Screening over Speech in Unselected Populations for Clinical Trials in AD (PROSPECT-AD): Study Design and Protocol

BACKGROUND

Speech impairments are an early feature of Alzheimer's disease (AD) and consequently, analysing speech performance is a promising new digital biomarker for AD screening. Future clinical AD trials on disease modifying drugs will require a shift to very early identification of individuals at risk of dementia. Hence, digital markers of language and speech may offer a method for screening of at-risk populations that are at the earliest stages of AD, eventually in combination with advanced machine learning. To this end, we developed a screening battery consisting of speech-based neurocognitive tests. The automated test performs a remote primary screening using a simple telephone.

OBJECTIVES

PROSPECT-AD aims to validate speech biomarkers for identification of individuals with early signs of AD and monitor their longitudinal course through access to well-phenotyped cohorts.

DESIGN

PROSPECT-AD leverages ongoing cohorts such as EPAD (UK), DESCRIBE and DELCODE (Germany), and BioFINDER Primary Care (Sweden) and Beta-AARC (Spain) by adding a collection of speech data over the telephone to existing longitudinal follow-ups. Participants at risk of dementia are recruited from existing parent cohorts across Europe to form an AD 'probability-spectrum', i.e., individuals with a low risk to high risk of developing AD dementia. The characterization of cognition, biomarker and risk factor (genetic and environmental) status of each research participants over time combined with audio recordings of speech samples will provide a well-phenotyped population for comparing novel speech markers with current gold standard biomarkers and cognitive scores.

PARTICIPANTS

N= 1000 participants aged 50 or older will be included in total, with a clinical dementia rating scale (CDR) score of 0 or 0.5. The study protocol is planned to run according to sites between 12 and 18 months.

MEASUREMENTS

The speech protocol includes the following neurocognitive tests which will be administered remotely: Word List [Memory Function], Verbal Fluency [Executive Functions] and spontaneous free speech [Psychological and/ or behavioral symptoms]. Speech features on the linguistic and paralinguistic level will be extracted from the recordings and compared to data from CSF and blood biomarkers, neuroimaging, neuropsychological evaluations, genetic profiles, and family history. Primary candidate marker from speech will be a combination of most significant features in comparison to biomarkers as reference measure. Machine learning and computational techniques will be employed to identify the most significant speech biomarkers that could represent an early indicator of AD pathology. Furthermore, based on the analysis of speech performances, models will be trained to predict cognitive decline and disease progression across the AD continuum.

CONCLUSION

The outcome of PROSPECT-AD may support AD drug development research as well as primary or tertiary prevention of dementia by providing a validated tool using a remote approach for identifying individuals at risk of dementia and monitoring individuals over time, either in a screening context or in clinical trials.

Description of a European memory clinic cohort undergoing amyloid-PET: The AMYPAD Diagnostic and Patient Management Study

INTRODUCTION

AMYPAD Diagnostic and Patient Management Study (DPMS) aims to investigate the clinical utility and cost-effectiveness of amyloid-PET in Europe. Here we present participants' baseline features and discuss the representativeness of the cohort.

METHODS

Participants with subjective cognitive decline plus (SCD+), mild cognitive impairment (MCI), or dementia were recruited in eight European memory clinics from April 16, 2018, to October 30, 2020, and randomized into three arms: ARM1, early amyloid-PET; ARM2, late amyloid-PET; and ARM3, free-choice.

RESULTS

A total of 840 participants (244 SCD+, 341 MCI, and 255 dementia) were enrolled. Sociodemographic/clinical features did not differ significantly among recruiting memory clinics or with previously reported cohorts. The randomization assigned 35% of participants to ARM1, 32% to ARM2, and 33% to ARM3; cognitive stages were distributed equally across the arms.

DISCUSSION

The features of AMYPAD-DPMS participants are as expected for a memory clinic population. This ensures the generalizability of future study results.

119 NeuroToolkit CSF biomarkers track the progression of Alzheimer’s disease at very early stages

Introduction

NeuroToolkit is a set of cerebrospinal fluid (CSF) biomarkers developed to identify Alzheimer’s disease co-pathologies, identify and characterize disease progression and treatment response. We assess the association between NeuroToolkit biomarkers and cerebral amyloid deposition in the ALFA+ cohort [1].

Methods

326 cognitively unimpaired individuals from the ALFA+ cohort [1] underwent a lumbar puncture and amyloid [18F]flutemetamol PET imaging. Biomarkers in NeuroToolkit (Figure 1) were determined using prototype Roche Elecsys® assays. CSF pTau levels were measured using the Elecsys® CSF assay. We cal- culated cross-correlation values between NeuroToolkit biomarkers and Centiloids. Voxel-wise associations between NeuroToolkit biomarkers and [18F]flutemetamol images were sought, accounting for the effect of various demographics. Additional analyses were performed after correcting also for the Aα42/40 ratio or Centiloid values.

Results

Figure 1. Shows associations between NeuroToolkit biomarkers and Centiloids. NeuroToolkit bio- markers were significantly associated with cerebral amyloid deposition measured by [18F]flutemetamol PET (Figure 2). Correcting for global amyloid deposition, higher levels CSF YKL-40, an astroglial activity marker, were associated to increased cerebral amyloid deposition in the inferior and lateral temporal lobe, in parietal and orbitofrontal areas, and the caudate heads (Figure 3).

Conclusions

Results of NeuroToolkit biomarkers support early involvement of the astroglial response to cerebral amyloid deposition.

Disclosure

This study was conducted through a collaboration with Roche Diagnostics International. These data will be presented at Advances in Alzheimer’s and Parkinson’s Therapies. Ref: Molinuevo. TRCI 2 (2016) 82–92

gwendlyn.kollmorgen@roche.com

DHA intake relates to better cerebrovascular and neurodegeneration neuroimaging phenotypes in middle-aged adults at increased genetic risk of Alzheimer disease

BACKGROUND

The number of APOE-ε4 alleles is a major nonmodifiable risk factor for sporadic Alzheimer disease (AD). There is increasing evidence on the benefits of dietary DHA (22:6n-3) before the onset of AD symptoms, particularly in APOE-ε4 carriers. Brain alterations in the preclinical stage can be detected by structural MRI.

OBJECTIVES

We aimed, in middle-aged cognitively unimpaired individuals at increased risk of AD, to cross-sectionally investigate whether dietary DHA intake relates to cognitive performance and to MRI-based markers of cerebral small vessel disease and AD-related neurodegeneration, exploring the effect modification by APOE-ε4 status.

METHODS

In 340 participants of the ALFA (ALzheimer and FAmilies) study, which is enriched for APOE-ε4 carriership (n = 122, noncarriers; n = 157, 1 allele; n = 61, 2 alleles), we assessed self-reported DHA intake through an FFQ. We measured cognitive performance by administering episodic memory and executive function tests. We performed high-resolution structural MRI to assess cerebral small vessel disease [white matter hyperintensities (WMHs) and cerebral microbleeds (CMBs)] and AD-related brain atrophy (cortical thickness in an AD signature). We constructed regression models adjusted for potential confounders, exploring the interaction DHA × APOE-ε4.

RESULTS

We observed no significant associations between DHA and cognitive performance or WMH burden. We observed a nonsignificant inverse association between DHA and prevalence of lobar CMBs (OR: 0.446; 95% CI: 0.195, 1.018; P = 0.055). DHA was found to be significantly related to greater cortical thickness in the AD signature in homozygotes but not in nonhomozygotes (P-interaction = 0.045). The association strengthened when analyzing homozygotes and nonhomozygotes matched for risk factors.

CONCLUSIONS

In cognitively unimpaired APOE-ε4 homozygotes, dietary DHA intake related to structural patterns that may result in greater resilience to AD pathology. This is consistent with the current hypothesis that those subjects at highest risk would obtain the largest benefits from DHA supplementation in the preclinical stage.This trial was registered at clinicaltrials.gov as NCT01835717.

Eating a Weekly Serving of Walnuts Relates to Beneficial Brain Imaging Phenotypes in a Cohort at Increased Risk of Alzheimer's Disease

Objectives

There is increasing evidence on the brain benefits of nut consumption. Magnetic resonance imaging (MRI) enables the detection of brain changes associated with neurodegenerative and vascular diseases. In middle-aged cognitively unimpaired subjects at increased risk of Alzheimer's disease (AD), we searched for cross-sectional associations between nut consumption and MRI-assessed brain phenotypes, including white matter hyperintensities (WMH, a marker of cerebral small vessel disease that confers increased risk of AD and stroke) and topographic patterns of gray matter volume (GMv).

Methods

We performed high-resolution structural MRI in 382 participants from the ALFA study (ALzheimer and FAmilies) cohort, which is enriched by family history of sporadic AD and APOE-ε4 carriership, the most prevalent genetic risk factor for AD. We assessed nut consumption by a food-frequency questionnaire containing five items related to nuts. WMH volume was normalized by intracranial volume (TIV) and rank-transformed. For WMH, we conducted univariate models with two factors: nut consumption (<1 and ≥1 serving/week) and being APOE-ε4 homozygote (yes/no), and their interaction, adjusting for age, gender, hypertension, hypercholesterolemia, and adherence to Mediterranean Diet. We also explored whether nut consumption related to differences in GMv using a voxel-based morphometry analysis corrected by age, gender, number of APOE-ε4 alleles, hypertension, hypercholesterolemia, adherence to Mediterranean Diet, and TIV.

Results

187 participants reported nut consumption of ≥1 serving/week, 148 of whom disclosed walnut consumption. Nut (or walnut) consumption of ≥1 serving/week related to a significantly lower WMH volume (P ≤ 0.035, both). We found no statistically significant nut × APOE-ε4 interactions. Participants reporting consumption of ≥1 walnut serving/week showed significantly greater GMv in areas including the anterior/middle cingulate cortex, which is relevant for cognition and has been associated with successful aging.

Conclusions

Nut (in particular walnut) consumption relates to beneficial phenotypes of both cerebral vasculature and regional GMv.

Funding Sources

Instituto de Salud Carlos III, Spain; “la Caixa” Foundation; California Walnut Commission.

Comparative Analysis of Different Definitions of Amyloid-β Positivity to Detect Early Downstream Pathophysiological Alterations in Preclinical Alzheimer

Amyloid-β (Aβ) positivity is defined using different biomarkers and different criteria. Criteria used in symptomatic patients may conceal meaningful early Aβ pathology in preclinical Alzheimer. Therefore, the description of sensitive cutoffs to study the pathophysiological changes in early stages of the Alzheimer's continuum is critical. Here, we compare different Aβ classification approaches and we show their performance in detecting pathophysiological changes downstream Aβ pathology. We studied 368 cognitively unimpaired individuals of the ALFA+ study, many of whom in the preclinical stage of the Alzheimer's continuum. Participants underwent Aβ PET and CSF biomarkers assessment. We classified participants as Aβ -positive using five approaches: (1) CSF Aβ42 < 1098 pg/ml; (2) CSF Aβ42/40 < 0.071; (3) Aβ PET Centiloid > 12; (4) Aβ PET Centiloid > 30 or (5) Aβ PET Positive visual read. We assessed the correlations between Aβ biomarkers and compared the prevalence of Aβ positivity. We determined which approach significantly detected associations between Aβ pathology and tau/neurodegeneration CSF biomarkers. We found that CSF-based approaches result in a higher Aβ-positive prevalence than PET-based ones. There was a higher number of discordant participants classified as CSF Aβ-positive but PET Aβ-negative than CSF Aβ-negative but PET Aβ-positive. The CSF Aβ 42/40 approach allowed optimal detection of significant associations with CSF p-tau and t-tau in the Aβ-positive group. Altogether, we highlight the need for sensitive Aβ -classifications to study the preclinical Alzheimer's continuum. Approaches that define Aβ positivity based on optimal discrimination of symptomatic Alzheimer's disease patients may be suboptimal for the detection of early pathophysiological alterations in preclinical Alzheimer.

AMYPAD Diagnostic and Patient Management Study: Rationale and design

INTRODUCTION

Reimbursement of amyloid-positron emission tomography (PET) is lagging due to the lack of definitive evidence on its clinical utility and cost-effectiveness. The Amyloid Imaging to Prevent Alzheimer's Disease-Diagnostic and Patient Management Study (AMYPAD-DPMS) is designed to fill this gap.

METHODS

AMYPAD-DPMS is a phase 4, multicenter, prospective, randomized controlled study. Nine hundred patients with subjective cognitive decline plus, mild cognitive impairment, and dementia possibly due to Alzheimer's disease will be randomized to ARM1, amyloid-PET performed early in the diagnostic workup; ARM2, amyloid-PET performed after 8 months; and ARM3, amyloid-PET performed whenever the physician chooses to do so.

ENDPOINTS

The primary endpoint is the difference between ARM1 and ARM2 in the proportion of patients receiving a very-high-confidence etiologic diagnosis after 3 months. Secondary endpoints address diagnosis and diagnostic confidence, diagnostic/therapeutic management, health economics and patient-related outcomes, and methods for image quantitation.

EXPECTED IMPACTS

AMYPAD-DPMS will supply physicians and health care payers with real-world data to plan management decisions.

Nonlinear cerebral atrophy patterns across the Alzheimer's disease continuum: impact of APOE4 genotype

The progression of Alzheimer's disease (AD) is characterized by complex trajectories of cerebral atrophy that are affected by interactions with age and apolipoprotein E allele ε4 (APOE4) status. In this article, we report the nonlinear volumetric changes in gray matter across the full biological spectrum of the disease, represented by the AD-cerebrospinal fluid (CSF) index. This index reflects the subject's level of pathology and position along the AD continuum. We also evaluated the associated impact of the APOE4 genotype. The atrophy pattern associated with the AD-CSF index was highly symmetrical and corresponded with the typical AD signature. Medial temporal structures showed different atrophy dynamics along the progression of the disease. The bilateral parahippocampal cortices and a parietotemporal region extending from the middle temporal to the supramarginal gyrus presented an initial increase in volume which later reverted. Similarly, a portion of the precuneus presented a rather linear inverse association with the AD-CSF index whereas some other clusters did not show significant atrophy until index values corresponded to positive CSF tau values. APOE4 carriers showed steeper hippocampal volume reductions with AD progression. Overall, the reported atrophy patterns are in close agreement with those mentioned in previous findings. However, the detected nonlinearities suggest that there may be different pathological processes taking place at specific moments during AD progression and reveal the impact of the APOE4 allele.

Monte Carlo simulations versus experimental measurements in a small animal PET system. A comparison in the NEMA NU 4-2008 framework

In this work a comparison between experimental and simulated data using GATE and PeneloPET Monte Carlo simulation packages is presented. All simulated setups, as well as the experimental measurements, followed exactly the guidelines of the NEMA NU 4-2008 standards using the microPET R4 scanner. The comparison was focused on spatial resolution, sensitivity, scatter fraction and counting rates performance. Both GATE and PeneloPET showed reasonable agreement for the spatial resolution when compared to experimental measurements, although they lead to slight underestimations for the points close to the edge. High accuracy was obtained between experiments and simulations of the system's sensitivity and scatter fraction for an energy window of 350-650 keV, as well as for the counting rate simulations. The latter was the most complicated test to perform since each code demands different specifications for the characterization of the system's dead time. Although simulated and experimental results were in excellent agreement for both simulation codes, PeneloPET demanded more information about the behavior of the real data acquisition system. To our knowledge, this constitutes the first validation of these Monte Carlo codes for the full NEMA NU 4-2008 standards for small animal PET imaging systems.

Quantification of rat brain SPECT with (123)I-ioflupane: evaluation of different reconstruction methods and image degradation compensations using Monte Carlo simulation

SPECT studies with (123)I-ioflupane facilitate the diagnosis of Parkinson's disease (PD). The effect on quantification of image degradations has been extensively evaluated in human studies but their impact on studies of experimental PD models is still unclear. The aim of this work was to assess the effect of compensating for the degrading phenomena on the quantification of small animal SPECT studies using (123)I-ioflupane. This assessment enabled us to evaluate the feasibility of quantitatively detecting small pathological changes using different reconstruction methods and levels of compensation for the image degrading phenomena. Monte Carlo simulated studies of a rat phantom were reconstructed and quantified. Compensations for point spread function (PSF), scattering, attenuation and partial volume effect were progressively included in the quantification protocol. A linear relationship was found between calculated and simulated specific uptake ratio (SUR) in all cases. In order to significantly distinguish disease stages, noise-reduction during the reconstruction process was the most relevant factor, followed by PSF compensation. The smallest detectable SUR interval was determined by biological variability rather than by image degradations or coregistration errors. The quantification methods that gave the best results allowed us to distinguish PD stages with SUR values that are as close as 0.5 using groups of six rats to represent each stage.

Gaba and serotonin molecular neuroimaging in essential tremor: a clinical correlation study

BACKGROUND

Essential tremor is the most common movement disorder in adults, but its exact etiology and pathophysiology are still not fully understood. There is some consensus, however, about the involvement of the cerebellum and accumulating evidence points towards a dysfunction of the gabaergic system. We hypothesize that the serotonin neurotransmission system may also play a role as it does in tremor in Parkinson disease. This study aimed to investigate the association between the severity of tremor symptoms and the gabaergic and serotoninergic neurotransmission systems in essential tremor.

MATERIAL AND METHODS

We measured the tremor clinical rating scale score and acquired DASB and Flumazenil PET scans in 10 patients who presented with essential tremor at different stages of clinical severity. Statistically significant correlations were sought between the scale scores and parametric binding potential images.

RESULTS

The correlation analysis of cerebellar Flumazenil uptake and tremor clinical rating scale scores reached statistical significance (R2 = 0.423, p = 0.041), whereas no association was detected in the DASB scans.

CONCLUSIONS

The severity of tremor correlated with the abnormalities found in GABA receptor binding, suggesting a primary gabaergic deficiency or a functional abnormality at the level of GABA(A) receptor subtypes. These results may assist in the rational development of new pharmacological treatments for essential tremor.

[Diagnostic imaging studies: do they create anxiety?]

Cancer is one of the main health problems in western countries. In 2008, it represented the first cause of death in men and the second one in women. When there is a diagnosis or suspicion of cancer, performing diagnostic imaging studies has an important role in the clinical activity and may have an elevated psychological impact.

OBJECTIVE

The purpose of this study was to evaluate the level of anxiety in oncology patients during the performance of a nuclear medicine study (PET-CT) in a Nuclear Medicine Service, by means of the State Trait Anxiety Inventory (STAI).

MATERIAL AND METHODS

A total of 200 cancer patients who underwent a PET-CT study in a Nuclear Medicine Service were administered the STAI to evaluate the level of anxiety generated during this test. The STAI is a validated questionnaire developed as a research tool on anxiety in healthy adults.

RESULTS

Of the 200 patients, two thirds (n=135) (67%) of the patients evaluated had anxiety. Of the 133, 93 (70%) of the patients who underwent PET-CT study for the first time were anxious whereas 42 (62.7%) of the patients who had undergone the study on previous occasions were anxious. Those patients with the greatest anxiety were those in whom the study was performed to initially stage the disease.

CONCLUSION

Performing the PET-CT study as an initial staging method and/or to evaluate tumor recurrence is an important and statistically significant generator of anxiety. There is a high emotional and cognitive impact associated to the participation of the diagnostic tests.

The effects of aging on dopaminergic neurotransmission: a microPET study of [11C]-raclopride binding in the aged rodent brain

Rodent models are frequently used in aging research to investigate biochemical age effects and aid in the development of therapies for pathological and non-pathological age-related degenerative processes. In order to validate the use of animal models in aging research and pave the way for longitudinal intervention-based animal studies, the consistency of cerebral aging processes across species needs to be evaluated. The dopaminergic system seems particularly susceptible to the aging process, and one of the most consistent findings in human brain aging research is a decline in striatal D2-like receptor (D2R) availability, quantifiable by positron emission tomography (PET) imaging. In this study, we aimed to assess whether similar age effects can be discerned in rat brains, using in vivo molecular imaging with the radioactive compound [(11)C]-raclopride. We observed a robust decline in striatal [(11)C]-raclopride uptake in the aged rats in comparison to the young control group, comprising a 41% decrement in striatal binding potential. In accordance with human studies, these results indicate that substantial reductions in D2R availability can be measured in the aged striatal complex. Our findings suggest that rat and human brains exhibit similar biochemical alterations with age in the striatal dopaminergic system, providing support for the pertinence of rodent models in aging research.

Dopamine D4 receptors modulate brain metabolic activity in the prefrontal cortex and cerebellum at rest and in response to methylphenidate

Methylphenidate (MP) is widely used to treat attention deficit hyperactivity disorder (ADHD). Variable number of tandem repeats polymorphisms in the dopamine D4 receptor (D(4)) gene have been implicated in vulnerability to ADHD and the response to MP. Here we examined the contribution of dopamine D4 receptors (D4Rs) to baseline brain glucose metabolism and to the regional metabolic responses to MP. We compared brain glucose metabolism (measured with micro-positron emission tomography and [(18)F]2-fluoro-2-deoxy-D-glucose) at baseline and after MP (10 mg/kg, i.p.) administration in mice with genetic deletion of the D(4). Images were analyzed using a novel automated image registration procedure. Baseline D(4)(-/-) mice had lower metabolism in the prefrontal cortex (PFC) and greater metabolism in the cerebellar vermis (CBV) than D(4)(+/+) and D(4)(+/-) mice; when given MP, D(4)(-/-) mice increased metabolism in the PFC and decreased it in the CBV, whereas in D(4)(+/+) and D(4)(+/-) mice, MP decreased metabolism in the PFC and increased it in the CBV. These findings provide evidence that D4Rs modulate not only the PFC, which may reflect the activation by dopamine of D4Rs located in this region, but also the CBV, which may reflect an indirect modulation as D4Rs are minimally expressed in this region. As individuals with ADHD show structural and/or functional abnormalities in these brain regions, the association of ADHD with D4Rs may reflect its modulation of these brain regions. The differential response to MP as a function of genotype could explain differences in brain functional responses to MP between patients with ADHD and healthy controls and between patients with ADHD with different D(4) polymorphisms.

Ventro-striatal reductions underpin symptoms of hyperactivity and impulsivity in attention-deficit/hyperactivity disorder

BACKGROUND

Models of attention-deficit/hyperactivity disorder (ADHD) classically emphasize the relevance of executive processes and, recently, reward circuits. The neural bases of reward processes have barely been explored in relation to this disorder, in contrast to extensive neuroimaging studies that examine executive functions in patients with ADHD. To our knowledge, no previous studies have analyzed the volume of the ventral striatum, a key region for reward processes in ADHD children.

METHODS

We used a manual region-of-interest approach to examine whether there were volumetric differences in the ventral striatum of ADHD children. Forty-two children/adolescents with ADHD (ages 6-18), and 42 healthy control subjects matched on age, gender, and handedness were selected for the study.

RESULTS

The ADHD children presented significant reductions in both right and left ventro-striatal volumes (t = 3.290, p = .001; and t = 3.486, p = .001, respectively). In addition, we found that the volume of the right ventral striatum negatively correlated with maternal ratings of hyperactivity/impulsivity (r = -.503, p = .003).

CONCLUSIONS

Our study provides neuroanatomical evidence of alterations in the ventral striatum of ADHD children. These findings coincide with previous explicative models as well as with recent reports in behavioral and functional neuroimaging studies. Furthermore, the negative correlations we observed strongly uphold the relation between the ventral striatum and symptoms of hyperactivity/impulsivity.

Detection of visual activation in the rat brain using 2-deoxy-2-[(18)F]fluoro-D: -glucose and statistical parametric mapping (SPM)

PURPOSE

This study was designed to assess changes in brain glucose metabolism in rats after visual stimulation.

MATERIALS AND METHODS

We sought to determine whether visual activation in the rat brain could be detected using a small-animal positron emission tomography (PET) scanner and 2-deoxy-2-[(18)F]fluoro-D: -glucose (FDG). Eleven rats were divided into two groups: (a) five animals exposed to ambient light and (b) six animals stimulated by stroboscopic light (10 Hz) with one eye covered. Rats were injected with FDG and, after 45 min of visual stimulation, were sacrificed and scanned for 90 min in a dedicated PET tomograph. Images were reconstructed by a three-dimensional ordered subset expectation maximization algorithm (1.8 mm full width at half maximum). A region-of-interest (ROI) analysis was performed on 14 brain structures drawn on coronal sections. Statistical parametric mapping (SPM) adapted for small animals was also carried out. Additionally, the brains of three rats were sliced into 20-microm sections for autoradiography.

RESULTS

Analysis of ROI data revealed significant differences between groups in the right superior colliculus, right thalamus, and brainstem (p < or = 0.05). SPM detected the same areas as the ROI approach. Autoradiographs confirmed the existence of hyperactivation in the left superior colliculus and auditory cortex.

CONCLUSIONS

To our knowledge, this is the first report that uses FDG-PET and SPM analysis to show changes in rat brain glucose metabolism after a visual stimulus.

Monitoring gene therapy by external imaging of mRNA: pilot study on murine erythropoietin

Gene therapy is anticipated as being an important medical development. Essential to its effectiveness is the appropriate activity (protein expression) in the expected target cells. A noninvasive diagnostic procedure of successful gene expression will be of paramount importance to validate its use or its misuse (eg, sports gene doping). Externally detectable labeled oligonucleotide hybridizing with the messenger RNA generated by the transferred gene has been proposed as a possibility to monitor successful gene therapy. The authors selected the erythropoietin gene (Epo) for a pilot study on erythropoietin protein expression in mouse muscle. Oligonucleotides of peptide nucleic acid (PNA) type capable of antisense binding to unique murine Epo-mRNA sequences were synthesized by solid phase methods, and elongated at the N-terminus with the HIV Tat (48-60) cell penetrating peptide. They were labeled with fluorescence and radioactive tags to verify penetration and longer half-life properties in Epo gene transfected C2C12 mouse muscle cells as compared with corresponding wild-type cells. Downregulation of newly expressed erythropoietin protein in such cells additionally confirmed the penetration and hybridizing properties of the selected labeled oligonucleotide. I-labeled Tat-PNAs were intravenously injected into mice that had previously received the Epo gene into the right tibialis muscle by DNA electrotransfer. Preferential accumulation of radioactivity in the transferred limb as compared with the contralateral limb was ascertained, especially for I-Tat-CTA CGT AGA CCA CT (labeled Tat-PNA 1). This study provides experimental data to support the potential use of external noninvasive image detection to monitor gene therapy. The extension of the approach to more sensitive methods for whole-body external detection such as positron emission tomography appears feasible.

Effect of anatomical variability, reconstruction algorithms and scattered photons on the SPM output of brain PET studies

Statistical parametric mapping (SPM) has become the standard technique to statistically evaluate differences between functional images. The aim of this paper was to assess the effect of anatomical variability of skull, the reconstruction algorithm and the scattering of photons in the brain on the output of an SPM analysis of brain PET studies. To this end, Monte Carlo simulation was used to generate suitable PET sinograms and bootstrap techniques were employed to increase the reliability of the conclusions. Activity distribution maps were obtained by segmenting thirty nine T1-weighted magnetic resonance images. Foci were placed on the posterior cingulate cortex (PCC) and the superior temporal cortex (STC) and activation factors ranging between -25% and +25% were simulated. Preprocessing of the reconstructed images and statistical analysis were performed using SPM2. Our findings show that intersubject anatomical differences can cause the minimum sample size to increase between 10 and 42% for posterior cingulate Cortex and between 40 and 80% for superior temporal cortex. Ideal scatter correction (ISC) allowed us to diminish the sample size up to 18% and fully 3D reconstruction reduced the minimum sample size between 8 and 33%. Detection sensitivity was higher for hypo-activation than for hyper-activation situations and higher for superior temporal cortex than for posterior cingulate cortex.

Dopaminergic deficiency in mice with reduced levels of the dual-specificity tyrosine-phosphorylated and regulated kinase 1A, Dyrk1A(+/-)

The dual-specificity tyrosine-phosphorylated and regulated kinase 1A (DYRK1A) gene encodes a protein kinase known to play a critical role in neurodevelopment. Mice with one functional copy of Dyrk1A (Dyrk1A(+/-)) display a marked hypoactivity and altered gait dynamics in basal conditions and in novel environments. Dopamine (DA) is a key neurotransmitter in motor behavior and genetic deletion of certain genes directly related to the dopaminergic system has a strong impact on motor activity. We have studied the effects of reduced Dyrk1A expression on the function of the nigrostriatal dopaminergic system. To characterize the dopaminergic system in DYRK1A(+/-) mice, we have used behavioral, pharmacological, histological, neurochemical and neuroimaging (microPET) techniques in a multidisciplinary approach. Dyrk1A(+/-) mice exhibited decreased striatal DA levels, reduced number of DA neurons in the substantia nigra pars compacta, as well as altered behavioral responses to dopaminergic agents. Moreover, microdialysis experiments revealed attenuated striatal DA release and positron emission tomography scan display reduced forebrain activation when challenged with amphetamine, in Dyrk1A(+/-) compared with wild-type mice. These data indicate that Dyrk1A is essential for a proper function of nigrostriatal dopaminergic neurons and suggest that Dyrk1A(+/-) mice can be used to study the pathogenesis of motor disorders involving dopaminergic dysfunction.

Impact of ventricular enlargement on the measurement of metabolic activity in spatially normalized PET

In pathologic brains with morphological alterations, the process of spatial normalization, as performed by SPM methods, may introduce a confounding effect in the measurement of metabolic activity data. To investigate the effect of the spatial normalization of PET images, we analyzed MRI and PET studies of 20 schizophrenic patients and 18 controls. Using a Talairach-based segmentation procedure and manual segmentation, we measured regional metabolic activity in the untransformed brains and after their spatial normalization. The effect of spatial normalization seems minimal for large ROIs like the main brain lobes, even in brains showing pronounced morphological abnormalities. However, the caudate nucleus shows a considerable change in metabolic activity values after normalization. This normalization effect is much larger in patients than in controls, and leads to artifactual differences between them. We obtained incorrect results (SPM analysis) regarding functional differences between patients and controls in the caudate due to this bias introduced by the spatial normalization. There was a significant correlation between the size of the lateral ventricles and the underestimation of metabolic activity of the caudate. Normalization bias seems to arise from a misalignment of the caudate in the normalized space, pixel overlap between the normalized caudate, and the caudate of the template being on average lower than 50% in both groups. Spatial normalization of the PET images of pathologic brains may introduce a potential source of error that should be taken into account in the analysis of functional data, in particular, in the study of small brain nuclei like the caudate.

Global and regional gray matter reductions in ADHD: A voxel-based morphometric study

Attention deficit hyperactivity disorder (ADHD) is a developmental disorder characterized by inattentiveness, motor hyperactivity and impulsivity. According to neuroimaging data, the neural substrate underlying ADHD seems to involve fronto-striatal circuits and the cerebellum. However, there are important discrepancies between various studies, probably due to the use of different techniques. The aim of this study is to examine cerebral gray (GM) and white (WM) matter abnormalities in a group of ADHD children using a voxel-based morphometry protocol. The sample consisted of 25 children/adolescents with DSM-IV TR diagnosis of ADHD (medicated, aged 6-16 years) who were compared with 25 healthy volunteer children/adolescents. ADHD brains on an average showed a global volume decrease of 5.4% as compared to controls. Additionally, there were regionally specific effects in the left fronto-parietal areas (left motor, premotor and somatosensory cortex), left cingulate cortex (anterior/middle/posterior cingulate), parietal lobe (precuneus bilaterally), temporal cortices (right middle temporal gyrus, left parahippocampal gyrus), and the cerebellum (bilateral posterior). There were no differences in WM volume between ADHD children and control subjects. The results are consistent with previous studies that used different techniques, and may represent a possible neural basis for some of the motor and attentional deficits commonly found in ADHD.

Hypofrontality in men with first-episode psychosis

BACKGROUND

Decreased metabolic activity in the prefrontal cortex during cognitive activation is a recurrent finding and a likely functional marker of schizophrenia.

AIMS

To investigate the occurrence of hypofrontality in patients with first-episode psychosis, with or without evolution to schizophrenia.

METHOD

We used fluorodeoxyglucose positron emission tomography during the performance of an attention task and magnetic resonance imaging to study the dorsolateral prefrontal region in 13 men with a first episode of psychosis. Data from patients who progressed to schizophrenia were compared with those of patients who did not meet criteria for this diagnosis after 2 years.

RESULTS

Patients who developed schizophrenia demonstrated a significant hypofrontality in the dorsolateral prefrontal cortex in comparison with the non-schizophrenia and control groups.

CONCLUSIONS

Our results suggest that hypofrontality could be a marker of schizophrenia at the time of the first psychotic episode, in agreement with neurodevelopmental theories of schizophrenia.

Influence of the normalization template on the outcome of statistical parametric mapping of PET scans

Spatial normalization is an essential preprocessing step in statistical parametric mapping (SPM)-based analysis of PET scans. The standard template provided with the SPM99 software package was originally constructed using (15)O-H(2)O PET scans and is commonly applied regardless of the tracer actually used in the scans being analyzed. This work studies the effect of using three different normalization templates in the outcome of the statistical analysis of PET scans: (1) the standard SPM99 PET template; (2) an (18)F-FDG PET template, constructed by averaging PET scans previously normalized to the standard template; and (3) an MRI-aided (18)F-FDG PET template, constructed by averaging PET scans normalized according to the deformation parameters obtained from MRI scans. A strictly anatomical MRI normalization of each PET was used as a reference, under the rationale that a normalization based only upon MRI should provide higher spatial accuracy. The potential bias involved in the normalization process was estimated in a clinical SPM study comparing schizophrenic patients with control subjects. For each between-group comparison, three SPM maps were obtained, one for each template. To evaluate the influence of the template, these SPM maps were compared to the reference SPM map achieved using the anatomical normalization. SPMs obtained by MRI-aided normalization showed the highest spatial specificity, and also higher sensitivity when compared to the standard normalization using the SPM99 (15)O-H(2)O template. These results show that the use of the standard template under inappropriate conditions (different tracer or mental state) may lead to inconsistent interpretations of the statistical analysis.

Cerebral metabolism and risperidone treatment in schizophrenia

This paper compares the metabolic changes associated with risperidone treatment in schizophrenia to those induced by haloperidol, as a representative typical neuroleptic. A group of 11 schizophrenic patients of recent onset underwent two [18F] fluoro-desoxi-glucose (FDG)-positron emission tomography (PET) scans at rest: the first one at the moment of the diagnosis, after a minimal treatment with haloperidol followed by wash-out, and the second one after 6 months on risperidone. The study also included 34 patients on chronic haloperidol for comparison. PET images were analyzed using Statistical Parametric Mapping (SPM'99) methods. The only change after treatment with risperidone with respect to the baseline was a slight increase in activity in the primary visual area and the right insula. Patients on chronic haloperidol showed increased activity in the motor cortex and cerebellum, as compared to both minimally treated and risperidone-treated patients. The pattern of metabolic changes induced by risperidone appears to be different from that produced by typical antipsychotics.

[Statistical parametric mapping (SPM) in nuclear medicine]

In the scope of medical research, functional neuroimaging analysis permits the study of pathological or cognitive cerebral processes by using statistical quantification techniques. A tool of increasing use is the SPM (Statistical Parametric Mapping) software due to its wide availability and the variety of statistical studies that can be made. Nevertheless, being unaware of the theoretical background on which it is based may easily lead to inaccurate results and even to the reaching of erroneous conclusions. The present article summarizes these theoretical principles and discusses the main key points of the method without requiring advanced mathematical knowledge.