(-)-Epicatechin prevents TNFα-induced activation of signaling cascades involved in inflammation and insulin sensitivity in 3T3-L1 adipocytes

Effects of epicatechin on cardiovascular function in middle-aged diet-induced obese rat models of metabolic syndrome

The current study aimed to investigate the cardiovascular effects of epicatechin, a flavonoid found in green tea and cocoa, in attenuating complications associated with metabolic syndrome in diet-induced obese rats. Male Wistar-Kyoto (WKY) rats aged 16 weeks were fed either standard rat chow or given a high-fat-high-carbohydrate (HFHC) diet for 20 weeks. Epicatechin treatment (5 mg/kg/d) was administered to a subset of WKY rats commencing at week 8 of the 20 week HFHC feeding period. Body weights, food, water and energy intakes, blood pressure, heart rate and glucose tolerance were measured throughout the treatment period. Oxidative stress and inflammatory markers, lipid levels, cardiac collagen deposition, cardiac electrical function, aortic and mesenteric vessel reactivity were examined after the treatment. Twenty weeks of HFHC feeding in WKY rats resulted in the development of metabolic syndrome indicated by the presence of abdominal obesity, dyslipidaemia, glucose intolerance and increased blood pressure. Epicatechin treatment was found to enhance the oxidative stress status in HFHC groups through an increase in serum nitric oxide levels and a decrease in 8-isoprostane concentrations. Furthermore, WKY-HFHC rats displayed a decrease in IL-6 levels. The lipid profiles in HFHC groups showed improvement, with a decrease in LDL-cholesterol and TAG and an increase in HDL-cholesterol levels observed in WKY-HFHC rats. However, epicatechin was not effective in preventing weight gain, glucose intolerance or hypertension in HFHC fed rats. Overall, the results of this study suggest that epicatechin has the potential to improve the underlying mechanisms associated with metabolic syndrome in obese rats.

[Tea polyphenols ameliorates acute lung injury in septic mice by inhibiting NLRP3 inflammasomes]

OBJECTIVE

To investigate the mechanism of tea polyphenols (TP) for regulating NLRP3 inflammasomes and alleviating acute lung injury in septic mice.

METHODS

Sixty C57BL/6 mice were randomly assigned into sham-operated, cecal ligation and puncture (CLP) and CLP +TP treatment groups, and survival of the mice was recorded after modeling in each group. The lung wet/dry weight ratio and myeloperoxidase (MPO) activity were determined, and lung injury of the mice was evaluated using HE staining and acute lung injury score. The expressions of IL-1β, TNF-α, IL-6, NLRP3, caspase-1 p10, ASC, MPO, and caspase-8 in the lung tissue were detected using ELISA, Western blotting, or immunohistochemical staining. MDA and H2O2 levels in the lungs were detected to evaluate the level of oxidative stress. Immunofluorescence assay was used to investigate the co-localization of NLRP3 and NOX4.

RESULTS

The postoperative mortality rate at 72 h, lung wet/dry weight ratio, MPO level and acute lung injury scores were significantly lower in CLP+TP group than in CLP group (P < 0.05). Treatment with TP significantly reduced the expressions of NLRP3-related inflammatory factors (P < 0.05) and lowered MDA and H2O2 levels in the lung tissue of the septic mice (P < 0.05). Immunofluorescence co-staining showed a lower level of NOX4 and NLRP3 co-localization in CLP+TP group than in CLP group.

CONCLUSION

TP inhibits NLRP3 inflammasome-associated inflammation to alleviate CLP-induced acute lung injury in mice through a regulatory mechanism that inhibits NOX4 expression and reduces oxidative stress in the lung tissue.

Research advances of Zanthoxylum bungeanum Maxim. polyphenols in inflammatory diseases

Zanthoxylum bungeanum Maxim., commonly known as Chinese prickly ash, is a well-known spice and traditional Chinese medicine ingredient with a rich history of use in treating inflammatory conditions. This review provides a comprehensive overview of the botanical classification, traditional applications, and anti-inflammatory effects of Z. bungeanum, with a specific focus on its polyphenolic components. These polyphenols have exhibited considerable promise, as evidenced by preclinical studies in animal models, suggesting their therapeutic potential in human inflammatory diseases such as ulcerative colitis, arthritis, asthma, chronic obstructive pulmonary disease, cardiovascular disease, and neurodegenerative conditions. This positions them as a promising class of natural compounds with the potential to enhance human well-being. However, further research is necessary to fully elucidate their mechanisms of action and develop safe and effective therapeutic applications.

Delphinidin-3-rutinoside from Blackcurrant Berries (Ribes nigrum): In Vitro Antiproliferative Activity and Interactions with Other Phenolic Compounds

Blackcurrant berries (Rigrum L.) are of great interest for food scientists/technologists as a source of delphinidin-3-rutinoside (D3R). This is an uncommon phenolic compound in diets that unveils potent antiproliferative activity besides its colour. Other phenolic compounds, such as chlorogenic acid (CA) and epicatechin (EC), also known by their antiproliferative effects, are abundant in foods and beverages. To design smart food/supplements combinations containing blackcurrant and improved anticancer properties at the gastrointestinal level, there is the need for more data concerning the combined effects of those molecules. In this work, synergistic, additive, or antagonistic effects against gastric and intestinal cancers of D3R, CA, and EC were assessed in vitro. The antiproliferative activity of D3R, CA, and EC, alone and in binary combinations (D3R+CA, D3R+EC, and CA+EC) on NCI-N87 (gastric) and Caco-2 (intestinal) cells, was assessed following the Chou-Talalay theorem at equipotent contributions (i.e., (IC₅₀)₁/(IC₅₀)₂). D3R presented the strongest antiproliferative activity of the single molecules tested, with IC₅₀ values of 24.9 µM and 102.5 µM on NCI-N87 and Caco-2 cells, respectively. The combinations D3R+CA and CA+EC were synergic against NCI-N87 until IC₅₀ and IC₇₅, respectively, while D3R+EC shifted from slight antagonism to synergism at higher doses. On Caco-2 cells, antagonism at low doses and synergism at high doses was observed. Therefore, the synergisms observed on the gastric cancer model at low doses occurred on the colon model only at high doses. Data herein described is vital to the targeted smart design of foods and supplements, as it is foreseen that the same combination of phenolic compounds causes different interactions/effects depending on the dose and gastrointestinal compartment.

Severe COVID-19-A Review of Suggested Mechanisms Based on the Role of Extracellular Matrix Stiffness

The severity of COVID-19 commonly depends on age-related tissue stiffness. The aim was to review publications that explain the effect of microenvironmental extracellular matrix stiffness on cellular processes. Platelets and endothelial cells are mechanosensitive. Increased tissue stiffness can trigger cytokine storm with the upregulated expression of pro-inflammatory cytokines, such as tumor necrosis factor alpha and interleukin IL-6, and tissue integrity disruption, leading to enhanced virus entry and disease severity. Increased tissue stiffness in critically ill COVID-19 patients triggers platelet activation and initiates plague formation and thrombosis development. Cholesterol content in cell membrane increases with aging and further enhances tissue stiffness. Membrane cholesterol depletion decreases virus entry to host cells. Membrane cholesterol lowering drugs, such as statins or novel chitosan derivatives, have to be further developed for application in COVID-19 treatment. Statins are also known to decrease arterial stiffness mitigating cardiovascular diseases. Sulfated chitosan derivatives can be further developed for potential use in future as anticoagulants in prevention of severe COVID-19. Anti-TNF-α therapies as well as destiffening therapies have been suggested to combat severe COVID-19. The inhibition of the nuclear factor kappa-light-chain-enhancer of activated B cells pathway must be considered as a therapeutic target in the treatment of severe COVID-19 patients. The activation of mechanosensitive platelets by higher matrix stiffness increases their adhesion and the risk of thrombus formation, thus enhancing the severity of COVID-19.

Catechins: Protective mechanism of antioxidant stress in atherosclerosis

Tea has long been valued for its health benefits, especially its potential to prevent and treat atherosclerosis (AS). Abnormal lipid metabolism and oxidative stress are major factors that contribute to the development of AS. Tea, which originated in China, is believed to help prevent AS. Research has shown that tea is rich in catechins, which is considered a potential source of natural antioxidants. Catechins are the most abundant antioxidants in green tea, and are considered to be the main compound responsible for tea's antioxidant activity. The antioxidant properties of catechins are largely dependent on the structure of molecules, and the number and location of hydroxyl groups or their substituents. As an exogenous antioxidant, catechins can effectively eliminate lipid peroxidation products. They can also play an antioxidant role indirectly by activating the endogenous antioxidant system by regulating enzyme activity and signaling pathways. In this review, we summarized the preventive effect of catechin in AS, and emphasized that improving the antioxidant effect and lipid metabolism disorders of catechins is the key to managing AS.

The effects of Dendrobium species on the metabolic syndrome: A review

Metabolic syndrome (MetS) is known as a global health challenge with different types of health conditions such as hypertension, hyperglycemia, the increasing prevalence of obesity, and hyperlipidemia. Despite much recent scientific progress, the use of traditional herbal medicines with fewer side effects is increasing worldwide. Dendrobium, the second-largest orchid genus, has been used as a natural source of drugs for the treatment of MetS. The beneficial effects of Dendrobium, including anti-hypertension, anti-hyperglycemia, anti-obesity, and anti-hyperlipidemic against MetS have been shown in the scientific evidence. The anti-oxidant and lipid-lowering effects of Dendrobium modulate hyperlipidemia via reducing lipid accumulation and maintaining lipid metabolism. Restoring pancreatic beta cells and regulating the insulin signaling pathway are involved in its antidiabetic properties. The hypotensive effects contribute to increasing nitric oxide (NO) generation and inhibiting extracellular signal-regulated kinase (ERK) signaling. More research projects, especially clinical trials, are needed to investigate the safety, efficacy, and pharmacokinetics of Dendrobium in patients. This review article provides, for the first time, comprehensive information about the efficacy of different species of Dendrobium. The described species can be a source of medicines for the treatment of MetS, which are reported in various evidence.

Dietary Supplementation with Epicatechin Improves Intestinal Barrier Integrity in Mice

Epicatechin (EPI) is a dietary flavonoid that is present in many foods and possesses various bioactivities. We assessed the effects of EPI supplementation on intestinal barrier integrity in mice. Thirty-six mice were assigned to three groups and fed a standard diet or a standard diet supplemented with 50 or 100 mg EPI/kg (n = 12 per group). After 21 days of rearing, blood and intestinal samples were collected from eight randomly selected mice. Supplementation with 50 and 100 mg/kg EPI decreased (p < 0.05) the serum diamine oxidase activity and _D-lactic acid concentration and increased (p < 0.05) the duodenal, jejunal, and ileal abundance of tight junction proteins, such as occludin. Moreover, it lowered (p < 0.05) the duodenal, jejunal, and ileal tumor necrosis factor-α contents and enhanced (p < 0.05) the duodenal and jejunal catalase activities and ileal superoxide dismutase activity. Supplementation with a lower dose (50 mg/kg) decreased (p < 0.05) the ileal interleukin-1β content, whereas supplementation with a higher dose (100 mg/kg) increased (p < 0.05) the duodenal and jejunal glutathione peroxidase activities. Furthermore, supplementation with 50 and 100 mg/kg EPI decreased (p < 0.05) cell apoptosis, cleaved cysteinyl aspartate-specific proteinase-3 (caspase-3), and cleaved caspase-9 contents in the duodenum, jejunum, and ileum. In conclusion, EPI could improve intestinal barrier integrity in mice, thereby suppressing intestinal inflammation and oxidative stress and reducing cell apoptosis.

Spinosin ameliorates insulin resistance by suppressing reactive oxygen species-associated inflammation

Objectives

Spinosin is the predominant C-glycoside flavonoid derived from the seeds of Zizyphus jujuba var. Spinosa (Rhamnaceae). The present study aimed to investigate the effects of spinosin on insulin resistance (IR) in vascular endothelium.

Materials and Methods

The anti-IR effect of spinosin was evaluated in a high-fat diet (HFD) treated mice model. The effects of spinosin pretreatment on reactive oxygen species (ROS)-associated inflammation in Human umbilical vein endothelial cells (HUVEC) were evaluated by western blot analysis and reverse transcription-polymerase chain reaction. The effect of spinosin on insulin-mediated endothelium-dependent vasodilation of rat aortae was further evaluated.

Results

Spinosin at 20 mg/kg alleviates increased mice's body weight, fasting serum glucose, oral glucose tolerance, serum insulin, insulin resistance index, and serum lipid of HFD-treated mice. Spinosin at 20 μM suppressed ROS overproduction, and inhibited ROS-related HUVEC inflammation by inhibiting mRNA expression of tumor necrosis factor-α and interleukin-6. In addition, spinosin at 0.1 μM showed a vasodilation effect of isoprenaline-pretreated rat aortae and increased insulin-mediated NO production in endothelial cells. These effects were shown to be related to the spinosin regulating serine/tyrosine phosphorylation of insulin receptor substrate-1 (IRS-1) facilitated/phosphoinositide 3-kinase (PI3K) signaling.

Conclusion

Spinosin may ameliorate IR and ROS-associated inflammation, and increase endothelial NO production by mediating IRS-1/PI3K/endothelial nitric oxide synthase (eNOS) pathway.

Effect of Passiflora setacea juice and its phenolic metabolites on insulin resistance markers in overweight individuals and on microglial cell activity

Passiflora setacea (PS) is a species of wild Brazilian passion fruit, rich in bioactive compounds. Scientific evidence suggests that food rich in polyphenols can modulate inflammation, thereby playing an important role in preventing chronic non-communicable diseases, such as type 2 diabetes (DT2) and cardiovascular diseases (CVD). This study aimed to investigate the effect of PS consumption on metabolic and inflammatory biomarkers in overweight male volunteers and to identify the underlying mechanism of action using an in vitro study using phenolic metabolites isolated from the plasma of volunteers at physiologically relevant concentrations. Volunteers participated in a double-blind, placebo-controlled (PB) study with two phases: phase I (acute study) and phase II (chronic study). In phase I, 15 volunteers ingested a single dose of 50 g, 150 g of PS pulp and PB in three different interventions. In phase II, nine volunteers ingested 50 g of PS or PB for 14 days. Blood samples were collected before (T0 h) and 3 h (T3 h) (phase I) or 15 days after (phase II) ingestion of PS or PB. Blood biochemical markers, HOMA IR, and inflammatory markers were analyzed and data on BMI, waist circumference, and consumption of polyphenol-rich foods were collected. Phenolic metabolites were extracted from plasma by solid-phase separation and were used to treat BV-2 cells stimulated by LPS or anacardic acid to assess p50, p65 and PPAR-γ activation. It was observed that the consumption of a single dose of PS juice significantly reduced basal insulin levels and HOMA IR. After prolonged consumption for two weeks, PS contributed to the reduction of circulating levels of IL-6. BV-2 cells treated with PS phenolic metabolites showed increased PPAR-γ activity, which resulted in an anti-inflammatory and anti-diabetic effect of PS metabolites. In conclusion, PS juice consumption exerts beneficial effects on inflammatory markers in overweight individuals, being a possible and important tool in the prevention of T2D and CVD in risk groups.

Obesity-associated biochemical markers of inflammation and the role of grain phytochemicals

The incidence of obesity or excessive fat accumulation in the body is increasing worldwide and has become one of the major growing health problems. Obese condition is linked with an increased level of body lipids, oxidative stress, and expression of inflammatory markers. This leads to plasma and hepatic hyperlipidemia, activation of proinflammatory cytokines (TNF-α, IL-6, and IL-1β), and transcriptional factors, which in turn lead to a high risk of cardiovascular diseases, insulin resistance, diabetes, asthma, rheumatological problem, and liver failure. Grains are the major staple food crops grown for consumption in most of the developing countries. Cereals and millets, such as rice, wheat, maize, barley, finger millet, foxtail millet, proso millet, kodo millet in the whole form with bran, germ, and endosperm, are found to be rich in phytochemicals, such as phenolics acids, vitamin E, phytosterols, carotenoids, antioxidants, dietary fiber, which have a potential health benefit on various lifestyle disorders. In this article, we summarize the findings and investigations regarding the anti-inflammatory effect of various grain phytochemicals in in vitro and in vivo models and their potential health benefits. PRACTICAL APPLICATIONS: The occurrence of obesity is rising globally and is becoming a major health concern. Obesity will lead to multiple health problems due to oxidative and inflammatory stress in the body. Whole forms of cereals and millets consumptions have shown to reduce the risk of metabolic disorders and several chronic diseases. Potential bioactive components in various grains will act on the inhibition ofbiochemical markers connected with inflammation and adipogenesis.

HM-chromanone attenuates TNF-α-mediated inflammation and insulin resistance by controlling JNK activation and NF-κB pathway in 3T3-L1 adipocytes

Obesity is a major public health problem worldwide and causes inflammation and insulin resistance in adipose tissue. We investigated the ability of (E)-5-hydroxy-7-methoxy-3-(2'-hydroxybenzyl)-4-chromanone (HM-chromanone) isolated from Portulaca oleracea to attenuate the activation of inflammatory cytokines and signaling pathways associated with tumor necrosis factor (TNF)-α-mediated inflammation and insulin resistance in 3T3-L1 adipocytes. TNF-α triggers the release of inflammatory cytokines and activation of the mitogen-activated protein kinase and nuclear factor (NF)-κB signaling pathways. In this study, HM-chromanone inhibited the production of inflammatory cytokines and chemokines [TNF-α, interleukin (IL)-6, IL-1β, and monocyte chemoattractant protein 1] involved in inflammation and insulin resistance. Furthermore, TNF-α treatment increased c-Jun-NH2 terminal kinase (JNK) phosphorylation, whereas HM-chromanone significantly decreased JNK phosphorylation in a dose-dependent manner. TNF-α treatment increased the activation of inhibitor kappa B (IκB) kinase (IKK), IκBα, and NF-κBp65 compared with that of the control. However, HM-chromanone significantly blocked IKK, IκBα, and NF-κBp65 activation. Upon adipocyte stimulation with TNF-α, phosphorylated insulin receptor substrate (pIRS)-1 serine 307 levels increased and pIRS-1 tyrosine 612 levels decreased compared with those of the control. Upon treatment with HM-chromanone, serine 307 phosphorylation of IRS-1 was inhibited and tyrosine 612 phosphorylation of IRS-1 was increased. Thus, HM-chromanone improved TNF-α-mediated inflammation and insulin resistance by regulating JNK activation and the NF-κB pathway, thereby reducing inflammatory cytokine secretion and inhibiting serine phosphorylation of IRS-1 in the insulin signaling pathway. These results suggest the potential of HM-chromanone to improve inflammatory conditions and insulin resistance in adipocytes.

Effects of Oral Administration of Bamboo (Dendrocalamus membranaceus) Leaf Flavonoids on the Antioxidant Capacity, Caecal Microbiota, and Serum Metabolome of Gallus gallus domesticus

The consumption of bamboo leaf flavonoids (BLFs) as novel dietary antioxidants has increased owing to their beneficial biological and pharmacological functions. This study assessed the in vivo effects of BLFs on antioxidant capacity, as well as caecal microbiota, serum metabolome, and health status. The Gallus gallus domesticus model and the oral administration approach were used with four treatment groups (basal diet, basal diet with 20 mg bacitracin/kg, basal diet with 50 mg BLF/kg, and basal diet with 250 mg BLF/kg). Ultra-high-performance liquid chromatography triple-quadrupole mass spectrometry analysis indicated that vitexin, fumaric acid, orientin, isoorientin, and p-coumaric acid were the predominant BLF components. From days 1 to 21, BLF increased the average daily gain and decreased the feed:gain of broilers. Moreover, BLF enhanced the serum antioxidant capacity and immune responses. Further, 16S rRNA sequencing showed that BLF modulated the caecal microbial community structure, which was dominated by Betaproteobacteriales, Erysipelatoclostridium, Parasutterella, Lewinella, Lactobacillus, and Candidatus Stoquefichus in BLF broilers. Among the 22 identified serum metabolites in BLF broilers, sphinganine, indole-3-acetaldehyde retinol, choline, 4-methylthio-2-oxobutanoic acid, and L-phenylalanine were recognised as biomarkers. In summary, BLFs appeared to modulate the caecal microbiome, alter the serum metabolome, and indirectly improve antioxidant capacity and health status.

( -)-Epicatechin and cardiometabolic risk factors: a focus on potential mechanisms of action

This review summarizes experimental evidence on the beneficial effects of ( -)-epicatechin (EC) attenuating major cardiometabolic risk factors, i.e., dyslipidemias, obesity (adipose tissue dysfunction), hyperglycemia (insulin resistance), and hypertension (endothelial dysfunction). Studies in humans are revised and complemented with experiments in animal models, and cultured cells, aiming to understand the molecular mechanisms involved in EC-mediated effects. Firstly, an assessment of EC metabolism gives relevance to both conjugated-EC metabolites product of host metabolism and microbiota-derived species. Integration and analysis of results stress the maintenance of redox homeostasis and mitigation of inflammation as relevant processes associated with cardiometabolic diseases. In these processes, EC appears having significant effects regulating NADPH oxidase (NOX)-dependent oxidant production, nitric oxide (NO) production, and energy homeostasis (mitochondrial biogenesis and function). The potential participation of cell membranes and membrane-bound receptors is also discussed in terms of direct molecular action of EC and EC metabolites reaching cells and tissues.

Alpinia officinarum water extract inhibits the atopic dermatitis-like responses in NC/Nga mice by regulation of inflammatory chemokine production

Alpinia officinarum (AO) has been traditionally used in Asia as an herbal medicine to treat inflammatory and internal diseases. However, the therapeutic effect of AO on atopic dermatitis (AD) is unclear. Therefore, we examined whether Alpinia officinarum water extract (AOWex) affects AD in vivo and in vitro. Oral administration of AOWex to NC/Nga mice with Dermatophagoies farina extract (DfE)-induced AD-like symptoms significantly reduced the severity of clinical dermatitis, epidermal thickness, and mast cell infiltration into the skin and ear tissue. Decreased total serum IgE, macrophage-derived chemokine (MDC), and regulated on activation, normal T-cell expressed and secreted (RANTES) levels were observed in DfE-induced NC/Nga mice in the AOWex-treated group. These effects were confirmed in vitro using HaCaT cells. Treatment with AOWex inhibited the expression of proinflammatory chemokines such as MDC, RANTES, IP-10 and I-TAC in interferon-γ and tumor necrosis factor-α-stimulated HaCaT cells. The anti-inflammatory effects of AOWex were due to its inhibitory action on MAPK phosphorylation (ERK and JNK), NF-κB, and STAT1. Furthermore, galangin, protocatechuic acid, and epicatechin from AOWex were identified as candidate anti-AD compounds. These results suggest that AOWex exerts therapeutic effects against AD by alleviating AD-like skin lesions, suppressing inflammatory mediators, and inhibiting major signaling molecules.

Polyphenols and Visual Health: Potential Effects on Degenerative Retinal Diseases

Dietary polyphenols are a group of natural compounds that have been proposed to have beneficial effects on human health. They were first known for their antioxidant properties, but several studies over the years have shown that these compounds can exert protective effects against chronic diseases. Nonetheless, the mechanisms underlying these potential benefits are still uncertain and contradictory effects have been reported. In this review, we analyze the potential effects of polyphenol compounds on some visual diseases, with a special focus on retinal degenerative diseases. Current effective therapies for the treatment of such retinal diseases are lacking and new strategies need to be developed. For this reason, there is currently a renewed interest in finding novel ligands (or known ligands with previously unexpected features) that could bind to retinal photoreceptors and modulate their molecular properties. Some polyphenols, especially flavonoids (e.g., quercetin and tannic acid), could attenuate light-induced receptor damage and promote visual health benefits. Recent evidence suggests that certain flavonoids could help stabilize the correctly folded conformation of the visual photoreceptor protein rhodopsin and offset the deleterious effect of retinitis pigmentosa mutations. In this regard, certain polyphenols, like the flavonoids mentioned before, have been shown to improve the stability, expression, regeneration and folding of rhodopsin mutants in experimental in vitro studies. Moreover, these compounds appear to improve the integration of the receptor into the cell membrane while acting against oxidative stress at the same time. We anticipate that polyphenol compounds can be used to target visual photoreceptor proteins, such as rhodopsin, in a way that has only been recently proposed and that these can be used in novel approaches for the treatment of retinal degenerative diseases like retinitis pigmentosa; however, studies in this field are limited and further research is needed in order to properly characterize the effects of these compounds on retinal degenerative diseases through the proposed mechanisms.

Systematic bioinformatic analysis of nutrigenomic data of flavanols in cell models of cardiometabolic disease

Flavanol intake positively influences several cardiometabolic risk factors in humans. However, the specific molecular mechanisms of action of flavanols, in terms of gene regulation, in the cell types relevant to cardiometabolic disease have never been systematically addressed. On this basis, we conducted a systematic literature review and a comprehensive bioinformatic analysis of genes whose expression is affected by flavanols in cells defining cardiometabolic health: hepatocytes, adipocytes, endothelial cells, smooth muscle cells and immune cells. A systematic literature search was performed using the following pre-defined criteria: treatment with pure compounds and metabolites (no extracts) at low concentrations that are close to their plasma concentrations. Differentially expressed genes were analyzed using bioinformatics tools to identify gene ontologies, networks, cellular pathways and interactions, as well as transcriptional and post-transcriptional regulators. The systematic literature search identified 54 differentially expressed genes at the mRNA level in in vitro models of cardiometabolic disease exposed to flavanols and their metabolites. Global bioinformatic analysis revealed that these genes are predominantly involved in inflammation, leukocyte adhesion and transendothelial migration, and lipid metabolism. We observed that, although the investigated cells responded differentially to flavanol exposure, the involvement of anti-inflammatory responses is a common mechanism of flavanol action. We also identified potential transcriptional regulators of gene expression: transcriptional factors, such as GATA2, NFKB1, FOXC1 or PPARG, and post-transcriptional regulators: miRNAs, such as mir-335-5p, let-7b-5p, mir-26b-5p or mir-16-5p. In parallel, we analyzed the nutrigenomic effects of flavanols in intestinal cells and demonstrated their predominant involvement in the metabolism of circulating lipoproteins. In conclusion, the results of this systematic analysis of the nutrigenomic effects of flavanols provide a more comprehensive picture of their molecular mechanisms of action and will support the future setup of genetic studies to pave the way for individualized dietary recommendations.

(-)-Epicatechin and Anthocyanins Modulate GLP-1 Metabolism: Evidence from C57BL/6J Mice and GLUTag Cells

BACKGROUND

Generated in intestinal L cells through cleavage of proglucagon (Gcg), glucagon-like peptide 1 (GLP-1) is secreted and rapidly inactivated by dipeptidyl peptidase IV (DPP-IV). GLP-1 regulates insulin secretion and overall glucose homeostasis. The capacity of dietary bioactives to increase GLP-1 circulating levels, and therefore increase insulin secretion and glucose metabolism, has gained significant interest of late.

OBJECTIVES

We evaluated the effects of (-)-epicatechin (EC) and different anthocyanins (ACs) and AC metabolites on GLP-1 metabolism in mice and on GLUTag cells.

METHODS

We fed 6-week-old C57BL/6J male mice a control diet or a control diet supplemented with either 40 mg AC or 20 mg EC/kg body weight for 14 weeks (AC) or 15 weeks (EC). Intestinal mRNA levels of Gcg and Dpp-iv were measured. In vitro, GLUTag cells were incubated in the presence or absence of different ACs, the AC metabolite protocatechuic acid (PCA), and EC. GLP-1 secretion and the main pathways involved in its release were assessed.

RESULTS

Long-term supplementation with EC or AC increased mouse GLP-1 plasma concentrations (55% and 98%, respectively; P < 0.05). In mice, 1) EC and AC increased Gcg mRNA levels in the ileum (91%) and colon (41%), respectively (P < 0.05); and 2) AC lowered ileum Dpp-iv mRNA levels (35%), while EC decreased plasma DPP-IV activity (15%; P < 0.05). In GLUTag cells, 1) cyanidin, delphinidin, PCA, and EC increased GLP-1 secretion (53%, 33%, 53%, and 68%, respectively; P < 0.05); and 2) cyanidin, delphinidin, EC, and PCA increased cyclin adenosine monophosphate levels (25-50%; P < 0.05) and activated protein kinase A (PKA; 100%, 50%, 80%, and 86%, respectively; P < 0.05).

CONCLUSIONS

In mice, EC and ACs regulated different steps in GLP-1 regulation, leading to increased plasma GLP-1. Cyanidin, delphinidin, PCA, and EC promoted GLP-1 secretion from GLUTag cells by activating the PKA-dependent pathway. These findings support the beneficial actions of these flavonoids in sustaining intestinal and glucose homeostasis through the modulation of the GLP-1 metabolism.

Grape pomace extract supplementation activates FNDC5/irisin in muscle and promotes white adipose browning in rats fed a high-fat diet

Irisin is a myokine regulated by peroxisome proliferator-activated receptor gamma co-activator-1α (PGC-1α) in the exercising skeletal muscle and released into the bloodstream after cleavage of FNDC5. Circulating irisin can up-regulate UCP-1 expression in white adipose tissue (WAT) promoting the formation of brown-like adipocytes. The aim of this study was to evaluate if supplementation with a grape pomace extract (GPE) could activate the FNDC5/irisin pathway via PGC-1α in rats fed a high fat diet (HFD). For this purpose we characterized the activation of: i. the FNDC5/irisin pathway and AMPK in skeletal muscle and ii. proteins involved in the formation of brown-like cells in epididymal WAT (eWAT). Consumption of the GPE activated the FNDC5/irisin pathway, increased AMPK phosphorylation in skeletal muscle and enhanced irisin plasma levels. In eWAT, the GPE increased the level of proteins involved in WAT browning, i.e. PGC-1α, PPARγ, PRDM16 and UCP-1. The GPE also prevented HFD-induced adipocyte hypertrophy and systemic insulin resistance. Consistently, in L6 myotubes, (-)-epicatechin (EC), a flavonoid abundant in the GPE, prevented palmitate-mediated downregulation of FNDC5/irisin protein expression and secretion, in part via PGC-1α activation. Consumption of the GPE, a winemaking residue rich in bioactive compounds, could be a beneficial strategy to counteract the adverse effects of Western style diets through the promotion of WAT browning.

Effects of Polyphenols on Insulin Resistance

Insulin resistance (IR) is apparent when tissues responsible for clearing glucose from the blood, such as adipose and muscle, do not respond properly to appropriate signals. IR is estimated based on fasting blood glucose and insulin, but some measures also incorporate an oral glucose challenge. Certain (poly)phenols, as supplements or in foods, can improve insulin resistance by several mechanisms including lowering postprandial glucose, modulating glucose transport, affecting insulin signalling pathways, and by protecting against damage to insulin-secreting pancreatic β-cells. As shown by intervention studies on volunteers, the most promising candidates for improving insulin resistance are (-)-epicatechin, (-)-epicatechin-containing foods and anthocyanins. It is possible that quercetin and phenolic acids may also be active, but data from intervention studies are mixed. Longer term and especially dose-response studies on mildly insulin resistant participants are required to establish the extent to which (poly)phenols and (poly)phenol-rich foods may improve insulin resistance in compromised groups.

Anti-inflammatory effects of troxerutin are mediated through elastase inhibition

CONTEXT

Obesity is a chronic low-grade inflammatory state associated with immune cell infiltration into the adipose tissue (AT). We hypothesize that the anti-obesity and anti-inflammatory effects of troxerutin (TX) are mediated through inhibition of elastase.

OBJECTIVE

To determine the inhibitory effect of TX on elastase in vitro and in tumor necrosis factor alpha (TNFα) induced 3T3-L1 adipocytes and the molecular interaction of TX with human neutrophil elastase (HNE).

MATERIALS AND METHODS

Differentiated 3T3-L1 adipocytes were pretreated with TX, elastatinal (ELAS) or sodium salicylate (SAL) before exposure to TNFα. Lipid accumulation, reactive oxygen species (ROS) generation and oxidant-antioxidant balance were examined. The mRNA and protein expression of TNFα, interleukin-6, monocyte chemoattractant protein-1, adiponectin, leptin, resistin, chemerin, and elastase were analyzed. Elastase inhibition by TX and ELAS in a cell free system and docking studies for HNE with TX and ELAS were performed.

RESULTS

TX, ELAS or SAL pretreatment had lowered lipid droplets formation and TG content. TX suppressed ROS generation, oxidative stress and improved antioxidant status. The expression of inflammatory cytokines and elastase was downregulated while that of adiponectin was upregulated by TX. The concentration required to produce 50% inhibition in vitro (IC₅₀) was 11.5 μM for TX and 16.9 μM for ELAS. TX showed hydrogen bonding and hydrophobic interactions with elastase.

DISCUSSION

TNFα induces inflammation of 3T3-L1 cells through elastase activation. TX inhibits elastase activity, downregulates expression and binds with elastase.

CONCLUSION

The antioxidant and anti-inflammatory activities of TX in AT could be of relevance in the management of obesity.

(-)-Epicatechin and the comorbidities of obesity

Obesity has major adverse consequences on human health contributing to the development of, among others, insulin resistance and type 2 diabetes, cardiovascular disease, non-alcoholic fatty liver disease, altered behavior and cognition, and cancer. Changes in dietary habits and lifestyle could contribute to mitigate the development and/or progression of these pathologies. This review will discuss current evidence on the beneficial actions of the flavan-3-ol (-)-epicatechin (EC) on obesity-associated comorbidities. These benefits can be in part explained through EC's capacity to mitigate several common events underlying the development of these pathologies, including: i) high circulating levels of glucose, lipids and endotoxins; ii) chronic systemic inflammation; iii) tissue endoplasmic reticulum and oxidative stress; iv) insulin resistance; v) mitochondria dysfunction and vi) dysbiosis. The currently known underlying mechanisms and cellular targets of EC's beneficial effects are discussed. While, there is limited evidence from human studies supplementing with pure EC, other studies involving cocoa supplementation in humans, pure EC in rodents and in vitro studies, support a potential beneficial action of EC on obesity-associated comorbidities. This evidence also stresses the need of further research in the field, which would contribute to the development of human dietary strategies to mitigate the adverse consequences of obesity.

(-)-Epicatechin protects thoracic aortic perivascular adipose tissue from whitening in high-fat fed mice

High adipose tissue (AT) accumulation in the body increases the risk for many metabolic and chronic diseases. This work investigated the capacity of the flavonoid (-)-epicatechin to prevent undesirable modifications of AT in mice fed a high-fat diet. Studies were focused on thoracic aorta perivascular AT (taPVAT), which is involved in the control of blood vessel tone, among other functions. Male C57BL/6J mice were fed for 15 weeks a high-fat diet with or without added (-)-epicatechin (20 mg per kg body weight per d). In high-fat diet fed mice, (-)-epicatechin supplementation: (i) prevented the expansion of taPVAT, (ii) attenuated the whitening of taPVAT (according to the adipocyte morphology, diameter, and uncoupling-protein 1 (UCP-1) levels) and (iii) blunted the increase in plasma glucose and cholesterol. The observed taPVAT modifications were not associated with alterations in the aorta wall thickness, aorta tumor necrosis factor-alpha (TNF-α) and NADPH-oxidase 2 (NOX2) expression, and endothelial nitric oxide synthase (eNOS) phosphorylation levels. In summary, our results indicate (-)-epicatechin as a relevant bioactive protecting from the slow and silent development of metabolic and chronic diseases as they are associated with excessive fat intake.

Antidiabetic Effects of Flavan-3-ols and Their Microbial Metabolites

Diet is one of the pillars in the prevention and management of diabetes mellitus. Particularly, eating patterns characterized by a high consumption of foods such as fruits or vegetables and beverages such as coffee and tea could influence the development and progression of type 2 diabetes. Flavonoids, whose intake has been inversely associated with numerous negative health outcomes in the last few years, are a common constituent of these food items. Therefore, they could contribute to the observed positive effects of certain dietary habits in individuals with type 2 diabetes. Of all the different flavonoid subclasses, flavan-3-ols are consumed the most in the European region. However, a large proportion of the ingested flavan-3-ols is not absorbed. Therefore, the flavan-3-ols enter the large intestine where they become available to the colonic bacteria and are metabolized by the microbiota. For this reason, in addition to the parent compounds, the colonic metabolites of flavan-3-ols could take part in the prevention and management of diabetes. The aim of this review is to present the available literature on the effect of both the parent flavan-3-ol compounds found in different food sources as well as the specific microbial metabolites of diabetes in order to better understand their potential role in the prevention and treatment of the disease.

Hydroethanolic stem bark extracts of Stryphnodendron adstringens impair M1 macrophages and promote M2 polarization

ETHNOPHARMACOLOGICAL RELEVANCE

Stryphnodendron adstringens has been used by indigenous Brazilian people to treat wound, infections, inflammation and other conditions.

AIM OF THE STUDY

This study aims to investigate the effect of S. adstringens on macrophage polarization.

METHODS

To prepare the hydroethanolic extract of Stryphnodendron adstringens (HESA), fresh bark was exposed to maceration, filtered and subsequently lyophilized. The extract HESA were analyzed by LC-DAD-MS to identify their constituents. Bone marrow cells were obtained from male C57BL/6 mice. Then, the cells were polarized into M1 or M2 subsets in the presence or absence of HESA. The membrane expression of TLR2, CD206, CCR7, class II MHC, and CD86, the intracellular expression of iNOS and IL-6 and the supernatant expression of IL-6 were determined by flow cytometry.

RESULTS

By LC-DAD-MS, twenty-four compounds could be detected from HESA and proanthocyanidins, flavan-3-ols, and chromones were identified. NO and iNOS were reduced in the HESA-treated cells. There was a reduction in IL6 in HESA-treated cells. The membrane expression of TLR2, CD206, CCR7, CD86, and class II MHC was reduced in HESA-treated cells. The densities of CD206 and IL-10 were found to be significantly increased in HESA-treated cells.

CONCLUSION

This work is the first to demonstrate that S. adstringens can modulate the functional polarization of macrophages into the M2 profile and suppress costimulatory molecules in M1 macrophages. These results corroborate with the ethnopharmacology use of S. adstringens, contributing to its pharmacological validation in wound treatment and expanding the knowledge about immunoregulatory action of this specie.

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.

Flavonoids and type 2 diabetes: Evidence of efficacy in clinical and animal studies and delivery strategies to enhance their therapeutic efficacy

Diabetes mellitus type 2 (T2DM) is a metabolic disorder develops due to the overproduction of free radicals where oxidative stress could contribute it. Possible factors are defective insulin signals, glucose oxidation, and degradation of glycated proteins as well as alteration in glutathione metabolism which induced hyperglycemia. Previous studies revealed a link between T2DM with oxidative stress, inflammation and insulin resistance which are assumed to be regulated by numerous cellular networks such as NF-κB, PI3K/Akt, MAPK, GSK3 and PPARγ. Flavonoids are ubiquitously present in the nature and classified according to their chemical structures for example, flavonols, flavones, flavan-3-ols, anthocyanidins, flavanones, and isoflavones. Flavonoids indicate poor bioavailability which could be improved by employing various nano-delivery systems against the occurrences of T2DM. These bioactive compounds exert versatile anti-diabetic activities via modulating targeted cellular signaling networks, thereby, improving glucose metabolism, α -glycosidase, and glucose transport or aldose reductase by carbohydrate metabolic pathway in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibres. Moreover, anti-diabetic properties of flavonoids also encounter diabetic related complications. This review article has designed to shed light on the anti-diabetic potential of flavonoids, contribution of oxidative stress, evidence of efficacy in clinical, cellular and animal studies and nano-delivery approaches to enhance their therapeutic efficacy. This article might give some new insights for therapeutic intervention against T2DM in near future.

Inflammatory Signaling and Brown Fat Activity

Obesity is characterized by a state of chronic inflammation in adipose tissue mediated by the secretion of a range of inflammatory cytokines. In comparison to WAT, relatively little is known about the inflammatory status of brown adipose tissue (BAT) in physiology and pathophysiology. Because BAT and brown/beige adipocytes are specialized in energy expenditure they have protective roles against obesity and associated metabolic diseases. BAT appears to be is less susceptible to developing inflammation than WAT. However, there is increasing evidence that inflammation directly alters the thermogenic activity of brown fat by impairing its capacity for energy expenditure and glucose uptake. The inflammatory microenvironment can be affected by cytokines secreted by immune cells as well as by the brown adipocytes themselves. Therefore, pro-inflammatory signals represent an important component of the thermogenic potential of brown and beige adipocytes and may contribute their dysfunction in obesity.

Sorbus umbellata (Desf.) Fritsch var. umbellata Leaves: Optimization of Extraction Conditions and Investigation Antimicrobial, Cytotoxic, and β-Glucuronidase Inhibitory Potential

This study aimed to optimize the extraction conditions for Sorbus umbellata (Desf.) Fritsch var. umbellata leaves to maximize the phenolic content and their antioxidant activity and to investigate β-glucuronidase (GUS) enzyme inhibitory, antimicrobial and cytotoxic potentials of the extracts obtained under optimum conditions. The optimum extraction conditions were found to be 78.2 and 79.7% solvent, 73.1 and 71.5 °C, and 89.9 and 88.8 min to maximize phenolic content and antioxidant activity, respectively. Low values of coefficient of variations indicate the high reliability and reproducibility of the conducted extraction experiments. Bioactivity results showed that extracts had cytotoxic effect on the MCF-7 and A549 cells where the highest cell proliferation inhibition was observed for the A549 cell line (71.8% at 150 μg/mL). Staphylococcus aureus showed highest zone of inhibition (19.3 mm) in all bacteria followed by Escherichia coli. Additionally, extracts displayed potential GUS inhibitory activity. In conclusion, Sorbus umbellata leaf extract can be obtained by optimized cost-saving extraction and has a potential bioactivity to be utilized as a food ingredient for high value-added products and/or nutraceuticals development where it can combat oxidative stress and GUS mediated reactive metabolite formation.

Oxidative stress and inflammation following sub-lethal oral exposure of cypermethrin in rats: mitigating potential of epicatechin

Cypermethrin (CYP), a synthetic pyrethroid is a common environmental toxicant owing to its wide usage as a broad-spectrum insecticide. Its exposure to non-target organisms, including man, elicits numerous adverse effects making it a major public health issue. Epicatechin (EC) has proven anti-oxidative and anti-inflammatory properties. The present study was undertaken to evaluate the protective efficacy of epicatechin with regards to altered oxidative and inflammatory parameters subsequent to CYP treatment in rats. Animals were divided into four groups. The first group served as the control, while groups 2, 3, and 4 were orally treated with EC (30 mg kg-1 body weight), CYP (25 mg kg-1 body weight), and CYP plus EC, respectively. Oral administration of CYP for 14 days increased the levels of oxidative stress markers such as malondialdehyde, lipid hydroperoxides, and advanced oxidized protein products in the liver and kidney. These were accompanied by a decrease in glutathione and total antioxidant capacity levels. The activity of the enzyme superoxide dismutase was increased while catalase and glutathione peroxidase activities were decreased in these organs. Moreover, CYP increased plasma levels of the pro-inflammatory cytokines, interleukin-6 and tumor necrosis factor alpha. The plasma content of the nitrative nucleic acid marker, 8-nitroguanine was also markedly elevated by CYP. Administration of EC to CYP-exposed rats mitigated the induced oxidative and inflammatory effects. These data suggest that EC can attenuate the toxic effects induced by CYP exposure.

Effect of Aruncus dioicus var. kamtschaticus Extract on Neurodegeneration Improvement: Ameliorating Role in Cognitive Disorder Caused by High-Fat Diet Induced Obesity

This study was performed to estimate the possibility of using an ethyl acetate fraction from Aruncus dioicus var. kamtschaticus (EFAD) on metabolic syndrome that is induced by a high-fat diet (HFD). It was demonstrated that EFAD suppresses lipid accumulation and improves insulin resistance (IR) caused by Tumor necrosis factor alpha (TNF-α) in in-vitro experiments using the 3T3-L1 cell. In in-vivo tests, C57BL/6 mice were fed EFAD at 20 and 40 mg/kg body weight (BW) for four weeks after the mice were fed HFD for 15 weeks to induce obesity. EFAD significantly suppressed the elevation of BW and improved impaired glucose tolerance in obese mice. Additionally, this study showed that EFAD has an ameliorating effect on obesity-induced cognitive disorder with behavioral tests. The effect of EFAD on peripheral-IR improvement was confirmed by serum analysis and western blotting in peripheral tissues. Additionally, EFAD showed an ameliorating effect on HFD-induced oxidative stress, impaired cholinergic system and mitochondrial dysfunction, which are interrelated symptoms of neurodegeneration, such as Alzheimer’s disease and central nervous system (CNS)-IR in brain tissue. Furthermore, we confirmed that EFAD improves CNS-IR by confirming the IR-related factors in brain tissue. Consequently, this study suggests the possibility of using EFAD for the prevention of neurodegeneration by improving metabolic syndrome that is caused by HFD.

The effects of polyphenols and other bioactives on human health

Although deficiencies in polyphenol intake do not result in specific deficiency diseases, adequate intake of polyphenols could confer health benefits, especially with regard to chronic diseases. Tea, cocoa, fruits, and berries, as well as vegetables, are rich in polyphenols. Flavan-3-ols from cocoa have been found to be associated with a reduced risk of stroke, myocardial infarction, and diabetes, as well as improvements in lipids, endothelial-dependent blood flow and blood pressure, insulin resistance, and systemic inflammation. The flavonoid quercetin and the stilbene resveratrol have also been associated with cardiometabolic health. Although polyphenols have been associated with improved cerebral blood flow, evidence of an impact on cognition is more limited. The ability of dietary polyphenols to produce clinical effects may be due, at least in part, to a bi-directional relationship with the gut microbiota. Polyphenols can impact the composition of the gut microbiota (which are independently associated with health benefits), and gut bacteria metabolize polyphenols into bioactive compounds that produce clinical benefits. Another critical interaction is that of polyphenols with other phytochemicals, which could be relevant to interpreting the health parameter effects of polyphenols assayed as purified extracts, whole foods, or whole food extracts.

Catechin attenuates TNF-α induced inflammatory response via AMPK-SIRT1 pathway in 3T3-L1 adipocytes

Chronic inflammation is a fundamental symptom of many diseases. Catechin possesses anti-oxidant and anti-inflammatory properties. However, the mechanism of catechin to prevent inflammation in 3T3-L1 adipocytes caused by TNF-α remains unknown. Therefore, the effects of catechin on the gene expression of cytokines and the activation of cell signals in TNF-α induced 3T3-L1 adipocytes were investigated. The effects of catechin on adipogenesis and cell viability were detected by Oil Red O staining and CCK-8 assay, respectively. The genes expression of cytokines was determined by real-time RT-PCR. The expression of NF-κB, AMPK, FOXO3a and SIRT1 on translation level was determined by western blotting analysis. The results demonstrated that catechin significantly enhanced adipogenesis and cell viability. catechin inhibited the gene expression of pro-inflammatory cytokines including IL-1α, IL-1β, IL-6, IL-12p35, and inflammatory enzymes including iNOS and COX-2, but enhanced the gene expression of anti-inflammatory cytokines including IL-4 and IL-10. Catechin also inhibited the activation of NF-κB, AMPK, FOXO3a and SIRT1, but increased the phosphorylation level of the above factors. All these results indicated that as a potential therapeutic strategy catechin has the ability of attenuating inflammatory response triggered by TNF-α through signaling cascades involved in inflammation and cytokines.

Flavonoids Alleviating Insulin Resistance through Inhibition of Inflammatory Signaling

During the past 20 years, many studies have focused on polyphenol compounds for their potential beneficial health effects. Flavonoids represent a large class of phenolic compounds found in fruits, vegetables, nuts, grains, cocoa, tea, and other beverages. Flavonoids have shown antioxidant and anti-inflammatory activities. Given the putative relationship between inflammation and insulin resistance, the consumption of flavonoids or flavonoid-rich foods has been suggested to reduce the risk of diabetes by targeting inflammatory signals. This is the first comprehensive review summarizing the current research progress on the inhibition of inflammation and alleviation of insulin resistance by flavonoids as well as the mechanistic link between these disorders. Laboratory and human studies on the activities of major flavonoids (flavones, isoflavones, flavonols, etc.) are discussed.

Flavonoids and Insulin-Resistance: From Molecular Evidences to Clinical Trials

Insulin-resistance is one of the main factors responsible for the onset and progression of Metabolic Syndrome (MetS). Among all polyphenols, the effects of flavonoids and their main food sources on insulin sensitivity have been widely evaluated in molecular and clinical studies. The aim of this review is to analyse the data observed in vitro, in vivo and in clinical trials concerning the effects of flavonoids on insulin resistance and to determine the molecular mechanisms with which flavonoids interact with insulin signaling.

Penta-O-galloyl-β-d-glucose, a hydrolysable tannin from Radix Paeoniae Alba, inhibits adipogenesis and TNF-α-mediated inflammation in 3T3-L1 cells

Penta-O-galloyl-β-d-glucose (PGG) was purified and identified from Radix Paeoniae Alba by HSCCC and HPLC/ESI-MS, and its inhibitory effects on adipogenesis and TNF-α-induced inflammation were assessed in 3T3-L1 cell line. The results showed that PGG dose-dependently reduced intracellular lipids accumulation, and this involved decrease the expression levels of major adipogenic markers, PPARγ, C/EBP α, through MAPKs inhibition. This was accompanied by a reduction of lipogenic genes, ACC, FAS, and SCD-1, involved in fatty acid synthesis. Furthermore, PGG also inhibited TNF-α-induced expression of inflammatory cytokines including IL-6 and MCP-1 in the matured 3T3-L1 adipocytes. The inhibitions were likely mediated by blocking the MAPKs and NF-κB activation. These findings highlighted that PGG could serve as a potent therapeutic agent for controlling obesity and obesity-related chronic inflammation.

Flavonoids from Camellia sinensis (L.) O. Kuntze seed ameliorates TNF-α induced insulin resistance in HepG2 cells

The aim of this study is to discuss the non-catechin flavonoids (NCF) from Camellia sinensis (L.) O. Kuntze seed improving TNF-α impaired insulin stimulated glucose uptake and insulin signaling. Flavonoids had anti-metabolic syndrome and anti-inflammatory properties. It had widely been known for biological activity of catechins in tea, but very few research reports discussed the biological activity of non-catechin flavonoids in tea seed. We used HepG2 cell to treat with 5 μM insulin or with 5 μM insulin + 30 ng/ml TNF-α. Detecting the glucose concentration of medium, insulin decreased the glucose levels of medium meant that insulin promoted glucose uptake into cells, but TNF-α inhibited the glucose uptake effect of insulin. Furthermore, insulin increased the protein expressions of IR, IRS-1, IRS-2, PI3K-α, Akt/PKB, GLUT-2, AMPK, GCK, pyruvate kinase, and PPAR-γ. TNF-α activated p65 and MAPKs (p38, JNK1/2 and ERK1/2), iNOS and COX-2 which worsened the insulin signaling expressions of IR, IRS-1, IRS-2, PI3K-α, Akt/PKB, GLUT-2, AMPK, GCK, pyruvate kinase, and PPAR-γ. We added NCF (500, 1000, 2000 ppm) to cell with insulin and TNF-α. Not only glucose levels of medium were lowered, and the protein expressions of insulin signaling were increased, but p38, JNK1/2, iNOS and COX-2 were also reduced. NCF could ameliorate TNF-α induced insulin resistance through inhibiting p38, JNK1/2, iNOS and COX-2, and suggested that it might be used in the future to help control insulin resistance. This finding is the first report to present the discovery.

Dietary fish oil ameliorates adipose tissue dysfunction in insulin-resistant rats fed a sucrose-rich diet improving oxidative stress, peroxisome proliferator-activated receptor γ and uncoupling protein 2

This work aims to assess the possible beneficial effects of dietary fish oil (FO) on the pre-existing adipose tissue dysfunction through the improvement or reversion of the mechanisms underlying oxidative stress and pro-inflammatory cytokines in dyslipemic insulin-resistant rats. Wistar rats were fed a sucrose rich diet (SRD) for 6 months. After that half of the animals continued with the SRD until month 8 while in the other half corn oil was replaced by FO for 2 months (SRD + FO). A reference group consumed a control diet all the time. In an epididymal fat pad, we analyzed antioxidant and oxidant enzyme activities, ROS content, glutathione redox state, the protein level of peroxisome proliferator-activated receptor gamma (PPARγ) and the expression and protein levels of uncoupling protein 2 (UCP2) as well as oxidative stress biomarkers and TNF-α and IL-6 plasma levels. Besides these, insulin sensitivity and the composition of fatty acid phospholipids of adipose tissue were measured. Compared with the SRD the SRD + FO fed group showed a decrease of fat pad weight and the antioxidant and oxidant enzyme activities and ROS content returned to control values along with normal plasma TNF-α and IL-6 levels. FO normalized both the decrease of PPARγ protein and the increase of protein and expression of UCP2. Furthermore, FO increased the n-3/n-6 fatty acid ratio in the adipose tissue phospholipids and normalized dyslipidemia and insulin resistance. Finally, these findings reinforce the view that dietary FO may exert a beneficial effect in ameliorating the dyslipidemia and insulin resistance in this animal model.

(-)-Epicatechin Reduces Blood Pressure and Improves Left Ventricular Function and Compliance in Deoxycorticosterone Acetate-Salt Hypertensive Rats

(−)-Epicatechin (E) is a flavanol found in green tea and cocoa and has been shown to attenuate tumour necrosis factor alpha (TNF-α)-mediated inflammation, improve nitric oxide levels, promote endothelial nitric oxide synthase (eNOS) activation and inhibit NADPH oxidase. This study investigated the effect of 28 days of low epicatechin dosing (1 mg/kg/day) on the cardiovascular function of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Wistar rats (n = 120, 8 weeks of age) underwent uninephrectomy and were randomised into four groups (uninephrectomy (UNX), UNX + E, DOCA, DOCA + E). DOCA and DOCA + E rats received 1% NaCl drinking water along with subcutaneous injections of 25 mg deoxycorticosterone-acetate (in 0.4 mL of dimethylformamide) every fourth day. UNX + E and DOCA + E rats received 1 mg/kg/day of epicatechin by oral gavage. Single-cell micro-electrode electrophysiology, Langendorff isolated-heart assessment and isolated aorta and mesenteric organ baths were used to assess cardiovascular parameters. Serum malondialdehyde concentration was used as a marker of oxidative stress. Myocardial stiffness was increased and left ventricular compliance significantly diminished in the DOCA control group, and these changes were attenuated by epicatechin treatment (p < 0.05). Additionally, the DOCA + E rats showed significantly reduced blood pressure and malondialdehyde concentrations; however, there was no improvement in left ventricular hypertrophy, electrophysiology or vascular function. This study demonstrates the ability of epicatechin to reduce blood pressure, prevent myocardial stiffening and preserve cardiac compliance in hypertrophied DOCA-salt rat hearts.

(-)-Epicatechin and its metabolites prevent palmitate-induced NADPH oxidase upregulation, oxidative stress and insulin resistance in HepG2 cells

While diets rich in fruit and vegetables can decrease the risk for type 2 diabetes (T2D), diets rich in fat and carbohydrates can increase it. The flavanol-3-ol (-)-epicatechin (EC) can improve insulin sensitivity both in humans and animal models of T2D. NADPH oxidases and oxidative stress can contribute to the development of insulin resistance. This study investigated the capacity of EC and EC metabolites (ECM) to downregulate NADPH oxidases and oxidative stress, and its association to an improvement of insulin sensitivity. This was studied in in vivo (high fat-fed mice) and in vitro (HepG2 cells) conditions of hepatic lipid overload. EC decreased NOX3/NOX4 liver expression and mitigated oxidative stress in high fat-fed mice. In HepG2 cells, incubation with palmitate increased: i) lipid deposition, ii) NOX3/NOX4 expression, iii) NADPH oxidase activity, and iv) oxidative stress; promoting v) the activation of redox-sensitive kinases (JNK and IKK), and vi) impaired insulin responses. Physiological concentrations of EC and ECM, and NADPH oxidase inhibitors (apocynin, VAS2870) prevented all those deleterious effects of palmitate. The obtained results points to NADPH oxidases as an important target in the capacity of EC to improve insulin sensitivity in conditions of liver lipid overload, as those associated with Western-style diets.

Grape pomace extract induced beige cells in white adipose tissue from rats and in 3T3-L1 adipocytes

This study investigated the effects of a grape pomace extract (GPE) rich in phenolic compounds on brown-like adipocyte induction and adiposity in spontaneously hypertensive (SHR) and control normotensive Wistar-Kyoto (WKY) rats fed a high-fat diet (HFD). HFD consumption for 10 weeks significantly increased epididymal white adipose tissue (eWAT) in WKY but not in SHR rats. Supplementation with GPE (300 mg/kg body weight/day) reduced adipocyte diameter and increased levels of proteins that participate in adipogenesis and angiogenesis, i.e., peroxisome-proliferator activated receptor gamma (PPARγ), vascular endothelial grow factor-A (VEGF-A) and its receptor 2 (VEGF-R2), and partially increased the uncoupling protein 1 (UCP-1) in WKY. In both strains, GPE attenuated adipose inflammation. In eWAT from SHR, GPE increased the expression of proteins involved in adipose tissue "browning," i.e., PPARγ-coactivator-1α (PGC-1α), PPARγ, PR domain containing 16 (PRDM16) and UCP-1. In primary cultures of SHR adipocytes, GPE-induced UCP-1 up-regulation was dependent on p38 and ERK activation. Accordingly, in 3T3-L1 adipocytes treated with palmitate, the addition of GPE (30 μM) activated the β-adrenergic signaling cascade (PKA, AMPK, p38, ERK). This led to the associated up-regulation of proteins involved in mitochondrial biogenesis (PGC-1α, PPARγ, PRDM16 and UCP-1) and fatty acid oxidation (ATGL). These effects were similar to those exerted by (-)-epicatechin and quercetin, major phenolic compounds in GPE. Overall, in HFD-fed rats, supplementation with GPE promoted brown-like cell formation in eWAT and diminished adipose dysfunction. Thus, winemaking residues, rich in bioactive compounds, could be useful to mitigate the adverse effects of HFD-induced adipose dysfunction.

(-)-Epicatechin and the Colonic 2,3-Dihydroxybenzoic Acid Metabolite Regulate Glucose Uptake, Glucose Production, and Improve Insulin Signaling in Renal NRK-52E Cells

SCOPE

(-)-Epicatechin (EC) and main colonic phenolic acids derived from flavonoid intake, such as 2,3-dihydroxybenzoic acid (DHBA), 3,4-dihydroxyphenylacetic acid (DHPAA), 3-hydroxyphenylpropionic acid (HPPA), and vanillic acid (VA), have been suggested to exert beneficial effects in diabetes, although the mechanism for their actions remains unknown. In this study, the modulation of glucose homeostasis and insulin signaling by the mentioned compounds on renal proximal tubular NRK-52E cells is investigated.

METHODS AND RESULTS

Levels of the glucose transporters SGLT-2 and GLUT-2, as well as glucose uptake, glucose production, and key proteins of the insulin pathways, namely insulin receptor (IR), insulin receptor substrate-1 (IRS-1), and PI3K/AKT pathway are analyzed. EC (5-20 μm) and DHBA (20 μm) reduced both renal glucose uptake and production. Interestingly, EC and DHBA did not modify the levels of SGLT-2 and GLUT-2, and modulated the expression of phosphoenolpyruvate carboxykinase via AKT leading to a diminished glucose production. EC and DHBA also enhanced the tyrosine phosphorylation and total IR and IRS-1 levels, and activated the PI3K/AKT pathway in NRK-52E cells.

CONCLUSION

EC and DHBA regulate the renal glucose homeostasis by modulating both glucose uptake and production, and strengthen the insulin signaling by activating key proteins of that pathway in NRK-52E cells.

(-)-Epicatechin protects the intestinal barrier from high fat diet-induced permeabilization: Implications for steatosis and insulin resistance

Increased permeability of the intestinal barrier is proposed as an underlying factor for obesity-associated pathologies. Consumption of high fat diets (HFD) is associated with increased intestinal permeabilization and increased paracellular transport of endotoxins which can promote steatosis and insulin resistance. This study investigated whether dietary (-)-epicatechin (EC) supplementation can protect the intestinal barrier against HFD-induced permeabilization and endotoxemia, and mitigate liver damage and insulin resistance. Mechanisms leading to loss of integrity and function of the tight junction (TJ) were characterized. Consumption of a HFD for 15 weeks caused obesity, steatosis, and insulin resistance in male C57BL/6J mice. This was associated with increased intestinal permeability, decreased expression of ileal TJ proteins, and endotoxemia. Supplementation with EC (2-20mg/kg body weight) mitigated all these adverse effects. EC acted modulating cell signals and the gut hormone GLP-2, which are central to the regulation of intestinal permeability. Thus, EC prevented HFD-induced ileum NOX1/NOX4 upregulation, protein oxidation, and the activation of the redox-sensitive NF-κB and ERK1/2 pathways. Supporting NADPH oxidase as a target of EC actions, in Caco-2 cells EC and apocynin inhibited tumor necrosis alpha (TNFα)-induced NOX1/NOX4 overexpression, protein oxidation and monolayer permeabilization. Together, our findings demonstrate protective effects of EC against HFD-induced increased intestinal permeability and endotoxemia. This can in part underlie EC capacity to prevent steatosis and insulin resistance occurring as a consequence of HFD consumption.

Effects of Cocoa Antioxidants in Type 2 Diabetes Mellitus

Type 2 Diabetes mellitus (T2D) is the most common form of diabetes and one of the most common chronic diseases. Control of hyperglycaemia by hypoglycaemic drugs is insufficient in for patients and nutritional approaches are currently being explored. Natural dietary compounds such as flavonoids, abundant in fruits and vegetables, have received broad attention because of their potential capacity to act as anti-diabetic agents. Especially cocoa flavonoids have been proved to ameliorate important hallmarks of T2D. In this review, an update of the most relevant reports published during the last decade in cell culture, animal models and human studies is presented. Most results support an anti-diabetic effect of cocoa flavonoids by enhancing insulin secretion, improving insulin sensitivity in peripheral tissues, exerting a lipid-lowering effect and preventing the oxidative and inflammatory damages associated to the disease. While it could be suggested that daily consumption of flavanols from cocoa or dark chocolate would constitute a potential preventive tool useful for the nutritional management of T2D, this recommendation should be cautious since most of commercially available soluble cocoa products or chocolates contain low amount of flavanols and are rich in sugar and calories that may aggravate glycaemic control in T2D patients.

Adipose Tissue-Specialized Immunologic Features Might Be the Potential Therapeutic Target of Prospective Medicines for Obesity

Excessive lipid accumulation in adipose tissue is either the source of obesity or the cause and result of chronic local inflammation, and recent studies indicate that the accumulation may induce many other specialized immunologic features with macrophages and epidemic diseases. We analyze the effective stages of immune cells in adipose tissue, including macrophage recruitment, macrophage polarization, and macrophage-like phenotype preadipocyte possession to find optimal sites as drug targets. Subsequently, some main signaling pathways are summarized in this review, including the AMP-activated protein kinase (AMPK) pathway, the JNK signaling pathway, and a novel one, the Notch signaling pathway. We illustrate all these points in order to determine the general pathogenesis of chronic low-grade local inflammation in adipose tissue and the related signaling pathways. In addition, signal-associated prospective compounds, such as berberine, are summarized and discussed with potential targets in pathogenesis. This might provide some possible thoughts and novel therapies for studying chronic inflammatory diseases, such as insulin resistance and type 2 diabetes mellitus.

LPS-induced renal inflammation is prevented by (-)-epicatechin in rats

This work investigated the capacity of (−)-epicatechin to prevent the renal damage induced by LPS administration in rats. Male Sprague Dawley rats were fed for 4 days a diet without or with supplementation with (−)-epicatechin (80 mg/kg BW/d), and subsequently i.p. injected with lipopolysaccharide (LPS). Six hours after injection, LPS-treated rats exhibited increased plasma creatinine and urea levels as indicators of impaired renal function. The renal cortex of the LPS-treated rats showed: i) increased expression of inflammatory molecules (TNF-α, iNOS and IL-6); ii) activation of several steps of NF-κB pathway; iii) overexpression of TLR4, and iv) higher superoxide anion production and lipid peroxidation index in association with increased levels of gp91^phox and p47^phox (NOX2) and NOX4. Pretreatment with dietary (−)-epicatechin prevented the adverse effects of LPS challenge essentially by inhibiting TLR4 upregulation and NOX activation and the consequent downstream events, e.g. NF-kB activation.

Anti-inflammatory actions of (-)-epicatechin in the adipose tissue of obese mice

Obesity and type 2 diabetes (T2D) are major public health concerns. Visceral adipose tissue inflammation is considered a significant contributor to obesity-associated T2D development. We previously showed that the flavan-3-ol (-)-epicatechin (EC) can mitigate insulin resistance in mice fed a high fat diet (HFD). This study investigated the capacity of EC to inhibit visceral adipose tissue inflammation occurring as a consequence of HFD consumption in C57BL/6J mice, and characterized the underlying mechanisms. In association with the development of obesity and insulin resistance, HFD consumption caused inflammation in the visceral adipose tissue as evidenced by activation of the pro-inflammatory transcription factor NF-κB and increased tissue levels of the macrophage marker F4/80, tumor necrosis factor alpha (TNFα), and the chemokine MCP-1. EC supplementation mitigated all these events. In addition, we observed activation of the three branches of the unfolded protein response (UPR), and upregulation of NADPH oxidases NOX4 and NOX2 in visceral fat of mice fed HFD. These can account, at least in part, for the associated oxidative stress and activation of the redox sensitive NF-κB. Notably, EC supplementation mitigated this and the release of pro-inflammatory proteins from metabolically stressed adipocytes. Attenuation of adipocyte endoplasmic reticulum (ER) and oxidative stress by EC could contribute to decreased inflammation and improved visceral adipose tissue insulin sensitivity. Our results support the concept that consumption of EC-rich foods could mitigate obesity-associated insulin resistance through attenuation of adipose tissue inflammation.