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

The Various Roles of PEDF in Cancer

Pigment epithelium-derived factor (PEDF) is a natural immunomodulator, anti-inflammatory, anti-angiogenic, anti-tumour growth and anti-metastasis factor, which can enhance tumour response to PEDF but can also conversely have pro-cancerous effects. Inflammation is a major cause of cancer, and it has been proven that PEDF has anti-inflammatory properties. PEDF's functional activity can be investigated through measuring metastatic and metabolic biomarkers that will be discussed in this review.

Serum Pigment Epithelium-Derived Factor Levels are Associated with Estradiol and Decrease After Adjusting for Alanine Aminotransferase in Chinese Women Based on Multiple Linear Regression Analysis

PURPOSE

To assess changes in pigment epithelium-derived factor (PEDF) levels in patients with metabolic syndrome (MetS) and to investigate sexual dimorphism in serum PEDF levels and their relationships with estradiol.

METHODS

A total of 318 individuals (145 men, 173 women) who underwent health examinations in our department were selected. Serum PEDF, estradiol and other metabolic parameters were determined. Homeostasis model assessment of insulin resistance (HOMA- IR) and homeostasis model assessment of β-cell function (HOMA-β) were calculated to evaluate insulin resistance and β-cell function, respectively. Multiple linear regression analysis was used to analyse the factors influencing serum PEDF.

RESULTS

Serum PEDF levels were significantly higher in subjects with MetS in both men and women (12.09±2.75 vs 8.97±3.19 μg/mL in men and 11.31±2.79 vs 8.40±2.32 μg/mL in women, MetS vs non-MetS, P<0.001). Correlation analysis showed that serum PEDF levels were significantly correlated with body mass index (BMI), waist circumference, waist-to-hip ratio, diastolic blood pressure (DBP), fasting and 2-h postprandial glucose, fasting and 2-h postprandial insulin, HOMA-β, HOMA-IR, hemoglobin A1c (HbA1c), alanine aminotransferase (ALT), aspartate aminotransferase (AST), uric acid (UA), triacylglycerol (TG) and high-density lipoprotein cholesterol (HDL-C). Elevated ALT, HOMA-IR and TG were significant predictors of increased PEDF concentrations. In women, estradiol was inversely correlated with PEDF levels (r=-0.25, P=0.011), and the association was no longer significant after adjustment for ALT.

CONCLUSION

PEDF could be used as a biomarker of MetS in both men and women. This study reported for the first time that circulating PEDF displays sexual dimorphism, which could be related to estrogen. The association between estrogen and circulating PEDF levels was attenuated after adjusting for ALT.

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.

Pigment Epithelial-Derived Factor Deficiency Accelerates Atherosclerosis Development via Promoting Endothelial Fatty Acid Uptake in Mice With Hyperlipidemia

Background

Endothelial cell injury, induced by dyslipidemia, is the initiation of atherosclerosis, resulting in an imbalance in endothelial fatty acid (FA) transport. Pigment epithelial‐derived factor (PEDF) is an important regulator in lipid metabolism. We hypothesized that PEDF is involved in endothelium‐mediated FA uptake under hyperlipidemic conditions.

Methods and Results

Circulating PEDF levels were higher in patients with atherosclerotic cardiovascular disease than in normal individuals. However, decreasing trends of serum PEDF levels were confirmed in both wild‐type and apolipoprotein E–deficient mice fed a long‐term high‐fat diet. Apolipoprotein E–deficient/PEDF‐deficient mice were generated by crossing PEDF‐deficient mice with apolipoprotein E–deficient mice, and then mice were fed with 24, 36, or 48 weeks of high‐fat diet. Greater increases in body fat and plasma lipids were displayed in PEDF‐deficient mice. In addition, PEDF deficiency in mice accelerated atherosclerosis, as evidenced by increased atherosclerotic plaques, pronounced vascular dysfunction, and increased lipid accumulation in peripheral tissues, whereas injection of adeno‐associated virus encoding PEDF exerted opposite effects. Mechanistically, PEDF inhibited the vascular endothelial growth factor B paracrine signaling by reducing secretion of protein vascular endothelial growth factor B in peripheral tissue cells and decreasing expression of its downstream targets in endothelial cells, including its receptors (namely, vascular endothelial growth factor receptor‐1 and neuropilin‐1), and FA transport proteins 3 and 4, to suppress endothelial FA uptake, whereas PEDF deletion in mice activated the vascular endothelial growth factor B signaling pathway, thus causing markedly increased lipid accumulation.

Conclusions

Decreasing expression of PEDF aggravates atherosclerosis by significantly impaired vascular function and enhanced endothelial FA uptake, thus exacerbating ectopic lipid deposition in peripheral tissues.

Pigment epithelium-derived factor inhibits adipogenesis in 3T3-L1 adipocytes and protects against high-fat diet-induced obesity and metabolic disorders in mice

Obesity is a major cause of metabolic syndrome and type II diabetes, and it presents with metabolic disorders, such as hyperglycemia, hyperlipidemia, and insulin resistance. Pigment epithelium-derived factor (PEDF), a protein isolated from retinal pigment epithelial cells, has multiple functions, including neuronal protection, antineoplastic effects, and anti-inflammatory activity. The aim of this study is to investigate the antiobesity effects of PEDF. The antiobesity effects of PEDF on fat accumulation, inflammation, energy expenditure, insulin resistance, and obesity-related physiological parameters and protein levels were assessed in high-fat diet (HFD)-induced obese mice in vivo and in 3T3-L1 adipocytes, palmitate (PA)-treated HepG2 cells, and C2C12 myotubes in vitro. In an in vivo assay, PEDF effectively decreased body weight gain, white adipose tissue mass, and inflammation and improved insulin resistance, dyslipidemia, and hyperglycemia in HFD-induced mice. In liver tissue, PEDF decreased lipid accumulation and fibrosis. In an in vitro assay, PEDF diminished the differentiation of 3T3-L1 preadipocytes. We also determined that PEDF promoted lipolysis and prolonged cell cycle progression, through the mTOR-S6K pathway and downstream transcription factors, such as peroxisome proliferator-activated receptor gamma, CCAAT/enhancer-binding protein α (CEBP-α), and CEBP-β. In addition, PEDF decreased reactive oxygen species production in PA-induced HepG2 cells and improved glucose uptake ability in PA-induced HepG2 cells and C2C12 myotubes. In the present study, PEDF protected against HFD-induced obesity and metabolic disorders in mice, inhibited adipogenesis, and improved insulin resistance. These results provide a new potential treatment for obesity in the future.

Inflammatory markers in children and adolescents with type 2 diabetes mellitus

This review examines the potential relationship between serum inflammation markers and type 2 diabetes mellitus (T2DM). Inflammation markers have been proposed as prognostic markers for the development of T2DM and its complications. Furthermore, modulation of the inflammatory process may offer future treatment strategies for T2DM. This review focuses on children and adolescents because there is usually little, if any, complications associated with other disease processes, use of medications, or active tobacco smoking. Furthermore, β-cell failure in young age cannot be solely explained by aging and exhaustion of β-cells due to insulin resistance. Pediatric studies have demonstrated that pro-inflammatory cytokines TNF-α, IL-6, IL-1β, IFNγ, PEDF, and fetuin A were increased in insulin resistance, while the anti-inflammatory cytokines adiponectin and omentin were decreased. Furthermore, TNF-α, fetuin A, FGF-21 were altered in obese children with T2DM suggesting a direct involvement in β-cell failure. Future studies focusing on children and adolescents may facilitate our understanding of T2DM as an inflammatory disease process.

Inflammation Markers in Type 2 Diabetes and the Metabolic Syndrome in the Pediatric Population

PURPOSE OF REVIEW

Chronic inflammation, adipokines, and hepatokines have been identified as basis of insulin resistance and β cell failure in animal models. We present our current knowledge concerning the potential relationship between these cytokines, inflammation, metabolic syndrome (MetS), and type 2 diabetes mellitus (T2DM) in the pediatric population.

RECENT FINDINGS

Pro-inflammatory cytokines related to insulin resistance and MetS in children are tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6, IL-1β, interferon gamma, pigment epithelium-derived factor, chemerin, vaspin, and fetuin A. Anti-inflammatory cytokines associated with insulin resistance and MetS in children are leptin, adiponectin, omentin, fibroblast growth factor (FGF)-21, osteocalcin, and irisin. These anti-inflammatory cytokines are decreased (adiponectin, omentin, and osteocalcin) or increased (leptin, FGF-21, and irisin) in obesity suggesting a resistance state. TNF-α, fetuin A, and FGF-21 are altered in obese children with T2DM suggesting an involvement in β cell failure. These cytokines, adipokines, and hepatokines may be able to predict development of MetS and T2DM and have a potential therapeutic target ameliorating insulin resistance.

Intra-individual variability and circadian rhythm of vascular endothelial growth factors in subjects with normal glucose tolerance and type 2 diabetes

Increased levels of systemic vascular endothelial growth factors (VEGFs) in patients with diabetes are associated with increased risk of microvessel disease. On the other hand, low VEGF levels after intravitreal antibody application may be associated with acute cardiovascular complications and treatment failure. Individual levels of systemic VEGF vary in a wide range depending on analytical methods and quality of diabetes control. So far only limited information exists on intraindividual fluctuations over longer periods and circadian rhythms. We analysed the intraindividual variance of VEGF-A, VEGF-C and placental growth factor (PLGF) in CTAD (citrate-theophylline-adenine-dipyridamol) plasma as well as VEGF-A in serum over a period of 6 months in patients with stable controlled type 2 diabetes (10 M, 10 F) and age and sex matched subjects with normal glucose tolerance (NGT). Furthermore, circadian levels of VEGFs were controlled hourly from 7:30 a.m. to 7:30 p.m. under standardized metabolic ward conditions. In addition, the relationship to metabolic, hormonal and inflammatory biomarkers was analyzed. VEGF-A, VEGF-C and PLGF remained stable in plasma and VEGF-A in serum over 6 months in both groups. No circadian change was observed in VEGF-A serum and plasma concentrations. A minor decrease of VEGF-C plasma levels was evident after 5 p.m. in both groups and a significant peak of PLGF concentrations occurred after lunch, which was more pronounced in T2DM. In multivariate analysis, only serum VEGF-A correlated to diabetes duration, whereas VEGF-C only correlated to HbA1c and fasting blood glucose. We did not observe significant intraindividual variances for VEGF-A in serum and VEGF-A, VEGF-C and PLGF in CTAD plasma over a period of 6 months. Taken together, a single morning measurement of systemic VEGF levels after 7:30 am appears to be a reliable parameter for the individual risk associated with abnormal VEGF concentrations in blood.

Trial Registration: NCT02325271

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.

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.

Metabolic syndrome in pediatrics

The ever growing prevalence of childhood obesity is being accompanied by an increase in the pediatric population of diseases once believed to be exclusive of the adulthood such as the metabolic syndrome (MS). The MS has been defined as the link between insulin resistance, hypertension, dyslipidemia, impaired glucose tolerance, and other metabolic abnormalities associated with an increased risk of atherosclerotic cardiovascular diseases in adults. In this review, we will discuss the peculiar aspects of the pediatric MS and the role of novel molecules and biomarkers in its pathogenesis.

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 (PEDF) suppresses IL-1β-mediated c-Jun N-terminal kinase (JNK) activation to improve hepatocyte insulin signaling

Pigment epithelium-derived factor (PEDF) is an antiinflammatory protein that circulates at high levels in the metabolic syndrome. Metabolic studies of PEDF knockout (KO) mice were conducted to investigate the relationship between PEDF, inflammatory markers, and metabolic homeostasis. Male PEDF KO mice demonstrated a phenotype consisting of increased adiposity, glucose intolerance, and elevated serum levels of metabolites associated with the metabolic syndrome. Genome expression analysis revealed an increase in IL-1β signaling in the livers of PEDF KO mice that was accompanied by impaired IRS and Akt signaling. In human hepatocytes, PEDF blocked the effects of an IL-1β challenge by suppressing activation of the inflammatory mediator c-Jun N-terminal kinase while restoring Akt signaling. RNA interference of PEDF in human hepatocytes was permissive for c-Jun N-terminal kinase activation and decreased Akt signaling. A metabolomics profile identified elevated circulating levels of tricarboxyclic acid cycle intermediates including succinate, an inducer of IL-1β, in PEDF KO mice. Succinate-dependent IL-1β expression was blocked by PEDF in PEDF KO, but not wild-type hepatocytes. In vivo, PEDF restoration reduced hyperglycemia and improved hepatic insulin signaling in PEDF KO mice. These findings identify elevated PEDF as a homeostatic mechanism in the human metabolic syndrome.

Metformin inhibits expression and secretion of PEDF in adipocyte and hepatocyte via promoting AMPK phosphorylation

OBJECTIVE

Pigment epithelium-derived factor (PEDF) plays an important role in obesity-induced insulin resistance (IR). The study aims to investigate the effect of metformin, a widely used agent to improve IR, on PEDF production both in vivo and in vitro.

METHODS

SD rats were divided into normal control group, high fat group (HF group), and metformin group (MET group). Hyperinsulinemic euglycemic clamp was performed to evaluate insulin sensitivity. IR models of 3T3-L1 and HepG2 cells were established and then treated with metformin and inhibitor of AMP activated protein kinase (AMPK).

RESULTS

In vivo, the HF group showed increased serum PEDF which is negatively correlated with insulin sensitivity, while the MET group revealed decreased serum PEDF and downregulated PEDF expression in fat and liver, concomitant with significantly improved IR. In vitro, the IR cells showed enhanced PEDF secretion and expression, whereas metformin lowered PEDF secretion and expression, accompanied with increased glucose uptake. Metformin stimulated AMPK phosphorylation in fat and liver of the obese rats, while in vitro, when combined with AMPK inhibitor, the effect of metformin on PEDF was abrogated.

CONCLUSIONS

Metformin inhibits the expression and secretion of PEDF in fat and liver via promoting AMPK phosphorylation, which is closely associated with IR improvement.

Adipo-myokines: two sides of the same coin--mediators of inflammation and mediators of exercise

This review summarizes the current literature regarding the most discussed contraction-regulated moykines like IL-6, IL-15, irisin, BDNF, ANGPTL4, FGF21, myonectin and MCP-1. It is suggested that the term myokine is restricted to proteins secreted from skeletal muscle cells, excluding proteins that are secreted by other cell types in skeletal muscle tissue and excluding proteins which are only described on the mRNA level. Interestingly, many of the contraction-regulated myokines described in the literature are additionally known to be secreted by adipocytes. We termed these proteins adipo-myokines. Within this review, we try to elaborate on the question why pro-inflammatory adipokines on the one hand are upregulated in the obese state, and have beneficial effects after exercise on the other hand. Both, adipokines and myokines do have autocrine effects within their corresponding tissues. In addition, they are involved in an endocrine crosstalk with other tissues. Depending on the extent and the kinetics of adipo-myokines in serum, these molecules seem to have a beneficial or an adverse effect on the target tissue.

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.

Identification and validation of novel contraction-regulated myokines released from primary human skeletal muscle cells

Proteins secreted by skeletal muscle, so called myokines, have been shown to affect muscle physiology and additionally exert systemic effects on other tissues and organs. Although recent profiling studies have identified numerous myokines, the amount of overlap from these studies indicates that the secretome of skeletal muscle is still incompletely characterized. One limitation of the models used is the lack of contraction, a central characteristic of muscle cells. Here we aimed to characterize the secretome of primary human myotubes by cytokine antibody arrays and to identify myokines regulated by contraction, which was induced by electrical pulse stimulation (EPS). In this study, we validated the regulation and release of two selected myokines, namely pigment epithelium derived factor (PEDF) and dipeptidyl peptidase 4 (DPP4), which were recently described as adipokines. This study reveals that both factors, DPP4 and PEDF, are secreted by primary human myotubes. PEDF is a contraction-regulated myokine, although PEDF serum levels from healthy young men decrease after 60 min cycling at VO2max of 70%. Most interestingly, we identified 52 novel myokines which have not been described before to be secreted by skeletal muscle cells. For 48 myokines we show that their release is regulated by contractile activity. This profiling study of the human skeletal muscle secretome expands the number of myokines, identifies novel contraction-regulated myokines and underlines the overlap between proteins which are adipokines as well as myokines.

Pathophysiology and treatment of diabetic retinopathy

In the past years, the management of diabetic retinopathy (DR) relied primarily on a good systemic control of diabetes mellitus, and as soon as the severity of the vascular lesions required further treatment, laser photocoagulation or vitreoretinal surgery was done to the patient. Currently, even if the intensive metabolic control is still mandatory, a variety of different clinical strategies could be offered to the patient. The recent advances in understanding the complex pathophysiology of DR allowed the physician to identify many cell types involved in the pathogenesis of DR and thus to develop new treatment approaches. Vasoactive and proinflammatory molecules, such as vascular endothelial growth factor (VEGF), play a key role in this multifactorial disease. Current properly designed trials, evaluating agents targeting VEGF or other mediators, showed benefits in the management of DR, especially when metabolic control is lacking. Other agents, directing to the processes of vasopermeability and angiogenesis, are under investigations, giving more hope in the future management of this still sight-threatening disease.