Changes in biomarkers of liver disease during successful combination antiretroviral therapy in HIV-HCV-coinfected individuals

BACKGROUND

We investigated changes in biomarkers of liver disease in HIV-HCV-coinfected individuals during successful combination antiretroviral therapy (cART) compared to changes in biomarker levels during untreated HIV infection and to HIV-monoinfected individuals.

METHODS

Non-invasive biomarkers of liver disease (hyaluronic acid [HYA], aspartate aminotransferase-to-platelet ratio index [APRI], Fibrosis-4 [FIB-4] index and cytokeratin-18 [CK-18]) were correlated with liver histology in 49 HIV-HCV-coinfected patients. Changes in biomarkers over time were then assessed longitudinally in HIV-HCV-coinfected patients during successful cART (n=58), during untreated HIV-infection (n=59), and in HIV-monoinfected individuals (n=17). The median follow-up time was 3.4 years on cART. All analyses were conducted before starting HCV treatment.

RESULTS

Non-invasive biomarkers of liver disease correlated significantly with the histological METAVIR stage (P<0.002 for all comparisons). The mean ±sd area under the receiver operating characteristic (AUROC) curve values for advanced fibrosis (≥F3 METAVIR) for HYA, APRI, FIB-4 and CK-18 were 0.86 ±0.05, 0.84 ±0.08, 0.80 ±0.09 and 0.81 ±0.07, respectively. HYA, APRI and CK-18 levels were higher in HIV-HCV-coinfected compared to HIV-monoinfected patients (P<0.01). In the first year on cART, APRI and FIB-4 scores decreased (-35% and -33%, respectively; P=0.1), mainly due to the reversion of HIV-induced thrombocytopaenia, whereas HYA and CK-18 levels remained unchanged. During long-term cART, there were only small changes (<5%) in median biomarker levels. Median biomarker levels changed <3% during untreated HIV-infection. Overall, 3 patients died from end-stage liver disease, and 10 from other causes.

CONCLUSIONS

Biomarkers of liver disease highly correlated with fibrosis in HIV-HCV-coinfected individuals and did not change significantly during successful cART. These findings suggest a slower than expected liver disease progression in many HIV-HCV-coinfected individuals, at least during successful cART.

Electrophoretically mediated microanalysis for characterization of the enantioselective CYP3A4 catalyzed N-demethylation of ketamine

Execution of an enzymatic reaction performed in a capillary with subsequent electrophoretic analysis of the formed products is referred to as electrophoretically mediated microanalysis (EMMA). An EMMA method was developed to investigate the stereoselectivity of the CYP3A4-mediated N-demethylation of ketamine. Ketamine was incubated in a 50 μm id bare fused-silica capillary together with human CYP3A4 Supersomes using a 100 mM phosphate buffer (pH 7.4) at 37°C. A plug containing racemic ketamine and the NADPH regenerating system including all required cofactors for the enzymatic reaction was injected, followed by a plug of the metabolizing enzyme CYP3A4 (500 nM). These two plugs were bracketed by plugs of incubation buffer to ensure proper conditions for the enzymatic reaction. The rest of the capillary was filled with a pH 2.5 running buffer comprising 50 mM Tris, phosphoric acid, and 2% w/v of highly sulfated γ-cyclodextrin. Mixing of reaction plugs was enhanced via application of -10 kV for 10 s. After an incubation of 8 min at 37°C without power application (zero-potential amplification), the capillary was cooled to 25°C within 3 min followed by application of -10 kV for the separation and detection of the formed enantiomers of norketamine. Norketamine formation rates were fitted to the Michaelis-Menten model and the elucidated values for V(max) and K(m) were found to be comparable to those obtained from the off-line assay of a previous study.

Postprandial effects of dark chocolate on portal hypertension in patients with cirrhosis: results of a phase 2, double-blind, randomized controlled trial

BACKGROUND

In cirrhosis, hepatic endothelial dysfunction as a result of oxidative stress contributes to the postprandial increase in hepatic venous pressure gradient (HVPG).

OBJECTIVE

We aimed at testing the hypothesis that dark chocolate, which holds potent antioxidant properties, might attenuate the postprandial increase in HVPG in patients with cirrhosis.

DESIGN

In this phase 2, double-blind, controlled study, 22 cirrhotic patients referred for HVPG measurement were included and randomly assigned to receive a liquid meal containing either dark chocolate (active treatment; 85% cocoa, 0.55 g/kg body wt; n = 11) or isocaloric amounts of white chocolate (devoid of cocoa flavonoids; control subjects; n = 11). HVPG, arterial pressure, portal blood flow, serum flavonoids (catechin and epicatechin), and nitric oxide were measured at baseline and 30 min after meal administration. The main outcome measure was the change in HVPG 30 min after the test meal.

RESULTS

Postprandial hyperemia was accompanied by a marked increase in HVPG in the white-chocolate group (16.0 ± 4.7-19.7 ± 4.1 mm Hg or +26.4 ± 12.7%; P < 0.0001), whereas the postprandial increase in HVPG was markedly attenuated in the dark-chocolate group (16.9 ± 2.9-18.7 ± 3.5 mm Hg or +11.5 ± 15.9%; P = 0.02 compared with white chocolate). Portal blood flow increased similarly after meals containing dark or white chocolate (median increase: 32% compared with 39%). Plasma flavonoids increased 15-50-fold after dark chocolate consumption. Dark but not white chocolate induced a mild increase in arterial pressure (+8.8 ± 8.8% compared with -0.3 ± 4.9%; P = 0.002).

CONCLUSION

In patients with cirrhosis, dark chocolate blunted the postprandial increase in HVPG by improving flow-mediated hepatic vasorelaxation and ameliorated systemic hypotension. This trial was registered at clinicaltrials.gov as NCT01408966.

Voluntary ingestion of antiparasitic drugs emulsified in honey represents an alternative to gavage in mice

The oral route is the most frequently used method of drug intake in humans. Oral administration of drugs to laboratory animals such as mice typically is achieved through gavage, in which a feeding needle is introduced into the esophagus and the drug is delivered directly into the stomach. This method requires technical skill, is stressful for animals, and introduces risk of injury, pain and morbidity. Here we investigated another method of drug administration. The benzimidazole derivative albendazole was emulsified in commercially available honey and administered to mice by voluntary feeding or gavage. Mice that received albendazole by either gavage or honey ingestion had virtually identical levels of serum albendazole sulfoxide, indicating that uptake and metabolism of albendazole was similar for both administration techniques. In addition, dosing mice with the albendazole-honey mixture for 8 wk had antiparasitic activity comparable to earlier studies using gavage for drug administration. Compared with gavage, voluntary ingestion of a drug in honey is more rapid, less stressful to the animal, and less technically demanding for the administrator. Because of its low cost and ready availability, honey presents a viable vehicle for drug delivery.

Inhibition of cytochrome P450 enzymes involved in ketamine metabolism by use of liver microsomes and specific cytochrome P450 enzymes from horses, dogs, and humans

OBJECTIVE

To identify and characterize cytochrome P450 enzymes (CYPs) responsible for the metabolism of racemic ketamine in 3 mammalian species in vitro by use of chemical inhibitors and antibodies.

SAMPLE

Human, canine, and equine liver microsomes and human single CYP3A4 and CYP2C9 and their canine orthologs.

PROCEDURES

Chemical inhibitors selective for human CYP enzymes and anti-CYP antibodies were incubated with racemic ketamine and liver microsomes or specific CYPs. Ketamine N-demethylation to norketamine was determined via enantioselective capillary electrophoresis.

RESULTS

The general CYP inhibitor 1-aminobenzotriazole almost completely blocked ketamine metabolism in human and canine liver microsomes but not in equine microsomes. Chemical inhibition of norketamine formation was dependent on inhibitor concentration in most circumstances. For all 3 species, inhibitors of CYP3A4, CYP2A6, CYP2C19, CYP2B6, and CYP2C9 diminished N-demethylation of ketamine. Anti-CYP3A4, anti-CYP2C9, and anti-CYP2B6 antibodies also inhibited ketamine N-demethylation. Chemical inhibition was strongest with inhibitors of CYP2A6 and CYP2C19 in canine and equine microsomes and with the CYP3A4 inhibitor in human microsomes. No significant contribution of CYP2D6 to ketamine biotransformation was observed. Although the human CYP2C9 inhibitor blocked ketamine N-demethylation completely in the canine ortholog CYP2C21, a strong inhibition was also obtained by the chemical inhibitors of CYP2C19 and CYP2B6. Ketamine N-demethylation was stereoselective in single human CYP3A4 and canine CYP2C21 enzymes.

CONCLUSIONS AND CLINICAL RELEVANCE

Human-specific inhibitors of CYP2A6, CYP2C19, CYP3A4, CYP2B6, and CYP2C9 diminished ketamine N-demethylation in dogs and horses. To address drug-drug interactions in these animal species, investigations with single CYPs are needed.

Enantioselective CE analysis of hepatic ketamine metabolism in different species in vitro

Ketamine, an injectable anesthetic and analgesic consisting of a racemic mixture of S-and R-ketamine, is routinely used in veterinary and human medicine. Nevertheless, metabolism and pharmacokinetics of ketamine have not been characterized sufficiently in most animal species. An enantioselective CE assay for ketamine and its metabolites in microsomal preparations is described. Racemic ketamine was incubated with pooled microsomes from humans, horses and dogs over a 3 h time interval with frequent sample collection. CE data revealed that ketamine is metabolized enantioselectively to norketamine (NK), dehydronorketamine and three hydroxylated NK metabolites in all three species. The metabolic patterns formed differ in production rates of the metabolites and in stereoselectivity of the hydroxylated NK metabolites. In vitro pharmacokinetics of ketamine N-demethylation were established by incubating ten different concentrations of racemic ketamine and the single enantiomers of ketamine for 8 min and data modeling was based on Michaelis-Menten kinetics. These data revealed a reduced intrinsic clearance of the S-enantiomer in the racemic mixture compared with the single S-enantiomer in human microsomes, no difference in equine microsomes and the opposite effect in canine microsomes. The findings indicate species differences with possible relevance for the use of single S-ketamine versus racemic ketamine in the clinic.

Enantioselective capillary electrophoresis for identification and characterization of human cytochrome P450 enzymes which metabolize ketamine and norketamine in vitro

Ketamine, a phencyclidine derivative, is used for induction of anesthesia, as an anesthetic drug for short term surgical interventions and in subanesthetic doses for postoperative pain relief. Ketamine undergoes extensive hepatic first-pass metabolism. Enantioselective capillary electrophoresis with multiple isomer sulfated β-cyclodextrin as chiral selector was used to identify cytochrome P450 enzymes involved in hepatic ketamine and norketamine biotransformation in vitro. The N-demethylation of ketamine to norketamine and subsequently the biotransformation of norketamine to other metabolites were studied via analysis of alkaline extracts of in vitro incubations of racemic ketamine and racemic norketamine with nine recombinantly expressed human cytochrome P450 enzymes and human liver microsomes. Norketamine was formed by CYP3A4, CYP2C19, CYP2B6, CYP2A6, CYP2D6 and CYP2C9, whereas CYP2B6 and CYP2A6 were identified to be the only enzymes which enable the hydroxylation of norketamine. The latter two enzymes produced metabolic patterns similar to those found in incubations with human liver microsomes. The kinetic data of ketamine N-demethylation with CYP3A4 and CYP2B6 were best described with the Michaelis-Menten model and the Hill equation, respectively. This is the first study elucidating the individual enzymes responsible for hydroxylation of norketamine. The obtained data suggest that in vitro biotransformation of ketamine and norketamine is stereoselective.