Effect of nonalcoholic steatohepatitis on renal filtration and secretion of adefovir

Investigation of metabolite alterations in the kidneys of methionine-choline-deficient mouse by mass spectrometry imaging

Methionine and choline both are essential nutrients which are needed for methyl group metabolism. A methionine-choline-deficient (MCD) diet leads to pathological changes in the kidney. The mechanism of the MCD diet is complex, and fundamental research is still required to provide a better understanding of the driving forces behind it. We evaluated the regional effects of the MCD diet on the metabolites of mouse kidney tissue using desorption electrospray ionization mass spectrometry imaging technology. A total of 20, 17, and 13 metabolites were significantly changed in the cortex, outer medulla, and inner medulla, respectively, of the mouse kidney tissue after the administration of the MCD diet. Among the discriminating metabolites, only three metabolites (guanidoacetic acid, serine, and nicotinamide riboside) were significantly increased, and all the other metabolites showed a significant decrease. The results showed that there were significant region-specific changes in the serine metabolism, carnitine metabolism, choline metabolism, and arginine metabolism. This study presents unique regional metabolic data, providing a more comprehensive understanding of the molecular characteristics of the MCD diet in the kidney.

Attenuated Ochratoxin A Transporter Expression in a Mouse Model of Nonalcoholic Steatohepatitis Protects against Proximal Convoluted Tubule Toxicity

Ochratoxin A (OTA) is an abundant mycotoxin, yet the toxicological impact of its disposition is not well studied. OTA is an organic anion transporter (OAT) substrate primarily excreted in urine despite a long half-life and extensive protein binding. Altered renal transporter expression during disease, including nonalcoholic steatohepatitis (NASH), may influence response to OTA exposure, but the impact of NASH on OTA toxicokinetics, tissue distribution, and associated nephrotoxicity is unknown. By inducing NASH in fast food-dieted/thioacetamide-exposed mice, we evaluated the effect of NASH on a bolus OTA exposure (12.5 mg/kg by mouth) after 3 days. NASH mice presented with less gross toxicity (44% less body weight loss), and kidney and liver weights of NASH mice were 11% and 24% higher, respectively, than healthy mice. Organ and body weight changes coincided with reduced renal proximal tubule cells vacuolation, degeneration, and necrosis, though no OTA-induced hepatic lesions were found. OTA systemic exposure in NASH mice increased modestly from 5.65 ± 1.10 to 7.95 ± 0.61 mg*h/ml per kg BW, and renal excretion increased robustly from 5.55% ± 0.37% to 13.11% ± 3.10%, relative to healthy mice. Total urinary excretion of OTA increased from 24.41 ± 1.74 to 40.07 ± 9.19 µg in NASH mice, and kidney-bound OTA decreased by ∼30%. Renal OAT isoform expression (OAT1-5) in NASH mice decreased by ∼50% with reduced OTA uptake by proximal convoluted cells. These data suggest that NASH-induced OAT transporter reductions attenuate renal secretion and reabsorption of OTA, increasing OTA urinary excretion and reducing renal exposure, thereby reducing nephrotoxicity in NASH. SIGNIFICANCE STATEMENT: These data suggest a disease-mediated transporter mechanism of altered tissue-specific toxicity after mycotoxin exposure, despite minimal systemic changes to ochratoxin A (OTA) concentrations. Further studies are warranted to evaluate the clinical relevance of this functional model and the potential effect of human nonalcoholic steatohepatitis on OTA and other organic anion substrate toxicity.

Altered cisplatin pharmacokinetics during nonalcoholic steatohepatitis contributes to reduced nephrotoxicity

Disease-mediated alterations to drug disposition constitute a significant source of adverse drug reactions. Cisplatin (CDDP) elicits nephrotoxicity due to exposure in proximal tubule cells during renal secretion. Alterations to renal drug transporter expression have been discovered during nonalcoholic steatohepatitis (NASH), however, associated changes to substrate toxicity is unknown. To test this, a methionine- and choline-deficient diet-induced rat model was used to evaluate NASH-associated changes to CDDP pharmacokinetics, transporter expression, and toxicity. NASH rats administered CDDP (6 mg/kg, i.p.) displayed 20% less nephrotoxicity than healthy rats. Likewise, CDDP renal clearance decreased in NASH rats from 7.39 to 3.83 mL/min, renal secretion decreased from 6.23 to 2.80 mL/min, and renal CDDP accumulation decreased by 15%, relative to healthy rats. Renal copper transporter-1 expression decreased, and organic cation transporter-2 and ATPase copper transporting protein-7b increased slightly, reducing CDDP secretion. Hepatic CDDP accumulation increased 250% in NASH rats relative to healthy rats. Hepatic organic cation transporter-1 induction and multidrug and toxin extrusion protein-1 and multidrug resistance-associated protein-4 reduction may contribute to hepatic CDDP sequestration in NASH rats, although no drug-related toxicity was observed. These data provide a link between NASH-induced hepatic and renal transporter expression changes and CDDP renal clearance, which may alter nephrotoxicity.

Physiologically-Based Pharmacokinetic Model of Morphine and Morphine-3-Glucuronide in Nonalcoholic Steatohepatitis

Nonalcoholic steatohepatitis (NASH), the progressive form of nonalcoholic fatty liver disease, is increasing in prevalence. NASH-related alterations in hepatic protein expression (e.g., transporters) and in overall physiology may affect drug exposure by altering drug disposition and elimination. The aim of this study was to build a physiologically-based pharmacokinetic (PBPK) model to predict drug exposure in NASH by incorporating NASH-related changes in hepatic transporters. Morphine and morphine-3-glucuronide (M3G) were used as model compounds. A PBPK model of morphine with permeability-limited hepatic disposition was extended to include M3G disposition and enterohepatic recycling (EHR). The model captured the area under the plasma concentration-time curve (AUC) of morphine and M3G after intravenous morphine administration within 0.82-fold and 1.94-fold of observed values from 3 independent clinical studies for healthy adult subjects (6, 10, and 14 individuals). When NASH-related changes in multidrug resistance-associated protein 2 (MRP2) and MRP3 were incorporated into the model, the predicted M3G mean AUC in NASH was 1.34-fold higher compared to healthy subjects, which is slightly lower than the observed value (1.63-fold). Exploratory simulations on other physiological changes occurring in NASH (e.g., moderate decreases in glomerular filtration rate and portal vein blood flow) revealed that the effect of transporter changes was most prominent. Additionally, NASH-related transporter changes resulted in decreased morphine EHR, which could be important for drugs with extensive EHR. This study is an important first step to predict drug disposition in complex diseases such as NASH using PBPK modeling.

Transporter Activity Changes in Nonalcoholic Steatohepatitis: Assessment with Plasma Coproporphyrin I and III

Expression and functional changes in the organic anion transporting polypeptide (OATP)-multidrug resistance-associated protein (MRP) axis of transporters are well reported in patients with nonalcoholic steatohepatitis (NASH). These changes can impact plasma and tissue disposition of endo- and exogenous compounds. The transporter alterations are often assessed by administration of a xenobiotic or by transporter proteomic analysis from liver biopsies. Using gene expression, proteomics, and endogenous biomarkers, we show that the gene expression and activity of OATP and MRP transporters are associated with disease progression and recovery in humans and in preclinical animal models of NASH. Decreased OATP and increased MRP3/4 gene expression in two cohorts of patients with steatosis and NASH, as well as gene and protein expression in multiple NASH rodent models, have been established. Coproporphyrin I and III (CP I and III) were established as substrates of MRP4. CP I plasma concentration increased significantly in four animal models of NASH, indicating the transporter changes. Up to a 60-fold increase in CP I plasma concentration was observed in the mouse bile duct-ligated model compared with sham controls. In the choline-deficient amino acid-defined high-fat diet (CDAHFD) model, CP I plasma concentrations increased by >3-fold compared with chow diet-fed mice. In contrast, CP III plasma concentrations remain unaltered in the CDAHFD model, although they increased in the other three NASH models. These results suggest that tracking CP I plasma concentrations can provide transporter modulation information at a functional level in NASH animal models and in patients. SIGNIFICANCE STATEMENT: Our analysis demonstrates that multidrug resistance-associated protein 4 (MRP4) transporter gene expression tracks with nonalcoholic steatohepatitis (NASH) progression and intervention in patients. Additionally, we show that coproporphyrin I and III (CP I and III) are substrates of MRP4. CP I plasma and liver concentrations increase in different diet- and surgery-induced rodent NASH models, likely explained by both gene- and protein-level changes in transporters. CP I and III are therefore potential plasma-based biomarkers that can track NASH progression in preclinical models and in humans.

The Effects of Hepatic Steatosis on the Natural History of HBV Infection

Fatty liver prevalence is increasing and becoming a global health burden. Chronic hepatitis B infection (CHB) is one of the most common chronic viral infections. Steatosis in CHB patients increases risk of cirrhosis and hepatocellular carcinoma. Data from studies on the interaction between CHB and nonalcoholic fatty liver disease are not conclusive. Liver biopsy is the gold standard for diagnosis of fatty liver; however, noninvasive diagnostic tests have been developed to diagnose and predict fibrosis in CHB/NAFLD. Treatment guidelines are not clear.

Pharmacokinetics of Boldine in Control and Mrp2-Deficient Rats

The aim of the present study was to describe the currently poorly understood pharmacokinetics (PK) of boldine in control rats (LW, Lewis rats), and Mrp2 transporter-deficient rats (TR-). Animals from the LW and TR- groups underwent a bolus dose study with 10 mg/kg of boldine applied either orally or intravenously in order to evaluate the major PK parameters. The TR- rats demonstrated significantly reduced total clearance with prolonged biological half-life (LW 12±4.6 versus TR- 20±4.4 min), decreased volume of distribution (LW 3.2±0.4 l/kg versus TR- 2.4±0.4 l/kg) and reduced bioavailability (LW 7 % versus TR- 4.5 %). Another set of LW and TR- rats were used for a clearance study with continuous intravenous administration of boldine. The LW rats showed that biliary and renal clearance formed less than 2 % of the total clearance of boldine. The treatment of samples with β glucuronidase showed at least a 38 % contribution of conjugation reactions to the overall clearance of boldine. The TR- rats demonstrated reduced biliary clearance of boldine and its conjugates, which was partly compensated by their increased renal clearance. In conclusion, this study presents the PK parameters of boldine and shows the importance of the Mrp2 transporter and conjugation reactions in the elimination of the compound.