Dataset Information

Cross-sectional and Test-Retest Characterization of PET with [(18)F]FP-(+)-DTBZ for ? Cell Mass Estimates in Diabetes.

ABSTRACT:

Purpose

The vesicular monoamine transporter, type 2 (VMAT2) is expressed by insulin producing ? cells and was evaluated as a biomarker of ? cell mass (BCM) by positron emission tomography (PET) with [(18)F]fluoropropyl-dihydrotetrabenazine ([(18)F]FP-(+)-DTBZ).

Procedures

We evaluated the feasibility of longitudinal pancreatic PET VMAT2 quantification in the pancreas in two studies of healthy controls and patients with type 1 or 2 diabetes. VMAT2 binding potential (BPND) was estimated voxelwise using a reference tissue method in a cross-sectional study, followed by assessment of reproducibility using a test-retest paradigm. Metabolic function was evaluated by stimulated c-peptide measurements.

Results

Pancreatic BPND was significantly decreased in patients with type 1 diabetes relative to controls and the test-retest variability was 9.4%.

Conclusions

Pancreatic VMAT2 content is significantly reduced in long-term diabetes patients relative to controls and repeat scans are sufficiently reproducible to suggest the feasibility clinically VMAT2 measurements in longitudinal studies of new onset diabetes.

SUBMITTER: Freeby MJ

PROVIDER: S-EPMC4783444 | biostudies-literature | 2016 Apr

REPOSITORIES: biostudies-literature

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Publications

Cross-sectional and Test-Retest Characterization of PET with [(18)F]FP-(+)-DTBZ for β Cell Mass Estimates in Diabetes.

Freeby Matthew J MJ Kringas Patricia P Goland Robin S RS Leibel Rudolph L RL Maffei Antonella A Divgi Chaitan C Ichise Masanori M Harris Paul E PE

Molecular imaging and biology 20150914 2

<h4>Purpose</h4>The vesicular monoamine transporter, type 2 (VMAT2) is expressed by insulin producing β cells and was evaluated as a biomarker of β cell mass (BCM) by positron emission tomography (PET) with [(18)F]fluoropropyl-dihydrotetrabenazine ([(18)F]FP-(+)-DTBZ).<h4>Procedures</h4>We evaluated the feasibility of longitudinal pancreatic PET VMAT2 quantification in the pancreas in two studies of healthy controls and patients with type 1 or 2 diabetes. VMAT2 binding potential (BPND) was estim ...[more]

PMID: 26370678

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Project description:Unlabelled(18)F-FP-(+)-DTBZ is a novel PET radiotracer targeting vesicular monoamine transporter type 2 (VMAT2). The goal was to explore the image features in normal human brains with (18)F-FP-(+)-DTBZ as a reference of molecular landmark for clinical diagnosis in Parkinson's disease (PD) and related disorders.Materials and methodsA total of 22 healthy subjects (59.3±6.0 years old) including 7 men and 15 women were recruited for MRI and (18)F-FP-(+)-DTBZ PET scans. A total number of 55 brain VOIs were selected for quantitation analysis. The regional specific uptake ratio (SUR) was calculated with occipital as reference from MRI-based spatially normalized (18)F-FP-(+)-DTBZ images. Regional percentage SUR to that of anterior putamen was calculated. Average SUR images were displayed in 2D and 3D space to illustrate the image patterns. The correlation between age and regional VMAT2 uptake was also examined.ResultsVisual assessment showed symmetric uptake of (18)F-FP-(+)-DTBZ and obviously highest in striatum, followed by nucleus accumbens, hypothalamus, substantia nigra, and raphe nuclei. Quantification analysis revealed striatal VMAT2 density of anterior putamen>posterior putamen>caudate nucleus. Other subcortical regions were with moderate VMAT2 distribution (6∼51% SUR of anterior putamen), while slightly lower VMAT2 was observed in cerebellum (10.60% SUR) and much lower in neocortex (<5% SUR). No significant correlation of SUR to age was found in subcortical regions.ConclusionUsing (18)F-FP-(+)-DTBZ PET, we showed the 2D and 3D imaging features of the VMAT2 distribution in vivo in healthy aging brains. The in vivo imaging characteristics of VMAT2 is consistent with the expression of VMAT2 in a recent autopsy study. Therefore, 3D visualization and higher image quality of (18)F-FP-(+)-DTBZ PET imaging might potentially be a powerful biomarker in detecting VMAT2 distribution of subcortical regions, and for Parkinson's disease and related neuropsychiatric disorders involving related monoaminergic systems.

Project description:18F-Fluoropropyl-(+)-dihydrotetrabenazine (18F-FP-(+)-DTBZ) is a vesicular monoamine transporter type 2 (VMAT2) radiotracer for positron emission tomography (PET) imaging to quantify human ?-cell mass. Renal cortex and spleen have been suggested as reference regions, however, little is known about 18F-FP-(+)-DTBZ binding in these regions including the fraction of radiometabolite. We compared the kinetics of 18F-FP-(+)-DTBZ and its inactive enantiomer 18F-FP-(-)-DTBZ in baboons, estimated the non-displaceable binding (VND) of the tracers, and used ex vivo studies to measure radiometabolite fractions.PET scans were conducted for up to 4h with (+) and (-) enantiomers. Displacement experiments using unlabeled (+) and (-) enantiomers of FP-DTBZ and fluvoxamine (to evaluate sigma-1 receptor binding) were performed. SUV curves were used to calculate displacement values in the pancreas, renal cortex, and spleen. Distribution volumes (VT) were computed, and three approaches for calculation of VND were compared: (1) 18F-FP-(+)-DTBZ reference VT, (2) 18F-FP-(-)-DTBZ pancreatic VT, and (3) a scaled 18F-FP-(+)-DTBZ reference VT values. Ex vivo study was conducted to measure radiometabolite fraction in homogenized tissue samples from baboons at 90min post-injection.Spleen uptake was lowest for both tracers. Highest uptake was in the pancreas with 18F-FP-(+)-DTBZ and renal cortex with 18F-FP-(-)-DTBZ. Substantial displacement effect was observed only with unlabeled FP-(+)-DTBZ in the 18F-FP-(+)-DTBZ studies. Radiometabolite fraction was higher in the renal cortex than the spleen. Approaches (1) and (3) with spleen to estimate VND provided lowest inter-subject variability of BPND.VT differences among organs and between enantiomers indicated that scaling of reference region values is needed for quantification of VMAT2 binding in the pancreas with 18F-FP-(+)-DTBZ. Since the kidney PET signal has greater partial volume averaging and more radiometabolites, the spleen was considered a more practical candidate for use as a scaled-reference region in the quantification of 18F-FP-(+)-DTBZ in the pancreas.

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