Vitamin D deficiency is associated with greater acute mortality in experimental intracerebral hemorrhage

Abstract

Presently, all clinical management strategies for intracerebral hemorrhage (ICH) are invariably supportive, and evidence to their efficacy remains contentious. ICH represents an enormous individual and global health burden owing to its devastating mortality rate and long-term morbidity. There remain significant knowledge gaps in terms of pathophysiology and effective neuroprotective strategies to mitigate the health burden wrought by ICH. Vitamin D deficiency (VDD) is a globally pervasive condition affecting almost 1 in 8 people. In recent years VDD is increasingly recognised to play complex roles in various cerebrovascular diseases. Recent meta-analyses of VD supplementation failed to demonstrate benefits in reducing risk and outcomes of stroke, however these results only applied for individuals with normal levels of vitamin D and failed to account for people in whom vitamin D was deficient. VDD is often overlooked in research, and even less is known about its relationship to ICH despite the two entities sharing overlapping and widely prevalent risk factors. In this study, the candidate describes the results of a preclinical mouse model of ICH comparing outcomes of mice with normal versus VDD status after stroke. The candidate utilized microsurgical techniques to infuse bacterial collagenase within the murine basal ganglia, achieving cerebrovascular rupture to cause ICH. Remarkably greater mortality was consistently demonstrated by VDD mice in the days following ICH, with 92% of normal mice and 56% of VDD mice surviving after stroke. The early occurrence of deaths suggested that the fatal mechanisms were related to primary brain injury and increased intracranial pressure. Across a battery of neurofunctional tests measuring motor function, coordination, reflexes, and balance, VDD mice performed consistently and significantly worse than their normal counterparts. To explore the causes of aggravated brain injury, T2*-weighted magnetic resonance imaging was performed 24 hours after stroke and at several acute timepoints up to 7 days; this helped characterize the in-vivo intracranial hematoma formation after ICH and document its dynamic changes over time. Importantly, the neuroimaging studies revealed larger volume of hematoma formation in VDD mice across all timepoints, indicating a greater extent of early hemorrhage despite identical vascular insult. Hematoma formation in normal mice at 24 hours was 13.9 mm3, compared with VDD mice demonstrating 18.7 mm3 of bleeding at the same timepoint. The observation of greater intracranial bleeding was further supported by ex-vivo evidence from Drabkin’s hemoglobin assay, finding significantly higher concentration of hemoglobin in affected cerebral hemispheres of VDD mice compared with normal mice. Further cytokine array studies preliminarily identified possible involvement of VCAM-1 and P-selectin, the upregulation of which is associated with endothelial dysfunction. This study provides the first evidence of an exacerbating role of VDD in the mortality and neurofunctional outcomes of ICH. Its functional role in the formation of primary brain injury and ensuing neuroinflammation remains unclear, despite the initial findings of this study. The possible benefit of addressing the eminently correctable condition of VDD in ICH, and the implications pertaining to large populations potentially at risk of even worse ICH, makes this newly uncovered relationship deserving of further study.