The effects of bisphenol A and bisphenol S on adipokine expression and glucose metabolism in human adipose tissue.

PURPOSE: The environmental endocrine disruptors, bisphenol A (BPA) and bisphenol S (BPS) are associated with the development of type 2 diabetes. We aim to study the effects of BPA or BPS exposure on adipokine expression in human adipose tissue and on adipocyte glucose uptake. METHODS: Human subcutaneous adipose tissue was treated for 24 or 72 h with environmentally-relevant and supraphysiological concentrations of BPA or BPS (1-104 nM). Following exposure, gene expression of proinflammatory cytokines, adipokines, and estrogen receptors was measured in adipose tissue. Glucose uptake and the insulin signalling pathway were analyzed in isolated adipocytes following adipose tissue culture with BPA for 24 h. RESULTS: Adipose tissue treated with BPA for 24 h had reduced expression of the proinflammatory genes (IL6, IL1B, TNFA) and adipokines (ADIPOQ, FABP4). BPA and BPS had no effect on the expression of other proinflammatory genes (IL33), adipokines (LEP), or receptors (ESR1, ESR2) after 72-h exposure. Adipose tissue treated with environmentally-relevant concentrations of BPA for 24 h had reduced insulin-stimulated glucose uptake, without altered gene and protein levels of key insulin signalling pathway markers. CONCLUSIONS: We found that human adipose tissue treated with environmentally-relevant concentrations of BPA for 24 h, but not BPS, reduced expression of proinflammatory genes and adipokines. Furthermore, BPA reduced glucose uptake in adipocytes independently of insulin signalling. Such mechanisms can contribute to the development of insulin resistance associated with BPA exposure.

Targeting perivascular and epicardial adipose tissue inflammation: therapeutic opportunities for cardiovascular disease.

Major shifts in human lifestyle and dietary habits toward sedentary behavior and refined food intake triggered steep increase in the incidence of metabolic disorders including obesity and Type 2 diabetes. Patients with metabolic disease are at a high risk of cardiovascular complications ranging from microvascular dysfunction to cardiometabolic syndromes including heart failure. Despite significant advances in the standards of care for obese and diabetic patients, current therapeutic approaches are not always successful in averting the accompanying cardiovascular deterioration. There is a strong relationship between adipose inflammation seen in metabolic disorders and detrimental changes in cardiovascular structure and function. The particular importance of epicardial and perivascular adipose pools emerged as main modulators of the physiology or pathology of heart and blood vessels. Here, we review the peculiarities of these two fat depots in terms of their origin, function, and pathological changes during metabolic deterioration. We highlight the rationale for pharmacological targeting of the perivascular and epicardial adipose tissue or associated signaling pathways as potential disease modifying approaches in cardiometabolic syndromes.

Visfatin and Rheumatoid Arthritis: Pathogenetic Implications and Clinical Utility.

OBJECTIVE: Analysis and generalization of data related to visfatin involvement in the pathogenesis of inflammation at various stages of rheumatoid arthritis. DATA SYNTHESIS: Visfatin is an adipocytokine which has also been identified in non-adipose tissues. It influences directly on the maturation of B cells, which are involved in autoantibody production and T cell activation. Visfatin can promote inflammation via regulation of pro-inflammatory cytokines including TNF, IL-1ß and IL-6. The concentration of circulating visfatin in rheumatoid arthritis patients is higher compared to healthy individuals. Several studies suggest that visfatin level is associated with rheumatoid arthritis activity, and its elevation may precede clinical signs of the relapse. In murine collagen-induced arthritis, visfatin levels were also found to be elevated both in inflamed synovial cells and in joint vasculature. Visfatin blockers have been shown to confer fast and long-term attenuation of pathological processes; however, most of their effects are transient. Other factors responsible for hyperactivation of the immune system can participate in this process at a later stage. Treatment of rheumatoid arthritis with a combination of these blockers and inhibitors of other mediators of inflammation can potentially improve treatment outcomes compared to current therapeutic strategies. Recent advances in the treatment of experimental arthritis in mice as well as the application of emerging treatment strategies obtained from oncology for rheumatoid arthritis management could be a source of novel adipokine-mediated anti-rheumatic drugs. CONCLUSION: The ongoing surge of interest in anticytokine therapy makes further study of visfatin highly relevant as it may serve as a base for innovational RA treatment.

Adipocytokines in Steatotic Liver Surgery/Transplantation.

Because of the shortage of liver grafts available for transplantation, the restrictions on graft quality have been relaxed, and marginal grafts, such as steatotic livers, are now accepted. However, this policy change has not solved the problem, because steatotic liver grafts tolerate ischemia-reperfusion (I/R) injury poorly. Adipocytokines differentially modulate steatosis, inflammation, and fibrosis and are broadly present in hepatic resections and transplants. The potential use of adipocytokines as biomarkers of the severity of steatosis and liver damage to aid the identification of high-risk steatotic liver donors and to evaluate hepatic injury in the postoperative period are discussed. The hope of finding new therapeutic strategies aimed specifically at protecting steatotic livers undergoing surgery is a strong impetus for identifying the mechanisms responsible for hepatic failure after major surgical intervention. Hence, the most recently described roles of adipocytokines in steatotic livers subject to I/R injury are discussed, the conflicting results in the literature are summarized, and reasons are offered as to why strategic pharmacologic control of adipocytokines has yet to yield clinical benefits. After this, the next steps needed to transfer basic knowledge about adipocytokines into clinical practice to protect marginal livers subject to I/R injury are presented. Recent strategies based on adipocytokine regulation, which have shown efficacy in various pathologies, and hold promise for hepatic resection and transplantation are also outlined.

Adipokines and Vascular Endothelial Growth Factor in Normal Human Breast Tissue in Vivo - Correlations and Attenuation by Dietary Flaxseed.

Exposure to sex steroids increases the risk of breast cancer but the exact mechanisms are yet to be elucidated. Events in the microenvironment are important for carcinogenesis. Diet containing phytoestrogens can affect the breast microenvironment and alter the risk of breast cancer. It has previously been shown that estrogen regulates extracellular levels of leptin, adiponectin, and VEGF in normal breast tissue in vivo. Whether these proteins correlate in breast tissue in vivo or if diet addition of flaxseed, a major source of phytoestrogens in Western diets, alters adipokine levels in breast tissue are unknown. We used microdialysis to sample proteins of normal human breast tissue and abdominal subcutaneous fat in situ in 34 pre-and postmenopausal women. In vitro, co-culture of breast cancer cells and primary human adipocytes was used. In vivo, in normal breast tissue, a significant positive correlation between VEGF and leptin was detected. No correlations were found in fat tissue. Co-culture of adipocytes and breast cancer cells per se increased the secretion of VEGF and leptin and enhanced the effects of estradiol compared to culture of either cell type alone. In vitro, inhibition of VEGF diminished the release of leptin while inhibition of leptin had no influence on VEGF secretion. The levels of leptin decreased and adiponectin increased after a dietary addition of 25 g of flaxseed/day for one menstrual cycle. We conclude that VEGF and leptin correlate significantly in normal human breast tissue in vivo and that dietary addition of flaxseed affect adipokine levels in the breast.

Lipogenesis in myoblasts and its regulation of CTRP6 by AdipoR1/Erk/PPARγ signaling pathway.

The induced lipogenesis and its regulation in C2C12 myoblasts remain largely unclear. Here, we found that the cocktail method could significantly induce lipogenesis through regulating lipid metabolic genes and Erk1/2 phosphorylation in myoblasts. Meanwhile, the expression and secretion of CTRP6 were increased during ectopic lipogenesis. Moreover, CTRP6 knockdown down-regulated the levels of lipogenic genes and phosphorylated Erk1/2 (p-Erk1/2) in the early lipogenic stage, whereas up-regulated p-Erk1/2 in the terminal differentiation. Interestingly, the effect of CTRP6 siRNA was attenuated by U0126 (a special p-Erk1/2 inhibitor) in myoblasts. Furthermore, AdipoR1, not AdipoR2, was first identified as a receptor of CTRP6 during the process of mitotic clonal expansion. Collectively, we suggest that CTRP6 mediates the ectopic lipogenesis through AdipoR1/Erk/PPARγ signaling pathway in myoblasts. Our findings will shed light on the novel biological function of CTRP6 during myoblast lipogenesis and provide a hopeful direction of improving meat quality of domestic animal by lipogenic regulation in skeletal muscle myoblasts.

Knockdown of CTRP6 inhibits adipogenesis via lipogenic marker genes and Erk1/2 signalling pathway.

C1q/tumor necrosis factor-related protein 6 (CTRP6), an adipose-tissue secretory factor, plays an important role in inflammatory reaction and carcinogenesis. However, the biological function of CTRP6 in adipogenesis remains unclear. In this study, we examined the effects of CTRP6 knockdown on lipogenesis of 3T3-L1 adipocytes. The results showed that after 3T3-L1 adipocytes transfected with anti-CTRP6 small interfering RNA (siRNA), not only levels of secreted CTRP6 protein in the culture medium but also the expression level of the CTRP6 protein in the 3T3-L1 adipocytes was significantly reduced (P < 0.01). In addition, the number of lipid droplets in the adipocytes was reduced, as well as the OD values reflecting the fat content being significantly decreased (P < 0.01). Meanwhile the levels of adipogenic markers, including peroxisome proliferator activated receptor γ (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), CCAAT/enhancer-binding protein ß (C/EBPß) and adipocyte fatty acid-binding protein 4 (aP2), were decreased after treatment with anti-CTRP6 siRNA, whereas the expression of adipose triglyceride lipase (ATGL) and triacylglycerol hydrolase (TGH) were increased. Furthermore, after transfection, activity of phosphorylated Erk1/2 (p-Erk1/2) was inhibited in the early stage of differentiation, but in terminal differentiation of adipocytes, its activity was activated. Taken together, the results indicate that knockdown of CTRP6 can inhibit adipogenesis of 3T3-L1 adipocytes through lipogenic marker genes and Erk1/2 signaling pathway.

Comparative effects of metformin and pioglitazone on YKL-40 in type 2 diabetes: a randomized clinical trial.

PURPOSE: Metformin and pioglitazone are believed to exert their long-term benefits by means of amelioration of chronic low-grade inflammation, a key event in development of diabetes and its long-term complications. The present trial was designed to investigate the comparative efficacy of the two anti-diabetes medications on serum concentrations of YKL-40, a novel marker of inflammation. METHODS: In a parallel-group, open-label, randomized trial setting (ClinicalTrials.gov Identifier No. NCT01521624), 84 newly diagnosed, medication-naïve type 2 diabetes patients were assigned to metformin 1,000 mg daily (n = 42) or pioglitazone 30 mg daily (n = 42). Serum concentrations of YKL-40, along with highly sensitive C-reactive protein, indices of glycemic control and lipid profile were measured at baseline and after 3 months. RESULTS: In the analyzed sample (metformin = 40, pioglitazone = 42), both medications were equally effective with regard to control of hyperglycemia, and hsCRP reduction (p > 0.05). However, metformin caused a significant decline in weight (p = 0.005), BMI (p = 0.004), and total cholesterol levels (p = 0.028) of the patients. Metformin also significantly reduced YKL-40 concentrations after 3 months (1.90 ± 17 vs. 1.66 ± 0.15 µg/L, p = 0.019). The amount of change in the pioglitazone arm did not reach statistical significance (2.18 ± 0.14 vs. 2.25 ± 0.16 µg/L, p = 0.687). When compared, metformin was significantly more effective than pioglitazone with respect to YKL-40 reduction in both univariate (p = 0.020, effect size = 6.7%) and multivariate models (p = 0.047, effect size = 5.7%). CONCLUSIONS: Metformin is more effective in reduction of YKL-40 concentration in short term and the effect seems to be independent of degree of glycemic control, or hsCRP reduction.

YKL-40 downregulation is a key factor to overcome temozolomide resistance in a glioblastoma cell line.

The frequent recurrence of glioblastoma multiforme (GBM) after standard treatment with temozolomide (TMZ) is a crucial issue to be solved in the clinical field. O6­methylguanine­DNA methyltransferase (MGMT) is considered one of the major mechanisms involved in TMZ resistance. However, some important mechanisms for TMZ resistance other than MGMT have recently been identified. In the present study, we established a TMZ-resistant (TMZ-R) U87 glioblastoma cell line in vitro and in vivo and investigated novel targeting molecules other than MGMT in those cells. The TMZ-R U87 glioblastoma cell line was established in vitro and in vivo. TMZ-R U87 cells showed a more invasive activity and a shorter survival time in vivo. Gene expression analysis using DNA microarray and quantitative PCR (qPCR) demonstrated that YKL­40, MAGEC1 and MGMT mRNA expression was upregulated 100-, 83- and 6-fold, respectively in the TMZ-R U87 cell line. Western blot analysis and qPCR demonstrated that STAT3 phosphorylation, STAT3 target genes and stem cell and mesenchymal marker genes were upregulated to a greater extent in the TMZ­resistant cell line. Notably, short hairpin (sh)RNA­based inhibition against the YKL­40 gene resulted in moderate growth inhibition in the resistant cells in vitro and in vivo. Additionally, YKL­40 gene inhibition exhibited significant suppression of the invasive activity and particularly partially restored the sensitivity to TMZ. Therefore, YKL­40 may be a novel key molecule in addition to MGMT, that is responsible for TMZ resistance in glioblastoma cell lines and could be a new target to overcome TMZ resistance in recurrent glioblastomas in the future.

Novel methylxanthine derivative-mediated anti-inflammatory effects in inflammatory bowel disease.

Family 18 chitinases have a binding capacity with chitin, a polymer of N-acetylglucosamine. Recent studies strongly suggested that chitinase 3-like 1 (CHI3L1, also known as YKL-40) and acidic mammalian chitinase, the two major members of family 18 chitinases, play a pivotal role in the pathogenesis of inflammatory bowel disease (IBD), bronchial asthma and several other inflammatory disorders. Based on the data from high-throughput screening, it has been found that three methylxanthine derivatives, caffeine, theophylline, and pentoxifylline, have competitive inhibitory effects against a fungal family 18 chitinase by specifically interacting with conserved tryptophans in the active site of this protein. Methylxanthine derivatives are also known as adenosine receptor antagonists, phosphodiesterase inhibitors and histone deacetylase inducers. Anti-inflammatory effects of methylxanthine derivatives have been well-documented in the literature. For example, a beneficial link between coffee or caffeine consumption and type 2 diabetes as well as liver cirrhosis has been reported. Furthermore, theophylline has a long history of being used as a bronchodilator in asthma therapy, and pentoxifylline has an immuno-modulating effect for peripheral vascular disease. However, it is still largely unknown whether these methylxanthine derivative-mediated anti-inflammatory effects are associated with the inhibition of CHI3L1-induced cytoplasmic signaling cascades in epithelial cells. In this review article we will examine the above possibility and summarize the biological significance of methylxanthine derivatives in intestinal epithelial cells. We hope that this study will provide a rationale for the development of methylxanthine derivatives, in particular caffeine, -based anti-inflammatory therapeutics in the field of IBD and IBD-associated carcinogenesis.

The Novel Secreted Adipokine WNT1-inducible Signaling Pathway Protein 2 (WISP2) Is a Mesenchymal Cell Activator of Canonical WNT.

WNT1-inducible-signaling pathway protein 2 (WISP2) is primarily expressed in mesenchymal stem cells, fibroblasts, and adipogenic precursor cells. It is both a secreted and cytosolic protein, the latter regulating precursor cell adipogenic commitment and PPARγ induction by BMP4. To examine the effect of the secreted protein, we expressed a full-length and a truncated, non-secreted WISP2 in NIH3T3 fibroblasts. Secreted, but not truncated WISP2 activated the canonical WNT pathway with increased ß-catenin levels, its nuclear targeting phosphorylation, and LRP5/6 phosphorylation. It also inhibited Pparg activation and the effect of secreted WISP2 was reversed by the WNT antagonist DICKKOPF-1. Differentiated 3T3-L1 adipose cells were also target cells where extracellular WISP2 activated the canonical WNT pathway, inhibited Pparg and associated adipose genes and, similar to WNT3a, promoted partial dedifferentiation of the cells and the induction of a myofibroblast phenotype with activation of markers of fibrosis. Thus, WISP2 exerts dual actions in mesenchymal precursor cells; secreted WISP2 activates canonical WNT and maintains the cells in an undifferentiated state, whereas cytosolic WISP2 regulates adipogenic commitment.

Therapeutic targets for rheumatoid arthritis: Progress and promises.

Recent therapeutic advancements in understanding of molecular and cellular mechanisms of rheumatoid arthritis (RA) have highlighted the strategies that aim to inhibit the harmful effects of up-regulated cytokines or other inflammatory mediators and to inhibit their associated signaling events. The utility of cytokine as therapeutic targets in RA has been unequivocally demonstrated by the success of tumor necrosis factor (TNF)-α blockade in clinical practice. Partial and non-responses to TNF-α blocking agents, however, together with the increasing clinical drive to remission induction, requires that further therapeutic targets be identified. Numerous proinflammatory mediators with their associated cell signaling events have now been demonstrated in RA, including interleukin (IL)-1 and IL-12 superfamilies. Continued efforts are ongoing to target IL-6, IL-15 and IL-17 in clinical trials with promising data emerging. In the present review, we focus on IL-7, IL-18, IL-32 and IL-10 family of cytokines (IL-19, IL-20 and IL-22) as they are implicated in contributing to the pathogenesis of RA, which could be targeted and offer new therapeutic options for RA therapy. Recent evidences also suggest that multiligand receptor for advanced glycation end products (RAGE), several adipokines and various components of immune system play a critical role in the pathophysiology of RA; therefore we have also highlighted them as therapeutic targets for RA therapy. Components of subcellular pathways, involve in nuclear transcription factor (NF)-κB, mitogen-activated protein kinases (MAPKs) and the Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway have also been discussed and offer several novel potential therapeutic opportunities for RA.

n-6:n-3 PUFA ratio is involved in regulating lipid metabolism and inflammation in pigs.

The objective of the present study was to investigate the optimal dietary n-6:n-3 PUFA ratios that regulate lipid metabolism and inflammation in pigs. A total of ninety-six cross-bred (Large White × Landrace) growing-finishing pigs (73·8 (SEM 1·6) kg) were chosen and fed one of the four isoenergetic diets with n-6:n-3 PUFA ratios of 1:1, 2·5:1, 5:1 and 10:1. The growth performance of pigs fed the diet with an n-6:n-3 PUFA ratio of 5:1 was the best, but the group fed the diet with an n-6:n-3 PUFA ratio of 1:1 had the highest muscle mass and the lowest adipose tissue mass (P< 0·05). The concentrations of IL-6 and IL-1ß of pigs fed the diet with an n-6:n-3 PUFA ratio of 1:1 were decreased compared with those of the other groups (P< 0·05). The concentration of adiponectin of pigs fed the diet with an n-6:n-3 PUFA ratio of 1:1 was also markedly decreased, but the concentration of leptin was increased compared with that of the groups fed the diets with n-6:n-3 PUFA ratios of 5:1 and 10:1 (P< 0·05). Additionally, the optimal dietary ratios of n-6:n-3 PUFA of 1:1 and 5:1 markedly suppressed the expression levels of lipid metabolism-related genes and proteins such as phosphoinositide-3-kinase-α, fatty acid transport protein-1 and PPARγ. They also significantly suppressed the expression levels of the inflammatory cytokines IL-1ß, TNF-α and IL-6. The results indicated that the optimal n-6:n-3 PUFA ratios of 1:1 and 5:1 exerted beneficial effects on lipid metabolism and inflammatory system, leading to the availability of more energy and nutrients for high performance and homeostatic pathways.

The role of S100B in the interaction between adipocytes and macrophages.

OBJECTIVE: The S100 calcium binding protein B (S100B) implicated in brain inflammation acts via the receptor of advanced glycation end products (RAGE) and is also secreted from adipocytes. We investigated the role of S100B in the interaction between adipocytes and macrophages using a cell-culture model. DESIGN AND METHODS: RAW264.7 macrophages (RAW) were stimulated by recombinant S100B to observe alterations in TNF-α and M1 markers; 3T3-L1 adipocytes (L1) were stimulated by TNF-α to examine S100B secretion. RAW and L1 were then mutually stimulated with conditioned media of each other, or co-cultured. The effects of S100B silencing or a RAGE-neutralizing antibody were also investigated. RESULTS: S100B upregulated TNF-α and M1 markers in RAW, and TNF-α augmented S100B secretion from L1. L1 conditioned media stimulated TNF-α secretion from RAW, and RAW conditioned media increased S100B secretion from L1. The co-culture of RAW and L1 increased TNF-α, S100B, and the expression of M1 markers and the MCP-1 receptor CCR2. The silencing of S100B or RAGE neutralization significantly ameliorated TNF-α hypersecretion from RAW that were stimulated with L1 conditioned media. CONCLUSIONS: Thus, S100B as an adipokine may play a role in the interaction between adipocytes and macrophages to establish a vicious paracrine loop.

Oral caffeine administration ameliorates acute colitis by suppressing chitinase 3-like 1 expression in intestinal epithelial cells.

BACKGROUND: The initial trigger of inflammatory bowel disease (IBD) can be partly attributed towards the interaction and invasion of intestinal epithelial cells (IECs) and submucosal compartments. Identifying safe and economical methods to block these interactions may help prevent the onset of early colitis. Chitinase 3-like 1 (CHI3L1) is an inducible host protein that facilitates bacterial attachment and invasion on/into IECs. Therefore, we test the hypothesis of inhibiting CHI3L1 using the pan-chitinase inhibitor caffeine to reduce the likelihood of early colitis onset. METHODS: IEC lines were treated with caffeine (2.5 or 5 mM) and analyzed for CHI3L1 expression and the impact on bacterial invasion. In vivo, mice were treated with 2.5 mM caffeine and induced with 3.5 % dextran sulfate sodium (DSS)-mediated colitis and subsequently analyzed colitis development. RESULTS: In vitro, caffeine treatment in IEC lines down-regulated CHI3L1 mRNA expression, which resulted in the reduction of bacterial invasion in a caffeine dose-dependent manner. In vivo, mice treated with caffeine displayed a delayed response towards DSS-induced colitis, characterized by lower body weight loss, clinical and histological scores. Bacterial translocation into other organs and pro-inflammatory cytokines production were also reduced in the caffeine-treated mice with DSS-induced colitis. Caffeine treatment also resulted in the loss of CHI3L1-associated AKT signaling pathway activation both in vitro and in vivo. CONCLUSION: Development of acute colitis is reduced upon caffeine treatment. The mechanism involves the down-regulation of CHI3L1 expression and its associated bacterial interaction effect. Therefore, caffeine is proposed as a safe and economical candidate for successful IBD management.

CHI3L1 plays a role in cancer through enhanced production of pro-inflammatory/pro-tumorigenic and angiogenic factors.

Elevated serum levels of a glycoprotein known as chitinase-3-like protein 1 (CHI3L1) have been correlated with poor prognosis and shorter survival of patients with cancer and inflammatory diseases. The biological and physiological functions of CHI3L1 in cancer have not yet been completely elucidated. In this review, we describe the role of CHI3L1 in inducing pro-inflammatory/pro-tumorigenic and angiogenic factors that could promote tumor growth and metastasis.

Losartan ameliorates renal injury, hypertension, and adipocytokine imbalance in 5/6 nephrectomized rats.

The mechanisms underlying insulin sensitivity and fat tissue distribution in chronic renal insufficiency remain unclear. Previous studies have shown the benefits of angiotensin II receptor blockers on moderately nourished to well-nourished patients with the metabolic syndrome. The current study explored the effect of losartan, the first selective angiotensin II receptor blocker, on insulin sensitivity and visceral fat tissue distribution in a 5/6 nephrectomized (N) rat model and investigated the expression of adipose tissue adipocytokines. Male Sprague-Dawley rats (200 g to 250 g) were subjected to 5/6 nephrectomy, and the adipocytes isolated from the visceral fat tissues were then studied. Results showed that desmin expression was significantly suppressed and systolic blood pressure was successfully normalized in the losartan-administered (NA) group. The weight of the visceral fat pad remarkably decreased in the N and NA groups (100 mg/500 ml drinking water) compared with the control group. The weight did not decrease further in the NA group compared with the N group. Insulin resistance was more remarkable in the N group compared with the control and NA groups. Moreover, the adipose tissue expression of adiponectin and leptin was downregulated whereas that of resistin was upregulated in the N group compared with the control group. However, the adiponectin, leptin, and resistin adipose tissue expression returned to their basal values in the NA group. These findings indicated that losartan administration ameliorated renal injury, systolic blood pressure, and adipocytokine imbalance of the adipose tissue in chronic renal insufficiency. Insulin sensitivity was not improved.

Simvastatin inhibits ox-LDL-induced inflammatory adipokines secretion via amelioration of ER stress in 3T3-L1 adipocyte.

Adipocytes behave as a rich source of pro-inflammatory cytokines including tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein 1 (MCP-1). Endoplasmic reticulum (ER) stress in adipocytes can alter adipokines secretion and induce inflammation. The aim of this study is to evaluate the effect of simvastatin on the ox-LDL-induced ER stress and expression and secretion of TNF-α and MCP-1 in 3T3-L1 adipocytes. Differentiated adipocytes were treated with various concentrations of ox-LDL (0-100 µg/ml) for 24h with or without simvastatin pre-treatment. The protein expressions of ER stress markers, glucose-regulated protein 78 (GRP78) and C/EBP homology protein (CHOP), were determined by Western blot analysis. The mRNA expressions of TNF-α and MCP-1 were measured by real-time PCR. The protein release of TNF-α and MCP-1 in culture medium were evaluated by ELISA. Ox-LDL treatment led to significant up-regulation of GRP78 and CHOP in dose-dependent manner. The expressions of TNF-α and MCP-1 were dose-dependently increased at mRNA and protein levels after ox-LDL intervention. The effects of ox-LDL on adipocytes were abolished by pre-treatment with 4-phenylbutyrate (4-PBA), a chemical chaperone known to ameliorate ER stress. Simvastatin could inhibit ox-LDL-induced ER stress and reduce the expression of TNF-α and MCP-1 at mRNA and protien level in dose dependent manner. In conclusion, ox-LDL can stimulate the expression and secretion of TNF-α and MCP-1 through its activation of ER stress in adipocytes. Simvastatin might exert direct anti-inflammatory effects in adipocytes through amelioration of ER stress.

The novel adipokine C1q/TNF-related protein-3 is expressed in human adipocytes and regulated by metabolic and infection-related parameters.

BACKGROUND: The growing family of C1Q/TNF-related proteins is characterized by structural homologies to the anti-inflammatory adipokine adiponectin. CTRP-3 was recently reported to function as an anti-inflammatory LPS-antagonist in vitro. MATERIAL AND METHODS: Human subcutaneous and visceral adipocytes and murine 3T3-L1 adipocytes were used for analysis of CTRP-3 expression and function. Western blot analysis of CTRP-3, siRNA mediated knockdown of CTRP-3, Oil red O staining, assessment of basal and epinephrine-induced lipolysis, ELISA-based measurements of supernatant chemokines, recombinant CTRP-3 protein expression, and Staphylococcus aureus (S. aureus) infection assays were used. RESULTS: CTRP-3 is expressed in subcutaneous and visceral adipocytes. CTRP-3 is positively regulated by insulin, whereas chronic LPS-exposure inhibits terminal adipocyte differentiation and CTRP-3 expression. Intracellular infection of adipocytes by S. aureus also decreases CTRP-3 expression. As demonstrated by siRNA-mediated cellular knockdown of CTRP-3 in adipocytes, CTRP-3 regulates resistin secretion and lipolysis. CONCLUSION: CTRP-3 is expressed in human adipocytes and plays an important role in adipocyte physiology such as lipolysis and adipokine secretion. Both, metabolic factors and infection/inflammation-related factors regulate CTRP-3 expression.