Apolipoprotein E, angiotensin-converting enzyme and kallikrein gene polymorphisms and the risk of Alzheimer's disease and vascular dementia

Genetic Susceptibility Variants of Vascular Dementia among Asians: A Systematic Review and Meta-Analysis

INTRODUCTION

Vascular dementia (VaD), a neurocognitive impairment directly related to vascular injury, is the second most common cause of age-related dementia. Although numerous studies have investigated candidate genetic polymorphisms associated with VaD in Asia, the genetics of VaD remains unclear.

METHODS

This review provides an updated meta-analysis of genetic polymorphisms associated with VaD in Asians, using the PRISMA guidelines. Published literature up to May 2021 was extracted from the PubMed, Scopus, Ovid, and EBSCOhost databases. Meta-analysis was conducted using the Open Meta analyst, Review Manager, and MedCalc® Statistical Software. Trial sequential analysis (TSA) was performed using TSA viewer software.

RESULTS

A total of 46 eligible studies, comprising 23 genes and 35 single nucleotide polymorphisms, were retrieved. The meta-analysis was conducted on the following genetic polymorphisms, APOE ε2/3/4, MTHFR rs1801131, ACE rs4340 (I/D) gene polymorphism, and a PSEN1 intron 8 variant. The pooled odds ratio (ORs) revealed a significant increase in the risk of VaD in the apolipoprotein E (APOE) ε4 allelic model (OR, 1.79, p < 0.001), and the methylenetetrahydrofolate reductase (MTHFR) rs1801133 polymorphism T allele in the allelic model (OR, 1.23, p = 0.013).

CONCLUSION

Our findings provide evidence that genetic polymorphisms of the APOE ε4 allele and MTHFR rs1801133 T allele increase the risk of developing VaD in Asians. However, future large-scale investigations examining particularly on South-Eastern and West-Asian populations are highly recommended.

Kallikrein-related peptidase's significance in Alzheimer's disease pathogenesis: A comprehensive survey

Alzheimer's disease (AD) and related dementias constitute an important global health challenge. Detailed understanding of the multiple molecular mechanisms underlying their pathogenesis constitutes a clue for the management of the disease. Kallikrein-related peptidases (KLKs), a lead family of serine proteases, have emerged as potential biomarkers and therapeutic targets in the context of AD and associated cognitive decline. Hence, KLKs were proposed to display multifaceted impacts influencing various aspects of neurodegeneration, including amyloid-beta aggregation, tau pathology, neuroinflammation, and synaptic dysfunction. We propose here a comprehensive survey to summarize recent findings, providing an overview of the main kallikreins implicated in AD pathophysiology namely KLK8, KLK6 and KLK7. We explore the interplay between KLKs and key AD molecular pathways, shedding light on their significance as potential biomarkers for early disease detection. We also discuss their pertinence as therapeutic targets for disease-modifying interventions to develop innovative therapeutic strategies aimed at halting or ameliorating the progression of AD and associated dementias.

Pharmacogenetics of angiotensin modulators according to APOE-ϵ4 alleles and the ACE insertion/deletion polymorphism in Alzheimer's disease

OBJECTIVE

In Alzheimer's disease (AD), angiotensin II receptor blockers (ARBs) could reduce cerebrovascular dysfunction, while angiotensin-converting enzyme inhibitors (ACEis) might increase brain amyloid-β by suppressing effects of the angiotensin-converting enzyme 1, an amyloid-β-degrading enzyme. However, ACEis could benefit patients with AD by reducing the amyloidogenic processing of the amyloid precursor protein, by central cholinergic and anti-inflammatory mechanisms, and by peripheral modulation of glucose homeostasis. We aimed to investigate whether the ACE insertion/deletion polymorphism is associated with clinical changes in patients with AD, while considering apolipoprotein E (APOE)-ϵ4 carrier status and blood pressure response to angiotensin modulators.

METHODS

Consecutive outpatients with late-onset AD were screened with cognitive tests and anthropometric measurements, while their caregivers were queried for functional and caregiver burden scores. Prospective pharmacogenetic associations were estimated for 1 year, taking APOE-ϵ4 carrier status and genotypes of the ACE insertion/deletion polymorphism into account, along with treatment with ACEis or ARBs.

RESULTS

For 193 patients (67.4% women, 53.4% APOE-ϵ4 carriers), the ACE insertion/deletion polymorphism was in Hardy-Weinberg equilibrium (p = 0.281), while arterial hypertension was prevalent in 80.3% (n = 124 used an ACEi, n = 21 used an ARB). ARBs benefitted mostly APOE-ϵ4 carriers concerning caregiver burden variations, cognitive and functional decline. ACEis benefitted APOE-ϵ4 non-carriers concerning cognitive and functional decline due to improved blood pressure control in addition to possible central mechanisms. The ACE insertion/deletion polymorphism led to variable response to angiotensin modulators concerning neurological outcomes and blood pressure variations.

CONCLUSION

Angiotensin modulators may be disease-modifiers in AD, while genetic stratification of samples is recommended in clinical studies.

Protective effect of apolipoprotein E epsilon 3 on sporadic Alzheimer's disease in the Chinese population: a meta-analysis

Alzheimer's disease (AD) is fast becoming one of the most expensive, deadly and burdensome diseases in this century. It has the fastest-growing disease burden in China. Apolipoprotein E (APOE) polymorphic alleles are generally considered to be the primary genetic determinant of AD risk: individuals with the E4 allele are at increased risk of AD compared with individuals with the more common E3 allele. Since the intensity of the association varies among different ethnic groups, a separate meta-analysis of the Chinese population is needed. We searched Chinese and English databases to sift through literature over the past 20 years. Data on the APOE genotype and AD were collected for correlation analysis. OR was calculated according to APOE allele and genotype. A publication bias analysis and sensitivity analysis were performed, and the main results were further verified by subgroup analysis. The 116 eligible studies enrolled 23,396 patients with AD and 25,568 healthy controls. The study subjects covered at least 30 of the 34 provincial-level administrative regions (including Taiwan). The partial sex ratio was as follows: AD male/female; 10,291/11,240; control male/female, 11,304/12,428, [Formula: see text] = 0.122, P = 0.727. The results of the meta-analysis of alleles showed that I² > 50% and Q statistics were significant for all genotypes; therefore, the random effect model was selected. The frequency of the ApoE ε4 allele in AD was higher than that in healthy controls, and the difference was statistically significant (OR 2.847, 95% CI [2.611-3.101], P < 0.001). The frequencies of ApoE ε3 and ε2 in AD were lower than those in healthy controls, and the differences were statistically significant (ε3: OR 0.539, 95% CI [0.504-0.576], P < 0.001; ε2: OR 0.771, 95% CI [0.705-0.843], P < 0.001). The results of the meta-analysis of AD genotype showed that ApoE ε2/ε4 (OR 1.521, 95% CI [1.270-1.823], P < 0.001), ε3/ε4 (OR 2.491, 95% CI [2.267-2.738], P < 0.001) and ε4/ε4 (OR 5.481, 95% CI [4.801-6.257], P < 0.001) allele genotype frequencies were higher than those of the healthy controls. The differences were all statistically significant. Moreover, the ApoE ε2/ε2 (OR 0.612, 95% CI [0.504-0.743], P < 0.001), ε2/ε3 (OR 0.649, 95% CI [0.585-0.714], P < 0.001) and ε3/ε3 (OR 0.508, 95% CI [0.468-0.551], P < 0.001) genotypes were less frequent in patients with AD than in healthy controls, and the differences were statistically significant. The results of the sensitivity analysis and subgroup analysis were consistent with those of the whole model. These results provide support for the protective effect of the ApoE ε3/ε3 genotype against the development of AD. This research is the most comprehensive meta-analysis of the correlation between APOE and AD in the Chinese population by analysing the distribution of the APOE gene in patients with AD reported in the last 20 years. It was concluded that the APOE ε3 allele had a protective effect against sporadic AD in the Chinese population, with great significance, and that its protective effect was stronger than that of the ε2 allele.

Effects of exercise training on brain metabolism and cognitive functioning in sleep apnea

Impaired glucose metabolism reflects neuronal/synaptic dysfunction and cognitive function decline in patients with obstructive sleep apnea (OSA). The study investigated the extent to which exercise training (ET) improves cerebral metabolic glucose rate (CMRgl) and cognitive function in patients with OSA. Patients with moderate to severe OSA were randomly assigned to ET (3 times/week, n = 23) or no intervention (control, n = 24). Echocardiography and apolipoprotein ε4 (APOEε4) genotyping were obtained at baseline. Both groups underwent cardiopulmonary exercise testing, polysomnography, cognitive tests, brain magnetic resonance imaging, and ¹⁸F-fluoro-2-deoxy-d-Glucose positron emission tomography (¹⁸FDG-PET) at baseline and study end. Compared with control, exercise-trained group had improved exercise capacity, decreased apnea–hypopnea index (AHI), oxygen desaturation and arousal index; increased attention/executive functioning, increased CMRgl in the right frontal lobe (P < 0.05). After ET an inverse relationships occurred between CMRgl and obstructive AHI (r = − 0.43, P < 0.05) and apnea arousal index (r = − 0.53, P < 0.05), and between the changes in CMRgl and changes in mean O₂ saturation during sleep and non-rapid eye movement sleep (r = − 0.43, P < 0.05), desaturation during arousal (r = − 0.44, P < 0.05), and time to attention function testing (r = − 0.46, P < 0.05). ET improves OSA severity and CMRg in the frontal lobe, which helps explain the improvement in attention/executive functioning. Our study provides promising data that reinforce the growing idea that ET may be a valuable tool to prevent hypoxia associated with decreased brain metabolism and cognitive functioning in patients with moderate to severe OSA.

Trial registration: NCT02289625 (13/11/2014).

Association of the angiotensin I converting enzyme (ACE) gene polymorphisms with recurrent aphthous stomatitis in the Czech population: case–control study

Background

Recurrent aphthous stomatitis (RAS) is multifactorial disease with unclear etiopathogenesis. The aim of this study was to determine distribution of the angiotensin I converting enzyme (ACE) gene polymorphisms and their influence on RAS susceptibility in Czech population.

Methods

The study included 230 subjects (143 healthy controls and 87 patients with RAS) with anamnestic, clinical and laboratory data. Five ACE gene polymorphisms (rs4291/rs4305/rs4311/rs4331/rs1799752 = ACE I/D) were determined by TaqMan technique.

Results

The allele and genotype distributions of the studied ACE I/D polymorphisms were not significantly different between subjects with/without RAS (P_corr > 0.05). However, carriers of II genotype were less frequent in the RAS group (OR = 0.48, 95% CI = 0.21–1.12, P = 0.059). Stratified analysis by sex demonstrated lower frequency of II genotype in women (OR = 0.33, 95% CI = 0.09–1.17, P < 0.035, P_corr > 0.05, respectively) than in men with RAS (P > 0.05). Moreover, the frequency of AGTGD haplotype was significantly increased in RAS patients (OR = 13.74, 95% CI = 1.70–110.79, P = 0.0012, P_corr < 0.05). In subanalysis, TGD haplotype was significantly more frequent in RAS patients (P < 0.00001) and CGI haplotype was less frequent in RAS patients (P < 0.01), especially in women (P = 0.016, P_corr > 0.05).

Conclusions

Our study indicates that while the AGTGD and TGD haplotypes are associated with increased risk of RAS development, CGI haplotype might be one of protective factors against RAS susceptibility in Czech population.

Angiotensin-converting enzyme polymorphisms AND Alzheimer's disease susceptibility: An updated meta-analysis

Background

Many studies among different ethnic populations suggested that angiotensin converting enzyme (ACE) gene polymorphisms were associated with susceptibility to Alzheimer’s disease (AD). However, the results remained inconclusive. In the present meta-analysis, we aimed to clarify the effect of ACE polymorphisms on AD risk using all available relevant data.

Methods

Systemic literature searches were performed using PubMed, Embase, Alzgene and China National Knowledge Infrastructure (CNKI). Relevant data were abstracted according to predefined criteria.

Results

Totally, 82 independent cohorts from 65 studies were included, focusing on five candidate polymorphisms. For rs1799752 polymorphism, in overall analyses, the insertion (I) allele conferred increased risk to AD compared to the deletion (D) allele (I vs. D: OR = 1.091, 95% CI = 1.007–1.181, p = 0.032); while the I carriers showed increased AD susceptibility compared with the D homozygotes (II + ID vs. DD: OR = 1.131, 95% CI = 1.008–1.270, p = 0.036). However, none of the positive results passed FDR adjustment. In subgroup analysis restricted to late-onset individuals, the associations between rs1799752 polymorphism and AD risk were identified using allelic comparison (OR = 1.154, 95% CI = 1.028–1.295, p = 0.015, FDR = 0.020), homozygotes comparison, dominant model and recessive model (II vs. ID + DD: OR = 1.272, 95% CI = 1.120–1.444, p < 0.001, FDR < 0.001). Nevertheless, no significant association could be revealed after excluding studies not in accordance with Hardy-Weinberg equilibrium (HWE). In North Europeans, but not in East Asians, the I allele demonstrated increased AD susceptibility compared to the D allele (OR = 1.096, 95% CI = 1.021–1.178, p = 0.012, FDR = 0.039). After excluding HWE-deviated cohorts, significant associations were also revealed under homozygotes comparison, additive model (ID vs. DD: OR = 1.266, 95% CI = 1.045–1.534, p = 0.016, FDR = 0.024) and dominant model (II + ID vs. DD: OR = 1.197, 95% CI = 1.062–1.350, p = 0.003, FDR = 0.018) in North Europeans. With regard to rs1800764 polymorphism, significant associations were identified particularly in subgroup of European descent under allelic comparison (T vs. C: OR = 1.063, 95% CI = 1.008–1.120, p = 0.023, FDR = 0.046), additive model and dominant model (TT + TC vs. CC: OR = 1.116, 95% CI = 1.018–1.222, p = 0.019, FDR = 0.046). But after excluding studies not satisfying HWE, all these associations disappeared. No significant associations were detected for rs4343, rs4291 and rs4309 polymorphisms in any genetic model.

Conclusions

Our results suggested the significant but modest associations between rs1799752 polymorphism and risk to AD in North Europeans. While rs4343, rs4291 and rs4309 polymorphisms are unlikely to be major factors in AD development in our research.

Genetic Variants Associated With Alzheimer Disease in the 22 Arab Countries: A Systematic Review

BACKGROUND AND AIMS

Alzheimer disease (AD) is a progressive and complex neurodegenerative disease. Approximately 70% of AD risk is attributed to genetic risk factors, including variants in amyloid precursor protein (APP), presenilin 1 (PSEN1), and presenilin 2 (PSEN2) genes. Several studies have revealed a considerable number of candidate loci and genes for AD among different ethnic populations. However, the outcomes of these studies have been inconsistent. In this study, we aimed to investigate the spectrum of variants that are associated with the onset and development of AD among 22 Arab countries.

METHODOLOGY

We systematically searched 4 literature databases (Science Direct, Scopus, PubMed, and Web of Science) from the date of inception until July 2020 using various search terms to obtain all the reported genetic data on Arab AD cases.

RESULTS

In total, 18 studies were included, comprising a total of 2173 individuals, of whom 888 were clinically diagnosed AD patients and were genetically tested for genes and variants associated with AD. A total of 27 variants in 8 genes were found to be associated with AD. Of these variants, 17 were unique to the Arab population and 10 were shared with other ethnic groups.

CONCLUSIONS

There is a dearth of studies on the genetics of AD in the Arab world. There seems to be distinctive genetic and clinical susceptibility profiles for Arab patients with AD.

Association between dementia and vascular disease-associated polymorphisms in a Tunisian population

PURPOSE

Dementia is a multifactorial idiopathic pathology caused by clinical, eDementia is a multifactorial idiopathic pathology caused by clinical, environmental and genetic factors. Hence, its etiology is still unknown. We aimed to evaluate the association between five genetic risk factors for vascular diseases and dementia individually and when gathered in haplotypes.

MATERIALS AND METHOD

We enrolled 200 dementia patients and 300 controls. All subjects were genotyped for vascular diseaseassociated polymorphisms in the genes coding for Apolipoprotein-E (ApoE), angiotensin converting enzyme (ACE) and Paraoxonase-1 (PON1).

RESULTS

The association between dementia risk and all the studied polymorphisms except of PON1-Q192R was found to be significant. Carrying the ApoE e4 allele seems to increase dementia risk by 4.32 fold (p = 0.001). The risk associated with ACE I and PON1-L55M T alleles were lower (2.58 and 2.11 fold, p < 0.001 and p = 0.015, respectively). When combined in haplotypes, these polymorphisms showed a cumulative and synergetic effect. GTICC haplotype appears to be associated with 9-fold dementia risk (p < 0.001), whereas AADTT seems to reduce dementia risk by 80% (p = 0.003).

CONCLUSION

Our results suggest that, ApoE ε4, ACE I and PON1-L55M T alleles are associated with dementia risk whether these polymorphisms were studied separately or gathered in haplotypes. Still, the contribution of each gene to the pathophysiological development of dementia must be more investigated.

Angiotensin-converting enzyme insertion/deletion polymorphism and the longitudinal progression of Alzheimer's disease

AIM

The angiotensin-converting enzyme gene (ACE) insertion (I)/deletion (D) polymorphism is considered a biologically plausible gene for Alzheimer's disease (AD) in cross-sectional studies. The present study aimed to investigate the longitudinal effect of ACE I/D polymorphism on AD progression.

METHODS

This 3-year observational study investigated the longitudinal effect of ACE I/D polymorphism on AD progression. Clinically diagnosed AD patients with a clinical dementia rating (CDR) of 0.5 or 1 were enrolled in the study. The Mini-Mental State Examination (MMSE), Cognitive Assessment Screening Instrument (CASI) and the CDR scale were carried out for all patients on the date of the initial interview and 36 ± 6 months after the initial evaluation.

RESULTS

A total of 177 patients with sporadic AD were enrolled in this study. Among all patients, those with the I/I genotype showed a higher risk of CDR deterioration (I/I versus I/D + D/D: adjusted OR 2.103, 95% CI 1.113-3.972; adjusted P = 0.022). Among 74 AD patients without hypertension, those with the I/I genotype showed significantly greater differences in the MMSE, CASI and the CDR-sum of box scores, and a higher risk of CDR deterioration (I/I versus I/D + D/D: adjusted OR 3.255, 95% CI 1.099-9.639; adjusted P = 0.033) after adjustment for possible confounders during the 3-year follow up.

CONCLUSIONS

Patients with AD who were homozygous for the I allele presented with a more rapid AD deterioration than did those who had other ACE genotypes, particularly those patients without hypertension. Geriatr Gerontol Int 2017; 17: 1544-1550.

Genetics of Vascular Dementia: Systematic Review and Meta-Analysis

BACKGROUND

Vascular dementia (VaD) is the second most common type of dementia. So far, little is known about the contribution of genetic polymorphisms to the risk of VaD. Many candidate genetic polymorphisms have been examined in a large number of studies. However, due to the conflicting results, the genetics of VaD is still behind the shadow.

OBJECTIVE

We conducted a comprehensive meta-analysis on associations between genetic polymorphisms of any gene and VaD to investigate the genetics of VaD.

METHOD

We sought the published studies of associations between any genetic polymorphism and VaD and critically appraised them. We assessed the effects of genetic models by calculating pooled odds ratios (ORs), investigating the origin of heterogeneity by subgroup analysis, and testing the robustness by random effect model and sensitivity analysis.

RESULTS

69 studies with 4,462 cases and 11,583 controls were included. We identified APOE ɛ2/ɛ3/ɛ4 and additional four genetic polymorphisms including MTHFR C677T, PON1 L55M, TGF-β1 +29C/T, and TNF-α -850C/T associated with VaD. Tested by random effect model and sensitivity analysis, the pooled results show nice robustness.

CONCLUSIONS

Our comprehensive meta-analysis highlighted the genetic contribution to sporadic VaD. Because of the small amount of data on associations between genetic polymorphisms, except for APOE, and VaD, more studies are needed to test the existing genetic polymorphisms and detect other related genetic variants.

Association between ACE polymorphism, cognitive phenotype and APOE E4 allele in a Tunisian population with Alzheimer disease

Angiotensin-converting enzyme (ACE) has shown altered activity in patients with neurological diseases. An insertion/deletion (I/D) polymorphism of the ACE gene encoding angiotensin-converting enzyme has been reported to be associated with the risk for Alzheimer's disease (AD), and is generally considered to be a disorder primarily affecting memory. We conducted a case-control study in a sample composed of 85 sporadic AD patients and 90 age- and sex-matched controls to investigate the possible effect of the polymorphism and cognitive profile. Our data revealed an association between the ACE polymorphism and AD risk. There was a significant difference in the ACE allele or genotype frequencies between cases and controls. The D/D genotype showed an increased risk for AD and in the amnestic group and the effect was independent on ApoE genotypes.

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.

Angiotensin-converting enzyme insertion/deletion polymorphism is not a major determining factor in the development of sporadic Alzheimer disease: evidence from an updated meta-analysis

Angiotensin-converting enzyme gene (ACE) insertion/deletion (I/D) polymorphism have long been linked to sporadic Alzheimer disease (SAD), but the established data remained controversial. To clarify this inconsistency, a comprehensive meta-analysis was conducted. Through searching of Pubmed, Embase, Alzgene, China National Knowledge Infrastructure (CNKI) and manually searching relevant references, 53 independent studies from 48 articles were included, involving a total of 8153 cases and 14932 controls. The strength of association was assessed by using odds ratios (ORs) with 95% confidence intervals (CIs). Further stratified analyses and heterogeneity analyses were tested, as was publication bias. Overall, significant associations were revealed between I/D polymorphism and SAD risk using allelic comparison (OR = 1.09, 95%CI = 1.01–1.17, p = 0.030), homozygote comparison (OR = 1.17, 95%CI = 1.01–1.34, p = 0.030) and the dominant model (OR = 1.16, 95%CI = 1.04–1.29, p = 0.008), but they were not sufficiently robust to withstand the false-positive report probability (FPRP) analyses. Otherwise, in subgroup analyses restricted to the high quality studies, the large sample size studies and studies with population-based controls, no significant association was observed in any genetic models. In summary, the current meta-analysis suggested that the ACE I/D polymorphism is unlikely to be a major determining factor in the development of SAD.

Apolipoprotein E gene polymorphism and Alzheimer's disease in Chinese population: a meta-analysis

The relationship between Apolipoprotein E (ApoE) genotype and the risk of Alzheimer's disease (AD) is relatively well established in Caucasians, but less established in other ethnicities. To examine the association between ApoE polymorphism and the onset of AD in Chinese population, we searched the commonly used electronic databases between January 2000 and November 2013 for relevant studies. Total 20 studies, including 1576 cases and 1741 controls, were retrieved. The results showed statistically significant positive association between risk factor ε4 allele carriers and AD in Chinese population (OR = 3.93, 95% CI = 3.37-4.58, P < 0.00001). Genotype ApoE ε4/ε4 and ε4/ε3 have statistically significant association with AD as well (ε4/ε4: OR = 11.76, 95% CI = 6.38-21.47, P < 0.00001; ε4/ε3: OR = 3.08, 95% CI = 2.57-3.69, P < 0.00001). Furthermore, the frequency of the ApoE ε3 is lower in AD than that in the health controls, and the difference of ε3 allele is also statistically significant (OR = 0.42, 95% CI = 0.37-0.47, P < 0.00001). No significant heterogeneity was observed among all studies. This meta-analysis suggests that the subject with at least one ApoE ε4 allele has higher risk suffering from AD than controls in Chinese population. The results also provide a support for the protection effect of ApoE ε3 allele in developing AD.

Activity-dependent neuroprotector homeobox protein: A candidate protein identified in serum as diagnostic biomarker for Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia of late life. To enhance our understanding of AD proteome, the serum proteins were analyzed using two-dimensional gel electrophoresis (2DE) combined with nano-high performance liquid chromatography electrospray ionization tandem mass spectrometry (nano-HPLC-ESI-MS/MS) followed by peptide fragmentation patterning. In this study, six protein spots with differential expression were identified. Five up-regulated proteins were identified as actin, apolipoprotein A-IV (Apo A-IV), inter-alpha-trypsin inhibitor heavy chain H4 (ITIH4), alpha-1-antitrypsin (AAT), and antithrombin-III (AT-III); one protein, activity-dependent neuroprotector homeobox protein (ADNP) was down-regulated in AD patients. These proteins with differential expression in the serum may serve as potential indicators of AD. Our results suggested that ADNP may play an important role in slowing the progression of clinical symptoms of AD.

ApoE gene polymorphism and vascular dementia in Chinese population: a meta-analysis

Vascular dementia is the second common cause of dementia, only second to Alzheimer's disease in later life. The Apolipoprotein E (ApoE) gene polymorphism as a risk factor in vascular dementia has been suggested, but direct evidence from genetic association studies remains inconclusive even in Chinese population. Therefore, we performed this meta-analysis in order to evaluate the relationship between ApoE gene polymorphism and susceptibility to vascular dementia in Chinese population by pooling data from all relevant case-control studies published domestically and abroad from January 1990 to May 2011. 18 case-control studies were selected. Meta-analysis results showed that the pooled OR value of vascular dementia subjects in Chinese population with ε4 allele carriers was 2.07 [95% CI (1.69, 2.53)], and the pooled OR value of vascular dementia subjects with E4/E4 genotype was 3.34 [95% CI (1.89, 5.88)]. These results suggest that ApoE polymorphism is significantly associated with susceptibility to vascular dementia in Chinese population. The subject with at least one ε4 allele or E4/E4 genotype has higher risk suffering from vascular dementia than others.

APOE polymorphism is associated with lipid profile, but not with arterial stiffness in the general population

Background

Cardiovascular diseases (CVD) are the main cause of death and disability in developed countries. In most cases, the progress of CVD is influenced by environmental factors and multifactorial inheritance. The purpose of this study was to investigate the association between APOE genotypes, cardiovascular risk factors, and a non-invasive measure of arterial stiffness in the Brazilian population.

Methods

A total of 1493 urban Brazilian individuals were randomly selected from the general population of the Vitoria City Metropolitan area. Genetic analysis of the APOE polymorphism was conducted by PCR-RFLP and pulse wave velocity analyzed with a noninvasive automatic device.

Results

Age, gender, body mass index, triglycerides, creatinine, uric acid, blood glucose, blood pressure phenotypes were no different between ε2, ε3 and ε4 alleles. The ε4 allele was associated with higher total-cholesterol (p < 0.001), LDL-C (p < 0.001), total-cholesterol/HDL-C ratio (p < 0.001), LDL/HDL-C ratio (p < 0.001), lower HDL-C values (p < 0.001) and higher risk to obesity (OR = 1.358, 95% CI = 1.019-1.811) and hyperuricemia (OR = 1.748, 95% CI = 1.170-2.611). Nevertheless, pulse wave velocity (p = 0.66) measures were no different between genotypes. The significant association between APOE genotypes and lipid levels persisted after a 5-year follow-up interval, but no interaction between time and genotype was observed for lipids longitudinal behavior.

Conclusion

The ε4 allele of the APOE gene is associated with a worse lipid profile in the Brazilian urban population. In our relatively young sample, the observed effect of APOE genotype on lipid levels was not translated into significant effects in arterial wall stiffness.

The genetics of white matter lesions

White matter lesions (WMLs), commonly seen as hyperintensities on T2-weighted MRI scans of healthy elderly individuals, are considered to be related to small vessel disease in the brain, and are often associated with subtle cognitive and functional impairments. WMLs also show a strong correlation with a wide range of neurodegenerative and neuropsychiatric disorders. Although a number of vascular risk factors for WMLs have been identified, genetic factors are also important with twin and family studies reporting high heritability. Mutations in several genes have been described that lead to monogenic disorders manifesting WMLs, such as Fabry disease and CADASIL. Because most individuals with WMLs do not have Mendelian disorders, most of the focus has been on single nucleotide polymorphisms as genetic risk markers for WMLs, either directly or through their interactions with other genes or medical risk factors. Candidate genes examined to date include those involved in cholesterol regulation and atherosclerosis, hypertension, neuronal repair, homocysteine levels, and oxidative stress pathways. In addition, although there have been a few genome-wide linkage studies, only one genome-wide association study has been performed. The majority of the genetic findings need independent replication, and studies need to be extended to other candidate genes. Collaborative efforts to examine genome-wide associations in large samples of both sexes of a broad age range using longitudinal studies are necessary. The identification of individuals genetically at risk of developing white matter lesions will have important implications for recognizing the etiology of WMLs and thereby developing clinical intervention strategies for their prevention.

Association of apolipoproteins e4 and c1 with onset age and memory: a study of sporadic Alzheimer disease in Taiwan

OBJECTIVE

To identify clinical manifestations and neuropsychological effects of Alzheimer disease (AD) in apolipoprotein (ApoE) e4 carriers and to investigate the relationships between ApoE HhaI polymorphism and apolipoprotein C1 (APOC1) HpaI polymorphism in Taiwanese patients with AD.

PARTICIPANTS AND METHODS

A total of 127 patients with AD and 191 elderly individuals were screened for ApoE and APOC1 polymorphism. All patients underwent neuropsychological testing, including a Mini-Mental Status Examination (MMSE), Clinical Dementia Rating (CDR), and/or the Visual Association Memory Test (VAMT) with Cognitive Abilities Screening Instrument.

RESULTS

The frequencies of the e4 and A alleles were significantly higher in the AD group. In the patients with AD, the e4 and A allele effects on those with an age-of-onset of 60 to 79 years were stronger than those with an age-of-onset of 80 years or higher. Visual Association Memory Test performance was significantly worse in e4-allele carriers but not in A-allele carriers, in the early AD, particularly in those affected with AD for less than 2 years. Although there was no statistically significant difference in genotypic frequency between patients and controls, the 2 genes were linked. In addition, the presence of the AA genotype concomitant with the e4 allele may be better associated with AD diagnosis than either factor alone.

CONCLUSION

We conclude that the e4 allele affects neuropsychological performance and illness morbidity. Concomitantly, ApoE e4 and APOC1 A alleles have a better association with AD than ApoE e4 alone. In addition, APOC1 may partially contribute to the pathogenesis of AD, but the nature of its relationship with e4 requires further investigation.

Association of angiotensin-converting enzyme gene promoter single nucleotide polymorphisms and haplotype with major depression in a northeastern Thai population

INTRODUCTION

Angiotensin-converting enzyme (ACE) is thought to influence the activity of the hypothalamic-pituitary-adrenocortical system, which shows hyperactivity in the majority of patients with major depressive disorder (MDD). This study aimed at determining an association between two single nucleotide polymorphisms (SNPs) (rs4291;-240A/T and rs4292;-93T/C) of the ACE gene promoter and MDD in northeastern Thais.Subjects and methods. In the present case-control study, genotyping of 187 unrelated patients with MDD (44.89+/-12.92 years) and 207 unrelated healthy controls (41.34+/-9.76 years) from the northeastern part of Thailand was performed using polymerase chain reaction-restriction fragment length polymorphism technique.

RESULTS

Comparing the two groups, no significant difference was observed with regard to either genotype distributions or allele frequencies of the -93T/C SNP of ACE. For the -240A/T SNP, a significant difference in genotype distributions was found (chi(2)=6.65, df=2, p=0.036).The presence of the -240A allele of ACE was associated with a decreased risk for MDD compared with the -240T allele (chi(2)=4.24, df=1, p=0.040, odds ratio=0.702 [95% confidence interval=0.508-0.971]). Moreover, haplotype frequency analysis revealed that the -240T/-93T combination was significantly over-represented in patients with MDD in comparison with controls (13.6% and 6.8%, p=0.002 on chi(2) test, empirical p=0.004).

CONCLUSIONS

In the present investigation, an association between the -240A allele and a reduced risk for MDD was observed, but the genotype distributions of controls were only just in marginal agreement with Hardy-Weinberg equilibrium.The T-T haplotype in the ACE gene was significantly associated with an increased risk for MDD.

Analyses of interaction effect between apolipoprotein E polymorphism and alcohol use as well as cholesterol concentrations on spontaneous deep intracerebral hemorrhage in the Taiwan population

BACKGROUND

To determine the interaction effect between APOE polymorphism and lipid concentrations and alcohol use on spontaneous deep intracerebral hemorrhage (SDICH) risks.

METHODS

We enrolled 217 SDICH patients and 280 controls. Anthropometrics, personal history, and concentrations of total cholesterol (TC), high-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-c), and triglyceride were collected. Genotyping was determined by PCR-based restriction and electrophoresis assay. Associations were tested adjusting for multiple covariables.

RESULTS

Compared with the commonest genotype epsilon 3 epsilon 3, epsilon 2 epsilon 3 was inversely associated with TC (p=0.023) and LDL-c concentrations (p=0.005) in women. No APOE-alcohol interaction effect on lipids concentration was found. However, in men, there was a marginal effect of interaction between alcohol and APOE genotype epsilon 2 epsilon 3 vs. epsilon 3 epsilon 3 on SDICH risks (p=0.003), which is independent of TC concentration. In the male non-alcohol group, SDICH proportion was lower in the subjects carrying APOE epsilon 2 epsilon 3 (27.6%) than in those with epsilon 3 epsilon 3 (41.1%). In contrast, in the male alcohol consumption group, APOE epsilon 2 epsilon 3 was associated with a higher SDICH rate (77.8%) compared to epsilon 3 epsilon 3 (58.0%).

CONCLUSIONS

Male subjects carrying genotype epsilon 2 epsilon 3 tend to have a higher SDICH risk than those who have epsilon 3 epsilon 3 when they have alcohol exposure, but may have more benefit from alcohol abstinence.

Non-apolipoprotein E and apolipoprotein E genetics of sporadic Alzheimer's disease

The genetic epidemiology of sporadic Alzheimer's disease (SAD) remains a very active area of research,making it one of the most prolifically published areas in medicine and biology. Numerous putative candidate genes have been proposed. However, with the exception of apolipoprotein E (APOE), the only confirmed genetic risk factor for SAD, all the other data appear to be not consistent. Nevertheless, the genetic risk for SAD attributable to the APOE gene in the general population is 20-0%, providing a strong evidence for the existence of additional genetic risk factors. The first part of the present article was dedicated to non-APOE genetics of SAD, reviewing chromosomes-by-chromosomes the available data concerning the major candidate genes. The second part of this article focused on some recently discovered aspects of the APOE polymorphism and their implications for SAD. An attempt to identify the future directions for non-APOE genetic research in SAD was also discussed.

Association of ACE I/D gene polymorphism with vascular dementia: a meta-analysis

BACKGROUND

Vascular dementia is the second common cause of dementia, only second to Alzheimer's disease in later life, and has a greater mortality risk than Alzheimer's disease among the elderly population group. The angiotensin-converting enzyme insertion/deletion polymorphism as a risk factor in vascular dementia has been suggested, but direct evidence from genetic association studies remain inconclusive. We performed a meta-analysis pooling data from all relevant studies in order to determine the effect of the insertion/deletion polymorphism on the vascular dementia.

METHODS

We applied a random-effects model or fixed-effects model to combine odds ratio and 95% confidence intervals. Q statistic was used to evaluate the homogeneity, and Egger's test and Funnel plot were used to assess publication bias.

RESULTS

A total of 10 studies were included worldwide. Publication bias was not observed. There was no evidence of the association of angiotensin-converting enzyme insertion/deletion polymorphism with the vascular dementia in general or in the Asian populations or in the Caucasian populations.

CONCLUSIONS

The angiotensin-converting enzyme insertion/deletion polymorphism might be neutral to vascular dementia.

PPP2R2B CAG repeat length in the Han Chinese in Taiwan: Association analyses in neurological and psychiatric disorders and potential functional implications

PPP2R2B, a protein widely expressed in neurons throughout the brain, regulates the protein phosphatase 2A (PP2A) activity for the microtubule-associated protein tau and other substrates. Altered PP2A activity has been implicated in spinocerebellar ataxia 12, Alzheimer's disease (AD), and other tauopathies. Through a case-control study and a reporter assay, we investigated the association of PPP2R2B CAG repeat polymorphism with Taiwanese AD, essential tremor (ET), Parkinson's disease (PD), and schizophrenia and clarified the functional implication of this polymorphism. The distribution of the alleles was not significantly different between patients and controls, with 68.6-76.1% alleles at lengths of 10, 13, and 16 triplets. No expanded alleles were detected in either group. However, the frequency of the individuals carrying the short 5-, 6-, and 7-triplet alleles was notably higher in patients with AD (5/180 [2.8%], Fisher's exact test, P = 0.003; including 2 homozygotes) and ET (4/132 [3.0%], Fisher's exact test, P < 0.001) than in the controls (1/625 [0.2%]). The PPP2R2B transcriptional activity was significantly lower in the luciferase reporter constructs containing the (CAG)(5-7) allele than in those containing the common 10-, 13-, and 16-triplet alleles in both neuroblastoma and embryonic kidney cells. Therefore, our preliminary results suggest that the PPP2R2B gene CAG repeat polymorphism may be functional and may, in part, play a role in conferring susceptibility to AD and ET in Taiwan.

Angiotensin-converting enzyme polymorphisms and risk of spontaneous deep intracranial hemorrhage in Taiwan

BACKGROUND AND PURPOSE

This study examines whether angiotensin-converting enzyme (ACE) gene polymorphisms are associated with the risk of spontaneous deep intracerebral hemorrhage (SDICH) in Taiwan using a case-control study.

METHODS

Totally, 217 SDICH patients and 283 controls were recruited. Associations of ACE A-240T and ACE I/D polymorphisms with SDICH were examined under the additive model and adjusted for gender, age, body mass index, total cholesterol level, smoking history, alcohol use, hypertension, and use of ACE inhibitors.

RESULTS

Hypertension, diabetes mellitus, family history of spontaneous intracerebral hemorrhage (SICH), and low cholesterol level increase risk of female SDICH, whereas hypertension, alcohol use, smoking history, family history of SICH, and low cholesterol level are an important risk factor for male SDICH. After adjusting for covariates, only haplotype ACE T-D (OR = 2.7, 95% CI, 1.1-6.5, P = 0.02) was associated with female SDICH.

CONCLUSIONS

This study demonstrates that environmental risk factors play a major role and ACE polymorphisms play a minor role in contributing risk of SDICH in Taiwan.

Pharmacogenomics in Alzheimer's disease

Pharmacological treatment in Alzheimer's disease (AD) accounts for 10-20% of direct costs, and fewer than 20% of AD patients are moderate responders to conventional drugs (donepezil, rivastigmine, galantamine, memantine), with doubtful cost-effectiveness. Both AD pathogenesis and drug metabolism are genetically regulated complex traits in which hundreds of genes cooperatively participate. Structural genomics studies demonstrated that more than 200 genes might be involved in AD pathogenesis regulating dysfunctional genetic networks leading to premature neuronal death. The AD population exhibits a higher genetic variation rate than the control population, with absolute and relative genetic variations of 40-60% and 0.85-1.89%, respectively. AD patients also differ in their genomic architecture from patients with other forms of dementia. Functional genomics studies in AD revealed that age of onset, brain atrophy, cerebrovascular hemodynamics, brain bioelectrical activity, cognitive decline, apoptosis, immune function, lipid metabolism dyshomeostasis, and amyloid deposition are associated with AD-related genes. Pioneering pharmacogenomics studies also demonstrated that the therapeutic response in AD is genotype-specific, with apolipoprotein E (APOE) 4/4 carriers the worst responders to conventional treatments. About 10-20% of Caucasians are carriers of defective cytochrome P450 (CYP) 2D6 polymorphic variants that alter the metabolism and effects of AD drugs and many psychotropic agents currently administered to patients with dementia. There is a moderate accumulation of AD-related genetic variants of risk in CYP2D6 poor metabolizers (PMs) and ultrarapid metabolizers (UMs), who are the worst responders to conventional drugs. The association of the APOE-4 allele with specific genetic variants of other genes (e.g., CYP2D6, angiotensin-converting enzyme [ACE]) negatively modulates the therapeutic response to multifactorial treatments affecting cognition, mood, and behavior. Pharmacogenetic and pharmacogenomic factors may account for 60-90% of drug variability in drug disposition and pharmacodynamics. The incorporation of pharmacogenetic/pharmacogenomic protocols to AD research and clinical practice can foster therapeutics optimization by helping to develop cost-effective pharmaceuticals and improving drug efficacy and safety.

Studies from emerging countries: an encouraging development

PURPOSE OF REVIEW

To summarize the findings of recent psychogeriatric research conducted in emerging countries.

RECENT FINDINGS

During the review period there have been new reports on the prevalence, clinical characteristics and pathogenic mechanisms of dementia in its various forms, epidemiological findings on depression, and psychological autopsy analyses of suicidal behaviors and psychiatric morbidities. New studies in social psychiatry have been conducted, especially on the trends of transgenerational support of the elderly and of interventions that may reduce psychiatric disease burdens and promote mental health in later life.

SUMMARY

These research findings support a better understanding of the prevalence, nature, and underlying risk and protective factors of the major psychiatric morbidities in the studied regions. Further exploration of the epidemiological profile of mental disorders in rural areas, research on the direct and indirect costs of psychogeriatric conditions, and evaluation of the cost-effectiveness and financial sustainability of early detection programs, treatment and rehabilitation models are warranted.