biomedicines Article Hypermethioninemia Leads to Fatal Bleeding and Increased Mortality in a Transgenic I278T Mouse Model of Homocystinuria Insun Park 1, Linda K. Johnson 2, Allaura Cox 3,4, Brian R. Branchford 3,4, Jorge Di Paola 3,4, Erez M. Bublil 5 and Tomas Majtan 1,* 1 Section of Genetics & Metabolism, Department of Pediatrics, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA;
[email protected] 2 Department of Pathology, University of Colorado Anschutz Medical Campus, Aurora, CO 80045, USA;
[email protected] 3 Section of Hematology/Oncology, Department of Pediatrics, University of Colorado School of Medicine, Aurora, CO 80045, USA;
[email protected] (A.C.);
[email protected] (B.R.B.);
[email protected] (J.D.P.) 4 University of Colorado Hemophilia and Thrombosis Center, Aurora, CO 80045, USA 5 Orphan Technologies Ltd., 8640 Rapperswil, Switzerland;
[email protected] * Correspondence:
[email protected]; Tel.: +1-303-724-3813 Received: 9 July 2020; Accepted: 22 July 2020; Published: 24 July 2020 Abstract: Severely elevated plasma homocysteine and methionine lead to thromboembolic events and strokes in homocystinuric (HCU) patients. Mouse models of HCU failed to exhibit prothrombotic phenotype, presumably due to lack of hypermethioninemia. We evaluated the impact of hypermethioninemia together with hyperhomocysteinemia on murine HCU phenotype and compared the efficacy of the current and novel therapies for HCU. High methionine intake decreased survival of I278T mice, which died from intestinal bleeding with hepatic and pancreatic failure. I278T mice on normal or increased methionine intake developed endothelial dysfunction, but paradoxically demonstrated delayed occlusion in an induced arterial thrombosis model.