Linking metabolites in eight bioactive forage species to their in vitro methane reduction potential across several cultivars and harvests.

An in vitro Hohenheim gas test was conducted to analyze the fermentation end-products from 17 cultivars of eight polyphenol containing forage species. The polyphenol composition and proanthocyanidin (PA) structural features of all the cultivars were analyzed with UPLC-MS/MS in leaves of vegetative or generative plants. The samples were incubated with and without polyethylene glycol (PEG, a tannin-binding agent) to separate the tannin-effect on methane (CH4, ml/200 mg DM) production from that of forage quality. Sulla and big trefoil, two particularly PA rich species, were found to have the highest CH4 reduction potential of up to 47% when compared to the samples without PEG. However, concomitant reduction in gas production (GP, ml/200 mg DM) of up to 44% was also observed. An increase in both GP and CH4 production under PEG treatments, confirms the role of tannins in CH4 reduction. Moreover, PA structural features and concentration were found to be an important source of variation for CH4 production from PA containing species. Despite having low polyphenol concentrations, chicory and plantain were found to reduce CH4 production without reducing GP. Additionally, interspecies variability was found to be higher than intraspecies variability, and these results were consistent across growth stages, indicating the findings' representativeness.

Diets for Dairy Cows with Different Proportions of Crude Protein Originating from Red Clover Silage versus Soybean Meal: Ruminal Degradation and Intestinal Digestibility of Amino Acids.

The purpose was to assess the effect of exchanging crude protein (CP) of soybean meal (SBM) with red clover silage (RCS) in total mixed rations (TMR) on ruminal degradation and intestinal digestibility (ID) of essential amino acids (EAA). Four TMR and their individual feed components were studied. The TMR were composed of forage and concentrates (75:25), with proportions of RCS in TMR of 0.15, 0.30, 0.45, and 0.60 on a dry matter basis, resulting in diet groups RCS15, RCS30, RCS45, and RCS60, respectively. The ruminal degradation of EAA was determined using the nylon bag technique. For this, samples of TMR and their individual feed components were ruminally incubated for 16 h. The feed residues of TMR obtained after 16 h of incubation were used for the determination of ID of EAA using the mobile-bag technique. Increasing RCS and reducing SBM proportions linearly increased (p < 0.01) the in situ ruminal degradation of individual EAA from 75.5% to 83.5%. The degradation of EAA followed the trend of CP degradation among TMR, except for Cys that was lower (p < 0.05) than that of CP in RCS60 (79.7% vs. 86.3%). The degradation of EAA in individual feed ingredients not always corresponded to the degradation of CP and was feed dependent. Increasing the proportions of RCS in the TMR linearly reduced (p < 0.001) the ID of EAA (except for Ile) from 78.2% to 67.3%. However, the ID of EAA did not always reflect the ID of CP, and in general, the differences between the ID of CP and EAA increased as RCS increased in the TMR. The ID values of most of the EAA were similar (p > 0.05) to ID of CP in RCS15 and RCS30, while they mostly differed (p < 0.05) in RCS45 and RCS60, and being higher for EAA than CP (except for Cys that was lower than CP, p < 0.05). Similar trends were observed for intestinal absorbable AA, resulting in higher values (p < 0.05) of intestinal absorbable for all EAA than of CP in diet RCS60. In conclusion, increasing levels of RCS in TMR reduced the extent of EAA flow into the small intestine, the ID of EAA, and consequently the intestinal absorbable EAA. Therefore, accurate determination of metabolizable AA must be considered for optimal diet formulation when including high proportions of RCS in diets of high-producing dairy cows.

Assessing the Potential of Diverse Forage Mixtures to Reduce Enteric Methane Emissions In Vitro.

Methane emissions from ruminants are a major contributor to agricultural greenhouse gas emissions. Thus, eight different forage species were combined in binary mixtures with Lolium perenne in increasing proportions, in vitro, to determine their methane reduction potential in ruminants. Species were sampled in two consecutive years where possible. The aims were: a) to determine if mixtures with specific forages, particularly those rich in plant specialized metabolites (PSM), can reduce methane emissions compared to ryegrass monocultures, b) to identify whether there is a linear-dose effect relationship in methane emissions from the legume or herb addition, and c) whether these effects are maintained across sampling years. Results showed that all dicot species studied, including the non-tannin-containing species, reduced methane production. The tannin-rich species, Sanguisorba minor and Lotus pedunculatus, showed the greatest methane reduction potential of up to 33%. Due to concomitant reductions in the forage digestibility, Cichorium intybus yielded the lowest methane emissions per digestible forage unit. Contrary to total gas production, methane production was less predictable, with a tendency for the lowest methane production being obtained with a 67.5% share of the legume or herb partner species. Thus, linear increments in the partner species share did not result in linear changes in methane concentration. The methane reduction potential differed across sampling years, but the species ranking in methane concentration was stable.

Influence of quercetin on the global DNA methylation pattern in pigs.

The plant flavonol quercetin causes multiple health-promoting effects in human and animals. In this study, we investigated the possible effects of quercetin on global DNA methylation in growing pigs after 7 weeks of feeding a quercetin-enriched diet. The results indicated that a trend for an improved feed conversion was observed in the quercetin fed group compared to the control group. Furthermore, quercetin influenced global DNA methylation by upregulating DNA methyltransferase 1 (DNMT1) in both mRNA and protein expressions in a tissue specific manner. The observed bioactivity of quercetin against the global methylation marker in pigs indicates that quercetin could be a potential inducer of DNA methylation which might be of economic significance for effective nutritional interventions affecting the health and productivity of animals.

Effect of alpha-linolenic acid in combination with the flavonol quercetin on markers of cardiovascular disease risk in healthy, non-obese adults: A randomized, double-blinded placebo-controlled crossover trial.

OBJECTIVES: Alpha-linolenic acid (ALA) and quercetin are characteristic compounds in plant-based diets. Cardioprotective effects have been described for both substances, although a possible benefit of combining ALA and quercetin has not, to our knowledge, been evaluated yet. The aim of this study was to investigate the potential independent and additive effects of ALA and quercetin on blood pressure (BP) and lipid and glucose metabolism, as well as on biomarkers of inflammation, oxidative stress, and antioxidant status in healthy, non-obese men and women. Another aim was to examine whether chronic supplementation of supranutritional doses of quercetin would result in an accumulation of plasma quercetin concentration over time. METHODS: In a double-blinded, placebo-controlled crossover trial, healthy volunteers were randomized to receive 3.6 g/d ALA plus 190 mg/d quercetin or placebo for 8 wk. Data from 67 individuals (34 men, 33 women, mean age: 24.6 y) were assessed. RESULTS: Plasma quercetin, tamarixetin, isorhamnetin, and kaempferol increased significantly from baseline to study end with ALA + quercetin but not with ALA + placebo. No significant effect on office systolic BP, mean 24 h ambulatory BP (ABP), or mean daytime ABP was seen in either study group. Both interventions significantly decreased total cholesterol, low-density lipoprotein cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B to a similar extent. No effect on high-density lipoprotein cholesterol, apolipoprotein A1, glucose, uric acid, oxidized low-density lipoprotein, C-reactive protein, or lipid-adjusted retinol, α-tocopherol, or ß-carotene was seen in either group. CONCLUSION: Although dietary supplements of 3.6 g/d ALA over an 8-wk period improved lipid profiles in healthy adults, antioxidative and oxidative status, inflammation, and BP remained unchanged. No evidence was seen for an additive or synergistic effect of ALA plus quercetin on markers of cardiovascular disease risk.

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.

Postruminal digestion of starch infused into the abomasum of heifers with or without exogenous amylase administration.

The effect of an exogenous amylase on postruminal digestion of starch infused into the abomasum of cattle was studied. Four rumen-cannulated heifers were fed 5.5 kg DM/d of a diet without starch, and assigned randomly to a crossover design. The experiment consisted of 2 periods lasting 23 d each with 10 d for adaptation to the diet followed by 13 d of abomasal infusion and sample collection. During the first 3 d of each infusion phase, isotonic saline solution was infused (1 liter/h) for measurement of baseline values in feces, followed by daily infusions of 880 g DM corn starch (1 kg/10 liters of water) without or with the addition of 2% of amylase. Titanium dioxide (10 g/d) was ruminally administered for estimation of fecal excretion. Digestion of starch in small intestine was calculated as the difference between the amounts of infused starch, disappeared from hindgut and fecal excretion. The apparent disappearance of starch from the hindgut was estimated based on the increment of microbial nitrogen (N) excretion due to starch infusion (1 g microbial N/100 g fermented starch) compared to baseline values. The concentration of purine bases in feces was used to estimate excretion of microbial N. Microbial N excretion increased with starch infusion (P < 0.05) but was not influenced by amylase (P = 0.81). Starch disappearance from the small intestine was not improved by amylase (P = 0.78) and averaged 85%. Amylase affected neither blood concentration of glucose (P = 0.80) nor of insulin (P = 0.26), but glucagon was lower without (P < 0.0001) than with amylase. The infusion of starch increased fecal excretion of total VFA (acetate, propionate, and butyrate) by 53% (P < 0.05), which indicates increased carbohydrate fermentation in the hindgut and incomplete digestion of starch in the small intestine. However, the excretion of total VFA was not affected by amylase (P = 0.66). Lactate excretion was higher at the second day of starch infusion (P < 0.05) without than with amylase, which suggests lower flow of starch from the small intestine to the hindgut due to a possible effect of amylase addition in animals not adapted to starch digestion. However, lactate excretion returned near to baseline values within 2 d, which was probably due to increase of lactate-utilizing bacteria and the adaptation of the microbial population in the hindgut. Further studies with higher starch levels and addition of amylase are recommended.

Impact of chocolate liquor on vascular lesions in apoE-knockout mice.

Cocoa polyphenols are thought to reduce the risk of cardiovascular diseases. Thus, cocoa-containing foods may have significant health benefits. Here, we studied the impact of chocolate liquor on vascular lesion development and plaque composition in a mouse model of atherosclerosis. Apolipoprotein E (apoE)-knockout mice were assigned to two groups and fed a Western diet that contained 250 g/kg of either chocolate liquor or a polyphenol-free isoenergetic control paste for 16 weeks. In addition to fat, protein, and fibers, the chocolate liquor contained 2 g/kg of polyphenols. Compared with the control group, mice fed the chocolate liquor had larger plaque areas in the descending aorta and aortic root, which were attributed to a higher mass of vascular smooth muscle cells (VSMCs) and collagen. Vascular lipid deposits and calcification areas did not differ between the two groups. The aortic tissue level of interleukin-6 (IL-6) mRNA was 5-fold higher in the mice fed chocolate liquor than in the control mice. Chocolate-fed mice exhibited an increased hepatic saturated to polyunsaturated fatty acid ratio than the controls. Although the chocolate liquor contained 14 µg/kg of vitamin D2, the chocolate liquor-fed mice did not have measurable 25-hydroxyvitamin D2 in the serum. These mice even showed a 25% reduction in the level of 25-hydroxyvitamin D3 compared with the control mice. Overall, present data may contribute to our understanding how chocolate constituents can impact vascular lesion development.

Effects of the flavonol quercetin and α-linolenic acid on n-3 PUFA status in metabolically healthy men and women: a randomised, double-blinded, placebo-controlled, crossover trial.

Increased dietary intake and tissue status of the long-chain n-3 PUFA, EPA and DHA, is associated with cardiovascular benefits. Epidemiological and animal studies suggest that concomitant nutritive intake of flavonoids may increase the conversion of α-linolenic acid (ALA) to longer-chain n-3 fatty acids EPA and DHA. We investigated the effects of increased ALA intake on fatty acid composition of serum phospholipids and erythrocytes in metabolically healthy men and women and whether fatty acid profiles and ALA conversion were affected by regular quercetin intake or sex. Subjects (n 74) were randomised to receive at least 3·3 g/d ALA with either 190 mg/d quercetin (ALA+quercetin) or placebo (ALA+placebo) in a double-blinded, placebo-controlled, crossover trial with 8-week intervention periods separated by an 8-week washout period. A total of seven subjects dropped out for personal reasons. Data from the remaining sixty-seven subjects (thirty-four males and thirty-three females) were included in the analysis. Both interventions significantly increased serum phospholipid ALA (ALA+placebo: +69·3 %; ALA+quercetin: +55·8 %) and EPA (ALA+placebo: +37·3 %; ALA+quercetin: +25·5 %). ALA + quercetin slightly decreased DHA concentration by 9·3 %. Erythrocyte ALA and EPA significantly increased with both interventions, whereas DHA decreased. Fatty acid composition did not differ between sexes. We found no effect of quercetin. Intake of 3·6 g/d ALA over an 8-week period resulted in increased ALA and EPA, but not DHA, in serum phospholipids and erythrocytes. Neither quercetin supplementation nor sex affected the increment of ALA and relative proportions of n-3 PUFA in serum phospholipids and erythrocytes.

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 ß-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.

Higher plasma quercetin levels following oral administration of an onion skin extract compared with pure quercetin dihydrate in humans.

PURPOSE: To investigate the plasma kinetics of quercetin derived from hard capsules filled with onion skin extract powder or quercetin dihydrate in humans. METHODS: In a randomized, single-blind, diet-controlled crossover study, 12 healthy subjects (six men and six women) aged 21-33 years were administered a single oral supra-nutritional dose of approximately 163 mg quercetin derived from onion skin extract powder (containing 95.3 % of total flavonoids as quercetin aglycone) or quercetin dihydrate (134 mg quercetin aglycone equivalent). Blood samples were collected before and during a 24-h period after quercetin administration. The concentrations of quercetin and its two monomethylated derivatives, isorhamnetin (3'-O-methyl quercetin), and tamarixetin (4'-O-methyl quercetin), were measured using HPLC with fluorescence detection after plasma enzymatic treatment. RESULTS: The systemic availability, determined by comparing the plasma concentration-time curves of quercetin, was 4.8 times higher, and the maximum plasma concentration (C max) was 5.4 times higher after ingestion of the onion skin extract than after ingestion of pure quercetin dihydrate. By contrast, t max did not differ significantly between the two formulations. The C max values for isorhamnetin and tamarixetin were 3.8 and 4.4 times higher, respectively, after administration of onion skin extract than after pure quercetin dihydrate. The plasma kinetics of quercetin were not significantly different in men and women. CONCLUSION: Quercetin aglycone derived from onion skin extract powder is significantly more bioavailable than that from quercetin dihydrate powder filled hard capsules.

No effects of quercetin from onion skin extract on serum leptin and adiponectin concentrations in overweight-to-obese patients with (pre-)hypertension: a randomized double-blinded, placebo-controlled crossover trial.

PURPOSE: Chronic low-level systemic and adipose tissue inflammation has been identified as a major etiologic factor in many chronic diseases, including hypertension and cardiovascular diseases. Evidence from experimental studies suggests anti-inflammatory effects of dietary flavonols such as quercetin. METHODS: We investigated the effects of regular intake of quercetin on leptin, adiponectin, biomarkers of inflammation, glucose and insulin in overweight-to-obese patients with pre- and stage 1 hypertension. Another objective was to assess the safety of daily quercetin supplementation measured by parameters of liver and kidney function and of hematology. Subjects (n = 70) were randomized to receive a supra-nutritional dose of 162 mg/d quercetin or placebo in a double-blinded, placebo-controlled crossover trial with 6-week treatment periods separated by a 6-week washout period. Two subjects dropped out for personal reasons. Only data from the remaining 68 subjects were included in the analysis. RESULTS: Compared to placebo, quercetin did not significantly affect serum concentrations of leptin and adiponectin, HOMA-AD or the ratios of leptin/adiponectin and adiponectin/leptin. Neither quercetin nor placebo significantly changed serum C-reactive protein and plasma tumor necrosis factor alpha. Compared to placebo, quercetin did not significantly affect glucose, insulin, HOMA-IR, blood biomarkers of liver and renal function, hematology and serum electrolytes. CONCLUSION: A supra-nutritional dose of 162 mg/d quercetin from onion skin extract for 6 weeks is safe but without significant effects on parameters of systemic and adipose tissue inflammation as well as glucose and insulin in overweight-to-obese subjects with (pre-)hypertension. This trial was registered at www.germanctr.de/ and http://apps.who.int/trialsearch/ as DRKS00000555.

Systemic Absorption of Catechins after Intraruminal or Intraduodenal Application of a Green Tea Extract in Cows.

Green tea catechins have various potential health benefits in humans including anti-inflammatory, anti-oxidative and hepato-protective effects. If present in the circulation, they might have similar effects in ruminants, which are exposed to oxidative stress and fatty liver disease such as dairy cows during the periparturient phase. However, the bioavailability of a substance is a prerequisite for any post absorptive effect in vivo. This study aimed to investigate the appearance of catechins from a green tea extract (GTE) in cattle plasma after intraruminal and intraduodenal administration because absorption is of major importance regarding the bioavailability of catechins. The studies were performed in 5 rumen-fistulated non-lactating heifers and 6 duodenally fistulated lactating dairy cows, respectively, equipped with indwelling catheters placed in a jugular vein. The GTE was applied intraruminally (10 and 50 mg/kg BW, heifers) or duodenally (10, 20 and 30 mg/kg BW, dairy cows) in a cross-over design with a 2 d washout period between different dosages. Blood samples were drawn following the GTE administration at various pre-defined time intervals. The concentration of the major GTE catechins (gallocatechin, epigallocatechin, catechin, epicatechin, epigallocatechin-gallate, epicatechin-gallate) in plasma samples were analysed by HPLC with electrochemical detection. Irrespective of the dose, almost none of the catechins originally contained in the GTE were detected in plasma samples after intraruminal application. In contrast, intraduodenal administration of GTE resulted in increased plasma concentrations of epicatechin, epigallocatechin, epigallocatechin gallate in a dose-dependent manner. Thus, we can conclude that intraruminally or orally administered catechins are intensively metabolized by ruminal microorganisms.

Quercetin Feeding in Newborn Dairy Calves Cannot Compensate Colostrum Deprivation: Study on Metabolic, Antioxidative and Inflammatory Traits.

Immaturity of the neonatal immune system is causative for high morbidity in calves and colostrum intake is crucial for acquiring passive immunity. Pathogenesis is promoted by reactive oxygen species accumulating at birth if counter-regulation is inadequate. The flavonol quercetin exerts antioxidative and anti-inflammatory effects that may enhance neonatal health. The aim of this work was to study effects of quercetin feeding on metabolic, antioxidative and inflammatory parameters in neonatal calves to investigate whether quercetin could compensate for insufficient colostrum supply. Twenty-eight newborn calves were assigned to two dietary groups fed colostrum or milk-based formula on day 1 and 2 and milk replacer thereafter. From day 2 onwards, 7 calves per diet group were additionally fed quercetin aglycone (50 mg/(kg body weight × day)). Blood samples were taken repeatedly to measure plasma concentrations of flavonols, glucose, lactate, total protein, albumin, urea, non-esterified fatty acids, triglycerides, cholesterol, insulin, glucagon, cortisol, immunoglobulins, fibrinogen, haptoglobin and serum amyloid A. Trolox equivalent antioxidative capacity, ferric reducing ability of plasma, thiobarbituric acid reactive species and F2-isoprostanes were analyzed to evaluate plasma antioxidative status. Expression of tumor necrosis factor, interleukin-1α, interleukin-1ß, serum amyloid A, haptoglobin, fibrinogen, C-reactive protein, catalase, glutathione peroxidase and superoxide dismutase mRNA were measured in liver tissue on day 8. Plasma flavonol concentrations were detectable only after quercetin-feeding without differences between colostrum and formula feeding. Plasma glucose, lactate, total protein, immunoglobulins, triglycerides, cholesterol, trolox equivalent antioxidative capacity and thiobarbituric acid reactive species were higher after colostrum feeding. Body temperature, fecal fluidity and plasma concentrations of cortisol and haptoglobin were higher in formula- than in colostrum-fed groups. Hepatic mRNA expression of tumor necrosis factor was higher after quercetin feeding and expression of C-reactive protein was higher after formula feeding. Data confirm that colostrum improves neonatal health and indicate that quercetin feeding cannot compensate for insufficient colostrum supply.

Effects of rutin and buckwheat seeds on energy metabolism and methane production in dairy cows.

Flavonoids are secondary plant metabolites with several health promoting effects. As dairy cows often suffer from metabolic imbalance and health problems, interest is growing in health improvements by plant substances such as flavonoids. Our group has recently shown that the flavonoids quercetin and rutin (a glucorhamnoside of quercetin) are bioavailable in cows when given via a duodenal fistula or orally, respectively, affect glucose metabolism, and have beneficial effects on liver health. Furthermore, flavonoids may reduce rumen methane production in vitro through their antibacterial properties. To test the hypothesis that rutin has effects on energy metabolism, methane production, and production performance in dairy cows, we fed rutin trihydrate at a dose of 100mg/kg of body weight to a group of 7 lactating dairy cows for 2 wk in a crossover design. In a second experiment, 2 cows were fed the same ration but were supplemented with buckwheat seeds (Fagopyrum tartaricum), providing rutin at a dose comparable to the first experiment. Two other cows receiving barley supplements were used as controls in a change-over mode. Blood samples were taken weekly and respiration measurements were performed at the end of each treatment. Supplementation of pure rutin, but not of rutin contained in buckwheat seeds, increased the plasma quercetin content. Methane production and milk yield and composition were not affected by rutin treatment in either form. Plasma glucose, ß-hydroxybutyrate, and albumin were increased by pure rutin treatment, indicating a possible metabolic effect of rutin on energy metabolism of dairy cows. In addition, we did not show that in vivo ruminal methane production was reduced by rutin. In conclusion, we could not confirm earlier reports on in vitro methane reduction by rutin supplementation in dairy cows in established lactation.

Bioavailability of quercetin in humans and the influence of food matrix comparing quercetin capsules and different apple sources.

The objective of the four-way cross-over pilot study was the investigation of quercetin bioavailability after ingestion of apple quercetin incorporated in different matrices and quercetin dihydrate capsule. Six healthy volunteers were given a standard diet supplemented with 71µmol quercetin equivalents from vacuum impregnated apple chips, apple peel extract capsules and apple peel. Quercetin dihydrate capsules were used as control. The vacuum impregnated apple chips were enriched with a quercetin rich apple peel extract. The ingestion of vacuum impregnated apple chips, apple peel extract capsules and apple peel resulted in similar plasma quercetin and plasma total flavonol concentrations compared to the quercetin dihydrate capsule. With regard to the bioavailabilities of all quercetin treatments, a reduced release from vacuum impregnated apple chips can be excluded. The apple peel matrix which is rich in indigestible dietary fibers impacted the profile of the plasma flavonol time curve similar to poor soluble quercetin dihydrate. Finally, the quercetin bioavailability of vacuum impregnated apple chips (AUC0-1440min: 104±24µmol·min∙L-1) as functional food was similar to the supplementation with apple peel extract capsules (AUC0-1440min: 87±27µmol∙min∙L-1).

Quercetin induces hepatic γ-glutamyl hydrolase expression in rats by suppressing hepatic microRNA rno-miR-125b-3p.

Exogenous factors such as food components including the flavonoid quercetin are suspected to influence micro RNA (miRNA) concentrations and thus possibly target enzymes involved in xenobiotic metabolism. This study therefore investigates the influence of orally administered quercetin on hepatic miRNA and the identification of enzyme target mRNAs relevant in drug metabolism. Male Wistar rats (n=16) were fed either a diet without (C) or with (Q) the addition of 100-ppm quercetin for 7 weeks and subsequently euthanized at the end of the dark phase. To avoid strong effects of food deprivation on hepatic metabolism, food was not removed until 5 h prior to the procedure. Liver was immediately dissected and snap-frozen in liquid nitrogen. Concentrations of 352 hepatic miRNA were measured in pool samples of each dietary group (n=8) using the RT(2) miRNA PCR Array System. Differential expression of miRNAs was assumed with fold changes ≥3. Target genes of differentially expressed miRNAs were identified using the database TargetScan. Because rno-miR-125b-3p showed the most prominent fold-change (-9) we further analyzed the expression of its top predicted target gene gamma-glutamyl hydrolase (GGH) by quantitative real-time PCR using hypoxanthine phosphoribosyltransferase 1 (hprt1) as endogenous control. Compared to controls, 23 miRNAs were differentially expressed in rats fed quercetin. A ninefold reduction in hepatic miRNA rno-miR-125b-3p was paralleled by significant induction of GGH mRNA in liver of quercetin fed rats. Because increased GGH expressions were repeatedly associated with resistance to methotrexate, concomitant intake with quercetin should be monitored carefully.

The Effects of Oral Quercetin Supplementation on Splanchnic Glucose Metabolism in 1-Week-Old Calves Depend on Diet after Birth.

BACKGROUND: Inadequate colostrum supply results in insufficient intake of macronutrients and bioactive factors, thereby impairing gastrointestinal development and the maturation of glucose metabolism in neonatal calves. The flavonoid quercetin has been shown to have health-promoting properties, including effects in diabetic animals. However, quercetin interacts with intestinal glucose absorption and might therefore exert negative effects in neonates. OBJECTIVE: We evaluated the interaction between neonatal diet and quercetin feeding on splanchnic glucose metabolism in neonatal calves. METHODS: Calves (n = 28) were assigned to 4 groups and fed either colostrum or a milk-based formula on days 1 and 2 and supplemented daily with 148 µmol quercetin aglycone/kg body weight [colostrum with quercetin (CQ+)/formula with quercetin (FQ+)] or without this substance [colostrum without quercetin (CQ-)/formula with quercetin (FQ-)] from days 2-8. From day 3 onward, all calves received milk replacer. A xylose absorption test was performed on day 3, and on day 7, blood samples were collected to study glucose first-pass uptake after [(13)C6]-glucose feeding and intravenous [6,6-(2)H2]-glucose bolus injection. Plasma concentrations of metabolites and hormones were measured by taking additional blood samples. A biopsy specimen of the liver was harvested on day 8 to measure the mRNA expression of gluconeogenic enzymes. RESULTS: Higher postprandial plasma concentrations of glucose, lactate, urea, adrenaline, noradrenaline, insulin, and glucagon on day 7 in colostrum-fed calves indicate that metabolic processes were stimulated. Postabsorptive xylose and glucose plasma concentrations each increased by an additional 26%, and splanchnic glucose turnover decreased by 35% in colostrum-fed calves, suggesting improved glucose absorption and lower splanchnic glucose utilization in colostrum-fed calves. Quercetin supplementation resulted in higher noradrenaline concentrations and enhanced peak absorption and oxidation of [(13)C6]-glucose by 10%. Liver mitochondrial phosphoenolpyruvate carboxykinase mRNA abundance was reduced by 34% in colostrum-deprived calves. CONCLUSIONS: Feeding colostrum during the first 2 d of life is crucial for maturation of splanchnic glucose metabolism in calves. Supplementing quercetin improves gastrointestinal absorption capacity, particularly in colostrum-deprived calves.

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.

Effects of a 6-wk intraduodenal supplementation with quercetin on energy metabolism and indicators of liver damage in periparturient dairy cows.

Periparturient dairy cows experience metabolic challenges that result in a negative energy balance (EB) and a range of postpartum health problems. To compensate for the negative EB, cows mobilize fatty acids from adipose tissues, which can lead to fatty liver disease, a periparturient metabolic disorder. Flavonoids, such as quercetin (Q), are polyphenolic substances found in all higher plants and have hepatoprotective potential and the ability to prevent or reduce lipid accumulation in the liver. In ruminants, few studies on the metabolic effects of Q are available, and thus this study was conducted to determine whether Q has beneficial effects on EB, lipid metabolism, and hepatoprotective effects in periparturient dairy cows. Quercetin was supplemented intraduodenally to circumvent Q degradation in the rumen. Cows (n=10) with duodenal fistulas were monitored for 7wk. Beginning 3wk before expected calving, 5 cows were treated with 100mg of quercetin dihydrate per kilogram of body weight daily in a 0.9% sodium chloride solution for a total period of 6wk, whereas the control cows received only the sodium chloride solution. The plasma flavonoid levels were higher in the Q-treated cows than in the control cows. A tendency for higher postpartum (pp) than antepartum (ap) plasma flavonoid levels was observed in the Q-treated cows than in the controls, which was potentially caused by a reduced capacity to metabolize Q. However, the metabolic status of the Q-treated cows did not differ from that of the control cows. The pp increases in plasma aspartate aminotransferase and glutamate dehydrogenase activities were less in the Q-treated cows than in the control cows. The Q had no effect on energy expenditures, but from ap to pp the cows had a slight decline in respiratory quotients. Irrespective of the treatment group, the oxidation of fat peaked after calving, suggesting that the increase occurred because of an increased supply of fatty acids from lipomobilization. In conclusion, supplementation with Q resulted in lower pp plasma aminotransferase and glutamate dehydrogenase, which indicated reduced liver damage. However, the direct effects of Q on the liver and the implications for animal performance remain to be investigated.