Erythroferrone Expression in Anemic Rheumatoid Arthritis Patients: Is It Disordered Iron Trafficking or Disease Activity?

Iron metabolism and arthritis: Exploring connections and therapeutic avenues

ABSTRACT

Iron is indispensable for the viablility of nearly all living organisms, and it is imperative for cells, tissues, and organisms to acquire this essential metal sufficiently and maintain its metabolic stability for survival. Disruption of iron homeostasis can lead to the development of various diseases. There is a robust connection between iron metabolism and infection, immunity, inflammation, and aging, suggesting that disorders in iron metabolism may contribute to the pathogenesis of arthritis. Numerous studies have focused on the significant role of iron metabolism in the development of arthritis and its potential for targeted drug therapy. Targeting iron metabolism offers a promising approach for individualized treatment of arthritis. Therefore, this review aimed to investigate the mechanisms by which the body maintains iron metabolism and the impacts of iron and iron metabolism disorders on arthritis. Furthermore, this review aimed to identify potential therapeutic targets and active substances related to iron metabolism, which could provide promising research directions in this field.

Prevalence of anemia in patients with rheumatoid arthritis and its association with dietary inflammatory index: A population-based study from NHANES 1999 to 2018

Anemia is common in patients with rheumatoid arthritis (RA), and it is unknown whether the dietary inflammatory index (DII) is linked to anemia. This study aimed to clarify the prevalence of anemia in RA patients and its association with the DII. The data utilized in this study were collected from the National Health and Nutrition Examination Survey database from 1999 to 2018. The prevalence of anemia in RA patients was estimated by ethnicity, sex, and age. Weighted multivariate logistic regression was utilized to explore the correlation between anemia risk and DII. The most crucial dietary factors related to the risk of anemia in RA patients were screened by stepwise regression. A nomogram model was established according to key dietary factors. A total of 10.25% (confidence interval, 8.58-11.92%) of RA patients will develop anemia, with the lowest prevalence around the age of 60. In addition, higher DII levels were discovered in anemic patients than in nonanemic patients. In multivariate regression models, an important positive association was revealed between anemia and growing quartiles of DII (Q4 vs Q1: odds ratio = 1.98; confidence interval, 1.25-3.15). In the subgroup analysis, the adjusted relation of DII with anemia in females, Mexicans, smokers, nondrinkers, and age groups ≥ 60 years was statistically significant. The same association was observed in the sensitivity analysis. A nomogram model based on stepwise regression screening of key dietary factors showed good discriminatory power to identify anemic risk in RA patients (area under the curve: 0.707). In patients with RA, high DII levels were associated with the risk of anemia. More attention should be given to controlling dietary inflammation to better prevent and treat anemia.

Effect of Recombinant Human Erythroferrone Protein on Hepcidin Gene (Hamp1) Expression in HepG2 and HuH7 Cells

Iron is essential for all living organisms. It is strictly controlled by iron transporters, transferrin receptors, ferroportin and hepcidin. Erythroferrone (ERFE) is an iron-regulatory hormone which is highly expressed in erythroblasts by erythropoietin (EPO) stimulation and osteoblasts independently of EPO by sequestering bone morphogenetic proteins and inhibiting hepatic hepcidin expression. Although the hepcidin suppressive function of ERFE is known, its receptors still require investigation. Here, we aim to identify ERFE receptors on the HepG2 and Huh7 cells responsible for ERFE. Recombinant ERFE (rERFE) was first produced in HEK293 cells transfected with pcDNA3.1 + ERFE, then purified and detected by Western blot. The liver cells were treated with an rERFE-rich medium of transfected HEK293 cells and a purified rERFE-supplemented medium at various time points, and hepcidin gene (Hamp1) expression was determined using qRT-PCR. The results show that 37-kD rERFE was expressed in HEK293 cells. Hamp1 was suppressed at 3 h and 6 h in Huh7 cells after rERFE treatments (p < 0.05), then restored to the original levels. Hamp1 was activated after treatment with purified rERFE for 24 h and 48 h. Together, these results reveal that ERFE suppressed Hamp1 expression in liver cells, possibly acting on membrane ERFE receptor, which in Huh7 cells was more sensitive to the ERFE concentrate.