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

The effects of Quercetin supplementation on cardiometabolic outcomes: An umbrella review of meta-analyses of randomized controlled trials

BACKGROUND

Quercetin is a bioactive flavonoid, but the effect of it on cardiometabolic factors has remained uncertain and previous findings from meta-analyses have been controversial.

OBJECTIVE

To provide an overview of the effects of Quercetin on cardiometabolic factors based on meta-analyses of randomized controlled trials (RCTs).

METHOD

MEDLINE, SciVerse Scopus, and Clarivate Analytics Web of Science databases were searched to identify eligible publications. As part of the umbrella review, we summarized pooled estimates, 95% CIs, heterogeneity, and publication bias. A GRADE (Grading of Recommendations Assessment, Development, and Evaluation) approach was used to rate the certainty of evidence.

RESULTS

Five meta-analyses including 18 eligible RCTs plus 5 RCTs that were not included in previous meta-analyses were found. The results indicated Quercetin does not affect diastolic blood pressure (DBP), lipid profile, inflammation, anthropometric indices, fasting plasma glucose (FBG), and homeostatic model assessment for insulin resistance (HOMA-IR). However, Quercetin supplementation could significantly reduce systolic blood pressure (SBP) (weighted mean difference (WMD): -1.9, 95% CI = -3.2 to -0.6, I2  = 88.3%) and insulin level (WMD: -1.07, 95% CI = -1.9 to -0.1, I2  = 75.0%). The certainty of evidence ranged from very low to moderate.

CONCLUSION

Quercetin supplementation has reducing effects on SBP and insulin levels but not other cardiometabolic parameters. More high-quality trials with longer follow-up durations may be required to obtain a more robust conclusion.

The Negative Impact of Insulin Resistance/Hyperinsulinemia on Chronic Heart Failure and the Potential Benefits of Its Screening and Treatment

This opinion article highlights the potential alterations caused by insulin resistance and hyperinsulinemia on the cardiovascular system and their negative impact on heart failure (HF), and describes the potential benefits of an early screening with consequent prompt treatment. HF is the final event of several different cardiovascular diseases. Its incidence has been increasing over the last decades because of increased survival from ischemic heart disease thanks to improvements in its treatment (including myocardial revascularization interventions) and the increase in life span. In particular, incidence of HF with preserved ejection fraction (HFpEF) is significantly increasing, and patients with HFpEF often are also affected by diabetes mellitus and insulin resistance (IR), with a prevalence > 45%. Concentric left ventricular (LV) remodeling and diastolic dysfunction are the main structural abnormalities that characterize HFpEF. It is well documented in the literature that IR with chronic hyperinsulinemia, besides causing type 2 diabetes mellitus, can cause numerous cardiovascular alterations, including endothelial dysfunction and increased wall thicknesses of the left ventricle with concentric remodeling and diastolic dysfunction. Therefore, it is conceivable that IR might play a major role in the pathophysiology and the progressive worsening of HF. To date, several substances have been shown to reduce IR/hyperinsulinemia and have beneficial clinical effects in patients with HF, including SGLT2 inhibitors, metformin, and berberine. For this reason, an early screening of IR could be advisable in subjects at risk and in patients with heart failure, to promptly intervene with appropriate therapy. Future studies aimed at comparing the efficacy of the substances used both alone and in association are needed.

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.

A Descriptive Review of the Action Mechanisms of Berberine, Quercetin and Silymarin on Insulin Resistance/Hyperinsulinemia and Cardiovascular Prevention

Insulin resistance (IR) and the associated hyperinsulinemia are early pathophysiological changes which, if not well treated, can lead to type 2 diabetes, endothelial dysfunction and cardiovascular disease. While diabetes care is fairly well standardized, the prevention and treatment of IR lacks a single pharmaceutical approach and many lifestyle and dietary interventions have been proposed, including a wide range of food supplements. Among the most interesting and well-known natural remedies, alkaloid berberine and the flavonol quercetin have particular relevance in the literature, while silymarin-the active principle of the Silybum marianum thistle-was traditionally used for lipid metabolism disorders and to sustain liver function. This review describes the major defects of insulin signaling leading to IR and the main properties of the three mentioned natural substances, their molecular targets and synergistic action mechanisms. The actions of berberine, quercetin and silymarin are partially superimposable as remedies against reactive oxygen intermediates generated by a high-lipid diet and by NADPH oxidase, which is triggered by phagocyte activation. Furthermore, these compounds inhibit the secretion of a battery of pro-inflammatory cytokines, modulate intestinal microbiota and are especially able to control the various disorders of the insulin receptor and post-receptor signaling systems. Although most of the evidence on the effects of berberine, quercetin and silymarin in modulating insulin resistance and preventing cardiovascular disease derive from experimental studies on animals, the amount of pre-clinical knowledge strongly suggests the need to investigate the therapeutic potential of these substances in human pathology.

Hypertension and cellular senescence

Essential or primary hypertension is a wordwide health problem. Elevated blood pressure (BP) is closely associated not only with increased chronological aging but also with biological aging. There are various common pathways that play a role in cellular aging and BP regulation. These include but not limited to inflammation, oxidative stress, mitochondrial dysfunction, air pollution, decreased klotho activity increased renin angiotensin system activation, gut dysbiosis etc. It has already been shown that some anti-hypertensive drugs have anti-senescent actions and some senolytic drugs have BP lowering effects. In this review, we have summarized the common mechanisms underlying cellular senescence and HT and their relationships. We further reviewed the effect of various antihypertensive medications on cellular senescence and suggest further issues to be studied.

The Potential of Flavonoids and Flavonoid Metabolites in the Treatment of Neurodegenerative Pathology in Disorders of Cognitive Decline

Flavonoids are a biodiverse family of dietary compounds that have antioxidant, anti-inflammatory, antiviral, and antibacterial cell protective profiles. They have received considerable attention as potential therapeutic agents in biomedicine and have been widely used in traditional complimentary medicine for generations. Such complimentary medical herbal formulations are extremely complex mixtures of many pharmacologically active compounds that provide a therapeutic outcome through a network pharmacological effects of considerable complexity. Methods are emerging to determine the active components used in complimentary medicine and their therapeutic targets and to decipher the complexities of how network pharmacology provides such therapeutic effects. The gut microbiome has important roles to play in the generation of bioactive flavonoid metabolites retaining or exceeding the antioxidative and anti-inflammatory properties of the intact flavonoid and, in some cases, new antitumor and antineurodegenerative bioactivities. Certain food items have been identified with high prebiotic profiles suggesting that neutraceutical supplementation may be beneficially employed to preserve a healthy population of bacterial symbiont species and minimize the establishment of harmful pathogenic organisms. Gut health is an important consideration effecting the overall health and wellbeing of linked organ systems. Bioconversion of dietary flavonoid components in the gut generates therapeutic metabolites that can also be transported by the vagus nerve and systemic circulation to brain cell populations to exert a beneficial effect. This is particularly important in a number of neurological disorders (autism, bipolar disorder, AD, PD) characterized by effects on moods, resulting in depression and anxiety, impaired motor function, and long-term cognitive decline. Native flavonoids have many beneficial properties in the alleviation of inflammation in tissues, however, concerns have been raised that therapeutic levels of flavonoids may not be achieved, thus allowing them to display optimal therapeutic effects. Dietary manipulation and vagal stimulation have both yielded beneficial responses in the treatment of autism spectrum disorders, depression, and anxiety, establishing the vagal nerve as a route of communication in the gut-brain axis with established roles in disease intervention. While a number of native flavonoids are beneficial in the treatment of neurological disorders and are known to penetrate the blood–brain barrier, microbiome-generated flavonoid metabolites (e.g., protocatechuic acid, urolithins, γ-valerolactones), which retain the antioxidant and anti-inflammatory potency of the native flavonoid in addition to bioactive properties that promote mitochondrial health and cerebrovascular microcapillary function, should also be considered as potential biotherapeutic agents. Studies are warranted to experimentally examine the efficacy of flavonoid metabolites directly, as they emerge as novel therapeutic options.

Potential Pharmaceutical Applications of Quercetin in Cardiovascular Diseases

Quercetin, as a member of flavonoids, has emerged as a potential therapeutic agent in cardiovascular diseases (CVDs) in recent decades. In this comprehensive literature review, our goal was a critical appraisal of the pathophysiological mechanisms of quercetin in relation to the classical cardiovascular risk factors (e.g., hyperlipidemia), atherosclerosis, etc. We also assessed experimental and clinical data about its potential application in CVDs. Experimental studies including both in vitro methods and in vivo animal models mainly outline the following effects of quercetin: (1) antihypertensive, (2) hypolipidemic, (3) hypoglycemic, (4) anti-atherosclerotic, and (5) cardioprotective (suppressed cardiotoxicity). From the clinical point of view, there are human studies and meta-analyses implicating its beneficial effects on glycemic and lipid parameters. In contrast, other human studies failed to demonstrate consistent favorable effects of quercetin on other cardiometabolic risk factors such as MS, obesity, and hypertension, underlying the need for further investigation. Analyzing the reason of this inconsistency, we identified significant drawbacks in the clinical trials’ design, while the absence of pharmacokinetic/pharmacodynamic tests prior to the studies attenuated the power of clinical results. Therefore, additional well-designed preclinical and clinical studies are required to examine the therapeutic mechanisms and clinical efficacy of quercetin in CVDs.

The Impact of Flavonols on Cardiovascular Risk

Cardiovascular disease (CVD) is the leading cause of deaths globally. The main target for prevention of cardiovascular (CV) risk are lifestyle changes, including particular dietary recommendations, involving high intake of fruits and vegetables. Flavonols are a subgroup of flavonoids—compounds present in fruits, vegetables, and tea—known for their antioxidative properties. There are many findings about the beneficial impact of flavonols on general CV risk and its factors, but mainly from in vitro and animal model studies. This paper summarizes data from human studies about flavonols’ impact on general CV risk and its factors. A high dietary intake of flavonols could decrease CVD mortality directly or through impact on selected CV factors; however, available data are inconsistent. Nonetheless, specific groups of patients (smoking men, hypertensive and diabetic patients) can potentially benefit from selected dietary modifications or flavonols (quercetin) supplementation. Future investigations about kaempferol and myricetin are needed.

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.

The Effect of Dietary Polyphenols on Vascular Health and Hypertension: Current Evidence and Mechanisms of Action

The aim of this review was to explore existing evidence from studies conducted on humans and summarize the mechanisms of action of dietary polyphenols on vascular health, blood pressure and hypertension. There is evidence that some polyphenol-rich foods, including berry fruits rich in anthocyanins, cocoa and green tea rich in flavan-3-ols, almonds and pistachios rich in hydroxycinnamic acids, and soy products rich in isoflavones, are able to improve blood pressure levels. A variety of mechanisms can elucidate the observed effects. Some limitations of the evidence, including variability of polyphenol content in plant-derived foods and human absorption, difficulty disentangling the effects of polyphenols from other dietary compounds, and discrepancy of doses between animal and human studies should be taken into account. While no single food counteracts hypertension, adopting a plant-based dietary pattern including a variety of polyphenol-rich foods is an advisable practice to improve blood pressure.

Screening of potential tropical fruits in protecting endothelial dysfunction in vitro

Background

High consumption of antioxidant-rich fruits and vegetables reduces the endothelial damage involved in cardiovascular disease pathogenesis.

Objective

To evaluate the phytochemical content, antioxidant and scavenging activities (FRAP, ORAC, OH^•, HOCl, H₂O₂, and O₂ ^-), endothelial H₂O₂-cytoprotective effect, nitric oxide (NO) release activation potential, and endothelial wound healing properties of 10 tropical fruits, comprising pineapple, sugar apple, papaya fruit, longan, mangosteen, lychee, langsat, mango, rambutan, and guava.

Design

Experimental study. The experiments were conducted in vitro using endothelial cell line EA.hy926.

Results

The high performance liquid chromatography (HPLC) phytochemical analysis indicated the presence of gallic acid and quercetin in all fruits, along with the overall absence of ellagic acid. Chlorogenic acid was only detected in three fruits, that is, pineapple, ripe papaya, and guava. The antioxidant and scavenging activities of all fruits were concentration-dependent. Only the H₂O₂ scavenging activity exhibited broad positive associations with other ROS-scavenging activities. Sugar apple and unripe papaya induced a significant reduction in H₂O₂-induced cell death in endothelial cells while pineapple, sugar apple, longan, and langsat activated NO release.

Discussion

All the studied tropical fruits contained bioactive phytoantioxidants with wide ranges of antioxidant capacity and scavenging activities. The endothelial functional tests were relevant to the screening for fruits that may benefit cardiovascular health. Among the four fruits that promoted endothelial wound closure, only sugar apple and unripe papaya induced cell migration and vascular capillary-like tube formation.

Conclusion

Sugar apple and unripe papaya are potential functional fruits that can protect against oxidative cell death and enhance endothelial wound healing.

The effect of inositol supplementation on blood pressure: A systematic review and meta-analysis of randomized-controlled trials

BACKGROUND & AIMS

Potential effects of inositol supplementation on blood pressure (BP) have been examined in several interventional studies. Nevertheless, findings in this context are controversial. Therefore, the current systematic review and meta-analysis aimed to comprehensively assess the impact of inositol supplementation on BP.

METHODS

Five online databases including Web of Science, Scopus, Embase, Cochrane, Google Scholar, and PubMed were systematically searched from inception to March 2020. We included all randomized clinical trials (RCTs) evaluating the effects of inositol supplementation on systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) in humans.

RESULTS

The random-effects meta-analysis of 7 eligible RCTs demonstrated the significant decline in both SBP (WMD - 5.69 mmHg; 95% CI - 7.35 to - 4.02, P < 0.001) and DBP (WMD - 7.12 mmHg; 95% CI - 10.18 to - 4.05, P < 0.001) following supplementation with inositol. Subgroup analysis showed that studies performed in individuals with metabolic syndrome with a longer duration (>8 weeks) and a dose of 4000 mg resulted in a more effective reduction in SBP and DBP with acceptable homogeneity.

CONCLUSIONS

The current meta-analysis, indicated that supplementation with inositol significantly decrease SBP and DBP. Further large-scale RCTs with better design are needed to confirm these findings.

Quercetin promotes osteogenic differentiation and antioxidant responses of mouse bone mesenchymal stem cells through activation of the AMPK/SIRT1 signaling pathway

Decrepitude and apoptosis of bone mesenchymal stem cells (BMSCs) induced by reactive oxygen species (ROS) lead to inhibited osteogenic differentiation, causing decreased bone density and osteoporosis. Quercetin, a bioactive component of Solanum muricatum extracts, promotes the osteogenic differentiation of BMSCs and ameliorates the symptoms of osteoporosis in vivo. However, the detailed mechanism underlying this process remains unclear. The study aims to reveal the regulatory mechanism of quercetin in BMSCs. Mouse BMSCs (mBMSCs) were isolated from the bone marrow and characterized by flow cytometry. QRT-PCR and western blot assays were performed to evaluate the expression levels of related genes and proteins. Alkaline phosphatase (ALP) staining and Oil Red O staining of lipids were used to estimate the osteogenesis and adipogenesis levels of mBMSCs, respectively. Quercetin treatment (2 and 5 μM) induced significant upregulation of antioxidant enzymes, SOD1 and SOD2, in mBMSCs. Quercetin promoted osteogenic differentiation and inhibited adipogenic differentiation of mBMSCs. Quercetin treatment enhanced the phosphorylation of AMPK protein and upregulated the expression of SIRT1, thus activating the AMPK/SIRT1 signaling pathway in mBMSCs. Quercetin promoted osteogenic differentiation and antioxidant responses of mBMSCs by activating the AMPK/SIRT1 signaling pathway.

Therapeutic Potential of Quercetin to Alleviate Endothelial Dysfunction in Age-Related Cardiovascular Diseases

The vascular endothelium occupies a catalog of functions that contribute to the homeostasis of the cardiovascular system. It is a physically active barrier between circulating blood and tissue, a regulator of the vascular tone, a biochemical processor and a modulator of coagulation, inflammation, and immunity. Given these essential roles, it comes to no surprise that endothelial dysfunction is prodromal to chronic age-related diseases of the heart and arteries, globally termed cardiovascular diseases (CVD). An example would be ischemic heart disease (IHD), which is the main cause of death from CVD. We have made phenomenal advances in treating CVD, but the aging endothelium, as it senesces, always seems to out-run the benefits of medical and surgical therapies. Remarkably, many epidemiological studies have detected a correlation between a flavonoid-rich diet and a lower incidence of mortality from CVD. Quercetin, a member of the flavonoid class, is a natural compound ubiquitously found in various food sources such as fruits, vegetables, seeds, nuts, and wine. It has been reported to have a wide range of health promoting effects and has gained significant attention over the years. A growing body of evidence suggests quercetin could lower the risk of IHD by mitigating endothelial dysfunction and its risk factors, such as hypertension, atherosclerosis, accumulation of senescent endothelial cells, and endothelial-mesenchymal transition (EndoMT). In this review, we will explore these pathophysiological cascades and their interrelation with endothelial dysfunction. We will then present the scientific evidence to quercetin's anti-atherosclerotic, anti-hypertensive, senolytic, and anti-EndoMT effects. Finally, we will discuss the prospect for its clinical use in alleviating myocardial ischemic injuries in IHD.

Quercetin and Its Metabolites Inhibit Recombinant Human Angiotensin-Converting Enzyme 2 (ACE2) Activity

Angiotensin-converting enzyme 2 (ACE2) is a host receptor for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Inhibiting the interaction between the envelope spike glycoproteins (S-proteins) of SARS-CoV-2 and ACE2 is a potential antiviral therapeutic approach, but little is known about how dietary compounds interact with ACE2. The objective of this study was to determine if flavonoids and other polyphenols with B-ring 3',4'-hydroxylation inhibit recombinant human (rh)ACE2 activity. rhACE2 activity was assessed with the fluorogenic substrate Mca-APK(Dnp). Polyphenols reduced rhACE2 activity by 15-66% at 10 μM. Rutin, quercetin-3-O-glucoside, tamarixetin, and 3,4-dihydroxyphenylacetic acid inhibited rhACE2 activity by 42-48%. Quercetin was the most potent rhACE2 inhibitor among the polyphenols tested, with an IC50 of 4.48 μM. Thus, quercetin, its metabolites, and polyphenols with 3',4'-hydroxylation inhibited rhACE2 activity at physiologically relevant concentrations in vitro.

A Spectrum of Topics for 2019: Advances in Neuroinflammation, Oxidative Stress, Obesity, Diabetes Mellitus, Cardiovascular Disease, Autism, Exosomes, and Central Nervous System Diseases

Advances in various fields were discussed in the reviews and original research articles published in 2019 in Current Pharmaceutical Design. Here, I review some of the major highlights for selected areas. A better understanding of disease mechanisms was a prominent recurrent theme and new therapeutic targets based on those mechanisms are highlighted here. Inflammation and oxidative stress are major features of many diseases, therefore, interventions to address these processes are reviewed. Although repurposing of old drugs occurred in several fields, drug targeting and drug delivery, especially of nanoparticles, also continues to be a major area of interest.

Overview of biological effects of Quercetin on ovary

Over the last few decades, using natural products has been increased to treat different diseases. Today, great attention has been pointed toward the usage of natural products such as flavonoids, especially Quercetin (QUR), in the treatment of diseases. QUR as a natural antioxidant has been traditionally used to prevent or treat a variety of diseases such as cancer, cardiovascular disease, polycystic ovary syndrome (PCOS), obesity, chronic inflammation, and reproductive system dysfunction. Several studies demonstrated that QUR acts as an anti-inflammatory, anti-apoptotic, antioxidant, and anticancer agent. With this in view, in this study, we intended to describe an overview of the biological effects of QUR on the ovary. QUR improves the quality of oocytes and embryos. It affects the proliferation and apoptosis and decreases the oxidative stress in granulosa cells (GCs). Furthermore, QUR can be used as a complementary and alternative therapy in ovarian cancer and it has beneficial effects in the treatment of PCOS patients. It seems that QUR as a supplementary factor has different activities for the treatment of different disorders and it also has bidirectional activities. However, further investigations are needed for understanding the efficacy of QUR in the treatment and improvement of gynecological patients.

The role of nutraceuticals in prevention and treatment of hypertension: An updated review of the literature

Hypertension (HTN) is a worldwide epidemic in both developed and developing countries. It is one of the leading causes of major health problems such as cardiovascular disease, stroke, and heart attack. In recent years, several studies have reported associations between specific dietary ingredients and improving HTN. Nutraceuticals are natural food components with pharmacological properties. Reports suggest that functional foods and nutraceutical ingredients might support patients to obtain the desired therapeutic blood pressure (BP) goals and reduce cardiovascular risks by modulating various risk factors such as oxidative stress, renin-angiotensin system hyperactivity, inflammation, hyperlipidemia, and vascular resistance. We review the recent clinical experiments that have evaluated the biological and pharmacological activities of several types of nutraceuticals, including sour tea, cocoa, common spices, vitamin C, vitamin E, lycopene, flavonoids, coenzyme Q10, milk's tripeptides, calcium, magnesium, polyunsaturated fatty acids, and prebiotics in preventing and treating HTN. This review summarizes recent knowledge about the impact of common nutraceuticals for the regulation of BP.