Low nanomolar caffeic acid attenuates high glucose-induced endothelial dysfunction in primary human umbilical-vein endothelial cells by affecting NF-κB and Nrf2 pathways

Impact of coffee and its bioactive compounds on the risks of type 2 diabetes and its complications: A comprehensive review

BACKGROUND

Coffee beans have a long history of use as traditional medicine by various indigenous people. Recent focus has been given to the health benefits of coffee beans and its bioactive compounds. Research on the bioactivities, applications, and effects of processing methods on coffee beans' phytochemical composition and activities has been conducted extensively. The current review attempts to provide an update on the biological effects of coffee on type 2 diabetes (T2D) and its comorbidities.

METHODS

Comprehensive literature search was carried out on peer-reviewed published data on biological activities of coffee on in vitro, in vivo and epidemiological research results published from January 2015 to December 2022, using online databases such as PubMed, Google Scholar and ScienceDirect for our searches.

RESULTS

The main findings were: firstly, coffee may contribute to the prevention of oxidative stress and T2D-related illnesses such as cardiovascular disease, retinopathy, obesity, and metabolic syndrome; secondly, consuming up to 400 mg/day (1-4 cups per day) of coffee is associated with lower risks of T2D; thirdly, caffeine consumed between 0.5 and 4 h before a meal may inhibit acute metabolic rate; and finally, both caffeinated and decaffeinated coffee are associated with reducing the risks of T2D.

CONCLUSION

Available evidence indicates that long-term consumption of coffee is associated with decreased risk of T2D and its complications as well as decreased body weight. This has been attributed to the consumption of coffee with the abundance of bioactive chemicals.

Caffeic acid and its derivative caffeic acid phenethyl ester as potential therapeutic compounds for cardiovascular diseases: A systematic review

Cardiovascular diseases (CVDs) contribute to major public health issues. Some studies have found that caffeic acid (CA) and caffeic acid phenethyl ester (CAPE) may effectively prevent or treat CVDs. However, there is a major need to sum up our current understanding of the possible beneficial or detrimental effects of CA and CAPE on CVDs and related mechanisms. Therefore, this study aimed to summarize the data on this topic. A methodical search was carried out on key databases, including Pubmed, Google Scholar, Scopus, and Web of Science, from the beginning to June 2024. Studies were then assessed for eligibility based on inclusion and exclusion criteria. Treatment with CA and CAPE significantly and positively affected cardiovascular health in various aspects, including atherosclerotic diseases, myocardial infarction, hypertension, cardiac arrhythmias, and hypercoagulation state. Several mechanisms were proposed to mediate these effects, including transcription factors and signaling pathways associated with antioxidant, cytostatic, and anti-inflammatory processes. CA and CAPE were found to have several beneficial effects via multiple mechanisms during the prevention and treatment of various CVDs. However, these promising effects were only reported through in vitro and animal studies, which reinforces the need for further evaluation of these effects via human clinical investigations.

Gut microbiota: a superior operator for dietary phytochemicals to improve atherosclerosis

Mounting evidence implicates the gut microbiota as a possible key susceptibility factor for atherosclerosis (AS). The employment of dietary phytochemicals that strive to target the gut microbiota has gained scientific support for treating AS. This study conducted a general overview of the links between the gut microbiota and AS, and summarized available evidence that dietary phytochemicals improve AS via manipulating gut microbiota. Then, the microbial metabolism of several dietary phytochemicals was summarized, along with a discussion on the metabolites formed and the biotransformation pathways involving key gut bacteria and enzymes. This study additionally focused on the anti-atherosclerotic potential of representative metabolites from dietary phytochemicals, and investigated their underlying molecular mechanisms. In summary, microbiota-dependent dietary phytochemical therapy is a promising strategy for AS management, and knowledge of "phytochemical-microbiota-biotransformation" may be a breakthrough in the search for novel anti-atherogenic agents.

Food Polyphenols as Preventive Medicine

Reactive oxygen species (ROS) are the initiators in foods and in the stomach of oxidized dietary lipids, proteins, and lipid-oxidation end-products (ALEs), inducing in humans the development of several chronic diseases and cancer. Epidemiological, human clinical and animal studies supported the role of dietary polyphenols and derivatives in prevention of development of such chronic diseases. There is much evidence that polyphenols/derivatives at the right timing and concentration, which is critical, acts mostly in the aerobic stomach and generally in the gastrointestinal tract as reducing agents, scavengers of free radicals, trappers of reactive carbonyls, modulators of enzyme activity, generators of beneficial gut microbiota and effectors of cellular signaling. In the blood system, at low concentration, they act as generators of electrophiles and low concentration of H2O2, acting mostly as cellular signaling, activating the PI3K/Akt-mediated Nrf2/eNOS pathways and inhibiting the inflammatory transcription factor NF-κB, inducing the cells, organs and organism for eustress, adaptation and surviving.

Chlorogenic acid as an indispensible partner of caffeic acid in coffee via selective regulation of prooxidative actions of caffeic acid

Chlorogenic acid (CGA) and caffeic acid (CA) are two major phenolic acids in coffee. Though the International Agency for Research on Cancer has classified CA as a Group2B carcinogen, coffee consumption seems generally safe within the usual levels of intake and is more likely to benefit health than to harm it. We thus speculated that CGA may effectively suppress the carcinogenic potential of CA. In a molar ratio achievable in vivo, this study shows that CGA can inhibit (i) copper reduction caused by CA, (ii) CA oxidation caused by copper, (iii) the formation of hydroxyl radicals by CA and copper, and (iv) DNA damage induced by CA, quercetin or (-)-epigallocatechin-3-gallate in the presence of copper. CA tends to undergo autoxidation to produce hydrogen peroxide and quinone, which further reacts with proteins to form quinoproteins. This autoxidation at a tolerable level normally induces beneficial adaptive responses. This study shows that CGA is less efficient than CA in producing hydrogen peroxide and quinoprotein; however, together they synergistically produce hydrogen peroxide and quinoprotein in vitro at a molar ratio achievable in vivo. In conclusion, CGA can selectively regulate the prooxidant activities of CA depending on whether copper is involved or not. CGA could be viewed as an indispensable partner of CA in coffee, given its dual role in suppressing the carcinogenic potential of CA and boosting CA autoxidation which is beneficial for disease prevention.

Anthocyanins and Vascular Health: A Matter of Metabolites

Anthocyanins are a subgroup of flavonoid polyphenols previously investigated for improving cardiovascular health and preventing the development of endothelial dysfunction. However, their poor bioavailability raises the question of whether the observed biological activity is due to their metabolites. Phenolic metabolites can reach higher plasma concentrations and can persist in the circulation for periods much longer than their original anthocyanin form; therefore, the biological activity and health promoting effects of anthocyanins may differ from their metabolites. To address this, recent studies have facilitated different cell models, in vivo studies and explored physiologically relevant concentrations to better understand their mechanisms of action. The criteria were chosen based on previous reports demonstrating that anthocyanins can improve endothelial function via modulation of the Akt-endothelial nitric oxide synthase pathway and transcription factors Nrf2 and NF-κB, which made it critical to assess the phenolic metabolites' modes of action via these pathways. This review demonstrates how phenolic metabolites differ in bioactivity from their precursor anthocyanin, demonstrating improved endothelial function in response to inflammatory mediators at concentrations that are tolerated in vivo. The review highlights the crucial need for further studies to focus on improving the bioavailability of metabolites in isolation and explore the effect of metabolites in mixtures.

Cyanidin-3-O-glucoside protects intestinal epithelial cells from palmitate-induced lipotoxicity

CONTEXT

Increased free fatty acids (FFAs) levels, typical in obesity condition, can contribute to systemic lipotoxicity and inflammation adversely influencing Inflammatory Bowel Disease development and progression. Anthocyanins possess health promoting properties mainly associated to the induction of Nrf2-regulated cytoprotective proteins.

OBJECTIVE

Using a novel experimental model, we evaluated the in vitro intracellular mechanisms involved in FFAs modulation of intestinal epithelial lipotoxicity and the protective effects of cyanidin-3-O-glucoside (C3G) in Caco-2 cells.

RESULTS

Caco-2 exposed to palmitic acid (PA) in the serosal (basolateral) side showed a combined state of epithelial inflammation, inducing NF-κB pathway and downstream cytokines, that was reverted by C3G apical pre-treatment. In addition, PA altered intracellular redox status and induced reactive oxygen species that were reduced by C3G via the redox-sensitive Nrf2 signalling.

DISCUSSION AND CONCLUSION

Results suggest that anti-inflammatory properties of anthocyanins, mediated by Nrf2, could represent an interesting tool for intestinal inflammatory disorders.

Caffeic Acid and Diseases-Mechanisms of Action

Caffeic acid belongs to the polyphenol compounds we consume daily, often in the form of coffee. Even though it is less explored than caffeic acid phenethyl ester, it still has many positive effects on human health. Caffeic acid can affect cancer, diabetes, atherosclerosis, Alzheimer's disease, or bacterial and viral infections. This review focuses on the molecular mechanisms of how caffeic acid achieves its effects.

Natural polyphenols: a potential prevention and treatment strategy for metabolic syndrome

Metabolic syndrome (MS) is the term for a combination of hypertension, dyslipidemia, insulin resistance, and central obesity as factors leading to cardiovascular and metabolic disease. Epidemiological investigation has shown that polyphenol intake is negatively correlated with the incidence of MS. Natural polyphenols are widely found in cocoa beans, tea, vegetables, fruits, and some Chinese herbal medicines; they are a class of plant compounds containing a variety of phenolic structural units, which are potent antioxidants and anti-inflammatory agents in plants. Polyphenols are composed of flavonoids (such as flavanols, anthocyanidins, anthocyanins, isoflavones, etc.) and non-flavonoids (such as phenolic acids, stilbenes, and lignans). Modern pharmacological studies have proved that polyphenols can reduce blood pressure, improve lipid metabolism, lower blood glucose, and reduce body weight, thereby preventing and improving MS. Due to the unique characteristics and potential development and application value of polyphenols, this review summarizes some natural polyphenols that could treat MS, including their chemical properties, plant sources, and pharmacological action against MS, to provide a basis for the further study of polyphenols in MS.

Can coffee silverskin be a useful tool to fight metabolic syndrome?

Coffee is one of the most consumed products in the world, and its by-products are mainly discarded as waste. In order to solve this problem and in the context of a sustainable industrial attitude, coffee by-products have been studied concerning their chemical and nutritional features for a potential application in foodstuffs or dietary supplements. Under this perspective, coffee silverskin, the main by-product of coffee roasting, stands out as a noteworthy source of nutrients and remarkable bioactive compounds, such as chlorogenic acids, caffeine, and melanoidins, among others. Such compounds have been demonstrating beneficial health properties in the context of metabolic disorders. This mini-review compiles and discusses the potential health benefits of coffee silverskin and its main bioactive components on metabolic syndrome, highlighting the main biochemical mechanisms involved, namely their effects upon intestinal sugar uptake, glucose and lipids metabolism, oxidative stress, and gut microbiota. Even though additional research on this coffee by-product is needed, silverskin can be highlighted as an interesting source of compounds that could be used in the prevention or co-treatment of metabolic syndrome. Simultaneously, the valorization of this by-product also responds to the sustainability and circular economy needs of the coffee chain.

Orphan GPR26 Counteracts Early Phases of Hyperglycemia-Mediated Monocyte Activation and Is Suppressed in Diabetic Patients

Diabetes is the ninth leading cause of death, with an estimated 1.5 million deaths worldwide. Type 2 diabetes (T2D) results from the body’s ineffective use of insulin and is largely the result of excess body weight and physical inactivity. T2D increases the risk of cardiovascular diseases, retinopathy, and kidney failure by two-to three-fold. Hyperglycemia, as a hallmark of diabetes, acts as a potent stimulator of inflammatory condition by activating endothelial cells and by dysregulating monocyte activation. G-protein couple receptors (GPCRs) can both exacerbate and promote inflammatory resolution. Genome-wide association studies (GWAS) indicate that GPCRs are differentially regulated in inflammatory and vessel cells from diabetic patients. However, most of these GPCRs are orphan receptors, for which the mechanism of action in diabetes is unknown. Our data indicated that orphan GPCR26 is downregulated in the PBMC isolated from T2D patients. In contrast, GPR26 was initially upregulated in human monocytes and PBMC treated with high glucose (HG) levels and then decreased upon chronic and prolonged HG exposure. GPR26 levels were decreased in T2D patients treated with insulin compared to non-insulin treated patients. Moreover, GPR26 inversely correlated with the BMI and the HbA1c of diabetic compared to non-diabetic patients. Knockdown of GPR26 enhanced monocyte ROS production, MAPK signaling, pro-inflammatory activation, monocyte adhesion to ECs, and enhanced the activity of Caspase 3, a pro-apoptotic molecule. The same mechanisms were activated by HG and exacerbated when GPR26 was knocked down. Hence, our data indicated that GPR26 is initially activated to protect monocytes from HG and is inhibited under chronic hyperglycemic conditions.

Treatment of Gastrointestinal Disorders-Plants and Potential Mechanisms of Action of Their Constituents

The worldwide prevalence of gastrointestinal diseases is about 40%, with standard pharmacotherapy being long-lasting and economically challenging. Of the dozens of diseases listed by the Rome IV Foundation criteria, for five of them (heartburn, dyspepsia, nausea and vomiting disorder, constipation, and diarrhoea), treatment with herbals is an official alternative, legislatively supported by the European Medicines Agency (EMA). However, for most plants, the Directive does not require a description of the mechanisms of action, which should be related to the therapeutic effect of the European plant in question. This review article, therefore, summarizes the basic pharmacological knowledge of synthetic drugs used in selected functional gastrointestinal disorders (FGIDs) and correlates them with the constituents of medicinal plants. Therefore, the information presented here is intended as a starting point to support the claim that both empirical folk medicine and current and decades-old treatments with official herbal remedies have a rational basis in modern pharmacology.

In Vitro Protective Effects of a Standardized Extract From Cynara Cardunculus L. Leaves Against TNF-α-Induced Intestinal Inflammation

Inflammatory bowel disease (IBD) represents a group of progressive disorders characterized by recurrent chronic inflammation of the gut. New unconventional therapies based on plant derived compounds capable of preventing and/or reducing acute or chronic inflammation could represent a valid alternative for the treatment or prevention of IBDs. Cynara cardunculus L. leaves, considered a food-waste suitable as a rich source of bioactive polyphenols including luteolin and chlorogenic acid, has been reported for its positive effects in digestive tract. The aim of the present work was to evaluate the in vitro molecular mechanisms of beneficial effects of a standardized polyphenol-rich extract obtained from the leaves of Cynara cardunculus L (CCLE) against acute intestinal inflammation induced by TNF-α on intestinal epithelial Caco-2 cells. CCLE prevented TNF-α-induced NF-κB inflammatory pathway and the overexpression of IL-8 and COX-2. In addition, CCLE was able to improve basal intracellular antioxidant power in both TNF-α-unexposed or -exposed Caco-2 cells and this effect was associated to the activation of Nrf2 pathway, a master regulator of redox homeostasis affecting antioxidant and phase II detoxifying genes, stimulating an adaptive cellular response. In conclusion, our data clearly evidenced that, although considered a waste, Cynara cardunculus leaves may be used to obtain extracts rich in bioactive polyphenols potentially useful for prevention and treatment of inflammatory intestinal diseases.

The Role of NRF2 in Obesity-Associated Cardiovascular Risk Factors

The raising prevalence of obesity is associated with an increased risk for cardiovascular diseases (CVDs), particularly coronary artery disease (CAD), and heart failure, including atrial fibrillation, ventricular arrhythmias and sudden death. Obesity contributes directly to incident cardiovascular risk factors, including hyperglycemia or diabetes, dyslipidemia, and hypertension, which are involved in atherosclerosis, including structural and functional cardiac alterations, which lead to cardiac dysfunction. CVDs are the main cause of morbidity and mortality worldwide. In obesity, visceral and epicardial adipose tissue generate inflammatory cytokines and reactive oxygen species (ROS), which induce oxidative stress and contribute to the pathogenesis of CVDs. Nuclear factor erythroid 2-related factor 2 (NRF2; encoded by Nfe2l2 gene) protects against oxidative stress and electrophilic stress. NRF2 participates in the regulation of cell inflammatory responses and lipid metabolism, including the expression of over 1000 genes in the cell under normal and stressed environments. NRF2 is downregulated in diabetes, hypertension, and inflammation. Nfe2l2 knockout mice develop structural and functional cardiac alterations, and NRF2 deficiency in macrophages increases atherosclerosis. Given the endothelial and cardiac protective effects of NRF2 in experimental models, its activation using pharmacological or natural products is a promising therapeutic approach for obesity and CVDs. This review provides a comprehensive summary of the current knowledge on the role of NRF2 in obesity-associated cardiovascular risk factors.

Activation of Nrf2/HO-1 signaling: An important molecular mechanism of herbal medicine in the treatment of atherosclerosis via the protection of vascular endothelial cells from oxidative stress

Introduction

Recently, Nrf2/HO-1 has received extensive attention as the main regulatory pathway of intracellular defense against oxidative stress and is considered an ideal target for alleviating endothelial cell (EC) injury.

Objectives

This paper aimed to summarized the natural monomers/extracts that potentially exert protective effects against oxidative stress in ECs.

Methods

A literature search was carried out regarding our topic with the keywords of “atherosclerosis” or “Nrf2/HO-1” or “vascular endothelial cells” or “oxidative stress” or “Herbal medicine” or “natural products” or “natural extracts” or “natural compounds” or “traditional Chinese medicines” based on classic books of herbal medicine and scientific databases including Pubmed, SciFinder, Scopus, the Web of Science, GoogleScholar, BaiduScholar, and others. Then, we analyzed the possible molecular mechanisms for different types of natural compounds in the treatment of atherosclerosis via the protection of vascular endothelial cells from oxidative stress. In addition, perspectives for possible future studies are discussed.

Results

These agents with protective effects against oxidative stress in ECs mainly include phenylpropanoids, flavonoids, terpenoids, and alkaloids. Most of these agents alleviate cell apoptosis in ECs due to oxidative stress, and the mechanisms are related to Nrf2/HO-1 signaling activation. However, despite continued progress in research on various aspects of natural agents exerting protective effects against EC injury by activating Nrf2/HO-1 signaling, the development of new drugs for the treatment of atherosclerosis (AS) and other CVDs based on these agents will require more detailed preclinical and clinical studies.

Conclusion

Our present paper provides updated information of natural agents with protective activities on ECs against oxidative stress by activating Nrf2/HO-1. We hope this review will provide some directions for the further development of novel candidate drugs from natural agents for the treatment of AS and other CVDs.

Polyphenols: Potential anti-inflammatory agents for treatment of metabolic disorders

Ample evidence highlights the potential benefits of polyphenols in health status especially in obesity-related metabolic disorders such as insulin resistance, type 2 diabetes, and cardiovascular diseases. Mechanistically, due to the key role of "Metainflammation" in the pathomechanism of metabolic disorders, recently much focus has been placed on the properties of polyphenols in obesity-related morbidities. This narrative review summarizes the current knowledge on the role of polyphenols, including genistein, chlorogenic acid, ellagic acid, caffeic acid, and silymarin in inflammatory responses pertinent to metabolic disorders and discusses the implications of this evidence for future directions. This review provides evidence that the aforementioned polyphenols benefit health status in metabolic disorders via direct and indirect regulation of a variety of target proteins involved in inflammatory signaling pathways. However, due to limitations of the in vitro and in vivo studies and also the lack of long-term human clinical trials studies, further high-quality investigations are required to firmly establish the clinical efficacy of the polyphenols for the prevention and management of metabolic disorders.

Influence of the Bioactive Diet Components on the Gene Expression Regulation

Diet bioactive components, in the concept of nutrigenetics and nutrigenomics, consist of food constituents, which can transfer information from the external environment and influence gene expression in the cell and thus the function of the whole organism. It is crucial to regard food not only as the source of energy and basic nutriments, crucial for living and organism development, but also as the factor influencing health/disease, biochemical mechanisms, and activation of biochemical pathways. Bioactive components of the diet regulate gene expression through changes in the chromatin structure (including DNA methylation and histone modification), non-coding RNA, activation of transcription factors by signalling cascades, or direct ligand binding to the nuclear receptors. Analysis of interactions between diet components and human genome structure and gene activity is a modern approach that will help to better understand these relations and will allow designing dietary guidances, which can help maintain good health.

Natural Polyphenols in Metabolic Syndrome: Protective Mechanisms and Clinical Applications

Metabolic syndrome (MetS) is a chronic disease, including abdominal obesity, dyslipidemia, hyperglycemia, and hypertension. It should be noted that the occurrence of MetS is closely related to oxidative stress-induced mitochondrial dysfunction, ectopic fat accumulation, and the impairment of the antioxidant system, which in turn further aggravates the intracellular oxidative imbalance and inflammatory response. As enriched anti-inflammatory and antioxidant components in plants, natural polyphenols exhibit beneficial effects, including improving liver fat accumulation and dyslipidemia, reducing blood pressure. Hence, they are expected to be useful in the prevention and management of MetS. At present, epidemiological studies indicate a negative correlation between polyphenol intake and MetS incidence. In this review, we summarized and discussed the most promising natural polyphenols (including flavonoid and non-flavonoid drugs) in the precaution and treatment of MetS, including their anti-inflammatory and antioxidant properties, as well as their regulatory functions involved in glycolipid homeostasis.

Coffee and Lower Risk of Type 2 Diabetes: Arguments for a Causal Relationship

Prospective epidemiological studies concur in an association between habitual coffee consumption and a lower risk of type 2 diabetes. Several aspects of these studies support a cause–effect relationship. There is a dependency on daily coffee dose. Study outcomes are similar in different regions of the world, show no differences between sexes, between obese versus lean, young versus old, smokers versus nonsmokers, regardless of the number of confounders adjusted for. Randomized controlled intervention trials did not find a consistent impact of drinking coffee on acute metabolic control, except for effects of caffeine. Therefore, lowering of diabetes risk by coffee consumption does not involve an acute effect on the post-meal course of blood glucose, insulin or insulin resistance. Several studies in animals and humans find that the ingestion of coffee phytochemicals induces an adaptive cellular response characterized by upregulation and de novo synthesis of enzymes involved in cell defense and repair. A key regulator is the nuclear factor erythroid 2-related factor 2 (Nrf2) in association with the aryl hydrocarbon receptor, AMP-activated kinase and sirtuins. One major site of coffee actions appears to be the liver, causing improved fat oxidation and lower risk of steatosis. Another major effect of coffee intake is preservation of functional beta cell mass via enhanced mitochondrial function, lower endoplasmic reticulum stress and prevention or clearance of aggregates of misfolded proinsulin or amylin. Long-term preservation of proper liver and beta cell function may account for the association of habitual coffee drinking with a lower risk of type 2 diabetes, rather than acute improvement of metabolic control.

Hyperglycemic Condition Causes Pro-Inflammatory and Permeability Alterations Associated with Monocyte Recruitment and Deregulated NFκB/PPARγ Pathways on Cerebral Endothelial Cells: Evidence for Polyphenols Uptake and Protective Effect

Hyperglycemia alters the function of cerebral endothelial cells from the blood-brain barrier, increasing the risk of cerebrovascular complications during diabetes. This study evaluated the protective effect of polyphenols on inflammatory and permeability markers on bEnd3 cerebral endothelial cells exposed to high glucose concentration. Results show that hyperglycemic condition increased nuclear factor kappa B (NFκB) activity, deregulated the expression of interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), cyclooxygenase-2 (COX-2), inducible nitric oxide synthase (iNOS), interleukin-10 (IL-10) and endothelial-leukocyte adhesion molecule (E-selectin) genes, raised MCP-1 secretion and elevated monocyte adhesion and transendothelial migration. High glucose decreased occludin, claudin-5, zona occludens-1 (ZO-1) and zona occludens-2 (ZO-2) tight junctions production and altered the endothelial permeability. Characterized polyphenolic extracts from the French medicinal plants Antirhea borbonica, Ayapana triplinervis, Dodonaea viscosa and Terminalia bentzoe, and their major polyphenols quercetin, caffeic, chlorogenic and gallic acids limited the pro-inflammatory and permeability alterations caused by high glucose. Peroxisome proliferator-activated receptor gamma (PPARγ) agonist also attenuated these damages while PPARγ antagonist aggravated them, suggesting PPARγ protective action. Interestingly, polyphenols improved PPARγ gene expression lowered by high glucose. Moreover, polyphenols were detected at the intracellular level or membrane-bound to cells, with evidence for breast cancer resistance protein (BCRP) efflux transporter role. Altogether, these findings emphasize the ability of polyphenols to protect cerebral endothelial cells in hyperglycemic condition and their relevance for pharmacological strategies aiming to limit cerebrovascular disorders in diabetes.

Natural Nrf2 Activators from Juices, Wines, Coffee, and Cocoa

Juices, wine, coffee, and cocoa are rich sources of natural polyphenolic compounds that have potent antioxidant activities proven by in vitro and in vivo studies. These polyphenolic compounds quench reactive oxygen and nitrogen species (RONS) or reactive free radicals and act as natural antioxidants which are also able to protect against reactive oxygen species (ROS)-mediated oxidative damage, which elevates cellular antioxidant capacity to induce antioxidant defense mechanisms by modulating transcription factors. Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is a transcription factor encoded in humans. It is activated as a result of oxidative stress and induces the expression of its target genes. This is one of the most important cellular defense mechanisms against oxidative stress. However, the oxidative stress alone is not enough to activate Nrf2. Hence phytochemicals, especially polyphenolics, act as natural Nrf2 activators. Herein, this review discusses the natural products identified in juices, coffee, cocoa and wines that modulate Nrf2 activity in cellular systems.

Angiopoietin-like 2 is a potential biomarker for diabetic foot patients

BACKGROUND

Circulating angiopoietin-like 2 (ANGPTL2) protein levels are known to be significantly increased in numerous chronic inflammatory diseases and are associated with the diagnosis and/or prognosis of cardiovascular diseases, diabetes, chronic kidney disease, and various types of cancers. However, no data regarding the relationship between ANGPTL2 and diabetic foot ulcers (DFUs) are available. Here, we explored the potential link between ANGPTL2 and DFUs.

METHODS

A total of 68 participants with type 2 diabetes mellitus (T2DM) were recruited, including 28 patients with DFU and 40 diabetic patients without DFUs. The clinical characteristics of T2DM patients with and without DFUs were compared. Serum concentrations of ANGPTL2 and VEGF were measured using enzyme-linked immunosorbent assay (ELISA) kits. The correlations between ANGPTL2 and clinical variables were analyzed. Multiple linear regression and logistic regression models were constructed to test the associations between ANGPTL2 and the severity and presence of DFUs.

RESULTS

Serum levels of ANGPTL2 were higher in patients with DFUs than those in diabetic controls. Serum ANGPTL2 levels were higher in the advanced stages of DFUs. Spearman correlation analysis revealed strong positive associations of ANGPTL2 with CRP, VEGF and ESR in all subjects. In addition, serum ANGPTL2 was still positively correlated with DFUs stage after adjusting the risk factors. After adjusting for age, sex, HbA1C and duration of diabetes, ANGPTL2 was found to be independently associated with the presence of DFUs.

CONCLUSIONS

Circulating ANGPTL2 levels are an independent risk factor for DFUs. This suggests that ANGPTL2 may play important roles in the development of DFUs, a possibility that needs to investigated in prospective studies.

Polyphenols by Generating H2O2, Affect Cell Redox Signaling, Inhibit PTPs and Activate Nrf2 Axis for Adaptation and Cell Surviving: In Vitro, In Vivo and Human Health

Human health benefits from different polyphenols molecules consumption in the diet, derived mainly by their common activities in the gastrointestinal tract and at the level of blood micro-capillary. In the stomach, intestine and colon, polyphenols act as reducing agents preventing lipid peroxidation, generation and absorption of AGEs/ALEs (advanced glycation end products/advanced lipid oxidation end products) and postprandial oxidative stress. The low absorption of polyphenols in blood does not support their activity as antioxidants and their mechanism of activity is not fully understood. The results are from in vitro, animal and human studies, detected by relevant oxidative stress markers. The review carries evidences that polyphenols, by generating H₂O₂ at nM concentration, exogenous to cells and organs, act as activators of signaling factors increasing cell Eustress. When polyphenols attain high concentration in the blood system, they generate H₂O₂ at µM concentration, acting as cytotoxic agents and Distress. Pre-treatment of cells or organisms with polyphenols, by generating H₂O₂ at low levels, inhibits cellular PTPs (protein tyrosine phosphatases), inducing cell signaling through transcription of the Nrf2 (nuclear factor erythroid 2-related factor 2) axis of adaptation and protection to oxidation stress. Polyphenols ingestion at the right amount and time during the meal acts synergistically at the level of the gastrointestinal tract (GIT) and blood system, for keeping the redox homeostasis in our organism and better balancing human health.

Cyanidin-3-O-glucoside restores insulin signaling and reduces inflammation in hypertrophic adipocytes

Obesity is a metabolic disorder characterized by excess adipose tissue, macrophages infiltration, and inflammation which in turn lead to insulin-resistance. Epidemiological evidences reported that anthocyanins possess not only high antioxidant and antiinflammatory activities, but also improve metabolic complications associated with obesity. The aim of this work was to evaluate the in vitro beneficial effects of cyanidin-3-O-glucoside (C3G) in counteracting inflammation and insulin-resistance in 3T3-L1 hypertrophic adipocytes exposed to palmitic acid (PA). In the present study murine 3T3-L1 adipocytes were pretreated with C3G for 24 h and then exposed to palmitic acid (PA) for 24 h. Real-time PCR, western blotting analysis and Oil Red O staining were applied for investigating the mechanism involved in adipocytes dysfunction. C3G pretreatment reduced lipid accumulation, PPARγ pathway and NF-κB pathway induced by PA in murine adipocytes. In addition, our data demonstrated that PA reduced insulin signaling via IRS-1 Ser³⁰⁷phosphorylation while C3G dose-dependently improved insulin sensitivity restoring IRS-1/PI3K/Akt pathway. Furthermore, C3G improved adiponectin mRNA levels altered by PA in 3T3-L1 murine and SGBS human adipocytes. Herein reported data demonstrate that C3G ameliorated adipose tissue dysfunction, thus suggesting new potential roles for this compound of nutritional interest in the prevention of pathological conditions linked to obesity.

Health Effects of Coffee: Mechanism Unraveled?

The association of habitual coffee consumption with a lower risk of diseases, like type 2 diabetes mellitus, chronic liver disease, certain cancer types, or with reduced all-cause mortality, has been confirmed in prospective cohort studies in many regions of the world. The molecular mechanism is still unresolved. The radical-scavenging and anti-inflammatory activity of coffee constituents is too weak to account for such effects. We argue here that coffee as a plant food has similar beneficial properties to many vegetables and fruits. Recent studies have identified a health promoting mechanism common to coffee, vegetables and fruits, i.e., the activation of an adaptive cellular response characterized by the upregulation of proteins involved in cell protection, notably antioxidant, detoxifying and repair enzymes. Key to this response is the activation of the Nrf2 (Nuclear factor erythroid 2-related factor-2) system by phenolic phytochemicals, which induces the expression of cell defense genes. Coffee plays a dominant role in that regard because it is the major dietary source of phenolic acids and polyphenols in the developed world. A possible supportive action may be the modulation of the gut microbiota by non-digested prebiotic constituents of coffee, but the available data are still scarce. We conclude that coffee employs similar pathways of promoting health as assumed for other vegetables and fruits. Coffee beans may be viewed as healthy vegetable food and a main supplier of dietary phenolic phytochemicals.

Protective Effects of Antioxidant Polyphenols against Hyperglycemia-Mediated Alterations in Cerebral Endothelial Cells and a Mouse Stroke Model

SCOPE

Hyperglycemia alters cerebral endothelial cell and blood-brain barrier functions, aggravating cerebrovascular complications such as stroke during diabetes. Redox and inflammatory changes play a causal role. This study evaluates polyphenol protective effects in cerebral endothelial cells and a mouse stroke model during hyperglycemia.

METHODS AND RESULTS

Murine bEnd.3 cerebral endothelial cells and a mouse stroke model are exposed to a characterized, polyphenol-rich extract of Antirhea borbonica or its predominant constituent caffeic acid, during hyperglycemia. Polyphenol effects on redox, inflammatory and vasoactive markers, infarct volume, and hemorrhagic transformation are determined. In vitro, polyphenols improve reactive oxygen species levels, Cu/Zn superoxide dismutase activity, and both NAPDH oxidase 4 and nuclear factor erythroid 2-related factor 2 (Nrf2) gene expression deregulated by high glucose. Polyphenols reduce Nrf2 nuclear translocation and counteract nuclear factor-ĸappa B activation, interleukin-6 secretion, and the altered production of vasoactive markers mediated by high glucose. In vivo, polyphenols reduce cerebral infarct volume and hemorrhagic transformation aggravated by hyperglycemia. Polyphenols attenuate redox changes, increase vascular endothelial-Cadherin production, and decrease neuro-inflammation in the infarcted hemisphere.

CONCLUSION

Polyphenols protect against hyperglycemia-mediated alterations in cerebral endothelial cells and a mouse stroke model. It is relevant to assess polyphenol benefits to improve cerebrovascular damages during diabetes.

Inhibition of long noncoding RNA MALAT1 suppresses high glucose-induced apoptosis and inflammation in human umbilical vein endothelial cells by suppressing the NF-κB signaling pathway

The study investigated the expression of long noncoding RNA (lncRNA) MALAT1 in high glucose (HG)-induced human vascular endothelial cells (HUVECs) and the role of MALAT1 in the apoptosis of HG-induced HUVECs. The HUVECs were cultured and induced with 25 mmol/L HG. After that, the HUVECs were transfected with MALAT1 siRNA. The expression levels of MALAT1 were detected with qPCR, whereas the expression levels of Bax, Bcl-2, cleaved-caspase-3, cleaved-caspase-9, p-65, and p-p65 were detected using Western blot. The roles of MALAT1 in cell activities, including apoptosis, were evaluated using the CCK-8 assay, TUNEL staining, and flow cytometry. The expression levels of inflammatory factors (TNF-α and IL-6) were measured using ELISA. The expression levels of MALAT1, TNF-α, and IL-6 in HUVECs were increased in the HG environment; however, when MALAT1 was silenced in the HUVECs, cell proliferation increased significantly, the expression levels of TNF-α, IL-6, Bax, cleaved-caspase-3, and cleaved-caspase-9 decreased, and the rate of apoptosis also decreased. Silencing MALAT1 inhibited the expression of p-p65 in HG-induced HUVECs. In conclusion, our study demonstrated that MALAT1 is upregulated in HG-induced HUVECs, and inhibition of MALAT1 inhibits HG-induced apoptosis and inflammation in HUVECs by suppression of the NF-κB signaling pathway.

Blueberry-Derived Exosome-Like Nanoparticles Counter the Response to TNF-α-Induced Change on Gene Expression in EA.hy926 Cells

Exosome-like nanoparticles (ELNs) are attracting interest as important vehicles of intercellular communication, both in prokaryotes and eukaryotes. Recently, dietary nanoparticles similar to mammalian exosomes have attracted attention for these features. In particular they appear to be relevant in the modulation of several cellular processes as well as candidate carriers of bioactive molecules (proteins, lipids, and nucleic acids, including miRNAs) with therapeutic value. Herein, we investigated the cellular uptake of blueberry-derived ELNs (B-ELNs) by a human stabilized endothelial cell line (EA.hy926) and the ability of B-ELNs to modulate the expression of inflammatory genes as the response of tumor necrosis factor-α (TNF-α). Our results indicate that 1) EA.hy926 cells internalize B-ELNs in a dose-dependent manner; 2) pretreatment with B-ELNs counters TNF-α-induced reactive oxygen species (ROS) generation and loss of cell viability and modulates the differential expression of 29 genes (fold change > 1.5) induced by TNF-α compared to control; 3) pathway analysis reveals their involvement in a total of 340 canonical pathways, 121 KEGG pathways, and 121 GO Biological processes; and 4) the intersection between differentially expressed (DE) genes and miRNAs contained in B-ELNs unveils a set of candidate target genes, such as prostaglandin I2 synthase (PTGIS), mitogen-activated protein kinase 14 (MAPK14), and phosphodiesterase 7A (PDE7A), for ELNs-contained cargo. In conclusion, our study indicates that B-ELNs can be considered candidate therapeutic carriers of bioactive compounds potentially able to protect vascular system against various stressors.

Coffee C21 and protection of DNA from strand breaks: evaluation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006

Following an application from Tchibo GmbH submitted for authorisation of a health claim pursuant to Article 13(5) of Regulation (EC) No 1924/2006 via the Competent Authority of Germany, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the scientific substantiation of a health claim related to Coffee C21 and protection of DNA from strand breaks. The scope of the application was proposed to fall under a health claim based on newly developed scientific evidence. The food proposed by the applicant as the subject of the health claim is Coffee C21. The Panel considers that Coffee C21, a coffee standardised by its concentration of caffeoylquinic acids (CQA), trigonelline and N-methylpyridinium (NMP), is sufficiently characterised in relation to the claimed effect. The Panel considers that the claimed effect, protection of DNA from strand breaks, is a beneficial physiological effect. Out of the two human intervention studies from which conclusion could be drawn, one study provides some evidence that daily consumption of Coffee C21 (750 mL/day) for 4 weeks decreases DNA strand breaks in habitual coffee drinkers after coffee withdrawal over the previous four weeks. However, the results of this study were not replicated in another study conducted under similar conditions in the same study centre. No studies performed in a different setting, from which conclusions could be drawn, were available. No evidence has been provided for a mechanism by which coffee (including Coffee C21) would reduce DNA damage in human cells by reducing DNA strand breaks. The Panel concludes that a cause and effect relationship has not been established between the consumption of Coffee C21 and protection of DNA from strand breaks.

Anthocyanins ameliorate palmitate-induced inflammation and insulin resistance in 3T3-L1 adipocytes

Increased adiposity has been associated with adipose tissue low-grade inflammation leading to insulin resistance. Adipocyte differentiation inhibitors are expected to be effective in preventing obesity and related diseases. Anthocyanins (ACNs) are associated to enhanced adipocyte function and protection from metabolic stress. Herein, we evaluated the in vitro protective effects of an ACN rich extract against palmitic acid (PA)-induced hypertrophy, inflammation, and insulin resistance in 3T3-L1 adipocytes. ACN extract pretreatment reduces lipid accumulation and peroxisome proliferators-activated receptor-γ protein levels induced by PA. In addition, PA induces inflammation with activation of NF-κB pathway, whereas ACN extract pretreatment dose-dependently inhibited this pathway. Furthermore, adipocyte dysfunction associated with hypertrophy induces insulin resistance by affecting phosphatidylinositol 3-kinase-protein kinase B/Akt axis, GLUT-1, and adiponectin mRNA levels. ACN extract pretreatment reverts these effects induced by PA and moreover was able to induce insulin pathway with levels higher than insulin control cells, supporting an insulin sensitizer role for ACNs. This study demonstrates a prevention potential of ACNs against obesity comorbidities, due to their protective effects against inflammation/insulin resistance in adipocytes. In addition, these results contribute to the knowledge and strategies on the evaluation of the mechanism of action of ACNs from a food source under basal and insulin resistance conditions related to obesity.

Alpha-lipoic acid, but not di-hydrolipoic acid, activates Nrf2 response in primary human umbilical-vein endothelial cells and protects against TNF-α induced endothelium dysfunction

The antioxidants role in cell response regulation attracted great interest in the last decades and it is undergoing to a profound reconsideration. The mere concept of "biological antioxidant" has been frequently misconceived or misused, possibly leading to the misinterpretation of some experimental observation. Organosulfur compounds in general and α-lipoic acid, a dithiol molecule, can be considered a typical example of the kind. Reduced α-lipoic acid, dehydrolipoic acid has been in fact originally considered a bona fide, reducing, electron donor molecule. A more recent approach, according to stoichiometric and thermodynamic evidences, lead to a reinterpretation of the biochemical role of "antioxidants". The electrophilic nature of oxidized nucleophilic molecules, including α-lipoic acid, renders more plausible a mechanism based on the ability to activate Nrf2/EpRE mediated hormetic response. In this study, we demonstrate that nmolar concentrations of oxidized α-lipoic acid, but not dehydrolipoic acid, protect human umbilical primary endothelial cells (HUVEC) from TNF-α induced dysfunction, inhibit NF-κB activation and block apoptosis following the activation of Nrf2 transcription factor. Our observations corroborate the concept that the major, if not the unique, mechanism by which α-lipoic acid can non-enzymatically exert its reducing activity is related to the electrophilic nature of the oxidized form.

Bioavailable Blueberry-Derived Phenolic Acids at Physiological Concentrations Enhance Nrf2-Regulated Antioxidant Responses in Human Vascular Endothelial Cells

SCOPE

Blueberry consumption is believed to confer a cardiovascular health advantage, but the active compounds and effects require characterization. This study aims to identify the polyphenol metabolites in plasma after blueberry juice intake and determine their bioactivity on endothelial cells.

METHODS AND RESULTS

Three healthy individuals are recruited to obtain profiles of bioavailable plasma polyphenol metabolites following intake of blueberry juice. Of 33 phenolic compounds screened, 12 aglycone phenolic acids are detected and their maximum plasma concentrations and circulation time determined. Using this information, the effect of three physiologically relevant mixtures of blueberry-derived phenolic acids is investigated for their ability to induce nuclear factor erythroid 2-related factor 2 (Nrf2)-nuclear translocation and downstream gene expression in human endothelial cells. Pretreatment with the phenolic acids for 18 h results in a significant upregulation of the Nrf2-regulated antioxidant response proteins heme oxygenase 1 (HO-1) and glutamate-cysteine ligase modifier subunit (GCLM), following 6 h exposure to 2.5 μm H₂ O₂ .

CONCLUSION

Physiologically relevant concentrations of blueberry-derived aglycone phenolic acids can induce Nrf2-regulated antioxidant response proteins in vascular endothelial cells in response to low μm concentrations of H₂ O₂ . Our results represent an advance over previous studies that have used single compounds or high concentrations in cell-based investigations.

Isoastragaloside I suppresses LPS-induced tight junction disruption and monocyte adhesion on bEnd.3 cells via an activating Nrf2 antioxidant defense system

ISOI rescued TJs disruption from ROS induced by LPS in bEnd.3 cells. ISOI ameliorated inflammatory response and decreased monocyte adhesion onto bEnd.3 cells induced with LPS. ISOI protected BBB integrity through activating Nrf2 antioxidant pathway.

The Role of Nrf2 in Cardiovascular Function and Disease

Free radicals, reactive oxygen/nitrogen species (ROS/RNS), hydrogen sulphide, and hydrogen peroxide play an important role in both intracellular and intercellular signaling; however, their production and quenching need to be closely regulated to prevent cellular damage. An imbalance, due to exogenous sources of free radicals and chronic upregulation of endogenous production, contributes to many pathological conditions including cardiovascular disease and also more general processes involved in aging. Nuclear factor erythroid 2-like 2 (NFE2L2; commonly known as Nrf2) is a transcription factor that plays a major role in the dynamic regulation of a network of antioxidant and cytoprotective genes, through binding to and activating expression of promoters containing the antioxidant response element (ARE). Nrf2 activity is regulated by many mechanisms, suggesting that tight control is necessary for normal cell function and both hypoactivation and hyperactivation of Nrf2 are indicated in playing a role in different aspects of cardiovascular disease. Targeted activation of Nrf2 or downstream genes may prove to be a useful avenue in developing therapeutics to reduce the impact of cardiovascular disease. We will review the current status of Nrf2 and related signaling in cardiovascular disease and its relevance to current and potential treatment strategies.

Caffeic acid attenuates the inflammatory stress induced by glycated LDL in human endothelial cells by mechanisms involving inhibition of AGE-receptor, oxidative, and endoplasmic reticulum stress

Type 2 diabetes mellitus is a worldwide epidemic and its atherosclerotic complications determine the high morbidity and mortality of diabetic patients. Caffeic acid (CAF), a phenolic acid present in normal diets, is known for its antioxidant properties. The aim of this study was to investigate CAF's anti-inflammatory properties and its mechanism of action, using cultured human endothelial cells (HEC) incubated with glycated low-density lipoproteins (gLDL). Levels of the receptor for advanced glycation end-products (RAGE), inflammatory stress markers (C reactive protein, CRP; vascular cell adhesion molecule-1, VCAM-1; monocyte chemoattractant protein-1, MCP-1), and oxidative stress and endoplasmic reticulum stress (ERS) markers were evaluated in gLDL-exposed HEC, in the presence/absence of CAF. RAGE silencing or blocking, specific inhibitors for oxidative stress (apocynin, N-acetyl-cysteine), and ERS (salubrinal) were used. The results showed that: (i) gLDL induced CRP synthesis and secretion through mechanisms involving NADPH oxidase-dependent oxidative stress and ERS in HEC; (ii) gLDL-RAGE interaction, oxidative stress, and ERS stimulated the secretion of VCAM-1 and MCP-1 in HEC; and (iii) CAF reduced the secretion of CRP, VCAM-1, and MCP-1 in gLDL-exposed HEC by inhibiting RAGE expression, oxidative stress, and ERS. In conclusion, CAF might be a promising alternative to ameliorate a wide spectrum of disorders due to its complex mechanisms of action resulting in anti-inflammatory and antioxidative properties. © 2017 BioFactors, 43(5):685-697, 2017.

Cyanidin-3-O-Glucoside Modulates the In Vitro Inflammatory Crosstalk between Intestinal Epithelial and Endothelial Cells

Intestinal epithelium represents a protective physical barrier and actively contributes to the mucosal immune system. Polarized basolateral intestinal secretion of inflammatory mediators, followed by activation of NF-κB signaling and inflammatory pathways in endothelial cells, efficiently triggers extravasation of neutrophils from the vasculature, therefore contributing to the development and maintenance of intestinal inflammation. Proper regulation of NF-κB activation at the epithelial interface is crucial for the maintenance of physiological tissue homeostasis. Many papers reported that anthocyanins, a group of compounds belonging to flavonoids, possess anti-inflammatory effects and modulate NF-κB activity. In this study, by using a coculture in vitro system, we aimed to evaluate the effects of TNF-α-stimulated intestinal cells on endothelial cells activation, as well as the protective effects of cyanidin-3-glucoside (C3G). In this model, TNF-α induced nuclear translocation of NF-κB and TNF-α and IL-8 gene expression in Caco-2 cells, whereas C3G pretreatment dose-dependently reduced these effects. Furthermore, TNF-α-stimulated Caco-2 cells induced endothelial cells activation with increased E-selectin and VCAM-1 mRNA, leukocyte adhesion, and NF-κB levels in HUVECs, which were inhibited by C3G. We demonstrated that selective inhibition of the NF-κB pathway in epithelial cells represents the main mechanism by which C3G exerts these protective effects. Thus, anthocyanins could contribute to the management of chronic gut inflammatory diseases.