Black patients with chronic hepatitis C have a lower sustained viral response rate than non-Blacks with genotype 1, but the same with genotypes 2/3, and this is not explained by more frequent dose reductions of interferon and ribavirin*.

In previous hepatitis C virus (HCV) treatment studies, Black patients not only had a lower sustained viral response (SVR) rate to interferon and ribavirin (RBV) than non-Black patients but also a higher frequency of HCV genotype 1 (GT-1) infection. The aim of this community-based study was to determine whether Black patients have a lower SVR rate independent of genotype. We prospectively enrolled 785 patients (24.8% Black, 71.5% White, 3.7% others) who received interferon alpha-2b 3 MU three times weekly + RBV 1000-1200 mg/day for 24 weeks (GT-2/3) or 48 weeks (GT-1). Black patients were more commonly infected with GT-1 (86.8%vs 64.8%, P < 0.001) and less frequently had an SVR compared with non-Black patients (8.4%vs 21.6%, P < 0.001). Within GT-1, Black patients had a lower SVR rate than non-Black patients (6.1%vs 14.1%, P = 0.004) but not within GT-2/3 (50.0%vs 36.5%, P = 0.47). Black patients had lower baseline haemoglobin levels (14.8 vs 15.3 g/dL, P < 0.001) and neutrophil counts (2900 vs 4100/mm(3), P < 0.001) and required more frequent dose reductions of RBV (29.8%vs 18.5%, P < 0.001) and interferon (4.7%vs 1.6%, P = 0.012). However, dose reductions were not associated with lower SVR rates while early treatment discontinuations were (2.9%vs 25.7%, P < 0.001). Independent predictors of SVR were GT-1 [odds ratio (OR) 0.33; 95% confidence interval (CI) 0.20-0.55; P < 0.001], Black race (OR 0.45; 95% CI 0.22-0.93; P = 0.030), and advanced fibrosis, stages 3 + 4 (OR 0.53; 95% CI 0.31-0.92; P = 0.023). In conclusion, Black patients infected with HCV GT-1 (but not GT-2/3) have a lower SVR rate than non-Black patients. This is not explained by their lower baseline haemoglobin levels and neutrophil counts that lead to higher rates of ribavirin and interferon dose reductions.

Troglitazone (Rezulin) and hepatic injury.

PURPOSE: Analyze US rates of reported severe liver disease for the oral hypoglycemic agent troglitazone from March 1997 through February 2000 and the possible effects of publicity on reporting. METHODS: The number of troglitazone reports with liver failure and or hospitalization with jaundice or hyperbilirubinemia, made to the FDA and/or Parke-Davis are used as numerators. The denominators are numbers of patients and person-time estimates of exposure. Additionally, the amount of publicity about troglitazone during its marketing is quantified. RESULTS: Approximately 1.92 million patients were treated with troglitazone from March 1997 through the end of February 2000 resulting in 1.6 million person-years of exposure. Reports of 83 cases of liver failure associated with troglitazone were received (1 in 23,000 patients or 1 in 20,000 person-years). Of the 83 cases, only 49 (59%) were classified by a hepatologist to be 'possibly' or 'probably' attributed to troglitazone. For the first, second, and third years of marketing, rates of reported hepatic failure per 100,000 person years exposure to troglitazone were 8.3, 5.3, and 2.7 respectively. Rates of reported liver disease involving hospitalizations with mention of jaundice and hyperbilirubinemia per 100,000 person-years were 16.0, 6.1, and 3.6 respectively for these years. During the 3-year marketing history of troglitazone, there were 470 lay press and 158 medical literature articles with mentions of hepatotoxicity for the drug. CONCLUSIONS: Rates of reported severe liver disease declined substantially during the second and third years of marketing of troglitazone. The decline followed increasingly stringent requirements for liver function test monitoring and may have been due to improved patient selection and management as a result of the widely publicized association between troglitazone and hepatotoxicity.

Downregulated in adenoma gene encodes a chloride transporter defective in congenital chloride diarrhea.

Congenital chloride diarrhea (CLD) is a recessively inherited disorder characterized by massive loss of chloride in stool. We previously identified mutations in the downregulated in adenoma (DRA) gene in patients with CLD and demonstrated that DRA encodes an intestine-specific sulfate transporter. To determine whether DRA is an intestinal chloride transporter and how mutations affect transport, Xenopus oocytes were injected with wild-type and mutagenized DRA cRNA and uptake of Cl- and SO2-4 was assayed. Both Cl- and SO2-4 were transported by wild-type DRA and an outwardly directed pH gradient stimulated Cl- uptake, consistent with Cl-/OH- exchange. Among three mutants, C307W transported both anions as effectively as wild-type, whereas transport activity was lost in V317del and the double mutant identified in 32 of 32 Finnish CLD patients. We conclude that DRA is a chloride transporter defective in CLD and that V317del is a functional mutation and C307W a silent polymorphism.

Sepsis and cholestasis.

Sepsis-associated cholestasis should always be considered as part of the differential diagnosis of jaundice in the hospitalized or critically ill patient. The development of a disproportionate elevation of serum bilirubin in comparison with serum alkaline phosphatase and serum aminotransferases should be considered an early warning sign of an underlying infection, even in the absence of fever, leukocytosis, or other signs or symptoms. Prompt recognition and appropriate medical and surgical intervention may reduce morbidity and mortality.

The neurotoxin 1-methyl-4-phenylpyridinium is a substrate for the canalicular organic cation/H+ exchanger.

Hepatic organic cation transport consists, in part, of carrier-mediated sinusoidal uptake stimulated by an inside-negative membrane potential and canalicular excretion driven by electroneutral organic cation/H+ exchange. Intracellular organic cation transport involves sequestration into acidified organelles, also mediated by organic cation/H+ exchange. A sinusoidal organic cation transporter has been cloned; however, canalicular organic cation transport has not been characterized at the molecular level. On the assumption that hepatic organic cation/H+ exchange resembles monoamine transport in synaptic vesicles, we examined, using canalicular rat liver plasma membrane vesicles, the transport of 1-methyl-4-phenylpyridinium (MPP+), a neurotoxin taken up by a synaptic vesicular monoamine transporter that has been cloned. Under voltage-clamped conditions, an outwardly directed H+ gradient stimulated [3H]MPP+ uptake, compared with uptake under pH-equilibrated conditions, consistent with electroneutral MPP+/H+ exchange. Substrates for canalicular organic cation/H+ exchange cis-inhibited pH-dependent MPP+ uptake. Equilibrium exchange of [14C]tetraethylammonium was inhibited by MPP+ in a concentration-dependent manner, consistent with a direct interaction of MPP+ with the organic cation carrier. Carrier-mediated MPP+ uptake exhibited saturability, with kinetic parameters similarto those described for canalicular tetraethylammonium+/H+ exchange. Canalicular [3H]MPP+ uptake was ATP-independent and, thus, distinct from P-glycoprotein-mediated efflux. The finding that MPP+ is a substrate for canalicular organic cation/H+ exchange is applicable to studies, using degenerate oligonucleotides complementary to sequences conserved in neurotransmitter transporters, aimed at cloning this transporter.

Evaluation of abnormal liver function tests.

Although the liver can be affected in a wide range of disorders, the differential diagnosis of abnormal liver function tests can be substantially narrowed by a comprehensive history and physical examination and by the recognition of relatively distinct biochemical patterns of liver injury. Although referral to a specialist may be required for the performance of, for example, percutaneous liver biopsy and long-term management of chronic liver disease, a presumptive diagnosis can usually be made in the vast majority of patients who present to primary care physicians with abnormal liver function tests.

Effect of endotoxin on bile acid transport in rat liver: a potential model for sepsis-associated cholestasis.

Intrahepatic cholestasis in the setting of extrahepatic bacterial infection has been attributed to the effects of endotoxin and cytokines such as tumor necrosis factor-alpha (TNF-alpha) on bile acid transport. To define the mechanism of sepsis-associated cholestasis, taurocholate transport was examined in basolateral (bLPM) and canalicular (cLPM) rat liver plasma membrane vesicles derived from control and endotoxin [lipopolysaccharide (LPS)]-treated animals and in plasma membrane vesicles prepared after TNF-alpha treatment. Na(+)-dependent [3H]taurocholate uptake and both membrane-potential-dependent and ATP-dependent [3H]taurocholate transport were reduced in bLPM and cLPM vesicles, respectively, after LPS treatment. In membrane vesicles from TNF-alpha-treated animals, Na(+)-dependent [3H]taurocholate uptake was also reduced. Northern blot hybridization, using cDNA probes for the putative sinusoidal bile acid transporter (Ntcp) and canalicular ecto-adenosinetriphosphatase, demonstrated decreased mRNA levels after LPS and TNF-alpha treatment. Immunoblot analysis of membrane extracts from LPS-treated animals revealed decreased levels of these putative bile acid transporters. Impaired bile acid transport at the sinusoidal and canalicular membrane domains by these and other mediators of the inflammatory response may account for sepsis-associated cholestasis.

Choline transport in rat liver basolateral plasma membrane vesicles.

Previous studies have demonstrated several pathways for the sinusoidal uptake of endogenous and exogenous organic cations, including two distinct organic cation:H+ exchanges and a separate carrier-mediated system driven by the inside-negative membrane potential. In this study, the driving force(s) for the uptake of the endogenous quaternary amine, choline, were determined in rat liver basolateral plasma membrane (blLPM) vesicles. Choline uptake into an osmotically sensitive space was not stimulated by an outwardly directed H+ or inwardly directed Na+ gradient. Instead, an inside-negative K+ diffusion potential stimulated choline uptake, suggesting the presence of a conductive pathway for choline uptake in bILPM vesicles. Conductive choline uptake was confirmed by inducing variable changes in the transmembrane potential with anions of different membrane permeability. Choline uptake in blLPM vesicles exhibitied 1) temperature dependency; 2) trans-stimulation; and 3) saturability, with an approximate Michaelis constant (Km) of 0.34 mmol/L and maximum velocity (Vmax) of 0.45 nmol/mg protein/15 s. Choline uptake in blLPM vesicles was cis-inhibited by the structurally similar derivative, hemicholinium-3 and acetylcholine, but not by substrates for other organic cation transport processes identified in blLPM vesicles, including thiamine, tetraethylammonium (TEA), tri-n-butyl-methylammonium (TBuMA), and N'-methylnicotinamide (NMN). These findings demonstrate an electrogenic pathway on the sinusoidal membrane for the uptake of this essential nutrient and support the existence of multiple pathways for the sinusoidal uptake of endogenous and exogenous organic cations.