Association between somatostatin gene polymorphisms and sporadic Alzheimer's disease in Chinese population

Recent evidence has suggested that down-regulation of somatostatin (SST) expression in the human brain during early stages of aging leads to an elevation in the steady-state levels of Aβ and therefore may be involved in Alzheimer's disease (AD) progression. We hypothesized that alterations in the SST gene might alter its expression or function and also play a role in the pathogenesis of sporadic AD (SAD). First, we sequenced the entire SST gene in 25 randomly selected controls and 25 SAD patients and then screened for C/T polymorphisms (rs4988514) in the 3′ un-translated region. We genotyped rs4988514 polymorphisms as well as apolipoprotein ?4 (APOE ?4) status in 309 SAD patients and 276 normal controls with restriction fragment length polymorphism (RFLP) analysis. Results showed that the C allele of the rs4988514 polymorphism had an increased incidence in the SAD group compared to the control group (p = 0.042). In subjects with the APOE ?4 allele, the presence of both the CC genotype and the C allele of this polymorphism were elevated in the SAD group compared to the control group (genotype p = 0.027, allele p = 0.011). In the whole study group, the age, sex, and APOE ?4 adjusted OR for the risk of AD in C allele carriers was 1.313 (95%CI = 1.068–2.234, p = 0.027) whereas within only APOE ?4 allele carriers, the adjusted OR increased to 2.734 (95%CI = 1.236–5.862, p = 0.012). Our results supported the notion that the C allele of the rs4988514 polymorphism may increase the risk for AD in the Chinese population and possibly have additive effect with the APOE ?4 allele.     

Association between promoter polymorphisms in anterior pharynx-defective-1a and sporadic Alzheimer's disease in the North Chinese Han population

Amyloid β-peptide (Aβ) deposition in brain is important in the development of sporadic Alzheimer's disease (SAD) and Aβ is produced through sequential cleaving of amyloid precursor protein (APP) by β-secretase and γ-secrease. Anterior pharynx-defective-1 (APH-1) is an important subunit of the gamma-secretase complex, and its expression level was associated with the activity of γ-secrease. We hypothesized that alterations in the APH-1 promoter region might alter APH-1 expression and the activity of γ-secrease, thus be involved in the SAD process. In the present study, we sequenced APH-1a promoter region in 20 randomly selected controls and 20 SAD patients and detected two polymorphisms which were −980C/G (rs3754048) and −21C/A (rs2275780). Then, we investigated genotypes and allele of these two polymorphisms as well as apolipoprotein ?4 (APOE ?4) status in 256 SAD patients and 276 normal controls with restriction fragment length polymorphisms analysis and sequencing. Results showed the GG genotype and G allele of −980C/G polymorphism were more frequent in the SAD group than that in the controls not only in the whole subjects (genotype P = 0.038, allele P = 0.01 respectively) but also in the APOE ?4 + subjects (genotype P = 0.048, allele P = 0.016 respectively). There was no statistical difference between SAD group and controls regarding to the frequency of alleles and genotypes of −21C/A whenever before or after stratification by APOE ?4. Our results suggest that there is an association between −980C/G and the development of SAD in the Northern Han Chinese population and that allele G may interact synergistically with the APOE ?4 allele to increase the risk of SAD.     

Low density lipoprotein receptor-related protein gene polymorphisms and risk for late-onset Alzheimer's disease in a Japanese population

Low density lipoprotein (LDL) receptor-related protein (LRP) gene polymorphisms located in the 5' region and in exon 3, and the apolipoprotein E (APOE) genotype were determined in 100 Japanese patients affected by late-onset Alzheimer's disease (AD). We matched 246 controls for age and found no association between the polymorphism located in the 5' region of the LRP gene. The distribution of LRP exon 3 genotypes and alleles did not differ between AD and the control groups. However, the frequency of T allele in the Alzheimer's group having APOE-epsilon4 was lower than that in the control group having APOE-epsilon4, but it was only marginally significant (p = 0.022). Age of onset was significantly younger in the patients with CC genotype than those carrying the T allele (p = 0.03), and this trend was more evident among non-APOE-epsilon4 carriers (p = 0.008). These results support the possibility that ApoE and LRP may contribute to the development of AD.     

Genetic variation in Clusterin gene and Alzheimer's disease risk in Han Chinese

Clusterin gene (CLU), also known as apolipoprotein J (ApoJ), is a strong candidate gene for late-onset Alzheimer's disease (LOAD) according to the Alzgene database. To further characterize this association and to isolate the variants contributing to the pathogenesis of LOAD in Han Chinese, we first sequenced a small sample (n = 100) to discover variants in the promoter, exons, the 5′ and 3′ untranslated regions, and exon–intron boundaries of CLU. Follow-up genotyping of identified variants in a larger sample (n = 1592). Sequencing analysis identified 18 variants. Analysis in the larger population revealed that only the rs9331949 C allele was significantly associated with an increased risk of LOAD, even after adjusting for multiple testing (p = 0.026). Logistic analysis identified the rs9331949 polymorphism was still strongly associated with LOAD (additive model: p = 0.004, odds ratio = 1.274; dominant model: p = 0.039, odds ratio = 1.239; recessive model: p = 0.002, OR = 1.975) after adjusting for sex, age, and APOE ε4 status. Our findings implicate CLU as a susceptibility gene for LOAD in Han Chinese.     

Association between promoter polymorphisms of the nicastrin gene and sporadic Alzheimer's disease in North Chinese Han population

Increasing evidences have shown that nicastrin (NCSTN) plays a crucial role in γ-cleavage of the amyloid precursor protein (APP). Inhibition of NCSTN demonstrated an altered γ-cleavage activity, suggesting its potential implication in developing Alzheimer's disease (AD). We detected the NCSTN gene promoter region in 359 sporadic AD (SAD) patients and 331 controls and found three promoter single nucleotide polymorphisms (SNPs): −1216C/A (rs2147471), −796T/G (rs10752637) and −436C/T (rs1324738). For −1216C/A, there were significant differences in the allele and genotype frequency between AD and control subjects (allele P = 0.031, genotype P = 0.017). The allele and genotype frequencies remained significant before and after APOE?4 stratification. The −1216CC carriers increased 2-fold risk for the development of SAD compared to the carriers with −1216CA and AA genotypes (OR = 2.049, 95%CI = 1.410–2.976, P = 0.000). For −796T/G, there were significant differences in the genotype frequency between SAD and control subjects (P = 0.009). This trend is still obvious in the subjects without APOE?4 allele. The −796GG carriers might decrease the risk compared to the carriers with −796TG and TT genotypes (OR = 0.602, 95%CI = 0.393–0.932, P = 0.022). No significant difference was detected either in genotype or in allele frequencies between SAD and control for −436C/T, even after APOE?4 stratification. The haplotype −1216A/−796G may be a protective factor for SAD (OR = 0.795, 95%CI = 0.636–0.995, P = 0.045). Our investigation suggests that −1216C/A and −796T/G are probably related to the development of SAD.     

Genetic variation in BIN1 gene and Alzheimer's disease risk in Han Chinese individuals

Genome-wide association studies have identified the bridging integrator 1 (BIN1) gene as the most important genetic susceptibility locus in late-onset Alzheimer's disease (LOAD) after apolipoprotein E for individuals of European ancestry. To further characterize this association and to isolate the variants within BIN1 contributing to LOAD in Han Chinese individuals, we conducted a 2-step design study in our cohort of 1133 LOAD patients and 1159 control subjects. Sequencing analysis identified 44 variants within BIN1. Follow-up genotyping analysis revealed that a novel missense mutation P318L appeared to exert risk effect for development of LOAD; and rs67327804 was also significantly associated with LOAD risk even after adjusting for age, gender, and apolipoprotein E ε4 status. Haplotype analysis confirmed that the “GA” haplotype derived from single-nucleotide polymorphisms in rs67327804 and rs1060743 showed a 1.4-fold increased risk of LOAD. Our findings provided the first independent evidence that variants in BIN1 were significantly associated with LOAD in Han Chinese individuals.     

Genetic variation in PICALM and Alzheimer's disease risk in Han Chinese

The current study was conducted to investigate the association of phosphatidylinositol-binding clathrin assembly protein gene (PICALM) with late-onset Alzheimer's disease (LOAD) risk in Han Chinese. We first sequenced PICALM for variants in a small sample (n = 100), and the selected variants were then genotyped in a larger cohort (n = 2292). Sequencing analysis identified 16 variants within PICALM including 5 new variants with extreme low frequency in the northern Han Chinese population. However, in the subsequent genotyping, none showed a significant association with LOAD risk after Bonferroni correction. These findings implicate that PICALM might not play a major role in the genetic predisposition to LOAD in Han Chinese.     

Lack of association between rs597668 polymorphism near EXOC3L2 and late-onset Alzheimer's disease in Han Chinese

Recently, an international genome-wide association study (GWAS) additionally found rs597668 near EXOC3L2/BLOC1S3/MARK4 was a new genome-wide significance locus associated with late-onset Alzheimer's disease (LOAD) in Caucasians. Follow-up replication studies were conducted almost exclusively in Caucasians, and the effects of the risk locus in other populations are as yet unknown. This study investigated the GWAS-associated locus near EXOC3L2 in 1205 unrelated Northern Han Chinese subjects comprising 598 LOAD patients and 607 healthy controls matched for gender and age. The results showed no significant differences in the genotypic or allelic distributions of rs597668 polymorphism between LOAD cases and healthy controls (genotype: P = 0.653; allele: P = 0.603), even after stratification for apolipoprotein E (APOE) ?4 status and statistical adjustment for age, gender and APOE ?4 status. This study suggests that the rs597668 polymorphism near EXOC3L2 may not play a major role in the susceptibility to LOAD in the Northern Han Chinese population.     

低密度脂蛋白受体相关蛋白5与骨量相关性的研究进展

骨最受多种遗传及环境因素共同影响,其中遗传因素对骨密度的影响大于60%.近年的研究显示,低密度脂蛋白受体相关蛋白5(LRP5)与成骨细胞分化、骨密度和/或骨质疏松性骨折关系密切.LRP5参与的骨量调控机制为骨质疏松症等疾病提供了新的治疗靶点,针对以上机制研制特异性激动剂或拈抗剂对开发新型抗骨质疏松药物具有重要意义.     

Tau-tubulin kinase-1 gene variants are associated with Alzheimer's disease in Han Chinese

Tau-tubuline kinase 1 (TTBK1) is a recently discovered brain-specific protein kinase involved in tau phosphorylation at AD-related sites. A recent large study has identified significant association of two single nucleotide polymorphisms (SNPs) (rs2651206 and rs7764257) in the TTBK1 gene with late-onset Alzheimer's disease (LOAD) in Spanish. Here, we performed a case–control study to clarify whether the risk for LOAD might be influenced by these polymorphisms in a large Chinese cohort consisting of 400 patients and 388 healthy controls. The minor alleles of the rs2651206 polymorphism within TTBK1 was significantly associated with a reduced risk of LOAD (odds ratio/OR = 0.69, P = 0.011). Furthermore, rs2651206 polymorphism was still strongly associated with LOAD (OR = 0.72, P = 0.05) after adjusted for age, gender, and the apolipoprotein E (APOE) ?4 status. Haplotype analysis identified the TG haplotype, deriving from the two minor alleles, to decrease the risk of LOAD (OR = 0.78, P = 0.037). This study provides the evidence that variations in the TTBK1 gene may play an important role in the pathogenesis of sporadic LOAD in a Han Chinese population.     

Lack of an association between Paraoxonase 1 gene polymorphisms (Q192R, L55M) and Alzheimer's disease: a meta-analysis

The association between Paraoxonase 1 (PON1) gene polymorphisms (Q192R, L55M) and Alzheimer's disease (AD) risk has been reported inconsistent results. To assess the association between PON1 polymorphisms and AD risk, a meta-analysis was performed. Based on comprehensive searches of the PubMed, Embase, Web of Science, Weipu, and CBM databases, a total of 10 studies including 3081 AD cases and 3054 controls were identified. The pooled odds ratio (OR) with 95% confidence interval (95% CI) were performed. There was no significant association between PON1 Q192R polymorphism and AD risk in all comparison models (R vs. Q, OR=0.89, 95% CI=0.82-0.96; RR vs. QQ, OR=0.83, 95% CI=0.68-1.01; RR+RQ vs. QQ, OR=0.86, 95% CI=0.75-0.97; and RR vs. QR+QQ, OR=0.94, 95% CI=0.81-1.11). For the PON1 L55M polymorphism, lack of an association was also found (L vs. M, OR=0.95, 95% CI=0.86-1.05; LL vs. MM, OR=0.67, 95% CI=0.51-0.88; LL vs. ML+MM, OR=0.82, 95% CI=0.69-0.98; and LL+ML vs. MM, OR=0.75, 95% CI=0.58-0.96). On subgroup analysis by ethnicity, similar results were found. Conclusively, the present meta-analysis revealed that PON1 gene polymorphisms (Q192R, L55M) were unlikely to contribute to AD susceptibility.     

Plasma oxidized low-density lipoprotein levels and risk of Alzheimer's disease

This study examines the association of plasma oxidized low-density lipoprotein (OxLDL) levels with all-cause dementia, including Alzheimer's disease (AD) and vascular dementia. Data are taken from the Canadian Study of Health and Aging, a population-based study of a representative sample of persons aged more than 65 years conducted from 1991 to 2002. The present study sample included 670 subjects of which, 155 developed all-cause dementia with 109 cases of AD and 32 of vascular dementia. In Cox regression models, no association between OxLDL and risks of dementia or subtypes was found. A triple interaction between OxLDL, sex, and history of cardiovascular disease on the risk of AD (p = 0.0077) was found. Increased levels of OxLDL were significantly associated with an increased risk of AD in men with a history of cardiovascular disease (hazard ratio = 1.11; 95% confidence interval 1.04–1.19); no association in women was found. These findings suggest that increased levels of OxLDL are not associated with the risk of dementia, AD, and vascular dementia. The association of OxLDL with AD in men with a history of cardiovascular disease merits further investigation.     

Vitamin D receptor gene polymorphism and its association with Parkinson's disease in Chinese Han population

Vitamin D plays an important role in neurodegenerative disorders as a crucial neuro-immunomodulator, and accumulating data have provided evidence for that vitamin D receptor (VDR) gene is a candidate gene for susceptibility to Parkinson's disease (PD). In this study, we performed a case-control study to demonstrate whether the risk for the development of onset of sporadic PD might be influenced by VDR gene polymorphisms in a Chinese cohort. Two hundred and sixty PD patients and 282 matched-healthy controls were genotyped for two representative single nucleotide polymorphisms (SNPs) in VDR gene (FokI C/T and BsmI G/A) by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) analysis in. Results from our study revealed that FokI C allele carriers were likely to associate with an increased risk of PD (P = 0.004) as well as early-onset PD (EOPD) (P = 0.010). Moreover, the frequency of FokI C allele was significantly increased in PD group and late-onset PD (LOPD) group relative to the control groups respectively (P = 0.023 and P = 0.033, respectively). For BsmI polymorphisms, no significant difference in genotype or allele distribution was found between PD patients and the controls, as well as gender- and age-related differences between PD patients and the controls subgroup. This study demonstrated a possible association between the VDR FokI T/C polymorphism and PD, indicating that VDR polymorphisms may well change genetic susceptibility to sporadic PD in a Han Chinese population.     

Implication of IL-33 gene polymorphism in Chinese patients with Alzheimer's disease

Interleukin-33 (IL-33), a newly described member of the IL-1 family, is located on chromosome 9p24, a chromosomal region of interest in Alzheimer's disease (AD) defined by many genome-wide studies. Three intronic rs1157505, rs11792633, and rs7044343 single nucleotide polymorphisms (SNPs) within IL-33 have recently been reported to be associated with risk of AD in Caucasian populations. In order to assess the involvement of the IL-33 polymorphisms in the risk of developing late onset AD (LOAD), we analyzed the genotype and allele distributions of these 3 polymorphisms in 704 Han Chinese subjects. The minor alleles of the rs11792633 polymorphism within IL-33 was significantly associated with a reduced risk of LOAD (odds ratio [OR] = 0.73, p = 0.005). Furthermore, rs11792633 polymorphism was still strongly associated with LOAD (dominant model: OR = 0.67, p = 0.015; recessive model: OR 0.57, p = 0.021; additive model: OR = 0.71, p = 0.004) after adjusting for age, gender, and the apolipoprotein E (APOE) ε4 status. Our results support the evidence that genetic variants of IL-33 affect susceptibility to LOAD in Han Chinese.     

Association between promoter polymorphisms of vascular endothelial growth factor gene and sporadic Alzheimer's disease among Northern Chinese Han

Increasing evidences suggest that polymorphisms within the promoter region of the vascular endothelial growth factor (VEGF) gene may elevate the risk for Alzheimer's disease (AD). In Northern Chinese Han, we found three polymorphisms in the VEGF promoter: −2578C/A (rs699947), −2549I/D (rs35569394) and −1154G/A (rs1570360). A strong linkage disequilibrium was detected between −2578C/A and −2549I/D. After adjusting the data by gender, age and the APOE?4 status using logistic regression, the −1154G/G genotype was found to increase the risk for sporadic AD (SAD) by 1.4-folds. In the subgroup of APOE?4 non-carriers, the −1154G allele and −2549D/−1154G haplotype were observed to be significantly higher in the 279 SAD patients than in the 317 healthy individuals. The present study provides the evidence that the −1154G allele and the −2549D/−1154G haplotype may be associated with the development of SAD in the individuals without APOE?4 allele.     

Association between neprilysin polymorphisms and sporadic Alzheimer's disease

The deposition of amyloid beta peptide (Abeta) in the form of plaques in the brain is a hallmark of Alzheimer's disease (AD). Neprilysin is the major Abeta-degradating enzyme and reduction in neprilysin activity could contribute to Alzheimer's by increasing the steady-state level of Abeta. To provide further evidence for the role of neprilysin in AD we genotyped 22 polymorphisms, 21 SNPs and the GT repeat in the promoter region, across the neprilysin gene in 298 Caucasian sporadic Alzheimer's patients and 298 age-matched controls. Several SNPs showed genotypic and allelic association to AD. SNP rs1836915, in linkage disequilibrium block 2, showed the greatest extent of genotypic association with AD (p=0.0076). We were unable to replicate any of the SNPs that were previously reported as putatively associated with AD. However, these novel findings add to the weight of evidence supporting the involvement of neprilysin in the aetiology of Alzheimer's disease.     

Ubc9 gene polymorphisms and late-onset Alzheimer's disease in the Korean population: A genetic association study

Ubiquitin-conjugating enzyme E2I (Ubc9) ligates small ubiquitin-related modifier (SUMO) to target proteins, resulting in changes of their localization, activity, or stability. Sumoylation of amyloid precursor protein (APP) was reported to be associated with decreased levels of beta amyloid (Aβ) aggregates, suggesting that sumoylation may play a role in the pathogenesis of Alzheimer's disease (AD). We investigated the association between genetic variations of Ubc9 gene (UBE2I) and late-onset Alzheimer's disease (AD). Five single nucleotide polymorphisms (SNPs) in UBE2I were genotyped in the DNA samples of 312 AD patients, 347 subjects with mild cognitive impairment (MCI), and 489 cognitively healthy controls. The genotype distribution of a polymorphism in intron 7 (rs761059) differed between AD cases and controls, with an adjusted odds ratio (OR) of 1.45 (p = 0.046, 95% CI: 1.01–2.08). One haplotype (ht2 CAGAG) was found in 14.0% of the AD patients and in 11.1% of the controls (p = 0.04, OR = 1.43. 95% CI; 1.01–2.01). Stratification by the ApoE-?4 allele gave no significant difference between the groups. When the samples were stratified by gender, the genotypes of two SNPs (rs8052688, rs8063) were significantly associated with the risk of MCI among women. Our investigation suggests that UBE2I polymorphisms might be associated with a risk of AD and MCI.