Thesis (Ph.D.)--Tufts University, 2004. / Adviser: Jeffrey Blumberg. Submitted to the School of Nutrition Science and Policy. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Zugl.: Kiel, Univ., Diss., 2009

Zugl.: Kiel, Univ., Diss., 2009

Chen Xiao. / "April 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web.

Quercetin is a flavonoid found in commonly consumed fruits and vegetables that has exhibited powerful antioxidant and anti-inflammatory properties in rodents and in vitro. In humans, the effect of quercetin on exercise induced oxidative stress and inflammation is still equivocal and need to be further investigated. A powerful antioxidant such as quercetin may inhibit the high levels of oxidative stress and inflammation associated with the high volume and intensity of exercise training seen with endurance-trained individuals. PURPOSE: To determine the effect of 28 days of daily quercetin supplementation on intensive endurance exercise induced cytokine response. vi METHODS: Thirteen trained cyclists (VO2peak 58.8 ± 3.9 ml/kg/min) were recruited for this study from the University of Texas at Austin and the local Austin, Texas community and participated in this placebo controlled, randomized, crossover designed study. After initial assessment of baseline data (VO2peak, lactate threshold, and two familiarization time trials), participants began daily supplementation with either an antioxidant supplement containing vitamins and quercetin (Q-VIT: 1000mg quercetin, 820mg Vitamin C, 40mg Vitamin B3) or the same vitamin supplement without quercetin (VIT: 820mg Vitamin C, 40mg Vitamin B3). A simulated time trial using an electromagnetically braked cycle ergometer in which subjects had to complete a set amount of work (kJ) as fast as possible was performed on the last day of supplementation. Blood collection was performed at three time points of the time trial days: before exercise (PRE), after warm up (MIN 20), and immediately after time trial exercise (POST). Measured plasma markers were Interleukin-6 (IL-6), C-Reactive Protein (CRP), and Interleukin-10 (IL-10). RESULTS: Q-VIT compared to VIT had no effect on pre, min 20 and post exercise plasma IL-6, CRP, and IL-10 ( P= 0.7, 0.08, and 0.32 respectively). However there was a trend that Q-VIT lowered plasma CRP compare to VIT ( P = 0.08). CONCLUSION: Chronic supplementation for 28 days with a quercetin based antioxidant supplement did not affect plasma cytokine before during or after exercise. The results of the current study suggest that chronic supplementation with quercetin does not influence plasma cytokine and exercise induced cytokine response in endurance-trained athletes. / text

Graduation date: 1962

Thesis (M.S.)--Oregon State University, 1966. / Typescript. Includes bibliographical references (leaves 50-53). Also available on the World Wide Web.

The incidence and mortality rate of melanoma have increased greatly worldwide in the last thirty years. There is currently no effective treatment for malignant melanoma. Signal transducer and activator of transcription 3 (STAT3) signaling is constantly activated in human melanoma, which promotes melanoma development and progression. c-Met is a receptor tyrosine kinase (RTK), and hepatocyte growth factor (HGF) is the only known ligand of c-Met. Abnormal activation of HGF/c-Met has been implicated in melanoma metastasis. Both the STAT3 and HGF/c-Met signaling pathways are proposed as melanoma therapeutic targets. The dietary flavonoid quercetin is a bioactive compound that possesses low toxicity and exerts anti-melanoma activities. However, the anti-melanoma mechanisms of quercetin have not been fully understood. In this study, we evaluated the anti-melanoma activities of quercetin and explored the underlying molecular mechanisms. Our results showed that quercetin treatments induced apoptosis, inhibited proliferation, migration and invasion of the melanoma cells. Mechanistic study indicated that quercetin inhibited the activation of STAT3 signaling by interfering with the phosphorylation of STAT3, thus reduced its nuclear localization. Quercetin inhibited STAT3 transcriptional activity, and down-regulated the STAT3 targeted genes such as Mcl-1, MMP-2, MMP-9 and VEGF, which are involved in cell survival, migration and invasion. More importantly, overexpression of constitutively active STAT3 partially reversed the anti-proliferative effect of quercetin, which might be correlated with the impaired effect on quercetin-mediated Mcl-1 and MMP-2 inhibition. Furthermore, quercetin suppressed A375 tumor growth and STAT3 activities in a xenografted mouse model, and inhibited murine B16F10 cells lung metastasis in mice. These findings suggest that inhibition of the STAT3 signaling pathway contributes to the anti-melanoma activities of quercetin. Next we studied the involvement of HGF/c-Met pathway in the anti-metastasis effect of quercetin. Quercetin treatment dose-dependently suppressed HGF-induced migration and invasion of melanoma cells. Further study showed that quercetin down-regulated the mRNA expression level of HGF and suppressed c-Met homo-dimerization. Quercetin also decreased c-Met protein expression, which was associated with reduced expression of fatty acid synthase. In addition, quercetin suppressed the phosphorylation of c-Met and its downstream molecules including Gab1, FAK, PAK and STAT3. Furthermore, overexpression of FAK or PAK significantly reduced the inhibitory effect of quercetin on the migration of melanoma cells. These findings suggest that suppression of HGF/c-Met signaling contributes to the anti-metastatic action of quercetin. Besides c-Met, many other RTKs are activated in melanoma. We then further determined whether quercetin could affect the activity of other RTKs. The phospho-RTK array assay showed that quercetin treatment inhibited the activation of ROR2, Tie2, RYK, ALK, c-Ret, DDR1, DDR2, EphB4, EphA1, EphA2, EphA4 and EphA5 in A2058 cells, and EphA7, RYK, ALK and DDR1 in A375 cells. Further investigations are warranted to verify the array results, and to determine the potential roles of these RTKs in quercetin-mediated anti-melanoma properties. Overall, our results demonstrate that quercetin exerts anti-melanoma activities. The anti-melanoma action of quercetin is, at least in part, due to the inhibition of the STAT3 and HGF/c-Met signaling pathways. Our findings provide further insights into the anti-melanoma activities of quercetin and the underlying molecular mechanisms, suggesting a potential role of quercetin in the prevention and treatment of melanoma.

Eksperimentinėje dalyje buvo tiriamas kvercetino ir jo glikozidų (rutino, izokvercitrino, hiperozido) poveikis žiurkės inkstų mitochondrijų oksidacinio fosforilinimo sistemai. Tyrimams naudojome Wistar veislės žiurkes. Tyrimų pobūdis – in vitro. Kvercetinas ir jo glikozidai, t.y. rutinas, hiperozidas ir izokvercitrinas (3 - 48 nM), stimuliuoja žiurkės inkstų mitochondrijų kvėpavimo greitį antroje metabolinėje būsenoje (t.y. atskiria oksidacijos ir fosforilinimo procesus). Mitochondrijų kvėpavimo greitį trečioje metabolinėje būsenoje stimuliavo kvercetinas ir rutinas, kiti flavonoidai statistiškai reikšmingo poveikio neturėjo. / In this research work we investigated the effect of quercetin and its glycosides (rutin, hyperoside, isoquercitrin) on rat kidney mitochondrial oxidative phosphorylation system. In these studies we used Wistar rats. Eksperimental model – in vitro. Quercetin and its glycosides, i.e. rutin, hyperoside and isoquercitrin (3 - 48 nM) stimulated rat kidney mitochondrial respiration rate in the second metabolic state (uncoupled the mitochondrial respiration). Quercetin and rutin stimulates mitochondrial State 3 respiration rate, other tested compounds had no effect.

Introduction: Lactase, in addition to its role in the digestion of lactose available in milk and dairy products, is implicated in the metabolism of a range of phenolic phytochemicals in the gut. Experiments with Caco-2 cells have shown that these cells which mimic the intestinal mucosa indicate that quercetin glucosides and quercetin aglycone (widely consumed in onions and apples) block glucose uptake from the gut by competing with glucose for the sodium-dependent SGLT-1 and sodium-independent GLUT-2 transporters respectively (Johnston et al., 2005a, Schulze et al., 2015). It has been suggested that dietary phenolics that block glucose uptake from the gut may reduce the risk of type 2 diabetes. However, the ability of quercetin glucosides to block SGLT-1 is lost or reduced when the glucoside moiety is cleaved off during lactase hydrolysis. It is currently unknown if lactose-tolerant individuals deglycosylate quercetin to a greater extent than lactose-intolerant individuals and therefore are less able to reduce glucose uptake from the intestine. The aim of in vitro study was to model human gut condition for glucose transport by using Caco-2 cell models and to model role of human intestinal LPH by incubation of Caco-2 cells with quercetin flavonoids and purified β-galactosidases and in vivo was to investigate whether lactose-tolerant and lactose-intolerant subjects show differences in the uptake of glucose. Methods: Caco-2 cells were cultured in DMEM full medium in 24 well plates. Thereafter, glucose uptake assay was conducted by using 3H-glucose in the presence and absence of sodium, to assess the effect of flavonoids such as phloridzin, quercetin 4'-glucoside, quercetin 3,4'-diglucoside, quercetin 3'-glucoside, and quercetin aglycone on glucose uptake. Transwell inserts were also used to demonstrate the bidirectional permeability through Caco-2 monolayers, transport of glucose from apical (SGLT-1) to basolateral side (GLUT-2). β-galactosidase enzyme assay was conducted by using β-galactosidase from Aspergillus oryzae, Caco-2 cells were treated with 100 μM quercetin glucosides, 25% w/v onion extract and β-galactosidase in order to model the hydrolysis of flavonoids by lactase in the small intestine. HPLC was carried out to determine if quercetin glucosides are found in onion extract and test whether β-galactosidase is active and result in deglycosylation of substrates such as individual quercetin glucosides and quercetin glucosides in onion extract. For the clinical study, lactose intolerance was identified by the hydrogen breath test (Gastrolyzer), and blood glucose levels were measured by taking finger-prick blood samples in several intervals (0, 15, 30, 60, 90, 120) minutes using an EKF glucose analyser. Results: Findings from the current in vitro research confirm that phloridzin is an inhibitor of sodium-dependent conditions (SGLT-1) transporter with 80% reduction, this therefore was used as a positive control. Quercetin 4'-glucoside and quercetin 3,4'-diglucoside at (100πM) significantly decreased the uptake of glucose in the presence of sodium with up to 75% reduction compared to control p < 0.01. However, no significant glucose inhibition was found from these quercetin glucosides in the absence of sodium condition (p > 0.5), whilst quercetin aglycone significantly inhibited the glucose uptake with 50% reduction compared to control at significance levels of (p = 0.02). HPLC data identified quercetin 3,4'-diglucoside and quercetin 4'-glucoside with RT = 4.082 min and 11.392 min in the onion extract by showing peaks at similar ranges with RT= 4.114 min and 11.385 min with their standards, and the concentration of quercetin 4'-glucoside was measured as the highest level (42μg/ml) in onion extract compared to 3,4'-glucoside and quercetin 3-glucoside. Further HPLC illustrated that, after incubation of quercetin glucosides and onion extract with β-galactosidase Aspergillus oryzae for 20, 40 and 60 minutes, the peaks occurred at similar RT =16.453 min and 16.441 min respectively in accordance with standard quercetin (RT=16.239 min), suggesting the deglycosylation of these compounds with β-galactosidase from Aspergillus oryzae. According to findings from the clinical study, reduction of peak glucose levels by an onion meal was higher in lactose-intolerant people than lactose-tolerant people (44.2% versus 19.3%, p = 0.042). Also, the area under the blood glucose curve was reduced more in lactose-intolerant people compared to lactose-tolerant people, however was not statistically significant (54.5% versus 42.1%, p = 0.425). Discussion: Our result suggests that quercetin 4'-glucoside and quercetin 3,4'-diglucosides and onion extract were the main inhibitors of glucose uptake in sodium-dependent conditions (SGLT-1). Whereas, quercetin aglycone inhibited GLUT-2 glucose transport on Caco-2 cell monolayers under sodium independent conditions. Our findings were in accordance to several previous studies (Boyer et al., 2005, Kwon et al., 2007, Schulze et al., 2015). Notably, in vitro studies were conducted to model whether the in vivo study is likely to succeed or not. Findings from our human study showed that glucose uptake was blocked by the onion solution and a diet containing quercetin glucosides (onion meal) may be of greater benefit for glycaemic control in lactose-intolerant people than in lactose-tolerant people.