Synchrony of biomarker variability indicates a critical transition: Application to mortality prediction in hemodialysis.

Critical transition theory suggests that complex systems should experience increased temporal variability just before abrupt state changes. We tested this hypothesis in 763 patients on long-term hemodialysis, using 11 biomarkers collected every two weeks and all-cause mortality as a proxy for critical transitions. We find that variability-measured by coefficients of variation (CVs)-increases before death for all 11 clinical biomarkers, and is strikingly synchronized across all biomarkers: the first axis of a principal component analysis on all CVs explains 49% of the variance. This axis then generates powerful predictions of mortality (HR95 = 9.7, p < 0.0001, where HR95 is a scale-invariant metric of hazard ratio; AUC up to 0.82) and starts to increase markedly ∼3 months prior to death. Our results provide an early warning sign of physiological collapse and, more broadly, a quantification of joint system dynamics that opens questions of how system modularity may break down before critical transitions.

PACE4-altCT isoform of proprotein convertase PACE4 as tissue and plasmatic biomarker for prostate cancer.

The proprotein convertase PACE4 has demonstrated value as a viable therapeutic target in prostate cancer (PCa). A novel isoform named PACE4-altCT, which arises in neoplastic lesions, plays an important role in tumor progression and has been validated as a pharmacological target. With the discovery of its overexpression in PCa and the alternative splicing of its pre-RNA to generate an oncogenic C-terminally modified isoform named PACE4-altCT, understanding and validating its value as a potential biomarker is of great interest either from prognostic or targeted therapy intervention. Expression of ERG in LNCaP cells was used to investigate the relationship between ERG expression occurring in PCa cells and PACE4-altCT expression by Western blot and qPCR. Using immunohistochemistry, the expression levels of PACE4 isoforms in patient tissues were investigated and correlated with ERG tumor status and Gleason score. An ELISA method was developed using affinity purified recombinant protein and used for quantitative analysis of plasma concentrations of PACE4-altCT and used for correlation. In contrast with the consensual isoform, PACE4-altCT was only strongly overexpressed in prostate cancer patients, correlated with ERG expression levels. Despite its intracellular retention PACE4-altCT could be detected in the plasma of most patients with prostate cancer, whereas it was only found at low levels in normal patients whereas total plasmatic PACE4 levels did not vary significantly between groups. Our study demonstrates that PACE4-altCT is strongly overexpressed in prostate cancer using both immunohistochemical and ELISA techniques and may have some interesting potential as a biomarker.

Effects of Sex and Physical Activity Level on Serum Biomarker-Based Physiological Dysregulation: The Impact to Predict Frailty and Mortality in the Quebec NuAge Cohort.

BACKGROUND: Age-related changes in biological processes such as physiological dysregulation (the progressive loss of homeostatic capacity) vary considerably among older adults and may influence health profiles in late life. These differences could be related, at least in part, to the impact of intrinsic and extrinsic factors such as sex and physical activity level (PAL). OBJECTIVES: The objectives of this study were (1) to assess the magnitude and rate of changes in physiologi-cal dysregulation in men and women according to PAL and (2) to determine whether/how sex and PAL mediate the apparent influence of physiological dysregulation on health outcomes (frailty and mortality). METHODS: We used data on 1,754 community-dwelling older adults (age = 74.4 ± 4.2 years; women = 52.4%) of the Quebec NuAge cohort study. Physiological dysregulation was calculated based on Mahalanobis distance of 31 biomarkers regrouped into 5 systems: oxygen transport, liver/kidney function, leukopoiesis, micronutrients, and lipids. RESULTS: As expected, mean physiological dysregulation significantly increased with age while PAL decreased. For the same age and PAL, men showed higher levels of physiological dysregulation globally in 3 systems: oxygen transport, liver/kidney function, and leukopoiesis. Men also showed faster global physiological dysregulation in the liver/kidney and leukopoiesis systems. Overall, high PAL was associated with lower level and slower rate of change of physiological dysregulation. Finally, while mortality and frailty risk significantly increased with physiological dysregulation, there was no evidence for differences in these effects between sexes and PAL. CONCLUSION: Our results showed that both sex and PAL have a significant effect on physiological dysregulation levels and rates of change. Also, although a higher PAL was associated with lower level and slower rate of change of physiological dysregulation, there was no evidence that PAL attenuates the effect of physiological dysregulation on subsequent declines in health at the end of life. Substantial work remains to understand how modifiable behaviors impact the relationship between physiological dysregulation, frailty, and mortality in men and women.

Lack of consensus on an aging biology paradigm? A global survey reveals an agreement to disagree, and the need for an interdisciplinary framework.

At a recent symposium on aging biology, a debate was held as to whether or not we know what biological aging is. Most of the participants were struck not only by the lack of consensus on this core question, but also on many basic tenets of the field. Accordingly, we undertook a systematic survey of our 71 participants on key questions that were raised during the debate and symposium, eliciting 37 responses. The results confirmed the impression from the symposium: there is marked disagreement on the most fundamental questions in the field, and little consensus on anything other than the heterogeneous nature of aging processes. Areas of major disagreement included what participants viewed as the essence of aging, when it begins, whether aging is programmed or not, whether we currently have a good understanding of aging mechanisms, whether aging is or will be quantifiable, whether aging will be treatable, and whether many non-aging species exist. These disagreements lay bare the urgent need for a more unified and cross-disciplinary paradigm in the biology of aging that will clarify both areas of agreement and disagreement, allowing research to proceed more efficiently. We suggest directions to encourage the emergence of such a paradigm.

Optimization of furin inhibitors to protect against the activation of influenza hemagglutinin H5 and Shiga toxin.

Proprotein convertases (PCs) are crucial in the processing and entry of viral or bacterial protein precursors and confer increased infectivity of pathogens bearing a PC activation site, which results in increased symptom severity and lethality. Previously, we developed a nanomolar peptide inhibitor of PCs to prevent PC activation of infectious agents. Herein, we describe a peptidomimetic approach that increases the stability of this inhibitor for use in vivo to prevent systemic infections and cellular damage, such as that caused by influenza H5N1 and Shiga toxin. The addition of azaß(3)-amino acids to both termini of the peptide successfully prevented influenza hemagglutinin 5 fusogenicity and Shiga toxin Vero toxicity in cell-based assays. The results from a cell-based model using stable shRNA-induced proprotein convertase knockdown indicate that only furin is the major proprotein convertase required for HA5 cleavage.