Serum allograft inflammatory factor-1 is a novel marker for diabetic nephropathy

Identification of novel therapeutic targets for chronic kidney disease and kidney function by integrating multi-omics proteome with transcriptome

BACKGROUND

Chronic kidney disease (CKD) is a progressive disease for which there is no effective cure. We aimed to identify potential drug targets for CKD and kidney function by integrating plasma proteome and transcriptome.

METHODS

We designed a comprehensive analysis pipeline involving two-sample Mendelian randomization (MR) (for proteins), summary-based MR (SMR) (for mRNA), and colocalization (for coding genes) to identify potential multi-omics biomarkers for CKD and combined the protein-protein interaction, Gene Ontology (GO), and single-cell annotation to explore the potential biological roles. The outcomes included CKD, extensive kidney function phenotypes, and different CKD clinical types (IgA nephropathy, chronic glomerulonephritis, chronic tubulointerstitial nephritis, membranous nephropathy, nephrotic syndrome, and diabetic nephropathy).

RESULTS

Leveraging pQTLs of 3032 proteins from 3 large-scale GWASs and corresponding blood- and tissue-specific eQTLs, we identified 32 proteins associated with CKD, which were validated across diverse CKD datasets, kidney function indicators, and clinical types. Notably, 12 proteins with prior MR support, including fibroblast growth factor 5 (FGF5), isopentenyl-diphosphate delta-isomerase 2 (IDI2), inhibin beta C chain (INHBC), butyrophilin subfamily 3 member A2 (BTN3A2), BTN3A3, uromodulin (UMOD), complement component 4A (C4a), C4b, centrosomal protein of 170 kDa (CEP170), serologically defined colon cancer antigen 8 (SDCCAG8), MHC class I polypeptide-related sequence B (MICB), and liver-expressed antimicrobial peptide 2 (LEAP2), were confirmed. To our knowledge, 20 novel causal proteins have not been previously reported. Five novel proteins, namely, GCKR (OR 1.17, 95% CI 1.10-1.24), IGFBP-5 (OR 0.43, 95% CI 0.29-0.62), sRAGE (OR 1.14, 95% CI 1.07-1.22), GNPTG (OR 0.90, 95% CI 0.86-0.95), and YOD1 (OR 1.39, 95% CI 1.18-1.64,) passed the MR, SMR, and colocalization analysis. The other 15 proteins were also candidate targets (GATM, AIF1L, DQA2, PFKFB2, NFATC1, activin AC, Apo A-IV, MFAP4, DJC10, C2CD2L, TCEA2, HLA-E, PLD3, AIF1, and GMPR1). These proteins interact with each other, and their coding genes were mainly enrichment in immunity-related pathways or presented specificity across tissues, kidney-related tissue cells, and kidney single cells.

CONCLUSIONS

Our integrated analysis of plasma proteome and transcriptome data identifies 32 potential therapeutic targets for CKD, kidney function, and specific CKD clinical types, offering potential targets for the development of novel immunotherapies, combination therapies, or targeted interventions.

Hub genes, key miRNAs and interaction analyses in type 2 diabetes mellitus: an integrative in silico approach

Diabetes is a rising global metabolic disorder and leads to long-term consequences. As a multifactorial disease, the gene-associated mechanisms are important to know. This study applied a bioinformatics approach to explore the molecular underpinning of type 2 diabetes mellitus through differential gene expression analysis. We used microarray datasets GSE16415 and GSE29226 to identify differentially expressed genes between type 2 diabetes and normal samples using R software. Following that, using the STRING database, the protein-protein interaction network was constructed and further analyzed by Cytoscape software. The EnrichR database was used for Gene Ontology and pathway enrichment analysis to explore key pathways and functional annotations of hub genes. We also used miRTarBase and TargetScan databases to predict miRNAs targeting hub genes. We identified 21 hub genes in type 2 diabetes, some showing more significant changes in the PPI network. Our results revealed that GLUL, SLC32A1, PC, MAPK10, MAPT, and POSTN genes are more important in the PPI network and can be experimentally investigated as therapeutic targets. Hsa-miR-492 and hsa-miR-16-5p are suggested for diagnosis and prognosis by targeting GLUL, SLC32A1, PC, MAPK10, and MAPT genes involved in the insulin signaling pathway. Insight: Type 2 diabetes, as a rising global and multifactorial disorder, is important to know the gene-associated mechanisms. In an integrative bioinformatics analysis, we integrated different finding datasets to put together and find valuable diagnostic and prognostic hub genes and miRNAs. In contrast, genes, RNAs, and enzymes interact systematically in pathways. Using multiple databases and software, we identified differential expression between hub genes of diabetes and normal samples. We explored different protein-protein interaction networks, gene ontology, key pathway analysis, and predicted miRNAs that target hub genes. This study reported 21 significant hub genes and some miRNAs in the insulin signaling pathway for innovative and potential diagnostic and therapeutic purposes.

AIF1: Function and Connection with Inflammatory Diseases

Macrophages are a type of immune cell distributed throughout all tissues of an organism. Allograft inflammatory factor 1 (AIF1) is a calcium-binding protein linked to the activation of macrophages. AIF1 is a key intracellular signaling molecule that participates in phagocytosis, membrane ruffling and F-actin polymerization. Moreover, it has several cell type-specific functions. AIF1 plays important roles in the development of several diseases: kidney disease, rheumatoid arthritis, cancer, cardiovascular diseases, metabolic diseases and neurological disorders, and in transplants. In this review, we present a comprehensive review of the known structure, functions and role of AIF1 in inflammatory diseases.

Allograft inflammatory factor-1 released from the cerebral microglia affect several organs in the body

Allograft inflammatory factor-1 (AIF-1) is expressed in microglia. Unilateral common carotid artery occlusion (UCCAO) was conducted to elucidate mechanisms that regulate AIF-1 expression in C57BL/6 male mice. Immunohistochemical reactivity of microglia against anti-AIF-1 antibody was increased significantly in the brain of this model. The increased AIF-1 production was further confirmed by ELISA using brain homogenate. Real-time PCR demonstrated that the increased AIF-1 production was regulated at the transcriptional level. Serum AIF-1 levels were further examined by ELISA and marked increase was observed on Day 1 of UCCAO. To examine the influence of AIF-1, immunohistochemical staining was performed and revealed that the immunoreactivity against anti-Iba-1 antibody was significantly increased in various organs. Among them, the accumulation of Iba-1⁺ cells were observed prominently in the spleen. Intraperitoneal injection of minocycline, a potent microglia inhibitor, reduced the number of Iba-1⁺ cells suggesting microglia activation-dependent accumulation. Based on these results, AIF-1 expression was further examined in the murine microglia cell line MG6. AIF-1 mRNA expression and secretion were up-regulated when the cells were cultured under hypoxic condition. Importantly, stimulation of the cells with recombinant AIF-1 induced the expression of AIF-1 mRNA. These results may suggest that increased AIF-1 production by microglia in cerebral ischemia regulate the AIF-1 mRNA expression at least in part by an autocrine manner.

AIF-1, a potential biomarker of aggressive tumor behavior in patients with non-small cell lung cancer

Allogeneic inflammatory factor-1 (AIF-1) overexpression has been reported to be associated with tumorigenesis and tumor metastasis. This study aimed to investigate the role of AIF-1 in the development and progression of non-small cell lung cancer (NSCLC). AIF-1, IL-6, and VEGF expressions in human NSCLC tissue were examined by immunofluorescence staining. Bioinformatics analyses were performed to identify AIF-1-related molecules and pathways in NSCLC. Human lung cancer A549 cell proliferation was assessed by CCK-8 assay, and cell migration was evaluated with wound-healing assay. IL-6 and VEGF secretions in A549 cell culture supernatants were quantified using the Elecsys IL-6 immunoassay kit and Vascular Endothelial Growth Factor Assay Kit. RT-PCR and western blot were performed to quantify the expressions of AIF-1, IL-6, and VEGF mRNAs and proteins involved in p38-MAPK and JAK/STAT3 signaling such as p-p38 and p-STAT3. The effects of AIF-1 on A549 cell proliferation and the expressions of IL-6 and VEGF were assessed using SB203580 and ruxolitinib. The results showed that AIF-1 expression was higher in human NSCLC tissue than that in paracancer tissue. High AIF-1 expression was associated with metastasis, higher TNM stage, and poorer survival. Bioinformatics connected AIF-1 to JAK/STAT signaling in NSCLC. AIF-1 increased A549 cell proliferation, migration, IL-6 secretion and, VEGF secretion, and these effects were attenuated by inhibition of p38-MAPK or JAK/STAT3 signaling. In conclusion, AIF-1 may promote aggressive NSCLC behavior via activation of p38-MAPK and JAK/STAT signaling.

The Effect of Allograft Inflammatory Factor-1 on Inflammation, Oxidative Stress, and Autophagy via miR-34a/ATG4B Pathway in Diabetic Kidney Disease

Increasing evidence suggests that disorders of inflammation, oxidative stress, and autophagy contribute to the pathogenesis of diabetic kidney disease (DKD). This study attempted to clarify the effect of allograft inflammatory factor-1 (AIF-1), miR-34a, and ATG4B on inflammation, oxidative stress, and autophagy in DKD both in vitro and in vivo experiments. In vivo, it was found that the levels of AIF-1, miR-34a, oxidative stress, and inflammatory factors were significantly increased in blood and urine samples of DKD patients and mouse models and correlated with the level of urinary protein. In vitro, it was also found that the expressions of AIF-1, miR-34a, ROS, and inflammatory factors were increased, while ATG4B and other autophagy related proteins were decreased in human renal glomerular endothelial cells (HRGECs) cultured with high concentration glucose medium (30 mmol/L). When AIF-1 gene was overexpressed, the levels of miR-34a, ROS, and inflammatory factors were significantly upregulated, and autophagy-related proteins such as ATG4B were downregulated, while downregulation of AIF-1 gene had the opposite effect. In addition, miR-34a inhibited the expression of ATG4B and autophagy-related proteins and increased the levels of ROS and inflammation. Furthermore, the result of luciferase reporter assay suggested that ATG4B was the target gene of miR-34a. When ATG4B gene was overexpressed, the level of autophagy was upregulated, and inflammatory factors were downregulated. Conversely, when ATG4B gene was inhibited, the level of autophagy was downregulated, and inflammatory factors were upregulated. Then, autophagy inducers inhibited the levels of inflammation and ROS, whereas autophagy inhibitors had the opposite function in HRGECs induced by glucose (30 mmol/L). In conclusion, the above data suggested that AIF-1 regulated the levels of inflammation, oxidative stress, and autophagy in HRGECs via miR-34a/ATG4B pathway to contribute to the pathogenesis of diabetic kidney disease.

Allograft inflammatory factor-1 in myeloid cells drives autoimmunity in type 1 diabetes

Allograft inflammatory factor-1 (AIF1) is a calcium-responsive cytoplasmic scaffold protein that directs hematopoiesis and immune responses within dendritic cells (DC) and macrophages. Although the role of AIF1 in transplant rejection and rheumatoid arthritis has been explored, little is known about its role in type 1 diabetes. Here, we show that in vivo silencing of AIF1 in NOD mice restrained infiltration of immune cells into the pancreas and inhibited diabetes incidence. Analyses of FACS-sorted CD45neg nonleukocyte populations from resected pancreatic islets showed markedly higher expression of insulin in the AIF1-silenced groups. Evaluation of CD45+ leukocytes revealed diminished infiltration of effector T cells and DC in the absence of AIF1. Transcriptional profiling further revealed a marked decrease in cDC1 DC-associated genes CD103, BATF3, and IRF8, which are required for orchestrating polarized type 1 immunity. Reduced T cell numbers within the islets were observed, with concomitant lower levels of IFN-γ and T-bet in AIF1-silenced cohorts. In turn, there was a reciprocal increase in functionally suppressive pancreas-resident CD25+Foxp3+CD4+ Tregs. Taken together, results show that AIF1 expression in myeloid cells plays a pivotal role in promoting type 1 diabetes and that its suppression restrains insulitis by shifting the immune microenvironment toward tolerance.

Extracellular allograft inflammatory factor-1 (AIF-1) potentiates Th1 cell differentiation and inhibits Treg response in human peripheral blood mononuclear cells from normal subjects

We identified the presence of AIF-1 (allograft inflammatory factor-1) in human peripheral blood mononuclear cells (PBMCs) from normal subjects by immunocytological methods. After isolation of different types of mononuclear cells by FACS (Fluorescence-activated cell sorting) with >95% purity, we studied the transcript levels of AIF-1 using qPCR. We observed the following order of AIF-1 mRNA expression in mononuclear cells: T-lymphocytes ˃ Monocytes ˃ B-lymphocytes ˃ NK. After T cell expansion of isolated PBMCs using anti-CD3-CD28 magnetic beads (Dynabeads®), AIF-1 increased intracellularly in the presence of brefeldin A; this finding, along with an increase in the medium in the absence of the drug, suggests that AIF-1 is processed in the Golgi apparatus and may be secreted extracellularly. In another set of experiments, interleukin-12 and anti-interleukin-4 were added to PBMCs during T cell expansion to promote Th1 polarization and to inhibit Th2 differentiation. In this case, the presence of 6 nM of rhAIF-1 (recombinant human AIF-1) increased the mRNA expression of interferon-ϒ and interleukin-2. In the same set of experiments, the incubation of PBMCs with rhAIF-1 (6 nM) promoted the decrease of mRNA expression of IL-10 and TGF-β, along with the decrease of CD25 and Foxp3 proteins. Furthermore, extracellular rhAIF-1 (6 nM) increased the survival of naive and effector T cells during Th1 polarization by inhibition of apoptosis, without causing changes in cell cycle rate and in retinoblastoma-cyclin-dependent kinase (Rb-CDK) activation. Taken together, rhAIF-1 treatment of PBMCs potentiates Th1 response and inhibits functionally suppressive CD25 + Foxp3 + Treg, which suggests an important immunomodulatory role in governing T cell response.

Role of allograft inflammatory factor-1 in pathogenesis of diseases

Allograft inflammatory factor-1 (AIF-1) is a 17 kDa calcium-binding protein produced by monocytes, macrophages, and lymphocytes; its synthesis is induced by INF-γ. The AIF-1 gene is located in the major histocompatibility complex (MHC) class III region on chromosome 6p21.3, surrounded by surface glycoprotein genes and complement cascade protein genes as well as TNF-α, TNF-β, and NF-κB genes. Increased expression of AIF-1 was observed in several diseases, including endometriosis, breast cancer, atherosclerosis, rheumatoid arthritis, and fibrosis. In this review, we summarise the role of AIF-1 in allograft rejection and the pathogenesis of diseases.

Aldosterone promotes renal interstitial fibrosis via the AIF‑1/AKT/mTOR signaling pathway

A number of studies have shown that aldosterone serves an important role in promoting renal interstitial fibrosis, although the specific mechanism remains to be elucidated. A previous study revealed that the fibrotic effect of aldosterone was associated with the expression of allograft inflammatory factor 1 (AIF‑1) in RAW264.7 macrophage cells, in a time‑ and concentration‑dependent manner. However, the exact mechanism through which aldosterone promotes renal interstitial fibrosis remains unknown. In the present study, the effects of aldosterone on renal inflammatory cell infiltration, collagen deposition and the expression levels of AIF‑1, phosphatidylinositol 3‑kinase (PI3K), AKT serine/threonine kinase (AKT), mammalian target of rapamycin (mTOR), the oxidative stress factor NADPH oxidase 2 (NOX2) and nuclear transcription factor erythroid‑related factor 2 (Nrf2) were assessed in normal rats, rats treated with aldosterone, rats treated with aldosterone and spironolactone and those treated with spironolactone only (used as the control). The effect of aldosterone on these factors was also investigated in the renal interstitium of unilateral ureteral obstruction (UUO) rats. Additionally, the AIF‑1 gene was overexpressed and knocked down in macrophage RAW264.7 cells, and the effects of aldosterone on PI3K, AKT, mTOR, NOX2 and Nrf2 were subsequently investigated. The results showed that aldosterone promoted inflammatory cell infiltration, collagen deposition and the expression of AIF‑1, PI3K, AKT, mTOR and NOX2, but inhibited the expression of Nrf2. In the UUO rats, aldosterone also promoted renal interstitial inflammatory cell infiltration, collagen deposition and the expression of AIF‑1, NOX2, PI3K, AKT and mTOR, whereas the expression of Nrf2 was downregulated by aldosterone compared with that in the UUO‑only group; the influence of aldosterone was counteracted by spironolactone in the normal and UUO rats. In vitro, aldosterone upregulated the expression levels of AKT, mTOR, NOX2 and Nrf2 in RAW264.7 cells compared with those in untreated cells. Suppressing the expression of AIF‑1 inhibited the effects of aldosterone, whereas the overexpression of AIF‑1 enhanced these effects in RAW264.7 cells. These findings indicated that aldosterone promoted renal interstitial fibrosis by upregulating the expression of AIF‑1 and that the specific mechanism may involve AKT/mTOR and oxidative stress signaling.

An isoform of AIF1 involved in breast cancer

Background

Inflammation is a major player in breast cancer (BC) progression. Allograft-inflammatory factor-1 (AIF1) is a crucial mediator in the inflammatory response. AIF1 reportedly plays a role in BC, but the mechanism remains to be elucidated. We identified two AIF1 isoforms, AIF1v1 and AIF1v3, which were differentially expressed between affected and unaffected sisters from families with high risk of BC with no deleterious BRCA1/BRCA2 mutations (BRCAX). We investigated potential functions of AIFv1/v3 in BC of varying severity and breast adipose tissue by evaluating their expression, and association with metabolic and clinical parameters of BC patients.

Methods

AIF1v1/v3 expression was determined in BC tissues and cell lines using quantitative real-time PCR. Potential roles and mechanisms were examined in the microenvironment (fibroblasts, adipose tissue, monocytes and macrophages), inflammatory response (cell reaction in BC subgroups), and metabolism [treatment with docosahexaenoic acid (DHA)]. Association of AIF1 transcript expression with clinical factors was determined by Spearman’s rank correlation. Bioinformatics analyses were performed to characterize transcripts.

Results

AIF1v1/v3 were mostly expressed in the less severe BC samples, and their expression appeared to originate from the tumor microenvironment. AIF1 isoforms had different expression rates and sources in breast adipose tissue; lymphocytes mostly expressed AIF1v1 while activated macrophages mainly expressed AIF1v3. Bioinformatics analysis revealed major structural differences suggesting distinct functions in BC progression. Lymphocytes were the most infiltrating cells in breast tumors and their number correlated with AIF1v1 adipose expression. Furthermore, DHA supplementation significantly lowered the expression of AIF1 isoforms in BRCAX cell lines. Finally, the expression of AIF1 isoforms in BC and breast adipose tissue correlated with clinical parameters of BC patients.

Conclusions

Results strongly suggest that AIF1v1 as much as AIF1v3 play a major role in the crosstalk between BC and infiltrating immune cells mediating tumor progression, implying their high potential as target molecules for BC diagnostic, prognostication and treatment.

Electronic supplementary material

The online version of this article (10.1186/s12935-018-0663-3) contains supplementary material, which is available to authorized users.

Identifying novel candidate biomarkers of RCC based on WGCNA analysis

AIM

Extracting differential expression genes (DEGs) is an effective approach to improve the accuracy of determining the candidate biomarker genes. However, the previous DEGs analysis methods ignore that the expression levels of genes in different pathology stages of cancers are complex and various.

METHODS

In our study, staging DEGs analysis and weighted gene co-expression network analysis were applied to gene expression data of renal cell carcinoma (RCC).

RESULTS

According to construct gene topology network for exploring hub genes, 12 genes were identified as hub genes.

CONCLUSION

Combining with the effect of hub gene expression level on RCC patient survival and different biological data analysis, three hub genes were found that they might be three novel candidate biomarkers of RCC.

Upregulation of allograft inflammatory factor‑1 expression and secretion by macrophages stimulated with aldosterone promotes renal fibroblasts to a profibrotic phenotype

Macrophages have been identified as a key cell type in the pathogenesis of renal interstitial fibrosis (RIF). However, the mechanism through which macrophages drive fibrosis remains unclear. The current study focuses on the effects and possible underlying mechanism of allograft inflammatory factor-1 (AIF-1), an inflammation-responsive scaffold protein expressed and secreted by macrophages, in promoting fibroblasts to a profibrotic phenotype. In vivo experiments indicated that AIF-1, CD68 and α-smooth muscle actin (α-SMA) were upregulated in kidney tissues of mice subjected to unilateral ureteric obstruction, while their expressions were inhibited by an aldosterone receptor antagonist, spironolactone. Double immunofluorescence staining revealed that AIF-1 expression co-localized with CD68-positive macrophages in the renal interstitium, indicating that AIF-1 expression in macrophages was increased in the RIF animal model. Furthermore, to identify the role of AIF-1 in promoting fibrosis, its expression and secretion by the RAW264.7 macrophage cell line were detected in vitro. The expression levels of α-SMA, phosphorylated p38 (p-p38) and fibronectin (FN) in fibroblasts were examined subsequent to co-culture with macrophages. The increase in AIF-1 expression and secretion was confirmed in RAW264.7 cells in response to aldosterone. After 72 h of co-culture between fibroblasts and macrophages stimulated with aldosterone, the α-SMA expression was induced in fibroblasts, with significantly increased expression levels of FN and p-p38 observed. In addition, AIF-1 expression was reduced by stable transfection of RAW264.7 cells with AIF-1 small interfering RNA, resulting in significantly reduced expression levels of α-SMA, p-p38 and FN in fibroblasts co-cultured with macrophages as compared with normal macrophages. These findings indicate that the expression of AIF-1 in macrophages is critical for the activation of renal fibroblasts to a profibrotic phenotype. AIF-1 expression was upregulated in macrophages, and may be a novel mechanism linking macrophages to the promotion of RIF via the p38 signaling pathway.

Gene expression profiling to identify the toxicities and potentially relevant human disease outcomes associated with environmental heavy metal exposure

Heavy metals are the most commonly encountered toxic substances that increase susceptibility to various diseases after prolonged exposure. We have previously shown that healthy volunteers living near a mining area had significant contamination with heavy metals associated with significant changes in the expression of some detoxifying genes, xenobiotic metabolizing enzymes, and DNA repair genes. However, alterations of most of the molecular target genes associated with diseases are still unknown. Thus, the aims of this study were to (a) evaluate the gene expression profile and (b) identify the toxicities and potentially relevant human disease outcomes associated with long-term human exposure to environmental heavy metals in mining area using microarray analysis. For this purpose, 40 healthy male volunteers who were residents of a heavy metal-polluted area (Mahd Al-Dhahab city, Saudi Arabia) and 20 healthy male volunteers who were residents of a non-heavy metal-polluted area were included in the study. Total RNA was isolated from whole blood using PAXgene Blood RNA tubes and then reversed transcribed and hybridized to the gene array using the Affymetrix U219 GeneChip. Microarray analysis showed about 2129 genes were identified and differentially altered, among which a shared set of 425 genes was differentially expressed in the heavy metal-exposed groups. Ingenuity pathway analysis revealed that the most altered gene-regulated diseases in heavy metal-exposed groups included hematological and developmental disorders and mostly renal and urological diseases. Quantitative real-time polymerase chain reaction closely matched the microarray data for some genes tested. Importantly, changes in gene-related diseases were attributed to alterations in the genes encoded for protein synthesis. Renal and urological diseases were the diseases that were most frequently associated with the heavy metal-exposed group. Therefore, there is a need for further studies to validate these genes, which could be used as early biomarkers to prevent renal injury.

Allograft inflammatory factor 1 (AIF-1) is a new human adipokine involved in adipose inflammation in obese women

BACKGROUND

Allograft inflammatory factor 1 (AIF-1) is a putative obesity gene. Our aim was to examine the expression of AIF-1 in human white adipose tissue (WAT) in relation to obesity and metabolic phenotypes in women.

METHODS

WAT secretion of AIF-1 was determined in subcutaneous adipose tissue pieces in vitro by ELISA from 5 subjects. mRNA expression of AIF-1 was determined by RT-qPCR in the isolated cell fractions of adipose tissue (n = 5-6 per group), in subcutaneous and visceral WAT pieces from non-obese (n = 12) and obese women (n = 23), and in some subcutaneous WAT also before and after weight reduction (n = 10). Finally, adipose AIF-1 mRNA was related to metabolic phenotypes in 96 subjects with a wide range of BMI.

RESULTS

AIF-1 was secreted in a time dependent fashion from WAT. The major source of AIF-1 was WAT resident macrophages. Expression of AIF-1 was similar in visceral and subcutaneous WAT and was two-fold increased in obese women (P < 0.01). AIF-1 mRNA expression levels were normalized after weight reduction (P < 0.01). Expression of AIF-1 was inversely correlated with insulin sensitivity as assessed by insulin tolerance test (KITT), and circulating levels of adiponectin (P = 0.02), and positively correlated with insulin resistance as estimated by HOMA (=0.0042).

CONCLUSIONS

AIF-1 is a novel adipokine produced mainly by macrophages within human WAT. Its expression is increased in obese women and associates with unfavourable metabolic phenotypes. AIF-1 may play a paracrine role in the regulation of WAT function through cross-talk between macrophages and other cell types within the adipose tissue.