Circulating soluble fibroblast activation protein (FAP) levels are independent of cardiac and extra-cardiac FAP expression determined by targeted molecular imaging in patients with myocardial FAP activation.

INTRODUCTION: Tissue Fibroblast Activation Protein alpha (FAP) is overexpressed in various types of acute and chronic cardiovascular disease. A soluble form of FAP has been detected in human plasma, and low circulating FAP concentrations are associated with increased risk of death in patients with acute coronary syndrome. However, little is known about the regulation and release of FAP from fibroblasts, and whether circulating FAP concentration is associated with tissue FAP expression. This study characterizes the release of FAP in human cardiac fibroblasts (CF) and analyzes the association of circulating FAP concentrations with in vivo tissue FAP expression in patients with acute (ST-segment elevation myocardial infarction, STEMI) and chronic (severe aortic stenosis, AS) myocardial FAP expression. METHODS AND RESULTS: FAP was released from CF in a time- and concentration-dependent manner. FAP concentration was higher in supernatant of TGFß-stimulated CF, and correlated with cellular FAP concentration. Inhibition of metallo- and serine-proteases diminished FAP release in vitro. Median FAP concentrations of patients with acute (77 ng/mL) and chronic (75 ng/mL, p = 0.50 vs. STEMI) myocardial FAP expression did not correlate with myocardial nor extra-myocardial nor total FAP volume (P ≥ 0.61 in all cases) measured by whole-body FAP-targeted positron emission tomography. CONCLUSION: We describe a time- and concentration dependent, protease-mediated release of FAP from cardiac fibroblasts. Circulating FAP concentrations were not associated with increased in vivo tissue FAP expression determined by molecular imaging in patients with both chronic and acute myocardial FAP expression. These data suggest that circulating FAP and tissue FAP expression provide complementary, non-interchangeable information.

Dysregulated activities of proline-specific enzymes in septic shock patients (sepsis-2).

The proline-specific enzymes dipeptidyl peptidase 4 (DPP4), prolylcarboxypeptidase (PRCP), fibroblast activation protein α (FAP) and prolyl oligopeptidase (PREP) are known for their involvement in the immune system and blood pressure regulation. Only very limited information is currently available on their enzymatic activity and possible involvement in patients with sepsis and septic-shock. The activity of the enzymes was measured in EDTA-plasma of patients admitted to the intensive care unit (ICU): 40 septic shock patients (sepsis-2) and 22 ICU control patients after major intracranial surgery. These data were used to generate receiver operating characteristic (ROC) curves. A survival analysis (at 90 days) and an association study with other parameters was performed. PRCP (day 1) and PREP (all days) enzymatic activities were higher in septic shock patients compared to controls. In contrast, FAP and DPP4 were lower in these patients on all studied time points. Since large differences were found, ROC curves were generated and these yielded area under the curve (AUC) values for PREP, FAP and DPP4 of 0.88 (CI: 0.80-0.96), 0.94 (CI: 0.89-0.99) and 0.86 (CI: 0.77-0.95), respectively. PRCP had a lower predicting value with an AUC of 0.71 (CI: 0.58-0.83). A nominally significant association was observed between survival and the DPP4 enzymatic activity at day 1 (p<0.05), with a higher DPP4 activity being associated with an increase in survival. All four enzymes were dysregulated in septic shock patients. DPP4, FAP and PREP are good in discriminating between septic shock patients and ICU controls and should be further explored to see whether they are already dysregulated in earlier stages, opening perspectives for their further investigation as biomarkers in sepsis. DPP4 also shows potential as a prognostic biomarker. Additionally, the associations found warrant further research.

Predictive value of cystatin C and neutrophil gelatinase-associated lipocalin in contrast-induced nephropathy: A meta-analysis.

BACKGROUND: There are still limited studies comprehensively examining the diagnostic performance of neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C in contrast-induced nephropathy (CIN). The study aimed to investigate and compare the predictive value of NGAL and cystatin C in the early diagnosis of CIN. METHODS AND MATERIALS: We searched the PubMed, EMBASE and Cochrane Library databases until November 10, 2019. The methodological quality of the included studies was assessed by the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) tool. Bivariate modeling and hierarchical summary receiver operating characteristic (HSROC) modeling were performed to summarize and compare the diagnostic performance of blood/urine NGAL and serum cystatin C in CIN. Subgroup and meta-regression analyses were performed according to the study and patient characteristics. RESULTS: Thirty-seven studies from thirty-one original studies were included (blood NGAL, 1840 patients in 9 studies; urine NGAL, 1701 patients in 10 studies; serum cystatin C, 5509 patients in 18 studies). Overall, serum cystatin C performed better than serum/urine NGAL (pooled DOR: 43 (95%CI: 12-152); AUROC: 0.93; λ: 3.79); serum and urine NGAL had a similar diagnostic performance (pooled DOR: 25 (95%CI: 6-108)/22(95%CI: 8-64); AUROC: 0.90/0.89; λ: 3.20/3.08). Meta-regression analysis indicated that the sources of heterogeneity might be CIN definition, assays, and nationalities. CONCLUSION: Both NGAL and cystatin C can serve as early diagnostic indicators of CIN, while cystatin C may perform better than NGAL.

Adipose tissue contribution to plasma fibroblast growth factor 21 and fibroblast activation protein in obesity.

Fibroblast growth factor 21 (FGF21) is an important regulator of energy metabolism. FGF21 is inactivated by fibroblast activation protein (FAP). We investigated whether FGF21 and/or FAP are secreted from human white adipose tissue of individuals with obesity by measuring total FGF21, active FGF21, and FAP concentrations in arterialized blood and venous blood draining the subcutaneous abdominal adipose tissue (scAT). Measurements were performed under fasting conditions and after a high fat meal before and after diet-induced weight loss in 16 adults with BMI 27-35 kg/m2. FGF21 was not released from scAT, neither before nor after weight loss in agreement with an undetectable gene expression of FGF21 in this tissue. Although scAT showed significant gene expression of FAP, no release of FAP from the tissue could be detected. The high fat meal increased postprandial circulating FGF21 but not FAP. Circulating levels of FAP but not FGF21 were significantly reduced after weight loss. On the other hand, FAP expression in scAT was increased. In conclusion, release from scAT does not appear to contribute to circulating concentrations of FGF21 and FAP and their responses to ingestion of a high fat meal or weight loss, respectively, in individuals with obesity.

FGF21 and glycemic control in patients with T1D.

PURPOSE: Fibroblast growth factor (FGF) 21 is a circulating hormone with an important role in metabolic regulation. FGF21 production in humans responds positively to glucose consumption and we hypothesize that serum FGF21 concentration is associated to glycemic control. METHODS: We enrolled 31 patients with type 1 diabetes (T1D) based on their HbA1c (well-regulated (HbA1c <53 mmol/mol), (n = 18) or poorly-regulated (HbA1c >69 mmol/mol), (n = 13). Twelve patients (39%) were diagnosed with retinopathy. Twenty healthy individuals comparable for age and gender distribution were included as a reference group. Serum FGF21, intact FGF21, fibroblast activation protein (FAP), adiponectin, and C-Reactive Protein (CRP) were measured by immunoassays. RESULTS: No correlation between FGF21 concentration and HbA1c was found. Patients with T1D had lower levels of circulating FGF21 as compared with the reference group, but the difference was nonsignificant (p = 0.12). Dividing the patients according to retinopathy, we found that T1D patients with retinopathy had significantly lower FGF21 concentrations (10.0 ng/L) as compared with the healthy reference group (37.1 ng/L), (p = 0.02). We found significantly higher levels of the FGF21 cleaving enzyme, FAP, in patients with T1D (97.2 µg/L) as compared with the healthy control group (78.5 µg/L), (p = 0.006). Interestingly, serum FAP levels correlated significantly with circulating FGF21 levels in T1D patients, but this correlation was not found in the healthy controls. CONCLUSIONS: We found no association between circulating FGF21 levels and HbA1c. T1D patients with retinopathy had significantly lower FGF21 levels as compared with healthy individuals, but it remains unclear if the lower levels of FGF21 are pathogenically related to the development of microvascular complications. Of note, serum FAP levels were significantly higher in all T1D patients as compared with the healthy individuals.

Higher serum levels of fibroblast growth factor 21 in old patients with cachexia.

OBJECTIVE: Fibroblast growth factor (FGF)21 is promptly induced by short fasting in animal models to regulate glucose and fat metabolism. Data on FGF21 in humans are inconsistent and FGF21 has not yet been investigated in old patients with cachexia, a complex syndrome characterized by inflammation and weight loss. The aim of this study was to explore the association of FGF21 with cachexia in old patients compared with their healthy counterparts. METHODS: Serum FGF21 and its inactivating enzyme fibroblast activation protein (FAP)-α were measured with enzyme-linked immunoassays. Cachexia was defined as ≥5% weight loss in the previous 3 mo and concurrent anorexia (Council on Nutrition appetite questionnaire). RESULTS: We included 103 patients with and without cachexia (76.9 ± 5.2 y of age) and 56 healthy controls (72.9 ± 5.9 y of age). Cachexia was present in 16.5% of patients. These patients had significantly higher total FGF21 levels than controls (952.1 ± 821.3 versus 525.2 ± 560.3 pg/mL; P = 0.012) and the lowest FGF21 levels (293.3 ± 150.9 pg/mL) were found in the control group (global P < 0.001). Although FAP-α did not differ between the three groups (global P = 0.082), bioactive FGF21 was significantly higher in patients with cachexia (global P = 0.002). Risk factor-adjusted regression analyses revealed a significant association between cachexia and total (ß = 649.745 pg/mL; P < 0.001) and bioactive FGF21 (ß = 393.200 pg/mL; P <0.001), independent of sex, age, and body mass index. CONCLUSIONS: Patients with cachexia exhibited the highest FGF21 levels. Clarification is needed to determine whether this is an adaptive response to nutrient deprivation in disease-related cachexia or whether the increased FGF21 values contribute to the catabolic state.

The development and validation of a combined kinetic fluorometric activity assay for fibroblast activation protein alpha and prolyl oligopeptidase in plasma.

BACKGROUND: Fibroblast activiation protein alpha (FAP) is considered a diagnostic and prognostic biomarker for various types of cancer. FAP shares substrate specificity with prolyl oligopeptidase (PREP), studied in (neuro)inflammation and neurodegeneration as well as cancer. Current assays inadequately discriminate between FAP and PREP and there is need for an assay that reliably quantitates the FAP/PREP activity ratio in plasma. METHODS: FAP and PREP activities were measured in human EDTA-plasma in presence of well characterized PREP and FAP inhibitors. RESULTS: A combined kinetic assay was developed in conditions to optimally measure FAP as well as PREP activity with Z-Gly-Pro-AMC as substrate. Limit of detection was 0.009 U/L and limit of quantitation was 0.027 U/L for the combined FAP-PREP assay. Within-run coefficient of variation was 3% and 4% and between-run precision was 7% and 12% for PREP and FAP, respectively. Accuracy was demonstrated by comparison with established end-point assays. Hemolysis interferes with the assay with 1.5 g/L hemoglobin as cut-off value. PREP (but not FAP) activity can increase upon lysis of platelets and red blood cells during sample preparation. CONCLUSION: With this new assay, on average 67% of the Z-Gly-Pro-AMC converting activity in plasma can be attributed to FAP.

Loss of alveolar bone density in postmenopausal, osteopenic women is associated with circulating levels of gelatinases.

OBJECTIVE: To determine whether circulating levels of two matrix metalloproteinases, MMP-2 and MMP-9, are associated with loss of alveolar bone density (ABD) or height (ABH), or with progression of periodontitis (relative clinical attachment level [RCAL]), among postmenopausal women with local and systemic bone loss. BACKGROUND: This study was planned as part of a 2-year randomized, double-blind, placebo-controlled, clinical trial examining efficacy/safety of subantimicrobial dose doxycycline (20 mg bid) in postmenopausal osteopenic women. This study examines whether serum levels of gelatinases are associated with local changes in the periodontium. METHODS: A sample of 113 women received periodontal maintenance for moderate to advanced chronic periodontitis and consented to analysis of stored serum biomarkers. Posterior vertical bitewings were taken, and serum collected, at baseline, one, and 2 years. ABD was determined by computer-assisted densitometric image analysis (CADIA), ABH by the Hausmann et al (1992, J Periodontol 63, 657) method, and RCAL by Florida Probe (every 6 months). MMPs were measured densitometrically on gelatin zymograms using denatured type I collagen as substrate and purified MMP-2 (72 kDa) and MMP-9 (92 kDa) as standards. Evidence of worsening in the periodontium at a tooth site was defined as a change from baseline of, for ABD, at least 14 densitometric units (for subcrestal locations) or 17 units (for crestal locations); of at least 0.4 mm for ABH; and of at least 1.5 mm for RCAL. Logistic regression models, while accounting for clustering, compared the odds of worsening in ABD, ABH, or RCAL, after 2 years of observation, between groups defined by baseline and concurrent levels of serum gelatinases. RESULTS: Changes in ABH and RCAL were not associated with circulating levels of MMP-2 or MMP-9. However, elevated odds of ABD loss over 24 months were associated, among smokers, with both baseline and concurrent levels of MMP-9 in the middle and highest tertile, and with concurrent levels of MMP-2 in the middle (but not the highest) tertile. Elevated odds of ABD loss were also associated, among women within 5 years of menopause, with baseline levels of MMP-2 in the highest tertile. CONCLUSION: Among postmenopausal osteopenic women, loss of ABD was associated, in smokers, with elevated circulating levels of MMP-9 and MMP-2. In those within 5 years of menopause, ABD loss was associated with elevated circulating levels of MMP-2.

A novel strategy for identifying early acute kidney injury in pediatric hematopoietic stem cell transplantation.

Acute kidney injury (AKI) is a common complication in pediatric hematopoietic stem cell transplantation (HSCT). Serum creatinine is an imprecise biomarker of AKI. We hypothesized that combining creatinine with serum cystatin C (cysC) and urinary neutrophil gelatinase-associated lipocalin (NGAL) more effectively characterizes AKI during the first 28 days of HSCT and better identifies patients at risk of adverse outcomes than creatinine alone. We prospectively assessed the type and severity of AKI in 80 consecutive allogeneic HSCT patients using weekly creatinine, cysC, and NGAL. We combined the biomarkers to define 7 Composite Types of AKI, including All Positive AKI (simultaneously detected creatinine, cysC, and NGAL AKI). Outcomes included renal replacement therapy and transplant-related mortality. In all, 75% of patients had AKI by at least one measure; 33% developed >1 type of AKI. Mild AKI often preceded Severe AKI. Patients with creatinine or NGAL AKI that were Severe or Repeated tended to have worse outcomes. The five patients with All Positive AKI had the highest rates of morbidity and mortality. AKI evaluation with creatinine, cysC, and NGAL provides a comprehensive profile of early AKI and narrowly identifies patients at highest risk of adverse outcomes, providing opportunities for early, impactful intervention.

Afterglow Resonance Energy Transfer Inhibition for Fibroblast Activation Protein-α Assay.

Traditional photoluminescence resonance energy transfer (PRET)-based sensors are widely applied, but still suffer from the severe background interference from in situ excitation. The afterglow nature of the persistent luminescence nanoparticles (PLNPs) allows optosensing after the stoppage of in situ illumination, and thus subtly overcomes that interference. We proposed a simple strategy for functionalizing PLNPs for bioanalytical applications and the new afterglow resonance energy transfer (ARET)-based assay for quantitative determination and imaging of fibroblast activation protein-alpha (FAPα) in live cells using Au-decorated Cr3+0.004:ZnGa2O4 as donor and Cy5.5-KGPNQC-SH as acceptor. The ARET between the donor and acceptor quenches the afterglow of the donor, and the cleavage of peptide KGPNQC by FAPα inhibits the ARET and restores the afterglow of the donor. The ARET-based assay of FAPα, with the linear range of 0.1-2.0 mg·L-1 (1.2-22.9 nM), LOD of 11 µg·L-1 (115 pM), and RSD of 3.9% (for 0.5 mg·L-1 FAPα, n = 5), displays higher sensitivity, lower limit of detection (LOD), and better anti-interference capability than the corresponding PRET-based assay. Besides, the ARET-based sensors are lighted up by the FAPα-positive U87MG and MDA-MB-435 cells, but kept in the dark when incubated in the FAPα-negative AD293 cells. The proposed ARET-based sensor can detect FAPα of U87MG and MDA-MB-435 living cells in human serum with the spiked recoveries of 95.6-103%. Our data demonstrated a simple and effective strategy for bridging PLNPs to bioanalytical applications, and an attractive ARET assay of FAPα.

Eccentric exercise increases circulating fibroblast activation protein α but not bioactive fibroblast growth factor 21 in healthy humans.

NEW FINDINGS: What is the central question of this study? The role of FGF21 as an exercise-induced myokine remains controversial. The aim of this study was to determine whether eccentric exercise would augment the release of FGF21 and/or its regulatory enzyme, fibroblast activation protein α (FAP), from skeletal muscle tissue into the systemic circulation of healthy human volunteers. What is the main finding and its importance? Eccentric exercise does not release total or bioactive FGF21 from human skeletal muscle. However, exercise releases its regulatory enzyme, FAP, from tissue(s) other than muscle, which might play a role in the inactivation of FGF21. ABSTRACT: The primary aim of the investigation was to determine whether eccentric exercise would augment the release of the myokine fibroblast growth factor 21 (FGF21) and/or its regulatory enzyme, fibroblast activation protein α (FAP), from skeletal muscle tissue into the systemic circulation of healthy human volunteers. Physically active young healthy male volunteers (age 25.0 ± 10.7 years; body mass index 23.1 ± 7.9 kg m-2 ) completed three sets of 25 repetitions (with 5 min rest in between) of single-leg maximal eccentric contractions using their non-dominant leg, whilst the dominant leg served as a control. Arterialized blood samples from a hand vein and deep venous blood samples from the common femoral vein of the exercised leg, along with blood flow of the superficial femoral artery using Doppler ultrasound, were obtained before and after each exercise bout and every 20 min during the 3 h recovery period. Muscle biopsy samples were taken at baseline, immediately and 3 and 48 h postexercise. The main findings showed that there was no significant increase in total or bioactive FGF21 secreted from skeletal muscle into the systemic circulation in response to exercise. Furthermore, skeletal muscle FGF21 protein content was unchanged in response to exercise. However, there was a significant increase in arterialized and venous FAP concentrations, with no apparent contribution to its release from the exercised leg. These findings raise the possibility that the elevated levels of FAP might play a role in the inactivation of FGF21 during exercise.

Circulating gelatinases are not prognostic of treatment response and survival in locally advanced rectal cancer patients undergoing preoperative chemoradiotherapy.

PURPOSE: To investigate whether the serum levels of matrix metalloproteinases (MMPs) are predictive on treatment response and survival in locally advanced rectal cancer (LARC) patients undergoing preoperative chemoradiotherapy. PATIENTS AND METHODS: Serum MMP-2 and MMP-9 was analyzed by enzyme-linked immunosorbent assay and obtained before, midway, and 1-month after the end of preoperative radiotherapy treatment. The prognostic significance of serum MMP-2 and MMP-9 levels and their association with other pathological findings for LARC patients were evaluated. RESULTS: Serum levels of MMP-2 or MMP-9 were found to decrease with increasing clinical stage and negative correlation was statistically significant (P < 0.05). There was no statistically significant difference in tumor response and survival between the low and high MMP-2 and MMP-9 groups. MMP-2 and MMP-9 were not correlated with local-regional recurrence. CONCLUSIONS: We propose that serum levels of MMP-2 and MMP-9 are not predictive on treatment response and survival in LARC patients.

Circulating fibroblast activation protein and dipeptidyl peptidase 4 in rheumatoid arthritis and systemic sclerosis.

AIM: To quantify circulating fibroblast activation protein (cFAP) and dipeptidyl peptidase 4 (cDPP4) protease activities in patients with rheumatoid arthritis (RA), systemic sclerosis (SSc), and a control group with mechanical back pain and to correlate plasma levels with disease characteristics. METHODS: Plasma was collected from patients with RA (n = 73), SSc (n = 37) and control subjects (n = 26). DPP4 and FAP were quantified using specific enzyme activity assays. RESULTS: Median cDPP4 was significantly lower in the RA group (P = 0.02), and SSc group (P = 0.002) compared with controls. There were no significant differences in median cFAP between the three groups. DPP4 and FAP demonstrated a negative correlation with inflammatory markers and duration of disease. There were no associations with disease subtypes in RA, including seropositive and erosive disease. Decreased cDPP4 was found in SSc patients with myositis. Plasma FAP was lower in RA patients receiving prednisone (P = 0.001) or leflunomide (P = 0.04), but higher with biologic agents (P = 0.01). RA patients receiving leflunomide also had decreased cDPP4 (P = 0.014). SSc patients receiving prednisone (P = 0.02) had lower cDPP4 but there was no association with cFAP. CONCLUSIONS: No association was found between cFAP and RA or SSc. Plasma DPP4 was decreased in RA and SSc when compared with controls. cDPP4 and cFAP correlated negatively with inflammatory markers and there were no significant correlations with disease characteristics in this RA cohort.

[Biomarkers of renal injury in contact ureteral lithotripsy].

AIM: To optimize the transurethral endoscopic management of patients with ureterolithiasis by measuring biomarkers of renal parenchymal damage. MATERIALS AND METHODS: One hundred fifty-one patients with solitary ureteral stones were tested for levels of cystatin C, neutrophil gelatinase-associated lipocalin, 2-microglobulin and interleukin 18. RESULTS: An increase in the levels of markers of renal injury was observed both in the preoperative period and after CULT. Differences in the values of these indices depended on the timing of the CULT, the size and location of the stone and the type of lithotripter. CONCLUSIONS: All patients were found to have damage to the renal tubular system. The established critical values of the markers of renal injury in ureterolithiasis may be used as diagnostic criteria for renal injury.

Circulating fibroblast activation protein activity and antigen levels correlate strongly when measured in liver disease and coronary heart disease.

BACKGROUND AND AIM: Circulating fibroblast activation protein (cFAP) is a constitutively active enzyme expressed by activated fibroblasts that has both dipeptidyl peptidase and endopeptidase activities. We aimed to assess the correlation between cFAP activity and antigen levels and to compare variations in levels. METHODS: In plasma of 465 control individuals, 368 patients with coronary heart disease (CHD) and 102 hepatitis C virus (HCV) infected patients with severe liver disease before and after liver transplant, cFAP activity levels were measured with a newly developed cFAP activity assay. In the same samples, cFAP antigen levels were measured using a commercially available cFAP ELISA. Correlation analyses between activity and antigen levels were performed by calculating Pearson's correlation coefficient (ρ). Additionally, normal ranges, determinants and differences between cohorts and between anticoagulants were investigated. RESULTS: cFAP activity and antigen levels significantly correlated in controls (ρ: 0.660, p<0.001) and in CHD patients (ρ: 0.709, p<0.001). cFAP activity and antigen levels in the HCV cohort were significantly lower in the samples taken after liver transplantation (p<0.001) and normalized toward levels of healthy individuals. Furthermore, cFAP activity and antigen levels were higher in men and significantly associated with body mass index. Also, cFAP activity and antigen levels were higher in EDTA plasma as compared to the levels in citrated plasma from the same healthy individuals. CONCLUSIONS: For analyzing cFAP levels, either activity levels or antigen levels can be measured to investigate differences between individuals. However, it is of importance that blood samples are collected in the same anticoagulant.

Gelatinases A and B and Antioxidant Enzyme Activity in the Early Phase of Acute Myocardial Infarction.

Oxidative stress plays important roles in the pathophysiology of acute myocardial infarction (AMI). The aim of this study was to investigate the correlation of the oxidative stress status and matrix metalloproteinase activity in AMI patients in comparison to controls. This study included 136 subjects: 68 patients with AMI (42 males/26 females; mean age 58.5 ± 10.5 years) and 68 controls (37 males/29 females; mean age 60.2 ± 12.4 years). Gelatinases A and B were assayed using gelatin zymography, enzyme activities were obtained spectrophotometrically. Gelatinase A and B activities were increased in the AMI patients' group compared to the control. Activities of serum superoxide dismutase (SOD) and xanthine oxidase (XO) were significantly higher in AMI patients (106.53 ± 23.45 U/l, P < 0.001 and 158.18 ± 29.59 U/l, P < 0.001) than in the control group (55.99 ± 10.79 U/l and 79.81 ± 7.93 U/l). The activity of catalase (CAT) in the sera of AMI patients was lower (271.31 ± 7.53 U/l, P < 0.005) than in the control group (305.94 ± 97.28 U/l). Plasma glutathione peroxidase (GPx) and glutathione reductase (GR) in AMI patients were significantly higher (582.47 ± 184.81 U/l, P < 0.001 and 59.64 ± 21.88 U/l, P < 0.001) than in the control group (275.32 ± 104.69 U/l and 47.71 ± 20.05 U/l). The present findings demonstrate activation of gelatinases A and B and oxidative stress markers in the early stage of AMI. Gelatinases, detected at high levels in AMI patients only, indicate their noticeable predisposition for becoming additional biomarkers of the early phase of AMI.

Evaluation of the circulating level of fibroblast activation protein α for diagnosis of esophageal squamous cell carcinoma.

To evaluate whether circulating fibroblast activation protein α (FAPα) could serve as a biomarker for the diagnosis of esophageal squamous cell carcinoma (ESCC), enzyme-linked immunosorbent assay (ELISA) was used to detect plasma FAPα in 556 participants including ESCC group, benign esophageal disease group, healthy controls and other cancer controls group. The levels of plasma FAPα were significantly decreased in ESCC patients (P < 0.001) and showed a positive correlation with HDL-C levels (R = 0.372, P < 0.001). The sensitivity and specificity of plasma FAPα were 56.1% and 85.6% based on the optimal cut-off (49.04 ng/ml, AUC = 0.714). The combination of FAPα and the traditional biomarkers (CEA, CYFR211 and SCCA) improved the sensitivity (41.5%) without compromising the specificity (95.0%). Contradictorily, the immunohistochemical staining revealed the overexpression of FAPα in stroma of ESCC tissues. So the source of soluble FAPα was further explored by qRT-PCR, Western blotting, ELISA and immunoprecipitation in fibroblast cell lines and mouse xenograft models. We found that the plasma FAPα was not correlated with the FAPα expressed in tumor, and the multi-organ might contribute to the circulating levels of FAPα including skeletal muscle, liver and bone marrow. These results indicated that the low plasma FAPα level might due to the systemic reaction to the presence of tumor and circulating FAPα level might be a potential indicator for diagnosing ESCC.

Changes in concentrations of circulating fibroblast activation protein alpha are associated with myocardial damage in patients with acute ST-elevation MI.

BACKGROUND: Fibroblast activation protein alpha (FAP) is a membrane-bound serine protease expressed by activated fibroblasts after myocardial infarction (MI). Reduced circulating FAP levels were associated with increased mortality in patients with acute coronary syndrome. We hypothesized that FAP concentrations are altered after acute ST-elevation MI (STEMI), and related to myocardial damage. METHODS: We measured circulating FAP concentrations in blood plasma of 60 patients on admission, day 1, day 3 and day 5 after STEMI, and in 25 apparently healthy blood donors as controls. RESULTS: Plasma FAP concentrations were lower in STEMI patients on admission (71ng/mL) than in blood donors (101ng/mL, P<0.0001). FAP concentrations declined in STEMI patients from admission to day 3 (66ng/mL, P<0.05) and day 5 (57ng/mL, P<0.05). FAP concentrations on day 5 were inversely correlated with maximum CK and maximum CRP levels. In a multiple linear regression analysis, maximum CRP was independently associated with low FAP concentrations on day 5 after STEMI. When stratified according to the absolute amount of FAP change from admission to day 5 (ΔFAP), patients with high ΔFAP (-22ng/mL) had worse left ventricular function, higher levels of hs-cTnT, CK on admission, maximum CK and CRP than patients with low ΔFAP (-3ng/mL). CONCLUSIONS: Our study first demonstrates alterations of circulating FAP concentrations acutely after STEMI. A greater decline of circulating FAP concentrations in the first 5days after STEMI is associated with increased myocardial damage and inflammation. Measurement of circulating FAP might help to better understand the relation of myocardial injury and inflammatory response in the individual patient.

Acute Ischemic Stroke Severity, Progression, and Outcome Relate to Changes in Dipeptidyl Peptidase IV and Fibroblast Activation Protein Activity.

Dipeptidyl peptidase IV (DPPIV) inhibition may be a promising therapeutic strategy for acute stroke treatment, given its potential to prolong the biological half-life of neuroprotective substrates. A related protease, fibroblast activation protein (FAP), was recently shown to inactivate the same substrates. Therefore, it should also be investigated as a potential target in stroke. The study aimed to investigate whether stroke severity and outcome correlate with DPPIV and FAP activities and their kinetics shortly after acute ischemic stroke. DPPIV and FAP activities were analyzed in the serum of 50 hyperacute stroke patients at admission, 1 day, 3 days, and 7 days after stroke onset and in 50 age-matched healthy controls. This was done as part of the Middelheim's Interdisciplinary Stroke Study. DPPIV activity tended to increase shortly after stroke compared to the control population. DPPIV and FAP activities steadily decreased in the first week after stroke onset. Higher infarct volumes (≥5 ml) and a more severe stroke (NIHSS >7) at admission were correlated with a stronger decrease in the activities of both enzymes. Moreover, these patients more often developed a progressive stroke, were more often institutionalized. Patients with a stronger increase in DPPIV activity at admission and decrease in the activity of both DPPIV and FAP during the first week after stroke onset had a more severe stroke and worse short-term outcomes.