Green Tea Intake and Risks for Dementia, Alzheimer's Disease, Mild Cognitive Impairment, and Cognitive Impairment: A Systematic Review

Current Quest in Natural Bioactive Compounds for Alzheimer's Disease: Multi-Targeted-Designed-Ligand Based Approach with Preclinical and Clinical Based Evidence

Alzheimer's disease is a common and most chronic neurological disorder (NDs) associated with cognitive dysfunction. Pathologically, Alzheimer's disease (AD) is characterized by the presence of β-amyloid (Aβ) plaques, hyper-phosphorylated tau proteins, and neurofibrillary tangles, however, persistence oxidative-nitrative stress, endoplasmic reticulum stress, mitochondrial dysfunction, inflammatory cytokines, pro-apoptotic proteins along with altered neurotransmitters level are common etiological attributes in its pathogenesis. Rivastigmine, memantine, galantamine, and donepezil are FDA approved drugs for symptomatic management of AD, whereas tacrine has been withdrawn because of hepatotoxic profile. These approved drugs only exert symptomatic relief and exhibit poor patient compliance. In the current scenario, the number of published evidence shows the neuroprotective potential of naturally occurring bioactive molecules via their antioxidant, anti-inflammatory, antiapoptotic and neurotransmitter modulatory properties. Despite their potent therapeutic implications, concerns have arisen in context to their efficacy and probable clinical outcome. Thus, to overcome these glitches, many heterocyclic and cyclic hydrocarbon compounds inspired by natural sources have been synthesized and showed improved therapeutic activity. Computational studies (molecular docking) have been used to predict the binding affinity of these natural bioactive as well as synthetic compounds derived from natural sources for the acetylcholine esterase, α/β secretase Nuclear Factor kappa- light-chain-enhancer of activated B cells (NF-kB), Nuclear factor erythroid 2-related factor 2(Nrf2) and other neurological targets. Thus, in this review, we have discussed the molecular etiology of AD, focused on the pharmacotherapeutics of natural products, chemical and pharmacological aspects and multi-targeted designed ligands (MTDLs) of synthetic and semisynthetic molecules derived from the natural sources along with some important on-going clinical trials.

Effect of natural leaf extracts as phytomedicine in curing geriatrics

Old age is viewed as an unavoidable, undesirable, and problem-ridden phase of life. As people age, they become more susceptible to disease and disability due to various factors like low immunity, decreased functionality of cells, DNA damage, higher incidence of inflammation, etc. Healthy aging is very important. The nutrition and health of the elderly is often neglected. Nutritional interventions could play an important part in the prevention of degenerative conditions of the elderly and an improvement of their quality of life. The medicinal properties of plants are always believed for its therapeutic effect and its efficiency in treating many without adverse effects. The role of phytomedicine in aging is very crucial as it possesses important bioactive compounds and constituents (such as polyphenols, flavonoids, phenolic acids, and others) which are considered to provide anti-aging properties as well as helps in reducing age-associated problems. Some natural leaves such as Moringa oleifera, curry leaves, guava leaves, green tea, olive leaves, Ginkgo biloba, thankuni leaves, grape leaves, vasaka leaves, and kulekhara leaves are found to have therapeutic effects against diseases like cancer, diabetes, immunosuppression, hepatic damage, and neurodegenerative disorders. Hence, this review aims at understanding the effectiveness of these natural products in curing the geriatric population and the mechanism by which the therapeutic effects are exerted by them.

Impact of Polyphenolic-Food on Longevity: An Elixir of Life. An Overview

Aging and, particularly, the onset of age-related diseases are associated with tissue dysfunction and macromolecular damage, some of which can be attributed to accumulation of oxidative damage. Recently, growing interest has emerged on the beneficial effects of plant-based diets for the prevention of chronic diseases including obesity, diabetes, and cardiovascular disease. Several studies collectively suggests that the intake of polyphenols and their major food sources may exert beneficial effects on improving insulin resistance and related diabetes risk factors, such as inflammation and oxidative stress. They are the most abundant antioxidants in the diet, and their intake has been associated with a reduced aging in humans. Polyphenolic intake has been shown to be effective at ameliorating several age-related phenotypes, including oxidative stress, inflammation, impaired proteostasis, and cellular senescence, both in vitro and in vivo. In this paper, effects of these phytochemicals (either pure forms or polyphenolic-food) are reviewed and summarized according to affected cellular signaling pathways. Finally, the effectiveness of the anti-aging preventive action of nutritional interventions based on diets rich in polyphenolic food, such as the diets of the Blue zones, are discussed.

Potential of Caffeine in Alzheimer's Disease-A Review of Experimental Studies

Alzheimer's disease (AD) is the most common type of dementia leading to progressive memory loss and cognitive impairment. Considering that pharmacological treatment options for AD are few and not satisfactory, increasing attention is being paid to dietary components that may affect the development of the disease. Such a dietary component may be caffeine contained in coffee, tea or energy drinks. Although epidemiological data suggest that caffeine intake may counteract the development of cognitive impairment, results of those studies are not conclusive. The aim of the present study is to review the existing experimental studies on the efficacy of caffeine against AD and AD-related cognitive impairment, focusing on the proposed protective mechanisms of action. In conclusion, the reports of studies on experimental AD models generally supported the notion that caffeine may exert some beneficial effects in AD. However, further studies are necessary to elucidate the role of caffeine in the effects of its sources on cognition and possibly AD risk.

Are Reactive Sulfur Species the New Reactive Oxygen Species?

Significance: Oxidative stress in moderation positively affects homeostasis through signaling, while in excess it is associated with adverse health outcomes. Both activities are generally attributed to reactive oxygen species (ROS); hydrogen peroxide as the signal, and cysteines on regulatory proteins as the target. However, using antioxidants to affect signaling or benefit health has not consistently translated into expected outcomes, or when it does, the mechanism is often unclear. Recent Advances: Reactive sulfur species (RSS) were integral in the origin of life and throughout much of evolution. Sophisticated metabolic pathways that evolved to regulate RSS were easily "tweaked" to deal with ROS due to the remarkable similarities between the two. However, unlike ROS, RSS are stored, recycled, and chemically more versatile. Despite these observations, the relevance and regulatory functions of RSS in extant organisms are generally underappreciated. Critical Issues: A number of factors bias observations in favor of ROS over RSS. Research conducted in room air is hyperoxic to cells, and promotes ROS production and RSS oxidation. Metabolic rates of rodent models greatly exceed those of humans; does this favor ROS? Analytical methods designed to detect ROS also respond to RSS. Do these disguise the contributions of RSS? Future Directions: Resolving the ROS/RSS issue is vital to understand biology in general and human health in particular. Improvements in experimental design and analytical methods are crucial. Perhaps the most important is an appreciation of all the attributes of RSS and keeping an open mind.

Association between tea consumption and cognitive impairment in middle-aged and older adults

Background

Biologic studies have suggested that tea may have neuroprotective activity. However, tea’s protective effect on cognitive function is controversial in human epidemiological studies, and no data, including the middle-aged, are available. The objective of this study was to investigate the association of habit, frequency, and types of tea consumption with incident cognitive impairment in middle-aged and older adults.

Methods

Data from the Asymptomatic Polyvascular Abnormalities in Community study were used (aged over 40y). We gathered information on tea consumption, including habit, frequency, and types, via a standardized questionnaire and assessed cognitive function by Mini-Mental State Examination (MMSE) and/or Montreal Cognitive Assessment (MoCA). Three thousand eight hundred sixty-eight and 806 participants were selected in MMSE and MoCA subgroups. Multivariate logistic regression models were utilized to examine associations between tea consumption and cognitive impairment in middle-aged and older participants.

Results

In MMSE analyses, after adjustment for potential confounding factors, habitual (odds ratio (OR) 0.47, [95% confidence interval (CI) 0.33–0.68], p < 0.001) and high frequency (p trend < 0.001) of tea intake were associated with a lower risk of cognitive impairment. The risk of cognitive impairment was lower in green tea consumption (OR 0.36, [95% CI 0.22–0.61], p < 0.001) than other types (OR 0.59, [95% CI 0.38–0.91], p = 0.017). In MoCA analyses, we got similar results.

Conclusions

Habitual tea consumption, especially high-frequency and green tea consumption, was significantly associated with a lower prevalence of cognitive impairment in middle-aged and older individuals.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-020-01848-6.

Green tea polyphenolic antioxidants oxidize hydrogen sulfide to thiosulfate and polysulfides: A possible new mechanism underpinning their biological action

Matcha and green tea catechins such as (−)-epicatechin (EC), (−)-epigallocatechin (EGC) and (−)-epigallocatechin gallate (EGCG) have long been studied for their antioxidant and health-promoting effects. Using specific fluorophores for H₂S (AzMC) and polysulfides (SSP4) as well as IC-MS and UPLC-MS/MS-based techniques we here show that popular Japanese and Chinese green teas and select catechins all catalytically oxidize hydrogen sulfide (H₂S) to polysulfides with the potency of EGC > EGCG >> EG. This reaction is accompanied by the formation of sulfite, thiosulfate and sulfate, consumes oxygen and is partially inhibited by the superoxide scavenger, tempol, and superoxide dismutase but not mannitol, trolox, DMPO, or the iron chelator, desferrioxamine. We propose that the reaction proceeds via a one-electron autoxidation process during which one of the OH-groups of the catechin B-ring is autooxidized to a semiquinone radical and oxygen is reduced to superoxide, either of which can then oxidize HS⁻ to thiyl radicals (HS^•) which react to form hydrogen persulfide (H₂S₂). H₂S oxidation reduces the B-ring back to the hydroquinone for recycling while the superoxide is reduced to hydrogen peroxide (H₂O₂). Matcha and catechins also concentration-dependently and rapidly produce polysulfides in HEK293 cells with the potency order EGCG > EGC > EG, an EGCG threshold of ~300 nM, and an EC₅₀ of ~3 μM, suggesting green tea also acts as powerful pro-oxidant in vivo. The resultant polysulfides formed are not only potent antioxidants, but elicit a cascade of secondary cytoprotective effects, and we propose that many of the health benefits of green tea are mediated through these reactions. Remarkably, all green tea leaves constitutively contain small amounts of H₂S₂.

Emerging Complementary and Integrative Therapies for Geriatric Mental Health

PURPOSE

The use of complementary and integrative medicine (CIM) is on the rise among diverse populations of older adults in the USA. CIM is commonly perceived as safer, less expensive, and more culturally acceptable. There is a growing body of evidence to support the use of CIM, especially mind-body therapies, diet and nutritional supplements used for mental disorders of aging.

RECENT FINDINGS

We summarize the results of the recent clinical trials and meta-analyses that provide the evidence for the role of CIM in treating older adults with mood or cognitive disorders that includes the use of diet and supplements, and mind-body therapies.

SUMMARY

Dietary and mind-body therapies have become increasingly popular and show the strongest evidence of efficacy for mood and cognitive disorders. Although the use of vitamins and supplements is the most popular CIM practice, only mixed evidence supports their use with additional concerns for herb (supplement)-drug interactions. Despite increasing use of CIM by the general population, information to guide clinicians providing care for older adults remains limited with variable scientific rigor of the available RCTs for a large number of commonly used CIM interventions for the mental health of older adults.

The role of nutraceuticals as a complementary therapy against various neurodegenerative diseases: A mini-review

In recent times, many scientists have given great attention to nutraceuticals (complementary medicine) as it widely used for promoting health status. In particular for the prevention and treatment of various neurological diseases or disorders without or less adverse effects. The current mini-review was intended to compile all popular (major) nutraceuticals against various neurodegenerative diseases (NDDs) including Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD) with special reference to clinical trials. Preliminary reviews indicated that nutraceuticals like curcumin, resveratrol, Epigallocatechin-3-gallate (EGCG), Coenzyme Q10, ω-3 FA (DHA/EPA/ALA), showed better neuroprotective activity against various NDDs in human setting (clinical trial). Hence this contribution will focus only on those popular nutraceuticals with proposed brief mechanisms (antioxidant, anti-inflammatory, mitochondrial homeostasis, autophagy regulation, promote neurogenesis) and its recommendation. This mini-review would aid common people to choose better nutraceuticals to combat various NDDs along with standard neuroprotective agents and modified lifestyle pattern.

Gender Differences in Cognitive Impairment among Rural Elderly in China

Elders in rural areas of developing countries are particularly vulnerable to cognitive impairment and gender disparities are notable. Yet, evidence related to gender differences in cognitive impairment in these settings is scarce. This study examined gender differences in cognitive impairment among elderly people aged 65 and above in rural China. A multi-site cross-sectional survey was conducted. In total, 550 males and 700 females were recruited. The Chinese version of the Mini-Mental Status Examination was applied for cognitive impairment screening. Demographic information, lifestyle factors, psychosocial factors, and health-related information were assessed. The prevalence of cognitive impairment was 40.0%in males and 45.1% in females, respectively. Females showed significant higher prevalence after age 75 (62.7% vs. 45.4%, p < 0.005). Older age, hearing impairment, and activities of daily living dependence were common factors associated with cognitive impairment in both females and males. For males, living in a neighborhood with poor social interactions and diabetes were risk factors, while tea consumption was a protective factor. For females, vision impairment and illiteracy were additional risk factors. Individualized interventions and standardized measurements of cognitive function should be developed to suit older populations living in rural and less-developed areas, through collective efforts involving all stakeholders and multidisciplinary teamwork.

Cognitive Function and Consumption of Fruit and Vegetable Polyphenols in a Young Population: Is There a Relationship?

Scientific evidence has shown the relationship between consumption of fruits and vegetables and their polyphenols with the prevention or treatment of diseases. The aim of this review was to find out whether the same relationship exists between fruits and vegetables and cognitive function, especially memory, in a young population. The mechanisms by which polyphenols of fruits and vegetables can exert cognitive benefits were also evaluated. These compounds act to improve neuronal plasticity through the protein CREB (Camp Response Element Binding) in the hippocampus, modulating pathways of signaling and transcription factors (ERK/Akt). In the same way, brain-derived neurotrophic factor (BDNF) is implicated in the maintenance, survival, growth, and differentiation of neurons. All these effects are produced by an increase of cerebral blood flow and an increase of the blood’s nitric oxide levels and oxygenation.

Function of Green Tea Catechins in the Brain: Epigallocatechin Gallate and its Metabolites

Over the last three decades, green tea has been studied for its beneficial effects, including anti-cancer, anti-obesity, anti-diabetes, anti-inflammatory, and neuroprotective effects. At present, a number of studies that have employed animal, human and cell cultures support the potential neuroprotective effects of green tea catechins against neurological disorders. However, the concentration of (−)-epigallocatechin gallate (EGCG) in systemic circulation is very low and EGCG disappears within several hours. EGCG undergoes microbial degradation in the small intestine and later in the large intestine, resulting in the formation of various microbial ring-fission metabolites which are detectable in the plasma and urine as free and conjugated forms. Recently, in vitro experiments suggested that EGCG and its metabolites could reach the brain parenchyma through the blood–brain barrier and induce neuritogenesis. These results suggest that metabolites of EGCG may play an important role, alongside the beneficial activities of EGCG, in reducing neurodegenerative diseases. In this review, we discuss the function of EGCG and its microbial ring-fission metabolites in the brain in suppressing brain dysfunction. Other possible actions of EGCG metabolites will also be discussed.