Quercetin inhibits fatty acid and triacylglycerol synthesis in rat-liver cells

Phytochemical Analysis and Anti-dyslipidemia and Antioxidant Activities of Pluchea dioscoridis: In Vitro, In Silico and In Vivo Studies

Pluchea dioscoridis (L.) DC. is a flowering wild plant used traditionally in the treatment of rhematic disorders. This study investigated the phytochemical and in vitro radical scavenging activity (RSA), and in vivo anti-hyperlipidemic, antioxidant and anti-inflammatory properties of P. dioscoridis. The antihyperlipidemic efficacy was determined in a rat model of dyslipidemia. The extract and fractions of P. dioscoridis showed RSA with the ethyl acetate (EA) fraction exhibiting the most potent activity. The phytochemical analysis of P. dioscoridis EA fraction (PDEAF) led to the isolation of five compounds (lupeol, quercetin, lupeol acetate, stigmasterol, and syringic acid). To evaluate its anti-hyperlipidemic effect, three doses of PDEAF were supplemented to rats for 14 days and poloxamer-407 was administered on day 15 to induce dyslipidemia. All doses of PDEAF decreased plasma triglycerides, cholesterol, low-density lipoprotein-cholesterol (LDL-C) and very low-density lipoprotein-cholesterol (vLDL-C), and increased plasma lipoprotein lipase (LPL). PDEAF upregulated hepatic LDL receptor and suppressed 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, decreased lipid peroxidation and tumor necrosis factor (TNF)-α and enhanced reduced glutathione (GSH) and enzymatic antioxidants in dyslipidmeic rats. In silico findings revealed the binding affinity of the isolated compounds towards LPL, HMG-CoA reductase, and LDL receptor. In conclusion, P. dioscoridis is rich in phytoconstituents, exhibited RSA and its EA fraction effectively prevented acute dyslipidemia and its associated oxidative stress and inflammatory response.

Exploration of the mechanism of Qi-Xian decoction in asthmatic mice using metabolomics combined with network pharmacology

Introduction: Qi-Xian Decoction (QXD), a traditional Chinese medicine (TCM) formula consisting of eight herbs, has been clinically used to treat asthma. However, the underlying mechanisms have not been completely elucidated. This study aimed to combine metabolomics and network pharmacology to reveal the mechanism of action of QXD in asthma treatment. Methods: An ovalbumin (OVA)-induced asthma mouse model was constructed to evaluate the therapeutic effects of QXD. Serum metabolomics and network pharmacology were combined to study the mechanism of anti-asthma action as well as the potential target, and related biological functions were validated. Results: The QXD treatment has demonstrated significant protective effects in OVA-induced asthmatic mice, as evidenced by its ability to inhibit inflammation, IgE, mucus overproduction, and airway hyperreactivity (AHR). Metabolomic analysis has revealed a total of 140 differential metabolites associated with QXD treatment. In addition, network pharmacology has identified 126 genes that are linked to the effects of QXD, including TNF, IL-6, IL1β, STAT3, MMP9, EGFR, JUN, CCL2, TLR4, MAPK3 and MAPK8. Through comprehensive gene-metabolite interaction network analysis, seven key metabolites have been identified and associated with the potential anti-asthmatic effect of QXD, with palmitic acid (PA) being the most notable among them. In vitro validation studies have confirmed the gene-metabolite interaction involving PA, IL-6, and MAPK8. Furthermore, our research has demonstrated that QXD treatment can effectively inhibit PA-promoted IL-6 expression in MH-S cells and reduce PA concentration in OVA-induced asthmatic mice. Conclusion: The regulation of metabolic pathways by QXD was found to be associated with its anti-asthmatic action, which provides insight into the mechanism of QXD in treating asthma.

Effects of different levels of dried onion powder on nutrient digestibility, biochemical parameters, and nitrogen balance in Wistar albino rats with induced hyperuricemia

Introduction: Onions (Allium cepa L.) are excellent sources of bioactive compounds and phytochemicals such as allicin, quercetin, fisetin, and other sulfurous compounds. Therefore, our study aimed to investigate the effects of dried onion powder on growth performance, nitrogen balance, and biochemical parameters in Wistar albino rats with induced hyperuricemia. Methods: A total of 24 rats were randomly divided into four groups, with six in each group: HU (positive control) and HOT1, HOT2, and HOT3 groups, which received a diet containing onion powder at concentrations of 11.13, 14.84, and 18.61 g/100 g, respectively. Hyperuricemia was induced in rats by administering a new formulation intraperitoneally (250 mg/kg potassium oxonate) and orally (40 mg/kg potassium bromate) daily for 14 days. After confirmation of hyperuricemia induction, rats were fed with onion-treated diets with various concentrations of quercetin for 21 days. Results: Significant decreases (p ≤ 0.05) in serum uric acid, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, total bilirubin, total cholesterol, and low-density lipoprotein were observed. An increasing trend (p ≤ 0.05) in the levels of hemoglobin (Hb), white blood cell (WBC), red blood cell (RBC), and platelet count was observed. An improvement in the levels of serum high-density lipoprotein, triglycerides, blood urea nitrogen, serum creatinine, serum total protein and neutrophils, lymphocytes, and monocytes was observed. A positive progress (p ≤ 0.05) was observed in growth performance and nutrient digestibility. Conclusion: In conclusion, a significantly lower uric acid level was observed in rats fed with HOT2 diet. Based on the ratio of the surface area (human/rat), the best recommended dose of onion for the incidence and prevention of hyperuricemia is 189.95 g, corresponding to the dose of 204 mg/day of quercetin in humans.

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.

Effect of Green and Red Thai Kratom (Mitragyna speciosa) on pancreatic digestive enzymes (alpha-glucosidase and lipase) and acetyl-carboxylase 1 activity: A possible therapeutic target for obesity prevention

Regular use of Thai kratom has been linked to reduced blood triglyceride levels and body mass index (BMI) in healthy individuals. We analyzed Green Thai Kratom (GTK) and Red Thai Kratom (RTK) to investigate their effects on pancreatic digestive enzymes. The ethanol extracts of GTK and RTK inhibited lipase activity more strongly than alpha-glucosidase activity, suggesting the presence of lipase inhibitors. Mitragynine, the major compound in GTK, showed potent lipase inhibition and moderate alpha-glucosidase inhibition. Quercetin, found in both extracts, strongly inhibited alpha-glucosidase but had limited effects on lipase. These findings suggest that mitragynine and quercetin may hinder triglyceride and starch digestion. Combination inhibition studies revealed synergistic effects between mitragynine and quercetin on alpha-glucosidase activity. Additionally, both GTK and RTK extracts reduced fat accumulation in 3T3-L1 adipocyte cells, with quercetin specifically inhibiting Acetyl-CoA carboxylase 1 (ACC1), a key enzyme in fatty acid biosynthesis. Thus, GTK and RTK extracts, particularly mitragynine and quercetin, exhibit potential anti-obesity effects. We report the novel finding that Thai kratom inhibits de novo fatty acid synthesis by targeting ACC1, resulting in decreased fat accumulation in adipocytes. Regular use of Thai kratom in specific populations may improve blood triglyceride levels and reduce BMI by inhibiting lipase, alpha-glucosidase, and ACC1 activity. Further clinical trials are needed to determine optimal dosage, duration, toxicity levels, and potential side effects of Kratom use.

The effects of phytochemicals on serum triglycerides in subjects with hypertriglyceridemia: A systematic review of randomized controlled trials

This systematic review aimed to evaluate the efficacy of phytochemicals on lipid parameters in patients with hypertriglyceridemia (HTG). A comprehensive search was performed in PubMed/Medline, Scopus, ISI Web of Science, and Google Scholar from inception up to October 2021 to recognize randomized controlled trials (RCTs) assessing the effects of phytochemicals on lipid profiles in patients with HTG. Forty-eight RCTs including 53 arms and comprising 3,478 HTG patients met the eligibility criteria. Phytochemicals significantly reduced the serum levels of triglycerides in 32 out 53 arms, total cholesterol in 22 out of 51, low-density lipoprotein cholesterol in 21 out of 48, very low-density lipoprotein cholesterol in 1 out of 5, apolipoprotein B in 2 out of 4, and lipoprotein(a) levels in 2 out of 4 arms. Furthermore, phytochemicals supplementation increased the levels of high-density lipoprotein cholesterol in 15 out of 48 arms. In brief, phytochemicals supplementation might have beneficial effects on HTG. In most of the studies, phytochemicals had a favorable effect on at least one of the lipid parameters.

Protective effect of quercetin against 5-fluorouracil-induced cardiac impairments through activating Nrf2 and inhibiting NF-κB and caspase-3 activities

5-Fluorouracil (5-FU) is a chemotherapy used to treat many types of cancer. Cardiotoxicity is one of the common drawbacks of 5-FU therapy. Quercetin (Qu) is a bioflavonoid with striking biological activities. This research aimed to assess the ameliorative effect of Qu against 5-FU-mediated cardiotoxicity. Thirty-five rats were allocated into five groups: control group (normal saline), 5-FU group (30 mg/kg, intraperitoneally), Qu group (50 mg/kg, oral), 25 mg/kg Qu+5-FU group, and 50 mg/kg Qu+5-FU. The experimental animals were received the above-mentioned drugs for 21 days. Results showed that 5-FU significantly elevated creatine kinase, lactate dehydrogenase, serum cholesterol and triglyceride, and upregulated troponin and renin mRNA expression. Additionally, cardiac oxidant/antioxidant imbalance was evident in elevated oxidants (malondialdehyde and nitric oxide) and depleted antioxidants (superoxide dismutase, catalase, glutathione peroxidase, and glutathione). 5-FU also downregulated the gene expression of nuclear factor erythroid 2-related factor 2. Furthermore, 5-FU significantly increased cardiac pro-inflammatory cytokines (tumor necrosis factor-alpha and interleukin-1 beta) and upregulated gene expression of nuclear factor kappa-B. 5-FU significantly enhanced cardiac apoptosis through upregulating caspase-3 expression and downregulating B-cell lymphoma 2. Immunohistochemical and histopathological examinations verified the above-mentioned findings. However, all these changes were significantly ameliorated in Qu pre-administered rats. Conclusively, Qu counteracted 5-FU-mediated cardiotoxicity through potent antioxidant, anti-inflammatory, and anti-apoptotic effects.

Quercetin: A Functional Food-Flavonoid Incredibly Attenuates Emerging and Re-Emerging Viral Infections through Immunomodulatory Actions

Many of the medicinally active molecules in the flavonoid class of phytochemicals are being researched for their potential antiviral activity against various DNA and RNA viruses. Quercetin is a flavonoid that can be found in a variety of foods, including fruits and vegetables. It has been reported to be effective against a variety of viruses. This review, therefore, deciphered the mechanistic of how Quercetin works against some of the deadliest viruses, such as influenza A, Hepatitis C, Dengue type 2 and Ebola virus, which cause frequent outbreaks worldwide and result in significant morbidity and mortality in humans through epidemics or pandemics. All those have an alarming impact on both human health and the global and national economies. The review extended computing the Quercetin-contained natural recourse and its modes of action in different experimental approaches leading to antiviral actions. The gap in effective treatment emphasizes the necessity of a search for new effective antiviral compounds. Quercetin shows potential antiviral activity and inhibits it by targeting viral infections at multiple stages. The suppression of viral neuraminidase, proteases and DNA/RNA polymerases and the alteration of many viral proteins as well as their immunomodulation are the main molecular mechanisms of Quercetin's antiviral activities. Nonetheless, the huge potential of Quercetin and its extensive use is inadequately approached as a therapeutic for emerging and re-emerging viral infections. Therefore, this review enumerated the food-functioned Quercetin source, the modes of action of Quercetin for antiviral effects and made insights on the mechanism-based antiviral action of Quercetin.

Quercetin Reduces Lipid Accumulation in a Cell Model of NAFLD by Inhibiting De Novo Fatty Acid Synthesis through the Acetyl-CoA Carboxylase 1/AMPK/PP2A Axis

Dysregulation of de novo lipogenesis (DNL) has recently gained strong attention as being one of the critical factors that contribute to the assessment of non-alcoholic fatty liver disease (NAFLD). NAFLD is often diagnosed in patients with dyslipidemias and type 2 diabetes; thus, an interesting correlation can be deduced between high hematic free fatty acids and glucose excess in the DNL dysregulation. In the present study, we report that, in a cellular model of NAFLD, the coexistence of elevated glucose and FFA conditions caused the highest cellular lipid accumulation. Deepening the molecular mechanisms of the DNL dysregulation—RT-qPCR and immunoblot analysis demonstrated increased expression of mitochondrial citrate carrier (CiC), cytosolic acetyl-CoA carboxylase 1 (ACACA), and diacylglycerol acyltransferase 2 (DGAT2) involved in fatty acids and triglycerides synthesis, respectively. XBP-1, an endoplasmic reticulum stress marker, and SREBP-1 were the transcription factors connected to the DNL activation. Quercetin (Que), a flavonoid with strong antioxidant properties, and noticeably reduced the lipid accumulation and the expression of SREBP-1 and XBP-1, as well as of their lipogenic gene targets in steatotic cells. The anti-lipogenic action of Que mainly occurs through a strong phosphorylation of ACACA, which catalyzes the committing step in the DNL pathway. The high level of ACACA phosphorylation in Que-treated cells was explained by the intervention of AMPK together with the reduction of enzymatic activity of PP2A phosphatase. Overall, our findings highlight a direct anti-lipogenic effect of Que exerted through inhibition of the DNL pathway by acting on ACACA/AMPK/PP2A axis; thus, suggesting this flavonoid as a promising molecule for the NAFLD treatment.

Nonalcoholic fatty liver disease: The role of quercetin and its therapeutic implications

Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease, affecting almost one-third of the general population and 75% of obese patients with type 2 diabetes. The aim of this article is to review the current evidence concerning the role of quercetin, a natural compound and flavonoid, and its possible therapeutic effects on this modern-day disease. Despite the fact that the exact pathophysiological mechanisms through which quercetin has a hepatoprotective effect on NAFLD are still not fully elucidated, this review clearly demonstrates that this flavonoid has potent antioxidative stress action and inhibitory effects on hepatocyte apoptosis, inflammation, and generation of reactive oxygen species, factors which are linked to the development of the disease. NAFLD is closely associated with increased dietary fat consumption, especially in Western countries. The hepatoprotective effect of quercetin against NAFLD merits serious consideration and further validation by future studies.

Dietary Curcumin Improves Energy Metabolism, Brain Monoamines, Carcass Traits, Muscle Oxidative Stability and Fatty Acid Profile in Heat-Stressed Broiler Chickens

The aim of the present study was to elucidate the impacts of dietary curcumin supplementation on energy metabolism, brain monoamines and muscle oxidative stability in heat-stressed broilers. In total, 120 day-old chicks were allocated into three equal groups of four replicates. The first group (T₁) was maintained on a thermoneutral condition, while the second group (T₂) was subjected to 8 h of thermal stress (34 °C), and both groups fed the basal diet with no supplement. The third group (T₃) was exposed to the same thermal stress conditions and fed the basal diet supplemented with curcumin (100 mg kg^-1 diet). The dietary curcumin supplementation significantly increased the breast yield (p = 0.004), but reduced the percentage of abdominal fat (p = 0.017) compared with the T₂ group. The addition of curcumin to broiler diets significantly improved the levels of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) in breast and thigh muscles compared with the T₂ group (p < 0.05). The curcumin-supplemented group showed significantly lower levels of malondialdehyde in the breast and thigh muscles than that of the T₂ group (p = 0.001 and 0.015, respectively). The dietary curcumin supplementation significantly improved the levels of ATP and CoQ10 in liver tissues (p = 0.012 and 0.001, respectively) and brain serotonin (p = 0.006) as compared to the T2 group. Meanwhile, the heat-stressed group showed significantly higher levels of ADP and Na,K-ATPase in the liver tissues than that of the other experimental groups (p = 0.011 and 0.027, respectively). It could be concluded that dietary curcumin supplementation may improve carcass yield, energy biomarkers, brain serotonin and muscle oxidative stability of heat-stressed broiler chickens.

Quercetin and metabolic syndrome: A review

Metabolic syndrome (MetS) is a complex of diseases that lead to mortality due to the development of cardiovascular problems. Quercetin, as an important flavonoid, has various properties such as decreasing blood pressure, anti-hyperlipidemia, anti-hyperglycemia, anti-oxidant, antiviral, anticancer, anti-inflammatory, anti-microbial, neuroprotective, and cardio-protective effects. In this review article, we collected original articles from different sources such as Google Scholar, Medline, Scopus, and Pubmed, which is related to the effect of quercetin on the improvement of the signs of MetS, including elevated glucose level, hyperlipidemia, obesity, and blood pressure. According to these data, quercetin may also have a role in the management of metabolic disorders via different mechanisms such as increasing adiponectin, decreasing leptin, anti-oxidant activity, reduction of insulin resistance, the elevation of insulin level, and blocking of calcium channel. We have attempted to make some recommendations on the quercetin application in patients. However, it needs to do further clinical trials and more investigations to show the real clinical value of quercetin on metabolic syndrome.

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.

Quercetin and lithium chloride potentiate the protective effects of carvedilol against renal ischemia-reperfusion injury in high-fructose, high-fat diet-fed Swiss albino mice independent of renal lipid signaling

Renal ischemia-reperfusion injury (R-IRI) is the main cause of acute renal failure. Carvedilol has been shown to protect against R-IRI. However, the underlying mechanisms are still not completely clarified. This study aimed to investigate the role of lipid signaling in mediating carvedilol protective effects against R-IRI in insulin-resistant mice by using two different lipid signaling modulators, quercetin and lithium chloride (LiCl). Mice were fed high-fructose, high-fat diet (HFrHFD) for 16 weeks to induce insulin resistance. At the end of feeding period, mice were randomly distributed into five groups; Sham, R-IRI, Carvedilol (20 mg/kg, i.p.), Carvedilol + Quercetin (10 mg/kg, i.p.), Carvedilol + LiCl (200 mg/kg, i.p.). R-IRI was performed by applying 30 min of unilateral renal ischemia followed by one hour of reperfusion. Quercetin and LiCl were administered 30 min before carvedilol administration and carvedilol was administered 30 min before ischemia. Changes in kidney function tests, histopathology, fibrosis area, lipid signaling, inflammatory, apoptosis and oxidative stress markers in the kidney were measured. Results showed that R-IRI decreased kidney function, impaired renal tissue integrity, modulated lipid signaling and increased renal inflammation, apoptosis and oxidative stress. Carvedilol treatment decreased the detrimental effects induced by R-IRI. In addition, pre-injection of both quercetin and LiCl potentiated the reno-protective effects of carvedilol against R-IRI independent of changes in lipid mediators like phosphatidyl inositol 4,5 bisphosphate (PIP2) and diacylglycerol (DAG). In conclusion, quercetin and LiCl potentiate the protective effects of carvedilol against R-IRI in HFrHFD-fed mice by reducing inflammation and oxidative stress independent of lipid signaling.

An Overview of the Mechanism of Penthorum chinense Pursh on Alcoholic Fatty Liver

Alcohol liver disease (ALD) caused by excessive alcohol consumption is a progressive disease, and alcohol fatty liver disease is the primary stage. Currently, there is no approved drug for its treatment. Abstinence is the best way to heal, but patients' compliance is poor. Unlike other chronic diseases, alcohol fatty liver disease is not caused by nutritional deficiencies; it is caused by the molecular action of ingested alcohol and its metabolites. More and more studies have shown the potential of Penthorum chinense Pursh (PCP) in the clinical use of alcohol fatty liver treatment. The purpose of this paper is to reveal from the essence of PCP treatment of alcohol liver mechanism mainly by the ethanol dehydrogenase (ADH) and microsomal ethanol oxidation system-dependent cytochrome P4502E1 (CYP2E1) to exert antilipogenesis, antioxidant, anti-inflammatory, antiapoptotic, and autophagy effects, with special emphasis on its mechanisms related to SIRT1/AMPK, KEAP-1/Nrf2, and TLR4/NF-κB. Overall, data from the literature shows that PCP appears to be a promising hepatoprotective traditional Chinese medicine (TCM).

Protective Effects of Polyphenols Present in Mediterranean Diet on Endothelial Dysfunction

Endothelial dysfunction tends to be the initial indicator in proinflammatory state and macro- and microvascular complications, such as atherosclerosis and cardiovascular diseases. It has been shown that certain compounds in diet can generate beneficial effects on cardiovascular disease due to its interactions with endothelial cells. Thus, this review is aimed at investigating whether certain polyphenols present in the Mediterranean diet, specifically catechin, quercetin, resveratrol, and urolithin, could exert positive effects on endothelial dysfunction. After analysis of numerous papers, we found that polyphenols aiding endothelial function is beneficial not only for patients with cardiovascular disease, diabetes, or endothelial dysfunction but for all people as it can improve the effects of aging on the endothelia. The additional benefit of these polyphenols on weight loss further improves health and lowers the risk of several diseases, including those caused by endothelial dysfunction. However, it is important to note that the dosages in the majorities of the studies mentioned in this review were of supplemental rather than nutritionally relevant quantities, and therefore, the recommended dosages are difficult to determine.

Protective effects of quercetin against oxidative stress induced by bisphenol-A in rat cardiac mitochondria

Research has shown a relationship between the exposures to a chemical agent called bisphenol-A (BPA), which is extensively used in the production of polycarbonate plastics and the incidence of cardiovascular diseases. This association is most likely caused by the BPA's ability to disrupt multiple cardiac mechanisms, including mitochondrial functions. Therefore, this study aimed to explore the ability of quercetin (QUER) to limit the cardiotoxic effect of BPA in the rat's cardiac mitochondria. The experiment was carried out on 32 male Wistar rats, which were randomly assigned to four groups. The negative control group received olive oil; the positive control group received olive oil plus BPA (250 mg/kg); the third group received olive oil, BPA, and QUER (75 mg/kg); and the fourth group received olive oil and QUER, all orally for 14 days. The rats were slaughtered 24 h after the last treatment. The measured parameters included creatine kinase-MB (CK-MB) and lactate dehydrogenase (LDH) as the biomarkers of cardiotoxicity, triglyceride (TG), total cholesterol (TC), and low-density and high-density lipoprotein cholesterol (LDL-C and HDL-C) as the measures of dyslipidemia, glutathione (GSH) content, catalase activity (CAT), reactive oxygen species (ROS), lipid peroxidation (LPO), and the level of damage to the mitochondrial membranes as the indicators of the impact of QUER on the BPA cardiotoxic effect. Finally, the rats treated with QUER showed better results in terms of serum CK-MB, serum LDH, serum lipid profile, GSH level, CAT activity, mitochondrial membrane potential (ΔΨm), LPO, and ROS. According to the results, QUER could be used as a protective agent against BPA-induced mitochondrial toxicity.

SSO and other putative inhibitors of FA transport across membranes by CD36 disrupt intracellular metabolism, but do not affect FA translocation

Membrane-bound proteins have been proposed to mediate the transport of long-chain FA (LCFA) transport through the plasma membrane (PM). These proposals are based largely on reports that PM transport of LCFAs can be blocked by a number of enzymes and purported inhibitors of LCFA transport. Here, using the ratiometric pH indicator (2',7'-bis-(2-carboxyethyl)-5-(and-6-)-carboxyfluorescein and acrylodated intestinal FA-binding protein-based dual fluorescence assays, we investigated the effects of nine inhibitors of the putative FA transporter protein CD36 on the binding and transmembrane movement of LCFAs. We particularly focused on sulfosuccinimidyl oleate (SSO), reported to be a competitive inhibitor of CD36-mediated LCFA transport. Using these assays in adipocytes and inhibitor-treated protein-free lipid vesicles, we demonstrate that rapid LCFA transport across model and biological membranes remains unchanged in the presence of these purported inhibitors. We have previously shown in live cells that CD36 does not accelerate the transport of unesterified LCFAs across the PM. Our present experiments indicated disruption of LCFA metabolism inside the cell within minutes upon treatment with many of the "inhibitors" previously assumed to inhibit LCFA transport across the PM. Furthermore, using confocal microscopy and a specific anti-SSO antibody, we found that numerous intracellular and PM-bound proteins are SSO-modified in addition to CD36. Our results support the hypothesis that LCFAs diffuse rapidly across biological membranes and do not require an active protein transporter for their transmembrane movement.

Quercetin inhibition of SREBPs and ChREBP expression results in reduced cholesterol and fatty acid synthesis in C6 glioma cells

Quercetin (Que), a widely distributed flavonoid in the human diet, exerts neuroprotective action because of its property to antagonize oxidative stress. Here, we investigated the effects of Que on lipid synthesis in C6 glioma cells. A rapid Que-induced inhibition of cholesterol and, to a lesser extent, of fatty acid synthesis from [1-¹⁴C]acetate was observed. The maximum decrease was detected at the level of palmitate, the end product of de novo fatty acid synthesis. The effect of Que on the enzyme activities of acetyl-CoA carboxylase 1 (ACC1) and fatty acid synthase (FAS), the two enzymes of this pathway, was investigated directly in situ in permeabilized C6 cells. An inhibitory effect on ACC1 was observed after 4 h of 25 μM Que treatment, while FAS activity was not affected. A reduction of polar lipid biosynthesis was also detected. A remarkable decrease of 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) activity, regulatory enzyme of cholesterol synthesis, was evidenced. Expression studies demonstrated that Que acts at transcriptional level, by reducing the mRNA abundance and protein amount of ACC1 and HMGCR. Deepening the molecular mechanism, we found that Que decreased the expression of SREBP-1 and SREBP-2, transcriptional factors representing the main regulators of de novo fatty acid and cholesterol synthesis, respectively. Que also reduced the nuclear content of ChREBP, a glucose-induced transcription factor involved in the regulation of lipogenic genes. Our results represent the first evidence that a direct and rapid downregulatory effect of Que on cholesterol and de novo fatty acid synthesis is elicited in C6 cells.

Quercetin Effects on Hepatotoxicity Induced by Titanium Dioxide Nanoparticles in Rats

Background: Most nanoparticles have adverse impacts on the liver, which is a vital body organ, by the induction of oxidative stress. Objectives: This study was designed to evaluate the hepatoprotective effects of quercetin (QCT) against the toxicity of nanoscale titanium dioxide (NTiO2) in Wistar rats. Methods: The present study was conducted on 32 adult female Wistar rats assigned into 4 groups of control, NTiO2 (50 mg/kg), NTiO2 + Quercetin (50 + 75 mg/kg), and Quercetin (75 mg/kg). The animals exposed to NTiO2 were administered by 50 mg/kg of NTiO2 for 21 days. The Quercetin + NTiO2 rats received Quercetin before exposing to NTiO2 for 7 days. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) of serum were considered indicators of the hepatotoxicity. The oxidative stress was assessed by measuring the activity of catalase (CAT) and superoxide dismutase (SOD) as well as the level of malondialdehyde (MDA) in the liver. TUNEL assay and histological changes were also assessed. Results: The NTiO2 significantly elevated the MDA level (P < 0.01), enhanced the serum biomarker levels, reduced the CAT (P < 0.01) and SOD (P < 0.01) activities. The NTiO2 also aggregated the red blood cells, and caused inflammatory cell infiltration, nuclear pyknosis and fat deposit in hepatocytes, as well as induced apoptosis in the liver tissue. Pretreatment with QCT quenched oxidative stress, attenuated the histological changes, elevated the CAT (P < 0.01) and SOD (P < 0.01) activities, normalized the serum biomarker levels and decreased apoptosis (P < 0.001). Conclusions: The QCT has an inhibitory impact on hepatotoxicity induced by nanoparticles in rats.

Effects of dietary curcumin and acetylsalicylic acid supplements on performance, muscle amino acid and fatty acid profiles, antioxidant biomarkers and blood chemistry of heat-stressed broiler chickens

The objective was to investigate the effects of dietary curcumin and acetylsalicylic acid (ASA) on the performance and physiological responses of broiler chickens under chronic thermal stress. One hundred and sixty day-old male chicks (Ross 308) were divided equally into 4 groups (each contained 4 replicates). On the day 22 of age and thereafter, the first group (TN) was raised in a thermoneutral condition (23 ± 1 °C), while the second group (HS) was subjected to 8 h of thermal stress (34 °C) and both groups fed the basal diet with no supplements. The third (CR) and fourth (AS) groups were subjected to the same thermal stress conditions and fed curcumin-supplemented diet (100 mg curcumin kg^-1 diet) and ASA-supplemented diet (1 g ASA kg^-1 diet), respectively. Dietary treatment had a significant effect on ADFI (P = 0.041), average daily gain (P = 0.013) and final body weight (P = 0.001). The curcumin-supplemented had higher values for these measures compared with other experimental groups (P < 0.05). Also, the dietary curcumin supplement significantly increased the carcass yield as compared to the HS group (P < 0.05). Compared with the HS group, the dietary curcumin and ASA supplements decreased the concentration of malondialdehyde in the breast muscles (P = 0.014). Both dietary supplements exhibited a marked ability to restore the serum TAC, Na and K in heat-stressed broiler chickens. The current study reported a remarkable ability of curcumin supplement to restore the concentrations of polyunsaturated fatty acids (PUFA) in the breast muscles of heat-stressed broilers, including α-linolinec acid and Docosahexaenoic acid (P = 0.009 and 0.001, respectively). It could be concluded that supplemental dietary curcumin or ASA enhanced growth performance and antioxidant biomarkers of heat-stressed broilers. Moreover, curcumin might be an effective dietary supplement to alleviate the adverse effect of chronic thermal stress on carcass yield and meat quality.

Effects of Quercetin on Expression of Genes of Carbohydrate and Lipid Metabolism Enzymes in the Liver of Rats Receiving High-Fructose Ration

We studied the expression of genes encoding enzymes of carbohydrate and lipid metabolism ketohexokinase (Khk), glucokinase (Gck), pyruvate kinase (Pklr), acetyl-Co-carboxylase (Acaca), fatty acid synthase (Fasn), stearoyl-CoA desaturase (Scd), and their transcription regulators ChREBP (Mlxipl), SREBP-1c (Srebf1), and PPARα (Ppara) in rat liver. Control group rats received a semisynthetic ration over 20 weeks. Experimental group 1 received a semisynthetic ration and 20% fructose solution instead of drinking water. Experimental group 2 rats received a semisynthetic ration with quercetin (0.1% fodder weight) and 20% fructose solution. Consumption of 20% fructose solution (experimental group 1) led to an increase in Scd expression in comparison with the control and did not affect the expression of other genes. Addition of quercetin to the ration (experimental group 2) led to a decrease in the expression of Khk, Gck, Fasn, Scd, Mlxipl, and Ppara genes in comparison with experimental group 1. The results suggest that quercetin reduced the expression of genes of carbohydrate and lipid metabolism enzymes in the liver of rats receiving high-fructose ration.

Oral Supplementation Effect of Iron and its Complex Form With Quercetin on Oxidant Status and on Redistribution of Essential Metals in Organs of Streptozotocin Diabetic Rats

Background and aims: Quercetin, is a polyphenolic antioxidant compound. It is able to form complex with metal ions such as iron and exerts a broad range of biological activities like improving metabolic disorders. This research aims at investigating the effect of oral supplementation of iron (2.5mg Fe/Kg/day) and its complex form (molar ratio 1:5; 2.5mg/25mg/Kg/day) with quercetin (25mg/Kg/day) on lipid metabolism, oxidant status and trace elements contents in organs of Wistar diabetic rats (45 mg/kg/rat.ip of streptozotocin) during eight weeks of experimentation.

Material and method: To achieve this, liver and adipose tissue enzymes activities, NO • , O2 −• , TBARs, carbonyl protein levels in plasma were analysed. Metals (Cu, Fe, Mg, Zn) analysis of organs were determined by inductively coupled plasma atomic emission spectroscopy.

Results: Iron supplemented alone induced a noticeable disorder in lipid, lipoprotein, lipases and oxidant status. Yet, it caused an imbalance in the redistribution of metals in the organs of diabetic and non diabetic rats. Iron-quercetin complex was shown as less harmful and more beneficial than iron supplemented alone.

Conclusions: This complex could reverse oxidative stress and iron deficiency mostly caused by the diabetic disease but at the same time it induces an imbalance in redistribution of other essential metals.

Differential Impact of Flavonoids on Redox Modulation, Bioenergetics, and Cell Signaling in Normal and Tumor Cells: A Comprehensive Review

SIGNIFICANCE

Flavonoids can interact with multiple molecular targets to elicit their cellular effects, leading to changes in signal transduction, gene expression, and/or metabolism, which can, subsequently, affect the entire cell and organism. Immortalized cell lines, derived from tumors, are routinely employed as a surrogate for mechanistic studies, with the results extrapolated to tissues in vivo. Recent Advances: We review the activities of selected flavonoids on cultured tumor cells derived from various tissues in comparison to corresponding primary cells or tissues in vivo, mainly using quercetin and flavanols (epicatechin and (-)-epigallocatechin gallate) as exemplars. Several studies have indicated that flavonoids could retard cancer progression in vivo in animal models as well as in tumor cell models.

CRITICAL ISSUES

Extrapolation from in vitro and animal models to humans is not straightforward given both the extensive conjugation and complex microbiota-dependent metabolism of flavonoids after consumption, as well as the heterogeneous metabolism of different tumors.

FUTURE DIRECTIONS

Comparison of data from studies on primary cells or in vivo are essential not only to validate results obtained from cultured cell models, but also to highlight whether any differences may be further exploited in the clinical setting for chemoprevention. Tumor cell models can provide a useful mechanistic tool to study the effects of flavonoids, provided that the limitations of each model are understood and taken into account in interpretation of the data.

Bioavailability of Quercetin from Onion Extracts after Intraruminal Application in Cows

The aim of the present study was to investigate the bioavailability of quercetin from onion bulb (OB) and onion skin (OS) extracts in ruminants. Three non-lactating cows equipped with a permanent rumen fistula intraruminally received equimolar amounts of quercetin as either aglycone, rutin, or OB or OS extract, respectively, at a dose of 50 mg of quercetin equivalents/kg of body weight. Blood samples were drawn before and frequently within the 24 h period after application of the respective substance. Quercetin and quercetin metabolites with an intact flavonol structure (kaempferol, isorhamnetin, and tamarixetin) were analyzed in plasma samples by high-performance liquid chromatography with fluorescence detection. All quercetin sources administered resulted in a fast increase of the plasma concentrations of quercetin and total flavonols (sum of quercetin and its metabolites), followed by a rapid decline, whereby significant higher concentrations occurred with OB extract and rutin compared to quercetin aglycone and OS extract, respectively. The results clearly demonstrate a higher systemic availability of quercetin from OB extract and rutin. Taken together, OB extract with a high content of quercetin glucosides is an interesting source for the application of quercetin to ruminants.

Therapeutic potential of quercetin as a cardiovascular agent

Flavonoids are integral components of various vegetation and in foods; consequently, they represent an inevitable part of the diet. Historical and epidemiological proof recommend that diet plans consisting of flavonoids such as quercetin have positive health benefits, especially on the heart. Flavonoids have been proven to be active against hypertension, inflammation, diabetes and vascular diseases. Quercetin exhibits significant heart related benefits as inhibition of LDL oxidation, endothelium-independent vasodilator effects, reduction of adhesion molecules and other inflammatory markers, the protective effect on nitric oxide and endothelial function under conditions of oxidative stress, prevention of neuronal oxidative and inflammatory damage and platelet antiaggregant effects. Searching for experimental evidence to validate the cardioprotective effects of quercetin, we review here the recent detailed in vivo studies. Quercetin and its derivatives lead to an enhancement in heart features, indicating the prospective for quercetin to be used therapeutically in the treatment of cardiac diseases. Several evidence-based studies suggest mechanisms to observe cardiovascular diseases such as aging effects, hypertension, angiotensin-converting enzyme activity and endothelial-dependent and independent functions. Different animal models including human are also used to elucidate the in vivo role of quercetin in cardiovascular diseases. The role of quercetin and its derivatives may go beyond their existence in food and has potential as a lead molecule in drug development programs.

Quercetin Lowers Plasma Triglycerides Accompanied by White Adipose Tissue Browning in Diet-Induced Obese Mice

Obesity and dyslipidemia are major risk factors for the development of cardiovascular diseases (CVD). Quercetin, a natural flavonoid, lowers plasma triglycerides (TG) in human intervention studies, and its intake is associated with lower CVD risk. The aim of this study was to elucidate the mechanism by which quercetin lowers plasma TG levels in diet-induced obesity. C57Bl/6J mice received a high-fat diet (45% of calories derived from fat) with or without quercetin (0.1% w/w) for 12 weeks. Quercetin decreased plasma TG levels from nine weeks onwards (−19%, p < 0.05), without affecting food intake, body composition, or energy expenditure. Mechanistically, quercetin did not reduce intestinal fatty acid (FA) absorption. Rather, quercetin induced a slight reduction in liver Apob expression (−13%, p < 0.05), which suggests decreased very-low density lipoprotein-TG production. Interestingly, quercetin also markedly increased the uptake of [³H]oleate, which was derived from glycerol tri[³H]oleate-labeled lipoprotein-like particles by subcutaneous white adipose tissue (sWAT, +60%, p < 0.05). Furthermore, quercetin also markedly increased mRNA expression of Ucp1 (+229%, p < 0.05) and Elovl3 (+138%, p < 0.05), specifically in sWAT. Accordingly, only quercetin-treated animals showed uncoupling protein-1 protein-positive cells in sWAT, which is fully compatible with increased browning. Taken together, the TG-lowering effect of quercetin may, at least in part, be due to increased TG-derived FA uptake by sWAT as a consequence of browning.

Quercetin ameliorates HFD-induced NAFLD by promoting hepatic VLDL assembly and lipophagy via the IRE1a/XBP1s pathway

The consumption of a quercetin-rich diet has been well-established as a feasible method against non-alcoholic fatty liver disease (NAFLD); however, the molecular mechanisms underlying the progression of NAFLD and its intervention by quercetin remain largely obscure. Male Sprague-Dawley rats fed high-fat diet (HFD), and HepG2 cells stimulated with free fatty acid, were treated with quercetin and various pharmacological reagents to explore the effect of signaling pathways involved in endoplasmic reticulum stress on very low-density lipoprotein (VLDL) assembly and lipophagy. Quercetin intake decreased hepatic TG content by 39%, with a 1.5-fold increase in VLDL, and up-regulated spliced X-box binding protein 1 (XBP1s) expression compared with the HFD group. Thapsigargin or STF-083010 (an IRE1α endonuclease inhibitor) decreased VLDL content in a dose-dependent manner, partially counteracting the protective effects of quercetin, 4-PBA or APY-29 (an IRE1α endonuclease activator). Additionally, microsomal TG-transfer protein complex expression was increased with quercetin-treated and down-regulated by STF-083010. Moreover, quercetin increased co-localization of lysosomes with lipid droplets (LDs) accompanied by decreased p62 accumulation. STF-083010 partially abolished the effect of quercetin on LDs autophagy in an mTOR-independent manner. Collectively, these findings demonstrate that hepatic VLDL assembly and lipophagy are the main targets of quercetin against NAFLD via the IRE1a/XBP1s pathway.

Evaluation of phenolic compounds and lipid-lowering effect of Morus nigra leaves extract

Morus nigra L. (Moraceae) is a tree known as black mulberry and the leaves are used in folk medicine in the treatment of diabetes, high cholesterol and menopause symptoms. The aim of this study was to evaluate the M. nigra leaves phytochemical profile in different extractions and the hypolipidemic effect of the infusion comparing to the fenofibrate. Morus nigra infusion (MN) showed higher amounts of phenolics and flavonoids (83.85 mg/g and 79.96 µg/g, respectively), as well as antioxidant activity (83.85%) than decoction or hydromethanolic extracts. Although, decoction showed the best result for ascorbic acid (4.35 mg/100 g) than hydromethanolic or infusion (2.51 or 2.13 mg/100 g, respectively). The phenolic acids gallic, chlorogenic and caffeic and the flavonoids quercetin, rutin and catechin were found in the M. nigra extracts. Hyperlipidemic rats treated with 100, 200 or 400 mg/kg of MN decreased serum cholesterol, triglycerides and normalized lipoproteins. Furthermore, MN inhibited lipid peroxidation in liver, kidney and brain of hyperlipidemic rats. This study provides evidence that M. nigra leaves extracts are rich in polyphenols, mainly chlorogenic acid, which normalized hyperlipidemic disturbance. The results suggest a potential therapeutic effect of the M. nigra leaves infusion on dislipidemic condition and related oxidative stress.

Hypoglycemic, Hypolipidemic, and Wound Healing Potential of Quercetin in Streptozotocin-Induced Diabetic Rats

Background:

Among the dietary polyphenolic, quercetin is the most common compound available in vegetables and fruits. The phytochemicals are used to treat diabetic wounds and diabetes, and specifically dietary polyphenols are being extensively studied for their anti-inflammatory and antioxidant abilities.

Objective:

The objective of the study was to assess the hypoglycemic, hypolipidemic, and wound healing potential of quercetin in streptozotocin (STZ)-induced diabetic Wistar rats.

Materials and Methods:

Induction of diabetes was done by intraperitoneally administration of STZ at the dose of 55 mg/kg in Wistar rats. An excision wound was created in diabetic rats that were treated with quercetin (100 mg/kg) orally and quercetin ointment topically to evaluate the antidiabetic and wound healing potential of quercetin.

Results:

Repeated oral administration of quercetin along with topical application of quercetin ointment in diabetic rats normalized the altered blood glucose, hydroxyproline, and glucosamine levels. Topical application of quercetin ointment alone on the excised wound was sufficient enough to heal the wound area in diabetic rats.

Conclusions:

The result of the present study indicates that quercetin produces hypoglycemic effect in STZ-induced diabetic rats and normalized plasma lipids and protein profiles. Besides, this quercetin also has an excellent wound healing property when applied topically on the wound area in diabetic rats.

SUMMARY

Quercetin has hypoglycaemic and hypolipidemic potential in streptozotocin induced diabetes in wistar rats

Dermal application along with oral administrations of quercetin has more effective in wound healing in diabetic animals

Histopathological studies of pancreas, skin and liver shows significant reduction in archaeological alterations on quercetin administrations in diabetic rats.

Abbreviation used: STZ: Streptozotocin; CMC: Carboxy methyl cellulose; HDL: High density lipoproteins; LDL: low density lipoproteins.

Effects of quercetin supplementation on lipid profile: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

In spite of promising experimental findings, randomized controlled trials (RCTs) have yielded mixed results on the impact of quercetin supplementation on plasma lipid levels.

AIM

The present study aimed to quantify the effects of quercetin on plasma lipids using a meta-analysis of RCTs.

METHODS

A systematic literature search of Medline was conducted for RCTs that investigated the efficacy of quercetin supplementation on plasma lipids comprising total cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides. Weighted mean differences (WMDs) and 95% confidence intervals (CIs) were calculated for net changes in lipid concentrations using a random-effects model. Meta-regression analysis was conducted to assess the effect of quercetin dose and duration of supplementation as moderators on the calculated effect measures.

RESULTS

Five RCTs totaling 442 subjects (221 in the quercetin and 221 in the control group) fulfilled the eligibility criteria and selected for analyses. Combined estimate of effect size for the impact of quercetin on plasma LDL-C (WMD: 1.43 mg/dL, 95% CI: -0.92-3.78, p = 0.23), HDL-C (WMD: 0.26 mg/dL, 95% CI: -0.74-1.25, p = 0.61) and triglycerides (WMD: -9.42 mg/dL, 95% CI: -27.80-8.96, p = 0.32) was not statistically significant. However, a borderline significant but clinically non-relevant increase in total cholesterol was observed (WMD: 3.13 mg/dL, 95% CI: -0.01-6.27, p = 0.05). When the analysis was confined to the subgroups of studies with quercetin doses ≥500 mg/day and follow-up of ≥ 4 weeks, a significant increase in total cholesterol (WMD: 3.57 mg/dL, 95% CI: 0.21-6.92, p = 0.04) and a decline in triglycerides (WMD: -24.54 mg/dL, 95% CI: -33.09 to -15.99, p < 0.00001) was observed, but LDL-C and HDL-C concentrations remained unchanged (p > 0.05). Changes in plasma triglycerides, but not other indices of lipid profile, were significantly associated with quercetin dose (slope: -0.057; 95% CI: -0.103 to -0.010; p = 0.02) and duration of supplementation (slope: -5.314; 95% CI: -9.482 to -1.147; p = 0.01).

CONCLUSION

Available evidence from RCTs does not suggest any clinically relevant effect of quercetin supplementation on plasma lipids, apart from a significant reduction of triglycerides at doses above 50 mg/day.

Effect of Quercetin on Hepatitis C Virus Life Cycle: From Viral to Host Targets

Quercetin is a natural flavonoid, which has been shown to have anti hepatitis C virus (HCV) properties. However, the exact mechanisms whereby quercetin impacts the HCV life cycle are not fully understood. We assessed the effect of quercetin on different steps of the HCV life cycle in Huh-7.5 cells and primary human hepatocytes (PHH) infected with HCVcc. In both cell types, quercetin significantly decreased i) the viral genome replication; ii) the production of infectious HCV particles and iii) the specific infectivity of the newly produced viral particles (by 85% and 92%, Huh7.5 and PHH respectively). In addition, when applied directly on HCV particles, quercetin reduced their infectivity by 65%, suggesting that it affects the virion integrity. Interestingly, the HCV-induced up-regulation of diacylglycerol acyltransferase (DGAT) and the typical localization of the HCV core protein to the surface of lipid droplets, known to be mediated by DGAT, were both prevented by quercetin. In conclusion, quercetin appears to have direct and host-mediated antiviral effects against HCV.

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

PURPOSE

To determine whether postprandial metabolic and vascular responses induced by a high-fat and high-carbohydrate meal are attenuated by ingestion of the flavonol quercetin.

METHODS

Twenty-two overweight-to-obese hypertensive patients participated in a randomized, double-blind, controlled, crossover meal study. They consumed a test meal (challenge) rich in energy (4754 kJ), fat (61.6 g), saturated fatty acids (53 % of total fatty acids), and carbohydrates (113.3 g) with either placebo or 54 mg quercetin. Blood pressure, reactive hyperemia index (RHI), high-sensitive C-reactive protein (hs-CRP), soluble endothelial-derived adhesion molecules, parameters of lipid and glucose metabolism, and markers of antioxidant status were measured before the meal and at 2 and 4 h postprandially.

RESULTS

Systolic and diastolic blood pressure increased significantly over time, but were not affected by treatment (placebo or quercetin). During both treatments, serum endothelin-1, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and plasma asymmetric dimethylarginine slightly decreased over time, whereas RHI increased. Serum triglycerides, total cholesterol, and insulin significantly increased, whereas HDL cholesterol and glucose significantly decreased over time, again with no effect of treatment. Plasma α-tocopherol significantly increased, and plasma Trolox equivalent antioxidative capacity decreased over time. Serum hs-CRP, plasma retinol, and β-carotene did not significantly change during the trial.

CONCLUSION

In hypertensive patients, a high-energy meal did not lead to postprandial impairment of vascular endothelial function. Postprandial metabolic responses induced by the challenge, such as lipemia and insulinemia, were not attenuated by the concomitant ingestion of quercetin.

CLINICAL TRIAL

This trial was registered at www.germanctr.de/ and http://apps.who.int/trialsearch/ as DRKS00000555.

Synergistic effect of quercetin and 6-gingerol treatment in streptozotocin induced type 2 diabetic rats and poloxamer P-407 induced hyperlipidemia

Ginger and quercetin have been reported to have significant antidiabetic effects.

Quercetin reduces obesity-induced hepatosteatosis by enhancing mitochondrial oxidative metabolism via heme oxygenase-1

BACKGROUND

Obesity-induced hepatic lipid accumulation causes lipotoxicity, mitochondrial dysfunction, oxidative stress, and insulin resistance, and is implicated in non-alcoholic hepatic pathologies such as steatohepatitis and fibrosis. Heme oxygenase-1 (HO-1), an important antioxidant enzyme catalyzing the rate-limiting step in heme degradation, protects against oxidative stress, inflammation, and metabolic dysregulation. Here, we demonstrate that the phytochemical, quercetin, a natural polyphenol flavonoid, protects against hepatic steatosis in obese mice fed a high-fat diet, and that it does so by inducing HO-1 and stimulating increased hepatic mitochondrial oxidative metabolism.

METHODS

Male C57BL/6 mice were fed a regular diet (RD), a high-fat diet (HFD), and an HFD supplemented with quercetin for 9 weeks. Levels of mitochondrial biogenesis and oxidative metabolic transcripts/proteins were measured by real-time PCR and/or Western blotting. HO-1 transcripts/proteins were measured real-time PCR and/or Western blotting.

RESULTS

Quercetin upregulated genes involved in mitochondrial biogenesis and oxidative metabolism in lipid-laden hepatocytes and the livers of HFD-fed obese mice, and this was accompanied by increased levels of the transcription factor, nuclear erythroid 2-related factor 2 (Nrf-2), and HO-1 protein. The HO-1 inducer hemin and the HO-1 byproduct carbon monoxide (CO) also enhanced hepatic oxidative metabolism in HFD-fed obese mice. Moreover, the metabolic changes and the lipid-lowering effects of quercetin were completely blocked by the HO-1 inhibitor ZnPP and by deficiency of Nrf-2.

CONCLUSION

These findings suggest that quercetin stimulates hepatic mitochondrial oxidative metabolism by inducing HO-1 via the Nrf-2 pathway. Quercetin may be useful in protecting against obesity-induced hepatosteatosis.

Effects of a quercetin-rich onion skin extract on 24 h ambulatory blood pressure and endothelial function in overweight-to-obese patients with (pre-)hypertension: a randomised double-blinded placebo-controlled cross-over trial

The polyphenol quercetin may prevent CVD due to its antihypertensive and vasorelaxant properties. We investigated the effects of quercetin after regular intake on blood pressure (BP) in overweight-to-obese patients with pre-hypertension and stage I hypertension. In addition, the potential mechanisms responsible for the hypothesised effect of quercetin on BP were explored. Subjects (n 70) were randomised to receive 162 mg/d quercetin from onion skin extract powder or placebo in a double-blinded, placebo-controlled cross-over trial with 6-week treatment periods separated by a 6-week washout period. Before and after the intervention, ambulatory blood pressure (ABP) and office BP were measured; urine and blood samples were collected; and endothelial function was measured by EndoPAT technology. In the total group, quercetin did not significantly affect 24 h ABP parameters and office BP. In the subgroup of hypertensives, quercetin decreased 24 h systolic BP by -3·6 mmHg (P=0·022) when compared with placebo (mean treatment difference, -3·9 mmHg; P=0·049). In addition, quercetin significantly decreased day-time and night-time systolic BP in hypertensives, but without a significant effect in inter-group comparison. In the total group and also in the subgroup of hypertensives, vasoactive biomarkers including endothelin-1, soluble endothelial-derived adhesion molecules, asymmetric dimethylarginine, angiotensin-converting enzyme activity, endothelial function, parameters of oxidation, inflammation, lipid and glucose metabolism were not affected by quercetin. In conclusion, supplementation with 162 mg/d quercetin from onion skin extract lowers ABP in patients with hypertension, suggesting a cardioprotective effect of quercetin. The mechanisms responsible for the BP-lowering effect remain unclear.

Total saponins from Rosa laevigata Michx fruit attenuates hepatic steatosis induced by high-fat diet in rats

The protective effects of total saponins from Rosa laevigata Michx fruit (RLTS) in high-fat diet (HFD)-induced rats were investigated. The results showed that oral administration of RLTS attenuated hepatic steatosis, significantly reduced the levels of body weight, alanine transaminase, aspartate transaminase, total cholesterol, total triglyceride, free fatty acids, low density lipoprotein, blood glucose, insulin and malondialdehyde, and increased high density lipoprotein and glutathione levels compared with the model group. Further investigations showed that RLTS affected fatty acid synthesis, fatty acid β-oxidation, fatty acid ω-oxidation, total cholesterol and triglyceride metabolism and synthesis. Moreover, the extract obviously suppressed HFD-induced oxidative stress and inflammation. These results suggest that RLTS should be developed to be one functional food or health product against non-alcoholic fatty liver disease (NAFLD) in the future.

Lipid stability, antioxidant potential and fatty acid composition of broilers breast meat as influenced by quercetin in combination with α-tocopherol enriched diets

Background

Dietary supplementation of antioxidants is a vital route to affect the oxidative stability and fatty acid profile of broiler meat. The supplementation of feed with antioxidants decreases degradation of lipids in muscles thereby enhances meat stability.

Methods

The present study was carried out to investigate the influence of dietary quercetin in combination with α-tocopherol on growth performance, antioxidant potential, lipid stability and fatty acid composition in breast meat of birds. Accordingly, one day old 300 Hubbard strain male broiler birds were given three levels of quercetin @100, 200 and 300 mg/kg feed in combination with α-tocopherol @150, 225 and 300 mg/kg feed. The resultant meat was subjected to antioxidant assay, lipid stability, quantification of antioxidants followed by fatty acid profile of broiler breast meat.

Results

The results explicated that feed treatments imparted momentous effect on gain in weight, and feed conversion efficiency however, intake of feed in birds affected non-momentously. The highest weight gain recorded in T9 as 2374.67 & 2388 g/bird followed by T8 & T6 2350 & 2353.33 and 2293.33 & 2307 g/bird, respectively whilst the lowest in T0 as 1992.67 & 1999 g/bird during the experimental year 2013 and 2014. The results regarding antioxidant potential revealed that among treatments, T9 exhibited highest values for total phenolic contents (TPC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) & ferric reducing antioxidant power assay (FRAP) i.e. 158.70 ± 0.84 mg GAE/100 g, 82.40 ± 0.93 % and 682 ± 2.11 μmol/Fe^+2/g, respectively as compared to T0 104.27 ± 1.64 mg GAE/100 g, 54.71 ± 0.64 % and 542.67 ± 1.74 μmol/Fe⁺² /g of meat, correspondingly. The TBARS assay indicated that malondialdehydes production in meat increased during storage however, antioxidants deposition varied significantly among treatments. Fatty acid compositional analysis revealed that addition of quercetin with α-tocopherol in the bird’s diet decreased the fatty acid generation particularly saturated fatty acids.

Conclusion

Conclusively, dietary supplementation of quercetin along with α-tocopherol improves growth performance, antioxidant capacity, stability of lipids and fatty acid composition in breast meat of birds.

Herbal SGR Formula Prevents Acute Ethanol-Induced Liver Steatosis via Inhibition of Lipogenesis and Enhancement Fatty Acid Oxidation in Mice

Our previous study indicated that herbal SGR formula partially attenuates ethanol-induced fatty liver, but the underlying mechanisms remain unclear. In the present study, mice were pretreated with SGR (100 and 200 mg/kg/d bw) for 30 d before being exposed to ethanol (4.8 g/kg bw). The biochemical indices and histopathological changes were examined to evaluate the protective effects and to explore potential mechanisms by investigating the adiponectin, tumor necrosis factor-α (TNF-α), peroxisome proliferators-activated receptor-α (PPAR-α), sterol regulatory element binding protein-1c (SREBP-1c), adenosine monophosphate-activated protein kinase (AMPK), and so forth. Results showed that SGR pretreatment markedly inhibited acute ethanol-induced liver steatosis, significantly reduced serum and hepatic triglyceride (TG) level, and improved classic histopathological changes. SGR suppressed the protein expression of hepatic SREBP-1c and TNF-α and increased adiponectin, PPAR-α, and AMPK phosphorylation in the liver. Meanwhile, acute toxicity tests showed that no death or toxic side effects within 14 days were observed upon oral administration of the extracts at a dose of 16 g/kg body wt. These results demonstrate that SGR could protect against acute alcohol-induced liver steatosis without any toxic side effects. Therefore, our studies provide novel molecular insights into the hepatoprotective effect of SGR formula, which may be exploited as a therapeutic agent for ethanol-induced hepatosteatosis.