Vascular pathology of 20-month-old hypercholesterolemia mice in comparison to triple-transgenic and APPSwDI Alzheimer's disease mouse models.

Abstract

Several studies have shown that elevated plasma cholesterol levels (i.e. hypercholesterolemia) serve as a risk factor for late-onset Alzheimer's disease (AD). However, it remains unclear how hypercholesterolemia may contribute to the onset and progression of AD pathology. In order to determine the role of hypercholesterolemia at various stages of AD, we evaluated the effects of high cholesterol diet (5% cholesterol) in wild-type (WT; C57BL6) and triple-transgenic AD (3xTg-AD; Psen1, APPSwe, tauB301L) mice at 7, 14, and 20 months. The transgenic APP-Swedish/Dutch/Iowa AD mouse model (APPSwDI) was used as a control since these animals are more pathologically-accelerated and are known to exhibit extensive plaque deposition and cerebral amyloid angiopathy. Here, we describe the effects of high cholesterol diet on: (1) cognitive function and stress, (2) AD-associated pathologies, (3) neuroinflammation, (4) blood–brain barrier disruption and ventricle size, and (5) vascular dysfunction. Our data show that high dietary cholesterol increases weight, slightly impairs cognitive function, promotes glial cell activation and complement-related pathways, enhances the infiltration of blood-derived proteins and alters vascular integrity, however, it does not induce AD-related pathologies. While normal-fed 3xTg-AD mice display a typical AD-like pathology in addition to severe cognitive impairment and neuroinflammation at 20 months of age, vascular alterations are less pronounced. No microbleedings were seen by MRI, however, the ventricle size was enlarged. Triple-transgenic AD mice, on the other hand, fed a high cholesterol diet do not survive past 14 months of age. Our data indicates that cholesterol does not markedly potentiate AD-related pathology, nor does it cause significant impairments in cognition. However, it appears that high cholesterol diet markedly increases stress-related plasma corticosterone levels as well as some vessel pathologies. Together, our findings represent the first demonstration of prolonged high cholesterol diet and the examination of its effects at various stages of cerebrovascular- and AD-related disease.