Time-course regulation of survival pathways by epicatechin on HepG2 cells

From Cocoa to Chocolate: Effect of Processing on Flavanols and Methylxanthines and Their Mechanisms of Action

Despite the health benefits associated with the ingestion of the bioactive compounds in cocoa, the high concentrations of polyphenols and methylxanthines in the raw cocoa beans negatively influence the taste, confer the astringency and bitterness, and affect the stability and digestibility of the cocoa products. It is, therefore, necessary to process cocoa beans to develop the characteristic color, taste, and flavor, and reduce the astringency and bitterness, which are desirable in cocoa products. Processing, however, affects the composition and quantities of the bioactive compounds, resulting in the modification of the health-promoting properties of cocoa beans and chocolate. In this advanced review, we sought to better understand the effect of cocoa's transformational process into chocolate on polyphenols and methylxanthine and the mechanism of action of the original flavanols and methylxanthines. More data on the cocoa processing effect on cocoa bioactives are still needed for better understanding the effect of each processing step on the final polyphenolic and methylxanthine composition of chocolate and other cocoa products. Regarding the mechanisms of action, theobromine acts through the modulation of the fatty acid metabolism, mitochondrial function, and energy metabolism pathways, while flavanols mainly act though the protein kinases and antioxidant pathways. Both flavanols and theobromine seem to be involved in the nitric oxide and neurotrophin regulation.

Unravelling Potential Health-Beneficial Properties of Corema album Phenolic Compounds: A Systematic Review

Corema (C.) album belongs to the family Ericaceae and can be found in the Iberian Peninsula, especially on the coastal areas facing the Atlantic coast. C. album berries have been used for centuries in traditional medicine. Recent studies have revealed that not only the berries but also the leaves have relevant antioxidant, antiproliferative, and anti-inflammatory properties, bringing this plant to the forefront of discussion. A systematic review of the literature was carried out to summarize the phenolic compounds and bioactive properties identified in C. album berries and leaves and to search for research gaps on this topic. The search was conducted in three electronic databases (PubMed, SCOPUS, and Web of Science) using PRISMA methodology. The inclusion criteria were the chemical compositions of the berries, leaves, or their extracts and their bioactive properties. The exclusion criteria were agronomic and archaeological research. The number of studies concerning phenolic compounds' composition and the bioactive properties of C. album berries and leaves is still limited (11 articles). However, the variety of polyphenolic compounds identified make it possible to infer new insights into their putative mechanism of action towards the suppression of NF-kB transcription factor activation, the modulation of inflammatory mediators/enzymes, the induction of apoptosis, the modulation of mitogen activated protein kinase, cell cycle arrest, and the reduction of oxidative stress. These factors can be of major relevance concerning the future use of C. album as nutraceuticals, food supplements, or medicines. Nevertheless, more scientific evidence concerning C. album's bioactivity is required.

Pinus roxburghii and Nauplius graveolens Extracts Elevate Apoptotic Gene Markers in C26 Colon Carcinoma Cells Induced in a BALB/c Mouse Model

The present study aimed to evaluate the chemopreventive potential of Pinus roxburghii branch (P. roxburghii) and Nauplius graveolens (N. graveolens) extracts against human colorectal cancer (CRC) induced by C26 murine cells in a BALB/c mouse model. Real-time qRT-PCR was used to evaluate the apoptotic pathway by measuring the relative mRNA expression levels of the Bcl-2, Bax, Cas3, NF-κB, and PI3k genes. At the termination of the 30-day period, blood samples were collected to assay the biomarkers. The results showed a significant increase (p < 0.05) in the levels of TGF-β, CEA, CA19-9, malondialdehyde, ALT, AST, ALP, urea, and creatinine in the positive control compared to the negative control group. In addition, the glutathione reductase activity and total antioxidant activity were reduced in the positive control compared to the negative control. The biomarkers mentioned above were restored to almost normal levels after administering a safe dose (1/10) of a lethal dose of P. roxburghii and N. graveolens extracts. Administration of one-tenth of the LD50 of P. roxburghii and N. graveolens extracts caused a significant upregulation of the expression of Bax and Cas-3 and downregulation of the Bcl-2, NF-ĸB, and PI3k genes vs. the GAPDH gene as a housekeeping gene compared to the control group. Furthermore, the Bax/Bcl-2 ratio increased upon treatment. After administration of P. roxburghii and N. graveolens at a safe dose (1/10) of a lethal dose, the results showed improvement in both body weight gain and a significant decrease (p < 0.05) in tumor volume. Histopathological changes supported these improvements. Conclusively, the research outputs show that P. roxburghii and N. graveolens extracts can be utilized as potential chemopreventive agents for CRC treatment by stimulating cancer cell apoptosis and suppressing CRC survival and proliferation.

Protective effect of gamma-aminobutyric acid against oxidative stress by inducing phase II enzymes in C2C12 myoblast cells

In this study, the cytoprotective effect of gamma-aminobutyric acid (GABA) via inducing phase II enzymes in C2C12 myoblasts was evaluated. The highest concentration of GABA (100 μM) significantly increased the cell viability by approximately 90% in hydrogen peroxide-induced C2C12 cells. The treatment with GABA (100 μM) effectively decreased the glutathione (GSH) depletion and the activities of antioxidant enzymes such as catalase (CAT) and superoxide dismutase (SOD). And, reactive oxygen species (ROS) levels were effectively reduced by about 50% in GABA-treated cells. In addition, the protein expression of phase II enzymes, such as NADPH:quinone oxidoreductase 1 and heme oxygenase-1 was significantly increased by GABA treatment. Moreover, GABA treatment increased the nuclear factor erythroid 2-related factor 2 (Nrf2) protein expression in the nucleus of C2C12 myoblasts. Altogether, the results in this study indicate that GABA possesses the cytoprotective effects against oxidative insults by regulating the GSH levels, CAT and SOD activities, ROS scavenging activities, and expression of phase II enzymes through the activation of Nrf2 in C2C12 cells. Hence, this study suggests that the GABA supplementation could be effective in alleviating oxidative stress-induced muscle damage. PRACTICAL APPLICATIONS: GABA exists in the germ and bran layers of rice and is well-known as the inhibitory neurotransmitter in the central nervous system. GABA also has various health beneficial effects, such as preventing chronic alcohol-related diseases and lowering blood pressure. The present study shows the cytoprotective effect of GABA against oxidative stress in C2C12 myoblasts, and suggests that GABA has great potential as a functional food ingredient for attenuating oxidative stress-induced muscle damage.

Safety and biological activity evaluation of Uncaria rhynchophylla ethanolic extract

Uncaria rhynchophylla (UR) belongs to the Rubiaceae family, and its dried hooks are usually used in traditional medicine. It is effective in treating diseases related to the central nervous system. This study aimed to evaluate the safety of UR extract, investigate its antimutagenic and antioxidative activities, and elucidate its active components. Extraction and fractionation of the UR extract resulted in yields of 6.71%, 0.037%, 0.042%, 0.152%, 0.332%, and 5.132%, for hexane, ether, DCM, EtOAC, and aqueous fractions, respectively. The four indole alkaloids, total phenolic content (TPC), and total flavonoid content (TFC) of UR extract and its subfractions were measured. Alkaloid content was highest in the UR extract. TPC was the highest in the EtOAC fraction (373.7 ± 20.9 mg gallic acid equivalent (GAE)/g), whereas TFC was the highest in the UR extract (33.5 ± 2.4 mg quercetin equivalent (QE)/g). To assess the safety of UR extract mutagenicity, cytotoxicity, and oxidative stress inducibility assays were performed. The UR extract (2000 µg/plate) showed excellent antimutagenic activity (above 90%) against BaP in both TA98 and TA100 strains. The UR extract exhibited efficient DPPH (RC₅₀ 239.2 ± 16.5 µg/mL) and ABTS scavenging activity (RC₅₀ 458.7 ± 25.0 µg/mL). The UR extract (150 µg/mL) showed cytoprotective activity (65.6% ± 9.2%) against t-BHP. Among the subfractions, the EtOAC fraction possessed the strongest activities, overall. UR generally showed excellent biological activity at nontoxic concentrations (determined in vitro in current work), although the chemical composition of UR requires further investigation prior to its potential future use.

Advances in physiological functions and mechanisms of (-)-epicatechin

(-)-Epicatechin (EC) is a flavanol easily obtained through the diet and is present in tea, cocoa, vegetables, fruits, and cereals. Recent studies have shown that EC protects human health and exhibits prominent anti-oxidant and anti-inflammatory activities, enhances muscle performance, improves symptoms of cardiovascular and cerebrovascular diseases, prevents diabetes, and protects the nervous system. With the development of modern medical and biotechnology research, the mechanisms of action associated with EC toward various chronic diseases are becoming more apparent, and the pharmacological development and utilization of EC has been increasingly clarified. Currently, there is no comprehensive systematic introduction to the effects of EC and its mechanisms of action. This review presents the latest research progress and the role of EC in the prevention and treatment of various chronic diseases and its protective health effects and provides a theoretical basis for future research on EC.

The non-saponin fraction of Korean Red Ginseng (KGC05P0) decreases glucose uptake and transport in vitro and modulates glucose production via down-regulation of the PI3K/AKT pathway in vivo

Background

The non-saponin fraction of Korean Red Ginseng has been reported to have many biological activities. However, the effect of this fraction on anti-diabetic activity has not been elucidated in detail. In this study, we investigated the effects of KGC05P0, a non-saponin fraction of Korean Red Ginseng, on anti-diabetic activity in vitro and in vivo.

Methods

We measured the inhibition of commercially obtained α-glucosidase and α-amylase activities in vitro and measured the glucose uptake and transport rate in Caco-2 cells. C57BL/6J mice and C57BLKS/J^db/db (diabetic) mice were fed diets with or without KGC05P0 for eight weeks. To perform the experiments, the groups were divided as follows: normal control (C57BL/6J mice), db/db control (C57BLKS/J^db/db mice), positive control (inulin 400 mg/kg b.w.), low (KGC05P0 100 mg/kg b.w.), medium (KGC05P0 200 mg/kg b.w.), and high (KGC05P0 400 mg/kg b.w.).

Results

KGC05P0 inhibited α-glucosidase and α-amylase activities in vitro, and decreased glucose uptake and transport rate in Caco-2 cells. In addition, KGC05P0 regulated fasting glucose level, glucose tolerance, insulin, HbA1c, carbonyl contents, and proinflammatory cytokines in blood from diabetic mice and significantly reduced urinary glucose excretion levels. Moreover, we found that KGC05P0 regulated glucose production by down-regulation of the PI3K/AKT pathway, which inhibited gluconeogenesis.

Conclusion

Our study thereby demonstrated that KGC05P0 exerted anti-diabetic effects through inhibition of glucose absorption and the PI3K/AKT pathway in in vitro and in vivo models of diabetes. Our results suggest that KGC05P0 could be developed as a complementary food to help prevent T2DM and its complications.

Antiproliferative and cytotoxic effects of green coffee and yerba mate extracts, their main hydroxycinnamic acids, methylxanthine and metabolites in different human cell lines

This work aimed at studying the effects of green coffee bean (GCBE) and yerba mate (YME) extracts, their main phenolic components (5-caffeoylquinic acid, 5-CQA; 3,5-dicaffeoylquinic acid, 3,5-DCQA) and metabolites (ferulic acid, FA; caffeic acid, CA; dihydrocaffeic acid, DHCA; and dihydroferulic acid, DHFA) along with caffeine (CAF) on the viability and proliferation of different human cell lines. Extracts (10-1000 μg/mL) and standards (10-1000 μM) were assayed in colon (Caco-2), lung (A549), oesophageal (OE-33), urinary bladder (T24) human carcinoma cells, and a non-cancer cell line (CCD-18Co). YME significantly reduced viability of cancer cells at all assayed concentrations, the higher doses also reducing cell proliferation. GCBE effects on cell viability were more effective at 100 and 1000 μg/mL, showing modest effects on cell proliferation. The highest doses of 5-CQA and 3,5-DCQA reduced cell viability and proliferation in all cell lines, whereas FA, DHCA and DHFA had lower and variable effects. Caffeine had no effect. Dietary-attainable concentrations (0.1, 1 and 10 μg/mL) of YME were tested for cytotoxicity and reactive oxygen species generation, showing no cytotoxic effect. Low concentrations of all tested compounds were non-cytotoxic to CCD-18Co cells.

CONCLUSION

YME and to a lower degree GCBE, their phenolic components and metabolites may decrease cancer cell viability and proliferation.

Ouabain and BDNF Crosstalk on Ganglion Cell Survival in Mixed Retinal Cell Cultures

Brain-derived neurotrophic factor (BDNF) is a well-known and well-studied neurotrophin. Most biological effects of BDNF are mediated by the activation of TrkB receptors. This neurotrophin regulates several neuronal functions as cell proliferation, viability, and differentiation. Ouabain is a steroid that binds to the Na(+)/K(+) ATPase, inducing the activation of several intracellular signaling pathways. Previous data from our group described that ouabain treatment increases retinal ganglion cells survival (RGC). The aim of the present study was to evaluate, if this cardiac glycoside can have a synergistic effect with BDNF, the classical trophic factor for retinal ganglion cells, as well as investigate the intracellular signaling pathways involved. Our work demonstrated that the activation of Src, PLC, and PKCδ participates in the signaling cascade mediated by 50 ng/mL BDNF, since their selective inhibitors completely blocked the trophic effect of BDNF. We also demonstrated a synergistic effect on RGC survival when we concomitantly used ouabain (0.75 nM) and BDNF (10 ng/mL). Moreover, the signaling pathways involved in this synergistic effect include Src, PLC, PKCδ, and JNK. Our results suggest that the synergism between ouabain and BDNF occurs through the activation of the Src pathway, JNK, PLC, and PKCδ.

Cocoa flavonoids protect hepatic cells against high-glucose-induced oxidative stress: relevance of MAPKs

SCOPE

Oxidative stress plays a main role in the pathogenesis of type 2 diabetes mellitus. Cocoa and (-)-epicatechin (EC), a main cocoa flavanol, have been suggested to exert beneficial effects in type 2 diabetes mellitus because of their protective effects against oxidative stress and insulin-like properties. In this study, the protective effect of EC and a cocoa phenolic extract (CPE) against oxidative stress induced by a high-glucose challenge, which causes insulin resistance, was investigated on hepatic HepG2 cells.

METHODS AND RESULTS

Oxidative status, phosphorylated mitogen-activated protein kinases (MAPKs), nuclear factor E2 related factor 2 (Nrf2) and p-(Ser)-IRS-1 expression, and glucose uptake were evaluated. EC and CPE regulated antioxidant enzymes and activated extracellular-regulated kinase and Nrf2. EC and CPE pre-treatment prevented high-glucose-induced antioxidant defences and p-MAPKs, and maintained Nrf2 stimulation. The presence of selective MAPK inhibitors induced changes in redox status, glucose uptake, p-(Ser)- and total IRS-1 levels that were observed in CPE-mediated protection.

CONCLUSION

EC and CPE recovered redox status of insulin-resistant HepG2 cells, suggesting that the functionality in EC- and CPE-treated cells was protected against high-glucose-induced oxidative insult. CPE beneficial effects on redox balance and insulin resistance were mediated by targeting MAPKs.

An aqueous pomegranate seed extract ameliorates oxidative stress of human hepatoma HepG2 cells

BACKGROUND

Aqueous pomegranate seed extract (PSE), a by-product of the pomegranate juice industry, was recently identified as a potential antiglycative ingredient. Ellagic acid was proposed as the major polyphenol responsible for the antiglycative activity as exerted in in vitro models. However, there is no information on safety aspects of this extract in biological systems before its application as ingredient. The cytotoxicity of PSE (1-100 µg mL(-1) ) was evaluated by determining its effect on cell viability and redox status of cultured HepG2 cells. The protective effect of the PSE against oxidative stress induced by tert-butyl hydroperoxide (t-BOOH) was also investigated.

RESULTS

No changes in cell integrity or intrinsic antioxidant status resulted from a direct treatment with aqueous PSE, even at high dosage. In addition, reactive oxygen species (ROS) induced by t-BOOH were reduced by 21% when cells were pretreated with 100 µg mL(-1) of aqueous PSE at 180 min. The range of concentrations investigated was effective in decreasing the ROS formation but not in a dose-dependent manner.

CONCLUSION

Aqueous pomegranate seed extract enhances human hepatoma cells integrity and resistance to cope with a stressful situation at concentration up to 100 µg mL(-1) .

Cocoa flavonoids attenuate high glucose-induced insulin signalling blockade and modulate glucose uptake and production in human HepG2 cells

Insulin resistance is the primary characteristic of type 2 diabetes. Cocoa and its main flavanol, (-)-epicatechin (EC), display some antidiabetic effects, but the mechanisms for their preventive activities related to glucose metabolism and insulin signalling in the liver remain largely unknown. In the present work, the preventive effect of EC and a cocoa polyphenolic extract (CPE) on insulin signalling and on both glucose production and uptake are studied in insulin-responsive human HepG2 cells treated with high glucose. Pre-treatment of cells with EC or CPE reverted decreased tyrosine-phosphorylated and total levels of IR, IRS-1 and -2 triggered by high glucose. EC and CPE pre-treatment also prevented the inactivation of the PI3K/AKT pathway and AMPK, as well as the diminution of GLUT-2 levels induced by high glucose. Furthermore, pre-treatment of cells with EC and CPE avoided the increase in PEPCK levels and the diminished glucose uptake provoked by high glucose, returning enhanced levels of glucose production and decreased glycogen content to control values. These findings suggest that EC and CPE improved insulin sensitivity of HepG2 treated with high glucose, preventing or delaying a potential hepatic dysfunction through the attenuation of the insulin signalling blockade and the modulation of glucose uptake and production.

Cocoa phenolic extract protects pancreatic beta cells against oxidative stress

Diabetes mellitus is associated with reductions in glutathione, supporting the critical role of oxidative stress in its pathogenesis. Antioxidant food components such as flavonoids have a protective role against oxidative stress-induced degenerative and age-related diseases. Flavonoids constitute an important part of the human diet; they can be found in most plant foods, including green tea, grapes or cocoa and possess multiple biological activities. This study investigates the chemo-protective effect of a cocoa phenolic extract (CPE) containing mainly flavonoids against oxidative stress induced by tert-butylhydroperoxide (t-BOOH) on Ins-1E pancreatic beta cells. Cell viability and oxidative status were evaluated. Ins-1E cells treatment with 5–20 μg/mL CPE for 20 h evoked no cell damage and did not alter ROS production. Addition of 50 μM t-BOOH for 2 h increased ROS and carbonyl groups content and decreased reduced glutathione level. Pre-treatment of cells with CPE significantly prevented the t-BOOH-induced ROS and carbonyl groups and returned antioxidant defences to adequate levels. Thus, Ins-1E cells treated with CPE showed a remarkable recovery of cell viability damaged by t-BOOH, indicating that integrity of surviving machineries in the CPE-treated cells was notably protected against the oxidative insult.

Cocoa flavonoids improve insulin signalling and modulate glucose production via AKT and AMPK in HepG2 cells

SCOPE

Cocoa and (-)-epicatechin (EC), a main cocoa flavanol, have been suggested to exert beneficial effects in diabetes, but the mechanism for their insulin-like effects remains unknown. In this study, the modulation of insulin signalling by EC and a cocoa phenolic extract (CPE) on hepatic HepG2 cells was investigated by analysing key proteins of the insulin pathways, namely insulin receptor, insulin receptor substrate (IRS) 1 and 2, PI3K/AKT and 5'-AMP-activated protein kinase (AMPK), as well as the levels of the glucose transporter GLUT-2 and the hepatic glucose production.

METHODS AND RESULTS

EC and CPE enhanced the tyrosine phosphorylation and total insulin receptor, IRS-1 and IRS-2 levels and activated the PI3K/AKT pathway and AMPK in HepG2 cells. CPE also enhanced the levels of GLUT-2. Interestingly, EC and CPE modulated the expression of phosphoenolpyruvate carboxykinase, a key protein involved in the gluconeogenesis, leading to a diminished glucose production. In addition, EC- and CPE-regulated hepatic gluconeogenesis was prevented by the blockage of AKT and AMPK.

CONCLUSION

Our data suggest that EC and CPE strengthen the insulin signalling by activating key proteins of that pathway and regulating glucose production through AKT and AMPK modulation in HepG2 cells.

Cocoa flavanol metabolites activate HNF-3β, Sp1, and NFY-mediated transcription of apolipoprotein AI in human cells

SCOPE

To identify the mechanisms by which cocoa induces HDL levels and since apolipoprotein AI (ApoAI) is the major protein in HDLs, we analyzed, upon incubation with cocoa metabolites, ApoAI mRNA levels, its transcriptional regulation, and the levels of the transcription factors involved in this process.

METHODS AND RESULTS

Epicatechin and cocoa metabolites caused an increase in ApoAI expression in HepG2 cells. Electrophoretic mobility shift assays revealed the involvement of Sites A and B of the ApoAI promoter in the induction of ApoAI mRNA upon incubation with cocoa metabolites. Using supershift assays, we demonstrated the binding of HNF-3β, HNF-4, ER-α, and RXR-α to Site A and the binding of HNF-3β, NFY, and Sp1 to Site B. Luciferase assays performed with a construct containing Site B confirmed its role in the upregulation of ApoAI by cocoa metabolites. Incubation with 3-methyl-epicatechin led to an increase in HNF-3β mRNA, HNF-3β, ER-α, Sp1, and NFY protein levels and the activation of ApoAI transcription mediated by NFY, Sp1, and ER-α.

CONCLUSION

The activation of ApoAI transcription through Site B by cocoa flavanol metabolites is mainly mediated by an increase in HNF-3β, with a significant contribution of Sp1 and NFY, as a mechanism for the protective role of these compounds in cardiovascular diseases.

Purple sweet potato color protects mouse liver against d-galactose-induced apoptosis via inhibiting caspase-3 activation and enhancing PI3K/Akt pathway

Purple sweet potato color (PSPC) has been shown to possess hepatoprotective effects in our previous study. To clarify the detailed mechanism of hepatoprotective effects of PSPC, we investigated the potential protective effect of PSPC against caspase-3 activation induced by d-gal, as well as its influence on Bcl-2 levels and PI3K/Akt cell survival pathway. The results of TUNEL assay showed that PSPC effectively suppressed the d-gal-induced hepatocytes apoptosis, suggesting that anti-apoptosis mechanism was involved in PSPC-mediated protection against d-gal-induced liver injury in mouse. PSPC significantly increased GSH levels and promoted a marked increase in the activities of GSH related enzymes including GR, GST in d-gal-treated mice. The activation and activity of caspase-3 were markedly inhibited by the treatment of PSPC in the livers of d-gal-treated mice. Furthermore, the level of Bcl-2 was significantly raised, and the levels of PI3K p110 and phosphorylated Akt were also largely enhanced by the treatment of PSPC in the livers of d-gal-treated mice. In conclusion, these results suggested that PSPC could protect mouse liver against d-gal-induced hepatocyte apoptosis via attenuating oxidative stress, inhibiting the activation of caspase-3 and enhancing cell survival signaling (enhancing the level of anti-apoptotic protein Bcl-2 and the activation of PI3K/Akt pathway).

Epicatechin induces NF-κB, activator protein-1 (AP-1) and nuclear transcription factor erythroid 2p45-related factor-2 (Nrf2) via phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) and extracellular regulated kinase (ERK) signalling in HepG2 cells

The dietary flavonoid epicatechin has been reported to exhibit a wide range of biological activities. The objective of the present study was to investigate the time-dependent regulation by epicatechin on the activity of the main transcription factors (NF-κB, activator protein-1 (AP-1) and nuclear transcription factor erythroid 2p45-related factor (Nrf2)) related to antioxidant defence and survival and proliferation pathways in HepG2 cells. Treatment of cells with 10 μm-epicatechin induced the NF-κB pathway in a time-dependent manner characterised by increased levels of IκB kinase (IKK) and phosphorylated inhibitor of κB subunit-α (p-IκBα) and proteolytic degradation of IκB, which was consistent with an up-regulation of the NF-κB-binding activity. Time-dependent activation of the AP-1 pathway, in concert with enhanced c-Jun nuclear levels and induction of Nrf2 translocation and phosphorylation were also demonstrated. Additionally, epicatechin-induced NF-κB and Nrf2 were connected to reactive oxygen species intracellular levels and to the activation of cell survival and proliferation pathways, being phosphatidylinositol-3-kinase/protein kinase B (PI3K/AKT) and extracellular regulated kinase (ERK) associated to Nrf2 modulation and ERK to NF-κB induction. These data suggest that the epicatechin-induced survival effect occurs by the induction of redox-sensitive transcription factors through a tight regulation of survival and proliferation pathways.