Tubular Secretion in CKD.

Renal function generally is assessed by measurement of GFR and urinary albumin excretion. Other intrinsic kidney functions, such as proximal tubular secretion, typically are not quantified. Tubular secretion of solutes is more efficient than glomerular filtration and a major mechanism for renal drug elimination, suggesting important clinical consequences of secretion dysfunction. Measuring tubular secretion as an independent marker of kidney function may provide insight into kidney disease etiology and improve prediction of adverse outcomes. We estimated secretion function by measuring secreted solute (hippurate, cinnamoylglycine, p-cresol sulfate, and indoxyl sulfate) clearance using liquid chromatography-tandem mass spectrometric assays of serum and timed urine samples in a prospective cohort study of 298 patients with kidney disease. We estimated GFR by mean clearance of creatinine and urea from the same samples and evaluated associations of renal secretion with participant characteristics, mortality, and CKD progression to dialysis. Tubular secretion rate modestly correlated with eGFR and associated with some participant characteristics, notably fractional excretion of electrolytes. Low clearance of hippurate or p-cresol sulfate associated with greater risk of death independent of eGFR (hazard ratio, 2.3; 95% confidence interval, 1.1 to 4.7; hazard ratio, 2.5; 95% confidence interval, 1.0 to 6.1, respectively). Hazards models also suggested an association between low cinnamoylglycine clearance and risk of dialysis, but statistical analyses did not exclude the null hypothesis. Therefore, estimates of proximal tubular secretion function correlate with glomerular filtration, but substantial variability in net secretion remains. The observed associations of net secretion with mortality and progression of CKD require confirmation.

Identification, replication, and functional fine-mapping of expression quantitative trait loci in primary human liver tissue.

The discovery of expression quantitative trait loci ("eQTLs") can help to unravel genetic contributions to complex traits. We identified genetic determinants of human liver gene expression variation using two independent collections of primary tissue profiled with Agilent (n = 206) and Illumina (n = 60) expression arrays and Illumina SNP genotyping (550K), and we also incorporated data from a published study (n = 266). We found that ∼30% of SNP-expression correlations in one study failed to replicate in either of the others, even at thresholds yielding high reproducibility in simulations, and we quantified numerous factors affecting reproducibility. Our data suggest that drug exposure, clinical descriptors, and unknown factors associated with tissue ascertainment and analysis have substantial effects on gene expression and that controlling for hidden confounding variables significantly increases replication rate. Furthermore, we found that reproducible eQTL SNPs were heavily enriched near gene starts and ends, and subsequently resequenced the promoters and 3'UTRs for 14 genes and tested the identified haplotypes using luciferase assays. For three genes, significant haplotype-specific in vitro functional differences correlated directly with expression levels, suggesting that many bona fide eQTLs result from functional variants that can be mechanistically isolated in a high-throughput fashion. Finally, given our study design, we were able to discover and validate hundreds of liver eQTLs. Many of these relate directly to complex traits for which liver-specific analyses are likely to be relevant, and we identified dozens of potential connections with disease-associated loci. These included previously characterized eQTL contributors to diabetes, drug response, and lipid levels, and they suggest novel candidates such as a role for NOD2 expression in leprosy risk and C2orf43 in prostate cancer. In general, the work presented here will be valuable for future efforts to precisely identify and functionally characterize genetic contributions to a variety of complex traits.

Use of electronic health record data from diverse primary care practices to identify and characterize patients' prescribed common medications.

We use prescription of statin medications and prescription of warfarin to explore the capacity of electronic health record data to (1) describe cohorts of patients prescribed these medications and (2) identify cohorts of patients with evidence of adverse events related to prescription of these medications. This study was conducted in the WWAMI region Practice and Research Network (WPRN)., a network of primary care practices across Washington, Wyoming, Alaska, Montana and Idaho DataQUEST, an electronic data-sharing infrastructure. We used electronic health record data to describe cohorts of patients prescribed statin or warfarin medications and reported the proportions of patients with adverse events. Among the 35,445 active patients, 1745 received at least one statin prescription and 301 received at least one warfarin prescription. Only 3 percent of statin patients had evidence of myopathy; 51 patients (17% of those prescribed warfarin) had a bleeding complication. Primary-care electronic health record data can effectively be used to identify patients prescribed specific medications and patients potentially experiencing medication adverse events.

Cytochrome p450 enzyme polymorphism frequency in indigenous and native american populations: a systematic review.

OBJECTIVE: The purpose of our study was to evaluate the evidence on the prevalence of cytochrome P450 enzyme polymorphisms as potential genetic factors influencing drug efficacy and safety in the indigenous populations of the American hemispheres. METHODS: We conducted a systematic review of studies published between 1985 and 2006 using the Pubmed database. RESULTS: We identified only 10 original research studies on CYP2A6, CYP2D6, CYP2C9, CYP2C19 and CYP2E1 in 13 indigenous American populations. Interethnic differences in the frequency of CYP450 genetic variants existed both among the examined indigenous populations and in comparison with African, Asian and European populations. CONCLUSIONS: There are surprisingly few data on CYP450 enzyme polymorphisms in indigenous American populations, and it is difficult to draw any clear inferences about how these populations might be expected to respond to drugs in relation to other racial or ethnic groups. This lack of information could create a barrier to the use of pharmacogenetic testing in these populations. Collaborative partnerships between indigenous communities and researchers are needed to avail the clinical benefits of CYP450 enzyme polymorphism testing to indigenous populations.

Cumulative Antidepressant Use and Risk of Dementia in a Prospective Cohort Study.

OBJECTIVES: To determine whether antidepressant use is associated with dementia risk. DESIGN: Prospective cohort study. SETTING: Kaiser Permanente Washington (KPWA), an integrated healthcare delivery system. PARTICIPANTS: Community-dwelling individuals aged 65 and older without dementia and with 10 years or more of KPWA enrollment at baseline (N=3,059). MEASUREMENTS: Primary exposures were selective serotonin reuptake inhibitors (paroxetine vs other), tricyclic antidepressants, and serotonin antagonist and reuptake inhibitors. Using health plan pharmacy data, we calculated cumulative medication exposure, defined as total standardized daily doses (TSDDs), over rolling 10-year windows. Exposure in the most recent year was excluded to avoid use related to prodromal symptoms. The Cognitive Abilities Screening Instrument was administered every 2 years; low scores triggered clinical evaluation and consensus diagnosis procedures. Dementia risk was estimated according to medication use using Cox proportional hazards models. RESULTS: During a mean follow-up of 7.7 years, 775 participants (25%) developed dementia; 659 (22%) developed possible or probable Alzheimer's disease. Individual antidepressant classes were not associated with differences in dementia risk, although paroxetine use was associated with higher risk of dementia for all TSDD categories than no use (0-90 TSDDs: hazard ratio (HR)=1.69, 95% confidence interval (CI)=1.18-2.42; 91-365 TSDDs: HR=1.40, 95% CI=0.88-2.23; 366-1095 TSDDs: HR=2.13, 95% CI=1.32-3.43; ≥1095 TSDDs: HR=1.42, 95% CI=0.82-2.46). CONCLUSION: Most commonly prescribed nonanticholinergic depression medications used in late life do not appear to be associated with dementia risk. Paroxetine and other anticholinergic antidepressants may be exceptions in older individuals. Future studies are warranted to improve scientific understanding of potential associations in other settings and populations.