GDF-15 is increased during early reperfusion following aortic valve replacement

Growth Differentiation Factor 15 in Severe Aortic Valve Stenosis: Relationship with Left Ventricular Remodeling and Frailty

Background: Frailty is an important outcome predictor in patients with aortic stenosis who are candidates for transcatheter or surgical aortic valve replacement (AVR). Growth/differentiation factor 15 (GDF15) is a cytokine playing a role in the pathophysiology of ventricular remodeling. We assessed its potential role as an independent soluble biomarker of frailty in these patients. Methods: We studied 62 patients (age, mean 79 years, 95% confidence interval (CI) 77-81; 54.8% female) with severe aortic valve stenosis and candidates for AVR. We systematically assessed pre-intervention GDF15 levels for their relationship with frailty (Katz score) and echocardiographic parameters of left ventricular dysfunction/remodeling. Fifteen hypertensive patients with left ventricular (LV) hypertrophy served as controls. Results: Patients with aortic valve stenosis featured higher GDF15 levels than controls (1773, 95% CI 1574-1971 pg/mL vs. 775, 95% CI 600-950 pg/mL, respectively, p < 0.0001). Subjects in the upper GDF15 tertile were older (p = 0.004), with a more advanced NYHA functional class (p = 0.04) and a higher prevalence of impaired renal function (p = 0.004). Such patients also showed a higher frailty score (p = 0.04) and higher indices of LV dysfunction, including reduced global longitudinal strain (p = 0.01) and a higher left ventricular mass (p = 0.001). GDF15 was significantly related to the Katz score, and predicted (OR 1.05; 95% CI 0.9-1.1; p = 0.03) a low (<5) Katz score, independent of the relationship with LV mass, age, renal function or indices of LV dysfunction. Conclusions: GDF15 is increased in patients with severe aortic stenosis and appears to be a soluble correlate of patients' frailty, independent of indices of left ventricular dysfunction.

Nrf2 Sequesters Keap1 Preventing Podosome Disassembly: A Quintessential Duet Moonlights in Endothelium

AIMS

Nrf2 (nuclear factor erythroid 2-like 2) is a transcription factor known to modulate blood vessel formation. Various experimental settings, however, attribute to Nrf2 either stimulatory or repressive influence on angiogenesis. Our findings unveil the mechanism of Nrf2-dependent vessel formation, which reaches beyond transactivation of gene expression and reconciles previous discrepancies.

RESULTS

We provide evidence that growth differentiation factor 15 (GDF-15)- and stromal cell-derived factor 1 (SDF-1)-induced angiogenesis strongly depends on the presence of Nrf2 protein but does not rely on its transcriptional activity. Instead, Nrf2 serves as a protein restraining Keap1 (Kelch-like ECH-associated protein 1), its known transcriptional repressor. Angiogenic response is abrogated in Nrf2-deficient endothelial cells but not in cells expressing dominant negative form or Keap1-binding fragment of Nrf2. Deficiency of Nrf2 protein available for Keap1 leads to the overabundance of RhoGAP1 (Rho GTPase-activating protein 1), the protein regulating cell division cycle 42 (Cdc42) activity. This impairs podosome assembly and disrupts actin rearrangements, thereby preventing angiogenesis. Effects of Nrf2 deficiency can be rescued by concomitant knockdown of RhoGAP1 or Keap1. Importantly, in the established murine model of Nrf2 deficiency, the N-terminal fragment of Nrf2 containing Keap1 binding domain is preserved. Thus, this model can be used to characterize Nrf2 as a transcription factor, but not as a Keap1-sequestering protein. Innovation and Conclusion: To date, the significance of Nrf2 in cell function has been ascribed solely to the regulation of transcription. We demonstrate that Nrf2 serves as a protein tethering Keap1 to allow podosome assembly and angiogenesis. Moreover, we emphasize that the new Nrf2 function of a Keap1 scavenger implies revisiting the interpretation of some of the previous data on the Nrf2-Keap1 system.

Early troponin T and prediction of potentially correctable in-hospital complications after coronary artery bypass grafting surgery

Background

Peak levels of troponin T (TnT) reliably predict morbidity and mortality after cardiac surgery. However, the therapeutic window to manage CABG-related in-hospital complications may close before the peak is reached. We investigated whether early TnT levels correlate as well with complications after coronary artery bypass grafting (CABG) surgery.

Methods

A 12 month consecutive series of patients undergoing elective isolated CABG procedures (mini-extra-corporeal circuit, Cardioplegic arrest) was analyzed. Logistic regression modeling was used to investigate whether TnT levels 6 to 8 hours after surgery were independently associated with in-hospital complications (either post-operative myocardial infarction, stroke, new-onset renal insufficiency, intensive care unit (ICU) readmission, prolonged ICU stay (>48 hours), prolonged need for vasopressors (>24 hours), resuscitation or death).

Results

A total of 290 patients, including 36 patients with complications, was analyzed. Early TnT levels (odds ratio (OR): 6.8, 95% confidence interval (CI): 2.2-21.4, P=.001), logistic EuroSCORE (OR: 1.2, 95%CI: 1.0-1.3, P=.007) and the need for vasopressors during the first 6 postoperative hours (OR: 2.7, 95%CI: 1.0-7.1, P=.05) were independently associated with the risk of complications. With consideration of vasopressor use during the first 6 postoperative hours, the sum of specificity (0.958) and sensitivity (0.417) of TnT for subsequent complications was highest at a TnT cut-off value of 0.8 ng/mL.

Conclusion

Early TnT levels may be useful to guide ICU management of CABG patients. They predict clinically relevant complications within a potential therapeutic window, particularly in patients requiring vasopressors during the first postoperative hours, although with only moderate sensitivity.