Experimental non-alcoholic fatty liver disease results in decreased hepatic uptake transporter expression and function in rats

Impact of non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) on the expression and function of hepatobiliary transporters: A comprehensive mechanistic review

The liver plays a central role in the biotransformation and disposition of endogenous molecules and xenobiotics. In addition to drug-metabolizing enzymes, transporter proteins are key determinants of drug hepatic clearance. Hepatic transporters are transmembrane proteins that facilitate the movement of chemicals between sinusoidal blood and hepatocytes. Other drug transporters translocate molecules from hepatocytes into bile canaliculi for biliary excretion. The formers are known as basolateral, while the latter are known as canalicular transporters. Also, these transporters are classified into two super-families, the solute carrier transporter (SLC) and the adenosine triphosphate (ATP)-binding cassette (ABC) transporter. The expression and function of transporters involve complex regulatory mechanisms, which are contributing factors to interindividual variability in drug pharmacokinetics and disposition. A considerable number of liver diseases are known to alter the expression and function of drug transporters. Among them, non-alcoholic fatty liver disease (NAFLD) is a chronic condition with a rapidly increasing incidence worldwide. NAFLD, recently reclassified as metabolic dysfunction-associated steatotic liver disease (MASLD), is a disease continuum that includes steatosis with or without mild inflammation (NASH), and potentially neuroinflammatory pathology. NASH is additionally characterized by the presence of hepatocellular injury. During NAFLD and NASH, drug transporters exhibit altered expression and function, leading to altered drug pharmacokinetics and pharmacodynamics, thus increasing the risk of adverse drug reactions. The purpose of the present review is to provide comprehensive mechanistic information on the expression and function of hepatic transporters under fatty liver conditions and hence, the impact on the pharmacokinetic profiles of certain drugs from the available pre-clinical and clinical literature.

Ability of dynamic gadoxetic acid-enhanced magnetic resonance imaging combined with water-specific T1 mapping to reflect inflammation in a rat model of early-stage nonalcoholic steatohepatitis

Background

Gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) has shown potential in reflecting the hepatic function alterations in nonalcoholic steatohepatitis (NASH). The purpose of this study was to evaluate whether Gd-EOB-DTPA combined with water-specific T1 (wT1) mapping can be used to detect liver inflammation in the early-stage of NASH in rats.

Methods

In this study, 54 rats with methionine- and choline-deficient (MCD) diet-induced NASH and 10 normal control rats were examined. A multiecho variable flip angle gradient echo (VFA-GRE) sequence was performed and repeated 40 times after the injection of Gd-EOB-DTPA. The wT1 of the liver and the reduction rate of wT1 (rrT1) were calculated. All rats were histologically evaluated and grouped according to the NASH Clinical Research Network scoring system. Quantitative real-time polymerase chain reaction (qRT-PCR) was performed to detect the expression of Gd-EOB-DTPA transport genes. Analysis of variance and least significant difference tests were used for multiple comparisons of quantitative results between all groups. Multiple regression analysis was applied to identify variables associated with precontrast wT1 (wT1pre), and receiver operating characteristic (ROC) analysis was performed to assess the diagnostic performance.

Results

The rats were grouped according to inflammatory stage (G0 =4, G1 =15, G2 =12, G3 =23) and fibrosis stage (F0 =26, F1 =19, F2 =9). After the infusion of Gd-EOB-DTPA, the rrT1 showed significant differences between the control and NASH groups (P<0.05) but no difference between the different inflammation and fibrosis groups at any time points. The areas under curve (AUCs) of rrT1 at 10, 20, and 30 minutes were only 0.53, 0.58, and 0.61, respectively, for differentiating between low inflammation grade (G0 + G1) and high inflammation grade (G2 + G3). The MRI findings were verified by qRT-PCR examination, in which the Gd-EOB-DTPA transporter expressions showed no significant differences between any inflammation groups.

Conclusions

The wT1 mapping quantitative method combined with Gd-EOB-DTPA was not capable of discerning the inflammation grade in a rat model of early-stage NASH.

SLCO1B1 Genetic Variation Influence on Atorvastatin Systemic Exposure in Pediatric Hypercholesterolemia

This clinical study examined the influence of SLCO1B1 c.521T>C (rs4149056) on plasma atorvastatin concentrations in pediatric hypercholesterolemia. The participants (8-21 years), including heterozygous (c.521T/C, n = 13), homozygous (c.521C/C, n = 2) and controls (c.521T/T, n = 13), completed a single-oral-dose pharmacokinetic study. Similar to in adults, the atorvastatin (AVA) area-under-concentration-time curve from 0 to 24 h (AUC0-24) was 1.7-fold and 2.8-fold higher in participants with c.521T/C and c.521C/C compared to the c.521T/T participants, respectively. The inter-individual variability in AVA exposure within these genotype groups ranged from 2.3 to 4.8-fold, indicating that additional factors contribute to the inter-individual variability in the AVA dose-exposure relationship. A multivariate model reinforced the SLCO1B1 c.521T>C variant as the central factor contributing to AVA systemic exposure in this pediatric cohort, accounting for ~65% of the variability in AVA AUC0-24. Furthermore, lower AVA lactone concentrations in participants with increased body mass index contributed to higher exposure within the c.521T/T and c.521T/C genotype groups. Collectively, these factors contributing to higher systemic exposure could increase the risk of toxicity and should be accounted for when individualizing the dosing of atorvastatin in eligible pediatric patients.

Comparison of pharmacokinetic profiles of seven major bioactive components in normal and non-alcoholic fatty liver disease (NAFLD) rats after oral administration of Ling-Gui-Zhu-Gan decoction by UPLC-MS/MS

A sensitive and rapid ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was hereby developed for the determination of seven components, namely, glycyrrhizic acid, glycyrrhetinic acid, dehydrotumulosic acid, isoliquiritin, liquiritin, atractylenolide III, and cinnamic acid, in the plasma of rats after the oral administration of Ling-Gui-Zhu-Gan decoction (LGZGD). Besides, this very method was methodologically validated for specificity, linearity, inter-day and intra-day precision, accuracy, matrix effect, extraction recovery, and stability. It was also successfully used for the first time to compare the pharmacokinetic characteristics of the seven components after oral administration of LGZGD to normal rats and non-alcoholic fatty liver disease (NAFLD) rats. The results indicated significant differences between the pharmacokinetic characteristics of normal and NAFLD rats. To further reveal the different pharmacokinetic behaviors, the expressions of enzymes and transporters in the liver of normal and NAFLD rats were detected using UPLC-MS/MS. In the NAFLD rats, UDP-glucuronosyltransferase 1-1 (UGT1A1) and nine transporters were significantly inhibited and a positive correlation was observed between them and the AUC of the major components. The present results indicate that the pharmacokinetic differences between the normal and NAFLD rats might be attributed to the significant lower expression levels of both the metabolic enzyme UGT1A1 and nine transporter proteins in the NAFLD rats than in the normal rats. Meanwhile, UGT1A1 and the nine transporter proteins might be used as potential biomarkers to assess the ameliorative effect of LGZGD on NAFLD, which could provide useful information to guide the clinical application of LGZGD.

Evaluation of the role of kefir in management of non-alcoholic steatohepatitis rat model via modulation of NASH linked mRNA-miRNA panel

Non-alcoholic steatohepatitis (NASH) is the clinically aggressive variant of non-alcoholic fatty liver disease. Hippo pathway dysregulation can contribute to NASH development and progression. The use of probiotics is effective in NASH management. Our aim is to investigate the efficacy of kefir Milk in NASH management via modulation of hepatic mRNA-miRNA based panel linked to NAFLD/NASH Hippo signaling and gut microbita regulated genes which was identified using bioinformatics tools. Firstly, we analyzed mRNAs (SOX11, SMAD4 and AMOTL2), and their epigenetic regulator (miR-6807) followed by validation of target effector proteins (TGFB1, IL6 and HepPar1). Molecular, biochemical, and histopathological, analyses were used to evaluate the effects of kefir on high sucrose high fat (HSHF) diet -induced NASH in rats. We found that administration of Kefir proved to prevent steatosis and development of the inflammatory component of NASH. Moreover, Kefir improved liver function and lipid panel. At the molecular level, kefir down-regulated the expression of miR 6807-5p with subsequent increase in the expression of SOX 11, AMOTL2 associated with downregulated SMAD4, resulting in reduction in the expression of the inflammatory and fibrotic markers, IL6 and TGF-β1 in the treated and prophylactic groups compared to the untreated rats. In conclusion, Kefir suppressed NASH progression and improved both fibrosis and hepatic inflammation. The produced effect was correlated with modulation of SOX11, SMAD4 and AMOTL2 mRNAs) - (miR-6807-5p) - (TGFB, IL6 and, HepPar1) expression.

Evodiamine decreased the systemic exposure of pravastatin in non-alcoholic steatohepatitis rats due to the up-regulation of hepatic OATPs

CONTEXT

Patients with non-alcoholic steatohepatitis (NASH) may have a simultaneous intake of pravastatin and evodiamine-containing herbs.

OBJECTIVE

The effect of evodiamine on the pharmacokinetics of pravastatin and its potential mechanisms were investigated in NASH rats.

MATERIALS AND METHODS

The NASH model was conducted with feeding a methionine choline-deficient (MCD) diet for 8 weeks. Sprague-Dawley rats were randomised equally (n = 6) into NASH group, evodiamine group (10 mg/kg), pravastatin group (10 mg/kg), and evodiamine (10 mg/kg) + pravastatin (10 mg/kg) group. Normal control rats were fed a standard diet. Effects of evodiamine on the pharmacokinetics, distribution, and uptake of pravastatin were investigated.

RESULTS

Evodiamine decreased C_max (159.43 ± 26.63 vs. 125.61 ± 22.17 μg/L), AUC_0-t (18.17 ± 2.52 vs. 14.91 ± 2.03 mg/min/L) and AUC_0-∞ (22.99 ± 2.62 vs. 19.50 ± 2.31 mg/min/L) of orally administered pravastatin in NASH rats, but had no significant effect in normal rats. Evodiamine enhanced the uptake (from 154.85 ± 23.17 to 198.48 ± 26.31 pmol/mg protein) and distribution (from 736.61 ± 108.07 to 911.89 ± 124.64 ng/g tissue) of pravastatin in NASH rat liver. The expression of Oatp1a1, Oatp1a4, and Oatp1b2 was up-regulated 1.48-, 1.38-, and 1.51-fold by evodiamine. Evodiamine decreased the levels of IL-1β, IL-6, and TNF-α by 27.82%, 24.76%, and 29.72% in NASH rats, respectively.

DISCUSSION AND CONCLUSIONS

Evodiamine decreased the systemic exposure of pravastatin by up-regulating the expression of OATPs. These results provide a reference for further validation of this interaction in humans.

Salvia miltiorrhiza Bge. (Danshen) in the Treating Non-alcoholic Fatty Liver Disease Based on the Regulator of Metabolic Targets

Non-alcoholic fatty liver disease (NAFLD) is rapidly prevalent due to its strong association with increased metabolic syndrome such as cardio- and cerebrovascular disorders and diabetes. Few drugs can meet the growing disease burden of NAFLD. Salvia miltiorrhiza Bge. (Danshen) have been used for over 2,000 years in clinical trials to treat NAFLD and metabolic syndrome disease without clarified defined mechanisms. Metabolic targets restored metabolic homeostasis in patients with NAFLD and improved steatosis by reducing the delivery of metabolic substrates to liver as a promising way. Here we systematic review evidence showing that Danshen against NAFLD through diverse and crossing mechanisms based on metabolic targets. A synopsis of the phytochemistry and pharmacokinetic of Danshen and the mechanisms of metabolic targets regulating the progression of NAFLD is initially provided, followed by the pharmacological activity of Danshen in the management NAFLD. And then, the possible mechanisms of Danshen in the management of NAFLD based on metabolic targets are elucidated. Specifically, the metabolic targets c-Jun N-terminal kinases (JNK), sterol regulatory element-binding protein-1c (SREBP-1c), nuclear translocation carbohydrate response element–binding protein (ChREBP) related with lipid metabolism pathway, and peroxisome proliferator-activated receptors (PPARs), cytochrome P450 (CYP) and the others associated with pleiotropic metabolism will be discussed. Finally, providing a critical assessment of the preclinic and clinic model and the molecular mechanism in NAFLD.

Glutathione S-transferase Mu 2 inhibits hepatic steatosis via ASK1 suppression

Hepatic steatosis is the main characteristic of some liver metabolism diseases. However, unclear molecular mechanism of hepatic steatosis impedes the therapy of this hepatic steatosis. Glutathione-S-transferase mu 2 (GSTM2), as a member of phase II drug metabolizing enzymes (DMEs), regulates cellular antioxidant and detoxificant. GSTM2 was highly up-regulated in hepatic steatosis tissues and high-fat diet (HFD) fed mice. Loss-of-function GSTM2 mouse model demonstrated that GSTM2 protected mice from excess fat accumulation. Mechanistically, GSTM2 interacted with ASK1 and suppressed its phosphorylation and the activation of subsequent downstream p38-JNK signalling. Moreover, GSTM2 overexpression in the liver effectively ameliorated hepatic lipid accumulation. Therefore, we identified GSTM2 as an important negative regulator in progression of hepatic steatosis via both its detoxification/antioxidant and inhibition of ASK1-p38/JNK signalling. This study showed potential therapeutic function of the DME in progression of hepatic steatosis.

Jin et al. investigate the underlying mechanisms of hepatic steatosis and show that Glutathione-S-transferase mu 2 (GSTM2), which is a drug metabolizing enzyme (DME), is upregulated in hepatic steatosis tissue from mice fed with a high fat diet. They show that GSTM2 is a negative regulator of hepatic steatosis via both detoxification/antioxidant and inhibition of ASK1-p38/JNK signalling, which sheds light on its potential as a therapeutic target.

Citrus depressa Hayata Peel Ameliorates Nonalcoholic Fatty Liver and Modulates the Hepatic Drug-metabolizing Enzymes and Transporters in Rats Fed a High-fat Diet

Citrus depressa Hayata is a small, green citrus fruit native to Taiwan and Japan. The citrus peel contains polymethoxylated flavones, including nobiletin and tangeretin, and might have strong antioxidant and...

Gd-EOB-DTPA-enhanced MRI-a noninvasive and short-term assessment method for liver necroinflammation after direct-acting antiviral (DAA) therapy in patients with chronic hepatitis C

PURPOSE

To assess liver necroinflammation in HCV patients undergone antiviral therapy by Gd-EOB-DTPA-enhanced MRI with histopathologic analyses as reference.

METHODS

HCV patients were enrolled in this prospective study before antiviral treatment between 09-2016 and 07-2017. Unenhanced MR, Gd-EOB-DTPA-enhanced MR, and liver biopsy were performed before and 24 weeks after treatment of daclatasvir with asunaprevir (DAA). DWI was obtained using a breath-hold single-shot echo planar spin-echo sequence. Twenty minutes after administration of Gd-EOB-DTPA, the relative enhancement (RE) and the contrast enhancement index (CEI) were recorded. Liver necroinflammatory activity grades (G0-18) were categorized on the Ishak Scoring systems. CEI, RE, and DWI of baseline and 24 weeks after treatment were compared by paired t test. Relationship between MR parameters and histologic scores was evaluated by Pearson's correlation. Receiver operating characteristic analysis evaluated the measurements' diagnostic performance. MRI variability between two readers was assessed using the intraclass correlation coefficient.Results RESULTS: A decrease of liver necroinflammatory activity grade (p < 0.0001) was detected in final cohort (n = 21; mean age 44 years; 23 to 67 years; 11 F, 10 M). Statistical results of 42 person-times in 21 patients at baseline and follow-up showed CEI and ADC were significantly different (p = 0.006 and 0.036) across histologic grades of liver necroinflammation. Significant increase of CEI, RE, and ADC (p = 0.0004, 0.0032, 0.0110) 24 weeks after DAA treatment was seen. Additionally, CEI was correlated to necroinflammatory grade (r =  - 0.596, p = 0.006). AUROC for CEI, ADC, and CEI combined with ADC to differentiate patients with none and mild (G0-6) from patients with moderate and severe necroinflammation (G7-18) was 0.834 (95% CI 0.712-0.956, 0.724(95% CI 0.565-0.884) and 0.837(95% CI 0.717-0.956).

CONCLUSION

Gd-EOB-DTPA-enhanced MRI by CEI could be used as a noninvasive imaging biomarker to distinguish grades of necroinflammatory activity in patients with HCV after DAAs therapy at early stage and CEI combined with ADC could get a better diagnostic accuracy.

Pharmacokinetic herb-disease-drug interactions: Effect of ginkgo biloba extract on the pharmacokinetics of pitavastatin, a substrate of Oatp1b2, in rats with non-alcoholic fatty liver disease

ETHNOPHARMACOLOGICAL RELEVANCE

Ginkgo biloba L. is a traditional Chinese medicine for hyper lipaemia. Ginkgo flavonols and terpene lactones are responsible for the lipid-lowering effect in non-alcoholic fatty liver disease (NAFLD). However, the pharmacokinetics of ginkgo flavonols and terpene lactones in NAFLD was not clarified.

AIM OF THE STUDY

To investigate the effects of Ginkgo biloba L. leaves extracts (EGB) and NAFLD on hepatocyte organic anion transporting polypeptide (Oatp)1b2, and to assess the pharmacokinetics of EGB active ingredients in NAFLD rats.

MATERIALS AND METHODS

Male rats were fed with a high-fat diet to induce NAFLD models. The pharmacokinetic characteristics of EGB active ingredients were studied in NAFLD rats after two or four weeks of treatment with 3.6, 10.8, and 32.4 mg/kg EGB. The effects of NAFLD and EGB were investigated on the systemic exposure of pitavastatin, a probe substrate of Oatp1b2. The inhibitory effects of ginkgo flavonols and terpene lactones on OATP1B1-mediated uptake of ³H-ES were tested in hOATP1B1-HEK293 cells.

RESULTS

The plasma exposure of ginkgolides and flavonols in NAFLD rats increased in a dose-dependent manner following oral administration of EGB at 3.6-32.4 mg/kg. The half-lives of ginkgolides A, B, C, and bilobalide (2-3 h) were shorter than quercetin, kaempferol, and isorhamnetin (approximately 20 h). NAFLD reduced the plasma pitavastatin exposure by about 50 % due to the increased Oatp1b2 expression in rat liver. Increased EGB (from 3.6 to 32.4 mg/kg) substantially increased the C_max and AUC_0-t of pitavastatin by 1.8-3.2 and 1.3-3.0 folds, respectively. In hOATP1B1-HEK293 cells, kaempferol and isorhamnetin contributed to the inhibition of OATP1B1-mediated uptake of ³H-ES with IC₅₀ values of 3.28 ± 1.08 μM and 46.12 ± 5.25 μM, respectively.

CONCLUSIONS

NAFLD and EGB can alter the activity of hepatic uptake transporter Oatp1b2 individually or in combination. The pharmacokinetic herb-disease-drug interaction found in this research will help inform the clinical administration of EGB or Oatp1b2 substrates.

Review article: therapeutic aspects of bile acid signalling in the gut-liver axis

BACKGROUND

Bile acids are important endocrine modulators of intestinal and hepatic signalling cascades orchestrating critical pathophysiological processes in various liver diseases. Increasing knowledge on bile acid signalling has stimulated the development of synthetic ligands of nuclear bile acid receptors and other bile acid analogues.

AIM

This review summarises important aspects of bile acid-mediated crosstalk between the gut and the liver ("gut-liver axis") as well as recent findings from experimental and clinical studies.

METHODS

We performed a literature review on bile acid signalling, and therapeutic applications in chronic liver disease.

RESULTS

Intestinal and hepatic bile acid signalling pathways maintain bile acid homeostasis. Perturbations of bile acid-mediated gut-liver crosstalk dysregulate transcriptional networks involved in inflammation, fibrosis and endothelial dysfunction. Bile acids induce enterohepatic feedback signalling by the release of intestinal hormones, and regulate enterohepatic circulation. Importantly, bile acid signalling plays a central role in maintaining intestinal barrier integrity and antibacterial defense, which is particularly relevant in cirrhosis, where bacterial translocation has a profound impact on disease progression. The nuclear bile acid farnesoid X receptor (FXR) is a central intersection in bile acid signalling and has emerged as a relevant therapeutic target.

CONCLUSIONS

Experimental evidence suggests that bile acid signalling improves the intestinal barrier and protects against bacterial translocation in cirrhosis. FXR agonists have displayed efficacy for the treatment of cholestatic and metabolic liver disease in randomised controlled clinical trials. However, similar effects remain to be shown in advanced liver disease, particularly in patients with decompensated cirrhosis.

Multidirectional facets of obesity management in the metabolic syndrome population after liver transplantation

The obesity pandemic has resulted in an increasing demand for liver transplantation and has significantly altered the profile of liver transplant candidates in addition to affecting posttransplantation outcomes. In this review, we discuss a broad range of clinical approaches that warrant attention to provide comprehensive and patient‐centred medical care to liver transplant recipients, and to be prepared to confront the rapidly changing clinical challenges and ensuing dilemmas. Adipose tissue is a complex and metabolically active organ. Visceral fat deposition is a key predictor of overall obesity‐related morbidity and mortality. Limited pharmacological options are available for the treatment of obesity in the liver transplant population. Bariatric surgery may be an alternative in eligible patients. The rapidly increasing prevalence of nonalcoholic fatty liver disease (NAFLD) is a global concern; NAFLD affects both pre‐ and posttransplantation outcomes. Numerous studies have investigated pharmacological and nonpharmacological management of NAFLD and some of these have shown promising results. Liver transplant recipients are constantly exposed to numerous factors that result in intestinal microbiota alterations, which were linked to the development of obesity, diabetes type 2, metabolic syndrome (MS), NAFLD, and hepatocellular cancer. Microbiota modifications with probiotics and prebiotics bring gratifying results in the management of metabolic complications. Fecal microbiota transplantation (FMT) is successfully performed in many medical indications. However, the safety and efficacy profiles of FMT in immunocompromised patients remain unclear. Obesity together with immunosuppressive treatment, may affect the pharmacokinetic and/or pharmacodynamic properties of coadministered medications. Individualized immunosuppressive regimens are recommended following liver transplantation to address possible metabolic concerns. Effective and comprehensive management of metabolic complications is shown to yield multiple beneficial results in the liver transplant population and may bring gratifying results in improving long‐term survival rates.

Probiotic-prebiotic-synbiotic modulation of (YAP1, LATS1 and NF2 mRNAs/miR-1205/lncRNA SRD5A3-AS1) panel in NASH animal model

AIM

To investigate the prophylactic efficacy of gut microbiota-based treatments on nonalcoholic steatohepatitis (NASH) management via modulation of Hippo signaling pathway-related genes (YAP1, LATS1 and NF2), and their epigenetic regulators (miR-1205 and lncRNA SRD5A3-AS1) retrieved from in-silico data analysis.

MATERIALS & METHODS

Histopathological, biochemical, molecular and immunohistochemistry analyses were used to assess the effects of multistrain probiotic mixture and prebiotic inulin fiber on high sucrose high fat (HSHF) diet-induced NASH in rats. These treatments were administered orally either alone or in combination, along with HSHF diet.

RESULTS

Both probiotic mixture and prebiotic inulin fiber attenuated steatosis, inflammation and fibrosis grades in HSHF diet-induced NASH rats. Moreover, the applied treatments significantly prevented the elevation of serum liver enzymes and improved lipid panel. At the molecular level, both treatments down-regulated hepatic YAP1 mRNA and miR-1205 expressions, and concomitantly up-regulated the expression of hepatic LATS1& NF2 mRNAs and the lncRNA SRD5A3-AS1. At the protein level, both treatments decreased the hepatic content of the inflammatory marker IL6 and the fibrotic marker TGFβ1. Moreover, an observable reduction in α-SMA together with noticeable elevation in LATS1/2 protein expression levels were detected in liver sections compared to the untreated rats.

CONCLUSION

Probiotic mixture and prebiotic inulin fiber, either alone or in combination, attenuated NASH progression and ameliorated both fibrosis and hepatic inflammation in the applied animal model. The produced effect was correlated with modulation of the retrieved (YAP1, LATS1 and NF2) - (miR-1205) - (lncRNA SRD5A3-AS1) RNA panel.

Application of a PBPK model to elucidate the changes of systemic and liver exposures for rosuvastatin, carotegrast, and bromfenac followed by OATP inhibition in monkeys

The impact of organic anion‐transporting polypeptide (OATP) inhibition on systemic and liver exposures of three OATP substrates was investigated in cynomolgus monkeys. A monkey physiologically‐based pharmacokinetic (PBPK) model was constructed to describe the exposure changes followed by OATP functional attenuation. Rosuvastatin, bromfenac, and carotegrast were administered as a single intravenous cassette dose (0.5 mg/kg each) in monkeys with and without predosing with rifampin (RIF; 20 mg/kg) orally. The plasma exposure of rosuvastatin, bromfenac, carotegrast, and OATP biomarkers, coproporphyrin I (CP‐I) and CP‐III were increased 2.3, 2.1, 9.1, 5.4, and 8.8‐fold, respectively, when compared to the vehicle group. The liver to plasma ratios of rosuvastatin and bromfenac were reduced but the liver concentration of the drugs remained unchanged by RIF treatment. The liver concentrations of carotegrast, CP‐I, and CP‐III were unchanged at 1 h but increased at 6 h in the RIF‐treated group. The passive permeability, active uptake, and biliary excretion were characterized in suspended and sandwich‐cultured monkey hepatocytes and then incorporated into the monkey PBPK model. As demonstrated by the PBPK model, the plasma exposure is increased through OATP inhibition while liver exposure is maintained by passive permeability driven from an elevated plasma level. Liver exposure is sensitive to the changes of metabolism and biliary clearances. The model further suggested the involvement of additional mechanisms for hepatic uptakes of rosuvastatin and bromfenac, and of the inhibition of biliary excretion for carotegrast, CP‐I, and CP‐III by RIF. Collectively, impaired OATP function would not reduce the liver exposure of its substrates in monkeys.

Increased penetration of diphenhydramine in brain via proton-coupled organic cation antiporter in rats with lipopolysaccharide-induced inflammation

Uptake transporters in brain microvascular endothelial cells (BMECs) are involved in the penetration of basic (cationic) drugs such as diphenhydramine (DPHM) into the brain. Lipopolysaccharide (LPS)-induced inflammation alters the expression levels and activities of uptake transporters, which change the penetration of DPHM into the brain. A brain microdialysis study showed that the unbound brain-to-plasma partition coefficient (K_p,uu,brain) for DPHM in LPS rats was approximately two times higher than that in control rats. The transcellular transport of DPHM to BMECs was increased when BMECs were cultured with serum from LPS rats. Compared with control rats or BMECs, the brain uptake of DPHM in LPS rats was increased and the intracellular accumulation of DPHM was increased under a high intracellular pH in BMECs from LPS rats, respectively. Treatment of BMECs with transporter inhibitors or inflammatory cytokines had little impact on the intracellular accumulation of DPHM in BMECs. This study suggests that LPS-induced inflammation promotes unidentified proton-coupled organic cation (H⁺/OC) antiporters that improve the penetration of DPHM into rat brain via the blood-brain barrier.

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The unbound brain-to-plasma partition coefficient for diphenhydramine (DPHM) was increased in lipopolysaccharide-induced inflammation in rats.

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The uptake of DPHM to brain microvascular endothelial cells (BMECs) was promoted by treatments of serum from rats with inflammation.

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Treatment of BMECs with transporter inhibitors or inflammatory cytokines had little impact on the intracellular accumulation of DPHM in BMECs.

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LPS-induced inflammation promotes unidentified proton-coupled organic cation antiporters that improve the brain penetration of DPHM.

Pharmacokinetic changes of clozapine and norclozapine in a rat model of non-alcoholic fatty liver disease induced by orotic acid

Impaired in vitro oxidation of clozapine has been reported in steatotic rat liver due to downregulation of cytochrome P450 (CYP) 1A. Pharmacokinetic changes of clozapine and its major metabolite, norclozapine, were evaluated in a rat model of non-alcoholic fatty liver disease (NAFLD) induced by orotic acid. Significantly slower in vitro CL_int for formation of norclozapine from clozapine was observed in NAFLD rats than in control rats as a result of the reduced protein expression and metabolic activity of CYP1A1/2. However, systemic exposures to clozapine in NAFLD rats were comparable to those in controls after intravenous (4 mg/kg) and oral (10 mg/kg) administration of clozapine. Of note, the AUC of the norclozapine and AUC_norclozapine/AUC_clozapine ratio following intravenous and oral administration of clozapine rather increased significantly in NAFLD rats, as a result of the slowed subsequent metabolism of norclozapine via CYP1A1/2. Steady-state brain concentrations of both clozapine and norclozapine were significantly higher in NAFLD rats than those in control rats following intravenous infusion of clozapine. Increased systemic exposure to norclozapine and elevated brain concentrations of clozapine and norclozapine observed in NAFLD rats imply that further studies are warranted on the pharmacotherapy of clozapine in patients with pre-existing or drug-induced hepatic steatosis.

Zucker Lean Rats With Hepatic Steatosis Recapitulate Asymptomatic Metabolic Syndrome and Exhibit Greater Sensitivity to Drug-Induced Liver Injury Compared With Standard Nonclinical Sprague-Dawley Rat Model

Fatty liver disease is a potential risk factor for drug-induced liver injury (DILI). Despite advances in nonclinical in vitro and in vivo models to assess liver injury during drug development, the pharmaceutical industry is still plagued by idiosyncratic DILI. Here, we tested the hypothesis that certain features of asymptomatic metabolic syndrome (namely hepatic steatosis) increase the risk for DILI in certain phenotypes of the human population. Comparison of the Zucker Lean (ZL) and Zucker Fatty rats fed a high fat diet (HFD) revealed that HFD-fed ZL rats developed mild hepatic steatosis with compensatory hyperinsulinemia without increases in liver enzymes. We then challenged steatotic HFD-fed ZL rats and Sprague-Dawley (SD) rats fed normal chow, a nonclinical model widely used in the pharmaceutical industry, with acetaminophen overdose to induce liver injury. Observations in HFD-fed ZL rats included increased liver injury enzymes and greater incidence and severity of hepatic necrosis compared with similarly treated SD rats. The HFD-fed ZL rats also had disproportionately higher hepatic drug accumulation, which was linked with abnormal hepatocellular efflux transporter distribution. Here, we identify ZL rats with HFD-induced hepatic steatosis as a more sensitive nonclinical in vivo test system for modeling DILI compared with SD rats fed normal chow.

Intestinal absorption and hepatic elimination of drugs in high-fat high-cholesterol diet-induced non-alcoholic steatohepatitis rats: exemplified by simvastatin

BACKGROUND AND PURPOSE

Altered drug pharmacokinetics is a significant concern in non-alcoholic steatohepatitis (NASH) patients. Although high-fat high-cholesterol (HFHC) diet-induced NASH (HFHC-NASH) rats could simulate the typical dysregulation of cholesterol in NASH patients, experimental investigation on the altered drug pharmacokinetics in this model are limited. Thus, the present study comprehensive investigates the nature of such altered pharmacokinetics using simvastatin as the model drug.

EXPERIMENTAL APPROACH

Pharmacokinetic profiles of simvastatin and its active metabolite simvastatin acid together with compartmental pharmacokinetic modelling were used to identify the key factors involved in the altered pharmacokinetics of simvastatin in HFHC-NASH rats. Experimental investigations via in situ single-pass intestinal perfusion and intrahepatic injection of simvastatin were carried out. Histology, Ces1 activities and mRNA/protein levels of Oatp1b2/CYP2c11/P-gp in the small intestine/liver of healthy and HFHC-NASH rats were compared.

KEY RESULTS

Reduced intestinal absorption and more extensive hepatic elimination in HFHC-NASH rats resulted in less systemic exposures of simvastatin/simvastatin acid. In the small intestine of HFHC-NASH rats, thicker intestinal wall with more collagen fibres, increased Ces1 activity and up-regulated P-gp protein decreased the permeability of simvastatin, accelerated the hydrolysis of simvastatin and promoted the efflux of simvastatin acid respectively. In the liver of HFHC-NASH rats, higher hepatic P-gp expression accelerated the hepatic elimination of simvastatin.

CONCLUSION AND IMPLICATIONS

Altered histology, Ces1 activity and P-gp expression in the small intestine/liver were identified to be the major contributing factors leading to less systemic exposure of drugs in HFHC-NASH rats, which may be applicable to NASH patients.

Can gadoxetic acid–enhanced magnetic resonance imaging be used to avoid liver biopsy in patients with nonalcoholic fatty liver disease?

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a major cause of liver disease worldwide. The diagnosis of nonalcoholic steatohepatitis (NASH), the most severe form of NAFLD, is crucial and has prognostic and therapeutic implications. However, currently this diagnosis is based on liver biopsy and has several limitations.

AIM

To evaluate the performance of gadoxetic acid–enhanced magnetic resonance imaging (GA-MRI) in differentiating isolated steatosis from NASH in patients with NAFLD.

METHODS

In this prospective study, 56 patients with NAFLD (18 with isolated steatosis and 38 with NASH) underwent GA-MRI. The contrast enhancement index (CEI) was calculated as the rate of increase of the liver-to-muscle signal intensity ratio from before and 20 min after intravenous GA administration. Between-group differences in mean CEI were examined using Student's t test. The area under the receiver operator characteristic curve and the diagnostic performance of gadoxetic acid–enhanced magnetic resonance imaging were evaluated.

RESULTS

The mean CEI for all subjects was 1.82 ± 0.19. The mean CEI was significantly lower in patients with NASH than in those with isolated steatosis (P = 0.008). Two CEI cut-off points were used: < 1.66 (94% specificity) to characterize NASH and > 2.00 (89% sensitivity) to characterize isolated steatosis. CEI values between 1.66 and 2.00 indicated liver biopsy, and the procedure could be avoided in 40% of patients with NAFLD.

CONCLUSION

GA-MRI is an effective noninvasive method that may be useful for the differentiation of NASH from isolated steatosis, and could help to avoid liver biopsy in patients with NAFLD.

Protective Mechanism of Common Buckwheat (Fagopyrum esculentum Moench.) against Nonalcoholic Fatty Liver Disease Associated with Dyslipidemia in Mice Fed a High-Fat and High-Cholesterol Diet

This study aimed to investigate the protective mechanism of common buckwheat (Fagopyrum esculentum Moench.) against nonalcoholic fatty liver disease (NAFLD) associated with dyslipidemia in mice that were fed a high-fat and high-cholesterol diet (HFD). Results showed that oral supplementation of common buckwheat significantly improved physiological indexes and biochemical parameters related to dyslipidemia and NAFLD in mice fed with HFD. Furthermore, the HFD-induced reductions in fecal short-chain fatty acids were reversed by common buckwheat intervention, which also increased the fecal bile acid (BA) abundance compared with HFD-induced hyperlipidemic mice. Liver metabolomics based on ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry demonstrated that common buckwheat supplementation made significant regulatory effects on the pentose phosphate pathway, starch and sucrose metabolism, primary BA biosynthesis, and so forth. The results of high-throughput sequencing revealed that common buckwheat supplementation significantly altered the structure of the intestinal microbiota in mice fed with HFD. The correlations between lipid metabolic parameters and intestinal microbial phylotypes were also revealed by the heatmap and network. Additionally, common buckwheat intervention regulated the mRNA expressions of genes responsible for liver lipid metabolism and BA homeostasis, thus promoting BA synthesis and excretion. These findings confirmed that common buckwheat has the outstanding ability of improving lipid metabolism and could be used as a potential functional food for the prevention of NAFLD and hyperlipidemia.

Impact of SLCO1B1 Genetic Variation on Rosuvastatin Systemic Exposure in Pediatric Hypercholesterolemia

This study investigated the impact of SLCO1B1 genotype on rosuvastatin systemic exposure in hypercholesterolemic children and adolescents. Participants (8–21 years) with at least one allelic variant of SLCO1B1 c.521T>C (521TC, n = 13; 521CC, n = 2) and wild type controls (521TT, n = 13) completed a single oral dose pharmacokinetic study. The variability contributed by SLCO1B1 c.521 sequence variation to rosuvastatin (RVA) systemic exposure among our pediatric cohort was comparable to previous studies in adults. RVA concentration‐time curve from 0–24 hours (AUC_0–24) was 1.4‐fold and 2.2‐fold higher in participants with c.521TC and c.521CC genotype compared 521TT participants, respectively. Interindividual variability of RVA exposure within SLCO1B1 genotype groups exceeded the ~ 1.5‐fold to 2‐fold difference in mean RVA exposure observed among SLCO1B1 genotype groups, suggesting that other factors also contribute to interindividual variability in the rosuvastatin dose‐exposure relationship. A multivariate model performed confirmed SLCO1B1 c.521T>C genotype as the primary factor contributing to RVA systemic exposure in this pediatric cohort, accounting for ~ 30% of the variability RVA AUC_0–24. However, of the statins investigated to date in the pediatric population, RVA has the lowest magnitude of variability in systemic exposure.

The pharmacokinetics of mycophenolic acid in rats with orotic acid induced nonalcoholic fatty liver disease

Post-transplantation nonalcoholic fatty liver disease (NAFLD) is common in liver transplant recipients. Changes in the expression levels and activities of drug-metabolizing enzymes and drug transporters have been reported in patients with NAFLD and relevant rodent models. Here, we evaluated whether the pharmacokinetics of mycophenolic acid (MPA), an immunosuppressant, would be altered in rats with NAFLD. NAFLD was induced by feeding a diet containing 1% (w/w) orotic acid for 20 days. The extent of hepatic glucuronidation of MPA to a major metabolite, mycophenolic acid-7-O-glucuronide (MPAG), did not differ between rats with NAFLD and controls. The expression levels of hepatic multidrug resistance-associated protein 2, responsible for biliary excretion of MPAG, were comparable in rats with NAFLD and controls; the biliary excretion of MPAG was also similar in the two groups. Compared with control rats, rats with NAFLD did not exhibit significant changes in the areas under the plasma concentration – time curves of MPA or MPAG after intravenous (5 mg/kg) or oral (10 mg/kg) administration of MPA. However, delayed oral absorption of MPA was observed in rats with NAFLD compared with controls; the MPA and MPAG peak plasma concentrations fell significantly and the times to achieve them were prolonged following oral administration of MPA.

Pharmacokinetics and Pharmacodynamics of Drugs in Obese Pediatric Patients: How to Map Uncharted Clinical Territories

Clinicians are increasingly faced with challenges regarding the pharmacological treatment of obese pediatric patients. To provide guidance for these treatments, a better understanding of the impact of obesity on pharmacological processes in children is needed. Results on pharmacological studies in adults show however ambiguous patterns regarding the impact of obesity on ADME processes or on drug pharmacodynamics. Additionally, based on the limited research performed in obese pediatric patients, it becomes clear that findings from obese adults cannot be expected to always translate directly to similar findings in obese children. To improve knowledge on drug pharmacology in obese pediatric patients, studies should focus on quantifying the impact of maturation, obesity, and other relevant variables on primary pharmacological parameters and on disentangling systemic (renal and/or hepatic) and presystemic (gut and/or first-pass hepatic) clearance. For this, data is required from well-designed clinical trials that include patients with not only a wide range in age but also a range in excess body weight, upon oral and intravenous dosing. Population modelling approaches are ideally suitable for this purpose and can also be used to link the pharmacokinetics to pharmacodynamics and to derive drug dosing regimens. Generalizability of research findings can be achieved by including mechanistic aspects in the data analysis, for instance, using either extrapolation approaches in population modelling or by applying physiologically based modelling principles. It is imperative that more and smarter studies are performed in obese pediatric patients to provide safe and effective treatment for this special patient population.

Interaction of Oatp1b2 expression and nonalcoholic steatohepatitis on pravastatin plasma clearance

The downregulation of hepatic uptake transporters, including those of the OATP family, are a well known consequence of nonalcoholic steatohepatitis (NASH). Prior studies have shown that the combination of NASH and Oatp1b2 knockout synergistically reduces the clearance of pravastatin (PRAV) in the methionine and choline deficient (MCD) mouse model of NASH, and the current study therefore aimed to determine the impact of NASH and genetic heterozygosity of Oatp1b2 on PRAV clearance, modeling the overlap between the 24% of the human population who are heterozygous for non-functioning OATP1B1, and the ~15% with NASH, potentially placing these people at higher risk of statin-induced myopathy. Therefore, male C57BL/6 wild-type (WT), Oatp1b2+/- (HET), and Oatp1b2-/- (KO) mice were fed either a control (methionine and choline sufficient) or methionine and choline-deficient (MCD) diet to induce NASH. After six weeks of feeding, pravastatin was administered via the carotid artery. Blood and bile samples were collected throughout 90 min after PRAV administration. The concentration of PRAV in plasma, bile, liver, kidney, and muscle was determined by liquid chromatography-tandem mass spectrometry. MCD diet did not alter the plasma AUC values of PRAV in either WT or HET mice. However, the MCD diet increased plasma AUC by 4.4-fold in KO mice. MCD diet and nonfunctional Oatp1b2 synergistically increased not only plasma AUC but also the extrahepatic tissue concentration of pravastatin, whereas the partially decreased function of Oatp1b2 and NASH together were insufficient in significantly altering PRAV pharmacokinetics. These data suggest that a single copy of fully functional OATP1B1 in NASH patients may be sufficient to avoid the increase of pravastatin toxicity.

Overview of organic anion transporters and organic anion transporter polypeptides and their roles in the liver

Organic anion transporters (OATs) and organic anion transporter polypeptides (OATPs) are classified within two SLC superfamilies, namely, the SLC22A superfamily and the SLCO superfamily (formerly the SLC21A family), respectively. They are expressed in many tissues, such as the liver and kidney, and mediate the absorption and excretion of many endogenous and exogenous substances, including various drugs. Most are composed of 12 transmembrane polypeptide chains with the C-terminus and the N-terminus located in the cell cytoplasm. OATs and OATPs are abundantly expressed in the liver, where they mainly promote the uptake of various endogenous substrates such as bile acids and various exogenous drugs such as antifibrotic and anticancer drugs. However, differences in the locations of glycosylation sites, phosphorylation sites, and amino acids in the OAT and OATP structures lead to different substrates being transported to the liver, which ultimately results in their different roles in the liver. To date, few articles have addressed these aspects of OAT and OATP structures, and we study further the similarities and differences in their structures, tissue distribution, substrates, and roles in liver diseases.

Western Diet-Induced Metabolic Alterations Affect Circulating Markers of Liver Function before the Development of Steatosis

Since nutrition might have a significant impact on liver function, we analyzed the early effect of Western-type diet on hepatic tissue and lipid and drug metabolism in Wistar–Kyoto rats (n = 8); eight rats fed with a standard diet were used as controls. Histological analysis of liver tissue was performed, and plasma biochemical parameters were measured. Plasma concentration of six bile acids was determined by ultra-liquid chromatography-tandem mass spectrometry UHPLC-MS/MS. Hepatic gene expressions of enzymes involved in drug and lipid metabolism were assessed by means of real-time reverse transcription (qRT)-PCR. Liver of rats fed with a Western diet did not show macroscopic histological alterations, but number and diameter of lipid droplets increased, as well as DGAT1, GPAT4, SCD, FASN and SREBP2 expression. Furthermore, Western diet-fed animals showed an increase in the activation of hepatic stellate cells and macrophage number in liver tissue, as well as a significant increase in AST and bilirubin levels (p < 0.01), and in the LDL:HDL cholesterol ratio (p < 0.001). Plasma chenodeoxycholic acid concentration increased significantly, whereas cholic acid decreased (p < 0.05), and cytochrome P450 genes were generally downregulated. Significant changes in hepatic lipid and drug metabolism are early induced by the Western diet, prior to steatosis development. Such changes are associated with a peculiar alteration in circulating bile acids, which could represent an early marker of non-alcoholic fatty liver disease (NAFLD) development.

Impact of Genetic Variation on Pravastatin Systemic Exposure in Pediatric Hypercholesterolemia

This study investigated the impact of SLCO1B1 genotype on pravastatin systemic exposure in children and adolescents with hypercholesterolemia. Participants (8-20 years) with at least one allelic variant of SLCO1B1 c.521T>C (521TC, n = 15; 521CC, n = 2) and wild-type controls (521TT, n = 15) completed a single oral dose pharmacokinetic study. Interindividual variability of pravastatin acid (PVA) exposure within SLCO1B1 genotype groups exceeded the approximately twofold difference in mean PVA exposure observed between SLCO1B1 genotype groups (P > 0.05, q > 0.10). The 3'α-iso-pravastatin acid and lactone isomer formation in the acidic environment of the stomach prior to absorption also was variable and affected PVA exposure in all genotype groups. The SLCO1B1 c.521 gene variant contributing to variability in systemic exposure to PVA in our pediatric cohort was comparable to previous studies in adults. However, other demographic and physicochemical factors seem to also contribute to interindividual variability in the dose-exposure relationship.

Asking the Right Questions With Animal Models: Methionine- and Choline-Deficient Model in Predicting Adverse Drug Reactions in Human NASH

In the past few decades, great conceptual and technological advances have been made in the field of toxicology, but animal model-based research still remains one of the most widely used and readily available tools for furthering our current knowledge. However, animal models are not perfect in predicting all systemic toxicity in humans. Extrapolating animal data to accurately predict human toxicities remains a challenge, and researchers are obligated to question the appropriateness of their chosen animal model. This paper provides an assessment of the utility of the methionine- and choline-deficient (MCD) diet fed animal model in reflecting human nonalcoholic steatohepatitis (NASH) and the potential risks of adverse drug reactions and toxicities that are associated with the disease. As a commonly used NASH model, the MCD model fails to exhibit most metabolic abnormalities in a similar manner to the human disease. The MCD model, on the other hand, closely resembles human NASH histology and reflects signatures of drug transporter alterations in humans. Due to the nature of the MCD model, it should be avoided in studies of NASH pathogenesis, metabolic parameter evaluation, and biomarker identification. But it can be used to accurately predict altered drug disposition due to NASH-associated transporter alterations.

Non-invasive Evaluation of NAFLD with Indocyanine Green Clearance Test: a Preliminary Study in Morbidly Obese Patients Undergoing Bariatric Surgery

BACKGROUND

Overweight and obesity dramatically increased in the last years. Hepatic complication of obesity, integrated in the term of non-alcoholic fatty liver disease (NAFLD), is a spectrum of abnormality ranging from steatosis to non-alcoholic steatohepatitis (NASH), potentially leading to cirrhosis. Liver biopsy remains the gold standard to evaluate the stage of NAFLD; however, the procedure is invasive. The indocyanine green (ICG) clearance test is performed since years to assess hepatic function before partial hepatectomy, or after liver transplantation. This study was designed to detect liver complications with the ICG clearance test in a population of obese patients scheduled for bariatric surgery.

METHODS

In a prospective cohort study, morbidly obese individuals receiving bariatric surgery with scheduled hepatic biopsies were investigated. Liver function was determined by the ICG test preoperatively, and blood samples were collected. Liver biopsy specimens were obtained for each patient and classified according to the NAFLD activity score (NAS) by a single pathologist that was blinded to the results of the ICG test.

RESULTS

Twenty-six patients were included (7 male and 19 female). The mean age of participants was 45.8 years; the mean body mass index was 41.4 kg/m². According to the NAS, 6 (23.1%) patients revealed manifest NASH, and 5 patients were considered borderline (19.2%). A closed correlation was observed between the ICG clearance test and hepatic steatosis (r = 0.43, p = 0.03), NAS (r = 0.44, p = 0.025), and fibrosis (r = 0.49, p = 0.01).

CONCLUSIONS

In obese patients, non-invasive evaluation of liver function with the indocyanine green clearance test correlated with histological features of NAFLD. This may detect non-invasively hepatopathy in obese population and could motive biopsy.

Gene-by-Environment Interaction of Bcrp-/- and Methionine- and Choline-Deficient Diet-Induced Nonalcoholic Steatohepatitis Alters SN-38 Disposition

Disease progression to nonalcoholic steatohepatitis (NASH) has profound effects on the expression and function of drug-metabolizing enzymes and transporters, which provide a mechanistic basis for variable drug response. Breast cancer resistance protein (BCRP), a biliary efflux transporter, exhibits increased liver mRNA expression in NASH patients and preclinical NASH models, but the impact on function is unknown. It was shown that the transport capacity of multidrug resistance protein 2 (MRP2) is decreased in NASH. SN-38, the active irinotecan metabolite, is reported to be a substrate for Bcrp, whereas SN-38 glucuronide (SN-38G) is a Mrp2 substrate. The purpose of this study was to determine the function of Bcrp in NASH through alterations in the disposition of SN-38 and SN-38G in a Bcrp knockout (Bcrp^-/- KO) and methionine- and choline-deficient (MCD) model of NASH. Sprague Dawley [wild-type (WT)] rats and Bcrp^-/- rats were fed either a methionine- and choline-sufficient (control) or MCD diet for 8 weeks to induce NASH. SN-38 (10 mg/kg) was administered i.v., and blood and bile were collected for quantification by liquid chromatography-tandem mass spectrometry. In Bcrp^-/- rats on the MCD diet, biliary efflux of SN-38 decreased to 31.9%, and efflux of SN-38G decreased to 38.7% of control, but WT-MCD and KO-Control were unaffected. These data indicate that Bcrp is not solely responsible for SN-38 biliary efflux, but rather implicate a combined role for BCRP and MRP2. Furthermore, the disposition of SN-38 and SN-38G is altered by Bcrp^-/- and NASH in a gene-by-environment interaction and may result in variable drug response to irinotecan therapy in polymorphic patients.

Deletion of Thioredoxin-interacting protein ameliorates high fat diet-induced non-alcoholic steatohepatitis through modulation of Toll-like receptor 2-NLRP3-inflammasome axis: Histological and immunohistochemical study

Endemic prevalence of obesity is associated with alarming increases in non-alcoholic steatohepatitis (NASH) with limited available therapeutics. Toll-like receptor2 (TLR2) and Nod-like receptor protein 3 (NLRP3) Inflammasome are implicated in hepatic steatosis, inflammation and fibrosis; the histological landmark stages of NASH. TXNIP, a member of α-arrestin family activates NLRP3 in response to various danger stimuli. The aim of current work was to investigate the effect of TXNIP genetic deletion on histological manifestations of high fat diet-induced steatohepatitis and activation of TLR2-NLRP3-inflammasome axis. Wild-type mice (WT) and TXNIP knock out (TKO) littermates were randomized to normal diet (WT-ND and TKO-ND) or high fat diet (HFD, 60% fat) (WT-HFD and TKO-HFD). After 8-weeks, liver samples from all groups were evaluated by histological, immunohistochemical and western blot analysis. HFD resulted in significant induction of micro and macrovesicular hepatic steatosis, that was associated with increased inflammatory immune cell infiltration in WT-HFD compared with WT-ND and TKO-ND controls, but not in TKO-HFD group. In parallel, WT-HFD group showed significant fibrosis and α-SMA expression; a marker of pro-fibrotic stellate-cell activation, in areas surrounding the central vein and portal circulation, versus all other groups. Western blot revealed increased activation of TLR2-NLRP3 inflammasome pathway and downstream IL-1β and TNFα in WT-HFD group, but not in TKO-HFD group. IL-1β expression coincided within the same areas of steatosis, inflammatory cell infiltration, collagen deposition and α-SMA expression in WT-HFD mice, that was significantly reduced in TKO-HFD mice. In conclusion, TXNIP deletion ameliorates the HFD-induced steatosis, inflammatory and fibrotic response via modulation of TLR2-NLRP3 inflammasome axis. Targeting TXNIP-TLR2-NLRP3 pathway may provide potential therapeutic modalities for NASH treatment.

Obesity and drug pharmacology: a review of the influence of obesity on pharmacokinetic and pharmacodynamic parameters

INTRODUCTION

The rising prevalence of obesity confronts clinicians with dosing problems in the (extreme) overweight population. Obesity has a great impact on key organs that play a role in the pharmacokinetics (PK) and pharmacodynamics (PD) of drugs, however the ultimate impact of these changes on how to adapt the dose may not always be known. Areas covered: In this review, physiological changes associated with obesity are discussed. An overview is provided on the alterations in absorption, distribution, drug metabolism and clearance in (morbid) obesity focusing on general principles that can be extracted from pharmacokinetic studies. Also, relevant pharmacodynamic considerations in obesity are discussed. Expert opinion: Over the last two decades, increased knowledge is generated on PK and PD in obesity. Future research should focus on filling in the knowledge gaps that remain, especially in connecting obesity-related physiological changes with changes in PK and/or PD and vice versa. Ultimately, this knowledge can be used to develop physiologically based PK and PD models on the basis of quantitative systems pharmacology principles. Moreover, efforts should focus on thorough prospective evaluation of developed model-based doses with subsequent implementation of these dosing recommendations in clinical practice.

Effect of Disease Pathologies on Transporter Expression and Function

Transporters are important determinants of drug absorption, distribution, and excretion. The clinical relevance of drug transporters in drug disposition and toxicology depends on their localization in liver, kidney, and brain. There has been growing evidence regarding the importance of disease status on alterations in metabolizing enzymes and transporter proteins. This review focuses on uptake and efflux transporter proteins in liver, kidney, and brain and discusses mechanisms of altered transporter expression and function secondary to disease.

Impaired N-linked glycosylation of uptake and efflux transporters in human non-alcoholic fatty liver disease

BACKGROUND & AIMS

N-linked glycosylation of proteins is critical for proper protein folding and trafficking to the plasma membrane. Drug transporters are one class of proteins that have reduced function when glycosylation is impaired. N-linked glycosylation of plasma proteins has also been investigated as a biomarker for several liver diseases, including non-alcoholic fatty liver disease (NAFLD). The purpose of this study was to assess the transcriptomic expression of genes involved in protein processing and glycosylation, and to determine the glycosylation status of key drug transporters during human NAFLD progression.

METHODS

Human liver samples diagnosed as healthy, steatosis, and non-alcoholic steatohepatitis (NASH) were analysed for gene expression of glycosylation-related genes and for protein glycosylation using immunoblot.

RESULTS

Genes involved in protein processing in the ER and biosynthesis of N-glycans were significantly enriched for down-regulation in NAFLD progression. Included in the down regulated N-glycan biosynthesis category were genes involved in the oligosaccharyltransferase complex, N-glycan quality control, N-glycan precursor biosynthesis, N-glycan trimming to the core, and N-glycan extension from the core. N-glycan degradation genes were unaltered in the progression to NASH. Immunoblot analysis of the uptake transporters organic anion transporting polypeptide-1B1 (OATP1B1), OATP1B3, OATP2B1, and Sodium/Taurocholate Co-transporting Polypeptide (NTCP) and the efflux transporter multidrug resistance-associated protein 2 (MRP2) demonstrated a significant loss of glycosylation following the progression to NASH.

CONCLUSIONS

These data suggest that the loss of glycosylation of key uptake and efflux transporters in humans NASH may influence transporter function and contribute to altered drug disposition observed in NASH.

肝脏转运体表达和功能的变化对肝疾病的影响

转运体是药物吸收、分布、代谢和排泄的重要决定因素, 在肝脏表达尤为广泛. 肝脏转运体可以摄取大多数内源性物质、营养物质和外源性物质进入肝脏, 在肝脏内经过一系列的代谢转化, 最终将其外排入胆汁, 并由胆汁排到肝外. 越来越多的证据表明, 肝脏疾病状态下转运体的表达和功能会发生改变, 影响药物在体内的处置过程, 进而增加药物相互作用的可能性, 同时加大了疾病药物治疗的难度. 本文从肝脏摄取型和外排型转运体两方面出发, 针对肝脏转运体表达和功能的变化对肝疾病的影响作一综述.

Metabolomic profiling distinction of human nonalcoholic fatty liver disease progression from a common rat model

OBJECTIVE

Characteristic pathological changes define the progression of steatosis to nonalcoholic steatohepatitis (NASH) and are correlated to metabolic pathways. A common rodent model of NASH is the methionine and choline deficient (MCD) diet. The objective of this study was to perform full metabolomic analyses on liver samples to determine which pathways are altered most pronouncedly in this condition in humans, and to compare these changes to rodent models of nonalcoholic fatty liver disease (NAFLD).

METHODS

A principal component analysis for all 91 metabolites measured indicated that metabolome perturbation is greater and less varied for humans than for rodents.

RESULTS

Metabolome changes in human and rat NAFLD were greatest for the amino acid and bile acid metabolite families (e.g., asparagine, citrulline, gamma-aminobutyric acid, lysine); although, in many cases, the trends were reversed when compared between species (cholic acid, betaine).

CONCLUSIONS

Overall, these results indicate that metabolites of specific pathways may be useful biomarkers for NASH progression, although these markers may not correspond to rodent NASH models. The MCD model may be useful when studying certain end points of NASH; however, the metabolomics results indicate important differences between humans and rodents in the biochemical pathogenesis of the disease.

Effect of Liver Disease on Hepatic Transporter Expression and Function

Liver disease can alter the disposition of xenobiotics and endogenous substances. Regulatory agencies such as the Food and Drug Administration and the European Medicines Evaluation Agency recommend, if possible, studying the effect of liver disease on drugs under development to guide specific dose recommendations in these patients. Although extensive research has been conducted to characterize the effect of liver disease on drug-metabolizing enzymes, emerging data have implicated that the expression and function of hepatobiliary transport proteins also are altered in liver disease. This review summarizes recent developments in the field, which may have implications for understanding altered disposition, safety, and efficacy of new and existing drugs. A brief review of liver physiology and hepatic transporter localization/function is provided. Then, the expression and function of hepatic transporters in cholestasis, hepatitis C infection, hepatocellular carcinoma, human immunodeficiency virus infection, nonalcoholic fatty liver disease and nonalcoholic steatohepatitis, and primary biliary cirrhosis are reviewed. In the absence of clinical data, nonclinical information in animal models is presented. This review aims to advance the understanding of altered expression and function of hepatic transporters in liver disease and the implications of such changes on drug disposition.

Trafficking and other regulatory mechanisms for organic anion transporting polypeptides and organic anion transporters that modulate cellular drug and xenobiotic influx and that are dysregulated in disease

Organic anion transporters (OATs) and organic anion-transporting polypeptides (OATPs), encoded by a number of solute carrier (SLC)22A and SLC organic anion (SLCO) genes, mediate the absorption and distribution of drugs and other xenobiotics. The regulation of OATs and OATPs is complex, comprising both transcriptional and post-translational mechanisms. Plasma membrane expression is required for cellular substrate influx by OATs/OATPs. Thus, interest in post-translational regulatory processes, including membrane targeting, endocytosis, recycling and degradation of transporter proteins, is increasing because these are critical for plasma membrane expression. After being synthesized, transporters undergo N-glycosylation in the endoplasmic reticulum and Golgi apparatus and are delivered to the plasma membrane by vesicular transport. Their expression at the cell surface is maintained by de novo synthesis and recycling, which occurs after clathrin- and/or caveolin-dependent endocytosis of existing protein. Several studies have shown that phosphorylation by signalling kinases is important for the internalization and recycling processes, although the transporter protein does not appear to be directly phosphorylated. After internalization, transporters that are targeted for degradation undergo ubiquitination, most likely on intracellular loop residues. Epigenetic mechanisms, including methylation of gene regulatory regions and transcription from alternate promoters, are also significant in the regulation of certain SLC22A/SLCO genes. The membrane expression of OATs/OATPs is dysregulated in disease, which affects drug efficacy and detoxification. Several transporters are expressed in the cytoplasmic subcompartment in disease states, which suggests that membrane targeting/internalization/recycling may be impaired. This article focuses on recent developments in OAT and OATP regulation, their dysregulation in disease and the significance for drug therapy.

Changes in drug transport and metabolism and their clinical implications in non-alcoholic fatty liver disease

INTRODUCTION

The incidence of non-alcoholic fatty liver disease (NAFLD) is rising, especially in Western countries. Drug treatment in patients with NAFLD is common since it is linked to other conditions like diabetes, obesity, and cardiovascular disease. Consequently, changes in drug metabolism may have serious clinical implications. Areas covered: A literature search for studies in animal models or patients with obesity, fatty liver, non-alcoholic steatohepatitis (NASH) or NASH cirrhosis published before November 2016 was performed. After discussing epidemiology and animal models for NAFLD, we summarized both basic as well as clinical studies investigating changes in drug transport and metabolism in NAFLD. Important drug groups were assessed separately with emphasis on clinical implications for drug treatment in patients with NAFLD. Expert opinion: Given the frequency of NAFLD even today, a high degree of drug treatment in NAFLD patients appears safe and well-tolerated despite considerable changes in hepatic uptake, distribution, metabolism and transport of drugs in these patients. NASH causes changes in biliary excretion, systemic concentrations, and renal handling of drugs leading to alterations in drug efficacy or toxicity under specific circumstances. Future clinical drug studies should focus on this special patient population in order to avoid serious adverse events in NAFLD patients.

Constitutive androstane receptor activation promotes bilirubin clearance in a murine model of alcoholic liver disease

Increased plasma levels of bilirubin have been reported in rat models and patients with alcoholic liver disease (ALD). The constitutive androstane receptor (CAR) is a known xenobiotic receptor, which induces the detoxification and transport of bilirubin. In the present study, the bilirubin transport regulatory mechanisms, and the role of CAR activation in hepatic and extrahepatic bilirubin clearance were investigated in a murine model of ALD. The mice were fed a Lieber-DeCarli ethanol diet or an isocaloric control diet for 4 weeks, followed by the administration of CAR agonists, 1,4-bis-[2-(3,5-dichlorpyridyloxy)]benzene (TCPOBOP) and phenobarbital (PB), and their vehicles to examine the effect of the pharmacological activation of CAR on serum levels of bilirubin and on the bilirubin clearance pathway in ALD by serological survey, western blotting and reverse transcription-quantitative polymerase chain reaction. The results showed that chronic ethanol ingestion impaired the nuclear translocation of CAR, which was accompanied by elevated serum levels of bilirubin, suppression of the expression of hepatic and renal organic anion transporting polypeptide (OATP) 1A1 and hepatic multidrug resistance-associated protein 2 (MRP2), and induction of the expression of UDP-glucuronosyltransferase (UGT) 1A1. The activation of CAR by TCPOBOP and PB resulted in downregulation of the serum levels of bilirubin followed by selective upregulation of the expression levels of OATP1A1, OATP1A4, UGT1A1 and MRP2 in ALD. These results revealed the bilirubin transport regulatory mechanisms and highlighted the importance of CAR in modulating the bilirubin clearance pathway in the ALD mouse model.

Hepatic gadoxetic acid uptake as a measure of diffuse liver disease: Where are we?

MRI has emerged as the most comprehensive noninvasive diagnostic tool for focal liver lesions and diffuse hepatobiliary disorders. The introduction of hepatobiliary contrast agents, most notably gadoxetic acid (GA), has expanded the role of MRI, particularly in the functional imaging of chronic liver diseases, such as nonalcoholic fatty liver disease (NAFLD). GA-enhanced MRI (GA-MRI) may help to distinguish between the two subgroups of NAFLD, simple steatosis and nonalcoholic steatohepatitis. Furthermore, GA-MRI can be used to stage fibrosis and cirrhosis, predict liver transplant graft survival, and preoperatively estimate the risk of liver failure should major resection be undertaken. The amount of GA uptake can be estimated, using static images, by the relative liver enhancement, hepatic uptake index, and relaxometry of T1-mapping during the hepatobiliary phase. On the contrary, the hepatic extraction fraction and liver perfusion can be measured on dynamic imaging. Importantly, there is currently no clear consensus as to which of these MR-derived parameters is the most suitable for assessing liver dysfunction. This review article aims to describe the current role of GA-enhanced MRI in quantifying liver function, primarily in diffuse hepatobiliary disorders.

LEVEL OF EVIDENCE

3 J. Magn. Reson. Imaging 2017;45:646-659.

Activation of an endothelial Notch1-Jagged1 circuit induces VCAM1 expression, an effect amplified by interleukin-1β

The Notch1 and Notch4 signaling pathways regulate endothelial cell homeostasis. Inflammatory cytokines induce the expression of endothelial adhesion molecules, including VCAM1, partly by downregulating Notch4 signaling. We investigated the role of endothelial Notch1 in this IL-1β-mediated process. Brief treatment with IL-1β upregulated endothelial VCAM1 and Notch ligand Jagged1. IL-1β decreased Notch1 mRNA levels, but levels of the active Notch1ICD protein remained constant. IL-1β-mediated VCAM1 induction was downregulated in endothelial cells subjected to pretreatment with a pharmacological inhibitor of the γ-secretase, which activates Notch receptors, producing NotchICD. It was also downregulated in cells in which Notch1 and/or Jagged1 were silenced.Conversely, the forced expression of Notch1ICD in naïve endothelial cells upregulated VCAM1 per se and amplified IL-1β-mediated VCAM1 induction. Jagged1 levels increased and Notch4 signaling was downregulated in parallel. Finally, Notch1ICD and Jagged1 expression was upregulated in the endothelium of the liver in a model of chronic liver inflammation.In conclusion, we describe here a cell-autonomous, pro-inflammatory endothelial Notch1-Jagged1 circuit (i) triggering the expression of VCAM1 even in the absence of inflammatory cytokines and (ii) enhancing the effects of IL-1β. Thus, IL-1β regulates Notch1 and Notch4 activity in opposite directions, consistent with a selective targeting of Notch1 in inflamed endothelium.

Effects of Nonalcoholic Fatty Liver Disease on Hepatic CYP2B1 and in Vivo Bupropion Disposition in Rats Fed a High-Fat or Methionine/Choline-Deficient Diet

Nonalcoholic fatty liver disease (NAFLD) refers to hepatic pathologies, including simple fatty liver (SFL), nonalcoholic steatohepatitis (NASH), fibrosis, and cirrhosis, that may progress to hepatocellular carcinoma. These liver disease states may affect the activity and expression levels of drug-metabolizing enzymes, potentially resulting in an alteration in the pharmacokinetics, therapeutic efficacy, and safety of drugs. This study investigated the hepatic cytochrome P450 (CYP) 2B1-modulating effect of a specific NAFLD state in dietary rat models. Sprague-Dawley rats were given a methionine/choline-deficient (MCD) or high-fat (HF) diet to induce NASH and SFL, respectively. The induction of these disease states was confirmed by plasma chemistry and liver histological analysis. Both the protein and mRNA levels of hepatic CYP2B1 were considerably reduced in MCD diet-fed rats; however, they were similar between the HF diet-fed and control rats. Consistently, the enzyme-kinetic and pharmacokinetic parameters for CYP2B1-mediated bupropion metabolism were considerably reduced in MCD diet-fed rats; however, they were also similar between the HF diet-fed and control rats. These results may promote a better understanding of the influence of NAFLD on CYP2B1-mediated metabolism, which could have important implications for the safety and pharmacokinetics of drug substrates for the CYP2B subfamily in patients with NAFLD.