T. L. Murphy

Hephaestin, a ceruloplasmin homologue implicated in intestinal iron transport, is defective in the sla mouse

Iron is essential for many cellular functions; consequently, disturbances of iron homeostasis, leading to either iron deficiency or iron overload, can have significant clinical consequences. Despite the clinical prevalence of these disorders, the mechanism by which dietary iron is absorbed into the body is poorly understood. We have identified a key component in intestinal iron transport by study of the sex–linked anaemia (sla) mouse, which has a block in intestinal iron transport. Mice carrying the sla mutation develop moderate to severe microcytic hypochromic anaemia. Although these mice take up iron from the intestinal lumen into mature epithelial cells normally, the subsequent exit of iron into the circulation is diminished. As a result, iron accumulates in enterocytes and is lost during turnover of the intestinal epithelium. Biochemical studies have failed to identify the underlying difference between sla and normal mice, therefore, we used a genetic approach to identify the gene mutant in sla mice. We describe here a novel gene, Heph, encoding a transmembrane–bound ceruloplasmin homologue that is mutant in the sla mouse and highly expressed in intestine. We suggest that the hephaestin protein is a multi–copper ferroxidase necessary for iron egress from intestinal enterocytes into the circulation and that it is an important link between copper and iron metabolism in mammals.

Dose‐dependent pharmacokinetics of caffeine in humans: Relevance as a test of quantitative liver function

Caffeine clearance was determined in 13 healthy control subjects and in 13 patients with histologically proven cirrhosis. On separate occasions, 70 mg, 200 mg, and 300 mg single doses of anhydrous caffeine were administered orally with decaffeinated coffee to each subject. Subjects were analyzed individually, acting as their own controls, thus reducing interindividual variability. The present study showed that caffeine exhibited dose‐dependent pharmacokinetics, particularly in subjects who showed high initial clearance with the low dose (70 mg) of caffeine. There was a significant decrease in caffeine clearance with increasing dose from 70 mg to 300 mg (n = 26, p < 0.01, Dunnetts test), indicating saturable caffeine metabolism in the dose range tested. These findings imply that if caffeine is to be used as a guide to deteriorating liver function, serial caffeine clearance estimations should be performed in each individual subject, with use of the same dose of caffeine each time.

Serum hyaluronic acid with serum ferritin accurately predicts cirrhosis and reduces the need for liver biopsy in C282Y hemochromatosis

Diagnosing the presence of cirrhosis is crucial for the management of patients with C282Y hereditary hemochromatosis (HH). HH patients with serum ferritin >1,000 μg/L are at risk of cirrhosis; however, the majority of these patients do not have cirrhosis. Noninvasive markers of hepatic fibrosis may assist in determining which patients with a serum ferritin >1,000 μg/L have cirrhosis and require liver biopsy. This study evaluated the utility of current diagnostic algorithms for detecting cirrhosis, including serum ferritin concentration, platelet counts, and aspartate aminotransferase (AST) levels, in combination with serum markers of fibrosis, hyaluronic acid and collagen type IV (CLIV), in predicting cirrhosis in HH patients. Stage of fibrosis, serum hyaluronic acid and CLIV levels, were measured in 56 patients with HH. No patient with a serum ferritin <1,000 μg/L had cirrhosis, but only 40% of patients with serum ferritin >1,000 μg/L were cirrhotic. A combination of platelet count (<200 × 109/L), elevated AST, and serum ferritin >1,000 μg/L did not detect 30% of cirrhotic subjects. Serum hyaluronic acid was increased in HH compared with controls (42.0 ± 9.8 ng/mL versus 19.3 ± 1.8 ng/mL; P = 0.02). A hyaluronic acid concentration >46.5 ng/mL was 100% sensitive and 100% specific in identifying patients with cirrhosis. In patients with serum ferritin >1,000 μg/L, hyaluronic acid levels were significantly elevated in patients with cirrhosis versus those without cirrhosis (137 ± 34.4 ng/mL versus 18.6 ± 1.5 ng/mL, respectively; P = 0.006). CLIV >113 ng/mL was 100% sensitive but only 56% specific for cirrhosis (area under the curve = 0.78; P = 0.01). Conclusion: In HH, the measurement of hyaluronic acid in patients with serum ferritin >1,000 μg/L is a noninvasive, accurate, and cost‐effective method for the diagnosis of cirrhosis. (HEPATOLOGY 2009;49:418–425.)

INFLUENCE OF ALCOHOL AND CAFFEINE CONSUMPTION ON CAFFEINE ELIMINATION

1. Ten healthy male volunteers were each studied on four separate occasions to assess the role of regular caffeine and alcohol intake on caffeine elimination. Antipyrine disappearance was also studied as an established quantitative test of hepatic microsomal function.

The Effect of Smoking On Caffeine Elimination - Implications for its Use as a Semiquantitative Test of Liver-Function

1. The effects of caffeine ingestion and cigarette smoking on caffeine and antipyrine pharmacokinetics were studied using normal subjects as their own controls before and after cessation of smoking in an attempt to minimize genetic and other environmental influences.

Hepcidin regulation in wild-type and Hfe knockout mice in response to alcohol consumption: Evidence for an alcohol-induced hypoxic response

BACKGROUND/AIMS Expression of Hamp1, the gene encoding the iron regulatory peptide hepcidin, is inappropriately low in HFE-associated hereditary hemochromatosis and Hfe knockout mice (Hfe(-/-)). Since chronic alcohol consumption is also associated with disturbances in iron metabolism, we investigated the effects of alcohol consumption on hepcidin mRNA expression in Hfe(-/-) mice. METHODS Hfe(-/-) and C57BL/6 (wild-type) mice were pair-fed either an alcohol liquid diet or control diet for up to 8 weeks. The mRNA levels of hepcidin and ferroportin were measured at the mRNA level by RT-PCR and protein expression of hypoxia inducible factor-1 alpha (HIF-1alpha) was measured by western blot. RESULTS Hamp1 mRNA expression was significantly decreased and duodenal ferroportin expression was increased in alcohol-fed wild-type mice at 8 weeks. Time course experiments showed that the decrease in hepcidin mRNA was not immediate, but was significant by 4 weeks. Consistent with the genetic defect, Hamp1 mRNA was decreased and duodenal ferroportin mRNA expression was increased in Hfe(-/-) mice fed on the control diet compared with wild-type animals and alcohol further exacerbated these effects. HIF-1alpha protein levels were elevated in alcohol-fed wild-type animals compared with controls. CONCLUSION Alcohol may decrease Hamp1 gene expression independently of the HFE pathway possibly via alcohol-induced hypoxia.

Increased duodenal expression of divalent metal transporter 1 and iron-regulated gene 1 in cirrhosis

Hepatic hemosiderosis and increased iron absorption are common findings in cirrhosis. It has been proposed that a positive relation exists between intestinal iron absorption and the development of hepatic hemosiderosis. The current study investigated the duodenal expression of the iron transport molecules divalent metal transporter 1 (DMT1 [IRE]), iron‐regulated gene 1 (Ireg1 [ferroportin]), hephaestin, and duodenal cytochrome b (Dyctb) in 46 patients with cirrhosis and 20 control subjects. Total RNA samples were extracted from duodenal biopsy samples and the expression of the iron transport genes was assessed by ribonuclease protection assays. Expression of DMT1 and Ireg1 was increased 1.5 to 3‐fold in subjects with cirrhosis compared with iron‐replete control subjects. The presence of cirrhosis per se and serum ferritin (SF) concentration were independent factors that influenced the expression of DMT1. However, only SF concentration was independently associated with Ireg1 expression. In cirrhosis, the expression of DMT1 and Ireg1 was not related to the severity of liver disease or cirrhosis type. There was no correlation between the duodenal expression of DMT1 and Ireg1 and the degree of hepatic siderosis. In conclusion, the presence of cirrhosis is an independent factor associated with increased expression of DMT1 but not Ireg1. The mechanism by which cirrhosis mediates this change in DMT1 expression has yet to be determined. Increased expression of DMT1 may play an important role in the pathogenesis of cirrhosis‐associated hepatic iron overload. (HEPATOLOGY 2004;39:492–499.)

Carbohydrate-Deficient Transferrin in Alcoholics with Liver-Disease

Abstract To assess the relationship between carbohydrate‐deficient transferrin (CDT) and alcoholic liver disease, we measured the ratio of carbohydrate‐deficient transferrin to total transferrin (rCDT) in 32 male alcoholics with liver disease (Child‐Pugh class A, 8; B, 11; C, 13) and 14 male alcoholics without clinically evident liver disease. Twenty of 32 with liver disease and six of 14 without clinically apparent liver disease had recent abstinence. The 32 patients with liver disease were assessed, in addition to the Child‐Pugh class, using a linear prognostic score, the Combined Clinical and Laboratory Index (CCLI). Transferrin and CDT were measured by isocratic anion exchange chromatography and a radio‐immunoassay. When the total group (n= 46) was divided into those with recent abstinence (n= 26) and those without (n= 20), the rCDT was lower in the abstainers than non‐abstainers (0.7 ± 0.6 vs 2.9 ± 2.4, P < 0.005). Similarly, abstainers with liver disease (n= 20) had a significantly lower rCDT than non‐abstainers (n= 12) with liver disease (0.7 ± 0.7 vs 3.5 ± 2.8, P < 0.005). The rCDT in the 20 abstaining patients with liver disease did not differ significantly between Child‐Pugh classes. Furthermore, there was no correlation between the CCLI and rCDT (r= 0.05). We conclude that the relationship between rCDT and alcohol abuse is not appreciably altered by the presence of clinically severe liver disease in male alcoholics.

The protective effects of corn-oil diet against alcohol and iron-induced hepatotoxicity in a mouse model of hemochromatosis

This journal suppl. contain abstracts of the 62nd Annual Meeting of the American Association for the Study of Liver Diseases: The Liver Meeting 2011This journal suppl. contain abstracts of the 62nd Annual Meeting of the American Association for the Study of Liver Diseases: The Liver Meeting 2011Nutzungsbedingungen Die ETH-Bibliothek ist Anbieterin der digitalisierten Zeitschriften. Sie besitzt keine Urheberrechte an den Inhalten der Zeitschriften. Die Rechte liegen in der Regel bei den Herausgebern. Die auf der Plattform e-periodica veröffentlichten Dokumente stehen für nicht-kommerzielle Zwecke in Lehre und Forschung sowie für die private Nutzung frei zur Verfügung. Einzelne Dateien oder Ausdrucke aus diesem Angebot können zusammen mit diesen Nutzungsbedingungen und den korrekten Herkunftsbezeichnungen weitergegeben werden. Das Veröffentlichen von Bildern in Printund Online-Publikationen ist nur mit vorheriger Genehmigung der Rechteinhaber erlaubt. Die systematische Speicherung von Teilen des elektronischen Angebots auf anderen Servern bedarf ebenfalls des schriftlichen Einverständnisses der Rechteinhaber.

CHANGES IN DUODENAL IRON TRANSPORT GENE EXPRESSION IN RATS FOLLOWING A SWITCH TO AN IRON DEFICIENT DIET OCCUR BEFORE ALTERATIONS IN BODY IRON STORES

Introduction and aims  The level of body iron stores is an important factor controlling the rate of intestinal iron absorption but how storage iron influences intestinal iron transport is unclear. A switch from a control diet to an iron deficient diet results in an increase in iron absorption within 5 days; long before any changes in body iron stores or haematological parameters. To investigate the mechanism by which this occurs, we have studied the adaptation in expression of iron transport genes in rat duodenum following the change to an iron deficient diet.