# Investigating the Effect and Mechanism of Protocatechuic Aldehyde on Vascular Dementia Based on Multi-Omics Approach

## TL;DR

This study explores how protocatechuic aldehyde improves vascular dementia by affecting brain metabolism and reducing cognitive dysfunction in rats.

## Contribution

The study reveals a novel mechanism involving glutamate metabolism and lactate shuttle enhancement in the therapeutic action of protocatechuic aldehyde.

## Key findings

- PAL improved cognitive function and reduced neuronal degeneration in 2VO rats.
- PAL downregulated glutamate-releasing protein vGLUT1 and enhanced lactate shuttle-related proteins.
- PAL reduced glutamate levels and increased lactate and ATP in co-cultured cells, lowering apoptosis.

## Abstract

Background: The therapeutic effect and mechanism of protocatechuic aldehyde (PAL) on vascular dementia (VaD) were studied from a multi-group perspective. Methods: The pharmacological property of PAL was assessed by using both an in vivo two-vessel occlusion (2VO) rat model and an in vitro astrocyte–neuron co-culture system with oxygen–glucose deprivation (OGD) injury. On the basis of neurobehavioral test, Morris’ water maze test and hematoxylin and eosin staining, the pathological transformation of cognitive function and ischemic cerebral tissue was assessed. Key metabolites and targets through the comprehensive analysis of brain tissue and plasma metabolomics and transcriptomics were screened. Western blot and immunofluorescence were measured to assess proteins related to glutamate release, lactate shuttle and glycolysis. Results: PAL markedly improved the cognitive dysfunction of 2VO rats and reduced the nerve function score. The degeneration of neurons in the Hippocampal CA1 region was appreciably reduced. A total of eight common metabolites, including L-glutamate and L-glutamine, have been identified from plasma and brain sources. The pathway enrichment of glutamate metabolism is closely related to multiple energy metabolic pathways related to glycolysis. Combined with transcriptomic analysis and in vivo experiments, it was found that PAL can significantly downregulate the expression of the glutamate-releasing protein vGLUT1 and promote the process of glutamate transformation into glutamine. At the same time, it enhances the expression of lactate production, shuttle and utilization of related proteins GLUT-1, HK2, PFK, LDHA/B and PDH, MCT1/2/4. In the subsequent cell co-culture system, we confirmed that PAL can effectively lower the expression of vGLUT1, reduce the content of glutamate, and promote the lactate shuttle process, thus increasing the content of lactate and ATP and reducing apoptosis. Conclusions: PAL is associated with upregulation of key glycolytic enzymes and MCTs, suggesting a potential enhancement of the lactate shuttle mechanism. This process may involve the regulation of glutamate metabolism and coordinated modulation of energy metabolism pathways such as glycolysis, thereby improving intercellular energy supply and contributing to the therapeutic effects observed in vascular dementia. This study provides a mechanistic basis and preclinical evidence for the clinical development of PAL.