In Vivo Elevation of Mitochondrial Activity and Amyloid Deposition, but Inversely Correlated, in Early-stage Senescence-Accelerated Mice: A Positron Emission Tomography Study

Abstract Background: While marked reductions in neural activity and mitochondrial function have been reported in Alzheimer’s disease (AD), the degree of mitochondrial activity in mild cognitive impairment (MCI) or early-stage AD remains unexplored. Here, we used positron emission tomography (PET) to examine the direct relationship between mitochondrial activity (18F-BCPP-EF) and β-amyloid (Aβ) deposition (11C-PiB), followed by immunohistochemistry for ATPB (an ATP synthase on the mitochondrial inner membrane), in the same brains of senescence-accelerated mouse prone 10 (SAMP10) mice, an Aβ-developing neuroinflammatory animal model showing accelerated senescence with deterioration in cognitive functioning similar to that in MCI.Results: The SUVRs of 18F-BCPP-EF and 11C-PiB were significantly higher in the 15-week-old SAMP10 mice than in the control and 5-week-old SAMP10 mice. The two parameters were found to negatively correlate with each other. Consistent with these binding results, the immunohistochemical analysis demonstrated upregulation of ATPB in neurons, astrocytes, and microglia, but not in pericytes, in the 15-week-old SAMP10 mice. Conclusions: The present results provide in vivo evidence of an increase in mitochondrial energy production and amyloid burden at an early stage in SAMP10 mice. The inverse correlation between these two phenomena suggests a concurrent compensatory increase in neuronal energy production and Aβ-induced elevation of neuroinflammatory responses in glial cells, as confirmed immunohistochemically. The combination of PET and immunohistochemistry allowed in vivo evaluation of altered mitochondrial activity during neuropathological processes, including Aβ accumulation, in an animal model of AD spectrum disorder.