Nervonic acid and 15-epi-PGA1 mediate systemic mitochondrial dysfunction in AD dementia.

Systemic mitochondrial dysfunction is apparent in the pathophysiology of Alzheimer's disease (AD). However, the factors driving bioenergetic decline remain unclear. This study utilized serum samples from older adults with normal cognition, mild cognitive impairment, and dementia to identify circulating molecules that can drive mitochondrial dysfunction in the context of AD. We used mass spectrometry to measure the abundance of lipid metabolites and applied tiered selection criteria to identify candidate "mito-inhibitory" molecules. These criteria were based on correlations with (1) in vitro bioenergetic effects of whole serum samples on naïve cells, (2) the bioenergetic capacity of blood cells from the serum donor, and (3) cognition, as measured by the modified mini-mental state exam. Mito-inhibitory lipid candidates were validated by examining their bioenergetic effects on neurons, myoblasts, and fibroblasts in vitro. Our results indicate that nervonic acid and 15-epi Prostaglandin A1 (15-epi-PGA1) are elevated in participants with dementia compared to those with normal cognition. Importantly, both metabolites inhibited mitochondrial function across multiple cell types in vitro. High resolution respirometric analyses reveal that inhibitory effects from lipid treatment occur via broad inhibition of the electron transfer system (ETS) with no change in overall mitochondrial content. This study provides insights into the mechanisms underlying systemic bioenergetic decline associated with AD dementia. The identification of circulating factors that drive mitochondrial bioenergetic decline may inform the development of mitochondrial therapeutics for AD.