Acute intake of quercetin from onion skin extract does not influence postprandial blood pressure and endothelial function in overweight-to-obese adults with hypertension: a randomized, double-blind, placebo-controlled, crossover trial

An ethnopharmacological, phytochemical, and pharmacological overview of onion (Allium cepa L.)

ETHNOPHARMACOLOGICAL RELEVANCE

Onion (Allium cepa L.) is one of the most widely distributed species within the Allium genus of family Amaryllidaceae. Onion has been esteemed for its medicinal properties since antiquity. It has been consumed for centuries in various indigenous cultures for the management of several ailments including microbial infections, respiratory, gastrointestinal, skin and cardio-vascular disorders, diabetes, renal colic, rheumatism, sexual impotence, menstrual pain, and headache. However, so far, there is a scarcity of recent data that compiles the plant chemistry, traditional practices, biological features, and toxicity.

AIM OF THE WORK

The aim of this review is to provide a comprehensive and analytical overview of ethnopharmacological uses, phytochemistry, pharmacology, industrial applications, quality control, and toxicology of onion, to offer new perspectives and broad scopes for future studies.

MATERIALS AND METHODS

The information gathered in this review was obtained from various sources including books, scientific databases such as Science Direct, Wiley, PubMed, Google Scholar, and other domestic and foreign literature.

RESULTS

Onion has a long history of use as a traditional medicine for management of various conditions including infectious, inflammatory, respiratory, cardiovascular diseases, diabetes, and erectile dysfunction. More than 400 compounds have been identified in onion including flavonoids, phenolic acids, amino acids, peptides, saponins and fatty acids. The plant extracts and compounds showed various pharmacological activities such as antimicrobial, antidiabetic, anti-inflammatory, anti-hyperlipidemic, anticancer, aphrodisiac, cardioprotective, and neuroprotective activities. In addition to its predominant medicinal uses, onion has found various applications in the functional food industry.

CONCLUSION

Extensive literature analysis reveals that onion extracts and bioactive constituents possess diverse pharmacological activities that can be beneficial for treating various diseases. However, the current research primarily revolves around the documentation of ethnic pharmacology and predominantly consists of in vitro studies, with relatively limited in vivo and clinical studies. Consequently, it is imperative for future investigations to prioritize and expand the scope of in vivo and clinical research. Additionally, it is strongly recommended to direct further research efforts towards toxicity studies and quality control of the plant. These studies will help bridge the current knowledge gaps and establish a solid basis for exploring the plant's potential uses in a clinical setting.

Research progress of quercetin in cardiovascular disease

Quercetin is one of the most common flavonoids. More and more studies have found that quercetin has great potential utilization value in cardiovascular diseases (CVD), such as antioxidant, antiplatelet aggregation, antibacterial, cholesterol lowering, endothelial cell protection, etc. However, the medicinal value of quercetin is mostly limited to animal models and preclinical studies. Due to the complexity of the human body and functional structure compared to animals, more research is needed to explore whether quercetin has the same mechanism of action and pharmacological value as animal experiments. In order to systematically understand the clinical application value of quercetin, this article reviews the research progress of quercetin in CVD, including preclinical and clinical studies. We will focus on the relationship between quercetin and common CVD, such as atherosclerosis, myocardial infarction, ischemia reperfusion injury, heart failure, hypertension and arrhythmia, etc. By elaborating on the pathophysiological mechanism and clinical application research progress of quercetin's protective effect on CVD, data support is provided for the transformation of quercetin from laboratory to clinical application.

Circuits and Biomarkers of the Central Nervous System Relating to Astronaut Performance: Summary Report for a NASA-Sponsored Technical Interchange Meeting

Biomarkers, ranging from molecules to behavior, can be used to identify thresholds beyond which performance of mission tasks may be compromised and could potentially trigger the activation of countermeasures. Identification of homologous brain regions and/or neural circuits related to operational performance may allow for translational studies between species. Three discussion groups were directed to use operationally relevant performance tasks as a driver when identifying biomarkers and brain regions or circuits for selected constructs. Here we summarize small-group discussions in tables of circuits and biomarkers categorized by (a) sensorimotor, (b) behavioral medicine and (c) integrated approaches (e.g., physiological responses). In total, hundreds of biomarkers have been identified and are summarized herein by the respective group leads. We hope the meeting proceedings become a rich resource for NASA's Human Research Program (HRP) and the community of researchers.

Effects of quercetin supplementation on endothelial dysfunction biomarkers and depression in post-myocardial infarction patients: A double-blind, placebo-controlled, randomized clinical trial

BACKGROUND

Endothelial dysfunction and depression are highly prevalent in patients who have experienced a myocardial infarction (MI). Epidemiological studies have pointed out that a diet rich in flavonoids, e.g., quercetin, can prevent the development of these biological phenomena. Therefore, we aimed to investigate the effects of quercetin supplementation on the levels of intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) and on depression in post-MI subjects.

METHODS

Eighty-eight post-MI patients who had experienced their first MI (body mass index ≤35 kg/m2, age 30-65 years) were recruited from the Rasool-e-Akram and Afshar Hospitals, Iran, and included in this randomized, placebo-controlled, double-blind parallel study. The participants were randomly assigned to receive a daily dose of 500 mg quercetin (n = 44) or placebo (n = 44) for 8 weeks. Serum concentrations of ICAM-1 and VCAM-1 were quantified by ELISA and depression levels were assessed using the Beck's Depression Inventory (BDI-II) questionnaire at baseline and at 8-week follow-up.

RESULTS

Seventy-six participants completed the study, but the intention-to-treat (ITT) analysis was conducted for all 88 participants who were randomized into the intervention groups. No significant changes in serum concentrations of ICAM-1 or VCAM-1 (P = 0.21 and P = 0.80, respectively) were observed after 8 weeks of quercetin supplementation versus placebo. In addition, depression levels did not differ significantly between the quercetin and placebo groups.

CONCLUSION

Our findings demonstrated that in post-MI patients, daily supplementation with quercetin (500 mg/day) for 8 weeks did not affect endothelial dysfunction biomarkers and depression levels. This trial was registered at IRCT.ir as IRCT20190428043405N1.

Pharmacological Activity of Flavonoid Quercetin and Its Therapeutic Potential in Testicular Injury

Quercetin is a natural flavonoid widely found in natural fruits and vegetables. Recent studies have shown that quercetin mediates multiple beneficial effects in a variety of organ damage and diseases, and is considered a healthcare supplement with health-promoting potential. Male infertility is a major health concern, and testicular damage from multiple causes is an important etiology. Previous studies have shown that quercetin has a protective effect on reproductive function. This may be related to the antioxidant, anti-inflammatory, and anti-apoptotic biological activities of quercetin. Therefore, this paper reviews the mechanisms by which quercetin exerts its pharmacological activity and its role in testicular damage induced by various etiologies. In addition, this paper compiles the application of quercetin in clinical trials, demonstrating its practical effects in regulating blood pressure and inhibiting cellular senescence in human patients. However, more in-depth experimental studies and clinical trials are needed to confirm the true value of quercetin for the prevention and protection against testicular injury.

Ageing, Metabolic Dysfunction, and the Therapeutic Role of Antioxidants

The gradual ageing of the world population has been accompanied by a dramatic increase in the prevalence of obesity and metabolic diseases, especially type 2 diabetes. The adipose tissue dysfunction associated with ageing and obesity shares many common physiological features, including increased oxidative stress and inflammation. Understanding the mechanisms responsible for adipose tissue dysfunction in obesity may help elucidate the processes that contribute to the metabolic disturbances that occur with ageing. This, in turn, may help identify therapeutic targets for the treatment of obesity and age-related metabolic disorders. Because oxidative stress plays a critical role in these pathological processes, antioxidant dietary interventions could be of therapeutic value for the prevention and/or treatment of age-related diseases and obesity and their complications. In this chapter, we review the molecular and cellular mechanisms by which obesity predisposes individuals to accelerated ageing. Additionally, we critically review the potential of antioxidant dietary interventions to counteract obesity and ageing.

Red onion skin active ingredients, extraction and biological properties for functional food applications

Onion is an important vegetable in the world and the second most important vegetable crop after tomato.Hence, the onion waste, such as onion skin, is produced in abundance causing environmental problems. Due to its bioactive compounds, especially phenolics and flavonoids, red onion skin can be used through appropriate methods for producing value-added products. These phytochemicals are proven to prevent oxidative stress and broad spectrum of microorganisms beside having diverse beneficial biological properties. Extraction step is the most critical processing in making phytonutrient available. Various approaches including conventional and non-conventional technologies applied for extracting different compounds from red onion wastes was summarized in this study. To evaluate the industrial application potential, the use of natural bioactives derived from red onion skin for elaboration of various food systems has been also investigated.

Targeting Cardiovascular Diseases by Flavonols: An Update

Flavonols are one of the most plentiful flavonoid subclasses found in natural products and are extensively used as dietary supplements. Numerous in vitro and in vivo studies have shown the cardioprotective properties of flavonols, especially quercetin. This group of substances exerts positive impacts primarily due to their antiatherogenic, antithrombotic, and antioxidant activities. The potential of flavonols to promote vasodilation and regulation of apoptotic processes in the endothelium are other beneficial effects on the cardiovascular system. Despite promising experimental findings, randomized controlled trials and meta-analyses have yielded inconsistent results on the influence of these substances on human cardiovascular parameters. Thus, this review aims to summarize the most recent clinical data on the intake of these substances and their effects on the cardiovascular system. The present study will help clinicians and other healthcare workers understand the value of flavonol supplementation in both subjects at risk for cardiovascular disease and patients with cardiovascular diseases.

Does timing of phytonutrient intake influence the suppression of postprandial oxidative stress? A systematic literature review

BACKGROUND

Postprandial oxidative stress markers in blood are generated transiently from various tissues and cells following high-fat and/or high-carbohydrate (HFHC) meals, and may be suppressed by certain phytonutrients, such as polyphenols and carotenoids. However, the transient presence of phytonutrients in circulation suggests that timing of consumption, relative to the meal, could be important. This systematic review investigates the effect of timing of phytonutrient intake on blood markers of postprandial oxidative processes.

METHOD

EMBASE, Medline, Scopus and Web of Science were searched up to December 2020. Eligible studies met the criteria: 1) healthy human adults; 2) phytonutrient(s) consumed in solid form within 24 h of a HFHC meal; 3) postprandial measurements of oxidative stress or antioxidants in blood; and 4) controlled study design. Cohen's d effect sizes were calculated to compare studies.

RESULTS

Nine studies, involving 256 participants, were included. Phytonutrients were consumed either at the same time, 1 h before, or the day (>12 h) before a HFHC meal. Significant decreases in blood markers - plasma lipid hydroperoxides, plasma malondialdehyde, serum sNox2-dp, serum 8-iso-PGF2α, platelet p47phox phosphorylation, and Keap-1 and p47phox protein levels in mononuclear cells (MNCs) - were observed where the phytonutrient was consumed together with the challenge meal (n = 4). Lack of any effect on oxidative stress markers was observed where phytonutrients were consumed with (n = 1), 1 h before (n = 1), and the day before (n = 2) the HFHC meal.

CONCLUSION

Phytonutrients consumed with a HFHC meal significantly suppressed some markers of oxidative stress in blood. Although there were only a limited number of studies, it appears that suppression appeared effective at the time of peak phytonutrient concentration in plasma. However, further studies are required to confirm the observations and systematically optimise the effect of timing.

Recent Advances in Bioactive Compounds, Health Functions, and Safety Concerns of Onion (Allium cepa L.)

Onion (Allium cepa L.) is a common vegetable, widely consumed all over the world. Onion contains diverse phytochemicals, including organosulfur compounds, phenolic compounds, polysaccharides, and saponins. The phenolic and sulfur-containing compounds, including onionin A, cysteine sulfoxides, quercetin, and quercetin glucosides, are the major bioactive constituents of onion. Accumulated studies have revealed that onion and its bioactive compounds possess various health functions, such as antioxidant, antimicrobial, anti-inflammatory, anti-obesity, anti-diabetic, anticancer, cardiovascular protective, neuroprotective, hepatorenal protective, respiratory protective, digestive system protective, reproductive protective, and immunomodulatory properties. Herein, the main bioactive compounds in onion are summarized, followed by intensively discussing its major health functions as well as relevant molecular mechanisms. Moreover, the potential safety concerns about onion contamination and the ways to mitigate these issues are also discussed. We hope that this paper can attract broader attention to onion and its bioactive compounds, which are promising ingredients in the development of functional foods and nutraceuticals for preventing and managing certain chronic diseases.

Effect of onion on blood lipid profile: A meta-analysis of randomized controlled trials

BACKGROUND

Studies indicate that onion supplementation may be effective in the treatment of dyslipidemia; however, the results remain controversial. This meta-analysis was conducted to evaluate potential benefits of onion on lipid profile.

METHODS

Up to 12 October 2020, PubMed, Cochrane Library, Web of Science, and Scopus were searched for randomized controlled trials evaluating the effects of onion on lipid profile. Mean differences (MD) and 95% confidence intervals (CI) were calculated. Meta-analysis was conducted using the fixed-effects model.

RESULTS

Ten trials with 446 participants in total were included in the meta-analysis. The pooled findings of 10 studies suggested that onion supplementation significantly improved high-density lipoprotein cholesterol (HDL) (MD: 2.29 mg/dl; 95% CI: 0.87, 3.72; I 2 = 0%) and low-density lipoprotein cholesterol (LDL) (MD: -6.64 mg/dl; 95% CI: -10.91, -2.36; I 2 = 32%),while onion supplementation did not significantly lower triglycerides (TG) (MD: -6.55 mg/dl; 95% CI: -15.64, 2.53; I 2 = 45%). Analysis of nine trials showed a significant reduction in total cholesterol (TC) (MD: -5.39 mg/dl; 95% CI: -10.68, -0.09; I 2 = 49%) in patients with onion supplementation compared to the control group.

CONCLUSION

In summary, supplementation of onion was beneficial to control dyslipidemia, including improving levels of HDL, LDL, and TC, but could not reduce TG level. The therapeutic benefits of onion for dyslipidemia need to be treated with caution considering that some of the results are not robust.

C-Glucosylation as a tool for the prevention of PAINS-induced membrane dipole potential alterations

The concept of Pan-Assay Interference Compounds (PAINS) is regarded as a threat to the recognition of the broad bioactivity of natural products. Based on the established relationship between altered membrane dipole potential and transmembrane protein conformation and function, we investigate here polyphenols' ability to induce changes in cell membrane dipole potential. Ultimately, we are interested in finding a tool to prevent polyphenol PAINS-type behavior and produce compounds less prone to untargeted and promiscuous interactions with the cell membrane. Di-8-ANEPPS fluorescence ratiometric measurements suggest that planar lipophilic polyphenols-phloretin, genistein and resveratrol-act by decreasing membrane dipole potential, especially in cholesterol-rich domains such as lipid rafts, which play a role in important cellular processes. These results provide a mechanism for their labelling as PAINS through their ability to disrupt cell membrane homeostasis. Aiming to explore the role of C-glucosylation in PAINS membrane-interfering behavior, we disclose herein the first synthesis of 4-glucosylresveratrol, starting from 5-hydroxymethylbenzene-1,3-diol, via C-glucosylation, oxidation and Horner-Wadsworth-Emmons olefination, and resynthesize phloretin and genistein C-glucosides. We show that C-glucosylation generates compounds which are no longer able to modify membrane dipole potential. Therefore, it can be devised as a strategy to generate bioactive natural product derivatives that no longer act as membrane dipole potential modifiers. Our results offer a new technology towards rescuing bioactive polyphenols from their PAINS danger label through C-C ligation of sugars.

Eicosapentaenoic Acid Is Associated with Decreased Incidence of Alzheimer's Dementia in the Oldest Old

BACKGROUND

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFAs) may have different effects on cognitive health due to their anti- or pro-inflammatory properties.

METHODS

We aimed to prospectively examine the relationships between n-3 and n-6 PUFA contents in serum phospholipids with incident all-cause dementia and Alzheimer's disease dementia (AD). We included 1264 non-demented participants aged 84 ± 3 years from the German Study on Ageing, Cognition, and Dementia in Primary Care Patients (AgeCoDe) multicenter-cohort study. We investigated whether fatty acid concentrations in serum phospholipids, especially eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), alpha-linolenic acid (ALA), linoleic acid (LA), dihomo-γ-linolenic acid (DGLA), and arachidonic acid (AA), were associated with risk of incident all-cause dementia and AD.

RESULTS

During the follow-up window of seven years, 233 participants developed dementia. Higher concentrations of EPA were associated with a lower incidence of AD (hazard ratio (HR) 0.76 (95% CI 0.63; 0.93)). We also observed that higher concentrations of EPA were associated with a decreased risk for all-cause dementia (HR 0.76 (95% CI 0.61; 0.94)) and AD (HR 0.66 (95% CI 0.51; 0.85)) among apolipoprotein E ε4 (APOE ε4) non-carriers but not among APOE ε4 carriers. No other fatty acids were significantly associated with AD or dementia.

CONCLUSIONS

Higher concentrations of EPA were associated with a lower risk of incident AD. This further supports a beneficial role of n-3 PUFAs for cognitive health in old age.

Quercetin: Its Main Pharmacological Activity and Potential Application in Clinical Medicine

Quercetin is a flavonoid compound widely present in plants and exhibits a variety of biological activities. Research on quercetin has shown its potential for medical application. In this research, we elucidate its antioxidant mechanism and the broad-spectrum antibacterial and antiparasite properties; summarise its potential application in antioncology and cardiovascular protection and anti-immunosuppression treatment; and demonstrate its ability to alleviate the toxicity of mycotoxins. This research is expected to offer some insights and inspirations for the further study of quercetin, its properties, and the scientific basis for its better application in clinical practice.

Allium Flavonols: Health Benefits, Molecular Targets, and Bioavailability

Allium species are revered worldwide as vegetables, condiments, and spices as well as the therapeutic agents in traditional medicine. The bioactive compounds in alliums mainly include organosulfur compounds, polyphenols, dietary fibers, and saponins. Flavonoids, particularly flavonols from alliums, have been demonstrated to have the antioxidant, anticancer, hypolipidemic, anti-diabetic, cardioprotective, neuroprotective, and antimicrobial activities. However, flavonols are mostly characterized from onions and have not been comprehensively reviewed across different species. This article therefore focuses on flavonol profiles from different Allium species, their health effects, underlying molecular mechanisms, and bioavailability. Intriguingly, the functional health effects of flavonols were mainly ascribed to their antioxidant and anti-inflammatory activities involving a cascade of multiple signaling pathways. Although the Allium-derived flavonols offer tremendous potential in preventing chronic disease risks, in-depth studies are needed to translate their clinical application.

Acute Effects of Three Different Meal Patterns on Postprandial Metabolism in Older Individuals with a Risk Phenotype for Cardiometabolic Diseases: A Randomized Controlled Crossover Trial

SCOPE

The aim of this study is to investigate acute postprandial responses to intake of meals typical for Mediterranean and Western diets.

METHODS

In a randomized crossover design, overweight and obese participants with a risk phenotype for cardiometabolic diseases consumed three different isoenergetic meals: Western diet-like high-fat (WDHF), Western diet-like high-carbohydrate (WDHC), and Mediterranean diet (MED) meal. Blood samples are collected at fasting and 1, 2, 3, 4, 5 h postprandially and analyzed for parameters of lipid and glucose metabolism, inflammation, oxidation, and antioxidant status.

RESULTS

Compared to MED and WDHF meals, intake of a WDHC meal results in prolonged and elevated increases in glucose and insulin. Elevations for triglycerides are enhanced after the WDHF meal compared to the MED and the WDHC meal. Glucagon-like peptide-1 and interleukin-6 increase postprandially without meal differences. Apart from vitamin C showing an increase after the MED meal and a decrease after WDHF and WDHC meals, antioxidant markers decrease postprandially without meal differences. Plasma interleukin-1β is not affected by meal intake.

CONCLUSIONS

Energy-rich meals induce hyperglycemia, hyperlipemia, an inflammatory response, and a decrease in antioxidant markers. A meal typical for the Mediterranean diet results in favorable effects on glycemic, insulinemic, and lipemic responses.

Prenatal and early postnatal food restrictions cause changes in brain oxidative status and orexigenic/anorexigenic hormones in the offspring of rats: prevention by quercetin and kaempferol

Brain oxidative signaling pathways have been identified as important targets for alleviating food deprivation-induced changes in metabolic gate-ways. Previous studies have shown that prenatal and early postnatal malnutrition alters leptin and ghrelin signaling via oxidative pathways. Thus, it has been hypothesized that agents with antioxidant properties might be beneficial for the mitigation of prenatal and early postnatal food scarcity-induced oxidative damage. Quercetin and kaempferol are natural bioflavonoids with proven antioxidant properties. In this study, we evaluated their effects on prenatal maternal food consumption, maternal and pup weights, biomarkers of orexigenic and anorexigenic hormones and oxidative stress in rats. Rats were allotted into different treatment groups (n ​= ​6) in three different experiments (prenatal, postnatal food-deprivations or both). Prenatal-food restriction (PrNFR) was induced by 50% of ad libitum accessible diet during pregnancy till parturition and postnatal-food restriction (PsNFR) was simulated by litter-enlargement to 16 pups per mother from postnatal day (PND) 2. Rats in each experiment were concurrently treated with vehicle (10 ​mL/kg), quercetin (50, 100 and 200 ​mg/kg, p.o.) or kaempferol (50, 100 and 200 ​mg/kg, p.o.) respectively. A third experimental group consisted of both protocols. Quercetin and kaempferol dose-dependently increased the body weights of pups exposed to PrNFR, PsNFR and PrNFR-PsNFR at PNDs 1-22 respectively. Both compounds increased maternal body weights but attenuated maternal food-intake at prenatal days 7 and 14 due by PrNFR. Quercetin and kaempferol reduced brain malondialdehyde concentrations and increased glutathione levels in PrNFR, PsNFR and PrNFR-PsNFR-exposed offspring of rats. Importantly, quercetin and kaempferol significantly (p ​< ​0.05) prevented PrNFR-, PsNFR- or PrNFR-PsNFR-induced alterations in leptin and ghrelin levels. Cumulatively, quercetin and kaempferol increased pup and maternal weights and attenuated maternal food-intake of rats submitted to PrNFR, PsNFR and PrNFR-PsNFR respectively, likely via nutrigenomic modulations of orexigenic/anorexigenic hormones and inhibition of brain oxidative stress.

The Effects of Quercetin Supplementation on Blood Pressures and Endothelial Function Among Patients with Metabolic Syndrome and Related Disorders: A Systematic Review and Meta-analysis of Randomized Controlled Trials

BACKGROUND

This systematic review and meta-analysis of randomized controlled trials (RCTs) were performed to determine the effect of quercetin administration on blood pressures and endothelial function among patients with metabolic syndrome (MetS) and related disorders.

METHODS

We searched systematically online databases including Cochrane Library, EMBASE, MEDLINE, and Web of Science to identify the relevant RCTs until December 2018. Q-test and I2 statistics were applied to assess heterogeneity among the included studies. Data were pooled using a random-effects model and weighted mean difference (WMD) was considered as the overall effect size.

RESULTS

Out of 284 citations, 8 RCTs were included in the meta-analysis. We found a significant reduction in systolic blood pressure (SBP) (WMD: -1.69; 95% CI: -3.22, -0.17) following the intake of quercetin supplements. However, quercetin supplementation did not significantly affect diastolic blood pressure (DBP) (WMD: -3.14; 95% CI: -8.24, 1.95), vascular cell adhesion molecule 1 (VCAM-1) (WMD: -24.49; 95% CI: -53.74, 4.77) and intercellular adhesion molecule 1 (ICAM-1) (WMD: -5.78; 95% CI: -12.93, 1.38).

CONCLUSION

In summary, the current meta-analysis demonstrated that quercetin supplementation significantly reduced SBP, yet did not affect DBP, VCAM-1 and ICAM-1 among patients with MetS and related disorders.

Moderate Postmeal Walking Has No Beneficial Effects Over Resting on Postprandial Lipemia, Glycemia, Insulinemia, and Selected Oxidative and Inflammatory Parameters in Older Adults with a Cardiovascular Disease Risk Phenotype: A Randomized Crossover Trial

BACKGROUND

Research suggests that postprandial events, as risk factors for cardiovascular diseases (CVDs), are influenced by meal composition and exercise.

OBJECTIVES

We investigated the effect of walking versus rest on postprandial metabolic, inflammatory, and oxidative events following the consumption of test meals reflecting 2 different dietary patterns in older adults with an increased CVD risk.

METHODS

A randomized crossover trial was conducted in 26 men and women (aged 70 ± 5 y; BMI 30.3 ± 2.3 kg/m2). Each adult participated in 4 treatments combining 1 of 2 iso-energetic (4300 kJ) meals [Western diet high-fat meal (WD): total fat, 59.4 g; saturated fatty acids, 32.0 g, dietary fiber, 4.2 g; or Mediterranean-type diet meal (MD): total fat, 40.1 g; saturated fatty acids, 5.1 g; dietary fiber, 14.5 g] with 30 min walking (4.6 ± 0.1 km/h) or rest. Primary (serum triglycerides) and secondary [serum nonesterified fatty acids (NEFAs); parameters of glucose metabolism, inflammation, endothelial activation, oxidation; blood pressure/heart rate] outcomes were measured at fasting and 1.5, 3.0, and 4.5 h postprandially. Data were analyzed by linear mixed models.

RESULTS

Triglycerides were higher after the WD than after the MD [AUC in mmol/L × min: Western diet high-fat meal plus postprandial walking (WD-W), 218 ± 15.2; Western diet high-fat meal plus postprandial resting (WD-R), 207 ± 12.6; Mediterranean-type diet meal plus postprandial walking (MD-W), 139 ± 9.83; Mediterranean-type diet meal plus postprandial resting (MD-R), 149 ± 8.15; P  < 0.001]. No meal or activity effect was observed for NEFAs based on AUC data (WD-W, -43.5 ± 7.08; WD-R, -49.2 ± 6.94; MD-W, -48.0 ± 11.6; MD-R, -67.6 ± 7.58). Plasma glucose was higher after the MD than after the WD (WD-W, 222 ± 34.9; WD-R, 177 ± 32.8; MD-W, 314 ± 44.4; MD-R, 275 ± 57.8; P  < 0.001), as was serum insulin (AUC in nmol/L × min: WD-W, 82.0 ± 10.3; WD-R, 88.6 ± 12.8; MD-W, 129 ± 14.7; MD-R, 138 ± 20.5; P < 0.001). Plasma IL-6 was higher after walking than after resting (AUC in pg/mL × min: WD-W, 72.0 ± 34.0; WD-R, 14.3 ± 38.8; MD-W, 70.8 ± 39.4; MD-R, 5.60 ± 26.0; P < 0.05). Plasma vitamin C was higher after the MD than after the WD (P < 0.001) and after walking than after resting (P < 0.05; AUC in mg/L × min: WD-W, -305 ± 59.6; WD-R, -396 ± 84.0; MD-W, 113 ± 56.4; MD-R, -44.5 ± 48.1). We observed no meal or activity effects on parameters of oxidation and endothelial adhesion molecules. Our data revealed no significant meal × activity effects on all outcomes.

CONCLUSIONS

In older adults with an increased CVD risk, the MD was associated with superior effects on several postprandial parameters (e.g., triglycerides), in comparison to the WD. Data revealed no relevant differences regarding the effects of postmeal walking and resting. None of the 4 treatments can be rated as superior regarding their acute effects on the shown postprandial metabolic, oxidative, and inflammatory parameters. The trial was registered at German Clinical Trials Register (DRKS; http://www.germanctr.de and http://www.drks.de) under identifier DRKS00012409.

Quercetin and Epigallocatechin Gallate in the Prevention and Treatment of Obesity: From Molecular to Clinical Studies

Obesity is a worldwide epidemic, which is characterized by the excess accumulation of adipose tissue and to an extent that impairs both the physical and psychosocial health and well-being. There are several weight-loss strategies available, including dietary modification, pharmacotherapy, and bariatric surgery, but many are ineffective or not a long-term solution. Bioactive compounds present in medicinal plants and plant extracts, like polyphenols, constitute the oldest and most extensive form of alternative treatments for the prevention and management of obesity. Their consumption is currently increasing in the population due to the high cost, potential adverse effects, and limited benefits of the currently available pharmaceutical drugs. A great number of studies has explored how dietary polyphenols can interfere with the different mechanisms associated with obesity development. They suggest that these compounds can decrease energy and food intake, lipogenesis, and preadipocyte differentiation and proliferation, while increasing energy expenditure, lipolysis, and fat oxidation. Both quercetin, one of the most common dietary flavonols in the western diet, and epigallocatechin gallate (EGCG), the most abundant polyphenol in green tea, exhibit antiobesity effects in adipocyte cultures and animal models. However, the extrapolation of these potential benefits to obese humans remains unclear. Although quercetin supplementation does not seem to exert any beneficial effects on body weight, this polyphenol could prevent the obesity-associated mortality by reducing cardiovascular disease risk. An important consideration for the design of further trials is the occurrence of gene polymorphisms in key enzymes involved in flavanol metabolism, which determines a subject's sensitivity to catechins and seems, therefore, crucial for the success of the antiobesity intervention. Although the evidence supporting antiobesity effects is more consistent in EGCG than with quercetin studies, they could still be beneficial by reducing the cardiovascular risk of obese subjects, rather than inducing body weight loss.

The effects of quercetin supplementation on lipid profiles and inflammatory markers among patients with metabolic syndrome and related disorders: A systematic review and meta-analysis of randomized controlled trials

Aims: This systematic review and meta-analysis of randomized controlled trials (RCTs) was performed to determine the effect of quercetin administration on lipid profiles and inflammatory markers among patients with metabolic syndrome (MetS) and related disorders.Methods: We searched systematically online databases including Cochrane Library, EMBASE, MEDLINE, and Web of Science to identify the relevant RCTs until November 2018. Q-test and I2 statistics were applied to assess heterogeneity among included studies. Data were combined using fixed- or random-effects model and presented as standardized mean difference (SMD) with 95% confidence interval (CI).Results: Out of 591 citations, 16 RCTs were included in the meta-analysis. The pooled findings showed that quercetin consumption significantly decreased total-cholesterol (SMD = -0.98; 95% CI, -1.48, -0.49; p < 0.001; I2: 94.0), LDL-cholesterol (SMD = -0.88; 95% CI, -1.35, -0.41; p < 0.001; I2: 92.7) and C-reactive protein (CRP) levels (-0.64; 95% CI, -1.03, -0.25; p = 0.001; I2: 90.2). While, quercetin supplementation did not significantly affect triglycerides (TG) (SMD = -0.32; 95% CI, -0.68, 0.04; p = 0.08; I2: 84.8), HDL-cholesterol (SMD = 0.20; 95% CI, -0.20, 0.24; p = 0.84; I2: 70.6), interleukin 6 (IL-6) (SMD = -0.69; 95% CI, -1.69, 0.31; p = 0.17; I2: 94.5) and tumor necrosis factor-alpha (TNF-α) levels (SMD = -0.06; 95% CI, -0.25, 0.14; p = 0.58; I2: 35.6)Conclusions: In summary, the current meta-analysis demonstrated that quercetin supplementation significantly reduced total-cholesterol, LDL-cholesterol, and CRP levels, yet did not affect triglycerides, HDL-cholesterol, IL-6 and TNF-α among patients with MetS and related disorders.

Clinical Advances in Immunonutrition and Atherosclerosis: A Review

Atherosclerosis is a chronic low-grade inflammatory disease that affects large and medium-sized arteries and is considered to be a major underlying cause of cardiovascular disease (CVD). The high risk of mortality by atherosclerosis has led to the development of new strategies for disease prevention and management, including immunonutrition. Plant-based dietary patterns, functional foods, dietary supplements, and bioactive compounds such as the Mediterranean Diet, berries, polyunsaturated fatty acids, ω-3 and ω-6, vitamins E, A, C, and D, coenzyme Q10, as well as phytochemicals including isoflavones, stilbenes, and sterols have been associated with improvement in atheroma plaque at an inflammatory level. However, many of these correlations have been obtained in vitro and in experimental animals' models. On one hand, the present review focuses on the evidence obtained from epidemiological, dietary intervention and supplementation studies in humans supporting the role of immunonutrient supplementation and its effect on anti-inflammatory response in atherosclerotic disease. On the other hand, this review also analyzes the possible molecular mechanisms underlying the protective action of these supplements, which may lead a novel therapeutic approach to prevent or attenuate diet-related disease, such as atherosclerosis.

Beneficial effects of murtilla extract and madecassic acid on insulin sensitivity and endothelial function in a model of diet-induced obesity

Infusions of murtilla leaves exhibit antioxidant, analgesic, and anti-inflammatory properties. Several compounds that are structurally similar to madecassic acid (MA), a component of murtilla leaf extract (ethyl acetate extract, EAE), have been shown to inhibit protein tyrosine phosphatase 1B (PTP1P). The aim of this study was to evaluate if EAE and two compounds identified in EAE (MA and myricetin [MYR]) could have a beneficial effect on systemic and vascular insulin sensitivity and endothelial function in a model of diet-induced obesity. Experiments were performed in 5-week-old male C57BL6J mice fed with a standard (LF) or a very high-fat diet (HF) for 4 weeks and treated with EAE, MA, MYR, or the vehicle as control (C). EAE significantly inhibited PTP1B. EAE and MA, but not MYR, significantly improved systemic insulin sensitivity in HF mice and vascular relaxation to Ach in aorta segments, due to a significant increase of eNOS phosphorylation and enhanced nitric oxide availability. EAE, MA, and MYR also accounted for increased relaxant responses to insulin in HF mice, thus evidencing that the treatments significantly improved aortic insulin sensitivity. This study shows for the first time that EAE and MA could constitute interesting candidates for treating insulin resistance and endothelial dysfunction associated with obesity.

Cardiovascular Effects of Flavonoids

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Cardiovascular Disease (CVD) is the major cause of death worldwide, especially in Western society. Flavonoids are a large group of polyphenolic compounds widely distributed in plants, present in a considerable amount in fruit and vegetable. Several epidemiological studies found an inverse association between flavonoids intake and mortality by CVD. The antioxidant effect of flavonoids was considered the main mechanism of action of flavonoids and other polyphenols. In recent years, the role of modulation of signaling pathways by direct interaction of flavonoids with multiple protein targets, namely kinases, has been increasingly recognized and involved in their cardiovascular protective effect. There are strong evidence, in in vitro and animal experimental models, that some flavonoids induce vasodilator effects, improve endothelial dysfunction and insulin resistance, exert platelet antiaggregant and atheroprotective effects, and reduce blood pressure. Despite interacting with multiple targets, flavonoids are surprisingly safe. This article reviews the recent evidence about cardiovascular effects that support a beneficial role of flavonoids on CVD and the potential molecular targets involved.

Biological Properties and Bioactive Components of Allium cepa L.: Focus on Potential Benefits in the Treatment of Obesity and Related Comorbidities

Common onion (Allium cepa L.) is one of the oldest cultivated plants, utilized worldwide as both vegetable and flavouring. This species is known to contain sulphur amino acids together with many vitamins and minerals. A variety of secondary metabolites, including flavonoids, phytosterols and saponins, have also been identified. Despite the predominant use of this plant as food, a wide range of beneficial effects have also been proved. Different biological properties, such as antioxidant, antimicrobial and antidiabetic, have been reported. The aim of this review is to provide an overview of the studies concerning the beneficial effects of this species against obesity and its related comorbidities, such as hyperlipidaemia, hypertension and diabetes. Both in vitro and in vivo results about onion dietary supplementation have been taken into account. Furthermore, this review examines the possible role of onion bioactive components in modulating or preventing weight-gain or related diseases, as well as the possible mechanisms behind their activity.

Pharmacological Effect of Quercetin in Hypertension and Its Potential Application in Pregnancy-Induced Hypertension: Review of In Vitro, In Vivo, and Clinical Studies

Since improving maternal and child health is a public health priority worldwide, the main aim of treatment of hypertension in pregnant women is to prevent complications during pregnancy, labor, and postpartum. In consequence, much attention is paid to the use of antihypertensive drugs that can be used safely during pregnancy. Several side effects of methyldopa, which is currently the most commonly used antihypertensive drug in pregnant women, mean that the search for an effective and safe alternative still continues. Flavonoid compounds present in medicinal plants, vegetables, and fruits may be a promising source of new drugs. In this aspect, quercetin, a well-known flavonoid due to its antihypertensive action, may be considered a prototype for safe antihypertensive drugs. This review focuses on the selective activity of quercetin. Based on recent studies, a few problems were discussed, including (1) pathology of pregnancy-induced hypertension; (2) search for new pharmacological treatments of pregnancy-induced hypertension; (3) issues with the use of herbal extracts during pregnancy; (4) flavonoids as natural active chemical compounds; (5) quercetin: its action during pregnancy, in vitro and in vivo pharmacological activities, clinical trials, and meta-analysis; (6) quercetin intake during pregnancy; (7) other natural compounds tested during pregnancy; (8) potential problems with the use of quercetin; (9) safety profile of quercetin. Various studies have shown a beneficial effect of quercetin on vascular endothelial function and its antioxidative and anti-inflammatory activity on cellular and tissue level. It is known that in animal models quercetin affects positively the development of embryo, fetus, and placenta. Because this flavonoid did not have teratogenic and abortive effect, it is generally recognized as safe. For this reason it should be appreciated and studied in the aspect of its potential use in the prevention and treatment of pregnancy-induced hypertension among women in this risk group.

The role of polyphenols in modern nutrition

Polyphenols are found in plant‐based foods and beverages, notably apples, berries, citrus fruit, plums, broccoli, cocoa, tea and coffee and many others. There is substantial epidemiological evidence that a diet high in polyphenol‐rich fruit, vegetables, cocoa and beverages protects against developing cardiovascular disease and type 2 diabetes. The absorption and metabolism of these compounds have been well described and, for many, the gut microbiota play a critical role in absorption; taking into consideration the parent compound and the metabolites from colon bacteria catabolism, more than 80% of a dose can be absorbed and ultimately excreted in the urine. Common polyphenols in the diet are flavanols (cocoa, tea, apples, broad beans), flavanones (hesperidin in citrus fruit), hydroxycinnamates (coffee, many fruits), flavonols (quercetin in onions, apples and tea) and anthocyanins (berries). Many intervention studies, mechanistic in vitro data and epidemiological studies support a role for polyphenols against the development of chronic diseases. For example, flavanols decrease endothelial dysfunction, lower blood pressure and cholesterol, and modulate energy metabolism. Coffee and tea both reduce the risk of developing type 2 diabetes, through action of their constituent polyphenols. Despite extensive research, the exact mechanisms of action of polyphenols in the human body have not been decisively proven, but there is strong evidence that some targets such as nitric oxide metabolism, carbohydrate digestion and oxidative enzymes are important for health benefits. Consumption of polyphenols as healthy dietary components is consistent with the advice to eat five or more portions of fruit and vegetables per day, but it is currently difficult to recommend what ‘doses’ of specific polyphenols should be consumed to derive maximum benefit.

New Insights on the Use of Dietary Polyphenols or Probiotics for the Management of Arterial Hypertension

Arterial hypertension (AH) is one of the most prevalent risk factors for cardiovascular diseases (CD) and is the main cause of deaths worldwide. Current research establish that dietary polyphenols may help to lower blood pressure (BP), thus contributing to the reduction of cardiovascular complications. In addition, the health benefits of probiotics on BP have also attracted increased attention, as probiotics administration modulates the microbiota, which, by interacting with ingested polyphenols, controls their bioavalability. The aim of the present mini-review is to summarize and clarify the effects of dietary polyphenols and probiotics administration on BP using combined evidence from clinical and experimental studies, as well as to discuss the current debate in the literature about the usefulness of this nutritional approach to manage BP. Clinical trials and experimental studies have demonstrated that consuming dietary polyphenols or probiotics in adequate amounts may improve BP, ranging from modest to greater effects. However, the mechanisms linking probiotic intake and reduced BP levels need to be further elucidated as a definitive consensus on the link between intake of polyphenols or probiotics and improvement of AH has not been reached yet.