ACE genotype and cognitive decline in an African-Caribbean population

Genetic variation in angiotensin converting-enzyme affects the white matter integrity and cognitive function of amnestic mild cognitive impairment patients

Angiotensin-converting enzyme (ACE) gene has been implicated in amnestic mild cognitive impairment (aMCI). Most human genetic studies have focused on ACE insertion (I)/deletion (D) polymorphism and yielded conflicting results. In this work, we evaluated the relationships between cognitive function, serum ACE level, brain white matter (WM) integrity, and ACE I/D polymorphism in 48 patients with aMCI and 36 well matched control subjects from south China. In aMCI patients, D allele frequency was higher (D/I ratio=0.51:0.49) than that of the control subjects (D/I ratio=0.43:0.57); however, the difference was not statistically significant (p>0.05). The D carriers in aMCI subjects performed significantly poorer on auditory-verbal learning test (AVLT) -delayed recall than the I homozygous group (p=0.035). These carriers had higher serum ACE level than the I homozygous carriers of aMCI (p=0.037). In the aMCI group, D carriers showed significantly lower fractional anisotropy (FA) values in the left middle frontal gyrus, left anterior cingulate, right gyrus parahippocampalis, right inferior parietal lobule, and bilateral anterior central gyrus than the I homozygotes carriers. However, no significant difference was observed in FA values between I homozygotes and D carriers in the control subjects. The ACE D allele in aMCI patients may increase the risk of cognitive impairment. A high serum ACE level possibly plays an important role in the incidence of aMCI.

Association between an angiotensin-converting enzyme gene polymorphism and Alzheimer's disease in a Tunisian population

BACKGROUND

The angiotensin-converting enzyme gene (ACE) insertion/deletion (I/D or indel) polymorphism has long been linked to Alzheimer's disease (AD), but the interpretation of established data remains controversial. The aim of this study was to determine whether the angiotensin-converting enzyme is associated with the risk of Alzheimer's disease in Tunisian patients.

METHODS

We analyzed the genotype and allele frequency distribution of the ACE I/D gene polymorphism in 60 Tunisian AD patients and 120 healthy controls.

RESULTS

There is a significantly increased risk of AD in carriers of the D/D genotype (51.67% in patients vs. 31.67% in controls; p = .008, OR = 2.32). The D allele was also more frequently found in patients compared with controls (71.67% vs. 56.25%; p = .003, OR = 2.0). Moreover, as assessed by the Mini-Mental State Examination, patient D/D carriers were more frequently found to score in the severe category of dementia (65%) as compared to the moderate category (32%) or mild category (3%).

CONCLUSIONS

The D/D genotype and D allele of the ACE I/D polymorphism were associated with an increased risk in the development of AD in a Tunisian population. Furthermore, at the time of patient evaluation (average age 75 years), patients suffering with severe dementia were found predominantly in D/D carriers and, conversely, the D/D genotype and D allele were more frequently found in AD patients with severe dementia. These preliminary exploratory results should be confirmed in larger studies and further work is required to explore and interpret possible alternative findings in diverse populations.

Potential cognitive decline linked to angiotensin-converting enzyme gene but not hypertension: Evidence from cognitive event-related potentials

OBJECTIVES

The aims of the present study were to investigate the effect of hypertension and angiotensin-converting enzyme (ACE) genotypes on cognitive event-related potentials (ERPs), and whether the impact of ACE genotypes on P300 is related to the influence of hypertension.

METHODS

Using the Cognitive Abilities Screening Instrument (CASI), we recruited 97 mentally healthy middle-aged and older adults. Medical histories were collected, and blood pressure, ACE insertion/deletion polymorphisms and ERPs in an auditory oddball task were measured for all participants.

RESULTS

When the participants were stratified according to the presence or absence of hypertension, there were no differences in CASI score, percentage of ACE genotypes and ERPs. The subjects with the D/D homozygote displayed lower amplitude and longer latency of P300, although there were no differences in CASI score and the percentage of hypertension.

CONCLUSIONS

The subjects with the D/D genotype tended to have decreased amplitude and prolonged latency of P300 ERPs which reflected subtle cognitive impairment. There were no associations between hypertension, CASI score and P300 measurements.

SIGNIFICANCE

Using ERPs, potential cognitive decline was linked to ACE genotypes, independently of the effect of hypertension.

ACE polymorphism and use of ACE inhibitors: effects on memory performance

Memory is an important cognition function, being fundamental to the development and independence of individuals. Our aim was to investigate the influence apolipoprotein E (APOE) and angiotensin I-converting enzyme (ACE) polymorphism and ACE inhibitors use, besides their interaction on memory performance of healthy subjects over 50 years. The sample consisted of 205 subjects assessed for five types of episodic memory, using Wechsler Memory Scale-Revised (WMS-R), who answered a questionnaire about drug use and were assessed for the ACE insertion/deletion polymorphism and APOE polymorphism. We found no influence of the APOE gene. The use of ACE inhibitors beneficially influenced learning ability scores (p = 0.02). Besides, I allele carriers of ACE polymorphism showed higher verbal memory scores compared with homozygous DD. Also, we observed an interaction influencing learning ability between the ACE polymorphism and the use of inhibitors, the beneficial influence of the I allele was present only in individuals who make use of ACE inhibitors. We conclude that the ACE gene has influence on memory performance, and that this influence is modulated by ACE inhibitors use.

Influence of Alzheimer's disease genes on cognitive decline: the Guangzhou Biobank Cohort Study

Cognitive decline is a reduction in cognitive ability usually associated with aging, and those with more extreme cognitive decline either have or are at risk of progressing to mild cognitive impairment and dementia including Alzheimer's disease (AD). We hypothesized that genetic variants predisposing to AD should be predictive of cognitive decline in elderly individuals. We selected 1325 subjects with extreme cognitive decline and 1083 well-matched control subjects from the Guangzhou Biobank Cohort Study in which more than 30,000 southern Chinese older people have been recruited and followed up. Thirty single-nucleotide polymorphisms in 29 AD-associated genes were genotyped. No statistically significant allelic associations with cognitive decline were found by individual variant analysis. At the level of genotypic association, we confirmed that the APOE ε4 homozygote significantly accelerated cognitive decline and found that carriers of the ACE rs1800764_C allele were more likely to show cognitive decline than noncarriers, particularly in those without college education. However, these effects do not survive after multiple testing corrections, and together they only explain 1.7% of the phenotypic variance in cognitive score change. This study suggests that AD risk variants and/or genes are not powerful predictors of cognitive decline in our Chinese sample.

No association of angiotensin I converting enzyme I/D polymorphism with domain-specific cognitive function in aged men without dementia

Previous research studies have related the insertion/deletion (I/D) polymorphism of the angiotensin I converting enzyme (ACE) gene to cognitive function in various neuropsychiatric or neurodegenerative disorders, but not yet investigated its genetic association with specific cognitive domains. Thus, the aim of this study was to assess the possible association of the ACE I/D polymorphism with domain-specific cognitive function in normal cognitive aging. Four hundred and sixty-nine-aged ethnic Chinese men without dementia were enrolled for genotyping and evaluated using several neuropsychological tests [Mini-Mental Status Examination (MMSE), Digit Span Forward and Backward, and Cognitive Ability Screening Instrument Chinese language version (CASI C-2.0)]. No direct association was found between ACE genotypes and the MMSE, Digit Span tests, or CASI total scores. Although subjects with I/I genotype had the lowest cognitive performance in the CASI visual construction domain (P = 0.031), this statistical difference disappeared after correction for multiple comparisons. This study suggests that the ACE I/D polymorphism does not have any genetic association with global or specific cognitive domain in aged men without dementia.

ACE I/D polymorphism affects cognitive function and gray-matter volume in amnestic mild cognitive impairment

To characterize the correlates of cognitive function, serum concentrations of angiotensin converting enzyme (ACE) and brain structure with the ACE insertion or deletion (I/D) polymorphism were analyzed in subjects with amnestic-mild cognitive impairment (aMCI). A group of 48 subjects meeting criteria for aMCI and 36 age-matched control subjects were assessed using a comprehensive battery of standardized neuropsychological tests and magnetic resonance imaging (MRI). The ACE gene's I/D polymorphism was analyzed by means of PCR, and serum ACE concentrations were measured using ultraviolet spectrophotometry. Genotype effects on neuropsychological domains and MRI gray matter volume (GMV) measurements (optimized voxel-based morphometry) were examined using general linear models. The D carriers among the aMCI subjects performed significantly worse on AVLT-delayed recall compared to the I homozygous group. The D carriers had higher serum ACE concentrations than did the I homozygous carriers, though this difference only reached statistical significance in the aMCI group. Compared with the I homozygous carriers, in the aMCI group, D carriers showed smaller GMV of the bilateral middle frontal gyrus, right cuneus, right precentral gyrus, right medial frontal gyrus, right superior frontal gyrus, and left postcentral gyrus. However, there was no significant difference in GMV between I homozygous and D carriers in the normal control group. The study suggests that ACE genotype has considerable effect on the cognitive performance of aMCI subjects, particularly episodic memory, serum activity of ACE, and the structure of specified brain regions. The ACE D allele may be a genetic risk factor for greater atrophy of gray matter in aMCI.

The associations of apolipoprotein E and angiotensin-converting enzyme polymorphisms and cognitive function in Type 1 diabetes based on an 18-year follow-up of the DCCT cohort

AIMS

Specific polymorphisms of the apolipoprotein E (APOE) and angiotensin-converting enzyme (ACE) genes appear to increase risk for Alzheimer's disease and cognitive dysfunction in the general population, yet little research has examined whether genetic factors influence risk of cognitive dysfunction in patients with Type 1 diabetes. The long-term follow-up of the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) population provides an opportunity to examine if specific genetic variations in APOE and ACE alter risk for cognitive decline.

METHODS

Neurocognitive function in Type 1 diabetic subjects from the DCCT/EDIC study was assessed at DCCT entry and re-assessed approximately 18 years later, using a comprehensive cognitive test battery. Glycated haemoglobin (HbA(1c)) and the frequency of severe hypoglycaemic events leading to coma or seizures were measured over the 18-year follow-up. We determined whether the APO epsilon4 and ACE intron 16 indel genotypes were associated with baseline cognitive function and with change over time, and whether they conferred added risk in those subjects experiencing severe hypoglycaemic events or greater glycaemic exposure.

RESULTS

None of the APOE or ACE polymorphisms were associated with either baseline cognitive performance or change in cognition over the 18-year follow-up. Moreover, none of the genotype variations altered the risk of cognitive dysfunction in those subjects with severe hypoglycaemic episodes or high HbA(1c).

CONCLUSIONS

In this sample of young and middle-aged adults with Type 1 diabetes, APO epsilon4 and ACE D alleles do not appear to increase risk of cognitive dysfunction.

Sialic acid, homocysteine and CRP: potential markers for dementia

To investigate whether sialic acid could discriminate between healthy age matched controls and patients with dementias of the Alzheimer's type (AD), and pure vascular dementia (VaD). 27 patients and 51 controls were administered the Mini-Mental State Examination (MMSE) and had blood analyzed for levels of total sialic acid, total homocysteine (tHcy), and C-reactive protein (CRP). Significant differences were found between the mean MMSE scores for patients with dementia compared with controls. Sialic acid levels were significantly higher in patients with AD compared with controls and homocysteine levels were higher in VaD. Sialic acid levels discriminated between patients with dementia of the Alzheimer's type and healthy controls only. The MMSE could discriminate between controls and patients with dementia but not between the subtypes and homocysteine was significant for patients with VaD.

Psychiatry of old age and ethnic minority older people in the United Kingdom

This review examines the demographic changes, the epidemiology of mental disorders and suicides, the potential risk and protective factors, access to secondary care old age psychiatry services (OAPSs) and the policy context pertaining to older people from ethnic minority groups in the United Kingdom. The number of older people from ethnic minority groups is increasing. The prevalence of mental disorders in older people from ethnic minority groups is either similar to or higher than that in the indigenous population. Therefore, the number of older people from ethnic minority groups with psychiatric morbidity is also increasing. Ethnic minority older people also have inequity of access to secondary care OAPSs. There is an urgent need to develop and implement practical strategies to improve access by older people from ethnic minority groups to OAPSs.

A systematic review of the prevalence and covariates of dementia or relative cognitive impairment in the older African-Caribbean population in Britain

OBJECTIVES

To collate evidence regarding the prevalence and predictors of dementia or relative cognitive impairment in older, African-Caribbean people in Britain, as compared to their white, British peers.

DESIGN

We conducted a systematic literature review by searching electronic databases, contacting experts in the field and searching the references of identified papers for studies fulfilling our predefined inclusion criteria. They were divided into those measuring the prevalence or incidence of dementia or cognitive impairment, and those investigating risk factors. Each study selected for inclusion, was evaluated by two of the three authors using a standardised checklist and assigned a numerical score for quality.

RESULTS

Eleven papers fulfilled the selection criteria. Two cross-sectional surveys had calculated prevalence of dementia in a sample of British African-Caribbean people. A further prevalence study had estimated dementia prevalence in a mixed sample of African and African-Caribbean participants. All the comparative studies found an excess of dementia in African-Caribbean people when compared to the indigenous, white population but in one study, this was not statistically significant. Seven studies investigated potential predictive factors for cognitive impairment or cognitive decline. One study investigated the association between hypertension, dementia and country of birth.

CONCLUSIONS

The published research in this area is limited. The available studies consistently indicate an excess of dementia in older African-Caribbean people when compared to the indigenous white population. However, the magnitude of this difference and the associated risk factors are not clear, and warrant further investigation.

Markers of inflammation and cognitive decline in an African-Caribbean population

BACKGROUND

Inflammatory processes may play an important role in cognitive decline and dementia. We investigated the prospective association between levels of three markers of inflammation, plasma interleukin-6 (IL-6), serum C-reactive protein (CRP), serum amyloid A (SAA), and cognitive decline in an African-Caribbean community population.

METHODS

Of 290 participants aged 55-75 years at baseline sampled from Primary Care registration lists in south London, 216 (75%) were re-interviewed after 3 years. Baseline plasma concentrations of IL-6, CRP and SAA were ascertained through immunoassays. A battery of psychometric tests was administered on both occasions and decline in both individual tests and a composite outcome was analysed.

RESULTS

After adjustment for potential confounding factors, raised levels of IL-6 (>3.1 pg/ml) were associated with cognitive decline in the total sample (odds ratio 2.9, 95% CI 1.1-7.5), but no associations were found for CRP or SAA. Raised IL-6 was most strongly associated with decline in orientation and immediate verbal recall tasks, with weaker associations for delayed recall and psychomotor speed.

CONCLUSIONS

Raised IL-6 but not CRP predicted cognitive decline in this population Inflammatory changes associated with cognitive decline may be specific to particular causal pathways.

Potential biomarkers for dementia in Trinidad and Tobago

Biomarkers that could possibly discriminate between healthy controls and patients with dementias of the Alzheimer's type (AD) and vascular dementia (VaD) were investigated. The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition TR (DSM IV TR) was used to diagnose for dementia in Trinidad. Healthy seniors greater than 60 years old were controls. All participants were administered the Mini-Mental State Examination (MMSE) and had blood analyzed for levels of C-reactive protein (CRP), total homocysteine (tHcy) and microglial antibodies (MgAb). Plasma tHcy was determined on the Abbot AxSym, serum CRP concentrations were measured using the Tina-Quant sCRP (Latex) high sensitive immunoturbidimetric assay and serum MgAb were examined on frozen rat brain sections. The study was carried out on 29 patients that fulfilled the inclusion criteria and 46 controls. Of the patients 65.5% had AD and 34.5% had VaD. Significant differences were found between the mean MMSE scores of the different types of dementias and controls. MgAb presence as well as tHcy were able to distinguish between controls and dementia of the AD and VaD type, respectively. The MMSE is a good discriminative tool for dementias. Serum MgAbs are a possible biomarker for Alzheimer disease pathology and tHcy is elevated in patients with vascular dementia.

Genetic influences on outcome following traumatic brain injury

Several genes have been implicated as influencing the outcome following traumatic brain injury (TBI). Currently the most extensively studied gene has been APOE. APOE can influence overall and rehabilitation outcome, coma recovery, risk of posttraumatic seizures, as well as cognitive and behavioral functions following TBI. Pathologically, APOE is associated with increased amyloid deposition, amyloid angiopathy, larger intracranial hematomas and more severe contusional injury. The proposed mechanism by which APOE affects the clinicopathological consequences of TBI is multifactorial and includes amyloid deposition, disruption of cytoskeletal stability, cholinergic dysfunction, oxidative stress, neuroprotection and central nervous system plasticity in response to injury. Other putative genes have been less extensively studied and require replication of the clinical findings. The COMT and DRD2 genes may influence dopamine dependent cognitive processes such as executive/frontal lobe functions. Inflammation which is a prominent component in the pathophysiological cascade initiated by TBI, is in part is mediated by the interleukin genes, while apoptosis that occurs as a consequence of TBI may be modulated by polymorphisms of the p53 gene. The ACE gene may affect TBI outcome via mechanisms of cerebral blood flow and/or autoregulation and the CACNA1A gene may exert an influence via the calcium channel and its effect on delayed cerebral edema. Although several potential genes that may influence outcome following TBI have been identified, future investigations are needed to validate these genetic studies and identify new genes that might influence outcome following TBI.

No observable relationship between the ACE gene insertion/deletion polymorphism and psychometric IQ and psychomotor ability in Chinese children

The primary aim of this study was to investigate the impact of the angiotensin I-converting enzyme gene (ACE) on general cognitive ability, specific cognitive ability and psychomotor function in Chinese children. In total, 450 children completed both C-WISC tests and ACE I/D genotyping. Of these, 320 children were examined using psychomotor tests. The quantitative traits of psychometric IQ and psychomotor abilities were calculated to determine whether there were any significant differences related to their ACE genotypes on the basis of an analysis of variance. F test results showed no significant differences with regard to any aspect of intelligence or psychomotor performance relative to the various ACE I/D genotypes (all p > 0.05). Our study suggests that ACE I/D do not have a measurable impact on any aspects of IQ or psychomotor ability and that psychomotor ability correlates well with IQ in Chinese children.