Association between angiotensin-converting enzyme and Alzheimer disease

BACKGROUND

Angiotensin-converting enzyme has been reported to show altered activity in patients with neurologic diseases. An insertion-deletion polymorphism in ACE has recently been linked to heart disease, cerebrovascular disease, and AD.

OBJECTIVE

To determine whether the angiotensin-converting enzyme (ACE) is associated with risk of Alzheimer disease (AD).

METHODS

We investigated the ACE polymorphism as a potential risk factor for AD in 151 patients with AD and 206 ethnically matched controls from Russia and in 236 patients with AD and 169 controls from North America by means of allele association methods and logistic regression.

RESULTS

None of the ACE genotypes was associated with increased susceptibility to AD in the total sample or in subsets stratified by apolipoprotein E gene (APOE) epsilon4 status. However, the D allele was more frequent among AD cases between ages 66 and 70 years compared with controls in both the Russian (P = .02) and North American (P = .001) datasets. In this age group, the effect of D (odds ratio, 11.2; 95% confidence interval, 2.9-44.0) appeared to be independent of and equal or greater in magnitude to the effect of APOE epsilon4 (odds ratio, 7.8; 95% confidence interval, 3.5-7.4).

CONCLUSIONS

Our results suggest that APOE and ACE genotypes may be independent risk factors for late-onset AD, but the ACE association needs to be confirmed in independent samples in which the time and extent of vascular cofactors can be assessed.

5-HT2A receptor gene polymorphisms in anorexia nervosa and bulimia nervosa

To examine the distribution of different polymorphisms in genes of the 5-HT system in patients with anorexia nervosa (AN) and bulimia nervosa (BN), we analyzed the distribution of a polymorphism (-1438G/A) and the presence of known mutations in 5-HT2A and 5-HT2C receptor genes in 168 Italian female patients affected by AN and BN. Patients with AN restricting type (ANr) only, unlike those with AN binge eating/purging type (ANp) and BN purging type (BNp), showed a statistically significant difference in 5-HT2A-1438A/A genotype frequency with respect to controls. With regard to the other polymorphisms, no differences were found in the studied groups with respect to controls. 5-HT2A promoter polymorphism is probably implicated in the susceptibility to eating disorders and its involvement is more significant in ANr, when compared with ANp and BNp.

Association of the estrogen receptor alpha gene polymorphisms with sporadic Alzheimer's disease

Alzheimer's disease (AD) is a multifactorial disorder determined by the interaction of genetic, metabolic, and environmental factors. In the common late-onset familial and sporadic forms of AD apolipoprotein E type 4 allele (APOE-epsilon4) is now widely accepted as a major risk factor. The association of estrogen treatment with a reduction in the risk of AD together with the modulation by estrogen of the secretory metabolism of the amyloid precursor protein offers new possibilities for identification of other AD susceptibility genes, as those encoding for the estrogen receptors (ERs). A total of 193 patients with sporadic late-onset AD, meeting the NINCDS-ADRDA criteria, and a total of 202 control subjects, age and education matched, were included in this study. PvuII and XbaI ERalpha and HhaI APOE gene polymorphisms were evaluated in genomic DNA by Polymerase Chain Reaction (PCR). The frequency of the various ERalpha genotypes by the combination of P, p and X, x was calculated for controls and AD patients stratified based on ApoE typing. When the two ERalpha gene polymorphisms were analyzed in combination, 7 genotypes were recognized, with a significantly increased prevalence of PPXX genotype in AD patients compared to controls (P = 0.0001). Risk of AD increased by a factor of 7.6 (CI [1.10-62.3]) in homozygous APOE-epsilon4 individuals with PPXX ERalpha genotype. These results are consistent with a segregation of PPXX ERalpha genotype with a higher risk of developing late-onset sporadic AD in the Italian population. The ERalpha gene appears to interact with the APOE-epsilon4 genotype in determining AD susceptibility.

Gluthatione level is altered in lymphoblasts from patients with familial Alzheimer's disease

Intracellular levels of glutathione (GSH), glutathione disulphide (GSSG), glutamic acid and gamma-glutamyl cysteine synthetase (gamma-GCS) were measured in lymphoblast lines from patients with familial and sporadic Alzheimer's disease (AD) and from age-matched controls. Lymphoblasts carrying presenilins (PS) and amyloid precursor protein (APP) genes mutations showed significantly decreased GSH content with respect to controls. Levels of GSSG and glutamic acid, as well as the activity of gamma-GCS were not significantly different in lymphoblasts carrying genes mutations as compared with control cells. These results indicate that even peripheral cells not involved in the neurodegenerative process of AD show altered GSH content when carrying PS and APP genes mutations. The provided data appear to be in accordance with the known alteration of GSH levels in central nervous system and strengthen the hypothesis of oxidative stress as an important, possibly crucial mechanism in the pathogenesis of AD.

HLA A2 allele is associated with age at onset of Alzheimer's disease

The prevalence of the HLA A2 allele was investigated in a group of Italian patients with sporadic and early-onset familial Alzheimer's disease (AD and FAD) to analyze the potential association of this allele with early age of onset of the disease. The possible interaction between the HLA A2 allele and apolipoprotein E epsilon4 allele was analyzed. Our data suggest that A2 and epsilon4 alleles may have additive effects on AD onset, and that A2 may play an important role in determining or contributing to a very early age at onset. These findings further support the hypothesis of the involvement of an immune/inflammatory mechanism in the pathogenesis of AD.

Association between bleomycin hydrolase and Alzheimer's disease in caucasians

A recent study showed modest evidence for an increased frequency of the bleomycin hydrolase (BH) V/V genotype in Alzheimer's disease (AD) patients compared with non-demented controls. To test this hypothesis, we examined this polymorphism in 621 rigorously evaluated patients and 502 control subjects (all caucasian) but were unable to detect an association between BH and AD even after controlling for age, gender, and apolipoprotein E (ApoE) genotype. We conclude that this polymorphism does not account for inherited susceptibility to AD in the populations represented in this sample.

Evidence for an Alzheimer disease susceptibility locus on chromosome 12 and for further locus heterogeneity

CONTEXT

Alzheimer disease (AD) susceptibility genes have been identified on chromosomes 1, 14, 19, and 21, and a recent study has suggested a locus on chromosome 12.

OBJECTIVE

To confirm or refute the existence of a familial AD susceptibility locus on chromosome 12 in an independent sample of familial AD cases.

DESIGN

Retrospective cohort study. DNA data for 6 chromosome 12 genetic markers were evaluated using parametric lod score and nonparametric linkage methods and linkage heterogeneity tests. The latter include the admixture test of homogeneity in the total group of families and the predivided sample test in families stratified by the presence or absence of an apolipoprotein E (APOE) epsilon4 allele among affected members. Parametric analyses were repeated assuming autosomal dominant inheritance of AD and either age- and sex-dependent penetrance or zero penetrance for the analysis of unaffected relatives.

SETTING

Clinical populations in the continental United States, Canada, Argentina, and Italy.

PATIENTS

Fifty-three white families composed of multiple members affected with AD, from whom DNA samples were obtained from 173 patients with AD whose conditions were diagnosed using established criteria and from 146 nondemented relatives.

MAIN OUTCOME MEASURE

Presence of an APOE epsilon4 allele among affected family members.

RESULTS

Using parametric methods, no evidence for linkage to the region spanned by the chromosome 12 markers could be detected if familial AD is assumed to arise from the same genetic locus in all 53 families. However, significant evidence for linkage was detected in the presence of locus heterogeneity using the admixture test (odds ratio, 15, 135:1). The estimated proportion of linked families within the 53 families examined varied between 0.40 and 0.65, depending on the genetic model assumed and APOE status. The precise location of the AD gene could not be determined, but includes the entire region suggested previously. Nonparametric linkage analysis confirmed linkage to chromosome 12 with the strongest evidence at D12S96 (P<.001).

CONCLUSIONS

Our data provide independent confirmation of the existence of an AD susceptibility locus on chromosome 12 and suggest the existence of AD susceptibility genes on other chromosomes. Screening a larger set of families with additional chromosome markers will be necessary for identifying the chromosome 12 AD gene.

Absence of association between Alzheimer disease and the -491 regulatory region polymorphism of APOE

A novel polymorphism (-491 A/T) within the regulatory region on the apolipoprotein E gene has recently been reported to be associated with risk for Alzheimer disease (AD). To test this association in an independent data set, we have examined this polymorphism in a sample of 88 well-characterized AD cases and compared the allele frequency and genotype frequencies for this polymorphism with those observed in 112 cognitively normal subjects drawn from the same ethnic group. These results suggest that in the current data set at least, the -491 A/T polymorphism is not associated with risk for AD, but may be in partial linkage disequilibrium with the APOE epsilon2/epsilon3/epsilon4 polymorphism.

Analysis of the butyrylcholinesterase gene and nearby chromosome 3 markers in Alzheimer disease

The K-variant of butyrylcholinesterase (BCHE-K) recently has been reported to be associated with Alzheimer disease (AD) in carriers of the epsilon4 allele of the apolipoprotein E (APOE) gene. We have re-examined the frequency of the BCHE-K allele in a large data set of both sporadic and familial cases of AD disease, and we have also examined the segregation of three genetic markers on chromosome 3 near BCHE . Our data neither support an association of BCHE-K with sporadic or familial AD, nor do they suggest the existence of another gene nearby on chromosome 3 as a common cause of familial AD.

Growth properties and growth factor responsiveness in skin fibroblasts from centenarians

Human fibroblast cultures, which have a finite replicative lifespan in vitro, are the most widely used model for the study of senescence at the cellular level. An inverse relationship between replicative capability and donor age has been reported in human fibroblast strains. We studied the growth capacity of fibroblast primary cultures derived from people whose lifespan was as closer as possible to the expected maximum human lifespan, i.e. people over one hundred. Our data suggest that outgrowth of fibroblasts from biopsies, growth kinetics at different population doubling levels, capability to respond to a classical mitogenic stimulus (such as 20% serum) and a variety of growth factors, were remarkably similar in fibroblasts from centenarians and young controls. On the whole, our data challenge the tenet of a simple and strict relationship between in vivo aging and in vitro proliferative capability of human fibroblasts, at least at the individual level.

No implication of apolipoprotein E polymorphism in Italian schizophrenic patients

Numerous studies have provided evidence for a genetic association of the Apolipoprotein E (ApoE) epsilon4 allele and late onset familial and sporadic Alzheimer's disease (AD). Clinical observations show that a proportion of schizophrenic patients may suffer from severe cognitive impairment. That could reflect a particular clinical aspect of this mental disorder or a common, yet unknown, neurodegenerative mechanism. We analysed the ApoE gene polymorphism in a sample of 69 Italian patients with schizophrenia, 140 AD patients and 121 controls. In schizophrenic patients, the distribution of ApoE genotypes does not significantly differ from that of controls. No effect of the ApoE genotype on age of onset was found. The frequency of ApoE alleles in Italian schizophrenic patients is comparable with control values, suggesting that ApoE polymorphism does not represent a risk factor for schizophrenia.

Implication of alpha1-antichymotrypsin polymorphism in familial Alzheimer's disease

A common polymorphism in the alpha1-antichymotrypsin (ACT) gene has been shown to modify the Apolipoprotein E (ApoE) epsilon4-associated Alzheimer's disease (AD) risk identifying the combination of the ACT/AA and ApoE epsilon4/epsilon4 genotypes as a potential susceptibility marker for AD. Using the polymerase chain reaction, we analyzed the segregation of the ACT and ApoE polymorphisms in familial Alzheimer's disease (FAD) patients carrying mutations in Presenilin (PS) and APP genes and in both early onset (EO) and late onset (LO) FAD patients without known mutations. Our data suggest that ACT does not represent an additional risk factor for PS and APP mutated families. However, in LOFAD patients a high frequency of the combined ACT/AA and ApoE epsilon4/epsilon4 genotypes suggest that ACT may interact with ApoE and play a role in LOFAD.

Inherent abnormalities in oxidative metabolism in Alzheimer's disease: interaction with vascular abnormalities

Extensive studies over the last 20 years have documented the existence of inherent abnormalities in oxidative/energy metabolism in Alzheimer's disease (AD). These abnormalities can be linked to characteristics of AD by plausible pathophysiological mechanisms for which there is abundant, robust evidence. The inherent abnormalities in cerebral metabolism of oxygen and glucose can reasonably be expected to interact synergistically with vascular compromise of cerebral oxygen and glucose metabolism in causing brain damage in AD.

Analysis of apolipoprotein E, alpha1-antichymotrypsin and presenilin-1 genes polymorphisms in dementia caused by normal pressure hydrocephalus in man

Normal pressure hydrocephalus (NPH) is characterized by dementia, gait disorders and urinary incontinence. Apolipoprotein E (ApoE) epsilon4 allele has been associated with severity of dementia in Alzheimer's disease (AD) and in other forms of dementia. Moreover, homozygosity of the A allele of the alpha1-antichymotrypsin (ACT) gene and of allele 1 of the presenilin-1 (PS-1) gene was associated with an increased risk for late onset AD. We analyzed the distribution of ApoE, ACT and PS-1 genotypes and the corresponding allele frequencies in 13 NPH patients. No differences were found in ACT and PS-1 polymorphism distributions in the patients studied with respect to the control group. An increased ApoE epsilon4 allele frequency was observed in NPH patients with respect to controls, thus suggesting that epsilon4 allele may also be involved in the pathogenesis of the disease.

Alpha1 antichymotrypsin signal peptide polymorphism in sporadic Creutzfeldt-Jakob disease

In Creutzfeldt-Jakob disease (CJD), a transmissible spongiform encephalopathy, the deposition of the pathological prion protein (PrP-res) in the brain of affected individuals is the key event that triggers the appearance of the disease. Since a polymorphism in the signal peptide of the serine-protease inhibitor alpha1 antichymotrypsin (ACT) is one of the factors that may enhance amyloid formation, we studied this polymorphism in 63 CJD patients and 103 control subjects. No difference in allele frequencies and genotype distribution was found between CJD cases and controls, nor any difference was found between the ACT genotype and the age at onset and disease duration. Interestingly, there was a significantly different (P = 0.04) ACT distribution between CJD patients and controls in apolipoprotein E (ApoE) E4, and the interaction between ACT and ApoE was almost significant (P = 0.053). Further studies on a larger number of patients will clarify whether this association can identify a possible risk factor for CJD.

Presenilin-1 gene intronic polymorphism in sporadic and familial Alzheimer's disease

A recent observation has shown a genetic association between an intronic polymorphism in the Presenilin-1 (PS-1) gene and late onset Alzheimer's disease (AD). The homozygosity of the 1 allele in the PS-1 gene was associated with a doubling of the risk for late onset AD. However, contrasting results have been published. We analyzed the distribution of the PS-1 intronic polymorphism in patients with sporadic AD and in seven familial AD (FAD) families carrying pathogenetic mutations in the amyloid precursor protein (APP) and Presenilin (PS-1 and PS-2) genes. Significant differences in PS-1 allele frequencies were observed in the Presenilin genes mutated families but not in late onset AD patients and in APP mutated families.

Confirmation of association between expanded CAG/CTG repeats and both schizophrenia and bipolar disorder

Recent studies have suggested that expanded CAG/CTG repeats contribute to the genetic aetiology of schizophrenia and bipolar disorder. However, the nature of this contribution is uncertain and difficult to predict from other known trinucleotide repeat diseases that display much simpler patterns of inheritance. We have sought to replicate and extend earlier findings using Repeat Expansion Detection in an enlarged sample of 152 patients with schizophrenia, 143 patients with bipolar disorder, and 160 controls. We have also examined DNA from the parents of 62 probands with schizophrenia or bipolar disorder. Our results confirm our earlier, preliminary findings of an association between expanded trinucleotide repeats and both schizophrenia and bipolar disorder. However, our data do not support the hypothesis that trinucleotide repeat expansion can alone explain the complex patterns of inheritance of the functional psychoses neither can this mechanism fully explain apparent anticipation.

Apolipoprotein E and alpha1-antichymotrypsin polymorphism in Alzheimer's disease

A recent observation has shown that a common polymorphism in the alpha1-antichymotrypsin (ACT) gene modifies the apolipoprotein E (ApoE) epsilon4-associated Alzheimer's disease (AD) risk identifying the combination of the ACT/AA and ApoE epsilon4/epsilon4 genotypes as a potential susceptibility marker for AD. We analyzed the segregation of the ApoE and ACT polymorphism in sporadic and familial AD patients. In none of the sporadic AD patients did we find the combination of the ACT/AA and ApoE epsilon4/epsilon4 genotypes. The frequency of ApoE epsilon4/epsilon4 homozygosity in the AD sample resulted highest for the ACT/ TT genotype (17.6%). Our data fail to confirm any additional association with AD beyond the ApoE epsilon4 allele with any ACT genotype, suggesting that ACT does not represent an additional risk factor for AD.