Plasma hydrogen sulfide: A biomarker of Alzheimer's disease and related dementias

While heart disease remains a common cause of mortality, cerebrovascular disease also increases with age, and has been implicated in Alzheimer's disease and related dementias (ADRD). We have described hydrogen sulfide (H2S), a signaling molecule important in vascular homeostasis, as a biomarker of cardiovascular disease. We hypothesize that plasma H2S and its metabolites also relate to vascular and cognitive dysfunction in ADRD. We used analytical biochemical methods to measure plasma H2S metabolites and MRI to evaluate indicators of microvascular disease in ADRD. Levels of total H2S and specific metabolites were increased in ADRD versus controls. Cognition and microvascular disease indices were correlated with H2S levels. Total plasma sulfide was the strongest indicator of ADRD, and partially drove the relationship between cognitive dysfunction and white matter lesion volume, an indicator of microvascular disease. Our findings show that H2S is dysregulated in dementia, providing a potential biomarker for diagnosis and intervention. Scheme for sulfide dysregulation in ADRD. In ADRD, increased accumulation of sulfides, measured in plasma, may reflect increased formation of H2S metabolites produced in the vascular compartment. Several sulfide species are known to impair blood brain barrier leading to persistent excitotoxic stress and subsequent destructive changes in brain microvascular structure and cognitive function seen in ADRD.