Visfatin as a therapeutic target for rheumatoid arthritis

The interplay between extracellular NAMPT and inflammatory cytokines in preeclampsia

Preeclampsia (PE) is the major cause of maternal-fetal mortality and morbidity. Its pathophysiology is not elucidated, but there is evidence for the role of visfatin/nicotinamide phosphoribosyl transferase (NAMPT), mainly due to its relation to endothelial dysfunction, a hallmark of PE. However, there is heterogeneous data regarding visfatin/NAMPT in healthy pregnancy (HP) and PE. Therefore, we performed a search on MEDLINE/PubMed using the terms "visfatin and preeclampsia" and "NAMPT and preeclampsia, and we selected 23 original articles: 12 articles reported increased levels in PE compared to HP, only four articles showed lower levels and eight articles did not find differences regarding visfatin/NAMPT in the groups studied. It is widely acknowledged that levels detected in plasma, serum, or placenta can be influenced by the size of the population and sample analyzed, as well as genetic factors. We further discussed the correlations of visfatin/NAMPT with clinical biomarkers in PE and inflammatory pathways. Considering the common inflammatory mechanisms between PE and visfatin/NAMPT, few studies have recently performed serum or plasma dosages. In conclusion, further studies are needed to highlight the potential role of visfatin/NAMPT in the pathophysiology of PE. This will provide comparative evidence to establish it as a biomarker for disease outcomes and treatment.

Expression of visfatin in gingival crevicular fluid and gingival tissues in different periodontal conditions: a cross-sectional study

BACKGROUND

Studies have shown that visfatin is an inflammatory factor closely related to periodontitis. We examined the levels of visfatin in gingival crevicular fluid (GCF) and gingival tissues under different periodontal conditions, in order to provide more theoretical basis for exploring the role of visfatin in the pathogenesis of periodontitis.

METHODS

We enrolled 87 subjects, with 43 in the chronic periodontitis (CP) group, 21 in the chronic gingivitis (CG) group, and 23 in the periodontal health (PH) group. Periodontal indexes (PD, AL, PLI, and BI) were recorded. GCF samples were collected for visfatin quantification, and gingival tissues were assessed via immunohistochemical staining.

RESULTS

Visfatin levels in GCF decreased sequentially from CP to CG and PH groups, with statistically significant differences (P < 0.05). The CP group exhibited the highest visfatin levels, while the PH group had the lowest. Gingival tissues showed a similar trend, with significant differences between groups (P < 0.001). Periodontal indexes were positively correlated with visfatin levels in both GCF and gingival tissues (P < 0.001). A strong positive correlation was observed between visfatin levels in GCF and gingival tissues (rs = 0.772, P < 0.001).

CONCLUSION

Greater periodontal destruction corresponded to higher visfatin levels in GCF and gingival tissues, indicating their potential collaboration in damaging periodontal tissues. Visfatin emerges as a promising biomarker for periodontitis and may play a role in its pathogenesis.

Exerkines and osteoarthritis

Osteoarthritis (OA) is the most prevalent chronic joint disease, with physical exercise being a widely endorsed strategy in its management guidelines. Exerkines, defined as cytokines secreted in response to acute and chronic exercise, function through endocrine, paracrine, and/or autocrine pathways. Various tissue-specific exerkines, encompassing exercise-induced myokines (muscle), cardiokines (heart), and adipokines (adipose tissue), have been linked to exercise therapy in OA. Exerkines are derived from these kines, but unlike them, only kines regulated by exercise can be called exerkines. Some of these exerkines serve a therapeutic role in OA, such as irisin, metrnl, lactate, secreted frizzled-related protein (SFRP), neuregulin, and adiponectin. While others may exacerbate the condition, such as IL-6, IL-7, IL-15, IL-33, myostatin, fractalkine, follistatin-like 1 (FSTL1), visfatin, activin A, migration inhibitory factor (MIF), apelin and growth differentiation factor (GDF)-15. They exerts anti-/pro-apoptosis/pyroptosis/inflammation, chondrogenic differentiation and cell senescence effect in chondrocyte, synoviocyte and mesenchymal stem cell. The modulation of adipokine effects on diverse cell types within the intra-articular joint emerges as a promising avenue for future OA interventions. This paper reviews recent findings that underscore the significant role of tissue-specific exerkines in OA, delving into the underlying cellular and molecular mechanisms involved.

Adipokines in Rheumatoid Arthritis: Emerging Biomarkers and Therapeutic Targets

Rheumatoid arthritis (RA) is a chronic inflammatory disease manifested by joint involvement, extra-articular manifestations, and general symptoms. Adipose tissue, previously perceived as an inert energy storage organ, has been recognised as a significant contributor to RA pathophysiology. Adipokines modulate immune responses, inflammation, and metabolic pathways in RA. Although most adipokines have a pro-inflammatory and aggravating effect on RA, some could counteract this pathological process. The coexistence of RA and sarcopenic obesity (SO) has gained attention due to its impact on disease severity and outcomes. Sarcopenic obesity further contributes to the inflammatory milieu and metabolic disturbances. Recent research has highlighted the intricate crosstalk between adipose tissue and skeletal muscle, suggesting potential interactions between these tissues in RA. This review summarizes the roles of adipokines in RA, particularly in inflammation, immune modulation, and joint destruction. In addition, it explores the emerging role of adipomyokines, specifically irisin and myostatin, in the pathogenesis of RA and their potential as therapeutic targets. We discuss the therapeutic implications of targeting adipokines and adipomyokines in RA management and highlight the challenges and future directions for research in this field.

Extracellular nicotinamide phosphoribosyltransferase: role in disease pathophysiology and as a biomarker

Nicotinamide phosphoribosyltransferase (NAMPT) plays a central role in mammalian cell metabolism by contributing to nicotinamide adenine dinucleotide biosynthesis. However, NAMPT activity is not limited to the intracellular compartment, as once secreted, the protein accomplishes diverse functions in the extracellular space. Extracellular NAMPT (eNAMPT, also called visfatin or pre-B-cell colony enhancing factor) has been shown to possess adipocytokine, pro-inflammatory, and pro-angiogenic activities. Numerous studies have reported the association between elevated levels of circulating eNAMPT and various inflammatory and metabolic disorders such as obesity, diabetes, atherosclerosis, arthritis, inflammatory bowel disease, lung injury and cancer. In this review, we summarize the current state of knowledge on eNAMPT biology, proposed roles in disease pathogenesis, and its potential as a disease biomarker. We also briefly discuss the emerging therapeutic approaches for eNAMPT inhibition.

Preclinical Characterization of Pharmacologic NAD+ Boosting as a Promising Therapeutic Approach in Rheumatoid Arthritis

OBJECTIVE

We analyzed NAD+ metabolism in patients with rheumatoid arthritis (RA), its association with disease activity and clinical outcomes of RA, and the therapeutic potential of pharmacologic NAD+ boosting.

METHODS

Our study included 253 participants. In the first cohort, comprising 153 RA patients and 56 healthy donors, we assessed NAD+ levels and NAD+ -related gene pathways. We analyzed 92 inflammatory molecules by proximity extension assay. In the second cohort, comprising 44 RA patients starting anti-tumor necrosis factor (anti-TNF) drugs, we evaluated changes in NAD+ levels and their association with clinical response after 3 months. Mechanistic studies were performed ex vivo on peripheral blood mononuclear cells (PBMCs) from patients with RA to test the beneficial effects of NAD+ boosters, such as nicotinamide and nicotinamide riboside.

RESULTS

Reduced NAD+ levels were found in RA samples, in line with altered activity and expression of genes involved in NAD+ consumption (sirtuins, poly[ADP-ribose] polymerase, CD38), transport (connexin 43), and biosynthesis (NAMPT, NMNATs). Unsupervised clustering analysis identified a group of RA patients with the highest inflammatory profile, the lowest NAD+ levels, and the highest disease activity (as shown by the Disease Activity Score in 28 joints). NAD+ levels were modulated by anti-TNF therapy in parallel with the clinical response. In vitro studies using PBMCs from RA patients showed that nicotinamide riboside and nicotinamide increased NAD+ levels via NAMPT and NMNAT and reduced their prooxidative, proapoptotic, and proinflammatory status.

CONCLUSION

RA patients display altered NAD+ metabolism, directly linked to their inflammatory and disease activity status, which was reverted by anti-TNF therapy. The preclinical beneficial effects of NAD+ boosters, as shown in leukocytes from RA patients, along with their proven clinical safety, might pave the way for the development of clinical trials using these compounds.

NAMPT/SIRT1 Expression Levels in White Blood Cells Differentiate the Different Rheumatoid Arthritis Subsets: An Inspiration from Traditional Chinese Medicine

Background

Rheumatoid arthritis (RA) patients are prone to developing different metabolic complications. Traditional Chinese Medicine attributes this uncertainty to varied syndrome types.

Methods and Results

We retrospectively analyzed some serological indicators of active RA patients and healthy individuals. Randomly selected RA patients were divided into three groups according to NAMPT and SIRT1 expression levels in white blood cells (WBCs). Their disease severity and metabolic status were compared. Representative blood samples were subjected to a UPLC-MS/MS-based metabolomics analysis. Different human WBCs were treated with oleic acid and palmitic acid in vitro. The results indicated that blood glucose and lipid levels were decreased in RA patients, but their decrease was not in accordance with disease severity. Nutrients in the patients highly expressing SIRT1 were well preserved, with the lowest levels of RF and β-CTX and the highest levels of adiponectin and resistin. Most of them exhibited cold symptoms. When SIRT1 deficiency was obvious, lipid depletion became evident, irrespective of expression levels of NAMPT. Simultaneous high-expression of SIRT1 and NAMPT coincided with the increase in production of lactic acid and the prevalence of hot symptoms. Despite the low levels of IL-6, joint injuries were severe. The corresponding WBCs were especially sensitive to fatty acids anti-inflammatory treatments. The levels of CCL27, CCL11, CCL5, AKP, CRP and ESR were similar among all the groups.

Conclusion

NAMPT overexpression is a risk factor for joint injuries and nutrient depletion in RA. Supplementation with lipids would exert beneficial effects on these RA patients. Its aftermath would cause even severe inflammation. Contrarily, SIRT1 up-regulation restrains inflammation and lipid depletion.

The profile of adipokines associated with fibrosis and impaired microcirculation in systemic sclerosis

PURPOSE

Adipokines belong to a group of molecules mostly produced by adipose tissue. Abnormalities in the secretion of several adipokines have already implicated to play a pathogenic role in systemic sclerosis (SSc). However, the possible role of numerous molecules still needs to be clarified. The aim of the study was to determine whether the altered level of selected circulating adipokines might correlate with the intensity of fibrosis and vasculopathy in the course of SSc.

MATERIALS AND METHODS

Serum concentrations of chemerin, adipsin, retinol-binding protein 4, apelin, visfatin, omentin-1, and vaspin were determined with ELISA in the sera of patients with SSc (n ​= ​55) and healthy controls (n ​= ​25).

RESULTS

The serum concentration of adipsin (p ​= ​0.03) and visfatin (p ​= ​0.04) was significantly increased and the level of retinol-binding protein 4 (p ​= ​0.03) was decreased in diffuse compared to limited cutaneous SSc. Moreover, serum adipsin level correlated positively with the intensity of skin fibrosis measured with the modified Rodnan skin score (r ​= ​0.31, p ​= ​0.02) and was significantly higher in patients with pulmonary arterial hypertension than in those without the condition (p ​= ​0.03). The concentrations of adipsin (p ​= ​0.01) and visfatin (p ​= ​0.04) were significantly increased and the level of apelin (p ​= ​0.02) was decreased in patients with active digital ulcerations compared to individuals without this complication.

CONCLUSION

Adipsin may be considered a pivotal protein in the development of both fibrosis and impaired microcirculation. Its abnormal concentration reflects the intensity of skin thickening and the presence of pulmonary arterial hypertension. Adipsin, visfatin, and apelin are adipose tissue-derived molecules associated with digital vasculopathy.

Rheumatoid arthritis macrophages are primed for inflammation and display bioenergetic and functional alterations

OBJECTIVES

Myeloid cells with a monocyte/macrophage phenotype are present in large numbers in the RA joint, significantly contributing to disease; however, distinct macrophage functions have yet to be elucidated. This study investigates the metabolic activity of infiltrating polarized macrophages and their impact on pro-inflammatory responses in RA.

METHODS

CD14+ monocytes from RA and healthy control (HC) bloods were isolated and examined ex vivo or following differentiation into 'M1/M2' macrophages. Inflammatory responses and metabolic analysis ± specific inhibitors were quantified by RT-PCR, western blot, Seahorse XFe technology, phagocytosis assays and transmission electron microscopy along with RNA-sequencing (RNA-seq) transcriptomic analysis.

RESULTS

Circulating RA monocytes are hyper-inflammatory upon stimulation, with significantly higher expression of key cytokines compared with HC (P < 0.05) a phenotype which is maintained upon differentiation into mature ex vivo polarized macrophages. This induction in pro-inflammatory mechanisms is paralleled by cellular bioenergetic changes. RA macrophages are highly metabolic, with a robust boost in both oxidative phosphorylation and glycolysis in RA along with altered mitochondrial morphology compared with HC. RNA-seq analysis revealed divergent transcriptional variance between pro- and anti-inflammatory RA macrophages, revealing a role for STAT3 and NAMPT in driving macrophage activation states. STAT3 and NAMPT inhibition results in significant decrease in pro-inflammatory gene expression observed in RA macrophages. Interestingly, NAMPT inhibition specifically restores macrophage phagocytic function and results in reciprocal STAT3 inhibition, linking these two signalling pathways.

CONCLUSION

This study demonstrates a unique inflammatory and metabolic phenotype of RA monocyte-derived macrophages and identifies a key role for NAMPT and STAT3 signalling in regulating this phenotype.

NAMPT inhibition reduces macrophage inflammation through the NAD+/PARP1 pathway to attenuate liver ischemia-reperfusion injury

BACKGROUND

Liver ischemia-reperfusion injury (IRI) is a major complication in the perioperative period and often leads to liver failure and even systemic inflammation. Previous studies have suggested that the inflammatory response participated in the liver damage during liver IRI. Nicotinamide phosphoribosyl transferase (NAMPT) is required for the maintenance of cellular nicotinamide adenine dinucleotide (NAD+) levels, catalyzing the rate-limiting step in the NAD + salvage pathway. NAMPT is strongly upregulated during inflammation and constitutes an important mechanistic link between inflammatory, metabolic, and transcriptional pathways. The aim of our study was to investigate the role of NAMPT in liver IRI.

METHODS

We investigated the effect of pharmacological inhibition of NAMPT with FK866 in models of liver IRI. Liver damage was assessed by HE staining, serum ALT/AST, and TUNEL staining. To examine the mechanism, primary hepatocytes, liver macrophages and RAW264.7 cells were treated with or without NAMPT inhibitors before hypoxia-reoxygenation. Liver macrophages and RAW 264.7 cells activation in vitro was evaluated by western blotting, flow cytometry, and ELISA.

RESULT

We found that NAMPT was upregulated in liver IRI. Treatment with the NAMPT inhibitor FK866 ameliorated liver IRI and suppressed inflammation in mice. Although NAMPT plays an important role both in hepatocytes and liver macrophages, we focused on the impact of NAMPT on liver macrophages. The mechanism revealed that FK866 potently inhibited NAMPT activity, as demonstrated by reduced liver NAD+ and intracellular NAD+, resulting in reduced abundance and activity of NAD + -dependent enzymes, including poly (ADP-ribose) polymerase 1 (PARP1), thus inhibiting macrophage M1 polarization by reducing CD86, iNOS, TNF-α, and interleukin (IL)-1β. Taken together, our data suggested that NAMPT can regulate macrophage polarization through NAD+/PARP1 to ameliorate liver injury, and that FK866-mediated NAMPT blockade may be a therapeutic approach in liver IRI.

Importance of NAD+ Anabolism in Metabolic, Cardiovascular and Neurodegenerative Disorders

The role of nicotinamide adenine dinucleotide (NAD+) in ageing has emerged as a critical factor in understanding links to a wide range of chronic diseases. Depletion of NAD+, a central redox cofactor and substrate of numerous metabolic enzymes, has been detected in many major age-related diseases. However, the mechanisms behind age-associated NAD+ decline remains poorly understood. Despite limited conclusive evidence, supplements aimed at increasing NAD+ levels are becoming increasingly popular. This review provides renewed insights regarding the clinical utility and benefits of NAD+ precursors, namely nicotinamide (NAM), nicotinic acid (NA), nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN), in attenuating NAD+ decline and phenotypic characterization of age-related disorders, including metabolic, cardiovascular and neurodegenerative diseases. While it is anticipated that NAD+ precursors can play beneficial protective roles in several conditions, they vary in their ability to promote NAD+ anabolism with differing adverse effects. Careful evaluation of the role of NAD⁺, whether friend or foe in ageing, should be considered.

Serum nicotinamide phosphoribosyltransferase as a novel biomarker for non-traumatic osteonecrosis of the femoral head

OBJECTIVE

The aim of this study was to investigate the potential role of serum nicotinamide phosphoribosyltransferase (NAMPT) in non-traumatic osteonecrosis of femoral head (NONFH).

METHODS

A total of 113 NONFH patients and 81 healthy individuals were included in this study. The NAMPT levels in serum were measured by a commercial enzyme-linked immunosorbent assay kit. Radiographic progression was determined using Association Research Circulation Osseous (ARCO) classification system. Clinical severity was assessed by Harris hip score (HHS) and visual analogue scale (VAS). Correlations between serum NAMPT and radiographic progression as well as clinical severity were evaluated statistically. Receiver operating characteristic (ROC) curves were performed to evaluate the diagnostic values of NAMPT in NONFH potential and disease severity.

RESULTS

The serum NAMPT levels in NONFH patients were significantly lower than that in healthy controls. There were no significant differences among alcohol-induced group, steroids-induced group, and idiopathic group. NONFH patients with ARCO stage 4 had significant lower serum NAMPT levels in comparisons with ARCO stage 3 and 2, respectively. Lower serum NAMPT levels were also observed in bilateral NONFH cases compared with cases with unilateral NONFH. In addition, serum NAMPT was negatively correlated with ARCO stages and VAS scores, and positively correlated with HHS. ROC curve analysis indicated that serum NAMPT may serve as a novel biomarker for diagnosing early NONFH and for monitoring disease severity.

CONCLUSIONS

Our results suggest that serum NAMPT may serve as a novel biomarker for NONFH potential and disease severity.

Adipokines as targets in musculoskeletal immune and inflammatory diseases

Adipokines are the principal mediators in adipose signaling. Nevertheless, besides their role in energy storage, these molecules can be produced by other cells, such as immune cells or chondrocytes. Given their pleiotropic effects, research over the past few years has also focused on musculoskeletal diseases, showing that these adipokines might have relevant roles in worsening the disease or improving the treatment response. In this review, we summarize recent advances in our understanding of adipokines and their role in the most prevalent musculoskeletal immune and inflammatory disorders.

Organokines in Rheumatoid Arthritis: A Critical Review

Rheumatoid arthritis (RA) is a systemic autoimmune disease that primarily affects the joints. Organokines can produce beneficial or harmful effects in this condition. Among RA patients, organokines have been associated with increased inflammation and cartilage degradation due to augmented cytokines and metalloproteinases production, respectively. This study aimed to perform a review to investigate the role of adipokines, osteokines, myokines, and hepatokines on RA progression. PubMed, Embase, Google Scholar, and Cochrane were searched, and 18 studies were selected, comprising more than 17,000 RA patients. Changes in the pattern of organokines secretion were identified, and these could directly or indirectly contribute to aggravating RA, promoting articular alterations, and predicting the disease activity. In addition, organokines have been implicated in higher radiographic damage, immune dysregulation, and angiogenesis. These can also act as RA potent regulators of cells proliferation, differentiation, and apoptosis, controlling osteoclasts, chondrocytes, and fibroblasts as well as immune cells chemotaxis to RA sites. Although much is already known, much more is still unknown, principally about the roles of organokines in the occurrence of RA extra-articular manifestations.

Nicotinamide phosphoribosyltransferase (Nampt) of hybrid crucian carp protects intestinal barrier and enhances host immune defense against bacterial infection

Nicotinamide phosphoribosyltransferase (Nampt) can act extracellularly as a mediator of inflammation or intracellularly as a rate-limiting enzyme, regulating nicotinamide adenine dinucleotide (NAD) biosynthesis in the NAD salvage pathway. Nampt exerts important immunological functions during infection in mammals. However, the in vivo function of fish Nampt in immune regulation and inflammation is essentially unknown. With an aim to elucidate the antimicrobial mechanism of Nampt in fish, we in this study examined the function of Nampt from hybrid crucian carp. Hybrid crucian carp Nampt (WR-Nampt) possesses the conserved nicotinamide phosphoribosyltransferase domain and shows high similarity to that of mammalian Nampt. WR-Nampt is expressed in multiple tissues and is upregulated by bacterial infection. Overexpression of WR-Nampt significantly increased the number of goblet cells of distal intestine. In addition, WR-Nampt induced significant inductions in the expression of the antimicrobial molecules (IL-22, Hepcidin-1, LEAP-2 and MUC2) and tight junctions (ZO-1 and Occludin). Consistent with this, fish administered with WR-Nampt significantly alleviated the intestinal permeability and apoptosis, thereby enhancing host's resistance against bacterial infection. Together these results revealed the potential effect of WR-Nampt in intestinal barrier and immune defense against bacterial infection.

Circulating Mir-140 and leptin improve the accuracy of the differential diagnosis between psoriatic arthritis and rheumatoid arthritis: a case-control study

The differential diagnosis of psoriatic arthritis (PsA) and rheumatoid arthritis (RA) is difficult because of the lack of diagnostic clinical signs and reliable biomarkers. This study investigated microRNAs (miRNA) and adipokines as potential additional markers to discriminate PsA from RA. The expression profile of miRNA (miR-21, miR-140, miR-146a, miR-155, miR-181b, miR-223, miR-let-7e) and inflammatory cytokines (IL-1β, IL-6, IL-17a, IL-23a, TNF-α) from peripheral blood mononuclear cells of PsA and RA patients compared to healthy controls (HC) were evaluated by real-time PCR, and serum adipokines (adiponectin, chemerin, leptin, resistin, visfatin) and cytokines by ELISA assay. Univariable binary logistic regression was used to find the association between PsA and potential predictors. The gene expression of miRNA and cytokines and the serum levels of adipokines were found significantly different in PsA and RA patients compared to HC, as well as in PsA versus RA. MiR-140 gene expression resulted up-regulated in PsA patients and reduced in RA in comparison to HC, and, for the first time, significantly higher in PsA compared with RA. Serum levels of IL-23a and leptin were significantly increased in PsA and RA populations than in HC, as well as in PsA versus RA. Furthermore, circulating TNF-α was up-regulated in PsA and RA in comparison to controls, while resulted higher in RA than in PsA. Univariable binary logistic regression analysis found the above-mentioned markers associated to PsA versus RA. Our results first demonstrated an increased expression of circulating miR-140 and serum leptin in PsA patients compared to RA, which were identified as potential additional biomarkers to discriminate PsA from RA. Since the differential diagnosis of PsA and RA poses challenges in clinical practice, our data may help to enhance the diagnostic performance of PsA in daily practice.

Single-cell RNA-sequencing reveals distinct immune cell subsets and signaling pathways in IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is the most common primary glomerulonephritis globally. Increasing evidence suggests the importance of host immunity in the development of IgAN, but its dynamics during the early stage of IgAN are still largely unclear.

RESULTS

Here we successfully resolved the early transcriptomic changes in immune cells of IgAN by conducting single-cell RNA-sequencing (scRNA-seq) with peripheral blood mononuclear cells. The differentially expressed genes (DEGs) between control and IgAN were predominantly enriched in NK cell-mediated cytotoxicity and cell killing pathways. Interestingly, we discovered that the number and cytotoxicity of NK cells are significantly reduced in IgAN patients, where both the number and marker genes of NK cells were negatively associated with the clinical parameters, including the levels of urine protein creatinine ratio (UPCR), serum galactose-deficient IgA1 and IgA. A distinctive B cell subset, which had suppressed NFκB signaling was predominantly in IgAN and positively associated with disease progression. Moreover, the DEGs of B cells were enriched in different viral infection pathways. Classical monocytes also significantly changed in IgAN and a monocyte subset expressing interferon-induced genes was positively associated with the clinical severity of IgAN. Finally, we identified vast dynamics in intercellular communications in IgAN.

CONCLUSIONS

We dissected the immune landscape of IgAN at the single-cell resolution, which provides new insights in developing novel biomarkers and immunotherapy against glomerulonephritis.

Metabolites as drivers and targets in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease characterized by neovascularization, immune cell infiltration, and synovial hyperplasia, which leads to degradation of articular cartilage and bone, and subsequent functional disability. Dysregulated angiogenesis, synovial hypoxia, and immune cell infiltration result in a ‘bioenergetic crisis’ in the inflamed joint which further exacerbates synovial invasiveness. Several studies have examined this vicious cycle between metabolism, immunity, and inflammation and the role metabolites play in these interactions. To add to this complexity, the inflamed synovium is a multicellular tissue with many cellular subsets having different metabolic requirements. Metabolites can shape the inflammatory phenotype of immune cell subsets during disease and act as central signalling hubs. In the RA joint, the increased energy demand of stromal and immune cells leads to the accumulation of metabolites such as lactate, citrate, and succinate as well as adipocytokines which can regulate downstream signalling pathways. Transcription factors such as HIF1ɑ and mTOR can act as metabolic sensors to activate synovial cells and drive pro-inflammatory effector function, thus perpetuating chronic inflammation further. These metabolic intermediates may be potential therapeutic targets and so understanding the complex interplay between metabolites and synovial cells in RA may allow for identification of novel therapeutic strategies but also may provide significant insight into the underlying mechanisms of disease pathogenesis.

Nicotinamide phosphoribosyltransferase as a biomarker for the diagnosis of infectious pleural effusions

Nicotinamide phosphoribosyltransferase (NAMPT) has been reported to be involved in infectious diseases, but it is unknown whether it plays a role in infectious pleural effusions (IPEs). We observed the levels of NAMPT in pleural effusions of different etiologies and investigated the clinical value of NAMPT in the differential diagnosis of infectious pleural effusions. A total of 111 patients with pleural effusion were enrolled in the study, including 25 parapneumonic effusions (PPEs) (17 uncomplicated PPEs, 3 complicated PPEs, and 5 empyemas), 30 tuberculous pleural effusions (TPEs), 36 malignant pleural effusions (MPEs), and 20 transudative effusions. Pleural fluid NAMPT levels were highest in the patients with empyemas [575.4 (457.7, 649.3) ng/ml], followed by those with complicated PPEs [113.5 (103.5, 155.29) ng/ml], uncomplicated PPEs [24.9 (20.2, 46.7) ng/ml] and TPEs [88 (19.4, 182.6) ng/ml], and lower in patients with MPEs [11.5 (6.5, 18.4) ng/ml] and transudative effusions [4.3 (2.6, 5.1) ng/ml]. Pleural fluid NAMPT levels were significantly higher in PPEs (P < 0.001) or TPEs (P < 0.001) than in MPEs. Moreover, Pleural fluid NAMPT levels were positively correlated with the neutrophil percentage and lactate dehydrogenase (LDH) levels and inversely correlated with glucose levels in both PPEs and TPEs, indicating that NAMPT was implicated in the neutrophil-associated inflammatory response in infectious pleural effusion. Further, multivariate logistic regression analysis showed pleural fluid NAMPT was a significant predictor distinguishing PPEs from MPEs [odds ratio (OR) 1.180, 95% confidence interval (CI) 1.052-1.324, P = 0.005]. Receiver-operating characteristic (ROC) analysis demonstrated that NAMPT was a promising diagnostic factor for the diagnosis of infectious effusions, with the areas under the curve for pleural fluid NAMPT distinguishing PPEs from MPEs, TPEs from MPEs, and IPEs (PPEs and TPEs) from NIPEs were 0.92, 0.85, and 0.88, respectively. In conclusion, pleural fluid NAMPT could be used as a biomarker for the diagnosis of infectious pleural effusions.

Nicotinamide phosphoribosyltransferase inhibitor ameliorates mouse aging-induced cognitive impairment

Nicotinamide phosphoribosyltransferase (NAMPT) is the key enzyme for the synthesis of nicotinamide adenine dinucleotide (NAD) in the salvaging pathway. Though NAMPT inhibitors such as FK866 were originally developed as anti-cancer drugs, they also display neuroprotective effects. Here we show that the administration of FK866 at 0.5 mg/kg (ip, qod) for four weeks, i.e., ∼1% of the dose used for the treatment of cancer, significantly alleviates the aging-induced impairment of cognition and locomotor activity. Mechanistically, FK866 enhanced autophagy, reduced protein aggregation, and inhibited neuroinflammation indicated by decreasing TNFα, IL-6, GFAP, and Iba1 levels in the aged mouse brain. Though FK866 did not affect the total NAD and nicotinamide mononucleotide (NMN) levels in the mouse brain at the dose we used, FK866 increased nicotinamide (NAM) level in the young mouse brain and decreased NAM level in the aged mouse brain. On the other hand, FK866 did not affect the serum glucose, cholesterol, and triglyceride of young and aged mice and exhibited no effects on the various indices of young mice. Thus, the NAMPT inhibitor can be repurpose to counteract the cognitive impairment upon aging. We also envision that NAMPT inhibitor can be used for the treatment of age-related neurodegenerative diseases.

Adipokines and Chronic Rheumatic Diseases: from Inflammation to Bone Involvement

Besides its well-known role as energy storage tissue, adipose tissue is a biologically active tissue that can also be considered as an endocrine organ, as it is able to secrete adipokines. These bioactive factors, similar in structure to cytokines, are involved in several physiological and pathological conditions, such as glucose homeostasis, angiogenesis, blood pressure regulation, control of food intake, and also inflammation and bone homeostasis via endocrine, paracrine, and autocrine mechanisms. Given their pleiotropic functions, the role of adipokines has been evaluated in chronic rheumatic osteoarticular inflammatory diseases, particularly focusing on their effects on inflammatory and immune response and on bone alterations. Indeed, these diseases are characterized by different bone complications, such as local and systemic bone loss and new bone formation. The aim of this review is to summarize the role of adipokines in rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, osteoarthritis, and osteoporosis, especially considering their role in the pathogenesis of bone complications typical of these conditions.

Adipokines and Autoimmunity in Inflammatory Arthritis

Adipokines are adipose tissue-derived factors not only playing an important role in metabolism but also influencing other central processes of the body, such as inflammation. In autoimmune diseases, adipokines are involved in inflammatory pathways affecting different cell types. Many rheumatic diseases belong to the group of autoimmune diseases, for example rheumatoid arthritis (RA) and psoriatic arthritis. Due to the autoimmune responses, a chronic inflammatory milieu develops, which affects the whole body, including adipose tissue. Metabolic alterations such as obesity influence inflammatory responses in autoimmune diseases. Adipokines are bioactive mediators mainly produced by adipose tissue. Due to alterations of systemic adipokine levels, their role as biomarkers with diagnostic potential has been suggested in the context of rheumatic diseases. In the affected joints of RA patients, different synoviocytes but also osteoclasts, osteoblasts, and chondrocytes produce several adipokines, contributing to the unique inflammatory microenvironment. Adipokines have been shown to be potent modulatory effectors on different cell types of the immune system but also local cells in synovial tissue, cartilage, and bone. This review highlights the most recent findings on the role of adipokines in the pathophysiology of inflammatory arthritis with a distinct focus on RA in the quickly developing research field.

Mini-Review: The Contribution of Adipokines to Joint Inflammation in Inflammatory Rheumatic Diseases

Inflammatory rheumatic diseases (IRD) are complex disorders characterized by chronic inflammation of the joints and related skeletal structures. The most common forms of IRD are rheumatoid arthritis (RA) and spondyloarthritis (SpA), including axial SpA (axSpA) and psoriatic arthritis (PsA). Obesity is a frequent comorbidity in RA and PsA, and to a lesser extend in axial SpA. The association between obesity and IRD may be explained by the release from fat tissue of several bioactive proteins, namely adipokines. Adipokines are involved in the regulation of various processes such as lipid or glucose metabolism, but also inflammation. Adipokines are interrelated with the immune system, with both innate and adaptive immune cell connections. Several adipokines with pro-inflammatory effects have been identified such as leptin, visfatin or resistin. Conversely, adiponectin and more specifically its low molecular weight isoform, is considered to have antiinflammatory properties. In this review, we discuss the contribution of adipokines to the joint inflammation of IRD, the relation they have with immune pathways of these diseases, their links with the structural impact on peripheral joints and/or axial skeleton, and also the influence they may have on the cardiometabolic risk of IRD.

Aptamers for Proteins Associated with Rheumatic Diseases: Progress, Challenges, and Prospects of Diagnostic and Therapeutic Applications

Nucleic acid aptamers capable of affine and specific binding to their molecular targets have now established themselves as a very promising alternative to monoclonal antibodies for diagnostic and therapeutic applications. Although the main focus in aptamers’ research and development for biomedicine is made on cardiovascular, infectious, and malignant diseases, the use of aptamers as therapeutic or diagnostic tools in the context of rheumatic diseases is no less important. In this review, we consider the main features of aptamers that make them valuable molecular tools for rheumatologists, and summarize the studies on the selection and application of aptamers for protein biomarkers associated with rheumatic diseases. We discuss the progress in the development of aptamer-based diagnostic assays and targeted therapeutics for rheumatic disorders, future prospects in the field, and issues that have yet to be addressed.

NAMPT and NAPRT: Two Metabolic Enzymes With Key Roles in Inflammation

Nicotinamide phosphoribosyltransferase (NAMPT) and nicotinate phosphoribosyltransferase (NAPRT) are two intracellular enzymes that catalyze the first step in the biosynthesis of NAD from nicotinamide and nicotinic acid, respectively. By fine tuning intracellular NAD levels, they are involved in the regulation/reprogramming of cellular metabolism and in the control of the activity of NAD-dependent enzymes, including sirtuins, PARPs, and NADases. However, during evolution they both acquired novel functions as extracellular endogenous mediators of inflammation. It is well-known that cellular stress and/or damage induce release in the extracellular milieu of endogenous molecules, called alarmins or damage-associated molecular patterns (DAMPs), which modulate immune functions through binding pattern recognition receptors (PRRs), such as Toll-like receptors (TLRs), and activate inflammatory responses. Increasing evidence suggests that extracellular (e)NAMPT and eNAPRT are novel soluble factors with cytokine/adipokine/DAMP-like actions. Elevated eNAMPT were reported in several metabolic and inflammatory disorders, including obesity, diabetes, and cancer, while eNAPRT is emerging as a biomarker of sepsis and septic shock. This review will discuss available data concerning the dual role of this unique family of enzymes.