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Associations of genetically determined iron status across the phenome: A mendelian randomization study.

Gill, D; Benyamin, B; Moore, LSP; Monori, G; Zhou, A; Koskeridis, F; Evangelou, E; Laffan, M; Walker, AP; Tsilidis, KK; et al. Gill, D; Benyamin, B; Moore, LSP; Monori, G; Zhou, A; Koskeridis, F; Evangelou, E; Laffan, M; Walker, AP; Tsilidis, KK; Dehghan, A; Elliott, P; Hyppönen, E; Tzoulaki, I (2019) Associations of genetically determined iron status across the phenome: A mendelian randomization study. PLoS Med, 16 (6). e1002833. ISSN 1549-1676 https://doi.org/10.1371/journal.pmed.1002833
SGUL Authors: Gill, Dipender Preet Singh

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Abstract

BACKGROUND: Iron is integral to many physiological processes, and variations in its levels, even within the normal range, can have implications for health. The objective of this study was to explore the broad clinical effects of varying iron status. METHODS AND FINDINGS: Genome-wide association study (GWAS) summary data obtained from 48,972 European individuals (55% female) across 19 cohorts in the Genetics of Iron Status Consortium were used to identify 3 genetic variants (rs1800562 and rs1799945 in the hemochromatosis gene [HFE] and rs855791 in the transmembrane protease serine 6 gene [TMPRSS6]) that associate with increased serum iron, ferritin, and transferrin saturation and decreased transferrin levels, thus serving as instruments for systemic iron status. Phenome-wide association study (PheWAS) of these instruments was performed on 424,439 European individuals (54% female) in the UK Biobank who were aged 40-69 years when recruited from 2006 to 2010, with their genetic data linked to Hospital Episode Statistics (HES) from April, 1995 to March, 2016. Two-sample summary data mendelian randomization (MR) analysis was performed to investigate the effect of varying iron status on outcomes across the human phenome. MR-PheWAS analysis for the 3 iron status genetic instruments was performed separately and then pooled by meta-analysis. Correction was made for testing of multiple correlated phenotypes using a 5% false discovery rate (FDR) threshold. Heterogeneity between MR estimates for different instruments was used to indicate possible bias due to effects of the genetic variants through pathways unrelated to iron status. There were 904 distinct phenotypes included in the MR-PheWAS analyses. After correcting for multiple testing, the 3 genetic instruments for systemic iron status demonstrated consistent evidence of a causal effect of higher iron status on decreasing risk of traits related to anemia (iron deficiency anemia: odds ratio [OR] scaled to a standard deviation [SD] increase in genetically determined serum iron levels 0.72, 95% confidence interval [CI] 0.64-0.81, P = 4 × 10-8) and hypercholesterolemia (hypercholesterolemia: OR 0.88, 95% CI 0.83-0.93, P = 2 × 10-5) and increasing risk of traits related to infection of the skin and related structures (cellulitis and abscess of the leg: OR 1.25, 95% CI 1.10-1.42, P = 6 × 10-4). The main limitations of this study relate to possible bias from pleiotropic effects of the considered genetic variants and misclassification of diagnoses in the HES data. Furthermore, this work only investigated participants with European ancestry, and the findings may not be applicable to other ethnic groups. CONCLUSIONS: Our findings offer novel, to our knowledge, insight into previously unreported effects of iron status, highlighting a potential protective effect of higher iron status on hypercholesterolemia and a detrimental role on risk of skin and skin structure infections. Given the modifiable and variable nature of iron status, these findings warrant further investigation.

Item Type: Article
Additional Information: Copyright: © 2019 Gill et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Keywords: Adult, Aged, Biomarkers, Cohort Studies, Female, Genome-Wide Association Study, Humans, Iron, Male, Mendelian Randomization Analysis, Middle Aged, Phenotype, Prospective Studies, Humans, Iron, Cohort Studies, Prospective Studies, Phenotype, Adult, Aged, Middle Aged, Female, Male, Genome-Wide Association Study, Mendelian Randomization Analysis, Biomarkers, 11 Medical and Health Sciences, General & Internal Medicine
SGUL Research Institute / Research Centre: Academic Structure > Infection and Immunity Research Institute (INII)
Journal or Publication Title: PLoS Med
ISSN: 1549-1676
Language: eng
Dates:
DateEvent
20 June 2019Published
21 May 2019Accepted
Publisher License: Creative Commons: Attribution 4.0
Projects:
Project IDFunderFunder ID
UNSPECIFIEDWellcome Trusthttp://dx.doi.org/10.13039/100004440
MR/L01341X/1Medical Research Councilhttp://dx.doi.org/10.13039/501100000265
UNSPECIFIEDDepartment of Healthhttp://dx.doi.org/10.13039/501100000276
1084417National Health and Medical Research Councilhttp://dx.doi.org/10.13039/501100000925
1079583National Health and Medical Research Councilhttp://dx.doi.org/10.13039/501100000925
PubMed ID: 31220083
Go to PubMed abstract
URI: https://openaccess.sgul.ac.uk/id/eprint/112806
Publisher's version: https://doi.org/10.1371/journal.pmed.1002833

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