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Summary Background Spinal and bulbar muscular atrophy (SBMA) is caused by polyglutamine expansion in the androgen receptor, which results in ligand-dependent toxicity. Animal models have a neuromuscular deficit that is mitigated by androgen-reducing treatment. We aimed to assess the efficacy and safety of the 5α-reductase inhibitor dutasteride in patients with SBMA, and to identify outcome measures for use in future studies of the disease. Methods We undertook a randomised, double-blind, placebo-controlled, single-site clinical trial in ambulatory, symptomatic men with genetically confirmed SBMA. Participants were assigned by random number table to receive dutasteride (0·5 mg per day) or placebo orally for 24 months. Patients and investigators were masked to treatment allocation. The primary outcome measure was quantitative muscle assessment (QMA). The final efficacy analysis included all patients who were compliant with study treatment at 24 months. This trial was registered with ClinicalTrials.gov, NCT00303446. Findings 50 men were randomly assigned to treatment groups (25 dutasteride, 25 placebo), and 44 were included in the efficacy analysis (21 dutasteride, 23 placebo). At 24 months, the placebo group showed a decrease of 4·5% (−0·30 kg/kg) from baseline in weight-scaled muscle strength as indicated by QMA, and the dutasteride group had an increase in strength of 1·3% (0·14 kg/kg); the difference between groups (5·8%, 95% CI −5·9 to 17·6; p=0·28) was not significant. Prespecified secondary outcome measures of creatine kinase, muscle strength and function, motor nerve conduction, activities of daily living, and erectile function did not show a significant difference between the study groups in change from baseline. Quality of life, as measured by the physical component summary of the Medical Outcomes Study 36-item Short Form version 2, favoured dutasteride (change in score from baseline: placebo, −3·6%, vs dutasteride, 2·1%; p=0·01), whereas the mental component summary favoured placebo (3·3% vs −3·2%; p=0·03). The dutasteride group had fewer patients reporting falls than did the placebo group (9 vs 16; p=0·048); there were no other significant differences in reported adverse events. Interpretation Our study did not show a significant effect of dutasteride on the progression of muscle weakness in SBMA, although there were secondary indications of both positive and negative effects compared with placebo. A longer trial duration or larger number of patients might be needed to show an effect on disease progression. Performance testing, QMA, and quality of life measures were identified as potentially useful endpoints for future therapeutic trials. Funding US National Institutes of Health.

Background Nearly half of adults in the United States who are diagnosed with hypertension use blood-pressure-lowering medications. Yet there is a large interindividual variability in the response to these medications. Two complementary gene–environment interaction methods have been published and incorporated into publicly available software packages to examine interaction effects, including whether genetic variants modify the association between medication use and blood pressure. The first approach uses a gene–environment interaction term to measure the change in outcome when both the genetic marker and medication are present (the “interaction model”). The second approach tests for effect-size differences between strata of an environmental exposure (the “med-diff” approach). However, no studies have quantitatively compared how these methods perform with respect to 1 or 2 degree of freedom (DF) tests or in family-based data sets. We evaluated these 2 approaches using simulated genotype–medication response interactions at 3 single nucleotide polymorphisms (SNPs) across a range of minor allele frequencies (MAFs 0.1–5.4 %) using the Genetic Analysis Workshop 19 family sample. Results The estimated interaction effect sizes were on average larger in the interaction model approach compared to the med-diff approach. The true positive proportion was higher for the med-diff approach for SNPs less than 1 % MAF, but higher for the interaction model when common variants were evaluated (MAF >5 %). The interaction model produced lower false-positive proportions than expected (5 %) across a range of MAFs for both the 1DF and 2DF tests. In contrast, the med-diff approach produced higher but stable false-positive proportions around 5 % across MAFs for both tests. Conclusions Although the 1DF tests both performed similarly for common variants, the interaction model estimated true interaction effects with less bias and higher true positive proportions than the med-diff approach. However, if rare variation (MAF

Background There is great interindividual variation in systolic blood pressure (SBP) as a result of the influences of several factors, including sex, ancestry, smoking status, medication use, and, especially, age. The majority of genetic studies have examined SBP measured cross-sectionally; however, SBP changes over time, and not necessarily in a linear fashion. Therefore, this study conducted a genome-wide association (GWA) study of SBP change trajectories using data available through the Genetic Analysis Workshop 19 (GAW19) of 959 individuals from 20 extended Mexican American families from the San Antonio Family Studies with up to 4 measures of SBP. We performed structural equation modeling (SEM) while taking into account potential genetic effects to identify how, if at all, to include covariates in estimating the SBP change trajectories using a mixture model based latent class growth modeling (LCGM) approach for use in the GWA analyses. Results The semiparametric LCGM approach identified 5 trajectory classes that captured SBP changes across age. Each LCGM identified trajectory group was ranked based on the average number of cumulative years as hypertensive. Using a pairwise comparison of these classes the heritability estimates range from 12 to 94 % (SE = 17 to 40 %). Conclusion These identified trajectories are significantly heritable, and we identified a total of 8 promising loci that influence one’s trajectory in SBP change across age. Our results demonstrate the potential utility of capitalizing on extant genetic data and longitudinal SBP assessments available through GAW19 to explore novel analytical methods with promising results.