Vascular dysfunction has been implicated in Alzheimer's disease (AD). Risk factors for cardiovascular disease are also recognized as major risk factors for AD, although sex differences may impact this relationship. One such risk factor, Type 2 diabetes (T2D), is prevalent in our AD patient population, and increases the risk for AD by 65%. However the mechanisms underlying vascular and cognitive impairment in AD, and how diabetes worsens these responses remain unclear. There is emerging evidence that H2S may protect the brain against vascular dysfunction e.g. the blood brain barrier (BBB). In contrast, oxidized forms of H2S disrupt BBB. Therefore it is critical to understand how the balance between the different forms of H2S are changed during AD, to what extent this imbalance is exacerbated by T2D, and if this shift in the H2S balance correlates with vascular and cognitive changes. Because females are more susceptible to AD, the first iteration of this research supplement, initially focused on how sulfide metabolism perturbations in T2D altered BBB and cognitive disturbances in females. However, males are more susceptible to earlier and more severe cardiovascular disease, bringing up the question - if AD severity in males with T2D is comparable to females. Furthermore, the distribution of H2S between acid labile sulfide and sulfane sulfide pools in individuals with cardiovascular disease is different between males and females, which could further complicate the interaction of sex and AD. Consequently, in the current iteration, we will extend our studies correlating H2S/sulfide changes with cognitive, anatomic and blood flow disturbances to males. A well-characterized mouse model of AD (APPswe/PS1) accelerated by T2D diet will be employed (AIM 1a). Evaluation of male AD/T2D model, progressing from early, middle to late disease stages of experimental AD will describe the early biochemical changes and characteristics of AD/T2D associated with cognitive deficits in males as compared to females. In this subaim, we now also propose to use adenoviruses to transduce expression of CSE in vascular endothelium in both males and females. The overexpression of CSE will provide the first direct evidence that correcting H2S metabolism provides protection against AD accelerated by T2D.
AIM 1 b of this proposal will expand clinical participation to evaluate changes in plasma sulfides/H2S in male human/clinical AD complicated by T2D (and relevant controls) and associate these risks with cognitive performance and cardiovascular risks. MR brain imaging and cerebrovascular blood flow studies will be used to delineate those specific biomarkers and mechanisms which are related to AD severity. This highly focused, mechanistic and translational group of studies will help establish for the first time how T2D-mediated imbalances in H2S/sulfide exacerbates vascular and anatomic characteristics of AD in males versus females to impair learning/cognition. These studies are directly relevant to the NIH mission of understanding diseases like AD and application of these findings to enhance health and reduce illness and disability from AD.
Although vascular dysfunction is implicated in Alzheimer's disease (AD), whether and how Type 2 diabetic (T2D) vascular risks intensify cognitive impairment in AD differently in men versus women remains unclear. The gasotransmitter, hydrogen sulfide, is altered in both T2D and AD, and may contribute to the vascular perturbations in AD/T2D, although it also exhibits sex differences in its metabolism under disease conditions. Therefore we will test if T2D differentially alters hydrogen sulfide in males vs. females with AD, thus modifying the relative risk for developing vascular and cognitive dysfunction in AD/T2D patients.
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