A hybrid evaluation of the intestinal absorption performance of compounds from molecular structure.

Intestinal absorption of compounds is significant in drug research and development. To evaluate this efficiently, a method combining mathematical modeling and molecular simulation was proposed, from the perspective of molecular structure. Based on the quantitative structure-property relationship study, the model between molecular structure and their apparent permeability coefficients was successfully constructed and verified, predicting intestinal absorption of drugs and interpreting decisive structural factors, such as AlogP98, Hydrogen bond donor and Ellipsoidal volume. The molecules with strong lipophilicity, less hydrogen bond donors and receptors, and small molecular volume are more easily absorbed. Then, the molecular dynamics simulation and molecular docking were utilized to study the mechanism of differences in intestinal absorption of drugs and investigate the role of molecular structure. Results indicated that molecules with strong lipophilicity and small volume interacted with the membrane at a lower energy and were easier to penetrate the membrane. Likewise, they had weaker interaction with P-glycoprotein and were easier to escape from it and harder to export from the body. More in, less out, is the main reason these molecules absorb well.

Effects of Commonly used Surfactants, Poloxamer 188 and Tween 80, on the Drug Transport Capacity of Intestinal Glucose Transporters.

Some glycoside drugs can be transported through intestinal glucose transporters (IGTs). The surfactants used in oral drug preparations can affect the function of transporter proteins. This study aimed to investigate the effect of commonly used surfactants, Poloxamer 188 and Tween 80, on the drug transport capacity of IGTs. Previous studies have shown that gastrodin is the optimal drug substrate for IGTs. Gastrodin was used as a probe drug to evaluate the effect of these two surfactants on intestinal absorption in SD rats through pharmacokinetic and in situ single-pass intestinal perfusion. Then, the effects of the two surfactants on the expression of glucose transporters and tight-junction proteins were examined using RT-PCR and western blotting. Additionally, the effect of surfactants on intestinal permeability was evaluated through hematoxylin-eosin staining. The results found that all experimental for Poloxamer 188 (0.5%, 2.0% and 8.0%) and Tween 80 (0.1% and 2.0%) were not significantly different from those of the blank group. However, the AUC(0-∞) of gastrodin increased by approximately 32% when 0.5% Tween 80 was used. The changes in IGT expression correlated with the intestinal absorption of gastrodin. A significant increase in the expression of IGTs was observed at 0.5% Tween 80. In conclusion, Poloxamer 188 had minimal effect on the drug transport capacity of IGTs within the recommended limits of use. However, the expression of IGTs increased in response to 0.5% Tween 80, which significantly enhanced the drug transport capacity of IGTs. However, 0.1% and 2.0% Tween 80 had no significant effect.

Digestion and absorption characteristics of iron-chelating silver carp scale collagen peptide and insights into their chelation mechanism.

Iron deficiency is widespread throughout the world, supplementing sufficient iron or improving the bioavailability of iron is the fundamental strategy to solve the problem of iron scarcity. Herein, we explored a new form of iron supplement, iron chelates of silver carp scales (SCSCP-Fe) were prepared from collagen peptide of silver carp scales (SCSCP) and FeCl2·4H2O, the effects of external environment and simulated gastrointestinal digestive environment on the stability of SCSCP-Fe and the structural changes of peptide iron chelates during digestion were investigated. The results of in vitro iron absorption promotion showed that the iron bioavailability of SCSCP-Fe was higher than that of FeSO4. Two potential high iron chelating peptides DTSGGYDEY (DY) and LQGSNEIEIR (LR) were screened and synthesized from the SCSCP sequence by molecular dynamics and LC-MS/MS techniques. The FTIR results displayed that the binding sites of DY and LR for Fe2+ were the carboxyl group, the amino group, and the nitrogen atom on the amide group on the peptide. ITC results indicated that the chelation reactions of DY and LR with Fe2+ were mainly dominated by electrostatic interactions, forming chelates in stoichiometric ratios of 1:2 and 1:1, respectively. Both DY and LR had a certain ability to promote iron absorption. The transport of DY-Fe chelate may be a combination of the three pathways: PepT1 vector pathway, cell bypass, and endocytosis, while LR-Fe chelate was dominated by bivalent metal ion transporters. This study is expected to provide theoretical reference and technical support for the high-value utilization of silver carp scales and the development of novel iron supplements.

[Improvement of Intestinal and Transmucosal Absorption of Peptide and Protein Drugs].

It is well known that the oral bioavailability of hydrophilic and macromolecular drugs is generally very poor due to their poor membrane permeability characteristics. Among these poorly absorbed drugs, peptide and protein drugs are typical poorly absorbed drugs which have low stability and poor permeability in the gastrointestinal tract. Consequently, the clinical administration of peptide and protein drugs is presently limited to administration by injection. However, such frequent administration subjects the patients to considerable pain, and there is also the possibility of the manifestation of serious side effects. Therefore, various approaches have been examined to overcome the poor absorption characteristics of these drugs. These approaches include (1) to use additives including absorption enhancers and protease inhibitors, (2) to modify the chemical structure of peptide and protein drugs, and (3) to apply dosage forms to these drugs, (4) to develop a novel administration method for these drugs that can serve as an alternative to oral and injection administration. We demonstrated that intestinal and transmucosal absorption of peptide and protein drugs could be improved by using these approaches. These approaches may give us useful basic information to improve the intestinal and transmucosal absorption of peptide and protein drugs.

Development and validation of an LC-MS/MS method for the quantification of oral-sugar probes in plasma to test small intestinal permeability and absorptive capacity in the domestic cat (Felis catus).

A novel method for quantifying the concentration of lactulose, rhamnose, xylose, and 3-O-methylglucose (3-OMG) in cat plasma using liquid chromatography-mass spectrometry (LC-MS) was developed. Domestic male cats (n = 13) were orally dosed with a solution containing the four sugars to test the permeability and absorptive capacity of their intestinal barrier. Plasma samples were taken 3 h later and were prepared with acetonitrile (ACN), dried under N2, and reconstituted in 90 % ACN with 1 mM ammonium formate. Stable isotope labelled 13C standards for each analyte were used as internal standards. Chromatographic separation was conducted using a Phenomenex Luna NH2 column with a gradient elution system of deionized water and 90 % ACN with 1 mM ammonium formate at 300 µL/min for 13 min total analysis time. Recovery trials were conducted in triplicate over three days with RSD values (%) for each day ranging from 1.2 to 1.4 for lactulose, 5.4 - 6.0 for rhamnose, 3.3 - 5.5 for xylose, and 2.6 - 5.6 for 3-OMG. Inter-day variations for each analyte were not different (p > 0.05). Limit of detection and quantification were 0.2 and 0.7 µg/mL for lactulose, 0.8 and 2.4 µg/mL for rhamnose, 0.6 and 1.8 µg/mL for xylose, and 0.3 and 1.1 µg/mL for 3-OMG, respectively. Plasma sugar concentrations recovered from cats were above the limit of quantification and below the highest calibration standard, validating the use of this method to test intestinal permeability and absorptive capacity in cats.

Arsenite-Induced Drug-Drug Interactions in Rats.

Arsenite is an important heavy metal. Some Chinese traditional medicines contain significant amounts of arsenite. The aim of this study was to investigate subacute exposure of arsenite on activities of cytochrome P450 enzymes and pharmacokinetic behaviors of drugs in rats. Midazolam, tolbutamide, metoprolol, omeprazole, caffeine, and chlorzoxazone, the probe substrates for cytochrome P450 (CYP) s3A, 2C6, 2D, 2C11, 1A, and 2E, were selected as probe drugs for the pharmacokinetic study. Significant decreases in areas under the curves of probe substrates were observed in rats after consecutive 30-day exposure to As at 12 mg/kg. Microsomal incubation study showed that the subacute exposure to arsenite resulted in little change in effects on the activities of P450 enzymes examined. However, everted gut sac study demonstrated that such exposure induced significant decreases in intestinal absorption of these drugs by both passive diffusion and carrier-mediated transport. In addition, in vivo study showed that the arsenite exposure decreased the rate of peristaltic propulsion. The decreases in intestinal permeability of the probe drugs and peristaltic propulsion rate most likely resulted in the observed decreases in the internal exposure of the probe drugs. Exposure to arsenite may lead to the reduction of the efficiencies of pharmaceutical agents coadministered resulting from the observed drug-drug interactions. SIGNIFICANCE STATEMENT: Exposure to arsenite may lead to the reduction of the efficiencies of pharmaceutical agents coadministered resulting from the observed drug-drug interactions. The present study, we found that P450 enzyme probe drug exposure was reduced in arsenic-exposed animals (areas under the curve) and the intestinal absorption of the drug was reduced in the animals. Subacute arsenic exposure tends to cause damage to intestinal function, which leads to reduced drug absorption.

Hemoglobin Hydrolyzate Promotes Iron Absorption in the Small Intestine through Iron Binding Peptides.

Hemoglobin is an excellent source of iron supplements, and its hydrolyzate spontaneously binds iron during digestion and promotes iron absorption in vivo. However, the underlying mechanisms of what peptides bind and how they bind iron ions remain unclear. This study prepared the porcine hemoglobin hydrolyzate through enzymatic hydrolysis and acid treatment and investigated the mechanisms of hemoglobin hydrolyzate on iron absorption through the determination of iron levels in dietary intervention mice, iron binding site analyses, peptide digestion analyses, molecular simulation docking, and INT407 cell validation. The results showed that ingestion of the hemoglobin hydrolyzate diets increased iron levels in the blood of mice, accompanied by the upregulation of duodenal iron circulation-related genes such as ferritin, PCBP1, and HP. Carboxyl, imidazole groups, and aromatic amino acid residues were iron binding sites of hemoglobin hydrolyzate during digestion. VDEVGGEA and VDEVGGE were found to involve the spontaneous and efficient binding of hemoglobin hydrolyzate to iron ions in the intestinal cavity. In particular, the DEVGGE peptide was the typical sequence for hemoglobin hydrolytic peptides to exert iron binding activity.

In vitro gastrointestinal stability and intestinal absorption of ACE-1 and DPP4 inhibitory peptides from poultry by-product hydrolysates.

Bioactive peptides derived from food are promising health-promoting ingredients that can be used in functional foods and nutraceutical formulations. In addition to the potency towards the selected therapeutic target, the bioavailability of bioactive peptides is a major factor regarding clinical efficacy. We have previously shown that a low molecular weight peptide fraction (LMWPF) from poultry by-product hydrolysates possesses angiotensin-1-converting enzyme (ACE-1) and dipeptidyl-peptidase 4 (DPP4) inhibitory activities. The present study aimed to investigate the bioavailability of the bioactive peptides in the LMWPF. Prior to the investigation of bioavailability, a dipeptide YA was identified from this fraction as a dual inhibitor of ACE-1 and DPP4. Gastrointestinal (GI) stability and intestinal absorption of the bioactive peptides (i.e., YA as well as two previously reported bioactive dipeptides (VL and IY)) in the LMWPF were evaluated using the INFOGEST static in vitro digestion model and intestinal Caco-2 cell monolayer, respectively. Analysis of peptides after in vitro digestion confirmed that the dipeptides were resistant to the simulated GI conditions. After 4 hours of incubation, the concentration of the peptide from the apical side of the Caco-2 cell monolayer showed a significant decrease. However, the corresponding absorbed peptides were not detected on the basolateral side, suggesting that the peptides were not transported across the intestinal monolayer but rather taken up or metabolized by the Caco2 cells. Furthermore, when analyzing the gene expression of the Caco-2 cells upon peptide stimulation, a down-regulation of peptide transporters, the transcription factor CDX2, and the tight junction protein-1 (TJP1) was observed, suggesting the specific effects of the peptides on the Caco-2 cells. The study demonstrated that bioactive dipeptides found in the LMWPF were stable through in vitro GI digestion; however, the overall bioavailability may be hindered by inadequate uptake across the intestinal barrier.

The manganese transporter SLC39A8 links alkaline ceramidase 1 to inflammatory bowel disease.

The metal ion transporter SLC39A8 is associated with physiological traits and diseases, including blood manganese (Mn) levels and inflammatory bowel diseases (IBD). The mechanisms by which SLC39A8 controls Mn homeostasis and epithelial integrity remain elusive. Here, we generate Slc39a8 intestinal epithelial cell-specific-knockout (Slc39a8-IEC KO) mice, which display markedly decreased Mn levels in blood and most organs. Radiotracer studies reveal impaired intestinal absorption of dietary Mn in Slc39a8-IEC KO mice. SLC39A8 is localized to the apical membrane and mediates 54Mn uptake in intestinal organoid monolayer cultures. Unbiased transcriptomic analysis identifies alkaline ceramidase 1 (ACER1), a key enzyme in sphingolipid metabolism, as a potential therapeutic target for SLC39A8-associated IBDs. Importantly, treatment with an ACER1 inhibitor attenuates colitis in Slc39a8-IEC KO mice by remedying barrier dysfunction. Our results highlight the essential roles of SLC39A8 in intestinal Mn absorption and epithelial integrity and offer a therapeutic target for IBD associated with impaired Mn homeostasis.

2-Monoacylglycerol Mimetic Liposomes to Promote Intestinal Lymphatic Transport for Improving Oral Bioavailability of Dihydroartemisinin.

Purpose: Reducing the first-pass hepatic effect via intestinal lymphatic transport is an effective way to increase the oral absorption of drugs. 2-Monoacylglycerol (2-MAG) as a primary digestive product of dietary lipids triglyceride, can be assembled in chylomicrons and then transported from the intestine into the lymphatic system. Herein, we propose a biomimetic strategy and report a 2-MAG mimetic nanocarrier to target the intestinal lymphatic system via the lipid absorption pathway and improve oral bioavailability. Methods: The 2-MAG mimetic liposomes were designed by covalently bonding serinol (SER) on the surface of liposomes named SER-LPs to simulate the structure of 2-MAG. Dihydroartemisinin (DHA) was chosen as the model drug because of its disadvantages such as poor solubility and high first-pass effect. The endocytosis and exocytosis mechanisms were investigated in Caco-2 cells and Caco-2 cell monolayers. The capacity of intestinal lymphatic transport was evaluated by ex vivo biodistribution and in vivo pharmacokinetic experiments. Results: DHA loaded SER-LPs (SER-LPs-DHA) had a particle size of 70 nm and a desirable entrapment efficiency of 93%. SER-LPs showed sustained release for DHA in the simulated gastrointestinal environment. In vitro cell studies demonstrated that the cellular uptake of SER-LPs primarily relied on the caveolae- rather than clathrin-mediated endocytosis pathway and preferred to integrate into the chylomicron assembly process through the endoplasmic reticulum/Golgi apparatus route. After oral administration, SER-LPs efficiently promoted drug accumulation in mesenteric lymphatic nodes. The oral bioavailability of DHA from SER-LPs was 10.40-fold and 1.17-fold larger than that of free DHA and unmodified liposomes at the same dose, respectively. Conclusion: SER-LPs improved oral bioavailability through efficient intestinal lymphatic transport. These findings of the current study provide a good alternative strategy for oral delivery of drugs with high first-pass hepatic metabolism.

Impact of resistant starch: Absorption of dietary minerals, glycemic index and oxidative stress in healthy rats.

BACKGROUND & AIMS: Resistant starch (RS) is a prebiotic fiber that has been scientifically shown to control the development of obesity. Prebiotic role of RS has also seen to be very important as it helps gut bacteria to regulate fermentation and fatty acid production. This study aimed to check the different levels of RS on glycemic index, oxidative stress and mineral absorption rate in healthy rat models. To evaluate these objectives, the trial was conducted for 40 days of follow up; 10 days were the adjustment period and the collection period over 30 days. METHODS: Thirty-six healthy female Wistar rats were divided into 4 groups of (9 animals each) NC (Normal Control: without resistant starch), RS0.20 (resistant starch: 0.20 g/kg body weight), RS0.30 (resistant starch: 0.30 g/kg body weight), RS0.40 (resistant starch: 0.40 g/kg body weight). All the diets were isocaloric and isonitroginous. RESULTS: The impact of different levels of RS on the dry-matter intake (DMI) presented statistically significant results (p ≤ 0.05): DMI was reduced in RS (0.02) fed rats as compared to NC rats in first 3 weeks; and after 4th and 5th weeks, there was a DMI reduction of 28% in RS (0.04) fed rats. Moreover, there was no significant increase in the nutrient intake in all RS diets. The dry-matter (DM) digestibility was statistically significantly (P ≤ 0·05), which increased in all rats fed with different level of RS. The weight loss showed statistically significant results: RS (0.04) exhibited 19 g reduction in weight as compared with NC rats. Significant increase was observed in total oxidant status (TOS), in all the RS fed rats when compared with NC rats. The levels of Mg, Ca, Fe and Zn were shown to be decrease in feces analysis, which proves their better absorbance in gut. Statistically significant increase was observed in antioxidant capacity, whereas significant decrease was observed in the total weight of the animals, showing the role of RS in controlling obesity. CONCLUSIONS: Overall, significant results were found in all dosage level of RS but long term administration of the higher dosage level (RS0.40) may need to be studied for enhanced results. RS can help improve insulin sensitivity in overweight adults.

Effects of Three Kinds of Carbohydrate Pharmaceutical Excipients-Fructose, Lactose and Arabic Gum on Intestinal Absorption of Gastrodin through Glucose Transport Pathway in Rats.

BACKGROUND: Some glucoside drugs can be transported via intestinal glucose transporters (IGTs), and the presence of carbohydrate excipients in pharmaceutical formulations may influence the absorption of them. This study, using gastrodin as probe drug, aimed to explore the effects of fructose, lactose, and arabic gum on intestinal drug absorption mediated by the glucose transport pathway. METHODS: The influence of fructose, lactose, and arabic gum on gastrodin absorption was assessed via pharmacokinetic experiments and single-pass intestinal perfusion. The expression of sodium-dependent glucose transporter 1 (SGLT1) and sodium-independent glucose transporter 2 (GLUT2) was quantified via RT‒qPCR and western blotting. Alterations in rat intestinal permeability were evaluated through H&E staining, RT‒qPCR, and immunohistochemistry. RESULTS: Fructose reduced the area under the curve (AUC) and peak concentration (Cmax) of gastrodin by 42.7% and 63.71%, respectively (P < 0.05), and decreased the effective permeability coefficient (Peff) in the duodenum and jejunum by 58.1% and 49.2%, respectively (P < 0.05). SGLT1 and GLUT2 expression and intestinal permeability remained unchanged. Lactose enhanced the AUC and Cmax of gastrodin by 31.5% and 65.8%, respectively (P < 0.05), and increased the Peff in the duodenum and jejunum by 33.7% and 26.1%, respectively (P < 0.05). SGLT1 and GLUT2 levels did not significantly differ, intestinal permeability increased. Arabic gum had no notable effect on pharmacokinetic parameters, SGLT1 or GLUT2 expression, or intestinal permeability. CONCLUSION: Fructose, lactose, and arabic gum differentially affect intestinal drug absorption through the glucose transport pathway. Fructose competitively inhibited drug absorption, while lactose may enhance absorption by increasing intestinal permeability. Arabic gum had no significant influence.

Qualification of In Vitro Dissolution Absorption System 2 (IDAS2) with Caco-2 and MDCK Cell Monolayers: Dose Sensitivity Study Using BCS Class I and III Drugs.

This study aimed to validate the In vitro Dissolution Absorption System 2 (IDAS2) containing a biological barrier of Caco-2 or Madin-Darby canine kidney (MDCK) cell monolayer through dose sensitivity studies. Metoprolol and propranolol were selected as Biopharmaceutics Classification System (BCS) Class I model drugs, and atenolol as a Class III model drug. The IDAS2 is comprised of a dissolution vessel (500 mL) and two permeation chambers (2 × 8.0 mL) mounted with Caco-2 or MDCK cell monolayer. One or two immediate-release tablet(s) of the model drug were added to the dissolution vessel, and the time profiles of dissolution and permeation were observed. Greater than 85% of metoprolol and propranolol (tested at two dosing concentrations) were dissolved by 15 min, and all drugs were fully dissolved by 30 min. All three drugs were more permeable across Caco-2 cells than MDCK cells with a linear increase in permeation across both cells at both dose concentrations. Thus, the dose sensitivity of the IDAS2 was demonstrated using both cell barriers. These results indicate a successful qualification of IDAS2 for the development/optimization of oral formulations and that MDCK cells can be utilized as a surrogate for Caco-2 cells.

Whey Protein Sodium-Caseinate as a Deliverable Vector for EGCG: In Vitro Optimization of Its Bioaccessibility, Bioavailability, and Bioactivity Mode of Actions.

Epigallocatechin gallate (EGCG), the principal catechin in green tea, exhibits diverse therapeutic properties. However, its clinical efficacy is hindered by poor stability and low bioavailability. This study investigated solid particle-in-oil-in-water (S/O/W) emulsions stabilized by whey protein isolate (WPI) and sodium caseinate (NaCas) as carriers to enhance the bioavailability and intestinal absorption of EGCG. Molecular docking revealed binding interactions between EGCG and these macromolecules. The WPI- and NaCas-stabilized emulsions exhibited high encapsulation efficiencies (>80%) and significantly enhanced the bioaccessibility of EGCG by 64% compared to free EGCG after simulated gastrointestinal digestion. Notably, the NaCas emulsion facilitated higher intestinal permeability of EGCG across Caco-2 monolayers, attributed to the strong intermolecular interactions between caseins and EGCG. Furthermore, the emulsions protected Caco-2 cells against oxidative stress by suppressing intracellular reactive oxygen species generation. These findings demonstrate the potential of WPI- and NaCas-stabilized emulsions as effective delivery systems to improve the bioavailability, stability, and bioactivity of polyphenols like EGCG, enabling their applications in functional foods and nutraceuticals.

Ultrasound-assisted extraction of bioactive compounds from goji berries: Optimization, bioactivity, and intestinal permeability assessment.

Lycium barbarum L. berries have a remarkable chemical composition and extensive biological activities, being a valuable component of health and nutraceutical practices. Nevertheless, a deep insight on the intestinal permeation of the pro-healthy bioactive compounds is urgently needed to predict the real effects on human body. This study attempted, for the first time, to optimize the Ultrasound-Assisted Extraction (UAE) of goji berries using a Response Surface Methodology approach and establish the intestinal permeation of the principal pro-healthy compounds. The optimal extraction conditions were a solid:liquid ratio of 8.75 % for 56.21 min, using an intensity of 59.05 W/m2. The optimal extract displayed a remarkable antioxidant capacity, with LC/DAD-ESI-MS analysis unveiled a diverse phytochemical profile, encompassing different compounds (e.g. glu-lycibarbarspermidine F, 2-glu-kukoamine, rutin, 3,5-dicaffeoylquinic acid). The intestinal co-culture model demonstrated that glu-lycibarbarspermidine F (isomer 2) (73.70 %), 3,5-dicaffeoylquinic acid (52.66 %), and isorhamnetin-3-O-rutinoside (49.31 %) traversed the intestinal cell layer, exerting beneficial health-promoting effects.

Assessing seromuscular layer and serosa removal on intestinal permeability measurements in weaned piglet everted sac segments.

The integrity of the intestinal barrier is crucial for regulating the passage of pathogens and toxins, while facilitating nutrient absorption. The everted gut sac technique, an ex-vivo technique, can be used to study interventions on barrier function. This cost-effective approach utilizes relatively large gut segments to study specific intestinal regions. Typically, intact (non-stripped) intestinal segments are used, but their use may underestimate permeability due to the medial positioning of blood vessels relative to the seromuscular layer and serosa. However, removing these layers risks physical damage, resulting in an overestimation of intestinal permeability. Therefore, we investigated the impact of stripping jejunal segments on permeability to fluorescein isothiocyanate-dextran (FITC, 4 kDa) and tetramethylrhodamine isothiocyanate-dextran (TRITC, 40 kDa), and on the absorption of glucose, lysine, and methionine in jejunal segments from 80 piglets at 8 d postweaning. Piglets were subjected to either high or low sanitary housing conditions and diets provoking intestinal protein fermentation or not, expected to influence intestinal permeability. Stripping of the seromuscular layer and serosa increased the passage of 4 kDa FITC-dextran (stripped vs. non-stripped; 1.1 vs. 0.9 pmol/cm2/min, P < 0.001), glucose (40.0 vs. 19.1 pmol/cm2/min, P < 0.001), lysine (2.5 vs. 2.0 nmol/cm2/min, P < 0.001), and methionine (4.1 vs. 2.7 pmol/cm2/min, P < 0.001). As permeability increased, the differences in methionine passage between stripped and non-stripped intestinal segments also increased (slope = 1.30, P = 0.009). The coefficients of variation were comparable between stripped and non-stripped intestines (over all treatments, stripped vs. non-stripped 38% vs. 40%). Stripping, by isolating mucosal processes without introducing additional variation, is thus recommended for studies on intestinal permeability or absorption.

The intestinal barrier is vital for nutrient passage, while impeding pathogen and toxin translocation. The everted gut sac technique is used to study intestinal permeability, incubating an isolated, everted, intestinal segment filled with buffer solution in a medium containing the substances of interest. After incubation, the translocation of the substances into the created intestinal sac can be measured. Typically, intact intestinal segments are used, but under physiological conditions, nutrients do not need to pass the seromuscular layer and serosa to enter the blood flow. Therefore, removing these layers may be preferable, but, on the other hand, also risks physical damage. This study compared the use of non-stripped vs. stripped intestinal segments. Permeability to two markers (FITC-dextran, 4kDa and TRITC-dextran, 40 kDa), and absorption of glucose, lysine, and methionine were measured in non-stripped and stripped jejunal segments obtained from 80 piglets at 8 d postweaning. The piglets were housed under different hygiene and dietary conditions, which were anticipated to alter intestinal permeability. Stripping the seromuscular layer and serosa increased the passage of FITC-dextran, glucose, lysine, and methionine, without reducing assay precision due to physical damage. Thus, removal of the seromuscular layer and serosa is preferred for studying intestinal permeability or absorption.

In Vitro Digestion-In Situ Absorption Setup Employing a Physiologically Relevant Value of the Membrane Surface Area/Volume Ratio for Evaluating Performance of Lipid-Based Formulations: A Comparative Study with an In Vitro Digestion-Permeation Model.

The aim of this study is to establish and test an in vitro digestion-in situ absorption model that can mimic in vivo drug flux by employing a physiologically relevant value of the membrane surface area (S)/volume (V) ratio for accurate prediction of oral drug absorption from lipid-based formulations (LBFs). Three different types of LBFs (Type IIIA-MC, Type IIIA-LC, and Type IV) loaded with cinnarizine (CNZ), a lipophilic weak base with borderline permeability, and a control suspension were prepared. Subsequently, a simultaneous in vitro digestion-permeation experiment was conducted using a side-by-side diffusion cell with a dialysis membrane having a low S/V value. During digestion, CNZ partially precipitated for Type IV, while it remained solubilized in the aqueous phase for Type IIIA-MC and Type IIIA-LC in the donor compartment. However, in vitro drug fluxes for Type IIIA-MC and Type IIIA-LC were lower than those for Type IV due to the reduced free fraction of CNZ in the donor compartment. In pharmacokinetic studies, a similar improvement in in vivo oral exposure relative to suspension was observed, regardless of the LBFs used. Consequently, a poor correlation was found between in vitro permeation and areas under the plasma concentration-time curve (AUCoral) (R2 = 0.087). A luminal concentration measurement study revealed that this discrepancy was attributed to the extremely high absorption rate of CNZ in the gastrointestinal tract compared to that across a dialysis membrane evaluated by the in vitro digestion-permeation model, i.e., the absorption of CNZ in vivo was completed regardless of the extent of the free fraction, owing to the rapid removal of CNZ from the intestine. Subsequently, we aimed to predict the oral absorption of CNZ from the same formulations using a model that demonstrated high drug flux by employing the physiologically relevant S/V value and rat jejunum segment as an absorption sink (for replicating in vivo intestinal permeability). Predigested formulations were injected into the rat intestinal loop, and AUCloop values were calculated from the plasma concentration-time profiles. A better correlation was found between AUCloop and AUCoral (R2 = 0.72), although AUCloop underestimated AUCoral for Type IV due to the precipitation of CNZ during the predigestion process. However, this result indicated the importance of mimicking the in vivo drug absorption rate in the predictive model. The method presented herein is valuable for the development of LBFs.

Effect of knocking out mouse Slc44a4 on colonic uptake of the microbiota-generated thiamine pyrophosphate and colon physiology.

Humans and mammals obtain vitamin B1 from dietary and gut microbiota sources. A considerable amount of the microbiota-generated vitamin exists in the form of thiamine pyrophosphate (TPP), and colonocytes are capable of absorbing TPP via a specific carrier-mediated process that involves the colonic TPP transporter (cTPPT encoded by SLC44A4). Little is known about the relative contribution of the SLC44A4 transporter toward total colonic carrier-mediated TPP uptake and its role in colon physiology. To address these issues, we generated an Slc44a4 knockout (KO) mouse model (by Cre-Lox recombination) and found a near-complete inhibition in colonic carrier-mediated [3H]TPP uptake in the Slc44a4 KO compared with wild-type (WT) littermates. We also observed a significant reduction in KO mice's body weight and a shortening of their colon compared with WT. Using RNAseq and Ingenuity pathway analysis (IPA) approaches, we found that knocking out the colonic Slc44a4 led to changes in the level of expression of many genes, including upregulation in those associated with intestinal inflammation and colitis. Finally, we found that the Slc44a4 KO mice were more susceptible to the effect of the colitogenic dextran sodium sulfate (DSS) compared with WT animals, a finding that lends support to the recent prediction by multiple genome-wide association studies (GWAS) that SLC44A4 is a possible colitis susceptibility gene. In summary, the results of these investigations show that Slc44a4 is the predominant or only transporter involved in the colonic uptake of TPP, that the transporter is important for colon physiology, and that its deletion increases susceptibility to inflammation.NEW & NOTEWORTHY This study shows that Slc44a4 is the predominant or only transport system involved in the uptake of the gut microbiota-generated thiamine pyrophosphate (TPP) in the colon and that its deletion affects colon physiology and increases its susceptibility to inflammation.

On the processes limiting oral drug absorption when amorphous solid dispersions are administered after a high-calorie, high-fat meal: Sporanox® pellets.

OBJECTIVES: 1) Identify processes limiting the arrival of itraconazole at the intestinal epithelium when Sporanox® amorphous solid dispersion (ASD) pellets are transferred from the stomach through the upper small intestine, after a high-calorie, high-fat meal. 2) Evaluate whether itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine are useful for the assessment of dose effects in the fed state and food effects on plasma levels. METHODS: Itraconazole concentrations, apparent viscosity, and solubilization capacity were measured in aspirates from the upper gastrointestinal lumen collected during a recently performed clinical study in healthy adults. Published itraconazole concentrations in plasma, after a high-calorie high-fat meal and Sporanox® ASD pellets, and in contents of the upper small intestine of healthy adults, after administration of Sporanox® ASD pellets in the fasted state, were used to achieve the second objective. RESULTS: When Sporanox® ASD pellets (up to 200 mg) are transferred from the stomach through the upper small intestine, after a high-calorie, high-fat meal, itraconazole concentrations in the colloidal phase or the micellar phase of aqueous contents of the upper small intestine are unsaturated, in most cases. During the first 3 h post-dosing after a high-calorie, high-fat meal, the impact of dose (200 mg vs. 100 mg) on itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine seems to underestimate the impact of dose on plasma levels. When Sporanox® ASD pellets are administered after a high-calorie, high-fat meal at the 200 mg dose level, itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine are, on average, lower than those achieved in fasted state. CONCLUSIONS: When Sporanox® ASD pellets are transferred from the stomach to the upper small intestine after a high-calorie, high-fat meal, itraconazole's arrival at the intestinal epithelium seems to be limited by its arrival at the colloidal phase of aqueous contents of the upper small intestine. The impact of dose (100 mg vs. 200 mg) on plasma levels after a high-calorie, high-fat meal and during the gastrointestinal transfer of Sporanox® pellets requires consideration of pre-systemic itraconazole metabolism. At the 200 mg dose level, after taking into consideration differences in the volume of the contents of the upper small intestine between the fasted and the fed state during the gastrointestinal transfer of Sporanox® ASD pellets, itraconazole concentrations in the colloidal phase of aqueous contents of the upper small intestine suggest a mild negative food effect on average plasma levels; published clinical data are inconclusive.

P-gp inhibition and enhanced oral bioavailability of amikacin Sulfate: A novel approach using Thiolated Chito-PEGylated Lipidic Hybrids.

This study aimed to develop oral lipidic hybrids of amikacin sulfate (AMK), incorporating thiolated chitosan as a P-glycoprotein (P-gp) inhibitor to enhance intestinal absorptivity and bioavailability. Three formulations were designed: PEGylated Liposomes, Chitosan-functionalized PEGylated (Chito-PEGylated) Lipidic Hybrids, and Thiolated Chito-PEGylated Lipidic Hybrids. The physical characteristics of nanovesicles were assessed. Ex-vivo permeation and confocal laser scanning microscopy (CLSM) studies were conducted to evaluate the formulations' potential to enhance AMK intestinal permeability. In-vivo pharmacokinetic studies in rats and histological/biochemical investigations assessed the safety profile and oral bioavailability. The AMK-loaded Thiolated Chito-PEGylated Lipidic Hybrids exhibited favorable physical characteristics, higher ex-vivo permeation parameters, and verified P-gp inhibition via CLSM. They demonstrated heightened oral bioavailability (68.62% absolute bioavailability) and a sufficient safety profile. Relative bioavailability was significantly higher (1556.3% and 448.79%) compared to PEGylated Liposomes and Chito-PEGylated Lipidic Hybrids, respectively, indicating remarkable oral AMK delivery with fewer doses, reduced side effects, and enhanced patient compliance.