Insulin resistance-associated hepatic iron overload

Iron and the liver: update 2008

The cross-talk which has taken place in recent years between clinicians and scientists has resulted in a greater understanding of iron metabolism with the discovery of new iron-related genes including the hepcidin gene which plays a critical role in regulating systemic iron homeostasis. Consequently, the distinction between (a) genetic iron-overload disorders including haemochromatosis related to mutations in the HFE, hemojuvelin, transferrin receptor 2 and hepcidin genes and (b) non-haemochromatotic conditions related to mutations in the ferroportin, ceruloplasmin, transferrin and di-metal transporter 1 genes, and (c) acquired iron-overload syndromes has become easier. However, major challenges still remain which include our understanding of the regulation of hepcidin production, the identification of environmental and genetic modifiers of iron burden and organ damage in iron-overload syndromes, especially HFE haemochromatosis, indications regarding the new oral chelator, deferasirox, and the development of new therapeutic tools interacting with the regulation of iron metabolism.

[Insulin resistance in chronic hepatitits C]

OBJECTIVE

To revise the importance of insulin resistance in the development of chronic hepatitis C and its interference in the response to the antiviral treatment of these patients.

DATA SOURCE

Bibliographic revision of published papers in the MEDLINE and the authors data.

DATA SYNTHESIS

In the last years several published papers have demonstrated an important relationship between insulin resistance and chronic hepatitis C. Increased prevalence of type 2 diabetes mellitus, the development of hepatic steatosis (specially in non-3 genotype), a more rapid progression of hepatic disease and reduction in the sustained virological response to treatment with pegylated interferon plus ribavirin have been associated with insulin resistance in patients infected with HCV. The mechanism implied in the insulin resistance is the enhanced production of tumor necrosis factor by the HCV core. Tumor necrosis factor affects insulin receptor substrate phosphorylation, resulting in decreased glucose uptake and compensatory hyperinsulinemia. Increased liver iron accumulation and modification in the levels of adipocytokinemia can have an additional effect on insulin sensitivity in chronic C hepatitis.

CONCLUSIONS

Diagnosing and treating insulin resistance in patients with chronic hepatitis C could not only avoid complications but also prevent disease progression and increased the sustained virological rate to treatment with pegylated interferon plus ribavarin.

Pathways underlying iron accumulation in human nonalcoholic fatty liver disease

BACKGROUND

Mild iron overload is frequently observed in nonalcoholic fatty liver disease (NAFLD).

OBJECTIVE

We aimed to study putative pathways underlying iron accumulation in NAFLD.

DESIGN

Hepatic and duodenal expression of critical iron molecules in NAFLD patients with (n = 32) and without (n = 29) iron overload, hereditary hemochromatosis (n = 10), and controls (n = 20) were investigated. Phlebotomy treatment was performed in 14 NAFLD patients.

RESULTS

The hepatic expressions of the iron-export protein ferroportin-1 (FP-1) and of the iron-sensing molecule hemojuvelin (HJV) were significantly lower in NAFLD patients. The mRNA expression of the iron-regulatory peptide hepcidin was increased in NAFLD patients with iron overload, which was paralleled by low duodenal FP-1 expression. Hepatic mRNA and serum protein concentrations of tumor necrosis factor-alpha (TNF-alpha) were increased in NAFLD patients and were inversely correlated with both liver FP-1 and HJV mRNA and positively associated with body mass index and hepatic hepcidin mRNA. Accordingly, TNF-alpha inhibited the FP-1 and HJV mRNA formation in HepG2 cells. Phlebotomy treatment of NALFD patients reduced serum ferritin, transferrin saturation, and TNF-alpha concentrations and improved liver function tests.

CONCLUSIONS

Iron accumulation in NAFLD may result from an impaired iron export due to down-regulation of FP1 and ineffective hepatic iron sensing, as indicated by low HJV expression. TNF-alpha appears to play a role in exerting these regulatory changes. Increased hepcidin formation in iron-overloaded NAFLD patients, however, results in decreased duodenal FP-1 expression, whereas a reduction in liver FP-1 may perpetuate hepatic iron retention. Phlebotomy offers a safe and efficient therapy for these metabolic disturbances.

Current approach to hemochromatosis

Iron overload diseases of genetic origin are an ever changing world, due to major advances in genetics and molecular biology. Five major categories are now established: HFE-related or type1 hemochromatosis, frequently found in Caucasians, and four rarer diseases which are type 2 (A and B) hemochromatosis (juvenile hemochromatosis), type 3 hemochromatosis (transferrin receptor 2 hemochromatosis), type 4 (A and B) hemochromatosis (ferroportin disease), and a(hypo)ceruloplasminemia. Increased duodenal iron absorption and enhanced macrophagic iron recycling, both due to an impairment of hepcidin synthesis, account for the development of cellular excess in types 1, 2, 3, and 4B hemochromatosis whereas decreased cellular iron egress is involved in the main form of type 4A) hemochromatosis and in aceruloplasminemia. Non-transferrin bound iron plays an important role in cellular iron excess and damage. The combination of magnetic resonance imaging (for diagnosing visceral iron overload) and of genetic testing has drastically reduced the need for liver biopsy. Phlebotomies remain an essential therapeutic tool but the improved understanding of the intimate mechanisms underlying these diseases paves the road for innovative therapeutic approaches.

Hyperferritinemia in the Chinese and Asian community: a retrospective review of the University of British Columbia experience

BACKGROUND AND METHODS

Elevated serum ferritin is a common clinical finding. The etiology of hyperferritinemia in the Asia-Pacific population is less clear due to a low prevalence of known HFE mutations such as C282Y and H63D, as well as an increased prevalence of viral hepatitis and hereditary anemia. A retrospective case review of 80 patients of Asian ethnicity referred to three subspecialists in tertiary care teaching hospitals between January 1997 and March 2005 for assessment of hyperferritinemia was performed.

RESULTS

Only four patients (5%) had iron overload on liver biopsy or quantitative phlebotomy. Forty-nine patients (61%) had secondary causes for their hyperferritinemia, of which 26 had liver disease; 16 of those patients also had viral hepatitis. Thirteen patients fulfilled criteria for the insulin resistance syndrome. Other causes included hematological disorders (n=10), malignancy (n=2) and inflammatory arthritis (n=2). Twenty-seven cases (34%) of unexplained hyperferritinemia were found. Of a total of 22 patients who underwent liver biopsy, significant iron deposition was found in one patient. Fifteen patients underwent C282Y and H63D genotyping, with two cases of H63D heterozygosity. Fourteen patients had first-degree relatives with hyperferritinemia. Three families were identified with more than two members affected, which is suggestive of a possible hereditary hyperferritinemia syndrome.

CONCLUSION

Secondary causes of elevated ferritin in the Asian population, particularly liver disease, are common, but primary iron overload syndromes appear to be rare. In a significant proportion of patients, the etiology remains unexplained. The genetic basis for hyperferritinemia in Asians is poorly defined and requires further study.

Iron depletion by deferoxamine up-regulates glucose uptake and insulin signaling in hepatoma cells and in rat liver

Iron depletion improves insulin resistance in patients with nonalcoholic fatty liver disease and diabetes and also stabilizes the hypoxia-inducible factor (HIF)-1, resulting in increased glucose uptake in vitro. This study investigated the effect of iron depletion by deferoxamine on insulin signaling and glucose uptake in HepG2 hepatocytes and in rat liver. In HepG2 cells, deferoxamine stabilized HIF-1alpha and induced the constitutive glucose transporter Glut1 and the insulin receptor. Up-regulation of insulin receptor by deferoxamine was mimicked by the intracellular iron chelator deferasirox and the hypoxia inducer CoCl2 and required the HIF-1 obligate partner ARNT/HIF-1beta. Iron depletion increased insulin receptor activity, whereas iron supplementation had the opposite effect. Deferoxamine consistently increased the phosphorylation status of Akt/PKB and its targets FoxO1 and Gsk3beta, which mediate the effect of insulin on gluconeogenesis and glycogen synthesis, and up-regulated genes involved in glucose uptake and utilization. Iron depletion of Sprague-Dawley rats increased HIF-1alpha expression, improved glucose clearance, and was associated with up-regulation of insulin receptor and Akt/PKB levels and of glucose transport in hepatic tissue. Conversely, gluconeogenic genes were not affected. In rats with fatty liver because of a high-calorie and high-fat diet, glucose clearance was increased by iron depletion and decreased by iron supplementation. Thus, iron depletion by deferoxamine up-regulates glucose uptake, and increases insulin receptor activity and signaling in hepatocytes in vitro and in vivo.

Nonalcoholic fatty liver disease: from clinical recognition to treatment

Nonalcoholic fatty liver disease (NAFLD) is probably the most common spectrum of metabolic liver disease in the world, encompassing simple steatosis to steatohepatitis, advanced fibrosis, cirrhosis and hepatocellular carcinoma. NAFLD affects a significant part of the general population worldwide. The existing correlation between obesity and NAFLD in combination with the increase in the frequency of obesity in the developed world implies that the incidence and severity of NAFLD will increase in the near future. Newer data support the idea that NAFLD constitutes the more important cause of cryptogenic cirrhosis of the liver and a ground for the development of hepatocellular carcinoma. Liver biopsy remains the most specific and sensitive method to differentiate NAFLD, providing important information on the long-term prognosis of the patients. The 'two hit' hypothesis constitutes the currently prevailing theory for the development of NAFLD and nonalcoholic steatohepatitis. The first 'hit' is purported to be the increase of free fatty acids in hepatocytes, which results in a decrease of beta-oxidation. The second step includes all mechanisms contributing to the development of necroinflammation and fibrosis. Currently, an effective treatment for patients with NAFLD does not exist. Improvement in liver histology remains the primary goal of any therapeutic approach in patients with NAFLD. Viewing NAFLD in the frame of the metabolic syndrome opens the possibility that both the onset of the disease and disease progression could be prevented by changes in lifestyle. Physical exercise and a low calorie diet in combination with the gradual loss of body weight represent the cornerstone for the management of NAFLD patients.

Bloodletting ameliorates insulin sensitivity and secretion in parallel to reducing liver iron in carriers of HFE gene mutations

OBJECTIVE

To clarify the pathogenesis of diabetes associated with mutations of the hemochromatosis (HFE) gene, 17 carriers, 9 normal glucose tolerant (NGT) and 8 diabetic, were evaluated in an interventional trial.

RESEARCH DESIGN AND METHODS

At enrollment and after a 2-year bloodletting period, euglycemic-hyperinsulinemic clamp, oral glucose tolerance test (OGTT), liver histology (nonalcoholic fatty liver disease activity score [NAS]), and liver iron content (LIC) were assessed.

RESULTS

NGT subjects had significantly higher baseline insulin sensitivity (P <or= 0.001), secretion, and insulinogenic index (calculated from the OGTT) (P <or= 0.0001 for both) and lower LIC (P = 0.004) and NAS (P = 0.02) than diabetic patients. Baseline LIC correlated negatively with insulin secretion (NGT r(0) = -0.676, P <or= 0.0001; diabetes r(0) = -0.589, P = 0.02) and insulin sensitivity (M value) (NGT r(0) = -0.597, P = 0.009; diabetes r(0) = -0.535, P = 0.03) and positively with NAS (diabetes r(0) = 0.649, P = 0.007) and triglycerides (NGT r(0) = 0.563, P = 0.015). At month 24, circulating iron was reduced by 179 +/- 26% in NGT and 284 +/- 54% in diabetic subjects. Insulin secretion (NGT 20 +/- 4%; diabetes 33 +/- 7%) and insulin sensitivity (NGT 25 +/- 5%; diabetes 18 +/- 3%) increased. LIC decreased in both groups (NGT 126 +/- 42%; diabetes 61 +/- 13%), and NAS ameliorated (NGT 65.1 +/- 6.5 vs. 38.1 +/- 6.83; P <or= 0.0001; diabetes 2.1 +/- 10.7 vs. 69.9 +/- 10; P <or= 0.0001).

CONCLUSIONS

Iron depletion ameliorates insulin secretion and sensitivity in NGT and diabetic carriers of HFE gene mutations. This amelioration occurs in parallel with decreased LIC and improved NAS. These results justify glucose tolerance testing and prophylactic iron depletion in asymptomatic carriers as well.

Hepatic iron accumulation may be associated with insulin resistance in patients with chronic hepatitis C

BACKGROUND/AIM

Insulin resistance and hepatic iron overload are frequently demonstrated in hepatitis C virus (HCV)-related liver diseases. We investigated the relationship between insulin resistance and hepatic iron deposition in patients with chronic HCV infection.

METHODS

Insulin resistance was evaluated using the homeostasis model assessments for insulin resistance (HOMA-IR) in 56 non-diabetic non-obese patients with biopsy proven chronic hepatitis C. The relationship between insulin resistance and serum ferritin levels or the grade of hepatic iron deposition was assessed.

RESULTS

The levels of plasma immunoreactive insulin (IRI) and HOMA-IR were significantly correlated with serum ferritin levels and the grade of hepatic iron deposition (P = 0.003).Although IRI and HOMA-IR increased in parallel with the development of hepatic fibrosis, insulin resistance (HOMA-IR > 2) was observed in 11 (26.2%) of 42 patients even without severe fibrosis (F0-2). Among patients without severe fibrosis, IRI and HOMA-IR were significantly higher in patients with iron deposits than in those without iron deposits.

CONCLUSION

Hepatic iron overload may be associated with insulin resistance in patients with chronic hepatitis C, especially in patients with mild to moderate fibrosis.

Role of iron in hepatic fibrosis: One piece in the puzzle

Iron is an essential element involved in various biological pathways. When present in excess within the cell, iron can be toxic due to its ability to catalyse the formation of damaging radicals, which promote cellular injury and cell death. Within the liver, iron related oxidative stress can lead to fibrosis and ultimately to cirrhosis. Here we review the role of excessive iron in the pathologies associated with various chronic diseases of the liver. We also describe the molecular mechanism by which iron contributes to the development of hepatic fibrosis.

HFE gene in primary and secondary hepatic iron overload

Distinct from hereditary haemochromatosis, hepatic iron overload is a common finding in several chronic liver diseases. Many studies have investigated the prevalence, distribution and possible contributory role of excess hepatic iron in non-haemochromatotic chronic liver diseases. Indeed, some authors have proposed iron removal in liver diseases other than hereditary haemochromatosis. However, the pathogenesis of secondary iron overload remains unclear. The High Fe (HFE) gene has been implicated, but the reported data are controversial. In this article, we summarise current concepts regarding the cellular role of the HFE protein in iron homeostasis. We review the current status of the literature regarding the prevalence, hepatic distribution and possible therapeutic implications of iron overload in chronic hepatitis C, hepatitis B, alcoholic and non-alcoholic fatty liver diseases and porphyria cutanea tarda. We discuss the evidence regarding the role of HFE gene mutations in these liver diseases. Finally, we summarize the common and specific features of iron overload in liver diseases other than haemochromatosis.

Pathology of hepatic iron overload

Although progress in imaging and genetics allow for a noninvasive diagnosis of most cases of genetic iron overload, liver pathology remains often useful (1) to assess prognosis by grading fibrosis and seeking for associated lesions and (2) to guide the etiological diagnosis, especially when no molecular marker is available. Then, the type of liver siderosis (parenchymal, mesenchymal or mixed) and its distribution throughout the lobule and the liver are useful means for suggesting its etiology: HLA-linked hemochromatosis gene (HFE) hemochromatosis or other rare genetic hemochromatosis, nonhemochromatotic genetic iron overload (ferroportin disease, aceruloplasminemia), or iron overload secondary to excessive iron supply, inflammatory syndrome, noncirrhotic chronic liver diseases including dysmetabolic iron overload syndrome, cirrhosis, and blood disorders.

An open population screening study for HFE gene major mutations proves the low prevalence of C282Y mutation in Central Italy

BACKGROUND

The C282Y mutation in the HFE gene is responsible for most cases of hereditary haemochromatosis.

AIM

To investigate the allele frequency of HFE mutations and the associations between mutations and cases of iron overload or liver diseases in an open population of Central Italy.

METHODS

A total of 502 individuals over 8 years of age, comprising 203 males and 299 females, who were residents in Arsita (a small town in Central Italy), were assayed for: C282Y, H63D and S65C mutations of the HFE gene by TaqMan probes; body mass index, serum ferritin, transferrin saturation, transaminases, GGT, glucose, insulin, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, triglycerides, HBV and HCV serum markers. Information was obtained on alcohol intake. Liver ultrasound was performed in 334 (67%) subjects.

RESULTS

The allele frequencies for C282Y, H63D and S65C were 2%, 15%, and 0.01%, respectively. C282Y/wt was found in 19 subjects (4%), H63D/wt in 127 (25%), H63D/H63D in 11 (2%) and S65C/wt in one (2.0 per thousand). No homozygosity for C282Y or compound mutation (C282Y/H63D) was found in the study population, but 27 subjects (5%) had TfSat >45% (including 10 subjects with high serum ferritin). Overall, 49 subjects (9.8%) were HCV-RNA-positive. Logistic regression analysis indicated that male gender (P = 0.000) and hepatic steatosis (P = 0.017) were independent variables correlating to a high serum ferritin.

CONCLUSION

C282Y HFE mutation is less frequent in Central Italy than in Northern Italy.

Iron depletion by phlebotomy improves insulin resistance in patients with nonalcoholic fatty liver disease and hyperferritinemia: evidence from a case-control study

OBJECTIVES

Hyperferritinemia is frequently observed in nonalcoholic fatty liver disease (NAFLD), the hepatic manifestation of the metabolic syndrome characterized by hepatic insulin resistance and considered high cardiovascular risk. Iron depletion by phlebotomy has been reported to decrease insulin resistance in NAFLD in small, uncontrolled studies. Aims of this study were to define the relationship between ferritin and iron stores in patients with NAFLD, the effect of iron depletion on insulin resistance, and whether basal ferritin levels influence treatment outcome.

METHODS

Subjects were included if ferritin and/or ALT were persistently elevated after 4 months of standard therapy. Sixty-four phlebotomized subjects were matched 1:1 for age, sex, ferritin, obesity, and ALT levels with patients who underwent lifestyle modifications only. Insulin resistance was evaluated by insulin levels, determined by RIA and the HOMA-R index, at baseline and after 8 months.

RESULTS

Baseline ferritin levels were associated with body iron stores (P<0.0001). Iron depletion produced a significantly larger decrease in insulin resistance (P=0.0016 for insulin, P=0.0042 for HOMA-R) compared with nutritional counseling alone, independent of changes in BMI, baseline HOMA-R, and the presence of the metabolic syndrome. Iron depletion was more effective in reducing HOMA-R in patients in the top two tertiles of ferritin concentrations (P<0.05 vs controls), and in carriers of the mutations in the HFE gene of hereditary hemochromatosis (P<0.05 vs noncarriers).

CONCLUSIONS

Given that phlebotomy reduces insulin resistance, which is associated with liver tissue damage, future studies should evaluate the effect of iron depletion on liver histology and cardiovascular end points.

Liver iron is a surrogate marker of severe fibrosis in chronic hepatitis C

BACKGROUND/AIMS

Patients with chronic hepatitis C have frequently mild to moderate liver iron overload which increases with fibrosis stage. Thus, it has been postulated that iron could enhance the progression of fibrosis. However, the real impact of iron is still controversial. The study was undertaken to determine the effect of confounding variables. All factors known to influence both iron overload and fibrosis were taken into account.

METHODS

Five hundred and eighty-six patients, who had liver biopsy performed prior to antiviral treatment, were included. Serum ferritin and liver iron were correlated with clinical, biological and histological variables in univariate and multivariate analysis. The impact of iron on fibrosis was evaluated in multivariate analysis in the whole group and in the subgroup of 380 patients with available date of infection.

RESULTS

Hyperferritinemia, encountered in 27%, was associated with liver iron deposits in only 46% of cases. Liver iron was elevated in 17%, and correlated with age, male sex, and alcohol intake. The univariate strong link which existed between liver iron and fibrosis disappeared after adjustment for confounding variables.

CONCLUSIONS

According to the results of this study, liver iron should be considered more as a surrogate marker for disease severity than as a fibrogenic factor per se.

Restriction of dietary calories, fat and iron improves non-alcoholic fatty liver disease

BACKGROUND

The pathogenesis of non-alcoholic steatohepatitis (NASH) is unclear. Recent studies suggested that oxidative stress plays an important role in the mechanism of NASH. Excessive accumulation of iron in the liver causes oxidative stress. The aim of the present study was to evaluate the grade of hepatic iron accumulation and the therapeutic response to restriction of calories, fat and iron in patients with non-alcoholic fatty liver disease (NAFLD).

METHODS

Twenty-seven NAFLD patients were enrolled. The patients were categorized into two groups: 17 patients with NASH and 10 with simple steatosis. Twelve NAFLD patients (NASH, n = 9; simple steatosis, n = 3) were given a dietary prescription including restriction of energy, fat and iron.

RESULTS

Positive iron staining was observed in 71% and 50% of patients with NASH and simple steatosis, respectively. The average energy intake, fat energy fraction and iron intake decreased significantly 6 months after the beginning of the diet in all patients. In addition, the levels of serum transaminase and ferritin were significantly decreased.

CONCLUSION

Dietary restriction of calories, fat and iron improved NAFLD. Reduced serum ferritin levels appear to reduce oxidative stress in the liver.

Correlation of hepatic steatosis with body mass index, serum ferritin level and hepatic fibrosis in Japanese patients with chronic hepatitis C

AIMS

The present study was aimed at determining the predictors of hepatic steatosis and fibrosis in Japanese patients with chronic hepatitis C.

METHODS

The relationship between the degrees of hepatic steatosis or fibrosis and several clinical parameters was evaluated using univariate and multivariate analyses.

RESULTS

Steatosis was observed in 117 out of 184 patients (64%), including 45 patients (25%) with grade 1 (<10% of hepatocytes affected), 56 patients (30%) with grade 2 (10-30%), 12 patients (7%) with grade 3 (30-50%), and four patients (2%) with grade 4 (>50%). In the multivariate analysis, body mass index (BMI) (P = 0.0038) and serum ferritin (P < 0.0001) were selected as independent predictors of hepatic steatosis. Six of the 184 patients (3%) had stage 0 fibrosis (no fibrosis), 87 patients (47%) had stage 1, 55 patients (30%) had stage 2 and 36 patients (20%) had stage 3. In the multivariate analysis, platelet count (P = 0.0012), aspartate aminotransferase (AST) (P = 0.0219), hyaluronic acid (P < 0.0001) and the grade of steatosis (P = 0.0008) were selected as independent predictors of hepatic fibrosis.

CONCLUSION

Obesity and iron storage, as evaluated by BMI and serum ferritin level, respectively, have important roles in the pathogenesis of hepatic steatosis, which is a factor responsible for the development of hepatic fibrosis in Japanese patients with chronic hepatitis C.

Iron overload inHepc1−/−mice is not impairing glucose homeostasis

Diabetes Mellitus is found with increasing frequency in iron overload patients with hemochromatosis. In these conditions, the pancreas shows predominant iron overload in acini but also islet beta-cells. We assess glucose homeostasis status in iron-overloaded hepcidin-deficient mice. These mice presented with heavy pancreatic iron deposits but only in the acini. The beta-cell function was found unaffected with a normal production and secretion of insulin. The mutant mice were not diabetic, responded as the control group to glucose and insulin challenges, with no alteration of insulin signalling in the muscle and the liver. These results indicate that, beta-cells iron deposits-induced decreased insulin secretory capacity might be of primary importance to trigger diabetes in hemochromatosic patients.

Steatosis as a cofactor in other liver diseases: hepatitis C virus, alcohol, hemochromatosis, and others

As obesity prevalence rises, there is evidence that fatty liver disease can act synergistically with other chronic liver diseases to aggravate parenchymal injury. This is characterized best in chronic hepatitis C, where steatosis is caused by viral and metabolic effects. There is evidence that steatosis and its metabolic abnormalities also exacerbate other diseases, such as alcoholic liver disease, hemochromatosis, and, possibly, drug-induced liver disease. The pathogenesis seems related to increased susceptibility of steatotic hepatocytes to apoptosis, enhanced oxidative injury, and altered hepatocytic regeneration. Data suggest that active management of obesity may improve liver injury and decrease the progression of fibrosis in patients who have other chronic liver diseases.

Pathogenesis of non-alcoholic steatohepatitis: human data

Non-alcoholic fatty liver disease (NAFLD) has moved rapidly to the forefront of clinical disease, with a prevalence of 30% in the adult United States population and a definite but yet uncertain rate of progression to cirrhosis and end-stage liver disease. This disease has an impact on all areas of clinical medicine, with increasing prevalence and adversity. It is essential to understand the pathophysiologic mechanisms involved in NAFLD, so that therapeutic strategies can be developed. Although fatty liver may be caused by other factors, this review concentrates on fatty liver associated with insulin resistance, sometimes referred to as the primary form.

Serum, liver, and kidney proteomic analysis for the alloxan-induced type I diabetic mice after insulin gene transfer of naked plasmid through electroporation

Gene therapy has been reported to be effective in treating diabetes mellitus (DM), while little has been found out about the functional protein changes since. The liver and kidney play important roles in glucose absorption, metabolism, and excretion. Changes in the two organs may reflect pathologic alterations during DM, while the serum has a direct connection with most organs and pathological changes. We used alloxan to induce diabetic mice, electrotranferred the insulin gene into their sural muscles, and discovered that their blood glucose decreased to normal level. Consequently, proteomic approaches were applied to evaluate protein changes in the liver, kidney, and serum of normal, diabetic, and gene transferred mice. Forty-three proteins were found either up-regulated or down-reglulated in the liver, kidney, and serum of the alloxan-induced type I diabetic mice. Only five proteins in the liver, five proteins in the kidney, and seven proteins in the serum of diabetic mice were found to be back-regulated to normal levels after gene transfer. These back-regulated proteins are involved in lipid and glucose metabolism, associated with phosphorylation, signal transduction, oxidation, and immune inflammation. Our findings might promote a better understanding for the mechanism of DM, and provide novel targets for estimating the effects of gene therapy.

Effects of iron overload in a rat nutritional model of non-alcoholic fatty liver disease

BACKGROUND/AIMS

This study sought to determine whether excess hepatic iron potentiates liver injury in the methionine choline-deficient (MCD) model of non-alcoholic fatty liver disease (NAFLD).

METHODS

Iron-loaded rats were fed either MCD or control diets [MCD diet plus choline bitartrate (2 g/kg) and DL-methionine (3 g/kg)] for 4 and 12 weeks, after which liver pathology, hepatic iron, triglyceride, lipid peroxidation products and hydroxyproline (HYP) levels and serum alanine aminotransferase (ALT) levels were evaluated.

RESULTS

Iron supplementation in MCD animals resulted in histologic evidence of hepatic iron overload at 4 and 12 weeks and a 14-fold increase in hepatic iron concentration at 12 weeks (P < 0.001). Iron supplementation in these animals was associated with increased lobular necroinflammation at 4 weeks (P < 0.02) and decreased hepatic steatosis (P < 0.01), hepatic triglyceride levels (P < 0.01), hepatic-conjugated dienes (CD; P < 0.02) and serum ALT levels (P < 0.002) at 12 weeks. Reduced hepatic steatosis (P < 0.005) and CD (P < 0.01) were apparent by 4 weeks. Iron supplementation was associated with a trend towards increased perivenular fibrosis not hepatic HYP content.

CONCLUSION

Hepatic iron overload in the MCD model of NAFLD is associated with decreased hepatic lipid, decreased early lipid peroxidation products, increased necroinflammation and a trend towards increased perivenular fibrosis.

Molecular and clinical aspects of iron homeostasis: From anemia to hemochromatosis

The discovery in recent years of a plethora of new genes whose products are implicated in iron homeostasis has led to rapid expansion of our knowledge in the field of iron metabolism and its underlying complex regulation in both health and disease. Abnormalities of iron metabolism are among the most common disorders encountered in practical medicine and may have significant negative impact on physical condition and life expectancy. Basic insights into the principles of iron homeostasis and the pathophysiological and clinical consequences of iron overload, iron deficiency and misdistribution are thus of crucial importance in modern medicine. This review summarizes our current understanding of human iron metabolism and focuses on the clinically relevant features of hereditary and secondary hemochromatosis, iron deficiency anemia, anemia of chronic disease and anemia of critical illness. The interconnections between iron metabolism and immunity are also addressed, in as much as they may affect the risk and course of infections and malignancies.

Increased insulin secretory capacity but decreased insulin sensitivity after correction of iron overload by phlebotomy in hereditary haemochromatosis

AIMS/HYPOTHESIS

We recently demonstrated that humans with hereditary haemochromatosis have decreased insulin secretory capacity with a compensatory increase in insulin sensitivity. We therefore determined how these measures change after correction of tissue iron overload.

SUBJECTS AND METHODS

Five non-diabetic subjects who had been studied previously at the time of initial diagnosis by means of the OGTT and frequently sampled intravenous glucose tolerance tests (FSIVGTT) underwent phlebotomy to normalise their serum ferritin. After normalisation of ferritin they were studied again (33+/-4 months after the initial studies) by OGTT and FSIVGTT.

RESULTS

Normalisation of tissue iron stores resulted in an average 1.8-fold increase in the integrated area under the insulin curve during OGTT (p<0.0001), but no significant change in the area under the glucose curve (10% decrease, p=0.32). After phlebotomy, there was a 2.2-fold increase in insulin secretory capacity as determined by FSIVGTT (acute insulin response to glucose [AIRg], p<0.02) but a concomitant 70% fall in insulin sensitivity (Si, p<0.05). The disposition index (AIRgxSi) was unchanged (5% increase, p=0.90). BMI and fasting glucose were unchanged. At the time of diagnosis of haemochromatosis, four of the subjects had IGT. After normalisation of ferritin, two achieved NGT and two remained with IGT, despite 2.5- and 3.7-fold increases in insulin secretory capacity.

CONCLUSIONS/INTERPRETATION

Insulin secretory capacity improves after normalisation of iron stores in subjects with hereditary haemochromatosis. Glucose tolerance status improves incompletely because of decreased insulin sensitivity after phlebotomy. We conclude that tissue iron levels are an important determinant of insulin secretion and insulin action.

The clinical relevance of compound heterozygosity for the C282Y and H63D substitutions in hemochromatosis

BACKGROUND & AIMS

Two major mutations are defined within the hemochromatosis gene, HFE. Although the effects of the C282Y substitution have been well characterized, the clinical significance of the C282Y/H63D state remains unclear. This study assessed the phenotypic expression in C282Y/H63D subjects as compared with C282Y homozygotes.

METHODS

Data were obtained from 91 C282Y/H63D probands, 158 C282Y/H63D subjects identified through family screening, and 483 C282Y homozygotes. Subjects underwent clinical evaluation, genotyping, biochemical assessment, and liver biopsy examination where clinically indicated.

RESULTS

C282Y/H63D probands had significantly less clinical and biochemical expression than C282Y homozygotes. Biochemical expression was higher in C282Y/H63D probands than in C282Y/H63D subjects identified through family screening (P < .001). Of the C282Y/H63D subjects with serum ferritin levels greater than 1000 mug/L, all had known comorbid factors that could have contributed to the increased ferritin level. Of the 51 C282Y/H63D subjects who underwent liver biopsy examination, significantly increased iron stores were present in 9 subjects and hepatic fibrosis was present in 13. Twelve of the 13 had evidence of hepatic steatosis, excess alcohol consumption, or diabetes. The mobilizable iron level was significantly higher in C282Y homozygous males than in compound heterozygous males (P < .001). Genetic screening of C282Y/H63D first-degree relatives detected 5 C282Y homozygotes.

CONCLUSIONS

C282Y/H63D subjects referred for assessment had a high prevalence of increased iron indices but did not develop progressive clinical disease without comorbid factors such as steatosis, diabetes, or excess alcohol consumption. When fibrosis was seen, 1 or more comorbid factors almost always were present. Thus, phlebotomy therapy is warranted and cascade screening of relatives should be performed because expressing C282Y homozygotes may be detected.

Effects of phlebotomy therapy on cytochrome P450 2e1 activity and oxidative stress markers in dysmetabolic iron overload syndrome: a randomized trial

AIM

To assess the effects of iron removal on cytochrome P450 2E1 activity and oxidative stress in dysmetabolic iron overload syndrome.

METHODS

Forty-eight patients were randomized to phlebotomy therapy consisting of removal of 300-500 mL of blood every 14 days until serum ferritin levels dropped under 100 microg/L or to follow-up without phlebotomy therapy. Cytochrome P450 2E1 activity was measured at baseline and at the end of treatment by using the 6-hydroxychlorzoxazone/chlorzoxazone blood metabolic ratio, 2 h after the intake of 500 mg of chlorzoxazone.

RESULTS

In the treatment group, a mean of 3.9 +/- 1.3 L of blood was removed and serum ferritin levels dropped from 715 +/- 397 to 74 +/- 34 microg/L. Variation of cytochrome P450 2E1 activity was not significantly different between the 2 groups (0.07 +/- 0.26 vs. 0.03 +/- 0.19, P = 0.36). In the treatment group, low-density lipoprotein cholesterol and vitamin E were lowered after treatment compared with control group (-0.15 +/- 0.51 vs. 0.24 +/- 0.58, P = 0.002 and -1.3 +/- 4.4 vs. 2.3 +/- 5.2, P = 0.03, respectively). Inversely, vitamin C was increased (0.5 +/- 3.5 vs. -1.8 +/- 3.9, P = 0.03).

CONCLUSIONS

In dysmetabolic iron overload syndrome, reduction of iron stores does not significantly influence cytochrome P450 2E1 activity but is associated with a significant decrease of low-density lipoprotein cholesterol, suggesting that venesection therapy may be a suitable option in these patients.

Alpha 1-antitrypsin mutations in NAFLD: high prevalence and association with altered iron metabolism but not with liver damage

Hyperferritinemia, a common feature of nonalcoholic fatty liver disease (NAFLD), has been associated with steatohepatitis and fibrosis. Heterozygosity for alpha 1-antitrypsin (AAT) mutations is a cofactor of liver damage, and AAT influences inflammation and iron metabolism. This study evaluated the prevalence of the common AAT PiS/PiZ mutants in 353 patients with NAFLD, 195 of whom had hyperferritinemia, versus 114 matched controls and their influence on iron metabolism and the severity of liver damage in the 212 patients submitted to biopsy. PiS and PiZ alleles were searched for by restriction analysis. Thirty-eight patients (10.8%) carried non-MM genotypes versus 4/114 (3.5%) controls (P = .02). Patients carrying AAT mutations had higher ferritin (573 [454-966] vs. 348 [201-648]; P = .001) with similar transferrin saturation. The difference was more evident in males (P < .0001) and significant in patients not carrying HFE genotypes associated with iron overload (P = .015). The prevalence of non-MM genotypes was higher in patients with hyperferritinemia than in those without (28/195, 14% vs. 10/158, 6%, P = .016), and AAT mutations were associated with higher prevalence of sinusoidal siderosis (17/27, 63% vs. 70/180, 39%; P = .02), and sinusoidal/total iron score (46.3 +/- 38% vs. 25.1 +/- 35%, P = .01). Although ferritin was independently associated with fibrosis (P = .047), AAT mutations favoring sinusoidal iron deposition did not affect liver damage. In conclusion, AAT mutations are associated with hyperferritinemia and sinusoidal iron accumulation, but not with more severe liver damage in NAFLD.

[Epidemiology and natural history of primary nonalcoholic fatty liver disease]

The clinical impact of nonalcoholic fatty liver disease depends on its prevalence and natural history. The prevalence in the adult population is estimated to be about 23% and is on the increase. Thus, it has become the most common cause of persistent elevated liver enzymes, chronic liver disease, and cryptogenic cirrhosis in developed countries. The increasing prevalence of nonalcoholic fatty liver disease, which is approaching epidemic proportions, is parallel to that of other disorders associated with insulin resistance, especially obesity and type 2 diabetes mellitus. This entity occurs in men and women equally and in all age groups. The natural history is poorly defined mainly due to the scarcity of histologic follow-up studies. Although steatosis alone has a more benign clinical course, steatohepatitis is a progressive fibrotic disease, in which cirrhosis and liver-related death occur in a similar way to other causes of chronic liver diseases. Progression seems to be mainly dependent on the severity of histological damage at diagnosis, but age older than 40 years, obesity, and type 2 diabetes have also been associated with an increased risk of liver fibrosis and progression to cirrhosis.

High prevalence of abnormal glucose homeostasis secondary to decreased insulin secretion in individuals with hereditary haemochromatosis

AIMS/HYPOTHESIS

The prevalence and mechanisms of diabetes in hereditary haemochromatosis are not known. We therefore measured glucose tolerance, insulin secretory capacity and insulin sensitivity in adults with haemochromatosis.

SUBJECTS AND METHODS

Subjects recruited from referrals to a haemochromatosis clinic underwent OGTT and frequently sampled IVGTT. A chart review of former clinic patients was also performed.

RESULTS

The prevalence of diabetes (23%) and IGT (30%) was increased in haemochromatosis compared with matched control subjects (0% diabetes and 14% IGT). Subjects with haemochromatosis and diabetes were overweight (14%) or obese (86%). The prevalence of diabetes, as determined by chart review of fasting glucose values, in subjects who had haemochromatosis and were in the 40-79 years age range was 26%. Overall, patients with haemochromatosis and control subjects had similar values for acute insulin response to glucose and insulin sensitivity. However, patients with haemochromatosis and IGT had a 68% decrease in acute insulin response to glucose (p<0.02) compared with those with NGT. They were not insulin-resistant, exhibiting instead a 62% increase in insulin sensitivity (NS). Haemochromatosis subjects with diabetes exhibited further declines in acute insulin response to glucose, insulin resistance, or both.

CONCLUSIONS/INTERPRETATION

Diabetes and IGT are common in haemochromatosis, justifying screening for diabetes and therapeutic phlebotomy. The major abnormality associated with IGT is decreased insulin secretory capacity. Diabetes is usually associated with obesity and concomitant insulin resistance.

Hereditary hemochromatosis: genetic complexity and new diagnostic approaches

Since the discovery of the hemochromatosis gene (HFE) in 1996, several novel gene defects have been detected, explaining the mechanism and diversity of iron-overload diseases. At least 4 main types of hereditary hemochromatosis (HH) have been identified. Surprisingly, genes involved in HH encode for proteins that all affect pathways centered around liver hepcidin synthesis and its interaction with ferroportin, an iron exporter in enterocytes and macrophages. Hepcidin concentrations in urine negatively correlate with the severity of HH. Cytokine-mediated increases in hepcidin appear to be an important causative factor in anemia of inflammation, which is characterized by sequestration of iron in the macrophage system. For clinicians, the challenge is now to diagnose HH before irreversible damage develops and, at the same time, to distinguish progressive iron overload from increasingly common diseases with only moderately increased body iron stores, such as the metabolic syndrome. Understanding the molecular regulation of iron homeostasis may be helpful in designing innovative and reliable DNA and protein tests for diagnosis. Subsequently, evidence-based diagnostic strategies must be developed, using both conventional and innovative laboratory tests, to differentiate between the various causes of distortions of iron metabolism. This review describes new insights in mechanisms of iron overload, which are needed to understand new developments in diagnostic medicine.

Fatty liver in H63D homozygotes with hyperferritinemia

To study the clinical correlates of the H63D mu-tation we have analysed the phenotype of H63D homo-zygotes identified through mutation analysis in a referral laboratory. A total of 366 blood samples referred for HFE analysis were screened for C282Y and H63D mutations. Four H63D homozygotes were identified. All had raised serum ferritin but normal transferrin

saturation. They were negative for hepatitis B and C and only one patient consumed excess alcohol. In all 4 cases ultrasonography revealed fatty liver. In two patients a liver biopsy was done and showed mild siderosis with an unusual distribution and macrovesicular steatosis. These data confirm the association between fatty liver, hyperferritinemia and increased hepatic iron, but do not clarify whether siderosis was related to steatosis rather than homozygosity for the H63D mutation. Patients with fatty liver may complicate the interpretation of data in population studies of the expression of H63D homozygosity.

Localization of oxidized phosphatidylcholine in nonalcoholic fatty liver disease: impact on disease progression

Nonalcoholic steatohepatitis/nonalcoholic fatty liver disease is considered to be a hepatic manifestation of various metabolic disorders. However, its precise pathogenic mechanism is obscure. Oxidative stress and consequent lipid peroxidation seem to play a pivotal role in disease progression. In this study, we analyzed the localization of oxidized phosphatidylcholine (oxPC), a lipid peroxide that serves as a ligand for scavenger receptors, in livers of patients with this steatotic disorder. Specimens of non-alcoholic fatty liver disease (15 autopsy livers with simple steatosis and 32 biopsy livers with steatohepatitis) were examined via immunohistochemistry and immunoelectron microscopy using a specific antibody against oxPC. In addition, scavenger receptor expression, hepatocyte apoptosis, iron deposition, and inflammatory cell infiltration in the diseased livers were also assessed. Oxidized phosphatidylcholine was mainly localized to steatotic hepatocytes and some macrophages/Kupffer cells. A few degenerative or apoptotic hepatocytes were also positive for oxPC. Immunoelectron microscopy showed oxPC localized to cytoplasmic/intracytoplasmic membranes including lipid droplets. Steatotic livers showed enhanced expression of scavenger receptors. The number of oxPC cells was correlated with disease severity and the number of myeloperoxidase-positive neutrophils, but not with the degree of iron deposition. In conclusion, distinct localization of oxPC in liver tissues suggest that neutrophil myeloperoxidase-derived oxidative stress may be crucial in the formation of oxPC and the progression of steatotic liver disease.

Hepatic iron, liver steatosis and viral genotypes in patients with chronic hepatitis C

Hepatic iron has been described in hepatitis C virus (HCV) infection as an important cofactor of disease outcome. The mechanisms leading to hepatic iron deposits (HIDs) in HCV patients are partially understood. We investigated HIDs in the liver biopsies of a consecutive series of 242 HCV-infected patients with well-compensated liver disease. Serum ferritin was elevated in 20.7% and transferrin saturation in 19.0%, while 38.8% had stainable HIDs indicating that serum markers of systemic iron overload have low sensitivity in predicting HIDs in hepatitis C. A cut-off value of serum ferritin (350 microg/L in females and 450 microg/L in males) had good negative predictive value in excluding presence of mild-moderate HIDs (grade II-III). Hepatic iron deposits correlated by multivariate analysis with serum ferritin [odds ratio (OR) 1.008, 95% confidence interval (CI) 1.005-1.011] and albumin (OR 1.15, 95% CI 1.02-1.297). Hepatic iron deposits were more frequent in HCV-3-infected cases than in other genotypes (P = 0.027) while raised serum iron indices were more frequent in non-HCV-3 genotypes (P = 0.02). Furthermore, advanced fibrosis (F3-F4 by METAVIR) was more frequent in non-HCV-3 genotypes (P = 0.04). In HCV-3 cases there was a close association between HIDs and severe (grade II-III) steatosis (P < 0.00001). These results indicate that in well-compensated chronic hepatitis C HIDs are strongly associated with HCV-3 and viral-induced hepatic steatosis, while in the presence of other genotypes they might merely reflect a more advanced stage of liver disease and/or a systemic iron overload. Serum ferritin could identify a subgroup of patients in which the need of venesection could be excluded without liver biopsy.

Current Approaches to the Management of Hemochromatosis

The term hemochromatosis encompasses at least four types of genetic iron overload conditions, most of them recently distinguished from one another as a result of the identification of a series of genes related to iron metabolism. At least three of these entities (HFE hemochromatosis, juvenile hemochromatosis and transferrin receptor 2 hemochromatosis) involve systemic hepcidin deficiency as a key pathogenetic factor. Major advances in the management of hemochromatosis influence the diagnostic approach to the disease, with the development of an overall non invasive strategy, mainly based on clinical, biological (iron parameters and genetic testing), and imaging (especially magnetic resonance imaging) data. Therapeutic management remains, on the curative side, dominated by phlebotomy (venesection), practical aspects of which have been recently revisited by the Guidelines Department of the French “Haute Autorité de Santé.” However, innovative treatment approaches, based on the improved pathophysiological understanding of these diseases and the progress in iron chelation therapy, are emerging. Preventive therapy, focused on family screening, remains a key part of the management of hemochromatosis.

Current Approaches to the Management of Hemochromatosis

The term hemochromatosis encompasses at least four types of genetic iron overload conditions, most of them recently distinguished from one another as a result of the identification of a series of genes related to iron metabolism. At least three of these entities (HFE hemochromatosis, juvenile hemochromatosis and transferrin receptor 2 hemochromatosis) involve systemic hepcidin deficiency as a key pathogenetic factor. Major advances in the management of hemochromatosis influence the diagnostic approach to the disease, with the development of an overall non invasive strategy, mainly based on clinical, biological (iron parameters and genetic testing), and imaging (especially magnetic resonance imaging) data. Therapeutic management remains, on the curative side, dominated by phlebotomy (venesection), practical aspects of which have been recently revisited by the Guidelines Department of the French “Haute Autorité de Santé.” However, innovative treatment approaches, based on the improved pathophysiological understanding of these diseases and the progress in iron chelation therapy, are emerging. Preventive therapy, focused on family screening, remains a key part of the management of hemochromatosis.

Comparison of serum iron, total iron binding capacity, ferritin, and percent transferrin saturation in nine species of apparently healthy captive lemurs

Lemurs kept in captivity have been reported to be highly prone to accumulate excessive amounts of iron in tissues (hemosiderosis). Diagnosis of the condition is most commonly made during a postmortem examination because an antemortem diagnosis requires a liver biopsy, a procedure that may not be well tolerated by all animals. The lack of a noninvasive method to evaluate iron status in captive lemurs limits investigators' ability to effectively screen animals for the presence of hemosiderosis, and to detect the condition early when treatment protocols are most effective. This study was conducted in an effort to provide data regarding iron analyte values in healthy captive lemurs of multiple species. The relationship of various iron-related metabolites was evaluated in 177 clinically normal lemurs of nine different species. Serum iron (sI), total iron binding capacity (TIBC), and ferritin concentration were measured directly and the percent transferrin saturation (TS) was calculated. Significant differences in various iron metabolites were observed among several species, suggesting that normal reference values for iron metabolites in lemurs may need to be developed on a species by species basis.

[Iron overload and insulin resistance]

There is increasing evidence that moderately elevated body iron stores, below levels commonly found in genetic hemochromatosis, may be associated with adverse health outcomes. Genetic hemochromatosis, characterized by transferrin saturation (TS) greater than 45%, is most often linked to homozygosity of the HFE C282Y allele. The phenotype is also modulated by mutations of more recently discovered genes (including ferroportin, hemojuvelin, hepcidin, and transferrin receptor) and environmental factors (including alcohol, viruses, diet, blood loss). Iron overload without hemochromatosis is characterized by high levels of serum ferritin and normal TS, as seen in dysmetabolic hepatosiderosis. Elevated serum ferritin levels predict incident type 2 diabetes in prospective studies and have been associated with hypertension, dyslipidemia, glucose tolerance disturbances, central adiposity, and metabolic syndrome. High ferritin levels are not synonymous with iron overload and may in some cases be a simple marker of insulin resistance.