Electrocorticographic, astrocytic and transcriptomic signatures in the triple transgenic mouse model of Alzheimer's disease submitted to stearoyl-CoA desaturase inhibition

Alzheimer's disease (AD) is associated with cognitive deficits and sleep disturbances. Research suggests the involvement of dysfunctions in lipid metabolism in the brain of AD patients and animal models. The inhibition of stearoyl-CoA desaturase (SCD), a lipid-converting enzyme, was shown to restore memory in triple transgenic (3xTg)-AD mice. In the brain, astrocytes regulate the synthesis of specific lipids. This project tested whether the inhibition of SCD restores sleep in 3xTg-AD mice, and whether this associates with modifications in lipids, astrocytic function and the transcriptome. Wild-type (WT) and 3xTg-AD female mice received a SCD inhibitor (SCDi) or vehicle, which was followed by an electrocorticographic (ECoG) recording. Brain slices were stained for lipid droplets, astrocytic markers or processed for spatial transcriptomics. The reduced time spent awake (increased time spent in slow wave sleep) in 3xTg-AD mice was not restored by SCDi treatment. Rhythmic and scale-free ECoG activities were markedly altered in 3xTg-AD mice for all wake/sleep states, and SCDi changed these ECoG signatures differently in mutant in comparison to WT mice. GFAP-positive cell density and lipid droplet count were elevated in hippocampal CA1, and rescued by SCDi. The treatment also rescued the expression of several genes in a manner mainly overlapping between brain regions. The findings suggest that the multiple wake/sleep alterations in 3xTg-AD mice are not mitigated by SCD inhibition, but that this treatment can revert changes in hippocampal astrocytes, lipids and in the brain transcriptome. This work will benefit the understanding of the AD pathophysiology and associated sleep disturbances.