Metabolic Profiling of CHO-AβPP 695 Cells Revealed Mitochondrial Dysfunction Prior to Amyloid-β Pathology and Potential Therapeutic Effects of Both PPARγ and PPARα Agonisms for Alzheimer's Disease

Abstract

In this study, we performed gas chromatography time-of-flight mass spectrometry (GC-TOFMS)-based extracellular metabolic profiling on AβPP-transfected CHO cells (CHO-AβPP₆₉₅) and its wildtype. Orthogonal partial least squares discriminant analysis (OPLS-DA) was then used to identify discriminant metabolites, which gave clues on the effects of AβPP transgene on cellular processes. To confirm the hypotheses generated based on the metabolic data, we performed biochemical assays to gather further evidence to support our findings. The OPLS-DA showed a robust differentiation following 24 h of incubation (Q²(cum) = 0.884) and 15 discriminant metabolites were identified. In contrast, extracellular Aβ₄₂ was identified to increase significantly in CHO-AβPP₆₉₅ only after incubation for 48 h. The observed 24-h metabolic fluxes were associated with increased mitochondrial AβPP and reduced mitochondrial viabilities, which occurred before extracellular Aβ accumulation. We also investigated the therapeutic potential of peroxisome proliferator-activated receptor gamma (PPARγ) agonists, namely rosiglitazone (RSG) and pioglitazone (PIO), by employing the same approach to characterize the metabolic profiles of CHO-AβPP₆₉₅ treated with RSG and PIO, with or without their respective receptor blockers. Treatment with PIO was found to reduce the perturbation of the discriminant metabolites in CHO-AβPP₆₉₅ to a larger extent than treatment with RSG. We also attributed the PIO effects on the lowering of Aβ₄₂, and restoration of mitochondrial activity to PPARγ and PPARα agonism, respectively. Taken together, PIO was demonstrated to be therapeutically superior to RSG. Our findings provide further insights into early disease stages in this AβPP model, and support the advancement of PIO in AD therapy.