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Molecular Pharmacology of Green Tea

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A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Medicinal Chemistry".

Deadline for manuscript submissions: closed (30 April 2021) | Viewed by 89389

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Prof. Dr. Yukio Yoneda

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The Institute of Prophylactic Pharmacology, Kita-Shinagawa, Shinagawa, Tokyo 140-0001, Japan
Interests: amino acids; theanine; green tea; gene transcription; cellular differentiation; intracellular signal transduction; membrane receptors; membrane transporters; mitochondria; neural stem cells; mesenchymal stem cells; hematopoietic stem cells
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Special Issue Information

Dear Colleagues,

Green tea has been ingested for hundreds of years in Asian countries with reputed benefits for human health. Although a variety of bioactive molecules are found in green tea leaves, exact modes of actions as well as underlying molecular mechanisms are not fully clarified with the beneficial effectiveness of the lifestyle to drink green tea for people’s fitness to date. Sustained daily green tea ingestion is shown to improve cognition impairment in elderly people, for example, identification of the active ingredients is still in debate among scientists. These include polyphenols, caffeine, vitamins, amino acids, and others. Particular edible foods and beverages have often been beneficial for the prophylaxis and/or alleviation of unpleasant disabilities and dysfunctions following daily ingestion from childhood in young to elderly people suffering from health concerns. In contrast to medicines with inevitable side effects, these edible materials are in principle with guaranteed safety for human health in our history unless excessive amounts are consumed. A variety of edible materials and their ingredients have been used for dietary supplements and nutraceuticals for many reasons in recent years, whereas their individual scientific backgrounds are considerably poorer than drugs with validated evidence.

This Special Issue thus aims to recruit useful contributions for the promoted understanding of molecular aspects on the biochemistry and pharmacology of green tea and relevant ingredients responsible for the improvement of a variety of functional disturbances in humans. Patients do not have to suffer from heavily unpleasant disabilities due to severe symptoms of a particular disease as long as they pay more attention to their lifestyles than before. In this issue, I would like to contribute to the clarification and enlightenment of the scientific backgrounds of favorable and/or unfavorable pharmacology of green tea toward the urgent construction with orchestration of validified nutraceutical sciences as seen with pharmaceutical sciences as quickly as possible.

Prof. Yukio Yoneda
Guest Editor

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Keywords

green tea;
bioactive ingredients;
human healthcare;
lifestyle;
prophylaxis;
nutraceutical science;
guaranteed safety

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Published Papers (13 papers)

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26 pages, 4651 KiB

Open AccessArticle

Quality Assessment of Wild and Cultivated Green Tea from Different Regions of China

by Maciej Chowaniak, Marcin Niemiec, Zhiqiang Zhu, Naim Rashidov, Zofia Gródek-Szostak, Anna Szeląg-Sikora, Jakub Sikora, Maciej Kuboń, Salimzoda Amonullo Fayzullo, Usmon Mamur Mahmadyorzoda, Agnieszka Józefowska, Andrzej Lepiarczyk and Florian Gambuś

Molecules 2021, 26(12), 3620; https://doi.org/10.3390/molecules26123620 - 13 Jun 2021

Cited by 16 | Viewed by 3276

Abstract

Natural products have always enjoyed great popularity among consumers. Wild tea is an interesting alternative to tea from intensive plantations. The term “wild tea” is applied to many different varieties of tea, the most desirable and valued of which are native or indigenous tea plants. Special pro-health properties of wild tea are attributed to the natural conditions in which it grows. However, there are no complex studies that describe quality and health indicators of wild tea. The aim of this research was to evaluate the quality of wild and cultivated green tea from different regions of China: Wuzhishan, Baisha, Kunlushan, and Pu’Er. The assessment was carried out by verifying the concentration of selected chemical components in tea and relating it to the health risks they may pose, as well as to the nutritional requirements of adults. Wild tea was characterized by higher micronutrient concentration. The analyzed teas can constitute a valuable source of Mn in the diet. A higher concentration of nitrates and oxalates in cultivated tea can be associated with fertilizer use. The analyzed cultivated tea was a better source of antioxidants with a higher concentration of caffeine. There were no indications of health risks for wild or cultivated teas. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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12 pages, 1455 KiB

Open AccessArticle

Src Mediates Epigallocatechin-3-O-Gallate-Elicited Acid Sphingomyelinase Activation

by Motofumi Kumazoe, Mai Kadomatsu, Jaehoon Bae, Yushi Otsuka, Yoshinori Fujimura and Hirofumi Tachibana

Molecules 2020, 25(22), 5481; https://doi.org/10.3390/molecules25225481 - 23 Nov 2020

Cited by 8 | Viewed by 2936

Abstract

Epigallocatechin-3-O-gallate (EGCG) is one of the major bioactive compounds known to be present in green tea. We previously reported that EGCG shows selective toxicity through activation of the protein kinase B (Akt)/cyclic guanosine monophosphate (cGMP)/acid sphingomyelinase (ASM) axis via targeting its receptor 67-kDa laminin receptor (67LR), which is overexpressed in cancer. However, little is known about upstream mechanisms of EGCG-elicited ASM activation. In this study we show that the proto-oncogene tyrosine-protein kinase Src, also known as c-src, plays a crucial role in the anticancer effect of EGCG. We showed that EGCG elicits phosphorylation of Src at Tyr 416, a crucial phosphorylation site for its activity, and that the pharmacological inhibition of Src impedes the upstream events in EGCG-induced cell death signaling including upregulation of Akt activity, increase in cGMP levels, and activation of ASM. Moreover, focal adhesion kinase (FAK), which is involved in the phosphorylation of Src, is colocalized with 67LR. EGCG treatment enhanced interaction of FAK and 67LR. Consistent with these findings, pharmacological inhibition of FAK significantly neutralized EGCG-induced upregulation of Akt activity and activation of ASM. Taken together, FAK/Src play crucial roles in the upstream signaling of EGCG. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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12 pages, 1289 KiB

Open AccessArticle

Simultaneous Preparation of Abundant Flavonol Triglycosides from Tea Leaves

by Zhou-Tao Fang, Yi-Qing Lv, Chu-Jun Song, Jing Jin, Jian-Liang Lu, Hai-Rong Xu and Jian-Hui Ye

Molecules 2020, 25(21), 5140; https://doi.org/10.3390/molecules25215140 - 4 Nov 2020

Cited by 6 | Viewed by 3051

Abstract

Flavonol glycosides are important components of tea leaves, contributing to the bioactivities as well as bitterness and astringency of tea. However, the standards of many flavonol triglycosides are still not available, which restricts both sensory and bioactivity studies on flavonol glycosides. In the present study, we established a simultaneous preparation method of seven flavonol triglycoside individuals from tea leaves, which consisted of two steps: polyamide column enrichment and preparative HPLC isolation. The structures of seven flavonol triglycoside isolates were identified by mass and UV absorption spectra, four of which were further characterized by nuclear magnetic resonance spectra, namely, quercetin-3-O-glucosyl-rhamnosyl-glucoside, quercetin-3-O-rhamnosyl-rhamnosyl-glucoside, kaempferol-3-O-glucosyl-rhamnosyl-glucoside and kaempferol-O-rhamnosyl-rhamnosyl-glucoside. The purities of all isolated flavonol triglycosides were above 95% based on HPLC, and the production yield of total flavonol glycosides from dry tea was 0.487%. Our study provides a preparation method of flavonol triglycosides from tea leaves, with relatively low cost of time and solvent but high production yield. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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19 pages, 5031 KiB

Open AccessArticle

Monitoring the Diversity and Metabolic Shift of Gut Microbes during Green Tea Feeding in an In Vitro Human Colonic Model

by Mengyang Xu, Kundi Yang and Jiangjiang Zhu

Molecules 2020, 25(21), 5101; https://doi.org/10.3390/molecules25215101 - 3 Nov 2020

Cited by 22 | Viewed by 4519

Abstract

The human gut microbiome plays an important role in human health, and many factors such as environment, host genetics, age, and diet have been found to influence the microbial composition. Tea, as one of the widely consumed beverages, has been known for centuries to have antioxidant, anti-inflammatory, and anticancer effects. To investigate the impact of green tea polyphenol on the diversity and metabolic functions of human gut microbes, we applied an in vitro human colonic model (HCM) in this study to mimic a short-term green tea ingestion event and investigate its related changes to gut microbial composition and their metabolic functions. The pH, temperature, anaerobic environment, feeding nutrient, and time point in each compartment of the HCM were tightly controlled to simulate the intestinal system, and pooled human fecal samples of two healthy volunteers were used for the colon microbiota inoculation within the colonic model. By adding green tea extract (GTE) to the growth medium, the detailed impacts of GTE polyphenol on gut microbial population/diversity, gut microbial metabolites, metabolic pathways, and their associations were investigated via 16 S ribosomal DNA sequencing and liquid chromatography coupled tandem mass spectrometry (LC-MS/MS) analyses. Our data indicated that the treatment of green tea extract applied to gut microbiota can induce a significant decrease in the abundance of Firmicutes and a slight decrease in the abundance of Bacteroidetes, and these changes result in a decreased Firmicutes/Bacteroidetes ratio, which can be an effective indicator for successful GTE intervention, which may generate beneficial health effect to human. Meanwhile, the relative abundances of many detected bacteria genera among three HCM vessels changed through the GTE intervention. The overall effects of GTE on gut microbial beta-diversity were observed by multivariate statistical analyses, and the differences in metabolic profiles from different GTE treatment stages were detected. Moreover, we identified several associations between microbial population and microbial metabolites, which may assist us in establishing new hypotheses for future related studies. In summary, our study suggested that the microbial compositional changes induced by GTE also changed their metabolic functions, and consequentially, may change the host metabolism and impact human health. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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13 pages, 1054 KiB

Open AccessArticle

Antidepressant Effect of Shaded White Leaf Tea Containing High Levels of Caffeine and Amino Acids

by Keiko Unno, Daisuke Furushima, Yuzuki Nomura, Hiroshi Yamada, Kazuaki Iguchi, Kyoko Taguchi, Toshikazu Suzuki, Makoto Ozeki and Yoriyuki Nakamura

Molecules 2020, 25(15), 3550; https://doi.org/10.3390/molecules25153550 - 3 Aug 2020

Cited by 14 | Viewed by 4734

Abstract

The young leaves of green tea become lighter in color than usual when protected from sunlight by a shading net for about two weeks while growing. These leaves are called “shaded white leaf tea” or SWLT. In the eluate of SWLT, the amount of amino acids (361 mg/L) was significantly higher than that in regular tea (53.5 mg/L). Since theanine and arginine, the first and second most abundant amino acids in SWLT, have significant antistress effects, we examined the antistress effect of SWLT on humans. SWLT or placebo green tea (3 g) was eluted with room-temperature water (500 mL). Participants consumed the tea for one week prior to pharmacy practice and continued for 10 days in the practice period. The state-trait anxiety inventory, an anxiety questionnaire, tended to be scored lower in the SWLT group than the placebo, but other stress markers showed no differences. The effect of the difference in SWLT components examined with mice showed that aspartic acid and asparagine, which are abundant in SWLT, counteracted the antistress effects of theanine and arginine. Large amounts of caffeine also interfered with SWLT’s antistress effect. Thus, SWLT, which is high in caffeine and amino acids, suppressed depressant behavior in mice. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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14 pages, 3126 KiB

Open AccessArticle

Epigallocatechin-3-Gallate (EGCG), an Active Compound of Green Tea Attenuates Acute Lung Injury Regulating Macrophage Polarization and Krüpple-Like-Factor 4 (KLF4) Expression

by Saleh A. Almatroodi, Ahmad Almatroudi, Mohammed A. Alsahli, Mohammad A. Aljasir, Mansoor Ali Syed and Arshad Husain Rahmani

Molecules 2020, 25(12), 2853; https://doi.org/10.3390/molecules25122853 - 20 Jun 2020

Cited by 48 | Viewed by 5404

Abstract

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) are serious clinical complications with a high frequency of morbidity and mortality. The initiation and amplification of inflammation is a well-known aspect in the pathogenesis of ALI and related disorders. Therefore, inhibition of the inflammatory mediators could be an ideal approach to prevent ALI. Epigallocatechin-3-gallate (EGCG), a major constituent of green tea, has been shown to have protective effects on oxidative damage and anti-inflammation. The goal of the present study was to determine whether EGCG improves phenotype and macrophage polarisation in LPS-induced ALI. C57BL/6 mice were given two doses of EGCG (15 mg/kg) intraperitoneally (IP) 1 h before and 3 h after LPS instillation (2 mg/kg). EGCG treatment improved histopathological lesions, Total Leucocyte count (TLC), neutrophils infiltration, wet/dry ratio, total proteins and myeloperoxidase (MPO) activity in LPS-induced lung injury. The results displayed that EGCG reduced LPS-induced ALI as it modulates macrophage polarisation towards M2 status. Furthermore, EGCG also reduced the expression of proinflammatory M1 mediators iNOS TNF-α, IL-1β and IL-6 in the LPS administered lung microenvironment. In addition, it increased the expression of KLF4, Arg1 and ym1, known to augment the M2 phenotype of macrophages. EGCG also alleviated the expression of 8-OHdG, nitrotyrosine, showing its ability to inhibit oxidative damage. TREM1 in the lung tissue and improved lung regenerative capacity by enhancing Ki67, PCNA and Ang-1 protein expression. Together, these results proposed the protective properties of EGCG against LPS-induced ALI in may be attributed to the suppression of M1/M2 macrophages subtype ratio, KLF4 augmentation, lung cell regeneration and regulating oxidative damage in the LPS-induced murine ALI. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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14 pages, 1296 KiB

Open AccessFeature PaperArticle

Green Tea Catechins Trigger Immediate-Early Genes in the Hippocampus and Prevent Cognitive Decline and Lifespan Shortening

by Keiko Unno, Monira Pervin, Kyoko Taguchi, Tomokazu Konishi and Yoriyuki Nakamura

Molecules 2020, 25(7), 1484; https://doi.org/10.3390/molecules25071484 - 25 Mar 2020

Cited by 26 | Viewed by 5657

Abstract

Senescence-accelerated mouse prone 10 (SAMP10) mice, after ingesting green tea catechins (GT-catechin, 60 mg/kg), were found to have suppressed aging-related decline in brain function. The dose dependence of brain function on GT-catechin indicated that intake of 1 mg/kg or more suppressed cognitive decline and a shortened lifespan. Mice that ingested 1 mg/kg GT-catechin had the longest median survival, but the dose was less effective at suppressing cognitive decline. The optimal dose for improving memory acquisition was 60 mg/kg, and memory retention was higher in mice that ingested 30 mg/kg or more. To elucidate the mechanism by which cognitive decline is suppressed by GT-catechin, changes in gene expression in the hippocampus of SAMP10 mice one month after ingesting GT-catechin were analyzed. The results show that the expression of immediate-early genes such as nuclear receptor subfamily 4 (Nr4a), FBJ osteosarcoma oncogene (Fos), early growth response 1 (Egr1), neuronal PAS domain protein 4 (Npas4), and cysteine-rich protein 61 (Cyr61) was significantly increased. These results suggest that GT-catechin suppresses age-related cognitive decline via increased expression of immediate-early genes that are involved in long-term changes in plasticity of synapses and neuronal circuits. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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15 pages, 1675 KiB

Open AccessReview

Green Tea and Its Relation to Human Gut Microbiome

by Sergio Pérez-Burillo, Beatriz Navajas-Porras, Alicia López-Maldonado, Daniel Hinojosa-Nogueira, Silvia Pastoriza and José Ángel Rufián-Henares

Molecules 2021, 26(13), 3907; https://doi.org/10.3390/molecules26133907 - 26 Jun 2021

Cited by 72 | Viewed by 11667

Abstract

Green tea can influence the gut microbiota by either stimulating the growth of specific species or by hindering the development of detrimental ones. At the same time, gut bacteria can metabolize green tea compounds and produce smaller bioactive molecules. Accordingly, green tea benefits could be due to beneficial bacteria or to microbial bioactive metabolites. Therefore, the gut microbiota is likely to act as middle man for, at least, some of the green tea benefits on health. Many health promoting effects of green tea seems to be related to the inter-relation between green tea and gut microbiota. Green tea has proven to be able to correct the microbial dysbiosis that appears during several conditions such as obesity or cancer. On the other hand, tea compounds influence the growth of bacterial species involved in inflammatory processes such as the release of LPS or the modulation of IL production; thus, influencing the development of different chronic diseases. There are many studies trying to link either green tea or green tea phenolic compounds to health benefits via gut microbiota. In this review, we tried to summarize the most recent research in the area. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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29 pages, 1573 KiB

Open AccessReview

Advances in Nanodelivery of Green Tea Catechins to Enhance the Anticancer Activity

by Yike Jiang, Ziyi Jiang, Lan Ma and Qingrong Huang

Molecules 2021, 26(11), 3301; https://doi.org/10.3390/molecules26113301 - 31 May 2021

Cited by 39 | Viewed by 4780

Abstract

Cancer is one of the leading causes of death globally. A variety of phenolic compounds display preventative and therapeutic effects against cancers. Green teas are rich in phenolics. Catechins are the most dominant phenolic component in green teas. Studies have shown that catechins have anticancer activity in various cancer models. The anticancer activity of catechins, however, may be compromised due to their low oral bioavailability. Nanodelivery emerges as a promising way to improve the oral bioavailability and anticancer activity of catechins. Research in this area has been actively conducted in recent decades. This review provides the molecular mechanisms of the anticancer effects of catechins, the factors that limit the oral bioavailability of catechins, and the latest advances of delivering catechins using nanodelivery systems through different routes to enhance their anticancer activity. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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22 pages, 1435 KiB

Open AccessReview

Neuroprotective Properties of Green Tea (Camellia sinensis) in Parkinson’s Disease: A Review

by Dicson Sheeja Malar, Mani Iyer Prasanth, James Michael Brimson, Rajasekharan Sharika, Bhagavathi Sundaram Sivamaruthi, Chaiyavat Chaiyasut and Tewin Tencomnao

Molecules 2020, 25(17), 3926; https://doi.org/10.3390/molecules25173926 - 27 Aug 2020

Cited by 69 | Viewed by 9099

Abstract

Neurodegenerative disease is a collective term given for the clinical condition, which results in progressive degeneration of neurons and the loss of functions associated with the affected brain region. Apart from the increase in age, neurodegenerative diseases are also partly affected by diet and lifestyle practices. Parkinson’s disease (PD) is a slow onset neurodegenerative disorder and the second most common neurodegenerative disease, which affects the motor system. Although there is no prescribed treatment method to prevent and cure PD, clinical procedures help manage the disease symptoms. Green tea polyphenols are known for several health benefits, including antioxidant, anti-inflammatory, and neuroprotective activity. The current manuscript summarizes the possible mechanisms of neuroprotective potential of green tea with a special focus on PD. Studies have suggested that the consumption of green tea protects against free-radicals, inflammation, and neuro-damages. Several in vivo studies aid in understanding the overall mechanism of green tea. However, the same dose may not be sufficient in humans to elicit similar effects due to complex physiological, social, and cultural development. Future research focused on more clinical trials could identify an optimum dose that could impart maximum health benefits to impart neuroprotection in PD. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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40 pages, 2506 KiB

Open AccessReview

Potential Therapeutic Targets of Epigallocatechin Gallate (EGCG), the Most Abundant Catechin in Green Tea, and Its Role in the Therapy of Various Types of Cancer

by Saleh A. Almatroodi, Ahmad Almatroudi, Amjad Ali Khan, Fahad A. Alhumaydhi, Mohammed A. Alsahli and Arshad Husain Rahmani

Molecules 2020, 25(14), 3146; https://doi.org/10.3390/molecules25143146 - 9 Jul 2020

Cited by 259 | Viewed by 21329

Abstract

Epigallocatechin-3-gallate (EGCG), an active compound of green tea and its role in diseases cure and prevention has been proven. Its role in diseases management can be attributed to its antioxidant and anti-inflammatory properties. The anti-cancer role of this green tea compound has been confirmed in various types of cancer and is still being under explored. EGCG has been proven to possess a chemopreventive effect through inhibition of carcinogenesis process such as initiation, promotion, and progression. In addition, this catechin has proven its role in cancer management through modulating various cell signaling pathways such as regulating proliferation, apoptosis, angiogenesis and killing of various types of cancer cells. The additive or synergistic effect of epigallocatechin with chemopreventive agents has been verified as it reduces the toxicities and enhances the anti-cancerous effects. Despite its effectiveness and safety, the implications of EGCG in cancer prevention is certainly still discussed due to a poor bioavailability. Several studies have shown the ability to overcome poor bioavailability through nanotechnology-based strategies such as encapsulation, liposome, micelles, nanoparticles and various other formulation. In this review, we encapsulate therapeutic implication of EGCG in cancer management and the mechanisms of action are discussed with an emphasis on human clinical trials. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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14 pages, 554 KiB

Open AccessReview

Selective Upregulation by Theanine of Slc38a1 Expression in Neural Stem Cell for Brain Wellness

by Yukio Yoneda, Koichi Kawada and Nobuyuki Kuramoto

Molecules 2020, 25(2), 347; https://doi.org/10.3390/molecules25020347 - 15 Jan 2020

Cited by 8 | Viewed by 4758

Abstract

Theanine is an amino acid abundant in green tea with an amide moiety analogous to glutamine (GLN) rather than glutamic acid (Glu) and GABA, which are both well-known as amino acid neurotransmitters in the brain. Theanine has no polyphenol and flavonoid structures required for an anti-oxidative property as seen with catechins and tannins, which are more enriched in green tea. We have shown marked inhibition by this exogenous amino acid theanine of the uptake of [³H]GLN, but not of [³H]Glu, in rat brain synaptosomes. Beside a ubiquitous role as an endogenous amino acid, GLN has been believed to be a main precursor for the neurotransmitter Glu sequestered in a neurotransmitter pool at glutamatergic neurons in the brain. The GLN transporter solute carrier 38a1 (Slc38a1) plays a crucial role in the incorporation of extracellular GLN for the intracellular conversion to Glu by glutaminase and subsequent sequestration at synaptic vesicles in neurons. However, Slc38a1 is also expressed by undifferentiated neural progenitor cells (NPCs) not featuring a neuronal phenotype. NPCs are derived from a primitive stem cell endowed to proliferate for self-renewal and to commit differentiation to several daughter cell lineages such as neurons, astrocytes, and oligodendrocytes. In vitro culture with theanine leads to the marked promotion of the generation of new neurons together with selective upregulation of Slc38a1 transcript expression in NPCs. In this review, we will refer to a possible novel neurogenic role of theanine for brain wellness through a molecular mechanism relevant to facilitated neurogenesis with a focus on Slc38a1 expressed by undifferentiated NPCs on the basis of our accumulating findings to date. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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20 pages, 1560 KiB

Open AccessSystematic Review

Green Tea Catechin Association with Ultraviolet Radiation-Induced Erythema: A Systematic Review and Meta-Analysis

by Mahendra P. Kapoor, Masaaki Sugita, Yoshitaka Fukuzawa, Derek Timm, Makoto Ozeki and Tsutomu Okubo

Molecules 2021, 26(12), 3702; https://doi.org/10.3390/molecules26123702 - 17 Jun 2021

Cited by 18 | Viewed by 5527

Abstract

Catechins are a part of the chemical family of flavonoids, a naturally occurring antioxidant, and a secondary metabolite in certain plants. Green tea catechins are well recognized for their essential anti-inflammatory, photo-protective, antioxidant, and chemo-preventive functions. Ultraviolet radiation is a principal cause of damage to the skin. Studies observed that regular intake of green tea catechins increased the minimal dose of radiation required to induce erythema. The objectives of this systematic review and meta-analysis are to determine the effectiveness of green tea catechins in cutaneous erythema and elucidate whether green tea catechin consumption protects against erythema (sunburn) inflammation. A comprehensive literature search was conducted to identify the relevant studies. Two researchers carried out independent screening, data extraction, and quality assessment according to the guidelines of Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA). The pooled effect of green tea catechins on protection against erythema was assessed using approaches fixed-effects or random-effects model to quantify the effectiveness of green tea catechins in the erythema dose–response. Studies not be included in meta-analyses were summarized narratively. Six randomized controlled studies of enrolled studies regularly administrated green tea catechins orally for 6 to 12 weeks involving healthy volunteers comprising a total of 100 participants were included in the analysis. The results revealed green tea catechins have favorable protection against erythema inflammation even at increased minimal erythema dose (MED) of ultraviolet radiation. Meta-analysis results confirm oral supplementation of green tea catechins is highly effective at low-intensity ultraviolet radiation-induced erythema response (MED range; 1.25–1.30) compared to placebo, showing a significant pooling difference (p = 0.002) in erythema index (SMD: −0.35; 95% CI, −0.57 to −0.13; I² = 4%, p = 0.40) in the random-effects model. The pro-inflammatory signaling pathways through oral supplementation with green tea catechins are an attractive strategy for photo-protection in healthy human subjects and could represent a complementary approach to topical sunscreens. Therefore, studies that involved green tea catechin in topical applications to human subjects were also evaluated separately, and their meta-analysis is presented as a reference. The evidence indicates that regular green tea catechin supplementation is associated with protection against UV-induced damage due to erythema inflammation. Full article

(This article belongs to the Special Issue Molecular Pharmacology of Green Tea)

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