Catechol-O-methyltransferase haplotypes are associated with psychosis in Alzheimer disease

Division of Geriatrics and Neuropsychiatry, Department of Psychiatry, Graduate School of Public Health, University of Pittsburgh, Pittsburgh, PA 15213, USA.
Molecular Psychiatry (Impact Factor: 14.5). 11/2005; 10(11):1026-36. DOI: 10.1038/
Source: PubMed


Psychotic symptoms in subjects with Alzheimer disease (AD with psychosis, AD+P) define a phenotype characterized by greater cognitive burden than in AD without psychosis. We have proposed that genes of small effect may contribute to the risk for expression of psychosis in multiple disorders, including AD. Recently, sex-differential association of a three-locus haplotype, including a G-->A transition at codon 108/158 of catechol-O-methyltransferase (COMT) resulting in a Val-->Met substitution, has been reported to confer an increased risk for schizophrenia. The main objective of the study was to determine if COMT genetic variation is associated with risk of psychosis in AD, and included a case-control study of 373 individuals diagnosed with AD with, or without, psychosis. All subjects were characterized for alleles at the three loci associated with schizophrenia, RS737865, COMT G-->A 108/158 (RS4680), and RS165599, and for a C/T transition adjacent to an estrogen response element (ERE6) in the COMT P2 promoter region. Both single locus and haplotype tests of association were conducted. Logit models were used to examine independent and interacting effects of alleles at the associated loci. All analyses were stratified by sex. In female subjects, RS4680 demonstrated a modest association with AD+P; RS737865 demonstrated a trend towards an association. There was a highly significant association of AD+P with the four-locus haplotype, which resulted from additive effects of alleles at RS4680 and ERE6 (or RS737865, as this locus was in almost absolute linkage disequilibrium (LD) with ERE6). In male subjects, no single locus test was significant, but there remained a strong association between AD+P and the four-locus haplotype. This association appeared to result from interaction of the ERE6/RS737865, RS4680, and RS165599 loci. Genetic variation in COMT is associated with AD+P, and thus appears to contribute to psychosis risk across disorders. Sex-differential associations of COMT with psychosis may result from variation at, or in LD with, ERE6. Examination of variation at ERE6 in subjects with schizophrenia, and further examination of the independent and additive effects of variations in COMT on gene expression, is warranted.

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Available from: Bruce G Pollock, Dec 26, 2013
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    • "In subsequent studies, other single nucleotide polymorphisms were analyzed in addition to the rs4680 polymorphism. Positive associations with psychosis were confirmed at the haplotype level [27,28]. An increasing body of evidence relates COMT to the declarative episodic memory, which is greatly impaired in AD. "
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    ABSTRACT: Alzheimer's disease (AD) is the leading cause of dementia worldwide and is associated with individual, familial and social burdens. Catechol-O-methyltransferase (COMT) may have a prominent role in AD pathophysiology by affecting the metabolism of catecholamine neurotransmitters and estrogen. Although the COMT rs4680 gene polymorphism has been investigated as a susceptibility factor for AD, the results are inconsistent. The aim of this study was to examine the influence of the COMT rs4680 gene polymorphism as a risk factor for AD in the Han Chinese population and its synergistic effect with the apolipoprotein E (APOE)gene. A total of 137 AD patients and 194 healthy controls were analyzed. Clinical criteria and neuropsychological tests were used to establish diagnostic groups. All subjects were analyzed for the COMTrs4680 polymorphism and APOEgenotype. No significant differences were observed between AD and control subjects regarding the COMT genotype frequencies of Val/Val, Val/Met and Met/Met, but Met alleles were higher in AD than in control subjects (35.4 and 28.1%, p = 0.045). A minor synergistic effect between the genotypes GG and APOEε4 was observed in AD patients (OR: 5.707, 95% CI: 2.505-13.002, p < 0.001). This synergistic effect was greater in women, who showed higher OR of AD (16.007, 95% CI: 4.606-56.118, p < 0.001) versus the AD group with APOE ε4 (11.972, 95% CI: 5.534-25.902, p < 0.001). Furthermore, the COMT Met allele was an independent risk factor for AD without APOE ε4 allele carriers (OR: 1.806, 95% CI: 1.160-2.810, p = 0.009), especially in men (OR: 4.904, 95% CI: 2.381-10.099, p < 0.001). The COMT(Val158Met) polymorphism is not an independent risk factor for AD but shows a synergistic effect between the genotypes GG and APOEε4 that proves greater in women with AD. The COMT Met allele represents a risk factor in AD without APOE ε4 allele carriers, which is notable in men with AD.
    Full-text · Article · Jan 2014
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    • "In addition to effects on neurotransmitter receptors, the data suggest that there may also be effects involving neurotransmitters. Reduction in COMT transcripts could result in impaired catecholamine degradation, increasing levels of catecholamine neurotransmitters such as dopamine and noradrenaline, which may increase risks of psychiatric disorders such as psychosis in Alzheimer's disease or schizophrenia (Bray et al., 2003; Sweet et al., 2005). Hemochromatosis patients often complain of brain-related symptoms such as severe fatigue, inability to think clearly and memory problems (Allen et al., 2008; Beutler et al., 2002; Whitlock et al., 2006). "
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    ABSTRACT: Severe disruption of brain iron homeostasis can cause fatal neurodegenerative disease, however debate surrounds the neurologic effects of milder, more common iron loading disorders such as hereditary hemochromatosis, which is usually caused by loss-of-function polymorphisms in the HFE gene. There is evidence from both human and animal studies that HFE gene variants may affect brain function and modify risks of brain disease. To investigate how disruption of HFE influences brain transcript levels, we used microarray and real-time reverse transcription polymerase chain reaction to assess the brain transcriptome in Hfe(-/-) mice relative to wildtype AKR controls (age 10 weeks, n≥4/group). The Hfe(-/-) mouse brain showed numerous significant changes in transcript levels (p<0.05) although few of these related to proteins directly involved in iron homeostasis. There were robust changes of at least 2-fold in levels of transcripts for prominent genes relating to transcriptional regulation (FBJ osteosarcoma oncogene Fos, early growth response genes), neurotransmission (glutamate NMDA receptor Grin1, GABA receptor Gabbr1) and synaptic plasticity and memory (calcium/calmodulin-dependent protein kinase IIα Camk2a). As previously reported for dietary iron-supplemented mice, there were altered levels of transcripts for genes linked to neuronal ceroid lipofuscinosis, a disease characterized by excessive lipofuscin deposition. Labile iron is known to enhance lipofuscin generation which may accelerate brain aging. The findings provide evidence that iron loading disorders can considerably perturb levels of transcripts for genes essential for normal brain function and may help explain some of the neurologic signs and symptoms reported in hemochromatosis patients.
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    • "Contrary to other genes evaluated in AD behavioural genetics the results on the role of COMT are convergent in demonstrating the COMT*H genotype as a culprit implicated in the aetiology of psychosis in AD (however, the studies by Borroni et al. evaluate – at least in part – the same population, although in various aspects). The relevance of the HH genotype or H allele for AD psychosis has been observed both in isolation [44, 45, 95] and in interaction with three other loci forming a haplotype [96, 97]. Furthermore, in one of the studies COMT*H decreased the risk for disinhibition and euphoria grouped together as a “frontal” endophenotype. "
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    ABSTRACT: Behavioural and psychological symptoms of dementia (BPSD) are present in the course of the illness in up to 90% of patients with Alzheimer's disease (AD). They are the main source of caregiver burden and one of the major factors contributing to early institutionalization. The involvement of a genetic component in BPSD aetiology seems beyond controversy, though the exact significance of particular polymorphisms is uncertain in the majority of cases. Multiple genes have been assessed for their putative influence on BPSD risk. In this paper we review the behavioural genetics of AD, particularly the importance, with respect to BPSD risk, of genes coding for apolipoprotein E and proteins involved in the process of neurotransmission: serotonin receptors, serotonin transporter, COMT, MAO-A, tryptophan hydroxylase and dopamine receptors. A general conclusion is the striking inconsistency of the findings, unsurprising in the field of psychiatric genetics. The potential reasons for such discrepancy are exhaustively discussed.
    Full-text · Article · Apr 2011
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