Gastrointestinal Dialysis Research Articles

Spontaneous Riboflavin-Overproducing Limosilactobacillus reuteri for Biofortification of Fermented Foods.

Riboflavin-producing lactic acid bacteria represent a promising and cost-effective strategy for food biofortification, but production levels are typically insufficient to support daily human requirements. In this study, we describe the novel human isolate Limosilactobacillus reuteri AMBV339 as a strong food biofortification candidate. This strain shows a high natural riboflavin (vitamin B2) overproduction of 18.36 μg/ml, biomass production up to 6 × 1010 colony-forming units/ml (in the typical range of model lactobacilli), and pH-lowering capacities to a pH as low as 4.03 in common plant-based (coconut, soy, and oat) and cow milk beverages when cultured up to 72 h at 37°C. These properties were especially pronounced in coconut beverage and butter milk fermentations, and were sustained in co-culture with the model starter Streptococcus thermophilus. Furthermore, L. reuteri AMBV339 grown in laboratory media or in a coconut beverage survived in gastric juice and in a simulated gastrointestinal dialysis model with colon phase (GIDM-colon system) inoculated with fecal material from a healthy volunteer. Passive transport of L. reuteri AMBV339-produced riboflavin occurred in the small intestinal and colon stage of the GIDM system, and active transport via intestinal epithelial Caco-2 monolayers was also demonstrated. L. reuteri AMBV339 did not cause fecal microbiome perturbations in the GIDM-colon system and inhibited enteric bacterial pathogens in vitro. Taken together, our data suggests that L. reuteri AMBV339 represents a promising candidate to provide riboflavin fortification of plant-based and dairy foods, and has a high application potential in the human gastrointestinal tract.

Availability and Metabolic Fate of Olive Phenolic Alcohols Hydroxytyrosol and Tyrosol in the Human GI Tract Simulated by the In Vitro GIDM-Colon Model.

Hydroxytyrosol (HTyr) and tyrosol (Tyr) are the most well studied phenolic alcohols of olive oil and olive products demonstrating numerous and significant beneficial health effects. However, their activity in the human organism as food bioactives is strongly associated with their bioavailability and metabolism, while manifested through their metabolites. Nevertheless, there are limited studies investigating their biotransformation and mainly catabolism by gut microflora under a holistic interpretation close to the human organism. Thus, in the present study, the GastroIntestinal Dialysis (GIDM)-colon model, a continuous flow in vitro dialysis system mimicking physiological conditions during human gastrointestinal digestion, was used to explore the metabolism of HTyr and Tyr as pure compounds. The GIDM–colon model simulates absorption from the lumen to the mucosa, followed by the colon phase using pooled human fecal suspensions. Samples were collected at different time points and analyzed via LC–Orbitrap MS. An integrated approach combining Multivariate Data Analysis (MVA) and thorough dereplication procedures led to the identification of HTyr and Tyr metabolites in different phases (gastric, small intestine, and colon), yielding also valuable information about metabolites kinetics. To our knowledge, this is the first study reporting full spectrometric data of HTyr and Tyr metabolites along with possible transformation mechanisms in the GI tract.

Obesity influences the microbiotic biotransformation of chlorogenic acid

Obesity is a major public health problem. Gut microbiome dysbiosis has been associated with obesity, however, little is known on the effect of the dysbiosis on the microbiotic bio-transformation of xenobiotics. Fecal samples of lean (n = 9) and obese (n = 4) female volunteers were collected and characterized by 16 S rDNA gene sequencing. The microbiotic biotransformation of chlorogenic acid was studied using the collected fecal samples of lean and obese subjects in the colon stage of the gastro-intestinal dialysis model with colon stage (GIDM-Colon). The concentration of anaerobic bacteria was lower for all obese samples in comparison to the samples of the lean volunteers. Differences in gut microbiome composition and bacterial concentration were observed between the two populations. The obese gut microbiome presented a lower metabolic activity in comparison to the lean population. Chlorogenic acid was completely biotransformed after 24 h colonic dialysis in the lean population while it was still present in the obese population. Furthermore, 23 and 13 biotransformation products were identified in the lean and obese population, respectively; 11 unique biotransformation products from the caffeic, feruoylquinic and quinic acid pathways were identified in the lean population. The results confirm that changes in gut microbiota related to obesity are associated with differences in microbiotic biotransformation of xenobiotics and thus possibly influencing the activity, bioavailability and toxicity of orally administered xenobiotics and drugs.

In vitro gastrointestinal biotransformation and characterization of a Desmodium adscendens decoction: the first step in unravelling its behaviour in the human body.

The isolation and identification of the flavonoids present in a decoction of Desmodium adscendens was performed. In view of the oral use of the decoction, this work focused on the stability in gastrointestinal conditions and biotransformation by intestinal microflora in the colon of D-pinitol, vitexin and the flavonoid fraction of the decoction, as a first step in unravelling its behaviour in the human body. The freeze-dried decoction was first subjected to column chromatography. Subsequently an enriched flavonoid fraction, was separated by repeated semi-preparative high-performance liquid chromatography (HPLC) or by HPLC-SPE. The isolated compounds were elucidated by NMR. Biotransformation experiments were carried in an in vitro gastrointestinal dialysis model. The major flavonoids of a decoction of D. adscendens were characterized as vicenin-2, isoschaftoside, schaftoside, 2″-O-xylosylvitexin, 2″-O-pentosyl-C-hexosyl apigenin and a O-hexosyl-C-hexosyl apigenin, tentatively identified as 2″-O-glucosyl-vitexin. During their passage in the gastrointestinal dialysis model, vitexin and C-glycosides thereof were found to be stable. Only the O-glycosidic bonds of O-glycosides of vitexin or isovitexin were hydrolysed during the colonic phase. A D. adscendens decoction was found to be rich in vitexin and isovitexin glycosides from which vitexin and the C-glycosides thereof were found to be stable in the simulated gastrointestinal tract.

In Vitro and In Vivo Study of the Gastrointestinal Absorption and Metabolisation of Hymenocardine, a Cyclopeptide Alkaloid.

Hymenocardine is a cyclopeptide alkaloid present in the root bark of Hymenocardia acida. In traditional African medicine, the leaves and roots of this plant are used to treat malaria, and moderate in vitro antiplasmodial activity has been reported for hymenocardine. However, in view of its peptide-like nature, potential metabolisation after oral ingestion has to be taken into account when considering in vivo experiments. In this study, the stability and small intestinal absorption of hymenocardine was assessed using an in vitro gastrointestinal dialysis model. In addition, potential liver metabolisation was investigated in vitro by incubation with a human S9 fraction. Moreover, hymenocardine was administered to rats per os, and blood and urine samples were collected until 48 and 24 h after oral administration, respectively. All samples resulting from these three experiments were analyzed by LC-MS. Analysis of the dialysate and retentate, obtained from the gastrointestinal dialysis model, indicated that hymenocardine is absorbed unchanged from the gastrointestinal tract, at least in part. After S9 metabolisation, several metabolites of hymenocardine could be identified, the major ones being formed by the reduction and/or the loss of an N-methyl group. The in vivo study confirmed that hymenocardine is absorbed from the gastrointestinal tract unchanged, since it could be identified in both rat plasma and urine, together with hymenocardinol, its reduction product.

Development and Validation of an in vitro Experimental GastroIntestinal Dialysis Model with Colon Phase to Study the Availability and Colonic Metabolisation of Polyphenolic Compounds.

The biological effects of polyphenols depend on their mechanism of action in the body. This is affected by bioconversion by colon microbiota and absorption of colonic metabolites. We developed and validated an in vitro continuous flow dialysis model with colon phase (GastroIntestinal dialysis model with colon phase) to study the gastrointestinal metabolism and absorption of phenolic food constituents. Chlorogenic acid was used as model compound. The physiological conditions during gastrointestinal digestion were mimicked. A continuous flow dialysis system simulated the one-way absorption by passive diffusion from lumen to mucosa. The colon phase was developed using pooled faecal suspensions. Several methodological aspects including implementation of an anaerobic environment, adapted Wilkins Chalgren broth medium, 1.10(8) CFU/mL bacteria suspension as inoculum, pH adaptation to 5.8 and implementation of the dialysis system were conducted. Validation of the GastroIntestinal dialysis model with colon phase system showed a good recovery and precision (CV < 16 %). Availability of chlorogenic acid in the small intestinal phase (37 ± 3 %) of the GastroIntestinal dialysis model with colon phase is comparable with in vivo studies on ileostomy patients. In the colon phase, the human faecal microbiota deconjugated chlorogenic acid to caffeic acid, 3,4-dihydroxyphenyl propionic acid, 4-hydroxybenzoic acid, 3- or 4-hydroxyphenyl acetic acid, 2-methoxy-4-methylphenol and 3-phenylpropionic acid. The GastroIntestinal dialysis model with colon phase is a new, reliable gastrointestinal simulation system. It permits a fast and easy way to predict the availability of complex secondary metabolites, and to detect metabolites in an early stage after digestion. Isolation and identification of these metabolites may be used as references for in vivo bioavailability experiments and for investigating their bioactivity in in vitro experiments.

Study on Transport of Disopyramide into the Intestinal Lumen Aimed at Gastrointestinal Dialysis by Activated Charcoal in Rats

The characteristics of exsorption and/or excretion of disopyramide into the gastrointestinal lumen have been investigated after intravenous administration of the drug at doses of 10 and 30 mg kg-1 to rats by the in-situ single pass perfusion technique. Disopyramide was appreciably excreted into the bile where its levels were approximately ten-fold higher than those in the serum. The exsorption rate of disopyramide and mono-N-dealkyldisopyramide (MND) into the perfusate was increased with an increase in the serum level following an increase from 10 to 30 mg kg-1 in the dose of disopyramide. The average amounts of disopyramide exsorbed into the perfusate were 17.0 and 18.4% at the dose of 10 and 30 mg kg-1, respectively, whereas those of MND were less than 1% at both doses of disopyramide. Oral administration of activated charcoal reduced the serum disopyramide levels after intravenous administration of the drug (20 mg kg-1) compared with the control treatment. By oral administration of activated charcoal, t 1/2 and AUC were decreased to 89 and 82%, respectively, and Cltot was increased to 122% compared with the corresponding control treatment. Vd was not different between the treated rats and control rats. These results suggest that the oral administration of activated charcoal can enhance the clearance of disopyramide and MND from the blood.

Clinical effect of Xinqingning (新清宁) combined with low dose continuous gastrointestinal dialysis in treating uremia

To investigate the clinical effect of Xinqingning (XQN), a preparation of rhubarb, combined with low dose continuous gastrointestinal dialysis in treating uremia. Patients of uremia were divided into three groups at random, eighteen patients in the group A were treated with 1000 ml gastrointestinal dialysate (non-absorbed mannitol solution) orally 2-3 times a day, twenty patients in the group B treated with the same therapy as that in the group A, but combined with XQN 5-10 tablets 3 times per day and 19 patients in the group C treated by orally taken coated aldehyde oxystarch 5-10 g, 3 times a day. The therapeutic course for the three groups were 11 months. The changes in clinical manifestation, renal function, nutritional condition, and electrolytes before and after treatment were observed. After treatment, significant improvement was revealed in aspects of uremic symptoms, quality of life, nutritional condition, serum creatinine, urea nitrogen, serum phosphate, uric acid, CO2 combining power, creatine clearance, body weight and arm muscular circumference in the group A and B, as compared with those in the group C. In comparison of the group A and B, the group B showed a lower serum triglyceride and slower progression of chronic renal failure (CRF). All the criteria were not improved in the group C and with serum creatinine raised significantly. XQN combined low dose continuous gastrointestinal dialysis therapy was effective in definitely treating uremia, it provides a new therapeutic means of non-replacement therapy for CRF with uremia.

Influence of Activated Charcoal on the Disposition Kinetics of Methamphetamine Enantiomers in the Rat Following Intravenous Dosing

AbstractMethamphetamine (MAP) is a central nervous system stimulant that is widely abused by populations of several countries. There is no specific antidote for the treatment of an overdose. Activated charcoal administered orally has been used to enhance the systemic elimination of certain toxic substances via “gastrointestinal dialysis”. The results of in vitro studies have shown that MAP can be rapidly adsorbed from solution by activated charcoal. We have evaluated the effect of a single oral dose of activated charcoal on the disposition kinetics of MAP following a short iv infusion. Male Sprague–Dawley rats were given an oral dose of activated charcoal (Actidose-aqua, 1g/kg) 10min before a short iv infusion of racemic MAP; whereas the control group was given an equivalent volume of water. Enantiomers of MAP and metabolites in serum and urine were analyzed by an enantiomer-specific method which employed HPLC and detection of a fluorescent derivative. There were no differences in any of the disposition parameters between the two groups. Within each group, the clearance (CLS) of I-MAP was greater than that of d-MAP. However, there were no differences in the steady- state volume of distribution (VSS). The CLS (mL/(min kg)) and VSS (L/kg) values for I- and d-MAP in the control group were (mean ±SD): 55.8 ±20.4, 48.7 ±17.9, 2.64 ±1.16, and 2.90 ±1.36, respectively. The corresponding values in the charcoal-pretreated group were (mean ±SD): 57.4 ±23.4, 51.1 ±20.7, 2.79 ±1.32, and 2.98 ±1.47. These results suggest that oral activated charcoal does not enhance the elimination of MAP from the body.

Gastrointestinal dialysis of digoxin using cholestyramine.

The pharmacokinetic parameters of digoxin given intravenously (0.075 mg/kg) alone and following treatment with oral cholestyramine (8 gm in 50 ml water) were studied in rabbits. Pretreatment with cholestyramine produced a significant decrease in the serum concentration of digoxin and significantly enhances its systemic clearance as indicated by a statistically significant decrease in the area under the concentration-time curve (AUC), half time of elimination (t 1/2), and mean residence time (MRT). These findings indicate that the idea of gastrointestinal dialysis, known with activated charcoal, could be extended to ion-exchange resins that could be a potentially useful adjunctive measure in the management of drug overdose especially with commonly used drugs with a low therapeutic index like digoxin.

Potential pharmacodynamic effect of charcoal on theophylline neurotoxicity in normal rats

Previously, it has been found that repeated oral administration of activated charcoal (AC) to rats with renal failure markedly decreased the sensitivity of the CNS to the neurotoxic-convulsant effect of theophylline. The present study was designed to investigate whether this effect also occurs in normal rats. Normal rats received AC per os in either a single dose or in six doses every 8 h. Control animals received equal volumes of water. Two hours following the last AC dose, animals were infused IV with theophylline until the onset of maximal seizures. Although rats pretreated with repeated administrations of activated charcoal required a larger total theophylline dose to induce convulsions, the theophylline concentrations in the serum and brain at the onset of the neurotoxic episode were not affected by the charcoal pretreatment. It is, therefore, concluded that the gastrointestinal dialysis produced by the activated charcoal had no apparent effect on theophylline-induced neurotoxicity in normal rats.

Pharmacokinetic Simulation of the Effect of Multiple-Dose Activated Charcoal in Phenytoin Poisoning—Report of Two Pediatric Cases

Activated charcoal is commonly used to inhibit the absorption of phenytoin after acute overdose. There are also reports of multiple-dose activated charcoal (MDAC) increasing the clearance of phenytoin in adults. We describe our experience modeling phenytoin pharmacokinetics during therapy with MDAC in the treatment of two cases of acute phenytoin poisoning in children. After extensive attempts at modeling the serum phenytoin concentrations, simulations were performed to identify the possible consequences of MDAC administration. Phenytoin elimination was more rapid than was expected, based on previously reported phenytoin pharmacokinetic parameters. Moreover, the time to peak phenytoin concentration and time course of phenytoin intoxication appeared to be shorter than available reports of phenytoin intoxication treated with a single dose of activated charcoal. MDAC may prevent continued phenytoin absorption and increase phenytoin elimination rate via gastrointestinal dialysis. The effect of MDAC on the clearance of phenytoin can be described by a first-order elimination rate constant of approximately 0.02-0.04/h.

Repeated Oral Administration of Activated Charcoal for Treating Aspirin Overdose in Young Children

The data from our two patients indicates that gastrointestinal dialysis with repeated oral doses of activated charcoal may significantly enhance the elimination of overdoses of salicylate in young children. Limited experience precludes precise recommendations, but current evidence suggests that gastrointestinal dialysis should be evaluated further for treating pediatric salicylate intoxication.

Comparison of transport of procainamide and N-acetylprocainamide from blood into the intestinal lumen with that into the peritoneal cavity in rats.

Transfer of procainamide and its active metabolite, N-acetylprocainamide (NAPA) from the blood into the intestinal lumen was compared with that into the peritoneal cavity after i.v. administration of procainamide at the dose of 10 mg/kg to rats. The amounts of both drugs transferred from the blood into the intestinal lumen were much greater than those into the peritoneal cavity. The average amounts of procainamide transferred in 2 h into the intestinal lumen and the peritoneal cavity were 12.7% and 1.7% of dose (10 mg/kg), respectively, while those of NAPA were 3.5% and 1.4% of dose. The intestinal and peritoneal clearance values of procainamide were 143.5 and 59.4 ml/h, respectively, and those of NAPA were 32.6 and 13.5 ml/h. The difference in transfer rates across the intestinal and peritoneal membranes may be due to difference in the area of permeative surface and the extent of ionization in the dialysate. Consequently, it is expected that the gastrointestinal dialysis by oral administration of activated charcoal may serve as one of the more useful hemopurification methods than the peritoneal dialysis in procainamide and NAPA intoxication.

Magnesium toxicity secondary to catharsis during management of theophylline poisoning

Multiple doses of oral activated charcoal are used increasingly to promote elimination of toxins that have already reached the bloodstream; this is often referred to as gastrointestinal dialysis. Cathartics usually are used in conjunction to hasten transit of the charcoal-adsorbed toxin. In the present case, a regimen of activated charcoal and magnesium citrate was used to treat a patient with theophylline poisoning. It was effective in lowering the patient's serum theophylline concentration but produced an elevated magnesium level associated with decreased responsiveness, confusion, and diminished deep tendon reflexes. Magnesium citrate may not be the optimal cathartic for use in gastrointestinal dialysis, at least in selected patients. Sorbitol has been shown to produce a more rapid catharsis without disturbing magnesium serum concentrations. Therefore, the use of sorbitol in place of magnesium citrate, at least in selected patients, may be preferred.

Increased transport of theophylline into gastrointestinal lumen and gastrointestinal dialysis by activated charcoal in rats with hepatic cirrhosis.

The characteristics of exsorption and/or excretion of theophylline into the small intestinal lumen in rats with hepatic cirrhosis (HC rats) induced by carbon tetrachloride were investigated by an in situ single-pass perfusion technique. The serum concentrations of theophylline after i.v. administration of aminophylline (10 mg/kg) in the HC rats were significantly higher than those in normal rats during the experimental period. Moreover, the exsorption of theophylline from blood into the intestinal lumen was significantly increased in the HC rats compared with the normal rats. Treatments with oral activated charcoal reduced the serum theophylline levels in the HC rats. Consequently, gastrointestinal dialysis by oral administration of activated charcoal may be a useful method to remove poisonous drugs from the blood in patients with hepatic failure (including cirrhosis), which decreases the systemic clearance.

Stereoselective gastrointestinal clearance of disopyramide in rabbits treated with activated charcoal.

The ability of activated charcoal to enhance the drug elimination of two enantiomers, R- and S-disopyramide, was compared in rabbits. Orally administered activated charcoal significantly decreased the area under the serum concentration curve of R-disopyramide, whereas the same treatment had no effect on that of S-disopyramide. The difference could be explained by the difference in the hepatic extraction ratio of two enantiomers in rabbits. S-Disopyramide is a drug of high hepatic extraction ratio in rabbits and R-disopyramide is of intermediate hepatic extraction ratio. Equations were derived to illustrate the influence of the hepatic extraction ratio on the apparent gastrointestinal clearance. A higher hepatic extraction ratio decreases the apparent gastrointestinal clearance of a drug. This phenomenon may explain some unsuccessful experiments of gastrointestinal dialysis. When considering the use of activated charcoal to enhance systemic drug elimination, the hepatic extraction ratio of the drug should be included.

Transport of furosemide into the intestinal lumen and the lack of effect of gastrointestinal dialysis by charcoal in rats with acute renal failure.

The characteristics of exsorption and/or excretion of furosemide into the small intestinal lumen in rats with acute renal failure (ARF rat) were investigated by an in situ single-pass perfusion technique. The amount of furosemide, which was exsorbed into the intestinal lumen after an intravenous administration of the drug to rats was only very slight. The exsorption rate of the drug was significantly increased in ARF rats as compared with normal rats. The average amount of the drug exsorbed into the perfusate in normal rats was 0.83% of dose, whereas that in ARF rats was 1.83% of dose. The amounts of furosemide excreted into the bile in normal rats and ARF rats were 1.53% and 2.64%, respectively. The increased exsorption of furosemide in ARF rats appeared to be due primarily to the decreased binding of the drug to the serum protein, because only the unbound drug permeates through the intestinal membrane into the gastrointestinal (g.i.) tract, and, to some extent, to the increased nonrenal excretion caused by poor renal excretion. Oral activated charcoal had little effect on the serum furosemide levels after intravenous administration of the drug at a dose of 10 mg/kg in ARF rats. The lack of effect of activated charcoal on the elimination of the drug may be due to the small amount of the drug excreted into the g.i. tract.

Intravenous theophylline poisoning and multiple-dose charcoal in an animal model

Large overdoses of IV theophylline (50 to 100 mg/kg) were administered to five canines on two separate occasions. On day one, with no charcoal administered, theophylline levels were serially obtained between ten minutes and 12 hours after infusion and the animals were recovered from anesthesia. Three days later the same dose of theophylline was administered, but then 50 g activated charcoal was placed through a nasogastric tube into the duodenum every hour for eight doses. In all five animals tested, activated charcoal significantly decreased the area under the serum concentration-time curve, decreased the half-life of elimination, and increased the clearance of theophylline. This effect on pharmacokinetics was not seen when the nasogastric tube was put into the stomach instead of the small bowel because the charcoal administered did not pass beyond the pylorus. In a separate experiment in which bile theophylline concentrations were measured, it was demonstrated that enhanced elimination was not from interruption of enterohepatic circulation of theophylline. This suggests that the demonstrated physiologic mechanism is that of gastrointestinal dialysis.

Kinetics of Theophylline Clearance in Gastrointestinal Dialysis with Charcoal

The pharmacokinetic response of theophylline following the oral administration of activated charcoal was investigated in rabbits. Rabbits were continuously infused with a theophylline solution at a rate of 2.12mg/h. At the fourth hour of theophylline infusion, 20g of activated charcoal was administered by intubation to the rabbit (n=12). The concentration of theophylline in serum gradually decreased after the charcoal treatment. The magnitude of the change in theophylline concentration induced by charcoal varied among animals. By comparing the steady-state theophylline concentration in the control and treated animals, the total body clearance was found to increase from 94.4 ± 7.5 to 210 ± 27mL/h/kg (mean ± SE). The rate of change of theophylline concentration in serum following charcoal treatment was fitted with a simulation curve by assuming a stepwise increase in clearance immediately following the charcoal treatment. The results indicated that activated charcoal exerted its maximum effect in increasing theophylline clearance immediately after its administration.