Serum levels of pigment epithelium-derived factor (PEDF) are positively associated with visceral adiposity in Japanese patients with type 2 diabetes

Changes in serum pigment epithelium-derived factor levels after kidney transplantation in patients with end-stage renal disease

Background

Pigment epithelium-derived factor (PEDF) is a serin protease inhibitor and a potent inhibitor of angiogenesis. Its serum level has significant associations with metabolic parameters. However, little is known about the association between PEDF levels and lipid parameters in renal transplanted (TX) patients. Therefore, our aim was to investigate the relationship between PEDF level and lipid parameters in TX patients.

Methods

Seventy TX patients (47 males, 23 females, mean age 51.7 ± 12.4 years) and 34 healthy controls were enrolled. We examined the serum creatinine, C-reactive protein, fasting glucose and lipid parameters right before, then 1 and 6 months after TX. High-density lipoprotein (HDL)-associated paraoxonase-1 (PON1) activities were measured spectrophotometrically. Lipoprotein subfractions were determined by Lipoprint. PEDF and oxidized low-density liporotein (oxLDL) levels were measured by ELISA.

Results

Before transplantation, patients had had a significantly higher PEDF level compared to control subjects (p < 0.001). One month after transplantation, their PEDF level decreased significantly reaching the healthy controls’ level, and this lower level was maintained during the 6 months follow-up period as well. The initial oxLDL level was significantly higher, while PON1 activities were significantly lower in the patient group compared to the control group. We found a significant positive correlation between PEDF and total cholesterol, low-density lipoprotein (LDL)-cholesterol, triglyceride, oxLDL and small HDL subfraction; while negative correlations were found between PEDF and mean LDL size and large HDL subfraction during the entire follow-up period.

Conclusion

PEDF may play an important role in the increased oxidative stress and enhanced atherogenesis in renal transplant patients.

Glucose Variability is Independently Correlated with Serum Level of Pigment Epithelium-Derived Factor in Type 2 Diabetes

INTRODUCTION

Pigment epithelium-derived factor (PEDF) may play a role in cardiometabolic disorders. The aim of this study was to investigate which biochemical and clinical parameters are independently associated with serum PEDF levels in patients with type 2 diabetes mellitus (T2DM).

METHODS

We performed a cross-sectional analysis of 124 patients with T2DM who underwent continuous glucose monitoring (CGM) and blood chemistry analysis, including the diacron-reactive oxygen metabolites (d-ROMs) test and serum PEDF measurement (study 1). Then we investigated whether the changes in the studied biochemical and clinical parameters after 24 weeks of treatment (Δparameters) with anti-hyperglycemic agents, including sodium-glucose cotransporter 2 inhibitors, glucagon-like peptide 1 receptor agonists, and/or insulin and anti-hypertensive drugs and statins, were independently correlated with change in PEDF (ΔPEDF) in 52 of the patients with T2DM for whom there was sufficient serum samples to perform the post-treatment analysis (study 2). Serum levels of PEDF were measured with an enzyme-linked immunosorbent assay. CGM metrics were calculated on days 2 and 3. Oxidative stress was evaluated using the d-ROMs test.

RESULTS

Body mass index (BMI), triglycerides, fasting C-peptide, mean amplitude of glycemic excursions (MAGE), urinary albumin-to-creatinine ratio (UACR), and d-ROMs were positively associated with serum PEDF level, and high-density lipoprotein cholesterol (HDL-C) and estimated glomerular filtration rate (eGFR) were inversely associated with serum PEDF level. Because these parameters were correlated with each other, multivariate stepwise analysis was performed: eGFR, HDL-C, BMI, MAGE, and UACR remained significant (R² = 0.452). Furthermore, ΔMAGE and Δd-ROMs were positively correlated with ΔPEDF in study 2.

CONCLUSIONS

The results of this study suggest that MAGE may be independently correlated with elevations in serum PEDF level in patients with T2DM.

C1q/TNF-Related Protein-3 (CTRP-3) and Pigment Epithelium-Derived Factor (PEDF) Concentrations in Patients with Gestational Diabetes Mellitus: A Case-Control Study

Background: Gestational diabetes mellitus (GDM) is the most common metabolic disorder in pregnant women, defined as any degree of glucose intolerance with onset or first detected during pregnancy. Explanation of its pathogenesis is extremely important due to the possibility of preventing serious maternal and fetal complications. The aim of the study was to evaluate the concentrations of two molecules: C1q/tumor necrosis factor-related protein-3 (CTRP-3) and pigment epithelium-derived factor (PEDF) which may possibly participate in GDM development. To our knowledge, this is the first study in pregnant women with GDM evaluating CTRP-3 level. Methods: Serum CTRP-3 and PEDF concentration and clinical characteristics were detected in 172 pregnant women. These women were divided into two groups: normal glucose tolerance group (NGT, n = 54) and gestational diabetes mellitus group (GDM, n = 118). This second group was further divided into two subgroups depending on the treatment used: GDM 1—diet only (n = 75) and GDM 2—insulin treatment (n = 43). Results: Our study did not reveal any statistically significant difference between the concentration of PEDF in the control and GDM group. In our study there was a significantly higher concentration of CTRP-3 evaluated in the peripheral blood serum in patients with gestational diabetes (GDM) compared to those in the control group (8.84 vs. 4.79 ng/mL). Significantly higher values of CTRP-3 were observed in both the diet-treated subgroup and the group with insulin therapy when compared to control group (8.40 and 10.96, respectively vs. 4.79 ng/mL). Conclusion: PEDF concentration does not change in GDM, whereas an increased level of CTRP-3 may point to the key role of this adipokine in the development of GDM.

Two-hour postload plasma glucose and pigment epithelium-derived factor levels are markers of coronary artery inflammation in type 2 diabetic patients

BACKGROUND

We have previously found that pioglitazone attenuates inflammation in the left main trunk of coronary artery (LMT), evaluated as target-to-background ratio (TBR) by 18F-fluorodeoxyglucose-positron emission tomography/computed tomography (FDG-PET/CT) in patients with impaired glucose tolerance or type 2 diabetes.

OBJECTIVES

We assessed which clinical variables could predict the change in TBR in the LMT after 4-month add-on therapy with oral hypoglycemic agents (OHAs).

METHODS

A total of 38 type 2 diabetic patients with carotid atherosclerosis who had already received OHAs except for pioglitazone was enrolled. At baseline and 4 months after add-on therapy with pioglitazone or glimepiride, all patients underwent 75 g oral glucose tolerance test, blood chemistry analysis, and FDG-PET/CT.

RESULTS

Fasting plasma glucose, 30-, 60-, 90-, 120-minutes postload plasma glucose, HbA1c, and LMT-TBR values were significantly decreased by add-on therapy, whereas high-density lipoprotein-cholesterol and adiponectin levels were increased. Increased serum levels of pigment epithelium-derived factor (PEDF), a marker of insulin resistance and non-use of aspirin at baseline could predict the favorable response of LMT-TBR to add-on therapy. Moreover, Δ120-minutes postload plasma glucose and ΔPEDF were independent correlates of ΔLMT-TBR.

CONCLUSIONS

Our present study suggests that 120-minutes postload plasma glucose and PEDF values may be markers and potential therapeutic targets of coronary artery inflammation in type 2 diabetic patients.

CLINICAL TRIAL REGISTRATION

URL: http://clinicaltrials.gov . Unique identifier: NCT00722631. New markers for diabetes and CAD is on the horizon! Two-hour postload plasma glucose and pigment epithelium derived factor are markers of coronary artery inflammation in type 2 diabetic patients.

Therapeutic Potential of Pigment Epithelium-derived Factor in Cancer

Pigment epithelium-derived factor (PEDF) is one of the serine protease inhibitors with multifunctional properties, which is produced by various types of organs and tissues. There is an accumulating body of evidence that PEDF plays an important role in the maintenance of tissue homeostasis. Indeed, PEDF not only works as an endogenous inhibitor of angiogenesis, but also suppresses oxidative stress, inflammatory and thrombotic reactions in cell culture systems, animal models, and humans. Furthermore, we, along with others, have found that PEDF inhibits proliferation of, and induces apoptotic cell death in, numerous kinds of tumors. In addition, circulating as well as tumor expression levels of PEDF have been inversely associated with tumor growth and metastasis. These observations suggest that supplementation of PEDF proteins and/or enhancement of endogenous PEDF expression could be a novel therapeutic strategy for the treatment of cancer. Therefore, in this paper, we review the effects of PEDF on diverse types of cancer, and discuss its therapeutic perspectives.

Pigment Epithelium-Derived Factor Promotes the Growth and Migration of Human Esophageal Squamous Cell Carcinoma

Pigment epithelium-derived factor (PEDF) is an oncogene found in various types of cancers. However, how PEDF affects the development of human esophageal squamous cell carcinoma (ESCC) is unknown. This study investigates the role of PEDF in ESCC cell proliferation, migration, and cell cycle both in vitro and in vivo. The PEDF expression was examined in patient tumor samples and ESCC cell lines. Short hairpin RNA technology was used to inhibit the PEDF expression in ESCC EC9706 and KYSE150 cells. In vitro cell proliferation and migration assays were performed. The effects of PEDF on tumor growth and progression were examined in vivo in murine subcutaneous xenograft tumor models. It was found that PEDF was overexpressed in esophageal cancer cells and patient tumor tissues compared to normal control samples. PEDF enhanced cell cycle progression and inhibited cell apoptosis. Knock down of PEDF inhibited esophageal cell proliferation and migration in vitro. Moreover, Inhibition of PEDF significantly reduced tumor growth and tumor size in vivo. These results indicate that PEDF induce tumorigenesis in ESCC and can be a potential therapeutic target for cancer treatment.

Pigment epithelium-derived factor in lipid metabolic disorders

Pigment epithelium-derived factor (PEDF) is a secreted glycoprotein that has anti-angiogenic, anti-proliferative, neurotrophic and immunomodulatory properties. PEDF has recently emerged as a critical metabolic regulatory protein since the discovery of its modulatory activities in the lipolytic pathway by binding to adipose triglyceride lipase (ATGL). Despite being beneficial in maintaining the homeostasis of hepatic lipid accumulation, PEDF has been uncovered an unfavorable role associated with insulin resistance. The molecular events that connect these two apparent distinct observations have been controversial and remained largely unknown. Therefore in this short review, we attempt to summarize the current findings of PEDF regarding its lipid metabolic functions and provide perspectives in identifying PEDF as a potential therapeutic target in lipid disorders.

Association of Pigment Epithelium Derived Factor With von Willebrand Factor and Plasminogen Activator Inhibitor 1 in Patients With Type 2 Diabetes

To compare circulating pigment epithelium derived factor (PEDF) levels in type 2 diabetes patients (T2D) with and without metabolic syndrome (MetS+/-) to healthy controls and assess PEDF association with plasminogen activator inhibitor-1 (PAI-1) and von Willebrand factor (vWF) as markers of endothelial dysfunction. Fifty T2D individuals and forty healthy controls were included. PEDF, PAI-1, vWF, anthropological parameters, lipids, and markers of insulin resistance were investigated in all subjects. Compared to controls only MetS+ diabetics had higher PEDF levels [14.2 (10.2-16.0) mg/l vs. 11.1 (8.6-14.4) mg/l; p<0.05]. PEDF significantly correlated: positively with body mass index (ρ=0.25), smoking (ρ=0.21), C-reactive protein (ρ=0.22), triglycerides (ρ=0.38), non-HDL-cholesterol (ρ=0.39), apolipoprotein B (ρ=0.38), fasting glucose (ρ=0.22), glycated hemoglobin (ρ=0.24), C-peptide (ρ=0.28), insulin (ρ=0.26); and negatively with HDL-cholesterol (ρ=-0.42) and apolipoprotein A1 (ρ=-0.27). Independent association of PEDF with vWF in T2DMetS- subjects was found. Significantly elevated PEDF in T2DMet+ patients and its association with adverse metabolic profile confirmed PEDF as a marker of insulin resistance. Negative independent association of PEDF with vWF in T2DMetS- patients may reveal its angio-protective role.

The effects of pigment epithelium-derived factor on atherosclerosis: putative mechanisms of the process

Cardiovascular disease (CVD) is a leading cause of death worldwide. Atherosclerosis is believed to be the major cause of CVD, characterized by atherosclerotic lesion formation and plaque disruption. Although remarkable advances in understanding the mechanisms of atherosclerosis have been made, the application of these theories is still limited in the prevention and treatment of atherosclerosis. Therefore, novel and effective strategies to treat high-risk patients with atherosclerosis require further development. Pigment epithelium-derived factor (PEDF), a glycoprotein with anti-inflammatory, anti-oxidant, anti-angiogenic, anti-thrombotic and anti-tumorigenic properties, is of considerable interest in the prevention of atherosclerosis. Accumulating research has suggested that PEDF exerts beneficial effects on atherosclerotic lesions and CVD patients. Our group, along with colleagues, has demonstrated that PEDF may be associated with acute coronary syndrome (ACS), and that the polymorphisms of rs8075977 of PEDF are correlated with coronary artery disease (CAD). Moreover, we have explored the anti-atherosclerosis mechanisms of PEDF, showing that oxidized-low density lipoprotein (ox-LDL) reduced PEDF concentrations through the upregulation of reactive oxygen species (ROS), and that D-4F can protect endothelial cells against ox-LDL-induced injury by preventing the downregulation of PEDF. Additionally, PEDF might alleviate endothelial injury by inhibiting the Wnt/β-catenin pathway. These data suggest that PEDF may be a novel therapeutic target for the treatment of atherosclerosis. In this review, we will summarize the role of PEDF in the development of atherosclerosis, focusing on endothelial dysfunction, inflammation, oxidative stress, angiogenesis and cell proliferation. We will also discuss its promising therapeutic implications for atherosclerosis.

Pigment epithelium-derived factor: a key mediator in bone homeostasis and potential for bone regenerative therapy

Objectives

Pigment epithelium-derived factor (PEDF), a multifunctional endogenous glycoprotein, has a very wide range of biological actions, notably in bone homeostasis. The question has been raised regarding the place of PEDF in the treatment of bone disorders and osteosarcoma, and its potential for tumour growth suppression.

Methods

The PubMed database was used to compile this review.

Key findings

Pigment epithelium-derived factor's actions in osteoid tissues include promoting mesenchymal stem cell commitment to osteoblasts, increasing matrix mineralisation, and promoting osteoblast proliferation. It shows potential to improve therapeutic outcomes in treatment of multiple cancer types and regrowth of bone after trauma or resection in animal studies. PEDF may possibly have a reduced adverse effect profile compared with current osteo-regenerative treatments; however, there is currently very limited evidence regarding the safety or efficacy in human models.

Summary

Pigment epithelium-derived factor is very active within the body, particularly in osseous tissue, and its physiological actions give it potential for treatment of both bone disorders and multiple tumour types. Further research is needed to ascertain the adverse effects and safety profile of PEDF as a therapeutic agent.

Lactation-related changes in tissue expression of PEDF in dairy cows

Pigment epithelium-derived factor (PEDF) is evolving as metabolic regulatory protein. Albeit mostly considered in only pathological conditions related to excess energy intake resulting in obesity and insulin resistance, PEDF is likely to be involved in other physiological processes such as the homeorhetic adaptation of metabolism to lactation. We aimed to characterize the expression of PEDF and its association to the concomitant mobilization of body reserves during lactation in nonobese subjects. This mobilization is particularly distinct in dairy cows, and we therefore assessed the mRNA expression of PEDF and its putative receptors in different tissues in 2 trials with dairy cows fed with or without conjugated linoleic acids (CLAs). Conjugated linoleic acids depress milk fat synthesis and may thus reduce the drain of energy via milk. In pluriparous cows, the serum PEDF concentrations and the mRNA abundance in subcutaneous adipose tissue (scAT), as well as the hepatic and scAT mRNA abundance of the putative receptors, adipose triglyceride lipase, and laminin receptor 1, changed over time of sampling (day -21 until day 252 relative to calving). Conjugated linoleic acid treatment was associated with reduced PEDF concentrations in serum and lower PEDF mRNA abundance in scAT on day 21 postpartum. Comparing different tissues from primiparous cows, PEDF mRNA was highest in the liver, followed by scAT, visceral adipose tissue (AT), and mammary gland, and lowest in the muscle. Significant changes in PEDF expression with time of sampling were limited to AT in primiparous and pluriparous cows. Our data support a regulatory role for PEDF. The similarities between the time course of the serum concentrations of PEDF and its mRNA abundance in scAT may point to a regulatory role for AT rather than the liver for PEDF in dairy cows.

Comparison of plasma pigment epithelium-derived factor (PEDF), retinol binding protein 4 (RBP-4), chitinase-3-like protein 1 (YKL-40) and brain-derived neurotrophic factor (BDNF) for the identification of insulin resistance

AIMS

To evaluate and compare the association of four potential insulin resistance (IR) biomarkers (pigment-epithelium-derived factor [PEDF], retinol-binding-protein-4 [RBP-4], chitinase-3-like protein 1 [YKL-40] and brain-derived neurotrophic factor [BDNF]) with objective measures of IR.

METHODS

We studied 81 subjects with different metabolic profiles. All participants underwent a 5-point OGTT with calculation of multiple IR indexes. A subgroup of 21 participants additionally underwent a hyperinsulinemic-euglycemic clamp. IR was defined as belonging to the highest quartile of incremental area under the insulin curve (iAUCins), or to the lowest quartile of the insulin sensitivity index (ISI).

RESULTS

PEDF was associated with adiposity variables. PEDF and RBP4 increased linearly across quartiles of iAUCins (for PEDF p-trend=0.029; for RBP-4 p-trend=0.053). YKL-40 and BDNF were not associated with any adiposity or IR variable. PEDF and RBP-4 levels identified individuals with IR by the iAUCins definition: A PEDF cutoff of 11.9ng/mL had 60% sensitivity and 68% specificity, while a RBP-4 cutoff of 71.6ng/mL had 70% sensitivity and 57% specificity. In multiple regression analyses simultaneously including clinical variables and the studied biomarkers, only BMI, PEDF and RBP-4 remained significant predictors of IR.

CONCLUSIONS

Plasma PEDF and RBP4 identified IR in subjects with no prior diagnosis of diabetes.

Pigment Epithelium-Derived Factor Declines in Response to an Oral Glucose Load and Is Correlated with Vitamin D and BMI but Not Diabetes Status in Children and Young Adults

BACKGROUND

Pigment epithelium-derived factor (PEDF) is associated with obesity and diabetes complications in adults, yet little is known about PEDF in younger individuals. We investigated the relationship between PEDF and various metabolic biomarkers in young healthy volunteers (HV) and similar-aged patients with diabetes (type 1 and type 2).

METHODS

A fasting blood sample was collected in 48 HV, 11 patients with type 1 diabetes (T1D), and 11 patients with type 2 diabetes (T2D) 12-25 years of age. In 9 healthy subjects, PEDF was also serially measured during a frequently sampled oral glucose tolerance test (OGTT).

RESULTS

PEDF was positively correlated with BMI and systolic blood pressure and negatively correlated with vitamin D. Upon multivariable analysis, BMI and vitamin D were independent predictors of PEDF. Prior to adjustment, PEDF was highest in T2D patients (7,168.9 ± 4417.4 ng/mL) and lowest in individuals with T1D (2,967.7 ± 947.1 ng/mL) but did not differ by diagnosis when adjusted for BMI and vitamin D. Among volunteers who underwent an OGTT, PEDF declined by ∼20% in response to an oral glucose load.

CONCLUSION

PEDF was acutely regulated by a glucose load and was correlated with BMI but not with diabetes. The negative correlation with vitamin D, independent of BMI, raises the question whether PEDF plays a compensatory role in bone matrix mineralization.

Pigment epithelium-derived factor stimulates skeletal muscle glycolytic activity through NADPH oxidase-dependent reactive oxygen species production

Pigment epithelium-derived factor is a multifunctional serpin implicated in insulin resistance in metabolic disorders. Recent evidence suggests that exposure of peripheral tissues such as skeletal muscle to PEDF has profound metabolic consequences with predisposition towards chronic conditions such as obesity, type 2 diabetes, metabolic syndrome and polycystic ovarian syndrome. Chronic inflammation shifts muscle metabolism towards increased glycolysis and decreased oxidative metabolism. In the present study, we demonstrate a novel effect of PEDF on cellular metabolism in mouse cell line (C2C12) and human primary skeletal muscle cells. PEDF addition to skeletal muscle cells induced enhanced phospholipase A2 activity. This was accompanied with increased production of reactive oxygen species in a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-dependent manner that triggered a shift towards a more glycolytic phenotype. Extracellular flux analysis and glucose consumption assays demonstrated that PEDF treatment resulted in enhanced glycolysis but did not change mitochondrial respiration. Our results demonstrate that skeletal muscle cells express a PEDF-inducible oxidant generating system that enhances glycolysis but is sensitive to antioxidants and NADPH oxidase inhibition.

Emetine Di-HCl Attenuates Type 1 Diabetes Mellitus in Mice

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease characterized by beta cell destruction, insulin deficiency and hyperglycemia. Activated macrophages and autoimmune T cells play a crucial role in the pathogenesis of hyperglycemia in NOD murine diabetes models, but the molecular mechanisms of macrophage activation are unknown. We recently identified pigment epithelium-derived factor (PEDF) as an adipocyte-derived factor that activates macrophages and mediates insulin resistance. Reasoning that PEDF might participate as a proinflammatory mediator in murine diabetes, we measured PEDF levels in NOD mice. PEDF levels are significantly elevated in pancreas, in correlation with pancreatic TNF levels in NOD mice. To identify experimental therapeutics, we screened 2,327 compounds in two chemical libraries (the NIH Clinical Collection and Pharmakon-1600a) for leads that inhibit PEDF mediated TNF release in macrophage cultures. The lead molecule selected, "emetine" is a widely used emetic. It inhibited PEDF-mediated macrophage activation with an EC50 or 146 nM. Administration of emetine to NOD mice and to C57Bl6 mice subjected to streptozotocin significantly attenuated hyperglycemia, reduced TNF levels in pancreas, and attenuated insulitis. Together, these results suggest that targeting PEDF with emetine may attenuate TNF release and hyperglycemia in murine diabetes models. This suggests that further investigation of PEDF and emetine in the pathogenesis of human diabetes is warranted.

Pigment epithelium-derived factor (PEDF) regulates metabolism and insulin secretion from a clonal rat pancreatic beta cell line BRIN-BD11 and mouse islets

Pigment epithelium-derived factor (PEDF) is a multifunctional glycoprotein, associated with lipid catabolism and insulin resistance. In the present study, PEDF increased chronic and acute insulin secretion in a clonal rat β-cell line BRIN-BD11, without alteration of glucose consumption. PEDF also stimulated insulin secretion from primary mouse islets. Seahorse flux analysis demonstrated that PEDF did not change mitochondrial respiration and glycolytic function. The cytosolic presence of the putative PEDF receptor - adipose triglyceride lipase (ATGL) - was identified, and ATGL associated stimulation of glycerol release was robustly enhanced by PEDF, while intracellular ATP levels increased. Addition of palmitate or ex vivo stimulation with inflammatory mediators induced β-cell dysfunction, effects not altered by the addition of PEDF. In conclusion, PEDF increased insulin secretion in BRIN-BD11 and islet cells, but had no impact on glucose metabolism. Thus elevated lipolysis and enhanced fatty acid availability may impact insulin secretion following PEDF receptor (ATGL) stimulation.

Biomarkers of Metabolic Syndrome: Biochemical Background and Clinical Significance

Biomarkers of the metabolic syndrome are divided into four subgroups. Although dividing them in groups has some limitations, it can be used to draw some conclusions. In a first part, the dyslipidemias and markers of oxidative stress are discussed, while inflammatory markers and cardiometabolic biomarkers are reviewed in a second part. For most of them, the biochemical background and clinical significance are discussed, although here also a well-cut separation cannot always be made. Altered levels cannot always be claimed as the cause, risk, or consequence of the syndrome. Several factors are interrelated to each other and act in a concerted, antagonistic, synergistic, or modulating way. Most important conclusions are summarized at the end of every reviewed subgroup. Genetic biomarkers or influences of various food components on concentration levels are not included in this review article.

Anti-tumor effects of pigment epithelium-derived factor (PEDF): implication for cancer therapy. A mini-review

Pigment epithelium-derived factor (PEDF) is a secreted glycoprotein and a non-inhibitory member of the serine protease inhibitor (serpin) family. It is widely expressed in human fetal and adult tissues but its expression decreases with age and in malignant tissues. The main anti-cancer activities of PEDF derive from its dual effects, either indirectly on the tumor microenvironment (indirect antitumor action) or directly on the tumor itself (direct antitumor influence). The indirect antitumor activities of PEDF were uncovered from the early findings that it stimulates retinoblastoma cell differentiation and that additionally it possesses anti-angiogenic, anti-tumorigenic and anti-metastatic properties. The mechanisms of its direct antitumor effect, however, have not been fully elucidated. This review highlights recent progress in our understanding of the multifunctional activities of PEDF and, in particular, its anti-cancer signaling mechanisms. Additionally, we discuss the possibility of using novel phosphaplatin compounds that can upregulate PEDF expression as a chemotherapy for cancer treatment.

Elevated plasma pigment epithelium-derived factor in children with type 2 diabetes mellitus is attributable to obesity

BACKGROUND

Pigment epithelium-derived factor (PEDF) is a member of the serpin family secreted by adipocytes. Plasma PEDF is increased in obese children and adults. Adults with type 2 diabetes mellitus (T2DM) have higher circulating PEDF but there are no reports in children with T2DM.

OBJECTIVE

To compare PEDF concentration in children with T2DM to normal weight and obese children without T2DM and determine associations with anthropometric or serum factors.

METHODS

Participants were 34 obese children with T2DM diagnosed by American Diabetes Association (ADA) criteria, 61 normal weight [body mass index (BMI) 25-75 percentile] and 63 obese (BMI ≥ 95 percentile) children of age 8-18 yr. Plasma PEDF was measured in fasting plasma samples. Anthropometric, serum, and body composition (dual-energy x-ray absorptiometry, DXA) data were obtained for each subject to identify potential predictor variables.

RESULTS

PEDF was 55% higher (p = 0.001) in the T2DM group compared with normal weight children, but did not differ from obese children. In the T2DM group, fat mass and lean mass both individually predicted PEDF (r² = 0.22 and 0.17, p = 0.02 and p < 0.01, respectively). PEDF was positively correlated with homeostatic model assessment - insulin resistance (HOMA-IR) when all groups were combined (r² = 0.15, p<0.001).

CONCLUSIONS

Plasma PEDF was similar in the T2DM and obese groups, therefore, obesity, rather than diabetes, may account for the higher PEDF in children with T2DM compared with normal weight children. PEDF was positively associated with both lean mass and fat mass both of which may contribute to the circulating level of the protein, and potentially to PEDF's association with insulin resistance in obese children with and without diabetes.

PEDF and its roles in physiological and pathological conditions: implication in diabetic and hypoxia-induced angiogenic diseases

Pigment epithelium-derived factor (PEDF) is a broadly expressed multifunctional member of the serine proteinase inhibitor (serpin) family. This widely studied protein plays critical roles in many physiological and pathophysiological processes, including neuroprotection, angiogenesis, fibrogenesis and inflammation. The present review summarizes the temporal and spatial distribution patterns of PEDF in a variety of developing and adult organs, and discusses its functions in maintaining physiological homoeostasis. The major focus of the present review is to discuss the implication of PEDF in diabetic and hypoxia-induced angiogenesis, and the pathways mediating PEDF's effects under these conditions. Furthermore, the regulatory mechanisms of PEDF expression, function and degradation are also reviewed. Finally, the therapeutic potential of PEDF as an anti-angiogenic drug is briefly summarized.

PEDF-induced alteration of metabolism leading to insulin resistance

Pigment epithelium-derived factor (PEDF) is an anti-angiogenic, immunomodulatory, and neurotrophic serine protease inhibitor protein. PEDF is evolving as a novel metabolic regulatory protein that plays a causal role in insulin resistance. Insulin resistance is the central pathogenesis of metabolic disorders such as obesity, type 2 diabetes mellitus, polycystic ovarian disease, and metabolic syndrome, and PEDF is associated with them. The current evidence suggests that PEDF administration to animals induces insulin resistance, whereas neutralisation improves insulin sensitivity. Inflammation, lipolytic free fatty acid mobilisation, and mitochondrial dysfunction are the proposed mechanism of PEDF-mediated insulin resistance. This review summarises the probable mechanisms adopted by PEDF to induce insulin resistance, and identifies PEDF as a potential therapeutic target in ameliorating insulin resistance.

D-4F, an apolipoprotein A-I mimetic peptide, protects human umbilical vein endothelial cells from oxidized low-density lipoprotein-induced injury by preventing the downregulation of pigment epithelium-derived factor expression

AIM

To investigate the protective effects of D-4F, an apolipoprotein A-I mimetic peptide, on oxidized low-density lipoprotein (ox-LDL)-induced injury of vascular endothelial cells and the potential role of pigment epithelium-derived factor (PEDF).

METHODS

Cytotoxicity was assessed by the apoptotic rate, 3-(4,5-dimethylthiazol-2-y-l)-2,5-diphenyl-2H-tetrazolium bromide assay, and lactate dehydrogenase release. PEDF levels were analyzed with Western blot and quantitative real-time polymerase chain reaction. Redox status was measured by the levels of the reactive oxygen species, malondialdehyde, superoxide dismutase, and nitric oxide.

RESULTS

Ox-LDL reduced cell viability and induced apoptosis and LDH release from human umbilical vein endothelial cells, but the cytotoxic effects of ox-LDL were significantly inhibited by pretreatment with D-4F. Additionally, D-4F could scavenge intracellular reactive oxygen species, suppress the production of lipid peroxides, and improve endogenous antioxidant activity. Ox-LDL decreased PEDF expression in human umbilical vein endothelial cells in a concentration-dependent manner, and this decrease was markedly attenuated by D-4F. However, silencing PEDF by short interfering RNA blocked the inhibitory effects of D-4F on ox-LDL-induced oxidative stress and cellular injury.

CONCLUSIONS

D-4F effectively protects vascular endothelial cells against ox-LDL-induced injury by preventing the downregulation of PEDF expression.

Elevated circulating pigment epithelium-derived factor predicts the progression of diabetic nephropathy in patients with type 2 diabetes

CONTEXT

Pigment epithelium-derived factor (PEDF), a circulating glycoprotein with antiangiogenic, antioxidative, and anti-inflammatory properties, protects against diabetic nephropathy (DN) in animal models.

OBJECTIVE

We investigated whether circulating PEDF predicted the progression of DN in a 4-year prospective study.

DESIGN, SETTING, AND PARTICIPANTS

Baseline plasma PEDF levels were measured in type 2 diabetic subjects recruited from the Hong Kong West Diabetes Registry. The role of PEDF in predicting chronic kidney disease (CKD) and albuminuria progression was analyzed using Cox regression analysis.

MAIN OUTCOME MEASURE

We evaluated CKD progression, defined as deterioration in CKD staging and a 25% or greater drop in estimated glomerular filtration rate (eGFR) according to International Society of Nephrology statements.

RESULTS

At baseline, plasma PEDF levels increased progressively with CKD staging (P for trend <.001; n = 1136). Among 1071 subjects with baseline CKD stage ≤ 3, plasma PEDF levels were significantly higher in those with CKD progression (n = 171) during follow-up than those without (P < .001). Baseline PEDF was independently associated with CKD progression (hazard ratio = 2.76; 95% confidence interval = 1.39-5.47; P = .004), adjusted for age, sex, waist circumference, diabetes duration, hemoglobin A1c, systolic blood pressure, use of antihypertensive drugs, C-reactive protein, and eGFR. Elevated baseline PEDF was also associated with the development of microalbuminuria/albuminuria in a subgroup with normoalbuminuria and eGFR >60 mL/min/1.73 m(2) (n = 462) at baseline (hazard ratio = 2.75; 95% confidence interval = 1.01-7.49; P < .05), even after adjustment for potential confounders.

CONCLUSIONS

Elevated PEDF levels may represent a compensatory change in type 2 diabetic patients with renal disease and appear to be a useful marker for evaluating the progression of DN.

Augmented expression and secretion of adipose-derived pigment epithelium-derived factor does not alter local angiogenesis or contribute to the development of systemic metabolic derangements

Impaired coupling of adipose tissue expansion and vascularization is proposed to lead to adipocyte hypoxia and inflammation, which in turn contributes to systemic metabolic derangements. Pigment epithelium-derived factor (PEDF) is a powerful antiangiogenic factor that is secreted by adipocytes, elevated in obesity, and implicated in the development of insulin resistance. We explored the angiogenic and metabolic role of adipose-derived PEDF through in vivo studies of mice with overexpression of PEDF in adipocytes (PEDF-aP2). PEDF expression in white adipocytes and PEDF secretion from adipose tissue was increased in transgenic mice, but circulating levels of PEDF were not increased. Overexpression of PEDF did not alter vascularization, the partial pressure of O2, cellular hypoxia, or gene expression of inflammatory markers in adipose tissue. Energy expenditure and metabolic substrate utilization, body mass, and adiposity were not altered in PEDF-aP2 mice. Whole body glycemic control was normal as assessed by glucose and insulin tolerance tests, and adipocyte-specific glucose uptake was unaffected by PEDF overexpression. Adipocyte lipolysis was increased in PEDF-aP2 mice and associated with increased adipose triglyceride lipase and decreased perilipin 1 expression. Experiments conducted in mice rendered obese by high-fat feeding showed no differences between PEDF-aP2 and wild-type mice for body mass, adiposity, whole body energy expenditure, glucose tolerance, or adipose tissue oxygenation. Together, these data indicate that adipocyte-generated PEDF enhances lipolysis but question the role of PEDF as a major antiangiogenic or proinflammatory mediator in adipose tissue in vivo.

Clinical correlates of serum pigment epithelium-derived factor in type 2 diabetes patients

AIM

To determine if serum pigment epithelium-derived factor (PEDF) levels in Type 2 diabetes are related to vascular risk factors and renal function.

METHODS

PEDF was quantified by ELISA in a cross-sectional study of 857 male Veterans Affairs Diabetes Trial (VADT) subjects, and associations with cardiovascular risk factors and renal function were determined. In a subset (n=246) in whom serum was obtained early in the VADT (2.0±0.3 years post-randomization), PEDF was related to longitudinal changes in renal function over 3.1 years.

RESULTS

Cross-sectional study: In multivariate regression models, PEDF was positively associated with serum triglycerides, waist-to-hip ratio, serum creatinine, use of ACE inhibitors or angiotensin receptor blockers, and use of lipid-lowering agents; it was negatively associated with HDL-C (all p<0.05). Longitudinal study: PEDF was not associated with changes in renal function over 3.1 years (p>0.09).

CONCLUSIONS

Serum PEDF in Type 2 diabetic men was cross-sectionally associated with dyslipidemia, body habitus, use of common drugs for blood pressure and dyslipidemia, and indices of renal function; however, PEDF was not associated with renal decline over 3.1years.

Pigment epithelium-derived factor improves metabolic derangements and ameliorates dysregulation of adipocytokines in obese type 2 diabetic rats

Oxidative stress and inflammation in the adipose tissues contribute to the metabolic syndrome. Pigment epithelium-derived factor (PEDF) inhibits vascular inflammation through its anti-oxidative properties. However, it remains unclear whether PEDF could suppress adipocyte inflammation. We investigated the effects of long-term administration or suppression of PEDF on adipocyte inflammation and metabolic derangements in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, an animal model of type 2 diabetes with insulin resistance. Circulating and adipose tissue PEDF levels were increased as OLETF rats became more obese and insulin resistant. Long-term administration of PEDF improves metabolic parameters, ameliorates dysregulation of adipocytokines, and suppresses NADPH oxidase-induced oxidative stress and macrophage infiltration in the adipose tissues of OLETF rats, whereas these variables are exacerbated by the knockdown of PEDF by administering siRNAs. Our study suggests that PEDF could improve metabolic derangements by suppressing the inflammatory and oxidative reactions in adipose tissues of OLETF rats. PEDF levels may be elevated as a countersystem against obesity-related metabolic derangements.

Effect of a 12-month exercise intervention on serum biomarkers of angiogenesis in postmenopausal women: a randomized controlled trial

BACKGROUND

Increased physical activity is associated with decreased risk of several types of cancer, but underlying mechanisms are poorly understood. Angiogenesis, in which new blood vessels are formed, is common to adipose tissue formation/remodeling and tumor vascularization.

METHODS

We examined effects of a 12-month 45 minutes/day, 5 days/week moderate-intensity aerobic exercise intervention on four serum markers of angiogenesis in 173 sedentary, overweight, postmenopausal women, 50 to 75 years, randomized to intervention versus stretching control. Circulating levels of positive regulators of angiogenesis [VEGF, osteopontin (OPN), plasminogen activator inhibitor-1 (PAI-1)], and the negative regulator pigment epithelium-derived factor (PEDF), were measured by immunoassay at baseline and 12 months. Changes were compared using generalized estimating equations, adjusting for baseline levels of analytes and body mass index (BMI).

RESULTS

VEGF, OPN, or PAI-1 levels did not differ by intervention arm. Participants randomized to exercise significantly reduced PEDF (-3.7%) versus controls (+3.0%; P = 0.009). Reductions in fat mass were significantly associated with reductions in PAI-1 (Ptrend = 0.03; Ptrend = 0.02) and PEDF (Ptrend = 0.002; Ptrend = 0.01) compared with controls, or to those who gained any fat mass respectively. There was a significant association between decreases in VO2max, and increased reductions in PEDF (Ptrend = 0.03), compared with participants who increased their level of fitness.

CONCLUSIONS

Fat loss reduces circulating PAI-1 and PEDF. Changes in VO2max are associated with alterations in PEDF, but these associations are complex.

IMPACT

Unexpected reductions in PEDF with decreasing fat mass, and with decreasing VO2max, warrant further study, including examining the effects of different types and intensities of exercise; and role of dietary weight-loss with and without exercise.

Pigment epithelium-derived factor as a new predictor of mortality among chronic kidney disease patients treated with hemodialysis

Pigment epithelium-derived factor (PEDF) plays a protective role against atherosclerosis. Although serum PEDF level is increased in patients undergoing regular hemodialysis (HD), the pathophysiological role of PEDF in HD patients is unknown. We measured serum PEDF levels in 74 HD patients, and the association between serum PEDF and adverse events such as all-cause death and cardiovascular accident was evaluated prospectively. During the follow up of 45.4 ± 25.1 months, 24 patients (32.4%) experienced cardiovascular accident and 18 (24.3%) died. Significantly higher incidences of all-cause mortality and cardiovascular accident were observed in the lower PEDF group than in the higher PEDF group. After adjusting for propensity score calculated from multiple confounding factors (age, gender, systolic blood pressure, history of previous cardiovascular disease, level of carbonyl content, albumin, hemoglobin, total cholesterol, creatinine, C-reactive protein, dialysis vintage, Kt/V-urea and history of diabetes), lower predialytic PEDF was a significant risk factor for all-cause mortality (relative hazard = 6.060, standard error = 0.68467, P = 0.0085). Lower levels of predialytic PEDF was associated with an increased risk of mortality.

PEDF expression is inhibited by insulin treatment in adipose tissue via suppressing 11β-HSD1

Early intensive insulin therapy improves insulin sensitivity in type 2 diabetic patients; while the underlying mechanism remains largely unknown. Pigment epithelium-derived factor (PEDF), an anti-angiogenic factor, is believed to be involved in the pathogenesis of insulin resistance. Here, we hypothesize that PEDF might be down regulated by insulin and then lead to the improved insulin resistance in type 2 diabetic patients during insulin therapy. We addressed this issue by investigating insulin regulation of PEDF expression in diabetic conditions. The results showed that serum PEDF was reduced by 15% in newly diagnosed type 2 diabetic patients after insulin therapy. In adipose tissue of diabetic Sprague-Dawley rats, PEDF expression was associated with TNF-α elevation and it could be decreased both in serum and in adipose tissue by insulin treatment. In adipocytes, PEDF was induced by TNF-α through activation of NF-κB. The response was inhibited by knockdown and enhanced by over expression of NF-κB p65. However, PEDF expression was indirectly, not directly, induced by NF-κB which promoted 11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) expression in adipocytes. 11β-HSD1 is likely to stimulate PEDF expression through production of active form of glucocorticoids as dexamethasone induced PEDF expression in adipose tissue. Insulin inhibited PEDF by down-regulating 11β-HSD1 expression. The results suggest that PEDF activity is induced by inflammation and decreased by insulin through targeting 11β-HSD1/glucocorticoid pathway in adipose tissue of diabetic patients.

Association of serum pigment epithelium-derived factor with high-sensitivity C-reactive protein in women with polycystic ovary syndrome

BACKGROUND

The basic studies showed that Pigment epithelium-derived factor (PEDF) plays an important role in inflammation.

AIM

This study aims to investigate the association of serum PEDF with high-sensitivity C-reactive protein (hs-CRP) in women with polycystic ovary syndrome (PCOS).

METHODS

Ninety-six PCOS women and 63 healthy, age-matched controls were enrolled in this study. Serum levels of PEDF, hs-CRP, Complement C3 (C3), glucose, insulin, lipids, and total testosterone were measured. Ninety-six PCOS women and 20 controls underwent hyperinsulinemiceuglycemic clamp to assess their insulin sensitivity, which was expressed as M value.

RESULTS

Serum PEDF levels and hs- CRP levels were much higher in PCOS women than in controls. In PCOS women, PEDF positively correlated with body mass index (BMI), hs-CRP, C3, LDL cholesterol (LDL-c), and systolic blood pressure (SBP), and negatively correlated with M value and HDL cholesterol (HDL-c). After controlling for BMI, PEDF was still positively correlated with hs-CRP. Multiple linear regression analysis revealed that in PCOS women, hs-CRP, SBP, LDL-c and M value were independent determinants of serum PEDF.

CONCLUSION

The serum PEDF levels are closely associated with hs-CRP in women with PCOS. PEDF may play a role in the development of chronic inflammation in PCOS.

Circulating levels and subcutaneous adipose tissue gene expression of pigment epithelium-derived factor in polycystic ovary syndrome and normal women: a case control study

BACKGROUND

Polycystic ovary syndrome (PCOS) has been recognized as a metabolic disorder, manifested by abdominal obesity, insulin resistance, dyslipidemia and hypertension. Pigment epithelium-derived factor (PEDF), a member of the serine protease inhibitor family, is a pleiotropic protein known for its antiangiogenic, antioxidant, and neuroprotective properties and has been shown to induce insulin resistance and play a role in glucose metabolism. Recent studies investigating circulating PEDF levels show elevated serum PEDF in association with insulin resistance in normal-weight women with PCOS, but not in obese PCOS patients. The aims of this study were 1) to assess PEDF gene expression in subcutaneous adipose tissue (scAT) from women with PCOS and nonhirsute, ovulatory controls, and 2) to determine the circulating levels of PEDF in these groups.

METHODS

Total RNA was extracted from adipose tissue biopsy samples and reverse-transcribed to cDNA. Real-time quantitative PCR was performed to determine relative gene expression levels.

RESULTS

The 22 women with PCOS and 14 non-PCOS controls included in the study had similar age, BMI, and fasting glucose, triglycerides, and HDL-cholesterol levels. Participants with PCOS exhibited higher 2 h oral glucose tolerance test levels (p = 0.006), total (p = 0.026) and LDL-cholesterol (p = 0.036), Ferriman-Gallwey score (p = 0.003) and total testosterone (p = 0.001) as compared to controls. BMI-adjusted PEDF serum levels and scAT gene expression were similar in the PCOS and control groups (p = 0.622 and p = 0.509, respectively). Circulating PEDF levels were not associated with scAT PEDF gene expression. Multiple regression analysis revealed that, in women with PCOS, insulin contributed positively and significantly to serum PEDF (p = 0.027), independently of testosterone.

CONCLUSION

Serum PEDF levels and scAT gene expression were associated with metabolic risk factors, but did not differ between women with PCOS and age- and BMI-matched controls. Circulating levels and scAT gene expression of PEDF were not associated in the study subjects, suggesting additional sources for PEDF in addition to or instead of fat tissue.

More than a simple storage organ: adipose tissue as a source of adipokines involved in cardiovascular disease

Overweight and obesity in many countries have developed into a serious health problem by themselves and by their impact on other pathologies such as insulin resistance, type 2 diabetes, hypertension, heart disease and cancer. The modulation of these diseases by adipose tissue-derived biomolecules, so-called adipokines, could be the key to differentiate between metabolically healthy and unhealthy obesity. This review will discuss the pathophysiological role of selected adipokines, primarily focusing on cardiovascular diseases. Furthermore, we will highlight possible therapeutic approaches, which target these biomolecules.

The many facets of PEDF in drug discovery and disease: a diamond in the rough or split personality disorder?

INTRODUCTION

Pigment epithelium-derived factor (PEDF) was discovered as a neurotrophic factor secreted by retinal pigment epithelial cells. A decade later, it re-emerged as a powerful angiogenesis inhibitor guarding ocular function. Since then, significant advances were made identifying PEDF's mechanisms, targets and biomedical applications.

AREAS COVERED

The authors review several methodologies that have generated significant new information about the potential of PEDF as a drug. Furthermore, the authors review and discuss mechanistic and structure-function analyses combined with the functional mapping of active fragments, which have yielded several short bioactive PEDF peptides. Additionally, the authors present functional studies in knockout animals and human correlates that have provided important information about conditions amenable to PEDF-based therapies.

EXPERT OPINION

Through its four known receptors, PEDF causes a wide range of cellular events vitally important for the organism, which include survival and differentiation, migration and invasion, lipid metabolism and stem cell maintenance. These processes are deregulated in multiple pathological conditions, including cancer, metabolic and cardiovascular disease. PEDF has been successfully used in countless preclinical models of these conditions and human correlates suggest a wide utility of PEDF-based drugs. The most significant clinical application of PEDF, to date, is its potential therapeutic use for age-related macular degeneration. Moreover, PEDF-based gene therapy has advanced to early stage clinical trials. PEDF active fragments have been mapped and used to design short peptide mimetics conferring distinct functions of PEDF, which may address specific clinical problems and become prototype drugs.

Insulin resistance is associated with elevated serum pigment epithelium-derived factor (PEDF) levels in morbidly obese patients

Obesity is a significant risk factor for developing diabetes. Pigment epithelium-derived factor (PEDF) has been identified by experimental and clinical studies as both a causative and counter-regulatory factor in the metabolic syndrome. We set out to determine whether serum PEDF levels correlated with the degree of insulin resistance in morbidly obese patients. Sera from 53 patients who were evaluated prior to gastric bypass surgery were analyzed for PEDF levels using a commercial ELISA. None of the patients were on diabetes medications prior to enrollment. Baseline data included BMI, serum glucose and insulin, and homeostasis model assessment (HOMA) scores. Patients were stratified based on HOMA score and glucose levels into three groups: insulin sensitive (IS): HOMA <2 and glucose <126; insulin resistant (IR): HOMA >2 and glucose ≤126; and diabetes mellitus (DM): HOMA >2 and glucose >126. Pre- and post-gastric bypass sera from 12 patients were obtained for serial assessment of metabolic parameters and PEDF levels. PEDF secretion was assessed in primary human hepatocytes, HCC cells, and cultured adipocytes in the absence and presence of high glucose media. No significant differences in age, gender, and BMI were found among the three groups. PEDF levels were similar between IR patients and the other groups, but were significantly higher in DM compared to IS patients (p = 0.01). Serum PEDF in individual patients declined significantly after gastric bypass (p = 0.006). High glucose media led to significantly higher PEDF release by human hepatocytes in vitro (p = 0.016). These data demonstrate that serum PEDF concentrations better relate to insulin resistance than to adiposity and suggest that PEDF expression is closely linked to the development of insulin resistance.

Pigment epithelium-derived factor, insulin sensitivity, and adiposity in polycystic ovary syndrome: impact of exercise training

Pigment epithelium-derived factor (PEDF) is upregulated in obese rodents and is involved in the development of insulin resistance (IR). We aim to explore the relationships between PEDF, adiposity, insulin sensitivity, and cardiovascular risk factors in obese women with polycystic ovary syndrome (PCOS) and weight-matched controls and to examine the impact of endurance exercise training on PEDF. This prospective cohort intervention study was based at a tertiary medical center. Twenty obese PCOS women and 14 non-PCOS weight-matched women were studied at baseline. PEDF, cardiometabolic markers, detailed body composition, and euglycemic-hyperinsulinemic clamps were performed and measures were repeated in 10 PCOS and 8 non-PCOS women following 12 weeks of intensified aerobic exercise. Mean glucose infusion rate (GIR) was 31.7% lower (P = 0.02) in PCOS compared to controls (175.6 ± 96.3 and 257.2 ± 64.3 mg.m(-2).min(-1)) at baseline, yet both PEDF and BMI were similar between groups. PEDF negatively correlated to GIR (r = -0.41, P = 0.03) and high-density lipoprotein (HDL) (r = -0.46, P = 0.01), and positively to cardiovascular risk factors, systolic (r = 0.41, P = 0.02) and diastolic blood pressure (r = 0.47, P = 0.01) and triglycerides (r = 0.49, P = 0.004). The correlation with GIR was not significant after adjusting for fat mass (P = 0.07). Exercise training maintained BMI and increased GIR in both groups; however, plasma PEDF was unchanged. In summary, PEDF is not elevated in PCOS, is not associated with IR when adjusted for fat mass, and is not reduced by endurance exercise training despite improved insulin sensitivity. PEDF was associated with cardiovascular risk factors, suggesting PEDF may be a marker of cardiovascular risk status.

Identification of pigment epithelium-derived factor as an adipocyte-derived inflammatory factor

Obesity is a major risk factor for insulin resistance, type 2 diabetes mellitus and cardiovascular disease. The pathophysiology of obesity is associated with chronic low-grade inflammation. Adipose tissue in obesity is significantly infiltrated by macrophages that secrete cytokines. The mechanisms of interaction between macrophages and adipocytes, leading to macrophage activation and increased cytokine release, remain to be elucidated. We reasoned that an adipocyte-derived factor might stimulate activation of macrophages. We have identified pigment epithelium-derived factor (PEDF) as a mediator of inflammation that is secreted by adipocytes and mediates macrophage activation. Recombinant PEDF activates macrophages to release tumor necrosis factor (TNF) and interleukin-1 (IL-1). The PEDF receptor adipose triglyceride lipase (ATGL) is required for PEDF-mediated macrophage activation. Selective inhibition of ATGL on macrophages attenuates PEDF-induced TNF production, and PEDF enhances the phosphorylation of p38 and extracellular signal-regulated kinase 1/2 mitogen-activated protein kinases. PEDF administration to rats results in increased serum TNF levels, and insulin resistance. Together, these findings suggest that PEDF secreted by adipocytes contributes to the onset and maintenance of chronic inflammation in obesity, and may be a therapeutic target in ameliorating insulin resistance.

Efficacy of continuously administered PEDF-derived synthetic peptides against osteosarcoma growth and metastasis

The potent antiangiogenic pigment epithelium-derived factor (PEDF) has shown promise against osteosarcoma, a tumour that originates in the bone and metastasises to the lungs. Neurotrophic, antiangiogenic, antiproliferative, and antimetastatic properties of PEDF have been attributed to a number of functional epitopes on the PEDF glycoprotein. StVOrth-2 (residues 78–102) and StVOrth-3 (residues 90–114) are two PEDF-derived peptides based on these functional epitopes. StVOrth-2 has previously been shown to inhibit osteosarcoma cell proliferation, while StVOrth-3 increased osteosarcoma cell adhesion to collagen I in vitro. In this paper, we have evaluated systemically and continuously delivered StVOrth-2 and StVOrth-3 using a clinically relevant murine model of osteosarcoma with spontaneous metastasis. Treatment with StVOrth-2 or StVOrth-3 with microosmotic pumps was initiated after primary osteosarcoma was established in the tibia. While treatment with StVOrth-2 and StVOrth-3 did not appear to affect local tumour invasion, tumour necrosis or apoptosis, StVOrth-2 predominantly restricted the growth of primary tumours, while StVOrth-3 restricted the burden of pulmonary metastatic disease. No peptide caused gross toxicity in mouse tissues as assessed by measuring weight of animals, serum biochemistry, and gross tissue observation. The differential effects exhibited by StVOrth-2 and StVOrth-3 in this orthotopic model of osteosarcoma may be related to the functional epitopes on the PEDF glycoprotein that they represent.

Plasma concentration of pigment epithelium-derived factor is closely associated with blood pressure and predicts incident hypertension in Chinese: a 10-year prospective study

OBJECTIVES

Pigment epithelium-derived factor (PEDF) is secreted from the adipose tissue. It circulates at high concentrations, and was reported to play a causal role in obesity-induced insulin resistance and metabolic dysfunctions in mice. Previous cross-sectional studies also demonstrated plasma PEDF concentration correlated positively with systolic blood pressure (BP) and pulse pressure, and inversely with small artery elasticity. Here we investigated the relationship of plasma PEDF concentration with BP and incident hypertension in a 10-year prospective study.

METHODS

Baseline plasma PEDF concentrations were measured by ELISA in 520 Chinese subjects, aged 51 ± 12 years, followed up long-term from the population-based Hong Kong Cardiovascular Risk Factor Prevalence Study. The association between plasma PEDF concentration and BP was investigated in both cross-sectional and prospective studies, using multiple linear regression and path analyses. Cox proportional hazards analysis was used to determine whether baseline PEDF concentration was independently related to the subsequent development of hypertension over 10 years.

RESULTS

Baseline plasma concentrations of PEDF were higher in men (P < 0·001), and were directly related to systolic BP at 2 and 5 years, and to diastolic BP at 2 years, after adjustment for covariates. Of the 386 normotensive subjects at baseline, high baseline PEDF concentration was predictive of incident hypertension, independent of the effects of age, sex, baseline BP and obesity parameters (hazard ratio: 1·135; 95% CI: 1·039-1·241; P = 0·005).

CONCLUSION

Our data suggest that plasma PEDF concentration is significantly associated with BP, and incident hypertension. PEDF may be involved in the pathogenesis of hypertension in humans.

Association study of candidate gene polymorphisms and obesity in a young Mexican-American population from South Texas

BACKGROUND AND AIMS

Obesity is increasingly a health problem and a risk factor for diabetes in young Mexican-American populations. Genetic association studies in older, mostly non-Hispanic populations have reported that polymorphisms in the candidate genes HSD11B1, CRP, ADIPOQ, PPARG, ANKK1, ABCC8 and SERPINF1 are associated with obesity or diabetes. We analyzed the polymorphisms rs846910, rs1205, rs1501299, rs1801282, rs1800497, rs757110 and rs1136287 in these candidate genes, for association with obesity and metabolic traits in a young Mexican-American population from south Texas.

METHODS

Genotyping of the seven common SNPs were performed by allelic discrimination assays in 448 unrelated Mexican Americans (median age = 16 years) from south Texas. χ(2) tests and regression analyses using additive models were used for genetic association analyses adjusting for covariates; p values were corrected for multiple testing by permutation analyses.

RESULTS

rs1800497 (ANKK1) shows association with waist circumference (p = 0.009) and retains the association (p = 0.03) after permutation testing. Analysis of metabolic quantitative traits shows that rs846910 (HSD11B1) was associated with HOMA-IR (p = 0.04) and triglycerides (p = 0.03), and rs1205 (CRP) with HOMA-IR (p = 0.03) and fasting glucose levels (p = 0.007). However, the quantitative traits associations are not maintained after permutation analysis. None of the other SNPs in this study showed associations with obesity or metabolic traits in this young Mexican-American population.

CONCLUSIONS

We report a potential association between rs1800497 (linked to changes in brain dopamine receptor levels) and central obesity in a young Mexican-American population.

Systemically administered PEDF against primary and secondary tumours in a clinically relevant osteosarcoma model

Background:

Pigment epithelium-derived factor (PEDF) is an endogenous glycoprotein with a potential role as a therapeutic for osteosarcoma. Animal studies have demonstrated the biological effects of PEDF on osteosarcoma; however, these results are difficult to extrapolate for human use due to the chosen study design and drug delivery methods.

Methods:

In this study we have attempted to replicate the human presentation and treatment of osteosarcoma using a murine orthotopic model of osteosarcoma. The effects of PEDF on osteosarcoma cell lines were evaluated in vitro prior to animal experimentation. Orthotopic tumours were induced by intra-tibial injection of SaOS-2 osteosarcoma cells. Treatment with PEDF was delayed until after the macroscopic appearance of primary tumours. Pigment epithelium-derived factor was administered systemically via an implanted intraperitoneal micro-osmotic pump.

Results:

In vitro, PEDF inhibited proliferation, induced apoptosis and inhibited cell cycling of osteosarcoma cells. Pigment epithelium-derived factor promoted adhesion to Collagen I and inhibited invasion through Collagen I. In vivo, treatment with PEDF caused a reduction in both primary tumour volume and burden of pulmonary metastases. Systemic administration of PEDF did not cause toxic effects on normal tissues.

Conclusion:

Systemically delivered PEDF is effective in suppressing the size of primary and secondary tumours in an orthotopic murine model of osteosarcoma.

Combined serum proteomic and metabonomic profiling after laparoscopic sleeve gastrectomy in children and adolescents

AIM

The consequences of bariatric surgery on important metabolic and signaling pathways are still poorly understood. The aim of our study was to unravel the network of metabolic changes and obesity-related protein biomarkers in morbidly obese children and adolescents undergoing laparoscopic sleeve gastrectomy (LSG).

METHODS

In a prospective study, 6 children with morbid obesity who had failed a well-established conservative weight loss therapy underwent LSG. Pre- and 6 months postoperatively, a metabonomic profiling of 163 metabolites by mass spectrometry and protein profiling by ELISA (clusterin [CLU], pigment epithelium-derived factor [PEDF], retinol binding protein 4 [RBP4], paraoxonase 1 [PON1]) was performed to identify biomarkers of important pathways.

RESULTS

At referral for surgery, the mean age was 14.5 years (range 8-17), mean body mass index (BMI in kg/m(2)) was 48.13 (range 41.1-56.3). All patients showed various metabolic comorbidities. LSG was uneventful in all of them. At 6 months postsurgery, the mean BMI has dropped to 37.1 (range 28.4-40.6). Targeted serum metabonomics resulted in 7 metabolites, which were significantly affected by LSG. Among those, the amino acid phenylalanine was increased, and methionine decreased. The glycero-phospatidylcholine PCaaC38:5 were upregulated, and PCaaC40:2 and PCaaC42:1 were down regulated after 6 months compared with baseline. Further, sphingomyoline (SM) C26:0 and SM C26:1 were decreased after 6 months. The obesity-related biomarkers CLU, PEDF, and RBP4 were decreased, whereas PON1 levels were increased.

CONCLUSION

LSG leads to changes in amino acids and in lipid metabolism indicated by glycerol-phosphatidylcholines and SM. The pattern of protein biomarkers and metabolites might provide measures for the induced physiological changes and for therapy monitoring.

Effect of weight loss on serum pigment epithelium-derived factor levels

BACKGROUND

Cumulating evidence suggests that the broadly acting neurotrophic pigment epithelium-derived factor is associated with visceral adiposity, the metabolic syndrome, diabetes and exerts beneficial effects on atherosclerosis. To further elucidate the relationship between pigment epithelium-derived factor and metabolic perturbations characteristic of obesity, we examined the effect of pronounced weight loss on serum levels of pigment epithelium-derived factor.

MATERIALS AND METHODS

Thirty-six severely obese adults were examined before and 18 months after bariatric surgery. Abdominal fat distribution was determined by ultrasound, metabolic parameters by standard methods, pro-inflammatory biomarkers and serum pigment epithelium-derived factor levels by enzyme-linked immunosorbent assay.

RESULTS

Bariatric surgery resulted in a mean body mass index (BMI) reduction of 9·0 ± 5·0 kg m(-2) and concomitant improvements in glucose homoeostasis and lipid profile. Pigment epithelium-derived factor serum levels decreased from a median 11·0 μg mL(-1) (interquartile range: 3·8) to 9·2 μg mL(-1) (interquartile range: 4·5) (P < 0·0001). In univariate analysis, relative change in pigment epithelium-derived factor levels was significantly associated with change in weight, BMI, fat mass, visceral fat diameter, insulin, homoeostasis model for insulin resistance, triglyceride and leptin levels (all r > 0·370, P < 0·05). No associations were observed for C-reactive protein, interleukin-6 or tumour necrosis factor alpha. After adjustment for age, sex and smoking status, associations remained significant.

CONCLUSIONS

The beneficial effects of bariatric surgery-induced pronounced weight loss on glucose homoeostasis may partially be attributable to visceral adipose tissue reduction and concomitantly decreasing pigment epithelium-derived factor concentrations.

Combined proteomic and metabolomic profiling of serum reveals association of the complement system with obesity and identifies novel markers of body fat mass changes

Obesity is associated with multiple adverse health effects and a high risk of developing metabolic and cardiovascular diseases. Therefore, there is a great need to identify circulating parameters that link changes in body fat mass with obesity. This study combines proteomic and metabolomic approaches to identify circulating molecules that discriminate healthy lean from healthy obese individuals in an exploratory study design. To correct for variations in physical activity, study participants performed a one hour exercise bout to exhaustion. Subsequently, circulating factors differing between lean and obese individuals, independent of physical activity, were identified. The DIGE approach yielded 126 differentially abundant spots representing 39 unique proteins. Differential abundance of proteins was confirmed by ELISA for antithrombin-III, clusterin, complement C3 and complement C3b, pigment epithelium-derived factor (PEDF), retinol binding protein 4 (RBP4), serum amyloid P (SAP), and vitamin-D binding protein (VDBP). Targeted serum metabolomics of 163 metabolites identified 12 metabolites significantly related to obesity. Among those, glycine (GLY), glutamine (GLN), and glycero-phosphatidylcholine 42:0 (PCaa 42:0) serum concentrations were higher, whereas PCaa 32:0, PCaa 32:1, and PCaa 40:5 were decreased in obese compared to lean individuals. The integrated bioinformatic evaluation of proteome and metabolome data yielded an improved group separation score of 2.65 in contrast to 2.02 and 2.16 for the single-type use of proteomic or metabolomics data, respectively. The identified circulating parameters were further investigated in an extended set of 30 volunteers and in the context of two intervention studies. Those included 14 obese patients who had undergone sleeve gastrectomy and 12 patients on a hypocaloric diet. For determining the long-term adaptation process the samples were taken six months after the treatment. In multivariate regression analyses, SAP, CLU, RBP4, PEDF, GLN, and C18:2 showed the strongest correlation to changes in body fat mass. The combined serum proteomic and metabolomic profiling reveals a link between the complement system and obesity and identifies both novel (C3b, CLU, VDBP, and all metabolites) and confirms previously discovered markers (PEDF, RBP4, C3, ATIII, and SAP) of body fat mass changes.

Serum level of pigment epithelium-derived factor is a marker of atherosclerosis in humans

OBJECTIVE

Pigment epithelium-derived factor (PEDF) could play a protective role against atherosclerosis. However, there is no clinical study to examine the relationship between serum level of PEDF and atherosclerosis in humans.

METHODS/RESULTS

The study involved 317 consecutive outpatients in Kurume University Hospital (220 male and 97 female) with a mean age of 62.1±9.1. We examined whether serum level of PEDF were independently associated with vascular inflammation evaluated by [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET) and intima-media thickness (IMT) in carotid artery in humans. Carotid [(18)F]-FDG uptake, an index of vascular inflammation within the atherosclerotic plaques, was measured as standardized uptake value (SUV). Mean serum PEDF level, carotid SUV and IMT values were 13.5±1.1 μg/mL, 1.34±0.19, and 0.71±0.15 mm, respectively. In multiple stepwise regression analysis, estimated glomerular filtration rate (p<0.001), males (p<0.001), homeostasis model assessment of insulin resistance index (p<0.05), heart rate (p<0.05), triglycerides (p<0.05), carotid IMT (p<0.05), waist circumference (p<0.05) and carotid SUV (p<0.05) were independently correlated to PEDF level (R(2)=0.332).

CONCLUSION

The present study reveals that serum level of PEDF is independently associated with vascular inflammation and IMT, thus suggesting that PEDF level is a novel biomarker that could reflect atherosclerosis in humans.

Administration of pigment epithelium-derived factor inhibits left ventricular remodeling and improves cardiac function in rats with acute myocardial infarction

Oxidative stress and inflammation are involved in cardiac remodeling after acute myocardial infarction (AMI). We have found that pigment epithelium-derived factor (PEDF) inhibits vascular inflammation through its anti-oxidative properties. However, effects of PEDF on cardiac remodeling after AMI remain unknown. We investigated whether PEDF could inhibit left ventricular remodeling and improve cardiac function in rats with AMI. AMI was induced in 8-week-old Sprague-Dawley rats by ligation of the left ascending coronary artery. Rats were treated intravenously with vehicle or 10 μg PEDF/100 g b.wt. every day for up to 2 weeks after AMI. Each rat was followed until 16 weeks of age. PEDF levels in infarcted areas and serum were significantly decreased at 1 week after AMI and remained low during the observational periods. PEDF administration inhibited apoptotic cell death and oxidative stress generation around the infarcted areas at 2 and 8 weeks after AMI. Further, PEDF injection suppressed cardiac fibrosis by reducing transforming growth factor-β and type III collagen expression, improved left ventricular ejection fraction, ameliorated diastolic dysfunction, and inhibited the increase in left ventricular mass index at 8 weeks after AMI. The present study demonstrated that PEDF could inhibit tissue remodeling and improve cardiac function in AMI rats. Substitution of PEDF may be a novel therapeutic strategy for cardiac remodeling after AMI.

Circulating pigment epithelium-derived factor levels are associated with insulin resistance and decrease after weight loss

OBJECTIVE

We aimed to study circulating pigment epithelium-derived factor (PEDF) in vivo in association with insulin resistance and in vitro in human adipocytes.

METHODS

Circulating PEDF (ELISA) and metabolic profile were assessed in 125 Caucasian men. PEDF levels were also assessed in an independent cohort of subjects (n = 33) to study the effects of changing insulin action. PEDF gene expression and secretion were measured during differentiation of human preadipocytes.

RESULTS

In all subjects, PEDF was positively associated with body mass index (r = 0.326; P < 0.0001), waist-to-hip ratio (r = 0.380; P < 0.0001), HbA(1c), and fasting triglycerides and negatively with insulin sensitivity (r = -0.320; P < 0.0001). PEDF levels were significantly increased in subjects with altered glucose tolerance and type 2 diabetes. Of the inflammatory markers measured, PEDF levels were positively associated with serum soluble TNF-α receptor 1 and IL-10 in obese subjects. Interestingly, weight loss led to significantly decreased PEDF concentration from 34.8 ± 19.3 to 22.5 ± 14.2 μg/ml (P < 0.0001). Multiple linear regression analyses revealed that insulin sensitivity contributed independently to explain 14% of the variance in PEDF levels after controlling for the effects of body mass index, age, and log fasting triglycerides. Differences in PEDF observed after weight loss were related to changes in obesity, insulin resistance, and blood pressure measures. PEDF gene expression and secretion increased during differentiation of human preadipocytes.

CONCLUSION

Circulating PEDF is associated with insulin sensitivity. The findings show, for the first time in humans, that PEDF concentrations decrease significantly after weight loss in association with blood pressure. PEDF seems to be involved in human adipocyte biology.

Prognostic value of pigment epithelium-derived factor in patients with advanced heart failure

OBJECTIVE

Whereas angiogenesis, the formation of new blood vessels from preexisting vessels, may be beneficial in restoring failing myocardium, apoptosis may contribute to the progression of heart failure (HF). We investigated the role of pigment epithelium-derived factor (PEDF), a recently discovered antiangiogenic factor with additional proapoptotic effects, in patients with advanced HF.

METHODS

We assayed PEDF levels in 351 patients with advanced HF at baseline. During the median follow-up time of 16 months, 50% of patients experienced the composite end point of rehospitalization and/or death.

RESULTS

The risk of a clinical event increased with concentrations of the antiangiogenic marker PEDF, with a 1.94-fold higher risk in the third tertile compared with the first tertile (95% CI, 1.33-2.84). This association remained significant after adjustment for B-type natriuretic peptide (BNP) and other risk factors in a Cox regression model (P = .015). Experimental data revealed that PEDF may contribute to the progression of HF by inducing apoptosis in human cardiac myocytes and fibroblasts via activation of caspase 3.

CONCLUSIONS

We suggest a role of PEDF in the progression of HF by inducing apoptosis of human cardiac myocytes and fibroblasts. Our clinical data suggest that PEDF concentrations may have the potential to become a valuable marker of the prognosis of HF, in addition to BNP.

Pigment epithelium-derived factor (PEDF) as a therapeutic target in cardiovascular disease

In this review we discuss the role of pigment epithelium-derived factor (PEDF) as a possible new target molecule to therapeutically influence cardiovascular disease. PEDF is a multifunctional, pleiotropic protein with antiangiogenic, antitumorigenic, antioxidant, anti-inflammatory, antithrombotic, neurotrophic and neuroprotective properties. First identified in retinal pigment epithelium cells, it is expressed in various tissues throughout the body such as the eye, liver and adipose tissue. Recently PEDF has also been characterized in the heart. PEDF has been suggested to have a protective role in atherosclerosis, the main cause of coronary heart disease, myocardial infarction and heart failure due to its anti-inflammatory, antioxidant and antithrombotic effects in the vessel wall and platelets. Additionally PEDF has strong antiangiogenic effects by inducing apoptosis in endothelial cells and by regulating the expression of other angiogenic factors. Therefore blocking of PEDF locally for example in ischemic tissue in the heart might favour angiogenesis, induce neovascularization and lead to increased perfusion of the injured tissue. On the other hand, local overexpression of PEDF restricted to atherosclerotic lesions might block angiogenesis, inflammation and thrombosis at these sites and thus counteract destabilization and rupture of the lesion otherwise caused by inflammatory activation and excessive angiogenesis and inhibit subsequent thrombus formation.