Effects of ferric citrate supplementation on advanced glycation end products in a rat model of streptozotocin/nicotinamide-induced diabetes.

SCOPE: Diabetes is associated with the increased risks of anemia and activation of advanced glycation end products (AGEs) and the receptor for AGEs (RAGE). However, the effects of pharmacological doses of iron supplementation on AGE metabolism are less clear. The aim was to investigate the effect of ferric citrate supplementation on AGE metabolism. METHODS AND RESULTS: Diabetes was induced in overnight starved rats by intraperitoneal injections of 40 mg/kg streptozotocin and 120 mg/kg nicotinamide. Diabetic rats were fed a standard diet or pharmacological doses of ferric citrate (0.5, 1, 2, and 3 g of ferric iron/kg diet) for 10 weeks. Ferric citrate supplementation showed a dose-related effect on the hepatic steatosis score, malondialdehyde, cathepsin D, and glyoxalase I. A Western blot analysis revealed that >1 g of ferric iron suppressed hepatic AGE receptor 1 and high-mobility group-box 1 expressions but increased heme oxygenase-1 and RAGE expressions. Further analysis showed that high doses of ferric iron triggered sterol regulatory element-binding protein 1c, p38-mitogen-activated protein kinase, and nuclear factor-κB protein expressions. CONCLUSION: Overall, the present results suggest a dose-related effect of ferric citrate supplementation on AGE metabolism, and this effect was more evident at high iron doses (>1 g of ferric iron/kg diet).

Endoplasmic reticulum stress contributes to ferritin molecules-mediated macrophage migration via P-selectin glycoprotein ligand-1.

SCOPE: Obesity is associated with elevated serum ferritin and increased macrophage activation and infiltration; however, the causal mechanisms underlying this relationship remain undefined. METHODS AND RESULTS: Serum ferritin and soluble P-selectin glycoprotein ligand (sPSGL)-1 level were higher in obese adolescents and patients with moderate nonalcoholic fatty liver disease (NAFLD) compared with controls (all p < 0.05). Multivariate linear regression revealed that serum ferritin was independently associated with sPSGL-1 (B = 0.249, 95% confidence interval: 0.011-0.487, p = 0.041) after adjustment for covariates. The messenger (m) RNA expression of GRP78/Bip, ferritin, and PSGL-1 in leukocytes was greater in patients with nonalcoholic fatty liver disease than in controls. An animal study showed that a tunicamycin injection (an endoplasmic reticulum stress inducer) triggered serum sPSGL-1 and ferritin elevation (all p < 0.01). An in vitro study revealed that serum ferritin and apoferritin induced tumor necrosis factor-α and sPSGL-1 secretion (all p < 0.01). A wound healing assay showed that PSGL-1 blocking inhibited apoferritin-mediated macrophage migration. GRP78/Bip knockdown by the endotoxin EGF-SubA completely inhibited apoferritin-mediated macrophage migration and PSGL-1 expression at the protein and mRNA levels (all p < 0.05). CONCLUSION: ER stress associated mechanisms are required for apoferritin-/ferritin-mediated macrophage migration via the PSGL-1-dependent pathway.

Dose-related effects of ferric citrate supplementation on endoplasmic reticular stress responses and insulin signalling pathways in streptozotocin-nicotinamide-induced diabetes.

Diabetic patients are at high risk of developing anemia; however, pharmacological doses of iron supplementation may vary greatly depending on diabetes-related complications. The aim of this study was to investigate the dose-dependent effect of iron on glucose disposal with a special focus on endoplasmic reticular (ER) stress, iron metabolism, and insulin signalling pathways. Diabetes was induced in overnight fasted rats by intraperitoneal (i.p.) injections of 40 mg kg(-1) streptozotocin (STZ) and 100 mg kg(-1) nicotinamide. Diabetic rats were fed a standard diet (36.7 mg ferric iron per kg diet) or pharmacological doses of ferric citrate (0.5, 1, 2, and 3 g ferric iron per kg diet). Ferric citrate supplementation showed a dose-related effect on hepatic ER stress responses and total iron levels, which were associated with increased hepcidin and decreased ferroportin expressions. Iron-fed rats had increased sizes of their pancreatic islets and hyperinsulinemia compared to rats fed a standard diet. A western blot analysis revealed that iron feeding decreased total insulin receptor substrate 1 (IRS1), phosphorylated IRS1ser307, and AS160 but increased phosphorylated GSK-3ß. Iron supplementation inhibited the nuclear translocation of AKT but promoted FOXO1 translocation to nuclei. Ferric citrate supplementation showed a dose-related effect on ER stress responses, hepatic iron, and the insulin signaling pathway. Adverse effects were more evident at high iron doses (>1 g ferric iron per kg diet), which is equivalent to a 60 kg human male consuming >500 mg elemental iron per day.

Transient knock down of Grp78 reveals roles in serum ferritin mediated pro-inflammatory cytokine secretion in rat primary activated hepatic stellate cells.

Chronic liver diseases, including cancer, are characterized by inflammation and elevated serum ferritin (SF). However, the causal-relationship remains unclear. This study used primary rat hepatic stellate cells (HSC) as a model to investigate effects of physiological SF concentrations (10, 100 and 1000 pM) because HSCs play a central role in the development and progression of liver fibrosis. Physiological concentrations of SF, either horse SF or human serum, induced pro-inflammatory cytokine IL1ß, IL6 and TNFα secretion in rat activated HSCs (all p<0.05). By contrast, treatment did not alter activation marker αSMA expression. The presence of SF markedly enhanced expression of Grp78 mRNA (p<0.01). Furthermore, transient knock down of Grp78 by endotoxin EGF- SubA abolished SF-induced IL1ß and TNFα secretion in activated HSCs (all p<0.05). In conclusion, our results showed that at physiological concentrations SF functions as a pro-inflammatory mediator in primary rat HSCs. We also provide a molecular basis for the action of SF and identified Grp78-associated ER stress pathways as a novel potential therapeutic target for resolution of fibrosis and possible prevention of liver cancer.

Serum ferritin contributes to racial or geographic disparities in metabolic syndrome in Taiwan.

OBJECTIVES: Asians and Pacific Islanders have higher circulating serum ferritin (SF) compared with Caucasians but the clinical significance of this is unclear. There is a higher prevalence of metabolic syndrome (MetS) in Taiwanese Indigenous than Han Chinese. Genetically, Indigenous are related to Austronesians and account for 2 % of Taiwan's population. We tested the hypothesis that accumulation of Fe in the body contributes to the ethnic/racial disparities in MetS in Taiwan. DESIGN: A population-based, cross-sectional study. SETTING: National Nutrition and Health Survey in Taiwan and Penghu Island. SUBJECTS: A total of 2638 healthy adults aged ≥19 years. Three ethnic groups were included. RESULTS: Han Chinese and Indigenous people had comparable levels of SF. Austronesia origin was independently associated with MetS (OR = 2·61, 95 % CI 2·02, 3·36). After multiple adjustments, the odds for MetS (OR = 2·49, 95 % CI 1·15, 5·28) was significantly higher among Indigenous people in the highest SF tertile compared with those in the lowest tertile. Hakka and Penghu Islanders yielded the lowest risks (OR = 1·08, 95 % CI 0·44, 2·65 and OR = 1·21, 95 % CI 0·52, 2·78, respectively). Indigenous people in the highest SF tertile had increased risk for abnormal levels of fasting glucose (OR = 2·34, 95 % CI 1·27, 4·29), TAG (OR = 1·94, 95 % CI 1·11, 3·39) and HDL-cholesterol (OR = 2·10, 95 % CI 1·18, 3·73) than those in the lowest SF tertile. CONCLUSIONS: Our results raise the possibility that ethnic/racial differences in body Fe store susceptibility may contribute to racial and geographic disparities in MetS.