Background
Alzheimer’s disease (AD) is the most common cause of dementia in the United States, with approximately 95% of patients exhibiting sporadic Late‐Onset AD (LOAD), which lacks an inheritance ...pattern. Therefore, identifying phenotypic patterns are critical for understanding disease progression. Apolipoprotein E4 (APOE4), the strongest genetic risk factor of LOAD, increases AD risk by 3‐12 fold depending on copy number. Recent GWAS analysis elucidated the LOAD‐associated loci on the triggering receptor expressed on myeloid cell 2 (TREM2). APOE is a known ligand to the TREM2 receptor, and the R47H variant could increase the AD risk by 2‐3 fold. Preclinical studies of these risk alleles and their phenotypes are underway by MODEL‐AD.
Methods
Using PET/MRI and a novel analytical scheme, we established the perfusion‐metabolism profiles across 27 brain regions in both sexes by using 64Cu‐PTSM and 18F‐FDG in the APOE4 (APOE
E4/E4), TREM2 (TREM2
R47H), and double (APOE
E4/E4.TREM2
R47H) knockin (KI) mice, and compared these to blood chemistry and nanoString transcriptomic analysis.
Results
Longitudinal analysis comparing 12mo to 4mo time point revealed that male APOE4 mice and both sexes of TREM2 had hypo‐ perfusion and metabolism, while female APOE4 mice showed an uncoupled hyper‐perfusion and hypo‐metabolism phenotype, and was correlated to human AD pathology. In double KI mice, perfusion and metabolism showed a mixed phenotype which was region dependent. Cross‐sectional analysis of KI compared to C57BL/6J mice at 12mo showed an overall reduced glucose metabolism. Intriguingly, male APOE4, TREM2, and double mice showed hypo‐perfusion and metabolism, while female double mice showed metabolic uncoupling compared to C57BL/6J. Analysis of blood biochemistry in non‐fasted mice revealed no significant difference between genotypes in blood glucose with age. However, APOE4 decreased the blood cholesterol level (LDL, and HDL). RNAseq and immunohistology was peformed, and key genes involved in the regulation of cerebral perfusion, glucose transportation, and metabolism were altered.
Conclusions
These data suggest that the new perfusion‐metabolism strategy may be able to identify AD‐related patterns. Moreover, they replicate clinical manifestations of subjects with the same variants, suggesting additional mechanistic studies are needed to elucidate the mechanisms and etiology of this uncoupling phenomenon.
Background
The Preclinical Testing Core (PTC) of the Model Organism Development for Late Onset Alzheimer’s Disease (MODEL‐AD) consortium established a preclinical strategy with go/no‐go decision ...points that permits unbiased assessments of potential therapeutic agents. In models at disease‐relevant ages, this strategy includes: 1) drug formulation, stability, and in vivo pharmacokinetics (PK); and 2) pharmacodynamics (PD) readouts of target engagement and disease modifying activity via non‐invasive PET/MRI, behavior, and transcriptomics. As part of the pipeline validation, verubecestat (VER), a BACE1 inhibitor, was selected for testing in 5XFAD mice.
Methods
PK analysis was performed in 6 month aged 5XFAD mice of both sexes, for both oral gavage (PO) and drug milled into diet (10‐100 mg/kg) with blood and brain concentrations analyzed via LC/MS. PK/PD modeling determined dosing regimen for chronic treatments started at 3 months. All PD endpoints (n = 10‐15/sex/genotype/treatment) were measured at 6‐7 months of age, and included: 18‐FDG PET/MR, 18F‐AV45 PET/MR, autoradiography, immunohistochemistry, and behavioral assessments. Post treatment gene expression profiling was conducted using the nanoString and aligned to AMP‐AD consensus clusters.
Results
Initial PK analysis revealed rapid clearance of VER following PO dosing, thus all PD experiments were performed via chronic exposure to drug formulated in diet (10, 30, and 100 mg/kg/day). Prophylactic treatment with VER produced robust coat color changes consistent with hair color changes reported in the clinic. Moreover, VER resulted in dose‐dependent reductions in amyloid deposition via 18F‐AV45 PET, but did not alter glucose uptake via 18F‐FDG PET. VER failed to improve cognition in 5XFAD mice. Transcriptomics revealed dose depended genes expression that mapped to AMP‐AD consensus clusters for immune response, DNA repair, and RNA metabolism.
Conclusions
The effects of VER dosing on PD endpoints revealed the expected results consistent with clinical findings. Moreover, VER failed to improve cognitive behavior in 5XFAD mice, in line with the lack of cognitive improvement in patients. Together these data positive support for pipeline validation of the MODEL‐AD PTC, and highlight the importance for post‐treatment transcriptomics to align model systems with drug mechanism of actions.
Abstract
Background
The Preclinical Testing Core (PTC) of the Model Organism Development for Late Onset Alzheimer’s Disease (MODEL‐AD) consortium established a preclinical strategy with go/no‐go ...decision points that permits unbiased assessments of potential therapeutic agents. In models at disease‐relevant ages, this strategy includes: 1) drug formulation, stability, and in vivo pharmacokinetics (PK); and 2) pharmacodynamics (PD) readouts of target engagement and disease modifying activity via non‐invasive PET/MRI, behavior, and transcriptomics. As part of the pipeline validation, verubecestat (VER), a BACE1 inhibitor, was selected for testing in 5XFAD mice.
Methods
PK analysis was performed in 6 month aged 5XFAD mice of both sexes, for both oral gavage (PO) and drug milled into diet (10‐100 mg/kg) with blood and brain concentrations analyzed via LC/MS. PK/PD modeling determined dosing regimen for chronic treatments started at 3 months. All PD endpoints (n = 10‐15/sex/genotype/treatment) were measured at 6‐7 months of age, and included: 18‐FDG PET/MR, 18F‐AV45 PET/MR, autoradiography, immunohistochemistry, and behavioral assessments. Post treatment gene expression profiling was conducted using the nanoString and aligned to AMP‐AD consensus clusters.
Results
Initial PK analysis revealed rapid clearance of VER following PO dosing, thus all PD experiments were performed via chronic exposure to drug formulated in diet (10, 30, and 100 mg/kg/day). Prophylactic treatment with VER produced robust coat color changes consistent with hair color changes reported in the clinic. Moreover, VER resulted in dose‐dependent reductions in amyloid deposition via 18F‐AV45 PET, but did not alter glucose uptake via 18F‐FDG PET. VER failed to improve cognition in 5XFAD mice. Transcriptomics revealed dose depended genes expression that mapped to AMP‐AD consensus clusters for immune response, DNA repair, and RNA metabolism.
Conclusions
The effects of VER dosing on PD endpoints revealed the expected results consistent with clinical findings. Moreover, VER failed to improve cognitive behavior in 5XFAD mice, in line with the lack of cognitive improvement in patients. Together these data positive support for pipeline validation of the MODEL‐AD PTC, and highlight the importance for post‐treatment transcriptomics to align model systems with drug mechanism of actions.
Background. Dialysis patients have increased vascular calcification of the coronary arteries and aorta by electron beam CT scan. The purpose of the present study was to utilize an alternative ...machine, spiral CT, to assess calcification in end‐stage renal disease (ESRD) patients. Methods. Two groups of patients with ESRD were evaluated: group 1, those receiving a renal transplant (n=38); and group 2, those remaining on dialysis (n=33). All patients underwent quad‐slice spiral CT with retrospective gating to evaluate coronary artery and aorta calcification scores. Both area (Agatston method) and volume calculations were utilized, with retrospective gating in all but 16 subjects. Laboratory tests, medications and clinical characteristics were analysed. Results. Using spiral CT, the intra‐reader variability for coronary artery calcification (after correction for very low scores) was 0.9% mean / 0% median using the area (Agatston method) and 2.9% mean / 0% median using volume calculations. Group 1 patients were younger, more likely to be Caucasian and on peritoneal dialysis, had lower serum calcium and higher C‐reactive protein levels than group 2. In patients without vs those with coronary artery calcification, only longer duration of dialysis (34±64 vs 55±50 months, P=0.004; r=0.39, P=0.005) and increasing age (39±13 vs 54±10 years, P<0.001; r=0.29, P=0.039) were associated, whereas only increasing age was associated with aorta calcification. Conclusion. In ESRD patients, the factors correlating with coronary calcification were duration of dialysis and advancing age, whereas only age correlated with aorta calcification. Spiral CT offers an alternative technique for the assessment of these changes.
Abstract only
18
F‐NaF uptake has been investigated as an
in
vivo
biomarker of coronary artery calcification (CAC) in humans. CAC increases risk of fatal cardiac events in coronary artery disease ...(CAD) patients, thus making early diagnosis and clinical intervention extremely important. We assessed
18
F‐NaF positron emission tomography (PET) as a diagnostic tool for early CAC in a preclinical swine model of metabolic syndrome (MetS) and CAD by comparing multiple imaging modalities: PET, computed tomography (CT), intravascular ultrasound (IVUS), and histopathology for their sensitivity. MetS Ossabaw swine (N=11) with early‐stage CAD underwent ECG‐gated
18
F‐NaF PET/CT scans. Global cardiac and coronary tracking techniques were used to measure
18
F‐NaF uptake. MetS swine had almost 2‐fold increased
18
F‐NaF uptake in the conduit coronary arteries (p<0.05) and 2.5‐fold increased global molecular calcium score (p<0.05) compared to lean (N=3). IVUS resolved calcification in only 1 MetS pig. All pigs had Agatston CT calcium scores of 0. Histology revealed microcalcifications present in 36% of MetS pigs (NS). This is the first report of
18
F‐NaF uptake at an early stage of CAD and microcalcification prior to clinically significant, ossified lesions resolvable by IVUS and CT.
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