Understanding the role of the chromosome 15q25.1 in COPD through epigenetics and transcriptomics.

Chronic obstructive pulmonary disease (COPD) is a major health burden in adults and cigarette smoking is considered the most important environmental risk factor of COPD. Chromosome 15q25.1 locus is associated with both COPD and smoking. Our study aims at understanding the mechanism underlying the association of chromosome 15q25.1 with COPD through epigenetic and transcriptional variation in a population-based setting. To assess if COPD-associated variants in 15q25.1 are methylation quantitative trait loci, epigenome-wide association analysis of four genetic variants, previously associated with COPD (P < 5 × 10-8) in the 15q25.1 locus (rs12914385:C>T-CHRNA3, rs8034191:T>C-HYKK, rs13180:C>T-IREB2 and rs8042238:C>T-IREB2), was performed in the Rotterdam study (n = 1489). All four variants were significantly associated (P < 1.4 × 10-6) with blood DNA methylation of IREB2, CHRNA3 and PSMA4, of which two, including IREB2 and PSMA4, were also differentially methylated in COPD cases and controls (P < 0.04). Further additive and multiplicative effects of smoking were evaluated and no significant effect was observed. To evaluate if these four genetic variants are expression quantitative trait loci, transcriptome-wide association analysis was performed in 1087 lung samples. All four variants were also significantly associated with differential expression of the IREB2 3'UTR in lung tissues (P < 5.4 × 10-95). We conclude that regulatory mechanisms affecting the expression of IREB2 gene, such as DNA methylation, may explain the association between genetic variants in chromosome 15q25.1 and COPD, largely independent of smoking.

Baseline dietary glutamic acid intake and the risk of colorectal cancer: The Rotterdam study.

BACKGROUND: Animal studies have shown that glutamine supplementation may decrease colon carcinogenesis, but any relation with glutamine or its precursors has not been studied in humans. The primary aim of this study was to assess whether dietary glutamic acid intake was associated with colorectal cancer (CRC) risk in community-dwelling adults. A secondary aim was to evaluate whether the association could be modified by the body mass index (BMI). METHODS: This study was embedded in the Rotterdam study, which included a prospective cohort from 1990 onward that consisted of 5362 subjects who were 55 years old or older and were free of CRC at the baseline. Glutamic acid was calculated as a percentage of the total protein intake with a validated food frequency questionnaire at the baseline. Incident cases of CRC were pathology-based. RESULTS: During follow-up, 242 subjects developed CRC. Baseline dietary glutamic acid intake was significantly associated with a lower risk of developing CRC (hazard ratio [HR] per percent increase in glutamic acid of protein, 0.78; 95% confidence interval [CI], 0.62-0.99). After stratification for BMI, the risk reduction for CRC by dietary glutamic acid was 42% for participants with a BMI ≤ 25 kg/m(2) (HR per percent increase in glutamic acid of protein, 0.58; 95% CI, 0.40-0.85), whereas no association was found in participants with a BMI > 25 kg/m(2) (HR per percent increase in glutamic acid of protein, 0.97; 95% CI, 0.73-1.31). CONCLUSIONS: Our data suggest that baseline dietary glutamic acid intake is associated with a lower risk of developing CRC, but this association may be mainly present in nonoverweight subjects.

Use of tiotropium Respimat Soft Mist Inhaler versus HandiHaler and mortality in patients with COPD.

Tiotropium, a long-acting anticholinergic, is delivered via HandiHaler or via Respimat. Randomised controlled trials suggest that use of tiotropium Respimat increases the risk of dying. We compared the risk of mortality between tiotropium Respimat versus HandiHaler. Within the Integrated Primary Care Information database, we defined a source population of patients, aged ≥ 40 years, with ≥ 1 year of follow-up. Based on prescription data, we defined episodes of tiotropium use (Respimat or HandiHaler). The risk of mortality, within these episodes, was calculated using a Cox proportional hazard regression analysis. From the source population, 11 287 patients provided 24 522 episodes of tiotropium use. 496 patients died while being exposed to HandiHaler or Respimat. Use of Respimat was associated with almost 30% increased risk of dying (adjusted HR 1.27, 95% CI 1.03-1.57) with the highest risk for cardiovascular/cerebrovascular death (adjusted HR 1.56, 95% CI 1.08-2.25). The risk was higher in patients with co-existing cardiovascular disease (adjusted HR 1.36, 95% CI 1.07-1.73) than in patients without (adjusted HR 1.02, 95% CI 0.61-1.71). Use of tiotropium Respimat was associated with an almost 30% increase of mortality compared with HandiHaler and the association was the strongest for cardiovascular/cerebrovascular death. It is unclear whether this association is causal or due to residual confounding by chronic obstructive pulmonary disease severity.

A technical infrastructure to conduct randomized database studies facilitated by a general practice research database.

General practice research databases are increasingly used to study intended and unintended effects of treatments. However, confounding by indication remains a major problem. The randomized database study methodology has been proposed as a method to combine the strengths of observational database (generalizability) and the strength of the randomized clinical trial (RCT) design (randomization). We developed an infrastructure that enables the execution of randomized database studies with treatment randomization facilitated by a general practice research database. The requirements posed by the methodology of randomized database studies were facilitated by software components. Our assessment showed that it is technically possible to conduct randomized trials in general practice according to the randomized database design. The infrastructure facilitated the conduct of randomized database studies in general practice but some practical difficulties and methodological issues remain. The technical infrastructure seems to be both promising and potentially feasible to facilitate future randomized database studies, although the methodology needs to be evaluated in more detail.

Persistent leukocyturia and loss of renal function in a prospectively monitored cohort of HIV-infected patients treated with indinavir.

Symptomatic nephrotoxicity is a well-known complication of indinavir treatment. However, little is known about the relevance of other abnormalities, such as leukocyturia during use of indinavir. We determined the prevalence, risk factors, and consequences of persistent leukocyturia in a prospectively monitored cohort of indinavir users in three adult outpatient clinics. Patients were monitored for nephrotoxicity at regular visits (every 3 months) between August 1998 and September 2000. Monitoring involved urine dipstick analysis and microscopy for pH, erythrocytes, leukocytes, and indinavir crystals. The urine albumin concentration/creatinine concentration ratio and serum creatinine and indinavir plasma concentrations were measured, and urinary tract infection was excluded. Urologic symptoms were retrieved from medical records. Of 184 patients with at least one assessment, 35% had leukocyturia (i.e., >75 cells/microL) at least once during the study period, which coincided with mild increase in the serum albumin level, erythrocyturia, and crystalluria. Thirty-two (24%) of 134 patients with two or more assessments had persistent leukocyturia (i.e., on two or more occasions). Risk factors were indinavir plasma concentration of >9 mg/L, urine pH of >5.7, and crystalluria. Persistent leukocyturia was associated with a gradual loss of renal function but not with urologic symptoms. The data show that leukocyturia is a frequent finding and emphasize the need for monitoring renal function during indinavir treatment, even in the absence of urologic symptoms.