Article

Positron emission tomography of monoaminergic vesicular binding in aging and Parkinson disease

Department of Radiology, Division of Nuclear Medicine, The University of Michigan Medical School, Ann Arbor, 48109-0028, USA.
Journal of Cerebral Blood Flow & Metabolism (Impact Factor: 5.34). 10/2006; 26(9):1198-212. DOI: 10.1038/sj.jcbfm.9600276
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ABSTRACT The type-2 vesicular monoamine transporter (VMAT2) might serve as an objective biomarker of Parkinson disease (PD) severity. Thirty-one subjects with early-stage PD and 75 normal subjects underwent continuous intravenous infusion of (+)-[(11)C]dihydrotetrabenazine (DTBZ) and positron emission tomography (PET) imaging to estimate the striatal VMAT2 binding site density with equilibrium tracer modeling. Parkinson disease patients were evaluated clinically in the practically defined 'off' state with the Unified Parkinson Disease Rating Scale (UPDRS), the Hoehn and Yahr Scale (HY), and the Schwab and England Activities of Daily Living Scale (SE). In normal subjects there was age-related decline in striatal DTBZ binding, approximating 0.5% per year. In PD subjects, specific DTBZ binding was reduced in the caudate nucleus (CD; -44%), anterior putamen (-68%), and posterior putamen (PP; -77%). The PP-to-CD ratio of binding was reduced significantly in PD subjects. Dihydrotetrabenazine binding was also reduced by approximately 50% in the PD substantia nigra. Striatal binding reductions correlated significantly with PD duration and SE scores, but not with HY stage or with UPDRS motor subscale (UPDRS(III)) scores. Striatal and midbrain DTBZ binding was asymmetric in PD subjects, with greatest reductions contralateral to the most clinically affected limbs. There was significant correlation between asymmetry of DTBZ binding and clinical asymmetry measured with the UPDRS(III). In HY stage 1 and 1.5 subjects (n=16), PP DTBZ binding contralateral to the clinically unaffected body side was reduced by 73%, indicating substantial preclinical nigrostriatal pathology in PD. We conclude that (+)-[(11)C]DTBZ-PET imaging displays many properties necessary of a PD biomarker.

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Available from: Satoshi Minoshima, May 24, 2014
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    • "Each subject was scanned with vesicular monoamine transporter (VMAT2) PET radioligand, as a marker of dopamine neuronal integrity. The selection of VMAT2 (now known as SLC18A2) as the present 'gold standard' dopamine marker is based on extensive animal data suggesting that levels of VMAT2 are more resistant to drug-compensatory regulation affecting other dopamine markers such as the dopamine transporter (Kilbourn et al., 1996; Wilson et al., 1996; Kemmerer et al., 2003), and is well established in the literature as a tool for measuring striatal dopamine neuron degeneration in Parkinson's disease (Frey et al., 1996; Bohnen et al., 2006; Martin et al., 2008; Stoessl, 2011). Subjects were also scanned with 11 C-FLB 457, which binds to D2 receptors. "
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    ABSTRACT: The ability to dynamically use various aspects of cognition is essential to daily function, and reliant on dopaminergic transmission in cortico-striatal circuitry. Our aim was to investigate both striatal and cortical dopaminergic changes in patients with Parkinson's disease with mild cognitive impairment, who represent a vulnerable group for the development of dementia. We hypothesized severe striatal dopamine denervation in the associative (i.e. cognitive) region and cortical D2 receptor abnormalities in the salience and executive networks in Parkinson's disease with mild cognitive impairment compared with cognitively normal patients with Parkinson's disease and healthy control subjects. We used positron emission tomography imaging with dopaminergic ligands (11)C-dihydrotetrabenazine, to investigate striatal dopamine neuron integrity in the associative subdivision and (11)C-FLB 457, to investigate cortical D2 receptor availability in patients with Parkinson's disease (55-80 years of age) with mild cognitive impairment (n = 11), cognitively normal patients with Parkinson's disease (n = 11) and age-matched healthy control subjects (n = 14). Subjects were administered a neuropsychological test battery to assess cognitive status and determine the relationship between dopaminergic changes and cognitive performance. We found that patients with mild cognitive impairment had severe striatal dopamine depletion in the associative (i.e. cognitive) subdivision as well as reduced D2 receptor availability in the bilateral insula, a key cognitive hub, compared to cognitively normal patients and healthy subjects after controlling for age, disease severity and daily dopaminergic medication intake. Associative striatal dopamine depletion was predictive of D2 receptor loss in the insula of patients with Parkinson's disease with mild cognitive impairment, demonstrating interrelated striatal and cortical changes. Insular D2 levels also predicted executive abilities in these patients as measured using a composite executive z-score obtained from neuropsychological testing. Furthermore we assessed cortical thickness to ensure that D2 receptor changes were not confounded by brain atrophy. There was no difference between groups in cortical thickness in the insula, or any other cortical region of interest. These findings suggest that striatal dopamine denervation combined with insular D2 receptor loss underlie mild cognitive impairment in Parkinson's disease and in particular decline in executive function. Furthermore, these findings suggest a crucial and direct role for dopaminergic modulation in the insula in facilitating cognitive function.
    Brain 12/2013; 137(2). DOI:10.1093/brain/awt337 · 10.23 Impact Factor
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    • "We found that neocortical and thalamic acetylcholinesterase activity in the PD group showed substantial overlap with normal range activity, as evidenced by the small absolute mean difference (B10% decrease) across all PD patients compared with the control group for both neocortical and thalamic [ 11 C]methyl- 4-piperidinyl propionate acetylcholinesterase activity. This is strikingly different from the typical complete group separation for nigrostriatal denervation levels (especially at the level of the posterior putamen) between PD and control groups (Bohnen et al, 2006a). Our approach of defining a patient subgroup with below normal range cholinergic activity is intended as a more effective strategy to investigate clinical phenotypic variations because of cholinergic denervation in PD. "
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    • "An 11 C-MP4A PET study has reported a reduction in cortical binding in PD patients of 11% which increases to 30% in PDD patients (particularly in parietal areas) [117]. An 11 C-MP4A PET study has reported that 11 C- MP4A binding correlated with levels of striatal 18 F-DOPA uptake in a group of PD patients with and without dementia [54]. This is suggestive of a parallel reduction in DA and cholinergic function in PD. "
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