Alzheimer’s disease (AD) is an irreversible neurodegenerative disorder that slowly destroys memory, thinking skills, and eventually the ability to accomplish even the simplest daily tasks. The amyloid-beta (Aβ42) plays a central role in Alzheimer's disease; indeed, soluble oligomers of Aβ42 (ADDLs) accumulate and cause functional deficits prior to overt neuronal cell death or plaque deposition. Moreover, recent results have shown that glutamate pathway may play a substantial role in the AD pathogenesis since its early stages.
We have studied via NMR-based metabolomics the effects of ADDLs and glutamate addition (below toxicity levels) on neuroblastoma SH-SY5Y human derived cell cultures as compared to untreated cultures. Six independent replicates for each group (ADDLs, glutamate, untreated) were prepared and cell lysates and growth media were analyzed after incubation. All the 1H NMR spectra were recorded with a Bruker 600 MHz spectrometer using the Carr–Purcell–Meiboom–Gill (CPMG) one-dimensional sequence with water presaturation.
Our results demonstrated that glutamate treatment led to pronounced metabolic alterations, affecting both intra- and extracellular metabolite levels. Specifically, intracellular concentrations of 15 amino acids increased significantly, while 5 amino acids decreased in the extracellular compartment. Additionally, glutamate-treated cells exhibited lower intracellular levels of 2-oxoisocaproate, 3-methyl-2-oxovalerate, ATP, AMP, glutathione, and fumarate. Alanine and α-ketoglutarate levels were elevated both intra- and extracellularly. Extracellular levels of citrate, fumarate, lactate, fructose, choline, and myo-inositol were reduced, whereas intracellular sn-glycero-3-phosphocholine, taurine, and phosphocreatine levels were increased. In contrast, ADDLs treatment did not induce significant metabolic changes.
These findings underscore the sensitivity of cellular metabolism to glutamate-induced stress and highlight the potential of metabolomics in characterizing early biochemical responses in AD pathology. Importantly, the observed alterations may suggest that glutamate-induced metabolic shifts could represent early hallmarks of AD, paving the way for the development of novel therapeutic strategies.
