Diabetes and hypertension contribute to cerebral small vessel disease via enhanced activity of biomarkers, microparticles and exosomes: A prospective study in stroke patients and age-matched controls

Stroke is the leading cause of disability and second most common cause of death and dementia worldwide. Whilst the stroke incidence has steadily decreased in the high-income countries (HIC), during the last 30 years there has been an alarming increase of more than 20% in the low-middle income (L/MIC) countries. Stroke occurs at a higher frequency and younger age in highly prevalent amongst Arab and South East Asian (SE) communities. Prevalence, severity and management of vascular risk factors especially diabetes (DM), hypertension (HTN), hypercholesterolemia, smoking, psychosocial issues and lack of physical activity together with genetic variance may account for the differences in the incidence and morbidity between various populations. MR imaging studies in large cohorts frequently reveal cerebral small vessel disease (SVD) as most prominent in the periventricular and sub-cortical regions. These abnormalities increase with age and are more frequent in subjects with vascular risk factors, especially uncontrolled DM and HTN. SVD represent the earliest manifestation of cerebral ischemic injury, significantly increasing the risk of subsequent stroke, dementia, parkinsonism and death. The underlying mechanisms for such injury is likely to be a prothrombotic state, via endothelial dysfunction, impaired fibrinolysis, increased platelet aggregation, plaque instability and increased inflammation. SVD volumes have been shown to increase rapidly following an acute stroke. The underlying mechanisms for progressions are not fully understood. Recent evidence suggests increased inflammatory and endothelial biomarker activity may be evident in subjects with asymptomatic SVD and in patients with symptomatic stroke who have pre-existing SVD. This enhanced biomarker activity may have implications in the pathogenesis of SVD. We hypothesize that enhanced biomarker activity may be the key (especially in DM) resulting in the development of SVD. We also hypothesize that the progression of SVD lesions (in the presence of biomarkers) will be more aggressive in patients following an acute stroke compared to controls. We established a database of stroke patients admitted to the Hamad General Hospital (HGH) in 2014 that currently has information on ~5400 patients. The majority of patients have 3T MR imaging of the brain and a smaller cohort have biomarker measurements. The average age at presentation is 53.5±13.8 years with 51.9% of Arab patients and 46% of patients from SE have pre-diabetes or DM, with incidence of untreated and poorly treated HTN is very high. Despite of the young age of patients, 3T MRI reveals pre-existing SVD including silent strokes and microbleeds in more than 60%. Studying disease mechanisms is complex and requires a multidisciplinary approach. Our group comprises of researchers with expertise in clinical trials, brain imaging and basic laboratory methods. Our preliminary study in over 300 consecutive patients with acute stroke enrolled during the last 12 months was done to test the feasibility of our proposed study and to generate biomarker and MRI data to allow power calculations (see preliminary data) for our proposal. Our preliminary findings confirm the high incidence of SVD in patients with acute stroke. We have also shown that there are significant differences in biomarker levels in patients with and without pre-existing SVD. The overarching goal of our research is to understand the mechanisms of cerebral SVD in the general population (low-risk) and in patients with ischemic stroke (high-risk). We will investigate interaction of biomarker concentrations to disease progression with non-invasive imaging tools. To deliver this we have 2 primary and 2 secondary objectives: Primary Objective 1.To measure the presence and progression of SVD as measured by MRI at baseline and after 24 months in healthy controls and patients with stroke. Primary Objective 2.To study the effects of novel circulating biomarkers (IL-6P, MMP9, microparticles [MPs] and exosomes) in relation to the presence and progression of SVD as measured on MRI at baseline and after 24 months in healthy controls and patients with stroke. Secondary Objective 1.To study the effects of novel circulating biomarkers (IL-6P, MMP9, MPs and exosomes) in relation to the presence and progression of SVD as measured on MRI at baseline and after 24 months in healthy controls and patients with stroke after adjusting for demographic factors (age, gender, ethnicity) and clinical risk factors (HTN, DM, dyslipidemia, coronary artery disease (CAD), atrial fibrillation (AF) and smoking). Secondary Objective 2.To study the effects of novel circulating biomarkers (VEGF, E-Selectin, and P-Selectin) in relation to the presence and progression of SVD as measured on MRI at baseline and after 24 months in healthy controls and patients with stroke after adjusting for demographic factors (age, gender, ethnicity) and clinical risk factors (HTN, DM, dyslipidemia, CAD, AF and smoking). Patients and controls will undergo detailed assessment of conventional risk factors, cognitive tests, biomarker studies and 3T MRI at baseline and conclusion of study 2 years later. The subjects will be examined at 6 monthly intervals (clinical assessment and biomarkers studies). Based on published/preliminary studies, 713 ischemic stroke patients and 713 age matched healthy controls (1426 subjects) will be recruited. Controls will be recruited by Biobank as per their standard procedure. Upon completion of the study, we will have an understanding of the significance of SVD in controls and in patients with ischemic stroke. We will also determine the role of risk factors, especially DM and HTN and biomarkers activity in progression or development of new SVD lesions in the 2 cohorts. Comparisons between various ethnicities, will also allow for discovery of novel imaging abnormalities and biomarkers that predispose ‘at risk’ population to development and progression of SVD.

Hamad Medical Corporation