Effects of brain amyloid deposition and reduced glucose metabolism on the default mode of brain function in normal aging.

Brain ß-amyloid (Aß) deposition during normal aging is highlighted as an initial pathogenetic event in the development of Alzheimer's disease. Many recent brain imaging studies have focused on areas deactivated during cognitive tasks [the default mode network (DMN), i.e., medial frontal gyrus/anterior cingulate cortex and precuneus/posterior cingulate cortex], where the strength of functional coordination was more or less affected by cerebral Aß deposits. In the present positron emission tomography study, to investigate whether regional glucose metabolic alterations and Aß deposits seen in nondemented elderly human subjects (n = 22) are of pathophysiological importance in changes of brain hemodynamic coordination in DMN during normal aging, we measured cerebral glucose metabolism with [(18)F]FDG, Aß deposits with [(11)C]PIB, and regional cerebral blood flow during control and working memory tasks by H(2)(15)O on the same day. Data were analyzed using both region of interest and statistical parametric mapping. Our results indicated that the amount of Aß deposits was negatively correlated with hemodynamic similarity between medial frontal and medial posterior regions, and the lower similarity was associated with poorer working memory performance. In contrast, brain glucose metabolism was not related to this medial hemodynamic similarity. These findings suggest that traceable Aß deposition, but not glucose hypometabolism, in the brain plays an important role in occurrence of neuronal discoordination in DMN along with poor working memory in healthy elderly people.

In vivo changes in microglial activation and amyloid deposits in brain regions with hypometabolism in Alzheimer's disease.

PURPOSE: Amyloid ß protein (Aß) is known as a pathological substance in Alzheimer's disease (AD) and is assumed to coexist with a degree of activated microglia in the brain. However, it remains unclear whether these two events occur in parallel with characteristic hypometabolism in AD in vivo. The purpose of the present study was to clarify the in vivo relationship between Aß accumulation and neuroinflammation in those specific brain regions in early AD. METHODS: Eleven nootropic drug-naïve AD patients underwent a series of positron emission tomography (PET) measurements with [(11)C](R)PK11195, [(11)C]PIB and [(18)F]FDG and a battery of cognitive tests within the same day. The binding potentials (BPs) of [(11)C](R)PK11195 were directly compared with those of [(11)C]PIB in the brain regions with reduced glucose metabolism. RESULTS: BPs of [(11)C](R)PK11195 and [(11)C]PIB were significantly higher in the parietotemporal regions of AD patients than in ten healthy controls. In AD patients, there was a negative correlation between dementia score and [(11)C](R)PK11195 BPs, but not [(11)C]PIB, in the limbic, precuneus and prefrontal regions. Direct comparisons showed a significant negative correlation between [(11)C](R)PK11195 and [(11)C]PIB BPs in the posterior cingulate cortex (PCC) (p < 0.05, corrected) that manifested the most severe reduction in [(18)F]FDG uptake. CONCLUSION: A lack of coupling between microglial activation and amyloid deposits may indicate that Aß accumulation shown by [(11)C]PIB is not always the primary cause of microglial activation, but rather the negative correlation present in the PCC suggests that microglia can show higher activation during the production of Aß in early AD.

Metabolite alterations in the hippocampus of high-functioning adult subjects with autism.

The aim of the present study was to investigate metabolite alterations in the hippocampal formation as they relate to aggression in high-functioning adults with autism. We measured concentrations of N-acetylaspartate (NAA), choline-containing compounds (Cho), and creatine plus phosphocreatine (Cr+PCr) in the hippocampal formation by proton magnetic resonance spectroscopy in 12 non-medicated male subjects with autism and 12 age- and sex-matched controls. Aggression was scored in the autistic subjects using the Buss-Perry Aggression Questionnaire. The concentrations of Cho and Cr+PCr in the hippocampal formation in autistic subjects were significantly higher than the corresponding values in control subjects, and a significant positive correlation was observed between the concentrations of these metabolites in the hippocampal formation and scores on the Buss-Perry Aggression Questionnaire in autistic subjects. Results suggest that high-functioning adult subjects with autism have abnormal metabolite concentrations in the hippocampal formation, which may in part account for their aggression.

Failure to confirm genetic association of the FXYD6 gene with schizophrenia: the Japanese population and meta-analysis.

The FXYD domain-containing ion transport regulator 6 (FXYD6) gene encodes phosphohippolin that regulates cellular ion transport by altering the kinetic properties of Na,K-ATPase. Phosphohippolin is highly expressed in brain regions that are relevant to schizophrenia. The FXYD6 gene is located at chromosome 11q22-24, one of the most established linkage regions for schizophrenia. Therefore, it may be possible that genetic variants in FXYD6, including the regulatory genomic elements could cause abnormal function or expression of phosphohippolin and increase the genetic risk for schizophrenia. A previous study suggested that polymorphisms in FXYD6 are associated with schizophrenia in UK samples. However, conflicting results have been reported in the Japanese population. In this study, we aimed to test the prior genetic association findings using different samples from the ethnically homogeneous Japanese population (1,060 schizophrenic patients and 1,060 age- and sex-matched controls). From the FXYD6 gene, we examined six single nucleotide polymorphisms (rs11216573, rs555577, rs1815774, rs4938445, rs4938446, and rs497768), all of which were previously analyzed for association. We did not detect any significant allelic, genotypic or haplotypic association in our Japanese samples. Meta-analysis incorporating previous and the present studies also showed that the FXYD6 gene is not associated with schizophrenia. We conclude that the FXYD6 gene does not have a major influence on susceptibility to schizophrenia across populations.

VLDL-specific increases of fatty acids in autism spectrum disorder correlate with social interaction.

BACKGROUND: Abnormalities of lipid metabolism contributing to the autism spectrum disorder (ASD) pathogenesis have been suggested, but the mechanisms are not fully understood. We aimed to characterize the lipid metabolism in ASD and to explore a biomarker for clinical evaluation. METHODS: An age-matched case-control study was designed. Lipidomics was conducted using the plasma samples from 30 children with ASD compared to 30 typical developmental control (TD) children. Large-scale lipoprotein analyses were also conducted using the serum samples from 152 children with ASD compared to 122 TD children. Data comparing ASD to TD subjects were evaluated using univariate (Mann-Whitney test) and multivariate analyses (conditional logistic regression analysis) for main analyses using cofounders (diagnosis, sex, age, height, weight, and BMI), Spearman rank correlation coefficient, and discriminant analyses. FINDINGS: Forty-eight significant metabolites involved in lipid biosynthesis and metabolism, oxidative stress, and synaptic function were identified in the plasma of ASD children by lipidomics. Among these, increased fatty acids (FAs), such as omega-3 (n-3) and omega-6 (n-6), showed correlations with clinical social interaction score and ASD diagnosis. Specific reductions of very-low-density lipoprotein (VLDL) and apoprotein B (APOB) in serum of ASD children also were found by large-scale lipoprotein analysis. VLDL-specific reduction in ASD was correlated with APOB, indicating VLDL-specific dyslipidaemia associated with APOB in ASD children. INTERPRETATION: Our results demonstrated that the increases in FAs correlated positively with social interaction are due to VLDL-specific degradation, providing novel insights into the lipid metabolism underlying ASD pathophysiology. FUNDING: This study was supported mainly by MEXT, Japan.

Methamphetamine causes microglial activation in the brains of human abusers.

Methamphetamine is a popular addictive drug whose use is associated with multiple neuropsychiatric adverse events and toxic to the dopaminergic and serotonergic systems of the brain. Methamphetamine-induced neuropathology is associated with increased expression of microglial cells that are thought to participate in either pro-toxic or protective mechanisms in the brain. Although reactive microgliosis has been observed in animal models of methamphetamine neurotoxicity, no study has reported on the status of microglial activation in human methamphetamine abusers. The present study reports on 12 abstinent methamphetamine abusers and 12 age-, gender-, and education-matched control subjects who underwent positron emission tomography using a radiotracer for activated microglia, [(11)C](R)-(1-[2-chlorophenyl]-N-methyl-N-[1-methylpropyl]-3-isoquinoline carboxamide) ([(11)C](R)-PK11195). Compartment analysis was used to estimate quantitative levels of binding potentials of [(11)C](R)-PK11195 in brain regions with dopaminergic and/or serotonergic innervation. The mean levels of [(11)C](R)-PK11195 binding were higher in methamphetamine abusers than those in control subjects in all brain regions (>250% higher; p < 0.01 for all). In addition, the binding levels in the midbrain, striatum, thalamus, and orbitofrontal and insular cortices (p < 0.05) correlated inversely with the duration of methamphetamine abstinence. These results suggest that chronic self-administration of methamphetamine can cause reactive microgliosis in the brains of human methamphetamine abusers, a level of activation that appears to subside over longer periods of abstinence.

Voxel-based structural magnetic resonance imaging (MRI) study of patients with early onset schizophrenia.

BACKGROUND: Investigation into the whole brain morphology of early onset schizophrenia (EOS) to date has been sparse. We studied the regional brain volumes in EOS patients, and the correlations between regional volume measures and symptom severity. METHODS: A total of 18 EOS patients (onset under 16 years) and 18 controls matched for age, gender, parental socioeconomic status, and height were examined. Voxel-based morphometric analysis using the Brain Analysis Morphological Mapping (BAMM) software package was employed to explore alterations of the regional grey (GM) and white matter (WM) volumes in EOS patients. Symptoms were assessed using the Positive and Negative Syndrome Scale (PANSS). RESULTS: EOS patients had significantly reduced GM volume in the left parahippocampal, inferior frontal, and superior temporal gyri, compared with the controls. They also had less WM volume in the left posterior limb of the internal capsule and the left inferior longitudinal fasciculus. The positive symptom score of PANSS (higher values corresponding to more severe symptoms) was negatively related to GM volume in the bilateral posterior cingulate gyrus. The negative symptom score was positively correlated with GM volume in the right thalamus. As for the association with WM volume, the positive symptom score of PANSS was positively related to cerebellar WM (vermis region), and negatively correlated with WM in the brain stem (pons) and in the bilateral cerebellum (hemisphere region). CONCLUSION: Our findings of regional volume alterations of GM and WM in EOS patients coincide with those of previous studies of adult onset schizophrenia patients. However, in brain regions that had no overall structural differences between EOS patients and controls (that is, the bilateral posterior cingulate gyrus, the right thalamus, the cerebellum, and the pons), within-subject analysis of EOS patients alone revealed that there were significant associations of the volume in these areas and the symptom severity. These findings suggest that at an early stage of the illness, especially for those with onset before brain maturation, a wide range of disturbed neural circuits, including these brain regions that show no apparent morphological changes, may contribute to the formation of the symptomatology.

Depiction of microglial activation in aging and dementia: Positron emission tomography with [11C]DPA713 versus [11C]( R)PK11195.

The presence of activated microglia in the brains of healthy elderly people is a matter of debate. We aimed to clarify the degree of microglial activation in aging and dementia as revealed by different tracers by comparing the binding potential (BPND) in various brain regions using a first-generation translocator protein (TSPO) tracer [11C]( R)PK11195 and a second-generation tracer [11C]DPA713. The BPND levels, estimated using simplified reference tissue models, were compared among healthy young and elderly individuals and patients with Alzheimer's disease (AD) and were correlated with clinical scores. An analysis of variance showed category-dependent elevation in levels of [11C]DPA713 BPND in all brain regions and showed a significant increase in the AD group, whereas no significant changes among groups were found when [11C]( R)PK11195 BPND was used. Cognito-mnemonic scores were significantly correlated with [11C]DPA713 BPND levels in many brain regions, whereas [11C]( R)PK11195 BPND failed to correlate with the scores. As mentioned elsewhere, the present results confirmed that the second-generation TSPO tracer [11C]DPA713 has a greater sensitivity to TSPO in both aging and neuronal degeneration than [11C]( R)PK11195. Positron emission tomography with [11C]DPA713 is suitable for the delineation of in vivo microglial activation occurring globally over the cerebral cortex irrespective of aging and degeneration.

An association study between catechol-O-methyl transferase gene polymorphism and methamphetamine psychotic disorder.

OBJECTIVE: A series of methamphetamine psychosis reveals two kinds of clinical courses of methamphetamine psychosis: transient type and prolonged type. Furthermore, paranoid psychosis sometimes recurs without methamphetamine reuse, referred to as spontaneous relapse. Dysfunction of central dopaminergic neurotransmission has been implicated in the pathogenesis of these psychiatric states. Catechol-O-methyl transferase appears to play a unique role in regulating synaptic dopaminergic activity. This study aimed to investigate whether a functional polymorphism of the catechol-O-methyl transferase gene would be involved in the development of these psychiatric states. BASIC METHODS: We examined the functional polymorphism of val 158 met (catechol-O-methyl transferase) in 143 patients with methamphetamine psychosis and 200 healthy controls in Japan. The patients were divided into subgroups by several characteristic clinical features. MAIN RESULTS: We found a significant difference in the catechol-O-methyl transferase allele frequency between patients with spontaneous relapse and the controls (P=0.018, odds ratio=1.67). Odds ratio implied that the patients with spontaneous relapse had a nearly 1.7-fold higher rate of the low activity alleles (met) than the controls. CONCLUSIONS: Our results indicate that the met allele frequency of the catechol-O-methyl transferase is associated with patients who experienced methamphetamine psychosis and spontaneous relapse, suggesting that patients with a met allele appear to be at increased risk of an adverse response to methamphetamine.

Metabolite alterations in basal ganglia associated with psychiatric symptoms of abstinent toluene users: a proton MRS study.

Long-term toluene abuse causes a variety of psychiatric symptoms. However, little is known about abnormalities at the neurochemical level in the living human brain after long-term exposure to toluene. To detect neurochemical changes in the basal ganglia of subjects with a history of long-term toluene use, proton magnetic resonance spectroscopy (1H MRS) was performed in 12 abstinent toluene users and 13 healthy comparisons with no history of drug abuse. N-acetylaspartate (NAA), creatine plus phosphocreatine (Cr + PCr), choline-containing compounds (Cho), and myo-inositol (MI) levels were measured in the left and right basal ganglia. The Cho/Cr + PCr ratio, a marker of membrane metabolism, was significantly increased in the basal ganglia of toluene users in comparison to that of the control subjects. Furthermore, the increase in the Cho/Cr + PCr ratio was significantly correlated with the severity of residual psychiatric symptoms. These findings suggest that long-term toluene use causes membrane disturbance in the basal ganglia, which is associated with residual psychiatric symptoms that persist even after long-term abstinence from toluene use.

Microglial activation in young adults with autism spectrum disorder.

CONTEXT: A growing body of evidence suggests that aberrant immunologic systems underlie the pathophysiologic characteristics of autism spectrum disorder (ASD). However, to our knowledge, no information is available on the patterns of distribution of microglial activation in the brain in ASD. OBJECTIVES: To identify brain regions associated with excessively activated microglia in the whole brain, and to examine similarities in the pattern of distribution of activated microglia in subjects with ASD and control subjects. DESIGN: Case-control study using positron emission tomography and a radiotracer for microglia--[11C](R)-(1-[2-chrorophynyl]-N-methyl-N-[1-methylpropyl]-3 isoquinoline carboxamide) ([11C](R)-PK11195). SETTING: Subjects recruited from the community. PARTICIPANTS: Twenty men with ASD (age range, 18-31 years; mean [SD] IQ, 95.9 [16.7]) and 20 age- and IQ-matched healthy men as controls. Diagnosis of ASD was made in accordance with the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview-Revised. MAIN OUTCOME MEASURES: Regional brain [11C](R)-PK11195 binding potential as a representative measure of microglial activation. RESULTS: The [11C](R)-PK11195 binding potential values were significantly higher in multiple brain regions in young adults with ASD compared with those of controls (P < .05, corrected). Brain regions with increased binding potentials included the cerebellum, midbrain, pons, fusiform gyri, and the anterior cingulate and orbitofrontal cortices. The most prominent increase was observed in the cerebellum. The pattern of distribution of [11C](R)-PK11195 binding potential values in these brain regions of ASD and control subjects was similar, whereas the magnitude of the [11C](R)-PK11195 binding potential in the ASD group was greater than that of controls in all regions. CONCLUSIONS: Our results indicate excessive microglial activation in multiple brain regions in young adult subjects with ASD. The similar distribution pattern of regional microglial activity in the ASD and control groups may indicate augmented but not altered microglial activation in the brain in the subjects with ASD.

Plasma cytokine profiles in subjects with high-functioning autism spectrum disorders.

BACKGROUND: Accumulating evidence suggests that dysregulation of the immune system is involved in the pathophysiology of autism spectrum disorders (ASD). The aim of the study was to explore immunological markers in peripheral plasma samples from non-medicated subjects with high-functioning ASD. METHODOLOGY/PRINCIPAL FINDINGS: A multiplex assay for cytokines and chemokines was applied to plasma samples from male subjects with high-functioning ASD (n = 28) and matched controls (n = 28). Among a total of 48 analytes examined, the plasma concentrations of IL-1ß, IL-1RA, IL-5, IL-8, IL-12(p70), IL-13, IL-17 and GRO-α were significantly higher in subjects with ASD compared with the corresponding values of matched controls after correction for multiple comparisons. CONCLUSION/SIGNIFICANCE: The results suggest that abnormal immune responses as assessed by multiplex analysis of cytokines may serve as one of the biological trait markers for ASD.

Reduced acetylcholinesterase activity in the fusiform gyrus in adults with autism spectrum disorders.

CONTEXT: Both neuropsychological and functional magnetic resonance imaging studies have shown deficiencies in face perception in subjects with autism spectrum disorders (ASD). The fusiform gyrus has been regarded as the key structure in face perception. The cholinergic system is known to regulate the function of the visual pathway, including the fusiform gyrus. OBJECTIVES: To determine whether central acetylcholinesterase activity, a marker for the cholinergic system, is altered in ASD and whether the alteration in acetylcholinesterase activity, if any, is correlated with their social functioning. DESIGN: Using positron emission tomography and a radiotracer, N-[(11)C]methyl-4-piperidyl acetate ([(11)C]MP4A), regional cerebrocortical acetylcholinesterase activities were estimated by reference tissue-based linear least-squares analysis and expressed in terms of the rate constant k(3). Current and childhood autism symptoms in the adult subjects with ASD were assessed by the Autism Diagnostic Observation Schedule and the Autism Diagnostic Interview-Revised, respectively. Voxel-based analyses as well as region of interest-based methods were used for between-subject analysis and within-subject correlation analysis with respect to clinical variables. SETTING: Participants recruited from the community. PARTICIPANTS: Twenty adult subjects with ASD (14 male and 6 female; age range, 18-33 years; mean [SD] intelligence quotient, 91.6 [4.3]) and 20 age-, sex-, and intelligence quotient-matched healthy controls. RESULTS: Both voxel- and region of interest-based analyses revealed significantly lower [(11)C]MP4A k(3) values in the bilateral fusiform gyri of subjects with ASD than in those of controls (P < .05, corrected). The fusiform k(3) values in subjects with ASD were negatively correlated with their social disabilities as assessed by Autism Diagnostic Observation Schedule as well as Autism Diagnostic Interview-Revised. CONCLUSIONS: The results suggest that a deficit in cholinergic innervations of the fusiform gyrus, which can be observed in adults with ASD, may be related to not only current but also childhood impairment of social functioning.

Replication study of Japanese cohorts supports the role of STX1A in autism susceptibility.

Autism is a pervasive developmental disorder diagnosed in early childhood. Abnormalities of serotonergic neurotransmission have been reported in autism. Serotonin transporter (5-HTT), which modulates serotonin levels, is a major therapeutic target in autism. Therefore, factors that regulate 5-HTT expression might be implicated in autism. One candidate 5-HTT-regulatory protein is the presynaptic protein, syntaxin 1A (STX1A). We examined the association of STX1A with autism in a trio association study using DNA samples from Japanese trios with autistic probands. In TDT analysis, rs69510130 (p=0.027) showed nominal associations with autism; modest haplotype association was also observed. We further compared STX1A mRNA expression between the autistic and control groups in the postmortem brain. In the anterior cingulate gyrus region, STX1A expression in the autism group was found to be significantly lower than that of the control group. Thus, we suggest a possible role of STX1A in the pathogenesis of autism.

Further evidence for the role of MET in autism susceptibility.

MET receptor tyrosine kinase (MET)-mediated signaling has been implicated in multiple aspects of neocortical and cerebellar neuronal growth and maturation. A promoter functional SNP (rs1858830) that disrupts the transcription of MET has been reported to be strongly associated with autism spectrum disorders (ASD) in the Caucasian population. Here, we performed a trio association study of MET with ASD in Japanese subjects (n=126 trios). Based on the HapMap data on the Japanese population, 15 SNPs were chosen for the association study. One SNP located in intron 1, rs38841, showed a nominal association with autism (p=0.044; OR=1.61) when analyzed using the transmission disequilibrium test. To the best of our knowledge, this is the first replication study of the association of MET with autism, in any non-Caucasian population. Association of rs38841 with autism was further confirmed in 252 Caucasian trios from AGRE (p=0.0006). An interesting observation is that all three SNPs of MET (rs1858830, rs38845 and rs38841) shown to be associated with autism in three independent studies including the present one, are located towards the 5'end of the gene at a span of 9.4 kb. Our results provide further evidence for a possible role of MET in the pathogenesis of ASD.

Short allele of 5-HTTLPR as a risk factor for the development of psychosis in Japanese methamphetamine abusers.

Accumulating evidence suggests that genetic factors contribute to the vulnerability to methamphetamine (MAP) abuse and associated psychiatric symptoms. Chronic MAP abuse leads to psychosis, which may be of a transient or a prolonged type. Serotonergic dysfunction has been proposed as one of the contributory factors in the development of MAP psychosis. Our PET studies revealed that the serotonin transporter (5-HTT) density in global brain regions is significantly lower in MAP abusers. In this study, we examined the role of a functional polymorphism in the 5' flanking region of the 5-HTT gene (5-HTTLPR) in the development of MAP psychosis in a Japanese population. We analyzed DNA samples from 166 MAP patients (95 with transient and 71 with prolonged psychosis) and 197 age-, sex-, and geographic-origin-matched healthy controls. Patients were also subdivided according to the presence (n= 119) or absence (n= 148) of spontaneous relapse. We observed significant genotypic association of the 5-HTTLPR polymorphism with MAP psychosis (P= 0.022), particularly in patients who show prolonged psychosis. The frequency of the S allele in patients with prolonged psychosis was significantly higher than that of the controls (P= 0.045); it was further higher in patients with prolonged psychosis with spontaneous relapse (P= 0.004). 5-HTTLPR has been suggested to regulate the transcriptional activity of 5-HTT, with S alleles showing lesser transcriptional efficiency and also lower 5-HT(1A) receptor-binding potential. Prolonged MAP use, combined with the high frequency of 5-HTTLPR S-alleles, may lead to reduced 5-HTT levels and 5-HT(1A) receptor-binding potential in the brain, resulting in the dysfunction of the serotonergic system. Thus, we suggest a possible role for the 5-HTTLPR polymorphism in MAP psychosis.

Association analysis of SOD2 variants with methamphetamine psychosis in Japanese and Taiwanese populations.

SOD2 (superoxide dismutase 2) plays a crucial role in protecting the cells against damage caused by free radicals, by catalyzing their detoxification. On the other hand, cell damage caused by free radical generation following methamphetamine administration has been postulated as one of the possible pathophysiological mechanisms for methamphetamine psychosis. Hence, we investigated the association of SOD2 polymorphisms with the development of methamphetamine psychosis, in two independent populations of Japan and Taiwan. We recruited 116 patients with methamphetamine psychosis and 189 controls in Japan, and 135 patients with methamphetamine psychosis and 204 controls in Taiwan. The methamphetamine group was divided into two clinical subtypes: a transient type of psychosis (i.e., good prognosis) and a prolonged type of psychosis (i.e., poor prognosis), according to the course of the manifestation of psychosis. With reference to the genotypic and allelic frequencies of Ala/Val functional polymorphism in exon 2, we found significant differences between individuals with prolonged methamphetamine psychosis and control samples from Japan and Taiwan in the genotypic (P value 0.014 and 0.016, respectively) and in the allelic (P value 0.004 and 0.047, respectively) frequencies. Our results suggest that Ala/Val polymorphism of the SOD2 gene could be associated with the risk of developing methamphetamine psychosis.