Abstract: NAME FOR TOP OF PAGES: Ortatatli, et al./Archives of Medical Research 54 (2023) x–x Journal Pre-proof Potential Role of Vitamin D, ACE2 and the Proteases as TMPRSS2 and Furin on SARS-CoV-2 Pathogenesis and COVID-19 Severity Mesut Ortatatli , Tugba Fatsa , Tugba Fatsa , Deniz Dogan Mulazimoglu , Sema Oren , Cumhur Artuk , Tugrul Hosbul , Neslihan Kulahlıoglu , Levent Kenar PII: DOI: Reference: S0188-4409(23)00015-2 https://doi.org/10.1016/j.arcmed.2023.02.002 ARCMED 2814 To appear in: Archives of Medical Research Received date: Revised date: Accepted date: June 27, 2022 January 4, 2023 February 2, 2023 Please cite this article as: Mesut Ortatatli , Tugba Fatsa , Tugba Fatsa , Deniz Dogan Mulazimoglu , Sema Oren , Cumhur Artuk , Tugrul Hosbul , Neslihan Kulahlıoglu , Levent Kenar , Potential Role of Vitamin D, ACE2 and the Proteases as TMPRSS2 and Furin on SARSCoV-2 Pathogenesis and COVID-19 Severity, Archives of Medical Research (2023), doi: https://doi.org/10.1016/j.arcmed.2023.02.002 This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2023 Published by Elsevier Inc. on behalf of Instituto Mexicano del Seguro Social (IMSS). Arch Med Res 22-00784 Archives of Medical Research 54 (2023) x–x ORIGINAL ARTICLE Potential Role of Vitamin D, ACE2 and the Proteases as TMPRSS2 and Furin on SARS-CoV-2 Pathogenesis and COVID-19 Severity Mesut Ortatatli,a Tugba Fatsa,b Tugba Fatsa,b Deniz Dogan Mulazimoglu,c Sema Oren,b Cumhur Artuk,d Tugrul Hosbul,e Neslihan Kulahlıoglu,a and Levent Kenara a Department of Medical CBRN Defence, University of Health Sciences, Etlik, Ankara, Turkey b Molecular Application and Research Unit of R and D Laboratory, University of Health Sciences, Etlik, Ankara, Turkey c Department of Chest Diseases, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, Turkey d Department of Infectious Diseases and Clinical Microbiology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, Turkey e Departmentof Medical Microbiology, Gulhane Faculty of Medicine, University of Health Sciences, Etlik, Ankara, Turkey Received for publication June 27, 2022; accepted February 2, 2023 (ARCME-D-225-00784). Address reprint requets to: Mesut Ortatatli, Gülhane Eğitim ve Araştırma Hastanesi KBRN AD. 1 Arch Med Res 22-00784 Bşk.lığı, Ankara, Turkiye; Phone: (+00) (90) 312 304 3305; E-mail: mortatatli@gmail.com NAME FOR TOP OF PAGES: Ortatatli, et al./Archives of Medical Research 54 (2023) x–x Running title: Role of Vitamin D and ACE2 on COVID-19 Background. COVID-19, the 21st century pandemic disease caused by SARS-CoV-2, has shown a wide clinical spectrum ranging from asymptomatic to deadly serious pneumonia. Objective: In our study, the relationship between the pathogenesis and clinical severity of COVID-19 and vitamin D, ACE2, Furin and TMPRSS2 was investigated. Methods. Serum 25(OH)D, 1,25(OH)2D and ACE2 protein were measured in 85 COVID-19 cases, divided..