Glucuronidation and sulphation of paracetamol in HIV-positive patients and patients with AIDS

The impaired disposition of probe drugs is due to both liver and kidney dysfunctions in CCl(4)-model rats

The carbon tetrachloride (CCl(4))-treated model involving mature Sprague-Dawley rats has been historically relied upon to study liver injury and regeneration and to test drug efficacy and disposition. However, there few studies about phase II metabolic enzymes changes in CCl(4)-model rats. The metabolic and excretion tests of phenacetin and acetaminophen (APAP), and the mRNA test of cytochrome P4501A2 (CYP1A2) and phase II metabolic enzymes [sulfotransferase 1A1 (SULT1A1) and UDP-glucuronosyltransferase 1A6 (UGT1A6)] were studied in model rats after CCl(4) pretreatment. The result showed that the function and structure of liver and kidney was impaired by CCl(4) pretreatment, and a significant difference has been observed in the mRNA content of CYP1A2 (p<0.01) in model group, but there was no significant difference on the mRNA content of SULT1A1 and UGT1A6 in both groups. Compared to the control group, a significant higher content of phenacetin (p<0.01) and sulfate-APAP (AS, p<0.01) was observed in the metabolic tests of phenacetin and APAP. Statistically significant differences in cumulative urinary excretion levels of APAP, AG and AS for CCl(4) model rats were observed also. We have shown that impaired disposition of probe drugs in this model was due to both liver and kidney dysfunction in CCl(4)-model rats and we should consider the development of a new liver damage model without renal impairment.

A review of the evidence concerning hepatic glutathione depletion and susceptibility to hepatotoxicity after paracetamol overdose

Paracetamol (acetaminophen) poisoning is common throughout the world. The management of nonstaggered (acute) paracetamol overdose is based on the plasma paracetamol concentration plotted on a treatment nomogram. In the UK there are two treatment lines on this nomogram, with the lower treatment line used for individuals felt to be at ‘high risk’ of paracetamol-related hepatotoxicity either as a result of induction of cytochrome P450 isoenzymes or reduction of intrahepatic glutathione. In this article we review the risk factors that, in current guidelines, are felt to increase risk due to a reduction in intrahepatic glutathione concentrations. Based on our review of the published literature, we feel that cystic fibrosis, acute viral illness, malnutrition, and eating disorders such as anorexia nervosa are likely to be associated with reduction in intrahepatic glutathione concentrations, and that this risk is likely to be related to malnutrition secondary to the disease. Chronic hepatitis C infection is also associated with reduced glutathione concentrations, although this appears to be independent of any associated malnutrition. Ageing and acute fasting are not associated with an increased risk of paracetamol-related hepatotoxicity due to reductions in glutathione concentrations. Finally, the evidence for HIV infection is inconclusive, particularly as the majority of studies were conducted in the pre-anti-viral treatment (HAART) era; however it is likely that patients with symptomatic HIV/AIDS have reduced glutathione concentrations due to associated malnutrition. Although there have been few studies which have specifically investigated whether there is an association between reduced intrahepatic glutathione concentrations and increased risk of paracetamol-related hepatotoxicity, in our opinion, it is likely that the above conditions that are associated with reduced glutathione concentrations, will be associated with an increased risk of paracetamol-related hepatotoxicity.

Effect of widely used combinations of antiretroviral therapy on liver CYP3A4 activity in HIV-infected patients

AIMS

To evaluate the effects of combined antiretroviral drugs (HAART) on liver CYP3A4 activity using the [(14)C-N-methyl]-erythromycin breath test (ERMBT).

METHODS

HIV-infected patients (31 women, 30 men) with mean (+/- SD) age of 38 +/- 9 years were enrolled and underwent complete clinical and laboratory evaluation. Patients were divided into five groups and were treated with two nucleoside analogues (NAs) and one of the following: nelfinavir alone (n = 13), any ritonavir-boosted protease inhibitor with (n = 8) or without (n = 13) nevirapine, nevirapine alone (n = 15), or a third NA (n = 12). Three or four ERMBTs were performed 7 days prior to (D-7) and at the beginning of treatment (D0), D14 (only for patients taking nevirapine) and on D28.

RESULTS

Mean baseline liver CYP3A4 activity displayed high interindividual variability (47%) but low intraindividual variability (15%). Women had 30% higher ERMBT values than men [2.7 +/- 1.3 vs. 1.9 +/- 0.7; 95% confidence interval (CI) 20.5, 49.5; P = 0.003]. The ERMBT data correlated with body weight, alpha- and beta-globulins and alanin aminotransferases (0.10 < r(s) < 0.20; P < 0.01). Whereas nevirapine had no effect on liver CYP3A4 activity, nelfinavir-based and ritonavir-boosted drug regimens inhibited it by 69% (95% CI 64.7, 72.9; P = 0.005) and by 95% (95% CI 93.3, 96.7; P = 0.001), respectively.

CONCLUSION

Evaluation of the effect of HAART on liver CYP3A4 activity may aid in preventing inappropriate treatment regimens in HIV-infected patients.

Non-steroidal anti-inflammatory drugs for cancer prevention: promise, perils and pharmacogenetics

Aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) show indisputable promise as chemopreventive agents. Possible targets include cancers of the colon, stomach, breast and lung. However, recent studies raise concern about potential cardiovascular toxicity associated with the use of NSAIDs that specifically target the enzyme cyclooxygenase 2. These findings, and others that show that inherited genetic characteristics might determine preventive success, argue for new strategies that are tailored to individual medical history and genetic make-up.

Glucose production pathways by2H and13C NMR in patients with HIV-associated lipoatrophy

Patients with HIV taking protease inhibitors were selected for the presence (five subjects) or absence (five subjects) of lipoatrophy. Following an overnight fast, subjects were given oral (2)H(2)O in divided doses (5 mL/kg body water), [U-(13)C(3)] propionate (10 mg/kg), and acetaminophen (1000 mg). Glucose (from plasma) or acetaminophen glucuronide (from urine) were converted to monoacetone glucose for (2)H NMR and (13)C NMR analysis. The fraction of plasma glucose derived from gluconeogenesis was not significantly different between groups. However, flux from glycerol into gluconeogenesis relative to glucose production was increased from 0.20 +/- 0.13 among subjects without lipoatrophy to 0.42 +/- 0.12 (P < 0.05) among subjects with lipoatrophy, and the TCA cycle contribution was reduced. Lipoatrophy was associated with an abnormal profile of glucose production as assessed by (13)C and (2)H NMR of plasma and urine.