Stefaan Vervarcke

University of Leuven, Louvain, Flanders, Belgium

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Publications (8)18.18 Total impact

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    ABSTRACT: To examine the efficacy of a hop extract (standardized at 100mug 8-prenylnaringenin per day) for relief of menopausal discomforts. A 16-week randomized, double-blind, placebo-controlled, cross-over study was conducted with 36 menopausal women. The participants were randomly allocated to either placebo or active treatment (hop extract) for a period of eight weeks after which treatments were switched for another eight weeks. The Kupperman Index (KI), the Menopause Rating Scale (MRS) and a multifactorial Visual Analogue Scale (VAS) were assessed at baseline, and after eight and sixteen weeks. After 8 weeks, both active treatment and placebo significantly improved all outcome measures when compared to baseline with somewhat higher average reductions for placebo than for the active treatment. After 16 weeks only the active treatment after placebo further reduced all outcome measures, whereas placebo after active treatment resulted in an increase for all outcome measures. Although, the overall estimates of treatment efficacy (active treatment-placebo) based on linear mixed models do not show a significant effect, time-specific estimates of treatment efficacy indicate significant reductions for KI (P = 0.02) and VAS (P = 0.03) and a marginally significant reduction (P = 0.06) for MRS after 16 weeks. Whereas the first treatment period resulted in similar reductions in menopausal discomforts in both treatment groups, results from the second treatment period suggest superiority of the standardized hop extract over placebo. Thus, phytoestrogen preparations containing this standardized hop extract may provide an interesting alternative to women seeking relief of mild vasomotor symptoms.
    Phytomedicine: international journal of phytotherapy and phytopharmacology 02/2010; 17(6):389-96. · 2.97 Impact Factor
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    ABSTRACT: Hop-derived food supplements and beers contain the prenylflavonoids xanthohumol (X), isoxanthohumol (IX) and the very potent phyto-oestrogen (plant-derived oestrogen mimic) 8-prenylnaringenin (8-PN). The weakly oestrogenic IX can be bioactivated via O-demethylation to 8-PN. Since IX usually predominates over 8-PN, human subjects may be exposed to increased doses of 8-PN. A dietary intervention trial with fifty healthy post-menopausal Caucasian women was undertaken. After a 4 d washout period, participants delivered faeces, blank urine and breath samples. Next, they started a 5 d treatment with hop-based supplements that were administered three times per d and on the last day, a 24 h urine sample was collected. A semi-quantitative FFQ was used to estimate fat, fibre, alcohol, caffeine and theobromine intakes. The recoveries of IX, 8-PN and X in the urine were low and considerable inter-individual variations were observed. A five-fold increase in the dosage of IX without change in 8-PN concentration resulted in a significant lower IX recovery and a higher 8-PN recovery. Classification of the subjects into poor (60%), moderate (25%) and strong (15%) 8-PN producers based on either urinary excretion or microbial bioactivation capacity gave comparable results. Recent antibiotic therapy seemed to affect the 8-PN production negatively. A positive trend between methane excretion and 8-PN production was observed. Strong 8-PN producers consumed less alcohol and had a higher theobromine intake. From this study we conclude that in vivo O-demethylation of IX increases the oestrogenic potency of hop-derived products.
    British Journal Of Nutrition 12/2007; 98(5):950-9. · 3.30 Impact Factor
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    ABSTRACT: To examine the efficacy of a hop extract enriched in 8-prenylnaringenin (8-PN, the phytoestrogen in hops, Humulus lupulus L.) on relief of menopausal discomforts. A prospective, randomized, double-blind, placebo-controlled study over 12 weeks with 67 menopausal women, who were administered a hop extract standardized on 8-PN (100 or 250 microg). The responses were determined by means of a modified Kupperman index (KI) and a patients' questionnaire. All groups, including placebo, showed a significant reduction of the KI both after 6 weeks and after 12 weeks. The hop extract at 100 microg 8-PN was significantly superior to placebo after 6 weeks (P=0.023) but not after 12 weeks (P=0.086). No dose-response relationship could be established, as the higher dose (250 microg) was less active than the lower dose both after 6 weeks and after 12 weeks. Still, a trend for a more rapid decrease of KI was noticed for both active groups as compared to placebo. In particular, the decrease in hot flush score (isolated from the KI) was found significant for both treatment groups after 6 weeks (P<0.01) with respect to placebo. Results of the patients' questionnaire were consistent with those of the KI, with the most pronounced effects being observed for the 100-microg treatment. Daily intake of a hop extract, standardized on 8-PN as a potent phytoestrogen, exerted favorable effects on vasomotor symptoms and other menopausal discomforts. Hop-derived prenylated flavonoids may provide an attractive addition to the alternative treatments available for relief of hot flushes and other menopausal discomforts.
    Maturitas 05/2006; 54(2):164-75. · 2.84 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the possibility of mucosal vaccination in African catfish (Clarias gariepinus) with Vibrio anguillarum O2 bacterins. The antigen was administered via different routes: anal intubation, oral administration, intraperitoneal injection and immersion. To monitor the antigen uptake, a competitive ELISA was used. The antibody response was measured using an indirect ELISA. Increased antibody levels were found in bile and mucus upon anal intubation, which was not the case after intraperitoneal injection. The data indicate that oral vaccination of fish may be possible when antigens can reach the second gut segment in sufficient quantities and in the right form as confirmed by the recorded substantial induction of systemic and mucosal immunity. The results obtained are a strong indication for mucosal immune response and the two compartmental models for immune response in fish.
    Fish &amp Shellfish Immunology 03/2005; 18(2):125-33. · 2.96 Impact Factor
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    ABSTRACT: The impact on antigen uptake and antibody response by the addition of absorption enhancers to Vibrio anguillarum O2 antigen was studied in oral vaccination trials of African catfish (Clarias gariepinus). Oral vaccination was achieved by feeding lag time coated pellets. The lag time coat prevents premature release of the encapsulated vaccine in the tank, before ingestion of the pellets by the fish. To monitor the antigen uptake, a competitive ELISA was used. The antibody response was measured using an indirect ELISA. Feeding of bacterin-layered pellets without absorption enhancers resulted in a rather low antigen uptake and antibody levels. The addition of absorption enhancers such as sodium salicylate, sodium caprate and vitamin E TPGS increased the serum antigen levels and specific antibody levels in the systemic circulation. Skin mucus antibody levels were higher after oral vaccination compared to the IP and control group. The addition of absorption enhancers in the oral groups further increased the antibody levels obtained in the skin mucus.
    Fish &amp Shellfish Immunology 04/2004; 16(3):407-14. · 2.96 Impact Factor
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    ABSTRACT: The aim of this study was to investigate the success of oral vaccination application in African catfish using Vibrio anguillarum O2 bacterins. The antigen uptake was followed by competitive enzyme-linked immunosorbent assay (ELISA). Serum antibody response was measured using an indirect ELISA. Several in vivo administration methods were investigated. Intraperitoneal injection gave the highest absorption rate, with high antibody levels in the systemic circulation. Oral intubation of bacterin-layered pellets resulted in low antigen uptake and low antibody levels. The addition of absorption enhancers increased the serum antigen levels. An enteric coating applied on the pellets containing vaccine did not improve the immune response.
    Journal of Applied Ichthyology 03/2004; 20(2):134 - 138. · 0.90 Impact Factor
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    ABSTRACT: The aim of this study was to investigate African catfish (Clarias gariepinus) vaccination with Vibrio anguillarum O2 bacterins. To monitor the antigen uptake, a competitive enzyme-linked immunosorbent assay (ELISA) was developed. Serum antibody response was measured using an indirect ELISA. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblot data that characterize the immunoglobulin molecule of the African catfish are presented. The impact of acid conditions on the antigen proved to be stable above pH 4. A partition coefficient was calculated to determine the ability of transepithelial uptake. Two in vivo administration methods were investigated in the study. Intraperitoneal injection gave the highest absorption rate with high antibody levels in the systemic circulation, whereas immersion did not induce significant serum antibody levels.
    Journal of Applied Ichthyology 03/2004; 20(2):128 - 133. · 0.90 Impact Factor
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    ABSTRACT: The purpose of this work was to develop a release-delaying coat for drug-layered fish pellets, in order to prevent a premature release of the drug in the tank water but allowing a rapid release after uptake by the fish. Blank pellets were prepared in a rotary processor and drug layered in a Wurster coater with bovine serum albumin or riboflavin using hydroxypropyl methyl cellulose (HPMC) as a binder. On the drug-loaded pellets, different mixtures of ethyl cellulose (EC) and HPMC were applied as the release-delaying coat. The aim was to obtain less than 10% drug release during the first 10 min followed by a fast release after the "lag" period, resulting in a sigmoidal release profile. In order to prevent coat bursts it was necessary to increase the amount of plasticizer from 20 to 40% triethylcitrate. To have a complete coat around the pellets, the thickness of the coat (amount EC) was important up to a certain level. The EC/HPMC ratio had a decisive influence on optimizing the permeability of the coating and realizing a sigmoidal release profile. The release rate was studied as a function of several formulation variables and physicochemical parameters (salinity, pH, and temperature) of the dissolution medium as the coating system is intended for different fish species. Salinity of the water proved to be important as well as the temperature. The developed system seems to be promising for a lot of ichthyologic applications, although it has to be evaluated for each intended drug, keeping in mind the properties of the particles to be coated, the fish species, and the environment.
    Pharmaceutical Development and Technology 12/2002; 7(4):471-80. · 1.33 Impact Factor