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

Inhibition of visfatin/NAMPT affects ovarian proliferation, apoptosis, and steroidogenesis in pre-pubertal mice ovary

Pubertal ovarian function might be dependent on the factors present in the pre-pubertal stages. Visfatin regulates ovarian steroidogenesis in adult. To date, no study has investigated the role of visfatin either in pre-pubertal or pubertal mice ovary. Thus, we investigated the role of visfatin in pre-pubertal mice ovary in relation to steroidogenesis and proliferation and apoptosis in vitro by inhibiting the endogenous visfatin by a specific inhibitor, FK866. Inhibition of visfatin increased the estrogen secretion and also up-regulated the expression of CYP11A1, 17βHSD and CYP19A1 in mice ovary. Furthermore, active caspase3 was up-regulated along with the down-regulation of BAX and BCL2 in the pre-pubertal ovary after visfatin inhibition. The expression of GCNA, PCNA, and BrdU labeling was also decreased by FK866 treatment. These results suggest that visfatin inhibits steroidogenesis, increases proliferation, and suppresses apoptosis in the pre-pubertal mice ovary. So, visfatin is a new regulator of ovary function in pre-pubertal mice.

Visfatin/eNampt induces endothelial dysfunction in vivo: a role for Toll-Like Receptor 4 and NLRP3 inflammasome

Visfatin/extracellular-nicotinamide-phosphoribosyltranferase-(eNampt) is a multifaceted adipokine enhanced in type-2-diabetes and obesity. Visfatin/eNampt cause in vitro endothelial dysfunction and vascular inflammation, although whether the same effects are achieved in vivo is unknown. Toll-like receptor-4 (TLR4), a main surface pattern recognition receptor of innate immune system is a potential target for visfatin/eNampt. We studied its capacity to generate vascular dysfunction in vivo, focusing on TLR4 role and downstream activation of nod-like-receptor-protein-3 (NLRP3)-inflammasome. 4 month-old C57BL/6 mice were exposed to 7 days infusion of visfatin/eNampt, alone or together with FK 866 (Nampt enzymatic inhibitor), CLI 095 (TLR4 blocker), MCC 950 (NLRP3-inflammasome inhibitor), or anakinra (interleukin(IL)-1-receptor antagonist). Endothelial dysfunction was tested in isolated microvessels. In human umbilical endothelial cells (HUVEC), proteins related to the NLRP3-inflammasome phosphorylated p-65, NLRP3, caspase-1, pro-IL-1β, and mature IL-1β were determined by Western blot, while the inflammasome related apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC-specks) was studied by immunofluorescence. Impaired endothelium-dependent relaxations were observed in isolated mesenteric microvessels from visfatin/eNampt-infused mice. This effect was attenuated by co-treatment with FK 866 or CLI 095, supporting a role for Nampt enzymatic activity and TLR4 activation. Moreover, cultured HUVEC exposed to visfatin/eNampt showed higher expression and activation of NLRP3-inflammasome. Again, this effect relied on Nampt enzymatic activity and TLR4 activation, and it was abrogated by the inflammasome assembly blockade with MCC 950. The endothelial dysfunction evoked by visfatin/eNampt infusion in vivo was also sensitive to both MCC 950 and anakinra treatments, suggesting that the NLRP3-inflammasome-driven tissular release of IL-1β is the final mediator of endothelial damage. We conclude that Visfatin/eNampt produces in vivo vascular dysfunction in mice by a Nampt-dependent TLR4-mediated pathway, involving NLRP3-inflammasome and paracrine IL-1β. Thus, those targets may become therapeutic strategies for attenuating the adipokine-mediated vascular dysfunction associated to obesity and/or type-2-diabetes.

Polydatin Attenuates Atherosclerosis in ApoE -∕- Mice through PBEF Mediated Reduction of Cholesterol Deposition

Cholesterol metabolism becomes imbalanced during the formation of macrophage-derived foam cells. Pre-B-cell colony-enhancing factor (PBEF) has recently been found to affect lipid deposition and inflammation in atherosclerosis. Here, we aimed to study the effects and molecular mechanism of Polydatin on atherosclerosis in ApoE-knockout (ApoE -∕- ) mice. Thirty ApoE -∕- mice were fed a high-fat diet (HFD) for 12 weeks, and then treated with Polydatin for another 12 weeks. Whole aortas and cryosections were stained with oil red O. Blood lipid, PBEF and cytokine levels were measured by ELISA. The mRNAs of cholesterol metabolism-related genes were determined by qRT-PCR and protein levels by Western blotting. Cell cholesterol content and viability were determined in macrophages and RAW 264.7 cells. PBEF siRNA was used to study the effect of Polydatin on cholesterol metabolism in macrophages incubated with ox-LDL. Polydatin lowered blood lipids and decreased atherosclerotic lesions in ApoE -∕- mice. The expression of cytokines and the mRNA of cholesterol metabolism-related genes were markedly regulated by Polydatin. Meanwhile, PBEF mRNA and protein were both greatly down-regulated by Polydatin. In vitro, Polydatin protected RAW 264.7 cells treated by ox-LDL and inhibited cholesterol uptake by macrophages. The PBEF siRNA result indicates that Polydatin can modulate cholesterol metabolism in macrophages, partly through down-regulation of PBEF. In conclusion, Polydatin relieves atherosclerosis injury in ApoE -∕- mice, mainly through down-regulation of PBEF and inhibition of PBEF-inducing cholesterol deposits in macrophages.

Visfatin is regulated by interleukin‑6 and affected by the PPAR‑γ pathway in BeWo cells

Visfatin, an adipocytokine and cytosolic enzyme with nicotinamide phosphoribosyltransferase (Nampt) activity, is involved in the pathogenesis of numerous metabolic disorders. In addition, the nuclear receptor peroxisome proliferator-activated receptor-γ (PPAR-γ) serves important roles in anti-inflammatory reactions and regulates glucose and lipid metabolism. The aim of the present study was to investigate the effect of interleukin-6 (IL-6) on the expression and secretion of visfatin in BeWo cells, and to determine whether the PPAR-γ pathway is involved in the regulation of visfatin by IL-6. Therefore, BeWo cells were stimulated with serial concentrations of IL-6 or pioglitazone, and the expression levels of visfatin and PPAR-γ were determined by reverse transcription-quantitative polymerase chain reaction and western blotting. The results of the present study demonstrated that IL-6 downregulated the mRNA levels of visfatin and PPAR-γ, which were strongly associated. Activation of PPAR-γ by pioglitazone resulted in significantly increased expression of visfatin, which abrogated the inhibitory effect of IL-6 on visfatin in BeWo cells. Furthermore, treatment using pioglitazone alone increased the expression and secretion of the visfatin protein, compared with the control or IL-6 alone group. In summary, the findings of the present study suggested that IL-6 inhibited the expression of visfatin and PPAR-γ at the transcriptional level; in addition, activation of PPAR-γ upregulated visfatin at the mRNA and protein expression levels. Therefore, the PPAR-γ signaling pathway may be involved in the regulation of visfatin by IL-6 in BeWo cells. These results may provide novel insight into the roles of visfatin in trophoblastic cells. Furthermore, thiazolidinedione pioglitazone, by upregulating visfatin expression, may promote the energy metabolism of trophoblastic cells, maintain the function of the placenta and improve the outcome of pregnancy.

Adipokines demonstrate the interacting influence of central obesity with other cardiometabolic risk factors of metabolic syndrome in Hong Kong Chinese adults

OBJECTIVE

Metabolic syndrome (MetS) or prediabetes is a complex disorder that is defined by a clustering of cardiometabolic risk factors, including obesity, hypertriglyceridemia, reduced high-density lipoprotein (HDL) cholesterol, hypertension, and insulin resistance. Among cardiometabolic risk factors, central obesity plays a key role in the development of MetS through alterations in the secretion of adipokines and interacts with other MetS risk factors to unfavorably influence overall cardiometabolic risk. Obesity has grasped epidemic proportions in Asia, which has the highest number of people with diabetes in the world. But, the importance of central obesity in the clustering of all four MetS risk factors or vice versa in predicting severity of MetS has not yet been investigated in Asian population. Therefore, the present study examined the influence of central obesity on circulating levels of adipokines through its interaction with the clustering of cardiometabolic risk factors of MetS including hyperglycemia, hypertriglyceridemia, dyslipidemia and hypertension in Hong Kong Chinese adults.

SUBJECTS

Blood samples from 83 Hong Kong Chinese adults, who were previously screened for MetS according to the guideline of the United States National Cholesterol Education Program Expert Panel Adult Treatment Panel III criteria were selected. Insulin and adipokines, including visfatin, chemerin, plasminogen activator inhibitor-1 (PAI-1), resistin, C-C motif chemokine ligand 2 (CCL-2), interleukin-6 (IL-6), interleukin-8 (IL-8), interleukin-10 (IL-10), tumour necrosis factor-α (TNF-α), leptin and adiponectin were assessed.

RESULTS

The interacting effect of central obesity with all of the other four MetS risk factors increased the proinflammatory status of adipokines (TNF-α, leptin) and decreased the anti-inflammatory status of adipokine (adiponectin).

CONCLUSION

Our results indicate that the inflammatory status of MetS may be more severe in the presence of central obesity. Adipokines, as biomarkers for pathophysiological changes, may help to improve early patient identification and to predict MetS-associated morbidity and mortality.

The role of visfatin (PBEF/Nampt) in pregnancy complications

Visfatin (PBEF/Nampt) is an adipocytokine that exerts pleiotropic effects within the human body, particularly affecting its metabolism and immunity. Visfatin was originally identified as being secreted by peripheral blood lymphocytes acting as a pre-B-cell colony-enhancing factor (PBEF). However, it was subsequently reported to be expressed in almost every tissue of the human body, with visceral fat deposits being the main source of visfatin. In addition to its secreted form, visfatin may also be found intracellularly where it functions as a nicotinamide phosphoribosyltransferase (Nampt). Visfatin maternal plasma concentrations increase during pregnancy, suggesting its important role in this complicated process. Alterations in visfatin level also take place in patients during pregnancy complications. This review focuses on the ones that most commonly occur in connection with visfatin: preterm labor, pre-eclampsia and gestational diabetes mellitus. The review aims to provide a better understanding of the role of visfatin during pregnancy and the causes of its alteration in maternal plasma, highlighting the potential use of visfatin as a diagnostic marker of pregnancy complications in the future.

Serum from calorie-restricted animals delays senescence and extends the lifespan of normal human fibroblasts in vitro

The cumulative effects of cellular senescence and cell loss over time in various tissues and organs are considered major contributing factors to the ageing process. In various organisms, caloric restriction (CR) slows ageing and increases lifespan, at least in part, by activating nicotinamide adenine dinucleotide (NAD⁺)-dependent protein deacetylases of the sirtuin family. Here, we use an in vitro model of CR to study the effects of this dietary regime on replicative senescence, cellular lifespan and modulation of the SIRT1 signaling pathway in normal human diploid fibroblasts. We found that serum from calorie-restricted animals was able to delay senescence and significantly increase replicative lifespan in these cells, when compared to serum from ad libitum fed animals. These effects correlated with CR-mediated increases in SIRT1 and decreases in p53 expression levels. In addition, we show that manipulation of SIRT1 levels by either over-expression or siRNA-mediated knockdown resulted in delayed and accelerated cellular senescence, respectively. Our results demonstrate that CR can delay senescence and increase replicative lifespan of normal human diploid fibroblasts in vitro and suggest that SIRT1 plays an important role in these processes. (185 words).

Potential Peripartum Markers of Infectious-Inflammatory Complications in Spontaneous Preterm Birth

Spontaneous preterm birth significantly contributes to the overall neonatal morbidity associated with preterm deliveries. Nearly 50% of cases are associated with microbial invasion of the amniotic cavity followed by an inflammatory response. Robust diagnostic tools for neonates jeopardized by infection and inflammation may thus decrease the overall neonatal morbidity substantially. Amniotic fluid retrieved during labor retains fetal and pregnancy-related protein fingerprint and its sampling does not place any unwanted stress on women. Using exploratory and targeted methods we analyzed proteomes of amniotic fluid sampled at the end of spontaneous preterm labor prior to delivery from women with and without infection and inflammation. Exploratory data indicated several amniotic fluid proteins to be associated with infectious-inflammatory complications in spontaneous preterm birth. LC-SRM analysis subsequently verified statistically significant changes in lipocalin-1 (P = 0.047 and AUC = 0.67, P = 0.046), glycodelin (P = 0.013 and AUC = 0.73, P = 0.013), and nicotinamide phosphoribosyltransferase (P = 0.018 and AUC = 0.71, P = 0.01).

Nicotinamide phosphoribosyltransferase in malignancy: a review

Nicotinamide phosphoribosyltransferase (Nampt) catalyzes the rate-limiting step of nicotinamide adenine dinucleotide (NAD) synthesis. Both intracellular and extracellular Nampt (iNampt and eNampt) levels are increased in several human malignancies and some studies demonstrate increased iNampt in more aggressive/invasive tumors and in tumor metastases. Several different molecular targets have been identified that promote carcinogenesis following iNampt overexpression, including SirT1, CtBP, and PARP-1. Additionally, eNampt is elevated in several human cancers and is often associated with a higher tumor stage and worse prognoses. Here we review the roles of Nampt in malignancy, some of the known mechanisms by which it promotes carcinogenesis, and discuss the possibility of employing Nampt inhibitors in cancer treatment.

Visfatin as a novel mediator released by inflamed human endothelial cells

Background

Visfatin is a multifaceted adipokine whose circulating levels are enhanced in different metabolic diseases. Extracellular visfatin can exert various deleterious effects on vascular cells, including inflammation and proliferation. Limited evidence exists, however, on the capacity of human vascular cells to synthesize and release visfatin by themselves, under basal or pro-inflammatory conditions.

Methods and Results

Intracellular visfatin was detected by Western blot in non-stimulated human umbilical vein endothelial cells (HUVEC). However, exposing HUVEC for 18 h to a series of pro-inflammatory stimulus, such as interleukin (IL)-1β (1 to 10 ng/mL), tumor necrosis factor-α (1 to 10 ng/mL) or angiotensin II (10 pmol/L to 1 μmol/L) markedly enhanced intracellular visfatin content. Using IL-1β (10 ng/mL; 18 h), it was determined that the increase in intracellular visfatin, which was paralleled by enhanced visfatin mRNA levels, relied on a signalling mechanism involving both nuclear factor-κB and poly (ADP ribose) polymerase-1 activation. Moreover, IL-1β modified the sub-cellular localization of visfatin; while in non-stimulated HUVEC immunoreactive visfatin predominantly showed an intra-nuclear granular pattern, in IL-1β-inflamed cells an extra-nuclear filamentous staining, co-localising with F-actin fibers and suggesting a secretory pattern, was mainly found. Indeed, IL-1β promoted visfatin secretion, as determined by both ELISA and immunocytochemistry.

Conclusions

Human endothelial cells synthesize and release visfatin, particularly in response to inflammation. We suggest that the inflamed endothelium can be a source of visfatin, which arises as a local inflammatory mediator and a potential therapeutic target to interfere with vascular inflammation.

Stimulation of MMP-1 and CCL2 by NAMPT in PDL cells

Periodontitis is an inflammatory disease caused by pathogenic microorganisms and characterized by the destruction of the periodontium. Obese individuals have an increased risk of periodontitis, and elevated circulating levels of adipokines, such as nicotinamide phosphoribosyltransferase (NAMPT), may be a pathomechanistic link between both diseases. The aim of this in vitro study was to examine the regulation of periodontal ligament (PDL) cells by NAMPT and its production under inflammatory and infectious conditions. NAMPT caused a significant upregulation of 9 genes and downregulation of 3 genes, as analyzed by microarray analysis. Eight of these genes could be confirmed by real-time PCR: NAMPT induced a significant upregulation of EGR1, MMP-1, SYT7, ITPKA, CCL2, NTM, IGF2BP3, and NRP1. NAMPT also increased significantly the MMP-1 and CCL2 protein synthesis. NAMPT was significantly induced by interleukin-1β and the periodontal microorganism P. gingivalis. NAMPT may contribute to periodontitis through upregulation of MMP-1 and CCL2 in PDL cells. Increased NAMPT levels, as found in obesity, may therefore represent a mechanism whereby obesity could confer an increased risk of periodontitis. Furthermore, microbial and inflammatory signals may enhance the NAMPT synthesis in PDL cells and thereby contribute to the increased gingival and serum levels of this adipokine, as found in periodontitis.

Proteomic and systems biology analysis of the monocyte response to Coxiella burnetii infection

Coxiella burnetii is an obligate intracellular bacterial pathogen and the causative agent of Q fever. Chronic Q fever can produce debilitating fatigue and C. burnetii is considered a significant bioterror threat. C. burnetii occupies the monocyte phagolysosome and although prior work has explained features of the host-pathogen interaction, many aspects are still poorly understood. We have conducted a proteomic investigation of human Monomac I cells infected with the Nine Mile Phase II strain of C. burnetii and used the results as a framework for a systems biology model of the host response. Our principal methodology was multiplex differential 2D gel electrophoresis using ZDyes, a new generation of covalently linked fluorescent protein detection dyes under development at Montana State University. The 2D gel analysis facilitated the detection of changes in posttranslational modifications on intact proteins in response to infection. The systems model created from our data a framework for the design of experiments to seek a deeper understanding of the host-pathogen interactions.

Curcumin down-regulates visfatin expression and inhibits breast cancer cell invasion

Obesity is frequently associated with breast cancer. Such associations are possibly mediated by adipokines. Visfatin, an adipokine, has recently been shown to be related to the development and progression of breast cancer. Therefore, the down-regulation of visfatin may be a novel strategy for breast cancer therapy. Curcumin has anticancer activities by modulating multiple signaling pathways and genes. The purpose of this study was to investigate whether visfatin gene expression is affected by curcumin in human breast cancer cells and to characterize the functional role of visfatin in breast cancer. We found that the mRNA and protein levels of visfatin were down-regulated by curcumin in MDA-MB-231, MDA-MB-468, and MCF-7 breast cancer cells, along with decreased activity of constitutive nuclear factor (NF)-κB. We confirmed the repressive effect of curcumin on visfatin transcription by performing a visfatin promoter-driven reporter assay and identified two putative NF-κB-binding sites on visfatin promoter that are important for this effect. EMSA and chromatin immunoprecipitation analysis indicated the binding of p65 to the visfatin promoter, which was effectively blocked by curcumin. Enforced expression of p65 protein increased visfatin promoter activity, whereas blocking NF-κB signaling suppressed visfatin gene expression. Visfatin could enhance the invasion of MDA-MB-231 cells and also attenuate curcumin-induced inhibition of cell invasion; on the other hand, visfatin knockdown by small interfering RNA led to the reduction of cell invasion. Our data demonstrate, for the first time, that curcumin down-regulates visfatin gene expression in human breast cancer cells by a mechanism that is, at least in part, NF-κB dependent and suggest that visfatin may contribute to breast cancer cell invasion and link obesity to breast cancer development and progression.

Visfatin regulates the terminal processes of human labour and delivery via activation of the nuclear factor-κB pathway

The inflammatory process plays a pivotal role during the pathogenesis of human labour, both at term and preterm. Visfatin levels increase during normal human pregnancy and in infection associated preterm labour. The effects of visfatin in the processes of human labour and delivery, however, are not known. The aim of this study was to determine the effect of visfatin on the expression and release of pro-labour mediators in human placenta. Samples were obtained from normal pregnancies at the time of Caesarean section. Human placenta was incubated in the absence (basal control) or presence of a 50 ng/ml visfatin for 24 h (n=6). Inflammatory gene expression was analysed by quantitative RT-PCR (qRT-PCR), the medium was collected and cytokine, prostaglandin and 8-isoprostane (marker of oxidative stress) release was quantified by ELISA, and secretory protease activity by zymography. Visfatin significantly increased IL-6 and IL-8 gene expression and secretion, COX-2 expression and resultant prostaglandin (PG) E(2) and PGF(2α) release, and 8-isoprostane release. There was, however, no effect of visfatin on pro MMP-9 enzyme activity. These actions of visfatin were elicited via the nuclear factor-κB (NF-κB) pathway as visfatin induced the degradation of IκB-α (inhibitor of NF-κB) whilst increasing NF-κB p65 DNA binding activity. Further to this, visfatin-induced pro-labour responses were abrogated by treatment with the NF-κB inhibitor BAY 11-7082. Collectively, these data indicate that visfatin activates pro-inflammatory cytokine release and phospholipid metabolism in human placenta via activation of the NF-κB pathway. Thus, visfatin represents a novel cytokine linked to the events of human labour initiation.

Mechanistic insights into the link between visfatin gene C-1535T polymorphism and coronary artery disease: an in vitro study

Visfatin, a pro-inflammatory cytokine predominantly released from leucocytes, is correlated with coronary artery disease (CAD). We have previously reported that the -1535C>T polymorphism (rs1330082), which located on the promoter region of visfatin, was associated with decreased risk of CAD. Here, we investigated the underlying mechanism by which this polymorphism affects the genetic susceptibility to CAD. The difference of the promoter activities between -1535T variant and -1535C allele was tested by luciferase reporter gene assay. The difference of transcription factor binding activities between T and C allele was evaluated by electrophoretic mobility shift assay. In reporter gene assay, we showed that the T variant had a significantly reduced transcriptional activity compared with the C allele. The T-variant significantly attenuated the promoter binding affinity to nuclear transcription factors and this effect became much obvious after treatment with TNF-α. Moreover, competition experiment revealed that the retarded complex formed by T-1535- or C-1535-probe binding to nuclear extracts was nearly completely inhibited by unlabeled activator protein-1 (AP-1) specific probe, indicating that AP-1 might be the target nuclear effector. Taken together, our data provided potential mechanistic link between the visfatin -1535C>T polymorphism and reduced CAD risk.

Visfatin is regulated by rosiglitazone in type 2 diabetes mellitus and influenced by NFκB and JNK in human abdominal subcutaneous adipocytes

Visfatin has been proposed as an insulin-mimicking adipocytokine, predominantly secreted from adipose tissue and correlated with obesity. However, recent studies suggest visfatin may act as a proinflammatory cytokine. Our studies sought to determine the significance of this adipocytokine and its potential role in the pathogenesis of T2DM. Firstly, we examined the effects of diabetic status on circulating visfatin levels, and several other adipocytokines, demonstrating that diabetic status increased visfatin*, TNF-α*** and IL-6*** compared with non-diabetic subjects (*p<0.05, **p<0.01, ***p<0.001, respectively). We then assessed the effects of an insulin sensitizer, rosiglitazone (RSG), in treatment naïve T2DM subjects, on circulating visfatin levels. Our findings showed that visfatin was reduced post-RSG treatment [vs. pre-treatment (*p<0.05)] accompanied by a reduction in HOMA-IR**, thus implicating a role for insulin in visfatin regulation. Further studies addressed the intracellular mechanisms by which visfatin may be regulated, and may exert pro-inflammatory effects, in human abdominal subcutaneous (Abd Sc) adipocytes. Following insulin (Ins) and RSG treatment, our in vitro findings highlighted that insulin (100 nM), alone, upregulated visfatin protein expression whereas, in combination with RSG (10 nM), it reduced visfatin*, IKKβ** and p-JNK1/2*. Furthermore, inhibition of JNK protein exacted a significant reduction in visfatin expression (**p<0.01), whilst NF-κB blockade increased visfatin (*p<0.05), thus identifying JNK as the more influential factor in visfatin regulation. Additional in vitro analysis on adipokines regulating visfatin showed that only Abd Sc adipocytes treated with recombinant human (rh)IL-6 increased visfatin protein (*p<0.05), whilst rh visfatin treatment, itself, had no influence on TNF-α, IL-6 or resistin secretion from Sc adipocytes. These data highlight visfatin's regulation by insulin and RSG, potentially acting through NF-κB and JNK mechanisms, with only rh IL-6 modestly affecting visfatin regulation. Taken together, these findings suggest that visfatin may represent a pro-inflammatory cytokine that is influenced by insulin/insulin sensitivity via the NF-κB and JNK pathways.

Nicotinamide Phosphoribosyltransferase in Human Diseases

Nicotinamide phosphoribosyltransferase (NAMPT) was first reported as a pre-B-cell colony enhancing factor in 1994 with little notice, but it has received increasing attention in recent years due to accumulating evidence indicating that NAMPT is a pleiotropic protein such as a growth factor, a cytokine, an enzyme and a visfatin. Now, NAMPT has been accepted as an official name of this protein. Because of NAMPT's multiple functions in a variety of physiological processes, their dysregulations have been implicated in the pathogenesis of a number of human diseases or conditions such as acute lung injury, aging, atherosclerosis, cancer, diabetes, rheumatoid arthritis and sepsis. This review will cover the current understanding of NAMPT's structure and functions with an emphasis on recent progress of nicotinamide phosphoribosyltransferase's pathological roles in various human diseases and conditions. Future directions on exploring its Terra incognita will be offered in the end.

Liver X Receptor (LXR) activation negatively regulates visfatin expression in macrophages

Adipose tissue macrophages (ATM) are the major source of visfatin, a visceral fat adipokine upregulated during obesity. Also known to play a role in B cell differentiation (pre-B cell colony-enhancing factor (PBEF)) and NAD biosynthesis (nicotinamide phosphoribosyl transferase (NAMPT)), visfatin has been suggested to play a role in inflammation. Liver X Receptor (LXR) and Peroxisome Proliferator-Activated Receptor (PPAR)γ are nuclear receptors expressed in macrophages controlling the inflammatory response. Recently, we reported visfatin as a PPARγ target gene in human macrophages. In this study, we examined whether LXR regulates macrophage visfatin expression. Synthetic LXR ligands decreased visfatin gene expression in a LXR-dependent manner in human and murine macrophages. The decrease of visfatin mRNA was paralleled by a decrease of protein secretion. Consequently, a modest and transient decrease of NAD(+) concentration was observed. Interestingly, LXR activation decreased the PPARγ-induced visfatin gene and protein secretion in human macrophages. Our results identify visfatin as a gene oppositely regulated by the LXR and PPARγ pathways in human macrophages.

Circulating levels of visfatin, resistin and pro-inflammatory cytokine interleukin-8 in acute pancreatitis

BACKGROUND

Resistin and visfatin, hormones produced by adipose tissue, have pro-inflammatory potential; however, their role in acute pancreatitis (AP) has been investigated only rarely.

METHODS

The study group comprised 32 patients with alcoholic AP and 30 controls. In all cases AP was classified as C according to Balthazar's CT score and as severe according to Ranson's criteria. The serum level of visfatin, resistin, and interleukin(IL)-8 immunoassays were measured by ELISA on admission and on the third and fifth day of hospitalization.

RESULTS

On the admission day serum resistin and IL-8 concentrations in AP patients were significantly higher than in controls and they further increased on the third and fifth day of hospitalization. On the admission day serum visfatin levels in AP patients were significantly higher than in controls and further increased on the third day of hospitalization. On the fifth day the levels decreased; however, they were still higher than on admission. The correlation between visfatin and resistin as well as between C-reactive protein and visfatin, resistin and IL-8 levels has been found.

CONCLUSION

In the course of AP, visfatin and resistin levels increase in parallel with C-reactive protein. We speculate that those parameters may provide an additional tool for the prognosis and monitoring of AP. and IAP.

Visfatin is induced by peroxisome proliferator-activated receptor gamma in human macrophages

Obesity is a low-grade chronic inflammatory disease associated with an increased number of macrophages (adipose tissue macrophages) in adipose tissue. Within the adipose tissue, adipose tissue macrophages are the major source of visfatin/pre-B-cell colony-enhancing factor/nicotinamide phosphoribosyl transferase. The nuclear receptor peroxisome proliferator-activated receptor gamma (PPARgamma) exerts anti-inflammatory effects in macrophages by inhibiting cytokine production and enhancing alternative differentiation. In this study, we investigated whether PPARgamma modulates visfatin expression in murine (bone marrow-derived macrophage) and human (primary human resting macrophage, classical macrophage, alternative macrophage or adipose tissue macrophage) macrophage models and pre-adipocyte-derived adipocytes. We show that synthetic PPARgamma ligands increase visfatin gene expression in a PPARgamma-dependent manner in primary human resting macrophages and in adipose tissue macrophages, but not in adipocytes. The threefold increase of visfatin mRNA was paralleled by an increase of protein expression (30%) and secretion (30%). Electrophoretic mobility shift assay experiments and transient transfection assays indicated that PPARgamma induces visfatin promoter activity in human macrophages by binding to a DR1-PPARgamma response element. Finally, we show that PPARgamma ligands increase NAD(+) production in primary human macrophages and that this regulation is dampened in the presence of visfatin small interfering RNA or by the visfatin-specific inhibitor FK866. Taken together, our results suggest that PPARgamma regulates the expression of visfatin in macrophages, leading to increased levels of NAD(+).

SIRT1 markedly extends replicative lifespan if the NAD+ salvage pathway is enhanced

Sir2 mediates lifespan extension in lower eukaryotes but whether its mammalian homolog, sirtuin 1, silent mating type information regulation 2 homolog (SIRT1), is a longevity protein is controversial. We stably introduced the SIRT1 gene into human vascular smooth muscle cells (SMCs) and observed minimal extension of replicative lifespan. However, SIRT1 activity was found to be exquisitely dependent on nicotinamide phosphoribosyltransferase (Nampt) activity. Moreover, overexpression of Nampt converted SIRT1-overexpressing SMCs to senescence-resistant cells together with heightened SIRT1 activity, suppressed p21, and strikingly lengthened replicative lifespan. Thus, SIRT1 can markedly postpone SMC senescence, but this requires overcoming an otherwise vulnerable nicotinamide adenine dinucleotide salvage reaction in aging SMCs.

Maternal plasma visfatin in preterm labor

OBJECTIVE

Visfatin, a novel adipokine with diabetogenic and immunoregulatory properties, has been implicated in the pathophysiology of insulin resistance, as well as in various acute and chronic inflammatory disorders. We have previously reported that amniotic fluid concentrations of visfatin are higher in patients with preterm labor (PTL) and intra-amniotic infection than in patients with PTL without infection. The aim of this study was to determine whether spontaneous PTL with intact membranes and intra-amniotic infection/inflammation (IAI) is associated with changes in maternal plasma circulating visfatin concentrations.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) normal pregnant women (n = 123); (2) patients with an episode of PTL and intact membranes without IAI who delivered at term (n = 57); (3) PTL without IAI who delivered preterm (n = 47); and (4) PTL with IAI who delivered preterm (n = 57). Plasma visfatin concentrations were determined by ELISA. Non-parametric statistics were used for analysis.

RESULTS

(1) PTL with IAI leading to preterm delivery was associated with a higher median maternal plasma concentration of visfatin than normal pregnancy; (2) among patients with PTL, those with IAI had the highest median maternal concentration of visfatin; (3) the changes in maternal plasma visfatin remained significant after adjusting for maternal age, body mass index, gestational age at sampling, and birth weight.

CONCLUSION

(1) PTL with IAI is characterized by high maternal circulating visfatin concentrations; (2) these findings suggest that visfatin plays a role in the regulation of the metabolic adaptations to insults resulting in PTL in the context of IAI.

Necrotic cell death in human amniotic cells infected by Listeria monocytogenes

Listeria monocytogenes can cause a placental-foetal infection that results in spontaneous abortion, premature labour, stillbirth, or neonatal sepsis and meningitis. Bacteria cross the maternofoetal barrier at the villous syncytiotrophoblast level and subsequently spread from the placenta to the fetus. L. monocytogenes is able to induce different kinds of death in a variety of cells. Murine hepatocytes, murine T and human B lymphocytes, and murine dendritic cells die by apoptosis, whereas bacterial infection of murine and human macrophages leads mainly to necrotic cell death. As we previously described the efficient infection and growth of L. monocytogenes in a human amniotic cell line, we investigated the fate of these cells in order to analyse the mode of cell death. Our results provide biochemical and morphological evidence of necrotic death induced by L. monocytogenes infection.

NAMPT is essential for the G-CSF-induced myeloid differentiation via a NAD(+)-sirtuin-1-dependent pathway

We identified nicotinamide phosphoribosyltransferase (NAMPT), also known as pre-B cell colony enhancing factor (PBEF), as an essential enzyme mediating granulocyte colony-stimulating factor (G-CSF)-triggered granulopoiesis in healthy individuals and in individuals with severe congenital neutropenia. Intracellular NAMPT and NAD(+) amounts in myeloid cells, as well as plasma NAMPT and NAD(+) levels, were increased by G-CSF treatment of both healthy volunteers and individuals with congenital neutropenia. NAMPT administered both extracellularly and intracellularly induced granulocytic differentiation of CD34(+) hematopoietic progenitor cells and of the promyelocytic leukemia cell line HL-60. Treatment of healthy individuals with high doses of vitamin B3 (nicotinamide), a substrate of NAMPT, induced neutrophilic granulocyte differentiation. The molecular events triggered by NAMPT include NAD(+)-dependent sirtuin-1 activation, subsequent induction of CCAAT/enhancer binding protein-alpha and CCAAT/enhancer binding protein-beta, and, ultimately, upregulation of G-CSF synthesis and G-CSF receptor expression. G-CSF, in turn, further increases NAMPT levels. These results reveal a decisive role of the NAD(+) metabolic pathway in G-CSF-triggered myelopoiesis.

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.

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.

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.