Polyphenols and their anti-obesity role mediated by the gut microbiota: a comprehensive review

Hepatoprotective Effect of Kaempferol-A Review

Liver diseases, including chronic inflammation and related metabolic dysfunction-associated steatotic liver disease (MASLD), fibrosis and cirrhosis remain a growing global health burden. Currently, available pharmacotherapy for liver dysfunction has limited efficacy. Kaempferol, a naturally occurring flavonoid, has demonstrated significant hepatoprotective effects in preclinical models. This substance activates the SIRT1/AMPK signalling pathway, improves mitochondrial function, inhibits proinflammatory cytokine production via TLR4/NF-κB suppression and attenuates hepatic stellate cell activation by modulating the TGF-β/Smad pathway. In addition, kaempferol regulates the composition of the gut microbiota, thus improving bile acid metabolism and alleviating steatosis and fibrosis. This review presents an integrated analysis of recent in vitro and in vivo studies on the mode of action and utility of kaempferol in liver disease and hepatoprotection.

Curcumin Modulation of the Gut-Brain Axis for Neuroinflammation and Metabolic Disorders Prevention and Treatment

Curcumin, a polyphenolic compound derived from Curcuma longa, has gained significant attention for its potential therapeutic benefits, particularly counteracting inflammation, oxidative stress, and metabolic disorders. Its chemical structure, featuring conjugated double bonds between two aromatic rings, allows it to act as an electron donor, thereby mitigating free radical formation. Despite its poor solubility in water, curcumin is stable in acidic environments and undergoes significant metabolism in both the liver and the gut. Intestinal microbiota, particularly at the colon level, further metabolizes curcumin into several derivatives, including dihydrocurcumin and tetrahydrocurcumin, which exhibit antioxidant and anti-inflammatory properties. Studies suggest that curcumin can reduce body mass index (BMI) and improve other body composition parameters, especially when used in combination with lifestyle changes, though its bioavailability is low due to its rapid metabolism and the resulting low blood concentration. In obesity, dysfunctional adipose tissue remodeling and chronic inflammation play critical roles in the development of metabolic complications. Curcumin's anti-inflammatory properties are related to the inhibition of the NF-κB pathway, leading to the reduction in inflammatory markers in adipocytes and macrophages. Additionally, curcumin modulates oxidative stress by activating the NRF2 pathway, enhancing cellular antioxidant defenses. Emerging evidence also supports curcumin's potential in improving gut health by modulating microbiota composition, enhancing intestinal barrier function, and reducing systemic inflammation. This interaction with the gut-brain axis highlights the broader implications of curcumin in neuroprotection, as it positively affects cognitive function and mitigates neuroinflammation in neurodegenerative diseases like Alzheimer's. disease. Thus, curcumin holds promise as a multifaceted agent in the management of obesity and associated diseases.

Microbiome, Potential Therapeutic Agents: New Players of Obesity Treatment

Obesity is a global pandemic, and recent research has established a correlation between the microbiome and obesity, indicating potential treatment possibilities. This review evaluated the potential of the microbiome in treating obesity by targeting anti-adipogenesis and adipose tissue browning mechanisms. The microbiome impacts adipogenesis through lipogenesis and inflammation pathways and influences adipose tissue browning via the secretion of gut hormones and short-chain fatty acids. Understanding these mechanisms could pave the way for interventions targeting the gut microbiome to reduce obesity-related adiposity. While our understanding of the specific microbial species, metabolites, and signaling pathways involved in these processes is still limited, this review highlights the potential of microbiome-based therapies for obesity. Further research focused on identifying key microbial players and their mechanisms of action will be crucial for developing targeted and effective interventions. This will ultimately contribute to a more comprehensive understanding of obesity pathogenesis and facilitate the development of novel therapeutic strategies to combat this global health crisis.

Pandanus Amaryllifolius Roxb. Polyphenol Extract Alleviates NAFLD via Regulating Gut Microbiota and AMPK/AKT/mTOR Signaling Pathway

With the drastic changes in lifestyle, nonalcoholic fatty liver disease (NAFLD) has become a widespread health problem. Natural actives such as polyphenols have multi-target, multi-mechanism characteristics, and offer new opportunities for NAFLD treatment. This study established a high-fat diet (HFD)-induced NAFLD model in mice to investigate the molecular mechanism of Pandanus amaryllifolius Roxb. polyphenol extract (PAE) in alleviating NAFLD. The results showed that PAE significantly inhibited HFD-induced obesity, maintained glucose homeostasis, mitigated oxidative damage in liver tissue, and reduced liver steatosis. Moreover, PAE treatment remarkably reversed 16 endogenous DMs, and significantly affected glycerophospholipid metabolism, which increased the levels of phosphatidylcholine and phosphatidylethanolamine, and down-regulated choline and sn-glyceropl-3P. Further validation revealed that PAE was able to prevent NAFLD progression by regulating the AMPK/AKT/mTOR signaling pathway to enhance autophagy levels. Meanwhile, PAE treatment restored the balance of gut microbiota mainly by increasing the relative abundance of Bacteroidetes, decreasing the relative abundance of Firmicutes and the ratio of Firmicutes/Bacteroidetes. Overall, the findings highlight that the mechanism by which PAE alleviates NAFLD may be related to the regulation of the gut microbes and AMPK/AKT/mTOR signaling pathway, enriching the health-promoting effects of PAE on NAFLD.

Quercetin-Driven Akkermansia Muciniphila Alleviates Obesity by Modulating Bile Acid Metabolism via an ILA/m6A/CYP8B1 Signaling

Global health is increasingly challenged by the growing prevalence of obesity and its associated complications. Quercetin, one of the most important dietary flavonoids, is being explored as an effective therapy for obesity with its mechanism remains understudied. Here in this study, it is demonstrated that quercetin intervention significantly reverses obesity-related phenotypes through reshaping the overall structure of microbiota, especially boosting colonization of the beneficial gut commensal Akkermansia muciniphila (A. muciniphila). Enrichment of A. muciniphila leads to generate more indole-3-lactic acid (ILA) to upregulate the expression of 12α-hydroxylase (CYP8B1) via fat mass and obesity-associated protein (FTO)/ N6-methyladenosine (m6A)/YTHDF2 manner, thereby facilitating cholesterol converts to cholic acid (CA). CA in turn drastically suppresses lipid accumulation via activating the farnesoid X receptor (FXR) in adipose tissue. This work introduces a novel therapeutic target for addressing obesity and expands upon the current limited understanding of the mediator function of m6A modifications in microorganism-influenced bile acid (BA) metabolism.

Liubao tea extract restrains obesity-related hyperlipidemia via regulation of AMPK/p38/NF-κB pathway and intestinal microbiota

Liubao tea, a traditional dark tea, has gained widespread recognition for various health benefits. In this study, the effects of Liubao tea extract (LTE) on obesity-related hyperlipidemia and the potential mechanism involved were explored. Anti-obesity compounds such as tricetin, isovitexin, tiliroside, etc. in LTE were identified. In high-fat diet mouse models, LTE effectively reduced tissues, organs, and body weight growth, and restored abnormal serum lipid levels. LTE could reverse adipocyte enlargement, lipid accumulation, and hepatic microstructure abnormalities. Notably, LTE reshaped gut microbiota by boosting beneficial bacteria (e.g., Bacteroides, Akkermansia, Psychrobacter) and suppressing harmful bacteria (e.g., Dubosiella, Faecalibaculum). Spearman correlation analysis unveiled significant associations between serum lipid levels, weight gain, LTE dosage, and gut microbiota, underlining the modulatory effects of LTE on metabolic disorders via the regulation of intestinal microbiota. Collectively, LTE could serve as a potential therapy for obesity-related hyperlipidemia prevention.

Effects of Illumination Color on Hypothalamic Appetite-Regulating Gene Expression and Glycolipid Metabolism

Irregular illumination is a newly discovered ambient factor that affects dietary and metabolic processes. However, the effect of the modulation of long-term light exposure on appetite and metabolism remains elusive. Therefore, in this current study, we systematically investigated the effects of up to 8 weeks of exposure to red (RL), green (GL), and white light (WL) environments on appetite, food preferences, and glucose homeostasis in mice on both high-fat and low-fat dietary patterns. It was found that the RL group exacerbated high-fat-induced obesity in mice compared with GL- or WL-treated mice. RL-exposed mice exhibited worsened metabolic profiles, including impaired glucose tolerance/insulin sensitivity, elevated lipid levels, and reduced serum insulin levels. Serological analyses showed that RL exposure resulted in decreased leptin levels and increased levels of orexigenic and hunger hormones in mice. Further qPCR analysis showed that the expression levels of the hypothalamic appetite-related genes NPY and AgRP mRNA were upregulated in RL-treated mice, while the expression level of the appetite suppressor gene POMC mRNA was downregulated. The results of this study will be instructive for the regulation of appetite and metabolism from the perspective of illumination colors.

Pomegranate Peel Extract Mitigates Diarrhea-Predominant Irritable Bowel Syndromes via MAPK and NF-κB Pathway Modulation in Rats

BACKGROUND

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a common chronic functional gastrointestinal disorder that causes diarrheal and intestinal barrier disruptions. Although pomegranate peel extract (PPE) has been reported for the treatment of diarrheal and intestinal inflammation, its effectiveness and mechanisms specifically for the treatment of IBS-D remain unknown.

OBJECTIVES

This study aimed to explore the therapeutic effect of PPE on IBS-D and elucidate its underlying mechanisms.

METHODS

A high-fat diet, restraint stress, and senna gavage were combined to establish a rat model mimicking IBS-D, to evaluate the therapeutic effects of PPE. Network pharmacology analysis, serum medicinal chemistry, and transcriptomics were employed to investigate potential downstream signaling pathways. Findings were further validated through molecular docking and Western blot analysis.

RESULTS

The findings revealed that PPE significantly improved the symptoms of IBS-D, ameliorated intestinal inflammation, and promoted intestinal barrier function. The target genes in the MAPK and NF-κB signaling pathways were significantly enriched and down-regulated. Molecular docking and Western blot assays were performed to verify that PPE had a high affinity for the protein candidates in these pathways, and significantly down-regulated the expression of p-IκB, p-p65, p-JNK, p-p38, and p-ERK1/2.

CONCLUSIONS

The present study is the first to demonstrate that PPE alleviates diarrheal and intestinal damage in IBS-D, potentially by inhibiting MAPK and NF-κB signaling pathways. These findings suggest that PPE may provide a novel therapeutic option for IBS-D.

Dietary Polyphenols, Food Processing and Gut Microbiome: Recent Findings on Bioavailability, Bioactivity, and Gut Microbiome Interplay

Polyphenols are organic chemical compounds naturally present in plants, renowned for their anti-inflammatory, antioxidant, immunomodulatory, anticancer, and cardiovascular protective properties. Their bioactivity and bioavailability can vary widely depending on the methods of food processing and interactions with the gut microbiome. These factors can induce changes in polyphenols, affecting their ability to achieve their intended health benefits. Thus, it is essential to develop and apply food processing methods that optimize polyphenol content while maintaining their bioactivity and bioavailability. This review aims to explore how various food processing techniques affect the quantity, bioactivity, and bioavailability of polyphenols, as well as their interactions with the gut microbiome, which may ultimately determine their health effects.

The regulation of glucose and lipid metabolism through the interaction of dietary polyphenols and polysaccharides via the gut microbiota pathway

The interaction of polyphenols-polysaccharides-gut microbiota to promote health benefits has become a hotspot and direction for precise dietary intervention strategies and foundational research in biomedicine. Both dietary polyphenols and polysaccharides possess biological activities that regulate body health. Single components, due to their inherent structure and physicochemical properties, have a low bioavailability, thus are unable to exert their optimal effects. The compound structure formed by the interaction of polyphenols and polysaccharides can enhance their functional properties, thereby more effectively promoting health benefits and preventing diseases. This review primarily focuses on the roles played by polyphenols and polysaccharides in regulating glucose and lipid metabolism, the improvement of glucose and lipid metabolism through the gut microbial pathway by polyphenols and polysaccharides, and the mechanisms by which polyphenols and polysaccharides interact to regulate glucose and lipid metabolism. A considerable amount of preliminary research has confirmed the regulatory effects of plant polyphenols and polysaccharides on glucose and lipid metabolism. However, studies on the combined effects and mechanisms of these two components are still very limited. This review aims to provide a reference for subsequent research on their interactions and changes in functional properties.

Polyphenols in obesity and weight management: Are they worth further research? An umbrella review

Polyphenols are widely known for their putative antioxidant and anti-inflammatory effects and their potential protective role in several diseases such as type 2 diabetes, cardiovascular disease and cancer. They have also attracted significant interest as 'anti-obesity' agents, although with mechanisms of action that have been exclusively demonstrated in animal and in vitro studies. This umbrella review aims to evaluate current evidence surrounding the role of polyphenols in obesity and weight management and to establish the usefulness of these agents in combatting obesity. A search of systematic reviews and meta-analyses of randomised controlled trials was carried out. Nine systematic reviews (of which eight included a meta-analysis) were included. Evidence of polyphenols' effects on reducing bodyweight is mixed, and where the effects are significant, they are numerically small and unlikely to be of help in reducing bodyweight or preventing weight gain. Future research should focus on establishing the anti-inflammatory and antioxidant effects of polyphenols through well-designed randomised controlled trials. Such research could be more valuable and cost-effective since it has shown potential to improve human health.

Kiwifruit Peel Extract Improves the Alterations in Lipid Metabolism in High-fat Diet-fed Model Rats

Previous studies have demonstrated that the kiwifruit peel, which is usually discarded by consumers and factories, has the highest polyphenol content among all parts of the kiwifruit. To maximize the utilization of these waste resources, the aim of this study was to examine the regulatory effects of polyphenols extracted from kiwifruit peel (KPE) on lipid metabolism and investigate their underlying mechanisms. Thirty-two male Sprague‒Dawley rats were divided into four groups: those fed a normal diet, those fed a high-fat (HF) diet, and those fed a HF diet with a low dose of KPE solution (50 mg/kg) or a high dose of KPE (100 mg/kg) by gavage. The findings of the study revealed that KPE effectively reduced body weight gain and the increases in triglycerides and total cholesterol in serum induced by the HF diet (HFD). Additionally, KPE supplementation led to a significant decrease in hepatic fat accumulation, potentially by increasing hepatic oxidation abilities. Hepatic lipidomics demonstrated that KPE influenced various metabolic pathways, including linoleic acid metabolism, steroid biosynthesis, and the biosynthesis of unsaturated fatty acids in HFD-induced rats, which were associated with the downregulation of FATP2, ACC, FAS, GPAT, DGTA1, DGTA2, and PPARγ expression as well as the upregulation of AMPK, PGC-1α, CPT-1, and PPARα expression. These findings suggest that KPE has considerable regulatory effects in rats with dyslipidaemia, which may provide supporting information for the reuse of kiwifruit peel.

In vitro conversion of ellagic acid to urolithin A by different gut microbiota of urolithin metabotype A

The metabolite urolithin A, a metabolite of the dietary polyphenol ellagic acid (EA), has significant health benefits for humans. However, studies on the gut microbiota involved in ellagic acid metabolism are limited. In this study, we conducted in vitro fermentation of EA using human intestinal microbiome combined with antibiotics (vancomycin, polymyxin B sulfate, and amphotericin B). Liquid chromatography-mass spectrometry (LC-MS/MS) analysis demonstrated that the production capacity of urolithin A by gut microbiota co-treated with polymyxin B sulfate and amphotericin B (22.39 µM) was similar to that of untreated gut microbiota (24.26 µM). Macrogenomics (high-throughput sequencing) was used to analyze the composition and structure of the gut microbiota. The results showed that the abundance of Bifidobacterium longum, Bifidobacterium adolescentis, and Bifidobacterium bifidum in the gut microbiota without antibiotic treatment or co-treated with polymyxin B sulfate and amphotericin B during EA fermentation was higher than that in other antibiotic treatment gut microbiota. Therefore, B. longum, B. adolescentis, and B. bifidum may be new genera involved in the conversion of EA to urolithin A. In conclusion, the study revealed unique interactions between polyphenols and gut microbiota, deepening our understanding of the relationship between phenolic compounds like EA and the gut microbiota. These findings may contribute to the development of gut bacteria as potential probiotics for further development. KEY POINTS: • Intestinal microbiome involved in ellagic acid metabolism. • Gram-positive bacteria in the intestinal microbiome are crucial for ellagic acid metabolism. • Bifidobacterium longum, Bifidobacterium adolescentis, and Bifidobacterium bifidum participate in ellagic acid metabolism.

The Metabolic Syndrome, a Human Disease

This review focuses on the question of metabolic syndrome (MS) being a complex, but essentially monophyletic, galaxy of associated diseases/disorders, or just a syndrome of related but rather independent pathologies. The human nature of MS (its exceptionality in Nature and its close interdependence with human action and evolution) is presented and discussed. The text also describes the close interdependence of its components, with special emphasis on the description of their interrelations (including their syndromic development and recruitment), as well as their consequences upon energy handling and partition. The main theories on MS's origin and development are presented in relation to hepatic steatosis, type 2 diabetes, and obesity, but encompass most of the MS components described so far. The differential effects of sex and its biological consequences are considered under the light of human social needs and evolution, which are also directly related to MS epidemiology, severity, and relations with senescence. The triggering and maintenance factors of MS are discussed, with especial emphasis on inflammation, a complex process affecting different levels of organization and which is a critical element for MS development. Inflammation is also related to the operation of connective tissue (including the adipose organ) and the widely studied and acknowledged influence of diet. The role of diet composition, including the transcendence of the anaplerotic maintenance of the Krebs cycle from dietary amino acid supply (and its timing), is developed in the context of testosterone and β-estradiol control of the insulin-glycaemia hepatic core system of carbohydrate-triacylglycerol energy handling. The high probability of MS acting as a unique complex biological control system (essentially monophyletic) is presented, together with additional perspectives/considerations on the treatment of this 'very' human disease.

Dietary polyphenols maintain homeostasis via regulating bile acid metabolism: a review of possible mechanisms

The synthesis and metabolism of bile acids (BAs) have been implicated in various metabolic diseases, including obesity and diabetes. Dietary polyphenols, as natural antioxidants, play a vital role in synthesizing and metabolizing bile acids. This paper reviews the mechanism of dietary polyphenols involved in bile acid (BA) synthesis and metabolism. The impact of different gut microorganisms on BA profiles is discussed in detail. The regulation of BA metabolism by dietary polyphenols can be divided into two modes: (1) dietary polyphenols directly activate/inhibit farnesol X receptor (FXR) and Takeda G protein-coupled receptor (TGR5); (2) dietary polyphenols regulate BA synthesis and metabolism through changes in intestinal microorganisms. Research on direct activation/inhibition of FXR and TGR5 by polyphenols should be ramped up. In addition, the effect of dietary polyphenols on intestinal microorganisms has been paid more and more attention and has become a target that cannot be ignored.

Exploring the potential mechanism of Rubus corchorifolius L. fruit polyphenol-rich extract in mitigating non-alcoholic fatty liver disease by integration of metabolomics and transcriptomics profiling

Nonalcoholic fatty liver disease (NAFLD), as the commonest chronic liver disease, is accompanied by liver oxidative stress and inflammatory responses. Herein, the extract obtained from Rubus corchorifolius fruits was purified and characterized for its polyphenol composition. The liver protective effect of the purified R. corchorifolius fruit extract (RCE) on mice with high-fat-diet (HFD)-induced NAFLD were investigated, and the potential mechanisms were explored through the integration of transcriptomics and metabolomics. Results showed that the polyphenolic compounds in RCE mainly included (-)-epigallocatechin, procyanidin B2, keracyanin, vanillin, dihydromyricetin, and ellagic acid. In addition, RCE intervention ameliorated liver and mitochondrial damage, which was evidenced by decreased indices of oxidative stress, liver function markers, and lipid profile levels. The liver metabonomics research revealed that RCE intervention affected the metabolic pathways of metabolites, including linoleic acid metabolism, galactose metabolism, alanine, aspartate and glutamate metabolism, retinol metabolism, glycine, serine and threonine metabolism, tryptophan metabolism, aminoacyl-tRNA biosynthesis, riboflavin metabolism, starch and sucrose metabolism, and arachidonic acid metabolism. Additionally, liver transcriptomics research indicated that pathways like fatty acid degradation, circadian rhythm, valine, leucine and isoleucine degradation, primary bile acid biosynthesis, cytokine-cytokine receptor interaction, adipocytokine signaling pathway, glutathione metabolism, lipid and atherosclerosis were significantly enriched. The transcriptomics and metabolomics analysis demonstrated that RCE intervention had significant modulatory effects on the metabolic pathways associated with glycolipid metabolism. Moreover, RT-PCR results verified that RCE intervention regulated liver mRNA levels associated with the inflammatory response. Therefore, our findings suggest that the intake of RCE might be an effective strategy to alleviate liver damage.

A Comprehensive Review of Phytonutrients as a Dietary Therapy for Obesity

Obesity is a complex medical condition mainly caused by eating habits, genetics, lifestyle, and medicine. The present study deals with traditional diets like the Mediterranean diet, Nordic diet, African Heritage diet, Asian diet, and DASH, as these are considered to be sustainable diets for curing obesity. However, the bioavailability of phytonutrients consumed in the diet may vary, depending on several factors such as digestion and absorption of phytonutrients, interaction with other substances, cooking processes, and individual differences. Hence, several phytochemicals, like polyphenols, alkaloids, saponins, terpenoids, etc., have been investigated to assess their efficiencies and safety in the prevention and treatment of obesity. These phytochemicals have anti-obesity effects, mediated via modulation of many pathways, such as decreased lipogenesis, lipid absorption, accelerated lipolysis, energy intake, expenditure, and preadipocyte differentiation and proliferation. Owing to these anti-obesity effects, new food formulations incorporating these phytonutrients were introduced that can be beneficial in reducing the prevalence of obesity and promoting public health.

A Critical Review of Kaempferol in Intestinal Health and Diseases

Kaempferol, a secondary metabolite found in plants, is a naturally occurring flavonoid displaying significant potential in various biological activities. The chemical structure of kaempferol is distinguished by the presence of phenyl rings and four hydroxyl substituents, which make it an exceptional radical scavenger. Most recently, an increasing number of studies have demonstrated the significance of kaempferol in the regulation of intestinal function and the mitigation of intestinal inflammation. The focus of the review will primarily be on its impact in terms of antioxidant properties, inflammation, maintenance of intestinal barrier function, and its potential in the treatment of colorectal cancer and obesity. Future research endeavors should additionally give priority to investigating the specific dosage and duration of kaempferol administration for different pathological conditions, while simultaneously conducting deeper investigations into the comprehensible mechanisms of action related to the regulation of aryl hydrocarbon receptor (AhR). This review intends to present novel evidence supporting the utilization of kaempferol in the regulation of gut health and the management of associated diseases.

Chinese chestnut shell polyphenol extract regulates the JAK2/STAT3 pathway to alleviate high-fat diet-induced, leptin-resistant obesity in mice

Chinese chestnut shell is a by-product of chestnut food processing and is rich in polyphenols. This study sought to investigate the effect of chestnut shell polyphenol extract (CSP) on weight loss and lipid reduction in a 12-week high-fat diet (HFD)-induced murine obesity model. CSP (300 mg per kg body weight) was administered intragastrically daily. AG490, a JAK2 protein tyrosine kinase inhibitor, was also intraperitoneally injected. The results showed that an HFD induced leptin resistance (LR). Compared to corresponding values in the HFD group, CSP treatment improved blood lipid levels, weight, and leptin levels in obese mice (p < 0.01). Additionally, CSP treatment enhanced enzyme activity by improving total antioxidant capacity, attenuating oxidative stress, and reducing fat droplet accumulation and inflammation in the liver, epididymal, and retroperitoneal adipose tissue. CSP also activated the LEPR-JAK2/STAT3-PTP1B-SOCS-3 signal transduction pathway in hypothalamus tissue and improved LR while regulating the expression of proteins related to lipid metabolism (PPARγ, FAS, and LPL) in white adipose tissue in the retroperitoneal cavity. However, the amelioration of lipid metabolism by CSP was dependent on JAK2. Molecular docking simulation further demonstrated the strong binding affinity of procyanidin C1 (-10.3983297 kcal mol^-1) and procyanidin B1 (-9.12686729 kcal mol^-1) to the crystal structure of JAK2. These results suggest that CSP may be used to reduce HFD-induced obesity with potential application as a functional food additive.

The synergic effects and mechanism of KGM-DMY complex in the prevention of obesity and enhancement of fatigue resistance in mice

Dietary fibers (DFs) are normally consumed together with polyphenols. Further, both of them are two kinds of popular functional ingredients. However, studies have shown that the soluble DFs and polyphenols are antagonistic to their bioactivity due to the potential loss of the physical properties that drive their benefits. In this study, konjac glucomannan (KGM), dihydromyricetin (DMY), and KGM-DMY complex were fed to mice on normal chow diet (NCD) and high fat diet (HFD). The body fat content, serum lipid metabolites and time to exhaustion in swimming were compared. It was found that KGM-DMY had synergistic effects on the reduction of serum triglyceride, total glycerol content in HFD-fed mice, and extension of time to exhaustion in swimming in NCD-fed mice. The underlying mechanism was explored by antioxidant enzyme activity measurement, energy production quantification, and gut microbiota 16S rDNA profiling. KGM-DMY synergistically reduced the lactate dehydrogenase activity, malondialdehyde production, and alanine aminotransferase activities after swimming. Moreover, superoxide dismutase activities, glutathione peroxidase activities, glycogen and adenosine triphosphate contents were synergistically enhanced by KGM-DMY complex. In addition, according to gut microbiota gene expression analyses, KGM-DMY enhanced the ratio of Bacteroidota/Firmicutes and the abundance of Oscillospiraceae and Romboutsia. The abundance of Desulfobacterota was also reduced. To our knowledge, this was the first experiment that indicated that the complex of polyphenols and DF have synergistic effects in obesity prevention and fatigue resistance. The study provided a perspective for the formulation of obese preventive nutritional supplement in the food industry.

Hydroxytyrosol attenuates diquat-induced oxidative stress by activating Nrf2 pathway and modulating colonic microbiota in mice

This study was conducted to investigate the antioxidant effects of hydroxytyrosol (HT) administration in diquat (DQ)-challenged mice. The results showed that HT treatment markedly alleviated DQ-induced oxidative stress, which was indicated by the enhanced total antioxidant capacity (T-AOC), increased activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase and decreased malondialdehyde (MDA) concentration in serum. Additionally, HT increased the mRNA expression levels of NF-E2-related factor 2 (Nrf2) and its downstream genes, including NADPH quinone oxidoreductase 1 (NQO1) and catalase (CAT) in the small intestine of DQ-challenged mice. 16S rRNA gene sequencing results showed that HT treatment increased the relative abundance of Firmicutes and Lactobacillus and decreased the relative abundance of Bacteroidetes. Interestingly, Pearson correlation analysis showed that there were strong association between colonic Firmicutes, Lactobacillus, and Bacteroidetes and the activities of serum antioxidant enzymes. Meanwhile, HT significantly enhanced the colonic butyrate concentration in DQ-challenged mice. Additionally, HT treatment decreased the serum metabolites involving in glycerophospholipid metabolism, pentose, and glucuronate interconversions, which were associated with alleviated oxidative stress. These results indicate that oral administration of 100 mg/kg body weight HT alleviates oxidative stress in DQ-challenged mice, which may involve Nrf2 signaling pathways via modulation of colonic microbiota.

Protective effect of rosmarinic acid-rich extract from Trichodesma khasianum Clarke against microbiota dysbiosis in high-fat diet-fed obese mice

Hypertrophy of adipose tissues and dysbiosis are hallmarks of obesity. Although drugs are applied for obesity treatment, side effects limit their use. The anti-obesity capacity of rosmarinic acid (RA) has been documented. Trichodesma khasianum Clarke is an edible RA-rich plant grown in Taiwan. Our previous study found that an 80 % ethanol extract of T. khasianum Clarke leaves (80EETC) ameliorates gastric mucosal damage through its anti-inflammatory, antioxidant, and microbiota modulation abilities. However, the anti-obesity effect of 80EETC remains unclear. Therefore, the objective of this study was to explore the protective effects of low-dose 80EETC (125 mg/kg b.w., 80EETCL) or high-dose 80EETC (250 mg/kg b.w., 80EETCH) on obesity development through gut microbiota modulation in high-fat diet (HFD)-induced C57BL/6 mice. The results showed a high RA content (89.2 ± 7.4 mg/g) in 80EETC. 80EETC administration significantly decreased body weight, body fat ratio, serum lipid levels (TC, TG, and LDL-C), adipose tissue accumulation, malondialdehyde (MDA), and tumor necrosis factor-α (TNF-α) in HFD-fed mice. Furthermore, supplementation with 80EETC reduced the Firmicutes/Bacteroidetes ratio and enhanced the relative abundance of gut microbiota (p_Bacteroidetes, f_Lactobacillus, f_Muribaculaceae, f_Prevotellaceae, g_Lactobacillus, g_Prevotellaceae_NK3B31_group, g_Ruminococcaceae_UCG-013, and g_Ruminococcaceae_UCG-014), which negatively correlated with obesity-related factors such as body weight, energy intake, fat accumulation in adipose tissue, TC, TG, LDL, and MDA. In conclusion, RA-rich 80EETC had a protective effect against obesity development and it has potential in healthy food applications.

Red-fleshed apple flavonoid extract alleviates CCl4-induced liver injury in mice

In recent years, the global incidence of liver damage has increased. Despite the many known health benefits of red-fleshed apple flavonoids, their potential liver-protective effects have not yet been investigated. In this study, we analyzed the composition of red-fleshed apple flavonoid extract (RAFE) by high-performance liquid chromatography (HPLC). We then induced liver damage in mice with carbon tetrachloride (CCl4) and performed interventions with RAFE to analyze its effect on liver damage, using bifendate as a positive control. The results showed that catechin was the most abundant flavonoid in 'XJ4' RAFE (49.346 mg/100 g). In liver-injured mice, the liver coefficients converged to normal levels following RAFE intervention. Moreover, RAFE significantly reduced the enzymatic activity levels of glutamic oxaloacetic transaminase (ALT), glutamic alanine transaminase (AST), and alkaline phosphatase (ALP) in mouse serum. Furthermore, RAFE significantly increased the content or enzyme activity level of total glutathione, total antioxidant capacity, and superoxide dismutase, and significantly decreased the content of malondialdehyde in the liver of mice. In parallel, we performed histopathological observations of mouse livers for each group. The results showed that RAFE restored the pathological changes caused by CCl4 around the central hepatic vein in mice and resulted in tightly bound hepatocytes. The recovery effect of RAFE was dose-dependent in the liver tissue. Regarding intestinal microorganisms, we found that RAFE restored the microbial diversity in liver-injured mice, with a similar microbial composition in the RAFE intervention group and normal group. RAFE reduced the ratio of Firmicutes to Bacteroidetes, increased the levels of probiotic bacteria, such as Lactobacillus acidophilus, and Clostridium, and reduced the levels of harmful bacteria, such as Erysipelothrix Rosenbach. Therefore, RAFE ameliorated CCl4-induced liver damage by modulating the abundance and composition of intestinal microorganisms in mice. In conclusion, RAFE alleviated CCl4-induced liver damage in mice, with H-RAFE (5 mg kg-1) significantly improving liver damage in mice but M-RAFE (1 mg kg-1) significantly improving the imbalance of intestinal microorganisms in mice. Our research suggests that RAFE could be employed for the adjuvant treatment and prevention of liver damage, and may have important applications in food and medicine.

Plum supplementation and lipid profile: a systematic review and meta-analysis of randomised controlled trials

Plums are abundant in bioactive compounds which have been associated with numerous health benefits. In the present study, we aimed at examining the impact of plum supplementation on lipid profile of individuals. Electronic bibliographical databases were searched for relevant randomised clinical trials. Articles meeting our eligibility criteria were included for data extraction and final analysis. Weighted mean difference (WMD) was estimated using a random-effect model. Of the total articles retrieved in the initial search, nine articles were found to be eligible to be included in the analysis. Our results show that plum supplementation significantly improves total cholesterols levels in the unhealthy individuals. Moreover, plum supplementation reduces the LDL-c levels in the pooled sample (WMD = -11⋅52 mg/dl; 95 % CI -21⋅93, -1⋅11, P = 0⋅03, I ² = 98⋅7 %) and also in some of the subgroups of individuals (dried plum, unhealthy subjects, duration more than 8 weeks). Moreover, it had a significant reducing effect on TC levels just in unhealthy subjects. Although plum supplementation did not have any significant impact on serum levels of TG nor HDL-c. Our results show that supplementation with plums is potentially effective in reducing serum total cholesterol and LDL-c.

Dietary Polyphenols in Relation to Gut Microbiota Composition in Saudi Arabian Females

Polyphenols may modulate gut microbiota; however, limited studies have examined this relationship relative to obesity. We aim to investigate the association between polyphenol intake and gut microbiota composition in relation to obesity indices among Saudi Arabian females. This study included 92 adults stratified by body mass index (BMI) into controls (BMI ≥ 18.5−24.9 kg/m2; n = 48) and cases (BMI ≥ 30.0 kg/m2; n = 44), and further divided into high and low polyphenol intake by median intake (252 mg/1000 kcal/day). Fecal samples were collected to analyze the gut microbiota composition via the whole-genome shotgun sequencing technique. Results showed that Flavonifractor plautii and Clostridium bolteae were positively correlated with polyphenol intake in the total sample (r = 0.22, p = 0.03; r = 0.28, p = 0.01, respectively). There were inverse correlations between Blautia wexlerae and polyphenol intake (r = −0.56, p < 0.01) in the case group, and between Bacteroides thetaiotaomicron and polyphenol intake (r = −0.45, p = 0.03) in the control group. Those in the case group with low polyphenol intake, and those with high waist-to-hip ratio (WHR; ≥0.83), showed significantly lower alpha-diversity than those in the control group with normal WHR (<0.83), (p < 0.05). Findings suggest that polyphenols are correlated with specific bacteria and may play an important role in the modulation of gut microbiota and obesity management.

Herbal Tea Essences (HTE) Ameliorate HFD-Induced Obesity

Tea is one of the most popular beverages in the world. The health-promoting effects of tea and its individual constituents, including antiobesity and antihyperlipidaemia effects, have been well accepted. In this study, we evaluated the effects of herbal tea essence (HTE), a commercial product extracted from black tea, on HFD-induced obesity in mice. HTE effectively reduces the gain in body weight and improves glucose tolerance and insulin sensitivity after HFD treatment. HTE inhibits lipid accumulation in the body and reduces serum lipid contents. Furthermore, HTE negatively regulates the expression levels of genes that control lipogenesis and gluconeogenesis and upregulates the expression of genes for lipid β oxidation. The regulatory effects of HTE on these genes may occur through activation of the AKT, IRS-1, and AMPK signalling pathways. Our observations suggest that HTE could be a promising option for nutritional intervention in the treatment of obesity.

Polyphenols in Metabolic Diseases

Polyphenols (PPs) are a large group of phytochemicals containing phenolic rings with two or more hydroxyl groups. They possess powerful antioxidant properties, multiple therapeutic effects, and possible health benefits in vivo and in vitro, as well as reported clinical studies. Considering their free-radical scavenging and anti-inflammatory properties, these substances can be used to treat different kinds of conditions associated with metabolic disorders. Many symptoms of metabolic syndrome (MtS), including obesity, dyslipidemia, atherosclerosis, elevated blood sugar, accelerating aging, liver intoxication, hypertension, as well as cancer and neurodegenerative disorders, are substantially relieved by dietary PPs. The present study explores the bioprotective properties and associated underlying mechanisms of PPs. A detailed understanding of these natural compounds will open up new opportunities for producing unique natural PP-rich dietary and medicinal plans, ultimately affirming their health benefits.

The Effect of Whole-Grain Diet on the Gut Microbiota of the Elderly Individuals

A whole-grain (WG) diet affects human health in multiple ways. However, the effect of WG on the gut microbiota of the elderly individuals is still largely unknown. In this study, WG did not affect the microbial α-diversity but had a profound impact on the microbes' abundance in the elderly individuals. WG increased the abundance of Verrucomicrobia and decreased the abundance of Firmicutes. The prediction of microbial function showed that glucose metabolism and lipid metabolism were inhibited. In addition, the effects of WG on the gut microbiota of normal-weight (NW) and overweight (OW) individuals were different. WG increased Verrucomicrobia in the NW group and decreased Firmicutes in the OW group. Meanwhile, the effect of WG on gut microbiota showed gender characteristics, Firmicutes/Bacteroidetes ratio was decreased in women, while Verrucomicrobia abundance was increased in men. The use of WG could improve the microbial composition and promote the growth of beneficial microbes, which may be beneficial to the health of the elderly individuals.

Identification and Quantification of Urinary Microbial Phenolic Metabolites by HPLC-ESI-LTQ-Orbitrap-HRMS and Their Relationship with Dietary Polyphenols in Adolescents

This study aimed to develop and validate a liquid chromatography/electrospray ionization-linear ion trap quadrupole-Orbitrap-high-resolution mass spectrometry (HPLC/ESI-LTQ-Orbitrap-HRMS) method to identify and quantify urinary microbial phenolic metabolites (MPM), as well as to explore the relationship between MPM and dietary (poly)phenols in Spanish adolescents. A total of 601 spot urine samples of adolescents aged 12.02 ± 0.41 years were analyzed. The quantitative method was validated for linearity, limit of detection, limit of quantification, recovery, intra- and inter-day accuracy and precision, as well as postpreparative stability according to the criteria established by the Association of Official Agricultural Chemists International. A total of 17 aglycones and 37 phase II MPM were identified and quantified in 601 spot urine samples. Phenolic acids were the most abundant urinary MPM, whereas stilbenes, hydroxytyrosol, and enterodiol were the least abundant. Urinary hydroxycoumarin acids (urolithins) were positively correlated with flavonoid and total (poly)phenol intake. An HPLC-ESI-LTQ-Orbitrap-HRMS method was developed and fully validated to quantify MPM. The new method was performed accurately and is suitable for MPM quantification in large epidemiological studies. Urinary lignans and urolithins are proposed as potential biomarkers of grain and nut intake in an adolescent population.

Interactions between Salivary Proteins and Dietary Polyphenols: Potential Consequences on Gastrointestinal Digestive Events

The present review documents the current knowledge and hypotheses on how polyphenols-saliva interactions may modulate the bioaccessibility or bioavailability of nutrients and highlights research prospects in the field. After an updated description of the different classes of dietary polyphenols and their modifications by food processing or digestion, an overview of interactions between salivary proteins and polyphenols (with an emphasis on tannins) is provided. In vitro studies show that the solubility of salivary protein-tannin complexes in gastric conditions depends on the degree of tannin polymerization, while complexes are partly solubilized by bile salts. Salivary proteins-polyphenols interactions may affect digestive processes. For example, polyphenols can bind to and inhibit salivary amylase, with downstream consequences on starch digestion. Some salivary proteins (PRPs) prevent tannin-induced reduced protein digestibility, probably through binding tannins before they interact with digestive proteases. Salivary proteins may also act as scavenger molecules to limit the intestinal uptake of tannins.

Ultrasonic-assisted extraction of polyphenolic compounds from Paederia scandens (Lour.) Merr. Using deep eutectic solvent: optimization, identification, and comparison with traditional methods

Ultrasonic-assisted extraction (UAE) coupled with deep eutectic solvent (DES) is a novel, efficient and green extraction method for phytochemicals. In this study, the effects of 16 DESs coupled with UAE on the extraction rate of polyphenols from Paederia scandens (Lour.) Merr. (P. scandens), an edible and medicinal herb, were investigated. DES synthesised with choline chloride and ethylene glycol at a 1:2 M ratio resulted in the highest extractability. Moreover, the effects of extraction parameters were investigated by using a two-level factorial experiment followed by response surface methodology The optimal parameters (water content in DES of 49.2%, the actual ultrasonic power of 72.4 W, and ultrasonic time of 9.7 min) resulted in the optimal total flavonoid content (TFC) (27.04 mg CE/g DW), ferric-reducing antioxidant power (FRAP) value (373.27 μmol Fe(Ⅱ)E/g DW) and 2,2'-azino-bis(3-ethylbenzthiazoline)-6-sulfonic acid radical (ABTS⁺) value (48.64 μmol TE/g DW), closely matching the experimental results. Furthermore, a comparison study demonstrated that DES-UAE afforded the higher TFC and FRAP value than traditional extraction methods. 36 individual polyphenolic compounds were identified and quantified by ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) in P. scandens extracts, and of which 30 were found in the extracts obtained by DES-UAE. Additionally, DES-UAE afforded the highest sum of individual polyphenolic compound content. These results revealed that DES-UAE enhanced the extraction efficiency for polyphenols and provided a scientific basis for further processing and utilization of P. scandens.

Glycolipid Metabolism and Metagenomic Analysis of the Therapeutic Effect of a Phenolics-Rich Extract from Noni Fruit on Type 2 Diabetic Mice

The phenolics of noni fruit possess antihyperglycemic activity; however, the molecular mechanisms remain unclear. To understand the potential effects it has on type 2 diabetes (T2D), the glycolipid metabolism and gut microbiota regulation of phenolic-rich extracts from noni fruit (NFEs) were investigated. The results indicated that NFE could remarkably ameliorate hyperglycemia, insulin resistance, oxidative stress, and glycolipid metabolism via the adenosine 5'-monophosphate-activated protein kinase (AMPK) pathway in T2D mice. Furthermore, metagenomic sequencing results revealed that NFE intervention modulated the gut microbiota composition in T2D mice, characterized by increased abundance of unclassified_o_Bacteroidales, Alistipes, Prevotella, Lactobacillus, and Akkermansia and decreased abundance of Oscillibacter, Desulfovibrio, and significantly decreased the pathways related to carbohydrate metabolism, translation, amino acid metabolism, and nucleotide metabolism. Taken together, the results provided new evidence that the hypoglycemic and hypolipidemic activities of NFE in T2D were likely attributed to the activation of the liver AMPK pathway and modulation of gut microbiota.

Polyphenols from Fu Brick Tea Reduce Obesity via Modulation of Gut Microbiota and Gut Microbiota-Related Intestinal Oxidative Stress and Barrier Function

Fu brick tea (FBT) is a microbial-fermented tea, which is produced by the solid-state fermentation of tea leaves. Previous studies have proved that FBT aqueous extracts could attenuate obesity and gut microbiota dysbiosis. However, the bioactive components in FBT that contribute to these activities remain unclear. In this study, we aimed to investigate the effects of FBT polyphenols (FBTPs) on obesity, gut microbiota, and gut microbiota-related intestinal oxidative stress and barrier function and to further investigate whether the antiobesity effect of FBTPs was dependent on the alteration of gut microbiota. The results showed that FBTP supplementation effectively attenuated obesity in high-fat diet (HFD)-fed rats. FBTP supplementation improved the intestinal oxidative stress and intestinal barrier function, including intestinal inflammation and the integrity of the intestinal barrier. Furthermore, FBTP intervention significantly attenuated HFD-induced gut microbiota dysbiosis, characterized by increased phylogenetic diversity and decreased Firmicutes/Bacteroidetes ratio. Certain core microbes, including Akkermansia muciniphila, Alloprevotella, Bacteroides, and Faecalibaculum, were also found to be improved by FBTPs. Moreover, the antiobesity effect of FBTPs was gut microbiota-dependent, as demonstrated by a fecal microbiota transplantation experiment. Collectively, we concluded that FBTPs reduced obesity by modulating the gut microbiota and gut microbiota-related intestinal oxidative stress and barrier function. Therefore, FBTPs may be used as prebiotic agents to treat obesity and gut microbiota dysbiosis in obese individuals.

Food phenolics stimulate adipocyte browning via regulating gut microecology

Fat browning has piqued the interest of researchers as a potential target for treating obesity and related metabolic disorders. Recruitment of brown adipocytes leads to enhanced energy dissipation and reduced adiposity, thus facilitating the maintenance of metabolic homeostasis. Evidence is increasing to support the crucial roles of polyphenols and gut microecology in turning fat "brown". However, it is not clear whether the intestinal microecology is involved in polyphenol-mediated regulation of adipose browning, so this concept is worthy of exploration. In this review, we summarize the current knowledge, mostly from studies with murine models, supporting the concept that the effects of food phenolics on brown fat activation and white fat browning can be attributed to their regulatory actions on gut microecology, including microbial community profile, gut metabolites, and gut-derived hormones. Furthermore, the potential underlying pathways involved are also discussed. Basically, understanding gut microecology paves the way to determine the underlying roles and mechanisms of food phenolics in adipose browning.

Interference of dietary polyphenols with potentially toxic amino acid metabolites derived from the colonic microbiota

Each day, varying amounts of undigested or partially digested proteins reach the colon where they are metabolized by the microbiota, resulting in the formation of compounds such as ammonia, p-cresol, skatole, phenol, indole, and hydrogen sulfide (H₂S). In farm animals, the excessive production of these metabolites can affect the quality of meat and milk and is a source of contaminating emissions from animal manure. In humans, their accumulation is potentially harmful, and it has been proposed that they could be involved in the development of pathologies such as colorectal cancer and ulcerative colitis, among others. This review assesses the evidence supporting the use of dietary polyphenols to reduce the production of these metabolites. Most studies have used condensed (proanthocyanidins) or hydrolyzable (ellagitannins and gallotannins) tannins, and have been carried out in farm animals. Several show that the administration of tannins in pigs, chicken, and ruminants decreases the levels of ammonia, p-cresol, skatole, and/or H₂S, improving meat/milk quality and reducing manure odor. Direct application of tannins to manure also decreases ammonia emissions. Few studies were carried out in rats and humans and their results confirm, to a lesser extent, those reported in farm animals. These effects would be due to the capacity of tannins to trap ammonia and H₂S, and to modify the composition of the microbiota, reducing the bacterial populations producing metabolites. In addition, PACs prevent p-cresol and H₂S-induced alterations on intestinal cells in vitro. Tannins, therefore, appear as an interesting tool for improving the quality of animal products, human health, and the harmful emissions associated with breeding.