Angiotensin-converting enzyme gene and plasma protein level in Alzheimer's disease in Taiwanese

Targeting brain Renin-Angiotensin System for the prevention and treatment of Alzheimer's disease: Past, present and future

Alzheimer's disease (AD) is a well-known neurodegenerative disease characterized by the presence of two main hallmarks - Tau hyperphosphorylation and Aβ deposits. Notwithstanding, in the last few years the scientific evidence about the drivers of AD have been changing and nowadays age-related vascular alterations and several cardiovascular risk factors have been shown to trigger the development of AD. In this context, drugs targeting the Renin Angiotensin System (RAS), commonly used for the treatment of hypertension, are evidencing a high potential to delay AD development due to their action on brain RAS. Indeed, the ACE 1/Ang II/AT1R axis is believed to be upregulated in AD and to be responsible for deleterious effects such as increased oxidative stress, neuroinflammation, blood-brain barrier (BBB) hyperpermeability, astrocytes dysfunction and a decrease in cerebral blood flow. In contrast, the alternative axis - ACE 1/Ang II/AT2R; ACE 2/Ang (1-7)/MasR; Ang IV/ AT4R(IRAP) - seems to counterbalance the deleterious effects of the principal axis and to exert beneficial effects on memory and cognition. Accordingly, retrospective studies demonstrate a reduced risk of developing AD among people taking RAS medication as well as several in vitro and in vivo pre-clinical studies as it is herein critically reviewed. In this review, we first revise, at a glance, the pathophysiology of AD focused on its classic hallmarks. Secondly, an overview about the impact of the RAS on the pathophysiology of AD is also provided, focused on their four essential axes ACE 1/Ang II/AT2R; ACE 2/Ang (1-7)/MasR; Ang IV/ AT4R(IRAP) and ACE 1/Ang II/AT1R. Finally, the therapeutic potential of available drugs targeting RAS on AD, namely angiotensin II receptor blockers (ARBs) and angiotensin converting enzyme inhibitors (ACEIs), is highlighted and data supporting this hope will be presented, from in vitro and in vivo pre-clinical to clinical studies.

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.

Vascular Contribution to Cognition in Stroke and Alzheimer's Disease

Vascular factors to cognitive impairment in degenerative on non-degenerative diseases have been reported, examined, and debated for several decades. The various definitions of cognitive impairment due to vascular origins will make these results diverse. During this review, we are going to report currently update information of vascular contributions to cognitive function, in clinical or neuroimaging findings. Risks factors and their managements also will be discussed and reported to have a comprehensive review.

Biomarkers and Gene Polymorphisms in Members of Long- and Short-lived Families: A Longevity Study

Background

The influence of biomarkers in human lifespan has been investigated but with no clear results yet.

Materials and methods

Lipids, Uric Acid (UA), Adiponectin (ADIPOQ), Insulin-like Growth Factor (IGF-1), cholesteryl ester transfer protein (CETP) and angiotensin-converting enzyme (ACE) proteins, as well as CETP, ADIPOQ, insulin-like growth factor binding protein-3 (IGFBP3) and ACE-gene polymorphisms were evaluated in 149 Greek individuals. The Long-Lived Families (LON) (n=84) comprised of 3 generations: long-lived aged ≥90 years (P), offspring (FL1) and their grandchildren (FL2), while the Short-Lived Families (EAD) (n=65) where both parents died <75 years, comprised of 2 generations: middle-aged (FD1) and children (FD2).

Results

Serum CETP and IGF-1 levels were lower, whereas AdipoQ concentrations were higher in P compared with FL1 and FL2 members (CETP: p = 0.03 for both comparisons; IGF-1 p < 0.001 for both comparisons and ADIPOQ: p = 0.001 and p = 0.004, respectively). Furthermore, serum triglycerides, UA and glucose concentrations were higher in FD1 compared with FD2 subjects (p=0.001, 0.02 and ≤0.001, respectively). In FD2 and FL2, CETP levels were lower in individuals with B2B2 compared with B1B1 genotype (p=0.007). Additionally, ACE concentrations were higher in individuals with DD compared with II genotype in both Families (p=0.001). After adjustment for age and gender, CETP levels were lower in P and FL2 individuals with B2B2 compared with the B1B1 genotype (p=0.004 and 0.007, respectively).

Conclusion

Increase serum TGs, UA and GL concentrations were higher in the middle-aged individuals compared with their children in families independently of their lifespan. The serum adiponectin concentration was the highest in the oldest old individuals implying beneficial influence on lifespan. Independently of family's lifespan history, the youngest individuals with CETPB2B2 genotype, compared with individuals with CETPB1B1 genotypes, had lower serum CETP concentrations. The knowledge of the unfavourable gene(s)influencing human lifespan may be helpful in encouraging individuals to follow healthier lifestyle habits and better control their high-risk biomarkers.

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.

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.

Angiotensin-converting enzyme insertion/deletion polymorphism is associated with cerebral white matter changes in Alzheimer's disease

AIM

The presence of cerebral white matter changes (WMC) has been reported as an important predictor of the rapidity of cognitive decline in Alzheimer's disease (AD). The association between the angiotensin-converting enzyme (ACE) insertion/deletion (I/D) polymorphism and WMC in AD is yet to be elucidated. The present study aimed to examine the association between the ACE I/D polymorphism and WMC among AD patients in Taiwan.

METHODS

A total of 403 patients clinically diagnosed with AD were recruited in a cross-sectional study carried out in an area hospital in Kaohsiung, Taiwan. The ACE I/D polymorphism was genotyped, and cerebral white matter rating was carried out using the visual rating scale for age-related white matter changes.

RESULTS

The I allele was associated with a significantly lower total age-related white matter changes scale score compared with the D allele (4.83 vs 5.93, P = 0.013). The total age-related white matter changes scale score was significantly lower for the I/I genotype than for the I/D (4.37 vs 5.87, P = 0.009) and I/D + D/D genotypes (4.37 vs 5.91, P = 0.006), with no differences observed between the I/I + I/D and the D/D genotypes (5.08 vs 6.09, P = 0.373), after adjustment for age and hypertension. A stratified analysis by sex demonstrated that the I/I genotype was associated with significant lower WMC than other genotypes in women, but not in men.

CONCLUSIONS

The present study supports the hypothesis that the ACE I/D polymorphism is associated with the severity of WMC in patients with AD. Patients with AD who are homozygous for the I allele might be less likely to develop WMC, especially women. Geriatr Gerontol Int 2017; 17: 945-950.

Angiotensin-converting enzyme gene insertion-deletion polymorphism is a risk marker for Alzheimer's disease in a Chinese population: a meta-analysis of case-control studies

It has long been known that the polymorphisms of angiotensin-converting enzyme gene (ACE) are associated to increase risk of Alzheimer's disease (AD) in Chinese population. However, consistent results were not obtained among studies. This study is aimed to clarify the association between ACE insertion (I)/deletion (D) polymorphism (rs1799752) and AD. Literatures were searched from PubMed, Embase, Cochrane Library, CNKI, Wanfang and VIP databases without language restrictions. Eleven separate studies were suitable for the inclusion criterion. The selected studies contained 2,763 Chinese participants, including 1,383 in AD group and 1,380 controls. Pooled odds ratios (ORs) were calculated to assess the association between ACE I/D polymorphism and AD. Our case-control data indicated that ACE insertion is a risk allele in all genetic models: additive model (I vs. D: OR = 1.32, 95 % CI 1.07-1.62, P = 0.008), dominant model (II + ID vs. DD: OR = 1.61, 95 % CI 1.08-2.41, P = 0.02) and recessive model (II vs. ID + DD: OR = 1.39, 95 % CI 1.07-1.81, P = 0.01). Heterogeneity between studies was significant (P < 0.10) but not in stratification defined by the selection of controls (P > 0.10). After stratification according to the selection of controls, the carrier of ACE I allele remained a high risk for AD in population-based samples subgroup (I vs. D: P = 0.008, OR = 1.32, 95 % CI 1.07-1.61, P(heterogeneity) = 0.47, I (2) = 0 %). Our study provided solid evidence suggesting that ACE gene I/D polymorphism is a genetic risk factor for AD in Chinese population.

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.

Functional regulation of Alu element of human angiotensin-converting enzyme gene in neuron cells

The angiotensin-converting enzyme (ACE) insertion/deletion (I/D) genotype and its protein activity have been widely implicated to be associated with Alzheimer's disease (AD). However, whether the insertion sequence, Alu element, in intron 16 of the human ACE gene plays a functional role remains uncertain. To investigate the influence of the I/D polymorphism on ACE promoter, we recombined the I and D form fragments with the human ACE promoter sequence before the reporter gene in pSEAP-Basic2 vector. The effect of the Alu element on regulating the transcriptional activity of ACE promoter was examined using transient transfection in SH-SY5Y cells. We found that the I form fragment upregulated the transcriptional activity of ACE promoter by approximately 70% but that the D form fragment did not. Our study first reveals that Alu sequence in human ACE gene possesses a regulatory function on the ACE promoter activity in neuron. This novel finding bridges the gap between the association of ACE I/D genotype with AD, and suggests that Alu sequence is not merely a "junk" DNA in human ACE gene.