Pre-B cell colony-enhancing factor inhibits neutrophil apoptosis in experimental inflammation and clinical sepsis

Therapeutic potential of SIRT1 and NAMPT-mediated NAD biosynthesis in type 2 diabetes

Both genetic and environmental factors contribute to the pathogenesis of type 2 diabetes, and it is critical to understand the interplay between these factors in the regulation of insulin secretion and insulin sensitivity to develop effective therapeutic interventions for type 2 diabetes. For the past several years, studies on the mammalian NAD-dependent protein deacetylase SIRT1 and systemic NAD biosynthesis mediated by nicotinamide phosphoribosyltransferase (NAMPT) have demonstrated that these two regulatory components together play a critical role in the regulation of glucose homeostasis, particularly in the regulation of glucose-stimulated insulin secretion in pancreatic beta cells. These components also contribute to the age-associated decline in beta cell function, which has been suggested to be one of the major contributing factors to the pathogenesis of type 2 diabetes. In this review article, the roles of SIRT1 and NAMPT-mediated systemic NAD biosynthesis in glucose homeostasis and the pathophysiology of type 2 diabetes will be summarized, and their potential as effective targets for the treatment and prevention of type 2 diabetes will be discussed.

Maternal visfatin concentration in normal pregnancy

OBJECTIVE

Adipose tissue has now emerged as a powerful endocrine organ via the production of adipokines. Visfatin, a novel adipokine with diabetogenic and immuno-modulatory properties has been implicated in the pathophysiology of insulin resistance in patients with obesity and Type-2 diabetes mellitus. The aim of this study was to determine whether there are changes in the maternal plasma concentration of visfatin with advancing gestation and as a function of maternal weight.

STUDY DESIGN

In this cross-sectional study, maternal plasma concentrations of visfatin were determined in normal weight and overweight/obese pregnant women in the following gestational age groups: 1) 11-14 weeks (n=52); 2) 19-26 weeks (n=68); 3) 27-34 weeks (n=93); and 4) >37 weeks (n=60). Visfatin concentrations were determined by ELISA. Non parametric statistics were used for analysis.

RESULTS

1) The median maternal plasma visfatin concentration was higher in pregnant women between 19-26 weeks of gestation than that of those between 11-14 weeks of gestation (P<0.01) and those between 27-34 weeks of gestation (P<0.01); 2) among normal weight pregnant women, the median plasma visfatin concentrations of women between 19-26 weeks of gestation was higher than that of those between 11-14 weeks (P<0.01) and those between 27-34 weeks (P<0.01); and 3) among overweight/obese patients, the median maternal visfatin concentration was similar between the different gestational age groups.

CONCLUSION

The median maternal plasma concentration of visfatin peaks between 19-26 and has a nadir between 27-34 weeks of gestation. Normal and overweight/obese pregnant women differed in the pattern of changes in circulating visfatin concentrations as a function of gestational age.

Molecular analysis of tammar (Macropus eugenii) mammary epithelial cells stimulated with lipopolysaccharide and lipoteichoic acid

The immunological function of the metatherian mammary gland plays a crucial part in neonatal survival of the marsupial young. Marsupial pouch young do not develop adult like immune responses until just prior to leaving the pouch. The immune components of the maternal milk secretions are important during this vulnerable early post-partum period. In addition, infection of the mammary gland has not been recognized in metatherians, despite the ready availability of pathogens in the pouch. Regardless of which, little is known about the immunobiology of the mammary gland and the immune responses of mammary epithelial cells in metatherians. In this study, a molecular approach was utilized to examine the response of tammar (Macropus eugenii) mammary epithelial cells to Escherichia coli derived lipopolysaccharide (LPS) and Staphylococcus aureus derived lipoteichoic acid (LTA). Using custom-made cDNA microarrays, candidate genes were identified in the transciptome, which were involved in antigen presentation, inflammation, cell growth and proliferation, cellular damage and apoptosis. Quantification of mRNA expression of several of these candidate genes, along with seven other genes (TLR4, CD14, TNF-alpha, cathelicidin, PRDX1, IL-5 and ABCG2) associated with innate immunity in LPS and LTA challenged mammary epithelial cells and leukocytes, was assessed for up to 24 h. Differences in genes associated with cellular damage and pro-inflammatory cytokine production were seen between stimulated mammary epithelial cells and leukocytes. LTA challenge tended to result in lower level induction of pro-inflammatory cytokines, increased PRDX1 mRNA levels, suggesting increased oxidative stress, and increased CD14 expression, but in a non-TLR4-dependent manner. The use of functional genomic tools in the tammar identified differences in the response of tammar mammary epithelial cells (MEC) and leukocytes to challenge with LPS and LTA, and validates the utility of the approach. The results of this study are consistent with a model in which tammar mammary epithelial cells have the capacity to elicit a complex and robust immune response to pathogens.

Circulating visfatin in chronic obstructive pulmonary disease

OBJECTIVE

Malnutrition and continuous systemic inflammation occur frequently in patients with chronic obstructive pulmonary disease (COPD). Visfatin is a new adipokine, which increases in some inflammatory diseases. Its plasma level and relation with nutritional status and inflammation in COPD remain unknown. This study compared visfatin levels, nutritional status, and inflammation markers in patients with COPD and healthy controls.

METHODS

Plasma visfatin, tumor necrosis factor-alpha (TNF-alpha) and C-reactive protein (CRP) were measured in 35 patients with COPD and 28 healthy controls. Body composition was assessed with bioelectrical impedance analysis.

RESULTS

Significantly lower body mass index and percentage of body fat were observed in patients with COPD compared with control subjects. The levels of plasma visfatin were higher in the COPD group compared with healthy controls (2.07 +/- 0.18 versus 1.88 +/- 0.15 ng/mL, P < 0.001). Levels of TNF-alpha and CRP were also significantly higher in patients with COPD compared with controls. Plasma CRP and TNF-alpha were positively correlated with visfatin in the COPD group. No significant correlations were found between visfatin and body mass index or percentage of body fat in both groups.

CONCLUSION

Plasma visfatin levels increased in patients with COPD. This increased adipocytokine was significantly correlated with TNF-alpha and CRP. Visfatin may be a new proinflammatory adipocytokine in this disease.

Correlation of circulating full-length visfatin (PBEF/NAMPT) with metabolic parameters in subjects with and without diabetes: a cross-sectional study

OBJECTIVE

Here we use a novel ELISA that is specific for full-length visfatin (PBEF/NAMPT), compare it with the existing C-terminal based assay and use it to investigate associations of visfatin with metabolic parameters.

DESIGN, PATIENTS AND MEASUREMENTS

We established the specificity and effectiveness of the new ELISA and evaluated the associations of full-length visfatin with clinical, anthropometric and metabolic parameters in a cross-sectional study of 129 Thai subjects, consisting of 50 outpatients with type 2 diabetes and 79 healthy volunteers.

RESULTS

The new ELISA accurately recovered full-length recombinant visfatin and detected visfatin secreted by primary human and rat adipocytes. We found serum full-length visfatin was significantly higher in subjects with diabetes compared to their nondiabetic peers (median 2.75 vs. 2.22 ng/ml, P = 0.0142). After adjustment for age, gender and traditional metabolic risk factors, adjusted mean visfatin remained significantly higher in the diabetes group (3.80 vs. 2.10 ng/ml, P = 0.0021). On Spearman univariate correlation analysis, visfatin was significantly associated with resistin (r = 0.30, P = 0.0011), but not with any other anthropometric or metabolic variables, including adiponectin multimers. On multiple linear regression analysis, the only covariates independently associated with visfatin were diabetes (t = 3.11, P = 0.0024) and log resistin (t = 2.68, P = 0.0086).

CONCLUSIONS

Circulating visfatin is independently associated with diabetes and resistin concentration, but is not related to adiponectin multimers or other metabolic covariates. These data are suggestive of a potential role of visfatin in subclinical inflammatory states.

Extracellular Nampt promotes macrophage survival via a nonenzymatic interleukin-6/STAT3 signaling mechanism

Macrophages play key roles in obesity-associated pathophysiology, including inflammation, atherosclerosis, and cancer, and processes that affect the survival-death balance of macrophages may have an important impact on obesity-related diseases. Adipocytes and other cells secrete a protein called extracellular nicotinamide phosphoribosyltransferase (eNampt; also known as pre-B cell colony enhancing factor or visfatin), and plasma levels of eNampt increase in obesity. Herein we tested the hypothesis that eNampt could promote cell survival in macrophages subjected to endoplasmic reticulum (ER) stress, a process associated with obesity and obesity-associated diseases. We show that eNampt potently blocks macrophage apoptosis induced by a number of ER stressors. The mechanism involves a two-step sequential process: rapid induction of interleukin 6 (IL-6) secretion, followed by IL-6-mediated autocrine/paracrine activation of the prosurvival signal transducer STAT3. The ability of eNampt to trigger this IL-6/STAT3 cell survival pathway did not depend on the presence of the Nampt enzymatic substrate nicotinamide in the medium, could not be mimicked by the Nampt enzymatic product nicotinamide mononucleotide (NMN), was not blocked by the Nampt enzyme inhibitor FK866, and showed no correlation with enzyme activity in a series of site-directed mutant Nampt proteins. Thus, eNampt protects macrophages from ER stress-induced apoptosis by activating an IL-6/STAT3 signaling pathway via a nonenzymatic mechanism. These data suggest a novel action and mechanism of eNampt that could affect the balance of macrophage survival and death in the setting of obesity, which in turn could play important roles in obesity-associated diseases.

Pre-B cell colony-enhancing factor in lower vertebrates: first evidence of this cytokine being involved in antioxidant activity by reconstruction of a novel NAD salvage pathway in E. coli

The pre-B cell colony-enhancing factor identified in mammals is an important cytokine involved in multiple functions, such as immunoregulation, cellular proliferation and differentiation. However, little is known about its existence and function in lower vertebrates; therefore, we investigated the characterization, expression and especially the biofunction of this factor in Tetraodon nigroviridis, a model organism of lower vertebrates. We focus on the question of whether the pre-B cell colony-enhancing factor of lower vertebrates contributes to the NAD mediated antioxidant activity by its involvement in the biosynthesis of NAD through pyridine nucleotide cycles. Experimental data demonstrated that by transforming fish pre-B cell colony-enhancing factor into Escherichia coli cells, the amounts of NAD and NADP significantly increased, and cellular antioxidant activity greatly improved. This is the first report about vertebrate pre-B cell colony-enhancing factor acting as a nicotinamide phosphoribosyltransferase to reconstruct a pyridine nucleotide cycle III pathway in E. coli and playing an important role in antioxidant stress by up-regulation of NAD biosynthesis. We hope that our observations may enrich the study of pre-B cell colony-enhancing factor, and contribute to a better understanding of the molecular and functional evolution of the pre-B cell colony-enhancing factor family in both lower vertebrates and mammals as a whole.

Epicardial fat thickness: relationship with plasma visfatin and plasminogen activator inhibitor-1 levels in visceral obesity

BACKGROUND AND AIM

Epicardial fat (EF), a true visceral adipose tissue (VAT) deposited around the heart, is considered as possible cardiovascular risk indicator, in view of its ability to produce and release several inflammatory adipo-cytokines. It is still not known whether increased cardiac adiposity is related to increased inflammatory adipo-cytokines in obesity. The aim of this study was to evaluate whether echocardiographic EF thickness, an indicator of cardiac adiposity, is related to circulating levels of inflammatory adipo-cytokines such as visfatin and plasminogen activator inhibitor-1 (PAI-1) in visceral obesity.

METHODS AND RESULTS

EF thickness (measured by echocardiography), visfatin, PAI-1 antigen and some inflammatory markers were studied in 42 women, 27 of them severely obese (OB) (BMI 43.5+/-4.8 kg/m(2)) but with no apparent complications, and 15 normal-weight controls. Abdominal VAT in the OB was assessed by computed tomography. OB had thicker EF and higher visfatin and PAI-1 antigen concentrations than controls (P<0.0001). EF thickness, log-visfatin and log-PAI-1 antigen concentrations directly correlated with VAT (P<0.0001). Log-visfatin and log-PAI-1 antigen were correlated with EF thickness even after adjusting for indices of fat distribution (P<0.01 and P<0.001 respectively). Moreover, when dividing OB on the basis of median EF thickness, women with greater EF thickness had more VAT and higher adipo-cytokine concentrations and inflammatory markers.

CONCLUSIONS

This study suggests that EF thickness, an indicator of cardiac adiposity, may be significantly related to inflammatory adipo-cytokines in visceral-obese patients. This suggests EF might be used as an easy and reliable marker of visceral adiposity and inflammation and as a cardiovascular risk indicator.

Visfatin, low-grade inflammation and body mass index (BMI)

OBJECTIVE

Visfatin is an adipokine with revealing roles in inflammatory mechanisms but its implication in inflammation related to excessive adiposity/obesity is not studied yet. Our aim was to investigate the relations of visfatin with inflammation markers and body mass index (BMI) in the peripheral blood mononuclear cells (PBMCs), a type of cells closely related to inflammatory mechanisms.

DESIGN

Cross-sectional study, quantification of visfatin, TNF-alpha, IL-6 mRNA in PBMCs.

PATIENTS

Eighty-three supposed healthy individuals from the STANISLAS cohort, belonging in three BMI categories: BMI < 25 kg/m(2) (lean), 25 kg/m(2) <or= BMI < 30 kg/m(2) (overweight) or BMI >or= 30 kg/m(2) (obese).

MEASUREMENTS

We measured visfatin gene expression (by real-time quantitative PCR), in relation to gene expression of the pro-inflammatory cytokines TNF-alpha, IL-6 in PBMCs and to anthropometric parameters (weight, BMI, waist : hip ratio), blood pressure, lipid profile, glucose and inflammatory markers (C-reactive protein, lymphocyte count).

RESULTS

Visfatin expression in PBMCs was significantly associated with BMI in a negative way (r = -0.21, P = 0.05). Global anova analysis test for lean and over-weight/obese individuals showed a negative significant association between visfatin expression in PBMCs and BMI both for men and women (P = 0.05 and P = 0.01, respectively) and these associations remained significant after separating subjects in three groups (lean, overweight, obese) for men and women (P = 0.02 and P = 0.05, respectively). Correlation analysis between levels of expression of visfatin and TNF-alpha showed a significant positive linear association (r(2) = 0.27, P < 0.0001).

CONCLUSION

These findings reveal a probable new role of visfatin in inflammation reflected in PBMCs, in the context of obesity.

Augmentation of Pulmonary Epithelial Cell IL-8 Expression and Permeability by Pre-B-cell Colony Enhancing Factor

Background

Previous studies in our lab have identified Pre-B-cell colony enhancing factor (PBEF) as a novel biomarker in acute lung injury (ALI). The molecular mechanism of PBEF involvement in the pathogenesis of ALI is still incompletely understood. This study examined the role of PBEF in regulating pulmonary alveolar epithelial cell IL-8 expression and permeability.

Methods

Human pulmonary alveolar epithelial cells (cell line and primary cells) were transfected with human PBEF cDNA or PBEF siRNA and then cultured in the presence or absence of TNFα. PBEF and IL-8 expression were analyzed by RT-PCR and Western blotting. In addition, changes in pulmonary alveolar epithelial and artery endothelial cell barrier regulation with altered PBEF expression was evaluated by an in vitro cell permeability assay.

Results

Our results demonstrated that, in human pulmonary alveolar epithelial cells, the overexpression of PBEF significantly augmented basal and TNFα-stimulated IL-8 secretion by more than 5 to 10-fold and increased cell permeability by >30%; the knockdown of PBEF expression with siRNA significantly inhibited basal and TNFα-stimulated IL-8 secretion by 70% and IL-8 mRNA levels by 74%. Further, the knockdown of PBEF expression also significantly attenuated TNFα-induced cell permeability by 43%. Similar result was observed in human pulmonary artery endothelial cells.

Conclusion

These results suggest that PBEF may play a vital role in basal and TNFα-mediated pulmonary inflammation and pulmonary epithelial barrier dysfunction via its regulation of other inflammatory cytokines such as IL-8, which could in part explain the role of PBEF in the susceptibility and pathogenesis of ALI. These results lend further support to the potential of PBEF to serve as a diagnostic and therapeutic target to ALI.

Caspases as therapeutic targets

The development of small molecules to modulate caspase activity offers a novel therapeutic strategy in the treatment of apoptosis-related and inflammatory diseases. Caspases are key mediators of apoptosis and inflammation; deregulation of their activation or expression can lead to the development of conditions such as neurodegenerative and autoinflammatory disorders. This review details the different caspase-associated disorders while focusing on caspase-1 inhibition as a potential therapeutic strategy. Problems facing the development of effective and safe caspase therapeutics will also be addressed.

Essential role of pre-B-cell colony enhancing factor in ventilator-induced lung injury

RATIONALE

We previously demonstrated pre-B-cell colony enhancing factor (PBEF) as a biomarker in sepsis and sepsis-induced acute lung injury (ALI) with genetic variants conferring ALI susceptibility.

OBJECTIVES

To explore mechanistic participation of PBEF in ALI and ventilator-induced lung injury (VILI).

METHODS

Two models of VILI were utilized to explore the role of PBEF using either recombinant PBEF or PBEF(+/-) mice.

MEASUREMENTS AND MAIN RESULTS

Initial in vitro studies demonstrated recombinant human PBEF (rhPBEF) as a direct rat neutrophil chemotactic factor with in vivo studies demonstrating marked increases in bronchoalveolar lavage (BAL) leukocytes (PMNs) after intratracheal injection in C57BL/6J mice. These changes were accompanied by increased BAL levels of PMN chemoattractants (KC and MIP-2) and modest increases in lung vascular and alveolar permeability. We next explored the potential synergism between rhPBEF challenge (intratracheal) and a model of limited VILI (4 h, 30 ml/kg tidal volume) and observed dramatic increases in BAL PMNs, BAL protein, and cytokine levels (IL-6, TNF-alpha, KC) compared with either challenge alone. Gene expression profiling identified induction of ALI- and VILI-associated gene modules (nuclear factor-kappaB, leukocyte extravasation, apoptosis, Toll receptor pathways). Heterozygous PBEF(+/-) mice were significantly protected (reduced BAL protein, BAL IL-6 levels, peak inspiratory pressures) when exposed to a model of severe VILI (4 h, 40 ml/kg tidal volume) and exhibited significantly reduced expression of VILI-associated gene expression modules. Finally, strategies to reduce PBEF availability (neutralizing antibody) resulted in significant protection from VILI.

CONCLUSIONS

These studies implicate PBEF as a key inflammatory mediator intimately involved in both the development and severity of ventilator-induced ALI.

Crucial role of visfatin/pre-B cell colony-enhancing factor in matrix degradation and prostaglandin E2 synthesis in chondrocytes: possible influence on osteoarthritis

OBJECTIVE

Prostaglandin E2 (PGE2) is one of the main catabolic factors involved in osteoarthritis (OA), and metalloproteinases (MMPs) are crucial for cartilage degradation. PGE2 synthesis under inflammatory conditions is catalyzed by cyclooxygenase 2 and microsomal PGE synthase 1 (mPGES-1), whereas NAD+-dependent 15-hydroxy-PG dehydrogenase (15-PGDH) is the key enzyme implicated in PGE2 catabolism. The present study was undertaken to investigate the contribution of visfatin, an adipose tissue-derived hormone, to the pathophysiology of OA, by examining its role in PGE2 synthesis and matrix degradation.

METHODS

The synthesis of visfatin by human chondrocytes from OA patients, with and without stimulation with interleukin-1beta (IL-1beta) and the role of visfatin in PGE2 synthesis were analyzed by real-time reverse transcriptase-polymerase chain reaction (RT-PCR) and immunoblotting. The effects of visfatin (1-10 microg/ml) on mPGES-1 and 15-PGDH synthesis, on the subsequent release of PGE2, and on MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, and PG synthesis by primary immature mouse articular chondrocytes were examined by quantitative RT-PCR, immunoblotting, and enzyme-linked immunosorbent assay. Finally, small interfering RNA (siRNA) was used to assess the influence of visfatin on IL-1beta-induced release of PGE2 in immature mouse articular chondrocytes.

RESULTS

Human OA chondrocytes produced visfatin, and visfatin synthesis was increased by IL-1beta treatment. Visfatin, like IL-1beta, triggered excessive release of PGE2, due to increased mPGES-1 synthesis and decreased 15-PGDH synthesis. Visfatin knockout with siRNA reduced IL-1beta-induced PGE2 overrelease. Visfatin triggered ADAMTS-4 and ADAMTS-5 expression and MMP-3 and MMP-13 synthesis and release, and reduced synthesis of high molecular weight PG by immature mouse articular chondrocytes.

CONCLUSION

The findings of this study indicate that visfatin has a catabolic function in cartilage and may have an important role in the pathophysiology of OA.

The secretory function of adipocytes in the physiology of white adipose tissue

White adipose tissue, previously regarded as a passive lipid storage site, is now viewed as a dynamic tissue. It has the capacity to actively communicate by sending and receiving different types of signals. An overview of these signals, the external modulators that affect adipose tissue and the secreted signaling molecules, the adipokines, is presented. The secretory function is highlighted in relation to energy metabolism, inflammation and the extracellular matrix and placed in the context of adipose tissue biology. We observe that the endocrine function of adipocytes receives much attention, while its paracrine and autocrine functions are underestimated. Also, we provide examples that species specificity should not be neglected. We conclude that adipose tissue primarily is an energy storage organ, well supported by its secretory function.

Adipokines: the missing link between insulin resistance and obesity

White adipose tissue was believed to be just an energy-storage organ, but it is now recognized to be an active participant in energy homoeostasis and physiological functions such as immunity and inflammation. Macrophages are components of adipose tissue and actively participate in its activities. Adipose tissue is known to express and secrete a variety of products known as 'adipokines', including leptin, adiponectin, resistin and visfatin, as well as cytokines and chemokines such as tumor necrosis factor-alpha, interleukin-6 and monocyte chemoattractant protein-1. The release of adipokines by either adipocytes or adipose tissue-infiltrated macrophages leads to a chronic subinflammatory state that could play a central role in the development of insulin resistance and type 2 diabetes, and the increased risk of cardiovascular disease associated with obesity.

Pharmacological inhibition of nicotinamide phosphoribosyltransferase/visfatin enzymatic activity identifies a new inflammatory pathway linked to NAD

Nicotinamide phosphoribosyltransferase (NAMPT), also known as visfatin, is the rate-limiting enzyme in the salvage pathway of NAD biosynthesis from nicotinamide. Since its expression is upregulated during inflammation, NAMPT represents a novel clinical biomarker in acute lung injury, rheumatoid arthritis, and Crohn's disease. However, its role in disease progression remains unknown. We report here that NAMPT is a key player in inflammatory arthritis. Increased expression of NAMPT was confirmed in mice with collagen-induced arthritis, both in serum and in the arthritic paw. Importantly, a specific competitive inhibitor of NAMPT effectively reduced arthritis severity with comparable activity to etanercept, and decreased pro-inflammatory cytokine secretion in affected joints. Moreover, NAMPT inhibition reduced intracellular NAD concentration in inflammatory cells and circulating TNFα levels during endotoxemia in mice. In vitro pharmacological inhibition of NAMPT reduced the intracellular concentration of NAD and pro-inflammatory cytokine secretion by inflammatory cells. Thus, NAMPT links NAD metabolism to inflammatory cytokine secretion by leukocytes, and its inhibition might therefore have therapeutic efficacy in immune-mediated inflammatory disorders.

Making genomics functional: deciphering the genetics of acute lung injury

Acute lung injury (ALI) is a common and frequently devastating illness characterized by acute hypoxemic respiratory failure, profound inflammation, and flooding of the alveoli. Despite recent advances in ALI care, the morbidity and mortality of ALI continues to be unacceptably high. ALI-inciting events (e.g., sepsis, trauma, aspiration, pneumonia) are quite common, yet only a fraction of patients develop the syndrome. This heterogeneity of patients presenting with ALI has sparked interest in identifying the role of genetic factors that contribute to ALI susceptibility and prognosis. Recent advances in high-throughput sequencing and expression technologies now provide the tools to perform large-scale genomic analyses in complex disorders such as ALI; gene expression profiling and pathway analysis provide further insight into previously described molecular pathways involved in the syndrome. In this article, we describe the use of genomewide association studies, ortholog in silico techniques, utility of consomic rat methods, and candidate gene approaches using expression profiling and pathway analyses. These methods have confirmed suspected ALI candidate genes (e.g., IL-6 and MIF), but more impressively have identified novel genes (e.g., GADD45alpha and PBEF) not previously suspected in ALI. The analysis of the molecular pathways (e.g., the cytoskeleton in vascular barrier regulation) has identified additional genes contributing to the development and severity of ALI (e.g., MLCK), thereby providing therapeutic targets in this devastating illness.

The novel adipocytokine visfatin exerts direct cardioprotective effects

Visfatin is an adipocytokine capable of mimicking the glucose-lowering effects of insulin and activating the pro-survival kinases phosphatidylinositol-3-OH kinase (PI3K)-protein kinase B (Akt) and mitogen-activated protein kinase kinase 1 and 2 (MEK1/2)-extracellular signal-regulated kinase 1 and 2 (Erk 1/2). Experimental studies have demonstrated that the activation of these kinases confers cardioprotection through the inhibition of the mitochondrial permeability transition pore (mPTP). Whether visfatin is capable of exerting direct cardioprotective effects through these mechanisms is unknown and is the subject of the current study. Anaesthetized C57BL/6 male mice were subjected to in situ 30 min. of regional myocardial ischaemia and 120 min. of reperfusion. The administration of an intravenous bolus of visfatin (5 × 10⁻⁶μmol) at the time of myocardial reperfusion reduced the myocardial infarct size from 46.1 ± 4.1% in control hearts to 27.3 ± 4.0% (n≥ 6/group, P < 0.05), an effect that was blocked by the PI3K inhibitor, wortmannin, and the MEK1/2 inhibitor, U0126 (48.8 ± 5.5% and 45.9 ± 8.4%, respectively, versus 27.3 ± 4.0% with visfatin; n≥ 6/group, P < 0.05). In murine ventricular cardiomyocytes subjected to 30 min. of hypoxia followed by 30 min. of reoxygenation, visfatin (100 ng/ml), administered at the time of reoxygenation, reduced the cell death from 65.2 ± 4.6% in control to 49.2 ± 3.7%(n > 200 cells/group, P < 0.05), an effect that was abrogated by wortmannin and U0126 (68.1 ± 5.2% and 59.7 ± 6.2%, respectively; n > 200 cells/group, P > 0.05). Finally, the treatment of murine ventricular cardiomyocytes with visfatin (100 ng/ml) delayed the opening of the mPTP induced by oxidative stress from 81.2 ± 4 sec. in control to 120 ± 7 sec. (n > 20 cells/group, P < 0.05) in a PI3K- and MEK1/2-dependent manner. We report that the adipocytokine, visfatin, is capable of reducing myocardial injury when administered at the time of myocardial reperfusion in both the in situ murine heart and the isolated murine cardiomyocytes. The mechanism appears to involve the PI3K and MEK1/2 pathways and the mPTP.

Acute lung injury and cell death: how many ways can cells die?

Apoptosis has been considered as an underlying mechanism in acute lung injury/acute respiratory distress syndrome and multiorgan dysfunction syndrome. Recently, several alternative pathways for cell death (such as caspase-independent cell death, oncosis, and autophagy) have been discovered. Evidence of these pathways in the pathogenesis of acute lung injury has also come into light. In this article, we briefly introduce cell death pathways and then focus on studies related to lung injury. The different types of cell death that occur and the underlying mechanisms utilized depend on both experimental and clinical conditions. Lipopolysaccharide-induced acute lung injury is associated with apoptosis via Fas/Fas ligand mechanisms. Hyperoxia and ischemia-reperfusion injury generate reactive oxidative species, which induce complex cell death patterns composed of apoptosis, oncosis, and necrosis. Prolonged overexpression of inflammatory mediators results in increased production and activation of proteases, especially cathepsins. Activation and resistance to death of neutrophils also plays an important role in promoting parenchymal cell death. Knowledge of the coexisting multiple cell death pathways and awareness of the pharmacological inhibitors targeting different proteases critical to cell death may lead to the development of novel therapies for acute lung injury.

High mobility group box chromosomal protein 1 in patients with renal diseases

BACKGROUND/AIM

The high mobility group box chromosomal protein 1 (HMGB1), a nuclear DNA-binding protein, has recently been recognized as a new proinflammatory cytokine. The purpose of this study was to examine the significance of HMGB1 in patients with renal diseases.

METHODS

HMGB1 concentrations in sera were measured by enzyme-linked immunosorbent assay, and antibodies against HMGB1 were examined by Western blotting in patients who underwent renal biopsies and in healthy controls. Immunohistochemistry for HMGB1 was also performed.

RESULTS

Serum HMGB1 was more likely to be positive in patients who underwent renal biopsies as compared with the controls. Patients with anti-neutrophil cytoplasmic antibody-related glomerulonephritis (ANCA-GN) and those with Henoch-Schonlein purpura nephritis showed a significantly higher tendency to be HMGB1 positive. The presence of anti-HMGB1 antibody was not associated with the presence of serum HMGB1. Immunohistochemistry revealed that HMGB1 was expressed in mononuclear cells in the interstitium or in the glomeruli of some patients with ANCA-GN or IgA nephropathy (IgAN). Subanalysis demonstrated that among patients with IgAN, those who had crescent formation showed a higher tendency to be HMGB1 positive than those who did not.

CONCLUSIONS

HMGB1 was expressed in the sera of patients with renal diseases who underwent renal biopsies, especially among those who had vasculitis including ANCA-GN, Henoch-Schonlein purpura nephritis, and IgAN with glomerular crescents.

Sirt1 protects the heart from aging and stress

The prevalence of heart diseases, such as coronary artery disease and congestive heart failure, increases with age. Optimal therapeutic interventions that antagonize aging may reduce the occurrence and mortality of adult heart diseases. We discuss here how molecular mechanisms mediating life span extension affect aging of the heart and its resistance to pathological insults. In particular, we review our recent findings obtained from transgenic mice with cardiac-specific overexpression of Sirt1, which demonstrated delayed aging and protection against oxidative stress in the heart. We propose that activation of known longevity mechanisms in the heart may represent a novel cardioprotection strategy against aging and certain types of cardiac stress, such as oxidative stress.

Interleukin-1beta mediates LPS-induced inhibition of apoptosis in retinoic acid-differentiated HL-60 cells

Promyelocytic HL-60 cells differentiated to a neutrophilic phenotype by incubation with all-trans retinoic acid become constitutively apoptotic. Exposure to either LPS or IL-1beta inhibited the apoptosis of differentiated HL-60 cells. LPS induced the expression of pro-IL-1beta message, upregulated the activity of the interleukin-1beta converting enzyme (caspase-1), and increased the release of IL-1beta into the culture medium. Prevention of IL-1beta translation with an anti-sense oligonucleotide, or prevention of IL-1beta cellular binding with a blocking antibody, accelerated rates of spontaneous apoptosis, and abrogated the inhibitory effects of LPS. However inhibition of caspase-1 activity further inhibited constitutive apoptosis of mature HL-60 cells. These studies provide further evidence of a complex regulatory pathway that modulates the expression of granulocyte apoptosis during inflammation, and point to a specific role for IL-1beta as an autocrine survival factor.

Chronic stretching of amniotic epithelial cells increases pre-B cell colony-enhancing factor (PBEF/visfatin) expression and protects them from apoptosis

In normal pregnancy, the fetal membranes become increasingly distended towards term and in multifetal gestations they become over-distended. Apoptosis of the amniotic epithelium increases with advancing gestation and may contribute to fetal membrane weakening and rupture. The effects of chronic static stretching for 36h have been investigated using primary amniotic epithelial cells. Pre-B cell colony-enhancing factor (PBEF) is a stretch-responsive cytokine and expression of its gene, intracellular and secreted protein were all significantly increased by 4h and its secretion sustained over 36h, contrasting with the rapid increase and decline in expression of IL-8. Increased expression of SIRT1 and decreased p53 paralleled the changes in PBEF, are known to be responsive to PBEF, and contribute to cell survival. Distension had no effects on proliferation or necrosis but protected the cells from apoptosis, knocking-down PBEF with antisense probes abrogated this protective effect. There was increased immunostaining of PBEF in the compact layer of the amnion in multifetal tissues and significantly fewer apoptotic amniotic epithelial cells. These results show that chronic stretching of the amniotic epithelial cells increases PBEF expression, which protects them from apoptosis.

Role of adiponectin and PBEF/visfatin as regulators of inflammation: involvement in obesity-associated diseases

Obesity and obesity-related disorders play an important role in clinical medicine. Adipose tissue, with its soluble mediators called adipocytokines, has emerged as a major endocrine organ. These adipocytokines comprise many mediators such as adiponectin, PBEF (pre-B-cell-enhancing factor)/visfatin, leptin, resistin, retinol-binding protein-4 and others. They play major roles in key aspects of metabolism, such as insulin resistance, fatty acid oxidation, inflammation and immunity. Adiponectin, a prototypic adipocytokine, is of importance in the regulation of insulin resistance, as circulating levels are decreased in obesity and diseases associated with insulin resistance. Besides its major role in regulation of insulin sensitivity, recent evidence suggests potent anti-inflammatory functions for adiponectin. These effects are paralleled by other immune-regulatory properties, such as regulation of endothelial cell function. The in vitro effects of adiponectin have been corroborated by several studies demonstrating potent in vivo anti-inflammatory effects. Many other adipocytokines, such as PBEF/visfatin, leptin, resistin or retinol binding protein-4, are involved in the physiology and pathophysiology of adipocytes, adipose tissue and related diseases. PBEF/visfatin, another recently characterized adipocytokine, has been linked to several inflammatory disease states beyond insulin resistance, such as acute lung injury or inflammatory bowel diseases. It has been recognized for many decades that obesity is accompanied by an increase in cancer and potentially some immune-mediated diseases. Understanding this new exciting world of adipocytokines will be of importance in the development of novel therapies for obesity-associated diseases.

Visfatin enhances ICAM-1 and VCAM-1 expression through ROS-dependent NF-kappaB activation in endothelial cells

Visfatin has recently been identified as a novel visceral adipokine which may be involved in obesity-related vascular disorders. However, it is not known whether visfatin directly contributes to endothelial dysfunction. Here, we investigated the effect of visfatin on vascular inflammation, a key step in a variety of vascular diseases. Visfatin induced leukocyte adhesion to endothelial cells and the aortic endothelium by induction of the cell adhesion molecules, ICAM-1 and VCAM-1. Promoter analysis revealed that visfatin-mediated induction of CAMs is mainly regulated by nuclear factor-kappaB (NF-kappaB). Visfatin stimulated IkappaBalpha phosphorylation, nuclear translocation of the p65 subunit of NF-kappaB, and NF-kappaB DNA binding activity in HMECs. Furthermore, visfatin increased ROS generation, and visfatin-induced CAMs expression and NF-kappaB activation were abrogated in the presence of the direct scavenger of ROS. Taken together, our results demonstrate that visfatin is a vascular inflammatory molecule that increases expression of the inflammatory CAMs, ICAM-1 and VCAM-1, through ROS-dependent NF-kappaB activation in endothelial cells.

Sepsis: rethinking the approach to clinical research

The clinical syndrome of sepsis encompasses a highly heterogeneous group of clinical disorders, varying with respect to the site, bacteriology, and even presence of infection and with the clinical syndrome evolving in the host. Clinical trials of strategies to modulate the host response that mediates sepsis were first initiated 25 years ago. A continuing record of disappointment has characterized subsequent work, and only a single new therapy has been licensed for clinical use. Yet, these commercial disappointments obscure a vibrant body of new knowledge that has clarified the biology of the innate immune response whose deranged expression is responsible for sepsis and that has provided important new insights into the failings of the traditional model of clinical research in sepsis. This review highlights advances in basic biology and underlines insights from clinical research that may point to new and more effective ways of translating an understanding of innate immunity into effective treatments for a leading cause of global morbidity and mortality.

Plasma visfatin levels are positively associated with circulating interleukin-6 in apparently healthy Korean women

Even though visfatin has been suggested as a proinflammatory adipokine, there are few studies of the relationship between plasma visfatin concentrations and proinflammatory markers in the nondiabetic population. We showed that plasma visfatin concentrations were positively associated with circulating interleukin-6 levels and diastolic blood pressure independent of obesity in nondiabetic healthy Korean women. These results suggest that circulating visfatin may be related with some proinflammatory condition even in a nondiabetic state.

Cord serum visfatin at term birth: maternal smoking unmasks the relation to foetal growth

OBJECTIVE

Visfatin is an adipocytokine involved in insulin action and oxidative stress. The regulation of circulating concentrations in the human foetus is unknown. We studied whether, at term birth, the serum concentrations of visfatin are related to foetal size, both in the absence and in the presence of maternal smoking during pregnancy.

DESIGN

A cross-sectional, hospital-based study.

PATIENTS

Seventy-eight singleton, healthy neonates [39 girls and 39 boys; gestational age (GA) 39.5 +/- 0.2 weeks; birth weight (BW) 3.3 +/- 0.04 kg].

METHODS

Cord serum visfatin, insulin and IGF-I measured by specific immunoassays.

RESULTS

In infants from nonsmoking mothers (N = 48), cord serum visfatin levels were unrelated to either BW or birth length (BL). In infants from smoking mothers (N = 30), however, serum visfatin was inversely associated with both BW (r = -0.57; P < 0.001) and BL (r = -0.60; P < 0.0001) and it was directly associated with the number of cigarettes smoked (P < 0.05) in heavy smokers. In a multiple regression analysis, cord serum visfatin accounted for 36% of BW and 32% of BL variance in infants from smoking mothers. Cord serum visfatin was unrelated to insulin or IGF-I in either subgroup.

CONCLUSION

At term birth, there is no readily detectable relation between circulating visfatin and indices of foetal size; however, maternal smoking unmasked a strikingly inverse relationship between cord serum visfatin and the foetal growth status, indicating that smoking can elicit a rise or a fall of cord serum visfatin, depending on whether the foetus is, respectively, of smaller or larger size.

Visfatin/Pre-B cell colony-enhancing factor in amniotic fluid in normal pregnancy, spontaneous labor at term, preterm labor and prelabor rupture of membranes: an association with subclinical intrauterine infection in preterm parturition

OBJECTIVE

Visfatin, a novel adipokine originally discovered as a pre-B-cell colony enhancing factor, is expressed by amniotic epithelium, cytotrophoblast, and decidua and is over-expressed when fetal membranes are exposed to mechanical stress and/or pro-inflammatory stimuli. Visfatin expression by fetal membranes is dramatically up-regulated after normal spontaneous labor. The aims of this study were to determine if visfatin is detectable in amniotic fluid (AF) and whether its concentration changes with gestational age, spontaneous labor, preterm prelabor rupture of membranes (preterm PROM) and in the presence of microbial invasion of the amniotic cavity (MIAC).

METHODS

In this cross-sectional study, visfatin concentration in AF was determined in patients in the following groups: 1) mid-trimester (n=75); 2) term not in labor (n=27); 3) term in spontaneous labor (n=51); 4) patients with preterm labor with intact membranes (PTL) without MIAC who delivered at term (n=35); 5) patients with PTL without MIAC who delivered preterm (n=52); 6) patients with PTL with MIAC (n=25); 7) women with preterm PROM without MIAC (n=26); and 8) women with preterm PROM with MIAC (n=26). Non-parametric statistics were used for analysis.

RESULTS

1) The median AF concentration of visfatin was significantly higher in patients at term than in mid-trimester; 2) Among women with PTL who delivered preterm, the median visfatin concentration was significantly higher in patients with MIAC than those without MIAC; 3) Similarly, patients with PTL and MIAC had a higher median AF visfatin concentration than those with PTL who delivered at term; 4) Among women with preterm PROM, the median AF visfatin concentration was significantly higher in patients with MIAC than those without MIAC.

CONCLUSIONS

1) Visfatin is a physiologic constituent of AF; 2) The concentration of AF visfatin increases with advancing gestational age; 3) AF visfatin concentration is elevated in patients with MIAC, regardless of the membrane status, suggesting that visfatin participates in the host response against infection.

Dynamic regulation of neutrophil survival through tyrosine phosphorylation or dephosphorylation of caspase-8

Efficient expression of innate immunity is critically dependent upon the capacity of the neutrophil to be activated rapidly in the face of an acute threat and to involute once that threat has been eliminated. Here we report a novel mechanism regulating neutrophil survival dynamically through the tyrosine phosphorylation or dephosphorylation of caspase-8. Caspase-8 is tyrosine-phosphorylated in freshly isolated neutrophils but spontaneously dephosphorylates in culture, in association with the progression of constitutive apoptosis. Phosphorylation of caspase-8 on Tyr-310 facilitates its interaction with the Src-homology domain 2 containing tyrosine phosphatase-1 (SHP-1) and enables SHP-1 to dephosphorylate caspase-8, permitting apoptosis to proceed. The non-receptor tyrosine kinase, Lyn, can phosphorylate caspase-8 on Tyr-397 and Tyr-465, rendering it resistant to activational cleavage and inhibiting apoptosis. Exposure to lipopolysaccharide reduces SHP-1 activity and binding to caspase-8, caspase-8 activity, and rates of spontaneous apoptosis. SHP-1 activity is reduced and Lyn increased in neutrophils from patients with sepsis, in association with profoundly delayed apoptosis; inhibition of Lyn can partially reverse this delay. Thus the phosphorylation and dephosphorylation of caspase-8, mediated by Lyn and SHP-1, respectively, represents a novel, dynamic post-translational mechanism for the regulation of neutrophil apoptosis whose dysregulation contributes to persistent neutrophil survival in sepsis.

Adipokines as emerging mediators of immune response and inflammation

The scientific interest in the biology of white adipose tissue (WAT) has increased since the discovery of leptin in 1994. The description of the product of the gene obese (ob) demonstrated the role of adipose tissue in the physiopathology of obesity-related diseases, and helped to increase the identification of numerous other adipokines, many of a pro-inflammatory nature. It has become increasingly evident that WAT-derived adipokines can be considered as a hub between obesity-related exogenous factors, such as nutrition and lifestyle, and the molecular events that lead to metabolic syndrome, inflammatory and/or autoimmune conditions, and rheumatic diseases. In this Review, we will discuss the progress in adipokine research, focusing particular attention to the roles of leptin, adiponectin, resistin, visfatin, and other recently identified adipokines in inflammatory, autoimmune and rheumatic diseases.

Pre-B cell colony-enhancing factor/visfatin, a new marker of inflammation in rheumatoid arthritis with proinflammatory and matrix-degrading activities

OBJECTIVE

To study possible mechanisms that mediate induction of the recently described adipocytokine pre-B cell colony-enhancing factor (PBEF) in joints of patients with rheumatoid arthritis (RA), and to analyze whether levels of PBEF correlate with disease severity and whether PBEF itself has the potential to act as a proinflammatory and destructive mediator in RA.

METHODS

RA synovial fibroblasts (RASFs) and monocytes were stimulated with Toll-like receptor (TLR) ligands, cytokines, and recombinant human PBEF or were transfected with PBEF expression constructs or with PBEF-specific small interfering RNA. Production of interleukin-6 (IL-6), IL-8, and tumor necrosis factor alpha (TNFalpha) was measured by enzyme-linked immunosorbent assay, and expression of matrix metalloproteinases (MMPs) was assessed by real-time polymerase chain reaction. PBEF expression in synovial tissue, synovial fluid, serum, and SFs was assessed by immunohistochemistry, in situ hybridization, Western blotting, and enzyme immunoassays.

RESULTS

In RASFs, PBEF was up-regulated by TLR ligands and cytokines that are characteristically present in the joints of patients with RA. In synovial tissue, RASFs were the major PBEF-expressing cells. A predominance of PBEF was found in the synovial lining layer and at sites of invasion into cartilage. Levels of PBEF in serum and synovial fluid correlated with the degree of inflammation and clinical disease activity. Moreover, PBEF itself activated the transcription factors NF-kB and activator protein 1 and induced IL-6, IL-8, MMP-1, and MMP-3 in RASFs as well as IL-6 and TNFalpha in monocytes. PBEF knockdown in RASFs significantly inhibited basal and TLR ligand-induced production of IL-6, IL-8, MMP-1, and MMP-3.

CONCLUSION

Our findings establish PBEF as a proinflammatory and destructive mediator of joint inflammation in RA and identify PBEF as a potential therapeutic target.

Nampt/PBEF/Visfatin regulates insulin secretion in beta cells as a systemic NAD biosynthetic enzyme

Intracellular nicotinamide phosphoribosyltransferase (iNampt) is an essential enzyme in the NAD biosynthetic pathway. An extracellular form of this protein (eNampt) has been reported to act as a cytokine named PBEF or an insulin-mimetic hormone named visfatin, but its physiological relevance remains controversial. Here we show that eNampt does not exert insulin-mimetic effects in vitro or in vivo but rather exhibits robust NAD biosynthetic activity. Haplodeficiency and chemical inhibition of Nampt cause defects in NAD biosynthesis and glucose-stimulated insulin secretion in pancreatic islets in vivo and in vitro. These defects are corrected by administration of nicotinamide mononucleotide (NMN), a product of the Nampt reaction. A high concentration of NMN is present in mouse plasma, and plasma eNampt and NMN levels are reduced in Nampt heterozygous females. Our results demonstrate that Nampt-mediated systemic NAD biosynthesis is critical for beta cell function, suggesting a vital framework for the regulation of glucose homeostasis.

Is PBEF/visfatin/Nampt an authentic adipokine relevant to the metabolic syndrome?

Adipokines are peptides secreted by adipose tissue that affect whole-body energy metabolism. Their dysregulated production in obesity has implicated them as important mediators in the pathogenesis of obesity-related risk factors for diabetes and cardiovascular disease. PBEF/visfatin/Nampt has recently been described as a novel adipokine with insulin mimetic properties. However, whether it is an authentic adipokine relevant to the metabolic syndrome remains a matter of some debate.

Visfatin is released from 3T3-L1 adipocytes via a non-classical pathway

Visfatin is a secretory protein which exerts insulin mimetic and proinflammatory effects, also functioning as an intracellular enzyme to produce NAD. Plasma visfatin levels and visfatin mRNA expression in adipose tissues are increased in obese subjects. Visfatin does not have a decent cleavable signal sequence, and the mechanism, that mediates release of visfatin from adipocytes, remains poorly understood. In this study, we demonstrate that visfatin is released abundantly into culture medium from 3T3-L1 adipocytes. Subcellular fractionation analysis showed that visfatin was localized in the cytosol, but not in nucleus, membrane, vesicles, or mitochondria fractions. Visfatin release was not reduced by Brefeldin A and Monensin, inhibitors of endoplasmic reticulum (ER)-Golgi-dependent secretion. In addition, visfatin was not released on microvesicles. These results suggest that visfatin should be released from 3T3-L1 adipocytes via an ER-Golgi or microvesicles independent pathway.

Perinatal circulating visfatin levels in intrauterine growth restriction

OBJECTIVE

The objective of this study was to investigate possible alterations in circulating levels of the adipocytokine visfatin in intrauterine growth-restricted and normal pregnancies, given that these groups differ considerably in fetal nutrition, body fat mass, and metabolic/endocrine mechanisms.

METHODS

Serum visfatin levels were prospectively measured by enzyme immunoassay in 40 mothers and their 40 singleton term fetuses and neonates on postnatal days 1 and 4. Twenty neonates had intrauterine growth restriction (birth weight < or = 3rd customized centile, adjusted for parameters that influence growth potential), and 20 were appropriate for gestational age.

RESULTS

Circulating maternal visfatin levels were significantly elevated in pregnancies with intrauterine growth restriction compared with control pregnancies with appropriate-for-gestational-age infants and negatively correlated with customized centiles in the group with intrauterine growth restriction. Postnatal day-1 and -4 visfatin levels were significantly higher in neonates with intrauterine growth restriction compared with neonates who were appropriate for gestational age. Postnatal-day-1 prefeeding insulin levels were significantly lower in neonates with intrauterine growth restriction.

CONCLUSIONS

Pathologic conditions in pregnancy that lead to intrauterine growth restriction could be responsible for elevated maternal visfatin levels. Higher visfatin levels in neonates with intrauterine growth restriction may serve as an early marker with prognostic value for later development of insulin resistance or type 2 diabetes, whereas lower insulin levels may indicate reduced beta-cell mass and/or impaired beta-cell function.

Nicotinamide adenine dinucleotide metabolism as an attractive target for drug discovery

Nicotinamide adenine dinucleotide (NAD(+)) has crucial roles in many cellular processes, both as a coenzyme for redox reactions and as a substrate to donate ADP-ribose units. Enzymes involved in NAD(+) metabolism are attractive targets for drug discovery against a variety of human diseases, including cancer, multiple sclerosis, neurodegeneration and Huntington's disease. A small-molecule inhibitor of nicotinamide phosphoribosyltransferase, an enzyme in the salvage pathway of NAD(+) biosynthesis, is presently in clinical trials against cancer. An analog of a kynurenine pathway intermediate is efficacious against multiple sclerosis in an animal model. Indoleamine 2,3-dioxygenase plays an important role in immune evasion by cancer cells and other disease processes. Inhibitors against kynurenine 3-hydroxylase can reduce the production of neurotoxic metabolites while increasing the production of neuroprotective compounds. This review summarizes the existing knowledge on NAD(+) metabolic enzymes, with emphasis on their relevance for drug discovery.

The emerging role of adipokines as mediators of inflammation and immune responses

Interest in the biology of white adipose tissue (WAT) has increased dramatically since the discovery of leptin in 1994. The identification of the product of the gene obese (ob) threw light on the role of adipose tissue in the physiopathology of obesity-related diseases, and spurred the identification of numerous other adipokines, many of a pro-inflammatory nature. It has become increasingly evident that WAT-derived cytokines mediate between obesity-related exogenous factors (nutrition and lifestyle) and the molecular events that lead to metabolic syndrome and inflammatory and/or autoimmune conditions. Here, we review recent adipokine research, with particular attention to the roles of leptin, adiponectin, resistin, visfatin, apelin, vaspin and hepcidin in such conditions.

The adipocyte as an active participant in energy balance and metabolism

Obesity is responsible for the mounting incidence of metabolic disease in adult and pediatric populations. Understanding of the pathogenesis and maintenance of the obese state has advanced rapidly over the past 10 years. Bodily energy reserves are managed actively by complex systems that regulate food intake, substrate partitioning, and energy expenditure. An underlying assumption that circulating factors released from storage organs were able to signal bodily energy reserves was confirmed with the discovery of the leptin system. This proof of concept has spurred on the discovery of a multitude of other adipocyte-generated factors. These circulating factors signal to the brain and other organs of metabolic importance, including adipose tissue, liver, muscle, and the immune system. Adipose-derived factors have numerous implications for the basic biology of obesity and provide prospective targets for the amelioration of obesity and its adverse metabolic consequences. In this review we detail the current understanding of leptin as a prototypical adipose tissue-derived hormone related to appetite and obesity. We also describe other important adipose-derived factors in relation to their metabolic effect.

Pre-B-cell colony-enhancing factor gene polymorphisms and risk of acute respiratory distress syndrome*

OBJECTIVE

Pre-B-cell colony-enhancing factor (PBEF) levels are elevated in bronchoalveolar lavage fluid and serum of patients with acute lung injury. There are several suspected functional polymorphisms of the corresponding PBEF gene. We hypothesized that variations in PBEF gene polymorphisms alter the risk of developing acute respiratory distress syndrome (ARDS).

DESIGN

Nested case-control study.

SETTING

Tertiary academic medical center.

PATIENTS

We studied 375 patients with ARDS and 787 at-risk controls genotyped for the PBEF T-1001G and C-1543T polymorphisms.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patients with the -1001G (variant) allele had significantly greater odds of developing ARDS than wild-type homozygotes (odds ratio, 1.35; 95% confidence interval, 1.02-1.78). Patients with the -1543T (variant) allele did not have significantly different odds of developing ARDS than wild-type homozygotes (odds ratio, 0.86; 95% confidence interval, 0.65-1.13). When analysis was stratified by ARDS risk factor, -1543T was associated with decreased odds of developing ARDS in septic shock patients (odds ratio, 0.66; 95% confidence interval, 0.45-0.97). Also, -1001G was associated with increased hazard of intensive care unit mortality, whereas -1543T was associated with decreased hazard of 28-day and 60-day ARDS mortality, as well as shorter duration of mechanical ventilation. Similar results were found in analyses of the related GC (-1001G:-1543C) and TT (-1001T:-1543T) haplotypes.

CONCLUSIONS

The PBEFT-1001G variant allele and related haplotype are associated with increased odds of developing ARDS and increased hazard of intensive care unit mortality among at-risk patients, whereas the C-1543T variant allele and related haplotype are associated with decreased odds of ARDS among patients with septic shock and better outcomes among patients with ARDS.

Pre-B-cell Colony-enhancing Factor (PBEF/Visfatin) Gene Expression is Modulated by NF-κB and AP-1 in Human Amniotic Epithelial Cells

A localized intrauterine inflammatory response is often associated with the initiation of normal human parturition, whereas infection causes a similar but more florid response initiating preterm labor. Pre-B-cell colony-enhancing factor (PBEF) is expressed in the human fetal membranes and is up-regulated by labor, severe infection and inflammatory stimuli. The aim of this study was to determine the involvement of the transcription factors NF-kappaB and AP-1 in the response of PBEF to an inflammatory stimulus and compare it with IL-8. The results showed that this treatment of amniotic epithelial-like cells (WISH) and primary amniotic epithelial cells increased expression of PBEF and IL-8, but IL-8 responded 100-fold more than PBEF. IL-1beta treatment together with a panel of NF-kappaB and AP-1 inhibitors demonstrated the involvement of these transcription factors in the up-regulation of PBEF. These data show that an inflammatory stimulus in the fetal membranes inducing NF-kappaB and AP-1 would up-regulate PBEF as well as IL-8.

Serum visfatin in relation to visceral fat, obesity, and type 2 diabetes mellitus in Asian Indians

To investigate the role of the novel adipokine visfatin in type 2 diabetes mellitus and obesity and to examine its association with visceral and subcutaneous fat in Asian Indians, who have increased susceptibility to type 2 diabetes mellitus and coronary artery disease, 150 subjects with type 2 diabetes mellitus (75 men, 75 women) and 150 age- and sex-matched subjects with normal glucose tolerance were recruited from the Chennai Urban Rural Epidemiology Study, a population-based study done in Chennai, southern India. Anthropometric and biochemical measurements were done by using standardized techniques. Fasting serum visfatin levels were measured by enzyme-linked immunosorbent assay. Visceral and subcutaneous fat were measured by computerized tomography in a subset of 130 individuals. Serum visfatin levels were significantly higher in diabetic subjects compared with nondiabetic subjects (11.4+/-5.9 vs 9.8+/-4.3 ng/mL, P=.008). However, this association was lost when adjusted for body mass index (odds ratio [OR], 1.048; 95% confidence interval [CI], 0.997-1.101; P=.067) or waist circumference (OR, 1.050; 95% CI, 0.999-1.104; P=.057). Serum visfatin showed a significant association with obesity even after adjusting for age, sex, and type 2 diabetes mellitus (OR, 1.060; 95% CI, 1.005-1.119; P=.033). Visceral fat, but not subcutaneous fat, was significantly associated with serum visfatin levels even after adjusting for age, sex, type 2 diabetes mellitus, and body mass index (P=.002). In Asian Indians, serum visfatin levels are associated with obesity and visceral fat but not with subcutaneous fat. Although visfatin levels are increased in type 2 diabetes mellitus, the association seems to be primarily through obesity.

Plasma visfatin levels in patients with newly diagnosed and untreated type 2 diabetes mellitus and impaired glucose tolerance

Visfatin, a new adipokine, facilitates adipogenesis and has insulin-mimetic properties. We aimed to investigate the plasma visfatin levels in patients with newly diagnosed and untreated type 2 diabetes mellitus (T2DM) and impaired glucose tolerance (IGT), who had no obesity or hypertension. Twenty-two patients with T2DM, 18 subjects with IGT and 40 healthy controls were enrolled. Visfatin levels were measured along with the BMI, blood pressure, lipids, glucose, insulin, adiponectin and hsCRP levels, and HOMA-IR indexes. Age, sex and BMI were similar in all groups. Visfatin levels were higher in the diabetic group than the controls (p=0.01). There was no significant difference in the visfatin levels between the T2DM and IGT groups as well as IGT group and healthy controls. Plasma visfatin concentrations did not differ between men and women. Visfatin levels did not correlate with BMI, blood pressure, plasma adiponectin, insulin, hsCRP, glucose and lipid levels or HOMA-IR indexes in the three groups. These results indicate that hyperglycemia causes an increase in plasma visfatin levels and, as in people with T2DM but not with IGT, this increase gets more prominent as the glucose intolerance worsens.

Visfatin promotes angiogenesis by activation of extracellular signal-regulated kinase 1/2

Adipose tissue is highly vascularized and requires the angiogenic properties for its mass growth. Visfatin has been recently characterized as a novel adipokine, which is preferentially produced by adipose tissue. In this study, we report that visfatin potently stimulates in vivo neovascularization in chick chorioallantoic membrane and mouse Matrigel plug. We also demonstrate that visfatin activates migration, invasion, and tube formation in human umbilical vein endothelial cells (HUVECs). Moreover, visfatin evokes activation of the extracellular signal-regulated kinase 1/2 (ERK1/2) in endothelial cells, which is closely linked to angiogenesis. Inhibition of ERK activation markedly decreases visfatin-induced tube formation of HUVECs and visfatin-stimulated endothelial cell sprouting from rat aortic rings. Taken together, these results demonstrate that visfatin promotes angiogenesis via activation of mitogen-activated protein kinase ERK-dependent pathway and suggest that visfatin may play important roles in various pathophysiological angiogenesis including adipose tissue angiogenesis.

Neutrophil apoptosis: a marker of disease severity in sepsis and sepsis-induced acute respiratory distress syndrome

Introduction

Apoptosis of neutrophils (polymorphonuclear neutrophils [PMNs]) may limit inflammatory injury in sepsis and acute respiratory distress syndrome (ARDS), but the relationship between the severity of sepsis and extent of PMN apoptosis and the effect of superimposed ARDS is unknown. The objective of this study was to correlate neutrophil apoptosis with the severity of sepsis and sepsis-induced ARDS.

Methods

A prospective cohort study was conducted in intensive care units of three tertiary hospitals in Porto Alegre, southern Brazil. Fifty-seven patients with sepsis (uncomplicated sepsis, septic shock, and sepsis-induced ARDS) and 64 controls were enrolled. Venous peripheral blood was collected from patients with sepsis within 24 hours of diagnosis. All surgical groups, including controls, had their blood drawn 24 hours after surgery. Control patients on mechanical ventilation had blood collected within 24 hours of initiation of mechanical ventilation. Healthy controls were blood donors. Neutrophils were isolated, and incubated ex vivo, and apoptosis was determined by light microscopy on cytospun preparations. The differences among groups were assessed by analysis of variance with Tukeys.

Results

In medical patients, the mean percentage of neutrophil apoptosis (± standard error of the mean [SEM]) was lower in sepsis-induced ARDS (28% ± 3.3%; n = 9) when compared with uncomplicated sepsis (57% ± 3.2%; n = 8; p < 0.001), mechanical ventilation without infection, sepsis, or ARDS (53% ± 3.0%; n = 11; p < 0.001) and healthy controls (69% ± 1.1%; n = 33; p < 0.001) but did not differ from septic shock (38% ± 3.7%; n = 12; p = 0.13). In surgical patients with sepsis, the percentage of neutrophil apoptosis was lower for all groups when compared with surgical controls (52% ± 3.6%; n = 11; p < 0.001).

Conclusion

In medical patients with sepsis, neutrophil apoptosis is inversely proportional to the severity of sepsis and thus may be a marker of the severity of sepsis in this population.

The regulation of nicotinamide adenine dinucleotide biosynthesis by Nampt/PBEF/visfatin in mammals

PURPOSE OF REVIEW

Nicotinamide adenine dinucleotide (NAD) is a classic coenzyme in cellular redox reactions. Recently, NAD biochemistry has also been implicated in a broader range of biological functions in mammals, but the regulation of NAD biosynthesis has been poorly investigated. Recent progress in the field of NAD biochemistry has fueled new interest in the NAD biosynthetic pathways from its precursors and their physiological roles in metabolism. This review summarizes the latest knowledge on the NAD biosynthetic pathways and focuses on one of the key NAD biosynthetic enzymes, namely, nicotinamide phosphoribosyltransferase.

RECENT FINDINGS

Mammals predominantly use nicotinamide rather than nicotinic acid as a precursor for NAD biosynthesis. Nicotinamide phosphoribosyltransferase (Nampt) is the rate-limiting enzyme that converts nicotinamide to nicotinamide mononucleotide in the NAD biosynthetic pathway from nicotinamide in mammals. The same protein has also been identified as a cytokine (pre-B-cell colony-enhancing factor or PBEF) or an insulin-mimetic hormone (visfatin).

SUMMARY

We propose that the presumed multiple effects of Nampt/PBEF/visfatin may be entirely explained by its role as an intra and extracellular NAD biosynthetic enzyme. We also propose a new model of Namp/PBEF/visfatin-mediated systemic NAD biosynthesis and its possible physiological significance. Our model provides an important insight into developing preventive/therapeutic interventions for metabolic complications, such as obesity and diabetes.