Vascular cognitive impairment and dementia (VCID) is the second most common form of dementia after Alzheimer?s Disease (AD). VCID is one of the consequences of cerebral small-vessel disease (SVD). This vascular disorder produces cerebral perfusion deficits and, ultimately, cortical and/or subcortical lacunar strokes. Lacunar strokes can be ischemic or microhemorrhagic in nature and can result in long-term physical disabilities and death. Critical to the current proposal, lacunar strokes are a leading cause of VCID. Hypertension, hyperhomocysteinemia, diabetes and advanced age are independent, major risk factors for SVD and the resulting lacunar strokes. These factors are often clustered in individuals with both the highest risk for lacunar strokes and the worst outcomes. The current proposal is driven by the central hypothesis that combining major human risk factors for SVD in an animal model produces a synergistic effect that recapitulates the human disease etiology, giving rise to vascular injury that results in lacunar stokes and ultimately VCID. It is further hypothesized that combining these risk factors facilitates the coalescence of lacunar strokes and that the resulting augmentation of injury hastens behavioral deficits. In this study, will use the diet-induced hyperhomocysteinemia model of SVD in aged spontaneously hypertensive rats (SHR), which also produces an insulin-resistant phenotype. In addition, we will further drive the diabetic phenotype with 1) a high-fructose diet and 2) promoting a reduction in pancreatic beta cells through the use of the low-dose streptozocin. The superimposition of diabetes will further test our hypothesis that by combining a greater number of independent risk factors the progression of SVD?lacunar infarcts? VCID is accelerated and exacerbated. Our study will also leverage the use a novel, non-invasive imaging modality, multispectral optoacoustic tomography (MSOT), to identify and measure regions of perfusion/oxygenation deficits and correlate these with behavioral outcomes longitudinally and with final histological analysis of structural injury. Successful completion of this proposal will demonstrate that the combination of these risk factors recapitulates human sequelae of SVD?lacunar infarcts?VCID in an animal model. Ultimately, the development of this robust and highly relevant lacunar stroke/VCID animal model and imaging technique will permit pre-clinical testing of targets and lead compounds for lacunar stroke and VCID therapeutics. We plan to test our central hypothesis and accomplish our overall objective by pursuing the following Specific Aims: 1) Aim 1: Determine the synergistic effect of hypertension, diet-induced hyperhomocysteinemia, and aging on small-vessel disease, lacunar strokes and VCID in rats, and 2) Determine the impact of insulin-resistance and diabetes on lacunar strokes and VCID in a rat model of hypertension- hyperhomocysteinemia-aging. The proposed research is innovative because it represents a substantial departure from the status quo by shifting focus onto the investigation of how combining multiple human lacunar stroke and VCID risk factors that 1) promote vascular remodeling and 2) physically stress the microvasculature can recapitulate the human condition and result in acceleration and exacerbation of injury in an animal model.
The proposed research is relevant to public health because it is designed to increase our understanding of how human risk factors for stroke and dementia interact to worsen injury. This project will also help us develop a more clinically relevant model of cerebral small-vessel disease (SVD), lacunar strokes and vascular cognitive impairment and dementia (VCID) that will ultimately permit testing of therapeutic compounds to reduce injury in SVD and VCID. The project is relevant to the part of the NIH mission that pertains to developing fundamental knowledge that will help prevent disability and early loss of life.