In this study, we investigated the effects of chronic administration of an inhibitor of the b-site amyloid precursor protein-cleaving enzyme 1 (BACE1) on Alzheimer-related pathology by multitracer PET imaging in transgenic APPPS1-21 (TG) mice. Methods: Wild-type (WT) and TG mice received vehicle or BACE inhibitor (60 mg/kg) starting at 7 wk of age. Outcome measures of brain metabolism, neuroinflammation, and amyloid-b pathology were obtained through small-animal PET imaging with 18 F-FDG, 18 F-peripheral benzodiazepine receptor ( 18 F-PBR), and 18 F-florbetapir ( 18 F-AV45), respectively. Baseline scans were acquired at 6-7 wk of age and follow-up scans at 4, 7, and 12 mo. 18 F-AV45 uptake was measured at 8 and 13 mo of age. After the final scans, histologic measures of amyloid-b (4G8), microglia (ionized calcium binding adaptor molecule 1), astrocytes (glial fibrillary acidic protein), and neuronal nuclei were performed. Results: TG mice demonstrated significant age-associated increases in 18 F-AV45 uptake. An effect of treatment was observed in the cortex (P 5 0.0014), hippocampus (P 5 0.0005), and thalamus (P , 0.0001). Histology confirmed reduction of amyloid-b pathology in TG-BACE mice. Regardless of treatment, TG mice demonstrated significantly lower 18 F-FDG uptake than WT mice in the thalamus (P 5 0.0004) and hippocampus (P 5 0.0332). Neuronal nucleus staining was lower in both TG groups in the thalamus and cortex. 18 F-PBR111 detected a significant age-related increase in TG mice (P , 0.0001) but did not detect the treatment-induced reduction in activated microglia as demonstrated by histology. Conclusion: Although 18 F-FDG, 18 F-PBR111, and 18 F-AV45 all detected pathologic alterations between TG and WT mice, only 18 F-AV45 could detect an effect of BACE inhibitor treatment. However, changes in WT binding of 18 F-AV45 undermine the specificity of this effect.
Objective:In patients with epilepsy, psychiatric comorbidities can significantly affect the disease course and quality of life. Detecting and recognizing these comorbidities is central in determining an optimal treatment plan. One promising tool in detecting biomarkers for psychiatric comorbidities in epilepsy is positron emission tomography (PET). Methods: Behavioral and biochemical variables were cross-correlated with the results from two μPET scans using the tracers [ 18 F]fluoro-2-deoxy-D-glucose ([ 18 F]FDG) and 2′-methoxyphenyl-(N-2′-pyridinyl)-p-18 F-fluoro-benzamidoethylpiperazine ([ 18 F]MPPF) to explore potential biomarkers for neurobehavioral comorbidities in an electrically induced post-status epilepticus rat model of epilepsy.Results: In rats with epilepsy, μPET analysis revealed a local reduction in hippocampal [ 18 F]FDG uptake, and a local increase in [ 18 F]MPPF binding. These changes exhibited a correlation with burrowing as a "luxury" behavior, social interaction, and anxiety-associated behavioral patterns. Interestingly, hippocampal [ 18 F]FDG uptake did not correlate with spontaneous recurrent seizure activity. Significance: In the electrically induced post-status epilepticus rat model, we demonstrated hippocampal hypometabolism and its correlation with a range of neurobehavioral alterations. These findings require further confirmation in other preclinical models and patients with epilepsy and psychiatric disorders to address the value of [ 18 F]FDG uptake as an imaging biomarker candidate for psychiatric comorbidities in patients as well as for severity assessment in rodent epilepsy models.
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