Role of follistatin-like 1 levels and functions in calcific aortic stenosis

Background

Calcific aortic valve disease (CAVD) is a progressive disease resulting in severe calcific aortic stenosis (AS), and there is increasing interest in the discovery of novel biomarkers to identify patients with potential future calcific AS at an early stage. This study aimed to determine whether follistatin-like 1 (FSTL1) is associated with calcific AS events and its exact role in aortic valve calcification.

Methods

A prospective observational cohort study involving 656 patients was performed to investigate the relationship between serum FSTL1 and calcific AS incidence during a follow-up of 5 years. Furthermore, we detected FSTL1 levels in valvular interstitial cells (VICs) from calcified valves and explored the effects of FSTL1 on VIC osteogenic differentiation in vitro as well as the signaling pathways involved.

Results

During a median follow-up of 5 years, lower FSTL1 levels were associated with a significantly higher risk of calcific AS events (log rank test, P = 0.007). In addition, Cox multivariable regression analyses verified the predictive value of FSTL1 after adjusting for both demographic features and laboratory confounders. Consistent with our results for serum, a lower concentration of FSTL1 was observed in calcified human valves (n = 11) and mainly colocalized with VICs. Recombinant human FSTL1 (rhFSTL1) stimulation inhibited calcium deposition, alkaline phosphatase (ALP) activity, and osteogenic gene expression partly through the downregulation of the ERK1/2 pathway.

Conclusion

Taken together, this study provides a strong rationale to consider FSTL1 as a potential therapeutic target for calcific AS.

Follistatin-like 1 and Biomarkers of Neutrophil Activation Are Associated with Poor Short-Term Outcome after Lung Transplantation on VA-ECMO

The investigation of biomarkers associated with undesired outcome following lung transplantation (LuTX) is essential for a better understanding of the underlying pathophysiology, an earlier identification of susceptible recipients and the development of targeted therapeutic options. We therefore determined the longitudinal perioperative course of putative cytokines related to neutrophil activation (chemokine CC motif ligand 4 (CCL-4), interleukin (IL)-23 and Lipocalin 2 (LCN2)) and a cytokine that has been implicated in graft-versus-host disease (Follistatin-like 1 (FSTL1)) in 42 consecutive patients undergoing LuTX. We plotted receiver-operating curves (ROC) to assess the predictive power of the measured cytokines for short-term outcomes namely primary graft dysfunction (PGD), early complications requiring extracorporeal membrane oxygenation (ECMO), and a high postoperative sequential organ failure assessment (SOFA). All cytokines increased immediately after surgery. ROC analyses determined significant associations between CCL4 and a high SOFA score (area under the curve (AUC) 0.74 (95%CI:0.5−0.9; p < 0.05), between LCN2 and postoperative ECMO support (AUC 0.73 (95%CI:0.5−0.9; p < 0.05), and between FSTL1 and PGD (AUC 0.70 (95%CI:0.5−0.9; p < 0.05). The serum concentrations of the neutrophil-derived cytokines LCN2 and CCL4 as well as FSTL1 were all related to poor outcome after LuTX. The specific predictive power, however, still has to be assessed in larger trials. The potential role of FSTL1 as a biomarker in the development of PGD could be of great interest particularly since this protein appears to play a crucial role in allograft tolerance.

Aerobic exercise training-induced follistatin-like 1 secretion in the skeletal muscle is related to arterial stiffness via arterial NO production in obese rats

Follistatin‐like 1 (FSTL1), which is mainly secreted from skeletal muscle and myocardium, upregulates protein kinase B (Akt) and endothelial nitric oxide synthase (eNOS) phosphorylation in vascular endothelial cells. It is unclear whether skeletal muscle‐ and myocardium‐derived FSTL1 secretion induced by aerobic exercise training is involved in the reduction of arterial stiffness via arterial NO production in obese rats. This study aimed to clarify whether aerobic exercise training‐induced FSTL1 secretion in myocardium and skeletal muscle is associated with a reduction in arterial stiffness via arterial Akt‐eNOS signaling pathway in obese rats. Sixteen Otsuka Long‐Evans Tokushima Fatty (OLETF) obese rats were randomly divided into two groups: sedentary control (OLETF‐CON) and eight‐week aerobic exercise training (treadmill for 60min at 25m/min, 5days/week, OLETF‐AT). Eight Long‐Evans Tokushima Otsuka (LETO) rats were used as a healthy sedentary control group. In OLETF‐CON, serum FSTL1, arterial Akt and eNOS phosphorylation, and arterial nitrite/nitrate (NOx) levels were significantly lower, and carotid‐femoral pulse wave velocity (cfPWV) was significantly greater than those in LETO. These parameters were improved in the OLETF‐AT compared to the OLETF‐CON. In the OLETF‐AT, FSTL1 levels in slow‐twitch fiber‐rich soleus muscle were significantly greater than those in the OLETF‐CON, but not in myocardium, fast‐twitch fiber‐rich tibialis anterior muscle, and adipose tissue. Serum FSTL1 levels were positively correlated with soleus FSTL1, arterial eNOS phosphorylation, and NOx levels and negatively correlated with cfPWV. Thus, aerobic exercise training‐induced FSTL1 secretion in slow‐twitch fiber‐rich muscles may be associated with a reduction in arterial stiffness via arterial NO production in obese rats.

Haemodynamic Wall Shear Stress, Endothelial Permeability and Atherosclerosis-A Triad of Controversy

A striking feature of atherosclerosis is its patchy distribution within the vascular system; certain arteries and certain locations within each artery are preferentially affected. Identifying the local risk factors underlying this phenomenon may lead to new therapeutic strategies. The large variation in lesion prevalence in areas of curvature and branching has motivated a search for haemodynamic triggers, particular those related to wall shear stress (WSS). The fact that lesions are rich in blood-derived lipids has motivated studies of local endothelial permeability. However, the location of lesions, the underlying haemodynamic triggers, the role of permeability, the routes by which lipids cross the endothelium, and the mechanisms by which WSS affects permeability have all been areas of controversy. This review presents evidence for and against the current consensus that lesions are triggered by low and/or oscillatory WSS and that this type of shear profile leads to elevated entry of low density lipoprotein (LDL) into the wall via widened intercellular junctions; it also evaluates more recent evidence that lesion location changes with age, that multidirectional shear stress plays a key role, that LDL dominantly crosses the endothelium by transcytosis, and that the link between flow and permeability results from hitherto unrecognised shear-sensitive mediators.

Association between follistatin-related protein 1 and the functional status of patients with anti-neutrophil cytoplasmic antibody-associated vasculitis

BACKGROUND

Follistatin-like 1 (FSTL1) plays both pro-inflammatory and anti-inflammatory roles in the inflammatory processes. We investigated whether serum FSTL1 could predict the current anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV)-specific indices.

METHODS

We randomly selected 74 patients with AAV from a prospective and observational cohort of Korean patients with AAV. Clinical and laboratory data and AAV-specific indices were recorded. FSTL1 concentration was determined using the stored sera. The lowest tertile of the short-form 36-item health survey (SF-36) was defined as the current low SF-36. The cutoffs of serum FSTL1 for the current low SF-36 physical component summary (PCS) and SF-36 mental component summary (MCS) were extrapolated by the receiver operator characteristic curve.

RESULTS

The median age was 62.5 years (55.4% were women). Serum FSTL1 was significantly correlated with SF-36 PCS (r =  - 0.374), SF-36 MCS (r = -0.377), and C-reactive protein (CRP) (r = 0.307), but not with Birmingham vasculitis activity score (BVAS). In the multivariable linear regression analyses, BVAS, CRP, and serum FSTL1 were independently associated with the current SF-36 PCS (β = -0.255, β = -0.430, and β = -0.266, respectively) and the current SF-36 MCS (β = -0.234, β =-0.229, and β = -0.296, respectively). Patients with serum FSTL1 ≥779.8 pg/mL and those with serum FSTL1 ≥841.6 pg/mL exhibited a significantly higher risk of having the current low SF-36 PCS and SF-36 MCS than those without (relative risk 7.583 and 6.200, respectively).

CONCLUSION

Serum FSTL1 could predict the current functional status in AAV patients.

Follistatin-like 1 deficiency impairs T cell development to promote lung metastasis of triple negative breast cancer

Our study aims to detect the underlying mechanism of the suppressive effect of Follistatin-like 1 (FSTL1) on lung metastasis of triple negative breast cancer (TNBC). We found that FSTL1 had no effect on the proliferation and metastasis of 4T1 cells in vitro, while in the tumor-bearing Fstl1 heterozygous (Fstl1^+/-) mice, the number of anti-tumor T lymphocytes in the lung was significantly reduced with the increase in lung metastasis. Impaired development of T cells can cause dysfunction of adaptive immune system, which promotes cancer metastasis. Therefore the effect of FSTL1 on T cell development was further investigated. Lower population of T cells in periphery and decreased proliferation of CD4^- CD8^- double negative (DN) thymocytes and impairment development of T cells were found in Fstl1^+/- mice. Furthermore, high expression of FSTL1 in medullary thymus epithelial (mTEC) cells and decreased mRNA expression of inducible costimulator on activated T-cell ligand (Icosl) in mTEC^{sh Fstl1} were detected. Combining other studies that the generation of ICOSL by mTEC cells promotes CD4⁺ single positive (SP) thymocytes to produce IL-2, which promotes T cell development. Our results indicate FSTL1 deficiency in mTEC cells impairs T cell development to promote the lung metastasis of TNBC.

Regulation of Pulmonary Bacterial Immunity by Follistatin-Like Protein 1

Klebsiella pneumoniae is a common cause of antibiotic-resistant pneumonia. Follistatin-like protein 1 (FSTL-1) is highly expressed in the lung and is critical for lung homeostasis. The role of FSTL-1 in immunity to bacterial pneumonia is unknown. Wild-type (WT) and FSTL-1 hypomorphic (Hypo) mice were infected with Klebsiella pneumoniae to determine infectious burden, immune cell abundance, and cytokine production. FSTL-1 Hypo/TCRδ^-/- and FSTL-1 Hypo/IL17ra^-/- were also generated to assess the role of γδT17 cells in this model. FSTL-1 Hypo mice had reduced K. pneumoniae lung burden compared with that of WT controls. FSTL-1 Hypo mice had increased Il17a/interleukin-17A (IL-17A) and IL-17-dependent cytokine expression. FSTL-1 Hypo lungs also had increased IL-17A⁺ and TCRγδ⁺ cells. FSTL-1 Hypo/TCRδ^-/- displayed a lung burden similar to that of FSTL-1 Hypo and reduced lung burden compared with the TCRδ^-/- controls. However, FSTL-1 Hypo/TCRδ^-/- mice had greater bacterial dissemination than FSTL-1 Hypo mice, suggesting that gamma delta T (γδT) cells are dispensable for FSTL-1 Hypo control of pulmonary infection but are required for dissemination control. Confusing these observations, FSTL-1 Hypo/TCRδ^-/- lungs had an increased percentage of IL-17A-producing cells compared with that of TCRδ^-/- mice. Removal of IL-17A signaling in the FSTL-1 Hypo mouse resulted in an increased lung burden. These findings identify a novel role for FSTL-1 in innate lung immunity to bacterial infection, suggesting that FSTL-1 influences type-17 pulmonary bacterial immunity.

Follistatin-like 1 as a Novel Adipomyokine Related to Insulin Resistance and Physical Activity

BACKGROUND AND AIMS

Follistatin-like protein-1 (FSTL-1) is considered to be an adipokine or myokine that could be a potential regulator of metabolism. Our purpose is to investigate the relationship between circulating FSTL-1 levels and insulin resistance (IR) in type 2 diabetes mellitus (T2DM) and to identify the regulatory factors.

METHODS

FSTL-1 expression in C57BL/6J and db/db mice was examined by quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) and Western blots. Serum FSTL-1 levels were measured by enzyme-linked immunosorbent assay in 298 T2DM patients and 202 healthy controls. Changes in the circulating FSTL-1 level were observed during the oral glucose tolerance test, EHC (euglycemic-hyperinsulinemic clamp), lipid infusion, acute exercise, and cold-exposure test.

RESULTS

We found that FSTL-1 protein expression in the adipose tissue of db/db mice was significantly higher than that of wild-type mice. Importantly, circulating FSTL-1 levels in T2DM and overweight/obese participants were higher than those in healthy and lean individuals, and was related to HOMA-IR, adiponectin, and obesity- and metabolism-related parameters. In the intervention study, 45 minutes of physical activity was found to significantly increase the circulating FSTL-1 concentration in young, healthy participants. Further, FSTL-1 protein expression in adipose tissue rose dramatically in response to physical activity in mice. Hyperinsulinemia during EHC and acute elevated FFA induced by lipid infusion resulted in a significant decrease in the circulating FSTL-1 levels. However, no change was found in the circulating FSTL-1 levels in response to the oral glucose challenge or cold-exposure test.

CONCLUSIONS

FSTL-1 may be an adipomyokine associated with insulin resistance and physical activity, and circulating FSTL-1 levels are increased in patients with T2DM.

Targeting FSTL1 for Multiple Fibrotic and Systemic Autoimmune Diseases

Follistatin-like 1 (FSTL1) is a matricellular protein that is upregulated during development and disease, including idiopathic pulmonary fibrosis (IPF), keloid, and arthritis. The profibrotic and pro-inflammatory roles of FSTL1 have been intensively studied during the last several years, as well as in this report. We screened and identified epitope-specific monoclonal neutralizing antibodies (nAbs) to functionally block FSTL1. FSTL1 nAbs attenuated bleomycin-induced pulmonary and dermal fibrosis in vivo and transforming growth factor (TGF)-β1-induced dermal fibrosis ex vivo in human skin. In addition, FSTL1 nAbs significantly reduced existing lung fibrosis and skin fibrosis in experimental models. FSTL1 nAbs exerted their potent antifibrotic effects via reduced TGF-β1 responsiveness and subsequent myofibroblast activation and extracellular matrix production. We also observed that FSTL1 nAbs attenuated the severity of collagen-induced arthritis in mice, which was accompanied by reduced inflammatory responses in vitro. Our findings suggest that FSTL1 nAbs are a promising new therapeutic strategy for the treatment of multiple organ fibrosis and systemic autoimmune diseases.

Inhibition of MicroRNA-9-5p Protects Against Cardiac Remodeling Following Myocardial Infarction in Mice

Follistatin-like 1 (Fstl1) protects cardiomyocytes from a broad spectrum of pathologic injuries including myocardial infarction (MI). It is worthy of note that although cardiac Fstl1 is elevated in post-MI microenvironment, its cardioprotective role is still restricted to a limited extent considering the frequency and severity of adverse cardiac remodeling following MI. We therefore propose that intrinsic Fstl1-suppressing microRNA (miRNA) may exist in the heart and its neutralization may further facilitate post-MI recovery. Here, miR-9-5p is predicted as one of the potential Fstl1-targeting miRNAs whose expression is decreased in ischemic myocardium and reversely correlated with Fstl1. Luciferase activity assay further validated Fstl1 as a direct target of miR-9-5p. In addition, forced expression of miR-9-5p in H9c2 cells is concurrent with diminished expression of Fstl1 and vice versa. Importantly, transfection of miR-9-5p mimics in hypoxic H9c2 cells exacerbates cardiac cell death, lactate dehydrogenase release, reactive oxygen species accumulation, and malonyldialdehyde concentration. More importantly, in vivo silencing of miR-9-5p by a specific antagomir in a murine acute MI model effectively preserves post-MI heart function with attenuated fibrosis and inflammatory response. Further studies demonstrated that antagomir treatment stabilizes Fstl1 expression as well as blocks cardiac cell death and reactive oxygen species generation in both ischemia-challenged hearts and hypoxia-treated cardiomyoblasts. Finally, cytoprotection against hypoxic challenge by miR-9-5p inhibitor is partially reversed by knockdown of Fstl1, indicating a novel role of miR-9-5p/Fstl1 axis in survival defense against hypoxic challenge. In summary, these findings identified miR-9-5p as a mediator of hypoxic injury in cardiomyoblasts and miR-9-5p suppression prevents cardiac remodeling after acute MI, providing a potential strategy for early treatment against MI.

Epigenetic inactivation of follistatin-like 1 mediates tumor immune evasion in nasopharyngeal carcinoma

Follistatin like-1 (FSTL1) is a secreted glycoprotein involved in a series of physiological and pathological processes. However, its contribution to the development of cancer, especially the pathogenesis of nasopharyngeal carcinoma (NPC), remains to be elucidated. We aimed to investigate the dysregulation of FSTL1 and its possible function in NPC. FSTL1 was frequently downregulated in NPC cell lines and primary tumor biopsies by promoter hypermethylation. Ectopic expression of FSTL1 significantly suppressed the colony formation, proliferation, migration and invasion ability of NPC cells and induced cell apoptosis. Overexpression of FSTL1 decreased the tumorigenicity of NPC cells in vivo. In addition, the proliferation of NPC cells in vitro was inhibited by treatment with soluble recombinant FSTL1 protein. The protein level of FSTL1 was decreased in primary NPC tumors and was associated with downregulated interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α). Furthermore, recombinant human FSTL1 protein induced secretion of IL-1β and TNF-α in macrophage cultures, therefore FSTL1 might activate macrophages and attenuate the immune evasion of NPC cells. In conclusion, the epigenetic downregulation of FSTL1 may suppress the proliferation and migration of NPC cells, leading to dysfunctional innate responses in surrounding macrophages.

Effect of Omega-3 Polyunsaturated Fatty Acids Supplementation on Body Composition and Circulating Levels of Follistatin-Like 1 in Males With Coronary Artery Disease: A Randomized Double-Blind Clinical Trial

Adipokines are mediators of body composition and are involved in obesity-related complications such as cardiovascular disease. Omega-3 supplementation has not been studied in the setting of body composition and follistatin-like 1 (FSTL1) levels in patients with coronary artery disease (CAD). This study aimed to investigate the effect of omega-3 polyunsaturated fatty acid (ω-3 PUFA) supplementation on body composition indices and serum levels of FSTL1 in CAD patients. A total of 42 male (aged 45-65 years) subjects with angiographically confirmed CAD were included in this randomized, double-blind, placebo-controlled trial study. The subjects were randomly divided into omega-3 and placebo groups. During the 8-week intervention, the omega-3 group received 1,200 mg of omega-3 daily, while the placebo group received paraffin. Before and after the study, anthropometric measurements and body composition components were taken; serum FSTL1 levels were assessed by an enzyme-linked immunosorbent assay (ELISA) kit. In the omega-3 group, a significant 27.6% increase in serum FSTL1 was seen after 8 weeks of intervention ( p = .001), but no significant difference in posttreatment levels of FSTL1 was observed between the two groups ( p > .05). At the end of the study, a significant decrease in low-density lipoprotein cholesterol (LDL-C; 94.29 ± 22.04 vs. 112.24 ± 24.5; p = .01) and high-sensitivity C-reactive protein (hs-CRP; 1.92 ± 0.79 vs. 3.19 ± 2.51; p = .03) concentration was detected between the two groups. Changes in fasting blood sugar, fasting insulin, body composition, and anthropometric parameters were not significant within and between the groups. Oral omega-3 might increase FSTL1 and decrease LDL-C and hs-CRP concentrations in CAD patients. However, omega-3 supplementation did not have any effect on FSTL1 levels between the groups.

Up-Regulation of Follistatin-Like 1 By the Androgen Receptor and Melanoma Antigen-A11 in Prostate Cancer

BACKGROUND

High affinity androgen binding to the androgen receptor (AR) activates genes required for male sex differentiation and promotes the development and progression of prostate cancer. Human AR transcriptional activity involves interactions with coregulatory proteins that include primate-specific melanoma antigen-A11 (MAGE-A11), a coactivator that increases AR transcriptional activity during prostate cancer progression to castration-resistant/recurrent prostate cancer (CRPC).

METHODS

Microarray analysis and quantitative RT-PCR were performed to identify androgen-regulated MAGE-A11-dependent genes in LAPC-4 prostate cancer cells after lentivirus shRNA knockdown of MAGE-A11. Chromatin immunoprecipitation was used to assess androgen-dependent AR recruitment, and immunocytochemistry to localize an androgen-dependent protein in prostate cancer cells and tissue and in the CWR22 human prostate cancer xenograft.

RESULTS

Microarray analysis of androgen-treated LAPC-4 prostate cancer cells indicated follistatin-like 1 (FSTL1) is up-regulated by MAGE-A11. Androgen-dependent up-regulation of FSTL1 was inhibited in LAPC-4 cells by lentivirus shRNA knockdown of AR or MAGE-A11. Chromatin immunoprecipitation demonstrated AR recruitment to intron 10 of the FSTL1 gene that contains a classical consensus androgen response element. Increased levels of FSTL1 protein in LAPC-4 cells correlated with higher levels of MAGE-A11 relative to other prostate cancer cells. FSTL1 mRNA levels increased in CRPC and castration-recurrent CWR22 xenografts in association with predominantly nuclear FSTL1. Increased nuclear localization of FSTL1 in prostate cancer was suggested by predominantly cytoplasmic FSTL1 in benign prostate epithelial cells and predominantly nuclear FSTL1 in epithelial cells in CRPC tissue and the castration-recurrent CWR22 xenograft. AR expression studies showed nuclear colocalization of AR and endogenous FSTL1 in response to androgen.

CONCLUSION

AR and MAGE-A11 cooperate in the up-regulation of FSTL1 to promote growth and progression of CRPC. Prostate 77:505-516, 2017. © 2016 Wiley Periodicals, Inc.