C282Y Homozygous Patients Research Articles

Low serum transferrin levels in HFE C282Y homozygous subjects are associated with low CD8 + T lymphocyte numbers

Hereditary hemochromatosis (HH) is a genetic iron overload disease, in the majority of cases associated with homozygosity for the C282Y mutation of the HFE gene. In spite of this genetic homogeneity, there is a great clinical heterogeneity among HH patients. Low CD8 + lymphocyte numbers have been associated with a more severe expression of iron overload in HH patients, and in experimental models of iron overload. HH patients present low serum transferrin levels. Transferrin is an indispensable resource for lymphopoiesis. Lymphocyte homeostasis follows general ecology rules of population dynamics that involve competition for limiting resources. In the present study, we questioned whether transferrin levels could be associated with the anomalies seen previously in lymphocyte subset numbers in HH patients. Transferrin levels, total and subset T lymphocyte counts were done in 426 apparently healthy subjects genotyped for HFE. All HFE C282Y carriers presented significantly lower serum transferrin levels than the wild type group, a difference that could not be explained solely by the degree of iron overload. Significant differences were also seen in transferrin levels between males and females, with females presenting higher average serum Transferrin levels. In the population of subjects with Transferrin levels lower than 248 mg/dl, a positive correlation was seen between the peripheral CD8 + lymphocyte numbers and serum transferrin levels ( R 2 = 2.41; r = 0.16; P = 0.018). To test the possible limiting resource effect of transferrin, the correlation between transferrin levels and CD8 + lymphocyte numbers was scrutinized in 34 HH patients, homozygous for the C282Y mutation. In the homozygous males, where the lowest average transferrin levels were seen, another highly significant correlation was observed between Transferrin levels and CD8 + numbers. This correlation points to a possible role of transferrin as a limiting resource for MHC class I dependent lymphocyte proliferation, an effect that was not observed in C282Y homozygous female patients.

Bases moléculaires des hémochromatoses génétiques

Recent discoveries in molecular mechanisms of iron metabolism have changed the classical view of hereditary iron overload conditions. We present natural mutations in newly discovered genes and related phenotypes observed in patients with different form of haemochromatosis. Most haemochromatosis patients are homozygous for the C282Y mutation in the HFE gene. Ferroportin, TFR2, hemojuvelin and hepcidin mutations also cause iron overload. Recent data support the hypothesis that haemochromatosis should no longer be considered a monogenic disease but rather an oligogenic disorder. Several results suggest that haemochromatosis could result from digenic inheritance of mutations in HFE and HAMP. Other modifier genes probably influence penetrance in C282Y homozygous patients. Such genes could enhance or reduce the phenotypic expression in various iron overload conditions.

HAMPas a modifier gene that increases the phenotypic expression of theHFEpC282Y homozygous genotype

AbstractHereditary hemochromatosis is a genetically heterogeneous disease of iron metabolism. The most common form of the disorder is an adult-onset form that has mainly been associated with theHFEpC282Y/pC282Y genotype. The phenotypic expression of this genotype is very heterogeneous and could be modulated by both environmental factors and modifier genes. The non-HFEhereditary hemochromatosis forms include a juvenile onset form associated with mutations inHAMP. From a cohort of 392 C282Y homozygous patients, we found 5 carriers of an additionalHAMPmutation at the heterozygous state (pR59G, pG71D, or pR56X). We found that iron indices of these 5 patients were among the most elevated of the cohort. Moreover, we specified that theHAMPmutations were not detected in 300 control subjects. These results revealed that mutations inHAMPmight increase the phenotypic expression of the pC282Y/pC282Y genotype. From a cohort of 31 patients with at least one chromosome lacking anHFEmutation, we further identified 4 males carrying a heterozygousHAMPmutation (pR59G or pG71D). Based on a digenic model of inheritance, these data suggest that the association of heterozygous mutations in theHFEandHAMPgenes could lead, at least in some cases, to an adult-onset form of primary iron overload. (Blood. 2004;103:2835-2840)

Circadian variations of transferrin saturation levels in iron‐overloaded patients: implications for the screening of C282Y‐linked haemochromatosis

The phenotypic screening for genetic haemochromatosis (GH) relies upon the determination of transferrin saturation (TS). In large-scale screening programs, the time of blood sampling can be uneasy to control. We studied the circadian variations of TS at 08.00 hours, 12.00 hours, 18.00 hours and 00.00 hours in 46 C282Y homozygous patients (GH) and 47 non-GH patients (NH), to determine whether the time of blood sampling influenced the results of screening. In both groups, there were significant circadian variations in TS, with the highest values at 08.00 hours and the lowest at 00.00 hours. For any given time-point, TS was significantly higher in the GH group when compared with the NH group (P < 0.0001). For both groups, there was a significant decrease in TS between 08.00 hours and 00.00 hours (P < 0.0001) but this decrease was not as significant in GH when compared with NH patients (interaction P < 0.0073). Receiver operating characteristics (ROC) curves generated for TS at 08.00 hours, 12.00 hours, 18.00 hours and 00.00 hours, presented the same efficiency of diagnosis of GH, with TS threshold varying between 64% at 08.00 hours and 36% at 00.00 hours. In conclusion, for screening studies of C282Y homozygosity, determination of transferrin saturation may be performed at any time during the day.

Noninvasive prediction of cirrhosis in C282Y-linked hemochromatosis

The aim of the present study was to examine the predictive accuracy of noninvasive clinical and biochemical variables associated with cirrhosis among patients with C282Y homozygous hemochromatosis. Sixteen clinical and laboratory variables were recorded at the time of diagnosis in 193 Canadian C282Y homozygous patients. All patients underwent percutaneous liver biopsy and 27 (14%) had biopsy specimen–proven cirrhosis. Prediction of cirrhosis was assessed first by univariate regression analysis. Variables significantly related to cirrhosis were then evaluated by stepwise linear multivariate regression. Receiver operating characteristic curve analysis of the most informative variables from multivariate analysis was then used to devise a clinically applicable index for the noninvasive prediction of cirrhosis. This index was then validated in 162 C282Y homozygous patients in France. Ferritin, blood platelets, and aspartate transaminase (AST) level were selected for the clinical index. The combination of ferritin levels of 1,000 μg/L or greater, platelet levels of 200 × 10 9/L or less, and AST levels above the upper limit of normal led to a correct diagnosis of cirrhosis in 77% of Canadian patients. In the French patients, this led to a correct diagnosis of cirrhosis in 90%. In conclusion, in C282Y homozygous patients, a combination of easily measured laboratory variables (ferritin, platelets, AST) can be used to make the diagnosis of cirrhosis in approximately 81% of cases, reducing the need for liver biopsy. (H EPATOLOGY 2002;36:673-678.)

Peripheral lymphocytes and intracellular cytokines in C282Y homozygous hemochromatosis patients

Background/Aims: Several abnormalities in the immune status of hereditary hemochromatosis patients have been reported. We evaluated the peripheral blood lymphocytes phenotype and cytokine profile of CD8 + and CD4 + T cells in C282Y homozygous hereditary hemochromatosis patients compared to control subjects. Methods: Peripheral blood lymphocytes from 17 asymptomatic patients and 14 control subjects were analyzed. We determined the distribution of lymphocyte subsets and investigated at single-cell level by flow-cytometry the potential of cytokines production. The frequency of cytokine (interferon gamma, tumor necrosis factor alpha, interleukin 2 (IL-2), IL-4, IL-5, IL-10 and IL-13) producing cells was assessed in total T-lymphocytes, CD3 +CD8 + and CD3 +CD4 + subsets. Results: The patients studied showed a significant decrease of total lymphocyte count, T CD4 +CD3 +, CD28 +, CD8 +CD28 + lymphocytes and natural killer (NK) CD56 +CD16 +CD3 − cells. The reduction of CD28 + and CD8 +CD28 + lymphocyte count was inversely related to transferrin saturation index. An increase in the ability of T-cells to produce all the cytokines studied and a major increase in IL-4 and IL-10 production in the CD3 +CD8 + subset was found. Our results demonstrate that activated Th1 and Th2 lymphocytes coexist in the peripheral blood of hereditary hemochromatosis patients and that T-cytotoxic (Tc) 2 subset is more expanded than in control population. Conclusions: The association of a decreased number of T CD8 + cytotoxic lymphocytes and NK cells, and the development of Tc2 cells in asymptomatic C282Y homozygous patients represents an imbalance in their immune function that might contribute to the high incidence of hepatocarcinoma.

Insulin resistance–associated hepatic iron overload

Background & Aims: Hepatic iron overload has been reported in various metabolic conditions, including the insulin-resistance syndrome (IRS) and nonalcoholic steatohepatitis (NASH). The aim of this study was to show that such hepatic iron overload is part of a unique and unrecognized entity. Methods: A total of 161 non–C282Y-homozygous patients with unexplained hepatic iron overload were included. We determined the age; sex; presence of IRS (1 or more of the following: body mass index of >25, diabetes, or hyperlipidemia); serum iron tests and liver iron concentration (LIC; reference value, <36 μmol/g); liver function test results; C282Y and H63D HFE mutations; and liver histological status. Results: Patients were predominantly male and middle-aged. Most (94%) had IRS. Transferrin saturation was increased in 35% (median, 42%; range, 13%–94%). LIC ranged from 38 to 332 μmol/g (median, 90 μmol/g), and LIC/age ratio ranged from 0.5 to 4.8 (median, 1.8). Allelic frequencies of both HFE mutations were significantly increased compared with values in normal controls (C282Y, 20% vs. 9%; H63D, 30% vs. 17%), only because of a higher prevalence of compound heterozygotes. Patients with no HFE mutations had similar degrees of iron overload as those with other genotypes, except for compound heterozygotes, who had slightly more iron burden. Steatosis was present in 25% of patients and NASH in 27%. Portal fibrosis (grades 0–3) was present in 62% of patients (grade 2 or 3 in 12%) in association with steatosis, inflammation, and increased age. Sex ratio, IRS, transferrin saturation, and LIC did not vary with liver damage. Serum ferritin concentration, liver function test results, and fibrosis grade were more elevated in patients with steatosis and NASH than in others, but LIC and allelic frequencies of HFE mutations were similar. Conclusions: This study shows that patients with unexplained hepatic iron overload are characterized by a mild to moderate iron burden and the nearly constant association of an IRS irrespective of liver damage. GASTROENTEROLOGY 1999;117:1155-1163

Noninvasive prediction of fibrosis in C282Y homozygous hemochromatosis

Background & Aims: The diagnosis of hemochromatosis is now possible for C282Y homozygous patients using noninvasive molecular genetic tests. The aim of this study was to define noninvasive factors predictive of severe fibrosis (bridging fibrosis or cirrhosis) to avoid unnecessary liver biopsies in such patients. Methods: Clinical and biological data were recorded at the time of diagnosis in 197 French C282Y homozygous patients, 52 (26%) of whom had severe fibrosis. Variables significantly linked to severe fibrosis using univariate analysis were entered into a multivariate stepwise analysis. These variables were combined to obtain a simple index allowing for prediction of severe fibrosis. Results: Serum ferritin, hepatomegaly, and serum aspartate aminotransferase were selected using multivariate analysis. Their combination applied to the 96 patients with ferritin level of ≤1000 μg/L, normal aspartate aminotransferase values, and absence of hepatomegaly showed that no severe fibrosis was encountered in this subgroup of patients. The results were validated in 113 C282Y homozygous patients in Canada with a good reproducibility of negative prediction but a poor reproducibility of the positive prediction of severe fibrosis. Conclusions: In C282Y homozygous patients, the diagnosis of severe fibrosis relies on liver biopsy, but absence of severe fibrosis can be accurately predicted in most patients on the basis of simple clinical and biochemical variables. GASTROENTEROLOGY 1998;115:929-936

Heterozygosity for hereditary hemochromatosis is associated with more fibrosis in chronic hepatitis C

Hepatic iron has been associated with more aggressive liver disease in chronic viral hepatitis. We evaluated whether the recently described C282Y mutation of the hemochromatosis gene, designated HFE (responsible for at least 83% of hereditary hemochromatosis), was associated with more advanced liver disease in chronic hepatitis C. One hundred thirty-seven patients with biopsy-proven chronic hepatitis C were studied and liver biopsies scored for necroinflammation (grade 0-18) and fibrosis (stage 0-6). Genomic DNA was amplified by polymerase chain reaction and the C282Y mutation identified by restriction with RsaI and electrophoretic separation of restriction fragments. Ten (7.3%) patients had the C282Y mutation. No C282Y homozygous patients were identified. Age, sex distribution, and estimated weekly alcohol consumption were not significantly different between those with and without the mutation. Serum ferritin was higher in the heterozygotes (mean, 339 microg/L) compared with homozygous wild types (153 microg/L; P = .0005). In the majority of patients, liver iron was graded 0 out of 4, but hepatocyte iron staining was more commonly present in heterozygotes compared with homozygous normals (30% compared with 4% [P = .02]). Liver disease was more advanced in those with the mutant allele (mean fibrosis stage: 3.6, compared with wild type: 1.5 [P = .01]). Cirrhosis was found more often in those with the mutation (40%) compared with those without (8.7%) (P = .01; odds ratio: 7.6 [1.9-31.2]). There was no significant difference in inflammation scores between heterozygotes and wild type (mean, 5.4 compared with 4.1). Hepatitis C virus (HCV)-RNA titers were measured by branched DNA assay (HCV RNA 2.0-Chiron), and there was no difference between heterozygous and homozygous normal patients. Thus, despite relatively minor increases in iron stores, individuals who are heterozygous for hemochromatosis appear to develop more fibrosis in chronic hepatitis C. Venesection may be useful therapy in this subgroup.