Inter- not intraindividual differences in sTWEAK levels predict functional deterioration and mortality in patients with dilated cardiomyopathy

Relevance of pre-analytical blood management on the emerging cardiovascular protein biomarkers TWEAK and HMGB1 and on miRNA serum and plasma profiling

BACKGROUND

Disease-independent sources of biomarker variability include pre-analytical, analytical and biological variance. The aim of the present study was to evaluate whether the pre-analytical phase has any impact on the emerging heart disease TWEAK and HMGB1 protein markers and miRNA biomarkers, and whether peptidome profiling allows the identification of pre-analytical quality markers.

METHODS

An assessment was made of sample type (serum, EDTA-Plasma, Citrate-Plasma, ACD-plasma, Heparin-plasma), temperature of sample storage (room temperature or refrigerated), time of sample storage (0.5, 3, 6 and 9h) and centrifugation (one or two-step). Aliquots of all processed samples were immediately frozen (-80°C) before analysis. Proteins were assayed by ELISAs, miRNA expression profile by microarray and peptidome profiling by MALDI-TOF/MS.

RESULTS

Temperature, time and centrifugation had no impact on TWEAK and HMGB1 results, which were significantly influenced by matrix type, TWEAK levels being significantly higher (F=194.7, p<0.0001), and HMGB1 levels significantly lower (F=36.32, p<0.0001) in serum than in any other plasma type. Unsuitable miRNA results were obtained using Heparin-plasma. Serum miRNA expression profiles depended mainly on temperature, while EDTA-plasma miRNA expression profiles were strongly affected by the centrifugation method used. MALDI-TOF/MS allowed the identification of seven features as indices of pre-analytical serum (m/z at 1206, 1350, 1865 and 2021) or EDTA-plasma (m/z 1897, 2740 and 2917) degradation.

CONCLUSIONS

Serum and EDTA-plasma allow the analysis of both proteins and miRNA emerging biomarkers of heart diseases. Refrigerated storage prevents an altered miRNA expression profile also in cases of a prolonged time-interval between blood drawing and processing.

Left Ventricular Dysfunction and CXCR3 Ligands in Hypertension: From Animal Experiments to a Population-Based Pilot Study

Detecting left ventricular (LV) dysfunction at an early stage is key in addressing the heart failure epidemic. In proteome profiling experiments in mice subjected either to aortic banding or sham, the circulating CXCR3 ligands monokine induced by interferon-γ (MIG) and interferon-γ inducible protein 10 (IP10) were 5 to 40 fold up-regulated at eight weeks. We assessed the diagnostic value of circulating NT-pro BNP and CXCR3 ligands (MIG, IP10, Interferon-inducible T-cell alpha chemo-attractant [I–TAC]) in patients with hypertension (≥140/90 mm Hg) associated with subclinical (n = 19) or symptomatic (n = 16) diastolic LV dysfunction on echocardiography and healthy controls. NT–pro BNP, MIG, IP10, I–TAC all increased (p ≤ 0.014) across the categories of worsening left ventricular dysfunction. In patients with symptomatic disease, MIG, IP10, and I–TAC increased 210% (p = 0.015), 140% (p = 0.007) and 120% (p = 0.035) more than NT-pro BNP. The optimal discrimination limits, obtained by maximizing Youden’s index were 246 pmol/L, 65 pg/mL, 93 pg/mL, and 24 pg/mL, respectively. The odds ratios associated with the four biomarkers were significant (p ≤ 0.010), ranging from 4.00 for IP10 to 9.69 for MIG. With adjustment for NT–pro BNP, the CXCR3 ligands retained significance (p ≤ 0.028). Adding optimized thresholds for the CXCR3 ligands to NT–pro BNP enhanced (p ≤ 0.014) the integrated discrimination improvement and the net reclassification improvement. In conclusion, congruent with the concept that inflammation plays a key role in the pathogenesis of LV dysfunction, MIG, IP10 and I–TAC add diagnostic accuracy over and beyond NT–pro BNP.