Selenium affects the activity of black tea in preventing metabolic syndrome in high-fat diet-fed Sprague-Dawley rats

Global hotspots and trends in tea anti-obesity research: a bibliometric analysis from 2004 to 2024

Background

The prevalence of obesity and its related ailments is on the rise, posing a substantial challenge to public health. Tea, widely enjoyed for its flavors, has shown notable potential in mitigating obesity. Yet, there remains a lack of exhaustive bibliometric studies in this domain.

Methods

We retrieved and analyzed multidimensional data concerning tea and obesity studies from January 2004 to June 2024, using the Web of Science Core Collection database. This bibliometric investigation utilized tools such as Bibliometrix, CiteSpace, and VOSviewer to gather and analyze data concerning geographical distribution, leading institutions, prolific authors, impactful journals, citation patterns, and prevalent keywords.

Results

There has been a significant surge in publications relevant to this field within the last two decades. Notably, China, Hunan Agricultural University, and the journal Food and Function have emerged as leading contributors in terms of country, institution, and publication medium, respectively. Zhonghua Liu of Hunan Agricultural University has the distinction of most publications, whereas Joshua D. Lambert of The State University of New Jersey is the most cited author. Analyses of co-citations and frequently used keywords have identified critical focus areas within tea anti-obesity research. Current studies are primarily aimed at understanding the roles of tea components in regulating gut microbiota, boosting fat oxidation, and increasing metabolic rate. The research trajectory has progressed from preliminary mechanism studies and clinical trials to more sophisticated investigations into the mechanisms, particularly focusing on tea's regulatory effects on gut microbiota.

Conclusion

This study offers an intricate overview of the prevailing conditions, principal focus areas, and developmental trends in the research of tea's role against obesity. It delivers a comprehensive summary and discourse on the recent progress in this field, emphasizing the study's core findings and pivotal insights. Highlighting tea's efficacy in obesity prevention and treatment, this study also points out the critical need for continued research in this area.

Research Progress on the Effect and Mechanism of Tea Products with Different Fermentation Degrees in Regulating Type 2 Diabetes Mellitus

A popular non-alcoholic beverage worldwide, tea can regulate blood glucose levels, lipid levels, and blood pressure, and may even prevent type 2 diabetes mellitus (T2DM). Different tea fermentation levels impact these effects. Tea products with different fermentation degrees containing different functional ingredients can lower post-meal blood glucose levels and may prevent T2DM. There are seven critical factors that shed light on how teas with different fermentation levels affect blood glucose regulation in humans. These factors include the inhibition of digestive enzymes, enhancement of cellular glucose uptake, suppression of gluconeogenesis-related enzymes, reduction in the formation of advanced glycation end products (AGEs), inhibition of dipeptidyl peptidase-4 (DPP-4) activity, modulation of gut flora, and the alleviation of inflammation associated with oxidative stress. Fermented teas can be used to lower post-meal blood glucose levels and can help consumers make more informed tea selections.

Selenium reduces hepatopancreas lipid accumulation of grass carp (Ctenopharyngodon idella) fed high-fat diet via lipophagy activation

It has been reported that selenium (Se) can reduce hepatopancreas lipid accumulation induced by high-fat diet. However, its mechanism is still unknown. This study aims to investigate the specific mechanisms by which Se alleviates high-fat diet-induced lipid accumulation. Grass carp were fed control diet (4.8% lipid, Con), high-fat diet (8.8% lipid, HFD) or HFD supplemented with 0.3 mg/kg nano-Se (HSe0.3) for 10 weeks. Growth performance, Se deposition, lipid accumulation, hepatic ultrastructure, and gene and protein expression levels associated with autophagy were examined. Furthermore, oleic acid (OA) was used to incubate the grass carp hepatocytes (L8824) for 24 h, and then the L8824 were incubated with sodium selenite in presence or absence of an autophagy inhibitor for 24 h. L8824 was analyzed for triglyceride concentration, immunofluorescence, and gene and protein expression levels associated with autophagy. We found that dietary nano-Se improved the growth of fish fed HFD and also decreased hepatosomatic index and intraperitoneal fat ratio of fish fed HFD (P < 0.05). HFD significantly increased hepatopancreas lipid accumulation and decreased autophagic activity (P < 0.05). Treatment of grass carp fed HFD with nano-Se decreased lipid accumulation and restored hepatic autophagy (P < 0.05). In vitro, Se (100 μM sodium selenite) obviously activated autophagy in L8824 incubated with OA, and consequently reduced the lipid accumulation induced by OA (P < 0.05). Furthermore, using pharmacological inhibition (chloroquine) of the autophagy greatly diminished the beneficial effects of Se on alleviating OA-induced lipid accumulation and increased the co-localization of lipid droplets with autophagosome (P < 0.05), which indicated that Se increased autophagic flux. In conclusion, these results suggest that Se alleviates HFD-induced hepatopancreas lipid accumulation by activating lipophagy.

Impacts of selenium enrichment on nutritive value and obesity prevention of Cordyceps militaris: A nutritional, secondary metabolite, and network pharmacological analysis

This study aimed to compare the nutritive value and obesity prevention of ordinary Cordyceps militaris (CM) and selenium-enriched CM (SeCM). The results indicated that Se enrichment significantly increased the total carbohydrate and soluble dietary fiber content, while the protein and insoluble dietary fiber content decreased. Although the fat content was not affected, the medium and long-chain fatty acids content significantly changed. Moreover, Se enrichment significantly elevated the secondary metabolites belonging to terpenoids and alkaloids, which are linked with the enhanced biosynthesis of secondary metabolites. Both CM and SeCM reduced body weight, adipose accumulation, impaired glucose tolerance, and lipid levels in high-fat diet (HFD)-fed mice, and there was no significant difference between them. Network pharmacological analysis revealed that dietary CM and SeCM prevented HFD-induced obesity and associated metabolic diseases with multi-ingredients acting on multi-targets. Overall, Se enrichment improved the nutritive value of CM without altering its role in preventing obesity.

Selenium-Enriched and Ordinary Black Teas Regulate the Metabolism of Glucose and Lipid and Intestinal Flora of Hyperglycemic Mice

Black tea is one of the six major tea categories and has a variety of bioactivities. However, little is known about its comprehensive evaluation of hypoglycemic effects and potential mechanisms. In this study, we investigated the in vivo hypoglycemic activity and potential mechanism for aqueous extracts of ordinary black tea (BT) and selenium-enriched black tea (Se-BT) by using an established high-fat diet together with streptozotocin (STZ)-induced hyperglycemic mouse model. Additionally, we also explored their α-glucosidase inhibition activity. The results show that both BT and Se-BT had a favorable glycosidase inhibitory activity. Moreover, the intervention of BT and Se-BT could regulate the mRNA expression and the level of serum parameters related to glucose and lipid metabolisms. Accordingly, they could activate the phosphoinositide-3-kinase/protein kinase B (PI3K/Akt) signaling pathway and alleviate insulin resistance (IR) and hyperglycemia. Moreover, supplementation of BT and Se-BT increased the richness and diversity of intestinal flora and altered the abundance of beneficial and harmful bacteria. Both BT and Se-BT could regulate glucose metabolism, alleviate tissue damage, and restore intestinal flora dysbiosis, suggesting that they could be used as a natural functional food for preventing hyperglycemia.

Special tea products featuring functional components: Health benefits and processing strategies

The functional components in tea confer various potential health benefits to humans. To date, several special tea products featuring functional components (STPFCs) have been successfully developed, such as O-methylated catechin-rich tea, γ-aminobutyric acid-rich tea, low-caffeine tea, and selenium-rich tea products. STPFCs have some unique and enhanced health benefits when compared with conventional tea products, which can meet the specific needs and preferences of different groups and have huge market potential. The processing strategies to improve the health benefits of tea products by regulating the functional component content have been an active area of research in food science. The fresh leaves of some specific tea varieties rich in functional components are used as raw materials, and special processing technologies are employed to prepare STPFCs. Huge progress has been achieved in the research and development of these STPFCs. However, the current status of these STPFCs has not yet been systematically reviewed. Here, studies on STPFCs have been comprehensively reviewed with a focus on their potential health benefits and processing strategies. Additionally, other chemical components with the potential to be developed into special teas and the application of tea functional components in the food industry have been discussed. Finally, suggestions on the promises and challenges for the future study of these STPFCs have been provided. This paper might shed light on the current status of the research and development of these STPFCs. Future studies on STPFCs should focus on screening specific tea varieties, identifying new functional components, evaluating health-promoting effects, improving flavor quality, and elucidating the interactions between functional components.

Dietary selenomethionine attenuates obesity by enhancing beiging process in white adipose tissue

Imbalanced nutrient intake causes abnormal energy metabolism, which results in obesity. There is feasible evidence that selenium-rich (Se-rich) foods may alleviate obesity and enhance general public health, but the underlying mechanisms remain elusive. Herein we examined the effect of Se supplementation on white adipose tissue beiging process. The mice were fed with a normal diet or a Se-deficient high-fat diet (DHFD) until significant differences in terms of body weight, glucose tolerance and insulin sensitivity. Next, mice in the DHFD group were changed to a high-fat diet (HFD) containing specified amounts of selenomethionine (SeMet) (0, 150, 300, and 600 μg/kg) and continued to feed for 14 weeks. Notably, 150 μg/kg SeMet supplement highly protected mice from DHFD-induced obesity, insulin resistance, and lipid deposits in the liver and kidney, and featured by the enhanced beiging process in white adipose tissue and increased energy expenditure. Moreover, upon cold challenge, 150 μg/kg SeMet supplement enhanced cold tolerance in mice by inducing adipose beiging to promote energy expenditure, as evidenced by the increased expression of uncoupling protein-1 (UCP1) in adipocytes. Similarly, SeMet (10 μM) promoted the differentiation of beige adipocytes from the stromal vascular fraction. Collectively, our data support that optimal supplementation of SeMet could enhance the beiging process to attenuate HFD-induced obesity, which provides new insights into the relationship between dietary SeMet and type 2 diabetes.

Insights into the key quality components in Se-Enriched green tea and their relationship with Selenium

Selenium-enriched green tea (Se-GT) is of increasing interest because of its health benefits, but its quality components obtained limited research. In this study, Enshi Se-enriched green tea (ESST, high-Se green tea), Pingli Se-enriched green tea (PLST, low-Se green tea), and Ziyang green tea (ZYGT, common green tea) were subjected to sensory evaluation, chemical analysis, and aroma profiling. Chemical profiles in Se-GT were consistent with the taste attributes of the sensory analysis. 9 volatiles were identified as key odorants of Se-GT based on multivariate analysis. Correlations between Se and quality components were further assessed and highly Se-related compounds contents in these three tea samples were compared. The results showed that most amino acids and non-gallated catechins were highly negatively correlated with Se, while gallated catechins exhibited strong positive correlation with Se. And there were strong and significant associations between the key aroma compounds and Se. Moreover, 11 differential markers were found between Se-GTs and common green tea, including catechin, serine, glycine, threonine, l-theanine, alanine, valine, isoleucine, leucine, histidine, and lysine. These findings provide great potential for quality evaluation of Se-GT.

Research Progress on the Effects of Selenium on the Growth and Quality of Tea Plants

Selenium (Se) is an essential trace element for humans and animals, and it plays an important role in immune regulation and disease prevention. Tea is one of the top three beverages in the world, and it contains active ingredients such as polyphenols, theanine, flavonoids, and volatile substances, which have important health benefits. The tea tree has suitable Se aggregation ability, which can absorb inorganic Se and transform it into safe and effective organic Se through absorption by the human body, thereby improving human immunity and preventing the occurrence of many diseases. Recent studies have proven that 50~100.0 mg/L exogenous Se can promote photosynthesis and absorption of mineral elements in tea trees and increase their biomass. The content of total Se and organic selenides in tea leaves significantly increases and promotes the accumulation of polyphenols, theanine, flavonoids, and volatile secondary metabolites, thereby improving the nutritional quality of tea leaves. This paper summarizes previous research on the effects of exogenous Se treatment on the growth and quality of tea trees to provide a theoretical basis and technical support for the germplasm selection and exploitation of Se-rich tea.

Effects of Keemun and Dianhong Black Tea in Alleviating Excess Lipid Accumulation in the Liver of Obese Mice: A Comparative Study

Schematic diagram of the effects of two black teas in alleviating excess hepatic lipid accumulation.

Associations of the Dietary Iron, Copper, and Selenium Level With Metabolic Syndrome: A Meta-Analysis of Observational Studies

Background

Epidemiological studies have investigated the associations of dietary iron, copper, and selenium level with metabolic syndrome (MetS). However, their results are conflicting. This meta-analysis of observational study was, therefore, employed to investigate the associations above.

Methods

A comprehensive literature search was employed using PubMed, Web of Science, Embase, and Scopus database up to October 2021 (no restriction was set for the initiate time). The pooled relative risk (RR) of MetS for the highest vs. lowest dietary iron, copper, and selenium level was estimated, respectively.

Results

A total of 14 observational studies (55,131 participants) were identified as meeting the inclusion criteria. Specifically, 7 studies were related to the dietary iron level. The overall multivariable adjusted RR demonstrated that the dietary iron level was positively associated with MetS (RR = 1.27, 95% CI: 1.12–1.44; p &lt; 0.001). With regard to the dietary copper level, 7 studies were included for meta-analysis. The overall multivariable adjusted RR showed that the dietary copper level was inversely associated with MetS (RR = 0.85, 95% CI: 0.78–0.93; p &lt; 0.001). In addition, 4 studies were specified for the dietary selenium level. The overall multivariable adjusted RR indicated that the dietary selenium level was inversely associated with MetS (RR = 0.77, 95% CI: 0.63–0.95; p = 0.01) as well.

Conclusion

Our results suggest that the dietary iron level is positively associated with MetS, whereas a negative association between the dietary copper and selenium level and MetS is obtained. Further large well-designed prospective cohort studies are warranted to elaborate on the issues examined in this study.

Selenomethionine Ameliorates Cognitive Impairment, Decreases Hippocampal Oxidative Stress and Attenuates Dysbiosis in D-Galactose-Treated Mice

The prevalence of age-related cognitive impairment is increasing as the proportion of older individuals in the population grows. It is therefore necessary and urgent to find agents to prevent or ameliorate age-related cognitive impairment. Selenomethionine (SeMet) is a natural amino acid occurring in yeast and Brazil nuts. It mitigates cognitive impairment in an Alzheimer’s disease mouse model, however, whether it works on age-related cognitive impairment remains unknown. In this study, SeMet significantly improved the performance of D-galactose-treated mice in the novel object recognition test, passive avoidance task and Morris water maze test. SeMet reversed D-galactose-induced reduction of hippocampal acetylcholine levels, suppression of choline acetyltransferase activity and activation of acetyl cholinesterase. It decreased D-galactose-induced oxidative stress and increased the selenoprotein P levels in the hippocampus. Besides, it attenuated D-galactose-induced dysbiosis by increasing the α-diversity and modulating the taxonomic structure. Correlations between certain taxa and physiological parameters were observed. Our results provide evidence of the effectiveness of SeMet on ameliorating D-galactose-induced cognitive impairment and suggest SeMet has potential to be used in the prevention or adjuvant treatment of age-related cognitive impairment.

Anti-Hyperlipidemia and Gut Microbiota Community Regulation Effects of Selenium-Rich Cordyceps militaris Polysaccharides on the High-Fat Diet-Fed Mice Model

Supplementation of polysaccharides is a promising gut microbiota-targeted therapeutic method for obesity and metabolic diseases. Biological activities of Cordyceps militaris polysaccharides have been well reported, but the effect of selenium (Se)-rich C. militaris polysaccharides (SeCMP) on obesity and associated metabolic disorder and gut microbiota composition has been rarely studied. This study aimed to investigate the anti-obesity and gut microbiota modulatory effect of crude polysaccharides separated from Se-rich C. militaris on a high-fat diet (HFD)-fed C57BL/6J mice model. Mice were treated with a normal diet (CHOW), HFD alone, HFD plus C. militaris polysaccharides (CMP), or low/medium/high dosage of SeCMP for 8 weeks. Body weight, fat content, serum lipid, appetite hormone, lipid gene expression, inflammation cytokines, thermogenic protein, short-chain fatty acids (SCFAs), and gut microbiota structure of the mice were determined. Compared with HFD-fed mice, the serum triglyceride and low-density lipoprotein cholesterol (LDL-C) in the SeCMP-200 group were decreased by 51.5% and 44.1%, respectively. Furthermore, serum lipopolysaccharide-binding proteins (LBP), adiponectin level, and pro-inflammation gene expression in the colon and subcutaneous fat were inhibited, whereas anti-inflammation gene expression was improved, reflecting SeCMP-200 might mitigate obese-induced inflammation. Meanwhile, SeCMP-200 promoted satiety and thermogenesis of obese mice. It also significantly decreased gut bacteria, such as Dorea, Lactobacillus, Clostridium, Ruminococcus, that negatively correlated with obesity traits and increased mucosal beneficial bacteria Akkermansia. There was no significant difference between CMP and SeCMP-100 groups. Our results revealed a high dose of SeCMP could prevent HFD-induced dyslipidemia and gut microbiota dysbiosis and was potential to be used as functional foods.

Impact of Antibiotic-Induced Depletion of Gut Microbiota and Selenium Supplementation on Plasma Selenoproteome and Metal Homeostasis in a Mice Model

Selenium (Se) is a micronutrient involved in important health functions and it has been suggested to shape gut microbiota. Limited information on Se assimilation by gut microbes and the possible link with selenoproteins are available. For this purpose, conventional and gut microbiota-depleted BALB/c mice were fed a Se-supplemented diet. The absolute quantification of mice plasma selenoproteins was performed for the first time using heteroatom-tagged proteomics. The gut microbiota profile was analyzed by 16S rRNA gene sequencing. Se-supplementation modulated the concentration of the antioxidant glutathione peroxidase and the Se-transporter selenoalbumin as well as the metal homeostasis, being influenced by microbiota disruption, which suggests an intertwined mechanism. Se also modulated microbiota diversity and richness and increased the relative abundance of some health-relevant taxa (e.g., families Christensenellaceae, Ruminococcaceae, and Lactobacillus genus). This study demonstrated the potential beneficial effects of Se on gut microbiota, especially after antibiotic-treatment and the first associations between specific bacteria and plasma selenoproteins.

Omic methodologies for assessing metal(-loid)s-host-microbiota interplay: A review

Omic methodologies have become key analytical tools in a wide number of research topics such as systems biology, environmental analysis, biomedicine or food analysis. They are especially useful when they are combined providing a new perspective and a holistic view of the analytical problem. Methodologies for microbiota analysis have been mostly focused on genome sequencing. However, information provided by these metagenomic studies is limited to the identification of the presence of genes, taxa and their inferred functionality. To achieve a deeper knowledge of microbial functionality in health and disease, especially in dysbiosis conditions related to metal and metalloid exposure, the introduction of additional meta-omic approaches including metabolomics, metallomics, metatranscriptomics and metaproteomics results essential. The possible impact of metals and metalloids on the gut microbiota and their effects on gut-brain axis (GBA) only begin to be figured out. To this end new analytical workflows combining powerful tools are claimed such as high resolution mass spectrometry and heteroatom-tagged proteomics for the absolute quantification of metal-containing biomolecules using the metal as a "tag" in a sensitive and selective detector (e.g. ICP-MS). This review focus on current analytical methodologies related with the analytical techniques and procedures available for metallomics and microbiota analysis with a special attention on their advantages and drawbacks.

Cardamine hupingshanensis aqueous extract improves intestinal redox status and gut microbiota in Se-deficient rats

BACKGROUND

As an essential trace element for mammalian species, selenium (Se) possesses powerful antioxidant properties and is a potential regulator of intestinal microbiota. However, effects of Cardamine hupingshanensis aqueous extract (CE), rich in Se, on balancing the intestinal redox status and regulating gut microbiota have been neglected.

RESULTS

An Se-deficient rat model was established by feeding a low-Se diet (LD) for 5 weeks and CE was then supplemented to LD or normal-Se-diet (ND) rats. Antioxidant enzyme activities and short-chain fatty acids (SCFA) concentration were increased by CE in both LD and ND rats. CE improved the intestinal morphology of LD rats impaired by deficient Se. Intestinal microbiota demonstrated various changes; for example, Butyrivibrio was increased in LD rats, while Bacteroides, Christensenellaceae, Clostridiaceae and Blautia were enhanced in ND rats.

CONCLUSION

Our findings provide evidence that CE shows potential in improving intestinal redox status and regulating gut microbiota. © 2020 Society of Chemical Industry.

Diagnostic Criteria for Metabolic Syndrome in Diet-Induced Rodent Models: A Systematic Review

BACKGROUND

Thousands of publications in recent years have addressed the induction of metabolic syndrome (MetS) in rodents. However, the criteria and the reference values for diagnosing this disease have not been defined.

OBJECTIVE

Our main objective was to carry out a systematic review to gather evidence about the criteria for biochemical and anthropometric parameters in which scientific studies have relied on to report that rats developed MetS from a previous dietary manipulation.

METHODS

We compiled characteristics and findings of diet-induced MetS with high-fat, high-carbohydrate, high-fat/high-carbohydrates, and cafeteria diet from PubMed and Science Direct databases published in the last 5 years.

RESULTS

The results on the principal determinants for the syndrome, published in the reviewed articles, were chosen to propose reference values in the rat models of food induction.

CONCLUSION

The values obtained will serve as reference cut-of points in the development of the disease; in addition, the compilation of data will be useful in planning and executing research protocols in animal models.

Black tea benefits short-chain fatty acid producers but inhibits genus Lactobacillus in the gut of healthy Sprague-Dawley rats

BACKGROUND

The gut microbiota plays important roles in physiological and pathological processes of the host. The effect of black tea on the gut microbiota of healthy individuals remains unclear.

RESULTS

Healthy Sprague-Dawley (SD) rats were given black tea for 4 weeks, and cecum content, serum, intestinal, and hepatic samples were collected. The results showed that black tea increased α-diversity and modulated β-diversity of the gut microbiota. Additionally, black tea enriched several short-chain fatty acid (SCFA) producers but suppressed genus Lactobacillus. Further tests revealed that the enrichment of SCFA producers was associated with a decrease in the oxidative stress of cecum content caused by black tea, and related to increased luminal butyric acid levels and enhanced intestinal barrier function. The suppression of genus Lactobacillus was related to the increase in luminal total bile acids caused by black tea. In vitro tests showed that bile acids rather than black tea directly inhibited Lactobacillus strains. The reduction in genus Lactobacillus did not affect the effects of black tea on intestinal barrier function and lipid levels.

CONCLUSION

Our results imply that the effects of black tea on gut microbiota in healthy individuals are complex and provide a new perspective on the associations among black tea, gut microbiota, and health. © 2020 Society of Chemical Industry.

Analytical strategy coupled to chemometrics to differentiate Camellia sinensis tea types based on phenolic composition, alkaloids, and amino acids

Catechins, amino acids, and alkaloids are primary chemical components of tea and play a crucial role in determining tea quality. Their composition and content largely vary among different types of tea. In this study, a convenient chemical classification method was developed for six Camellia sinensis tea types (white, green, oolong, black, dark, and yellow) based on the quantification of their major components. Twenty-one free amino acids, 6 catechins, 2 alkaloids, and gallic acid in 24 teas were quantified using ultra-high-performance liquid chromatography (UHPLC). The total catechin contents in these tea samples ranged from 10.96 to 95.67 mg/g, while total free amino acid content ranged from 2.63 to 25.89 mg/g. Theanine (Thea) was the most abundant amino acid in all tea varieties. Catechin and amino acid levels in tea were markedly reduced upon fermentation of tea. Furthermore, high-temperature processing (roasting) during tea production induced degradation and epimerization of catechins, yielding epimerized catechins, simple catechins, and gallic acid. Principal component analysis revealed that major ester-catechins (EGCG and ECG), major amino acids (Thea), and major alkaloids (caffeine) are potential factors for distinguishing different types of tea. Linear discriminant analysis showed that 100% of teas were correctly classified in which (+)-catechin, ECG, EGC, gallic acid, GABA, cysteine, lysine, and threonine were the most discriminating compounds. This study shows that quantification of the major tea components combined with chemometric analysis, can serve as a simple, convenient, and reliable approach for classifying tea according to fermentation level. PRACTICAL APPLICATION: Different Camellia sinensis tea types can be produced worldwide but it is still challenging to know which chemical markers can be used to trace their production. in this paper we used a targeted methodology to classify six tea types (white, green, oolong, black, dark, and yellow) based on phenolic composition, alkaloids, and amino acids. The main chemical markers responsible for the discrimination were pinpointed with the use of chemometric tools.