Maurits Van Boven

Evidences for a satiating effect of defatted jojoba meal

Abstract Supplementation of food with increasing doses (3, 5, and 10%) of defatted jojoba meal induced a pronounced dose-dependent food intake reduction in fasted and non-fasted rats. This effect was more pronounced in non-fasted than in fasted rats, which is typical for satiety agents. Water intake was reduced to the pair-fed level in non-fasted rats with free access to water and receiving food supplemented with 10% defatted jojoba meal. This was also observed in fasted rats deprived of water during the fasting period and receiving food supplemented with 10% defatted jojoba meal. The reduced water intake in defatted jojoba meal treated rats was entirely due to the food intake reduction. These observations are in favour of the hypothesis that defatted jojoba meal induces its food intake reduction by stimulating satiety. Possible mechanisms are discussed.

Simmondsin: effects on meal patterns and choice behavior in rats.

Simmondsin, a glycoside from jojoba meal, decreases food intake after oral administration. The present experiments are designed to clarify the mechanism of simmondsins anorectic activity. The meal pattern analysis shows that simmondsin supplementation at different doses results in a dose-dependent food intake reduction, which is more pronounced after prior simmondsin experience. The effect of simmondsin on meal patterns (decreased meal size, meal duration and eating rate, increased latency to eat) is most severe at the highest concentration. Rats familiar with simmondsin more seriously postpone their first meal than with first contact, resulting in a decrease of the meal frequency and the day/night feeding ratio. Rats given the choice between a control diet and a simmondsin-supplemented (0.5%) diet, after half an hour, have a significant preference for the control diet. Simmondsin seems to have a specific flavor when mixed in the food since rats recognise the feeder containing simmondsin. The ability of simmondsin to induce conditioned taste aversion (CTA) was also investigated. Rats receiving simmondsin at concentrations of 0.15%, 0.25% or 0.5% during their conditioning develop significant taste aversions to the saccharin solutions. The performed experiments indicate that the simmondsin activity shows some analogy with the satiating molecule cholecystokinin (CCK) at first contact, but shows more analogy with the illness-inducing agent lithium chloride (LiCl) after prior experience with simmondsin. Rats familiar with simmondsin avoid simmondsin-supplemented food by directly monitoring its presence, and by learning to relate it to the postingestive consequences of consumption.

Development of a Fluoroimmunoassay for the Detection of Buprenorphine in Urine

The development of a fluoroimmunoassay for the detection of buprenorphine in urine samples is described. Fluorescein-norbuprenorphine and pseudobuprenorphine, the dimer of buprenorphine, were synthesized as tracer molecules. The antibodies were prepared by coupling the 2-diazobenzoic acid derivative of buprenorphine with bovine serum albumine, using the carbodiimide method. The assay was mainly used for the routine detection of buprenorphine in urine specimens of persons suspected of Temgesic abuse. The minimum detectable dose of the immunoassay was calculated to be 20 ng/mL.

PEGylation of cholecystokinin prolongs its anorectic effect in rats

The anorectic compound CCK-9 was coupled to polyethylene glycol 5 kDa, 10 kDa, 20 kDa and 30 kDa, under different reaction conditions. Conjugates were purified by HPLC and characterized by MALDI-TOF MS. A 96% PEGylation yield was obtained in buffer pH 7.5 after 6h reaction at 20 degrees C. The anorectic activity was tested in vivo in rats. A single bolus intra-peritoneal injection of non-modified CCK-9 resulted in a significant initial food intake reduction 30 min after food presentation (87% compared to paired control group). When PEG-CCK-9 conjugates modified with polymers of molecular weight up to 20 kDa were injected, lower but statistically significant initial food intake reductions were obtained (76% for PEG 10 kDa-CCK-9 conjugate compared to control group). The cumulative food intake reduction of non-modified CCK-9 is normalized within 1-2h, whereas the PEG-CCK-9 molecules showed a prolonged anorectic activity lasting for 6h for PEG 5 kDa-CCK-9; 23 h for PEG 10 kDa-CCK-9 and between 8h and 23 h for PEG 20 kDa-CCK-9. For PEG 30 kDa-CCK-9 conjugate, neither an initial nor a cumulative FI reduction was observed. PEG-CCK-9 conjugates show a significantly prolonged anorectic activity in comparison to the non-modified peptide. This effect is most evident for the PEG 10 kDa-CCK-9 conjugate.

Simultaneous determination of carbohydrates and simmondsins in jojoba seed meal (Simmondsia chinensis) by gas chromatography.

Separate methods for the analyses of soluble carbohydrates in different plants and simmondsins in jojoba seed meal are described. A reliable gas chromatographic procedure for the simultaneous quantification of D-pinitol, myo-inositoL sucrose, 5-alpha-D-galactopyranosyl-D-pinitol. 2-alpha-D-galactopyranosyl-D-pinitol, simmondsin, 4-demethylsimmondsin, 5-demethylsimmondsin and 4,5-didemethylsimmondsin as trimethylsilyl derivatives in jojoba seed meal has been developed. The study of different extraction mixtures allowed for the quantitative recovery of the 9 analytes by a mixture of methanol-water (80:20, v/v) in the concentration range between 0.1 and 4%. Comparison of the separation parameters on three different capillary stationary phases with MS detection allowed for the choice of the optimal gas chromatographic conditions for baseline separation of the analytes.

Dietary influences on 8‐MOP plasma levels in PUVA patients with psoriasis

To Study the effect of diet on 8‐MOP plasma levels, these levels were measured three times in twenty PUVA patients with psoriasis; while fasting, after a low‐fat breakfast, and after a fat‐rich breakfast.

Biodistribution and pharmacokinetics of PEG-10kDa-cholecystokinin-10 in rats after different routes of administration.

Cholecystokinin, produced in the proximal small intestine, is a short acting satiating peptide hormone. CCK-10, before and after mono-iodination, was previously coupled to 10kDa polyethylene glycol (PEG). The formed conjugates PEG10kDa-CCK-10 and PEG10kDa-[(127)I]-CCK-10 show after i.p. administration to rats a sustained food intake reduction during 8h in comparison to 2h for free CCK-10. The present study examined the blood pharmacokinetics of this pharmacological interesting molecule by means of PEG10kDa-[(123)I]-CCK-10 following intravenous, intraperitoneal, intramuscular and nasal administration and the biodistribution after i.p. administration. HPLC analysis with radiometric detection allowed the differentiation between inorganic iodide and the intact tracer in blood. Blood kinetics after i.v. injection was fitted to a bi-exponential with a distribution half-life of 15 min and with an elimination half-life of 8 hours for intact PEG10kDa-[(123)I]-CCK-10. The biodistribution studies showed a higher accumulation of the tracer for all administration routes in organs expressing CCK receptors localized in the gastrointestinal tract such as pancreas, duodenum and small intestine. No indication of blood brain barrier crossing for the conjugate could be observed independently of the administration route. Main clearance was via the urinary pathway.

Synthesis, Characterization and Satiety in Rats of PEG10kDa-CCK-10 and (Radio)Iodinated PEG10kDa-CCK-10

The iodination of CCK-10 and coupling with PEG 10kDa is described along with evaluation of their food intake reducing effects and in vitro stability. Labeling was performed by electrophilic substitution with both [127I] and [123I] iodide, using iodo-beads® as the oxidant. The reaction conditions were optimised. HPLC was used to follow reaction progression and for purification of the labeled compounds. The synthesized compounds were characterized by MALDI-TOF MS and 1H NMR spectroscopy. Radiochemical yields were 40 ± 3% for [123I]CCK-10; the conjugation with PEG 10kDa was quantitative. A specific activity of 2438 GBq/mmol was obtained. Plasma stability studies with PEG10kDa-[123I]- CCK-10 showed a de-iodination half-life of 27 hours. Food intake experiments in rats with PEG10kDa-[127I]-CCK-10 showed after a single bolus intra-peritoneal injection a food intake reduction during 8 hours equivalent with the results obtained for PEG10kDa-CCK-10 and with PEG10kDa-CCK-9. The pharmacological results obtained indicate that neither the introduction of an extra tyrosine in CCK-9 nor the introduction of a iodine label in tyrosine affects the prolonged food reduction activity of the CCK conjugate. The suitability of PEG10kDa [123I]-CCK-10 as an agent for mapping CCK receptors and pharmacokinetic studies has been shown.