Exogenous branched chain amino acids improve cognitive impairment by regulating glutamatergic synapses in chronic cerebral hypoperfusion rats

Vascular cognitive impairment (VCI) is the second most common cause of dementia. Chronic cerebral hypoperfusion (CCH) is the major driving factor for vascular pathology and clinical manifestations of VCI, leading to amino acids (AA) metabolic abnormalities, including glutamate (Glu), gamma aminobutyric acid (GABA), and branched chain amino acids (BCAAs). There is a positive association between BCAAs and cognitive function. However, the specific mechanism is unclear. In this study, we investigated the possible mechanisms underlying the beneficial effects of exogenous BCAAs on VCI. All rats, except for the Sham group, underwent bilateral carotid artery ligation surgery (2-vessel occlusion, 2VO) and were randomly divided into 5 groups: Sham, 2VO, 2VO + 2.5% BCAAs, 2VO + 5% BCAAs, 2VO + 10% BCAAs. The sham and 2VO groups were fed a standard diet, while the others received BCAA-supplemented diets. After 4 weeks, we measured cognitive function, the content of AA and expression of related proteins, as well as synaptic related structures and functions. We found that 2VO led to cognitive impairment, a decrease in BCAA and GABA contents, and an abnormal increase in Glu content. Additionally, the expression levels of AA-related proteins (BCAT1, GDH, GAD,VGLUT1, EAAT2), and synapse related proteins (PSD95, synapsin I, p-CAMK II α) were found to be decreased and synaptic structure was disrupted in 2VO rats, which were reversed after BCAA diets. This study suggested that supplementation with exogenous BCAAs can improve CCH-induced VCI by regulating glutamate metabolism and transport, while also improving synaptic structure and function.