Mechanism Of Intestinal Absorption Research Articles

Mechanism of Intestinal Epithelial Absorption and Electrophysiological Regulation of the Shrimp Peptide QMDDQ.

We investigated the absorption mechanism of the shrimp peptide QMDDQ in small intestines, explored its physiological function in inhibiting neuronal hyperactivity, and verified its entry into the brain in vivo to display functional activity. The everted rat sac model and a Caco-2 paracellular absorption monolayer model were used, indicating that QMDDQ has a good absorption capacity with an apparent permeability coefficient (Papp) > 1 × 10-6 cm/s and the absorption of QMDDQ was concentration-dependent. When the concentration of QMDDQ was 1 mM and the transport time was 180 min, the highest absorption concentration of QMDDQ was 41.17 ± 3.48 μM (P < 0.05). The myosin light-chain kinase (MLCK)-specific inhibitor ML-7 and activator MPA, Western blotting, and immunofluorescence results showed that QMDDQ absorption takes place by mediating the MLCK-p-MLCK-MLC signaling pathway, reversibly opening the zonula occludens-1 (ZO-1), occludin in tight junctions (TJs), upregulating claudin-2 expression, and reaching targets through blood to inhibit neuronal overactivity. Results of fluorescence imaging in vivo verified that QMDDQ could enter the brain 4 h after oral administration. The results provide a theoretical foundation for the mechanism of paracellular absorption of active peptides and a starting point for the development of functional foods for Alzheimer's disease intervention.

Three-Dimensional Scaffolds for Intestinal Cell Culture: Fabrication, Utilization, and Prospects.

The intestine is a visceral organ that integrates absorption, metabolism, and immunity, which is vulnerable to external stimulus. Researchers in the fields such as food science, immunology, and pharmacology have committed to developing appropriate in vitro intestinal cell models to study the intestinal absorption and metabolism mechanisms of various nutrients and drugs, or pathogenesis of intestinal diseases. In the past three decades, the intestinal cell models have undergone a significant transformation from conventional two-dimensional cultures to three-dimensional (3D) systems, and the achievements of 3D cell culture have been greatly contributed by the fabrication of different scaffolds. In this review, we first introduce the developing trend of existing intestinal models. Then, four types of scaffolds, including Transwell, hydrogel, tubular scaffolds, and intestine-on-a-chip, are discussed for their 3D structure, composition, advantages, and limitations in the establishment of intestinal cell models. Excitingly, some of the in vitro intestinal cell models based on these scaffolds could successfully mimic the 3D structure, microenvironment, mechanical peristalsis, fluid system, signaling gradients, or other important aspects of the original human intestine. Furthermore, we discuss the potential applications of the intestinal cell models in drug screening, disease modeling, and even regenerative repair of intestinal tissues. This review presents an overview of state-of-the-art scaffold-based cell models within the context of intestines, and highlights their major advances and applications contributing to a better knowledge of intestinal diseases. Impact statement The intestine tract is crucial in the absorption and metabolism of nutrients and drugs, as well as immune responses against external pathogens or antigens in a complex microenvironment. The appropriate experimental cell model in vitro is needed for in-depth studies of intestines, due to the limitation of animal models in dynamic control and real-time assessment of key intestinal physiological and pathological processes, as well as the "R" principles in laboratory animal experiments. Three-dimensional (3D) scaffold-based cell cultivation has become a developing tendency because of the superior cell proliferation and differentiation and more physiologically relevant environment supported by the customized 3D scaffolds. In this review, we summarize four types of up-to-date 3D cell culture scaffolds fabricated by various materials and techniques for a better recapitulation of some essential physiological and functional characteristics of original intestines compared to conventional cell models. These emerging 3D intestinal models have shown promising results in not only evaluating the pharmacokinetic characteristics, security, and effectiveness of drugs, but also studying the pathological mechanisms of intestinal diseases at cellular and molecular levels. Importantly, the weakness of the representative 3D models for intestines is also discussed.

Comparison of Ussing Chamber and Caco-2 Model in Evaluation of Intestinal Absorption Mechanism of Compounds from Different BCS Classifications.

Oral bioavailability (F), which is evaluated by permeability and solubility, is one of the key parameters in drug discovery. Currently, Caco-2 and Ussing chamber are both used in the study of intestinal permeability of drugs at different stages of drug development. However, comparative research between the Ussing chamber and Caco-2 for predicting the intestinal availability data (Fa×Fg) in humans has not been reported. In the present study, we evaluated the permeability of 22 drugs in rat intestines by Ussing chamber and compared them with the reported permeability data from Caco-2. In addition, the active transport of gabapentin was evaluated by Ussing Chamber. Intestine segments were selected by corresponding absorption site for Ussing chamber analysis. BCS Class I and II compounds were more absorbed in the duodenum and jejunum, and Class III and IV compounds were more absorbed in the ileum. Papp values in the Caco-2 model were moderately correlated with human Fa×Fg (R2=0.722), and the Papp of the rat in the Ussing chamber revealed a better correlation with human Fa×Fg (R2=0.952). In addition, we also used the Ussing chamber to identify the transporter of gabapentin, and the results showed that the active absorption of gabapentin was related to LAT1. Ussing chamber combined with rat intestinal tissue would be a significant tool for predicting the intestinal absorption and metabolism of compounds with diverse physiochemical characteristics.

Screening of anti-functional dyspepsia compounds in Cynanchum auriculatum: A spectrum-effect relationship analysis, and ATP-binding cassette transporters inhibitor evaluation

Ethnopharmacological relevanceFunctional dyspepsia (FD) is a disorder caused by abnormal gut–brain axis regulation and is highly prevalent in China. Cynanchum auriculatum (CA) is often used to treat FD in the ethnic minority areas of Guizhou. Although several CA-based products are currently available in the market, it is unclear which components of CA are efficacious and what their oral absorption mechanism is. Aim of the studyThis study aimed to screen anti-FD components of CA based on the spectrum-effect relationship. In addition, the study evaluated the intestinal absorption mechanism of these components using transporter inhibitors. Materials and methodsThe fingerprinting of compounds from CA extract and plasma after oral administration was conducted using ultra-high-performance liquid chromatography quadrupole-time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS). The intestinal contractile parameters were then measured in vitro using the BL-420F Biofunctional Experiment System. Multivariate statistical analysis of the result of spectrum-effect relationship assessment was used to elucidate the correlation between prominent peaks of CA-containing plasma and intestinal contractile activity. The effect of ATP-binding cassette (ABC) transporter inhibitors, such as the P-gp inhibitor verapamil, the MRR inhibitor indomethacin, and the BCRP inhibitor Ko143, on the directional transport of the predicted active ingredients was assessed in vivo. ResultsTwenty chromatographic peaks were identified in the CA extract. Of these, three were C21 steroids, four were organic acids, and one was a coumarin, and acetophenone by comparing with reference compounds. Additionally, it is discovered that there are totally 39 migratory components in CA-containing plasma, which was found to significantly promote the contractility of the isolated duodenum. Moreover, multivariate analysis of the spectrum-effect relationship demonstrated that 16 characteristic peaks (3, 6, 8, 10, 11, 13, 14, 18, 21, m1–m4, m7, m15, and m24) in CA-containing plasma were significantly associated with the anti-FD effect. These compounds included seven prototype compounds, i.e., cynanoneside A, syringic acid, deacylmetaplexigenin, ferulic acid, scopoletin, baishouwubenzophenone, and qingyangshengenin. The inhibition of ABC transporters demonstrated that the inhibitors verapamil and Ko143 significantly increased (P < 0.05) the uptake of scopoletin and qingyangshengenin. Thus, these compounds may be substrates for P-gp and BCRP. ConclusionsThe potential anti-FD components of CA and the effect of ABC transporter inhibitors on these active components were preliminarily clarified. These findings lay a foundation for subsequent in vivo studies.

Development of active jejunal glucose absorption in broiler chickens

Growth in chickens, especially meat-type chickens (broilers), is extremely rapid, but studies on the regulatory mechanism of intestinal glucose absorption with growth are few, contradictory, and unclear. Here, we investigated the regulation of intestinal glucose absorption with growth in broiler chickens using oral glucose gavage, intestinal Evans blue transit, intestinal glucose absorption, scanning electron microscopy, and glucose absorption- and cell junction-related gene expression analyses. Peak blood glucose levels after oral glucose gavage occurred at 10 and 50 min in chickens at 1 wk (C1W) and 5 wk (C5W) of age, respectively. The area under the curve for glucose levels was greater for the C5W than the C1W (P=0.035). The stain ratio in the small intestine in the C5W was lower than that in the C1W (P=0.01), but there were no differences in the tissue regions stained with Evans blue and the migration distance of Evans blue from Meckel's diverticulum. In everted sac and Ussing chamber experiments, we observed reduced intestinal glucose uptake and electrogenic glucose absorption in the jejunum of the C5W. Phloridzin, an inhibitor of sodium/glucose cotransporter 1 (SGLT1), suppressed the glucose-induced short-circuit current in the C1W (P=0.016) but not the C5W. Although the addition of NaCl solution stimulated the glucose-induced short-circuit current in the C1W, no differences between the treatments were observed (P=0.056), which was also the case in the C5W. Additionally, tissue conductance was diminished in the C5W compared with that in the C1W. Moreover, in the C5W, the intestinal tract was more developed and the jejunal villi were enlarged. In conclusion, glucose absorption throughout the intestine could be greater in C5W than in C1W; however, reduced SGLT1 sensitivity, decreased ion permeability, and intestinal overdevelopment lead to decreased local glucose absorption in the jejunum with growth in broiler chickens. These data provide a detailed analysis of intestinal glucose absorption in growing broiler chickens, and can contribute to the development of novel feeds.

DSPE-PEG polymer enhanced berberine absorption specifically in the small intestine of rats through paracellular passway.

This study focuses on investigating the potential impact of DSPE-PEG polymers on intestinal absorption and related mechanism of berberine in rats. Effect of DSPE-PEG polymer on intestinal absorption of berberine was investigated with an in situ closed-loop method in rats. To confirm the safety of DSPE-PEG polymer, morphological observation of rat intestine and measurement of biological markers in the intestinal perfusion of rats was performed. Underling mechanism behind promoting action of DSPE-PEG polymer was explored from its impact on the P-gp function and tight junction using in vitro diffusion chamber system, Caco-2 monolayer cells and western blot. DSPE-PEG polymer demonstrated significant enhancement action on the berberine absorption in rats without any obvious membrane toxicity. DSPE-PEG polymer (1.0%, w/v) induced the most significant promoting effect on berberine absorption specifically in the small intestine of rats. Results of mechanistic studies revealed that DSPE-PEG polymer might not regulate intestinal P-gp function, but significantly down-regulated the expression of tight junction-related proteins, which accordingly led to loosening the tight junctions of intestinal epithelium cells, and consequently increased paracellular absorption of berberine in rats. DSPE-PEG polymer, as an excellent absorption enhancer, seems very promising in increasing oral bioavailability of berberine.

Na+-dependent intestinal glucose absorption mechanisms and its luminal Na+ homeostasis across metamorphosis from tadpoles to frogs.

The abrupt morphological changes of the intestine during metamorphosis have been detailed in frogs. The features of intestinal metamorphosis are shortening of the intestine and remodeling of the intestinal epithelium. It is believed that the purpose of the morphological changes of the intestine is adaptation from aquatic herbivorous to carnivorous life. However, little is known about the physiological importance of these morphological changes. To elucidate the functional changes during metamorphosis, we measured luminal Na+ concentrations and Na+-dependent glucose uptake in tadpoles and adult African clawed frogs Xenopus laevis. The small intestine was isolated and divided into four segments in length, the luminal contents collected for analysis of ion concentration by ion chromatography. Phlorizin-sensitive glucose-induced short-circuit current (ΔIsc) was measured in intestinal preparations mounted in Ussing chambers. Although dietary sodium intake was extremely low in tadpoles, luminal Na+ concentration gradually increased along the proximal to the middle part of the intestine (>70 mM), and this Na+ concentration was comparable with that of carnivorous adult frogs. The increment of glucose-induced ΔIsc was observed in tadpole intestine. We also measured the ΔIsc induced by acetic acid, which is the major short-chain fatty acid produced by fermentation. The expression levels of mRNA for Na+-dependent glucose transporter 1 and tight junction protein claudin-15 in each intestinal segment was measured. These results suggest that luminal Na+ homeostasis is important and luminal Na+ is kept at a high concentration for Na+-dependent nutrient absorption mechanisms.

Fecal Microbiota, Bile Acids, Sterols, and Fatty Acids in Dogs with Chronic Enteropathy Fed a Home-Cooked Diet Supplemented with Coconut Oil.

Medium-chain fatty acids (MCFAs) are considered to be interesting energy sources for dogs affected by chronic enteropathies (CE). This study analyzed the clinical scores, fecal microbiota, and metabolomes of 18 CE dogs fed a home-cooked diet (HCD) supplemented with virgin coconut oil (VCO), a source of MCFA, at 10% of metabolizable energy (HCD + VCO). The dogs were clinically evaluated with the Canine Chronic Enteropathy Activity Index (CCECAI) before and at the end of study. Fecal samples were collected at baseline, after 7 days of HCD, and after 30 days of HCD + VCO, for fecal score (FS) assessment, microbial analysis, and determination of bile acids (BA), sterols, and fatty acids (FA). The dogs responded positively to diet change, as shown by the CCECAI improvement (p = 0.001); HCD reduced fecal fat excretion and HCD + VCO improved FS (p < 0.001), even though an increase in fecal moisture occurred due to HCD (p = 0.001). HCD modified fecal FA (C6:0: +79%, C14:0: +74%, C20:0: +43%, C22:0: +58%, C24:0: +47%, C18:3n-3: +106%, C20:4n-6: +56%, and monounsaturated FA (MUFA): -23%, p < 0.05) and sterol profile (coprostanol: -27%, sitostanol: -86%, p < 0.01). VCO increased (p < 0.05) fecal total saturated FA (SFA: +28%, C14:0: +142%, C16:0 +21%, C22:0 +33%) and selected MCFAs (+162%; C10:0 +183%, C12:0 +600%), while reducing (p < 0.05) total MUFA (-29%), polyunsaturated FA (-26%), campesterol (-56%) and phyto-/zoosterols ratio (0.93:1 vs. 0.36:1). The median dysbiosis index was <0 and, together with fecal BA, was not significantly affected by HCD nor by VCO. The HCD diet increased total fecal bacteria (p = 0.005) and the abundance of Fusobacterium spp. (p = 0.028). This study confirmed that clinical signs, and to a lesser extent fecal microbiota and metabolome, are positively influenced by HCD in CE dogs. Moreover, it has been shown that fecal proportions of MCFA increased when MCFAs were supplemented in those dogs. The present results emphasize the need for future studies to better understand the intestinal absorptive mechanism of MCFA in dogs.

Diets and cholesterol metabolism

<p indent="0mm">Cholesterol is an essential component of most biological membranes and is the precursor for synthesis of steroid hormones and bile acids. In addition, numerous proteins can be modified by cholesterol, which are essential for embryonic development and cell proliferation. However, high level of blood cholesterol is a major risk factor of atherosclerosis. Therefore, cholesterol metabolism is tightly regulated by mammalian cells. Humans acquire cholesterol through de novo biosynthesis and intestinal absorption from foods. Bao-Liang Song’s research team at Wuhan University has long been devoted to the research of cholesterol metabolism, and has made a series of important original discoveries. The team systematically elucidated the negative feedback regulatory pathway of cholesterol synthesis -- HMGCR degradation pathway, revealed the molecular pathway of dietary induction of cholesterol synthesis, and proposed a new lipid-lowering strategy. They also identified a series of important proteins in the intestinal cholesterol absorption pathway. They found a rare frameshift variant in the LIMA1 gene from a Chinese family of Kazakh ethnicity with inherited low LDL-C and reduced cholesterol absorption. They demonstrated LIMA1 as a key protein regulating intestinal cholesterol absorption. This article focuses on diets and cholesterol metabolism, and reviews the relevant mechanisms of cholesterol synthesis regulation and intestinal cholesterol absorption, as well as the important achievements made by the cholesterol research team of Wuhan University.

Mechanism of Enhanced Oral Absorption of a Nano-Drug Delivery System Loaded with Trimethyl Chitosan Derivatives.

IntroductionIn the previous study, nanoparticles coated with trimethyl chitosan (TMC) derivatives (PPTT-NPs) could promote the oral bioavailability of panax notoginseng saponins (PNS). Herein, we chose PPTT-NPs as a model drug to study the property and mechanism of intestinal absorption in vitro and in vivo.MethodsThe stability of PPTT-NPs was evaluated using simulated gastric fluid and simulated intestinal fluid. The uptake and transport of PPTT-NPs were investigated in Caco-2 and Caco-2&HT29 co-culture cells. The biosafety, intestinal permeability, adhesion, and absorption mechanism of PPTT-NPs were investigated using SD rats in vivo. The live imaging and biodistribution of PPTT-NPs were observed by IVIS. Furthermore, the effects on CYP3A4 of PPTT-NPs were investigated using testosterone as the probe substrate.ResultsThe results of the stability assay showed that PPTT-NPs had a strong tolerance to the pH and digestive enzymes in the gastrointestinal environment. In vitro cell experiments showed that the uptake of drugs exhibited a time-dependent. When the ratio of TMC-VB12 and TMC-Cys was 1:3, the uptake capacity of PPTT-NPs was the highest. PPTT-NPs could enhance the paracellular transport of drugs by reversibly opening a tight junction. Animal experiments demonstrated that PPTT-NPs have good biological safety. PPTT-NPs had good adhesion and permeability to small intestinal mucosa. Meanwhile, PPTT-NPs needed energy and various protein to participate in the uptake of drugs. The live imaging of NPs illustrated that PPTT-NPs could prolong the residence time in the intestine. Moreover, TMC-VB12 and TMC-Cys could reduce the metabolism of drugs by inhibiting CYP3A4 to a certain extent.ConclusionThe results show that TMC-VB12 and TMC-Cys are effective in the transport of PPTT-NPs. PPTT-NPs can increase the intestinal adhesion of drugs and exert high permeation by intestinal enterocytes which demonstrate significant and efficient potential for oral delivery of the BCS III drugs.

The intestinal absorption mechanism of chicoric acid and its bioavailability improvement with chitosan

Chicoric acid (CA), an active phenolic acid of Echinacea purpurea (Linn.) Moench, has been demonstrated to exhibit antioxidative, antiviral and immunological activities. A prior study showed that CA is a water-soluble compound with low bioavailability. The current study was performed to study the intestinal absorption mechanism of CA and improve its bioavailability using natural biodegradable chitosan. A Caco-2 monolayer cell model was established to characterise the mechanisms involved in the intestinal absorption of CA. The bioavailability improvement of CA was studied in Sprague–Dawley rats after oral (20 mg/kg) administration of 0.5% chitosan. In vitro, the results showed that the absorption transport of CA was fairly poor, with Papp values of 8.2 × 10−8 to 2.1 × 10−7 cm/s in the absorption direction and 1.5 × 10−7 to 2.6 × 10−7 cm/s in the secretory direction. The permeability was increased by EDTA and chitosan in both directions. Moreover, the transport through the intestinal monolayer was H+ dependent, and P-glycoprotein and OATP2B1 transporters were involved in the intestinal transport of CA. In vivo, the absorption of CA was increased and accelerated with chitosan in rats because the bioavailability was 1.74-fold that of the prototype drug. The above mentioned results indicated that CA was a poor absorption drug and that paracellular and carrier-mediated trancellular transport both participated in its transport route. Chitosan is an excellent absorption enhancer for CA. The transport characteristics uncovered in this study lay the groundwork for further studies directed toward the development and utilisation of its new formulations.

Effect of berbamine hydrochloride on the absorption of berberine hydrochloride in an in situ single-pass intestinal perfusion system in rats

Purpose: To investigate the intestinal absorption characteristics of berberine hydrochloride (BBH) under different perfusion conditions in rats.Methods: Based on the in situ single-pass intestinal perfusion model of rats, HPLC was used to determine the content of berberine hydrochloride in solution after perfusion under different conditions. The absorption rate constant (Ka), effective permeability coefficient (Papp) and cumulative absorption per unit area (Q) under different perfusion conditions were analyzed by one-way ANOVA.Results: The Papp and Ka of BBH in perfusion solution at pH 7.4 were greater than those in perfusion solution at pH 6 and 8. There was no significant difference (p &gt; 0.05) in Papp and Ka of duodenum, jejunum and ileum at high, medium and low concentrations of berberine hydrochloride perfusion solution. The Q increased linearly with increase of mass concentration of perfusion solution. The Ka and Papp of BBH in duodenum, jejunum, and ileum of BBH and berbamine hydrochloride (BAH) combined at different ratios were higher than those of BBH control group at the same BBH concentration, but absorption of BBH in the ratio B40:A50 and B30:A20 groups was highest. In the ratio of B40:A50 ratio, B30:A20 ratio group or the same concentration's BBH group, Ka and Papp of BBH decreased in the order of jejunum &gt; duodenum &gt; ileum.Conclusion: Berberine hydrochloride is absorbed in neutral environment of pH 7.4. The intestinal absorption mechanism of BBH is passive diffusion, and jejunum is the best intestinal segment for absorption. BAH promotes the absorption of BBH.

A Recent Ten-Year Perspective: Bile Acid Metabolism and Signaling.

Bile acids are important physiological agents required for the absorption, distribution, metabolism, and excretion of nutrients. In addition, bile acids act as sensors of intestinal contents, which are determined by the change in the spectrum of bile acids during microbial transformation, as well as by gradual intestinal absorption. Entering the liver through the portal vein, bile acids regulate the activity of nuclear receptors, modify metabolic processes and the rate of formation of new bile acids from cholesterol, and also, in all likelihood, can significantly affect the detoxification of xenobiotics. Bile acids not absorbed by the liver can interact with a variety of cellular recipes in extrahepatic tissues. This provides review information on the synthesis of bile acids in various parts of the digestive tract, its regulation, and the physiological role of bile acids. Moreover, the present study describes the involvement of bile acids in micelle formation, the mechanism of intestinal absorption, and the influence of the intestinal microbiota on this process.

One-Way Intestinal Perfusion of PVP/VA-Poloxamer 188-Curcuma longa L. Extract Solid Dispersion in Rats In Vivo and Its Effect on HSC-T6 Cell Proliferation.

Turmeric was the dried rhizome of Curcuma longa L., and its extract had important pharmacological effects such as anti-tumor, cholagogic, and antioxidant. However, curcuma extract had poor water solubility and low bioavailability, which had become the main limiting factor for its clinical application. The purpose of this study was to prepare PVP/VA-Poloxamer-188-curcuma extract solid dispersion (PAP-CSD) to improve the solubility and bioavailability of the curcuma extract. The intestinal absorption mechanism of solid dispersion of this extract was studied by one-way intestinal perfusion in rats. PAP-CSD,PVP/VA-curcuma extract solid dispersion (PA-CSD) and Poloxamer-188-curcuma extract solid dispersion (P-CSD) was able to improve the intestinal absorption of the curcuma extract (P < 0.05), and PAP-CSD (combined use of two carriers) was better than that of PA-CSD and P-CSD. CCK8 method was used to investigate the effects of the curcuma extract and PAP-CSD on the proliferation of hepatic stellate cells (HSC)-T6 cells. The inhibitory effect of PAP-CSD on the proliferation of HSC-T6 cells, related to the p38 MAPK pathway, was better than that of the curcuma extract.

Intestinal absorption mechanism of rotundic acid: Involvement of P-gp and OATP2B1

Ethnopharmacological relevanceIlicis Rotundae Cortex (IRC), the dried barks of Ilex rotunda Thunb. (Aquifoliaceae), has been used for the prevention or treatment of colds, tonsillitis, dysentery, and gastrointestinal diseases in folk medicine due to its antibacterial and anti-inflammatory effects. However, there is no report about the intestinal absorption of major compounds that support traditional usage. Aim of studyConsidering the potential of rotundic acid (RA) – major biologically active pentacyclic triterpenes found in the IRC, this study was purposed to uncover the oral absorption mechanism of RA using in situ single-pass intestinal perfusion (SPIP) model, in vitro cell models (Caco-2, MDCKII-WT, MDCKII-MDR1, MDCKII-BCRP, and HEK293-OATP2B1 cells) and in vivo pharmacokinetics studies in rats. Materials and methodsThe molecular properties (solubility, lipophilicity, and chemical stability) and the effects of principal parameters (time, compound concentrations, pH, paracellular pathway, and the different intestinal segments) were analyzed by liquid chromatography-tandem mass spectrometry. The susceptibility of RA to various inhibitors, such as P-gp inhibitor verapamil, BCRP inhibitor Ko143, OATP 2B1 inhibitor rifampicin, and absorption enhancer EGTA were assessed. ResultsRA was a compound with low water solubility (12.89 μg/mL) and strong lipophilicity (LogP = 4.1). RA was considered stable in all media during the SPIP and transport studies. The SPIP and cell experiments showed RA was moderate absorbed in the intestines and exhibited time, concentration, pH, and segment-dependent permeability. In addition, results from the cell model, in situ SPIP model as well as the in vivo pharmacokinetics studies consistently showed that verapamil, rifampicin, and EGTA might have significant effect on the intestinal absorption of RA. ConclusionThe mechanisms of intestinal absorption of RA might involve multiple transport pathways, including passive diffusion, the participation of efflux (i.e., P-gp) and influx (i.e., OATP2B1) transporters, and paracellular pathways.

Intestinal metabolism and absorption mechanism of multi-components in Gaultheria leucocarpa var. yunnanensis - An assessment using in situ and in vitro models, comparing gut segments in pathological with physiological conditions

Ethnopharmacological relevanceDianbaizhu (Gaultheria leucocarpa var. yunnanensis) as a Chinese folk medicine exerts significant treatment effects on rheumatoid arthritis (RA) with a long historical time. Our previous reports showed that the anti-rheumatic arthritis fraction (ARF) extracted and enriched from Dianbaizhu possessed good druggability, which was better than its single active ingredients. However, the intestinal transport characteristics and mechanism of ARF have not been elucidated to date. Aim of the studyIn order to illustrate the role of active ingredients of ARF in alleviating RA and promoting the development of dosage forms, the intestinal metabolism, absorption properties and mechanism of ARF in vitro and in situ models were investigated. Materials and methodsFirstly, after incubating with 4 intestinal segments (duodenum, jejunum, ileum, and colon), 7 key components in ARF, including MATG-B, (+)-catechin, MSTG-A, Gaultherin, chlorogenic acid, quercetin, and kaempferol were quantitatively analyzed by a high-performance liquid chromatography (HPLC). Secondly, combining the physiological and pathological rats, the in situ single-pass intestinal perfusion and in vitro everted gut sacs of rats were performed to investigate the absorption features and transport mechanisms of ARF using HPLC and HPLC-Q-TOF-MS/MS. Subsequently, in situ studies were employed to determine the effect of P-glycoprotein (P-gp) inhibitor (verapamil) on the transport characteristics of ARF in RA model rats. ResultsComparing the absorption parameters of ARF incubated in different intestinal segments, data showed that the absorption of ARF in the small intestine was significantly stronger than that of the colon (P < 0.01). The number of characterized prototype components was subjected to the incubation time, drug concentration and rat body condition, but not the intestinal segments. There were no significant differences in the number of metabolites among different intestinal segments, administration concentrations and incubation time. The best small intestinal absorption site of ARF was duodenum and ileum in normal and model rats, respectively. The Peff values of 7 index compounds were all higher than 0.2 × 10−4cm/s, and the Fa values of 7 index compounds were all greater than 20% in the in situ perfusion investigation. The results showed that MSTG-B, MSTG-A and Gaultherin were likely to be substrates of P-gp as verapamil significantly enhanced their Peff and Ka values, while other ingredients were not P-gp substrates. ConclusionsThe intestinal membrane permeability of ARF was good. Its intestinal absorption mechanisms mainly involved active transportation processes and passive diffusion. Besides, this report provided data support and basis for clinical development, bioavailability improvement and formulation design.

Gut microbiota-involved metabolism and intestinal absorption mechanisms in decreasing bioaccessibility of triadimefon in strawberry and grape

Gut microbiota-involved metabolism and intestinal absorption affecting bioaccessibility of triadimefon in strawberry and grape were investigated for the first time by coupling the in vitro digestion model with the Caco-2 cell model. Results showed that the gut microbiota decreased the bioaccessibility of triadimefon in strawberry by 31.00% but failed in grape, probably due to a negative modulation of the colon bacterial activity by dietary components in grapes. A strain of triadimefon-degrading bacteria, Stenotrophomonas maltophilia, was isolated from the gut microbiota and its degradation products were profiled. This study also clarified a significant reduction in transepithelial transport (up to 32.81%) of triadimefon as a result of the barrier effect of gut microbiota. These findings provide new insights on the function of the gut microbiota in pesticide bioaccessibility and highlight the importance of including gut microbiota in pesticide residue risk assessments.

Combination of a biopharmaceutic classification system and physiologically based pharmacokinetic models to predict absorption properties of baicalein in vitro and in vivo

To determine the in vitro and in vivo absorption properties of active ingredients of the Chinese medicine, baicalein, to enrich mechanistic understanding of oral drug absorption. The Biopharmaceutic Classification System (BCS) category was determined using equilibrium solubility, intrinsic dissolution rate, and intestinal permeability to evaluate intestinal absorption mechanisms of baicalein in rats in vitro . Physiologically based pharmacokinetic (PBPK) model commercial software GastroPlus™ was used to predict oral absorption of baicalein in vivo . Based on equilibrium solubility, intrinsic dissolution rate, and permeability values of main absorptive segments in the duodenum, jejunum, and ileum, baicalein was classified as a drug with low solubility and high permeability. Intestinal perfusion with venous sampling (IPVS) revealed that baicalein was extensively metabolized in the body, which corresponded to the low bioavailability predicted by the PBPK model. Further, the PBPK model predicted the key indicators of BCS, leading to reclassification as BCS-II. Predicted values of peak plasma concentration of the drug (C max ) and area under the curve (AUC) fell within two times of the error of the measured results, highlighting the superior prediction of absorption of baicalein in rats, beagles, and humans. The PBPK model supported in vitro and in vivo evidence and provided excellent prediction for this BCS class II drug. BCS and PBPK are complementary methods that enable comprehensive research of BCS parameters, intestinal absorption rate, metabolism, prediction of human absorption fraction and bioavailability, simulation of PK, and drug absorption in various intestinal segments across species. This combined approach may facilitate a more comprehensive and accurate analysis of the absorption characteristics of active ingredients of Chinese medicine from in vitro and in vivo perspectives.

Mechanism of Lentinan Intestinal Absorption: Clathrin-Mediated Endocytosis and Macropinocytosis.

Lentinan (LNT), a typical triple helix β-glucan extracted from Lentinus edodes, has been widely used as a functional food and an orally administered drug. However, its oral pharmacokinetics has been rarely reported. The aim of this work is to systematically study the pharmacokinetics and intestinal absorption mechanism of LNT after oral administration. Radioactive 99m-technetium (99mTc) was introduced to label LNT to determine the plasma concentration, tissue distribution, and excretion of the β-glucan in rats after oral administration. The results confirmed the absorption of LNT, with the maximal plasma concentration reached at 1 h. 5-([4,6-Dichlorotriazin-2-yl]amino)fluorescein (DTAF) was used to label LNT to explore the absorption mechanism of LNT, utilizing both a Ussing chamber and a monolayer of Caco-2 cells. These transport assays showed that LNT could penetrate through the intestine and epithelial monolayer, which was mediated by macropinocytosis and clathrin-mediated endocytosis. These findings provide a pharmacokinetic reference for LNT and help provide a greater understanding of the absorption of β-glucans in general.

Intestinal phosphorus absorption: recent findings in translational and clinical research.

The purpose of this review is to discuss recent findings in intestinal phosphorus absorption pathways, particularly the contributions of paracellular versus transcellular absorption, and the differential findings from studies using in vitro versus in vivo techniques of assessing phosphorus absorption in experimental animal studies. Experimental animal studies show that in vivo effects of low phosphorus diets, 1,25D, and chronic kidney disease on intestinal phosphorus absorption efficiency contradict effects previously established ex vivo/in vitro. Recent in vivo studies also suggest that the paracellular pathway accounts for the majority of phosphorus absorption in animals across very low to high luminal phosphate concentrations. The data from experimental animal studies correspond to recent human studies showing the effectiveness of targeted inhibition of paracellular phosphate absorption. Additionally, recent human studies have demonstrated that NaPi-2b inhibition alone does not appear to be effective in lowering serum phosphate levels in patients with chronic kidney disease. Pursuit of other transcellular phosphate transporter inhibitors may still hold promise. In vivo animal and human studies have added to our understanding of intestinal phosphorus absorption pathways, regulation, and mechanisms. This is beneficial for developing effective new strategies for phosphate management in patients with chronic kidney disease.