Iron-Status Indicators and HFE Gene Polymorphisms in Individuals with Amyotrophic Lateral Sclerosis: An Umbrella Review of Meta-analyses and Systematic Reviews.

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the progressive loss of motor neurons. Recent meta-analyses and systematic reviews suggest that HFE gene polymorphisms and iron-associated biomarkers may play a key role in the risk and occurrence of ALS. This umbrella study aimed to explore the roles of HFE gene polymorphisms and iron-associated biomarkers in individuals with ALS. A thorough search of three online scientific databases, namely Scopus, Web of Science, and PubMed, was conducted from their inception until September 13, 2024. The screening and selection processes were executed based on the PICO framework and eligibility criteria, followed by two independent reviewers. The Assessment of Multiple Systematic Reviews (AMSTAR)-2 and GRADE tools were utilized to assess the methodological quality and the certainty of evidence. Through an advanced search, 101 records were retrieved, of which eight meta-analyses and systematic reviews were selected for this umbrella review. A significant increase in iron concentrations was found in individuals with ALS compared to healthy controls (SMD, 0.26; 95% CI - 0.05, 0.57). Conversely, selected meta-analyses reported that serum transferrin concentrations in ALS patients were lower compared to healthy controls (SMD, - 0.15; 95% CI - 0.36, 0.05). Furthermore, mutations in H63D polymorphisms resulted in a 13% significant increase in the risk of ALS (OR, 1.13; 95% CI 1.05, 1.22). Our umbrella study of meta-analyses and systematic reviews reveals that individuals with ALS have lower serum concentrations of transferrin compared to healthy controls. Additionally, the H63D polymorphism in the HFE gene is associated with a slight increase in the risk of ALS. Future research should investigate broader aspects of iron-related biomarkers and HFE genes to elucidate their roles in ALS pathogenesis. Registration: Our umbrella study was registered in the International Prospective Register of Systematic Reviews (PROSPERO) with the identification number CRD42024559032 ( https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42024559032 ).