Current Bronchodilator Responsiveness Criteria Underestimate Asthma in Older Adults.

BACKGROUND: Asthma is common in older adults and is confirmed by demonstration of variable expiratory air-flow limitations, typically evaluated by spirometric assessment of bronchodilator responsiveness. However, many patients with clinically suspected asthma and documented air-flow obstruction do not exhibit a post-bronchodilator response that meets or exceeds current established guidelines. We investigated if extending the time from bronchodilator administration to assessment of bronchodilator response increases the yield of spirometry for the diagnosis of asthma in older adults. METHODS: This was a cross-sectional study. The subjects were non-smokers, ≥ 60 y old, and with suspected asthma. Subjects were characterized as (1) those with a positive bronchodilator response on the 30-min post-bronchodilator spirometry, (2) those with a positive bronchodilator response on the 60-min post-bronchodilator spirometry, and (3) those without a positive bronchodilator response but with a positive methacholine challenge test. Factors associated with a late response to bronchodilator were evaluated by using bivariate analysis and by multivariate analysis by using a logistic regression model. RESULTS: This study enrolled 165 subjects. Of these, 81 (49.1%) had a positive bronchodilator response on 30-min post-bronchodilator spirometry; 25 (15.2%) had a positive bronchodilator response on the 1-h post-bronchodilator spirometry; and 59 (35.8%) had no positive bronchodilator response but had a positive methacholine challenge test. On multivariable regression analysis, those with a higher baseline percentage of predicted FEV1, higher scores on a standard asthma control test, and wheezing and/or cough after exercise were more likely to either have a late bronchodilator response or no bronchodilator response. CONCLUSIONS: Our study showed that a late positive response to bronchodilator use was more common than previously presumed in older subjects with suspected asthma. Pulmonary function testing laboratories should consider routinely reassessing spirometry at 1 h after bronchodilator use if the earlier assessment did not reveal a significant response.

Expression and regulation of a low-density lipoprotein receptor exon 12 splice variant.

As low-density lipoprotein receptor (LDLR) contributes to cholesterol and amyloid beta homeostasis, insights into LDLR regulation may facilitate our understanding of cardiovascular disease and Alzheimer's disease. Previously, we identified LDLR isoforms that lacked exon 12 or exons 11-12 and that are predicted to encode soluble, dominant negative, LDLR. Moreover, these isoforms were associated with rs688, an exon 12 polymorphism that was associated with LDL-cholesterol and Alzheimer's disease risk. In this study, we present evidence that although the truncated LDLR isoforms are translated in vitro, they represent < 0.1% of CSF proteins. As these LDLR isoforms likely represent a loss of mRNA-encoding functional LDLR, we then focused upon identifying intron-exon boundary and exonic splicing enhancer elements critical to splicing. Exon 12 inclusion is enhanced by altering the 5' splice site in intron 12 towards a consensus splice donor sequence, consistent with its being a weak 5' splice site. Additionally, of the nine evolutionarily conserved putative splicing enhancer regions within exon 12, two regions that flank rs688 were critical to exon 12 inclusion. Overall, these results suggest that LDLR splice variants represent a loss of mRNA encoding functional LDLR and provide insights into the regulatory elements critical for LDLR exon 12 splicing.

Sex-dependent association of a common low-density lipoprotein receptor polymorphism with RNA splicing efficiency in the brain and Alzheimer's disease.

Since apoE allele status is the predominant Alzheimer's disease (AD) genetic risk factor, functional single nucleotide polymorphisms (SNPs) in brain apoE receptors represent excellent candidates for association with AD. Recently, we identified a SNP, rs688, as modulating the splicing efficiency of low-density lipoprotein receptor (LDLR) exon 12 in female human liver and in minigene-transfected HepG2 cells. Moreover, the rs688T minor allele was associated with significantly higher LDL and total cholesterol in women within the Framingham Offspring Study cohort. Since LDLR is a major apoE receptor in the brain, we hypothesized that rs688 modulates LDLR splicing in neural tissues and associates with AD. To evaluate this hypothesis, we first transfected LDLR minigenes into SH-SY5Y neuroblastoma cells and found that the rs688T allele reduces exon 12 inclusion in this neural model. We then evaluated the association of rs688 allele with exon 12 splicing efficiency in vivo by quantifying LDLR splicing in human anterior cingulate tissue obtained at autopsy; the rs688T allele is associated with decreased LDLR exon 12 splicing efficiency in aged males, but not females. Lastly, we evaluated whether rs688 associates with AD by genotyping DNA from 1457 men and 2055 women drawn from three case-control series. The rs688T/T genotype was associated with increased AD odds in males [recessive model, odds ratio (OR) of 1.49, 95% confidence interval (CI) of 1.13-1.97, uncorrected P = 0.005], but not in females. In summary, these studies identify a functional apoE receptor SNP that is associated with AD in a sex-dependent fashion.

Lack of genetic association of cholesteryl ester transfer protein polymorphisms with late onset Alzheimers disease.

Dysregulation of cholesterol homeostasis may be associated with the pathogenesis of coronary artery disease (CAD) and Alzheimers disease (AD). Recently, several single nucleotide polymorphisms (SNPs) in cholesteryl ester transfer protein (CETP) were associated with altered plasma CETP concentrations, cholesterol concentrations and CAD. Hence, these CETP SNPs represent excellent candidates for evaluating association with AD. To date, one study has evaluated the association between a single CETP SNP and AD. In this study, we examined three CETP SNPs to evaluate the genetic association of CETP with late onset AD on two study cohorts: the Religious Orders Study (ROS) series, including 85 AD and 70 non-AD individuals, and the University of Kentucky (UKY) series, including 78 AD and 84 non-AD individuals. Significant association between CETP genotypes or haplotypes and late onset AD was not detected in these two study cohorts. Moreover, the CETP genotypes and haplotypes were not significantly associated with AD when the populations were stratified for the presence or absence of apolipoprotein E4 (apoE4). In summary, CETP genetic variants were not associated with AD in two series.

Genetic association of low density lipoprotein receptor and Alzheimer's disease.

The low density lipoprotein receptor (LDLR) is an attractive candidate gene for genetic association with Alzheimer's disease (AD) because: (i) the LDLR is an apolipoprotein E (apoE) receptor, alleles of which have been associated with AD, (ii) LDLR resides at chromosome 19p13.3 within a region linked to AD, and (iii) LDLR modulates the homeostasis of cholesterol, which itself appears associated with AD. Therefore, we evaluated whether LDLR haplotypes alter the odds of AD by performing an association study examining three LDLR single nucleotide polymorphisms (SNPs) in 118 AD patients and 133 non-AD subjects. LDLR genotypes were obtained by TaqMan allelic discrimination assays. Although individual LDLR SNPs were not associated with AD, analyses of unambiguous haplotypes suggested the hypothesis that the 211 LDLR haplotype was associated with reduced odds of AD. We then evaluated this hypothesis in a second study cohort, i.e., the Religious Orders Study. These results supported the hypothesis that the 211 LDLR haplotype is associated with reduced odds of AD. Moreover, these data suggested further associations between LDLR variants and AD. Thus, LDLR variants appear significantly associated with AD and merit additional study.