Low plasma growth/differentiation factor 1 levels are associated with liver fibrosis in patients with stable angina.

BACKGROUND: Growth differentiation factor 1 (GDF1) is a member of the transforming growth factor-ß (TGF-ß) superfamily and a protective mediator against the development of post-infarction cardiac remodeling by negatively regulating MEK-ERK1/2 and Smad signaling pathways in the heart. The TGF-ß/SMAD pathway has been shown to play a key role in the development of hepatic fibrosis. In addition, fatty liver disease has been associated with reduced MEK/ERK1/2 signaling. However, no previous study has investigated the association between GDF1 and liver fibrosis. Therefore, the aim of this study was to investigate the association between plasma GDF1 and liver fibrosis in patients with stable angina. METHODS: We included 327 consecutive patients with stable angina. ELISA was used to measure circulating levels of GDF1, and the fibrosis-4 index was used to assess liver fibrosis. RESULTS: The advanced liver fibrosis group had lower median plasma GDF1 levels than those with minimal liver fibrosis. There was a significant negative association between GDF1 plasma level and fibrosis-4 index (r = -0.135, p = 0.019). A lower concentration of GDF1 was significantly and independently associated with an increased risk of liver fibrosis when concentration was analyzed as a continuous variable and by tertile. In addition, fibrosis-4 index, aspartate aminotransferase (AST)-to-platelet ratio index, and AST/alanine aminotransferase ratio were significantly associated with GDF1 concentration. CONCLUSIONS: Our results indicated an association between low plasma GDF1 and liver fibrosis in the enrolled patients. Further investigations into the role of plasma GDF1 in the pathogenesis of liver fibrosis are warranted.

Growth Differentiation Factor-15 Is a Predictor of Mortality in Critically Ill Patients with Sepsis.

Growth differentiation factor-15 (GDF-15) is a member of the transforming growth factor-ß superfamily related to inflammation and macrophage activation. Serum concentrations of GDF-15 can predict poor survival in chronic diseases, but its role in sepsis is obscure. Therefore, we investigated GDF-15 as a prognostic biomarker in critically ill patients. We measured GDF-15 levels in 219 critically ill patients (146 with sepsis, 73 without sepsis) upon admission to the intensive care unit (ICU), in comparison to 66 healthy controls. GDF-15 levels were significantly increased in ICU patients compared to controls. GDF-15 was further increased in sepsis and showed a strong association with organ dysfunction (kidney, liver and lactate) and disease severity (APACHE II and SOFA score). High GDF-15 concentrations at admission independently predicted ICU (HR 3.42; 95% CI 1.33-8.78) and overall mortality (HR 2.02, 95% CI 1.02-3.88) in all ICU critically ill patients as well as in a large subgroup of sepsis patients (ICU mortality: HR 3.16; 95% CI 1.10-9.07; overall mortality: HR 2.62; 95% CI 1.14-6.02). Collectively, serum GDF-15 levels are significantly increased in critically ill patients, associated with sepsis, organ failure, and disease severity. High GDF-15 levels at ICU admission predict short- and long-term mortality risk.

Analytically Sensitive Protein Detection in Microtiter Plates by Proximity Ligation with Rolling Circle Amplification.

BACKGROUND: Detecting proteins at low concentrations in plasma is crucial for early diagnosis. Current techniques in clinical routine, such as sandwich ELISA, provide sensitive protein detection because of a dependence on target recognition by pairs of antibodies, but detection of still lower protein concentrations is often called for. Proximity ligation assay with rolling circle amplification (PLARCA) is a modified proximity ligation assay (PLA) for analytically specific and sensitive protein detection via binding of target proteins by 3 antibodies, and signal amplification via rolling circle amplification (RCA) in microtiter wells, easily adapted to instrumentation in use in hospitals. METHODS: Proteins captured by immobilized antibodies were detected using a pair of oligonucleotide-conjugated antibodies. Upon target recognition these PLA probes guided oligonucleotide ligation, followed by amplification via RCA of circular DNA strands that formed in the reaction. The RCA products were detected by horseradish peroxidase-labeled oligonucleotides to generate colorimetric reaction products with readout in an absorbance microplate reader. RESULTS: We compared detection of interleukin (IL)-4, IL-6, IL-8, p53, and growth differentiation factor 15 (GDF-15) by PLARCA and conventional sandwich ELISA or immuno-RCA. PLARCA detected lower concentrations of proteins and exhibited a broader dynamic range compared to ELISA and iRCA using the same antibodies. IL-4 and IL-6 were detected in clinical samples at femtomolar concentrations, considerably lower than for ELISA. CONCLUSIONS: PLARCA offers detection of lower protein levels and increased dynamic ranges compared to ELISA. The PLARCA procedure may be adapted to routine instrumentation available in hospitals and research laboratories.