Lan Tan

The influence of cytochrome oxidase CYP2A6, CYP2B6, and CYP2C9 polymorphisms on the plasma concentrations of valproic acid in epileptic patients.

OBJECTIVESnTo investigate influences of the functional polymorphisms of Cytochrome P450 isozymes 2A6 (CYP2A6), 2B6 (CYP2B6), and 2C9 (CYP2C9) on pharmacokinetics of VPA in vivo.nnnPATIENTS AND METHODSnIn the study, we analyzed the genotypes of CYP2A6, CYP2B6, and CYP2C9 and their contribution to the steady-state standardized plasma VPA concentrations in 179 subjects with epilepsy of a Northern Han Chinese population. The genotypes were detected by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).nnnRESULTSnThe subjects with one or two variant CYP2A6*4 alleles showed higher mean plasma VPA concentrations compared with non-*4 alleles [(3.4+/-0.4)microg kg ml(-1)mg(-1) vs. (3.6+/-0.4)microg kg ml(-1)mg(-1), p=0.0055]. A significant difference [one-way ANOVA (p=0.0203)] was also found between mean plasma VPA concentrations and the CYP2B6 genotypes. In addition, subjects with the heterozygous genotype CYP2C9*3 had higher mean plasma VPA concentrations than did those subjects with the wild-type genotype [(3.9+/-0.4)microg kg ml(-1)mg(-1) vs. (3.4+/-0.4)microg kg ml(-1)mg(-1), p=0.0001].nnnCONCLUSIONnThe presently evaluated variant alleles in the CYP2A6, CYP2B6, and CYP2C9 genes may explain part of the substantial variability in VPA pharmacokinetics between different subjects.

Implication of CLU gene polymorphisms in Chinese patients with Alzheimer's disease.

BACKGROUNDnClusterin (also called apolipoprotein J) has a potential central role in the pathogenesis of Alzheimers disease (AD). Recently, two genome-wide association studies have identified three variants in CLU gene encoding clusterin associated with AD risk in Caucasians, while there are no studies on the association of CLU with AD risk in Asians.nnnMETHODSnThe study investigated 324 sporadic late-onset AD (LOAD) and 388 healthy controls matched for sex and age in a Han Chinese population. Three common genetic variants (rs2279590, rs11136000 and rs9331888) in CLU gene were genotyped using MALDI-TOF mass spectrometry.nnnRESULTSnThe minor allele (G) of the rs9331888 polymorphism within CLU was significantly associated with an increased risk of LOAD (OR=1.39, 95% CI=1.13-1.72, P=0.002). Logistic regression analysis revealed that the rs9331888 polymorphism presented strong associations with LOAD in the dominant, recessive and additive models. No significant differences in genotype and allele frequencies of the rs2279590 and rs11136000 polymorphisms were found between LOAD patients and controls. Haplotype analysis identified a risk haplotype (CCG) (OR=1.66) and a protective haplotype (CCC)(OR=0.70).nnnCONCLUSIONSnOur findings implicate CLU as a susceptibility gene for LOAD in Han Chinese.

Interleukin-18 promoter polymorphisms and risk of late onset Alzheimer's disease

Pro- and anti-inflammatory cytokines play an important role in Alzheimers disease (AD), and common polymorphisms of genes controlling their production have been shown to be associated with the susceptibility to sporadic AD. Interleukin (IL)-18 is a potent pro-inflammatory cytokine of the IL-1 superfamily, and increasing evidences indicate a crucial role for it in the pathogenesis of AD. To clarify the role of IL-18 as a potential cause for AD susceptibility, we investigated the effect of two functional polymorphisms in IL-18 promoter: -607 C/A (rs1946518) and -137 G/C (rs187238) for the risk of sporadic late onset Alzheimers disease (LOAD) in a Han Chinese population of 109 patients and 109 healthy controls matched for sex and age. All 218 subjects were also genotyped for the Apolipoprotein E (ApoE) polymorphisms. The results revealed that both -607 C allele and -137 G allele were associated with an increased risk of LOAD (odds ratios/OR=1.56, P=0.04, Power=0.96 and OR=1.85, P=0.03, Power=0.80, respectively), and these associations were influenced by the presence of ApoE epsilon4 alleles. Moreover, they showed a highly significant synergistical interaction with the ApoE epsilon4 allele (OR=5.70 and 4.64, respectively). Examination of the haplotypes identified the -607 C/-137 G haplotype to increase the risk of LOAD (OR=1.62, P=0.003, Power=0.97). These findings suggest that the functional polymorphisms in IL-18 promoter may be involved in the risk of developing sporadic LOAD in the Han Chinese population.

Polymorphisms at the β2-adrenergic receptor gene influence Alzheimer's disease susceptibility

Increasing evidence indicates that the beta2-adrenergic receptor (beta2-AR) may play an important role in Alzheimers disease (AD). We investigated the effect of two polymorphisms in the beta2-AR gene: Gly16Arg and Gln27Glu for the risk of sporadic Late Onset Alzheimers Disease (LOAD) in 109 patients and 109 healthy controls matched for sex and age in a Han Chinese population. Results revealed that both the 16Gly allele and the 27Glu allele of the beta2-AR gene were associated with an increased risk of LOAD (P=0.009, OR=1.652 and P=0.002, OR=2.846, respectively), and they also showed a highly significant interaction with the Apolipoprotein E gene (APOE) epsilon4 allele (OR=4.200 and 9.441, respectively). Examination of the haplotypes identified the Gly16Glu27 haplotype to increase the risk of LOAD (P=0.004). Our results suggest that variations in the beta2-AR gene play an important role in the pathogenesis of sporadic LOAD, and interact with the epsilon4 allele to markedly increase the LOAD risk.

Complement receptor 1 polymorphisms and risk of late-onset Alzheimer's disease

The amyloid beta-protein (Abeta)-induced complement system activation plays an important role in Alzheimers disease (AD). Complement receptor 1 (CR1) is thought to contribute to Abeta clearance. A recent large genome-wide association study (GWAS) has identified significant association of two single nucleotide polymorphisms (SNPs) (rs6656401 and rs3818361) in the CR1 gene with AD in Caucasians. Here, we performed a case-control study to clarify whether the risk for sporadic late-onset AD (LOAD) might be influenced by these polymorphisms in a large Chinese cohort consisting of 254 patients and 357 healthy controls. The results revealed that there were significant differences in genotype (P=0.02) and allele (P=0.007) frequencies of the SNP rs6656401 but no in rs3818361 between AD patients and controls. The A allele of rs6656401 was associated with an increased risk of LOAD (P=0.007, odds ratios/OR =1.652). In the subgroup of APOE epsilon4 non-carriers, both the A of rs6656401 and T allele of rs3818361 were observed to be significantly higher in case than in controls (P=0.002 and P=0.035, respectively). For rs6656401, the logistic regression analysis revealed that the (AA +AG) genotypes has a 2.4-fold increased risk compared with the GG genotype (P=0.049). Haplotype analysis identified the AT haplotype to increase the risk of LOAD (P=0.03, OR=2.44). This study provides the evidence that variations in the CR1 gene play an important role in the pathogenesis of sporadic LOAD in the Han Chinese population.

Genetic association of PICALM polymorphisms with Alzheimer's disease in Han Chinese

PICALM might play an important role in AD pathology through participating in altering synaptic vesicle cycling or APP endocytosis. A recent genome-wide study (GWAS) identified a single nucleotide polymorphism (SNP) rs3851179 in the 5 to the PICALM gene strongly associated with Alzheimers disease (AD) in Caucasians. In order to assess the involvement of the PICALM polymorphism in the risk of developing late-onset AD (LOAD), we analyzed the genotype and allele distributions of these three polymorphisms in 609 Han Chinese subjects. Our data showed no significant association between the PICALM rs3851179 polymorphism and LOAD (genotype distribution: P=0.43; allele frequency: P=0.25, odds ratio=0.87, 95% confidence interval=0.68 to 1.10), even after statistical adjustment for age, gender and apolipoprotein E (APOE) status. Our results suggest that the PICALM polymorphism may not play a major role in the development of LOAD in the Han Chinese population.

Blocking β2-adrenergic receptor attenuates acute stress-induced amyloid β peptides production

Environmental factors play an important role in the Alzheimers disease (AD) development and stress may accelerate the progression of AD. Beta-adrenergic receptors are activated by stress and may influence different aspects of cognitive function. So, it was hypothesized that stress may accelerate the pathological progression of AD by the activation of beta(2)-adrenergic receptor (beta(2)-AR). We have investigated the role of acute stress and activation of beta(2)-AR in amyloid beta (Abeta) peptides production in a mouse model of acute restraint stress. Injections of the beta(2)-AR-selective agonist clenbuterol hydrochloride enhanced the production of acute stress-induced Abeta peptides production; the beta(2)-AR-selective antagonist ICI 118,551 reduced Abeta peptides production. It is suggested that acute stress induces abnormal activation of beta(2)-AR which subsequently enhances Abeta peptides (the main neuropathological hallmarks of AD) production possibly resulting in the onset of AD. The findings indicate that new therapeutic strategies designed to blocking beta(2)-AR might be valuable for the prevention and treatment of AD.

Roles of β-adrenergic receptors in Alzheimer's disease: implications for novel therapeutics.

Alzheimers disease (AD), the most common cause of age-related dementia, is a progressive neurodegenerative disorder with an enormous unmet medical need. In recent years, several unexpected longitudinal and cross-sectional epidemiological studies reveal that beta-blockers treatment reduces the prevalence of AD in patients suffering from hypertension. Now, a newly population-based study of individuals with incident AD demonstrates that beta-blockers are also associated with delay of functional decline. Furthermore, accumulated convincing evidences from cell culture experiments and animal studies have also suggested that β-adrenergic receptors (β-ARs) may involve in the AD pathogenesis through effects on amyloid-β (Aβ) production or inflammation. This review explores clinical and experimental studies that might help to explain the roles of β-ARs in the AD pathogenesis and the potential underlying mechanisms and whether treatment with β-ARs antagonists provides a new therapeutic option for AD.

Toll-like receptor 2 -196 to -174 del polymorphism influences the susceptibility of Han Chinese people to Alzheimer's disease

BackgroundToll-like receptor 2 (TLR2) represents a reasonable functional and positional candidate gene for Alzheimers disease (AD) as it is located under the linkage region of AD on chromosome 4q, and functionally is involved in the microglia-mediated inflammatory response and amyloid-β clearance. The -196 to -174 del polymorphism affects the TLR2 gene and alters its promoter activity.MethodsWe recruited 800 unrelated Northern Han Chinese individuals comprising 400 late-onset AD (LOAD) patients and 400 healthy controls matched for gender and age. The -196 to -174 del polymorphism in the TLR2 gene was genotyped using the polymerase chain reaction (PCR) method.ResultsThere were significant differences in genotype (P = 0.026) and allele (P = 0.009) frequencies of the -196 to -174 del polymorphism between LOAD patients and controls. The del allele was associated with an increased risk of LOAD (OR = 1.31, 95% CI = 1.07-1.60, Power = 84.9%). When these data were stratified by apolipoprotein E (ApoE) ε4 status, the observed association was confined to ApoE ε4 non-carriers. Logistic regression analysis suggested an association of LOAD with the polymorphism in a recessive model (OR = 1.64, 95% CI = 1.13-2.39, Bonferroni corrected P = 0.03).ConclusionsOur data suggest that the -196 to -174 del/del genotype of TLR2 may increase risk of LOAD in a Northern Han Chinese population.

Mitochondrial transcription factor A (TFAM) polymorphisms and risk of late-onset Alzheimer's disease in Han Chinese

Chronic mitochondria DNA (mtDNA) damage and mitochondrial dysfunction induced by increased reactive oxygen species (ROS) have been proved to contribute to the development of Alzheimers disease (AD). Mitochondrial transcription factor A (TFAM) plays an important role in the maintenance of mtDNA integrity. Recently, some studies suggested two single nucleotide polymorphisms (SNPs) (rs1937 and rs2306604) in the TFAM gene are associated with sporadic late-onset AD (LOAD) in Caucasians. To explore the correlation between TFAM gene and LOAD, we performed a case-control study in a large Chinese cohort consisting of 394 patients and 390 healthy controls. The results showed that there were significant differences in genotype (P=0.03) and allele (P=0.04) frequencies of the SNP rs1937 between LOAD patients and controls. The minor C allele of rs1937 acted as a moderate protective factor of LOAD (P=0.04, odds ratios/OR=0.76). The logistic regression analysis also suggested an association of LOAD with SNP rs1937 (dominant model: P=0.03, OR=0.71; recessive model: P=0.02, OR=0.25; additive model: P=0.01, OR=0.68). No significant association was observed between rs2306604 and LOAD. Haplotype analysis identified the haplotype CC as a protective factor of LOAD (P=0.038, OR=0.76). This study provides the evidence that variations in TFAM are involved in the pathogenesis of sporadic LOAD in the Han Chinese population.