Microglial SCAP deficiency protects against diabetes-associated cognitive impairment through inhibiting NLRP3 inflammasome-mediated neuroinflammation.

ABSTRACT

Hyperglycemia-induced pathological microglial responses and subsequent neuronal damage are notable characteristics of diabetes-associated cognitive impairment (DACI). Cholesterol accumulation in the brain is a prevalent consequence of diabetes mellitus (DM), exacerbating pathological microglial responses. Regarding disordered glucose and lipid metabolism, the Sterol Regulatory Element-Binding Protein (SREBP) cleavage-activating protein (SCAP), a cholesterol sensor, exhibits increased expression and abnormal translocation from the endoplasmic reticulum to the Golgi, amplifying the inflammatory response. Therefore, we hypothesized that overexpression of microglia-SCAP and cholesterol accumulation in DM mice could induce pathological microglial responses associated with DACI. Our type 2 DM mice model presented an abnormal increase in microglial SCAP expression. The functional loss of microglia-specific SCAP in DM mice improved cognitive impairment, neuronal synaptic plasticity deficits, and abnormal microglial responses. Mechanistically, the accumulated SCAP directly bound to and enhanced the activation of the microglial-specific inflammatory amplifier, NLRP3 inflammasome, in Golgi, thereby increasing pathological microglial responses and promoting neuronal damage. These findings indicate an important regulatory axis of microglial responses from SCAP to the NLRP3 inflammasome pathway in microglia. These underscore the crosstalk between cholesterol disorders and pathological microglial responses, offering a promising avenue for pharmaceutical interventions in DACI.