Dietary iron overload enhances Western diet induced hepatic inflammation and alters lipid metabolism in rats sharing similarity with human DIOS.

Hepatic iron overload is often concurrent with nonalcoholic fatty liver disease (NAFLD). Dysmetabolic iron overload syndrome (DIOS) is characterized by an increase in the liver and body iron stores and metabolic syndrome components. Increasing evidences suggest an overlap between NAFLD with iron overload and DIOS; however, the mechanism how iron is involved in their pathogenesis remains unclear. Here we investigated the role of iron in the pathology of a rat model of NAFLD with iron overload. Rats fed a Western (high-fat and high-fructose) diet for 26 weeks represented hepatic steatosis with an increased body weight and dyslipidemia. Addition of dietary iron overload to the Western diet feeding further increased serum triglyceride and cholesterol, and enhanced hepatic inflammation; the affected liver had intense iron deposition in the sinusoidal macrophages/Kupffer cells, associated with nuclear translocation of NFκB and upregulation of Th1/M1-related cytokines. The present model would be useful to investigate the mechanism underlying the development and progression of NAFLD as well as DIOS, and to elucidate an important role of iron as one of the "multiple hits" factors.

Analyses of hemorrhagic diathesis in high-iron diet-fed rats.

Iron overload has been well recognized to cause oxidant-mediated cellular/tissue injury; however, little is known about the effects of iron overload on the blood coagulation system. We encountered an unexpected bleeding tendency in rats fed a high-iron diet in a set of studies using iron-modified diets. In this study, we investigated the mechanism of hemorrhagic diathesis induced by dietary iron overload in rats. Six-week-old F344/DuCrlCrlj male rats were fed a standard (containing 0.02% iron) or a high-iron diet (containing 1% iron) for 6 weeks and were then sampled for hematological, blood biochemical, coagulation, and pathological examinations. Serum and liver iron levels increased in rats fed the high-iron diet (Fe group) and serum transferrin was almost saturated with iron. However, serum transaminase levels did not increase. Moreover, plasma prothrombin time and activated partial thromboplastin time were significantly prolonged, regardless of the presence of hemorrhage. The activity of clotting factors II and VII (vitamin K-dependent coagulation factors) decreased significantly, whereas that of factor VIII was unaltered. Blood platelet levels were not influenced by dietary iron overload, suggesting that the bleeding tendency in iron-overloaded rats is caused by secondary hemostasis impairment. In addition, hemorrhage was observed in multiple organs in rats fed diets containing more than 0.8% iron. Our results suggest that iron overload can increase the susceptibility of coagulation abnormalities caused by latent vitamin K insufficiency.

[The role of iron overload in the progression of nonalcoholic steatohepatitis (NASH)].

Non-alcoholic steatohepatitis (NASH), one of the most common chronic liver diseases (CLD), is getting the most important cause of cirrhosis and hepatocellular carcinoma. Iron is an essential micronutrient for organisms. Once excess iron is accumulated in vital organs, dysfunctions of these organs can occur via the generation of reactive oxygen species. Hepatic iron overload is often seen in CLD patients. In NASH patients, iron accumulation in the liver is positively correlated with histological severity. Thus iron overload can contribute to progression of nonalcoholic fatty liver disease (NAFLD) to NASH. In a rat model of NASH, feeding of high-fat and high-iron diet increases hepatic inflammation with increased hepatic cytokine expression compared with feeding of high-fat diet only. In this model, iron is intensely accumulated in Kupffer cells/macrophages within the lesion, raising the possibility that iron-laden Kupffer cells/macrophages can play a key role in the enhancement of hepatic inflammation in NASH condition. On the other hand, in a rat model of liver cirrhosis, dietary iron overload clearly abrogates the development and progression of liver cirrhosis induced by repeated administration of thioacetamide (TAA). These findings suggest that iron overload can promote or suppress chronic liver diseases depending on the tissue microenvironment. Here we review and introduce the recent findings on the pathological roles of iron overload in the development and progression of NAFLD/NASH.

Dietary Iron Overload Abrogates Chemically-Induced Liver Cirrhosis in Rats.

Chronic liver disease is an intractable disease, which can progress to cirrhosis and hepatocellular carcinoma. Hepatic iron overload is considered to be involved in the progression of chronic liver diseases; however, the mechanism remains to be elucidated. Here we investigate the role of dietary iron overload using chemically-induced liver cirrhosis model. Rats were fed a high-iron or standard diet and were injected intraperitoneally with thioacetamide (TAA) or saline twice a week for 20 weeks. Rats with TAA treatment (TAA group) had progressive liver cirrhosis characterized by persistent hepatocellular injury, mononuclear cell inflammation and bridging fibrosis; these lesions were markedly reduced in rats with iron feeding and TAA treatment (Fe-TAA group). Rats with iron feeding alone (Fe group) had no evidence of liver injury. Hepatic expression of cleaved caspase-3, but not phospho-RIP3, was decreased in Fe-TAA group compared with that in TAA group. The number of TUNEL-positive (terminal deoxynucleotidyl transferase dUTP nick end labeling) apoptotic hepatocytes was lower in the Fe-TAA group than in the TAA group. Hepatic xenobiotic metabolism and lipid peroxidation were shown to be less related to the abrogation of liver cirrhosis. Our results suggested that dietary hepatic iron overload abrogates chemically-induced liver cirrhosis in rats, which could partly involve decreased hepatocellular apoptosis.

Dietary Iron Supplementation Alters Hepatic Inflammation in a Rat Model of Nonalcoholic Steatohepatitis.

Nonalcoholic fatty liver disease (NAFLD) is now the most common liver disease in the world. NAFLD can progress to nonalcoholic steatohepatitis (NASH), cirrhosis and eventually hepatocellular carcinoma. Acquired hepatic iron overload is seen in a number of patients with NAFLD; however, its significance in the pathology of NAFLD is still debated. Here, we investigated the role of dietary iron supplementation in experimental steatohepatitis in rats. Rats were fed a control, high-fat (HF), high-fat high-iron (HFHI) and high-iron (HI) diet for 30 weeks. Blood biochemical, histopathological and gut microbiota analyses were performed. Rats in HF and HFHI groups showed an ALT-dominant elevation of serum transaminases, hepatic steatosis, hepatic inflammation, and upregulation of proinflammatory cytokines. The number of large inflammatory foci, corresponding to lobular inflammation in NASH patients, was significantly higher in HFHI than in HF group; within the lesion, macrophages with intense iron staining were observed. Hepatic expression of TNFα was higher in HFHI than that in HF group. There was no significant change in hepatic oxidative stress, gut microbiota or serum endotoxin levels between HF and HFHI groups. These results suggested that dietary iron supplementation enhances experimental steatohepatitis induced by long-term high-fat diet feeding in rats. Iron-laden macrophages can play an important role in the enhancement of hepatic inflammation.

Anti-fibrotic Role of miR-214 in Thioacetamide-induced Liver Cirrhosis in Rats.

An increasing number of studies have focused on the role of microRNAs in liver fibrosis/cirrhosis. miR-214 has recently attracted more attention as a fibrosis-related factor; however, the molecular mechanisms in hepatic fibrogenesis remain largely unknown. Here, we investigate the pathological role of miR-214 during progression of liver cirrhosis in rats. Rats were injected intraperitoneally with thioacetamide at a dose of 100 mg/kg body weight, twice a week. The liver was collected at post first injection weeks 5, 10, 15, and 20. Hepatic expression of miR-214 was analyzed by real-time polymerase chain reaction, in situ hybridization, and laser microdissection. The effects of miR-214 overexpression were investigated by in vitro transfection using fibroblastic MT-9 cells. miR-214 was highly upregulated in the fibrotic area in parallel with the cirrhosis progression. miR-214 overexpression in MT-9 cells under transforming growth factor-ß1 stimulation resulted in decreased cell number and increased expression of cleaved caspase 3 and decreased expression of α-smooth muscle actin, suggesting that miR-214 induces apoptosis and inhibits myofibroblast differentiation in fibroblastic cells under stimulation of fibrogenic factors. These data indicate an anti-fibrotic role of miR-214 in chemically induced liver fibrosis/cirrhosis.