Alejandro Arias-Vásquez

Replication by the Epistasis Project of the interaction between the genes for IL-6 and IL-10 in the risk of Alzheimer's disease.

BackgroundChronic inflammation is a characteristic of Alzheimers disease (AD). An interaction associated with the risk of AD has been reported between polymorphisms in the regulatory regions of the genes for the pro-inflammatory cytokine, interleukin-6 (IL-6, gene: IL6), and the anti-inflammatory cytokine, interleukin-10 (IL-10, gene: IL10).MethodsWe examined this interaction in the Epistasis Project, a collaboration of 7 AD research groups, contributing DNA samples from 1,757 cases of AD and 6,295 controls.ResultsWe replicated the interaction. For IL6 rs2069837 AA × IL10 rs1800871 CC, the synergy factor (SF) was 1.63 (95% confidence interval: 1.10–2.41, p = 0.01), controlling for centre, age, gender and apolipoprotein E ε4 (APOEε4) genotype. Our results are consistent between North Europe (SF = 1.7, p = 0.03) and North Spain (SF = 2.0, p = 0.09). Further replication may require a meta-analysis. However, association due to linkage disequilibrium with other polymorphisms in the regulatory regions of these genes cannot be excluded.ConclusionWe suggest that dysregulation of both IL-6 and IL-10 in some elderly people, due in part to genetic variations in the two genes, contributes to the development of AD. Thus, inflammation facilitates the onset of sporadic AD.

Polymorphisms of the renin–angiotensin system are associated with blood pressure, atherosclerosis and cerebral white matter pathology

Background: The renin–angiotensin system is involved in the development of hypertension, atherosclerosis and cardiovascular disease. We studied the association between the M235T polymorphism of the angiotensinogen gene (AGT) and the C573T polymorphism of the angiotensin II type 1 receptor (AT1R) and blood pressure, carotid atherosclerosis and cerebrovascular disease. Methods: We genotyped over 6000 subjects from the Rotterdam Study and more than 1000 subjects from the Rotterdam Scan Study. We used logistic regression and univariate analyses, adjusting for age and sex with, for AGT, the MM and, for AT1R, the TT genotype as reference. Results: We found that AGT−235T increased systolic (p for trendu200a=u200a0.03) and diastolic blood pressure (p for trendu200a=u200a0.04). The prevalence of carotid plaques was increased 1.25-fold (95% CI 1.02–1.52) in AGT-TT carriers. There was a significant increase in mean volume deep subcortical white matter lesions (WML) for AGT-TT carriers (1.78 ml vs 1.09 ml in the reference group; pu200a=u200a0.008). A significant interaction was found between AGT and AT1R, further increasing the effect on periventricular and subtotal WML (p for interactionu200a=u200a0.02). We found a non-significant increased risk of silent brain infarction for AGT-TT carriers and AT1R-CC carriers, but no effect on stroke. Conclusion: We found an association between AGT and blood pressure, atherosclerosis and WML. Also, we found synergistic effects between AGT and AT1R on the development of WML. These findings raise the question of whether the renin–angiotensin system may be a therapeutic target for the prevention of cerebral white matter pathology.

Transferrin and HFE genes interact in Alzheimer's disease risk: the Epistasis Project.

Iron overload may contribute to the risk of Alzheimers disease (AD). In the Epistasis Project, with 1757 cases of AD and 6295 controls, we studied 4 variants in 2 genes of iron metabolism: hemochromatosis (HFE) C282Y and H63D, and transferrin (TF) C2 and -2G/A. We replicated the reported interaction between HFE 282Y and TF C2 in the risk of AD: synergy factor, 1.75 (95% confidence interval, 1.1-2.8, p = 0.02) in Northern Europeans. The synergy factor was 3.1 (1.4-6.9; 0.007) in subjects with the APOEε4 allele. We found another interaction, between HFE 63HH and TF -2AA, markedly modified by age. Both interactions were found mainly or only in Northern Europeans. The interaction between HFE 282Y and TF C2 has now been replicated twice, in altogether 2313 cases of AD and 7065 controls, and has also been associated with increased iron load. We therefore suggest that iron overload may be a causative factor in the development of AD. Treatment for iron overload might thus be protective in some cases.

The dopamine β-hydroxylase -1021C/T polymorphism is associated with the risk of Alzheimer's disease in the Epistasis Project

BackgroundThe loss of noradrenergic neurones of the locus coeruleus is a major feature of Alzheimers disease (AD). Dopamine β-hydroxylase (DBH) catalyses the conversion of dopamine to noradrenaline. Interactions have been reported between the low-activity -1021T allele (rs1611115) of DBH and polymorphisms of the pro-inflammatory cytokine genes, IL1A and IL6, contributing to the risk of AD. We therefore examined the associations with AD of the DBH -1021T allele and of the above interactions in the Epistasis Project, with 1757 cases of AD and 6294 elderly controls.MethodsWe genotyped eight single nucleotide polymorphisms (SNPs) in the three genes, DBH, IL1A and IL6. We used logistic regression models and synergy factor analysis to examine potential interactions and associations with AD.ResultsWe found that the presence of the -1021T allele was associated with AD: odds ratio = 1.2 (95% confidence interval: 1.06-1.4, p = 0.005). This association was nearly restricted to men < 75 years old: odds ratio = 2.2 (1.4-3.3, 0.0004). We also found an interaction between the presence of DBH -1021T and the -889TT genotype (rs1800587) of IL1A: synergy factor = 1.9 (1.2-3.1, 0.005). All these results were consistent between North Europe and North Spain.ConclusionsExtensive, previous evidence (reviewed here) indicates an important role for noradrenaline in the control of inflammation in the brain. Thus, the -1021T allele with presumed low activity may be associated with misregulation of inflammation, which could contribute to the onset of AD. We suggest that such misregulation is the predominant mechanism of the association we report here.

α-Adducin Polymorphism, Atherosclerosis, and Cardiovascular and Cerebrovascular Risk

Background and Purpose— Carriers of the 460Trp allele of the &agr;-adducin gene (ADD1) show higher rates of sodium reabsorption compared with homozygous carriers of the Gly460 allele and were found to have an increased risk of hypertension and cardiovascular disease. We studied the association between the Gly460Trp polymorphism and atherosclerosis, cardiovascular disease, and cerebrovascular disease. Methods— Intima-media thickness of the common carotid artery, as well as incident stroke and myocardial infarction, were studied within 6471 subjects of the Rotterdam Study. Within 1018 subjects of the Rotterdam Scan Study, prevalent silent brain infarcts and cerebral white matter lesions were studied. Subjects were grouped into 460Trp carriers (variant carriers) and homozygous carriers of the Gly460 allele (reference). Results— Intima-media thickness of the common carotid artery was 0.80 mm in variant carriers compared with 0.79 mm in the reference group (P=0.04). Variant carriers had an increased risk of any stroke (hazard ratio [HR], 1.22; 95% CI, 1.02 to 1.45), ischemic stroke (HR, 1.29; 95% CI, 1.02 to 1.63), hemorrhagic stroke (HR, 1.07; 95% CI, 0.59 to 1.92), and of myocardial infarction (HR, 1.33; 95% CI, 1.05 to 1.69). For any ischemic stroke, there was a significant interaction between the Gly460Trp polymorphism and hypertension. Variant carriers more often had a silent brain infarct (odds ratio, 1.36; 95% CI, 0.98 to 1.88) and had more subcortical white matter lesions than the reference group (1.45 vs1.24 mL; P=0.22). Conclusions— The Gly460Trp polymorphism is associated with atherosclerosis, cardiovascular disease, and cerebrovascular disease, especially in hypertensive subjects.

The cholesteryl ester transfer protein (CETP) gene and the risk of Alzheimer’s disease

Like the apolipoprotein E (APOE) gene, the most common genetic determinant for Alzheimer’s disease (AD), the cholesteryl ester transfer protein (CETP) is involved in lipid metabolism. We studied the I405V polymorphism of the CETP gene in relation to AD. We genotyped 544 AD cases and 5,404 controls from the Rotterdam study, using a TaqMan allelic discrimination assay. Odds ratios (ORs) for AD were estimated using logistic regression analysis. CETP VV carriers showed significantly increased high-density lipoprotein levels compared to the IV and II carriers. In the overall analysis of AD, the risk of disease for the VV carriers of the CETP polymorphism was non-significantly increased compared to II carriers ORVVu2009=u20091.33, 95% confidence interval (CI) 0.96–1.90 pu2009=u20090.08). In those without the APOE*4 allele, the risk of AD for VV carriers was increased 1.67-fold (95% CI 1.11–2.52, pu2009=u20090.01). The difference in the relationship between CETP and AD between APOE*4 carriers and APOE*4 non-carriers was statistically significant (p for interactionu2009=u20090.04). Our results suggest that the VV genotype of the I405V polymorphism of the CETP gene increases the risk of AD in the absence of the APOE*4 allele, probably through a cholesterol metabolism pathway in the brain.

The impact of apolipoprotein E on dementia in persons with Down's syndrome

Apolipoprotein E (APOE) is consistently associated with dementia in the general population. Findings on the role of this gene in persons with Downs syndrome (DS) are inconclusive. We studied the effects of APOE on mortality and dementia in a longitudinal prospective study of a large population-based sample of persons with DS (n=425), demented and non-demented. There was evidence that APOE epsilon4 is correlated with the rate of decline in the social competence rating scale (SRZ) (p=0.04). In our population, we found overall a modest but not statistical significant effect on the prevalence of dementia (OR=1.57, 95%CI: 0.87-2.82). We did observed a significant long-term effect on the incidence of dementia (HR=4.66, 95%CI: 1.35-16.14), but for those with a follow-up less than 3 years the risk was not significantly increased: HR=0.83 (95%CI 0.35-1.94). When pooling our data in a meta-analysis, the APOE epsilon4 allele shows a 1.59-fold (95%CI: 1.19-2.12) increase in risk of dementia in persons with DS. We conclude that APOE is influencing the risk of dementia in persons with DS.

Angiotensin converting enzyme gene, smoking and mortality in a population-based study.

Backgroundu2002 The genetic and environmental risk factors, which may influence longevity and mortality, have received much attention during more than one decade. One of the major risks for mortality is cardiovascular disease and the renin angiotensin system (RAS) plays a major role in maintaining blood pressure homeostasis. In this system, the Angiotensin Converting Enzyme (ACE) is one of the key regulators and has been studied in relation to cardiovascular disease and mortality. We aimed to evaluate if the ACE I/D polymorphism is related to total mortality in the elderly.

Relationship of the Ubiquilin 1 gene with Alzheimer's and Parkinson's disease and cognitive function

Ubiquilin 1 (UBQLN1) is involved in the ubiquitination machinery, which has been implicated in Alzheimers disease (AD) as well as Parkinsons disease (PD). A polymorphism in the gene encoding for UBQLN1 has been previously associated with a higher risk of AD. We studied the role of the SNP rs12344615 on the UBQLN 1 gene in AD, PD and cognitive function in a population-based study, the Rotterdam Study, and a family-based study embedded in the genetic research in isolated population (GRIP) program. The Rotterdam Study includes 549 patients with AD and 157 patients with PD. The GRIP program includes a series of 123 patients with AD and a study of 1049 persons who are characterized for cognitive function. Data were analysed using logistic and multiple regression analysis. We found no significant difference in risk of AD or PD by the UBQLN1 SNP rs12344615 in our overall and stratified analyses in the Rotterdam Study. In our family-based study, we did not find evidence for linkage of AD to the region including the UBQLN1 gene. In the family-based study we also failed to detect an effect of this polymorphism on cognitive function. Our results suggest that it is unlikely that the SNP rs12344615 of the UBQLN1 gene is related to the onset of AD, PD or cognitive function.

Cyclin-dependent kinase 5 is associated with risk for Alzheimer’s disease in a Dutch population-based study

Although the role of the Cdk5 protein in Alzheimer’s disease (AD) is well recognized, there have been relatively few studies investigating genetic variants in the CDK5 gene in AD. In this study, we assessed the association between five previously described single nucleotide polymorphisms (SNPs) in the CDK5 gene and late onset AD by means of logistic regression and haplotype association analyses. Including all prevalent and incident AD cases, we found a significantly increased risk of AD for carriers of the GG genotype of SNP rs2069442 (OR = 1.79, 95 % CI 1.16–2.79, p = 0.001) in those without APOE*4. When limiting the analysis to incident cases without APOE*4, carriers of the GG genotype showed a 1.9-fold increased risk of AD (95 % CI 1.16–3.10, p = 0.003). Variations in the CDK5 gene can be described in 5 haplotype blocks. In our analysis, the haplotype tagged by the G allele of SNP rs2069442 was significantly associated with AD (p = 0.05). In conclusion, our study suggests that CDK5 may be associated with AD.