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Investigating genetic determinants of liver disease and its associations with cardiovascular diseases

Parisinos, Constantinos Athos; (2022) Investigating genetic determinants of liver disease and its associations with cardiovascular diseases. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Background Dramatic modifications in lifestyle have given rise to an epidemic in chronic liver diseases, predominantly driven by non-alcoholic fatty liver disease (NAFLD). The more severe NAFLD phenotypes are associated with elevated liver iron, inflammation (steatohepatitis), scarring and liver failure (fibrosis, cirrhosis), and possibly with cardiovascular diseases (CVDs); genetic and population studies of these phenotypes and their links to CVDs have been limited. Aims 1) Investigate the genetic susceptibility underlying liver MRI phenotypes (iron and corrected T1 (cT1), a steatohepatitis proxy) and explore associations with other cardiometabolic traits. 2) Investigate whether liver fibrosis is an independent risk factor for CVDs. Methods We carried out genome-wide association studies (GWASs) of liver MRI phenotypes (iron (N = 8,289), and corrected T1 (a steatohepatitis proxy, N = 14,440)) in UK Biobank. We used genetics to investigate causality with other traits. We calculated a FIB-4 score (a validated non-invasive scoring system that predicts liver fibrosis) in 44,956 individuals in the UK and investigated its association with the incidence of five CVDs (ischaemic stroke, myocardial infarction, heart failure, peripheral arterial disease, atrial fibrillation (AF)). Results Three genetic variants known to influence hepcidin regulation (rs1800562 (C282Y) and rs1799945 (H63D) in HFE, rs855791 (V736A) in TMPRSS6) were associated with liver iron (p < 5 x 10-8). Mendelian randomisation provided evidence that central obesity causes higher liver iron. Four variants (rs75935921 in SLC30A10, rs13107325 in SLC39A8, rs58542926 in TM6SF2, rs738409 in PNPLA3) were associated with elevated cT1 (p < 5 x 10-8). Insulin resistance, type 2 diabetes, fatty liver, and BMI were causally associated with elevated cT1 whilst favourable adiposity was protective. In 44,956 individuals over a median of 5.4 years, adjusted models demonstrated strong associations of “suspected liver fibrosis” (FIB-4  1.3) with cirrhosis (Hazard ratio (HR 13.64 [10.79 – 17.26], p < 2 x 10-16)) and hepatocellular carcinoma (HR 11.64 [5.15 – 26.31], p = 3.5 x 10-9), but no association with the incidence of most CVDs, albeit a modest increase in AF risk (HR 1.18 [1.01 – 1.37]), when compared to individuals with a FIB-4 < 1.3. Conclusions This thesis provides genetic evidence that mechanisms underlying higher liver iron content are likely systemic rather than organ specific. The association between two metal ion transporters and cT1 indicates a new mechanism in steatohepatitis. There is little evidence to suggest that liver fibrosis is an independent risk factor for most CVDs, except possibly a small increase risk in incident AF risk. This thesis’ findings can be used to investigate causality, generate hypotheses for drug development and inform health policies.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Investigating genetic determinants of liver disease and its associations with cardiovascular diseases
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: UCL
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Population Health Sciences > Institute of Health Informatics
UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10155244
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