Coffees rich in chlorogenic acid or N-methylpyridinium induce chemopreventive phase II-enzymes via the Nrf2/ARE pathway in vitro and in vivo

Effects of coffee and tea consumption on glioma risk: An umbrella review of systematic reviews and meta-analyses

BACKGROUND

Coffee and tea are considered to have some effects on the risk of glioma as one of the most prevalent intracranial malignant tumors in adults. However, the precise effect of coffee and tea consumption on glioma is not obvious. This umbrella review aimed to evaluate the impact of tea and coffee consumption on glioma risk.

METHODS

Three online databases containing Scopus, Web of Science, and PubMed were thoroughly searched from the beginning to February 23, 2024 with no language constraints. Relying on I2 and Q statistics, a random-effect model or a fixed-effect model was applied. The PICO structure was followed as Population (Patients with glioma), Intervention (Coffee and tea consumption), Comparison (Standard treatment or placebo), and Outcome (Risk of glioma).

RESULTS

Totally, seven meta-analyses and systematic reviews contain 23,591 patients were included in this umbrella review. Coffee and tea consumption led to significant 15% and 16% reductions in glioma risk, respectively (RR = 0.85; 95% CI: 0.74, 0.98; RR = 0.84; 95% CI: 0.79, 0.89). The results did not change after subgroup analyses.

CONCLUSION

This umbrella review revealed that the coffee and tea consumption may decrease the glioma risk. Consumption of tea and coffee may be considered as dietary strategies against glioma.

PROSPERO REGISTRATION CODE

CRD42024521525.

Graphical exploration of 600- and 60-MHz proton NMR spectral datasets from ground roast coffee extracts

This article uses a variety of graphical and mathematical approaches to analyse 600- and 60-MHz ('benchtop') proton NMR spectra acquired from lipophilic and hydrophilic extracts of roasted coffee beans. The collection of 40 authenticated samples comprised various coffee species, cultivars and hybrids. The spectral datasets were analysed by a combination of metabolomics approaches, cross-correlation and whole spectrum methods, assisted by visualisation and mathematical techniques not conventionally employed to treat NMR data. A large amount of information content was shared between the 600-MHz and benchtop datasets, including in its magnitude spectral form, suggesting the potential for a lower cost, lower tech route to conducting informative metabolomics studies.

Hepatoprotective effects of chlorogenic acid on mice exposed to aflatoxin B1: Modulation of oxidative stress and inflammation

Aflatoxin B1 (AFB1) is widely distributed in crops and feeds, and ingestion of AFB1-contaminated crops is harmful to human/animal health. This study was designed to investigate hepatoprotective effects of chlorogenic acid (CGA), due to its excellent antioxidant and anti-inflammatory activities, on mice exposed to AFB1. Male Kunming mice were orally fed with CGA prior to daily AFB1 exposure for 18 consecutive days. The results showed that CGA treatment reduced the serum activity of aspartate aminotransferase, hepatic malondialdehyde content and pro-inflammatory cytokines synthesis, prevented histopathological changes of the liver, increased hepatic glutathione level, catalase activity and IL10 mRNA expression in mice subjected to AFB1. Taken together, CGA exerted the protective effect on AFB1-induced hepatic damage by modulating redox status and inflammation, suggesting that CGA may be a candidate compound for the treatment of aflatoxicosis.

Effects of dietary supplementation with chlorogenic acid on growth performance, antioxidant capacity, and hepatic inflammation in broiler chickens subjected to diquat-induced oxidative stress

This study was conducted to investigate the protective effects of chlorogenic acid (CGA) on broilers subjected to (DQ)-induced oxidative stress. In experiment 1, one hundred and ninety-two male one-day-old Ross 308 broiler chicks were distributed into 4 groups and fed a basal diet supplemented with 0, 250, 500, or 1,000 mg/kg CGA for 21 d. In experiment 2, an equivalent number of male one-day-old chicks were allocated to 4 treatments for a 21-d trial: 1) Control group, normal birds fed a basal diet; 2) DQ group, DQ-challenged birds fed a basal diet; and 3) and 4) CGA-treated groups: DQ-challenged birds fed a basal diet supplemented with 500 or 1,000 mg/kg CGA. The intraperitoneal DQ challenge was performed at 20 d. In experiment 1, CGA administration linearly increased 21-d body weight, and weight gain and feed intake during 1 to 21 d (P < 0.05). CGA linearly and/or quadratically increased total antioxidant capacity, catalase, superoxide dismutase, and glutathione peroxidase activities, elevated glutathione level, and reduced malondialdehyde accumulation in serum, liver, and/or jejunum (P < 0.05). In experiment 2, compared with the control group, DQ challenge reduced body weight ratio (P < 0.05), which was reversed by CGA administration (P < 0.05). DQ challenge increased serum total protein level, aspartate aminotransferase activity, and total bilirubin concentration (P < 0.05), which were normalized when supplementing 500 mg/kg and/or 1,000 mg/kg CGA (P < 0.05). DQ administration elevated hepatic interleukin-1β, tumor necrosis factor-α, and interleukin-6 levels (P < 0.05), and the values of interleukin-1β were normalized to control values when supplementing CGA (P < 0.05). DQ injection decreased serum superoxide dismutase activity, hepatic catalase activity, and serum and hepatic glutathione level, but increased malondialdehyde concentration in serum and liver (P < 0.05), and the values of these parameters (except hepatic catalase activity) were reversed by 500 and/or 1,000 mg/kg CGA. The results suggested that CGA could improve growth performance, alleviate oxidative stress, and ameliorate hepatic inflammation in DQ-challenged broilers.

The magical smell and taste: Can coffee be good to patients with cardiometabolic disease?

Coffee is a beverage consumed globally. Although few studies have indicated adverse effects, it is typically a beneficial health-promoting agent in a range of diseases, including depression, diabetes, cardiovascular disease, and obesity. Coffee is rich in caffeine, antioxidants, and phenolic compounds, which can modulate the composition of the gut microbiota and mitigate both inflammation and oxidative stress, common features of the burden of lifestyle diseases. This review will discuss the possible benefits of coffee on complications present in patients with diabetes, cardiovascular disease and chronic kidney disease, outwith the social and emotional benefits attributed to caffeine consumption.

Coffee Chlorogenic Acids Incorporation for Bioactivity Enhancement of Foods: A Review

The demand of foods with high antioxidant capacity have increased and research on these foods continues to grow. This review is focused on chlorogenic acids (CGAs) from green coffee, which is the most abundant source. The main CGA in coffee is 5-O-caffeoylquinic acid (5-CQA). Coffee extracts are currently the most widely used source to enhance the antioxidant activity of foods. Due to the solubility of CGAs, their extraction is mainly performed with organic solvents. CGAs have been associated with health benefits, such as antioxidant, antiviral, antibacterial, anticancer, and anti-inflammatory activity, and others that reduce the risk of cardiovascular diseases, type 2 diabetes, and Alzheimer's disease. However, the biological activities depend on the stability of CGAs, which are sensitive to pH, temperature, and light. The anti-inflammatory activity of 5-CQA is attributed to reducing the proinflammatory activity of cytokines. 5-CQA can negatively affect colon microbiota. An increase in anthocyanins and antioxidant activity was observed when CGAs extracts were added to different food matrices such as dairy products, coffee drinks, chocolate, and bakery products. The fortification of foods with coffee CGAs has the potential to improve the functionality of foods.

A Decade of Research on Coffee as an Anticarcinogenic Beverage

Coffee consumption has been investigated as a protective factor against cancer. Coffee is a complex beverage that contains more than 1000 described phytochemicals, which are responsible for its pleasant taste, aroma, and health-promoting properties. Many of these compounds have a potential therapeutic effect due to their antioxidant, anti-inflammatory, antifibrotic, and anticancer properties. The roasting process affects the phytochemical content, and undesirable compounds may be formed. In recent years, there have been contradictory publications regarding the effect of coffee drinking and cancer. Therefore, this study is aimed at evaluating the association of coffee consumption with the development of cancer. In PubMed, until July 2021, the terms “Coffee and cancer” resulted in about 2150 publications, and almost 50% of them have been published in the last 10 years. In general, studies published in recent years have shown negative associations between coffee consumption and the risk or development of different types of cancer, including breast, prostate, oral, oral and pharyngeal, melanoma, skin and skin nonmelanoma, kidney, gastric, colorectal, endometrial, liver, leukemic and hepatocellular carcinoma, brain, and thyroid cancer, among others. In contrast, only a few publications demonstrated a double association between coffee consumption and bladder, pancreatic, and lung cancer. In this review, we summarize the in vitro and in vivo studies that accumulate epidemiological evidence showing a consistent inverse association between coffee consumption and cancer.

Galangin mitigates iron overload-triggered liver injury: Up-regulation of PPARγ and Nrf2 signaling, and abrogation of the inflammatory responses

AIM

Hepatotoxicity is a critical consequence of the iron overload conditions such as hemochromatosis and blood transfusion-requiring anemia. Iron induces hepatotoxicity largely through disruption of cellular redox homeostasis and induction of inflammatory responses. The present work explored the hepatoprotective activity of the bio-active flavone galangin against iron-evoked hepatotoxicity.

MAIN METHODS

Iron overload model was established in male Wistar rats via intraperitoneal injection of 150 mg/kg iron-dextran subdivided over a ten-day experimental period. Galangin was administered in a daily oral dose of 15 mg/kg throughout the experimental period. Blood and liver tissue samples were collected on day eleven and subjected to biochemical and molecular investigations.

KEY FINDINGS

Galangin significantly reduced liver iron content and serum ferritin level, and alleviated the iron-evoked oxidative stress. It enhanced the liver cell integrity as reflected by decreased serum activity of the liver enzymes. Mechanistically, galangin up-regulated the redox-regulating transcription factor Nrf2 and its responsive proteins HO-1 and NQO1. Interestingly, galangin up-regulated the antioxidant and anti-inflammatory protein PPARγ and serum hepcidin levels under the iron overload conditions. Equally important, it diminished the nuclear shift of the inflammatory transcription factor NF-κB p65 and down-regulated the levels of the pro-inflammatory cytokines TNF-α and IL-1β.

SIGNIFICANCE

The results of the present study highlight the mitigating activity of galangin against iron-induced hepatotoxicity. The study accentuated targeting of Nrf2, PPARγ, and NF-κB signaling as potential contributing mechanisms. While clinical studies are still required, the current study supports the possible implementation of galangin in controlling iron overload-associated hepatotoxicity.

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.

Effects of coffee consumption on arterial stiffness and endothelial function: a systematic review and meta-analysis of randomized clinical trials

BACKGROUND

Endothelial function (EF) and arterial stiffness (AS) are predictors of cardiovascular disease. As previous research concerning the effect of coffee intake on EF and AS was controversial, we conducted a systematic review and meta-analysis to synthesize research.

METHODS

We performed a systematic search in PubMed, Scopus and Web of Science to find clinical trials investigating the effect of coffee intake on EF or AS up to March 2020.Random-effects models were used to estimate the pooled weighted mean difference (WMD) between intervention and control groups for randomized controlled trials (RCTs). Between study heterogeneity was estimated using Cochran's Q and the I ²-inconsistency index. Internal validity of included randomized trials was determined with the Cochrane Collaboration's tool for assessing the risk of bias.

RESULTS

Twenty-three articles were included for qualitative and 11 articles for quantitative synthesis. Meta-analysis of 14 RCTs (nine articles) indicated a positive short-term (postprandial) effect of coffee intake on flow-mediated dilation (FMD) as a measure of EF (WMD: 1.93%[95% CI: 1.10-2.75]; I ²= 97.9%). Meta-analysis of three long-term RCTs(two articles) found no such effect on FMD (WMD: -0.08% [-3.82 to 3.66]; I ²= 61.4%).Most short-term information was from studies at low or unclear risk of bias, while the proportion of long-term information from studies at high risk of bias was considerable.

CONCLUSION

The results from this meta-analysis suggest a beneficial short-term effect of coffee intake on EF as measured by FMD. However, there might be unfavorable effects on AS. Our findings must be interpreted cautiously as the number of studies were low and included studies had a considerable risk of bias.

Quantitative NMR Methodology for the Authentication of Roasted Coffee and Prediction of Blends

In response to the need from the food industry for new analytical solutions, a fit-for-purpose quantitative ¹H NMR methodology was developed to authenticate pure coffee (100% arabica or robusta) as well as predict the percentage of robusta in blends through the study of 292 roasted coffee samples in triplicate. Methanol was chosen as the extraction solvent, which led to the quantitation of 12 coffee constituents: caffeine, trigonelline, 3- and 5-caffeoylquinic acid, lipids, cafestol, nicotinic acid, N-methylpyridinium, formic acid, acetic acid, kahweol, and 16-O-methylcafestol. To overcome the chemical complexity of the methanolic extract, quantitative analysis was performed using a combination of traditional integration and spectral deconvolution methods. As a result, the proposed methodology provides a systematic methodology and a linear regression model to support the classification of known and unknown roasted coffees and their blends.

Coffee induces AHR- and Nrf2-mediated transcription in intestinal epithelial cells

Coffee induces a health-promoting adaptive response of cells in the body. Here, we investigated enterocyte responses to AHR agonists in coffee and measured their transport across a polarized intestinal epithelium. AHR-activating potencies of Turkish, filter, and instant coffee were determined using DR CALUX® bioassay, before and after intestinal metabolization by Caco-2 cells. Furthermore, effects of coffee on induction of AHR- and Nrf2-pathway genes in Caco-2 cells were evaluated by real-time qPCR. Coffee samples showed considerable AHR-activating potencies in DR CALUX® bioassay (up to 79% of positive control activity). After incubation with Caco-2 cells, AHR activity of different coffees was between 35 and 64% of their initial value, suggesting rapid uptake and metabolization by epithelial cells. Expression of AHR-regulated gene CYP1A1 increased up to 41-fold and most Nrf2-pathway genes were up-regulated by coffee. This in vitro study may support the notion that coffee bioactives contribute to antioxidant defense and detoxification processes in vivo.

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.

Factors affecting intake, metabolism and health benefits of phenolic acids: do we understand individual variability?

INTRODUCTION

Phenolic acids are important phenolic compounds widespread in foods, contributing to nutritional and organoleptic properties.

FACTORS AFFCETING INDIVIDUAL VARIABILITY

The bioavailability of these compounds depends on their free or conjugated presence in food matrices, which is also affected by food processing. Phenolic acids undergo metabolism by the host and residing intestinal microbiota, which causes conjugations and structural modifications of the compounds. Human responses, metabolite profiles and health responses of phenolics, show considerable individual variation, which is affected by absorption, metabolism and genetic variations of subjects.

OPINION

A better understanding of the gut-host interplay and microbiome biochemistry is becoming highly relevant in understanding the impact of diet and its constituents. It is common to study metabolism and health benefits separately, with some exceptions; however, it should be preferred that health responders and non-responders are studied in combination with explanatory metabolite profiles and gene variants. This approach could turn interindividual variation from a problem in human research to an asset for research on personalized nutrition.

The Effects of Dietary Supplements that Overactivate the Nrf2/ARE System

Background:

Inflammation is one of the most misunderstood aspects of human health. People have been encouraged to eat foods that have a high antioxidant capacity, and in vitro tests for total antioxidant capacity emerged. They were based on measuring the destruction of oxidized test compounds in direct reactions with the antioxidants in foods. Many dietary supplements arrived in the market. They contained purified antioxidants, such as resveratrol and EGCG that were and still are widely assumed by many to be quite healthy at any dose.

Methods:

The literature on inflammation and the Nrf2/ARE antioxidant system was searched systematically. Articles from prestigious, peer-reviewed journals were obtained and read. The information obtained from them was used to write this review article.

Results:

Over 150 articles and books were read. The information obtained from them showed that very few dietary antioxidants exert their effects by reacting directly with Reactive Oxygen and Nitrogen Species (RONS). Instead, most of the effective antioxidants activate the endogenous Nrf2/ARE antioxidant system. This helps prevent smoldering inflammation and the diseases that it can cause. However, when overactivated or activated constitutively, the Nrf2/ARE antioxidant system can cause some of these diseases, including many types of multidrug resistant cancer, autoimmune, neurodegenerative and cardiovascular diseases.

Conclusion:

Even though green tea, as well as many fruits, vegetables and spices are quite healthy, dietary supplements that deliver much higher doses of antioxidants may not be. People who are diagnosed with cancer and plan to start chemotherapy and/or radiotherapy should probably avoid such supplements. This is because multidrug resistant tumors can hijack and overactivate the Nrf2/ARE antioxidant system.

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.

Pharmacological action and potential targets of chlorogenic acid

Chlorogenic acid is a widely distributed natural compound with many important pharmacological effects, which are found in a variety of plants. It is also an important secondary metabolite in plants. As a natural plant extract from a wide range of sources, in vitro and in vivo studies have found that the main pharmacological effects of chlorogenic acid are antioxidant, antiinflammatory, antibacterial, antiviral, hypoglycemic, lipid lowering, anticardiovascular, antimutagenic, anticancer, immunomodulatory, etc. Therefore it may play an important role in promoting human health. For example, it can provide new ideas and new ways for the prevention and treatment of cardiovascular disease, cancer, diabetes, and other chronic diseases, but the specific mechanism of action is unclear. Due to the difficulty of extraction and purification, poor stability, poor solubility, low absolute bioavailability of oral administration, the possibility of allergies caused by injection, and so on, there are difficulties in its medicinal research and development. The further study of chlorogenic acid will provide an important theoretical basis for its rational use.

Reversing ROS-mediated neurotoxicity by chlorogenic acid involves its direct antioxidant activity and activation of Nrf2-ARE signaling pathway

Chlorogenic acid (CA), the ester of caffeic acid and quinic acid, is one of the most abundant polyphenols in coffee, and has multiple pharmacological functions. The present study is designed to explore the protection provided by CA against hydrogen peroxide (H₂ O₂ )-induced oxidative damages in the rat pheochromocytoma cells, and the underlying mechanisms engaged in this process. CA displays robust free radical-scavenging activity in vitro. More importantly, CA strikingly rescues the cells from the H₂ O₂ -mediated oxidative insults. Mechanistic studies revealed that CA upregulates a panel of phase II cytoprotective species, such as heme oxygenase-1, NAD(P)H: quinone oxidoreductase 1, glutathione, thioredoxin reductase 1, and thioredoxin 1. This neuroprotection is dependent on the activation of the transcription factor Nuclear factor erythroid 2-related factor 2 (Nrf2), as knockdown of Nrf2 abolishes such effect. Our results demonstrate that CA provides dual neuroprotection via directly neutralizing free radicals and indirectly inducing expression of Nrf2-driven cytoprotective enzymes, and suggest a potential therapeutic usage of CA as a neuroprotective agent. Coffee is one of the most popular drinks in the world, and our discovery may also contribute to understanding the beneficial effects of regular coffee consumption. © 2019 BioFactors, 45 (4):616-626, 2019.

Impact of cooking on the antioxidant activity of spice turmeric

Curcuminoids, as the main ingredient of turmeric, are popularly used in food additives and condiments, and are widely accepted to be beneficial for human health for their antioxidant activity. However, curcuminoids are highly susceptible in terms of thermal-induced degradation, and curry is usually boiled, roasted, or fried in the use of food additives and condiments. Thus, it is interesting to explore the effect of cooking on the antioxidant activity of curcuminoids. In the present study, the total antioxidant capacity (T-AOC) of cooked curcuminoids (boiled curcuminoids, roasted curcuminoids, and fried curcuminoids) processed through three heating conditions, and their protective effects against oxidative damage to rat pheochromocytoma (PC12) cells, a well-established neuronal model, were evaluated. It was found that cooking slightly lowered the T-AOC of curcuminoids, with boiled curcuminoids being relatively stronger than roasted curcuminoids, and fried curcuminoids being the weakest form. Both boiled and roasted curcuminoids could significantly improve cell viability, mitigate intracellular accumulation of reactive oxygen species and reduce malondialdehyde activity, reduce caspase-3 and caspase-9 protein expression, and increase superoxide dismutase activity of PC12 cells compared with the control group. In comparison with parent curcuminoids, the protective effects of cooked curcuminoids got relatively lower overall, with boiled curcuminoids being relatively stronger than roasted curcuminoids. In conclusion, the cooked curcuminoids, including boiled and roasted forms, still have antioxidant and neuroprotective activity.

Consumption of Chlorogenic Acids through Coffee and Health Implications

Chlorogenic acids (CGA) are the main antioxidant compounds in the Western diet, due to their high concentrations in coffee associated with the high consumption of the beverage. Until about 10 years ago, like many other phenolic compounds, CGA were thought to be poorly absorbed in the human digestive system. Along the years, large amounts of information on the absorption and metabolism of these compounds have been unveiled, and today, it is known that, on average, about one third of the consumed CGA from coffee is absorbed in the human gastrointestinal tract, although large inter-individual variation exists. Considering results from in vitro animal and human studies, it is possible to conclude that the antioxidant and anti-inflammatory effects of coffee CGA are responsible for, at least to a certain extent, the association between coffee consumption and lower incidence of various degenerative and non-degenerative diseases, in addition to higher longevity.

Amelioration of Oxidative Stress in Caco-2 Cells Treated with Pro-inflammatory Proteins by Chlorogenic Acid Isomers via Activation of the Nrf2-Keap1-ARE-Signaling Pathway

Understanding the potential effects of chlorogenic acid (CGA) isomers on the intestinal epithelium is important because coffee intake exposes consumers to the six major CGA isomers: 3-caffeoylquinic acid (3-CQA), 4-caffeoylquinic acid (4-CQA), 5-caffeoylquinic acid (5-CQA), 3,4-dicaffeoylquinic acid (3,4-diCQA), 3,5-dicaffeoylquinic acid (3,5-diCQA), and 4,5-dicaffeoylquinic acid (4,5-diCQA). The present study determined the relative effects of CGA isomers on the antioxidant status of inflamed Caco-2 intestinal cells by investigating the oxidative-stress-responsive pathway and nuclear-factor-erythroid-derived-2-like 2 (Nrf2) signaling. Differentiated Caco-2 cells were challenged with the inflammatory mediators PMA and IFNγ, as a model of intestinal inflammation in vitro. Significant redox ( p < 0.05) responses to these mediators were assessed by indirect measurement of induced generation of reactive oxygen species (ROS), as well as the expression of reduced (GSH) and oxidized (GSSG) glutathione. This translated to a 40% reduction in the GSH/GSSG ratio. We found that responses in these parameters were associated with increased Nrf2 activation ( p < 0.05). ROS generation and increased IL-8 secretion were found in challenged cells, indicating an association between induced oxidation and inflammatory status. Oxidative stress was ameliorated by CGA isomers, which scavenged intracellular ROS, increased GSH, and activated Nrf2 signaling. diCQA isomers were relatively more effective at reducing IL-8 ( p < 0.05). The observed increase in Nrf2 signaling led to upregulated expression of some Nrf2 target genes ( GPX2, KEAP1, and NFE2L2) in Caco-2 cells and activated the Nrf2-Keap1-ARE-signaling pathway. These findings indicate that CGA isomers present in coffee have bioactivity toward alleviating oxidative stress associated with intestinal inflammation.

Chlorogenic acids inhibit glutamate dehydrogenase and decrease intracellular ATP levels in cultures of chick embryo retina cells

Chlorogenic acids (CGAs) are a group of phenolic compounds found in worldwide consumed beverages such as coffee and green tea. They are synthesized from an esterification reaction between cinnamic acids, including caffeic (CFA), ferulic and p-coumaric acids with quinic acid (QA), forming several mono- and di-esterified isomers. The most prevalent and studied compounds are 3-O-caffeoylquinic acid (3-CQA), 4-O-caffeoylquinic acid (4-CQA) and 5-O-caffeoylquinic acid (5-CQA), widely described as having antioxidant and cell protection effects. CGAs can also modulate glutamate release from microglia by a mechanism involving a decrease of reactive oxygen species (ROS). Increased energy metabolism is highly associated with enhancement of ROS production and cellular damage. Glutamate can also be used as an energy source by glutamate dehydrogenase (GDH) enzyme, providing α-ketoglutarate to the tricarboxylic acid (TCA) cycle for ATP synthesis. High GDH activity is associated with some disorders, such as schizophrenia and hyperinsulinemia/hyperammonemia syndrome. In line with this, our objective was to investigate the effect of CGAs on GDH activity. We show that CGAs and CFA inhibits GDH activity in dose-dependent manner, reaching complete inhibition at high concentration with IC50 of 52 μM for 3-CQA and 158.2 μM for CFA. Using live imaging confocal microscopy and microplate reader, we observed that 3-CQA and CFA can be transported into neuronal cells by an Na⁺-dependent mechanism. Moreover, neuronal cells treated with CGAs presented lower intracellular ATP levels. Overall, these data suggest that CGAs have therapeutic potential for treatment of disorders associated with high GDH activity.

Use of Microarray Datasets to generate Caco-2-dedicated Networks and to identify Reporter Genes of Specific Pathway Activity

Intestinal epithelial cells, like Caco-2, are commonly used to study the interaction between food, other luminal factors and the host, often supported by microarray analysis to study the changes in gene expression as a result of the exposure. However, no compiled dataset for Caco-2 has ever been initiated and Caco-2-dedicated gene expression networks are barely available. Here, 341 Caco-2-specific microarray samples were collected from public databases and from in-house experiments pertaining to Caco-2 cells exposed to pathogens, probiotics and several food compounds. Using these datasets, a gene functional association network specific for Caco-2 was generated containing 8937 nodes 129711 edges. Two in silico methods, a modified version of biclustering and the new Differential Expression Correlation Analysis, were developed to identify Caco-2-specific gene targets within a pathway of interest. These methods were subsequently applied to the AhR and Nrf2 signalling pathways and altered expression of the predicted target genes was validated by qPCR in Caco-2 cells exposed to coffee extracts, known to activate both AhR and Nrf2 pathways. The datasets and in silico method(s) to identify and predict responsive target genes can be used to more efficiently design experiments to study Caco-2/intestinal epithelial-relevant biological processes.

The potential effects of chlorogenic acid, the main phenolic components in coffee, on health: a comprehensive review of the literature

Chlorogenic acid (CGA), an important biologically active dietary polyphenol, is produced by certain plant species and is a major component of coffee. Reduction in the risk of a variety of diseases following CGA consumption has been mentioned in recent basic and clinical research studies. This systematic review discusses in vivo animal and human studies of the physiological and biochemical effects of chlorogenic acids (CGAs) on biomarkers of chronic disease. We searched PubMed, Embase, Amed and Scopus using the following search terms: ("chlorogenic acid" OR "green coffee bean extract") AND (human OR animal) (last performed on April 1st, 2015) for relevant literature on the in vivo effects of CGAs in animal and human models, including clinical trials on cardiovascular, metabolic, cancerogenic, neurological and other functions. After exclusion of editorials and letters, uncontrolled observations, duplicate and not relevant publications the remaining 94 studies have been reviewed. The biological properties of CGA in addition to its antioxidant and anti-inflammatory effects have recently been reported. It is postulated that CGA is able to exert pivotal roles on glucose and lipid metabolism regulation and on the related disorders, e.g. diabetes, cardiovascular disease (CVD), obesity, cancer, and hepatic steatosis. The wide range of potential health benefits of CGA, including its anti-diabetic, anti-carcinogenic, anti-inflammatory and anti-obesity impacts, may provide a non-pharmacological and non-invasive approach for treatment or prevention of some chronic diseases. In this study, the effects of CGAs on different aspects of health by reviewing the related literatures have been discussed.

The Role of the Nrf2/ARE Antioxidant System in Preventing Cardiovascular Diseases

It is widely believed that consuming foods and beverages that have high concentrations of antioxidants can prevent cardiovascular diseases and many types of cancer. As a result, many articles have been published that give the total antioxidant capacities of foods in vitro. However, many antioxidants behave quite differently in vivo. Some of them, such as resveratrol (in red wine) and epigallocatechin gallate or EGCG (in green tea) can activate the nuclear erythroid-2 like factor-2 (Nrf2) transcription factor. It is a master regulator of endogenous cellular defense mechanisms. Nrf2 controls the expression of many antioxidant and detoxification genes, by binding to antioxidant response elements (AREs) that are commonly found in the promoter region of antioxidant (and other) genes, and that control expression of those genes. The mechanisms by which Nrf2 relieves oxidative stress and limits cardiac injury as well as the progression to heart failure are described. Also, the ability of statins to induce Nrf2 in the heart, brain, lung, and liver is mentioned. However, there is a negative side of Nrf2. When over-activated, it can cause (not prevent) cardiovascular diseases and multi-drug resistance cancer.

Thermal stability, antioxidant, and anti-inflammatory activity of curcumin and its degradation product 4-vinyl guaiacol

Curcumin is a secondary plant metabolite present in Curcuma longa L. Since curcumin is widely used as a food colorant in thermally processed food it may undergo substantial chemical changes which in turn could affect its biological activity. In the current study, curcumin was roasted at 180 °C up to 70 minutes and its kinetic of degradation was analyzed by means of HPLC-PDA and LC-MS, respectively. Roasting of curcumin resulted in the formation of the degradation products vanillin, ferulic acid, and 4-vinyl guaiacol. In cultured hepatocytes roasted curcumin as well as 4-vinyl guaiacol enhanced the transactivation of the redox-regulated transcription factor Nrf2, known to be centrally involved in cellular stress response and antioxidant defense mechanisms. The antioxidant enzyme paraoxonase 1 was induced by roasted curcumin and 4-vinyl guaiacol. Furthermore, roasted curcumin and 4-vinyl guaiacol decreased interleukin-6 gene expression in lipopolysaccharide stimulated murine macrophages. Current data suggest that curcumin undergoes degradation due to roasting and its degradation product exhibit significant biological activity in cultured cells.

Relationship between Caffeine and Levels of DNA Repair and Oxidative Stress in Women with and without a BRCA1 Mutation

BACKGROUND

Coffee consumption has been associated with a reduction in breast cancer risk among women with a BRCA1 mutation. The objective of this study was to evaluate whether major contributors of caffeine intake are associated with a reduction in DNA damage and/or oxidative stress in women with and without a BRCA1 mutation.

METHODS

Coffee, tea, soda and total caffeine consumption was collected by a dietary history questionnaire, and DNA repair capacity in lymphocytes was assessed by the comet assay (tail moments), micronucleus test (per 1,000 binucleated cells) and analysis of γ-H2AX staining (nuclear foci). The thiobarbituric acid-malondialdehyde and DTNB assays were used to estimate serum lipid peroxidation (µmol/l) and protein oxidation (µmol/l), respectively.

RESULTS

Among all women, high levels of caffeine and caffeinated coffee intake were associated with significantly lower levels of micronuclei (138.50 vs. 97.67, p = 0.04, and 138.12 vs. 97.70, p = 0.04). There was no significant relationship between caffeine, coffee, tea and soda intake and the other markers of DNA repair capacity and oxidative stress among all women and in analyses stratified by BRCA1 mutation status.

CONCLUSION

The chemopreventive effects of coffee and/or caffeine may be associated with improved capacity to efficiently repair DNA damage.

Coffee provides a natural multitarget pharmacopeia against the hallmarks of cancer

Coffee is the second most popular beverage in the world after water with a consumption of approximately two billion cups per day. Due to its low cost and ease of preparation, it is consumed in almost all countries and by all social classes of the population through different modes of preparation. Despites its simple appearance, a cup of coffee is in fact a complex mixture that contains hundreds of molecules, the composition and concentration of which vary widely and depend on factors including the origin of the coffee tree or its metabolism. Although an excessive consumption of coffee can be harmful, many molecules that are present in this black decoction exert anticancer properties. This review aims to describe the different primary coffee-containing substances that exert chemopreventive and bioactive activities against the different hallmarks and enabling characteristics of cancer, thus explaining the anticancer health benefit of black coffee.

Coffee Consumption and Risk of Hepatocellular Carcinoma and Intrahepatic Cholangiocarcinoma by Sex: The Liver Cancer Pooling Project

BACKGROUND

Coffee consumption has been reported to be inversely associated with hepatocellular carcinoma (HCC), the most common type of liver cancer. Caffeine has chemopreventive properties, but whether caffeine is responsible for the coffee-HCC association is not well studied. In addition, few studies have examined the relationship by sex, and no studies have examined whether there is an association between coffee and intrahepatic cholangiocarcinoma (ICC), the second most common type of liver cancer.

METHODS

In the Liver Cancer Pooling Project, a consortium of U.S.-based cohort studies, data from 1,212,893 individuals (HCC, n = 860; ICC, n = 260) in nine cohorts were pooled. Multivariable-adjusted hazard ratios (HR) and 95% confidence intervals (CI) were estimated using proportional hazards regression.

RESULTS

Higher coffee consumption was associated with lower risk of HCC (HR>3 cups/day vs. non-drinker, 0.73; 95% CI, 0.53-0.99; Ptrend cups/day = <0.0001). More notable reduced risk was seen among women than men (Pinteraction = 0.07). Women who consumed more than three cups of coffee per day were at a 54% lower risk of HCC (HR, 0.46; 95% CI, 0.26-0.81), whereas men had more modest reduced risk of HCC (HR, 0.93; 95% CI, 0.63-1.37). The associations were stronger for caffeinated coffee (HR>3 cups/day vs. non-drinker, 0.71; 95% CI, 0.50-1.01) than decaffeinated coffee (HR, 0.92; 95% CI, 0.55-1.54). There was no association between coffee consumption and ICC.

CONCLUSIONS

These findings suggest that, in a U.S. population, coffee consumption is associated with reduced risk of HCC.

IMPACT

Further research into specific coffee compounds and mechanisms that may account for these associations is needed.

Antioxidant property of coffee components: assessment of methods that define mechanisms of action

Coffee is a rich source of dietary antioxidants, and this property, coupled with the fact that coffee is one of the world's most popular beverages, has led to the understanding that coffee is a major contributor to dietary antioxidant intake. Brewed coffee is a complex food matrix with numerous phytochemical components that have antioxidant activity capable of scavenging free radicals, donating hydrogen and electrons, providing reducing activity and also acting as metal ion pro-oxidant chelators. More recent studies have shown that coffee components can trigger tissue antioxidant gene expression and protect against gastrointestinal oxidative stress. This paper will describe different in vitro, cell-free and cell-based assays that both characterize and compare the antioxidant capacity and mechanism of action of coffee and its bioactive constituents. Moreover, evidence of cellular antioxidant activity and correlated specific genomic events induced by coffee components, which are relevant to antioxidant function in both animal and human studies, will be discussed.

N-methylpyridinium, a degradation product of trigonelline upon coffee roasting, stimulates respiratory activity and promotes glucose utilization in HepG2 cells

N-Methylpyridinium (NMP) is a thermal degradation product of trigonelline formed upon coffee roasting and hypothesized to exert several health benefits in humans. Since for trigonelline evidence for hypoglycemic effects exists, we examined whether NMP also affects mechanisms of glucose utilization and cellular energy formation. For this purpose, the impact of trigonelline and NMP on respiratory activity, extracellular acidification, cellular adenosine nucleotides, energy supply from fatty acids and glucose as well as thermogenesis in HepG2 cells was analyzed. A 24 hour incubation with nanomolar concentrations of NMP enhanced oxygen consumption rates, resulting in increased ATP levels. Glucose was identified as the prevalent energy substrate as its uptake was augmented up to 18.1% ± 7.44% by NMP at 0.09 μM, whereas the uptake of fatty acids decreased upon NMP treatment. Cellular glucose uptake was also stimulated by trigonelline administration; however, a shift to the anaerobic energy production pathway was monitored. Both pyridine derivatives induced thermogenesis, although trigonelline presumably promoted proton leaks, while NMP increased the concentration of the uncoupling protein-2. We provide evidence that both compounds appear to stimulate cellular energy metabolism in HepG2 cells. Human intervention studies are warranted to ensure these effects in vivo.

Modulation of 3',5'-cyclic AMP homeostasis in human platelets by coffee and individual coffee constituents

3',5'-Cyclic AMP (cAMP) is one of the most important second messengers in mammalian cells, mediating a multitude of diverse cellular signalling responses. Its homeostasis is primarily regulated by adenylate cyclases and phosphodiesterases (PDE), the activities of which are partially dependent on the downstream events of adenosine receptor signalling. The present study was conducted to determine whether coffee constituents other than caffeine can influence the homeostasis of intracellular cAMP in vitro and in vivo by evaluating the effects of selected constituents present in coffee, coffee brews and coffee extracts on platelet PDE activity. In addition, to evaluate the potential effects of these constituents on platelet cAMP concentrations and PDE activity in humans, a 7-week pilot intervention study with eight subjects was conducted. The subjects consumed a regular commercial coffee and a low-caffeine coffee at a rate of 750 ml/d for 2 weeks each. The in vivo results revealed a highly significant inhibition of PDE activity (P< 0·001) after coffee intervention that was not directly dependent on the caffeine content of coffee. Although our in vitro and in vivo findings suggest that caffeine plays some role in the modulation of platelet cAMP status, other natural and roasting-associated compounds such as pyrazines and other currently unidentified species also appear to contribute significantly. In conclusion, moderate consumption of coffee can modulate platelet PDE activity and cAMP concentrations in humans, which may contribute to the putative beneficial health effects of coffee. Further detailed mechanistic investigations will be required to substantiate these beneficial effects and to elucidate the underlying mechanisms.

Potential antioxidant response to coffee - A matter of genotype?

In a human intervention study, coffee combining natural green coffee bean constituents and dark roast products was identified as a genotype-dependent inducer of the Nrf2/ARE pathway, significantly affecting Nrf2 gene expression and downstream GST1A1 and UGT1A1 gene transcription. The observed transcriptional changes correlated with the presence of specific Nrf2 genotypes suggesting their influence on both Nrf2 and subsequent ARE-dependent GST1A1 and UGT1A1 transcription. While the presence of the − 653 SNP seems to be advantageous, resulting in higher Nrf2, GST1A1 and UGT1A1 gene transcription following coffee consumption, in contrast, the presence of the − 651 SNP significantly down-regulated the response to the study coffee. Furthermore, the presence of the B/B genotype in GST1A1 along with the frequency of the [TA]_6/6 and [TA]_7/7 polymorphisms in UGT1A1 appeared to significantly increase sensitivity toward coffee-induced gene transcription. This data suggests that when examining the role of the Nrf2/ARE pathway in the regulation of antioxidative and chemopreventive phase II efficacy, individual genotypes should be included when considering the potency of bioactive food/food constituents and their therapeutic potential.

Reduction of advanced-glycation end products levels and inhibition of RAGE signaling decreases rat vascular calcification induced by diabetes

Advanced-glycation end products (AGEs) were recently implicated in vascular calcification, through a process mediated by RAGE (receptor for AGEs). Although a correlation between AGEs levels and vascular calcification was established, there is no evidence that reducing in vivo AGEs deposition or inhibiting AGEs-RAGE signaling pathways can decrease medial calcification. We evaluated the impact of inhibiting AGEs formation by pyridoxamine or elimination of AGEs by alagebrium on diabetic medial calcification. We also evaluated if the inhibition of AGEs-RAGE signaling pathways can prevent calcification. Rats were fed a high fat diet during 2 months before receiving a low dose of streptozotocin. Then, calcification was induced with warfarin. Pyridoxamine was administered at the beginning of warfarin treatment while alagebrium was administered 3 weeks after the beginning of warfarin treatment. Results demonstrate that AGEs inhibitors prevent the time-dependent accumulation of AGEs in femoral arteries of diabetic rats. This effect was accompanied by a reduced diabetes-accelerated calcification. Ex vivo experiments showed that N-methylpyridinium, an agonist of RAGE, induced calcification of diabetic femoral arteries, a process inhibited by antioxidants and different inhibitors of signaling pathways associated to RAGE activation. The physiological importance of oxidative stress was demonstrated by the reduction of femoral artery calcification in diabetic rats treated with apocynin, an inhibitor of reactive oxygen species production. We demonstrated that AGE inhibitors prevent or limit medial calcification. We also showed that diabetes-accelerated calcification is prevented by antioxidants. Thus, inhibiting the association of AGE-RAGE or the downstream signaling reduced medial calcification in diabetes.

Prevention of rat liver fibrosis and carcinogenesis by coffee and caffeine

Coffee has been inversely related to the incidence of human liver disease; however, whether caffeine is the component responsible for the beneficial effects of coffee remains controversial. This study evaluated the beneficial effects of coffee or caffeine in a medium-term bioassay for rat liver fibrosis/carcinogenesis induced by diethylnitrosamine (DEN) and carbon tetrachloride (CCl4). One week after the DEN injection, the groups started to receive conventional coffee, instant coffee or 0.1% caffeine ad libitum for 24 weeks. The groups receiving conventional coffee or caffeine presented a significant reduction in collagen content and mRNA expression of collagen I. The groups receiving instant coffee or caffeine had a significant reduction in the size and area of pre-neoplastic lesions and in the mean number of neoplastic lesions. A significant increase in liver bax protein levels was observed in the groups receiving instant coffee or caffeine as compared to the control group. These data indicate that the most pronounced hepatoprotective effect against fibrosis was observed in the groups receiving conventional coffee and 0.1% caffeine, and the greatest effects against liver carcinogenesis were detected in the groups receiving instant coffee and 0.1% caffeine.