Peripheral Blood VA/TREM2 Levels and Their Correlation Analysis With the Development and Autistic Symptoms in Children With ASD

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder characterized by social impairment, repetitive behaviors, and narrow interests. With advancements in diagnostic techniques, the prevalence of ASD has been increasing annually. However, due to its complex and diverse etiology, there is no definitive consensus on the pathogenic mechanism of ASD. Numerous studies indicate that genetics, environment, and other factors play crucial roles in the onset of ASD.

Vitamin A (VA) exerts its effects in the body through its active metabolite, retinoic acid (RA), which regulates the transcriptional activity and expression of downstream genes by binding to retinoic acid receptors (RARs/RXRs). Triggering Receptor Expressed on Myeloid Cells 2 (TREM2) is an immunoglobulin-like receptor present on microglial cells, with functions including inhibiting the production of inflammatory factors and engulfing apoptotic neurons. Recent foreign studies show a significant decrease in TREM2 levels in the brain tissue of ASD patients. However, there is limited research on the relationship between TREM2 and ASD.

In our previous animal experiments, we observed a reduction in TREM2 in the prefrontal cortex of the brain in ASD model rats. Administering overexpressed TREM2 improved autism-like behavior in ASD model rats, and supplementing RA upregulated the expression of RA-RARα and TREM2, modulated microglial cell activation, and improved autism-like behavior in rats. Therefore, we believe that the RA/RARα pathway regulates the TREM-2 signaling pathway, mediating changes in microglial cells, and TREM2 may be involved in the pathogenesis of ASD.

Soluble TREM2 (sTREM2) is formed by the extracellular domain shedding of TREM2 under the action of ADAM protease. Research indicates that the expression of sTREM2 can be detected in cerebrospinal fluid and plasma. However, the connection between VA, sTREM2 levels, and the behavioral and developmental levels of children with ASD remains unclear and requires further clinical research to validate. This will help deepen our understanding of TREM2 expression in ASD, its potential biological functions, and the role of RA.