A novel simulated media system for in vitro evaluation of bioequivalent intestinal drug solubility.

Orally administered solid drug must dissolve in the gastrointestinal tract before absorption to provide a systemic response. Intestinal solubility is therefore crucial but difficult to measure since human intestinal fluid (HIF) is challenging to obtain, varies between fasted (Fa) and fed (Fe) states and exhibits inter and intra subject variability. A single simulated intestinal fluid (SIF) cannot reflect HIF variability, therefore current approaches are not optimal. In this study we have compared literature Fa/FeHIF drug solubilities to values measured in a novel in vitro simulated nine media system for either the fasted (Fa9SIF) or fed (Fe9SIF) state. The manuscript contains 129 literature sampled human intestinal fluid equilibrium solubility values and 387 simulated intestinal fluid equilibrium solubility values. Statistical comparison does not detect a difference (Fa/Fe9SIF vs Fa/FeHIF), a novel solubility correlation window enclosed 95% of an additional literature Fa/FeHIF data set and solubility behaviour is consistent with previous physicochemical studies. The Fa/Fe9SIF system therefore represents a novel in vitro methodology for bioequivalent intestinal solubility determination. Combined with intestinal permeability this provides an improved, population based, biopharmaceutical assessment that guides formulation development and indicates the presence of food based solubility effects. This transforms predictive ability during drug discovery and development and may represent a methodology applicable to other multicomponent fluids where no single component is responsible for performance.

Watermelon-Derived Extracellular Vesicles Influence Human Ex Vivo Placental Cell Behavior by Altering Intestinal Secretions.

SCOPE: During pregnancy, mother-to-fetus transfer of nutrients is mediated by the placenta; sub-optimal placental development and/or function results in fetal growth restriction (FGR), and the attendant risk of stillbirth, neurodevelopmental delay, and non-communicable diseases in adulthood. A maternal diet high in fruit and vegetables lowers the risk of FGR but the association cannot be explained fully by known macro- and micronutrients. METHODS AND RESULTS: This study investigates if dietary-derived extracellular vesicles (EVs) can regulate placental function. The study characterizes the microRNA and protein cargo of EVs isolated from watermelon, show they are actively internalized by human intestinal epithelial cells in vitro, use mass spectrometry to demonstrate that they alter the intestinal secretome and bioinformatic analyses to predict the likely affected pathways in cells/tissues distal to gut. Application of the watermelon EV-modified intestinal secretome to human placental trophoblast cells and ex vivo tissue explants affects the trophoblast proteome and key aspects of trophoblast behavior, including migration and syncytialization. CONCLUSION: Dietary-derived plant EVs can modify intestinal communication with distal tissues, including the placenta. Harnessing the beneficial properties of dietary-derived plant EVs and/or exploiting their potential as natural delivery agents may provide new ways to improve placental function and reduce rates of FGR.

Small scale in vitro method to determine a bioequivalent equilibrium solubility range for fasted human intestinal fluid.

Drug solubility is a key parameter controlling oral absorption, but intestinal solubility is difficult to assess in vitro. Human intestinal fluid (HIF) aspirates can be applied but they are variable, difficult to obtain and expensive. Simulated intestinal fluids (SIF) are a useful surrogate but multiple recipes are available and the optimum is unknown. A recent study characterised fasted HIF aspirates using a multi-dimensional approach and determined nine bioequivalent SIF media recipes that represented over ninety percent of HIF compositional variability. In this study these recipes have been applied to determine the equilibrium solubility of twelve drugs (naproxen, indomethacin, phenytoin, piroxicam, aprepitant, carvedilol, zafirlukast, tadalafil, fenofibrate, griseofulvin, felodipine, probucol) previously investigated using a statistical design of experiment (DoE) approach. The bioequivalent solubility measurements are statistically equivalent to the previous DoE, enclose literature solubility values in both fasted HIF and SIF, and the solubility range is less than the previous DoE. These results indicate that the system is measuring the same solubility space as literature systems with the lower overall range suggesting improved equivalence to in vivo solubility, when compared to DoEs. Three drugs (phenytoin, tadalafil and griseofulvin) display a comparatively narrow solubility range, a behaviour that is consistent with previous studies and related to the drugs' molecular structure and properties. This solubility behaviour would not be evident with single point solubility measurements. The solubility results can be analysed using a custom DoE to determine the most statistically significant factor within the media influencing solubility. This approach has a lower statistical resolution than a formal DoE and is not appropriate if determination of media factor significance for solubilisation is required. This study demonstrates that it is possible to assess the fasted intestinal equilibrium solubility envelope using a small number of bioequivalent media recipes obtained from a multi-dimensional analysis of fasted HIF. The derivation of the nine bioequivalent SIF media coupled with the lower measured solubility range indicate that the solubility results are more likely to reflect the fasted intestinal solubility envelope than previous DoE studies and highlight that intestinal solubility is a range and not a single value.

Do Macrocyclic Peptide Drugs Interact with Bile Salts under Simulated Gastrointestinal Conditions?

Peptide drugs face several barriers to oral delivery, including enzymatic degradation in the gastrointestinal tract and low membrane permeability. Importantly, the direct interaction between various biorelevant colloids (i.e., bile salt micelles and bile salt-phospholipid mixed micelles) present in the aqueous gastrointestinal environment and peptide drug molecules has not been studied. In this work, we systematically characterized interactions between a water-soluble model peptide drug, octreotide, and a range of physiologically relevant bile salts in solution. Octreotide membrane flux in pure bile salt solutions and commercially available biorelevant media, i.e., fasted state simulated intestinal fluid (FaSSIF) and fed state simulated intestinal fluid (FeSSIF), was evaluated using a side-by-side diffusion cell equipped with a cellulose dialysis membrane. All seven micellar bile salt solutions as well as FaSSIF and FeSSIF decreased octreotide membrane flux, and dihydroxy bile salts were found to have a much larger effect than trihydroxy bile salts. An inverse relationship between octreotide membrane flux and pancreatic enzymatic stability was also observed; bile salt micelles and bile salt-phospholipid mixed micelles provided a protective effect toward enzymatic degradation and prolonged octreotide half-life in vitro. Diffusion ordered nuclear magnetic resonance (DOSY NMR) spectroscopy and dynamic light scattering (DLS) were used as complementary experimental techniques to confirm peptide-micelle interactions in solution. Experiments were also performed using desmopressin as a second model peptide drug; desmopressin interacted with bile salts in solution, albeit to a lower extent relative to octreotide. The findings described herein demonstrate that amphiphilic, water-soluble peptide drugs do interact with bile salts and phospholipids in solution, with an effect on peptide membrane flux and enzymatic stability. Correspondingly, oral peptide drug absorption and bioavailability may be impacted.

Berberine Slows the Progression of Prediabetes to Diabetes in Zucker Diabetic Fatty Rats by Enhancing Intestinal Secretion of Glucagon-Like Peptide-2 and Improving the Gut Microbiota.

Background: Berberine is a plant alkaloid that has multiple beneficial effects against intestine inflammation. In our previous study, we have found that berberine also possesses an antidiabetic effect. However, whether berberine is useful in the prevention of type 2 diabetes mellitus (T2DM) through its effect on intestine endocrine function and gut microbiota is unclear. Aim: To investigate the effects of berberine in the prevention of T2DM, as well as its effects on intestine GLP-2 secretion and gut microbiota in ZDF rats. Methods: Twenty Zucker Diabetic Fatty (ZDF) rats were fed a high-energy diet until they exhibited impaired glucose tolerance (IGT). The rats were then divided into two groups to receive berberine (100 mg/kg/d; berberine group) or vehicle (IGT group) by gavage for 3 weeks. Five Zucker Lean (ZL) rats were used as controls. Fasting blood glucose (FBG) was measured, an oral glucose tolerance test was performed, and the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) was calculated. Intestinal expression of TLR-4, NF-κB, TNF-α, mucin, zona occludens-1 (ZO-1) and occludin were assessed (immunohistochemistry). Plasma levels and glutamine-induced intestinal secretion of glucagon-like peptide-1 (GLP-1) and GLP-2 were measured (enzyme-linked immunosorbent assay). The plasma lipopolysaccharide (LPS) level was measured. Fecal DNA extraction, pyrosequencing, and bioinformatics analysis were performed. Results: After 3 weeks of intervention, diabetes developed in all rats in the IGT group, but only 30% of rats in the berberine group. Treatment with berberine was associated with reductions in food intake, FBG level, insulin resistance, and plasma LPS level, as well as increases in fasting plasma GLP-2 level and glutamine-induced intestinal GLP-2 secretion. Berberine could increase the goblet cell number and villi length, and also reverse the suppressed expressions of mucin, occludin, ZO-1 and the upregulated expressions of TLR-4, NF-κB and TNF-α induced in IGT rats (P<0.05). Berberine also improved the structure of the gut microbiota and restored species diversity. Conclusion: Berberine may slow the progression of prediabetes to T2DM in ZDF rats by improving GLP-2 secretion, intestinal permeability, and the structure of the gut microbiota.

Fasted and fed state human duodenal fluids: Characterization, drug solubility, and comparison to simulated fluids and with human bioavailability.

Accurate in vivo predictions of intestinal absorption of low solubility drugs require knowing their solubility in physiologically relevant dissolution media. Aspirated human intestinal fluids (HIF) are the gold standard, followed by simulated intestinal HIF in the fasted and fed state (FaSSIF/FeSSIF). However, current HIF characterization data vary, and there is also some controversy regarding the accuracy of FaSSIF and FeSSIF for predicting drug solubility in HIF. This study aimed at characterizing fasted and fed state duodenal HIF from 16 human volunteers with respect to pH, buffer capacity, osmolarity, surface tension, as well as protein, phospholipid, and bile salt content. The fasted and fed state HIF samples were further used to investigate the equilibrium solubility of 17 representative low-solubility small-molecule drugs, six of which were confidential industry compounds and 11 were known and characterized regarding chemical diversity. These solubility values were then compared to reported solubility values in fasted and fed state HIF, FaSSIF and FeSSIF, as well as with their human bioavailability for both states. The HIF compositions corresponded well to previously reported values and current FaSSIF and FeSSIF compositions. The drug solubility values in HIF (both fasted and fed states) were also well in line with reported solubility data for HIF, as well as simulated FaSSIF and FeSSIF. This indicates that the in vivo conditions in the proximal small intestine are well represented by simulated intestinal fluids in both composition and drug equilibrium solubility. However, increased drug solubility in the fed vs. fasted states in HIF did not correlate with the human bioavailability changes of the same drugs following oral administration in either state.

Effects of passage through the digestive tract on incretin secretion: Before and after birth.

AIMS/INTRODUCTION: It was reported that fetuses secrete endogenous incretin; however, the stimulants of fetal incretin secretion are not fully understood. To investigate the association between the passage of amniotic fluid through the intestinal tract and fetal secretion of incretin, we analyzed umbilical cord incretin levels of infants with duodenum atresia. MATERIALS AND METHODS: Infants born from July 2017 to July 2019 (infants with duodenum atresia and normal term or preterm infants) were enrolled. We measured and compared the concentrations of glucagon-like peptide-1 (GLP-1) and gastric inhibitory peptide/glucose-dependent insulinotropic polypeptide (GIP) in the umbilical vein and preprandial blood samples after birth. RESULTS: A total of 98 infants (47 term, 46 preterm and 5 with duodenum atresia) were included. In patients with duodenum atresia, umbilical vein GLP-1 and GIP levels were the same as those in normal infants. In postnatal samples, there were positive correlations between the amount of enteral feeding and preprandial serum concentrations of GLP-1 (r = 0.47) or GIP (r = 0.49). CONCLUSIONS: Our results show that enteral feeding is important for secretion of GLP-1 and GIP in postnatal infants, whereas the passage of amniotic fluid is not important for fetal secretion of GLP-1 and GIP. The effect of ingested material passing through the digestive tract on incretin secretion might change before and after birth. Other factors might stimulate secretion of GLP-1 and GIP during the fetal period.

Antidiarrheal activity of farnesol in rodents: Pharmacological actions and molecular docking.

Diarrhea is a condition in which the individual has about three or more daily bowel movements, followed by changes in stool consistency. It is currently considered as one of the worst public health problems due to the number of cases and deaths involved and difficulty of treatment. Thus, the use of natural products is an alternative for new treatments. Among these possibilities is Farnesol (C15H26O), a sesquiterpene found in different herbal species that has known biological activities. The objective of this study was to evaluate the antidiarrheal activity of Farnesol (FOH). Initially, FOH activity was evaluated in models of diarrhea and enteropooling induced by castor oil and PGE2. To evaluate motility, the opioid and cholinergic pathways were studied. In addition, the effect of FOH was investigated in the secretion model in intestinal loops treated with cholera toxin. FOH was evaluated for the ability to absorb fluids in intestinal loops and interact with GM1 receptors using the ELISA method and molecular docking. The dose of 50 mg/kg of FOH showed the best results in all antidiarrheal activity tests with castor oil and PGE2, being considered as the standard dose, reducing motility by anticholinergic mechanisms. There was a reduction in fluid secretion when FOH interacted directly with GM1 receptors; cholera toxin and molecular docking showed strong interaction between farnesol and these targets. In view of the results presented, the antidiarrheal activity occurs through anticholinergic, anti-inflammatory and anti-secretory action, making farnesol a potential candidate for the development of a new drug to treat diarrheal diseases.

In vitro and in situ study on characterization and mechanism of the intestinal absorption of 2,3,5,4'-tetrahydroxy-stilbene-2-O-ß-D-glucoside.

BACKGROUND: 2,3,5,4'-tetrahydroxystilbence-2-O-ß-D-glucoside (TSG) is a polyhydroxyphenolic compound, which exhibited a broad spectrum of pharmacological activities, such as anti-inflammatory, anti-depression, anti-oxidation and anti-atherosclerosis. However, the compound had poor bioavailability and the underlying absorption mechanisms had not been studied. Therefore, the purpose of this study was to investigate the intestinal absorption mechanism of TSG. METHODS: This study used Caco-2 cell monolayer model and single-pass intestinal perfusion model to explore the gastrointestinal absorption mechanisms of TSG. The effects of basic parameters such as drug concentration, time and pH on the intestinal absorption of TSG were analyzed by high performance liquid chromatography. The absorption susceptibility of TSG to three inhibitors, P-gp inhibitors verapamil hydrochloride and quinidine, and MRP2 inhibitor probenecid were also assessed. RESULTS: TSG was poorly absorbed in the intestines and the absorption of TSG in stomach is much higher than that in intestine. Both in vitro and in situ experiments showed that the absorption of TSG was saturated with increasing concentration and it was better absorbed in a weakly acidic environment pH 6.4. Moreover, TSG interacts with P-gp and MRP2, and TSG was not only the substrate of the P-gp and MRP2, but also affected the expression of P-gp and MRP2. CONCLUSIONS: It was concluded that the gastrointestinal absorption the most unique active ingredient and considered as the mechanisms of TSG involved processes passive transport and the participation of efflux transporters.

Effect of acid and in vitro digestion on conformation and IgE-binding capacity of major oyster allergen Cra g 1 (tropomyosin).

INTRODUCTION AND OBJECTIVES: The production and consumption of oysters is increasing annually because it can provide essential nutrients and benefit for human health, leading to frequent occurrence of severe allergic reactions observed in sensitized individuals. The aim of the present study was to investigate the effects of acid and protease treatment on the conformation and IgE-binding capacity of recombinant Crassostrea gigas tropomyosin (Cra g 1). RESULTS: Under acidic conditions, Cra g 1 did not undergo degradation, however, the changes obvious in the intensity of CD signal and ANS-binding fluorescence were observed, which was associated with a decrease in antibody reactivity. In simulated gastrointestinal fluid (SGF) and simulated intestinal fluid (SIF) digestion system, acid-treated Cra g 1 was relatively resistant to digestion, but the degradative patterns were very different. Moreover, owing to alterations of secondary structure and hydrophobic surface of the protein during digestive processing, antigenicity of acid-induced Cra g 1 reduced in SGF while it increased significantly in SIF. CONCLUSION: To our knowledge, this is the first study reporting that antigenicity of acid-treated oyster tropomyosin increased after SIF digestion. These results revealed that treatment with acid and pepsin, rather than trypsin, was an effective way of reducing IgE-binding capacity of tropomyosin from oyster.

Real-time measurements of milk fat globule membrane modulation during simulated intestinal digestion using electron paramagnetic resonance spectroscopy.

Milk Fat Globules with their unique interfacial structure and membrane composition are a key nutritional source for mammalian infants, however, there is a limited understanding of the dynamics of fat digestion in these structures. Lipid digestion is an interfacial process involving interactions of enzymes and bile salts with the interface of suspended lipid droplets in an aqueous environment. In this study, we have developed an electron paramagnetic resonance spectroscopy approach to evaluate real time dynamics of milk fat globules interfacial structure during simulated intestinal digestion. To measure these dynamics, natural milk fat globule membrane was labeled with EPR-active probe, partitioning of EPR probes into MFGs membrane was validated using saturation-recovery measurements and calculation of the depth parameter Φ. After validation, the selected spin probe was used to evaluate the membrane's fluidity as a measure of the interface's modulation in the presence of bile salts and pancreatic lipase. Independently, bile salts were found to have a rigidifying effect on the spin probed MFGM, while pancreatic lipase resulted in an increase in membrane fluidity. When combined, the effect of lipase appears to be diminished in the presence of bile salts. These results indicate the efficacy of EPR in providing an insight into small time scale molecular dynamics of phospholipid interfaces in milk fat globules. Understanding interfacial dynamics of naturally occurring complex structures can significantly aid in understanding the role of interfacial composition and structural complexity in delivery of nutrients during digestion.

Discovery of a novel chalcone derivative inhibiting CFTR chloride channel via AMPK activation and its anti-diarrheal application.

Secretory diarrhea is one of the most common causes of death world-wide especially in children under 5 years old. Isoliquiritigenin (ISLQ), a plant-derived chalcone, has previously been shown to exert anti-secretory action in vitro and in vivo by inhibiting CFTR Cl- channels. However, its CFTR inhibition potency is considerably low (IC50 > 10 µM) with unknown mechanism of action. This study aimed to identify novel chalcone derivatives with improved potency and explore their mechanism of action. Screening of 27 chalcone derivatives identified CHAL-025 as the most potent chalcone analog that reversibly inhibited CFTR-mediated Cl- secretion in T84 cells with an IC50 of ∼1.5 µM. As analyzed by electrophysiological and biochemical analyses, the mechanism of CFTR inhibition by CHAL-025 is through AMP-activated protein kinase (AMPK), a negative regulator of CFTR activity. Furthermore, Western blot analyses and molecular dynamics (MD) results suggest that CHAL-025 activates AMPK by binding at the allosteric site of an upstream kinase calcium/calmodulin-dependent protein kinase kinase ß (CaMKKß). Interestingly, CHAL-025 inhibited both cholera toxin (CT) and bile acid-induced Cl- secretion in T84 cells and prevented CT-induced intestinal fluid secretion in mice. Therefore, CHAL-025 represents a promising anti-diarrheal agent that inhibits CFTR Cl- channel activity via CaMKKß-AMPK pathways.

Inhibition of CFTR-mediated intestinal chloride secretion as potential therapy for bile acid diarrhea.

Bile acid diarrhea (BAD) is common with ileal resection, Crohn's disease, and diarrhea-predominant irritable bowel syndrome. Here, we demonstrate the efficacy of cystic fibrosis transmembrane conductance regulator (CFTR) inhibitor (R)-benzopyrimido-pyrrolo-oxazine-dione-27 (BPO-27) in reducing bile acid-induced fluid and electrolyte secretion in colon. Short-circuit current measurements in human T84 colonic epithelial cells and planar colonic enteroid cultures showed a robust secretory response following mucosal but not serosal addition of chenodeoxycholic acid (CDCA) or its taurine conjugate, which was fully blocked by CFTR inhibitors, including (R)-BPO-27. (R)-BPO-27 also fully blocked CDCA-induced secretory current in murine colon. CFTR activation by CDCA primarily involved Ca2+ signaling. In closed colonic loops in vivo, luminal CDCA produced a robust secretory response, which was reduced by ∼70% by (R)-BPO-27 or in CFTR-deficient mice. In a rat model of BAD produced by intracolonic infusion of CDCA, (R)-BPO-27 reduced the elevation in stool water content by >55%. These results implicate CFTR activation in the colon as a major prosecretory mechanism of CDCA, a bile acid implicated in BAD, and support the potential therapeutic efficacy of CFTR inhibition in bile acid-associated diarrheas.-Duan, T., Cil, O., Tse, C. M., Sarker, R., Lin, R., Donowitz, M., Verkman, A. S. Inhibition of CFTR-mediated intestinal chloride secretion as potential therapy for bile acid diarrhea.

Simulated human digestion of N1-aryl-2-arylthioacetamidobenzimidazoles and their activity against Herpes-simplex virus 1 in vitro.

Drug performance in the gastrointestinal tract (GIT) plays a crucial role in determining release and absorption. In the present work, we assessed the in vitro digestion of two synthetic N1-aryl-2-arylthioacetamidobenzimidazoles (NAABs), NAAB-496 and NAAB-503, using bio-relevant models of the human stomach and small intestine. The activity of NAAB-496 and NAAB-503 against herpes simplex virus (HSV-1) replication was also investigated. NAAB-496 was resistant to pepsin in the gastric environment, with a virtual 100% recovery, which decreased to 43.2% in the small intestine. NAAB-503 was sensitive to pepsin, with 65.7% degradation after 120 min gastric phase. 1H Nuclear magnetic resonance (NMR) post in vitro digestion highlighted an alteration of NAAB-496 after the gastric phase, whereas NAAB-503 appeared comparable to the original spectral data. Both NAAB-496 and NAAB-503 revealed some antiviral activity anti-HSV-1. The 50% effective concentration (EC50) of the compounds was 0.058 mg/mL for NAAB-496 and 0.066 for NAAB-503. Future studies will evaluate the behavior of NAAB-496 within pharmaceutical formulations.

Effect of lipids on absorption of carvedilol in dogs: Is coadministration of lipids as efficient as a lipid-based formulation?

Lipid-based formulations (LBFs) is a formulation strategy for enabling oral delivery of poorly water-soluble drugs. However, current use of this strategy is limited to a few percent of the marketed products. Reasons for that are linked to the complexity of LBFs, chemical instability of pre-dissolved drug and a limited understanding of the influence of LBF intestinal digestion on drug absorption. The aim of this study was to explore intestinal drug solubilization from a long-chain LBF, and evaluate whether coadministration of LBF is as efficient as a lipid-based drug formulation containing the pre-dissolved model drug carvedilol. Thus, solubility studies of this weak base were performed in simulated intestinal fluid (SIF) and aspirated dog intestinal fluid (DIF). DIF was collected from duodenal stomas after dosing of water and two levels (1 g and 2 g) of LBF. Similarly, the in vitro SIF solubility studies were conducted prior to, and after addition of, undigested or digested LBF. The DIF fluid was further characterized for lipid digestion products (free fatty acids) and bile salts. Subsequently, carvedilol was orally administered to dogs in a lipid-based drug formulation and coadministered with LBF, and drug plasma exposure was assessed. In addition to these studies, in vitro drug absorption from the different formulation approaches were evaluated in a lipolysis-permeation device, and the obtained data was used to evaluate the in vitro in vivo correlation. The results showed elevated concentrations of free fatty acids and bile salts in the DIF when 2 g of LBF was administered, compared to only water. As expected, the SIF and DIF solubility data revealed that carvedilol solubilization increased by the presence of lipids and lipid digestion products. Moreover, coadministration of LBF and drug demonstrated equal plasma exposure to the lipid-based drug formulation. Furthermore, evaluation of in vitro absorption resulted in the same rank order for the LBFs as in the in vivo dog study. In conclusion, this study demonstrated increased intestinal solubilization from a small amount of LBF, caused by lipid digestion products and bile secretion. The outcomes also support the use of coadministration of LBF as a potential dosing regimen in cases where it is beneficial to have the drug in the solid form, e.g. due to chemical instability in the lipid vehicle. Finally, the in vitro lipolysis-permeation used herein established IVIVC for carvedilol in the presence of LBFs.

Measurement of novel intestinal secretory and barrier pathways and effects of proteases.

The epithelial lining of the gastrointestinal (GI) tract in conjunction with the enteric nervous system (ENS) plays an important role in mediating solute absorption and secretion. A dysregulated ionic movement across the epithelium can result in GI diseases that manifest as either watery diarrhea or constipation. Hirschsprung disease is an example of an ENS disorder characterized by absence of enteric ganglia in distal gut resulting in obstructive phenotype. Receptor rearranged during transfection (RET) gene variants are the most commonly recognized genetic associations with Hirschsprung disease. In this issue of Neurogastroenterology and Motility, Russell et al demonstrate that RET mediates colonic ion transport through modulation of cholinergic nerves. They go on to show inhibition of RET can attenuate accelerated transit in a rat model. Normalizing secretory and absorptive defects has been an attractive therapeutic strategy. In addition to the intrinsic regulation of secretory processes, luminal mediators like bile acids, short-chain fatty acids, and proteases can affect both secretion and barrier function of the intestinal epithelium. Elevated levels of proteases have been identified in a wide range of GI diseases including irritable bowel syndrome. Proteases are known to cause visceral hypersensitivity and barrier disruption in vitro and in animal models. The goals of this review are to describe fundamental concepts related to intestinal epithelial secretion, the utility of Ussing chambers to measure ionic mechanisms and to discuss examples of novel signaling pathways; namely the RET signaling cascade in secretomotor neurons and effects of luminal proteases on barrier and ionic secretion.

Mimicking regional and fasted/fed state conditions in the intestine with the mucus-PVPA in vitro model: The impact of pH and simulated intestinal fluids on drug permeability.

Intestinal drug absorption following oral administration can be influenced by regional conditions (absorbing surface area, bacterial flora, motility, pH, mucus thickness) and food intake, all of which affect drug solubility and permeability. Therefore, it is crucial to assess the impact of these conditions on the drugability of drugs and formulations. In this study, the ability of the liposome-based mucus-PVPA in vitro permeability model to handle relevant intestinal pH conditions was evaluated, together with the investigation on the pH-dependent solubility and permeability profiles of five model drugs. This study additionally evaluated the impact of all commercially available versions of the fasted and fed state simulated intestinal fluids (SIFs) on the integrity of the barriers, and the permeabilities of one hydrophilic and one lipophilic compound were examined under these conditions. The model was found to be well-functioning in all tested pH conditions, and a pH-dependent trend was found for both solubility and permeability profiles for acidic and basic compounds, according to their degree of ionization. Moreover, the mucus layer and its pH-dependent viscosity particularly influenced the permeation of more lipophilic compounds. The PVPA barriers primarily maintained their functionality in the presence of the fed state SIFs, and the permeability of the two tested compounds showed to be influenced by their hydrophilicity/lipophilicity, their degree of interaction with mucus and by the bile salts and phospholipids content in the SIFs. Overall, the obtained results highlight the relevance of studying the effect that pH, mucus and SIFs have on intestinal drug absorption, and suggest the suitability of the mucus-PVPA model for such investigations.

Monkey orange fruit juice improves the nutritional quality of a maize-based diet.

This paper studied the nutritional impact of the use of juice from Strychnos cocculoides (monkey orange) in a maize-based porridge. Monkey orange juice is traditionally used to supplement maize porridge - a staple breakfast cereal especially for vulnerable groups. Monkey orange fruits contain high amounts of micronutrients and phenolic compounds and are widely distributed throughout sub-Saharan Africa. The valuable components can be efficiently extracted by traditional and pectinase maceration techniques. The bioaccessibility of minerals and main phenolic compounds in maize porridge (5 g maize meal) supplemented by monkey orange juice (100 ml) were assessed after in-vitro digestion together with the kinetics of starch degradation. Caffeic and protocatechuic acids exceeded 100%, and chlorogenic acid 81% bioaccessibility after simulated intestinal digestion. Rutin was undetected after the simulated intestinal phase due to precipitation in the pellet. In-vitro bioaccessibility of minerals ranged from 12 to 62% in monkey orange enriched porridge. A 50-70% decrease of starch hydrolysis was observed at the end of the simulated intestinal digestion of monkey orange maize porridge confirming the known potential of phenolic compounds to decrease the glycaemic index of starch-rich foods. Consequently monkey orange juice appeared a suitable ingredient to enrich staple maize porridge thanks to its micronutrients and health benefit potential. Similar relationships of other fruits and starchy foods warrant study as a means to improve the nutritional quality of the diets of malnourished populations.

Studies on the interactions between bile salts and food emulsifiers under in vitro duodenal digestion conditions to evaluate their bile salt binding potential.

During the last decade a special interest has been focused on studying the relationship between the composition and structure of emulsions and the extent of lipolysis, driven by the necessity of modulate lipid digestion to decrease or delay fats absorption or increase healthy fat nutrients bioavailability. Because bile salts (BS) play a crucial role in lipids metabolism, understanding how typical food emulsifiers affect the structures of BS under duodenal conditions, can aid to further understand how to control lipids digestion. In the present work the BS-binding capacity of three emulsifiers (Lecithin, Tween 80 and ß-lactoglobulin) was studied under duodenal conditions. The combination of several techniques (DLS, TEM, ζ-potential and conductivity) allowed the characterization of molecular assemblies resulting from the interactions, as modulated by the relative amounts of BS and emulsifiers in solution.

Involvement of butyrate in electrogenic K+ secretion in rat rectal colon.

Short-chain fatty acids (SCFAs), such as acetate, propionate, and butyrate, are synthesized from dietary carbohydrates by colonic bacterial fermentation. These SCFAs supply energy, suppress cancer, and affect ion transport. However, their roles in ion transport and regulation in the intracellular environment remain unknown. In order to elucidate the roles of SCFAs, we measured short-circuit currents (ISC) and performed RT-PCR and immunohistochemical analyses of ion transporters in rat rectal colon. The application of 30 mM butyrate shifted ISC in a negative direction, but did not attenuate the activity of epithelial Na+ channels (ENaC). The application of bumetanide, a Na+-K+-2Cl- cotransporter inhibitor, to the basolateral side reduced the negative ISC shift induced by butyrate. The application of XE991, a KCNQ-type K+ channel inhibitor, to the apical side decreased the ISC shift induced by butyrate in a dose-dependent manner. The ISC shift was independent of HCO3- and insensitive to ibuprofen, an SMCT1 inhibitor. The mucosa from rat rectal colon expressed mRNAs of H+-coupled monocarboxylate transporters (MCT1, MCT4, and MCT5, also referred to as SLC16A1, SLC16A3, and SLC16A4, respectively). RT-PCR and immunofluorescence analyses demonstrated that KCNQ2 and KCNQ4 localized to the apical membrane of surface cells in rat rectal colon. These results indicate that butyrate, which may be transported by H+-coupled monocarboxylate transporters, activates K+ secretion through KCNQ-type K+ channels on the apical membrane in rat rectal colon. KCNQ-type K+ channels may play a role in intestinal secretion and defense mechanisms in the gastrointestinal tract.