Veerareddy, Vaishnavi2024-04-302024-04-302024-01https://hdl.handle.net/11299/262849University of Minnesota M.S. thesis. 2024. Major: Pharmaceutics. Advisor: Karunya Kandimalla. 1 computer file (PDF); 61 pages.Alzheimer's disease (AD) is a common type of dementia observed in the elderly with brain amyloid beta (Aꞵ) deposits as one of its pathological hallmarks. Risk factors contributing to AD include age, genetics, inflammation, gut dysbiosis, and co-morbidities like diabetes, hypertension, and insulin resistance1. Recent studies have highlighted the necessity of investigating the combined effect of risk factors on AD onset and progression2. In addition, a majority of AD patients are diagnosed with cerebrovascular dysfunction, which is considered to be a significant contributor to the disease progression3. Moreover, the gut microbiome diversity was shown to be diminished in AD patients4. One of the interactions between the gut and the brain is mediated by gut microbial metabolites through the gut-brain axis5. Gut microbial metabolites include mainly short-chain fatty acids (acetate, propionate, butyrate) and trimethylamine N-oxide (TMAO)6. Particularly, butyrate treatment was shown to improve impaired cognition and reduce Aꞵ deposition in the AD brain, although the underlying mechanisms are yet to be characterized7. Previously, we reported the impact of insulin signaling on Aꞵ trafficking between the brain and the blood via the blood-brain barrier (BBB), which lines the cerebrovascular lumen and regulates Aꞵ levels in the brain8. However, the effect of gut microbiome metabolites on Aꞵ trafficking/accumulation at the BBB and endothelial insulin signaling remains unknown. In this study, we investigated the effect of one of the bacterial metabolites, sodium butyrate (NaBu), on Aꞵ accumulation at the BBB endothelium and the role of endothelial insulin signaling. The NaBu decreased Aꞵ40 with 6 h treatment and Aꞵ42 accumulation upon 2 h and 6 h treatments in BBB cell (hCMEC/D3) monolayers in vitro. Moreover, NaBu increased the phosphorylation of protein kinase B (PKB/AKT) and extracellular signal-regulated kinase (ERK) upon 6 h treatment. Inhibitor studies were conducted to evaluate if NaBu effect on Aꞵ accumulation at the BBB is regulated by insulin signaling. Treatment with AKT inhibitor (MK2206) and NaBu increased Aꞵ42 accumulation compared to the NaBu alone treated group. Similarly, treatment with MEK inhibitor (trametinib) and NaBu increased Aꞵ42 accumulation compared to the NaBu-treated group. These findings suggest the involvement of AKT and ERK pathways in NaBu-mediated changes in Aꞵ42 accumulation at the BBB. Also, NaBu affects the expression of transporters and receptors at the BBB. The NaBu treatment increased permeability glycoprotein (P-gp) and decreased receptors for advanced glycated end products (RAGE) compared to the Aꞵ treated group. Further, studies need to be conducted to elucidate mechanisms underlying NaBu effect on the BBB endothelium in AD. Keywords: Alzheimer’s, Aβ, Blood-brain barrier, dysbiosis, sodium butyrate, Insulin signaling, P-gp, RAGE.enAlzheimer'sBlood brain barrierGut dysbiosisInsulin signalingSodium butyrateThesis or Dissertation