An elevated deoxycholic acid level induced by high-fat feeding damages intestinal stem cells by reducing the ileal IL-22.

Long-term high-fat diet (HFD) destroys the intestinal mucosal barrier by damaging intestinal stem cells (ISCs). A HFD can increase the concentration of intestinal deoxycholic acid (DCA) and decrease the secretion of interleukin-22 (IL-22), which plays an important role in the proliferation, repair and regeneration of ISCs. We hypothesized that increased level of intestinal DCA induced by a HFD leads to ISC dysfunction by reducing the IL-22 levels in intestinal tissues. In this study, 2 weeks of a DCA diet or a HFD damaged ileal ISC and its proliferation and differentiation, resulting in a decrease in Paneth cells and goblet cells. Importantly, 2 weeks of a DCA diet or a HFD also reduced ileal IL-22 concentration, accompanied by a decreased number of group 3 innate lymphoid cells in ileal mucosa, which produce IL-22 after intestinal injury. Concurrent feeding with bile acid binder cholestyramine prevented all these changes induced by a HFD. In addition, in vitro study further confirmed that exogenous IL-22 reversed the decline in the proliferation and differentiation of ileal ISCs induced by DCA stimulation. Collectively, these results revealed that the decrease in intestinal IL-22 induced by DCA may be a novel mechanism by which HFD damages ISCs. The administration of IL-22 or a bile acid binder may provide novel therapeutic targets for the metabolic syndrome caused by a HFD.

Cholesterol-cyclodextrin complex as a replacement for egg yolk in bull semen extender: sperm characteristics post-thawing and in vivo fertility.

Egg yolk, a major semen extender constituent, lacks a defined composition, therefore, there are biosecurity concerns with use of egg yolk. Cryopreservation of bull semen without inclusion of animal protein in the semen extender, therefore, is an important consideration. Cholesterol may be delivered and incorporated into the sperm plasma membrane by cyclodextrins to protect sperm during cryopreservation. The aim of this study was to determine suitability of a cholesterol-cyclodextrin semen extender, without inclusion of egg yolk, for cryopreservation of bull semen. Bull semen was collected and cryopreserved in either egg yolk or with inclusions of three different concentrations of cholesterol-cyclodextrin complex (0.5, 1 or 2 mg/mL semen) in Tris-glycerol (TG) extender. Sperm motion characteristics examined using the computer-assisted sperm analysis, and plasma membrane and acrosome integrity examined using flow cytometry, were similar for all extenders. The inclusion of the greatest concentration of cholesterol-cyclodextrin complex (2 mg/mL semen) followed by dilution in TG extender resulted in lesser pregnancy rates (P <  0.05). There was a pregnancy rate of as great as 56 % when sperm cryopreserved in 0.5 mg/mL cholesterol-cyclodextrin Tris-glycerol extender were used for artificial insemination following imposing of a hormonal treatment regimen for synchrony of timing of ovarian functions among cows for conducting fixed-time artificial insemination (FTAI). Results indicate cholesterol-cyclodextrin Tris-glycerol extender, with a chemically defined composition and without inclusion of egg yolk, may be used to cryopreserve bull sperm with there being acceptable pregnancy rates when this semen is used for FTAI.

TcpP L152A Constitutively Activating Virulence Gene Expression in Vibrio cholerae.

Vibrio cholerae, the causative agent of severe watery diarrheal disease cholera, requires production of a number of virulence factors during infection which results from the activity of a cascading system of regulatory factors by sensing to different environmental signals. TcpP, a membrane-localized transcription activator in V. cholerae, activates virulence factors production by responding to human host signals. To better characterize the transmembrane helix in regard to its roles on TcpP positive effectors sensitivity, site-directed mutagenesis was performed to identify specific mutations in this region which could enhance TcpP transcription activity in the absence of stimuli, like bile salts. We found that TcpP L152A constitutively forms homodimer and activates toxT expression in the absence of bile salts. However, being active, TcpP L152A needs to form disulfide bonds between the cysteine residues in the periplasmic domain of TcpP. We also found that TcpP L152A showed a competitive advantage in the infant mouse colonization model by coadministrating the bile salt-sequestering resin cholestyramine. All these results demonstrate that the transmembrane helix of TcpP plays an important role in regulating TcpP transcription activity in response to its positive effectors.

Membrane cholesterol depletion reduces downstream signaling activity of the adenosine A2A receptor.

Cholesterol has been shown to modulate the activity of multiple G Protein-coupled receptors (GPCRs), yet whether cholesterol acts through specific interactions, indirectly via modifications to the membrane, or via both mechanisms is not well understood. High-resolution crystal structures of GPCRs have identified bound cholesterols; based on a ß2-adrenergic receptor (ß2AR) structure bound to cholesterol and the presence of conserved amino acids in class A receptors, the cholesterol consensus motif (CCM) was identified. Here in mammalian cells expressing the adenosine A2A receptor (A2AR), ligand dependent production of cAMP is reduced following membrane cholesterol depletion with methyl-beta-cyclodextrin (MßCD), indicating that A2AR signaling is dependent on cholesterol. In contrast, ligand binding is not dependent on cholesterol depletion. All-atom molecular simulations suggest that cholesterol interacts specifically with the CCM when the receptor is in an active state, but not when in an inactive state. Taken together, the data support a model of receptor state-dependent binding between cholesterol and the CCM, which could facilitate both G-protein coupling and downstream signaling of A2AR.

Determination of Degradation Kinetics and Effect of Anion Exchange Resin on Dissolution of Novel Anticancer Drug Rigosertib in Acidic Conditions.

Rigosertib is a novel anticancer drug in clinical development by Onconova therapeutics, Inc. Currently, it is in pivotal phase III clinical trials for myelodysplastic syndrome (MDS) patients. Chemically, it is a sodium salt of weak acid with low solubility in lower pH solutions. In the preliminary studies, it was found that rigosertib is unstable in acidic conditions and forms multiple degradation products. In this research, drug degradation kinetics of rigosertib were studied in acidic conditions. Rigosertib follows pseudo-first-order general acid catalysis reaction. Cholestyramine, which is a strong anion exchange resin, was used to form complex with drug to improve stability and dissolution in acidic conditions. Drug complex with cholestyramine showed better dissolution profile compared to drug alone. Effect of polyethylene glycol was investigated on the release of drug from the drug resin complex. Polyethylene glycol further improved dissolution profile by improving drug solubility in acidic medium.

Cholestyramine as a promising, strong anion exchange resin for direct capture of genetic biomarkers from raw pancreatic fluids.

The ability to capture cell-free DNA from the gastrointestinal tract, in a minimally invasive manner, could enhance our ability to diagnose gastrointestinal disease, or gain a better understanding of the spatial mapping of the intestinal microbiota. We, therefore, sought to identify a class of capture agents that could directly and efficiently sequester genetic material from intestinal fluids. As a particular case study, we examined the ability to capture DNA from pancreatic secretions, for potential application in enabling the sequestration of early, genetic biomarkers of pancreatic disease. We hypothesized that the cholestyramine series of strong cation exchange resins, which are FDA approved for the treatment of high cholesterol, may be capable of capturing DNA from pancreatic secretions. We identified a particular cholestyramine resin, DOWEX 1 × 2 100-200 mesh, which is able to efficiently capture and purify DNA from pancreatic fluid. Using only 200 µL of pancreatic secretions, we are able to recover 247 ± 182 ng of amplifiable human DNA, giving an estimated pancreatic fluid DNA content of 1.23 ± 0.91 ng/µL. To our knowledge, this is the first demonstration of a material that can effectively capture and purify DNA directly from untreated pancreatic fluids. Thus, our approach could hold high utility for the in vivo capture of DNA and disease biomarkers if incorporated into an appropriate sampling device. Biotechnol. Bioeng. 2017;114: 934-938. © 2016 Wiley Periodicals, Inc.

Development and in vitro characterization of a multiparticulate delivery system for acyclovir-resinate complex.

CONTEXT: Herpes viruses cause threatening infections in humans and stand second as causative agents for most human viral diseases, after influenza and cold viruses. OBJECTIVE: A novel multiparticulate delivery system for acyclovir (ACV), based on ion-exchange resin, was developed to achieve a gastro-mucoadhesive effect in order to effectively combat the herpes simplex virus. MATERIALS AND METHODS: A combination of ACV and cholestyramine resin was optimized and further entrapped within sodium alginate and Carbopol microbeads. The developed systems were evaluated for drug entrapment efficiency (DEE), percentage of mucoadhesion, and in vitro release characteristics in simulated gastric fluid (SGF, pH 1.2). RESULTS: With the aid of scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier-transform infrared spectroscopy (FTIR), the interaction of the resinate and polycations with alginate has been revealed, which consequently supports the formation of the membrane by the polyelectrolyte complex. The in vitro drug release studies demonstrate that formulations without the drug-resin complex (DRC) released the drug more rapidly than formulations containing DRC, which released the drug in a controlled manner, due the formation of a complex between drug and resin. DISCUSSION AND CONCLUSION: Preliminary results from this study suggest that these DRC-entrapped microbeads may be used to incorporate other antiviral drugs and could be effective against infections caused by herpes viruses. Such formulations developed could be subjected to in vivo studies in future, in order to prove complete clearance of herpes infections.

Protection of dried probiotic bacteria from bile using bile adsorbent resins.

Enteric coated oral tablets or capsules can deliver dried live cells directly into the intestine. Previously, we found that a live attenuated bacterial vaccine acquired sensitivity to intestinal bile when dried, raising the possibility that although gastric acid can be bypassed, significant loss of viability might occur on release from an enteric coated oral formulations. Here we demonstrate that some food-grade lyophilised preparations of Lactobacillus casei and Lactobacillus salivarius also show temporary bile sensitivity that can be rapidly reversed by rehydration. To protect dried bacterial cells from temporary bile sensitivity, we propose using bile acid adsorbing resins, such as cholestyramine, which are bile acid binding agents, historically used to lower cholesterol levels. Vcaps™ HPMC capsules alone provided up to 830-fold protection from bile. The inclusion of 50% w/w cholestyramine in Vcaps™ HPMC capsules resulted in release of up to 1700-fold more live Lactobacillus casei into simulated intestinal fluid containing 1% bile, when compared to dried cells added directly to bile. We conclude that delivery of dried live probiotic organisms to the intestine may be improved by providing protection from bile by addition of bile adsorbing resins and the use of HPMC capsules.

Bile acid binding resin improves metabolic control through the induction of energy expenditure.

BACKGROUND: Besides well-established roles of bile acids (BA) in dietary lipid absorption and cholesterol homeostasis, it has recently become clear that BA is also a biological signaling molecule. We have shown that strategies aimed at activating TGR5 by increasing the BA pool size with BA administration may constitute a significant therapeutic advance to combat the metabolic syndrome and suggest that such strategies are worth testing in a clinical setting. Bile acid binding resin (BABR) is known not only to reduce serum cholesterol levels but also to improve glucose tolerance and insulin resistance in animal models and humans. However, the mechanisms by which BABR affects glucose homeostasis have not been established. We investigated how BABR affects glycemic control in diet-induced obesity models. METHODS AND FINDINGS: We evaluated the metabolic effect of BABR by administrating colestimide to animal models for the metabolic syndrome. Administration of BABR increased energy expenditure, translating into significant weight reduction and insulin sensitization. The metabolic effects of BABR coincide with activation of cholesterol and BA synthesis in liver and thermogenesis in brown adipose tissue. Interestingly, these effects of BABR occur despite normal food intake and triglyceride absorption. Administration of BABR and BA had similar effects on BA composition and thermogenesis, suggesting that they both are mediated via TGR5 activation. CONCLUSION: Our data hence suggest that BABR could be useful for the management of the impaired glucose tolerance of the metabolic syndrome, since they not only lower cholesterol levels, but also reduce obesity and improve insulin resistance.

Assessment of cholesterol absorption inhibitors nanostructured aluminosilicate and cholestyramine using in vitro lipolysis model.

Protonated nanostructured aluminosilicate (NSAS) was previously reported as effective in decreasing intestinal absorption of cholesterol in rats. In this work, the effect of NSAS on modeled intraluminal distribution of cholesterol was assessed using an in vitro lipolysis model. In addition to NSAS, the effect of bile salt sequestrant cholestyramine on modeled intraluminal distribution of cholesterol was tested, as well as the effect of the absence of bile salts in the system. NSAS induced sharp redistribution of cholesterol from aqueous to sediment phase, which suggests that NSAS exerts its inhibition of cholesterol absorption by direct or indirect binding to cholesterol, followed by its precipitation and excretion with feces. Cholestyramine induced redistribution of cholesterol into both oil and sediment phase. The redistribution into the sediment phase in the presence of cholestyramine was more intensive than when bile acids were omitted from the system, which suggests potential cholesterol-lowering activity of this compound on the level of intraluminal processing of cholesterol. Assessment of intraluminal processing of cholesterol using in vitro dynamic lipolysis model can potentially become a valuable approach to assess the action of cholesterol absorption inhibitors in a fast and efficient manner.

Improvement of low bioavailability of a novel factor Xa inhibitor through formulation of cationic additives in its oral dosage form.

A clinical trial of (2S)-2-[4-[[(3S)-1-acetimidoyl-3-pyrrolidinyl]oxy]phenyl]-3-(7-amidino-2-naphtyl) propanoic acid (DX-9065) revealed that its oral bioavailability was only 3% when it was administered as a conventional capsule formulation. The low bioavailability of DX-9065 was likely caused by both its poor membrane permeability and its electrostatic interaction with anionic bile acids. We hypothesized that DX-9065 absorption would be enhanced when the cationic drug was free from the complex through its replacement with other cationic substances. Polystyrene nanospheres coated with cationic poly(vinylamine) and cholestyramine, which is clinically used as a cholesterol-lowering agent, dramatically prevented DX-9065 from interacting with chenodeoxycholic acid in vitro. Successive animal experiments showed that bioavailability of DX-9065 administered with these cationic substances was 2-3 times that of DX-9065 administered solely. A dry syrup formulation with one-half of a minimal cholesterol-lowering equivalent dose of cholestyramine was designed, and the clinical trial was resumed. A 1.3-fold increase in bioavailability of DX-9065 was observed when the dry syrup was administered. We successfully demonstrated that DX-9065 absorption was enhanced when the drug was administered with cationic additives; however, it appeared that the absorption-enhancing function of cholestyramine largely depended on its dose. The dose escalation is probably prerequisite for the significant improvement of DX-9065 absorption in humans.

Quantitative structure-property relationships modeling to predict in vitro and in vivo binding of drugs to the bile sequestrant, colesevelam (Welchol).

Quantitative structure-property relationship (QSPR) models were developed to correlate physicochemical properties of structurally unrelated drugs with extent of in vitro binding to colesevelam, and predicted values were compared with drug exposure changes in vivo following coadministration. The binding of 17 drugs to colesevelam was determined by an in vitro dissolution drug-binding assay. Data from several clinical studies in healthy volunteers to support administration of colesevelam in diabetic patients were also collected along with existing in vivo literature data and compared with in vitro results. Steric, electronic, and hydrophobic descriptors were calculated for test compounds, and univariate and partial least squares regression approaches were used to derive QSPR models to evaluate which of the molecular descriptors correlated best with in vitro binding. A quadrant analysis evaluated the correlation between predicted/actual in vitro binding results and the in vivo data. The in vitro binding assay exhibited high sensitivity, identifying those compounds with a low probability of producing relevant in vivo drug interactions. Drug lipophilicity was identified as the primary determinant of in vitro binding to colesevelam by the final univariate and partial least squares models (R(2) = 0.69 and 0.98; Q(2) = 0.48 and 0.59). The in vitro assay and in silico models represent predictive tools that may allow investigators to conduct only informative clinical drug interaction studies with colesevelam.

In vitro methods can forecast the effects of intragastric residence on dosage form performance.

Intragastric conditions can affect the performance of solid dosage forms. For two cases, the ability of in vitro methods to forecast these effects was investigated: first, the ability of cholestyramine to sequester bile salts in the fed small intestine and, second, disintegration times of hard gelatin capsules. After incubating cholestyramine for 90 min in milk gradually digested with pepsin, the binding of taurocholates from fed state simulating intestinal fluid onto the resin became non-specific and the affinity constant was reduced from 220 l/mole (without prior incubation) to 60 l/mole. These data are consistent with the comparatively poor performance of cholestyramine products when administered in the fed state. Scintigraphic studies showed that intragastric disintegration times of hard gelatin capsules are delayed in both the fasted and fed states according to the degree of cross-linking. These results were satisfactorily predicted by the in vitro disintegration times in fasted state simulating gastric fluid and in milk gradually digested with pepsin, whereas results were poorly predicted in compendial media. This work illustrates that recently proposed methods for simulating intragastric environment may be useful in predicting the performance of solid dosage forms.

Designing of the centers for adsorption of bile acids on a silica surface.

Silicas chemically modified with attached aminopropyl, imidazolyl, and trimethylsilyl groups, with adsorptive and coordinative grafted hemin were synthesized. Adsorption of some bile acids on the surface of hydroxylated silica, synthesized siliceous adsorbents and cholestyramine has been studied. It was found that the main contribution to the total adsorption is caused by electrostatic attraction between anions of bile acids and positively charged sites of the surface of modified silica and also by dispersion interactions between steroid skeleton of bile acids and functional groups of modified silicon dioxides. It was established that the kinetic parameters of adsorption and adsorptive capacity for all investigated siliceous adsorbents exceed similar characteristics for cholestyramine. The best of synthesized adsorbents is hemin-containing adsorbent IX, and the sequence of increase in its adsorptive capacity in relation to bile acids corresponds to the following series: I < III < II, IV < VI < V < VIII < VII < IX.

Recent advances on the use of adsorbent materials for detoxification of Fusarium mycotoxins.

The extensive use of adsorbents in the livestock industry has led to the introduction of a wide range of new products on the market, most of them claiming high in vitro mycotoxin adsorption capacity. However, adsorbents that may appear effective in vitro do not necessarily retain their efficacy when tested in vivo. Studies performed in our laboratory during the past few years aiming to evaluate the efficacy of various adsorbent materials in binding Fusarium mycotoxins are reported. Adsorption experiments were performed in in vitro screening tests for Fusarium mycotoxins at different pHs; by in vivo tests using the increase of the sphinganine to sphingosine ratio in rat urine and tissues as a biomarker of fumonisin exposure; and by a dynamic, computer-controlled, gastrointestinal model simulating the gastrointestinal tract of healthy pigs. Most of the commercially available mycotoxin-binders failed in sequestering in vitro Fusarium mycotoxins. Only for a small number of adsorbent materials was the ability to bind more than one mycotoxin demonstrated. Cholestyramine was proven to be an effective binder for fumonisins and zearalenone in vitro, which was confirmed for zearalenone in experiments using a dynamic gastrointestinal model and for fumonisins in in vivo experiments. No adsorbent materials, with the exception of activated carbon, showed relevant ability in binding deoxynivalenol and nivalenol. The in vitro efficacy of activated carbon toward fumonisins was not confirmed in vivo by the biomarker assay. The dynamic gastrointestinal model was a reliable tool to study the effectiveness of adsorbent materials in reducing the bioaccessibility of Fusarium mycotoxins, as an alternative to the more difficult and time-consuming studies with domestic livestock.

Adsorption of methotrexate and calcium leucovorin onto cholestyramine in vitro.

Methotrexate (MTX), an antimetabolite of folic acid, is a drug widely used in the treatment of different types of cancer. When high doses are administered, it is necessary to interrupt its action by administering calcium leucovorin (CaL). The main pathway of MTX and CaL elimination in humans occurs through the kidney, but about 10% is excreted in the faeces via the bile. Drugs, foods and sorbents in intestinal lumen modify MTX and CaL reabsorption. Individual and simultaneous studies on the adsorption of MTX and CaL from aqueous phosphate buffer by cholestyramine were carried out in order to calculate the adsorption process of MTX and CaL to cholestyramine, and to characterize the influence of CaL in the adsorption of MTX to cholestyramine and vice versa. The Langmuir binding isotherms determined in buffer solutions at pH 6 indicated a greater (12.58%) adsorption capacity of cholestyramine (1.43 mmol of drug/g of resin) than at pH 7 (1.25 mmol of drug/g of cholestyramine). The affinity constant of MTX to cholestyramine was a 45.27% higher (6.67 mM(-1)) than the affinity constant of CaL to the resin (3.65 mM(-1)). Results from simultaneous assays indicate that a displacement of the MTX bound to cholestyramine by CaL is not foreseeable. The results suggest that cholestyramine may be a potentially useful adjunctive therapy in the treatment of an overdose of MTX. Consequently, cholestyramine may be of clinical value in patients who develop early renal function impairment whilst undergoing MTX therapy.

Hydrophilic 7 beta-hydroxy bile acids, lovastatin, and cholestyramine are ineffective in the treatment of cerebrotendinous xanthomatosis.

We compared the effect of treatments with hydrophilic bile acids (ursodeoxycholic and ursocholic acids), cholestyramine, and lovastatin versus chenodeoxycholic acid in 4 patients with cerebrotendinous xanthomatosis (CTX). Bile acids and bile alcohols in plasma, bile, and urine before and after treatment were quantitated by gas-liquid chromatography. Untreated, all patients showed abnormal biliary bile acid composition: cholic acid (72.7%) and chenodeoxycholic acid (6.2%), and polyhydroxylated C(27)-bile alcohols (10.0%), and elevated plasma cholestanol levels. Treatment with hydrophobic chenodeoxycholic acid inhibited abnormal bile acid synthesis (virtual disappearance of C(27)-bile alcohols from plasma, bile, and urine and marked reduction of plasma cholestanol levels). Hydrophilic ursodeoxycholic and ursocholic acids did not inhibit abnormal bile acid synthesis, while cholestyramine increased abnormal bile acid synthesis (continued increased formation of polyhydroxylated C(27)-bile alcohols and further elevation of plasma cholestanol levels). Lovastatin did not affect abnormal bile acid synthesis or reduce plasma cholestanol levels. The results demonstrate that impaired side-chain oxidation in bile acid synthesis due to mutations of Cyp27 results in increased formation of polyhydroxylated C(27)-bile alcohols and cholestanol in CTX. Hydrophobic chenodeoxycholic acid, but not cholestyramine, lovastatin, or hydrophilic 7beta-hydroxy acids, inhibited the abnormal synthetic pathway. The role of chenodeoxycholic acid in downregulating abnormal bile acid synthesis in CTX is emphasized.

Assessing the zearalenone-binding activity of adsorbent materials during passage through a dynamic in vitro gastrointestinal model.

A novel approach is presented herein to study the intestinal absorption of mycotoxins by using a laboratory model that mimics the metabolic processes of the gastrointestinal (GI) tract of healthy pigs. This model was used to evaluate the small-intestinal absorption of zearalenone from contaminated wheat (4.1 mg/kg) and the effectiveness of activated carbon and cholestyramine at four inclusion levels (0.25, 0.5, 1 and 2%) in reducing toxin absorption. Approximately 32% of ZEA intake (247 microg) was released from the food matrix during 6 h of digestion and was rapidly absorbed at intestinal level. A significant reduction of intestinal absorption of ZEA was found after inclusion of activated carbon or cholestyramine, even at the lowest dose of adsorbents, with a more pronounced effect exhibited by activated carbon. In particular, when 2% of activated carbon or cholestyramine was added to the meal the ZEA intestinal absorption was lowered from 32% of ZEA intake to 5 and 16%, respectively. The sequestering effect of both adsorbents took place already during the first 2 h of digestion and persisted during the rest of the experiment. The GI-model is a rapid and physiologically relevant method to test the efficacy of adsorbent materials in binding mycotoxins and can be used to pre-screen mycotoxin/adsorbent combinations as an alternative to animal experiments.

A new approach in gastroretentive drug delivery system using cholestyramine.

We prepared cellulose acetate butyrate (CAB)-coated cholestyramine microcapsules as a intragastric floating drug delivery system endowed with floating ability due to the carbon dioxide generation when exposed to the gastric fluid. The microcapsules also have a mucoadhesive property. Ion-exchange resin particles can be loaded with bicarbonate followed by acetohydroxamic acid (AHA) and coated with CAB by emulsion solvent evaporation method. The drug concentration was monitored to maintain the floating property and minimum effective concentration. The effect of CAB: drug-resin ratio (2:1, 4:1, 6:1 w/w) on the particle size, floating time, and drug release was determined. Cholestyramine microcapsules were characterized for shape, surface characteristics, and size distribution; cholestyramine/acetohydroxamic acid interactions inside microcapsules were investigated by X-ray diffractometry. The buoyancy time of CAB-coated formulations was better than that of uncoated resin particles. Also, a longer floating time was observed with a higher polymer:drug resin complex ratio (6:1). With increasing coating thickness the particle size was increased but drug release rate was decreased. The drug release rate was higher in simulated gastric fluid (SGF) than in simulated intestinal fluid (SIF). The in vivo mucoadhesion studies were performed with rhodamine-isothiocyanate (RITC) by fluorescent probe method. The amount of CAB-coated cholestyramine microcapsules that remained in the stomach was slightly lower than that of uncoated resin particles. Cholestyramine microcapsules were distributed throughout the stomach and exhibited prolonged gastric residence via mucoadhesion. These results suggest that CAB-coated microcapsules could be a floating as well as a mucoadhesive drug delivery system. Thus, it has promise in the treatment of Helicobacter pylori.

In vitro and in vivo studies to assess the effectiveness of cholestyramine as a binding agent for fumonisins.

Several adsorbent materials were tested at I mg/ml for their in vitro capacity to adsorb fumonisin B1(FB1) from aqueous solutions. Cholestyramine showed the best adsorption capacity (85% from a solution containing 200 microg/ml FB1) followed by activated carbon (62% FB1). Bentonite adsorbed only 12% of the toxin from a solution containing 13 microg/ml FB1, while celite was not effective even at the lowest tested FB1 concentration (3.2 microg/ml). Cholestyramine was tested in vivo to evaluate its capacity to reduce the bioavailability of fumonisins (FBs) in rats fed diet contaminated with toxigenic Fusarium verticillioides culture material. Rats were exposed for one week to FBs-free diet, FBs-contaminated diet containing 6 or 20 microg/g FB1 + FB2 and the same FBs-contaminated diet added of 20 mg/g cholestyramine. The increase of sphinganine/sphingosine (SA/SO) ratio in urine and kidney of treated rats was used as specific and sensitive biomarker of fumonisin exposure. The addition of cholestyramine to the FBs-contaminated diets consistently reduced the effect of FBs by reducing significantly (P < 0.05) both urinary and renal SA/SO ratios.