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1. Metabonomic analysis, via a combination of untargeted and targeted liquid chromatography-mass spectrometry (LC-MS) and untargeted (1)H NMR spectroscopy-based metabolite profiling, was performed on aqueous (AQ) and organic liver extracts from control (SCID) and chimeric humanized (PXB) mice dosed with troglitazone at 0, 300 and 600 mg/kg/day for seven days. 2. LC-MS analysis of AQ liver extracts showed a more "human-like" profile for troglitazone metabolites for PXB, compared with SCID, mice. 3. LC-MS detected differences in endogenous metabolites, particularly lipid species in dosed mice, including elevated triacylglycerols and 1-alkyl,2-acylglycerophosphates as well as lowered diacylglycerophosphocholines and 1-alkyl,2-acylglycerophosphocholines for PXB compared with SCID mouse liver extracts. Following drug administration changes in the relative proportions of the ions for various unsaturated fatty acids were observed for both types of mouse, some of which were specific to PXB or SCID mice. 4.  (1)H NMR spectroscopy revealed that AQ PXB mouse liver extracts had elevated amounts of inosine, fumarate, creatine, aspartate, trimethylamine N-oxide, glycerophosphocholine, phosphocholine, choline, glutamine, glutamate, acetate, alanine and lactate relative to SCID mice and decreased histidine, glycogen, α- and β-glucose, taurine, and glutathione. Increased uracil and tyrosine concentrations were detected for PXB mice on troglitazone administration. 5. Metabonomic profiling thus showed clear differences between humanized and SCID mice, including after administration of troglitazone.

1. The biotransformation, hepatic transporter and blood chemistry effects of troglitazone were investigated following 7 days of dosing at 600 mg/kg/day to chimeric murinized or humanized FRG mice, Mo-FRG and Hu-FRG mice, respectively. 2. Clinical chemistry and histopathology analysis revealed a significant drop in humanization over the time course of the study for the Hu-FRG mice but no significant changes associated with troglitazone treatment in either the Mo-FRG or the Hu-FRG models. No changes in transporter expression in livers of these mice were observed. Oxidative and conjugative metabolic pathways were identified with a 15- to 18-fold increase in formation of troglitazone sulfate in the Hu-FRG mice compared with the Mo-FRG mice in blood and bile, respectively. This resembles the troglitazone metabolism in human and these data are comparable with the formation of this metabolite in the chimeric uPA(+/+)/SCID mice. 3. However, larger amounts of troglitazone glucuronide were also observed in the Hu-FRG mouse compared with the Mo-FRG mouse which may be an effect of the drop in humanization of the Hu-FRG mouse during the study. 4. Highly humanized mice have a considerable potential in providing a useful first insight into circulating human metabolites of candidate drugs metabolized in the liver.

This work aimed to investigate plasma pharmacokinetics and tissue distribution of a new acridine derivative 5-acridin-9-ylmethylene-3-(4-methyl-benzyl)-thiazolidine-2,4-dione (AC04) and its 1-oxo-AC04 metabolite disposition in Wistar rats. After a single AC04 1.5 mg/kg intravenous (i.v.) bolus dose, blood samples were taken up to 120 h. Plasma samples were deproteinization, and AC04 and metabolite were quantified by validated liquid chromatography in tandem with mass spectrometry method. Protein binding was determined by ultrafiltration. AC04 tissue disposition was evaluated after i.v. bolus dose. Individual AC04 concentration-time profiles were best fitted by a two-compartment model showing CL(tot) of 3.4 ± 3.4 L/h/kg, Vd(SS) of 137.9 ± 91.4 L/kg, AUC(0-∞) of 788 ± 483 ng·h/mL and a t(1/2) of 45.5 ± 31.5 h. Protein binding was 98.1 ± 1.6%. AC04 showed higher penetration into the lung, spleen and liver, with AUC(0-96) of 798,443, 263,211 and 303,722 ng·h/mL, respectively. The 1-oxo-AC04 metabolite represented 10% of AC04 plasma concentration, showing a t(1/2) of 23.2 ± 10.4 h. These results suggest that, despite the small free plasma fraction, AC04 penetrates extensively reaching high concentrations in most tissues residing for a long time, which is important for its activity on solid tumours. All results combined indicate that AC04 is potentially a good antitumour candidate.

The pharmacokinetics, biotransformation and hepatic transporter effects of troglitazone were investigated following daily oral dosing, at 300 and 600 mg/kg, for 7 days to control (SCID) and chimeric (PXB) mice with humanized livers. Clinical chemistry revealed no consistent pattern of changes associated with troglitazone treatment in the PXB mouse. Human MRP2 but not mouse mrp2 was down-regulated following troglitazone treatment. Pharmacokinetic analysis revealed similar T(max) values for troglitazone in both mouse groups, a mono- and bi-phasic elimination phase in PXB and SCID mice, respectively, but a 3- to 5- and 2- to 5-fold higher C(max) and AUC, respectively, in PXB mice. Oxidative and conjugative metabolic pathways were identified, with the sulfate being the predominant metabolite in PXB compared to SCID mice (4- to 13-fold increase in liver and blood, respectively). The glucuronide conjugate was predominant in SCID mice. There was no evidence of glutathione conjugation. The primary oxidative pathways were mono- and di-oxidations which may also be attributed to quinone or hydroquinone derivatives. Several metabolites were observed in PXB mice only. As the troglitazone metabolic profiles in the PXB mouse were similar to reported human data the PXB mouse model can provide a useful first insight into circulating human metabolites of xenobiotics metabolized in the liver.

The possible influence of the bile acid-sequestering agent cholestyramine (CSA), which is a basic co-medication in hypercholesterolemic patients, on the pharmacokinetics of rosiglitazone (RGL) and its circulating metabolite desmethylrosiglitazone (DMRGL) was investigated following a single oral and intravenous dose of RGL to Wistar rats. The pharmacokinetic parameters of RGL and DMRGL were evaluated following oral or intravenous administration of RGL to rats at 10 mg kg-1 with and without pre-treatment (0.5 h before RGL administration) of CSA at 0.057, 0.115, 0.23 and 0.34 g kg-1 doses. With an increase in CSA dose there was dose-dependent decrease in area under the curve (AUC)(0-infinity) and Cmax with no change in Tmax, Kel and t1/2 values for both RGL and DMRGL following oral administration of RGL. The oral bioavailability of RGL was reduced by 19.9, 35.6, 53.8 and 72.0% in rats following pre-treatment with CSA at 0.057, 0.115, 0.230 and 0.340 g kg-1, respectively. There was no change in the above-mentioned pharmacokinetic parameters for RGL and DMRGL in rats when RGL was given intravenously following pre-treatment with the above-mentioned oral doses of CSA. Another objective of the study was to determine the effect of staggered oral CSA dosing at 1, 2 and 4 h after oral RGL administration at 10 mg kg-1. AUC(0-infinity) of RGL and DMRGL was reduced following CSA staggered administration at 1 h, whereas 2- and 4-h staggered dose administration of CSA had no effect on the AUC(0-infinity) of RGL and DMRGL. Irrespective of CSA staggered dose administration there was no change in other pharmacokinetic parameters, namely Cmax, Tmax, Kel and t1/2. The apparent formation rate constant (Kf) of DMRGL was also calculated to show that only the absorption of RGL was affected, not the apparent formation rate of DMRGL. The authors also studied the in vitro adsorption of RGL (100, 250, 500 microg ml-1) at various pH conditions (pH 2, 4 and 7) and different concentrations of CSA (15, 30, 60 and 120 mg ml-1). The percentage binding of CSA was in the range 50-72% (at pH 2), 74-89% (at pH 4) and 97-100% (at pH 7). In conclusion, we carried out a systematic investigation demonstrating mechanistically the interaction potential of RGL when co-administered with CSA. The applicability of the metabolite data after intravenous and oral dosing and pH-based binding experiments further adds credence to the key findings.

1. The metabolism of a substituted 2,4-thiazolidinedione (P1) with dual PPARalpha/gamma activity was evaluated in male and female rats, dogs and monkeys. A para-hydroxylated metabolite (M1) with potent PPARgamma-selective agonist, was a major circulating drug-related component in female rats, dogs and monkeys, but not in male rats (M1-to-P1 exposure ratio of <1, 3-5, 5 and 5-11 in male rat, monkey, female rat, and dog, respectively). 2. M1 (%) formed in vitro (5, 53, 57-65, 67 and 67% in male rat, monkey, female rat, dog, and human liver microsomes, respectively), rank ordered with M1 (%) formed in vivo (24-45, 53-57, 78, 75-85%, for male rat, monkey, female rat and dog, respectively, after oral administration of P1). 3. The plasma clearance of M1 was higher in male rats (32 ml min(-1) kg(-1) compared with 6, 7 and 2 ml min(-1) kg(-1) in female rat, male monkey and male dogs, respectively). 4. The low amounts of M1 observed in male rats, with the appearance of products of the cleavage of the propyl group between the phenyl groups was probably due to the presence of the sex-specific CYP2C11, which cleaves P1 at the propyl bridge. None of the CYPs present in female rats cleaved P1 at this site and M1 was only produced by CYP2C6. In humans, only CYP2C8 and the polymorphic CYP2C19 produced M1.