Plasma Hydrogen Sulfide as a Biomarker for Alzheimer's Disease and Related Dementias

We have described hydrogen sulfide (H2S), a signaling molecule important in vascular homeostasis, as a biomarker of cardiovascular disease. There is accumulating evidence that vascular factors such as hypertension, hypercholesterolemia, and type 2 diabetes are associated with increased risk of Alzheimer's disease and related dementias (ADRD). Furthermore, in the brain, H2S acts as a neurotransmitter/second messenger produced following nerve excitation. It also modulates N-methyl-D-aspartate (NMDA) receptors during long term potentiation for memory consolidation. Three biochemical forms of reactive sulfur pools exist: free H2S, acid-labile (e.g. iron-sulfur clusters) and bound sulfide (e.g. persulfides, polysulfides). We hypothesize that H2S becomes dysregulated in ADRD, where vascular and cognitive functions are linked. We will use analytical biochemical methods to measure plasma H2S and its metabolites, and 3T MRI to evaluate indicators of microvascular disease in ADRD. We will compare H2S levels in people with and without cognitive dysfunction consistent with ADRD, and determine the specificity and sensitivity of H2S indistinguishing people with and without cognitive dysfunction. In addition, because previous studies report differences in the incidence and prevalence of ADRD by race and sex, we will compare outcomes across these groups as well. Finally, we will examine the potentially mediating role of H2S in the relationship between cognitive function and microvascular disease.