TBC2health: a database of experimentally validated health-beneficial effects of tea bioactive compounds

Sichuan dark tea improves lipid metabolism and prevents aortic lipid deposition in diet-induced atherosclerosis model rats

Background and aims

Sichuan dark tea (ST), Zangcha, is a traditional fermented Chinese tea found in Sichuan and Tibet and claimed for beneficial effects against lifestyle-related metabolic disorders. We examined the effects of ST on lipid metabolism and atherosclerosis.

Methods and results

Sichuan dark tea was given to fat-rich diet-induced atherosclerosis model rats in comparison with dark-fermented Chinese Pu-erh tea (PT) and Japanese green tea (GT). After 8 weeks of feeding, ST and PT induced an increase in high-density lipoprotein (HDL)-cholesterol and a decrease in glucose, and ST decreased triglyceride in plasma. ST also induced low pH in the cecum. There was no significant change in their body weight among the fat-feeding groups but a decrease was found in the visceral fat and liver weight in the ST group. Accordingly, ST reduced lipid deposition in the aorta in comparison with PT and GT. ST increased mRNA of LXRα, PPARα, PPARγ, and ABCA1 in the rat liver. The extract of ST stimulated the AMPK pathway to increase the expression of ABCA1 in J774 cells and increased expression of lipoprotein lipase and hormone-sensitive lipase in 3T3L1 cells, consistent with its anti-atherogenic effects in rats. High-performance liquid chromatography analysis showed unique spectra of original specific compounds of caffeine and catechins in each tea extract, but none of them was likely responsible for these effects.

Conclusion

Sichuan dark tea increases plasma HDL and reduces plasma triglyceride to decrease atherosclerosis through AMPK activation. Further study is required to identify specific components for the effects of this tea preparation.

A New Carbohydrate Food Quality Scoring System to Reflect Dietary Guidelines: An Expert Panel Report

Existing metrics of carbohydrate food quality have been based, for the most part, on favorable fiber- and free sugar-to-carbohydrate ratios. In these metrics, higher nutritional quality carbohydrate foods are defined as those with >10% fiber and <10% free sugar per 100 g carbohydrate. Although fiber- and sugar-based metrics may help to differentiate the nutritional quality of various types of grain products, they may not aptly capture the nutritional quality of other healthy carbohydrate foods, including beans, legumes, vegetables, and fruits. Carbohydrate food quality metrics need to be applicable across these diverse food groups. This report introduces a new carbohydrate food scoring system known as a Carbohydrate Food Quality Score (CFQS), which supplements the fiber and free sugar components of previous metrics with additional dietary components of public health concern (e.g., sodium, potassium, and whole grains) as identified by the Dietary Guidelines for Americans. Two CFQS models are developed and tested in this study: one that includes four dietary components (CFQS-4: fiber, free sugars, sodium, potassium) and one that considers five dietary components (CFQS-5: fiber, free sugars, sodium, potassium, and whole grains). These models are applied to 2596 carbohydrate foods in the Food and Nutrient Database for Dietary Studies (FNDDS) 2017−2018. Consistent with past studies, the new carbohydrate food scoring system places large percentages of beans, vegetables, and fruits among the top scoring carbohydrate foods. The whole grain component, which only applies to grain foods (N = 1561), identifies ready-to-eat cereals, oatmeal, other cooked cereals, and selected whole grain breads and crackers as higher-quality carbohydrate foods. The new carbohydrate food scoring system shows a high correlation with the Nutrient Rich Food (NRF9.3) index and the Nutri-Score. Metrics of carbohydrate food quality that incorporate whole grains, potassium, and sodium, in addition to sugar and fiber, are strategically aligned with multiple 2020−2025 dietary recommendations and may therefore help with the implementation of present and future dietary guidelines.

Transcription factor CsWRKY40 regulates L-theanine hydrolysis by activating the CsPDX2.1 promoter in tea leaves during withering

L-Theanine is a crucial secondary metabolite in tea and positively determines the potential quality and health benefits of tea products. Previous work found the content of L-theanine decreased during withering process, while the specific mechanism is still unknown. Here, weighted gene co-expression network analysis (WGCNA) was performed based on the transcriptome data obtained previously. The key hydrolysis gene CsPDX2.1 in L-theanine metabolism and seven candidate transcription factors were screened out. Among those transcription factors, CsWRKY40 presented the strongest activation on the CsPDX2.1 promoter (373.18-fold) by binding to W box element based on the dual luciferase assay and EMSA results. Meanwhile, CsWRKY40 protein was located in the nucleoplasm, while CsPDX2.1 was found in both the nucleoplasm and cytoplasm. Furthermore, it was confirmed that the water loss of tea leaves was the critical factor affecting the contents of ABA and L-theanine by activating the expression of CsPDX2.1 and CsPDX2.1 based on the analysis of the withering model, water-retention model and water-loss model. Our results provide a new insight into revealing the regulation mechanism of L-theanine hydrolysis metabolism.

A Comparative Metabolomic Analysis Reveals Difference Manufacture Suitability in "Yinghong 9" and "Huangyu" Teas (Camellia sinensis)

"Yinghong 9" is a widely cultivated large-leaf variety in South China, and the black tea made from it has a high aroma and strong sweet flavor. "Huangyu" is a light-sensitive tea variety with yellow leaves. It was cultivated from the bud-mutation of "Yinghong 9" and has a very low level of chlorophyll during young shoot development. Due to chlorophyll being involved in carbon fixation and assimilation, the changes in photosynthesis might potentially affect the accumulation of flavor metabolites, as well as the quality of "Huangyu" tea. Although "Huangyu" has a golden yellow color and high amino acid content, the mechanism underlying the formation of leaf color and drinking value remains unclear. The widely targeted metabolomics and GC-MS analysis were performed to reveal the differences of key metabolites in fresh and fermented leaves between "Yinghong 9" and "Huangyu." The results showed that tea polyphenols, total chlorophyll, and carotenoids were more abundant in "Yinghong 9." Targeted metabolomics analysis indicated that kaempferol-3-glycoside was more abundant in "Yinghong 9," while "Huangyu" had a higher ratio of kaempferol-3-glucoside to kaempferol-3-galactoside. Compared with "Yinghong 9" fresh leaves, the contents of zeaxanthin and zeaxanthin palmitate were significantly higher in "Huangyu." The contents of α-farnesene, β-cyclocitral, nerolidol, and trans-geranylacetone, which were from carotenoid degradation and involved in flowery-fruity-like flavor in "Huangyu" fermented leaves, were higher than those of "Yinghong 9." Our results indicated that "Huangyu" was suitable for manufacturing non-fermented tea because of its yellow leaf and flowery-fruity-like compounds from carotenoid degradation.

Identifying Conserved Functional Gene Modules Underlying the Dynamic Regulation of Tea Plant Development and Secondary Metabolism

Tea plants adjust development and metabolism by integrating environmental and endogenous signals in complex but poorly defined gene networks. Here, we present an integrative analysis framework for the identification of conserved modules controlling important agronomic traits using a comprehensive collection of RNA-seq datasets in Camellia plants including 189 samples. In total, 212 secondary metabolism-, 182 stress response-, and 182 tissue development-related coexpressed modules were revealed. Functional modules (e.g., drought response, theobromine biosynthesis, and new shoot development-related modules) and potential regulators that were highly conserved across diverse genetic backgrounds and/or environmental conditions were then identified by cross-experiment comparisons and consensus clustering. Moreover, we investigate the preservation of gene networks between Camellia sinensis and other Camellia species. This revealed that the coexpression patterns of several recently evolved modules related to secondary metabolism and environmental adaptation were rewired and showed higher connectivity in tea plants. These conserved modules are excellent candidates for modeling the core mechanism of tea plant development and secondary metabolism and should serve as a great resource for hypothesis generation and tea quality improvement.

Time-series transcriptomic analysis reveals novel gene modules that control theanine biosynthesis in tea plant (Camellia sinensis)

Theanine (thea) is a unique non-protein amino acid in tea plant (Camellia sinensis) and one of the most important small molecular compounds for tea quality and health effects. The molecular mechanism that maintains thea biosynthesis is not clear but may be reflected in complicated biological networks as other secondary metabolites in plants. We performed an integrative transcriptomic analysis of tea seedlings bud and leave over the time-course of ethylamine (EA) treatment that activated thea pathway. We identified 54 consistent differentially expressed genes (cDEGs, 25 upregulated and 29 downregulated) during thea activation. Gene Ontology (GO) functional enrichment analysis of upregulated genes and downregulated genes showed that they may function as a cascade of biological events during their cooperative contribution to thea biosynthesis. Among the total cDEGs, a diversity of functional genes (e.g., enzymes, transcription factors, transport and binding proteins) were identified, indicating a hierarchy of gene control network underlying thea biosynthesis. A gene network associated with thea biosynthesis was modeled and three interconnected gene functional modules were identified. Among the gene modules, several topologically important genes (e.g., CsBCS-1, CsRP, CsABC2) were experimentally validated using a combined thea content and gene expression analysis. Collectively, we presented here for the first time a comprehensive landscape of the biosynthetic mechanism of thea controlled by a underling gene network, which might provide a theoretical basis for the identification of key genes that contribute to thea biosynthesis.

TeaCoN: a database of gene co-expression network for tea plant (Camellia sinensis)

Background

Tea plant (Camellia sinensis) is one of the world’s most important beverage crops due to its numerous secondary metabolites conferring tea quality and health effects. However, only a small fraction of tea genes (especially for those metabolite-related genes) have been functionally characterized to date. A cohesive bioinformatics platform is thus urgently needed to aid in the functional determination of the remaining genes.

Description

TeaCoN, a database of gene co-expression network for tea plant, was established to provide genome-wide associations in gene co-expression to survey gene modules (i.e., co-expressed gene sets) for a function of interest. TeaCoN featured a comprehensive collection of 261 high-quality RNA-Seq experiments that covered a wide range of tea tissues as well as various treatments for tea plant. In the current version of TeaCoN, 31,968 (94% coverage of the genome) tea gene models were documented. Users can retrieve detailed co-expression information for gene(s) of interest in four aspects: 1) co-expressed genes with the corresponding Pearson correlation coefficients (PCC-values) and statistical P-values, 2) gene information (gene ID, description, symbol, alias, chromosomal location, GO and KEGG annotation), 3) expression profile heatmap of co-expressed genes across seven main tea tissues (e.g., leaf, bud, stem, root), and 4) network visualization of co-expressed genes. We also implemented a gene co-expression analysis, BLAST search function, GO and KEGG enrichment analysis, and genome browser to facilitate use of the database.

Conclusion

The TeaCoN project can serve as a beneficial platform for candidate gene screening and functional exploration of important agronomical traits in tea plant. TeaCoN is freely available at http://teacon.wchoda.com.

Identification of MYB Transcription Factors Regulating Theanine Biosynthesis in Tea Plant Using Omics-Based Gene Coexpression Analysis

Theanine (thea) is the most abundant free amino acid in tea plant (Camellia sinensis) and one of the most important secondary metabolites conferring tea quality and health benefits. Great effort has recently been made to functionally dissect enzyme genes (e.g., GS, GDH, GOGAT) responsible for in vivo thea accumulation. However, the transcriptional regulation of its biosynthesis remains to be explored. Starting from publicly available (condition-independent) tea transcriptome data, we performed an exhaustive coexpression analysis between transcription factor (TF) genes and thea enzyme genes in tea plant. Our results showed that two typical plant-specialized (secondary) metabolites related TF families, such as MYB, bHLH, together with WD40 domain proteins, were prominently involved, suggesting a potential MYB-bHLH-WD40 (MBW) complex-mediated regulatory pattern in thea pathway. Aiming at the most involved MYB family, we screened seven MYB genes as thea candidate regulators through a stringent multistep selection (e.g., filtering with condition-specific nitrogen-treated transcriptome data). The control of MYB regulators in thea biosynthesis was further demonstrated using an integrated analysis of thea accumulation and MYB expression in several major tea tissues, including leave, bud, root, and stem. Our investigation aided tea researchers in having a comprehensive view of transcriptional regulatory landscape in thea biosynthesis, serving as the first platform for studying molecular regulation in thea pathway and a paradigm for understanding the characteristic components biosynthesis in nonmodel plants.

Importance of the Nucleophilic Property of Tea Polyphenols

Tea is the second most popular beverage in the world after water. Vast accumulative evidence attest that tea consumption may promote human health, such as antioxidant, anti-obesity, and anticancer activities. Therefore, tea phytochemicals have drawn exceeding attention from researchers in structure confirmation, formation mechanism, component clarification, and bioactivity screening of interested constituents. Particularly, most investigations of chemical or biochemical reactions of catechins have concentrated on the B ring of the C6-C3-C6 skeleton. Hence, in this perspective, we reviewed the profound findings of the carbon-carbon (C-C) connection from the unambiguous characterization of novel A-ring addition derivatives of tea catechins, including catechin-carbonyl and catechin-theanine conjugates and the C-C formation mechanisms, and offered our view of the potential effects of catechin-carbonyl interactions on flavor generation and bioactive action in tea.

Introduction to the International Symposium on Chemistry, Flavor, and Health Effects of Tea

A symposium entitled "Chemistry, Flavor, and Health Effects of Tea" was held at the 256th American Chemical Society (ACS) Meeting in August 2018 in Boston, MA, U.S.A., and was sponsored by the ACS Division of Agricultural and Food Chemistry and the International Joint Laboratory on Tea Chemistry and Health Effects, Anhui Agricultural University, China. The purpose of the symposium was to bring together the leading tea researchers throughout the world to discuss the current state of knowledge as well as research needs with respect to chemistry and health beneficial properties of tea. Speakers from North America, Europe, and Asia delivered a total of 35 oral presentations. The presentations covered such diverse topics as polyphenol chemistry and flavor chemistry of tea, metabolomics application to identify the changes of phytochemical composition during processing, and health beneficial effects of drinking tea. This paper is intended to provide a brief summary of the presentations.

Using Caffeine and Free Amino Acids To Enhance the Transepithelial Transport of Catechins in Caco-2 Cells

Catechins are well-known to possess health-promoting functions. The interaction of the catechins with other components in tea could alter their absorption and efflux. This study investigated whether the absorption of catechins is affected by caffeine and amino acids using the Caco-2 monolayer cell model. We found that (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC) were all actively effluxed. Co-transportation of EGCG, ECG, or EC with caffeine, theanine, serine, or glycine increased their apparent permeability coefficient [ P_app(AP-BL)] value by 3.42-5.40- fold, 1.19-5.75-fold, and 1.55-8.01-fold, respectively. Meanwhile, their efflux ratio values were significantly decreased. Moreover, the expression of multi-drug resistance protein 2 (MRP2) after 3 h of incubation with either 50 μM EGCG or 50 μM EC was elevated by 1.58- and 2.98-fold, respectively, while 50 μM ECG had no significantly effects. In addition, the expression of P-glycoprotein (P-gp) after treatment with either 50 μM EGCG, 50 μM ECG, or 50 μM EC was enhanced by 1.53-, 1.63-, and 1.80-fold, respectively. The addition of either caffeine or any one of the three amino acids decreased the expression of both MRP2 and P-gp induced by EGCG, and the expression of P-gp induced by ECG or EC also decreased. In contrast, only glycine decreased the expression of MRP2 induced by EC. Taken together, our data indicated that caffeine and theanine, glycine, or serine in tea might increase the absorption of catechins by the selectively suppressed expression of the efflux transporters induced by catechins.

Deciphering the Rules of in Silico Autophagy Methods for Expediting Medicinal Research

Autophagy is a highly evolutionarily conserved cellular catabolic process responsible for degradation of damaged organelles and long-lived proteins. It is not surprising that scientific interest in the connection of autophagy and diseases has been growing. Over the past 2 decades, many new experimental approaches have been emerging in the field of targeting autophagy for medicinal research. Interestingly, in addition to experimental methods, a number of databases, Web servers, mathematics models, omics approaches, and systems biology network approaches related to autophagy have become available online, which may be collectively considered to be "in silico autophagy methods" for expediting current medicinal research. Thus, we have summarized a series of relevant in silico autophagy approaches for promoting the most appropriate usage of these resources for potential therapeutic purposes.

The natural phenolic compounds as modulators of NADPH oxidases in hypertension

BACKGROUND

Hypertension is a major public health problem worldwide. It is an important risk factor for other cardiovascular diseases such as coronary artery disease, stroke, heart failure, atrial fibrillation, peripheral vascular disease, chronic kidney disease, and atherosclerosis.

PURPOSE

There is strong evidence that excess ROS-derived NADPH oxidase (NOX) is an important agent in hypertension. It augments blood pressure in the presence of other pro-hypertensive factors such as angiotensin II (Ang II), an important and potent regulator of cardiovascular NADPH oxidase, activates NOX via AT1 receptors. NADPH oxidase, a multi-subunit complex enzyme, is considered as a key source of ROS production in the vasculature. The activation of this enzyme is needed for assembling Rac-1, p^40phox, p^47phox and p^67phox subunits. Since, hypertensive patients need to control blood pressure for their entire life and because drugs and other chemicals often induce adverse effects, the use of natural phenolic compounds which are less toxic and potentially beneficial may be good avenues of addition research in our understand of the underlying mechanism involved in hypertension. This review focused on several natural phenolic compounds as berberine, thymoquinone, catechin, celastrol, apocynin, resveratrol, curcumin, hesperidine and G-hesperidine, and quercetin which are NOX inhibitors. In addition, structure activity relationship of these compounds eventually as the most inhibitors was discussed.

METHODS

This comprehensive review is based on pertinent papers by a selective search using relevant keywords that was collected using online search engines and databases such as ScienceDirect, Scopus and PubMed. The literature mainly focusing on natural products with therapeutic efficacies against hypertension via experimental models both in vitro and in vivo was identified.

RESULTS

It has been observed that these natural compounds prevent NADPH oxidase expression and ROS production while increasing NO bioavailability. It have been reported that they improve hypertension due to formation of a stable radical with ROS-derived NADPH oxidase and preventing the assembly of NOX subunites.

CONCLUSION

It is clear that natural phenolic compounds have some potential inhibitory effect on NADPH oxidase activity. In comparison to other phenolic plant compounds, the structural variability of the flavonoids should off different impacts on oxidative stress in hypertension including inhibition of nadph oxidase and direct scavenging of free radicals.

TBC2target: A Resource of Predicted Target Genes of Tea Bioactive Compounds

Tea is one of the most popular non-alcoholic beverages consumed worldwide. Numerous bioactive constituents of tea were confirmed to possess healthy benefits via the mechanisms of regulating gene expressions or protein activities. However, a complete interacting profile between tea bioactive compounds (TBCs) and their target genes is lacking, which put an obstacle in the study of healthy function of tea. To fill this gap, we developed a database of target genes of TBCs (TBC2target, http://camellia.ahau.edu.cn/TBC2target) based on a pharmacophore mapping approach. In TBC2target, 6,226 interactions between 240 TBCs and 673 target genes were documented. TBC2target contains detailed information about each interacting entry, such as TBC, CAS number, PubChem CID, source of compound (e.g., green, black), compound type, target gene(s) of TBC, gene symbol, gene ID, ENSEMBL ID, PDB ID, TBC bioactivity and the reference. Using the TBC-target associations, we constructed a bipartite network and provided users the global network and local sub-network visualization and topological analyses. The entire database is free for online browsing, searching and downloading. In addition, TBC2target provides a BLAST search function to facilitate use of the database. The particular strengths of TBC2target are the inclusion of the comprehensive TBC-target interactions, and the capacity to visualize and analyze the interacting networks, which may help uncovering the beneficial effects of tea on human health as a central resource in tea health community.

The proposed biosynthesis of procyanidins by the comparative chemical analysis of five Camellia species using LC-MS

The genus Camellia (C.) contains many species, including C. sinensis, C. assamica, and C. taliensis, C. gymnogyna and C. tachangensis. The polyphenols of C. sinensis and C. assamica are flavan-3-ols monomers and their dimers and trimmers. However, the biosynthesis of procyanidins in Camellia genus remains unclear. In the present study, a comparative chemical analysis of flavan-3-ols, flavan-3-ols glycoside and procyanidins was conducted by high performance liquid chromatography (HPLC) and liquid chromatography diode array detection coupled with triple-quadrupole mass-spectrometry (LC-DAD-QQQ-MS). The results showed that C. tachangensis had a significant higher contents of (-)-epicatechin (EC) and (-)-epigallocatechin (EGC) compared with C. sinensis (p < 0.001). By contrast, higher levels of galloylated catechins were detected in C. sinensis. LC-DAD-MS/MS indicated that the main secondary metabolites of C. tachangensis were non-galloylated catechins, procyanidin dimers and trimers. Furthermore, (-)-epicatechin glucose (EC-glucose) and (-)-epigallocatechin glucose (EGC-glucose) were also abundant in C. tachangensis. A correlation analysis of EC-glucose and procyanidins dimers was conducted in five Camellia species. The levels of EC-glucose were closely related to the procyanidin dimers content. Thus, it was suggested that EC-glucose might be an important substrate for the biosynthesis of procyanidins.

Preventive Effects of Catechins on Cardiovascular Disease

Catechins are polyphenolic phytochemicals with many important physiological activities that play a multifaceted health care function in the human body, especially in the prevention of cardiovascular disease. In this paper, various experimental and clinical studies have revealed the role of catechins in the prevention and treatment of cardiovascular disorders, and we review the preventive effects of catechins on cardiovascular disease from the following aspects: Regulating lipid metabolism, regulating blood lipid metabolism, vascular endothelial protection, and reducing blood pressure.