Cardiovascular stress biomarker assessment of middle-aged non-athlete marathon runners.

BACKGROUND: Cardiovascular safety of marathon running in recreational runners remains unclear. We set up this study to comprehensively evaluate the effects of a marathon run on the profile of cardiovascular stress biomarkers in connection with transthoracic echocardiography. DESIGN AND METHODS: Thirty-three healthy male amateur runners, aged ≥50 years (mean age 57 ± 7) were enrolled. Venous blood samples were obtained before the marathon, just after the race, 2-4 and seven days after the marathon. Using novel single molecule counting technology we measured: plasma concentrations of high-sensitivity cardiac troponin I (hs-cTnI) and endothelin-1. N-terminal pro B-type natriuretic peptide was measured using electrochemiluminescence. Each participant had transthoracic echocardiography before and immediately after the race. RESULTS: We observed a sharp rise in the levels of all biomarkers after the race (all p < 0.01), which subsequently normalized after 2-4 days and stayed within normal range after seven days. Runners with intensive training programmes (>169 km/month, a median for the studied group) had lower hs-cTnI leak after the race (median 15.11 ng/ml and 31.2 ng/ml, respectively; p < 0.05). Neither transthoracic echocardiography measures of ventricles nor strain rates changed after the run. We observed a decrease in the left atrial volume index and increase in the maximal right atrial volumes (all p < 0.05). Changes in Doppler indices of diastolic function suggestive of alteration in left ventricular relaxation were observed. CONCLUSIONS: Marathon run is associated with sharp and significant rises in the biomarkers of cardiovascular stress. The profile of these changes, however, along with echocardiographic parameters, does not suggest irreversible myocardial damage.

A genome-wide assessment of the role of untagged copy number variants in type 1 diabetes.

Genome-wide association studies (GWAS) for type 1 diabetes (T1D) have successfully identified more than 40 independent T1D associated tagging single nucleotide polymorphisms (SNPs). However, owing to technical limitations of copy number variants (CNVs) genotyping assays, the assessment of the role of CNVs has been limited to the subset of these in high linkage disequilibrium with tag SNPs. The contribution of untagged CNVs, often multi-allelic and difficult to genotype using existing assays, to the heritability of T1D remains an open question. To investigate this issue, we designed a custom comparative genetic hybridization array (aCGH) specifically designed to assay untagged CNV loci identified from a variety of sources. To overcome the technical limitations of the case control design for this class of CNVs, we genotyped the Type 1 Diabetes Genetics Consortium (T1DGC) family resource (representing 3,903 transmissions from parents to affected offspring) and used an association testing strategy that does not necessitate obtaining discrete genotypes. Our design targeted 4,309 CNVs, of which 3,410 passed stringent quality control filters. As a positive control, the scan confirmed the known T1D association at the INS locus by direct typing of the 5' variable number of tandem repeat (VNTR) locus. Our results clarify the fact that the disease association is indistinguishable from the two main polymorphic allele classes of the INS VNTR, class I-and class III. We also identified novel technical artifacts resulting into spurious associations at the somatically rearranging loci, T cell receptor, TCRA/TCRD and TCRB, and Immunoglobulin heavy chain, IGH, loci on chromosomes 14q11.2, 7q34 and 14q32.33, respectively. However, our data did not identify novel T1D loci. Our results do not support a major role of untagged CNVs in T1D heritability.

A hybrid qPCR/SNP array approach allows cost efficient assessment of KIR gene copy numbers in large samples.

BACKGROUND: Killer Immunoglobulin-like Receptors (KIRs) are surface receptors of natural killer cells that bind to their corresponding Human Leukocyte Antigen (HLA) class I ligands, making them interesting candidate genes for HLA-associated autoimmune diseases, including type 1 diabetes (T1D). However, allelic and copy number variation in the KIR region effectively mask it from standard genome-wide association studies: single nucleotide polymorphism (SNP) probes targeting the region are often discarded by standard genotype callers since they exhibit variable cluster numbers. Quantitative Polymerase Chain Reaction (qPCR) assays address this issue. However, their cost is prohibitive at the sample sizes required for detecting effects typically observed in complex genetic diseases. RESULTS: We propose a more powerful and cost-effective alternative, which combines signals from SNPs with more than three clusters found in existing datasets, with qPCR on a subset of samples. First, we showed that noise and batch effects in multiplexed qPCR assays are addressed through normalisation and simultaneous copy number calling of multiple genes. Then, we used supervised classification to impute copy numbers of specific KIR genes from SNP signals. We applied this method to assess copy number variation in two KIR genes, KIR3DL1 and KIR3DS1, which are suitable candidates for T1D susceptibility since they encode the only KIR molecules known to bind with HLA-Bw4 epitopes. We find no association between KIR3DL1/3DS1 copy number and T1D in 6744 cases and 5362 controls; a sample size twenty-fold larger than in any previous KIR association study. Due to our sample size, we can exclude odds ratios larger than 1.1 for the common KIR3DL1/3DS1 copy number groups at the 5% significance level. CONCLUSION: We found no evidence of association of KIR3DL1/3DS1 copy number with T1D, either overall or dependent on HLA-Bw4 epitope. Five other KIR genes, KIR2DS4, KIR2DL3, KIR2DL5, KIR2DS5 and KIR2DS1, in high linkage disequilibrium with KIR3DL1 and KIR3DS1, are also unlikely to be significantly associated. Our approach could potentially be applied to other KIR genes to allow cost effective assaying of gene copy number in large samples.

Constitutive antiviral immunity at the expense of autoimmunity.

In this issue of Immunity, Funabiki et al. (2014) have identified in mice a mutation of the IFIH1 gene, encoding the viral receptor MDA5 that causes constitutive IFN production and fatal autoimmune disease. The authors show that the autoimmune disease-associated variant of human MDA5 is permanently switched on.