Intestinal First-pass Metabolism Research Articles

Addressing the ADME Challenges of Compound Loss in a PDMS-Based Gut-on-Chip Microphysiological System.

Microphysiological systems (MPSs) are promising in vitro technologies for physiologically relevant predictions of the human absorption, distribution, metabolism, and excretion (ADME) properties of drug candidates. However, polydimethylsiloxane (PDMS), a common material used in MPSs, can both adsorb and absorb small molecules, thereby compromising experimental results. This study aimed to evaluate the feasibility of using the PDMS-based Emulate gut-on-chip to determine the first-pass intestinal drug clearance. In cell-free PDMS organ-chips, we assessed the loss of 17 drugs, among which testosterone was selected as a model compound for further study based on its substantial ad- and absorptions to organ chips and its extensive first-pass intestinal metabolism with well-characterized metabolites. A gut-on-chip model consisting of epithelial Caco-2 cells and primary human umbilical vein endothelial cells (HUVECs) was established. The barrier integrity of the model was tested with reference compounds and inhibition of drug efflux. Concentration-time profiles of testosterone were measured in cell-free organ chips and in gut-on-chip models. A method to deduce the metabolic clearance was provided. Our results demonstrate that metabolic clearance can be determined with PDMS-based MPSs despite substantial compound loss to the chip. Overall, this study offers a practical protocol to experimentally assess ADME properties in PDMS-based MPSs.

Schisandrol A, the Major Active Constitute in Schisandra chinensis: A Review of Its Preparation, Biological Activities, and Pharmacokinetics Analysis.

Schisandra chinensis (S. chinensis) has a long history as a traditional Chinese medicine that is astringent, beneficial to vital energy, tonifies the kidney, tranquilizes the heart, etc. Significantly, Schisandrol A (SA) is extracted from S. chinensis and shows surprising and satisfactory biological activity, including anti-inflammatory, hepatoprotective, cardiovascular protection, and antitumor properties, among others. SA has a more pronounced protective effect on central damaged nerves among its numerous pharmacological effects, improving neurodegenerative diseases such as Alzheimer's and Parkinson's through the protection of damaged nerve cells and the enhancement of anti-oxidant capacity. Pharmacokinetic studies have shown that SA has a pharmacokinetic profile with a rapid absorption, wide distribution, maximal concentration in the liver, and primarily renal excretion. However, hepatic and intestinal first-pass metabolism can affect SA's bioavailability. In addition, the content of SA, as an index component of S. chinensis Pharmacopoeia, should not be less than 0.40%, and the content of SA in S. chinensis compound formula was determined with the help of high-performance liquid chromatography (HPLC), which is a stable and reliable method, and it can lay a foundation for the subsequent quality control. Therefore, this paper systematically reviews the preparation, pharmacological effects, pharmacokinetic properties, and content determination of SA with the goal of updating and deepening the understanding of SA, as well as providing a theoretical basis for the study of SA at a later stage.

Quantitative Translation of Substrate Intrinsic Clearance from Recombinant CYP1A1 to Humans.

CYP1A1 is a cytochrome P450 family 1 enzyme that is mostly expressed in the extrahepatic tissues. To understand the CYP1A1 contribution to drug clearance in humans, we examined the in vitro-in vivo extrapolation (IVIVE) of intrinsic clearance (CLint) for a set of drugs that are in vitro CYP1A1 substrates. Despite being strong in vitro CYP1A1 substrates, 82% of drugs gave good IVIVE with predicted CLint within 2-3-fold of the observed values using human liver microsomes and hepatocytes, suggesting they were not in vivo CYP1A1 substrates due to the lack of extrahepatic contribution to CLint. Only three drugs (riluzole, melatonin and ramelteon) that are CYP1A2 substrates yielded significant underprediction of in vivo CLint up to 11-fold. The fold of CLint underprediction was linearly proportional to human recombinant CYP1A1 (rCYP1A1) CLint, indicating they were likely to be in vivo CYP1A1 substrates. Using these three substrates, a calibration curve can be developed to enable direct translation from in vitro rCYP1A1 CLint to in vivo extrahepatic contributions in humans. In vivo CYP1A1 substrates are planar and small, which is consistent with the structure of the active site. This is in contrast to the in vitro substrates, which include large and nonplanar molecules, suggesting rCYP1A1 is more accessible than what is in vivo. The impact of CYP1A1 on first-pass intestinal metabolism was also evaluated and shown to be minimal. This is the first study providing new insights on in vivo translation of CYP1A1 contributions to human clearance using in vitro rCYP1A1 data.

A comprehensive review on Schisandrin and its pharmacological features.

Schisandrin stands as one of the primary active compounds within the widely used traditional medicinal plant Schisandra chinensis (Turcz.) Baill. This compound exhibits sedative, hypnotic, anti-aging, antioxidant, and immunomodulatory properties, showcasing its effectiveness across various liver diseases while maintaining a favorable safety profile. However, the bioavailability of schisandrin is largely affected by hepatic and intestinal first-pass metabolism, which limits the clinical efficacy of schisandrin. In this paper, we review the various pharmacological effects and related mechanisms of schisandrin, in order to provide reference for subsequent drug research and promote its medicinal value.

Molecular weight-dependent hyaluronic acid permeability and tight junction modulation in human buccal TR146 cell monolayers

The oral route is considered an attractive method for drug delivery, as it avoids the hepatic and intestinal first-pass metabolism processes. Hyaluronic acid (HA) beneficial effects to the human body include anti-aging and wound healing but its effects on oral barrier integrity and mechanical function have not yet been investigated. In this study, we analyzed oral barrier integrity and the paracellular pathway of HA transportation in TR146 cell monolayers during and after permeation and using low molecular weight HA (LMW-HA, <100 kDa) and high molecular weight HA (HMW-HA, >500 kDa). Cytotoxicity assays in TR146 cells revealed that neither LMW-HA or HMW-HA altered cell viability at concentrations <0.5 % during 24 h of treatment. HA-treated TR146 cell monolayers showed enhanced oral barrier integrity and reduced apparent permeability of fluorescein. Moreover, HA significantly increased tight junction (TJ)-related genes expression, including ZO-2, marvelD3, cingulin, claudin-1, claudin-3, and claudin-4 expression. Overall, the results of the present study indicate that HA can permeate across the oral barrier and enhance oral barrier function via the upregulated expression of TJ-related genes.

Dimethandrolone, a Potential Male Contraceptive Pill, is Primarily Metabolized by the Highly Polymorphic UDP-Glucuronosyltransferase 2B17 Enzyme in Human Intestine and Liver.

Dimethandrolone undecanoate (DMAU), an oral investigational male hormonal contraceptive, is a prodrug that is rapidly converted to its active metabolite, dimethandrolone (DMA). Poor and variable oral bioavailability of DMA after DMAU dosing is a critical challenge to develop it as an oral drug. The objective of our study was to elucidate the mechanisms of variable pharmacokinetics of DMA. We first identified DMA metabolites formed in vitro and in vivo in human hepatocyte incubation and serum samples following oral DMAU administration in men, respectively. The metabolite identification study revealed two metabolites, DMA-glucuronide (DMA-G; major) and the androstenedione analog of DMA (minor), in the hepatocyte incubations. After oral DMAU administration, only DMA-G was detected in serum, which was >100-fold compared with DMA levels, supporting glucuronidation as the major elimination mechanism for DMA. Next, 13 clinically relevant UDP-glucuronosyltransferase (UGT) enzymes were tested for their involvement in DMA-G formation, which revealed a major role of UDP-glucuronosyltransferase 2B17 (UGT2B17) isoform with a smaller contribution of UGT1A9 in DMA-G formation. These data were confirmed by dramatically higher DMA glucuronidation rates (>200- and sevenfold) in the high versus the null UGT2B17-expressing human intestinal and liver microsomes, respectively. Since human UGT2B17 is a highly variable enzyme with a 20%-80% gene deletion frequency, the in vitro data suggest a major role of UGT2B17 polymorphism on the first-pass metabolism of DMA. Further, considering DMA is a selective and sensitive UGT2B17 substrate, it could be used as a clinical probe of UGT2B17 activity. SIGNIFICANCE STATEMENT: Dimethandrolone (DMA) is an active metabolite of dimethandrolone undecanoate (DMAU), an investigational male hormonal contraceptive. Previous studies have indicated poor and inconsistent bioavailability of DMAU following oral administration. This study found that UDP-glucuronosyltransferase 2B17-mediated high intestinal first-pass metabolism is the key mechanism of variable DMA bioavailability.

Population pharmacokinetics and IVIVC for mesalazine enteric-coated tablets.

Although in-vivo bioequivalence (BE) study serves as a golden standard for establishing interchangeability of oral dosage forms, it remains challenging for products with high inter-subject variability such as mesalazine enteric-coated tablet to fulfil the BE criteria set by regulatory authorities. Mesalazine, as a BCS class IV drug, targets to be delivered to distal ileum or colon with a pH-sensitive polymer coating for the remission of ulcerative colitis. Through population pharmacokinetic (PK) analysis and in-vitro in-vivo correlation (IVIVC) modeling on the dissolution and BE data of a generic enteric-coated product (EM) and its reference Salofalk® 250mg tablet (SM), we for the first time revealed the underlying mechanism of the high inter-subject variability for such delayed-release formulation. It was also noted that the in-vivo start time of absorption (Ts) for EM and SM was positively correlated with their in-vitro lag time (Tlag) under the USP three-stage dissolution condition and reversely correlated with their in-vivo bioavailability. The varied oral bioavailability of mesalazine enteric-coated tablet was mainly due to the varied N-acetyltransferase activities along GI tract. Although such extensive intestinal first-pass metabolism with large individual differences led to a significant variation of mesalazine Cmax (coefficient of variation: 60-63.5%) and AUC0-t (coefficient of variation: 37.5-46.9%), the corresponding variations in the total absorbed mesalazine (mesalazine and its metabolite N-acetyl mesalazine) were significantly reduced by 12 to 45%. Since the BE purpose for mesalazine enteric-coated tablet focused on their comparable safety profiles, total absorbed mesalazine was recommended to be adopted for the development of the IVIVC model and BE evaluation for EM. All in all, our model-based approach has not only successfully identified the key factors that affect the BE of EM to guide its further formulation optimization, but also demonstrated the indispensable role of modeling in the development of generic pharmaceutical product at its early stages.

Species-dependent hepatic and intestinal metabolism of selective estrogen receptor degrader LSZ102 by sulfation and glucuronidation

1. LSZ102 is an orally bioavailable selective estrogen receptor degrader in clinical development for the treatment of breast cancer. Preclinical studies showed efficacy in xenograft models on oral dosing. However, oral bioavailability was relatively low in several preclinical species (7-33%), and was associated with first-pass metabolism, particularly intestinal first-pass. 2. To investigate metabolism and first-pass effects, metabolites were analysed in human plasma samples after oral dosing of LSZ102 to patients, rat plasma samples after oral dosing of [14C]LSZ102, and in vitro incubations of [14C]LSZ102 with human and rat hepatocytes and intestinal S9 fractions. The kinetics of human sulfotransferase enzymes potentially involved in metabolism of LSZ102 were characterized. 3. Sulfate metabolites were found to be the major components in human plasma, as well as in human hepatocytes and intestinal S9 fractions. Contrastingly, glucuronidation was predominant in rat plasma, hepatocytes and intestinal S9. LSZ102 was found to be metabolized by several human sulfotransferases expressed in liver and intestine. The combined metabolism data in rat and human provide supporting evidence for an extensive intestinal first-pass metabolism effect via sulfation in human but glucuronidation in rat. 4. As LSZ102 is metabolized by a number of different sulfotransferases, drug-drug interactions resulting from the inhibition of one sulfotransferase are unlikely. 5. Despite the observed species difference in metabolism, the major human metabolites of LSZ102, sulfate M5, glucuronide M4, and secondary glucuronide/sulfate metabolite M12, have no or weak pharmacological activity and are not considered a toxicity risk as they are phase II conjugative metabolites.

Predicting Intestinal and Hepatic First-Pass Metabolism of Orally Administered Testosterone Undecanoate

The bioavailability of orally administered drugs could be impacted by intestinal and hepatic first-pass metabolism. Testosterone undecanoate (TU), an orally administered ester prodrug of testosterone, is significantly subjected to first-pass metabolism. However, the individual contribution of intestinal and hepatic first-pass metabolism is not well determined. Therefore, the aim of the current study was to predict the metabolic contribution of each site. The hydrolysis–time profiles of TU incubation in human liver microsomes and Caco-2 cell homogenate were used to predict hepatic and intestinal first-pass metabolism, respectively. The in vitro half-life (t1/2 inv) for the hydrolysis of TU in microsomal mixtures was 28.31 ± 3.51 min. By applying the “well-stirred” model, the fraction of TU that could escape hepatic first-pass metabolism (FH) was predicted as 0.915 ± 0.009. The incubation of TU in Caco-2 cell homogenate yielded t1/2 inv of 109.28 ± 21.42 min, which was applied in a “Q gut” model to estimate the fraction of TU that would escape intestinal first-pass metabolism (FG) as 0.114 ± 0.02. Accordingly, only 11% of the absorbed fraction of TU could escape intestinal metabolism, while 91% can pass through hepatic metabolism. Hence, compared to the liver, the intestinal wall is the main site where TU is significantly metabolised during first-pass effect.

Dextran sulfate sodium-induced colitis and ginseng intervention altered oral pharmacokinetics of cyclosporine A in rats

Ethnopharmacological relevanceApplication of cyclosporine A (CsA) as a rescue treatment in acute severe ulcerative colitis (UC) is limited by its narrow therapeutic window and great interpatient variability. As a substrate of cytochrome P450 3A enzyme (CYP3A) and P-glycoprotein (P-gp), the oral pharmacokinetics of CsA is susceptible to disease status and concomitant medications. Combined treatment with ginseng, a famous medicinal herb frequently prescribed for ameliorating abnormal immune response in many diseases including UC, showed immunologic safety in CsA-based immunosuppression. Aim of the studySince the therapeutic levels of CsA can be achieved within 24 h, this study first assessed the impact of acute colitis and ginseng intervention on the single oral dose pharmacokinetics of CsA and explored the underlying mechanisms in dextran sulfate sodium (DSS)-induced colitis rats and Caco-2 cells. Materials and methodsRats received drinking water (normal group), 5% DSS (UC group), or 5% DSS plus daily oral ginseng extract (GS+UC group). On day 7, GS+UC group only received an oral dose of CsA (5 mg/kg), while animals of normal or UC group received an oral, intravenous (1.25 mg/kg), or intraperitoneal dose of CsA (1.25 mg/kg), respectively. Blood, liver/intestine tissues and fecal samples were collected for determining CsA and main hydroxylated metabolite HO-CsA or measuring hepatic/intestinal CYP3A activity. Caco-2 cells were incubated with gut microbial culture supernatant (CS) of different groups or ginseng (decoction or polysaccharides), and then CYP3A, P-gp and tight junction (TJ) proteins were determined. ResultsOral CsA exhibited enhanced absorption, systemic exposure and tissue accumulation, and lower fecal excretion, while intravenous or intraperitoneal CsA showed lower systemic exposure and enhanced distribution, in colitis rats. Diminished intestinal and hepatic P-gp expression well explained the changes with DSS-induced colitis. Moreover, blood exposures of HO-CsA in both normal and colitis after oral dosing were significantly higher than intravenous/intraperitoneal dosing, supporting the dominant role of intestinal first-pass metabolism. Interestingly, colitis reduced CYP3A expression in intestine and liver but only potentiated intestinal CYP3A activity, causing higher oral systemic exposure of HO-CsA. Oral ginseng mitigated colitis-induced down-regulation of CYP3A and P-gp expression, facilitated HO-CsA production, biliary excretion and colonic sequestration of CsA, while not affected CsA oral systemic exposure. In Caco-2 cells, gut microbial CS from both colitis and GS+UC group diminished P-gp function, while ginseng polysaccharides directly affected ZO-1 distribution and suppressed TJ proteins expression, explaining unaltered oral CsA systemic exposure. ConclusionsDSS-induced colitis significantly altered oral CsA disposition through regulating intestinal and hepatic P-gp and CYP3A. One-week ginseng treatment enhanced colonic accumulation while not altered the systemic exposure of CsA after single oral dosing, indicating pharmacokinetic compatibility between the two medications.

Extent and rate of oral drug absorption in minipigs: Comparison with mice, rats and humans

In this study, in order to evaluate the usability of minipigs as an experimental animal in the oral drug development process, extent and rate of oral absorption of 17 commercially drugs were investigated in minipigs and compared with those in mice rats and humans. Extent of oral bioavailability (BA) of tested drugs tended to be lower in minipigs as well as in mice and rats than in humans. From a pharmacokinetic (PK) analysis, it was revealed that the higher activity of intestinal first-pass metabolism, thus the lower intestinal availability, is a major factor causing the lower extent of BA in minipigs, rats and mice than in humans. Whereas the similar value of hepatic availability was observed between minipigs and humans, suggesting the advantage of minipigs to use in oral absorption study for high hepatic clearance drugs. On the other hand, from the plasma concentration-time profiles of orally administered drugs, gastric emptying and intestinal transit rates in minipigs were indicated to be slower than other animals and humans. These slow processes of gastrointestinal transit in minipigs might cause the difficulty in simulating the time-course of plasma concentrations of orally administered drugs in humans, especially as sustained release or controlled release products.

In-Depth Characterization of EpiIntestinal Microtissue as a Model for Intestinal Drug Absorption and Metabolism in Human.

The Caco-2 model is a well-accepted in vitro model for the estimation of fraction absorbed in human intestine. Due to the lack of cytochrome P450 3A4 (CYP3A4) activities, Caco-2 model is not suitable for the investigation of intestinal first-pass metabolism. The purpose of this study is to evaluate a new human intestine model, EpiIntestinal microtissues, as a tool for the prediction of oral absorption and metabolism of drugs in human intestine. The activities of relevant drug transporters and drug metabolizing enzymes, including MDR1 P-glycoprotein (P-gp), breast cancer resistance protein (BCRP), CYP3A4, CYP2J2, UDP-glucuronosyltransferases (UGT), carboxylesterases (CES), etc., were detected in functional assays with selective substrates and inhibitors. Compared to Caco-2, EpiIntestinal microtissues proved to be a more holistic model for the investigation of drug absorption and metabolism in human gastrointestinal tract.

Bergamottin can be used to assess CYP3A-mediated intestinal first-pass metabolism without affecting P-glycoprotein-mediated efflux in rats

1. We investigated whether bergamottin would be useful for evaluating CYP3A-mediated intestinal metabolism in rats utilising its characteristics as a mechanism-based inhibitor of CYP3A.2. Buspirone and fexofenadine, probe substrates of CYP3A and P-glycoprotein (P-gp), respectively, were orally co-administered to rats with bergamottin (2.5 mg/kg) or orally administered 2 h after bergamottin pre-treatment. The effect of bergamottin pre-treatment on hepatic CYP3A specifically was investigated with intravenous administration of buspirone. The kobs of bergamottin for CYP3A was calculated based on the portal unbound Cmax.3. Co-administration of bergamottin significantly increased the AUC0–inf for buspirone and fexofenadine by 1.6-fold and 1.7-fold, respectively, indicating that bergamottin inhibited both CYP3A and P-gp.4. Bergamottin pre-treatment significantly elevated the AUC0–inf of oral buspirone by 3.7-fold but exerted no effect on the pharmacokinetics of intravenous buspirone, indicating that bergamottin pre-treatment selectively inhibited CYP3A-mediated intestinal metabolism without affecting the hepatic CYP3A. These findings were supported by the result that the kobs (0.00000118 min−1) of bergamottin for CYP3A was lower than the kdeg (0.0005 min−1) for CYP3A. Furthermore, bergamottin pre-treatment did not affect the pharmacokinetics of oral fexofenadine, suggesting that P-gp was not influenced.5. These profiles of bergamottin enable the convenient assessment of CYP3A-mediated intestinal metabolism.

Effects of Different Methionine Sources on Methionine Metabolism in the IPEC-J2 Cells.

As one of the essential amino acids, methionine (Met) plays an important role in biological events such as methylation and antioxidant properties besides its function in protein synthesis. Different Met sources have been used in animal production, but their effects on Met metabolic pathways are not well understood. In the present study, we investigated the effects of different Met sources (L-Met, DL-Met, DL-2-hydroxy-4-(methylthio)butanoic acid (DL-HMTBA), and DL-methionyl-DL-methionine (DL-MM)) on the metabolism of Met in small intestinal porcine epithelial cell line (IPEC-J2) and the contents of extracellular Met sources. The results showed that concentrations of intracellular Met, S-adenosylmethionine (SAM), S-adenosylhomocysteine (SAH), and the ratio of SAM to SAH in the DL-HMTBA group were significantly lower than that in other Met source groups, while the content of 5-methyltetrahydrofolate (5-MTHF) was significantly higher. Moreover, the mRNA levels of MAT2A, AHcy, CBS, MTHFR, and MTR in the DL-HMTBA group were significantly higher than those in other Met source groups. Further study showed that the total content of extracellular Met sources was highest in the DL-HMTBA group, followed by DL-MM group, followed by L-Met and DL-Met groups. These results demonstrated that DL-HMTBA mainly affects the transmethylation and remethylation of Met and it can promote the trans-sulfur metabolism of Met when compared with other Met sources. In addition, most DL-HMTBA and a small amount of DL-MM can escape the intestinal first-pass metabolism and then provide more extracellular Met sources than L-Met and DL-Met. Therefore, this study can provide a theoretical basis for the selection of Met sources in livestock.

Dose-Dependent Pharmacokinetics of Tofacitinib in Rats: Influence of Hepatic and Intestinal First-Pass Metabolism.

This study investigated the pharmacokinetics of tofacitinib in rats and the effects of first-pass metabolism on tofacitinib pharmacokinetics. Intravenous administration of 5, 10, 20, and 50 mg/kg tofacitinib showed that the dose-normalized area under the plasma concentration-time curve from time zero to infinity (AUC) was significantly higher at 50 mg/kg than at lower doses, a difference possibly due to saturation of the hepatic metabolism of tofacitinib. Oral administration of 10, 20, 50, and 100 mg/kg tofacitinib showed that the dose-normalized AUC was significantly higher at 100 mg/kg than at lower doses, a difference possibly due to saturation of the intestinal metabolism of tofacitinib. Following oral administration of 10 mg/kg tofacitinib, the unabsorbed fraction from the rat intestine was 3.16% and the bioavailability (F) was 29.1%. The AUC was significantly lower (49.3%) after intraduodenal, compared to intraportal, administration, but did not differ between intragastric and intraduodenal administration, suggesting that approximately 46.1% of orally administered tofacitinib was metabolized through an intestinal first-pass effect. The AUC was also significantly lower (42%) after intraportal, compared to intravenous, administration, suggesting that the hepatic first-pass effect on tofacitinib after entering the portal vein was approximately 21.3% of the oral dose. Taken together, these findings suggest that the low F of tofacitinib is due primarily to intestinal first-pass metabolism.

Mechanisms of poor oral bioavailability of flavonoid Morin in rats: From physicochemical to biopharmaceutical evaluations

We recently reported that the absolute oral bioavailability of flavonoid Morin was extremely low at 0.45%, resulting in unsatisfied therapeutic efficacy in vivo. The present study was aimed to systemically assess the pre-absorption risks of Morin for rationale formulation design. Physicochemical properties of Morin were evaluated using in vitro assays including water solubility and stability in simulated gastric, intestinal fluids, followed by permeability tests in Caco-2 cells. The results suggested that both poor solubility and low membrane permeability were rate-limiting steps for oral absorption of Morin. Pharmacokinetic studies were performed via a series of administration routes in a dual-vein cannulated rat model. In contrast to high bioavailability (92.92%) and negligible metabolites of Morin in intraportal administered rats, Morin exhibited low bioavailability (5.28%) and considerable amount of metabolites in rats following intraduodenal administration, suggested that intestinal first-pass metabolism made a major contribution to its poor oral absorption. Morin-phospholipid complex loaded self-emulsifying drug delivery system (MPC-SENDDS) exhibited comparable plasma concentration of metabolites to parent drug after oral administration, indicated that MPC-SNEDDS failed to bypass first-pass metabolism and therefore showed compromised oral absorption enhancement. The present study could promote the development of more efficient oral formulations of Morin with optimized absorption enhancement.

Soybean soluble polysaccharide enhances absorption of soybean genistein in mice

This study was designed to probe the promoting effects of soybean soluble polysaccharide (SSPS) on bioavailability of genistein in mice and the underlying molecular mechanism. Male Kunming mice (n=8) were administered intragastrically with either saline, SSPS (5mg/kgbw), genistein (100mg/kgbw), or SSPS (5 or 50mg/kgbw) together with genistein (100mg/kgbw) for consecutive 28days. UPLC-qTOF/MS analysis showed that co-administration of SSPS and genistein in mice caused significant elevation in the urinary levels of genistein and its metabolites (p<0.05). Furthermore, the fecal excretion of genistein was also enhanced by co-administration of SSPS. However, the feces level of dihydrogenistein, a characteristic metabolite of genistein degraded by gut microorganism, was dose-dependently decreased by the combined treatment of SSPS. Additionally, co-treatment of SSPS with genistein also decreased the small intestinal levels of uridinediphosphate-glucuronosyltransferase (UGT), sulfotransferase (SULT), P-glycoprotein (P-gp), multidrug resistance-associated protein-1 (MRP1), and multidrug resistance-associated protein-2 (MRP2) in mice. These findings suggest that the inhibition of SSPS against small intestinal first-pass metabolism of genistein is involved in the promoting effect of genistein bioavailability in mice.

Time-Dependent Metabolism of Luteolin by Human UDP-Glucuronosyltransferases and Its Intestinal First-Pass Glucuronidation in Mice.

Luteolin is a well-known flavonoid with various pharmacological properties but has low bioavailability due to glucuronidation. This study investigated the time-course of luteolin glucuronidation by 12 human UDP-glucuronosyltransferases (UGTs) and its intestinal first-pass metabolism in mice. Six metabolites, including two novel abundant diglucuronides [3',7-O-diglucuronide (diG) and 4',7-diG] and four known ones, were identified. UGT1A6 and UGT1A9 generated almost only monoglucuronides (G's). The production of 3',7-diG followed a sequential time-dependent process along with decrease of 3'-G mainly by UGT1A1, indicating that 3',7-diG was produced from 3'-G. Metabolism in mice intestine differed from that in humans. Probenecid, a nonspecific UGT inhibitor, did not affect absorption but significantly inhibited production of 7-, 4'-, and 3'-G, and enhanced the formation of another novel metabolite, 5-G, in mice. In conclusion, diglucuronide formation is time-dependent and isoform-specific. UGT1A1 preferentially generates diG, whereas UGT1A6 and UGT1A9 share a preference for G production.

High gastrointestinal permeability and local metabolism of naringenin: influence of antibiotic treatment on absorption and metabolism.

The present study aims to determine the permeability of naringenin in the stomach, small intestine and colon, to evaluate intestinal and hepatic first-pass metabolism, and to study the influence of the microbiota on the absorption and disposition of naringenin (3.5 μg/ml). A single-pass intestinal perfusion model in mice (n 4-6) was used. Perfusate (every 10 min), blood (at 60 min) and bile samples were taken and analysed to evaluate the presence of naringenin and its metabolites by an HPLC-MS/MS method. To study the influence of the microbiota on the bioavailability of naringenin, a group of animals received the antibiotic rifaximin (50 mg/kg per d) for 5 d, and naringenin permeability was determined in the colon. Naringenin was absorbed well throughout the gastrointestinal tract but mainly in the small intestine and colon (mean permeability coefficient 7.80 (SD 1.54) × 10(-4) cm/s and 5.49 (SD 1.86) × 10(-4) cm/s, respectively), at a level similar to the highly permeable compound, naproxen (6.39 (SD 1.23) × 10(-4) cm/s). According to the high amounts of metabolites found in the perfusate compared to the bile and plasma, naringenin underwent extensive intestinal first-pass metabolism, and the main metabolites excreted were sulfates (84.00 (SD 12.14)%), followed by glucuronides (8.40 (SD 5.67)%). Phase II metabolites were found in all perfusates from 5 min of sampling. Mice treated with rifaximin showed a decrease in naringenin permeability and in the amounts of 4-hydroxyhippuric acid and hippuric acid in the lumen. Naringenin was well absorbed throughout the gastrointestinal tract and its poor bioavailability was due mainly to high intestinal metabolism.

No impact of vitamin D on the CYP3A biomarker 4β-hydroxycholesterol in patients with abnormal glucose regulation.

PurposeTo investigate the effect of vitamin D3 on hepatic Cytochrome P450 enzyme (CYP) 3A4 in patients with abnormal glucose regulation using the endogenous marker 4β-hydroxycholesterol (4β-OHC):cholesterol ratio.MethodsThe present study took advantage of a trial primarily aiming to investigate the effect of vitamin D3 on beta cell function and insulin sensitivity in patients with abnormal glucose regulation. 44 subjects were randomized to receive vitamin D3, 30000 IU given orally once weekly or placebo for 8 weeks. The two sample t-test was used to test the means of the intra-individual differences of 4β-OHC:cholesterol ratio between the two groups.ResultsMean (SD) 4β-OHC in the whole group of patients before and after the intervention was 26 (11) ng/ml and 26 (12). Mean (SD) 4β-OHC:cholesterol ratio in the whole group of patients before and after the intervention was 0.12 (0.046) and 0.13 (0.047). In the Vitamin D group mean (SD) serum 25-OH-vitamin D3 increased from 46 (16) to 85nM (13) during the corresponding time period. To investigate the impact of vitamin D3 on hepatic CYP3A4 we calculated the mean intra-individual differences in 4β-OHC:cholesterol ratio (delta 4β-OHC:cholesterol ratio) before versus after the intervention in the two treatment groups. The difference (95% CI) between delta 4β-OHC:cholesterol ratio in the control group and intervention group was -0.0010 (-0.0093, 0.0072), a difference being not statistically significant (p = 0.80).ConclusionsWe provide further evidence that vitamin D3 may not substantially affect hepatic CYP3A4. This does not exclude the possibility of an impact of intestinal first-pass metabolism of orally administered drugs which should be investigated.Trial RegistrationClinicalTrials.gov NCT01497132