Dietary EVOO Polyphenols and Gut Microbiota Interaction: Are There Any Sex/Gender Influences?

Accumulating evidence indicates that regular consumption of extra virgin olive oil (EVOO), the main source of fat in the Mediterranean diet, is associated with beneficial health effects and a reduced risk of developing chronic degenerative disorders. The beneficial effects of EVOO can be attributed to its unique composition in monounsaturated fats and phenolic compounds that provide important antioxidant, anti-inflammatory, and immune-modulating activities. On the other hand, it is well known that the gut microbiota has several important roles in normal human physiology, and its composition can be influenced by a multitude of environmental and lifestyle factors, among which dietary components play a relevant role. In the last few years, the two-way interaction between polyphenols, including those in EVOO, and the gut microbiota, i.e., the modulation of the microbiota by polyphenols and that of polyphenol metabolism and bioavailability by the microbiota, has attracted growing attention, being potentially relevant to explain the final effects of polyphenols, as well as of the microbiota profile. Furthermore, sex and gender can affect dietary habits, polyphenol intake, and nutrient metabolism. Lastly, it has been recently suggested that differences in gut microbiota composition could be involved in the unequal incidence of metabolic diseases observed between women and men, due to sex-dependent effects on shaping gut microbiota profiles according to diet. This review summarizes the most recent studies on the relationship between EVOO polyphenols and the gut microbiota, taking into account possible influences of sex and gender in modulating such an interaction.

Improving Nutrition Knowledge and Skills by the Innovative Education Program MaestraNatura in Middle School Students of Italy.

Promoting a healthy diet, mainly in youths, is the most effective action to prevent and fight dietary excesses and nutritional imbalance in the population. MaestraNatura (MN) is an innovative nutritional education program aimed at promoting a healthy lifestyle in first-level secondary school students. The study evaluated the effectiveness of the MN program in improving knowledge in students following the MN program (MN group) with respect to a control group (CO group) undergoing a "traditional" nutritional education path. To this end, the nutrition knowledge of the two groups was assessed by three multi-choice questionnaires. The results showed a significant improvement in knowledge (p < 0.001) in the MN group with respect to the CO group for all the questionnaires. Furthermore, the students' ability to transfer the principles of nutrition guidelines to the real context of daily meals was determined by asking the MN group to create a weekly food plan before (T0) and after (T1) the completion of the MN program. The MN group demonstrated improved performance in organizing the weekly menu plan at T1 with respect to T0 (p = 0.005). In conclusion, the MN nutritional education program appears to be an effective tool for improving knowledge and skills on nutritional issues, especially in those students with a lower starting level of knowledge and ability.

Dietary Fatty Acids at the Crossroad between Obesity and Colorectal Cancer: Fine Regulators of Adipose Tissue Homeostasis and Immune Response.

Colorectal cancer (CRC) is among the major threatening diseases worldwide, being the third most common cancer, and a leading cause of death, with a global incidence expected to increase in the coming years. Enhanced adiposity, particularly visceral fat, is a major risk factor for the development of several tumours, including CRC, and represents an important indicator of incidence, survival, prognosis, recurrence rates, and response to therapy. The obesity-associated low-grade chronic inflammation is thought to be a key determinant in CRC development, with the adipocytes and the adipose tissue (AT) playing a significant role in the integration of diet-related endocrine, metabolic, and inflammatory signals. Furthermore, AT infiltrating immune cells contribute to local and systemic inflammation by affecting immune and cancer cell functions through the release of soluble mediators. Among the factors introduced with diet and enriched in AT, fatty acids (FA) represent major players in inflammation and are able to deeply regulate AT homeostasis and immune cell function through gene expression regulation and by modulating the activity of several transcription factors (TF). This review summarizes human studies on the effects of dietary FA on AT homeostasis and immune cell functions, highlighting the molecular pathways and TF involved. The relevance of FA balance in linking diet, AT inflammation, and CRC is also discussed. Original and review articles were searched in PubMed without temporal limitation up to March 2021, by using fatty acid as a keyword in combination with diet, obesity, colorectal cancer, inflammation, adipose tissue, immune cells, and transcription factors.

Protocatechuic acid influences immune-metabolic changes in the adipose tissue of pregnant women with gestational diabetes mellitus.

Gestational diabetes mellitus (GDM) is associated with immune metabolic changes that increase women's risk of developing metabolic disorders later in life. Nutritional intervention is a crucial component in reducing the burden of these pathological features. We examined whether protocatechuic acid (PCA), a major metabolite of anthocyanins abundant in plant food, is able to exert insulin-mimetic activity and modulate inflammation in the visceral adipose tissue (VAT) obtained at delivery, from pregnant women with GDM or normal glucose tolerance (NGT). PCA stimulated glucose uptake in the VAT from both GDM and NGT women. This capability was associated with increased phosphorylation of p38 mitogen-activated protein kinase (p38MAPK), as further demonstrated by the inhibitory effect of SB203580, a p38MAPK inhibitor, on PCA-induced glucose uptake. The GDM-VAT expressed lower adiponectin levels and PCA stimulated adiponectin release in the NGT-VAT and, albeit to a lower extent, in the GDM-VAT. Higher levels of IL6 and TNFα were secreted by the GDM-VAT compared with the NGT one, and PCA had no effects on them. PCA reduced the overexpression of vasoactive intestinal peptide receptor 2 (VPAC2) in the GDM-VAT. Further studies are needed to establish whether and how anthocyanins and food rich in these compounds may contribute to prevent or delay metabolic disorders in women with GDM.

Promoting Health and Food Literacy through Nutrition Education at Schools: The Italian Experience with MaestraNatura Program.

MaestraNatura is an innovative nutrition education program aimed at both enhancing awareness about the importance of a healthy food-lifestyle relationship and the ability to transfer the theoretical principles of nutrition guidelines to everyday life. The educational contents of the program resulted from the analysis of the answers to a questionnaire submitted to students aged 6-13 in order to assess their degree of knowledge about nutritional facts. Educational paths were specifically designed and implemented to address the main knowledge gaps identified through the analysis of the answers and were then tested for teachers' satisfaction in a sample of 56 schools in the north, centre, and south of Italy, involving 790 classes, 600 teachers, and 15,800 students. The results showed an approval rating from teachers from 90% to 94%. Said paths were designed for primary (6-10 years old) and first-level secondary (11-13 years old) school students. In addition, in a pilot study carried out in nine Educational Institutes located in an area close to Rome (Lazio region), a specific path was tested for effectiveness in increasing students' knowledge about fruit and vegetables by conducting questionnaires before (T0) and after (T1) the didactic activities. Results showed a significant increase in right answers at T1 with respect to T0 (z = 2.142, p = 0.032). Fisher's exact probability test showed an answer variability depending on the issue considered. In conclusion, this work could be considered as a first necessary step toward the definition of new educational program, aimed at increasing food literacy and favouring a healthier relationship with food, applicable in a widespread and effective manner, also outside of Italy.

Obesity-Associated Inflammation: Does Curcumin Exert a Beneficial Role?

Curcumin is a lipophilic polyphenol, isolated from the plant turmeric of Curcuma longa. Curcuma longa has always been used in traditional medicine in Asian countries because it is believed to have numerous health benefits. Nowadays it is widely used as spice component and in emerging nutraceutical food worldwide. Numerous studies have shown that curcumin possesses, among others, potential anti-inflammatory properties. Obesity represents a main risk factor for several chronic diseases, including type 2 diabetes, cardiovascular disease, and some types of cancer. The establishment of a low-grade chronic inflammation, both systemically and locally in adipose tissue, occurring in obesity most likely represents a main factor in the pathogenesis of chronic diseases. The molecular mechanisms responsible for the onset of the obesity-associated inflammation are different from those involved in the classic inflammatory response caused by infections and involves different signaling pathways. The inflammatory process in obese people is triggered by an inadequate intake of nutrients that produces quantitative and qualitative alterations of adipose tissue lipid content, as well as of various molecules that act as endogenous ligands to activate immune cells. In particular, dysfunctional adipocytes secrete inflammatory cytokines and chemokines, the adipocytokines, able to recruit immune cells into adipose tissue, amplifying the inflammatory response also at systemic level. This review summarizes the most recent studies focused at elucidating the molecular targets of curcumin activity responsible for its anti-inflammatory properties in obesity-associated inflammation and related pathologies.

Lampaya Medicinalis Phil. decreases lipid-induced triglyceride accumulation and proinflammatory markers in human hepatocytes and fat body of Drosophila melanogaster.

BACKGROUND: Excess hepatic triglyceride (TG) accumulation (steatosis) commonly observed in obesity, may lead to non-alcoholic fatty liver disease (NAFLD). Altered regulation of intracellular lipid droplets (LD) and TG metabolism, as well as activation of JNK-mediated proinflammatory pathways may trigger liver steatosis-related disorders. Drosophila melanogaster is an animal model used for studying obesity and its associated disorders. In Drosophila, lipids and glycogen are stored in the fat body (FB), which resembles mammalian adipose tissue and liver. Dietary oversupply leads to obesity-related disorders, which are characterized by FB dysfunction. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in folk medicine of Chile to counteract inflammatory diseases. Hydroethanolic extract of lampaya (HEL) contains considerable amounts of flavonoids that may explain its anti-inflammatory effect. METHODS: We studied whether HEL affects palmitic acid (PA, C16:0) and oleic acid (OA; C18:1)-induced TG accumulation and proinflammatory marker content in HepG2 hepatocytes as well as impaired lipid storage and proinflammatory molecule expression in Drosophila melanogaster fed a high-fat diet (HFD). RESULTS: In HepG2 hepatocytes, exposure to OA/PA elevated TG content, FABP4, ATGL and DGAT2 expression, and the JNK proinflammatory pathway, as well as TNF-α and IL-6 production, while diminished FAS expression. These effects were prevented by HEL co-treatment. In Drosophila larvae fed a HFD, HEL prevented TG accumulation and downregulated proinflammatory JNK pathway activation. CONCLUSION: HEL effect counteracting OA/PA- and HFD-induced lipid accumulation and proinflammatory marker expression in HepG2 hepatocytes and Drosophila larvae may represent a preventive approach against hepatic steatosis and inflammation, associated to obesity and NAFLD.

Hydroethanolic Extract of Lampaya Medicinalis Phil. (Verbenaceae) Decreases Proinflammatory Marker Expression in Palmitic Acid-exposed Macrophages.

BACKGROUND: Obesity is a major health problem associated with increased comorbidities, which are partially triggered by inflammation. Proinflammatory macrophage infiltration in adipose tissue of individuals with obesity increases chronic inflammation. Obesity is associated with elevated plasma levels of saturated fatty acids, such as palmitic acid (PA), which promotes inflammation in vivo and in vitro. Infusions of Lampaya medicinalis Phil. (Verbenaceae) are used in the folk medicine of Northern Chile to counteract inflammation of rheumatic diseases. Hydroethanolic extract of lampaya (HEL) contains spectrophotometrically defined compounds that may contribute to the observed effect on inflammation. METHODS: We evaluated the phytochemical composition of HEL by high-performance liquid chromatography coupled to diode array detection (HPLC-DAD) and liquid chromatography-electrospray ionization- tandem mass spectrometry (LC-ESI-MS/MS). We assessed whether the exposure to HEL affects PA-induced expression of proinflammatory factors in THP-1 macrophages. RESULTS: HPLC-DAD and LC-ESI-MS/MS analyses showed the presence of considerable amounts of flavonoids in HEL. The PA-induced phosphorylation of the inflammatory pathway mediators IKK and NF-κB, as well as the elevated expression and secretion of proinflammatory cytokines (IL-6, TNF-α), were reduced in cells pre-exposed to HEL. CONCLUSION: These findings give new insights about the effect of HEL reducing IKK/NF-κB proinflammatory pathway, likely explained by the number of flavonoids contained in the extract. More studies would be needed to define the possible role of Lampaya as a preventive approach in subjects with obesity whose circulating PA might contribute to chronic inflammation.

Gender-related sociocultural differences and COVID-19: what influence on the effects of the pandemic?

In the first stages of the pandemic, the adverse outcomes of COVID-19 were significantly higher in men than in women most likely as the effect of biological, hormonal, metabolic differences between the two sexes. However, gender-related differences in lifestyles and social roles can also greatly influence the course of disease. To fully understand the influence of gender in the COVID-19 outbreak, the collection and dissemination of disaggregated data must be enhanced to allow a better knowledge of the effects of SARS-CoV-2 infection in men and women, not only from a biomedical point of view, but also considering the risk factors associated with the different roles that they play in the society.

Cross-talk between fetal membranes and visceral adipose tissue involves HMGB1-RAGE and VIP-VPAC2 pathways in human gestational diabetes mellitus.

AIMS: Gestational diabetes mellitus (GDM) is defined as glucose intolerance that is first diagnosed during pregnancy. Maternal adipose tissue and fetal membranes secrete various molecules that are relevant players in the pathogenesis of GDM. This pilot study aimed to examine whether the expression of the high mobility group box 1 protein (HMGB1) and its receptor for advanced glycation end products (RAGE), and the vasoactive intestinal peptide (VIP) and its receptors (VPAC-1,-2) were modified in pregnant women with GDM. METHODS: Fetal membranes (FMs), omental adipose tissue (VAT) explants, and serum samples were obtained from 12 women with GDM and 12 with normal glucose tolerance (NGT) at delivery. The expression of HMGB1, RAGE and VIP, VPAC-1,-2 was detected by Western Blotting in explants; circulating levels and "in vitro" release of HMGB1 and VIP were measured by ELISA tests. RESULTS: HMGB1 tissue expression was higher in FMs obtained from GDM women (p = 0.02) than in FMs from NGT women. VPAC2 (p = 0.03) and RAGE (p = 0.03) tissue expressions were significantly increased in VAT from GDM subjects. Only FMs of NGT released detectable levels of HMGB1, which was not observed in samples obtained from GDM. VAT of GDM released lower levels of VIP (p = 0.05) than NGT samples. CONCLUSIONS: This study indicates that a fine tuned regulation exists between FMs and VAT throughout pregnancy to maintain immune metabolic homeostasis. In GDM a balance between inflammatory and anti-inflammatory mediators has been observed. Further studies are needed to establish their exact role on fetal and maternal outcomes in GDM.

Recent Evidence on the Role of Dietary PUFAs in Cancer Development and Prevention.

BACKGROUND: Scientific evidence has been accumulated about the effects of polyunsaturated fatty acids (PUFAs) on human health. The hypothesis that n-3 PUFAs might improve the efficiency of anticancer drugs has recently been considered. The role of n-6 PUFAs, in contrast, needs to be better assessed. However, the effective mechanisms of action of PUFAs have not been fully clarified yet. This review aims to report the most updated evidence on the role of n-6 and n-3 PUFAs in the development and treatment of human cancers, focusing on the potential mechanisms by which PUFAs exert their effects. METHODS: We undertook a structured search in PubMed on February 17th 2017 for peer-reviewed research articles published from 2013. The search syntax used was: PUFA or PUFAs and cancer. RESULTS: Contradictory results were found, most likely due to the genetic background, the different dietary sources used, the interaction among different nutrients, and the tumor subtypes. However, the more recent findings strongly support the use of n-3 PUFAs in cancer prevention and treatment. On the other hand, n-6 PUFAs are often associated with an increased risk of cancer, even if recently their beneficial effects have also been highlighted. CONCLUSION: N-3 PUFAs may represent a potential therapeutic agent contributing to treat at least some type of human cancers. However, studies with larger sample sizes and longer follow-up times are still needed. To increase the knowledge about how food and nutrition can improve human health it is advisable to deliver an open access nutritional database.

Anti-inflammatory Activity of Extra Virgin Olive Oil Polyphenols: Which Role in the Prevention and Treatment of Immune-Mediated Inflammatory Diseases?

BACKGROUND AND OBJECTIVE: Altered inflammatory response characterizes chronic immunemediated inflammatory diseases (IMID) such as rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, systemic lupus erythematosus, and psoriasis. Accumulating evidence indicates that regular consumption of extra virgin olive oil (EVOO), the main source of fat in the Mediterranean diet, is associated with a reduced risk of developing chronic degenerative disorders such as cardiovascular diseases, type 2 diabetes and cancer. The beneficial effects on health of EVOO have been attributed, besides to the monounsaturated fats content, to the presence of phenolic compounds that have antioxidant, anti-inflammatory and immunomodulatory properties. The purpose of this review is to provide an overview of the effects of EVOO polyphenols on IMID highlighting the potential mechanisms of action. METHODS: Scientific papers were found by searching in PubMed up to May 2017 using the following key words: rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, systemic lupus erythematosus, and psoriasis also in combination with EVOO, phenolic compounds, oleuropein, oleocantal, hydroxytyrosol,tyrosol and oleochantal. RESULTS: In vitro and in vivo studies indicate that EVOO and its polyphenols can improve diseases symptoms in IMID, by acting both at local and systemic levels and by modulating several molecular pathways. Nevertheless, there are not sufficient data to achieve specific nutritional guidelines. CONCLUSION: Further research is needed to evaluate the real contribution of EVOO and its phenolic compounds in modulating the IMID-associated inflammatory perturbations, in order to develop appropriate nutritional recommendations.

Distinct Blood and Visceral Adipose Tissue Regulatory T Cell and Innate Lymphocyte Profiles Characterize Obesity and Colorectal Cancer.

Visceral adipose tissue (VAT) is a main site where metabolic and immunologic processes interplay to regulate, at local and systemic level, the inflammatory status and immune response. Obesity-associated inflammation and immune dysfunctions are inextricably linked to tumor but, in spite of intense efforts, the mechanisms underpinning this association remain elusive. In this report, we characterized the profile of VAT-associated and circulating innate lymphocyte and regulatory T (Treg) cell subsets underlying inflammatory conditions, such as obesity and colorectal cancer (CRC). Analysis of NK, NKT-like, γδ T, and Treg cell populations in VAT and blood of healthy lean subjects revealed that CD56hi NK and OX40+ Treg cells are more abundant in VAT with respect to blood. Conversely, CD56dim NK and total Treg cells are most present in the circulation, while γδ T lymphocytes are uniformly distributed in the two compartments. Interestingly, a reduced frequency of circulating activated Treg cells, and a concomitant preferential enrichment of OX40-expressing Treg cells in VAT, were selectively observed in obese (Ob) subjects, and directly correlated with body mass index. Likewise, CRC patients were characterized by a specific enrichment of VAT-associated NKT-like cells. In addition, Ob and CRC-affected individuals shared a significant reduction of the Vγ9Vδ2/γδ T cell ratio at systemic level. The alterations in the relative proportions of Treg and NKT-like cells in VAT were found to correlate with the content of pro- and anti-inflammatory polyunsaturated fatty acids (PUFA), respectively. Overall, these results provide evidence for distinct alterations of the immune cell repertoire in the periphery with respect to the VAT microenvironment that uniquely characterize or are shared by different inflammatory conditions, such as obesity and CRC, and suggest that VAT PUFA composition may represent one of the factors that contribute to shape the immune phenotypes.

ω3 Polyunsaturated Fatty Acids as Immunomodulators in Colorectal Cancer: New Potential Role in Adjuvant Therapies.

Diet composition may affect the onset and progression of chronic degenerative diseases, including cancer, whose pathogenesis relies on inflammatory processes. Growing evidence indicates that diet and its components critically contribute to human health, affecting the immune system, secretion of adipokines, and metabolic pathways. Colorectal cancer (CRC) is one of the leading causes of death worldwide. Antineoplastic drugs are widely used for CRC treatment, but drug resistance and/or off-target toxicity limit their efficacy. Dietary ω3 polyunsaturated fatty acids (PUFA) have been gaining great interest in recent years as possible anti-inflammatory and anticancer agents, especially in areas such as the large bowel, where the pro-inflammatory context promotes virtually all steps of colon carcinogenesis. Growing epidemiological, experimental, and clinical evidence suggests that ω3 PUFA may play a role in several stages of CRC management exhibiting antineoplastic activity against human CRC cells, improving the efficacy of radiation and chemotherapy, ameliorating cancer-associated secondary complications, and preventing CRC recurrence. These effects are most likely related to the immunomodulatory activities of ω3 PUFA that are able to influence several aspects of the inflammatory process ranging from inflammasome activation, leukocyte recruitment, production of immune mediators to differentiation, and activation of immune cells. In this review, we will focus on the potential use of ω3 PUFA as adjuvant agents together with chemo/radiotherapy, highlighting the immunomodulatory effects most likely responsible for their beneficial effects in different stages of CRC management.

Visceral fat adipocytes from obese and colorectal cancer subjects exhibit distinct secretory and ω6 polyunsaturated fatty acid profiles and deliver immunosuppressive signals to innate immunity cells.

Obesity is a low-grade chronic inflammatory state representing an important risk factor for colorectal cancer (CRC). Adipocytes strongly contribute to inflammation by producing inflammatory mediators. In this study we investigated the role of human visceral fat adipocytes in regulating the functions of innate immunity cells. Adipocyte-conditioned media (ACM) from obese (n = 14) and CRC (lean, n = 14; obese, n = 13) subjects released higher levels of pro-inflammatory/immunoregulatory factors as compared to ACM from healthy lean subjects (n = 13). Dendritic cells (DC), differentiated in the presence of ACM from obese and CRC subjects, expressed elevated levels of the inhibitory molecules PD-L1 and PD-L2, and showed a reduced IL-12/IL-10 ratio in response to both TLR ligand- and γδ T lymphocyte-induced maturation. Furthermore, CRC patient-derived ACM inhibited DC-mediated γδ T cell activation. The immunosuppressive signals delivered by ACM from obese and CRC individuals were associated with a pro-inflammatory secretory and ω6 polyunsaturated fatty acid profile of adipocytes. Interestingly, STAT3 activation in adipocytes correlated with dihomo-γlinolenic acid content and was further induced by arachidonic acid, which conversely down-modulated PPARγ. These results provide novel evidence for a cross-talk between human adipocytes and innate immunity cells whose alteration in obesity and CRC may lead to immune dysfunctions, thus setting the basis for cancer development.

Gender-related differences in lifestyle may affect health status.

Consistent epidemiological and clinical evidence strongly indicates that chronic non-communicable diseases are largely associated with four lifestyle risk factors: inadequate diet, physical inactivity, tobacco use, and excessive alcohol use. Notably, obesity, a worldwide-growing pathological condition determined by the combination between inadequate diet and insufficient physical activity, is now considered a main risk factor for most chronic diseases. Dietary habits and physical activity are strongly influenced by gender attitudes and behaviors that promote different patterns of healthy or unhealthy lifestyles among women and men. Furthermore, different roles and unequal relations between genders strongly interact with differences in social and economic aspects as well as cultural and societal environment. Because of the complex network of factors involved in determining the risk for chronic diseases, it has been promoting a systemic approach that, by integrating sex and gender analysis, explores how sex-specific biological factors and gender-related social factors can interact to influence the health status.

Could gestational diabetes mellitus be managed through dietary bioactive compounds? Current knowledge and future perspectives.

Gestational diabetes mellitus (GDM) is a serious problem growing worldwide that needs to be addressed with urgency in consideration of the resulting severe complications for both mother and fetus. Growing evidence indicates that a healthy diet rich in fruit, vegetables, nuts, extra-virgin olive oil and fish has beneficial effects in both the prevention and management of several human diseases and metabolic disorders. In this review, we discuss the latest data concerning the effects of dietary bioactive compounds such as polyphenols and PUFA on the molecular mechanisms regulating glucose homoeostasis. Several studies, mostly based on in vitro and animal models, indicate that dietary polyphenols, mainly flavonoids, positively modulate the insulin signalling pathway by attenuating hyperglycaemia and insulin resistance, reducing inflammatory adipokines, and modifying microRNA (miRNA) profiles. Very few data about the influence of dietary exposure on GDM outcomes are available, although this approach deserves careful consideration. Further investigation, which includes exploring the 'omics' world, is needed to better understand the complex interaction between dietary compounds and GDM.

Regulation of Dendritic Cell Function by Dietary Polyphenols.

Marked changes in socioeconomic status, cultural traditions, population growth, and agriculture have been affecting diets worldwide. Nutrition is known to play a pivotal role in the pathogenesis of several chronic diseases, and the use of bioactive food compounds at pharmacologic doses is emerging as a preventive and/or therapeutic approach to target metabolic dysregulations occurring in aging, obesity-related chronic diseases, and cancer. Only recently have data on the effects of specific nutrients or food on the immune system become available, and studies regarding the human immune system are still in their infancy. Beyond providing essential nutrients, diet can actively influence the immune system. Understanding how diet and nutritional status influence the innate and adaptive arms of our immune system represents an area of scientific need, opportunity, and challenge. The insights gleaned should help to address several pressing global health problems. Recently, biologically active polyphenols, which are widespread constituents of fruit and vegetables, have gained importance as complex regulators of various cellular processes, critically involved in the maintenance of body homeostasis. This review outlines the potential effects of polyphenols on the function of dendritic cells (DCs), key players in the orchestration of the immune response. Their effects on different aspects of DC biology including differentiation, maturation, and DC capacity to shift immune response toward tolerance or immune activation will be outlined.

Protocatechuic Acid Prevents oxLDL-Induced Apoptosis by Activating JNK/Nrf2 Survival Signals in Macrophages.

Protocatechuic acid (PCA), one of the main metabolites of complex polyphenols, exerts numerous biological activities including antiapoptotic, anti-inflammatory, and antiatherosclerotic effects. Oxidised LDL have atherogenic properties by damaging arterial wall cells and inducing p53-dependent apoptosis in macrophages. This study was aimed at defining the molecular mechanism responsible for the protective effects of PCA against oxidative and proapoptotic damage exerted by oxLDL in J774 A.1 macrophages. We found that the presence of PCA in cells treated with oxLDL completely inhibited the p53-dependent apoptosis induced by oxLDL. PCA decreased oxLDL-induced ROS overproduction and in particular prevented the early increase of ROS. This decrease seemed to be the main signal responsible for maintaining the intracellular redox homeostasis hindering the activation of p53 induced by ROS, p38MAPK, and PKCδ. Consequently the overexpression of the proapoptotic p53-target genes such as p66Shc protein did not occur. Finally, we demonstrated that PCA induced the activation of JNK, which, in turn, determined the increase of nuclear Nrf2, leading to inhibition of the early ROS overproduction. We concluded that the antiapoptotic mechanism of PCA was most likely related to the activation of the JNK-mediated survival signals that strengthen the cellular antioxidant defences rather than to the PCA antioxidant power.

Protocatechuic acid activates key components of insulin signaling pathway mimicking insulin activity.

SCOPE: Insulin resistance represents an independent risk factor for metabolic and cardiovascular diseases. Researchers have been interested in identifying active harmless compounds, as many insulin-sensitizing drugs have shown unwanted side-effects. It has been demonstrated that anthocyanins and one of their representative metabolites, protocatechuic acid (PCA), ameliorate hyperglycemia, and insulin sensitivity. This study investigated the mechanism of action of PCA responsible for the glucose uptake upregulation. METHODS AND RESULTS: In human visceral adipocytes, PCA stimulated insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation (+40% with respect to untreated cells) and the downstream events, i.e. phosphoinositide 3-kinase binding to IRS-1 and Akt phosphorylation (+100%, +180%, respectively, with respect to untreated cells). The insulin-like activity of PCA seemed to be mediated by insulin receptor since by inhibiting its autophosphorylation, the PCA effects were completely abolished. Furthermore, PCA was able to activate adenosine monophosphate-activated protein kinase, a serine/threonine kinase whose activation elicits insulin-sensitizing effects. CONCLUSION: This study showed that PCA stimulates the insulin signaling pathway in human adipocytes increasing GLUT4 translocation and glucose uptake. Decreasing insulin resistance is a most desirable aim to be reached for an effective therapeutic/preventive action against metabolic syndrome and type 2 diabetes. Identifying specific food/food components able to improve glucose metabolism can offer an attractive, novel, and economical strategy.