically present in tea plants, is crucial for theanine biosynthesis. Serine decarboxylase (SDC), found in many plants, is a protein most closely related to AlaDC. To investigate whether the new gene AlaDC originate from gene SDC and to determine the biochemical properties of the two proteins from Camellia sinensis, the sequences of CsAlaDC and CsSDC were analyzed and the two proteins were over-expressed, purified, and characterized.

Results

The results showed that exon-intron structures of AlaDC and SDC were quite similar and the protein sequences, encoded by the two genes, shared a high similarity of 85.1%, revealing that new gene AlaDC originated from SDC by gene duplication. CsAlaDC and CsSDC catalyzed the decarboxylation of alanine and serine, respectively. CsAlaDC and CsSDC exhibited the optimal activities at 45 °C (pH 8.0) and 40 °C (pH 7.0), respectively. CsAlaDC was stable under 30 °C (pH 7.0) and CsSDC was stable under 40 °C (pH 6.0–8.0). The activities of the two enzymes were greatly enhanced by the presence of pyridoxal-5′-phosphate. The specific activity of CsSDC (30,488 IU/mg) was 8.8-fold higher than that of CsAlaDC (3467 IU/mg).

Conclusions

Comparing to CsAlaDC, its ancestral enzyme CsSDC exhibited a higher specific activity and a better thermal and pH stability, indicating that CsSDC acquired the optimized function after a longer evolutionary period. The biochemical properties of CsAlaDC might offer reference for theanine industrial production.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12896-021-00674-x.

Protective Effect of Natural Products against Huntington's Disease: An Overview of Scientific Evidence and Understanding Their Mechanism of Action

Huntington's disease (HD), a neurodegenerative disease, normally starts in the prime of adult life, followed by a gradual occurrence of characteristic psychiatric disturbances and cognitive and motor dysfunction. To the best of our knowledge, there is no treatment available to completely mitigate the progression of HD. Among various therapeutic approaches, exhaustive literature reports have confirmed the medicinal benefits of natural products in HD experimental models. Building on this information, this review presents a brief overview of the neuroprotective mechanism(s) of natural products against in vitro/in vivo models of HD. Relevant studies were identified from several scientific databases, including PubMed, ScienceDirect, Scopus, and Google Scholar. After screening through literature from 2005 to the present, a total of 14 medicinal plant species and 30 naturally isolated compounds investigated against HD based on either in vitro or in vivo models were included in the present review. Behavioral outcomes in the HD in vivo model showed that natural compounds significantly attenuated 3-nitropropionic acid (3-NP) induced memory loss and motor incoordination. The biochemical alteration has been markedly alleviated with reduced lipid peroxidation, increased endogenous enzymatic antioxidants, reduced acetylcholinesterase activity, and increased mitochondrial energy production. Interestingly, following treatment with certain natural products, 3-NP-induced damage in the striatum was ameliorated, as seen histologically. Overall, natural products afforded varying degrees of neuroprotection in preclinical studies of HD via antioxidant and anti-inflammatory properties, preservation of mitochondrial function, inhibition of apoptosis, and induction of autophagy.

Platycodon grandiflorum Root Protects against Aβ-Induced Cognitive Dysfunction and Pathology in Female Models of Alzheimer's Disease

Alzheimer's disease (AD) is a devastating neurodegenerative disease characterized by irreversible cognitive dysfunction. Amyloid beta (Aβ) peptide is an important pathological factor that triggers the progression of AD through accumulation and aggregation, which leads to AD-related pathologies that consequently affect cognitive functions. Interestingly, several studies have reported that Platycodon grandiflorum root extract (PGE), besides exhibiting other bioactive effects, displays neuroprotective, anti-neuroinflammatory, and cognitive-enhancing effects. However, to date, it is not clear whether PGE can affect AD-related cognitive dysfunction and pathogenesis. Therefore, to investigate whether PGE influences cognitive impairment in an animal model of AD, we conducted a Y-maze test using a 5XFAD mouse model. Oral administration of PGE for 3 weeks at a daily dose of 100 mg/kg significantly ameliorated cognitive impairment in 5XFAD mice. Moreover, to elucidate the neurohistological mechanisms underlying the PGE-mediated alleviative effect on cognitive dysfunction, we performed histological analysis of hippocampal formation in these mice. Histopathological analysis showed that PGE significantly alleviated AD-related pathologies such as Aβ accumulation, neurodegeneration, oxidative stress, and neuroinflammation. In addition, we observed a neuroprotective and antioxidant effect of PGE in mouse hippocampal neurons. Our findings suggest that administration of PGE might act as one of the therapeutic agents for AD by decreasing Aβ related pathology and ameliorating Aβ induced cognitive impairment.

L-theanine suppresses the metastasis of prostate cancer by downregulating MMP9 and Snail

Prostate cancer (PCa) is a very prevalent male-specific malignancy; most PCa patients eventually die as a result of metastasis. L-theanine (C7H14N2O3), a nonprotein amino acid derivative from green tea leaves, has been demonstrated to act as an anticarcinogen through proapoptotic and antiproliferative effects. However, the antimetastatic effect of L-theanine in tumor cells and its underlying mechanism are still unclear. Here, we found that L-theanine could suppress invasion, migration, and increase cell-cell adhesion of prostate cancer cells in vitro and in vivo. We also found that L-theanine could inhibit the epithelial-mesenchymal transition process in PCa. Our study revealed that L-theanine could downregulate MMP9, N-cadherin, Vimentin, Snail, and upregulate E-cadherin. Furthermore, L-theanine suppressed the transcription of MMP9 and Snail by significantly inhibiting the ERK/NF-κB signaling pathway and the binding activity of p65 to the promoter regions of MMP9 and Snail. All of these findings suggest that L-theanine has therapeutic potential for metastatic PCa and may be considered a promising candidate for antimetastatic therapy of prostate cancer.

Silymarin alleviates docetaxel-induced central and peripheral neurotoxicity by reducing oxidative stress, inflammation and apoptosis in rats

Docetaxel (DTX) is a chemotherapeutic agent used in the treatment of various malignancies but is often associated with central and peripheral neurotoxicity. The aim of this study was to investigate the neuroprotective effect of silymarin (SLM) against DTX-induced central and peripheral neurotoxicities in rats. Rats received 25 and 50 mg/kg body weight SLM orally for seven consecutive days after receiving a single injection of 30 mg/kg body weight DTX on the first day. SLM significantly decreased brain lipid peroxidation level and ameliorated brain glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities in DTX-administered rats. SLM attenuated levels of nuclear factor kappa B (NF-κB), tumor necrosis factor-α (TNF-α), glial fibrillary acidic protein (GFAP) and activity of p38α mitogen-activated protein kinase (p38α MAPK) whereas caused an increase in levels of neural cell adhesion molecule (NCAM) in the brain and sciatic nerve of DTX-induced rats. In addition, SLM improved the histological structure of the brain and sciatic nerve tissues and decreased the expression of c-Jun N-terminal kinase (JNK) in the sciatic nerve whereas increased cyclic AMP response element binding protein (CREB) expression in the brain induced by DTX. Additionally, SLM markedly up-regulated the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase-1 (HO-1) and B-cell lymphoma-2 (Bcl-2) and downregulated the expression of Bcl-2 associated X protein (Bax) in the brain and sciatic nerve tissues of DTX-induced rats. Our results show that SLM can protect DTX-induced brain and sciatic nerve injuries by enhancing the antioxidant defense system and suppressing apoptosis and inflammation.

L-theanine: an astounding sui generis amino acid in poultry nutrition

L-theanine (γ-Glutamylethylamide) is a nonprotein water soluble amino acid (AA) mostly found in leaves of Camellia sinensis (green tea). This is a key component of green tea and is considered as the most abundant form of total AAs in green tea (i.e., about 50%). L-theanine is an exclusive taste ingredient of tea producing an attractive flavor and aroma in tea. It has biological effects such as antioxidant, growth promoter, immune booster, anti-stresser, hepatoprotective, antitumor, antiaging, antimicrobial, anti-inflammatory, and antianxiety activities that are worth noticing. It could reduce the oxidative impairment by reducing the synthesis of reactive oxygen species, oxidative parameters, and lipid damage as well as increasing the activity of antioxidant enzymes. The oral ingestion of L-theanine enhanced γδ T-cell proliferation. Therefore, it is being considered an essential compound of green tea that has the ability to improve immune function. The L-theanine can be used as a potential treatment for hepatic injury and immune-related liver diseases via the downregulation of the inflammatory response through the initiation of nitric oxide synthesis and glutathione production which are likely to be critical for the control of hepatic diseases as well as for the improvement of immune function. In addition, it could be used as a best natural feed additive with a potent antistressor by decreasing the levels of corticosterone, dopamine, and noradrenaline. After systematically reviewing the literature, it is noticed that most studies were carried out on mice, pig, human, and butterfly; while dietary supplementation studies of L-theanine in animal and poultry especially among broilers are very limited because of less awareness of this AA. So, the aim of this review is to encourage the veterinarian and poultry researchers to conduct more research at the molecular level about this AA to expose its more beneficial effects and its mechanism of absorption for potential use of this unique green tea AA in poultry nutrition.

Anti-Alzheimer's disease activity of secondary metabolites from Xanthoceras sorbifolia Bunge

Xanthoceras sorbifolia Bunge is an edible oil tree species peculiar to China and it has long been used as a traditional medicine for enuresis in children. In this study, we investigated the active components in X. sorbifolia and eight barrigenol-type triterpenoids were isolated and identified. All the isolated compounds were tested first for H₂O₂-induced oxidative stress on human SH-SY5Y cells. Then Y-maze, Morris water maze, novel object recognition and passive avoidance tests were conducted to evaluate the improved effect of selected compounds with neuroprotective activity on ICV Aβ_1-42 mice. Among all the tested compounds, XS-8 exhibited significant protective effects against learning and memory impairments induced by ICV-Aβ_1-42. The XS-8 treatment significantly altered Aβ-induced hippocampal oxidative defense (increased MDA, nitrite and decreased SOD, glutathione) and pro-inflammatory levels (increased IL-1β and IL-18). The present study strongly suggests that X. sorbifolia is a promising plant resource for AD use and other neurodegenerative diseases.

Physiological and Defense Responses of Tea Plants to Elevated CO2: A Review

Rising atmospheric carbon dioxide, an important driver of climate change, has multifarious effects on crop yields and quality. Despite tremendous progress in understanding the mechanisms of plant responses to elevated CO₂, only a few studies have examined the CO₂-enrichment effects on tea plants. Tea [Camellia sinensis (L.)], a non-deciduous woody perennial plant, operates massive physiologic, metabolic and transcriptional reprogramming to adapt to increasing CO₂. Tea leaves elevate photosynthesis when grown at CO₂-enriched environment which is attributed to increased maximum carboxylation rate of RuBisCO and maximum rates of RuBP regeneration. Elevated CO₂-induced photosynthesis enhances the energy demand which triggers respiration. Stimulation of photosynthesis and respiration by elevated CO₂ promotes biomass production. Moreover, elevated CO₂ increases total carbon content, but it decreases total nitrogen content, leading to an increased ratio of carbon to nitrogen in tea leaves. Elevated CO₂ alters the tea quality by differentially influencing the concentrations and biosynthetic gene expression of tea polyphenols, free amino acids, catechins, theanine, and caffeine. Signaling molecules salicylic acid and nitric oxide function in a hierarchy to mediate the elevated CO₂-induced flavonoid biosynthesis in tea leaves. Despite enhanced synthesis of defense compounds, tea plant defense to some insects and pathogens is compromised under elevated CO₂. Here we review the physiological and metabolic responses of tea plants to elevated CO₂. In addition, the potential impacts of elevated CO₂ on tea yield and defense responses are discussed. We also show research gaps and critical research areas relating to elevated CO₂ and tea quality for future study.

Theanine attenuates hippocampus damage of rat cerebral ischemia-reperfusion injury by inhibiting HO-1 expression and activating ERK1/2 pathway

AIMS

Theanine, as a naturally occurring component in tea, has been shown to deliver benefits against various diseases. However, the exact molecular mechanisms underlying theanine's protective actions against cerebral ischemia/reperfusion (IR) injury still remains largely unknown.

MAIN METHODS

In this study, rat cerebral IR injury model was established and were randomly divided into the following five groups: Sham (SH), IR, IR + Theanine (TH), IR + TH+ heme oxygenase-1 (HO-1) inducer cobalt protoporphyrin (Copp), and IR + Copp groups.

KEY FINDINGS

We found that theanine significantly inhibited neuron damage and apoptosis in the hippocampus during the 48 h detection period, as detected by hematoxylin and eosin (HE) and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. Meanwhile, reduced levels of malondialdehyde (MDA) and elevated activities of superoxide dismutase (SOD), glutathione (GSH), and glutathione peroxidase (GSH-PX) were observed in the theanine-treated group. Enzyme-linked immunosorbent (ELISA) assay also revealed that theanine markedly decreased the levels of inflammatory cytokines, such as IL-6, IL-1β, and TNF-α, in IR rats. The anti-apoptotic effect of theanine on IR injury was further verified by flow cytometry assay. Besides, theanine dramatically inhibited HO-1 expression and activity but increased extracellular signal-regulated kinase 1/2 (ERK1/2) activity in hippocampal tissue from rats with cerebral IR injury. However, co-treatment with Copp remarkably abolished the protective effects of theanine on cerebral IR injury.

SIGNIFICANCE

These findings demonstrated that the neuroprotective role of theanine was associated with its anti-oxidative, anti-inflammatory, and anti-apoptotic properties, which might be through regulation of HO-1 activation in rats with cerebral IR injury.

GABA and l-theanine mixture decreases sleep latency and improves NREM sleep

CONTEXT

γ-Aminobutyric acid (GABA) is the main inhibitory neurotransmitter and it is well established that activation of GABA_A receptors favours sleep. l-Theanine, a naturally occurring amino acid first discovered in green tea, is a well-known anti-anxiety supplement with proven relaxation benefits.

OBJECTIVE

This study investigated the potential synergistic sleep enhancement effect of GABA/l-theanine mixture.

MATERIALS AND METHODS

Pentobarbital-induced sleep test was applied to find proper concentration for sleep-promoting effect in ICR mice. Electroencephalogram (EEG) analysis was performed to investigate total sleeping time and sleep quality in normal SD rats and caffeine-induced awareness model. Real-time polymerase chain reaction (RT-PCR) was applied to investigate whether the sleep-promoting mechanism of GABA/l-theanine mixture involved transcriptional processes.

RESULTS

GABA/l-theanine mixture (100/20 mg/kg) showed a decrease in sleep latency (20.7 and 14.9%) and an increase in sleep duration (87.3 and 26.8%) compared to GABA or theanine alone. GABA/l-theanine mixture led to a significant increase in rapid eye movement (REM) (99.6%) and non-REM (NREM) (20.6%) compared to controls. The use of GABA/l-theanine mixture rather than GABA or l-theanine alone restored to normal levels sleep time and quality in the arousal animal model. The administration of GABA/l-theanine led to increased expression of GABA and the glutamate GluN1 receptor subunit.

CONCLUSIONS

GABA/l-theanine mixture has a positive synergistic effect on sleep quality and duration as compared to the GABA or l-theanine alone. The increase in GABA receptor and GluN1 expression is attributed to the potential neuromodulatory properties of GABA/l-theanine combination, which seems to affect sleep behaviour.

Effects of Food Processing on In Vivo Antioxidant and Hepatoprotective Properties of Green Tea Extracts

Food processing can affect the nutrition and safety of foods. A previous study showed that tannase and ultrasound treatment could significantly increase the antioxidant activities of green tea extracts according to in vitro evaluation methods. Since the results from in vitro and in vivo experiments may be inconsistent, the in vivo antioxidant activities of the extracts were studied using a mouse model of alcohol-induced acute liver injury in this study. Results showed that all the extracts decreased the levels of aspartate transaminase and alanine aminotransferase in serum, reduced the levels of malondialdehyde and triacylglycerol in the liver, and increased the levels of catalase and glutathione in the liver, which can alleviate hepatic oxidative injury. In addition, the differences between treated and original extracts were not significant in vivo. In some cases, the food processing can have a negative effect on in vivo antioxidant activities. That is, although tannase and ultrasound treatment can significantly increase the antioxidant activities of green tea extracts in vitro, it cannot improve the in vivo antioxidant activities, which indicates that some food processing might not always have positive effects on products for human benefits.

Shaping the Nrf2-ARE-related pathways in Alzheimer's and Parkinson's diseases

A failure in redox homeostasis is a common hallmark of Alzheimer's Disease (AD) and Parkinson's Disease (PD), two age-dependent neurodegenerative disorders (NDD), causing increased oxidative stress, oxidized/damaged biomolecules, altered neuronal function and consequent cell death. Activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a redox-regulated transcription factor, results in upregulation of cytoprotective and antioxidant enzymes/proteins, protecting against oxidative stress. Nrf2 regulation is achieved by various proteins and pathways, at both cytoplasmatic and nuclear level; however, the elaborate network of mechanisms involved in Nrf2 regulation may restrain Nrf2 pathway normal activity. Indeed, altered Nrf2 activity is involved in aging and NDD, such as AD and PD. Therefore, understanding the diversity of Nrf2 control mechanisms and regulatory proteins is of high interest, since more effective NDD therapeutics can be identified. In this review, we first introduce Keap1-Nrf2-ARE structure, function and regulation, with a special focus on the several pathways involved in Nrf2 positive and negative modulation, namely p62, PKC, PI3K/Akt/GSK-3β, NF-kB and p38 MAPK. We then briefly describe the evidences for oxidative stress and Nrf2 pathway deregulation in different stages of NDDs. Finally, we discuss the potential of Nrf2-related pathways as potential therapeutic targets to possibly prevent or slowdown NDD progression.

Role of p38/MAPKs in Alzheimer's disease: implications for amyloid beta toxicity targeted therapy

A myriad of environmental and genetic factors, as well as the physiologic process of aging, contribute to Alzheimer's disease (AD) pathology. Neuroinflammation is and has been a focus of interest, as a common gateway for initiation of many of the underlying pathologies of AD. Amyloid beta (Aβ) toxicity, increasing RAGE expression, tau hyperphosphorylation, induction of apoptosis, and deregulated autophagy are among other mechanisms, partly entangled and being explained by activation of mitogen-activated protein kinase (MAPK) and MAPK signaling. p38 MAPK is the most essential regulator of Aβ induced toxicity from this family. p38 induces NF-κB activation, glutamate excitotoxicity, and disruption of synaptic plasticity, which are other implications of all justifying the p38 MAPK as a potential target to break the vicious Aβ toxicity cycle. Until recently, many in vivo and in vitro studies have investigated the effects of p38 MAPK inhibitors in AD. The pyridinyl imidazole compounds SB202190 and SB203580 have shown promising anti-apoptotic results in vivo. MW108 inhibits activation of p38 and is able to postpone cognitive decline in animal models. The PD169316, with anti-inflammatory, anti-oxidative, and anti-apoptotic features, has improved spatial memory in vivo. Natural compounds from Camellia sinensis (green tea), polyphenols from olive oil, pinocembrin from propolis, and the puerarine extract isoflavones, have shown strong anti-apoptotic features, mediated by p38 MAPK inhibition. Use of these drug targets is limited due to central nervous system side effects or cross-reactivity with other kinases, predicting the low efficacy of these drugs in clinical trials.

Steroid-Enriched Fraction of Achyranthes bidentata Protects Amyloid β Peptide 1-40-Induced Cognitive Dysfunction and Neuroinflammation in Rats

The roots of Achyranthes bidentata Blume (AB) is commonly used in the treatment of osteoporosis and dementia in traditional Chinese medicine. Pharmacological reports evidenced that AB possessed anti-osteoarthritis effects. However, there is little literature about the anti-dementia activities of AB. The present study was designed to prepare steroid-enriched fraction of AB (ABS) and investigate whether ABS can protect from cognitive dysfunction and neuroinflammation against Aβ 1-40-induced Alzheimer's disease (AD) model in rats. ABS only contained 135.11 ± 4.28 mg of ecdysterone per gram. ABS (50 mg/kg) reversed the dysfunction of exploratory activity and memory function on plus-maze and Morris water maze caused by Aβ 1-40 in rats. ABS (50 mg/kg) also decreased amyloid deposition, neurofibrillary tangle, neural damage, activated astrocyte, and microglial caused by Aβ 1-40. Furthermore, ABS reversed the phenomenon of neural oxidative damage and neuroinflammation, including the higher levels of MDA and cytokines, and the lower activities of antioxidant enzymes and GSH levels caused by Aβ 1-40 in rat cortex and hippocampus. Finally, ABS restored the activation of ERK pathway and decreased NF-κB phosphorylation and translocation altered by Aβ 1-40. ABS alone (50 mg/kg) promoted cognitive function, activated brain antioxidant defense system, and decreased brain TNF-α levels in sham group. Therefore, ABS has the cognition-promoting and antidementia potential. Steroids especial ecdysterone are major active components of AB. The action mechanism is due to decreasing oxidative stress and neuroinflammation through modulating ERK pathway, NF-κB phosphorylation, and translocation in Aβ 1-40-induced AD rat model.

Natural silibinin modulates amyloid precursor protein processing and amyloid-β protein clearance in APP/PS1 mice

Silibinin has been shown to attenuate cognitive dysfunction and inhibit amyloid-beta (Aβ) aggregation in Alzheimer's disease (AD) models. However, the underlying mechanism by which silibinin improves cognition remains poorly understood. In this study, we investigated the effect of silibinin on β-secretase levels, Aβ enzymatic degradation, and oxidative stress in the brains of APP/PS1 mice with cognitive impairments. Oral administration of silibinin for 2 months significantly attenuated the cognitive deficits of APP/PS1 mice in the Y-maze test, novel object recognition test, and Morris water maze test. Biochemical analyses revealed that silibinin decreased Aβ deposition and the levels of soluble Aβ1-40/1-42 in the hippocampus by downregulating APP and BACE1 and upregulating NEP in APP/PS1 mice. In addition, silibinin decreased the MDA content and increased the activities of the antioxidant enzymes CAT, SOD, and NO. Based on our findings, silibinin is a potentially promising agent for preventing AD-associated Aβ pathology.

PQM130, a Novel Feruloyl-Donepezil Hybrid Compound, Effectively Ameliorates the Cognitive Impairments and Pathology in a Mouse Model of Alzheimer's Disease

Alzheimer's disease (AD) is the most frequent type of dementia in older people. The complex nature of AD calls for the development of multitarget agents addressing key pathogenic processes. Donepezil, an acetylcholinesterase inhibitor, is a first-line acetylcholinesterase inhibitor used for the treatment of AD. Although several studies have demonstrated the symptomatic efficacy of donepezil treatment in AD patients, the possible effects of donepezil on the AD process are not yet known. In this study, a novel feruloyl-donepezil hybrid compound (PQM130) was synthesized and evaluated as a multitarget drug candidate against the neurotoxicity induced by Aβ1-42 oligomer (AβO) injection in mice. Interestingly, PQM130 had already shown anti-inflammatory activity in different in vivo models and neuroprotective activity in human neuronal cells. The intracerebroventricular (i.c.v.) injection of AβO in mice caused the increase of memory impairment, oxidative stress, neurodegeneration, and neuroinflammation. Instead, PQM130 (0.5-1 mg/kg) treatment after the i.c.v. AβO injection reduced oxidative damage and neuroinflammation and induced cell survival and protein synthesis through the modulation of glycogen synthase kinase 3β (GSK3β) and extracellular signal-regulated kinases (ERK1/2). Moreover, PQM130 increased brain plasticity and protected mice against the decline in spatial cognition. Even more interesting is that PQM130 modulated different pathways compared to donepezil, and it is much more effective in counteracting AβO damage. Therefore, our findings highlighted that PQM130 is a potent multi-functional agent against AD and could act as a promising neuroprotective compound for anti-AD drug development.