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Understanding the complex interactions between metabolism and the immune system ("metaflammation") is crucial for the identification of key immunomodulatory factors as potential therapeutic targets in obesity and in cardiovascular diseases. Cathelicidin antimicrobial peptide (CAMP) is an important factor of innate immunity and is expressed in adipocytes. CAMP, therefore, might play a role as an adipokine in metaflammation and adipose inflammation. TNFα, cell-free nucleic acids (cfDNA), and toll-like receptor (TLR) 9 are components of the innate immune system and are functionally active in adipose tissue. The aim of the present study was to investigate the impact of TNFα and cfDNA on CAMP expression in adipocytes. Since cfDNA acts as a physiological TLR9 agonist, we additionally investigated TLR9-mediated CAMP regulation in adipocytes and adipose tissue. CAMP gene expression in murine 3T3-L1 and human SGBS adipocytes and in murine and human adipose tissues was quantified by real-time PCR. Adipocyte inflammation was induced in vitro by TNFα and cfDNA stimulation. Serum CAMP concentrations in TLR9 knockout (KO) and in wildtype mice were quantified by ELISA. In primary adipocytes of wildtype and TLR9 KO mice, CAMP gene expression was quantified by real-time PCR. CAMP gene expression was considerably increased in 3T3-L1 and SGBS adipocytes during differentiation. TNFα significantly induced CAMP gene expression in mature adipocytes, which was effectively antagonized by inhibition of PI3K signaling. Cell-free nucleic acids (cfDNA) significantly impaired CAMP gene expression, whereas synthetic agonistic and antagonistic TLR9 ligands had no effect. CAMP and TLR9 gene expression were correlated positively in murine and human subcutaneous but not in intra-abdominal/visceral adipose tissues. Male TLR9 knockout mice exhibited lower systemic CAMP concentrations than wildtype mice. CAMP gene expression levels in primary adipocytes did not significantly differ between wildtype and TLR9 KO mice. These findings suggest a regulatory role of inflammatory mediators, such as TNFα and cfDNA, in adipocytic CAMP expression as a novel putative molecular mechanism in adipose tissue innate immunity. [ABSTRACT FROM AUTHOR]

Recent investigation has revealed the significant role of Cathelicidin antimicrobial peptide (CAMP) in infection defense and innate immunity processes in adipose tissue. Meanwhile, knowledge of its regulation and functions in metabolic contexts as an adipokine remains sparce. The present study investigated the postprandial regulation of circulating CAMP levels during oral glucose tolerance tests (OGTTs). Eighty-six metabolically healthy volunteers participated in a standardized 75 g-2 h-OGTT setting. The effects of exogenous glucose, insulin, and incretins on CAMP expression in human adipocyte culture (cell-line SGBS) were studied in vitro. CAMP concentrations in blood serum samples were measured by ELISA techniques and adipocyte gene expression levels were quantified by real-time PCR. Of note, base-line CAMP serum quantities were negatively correlated with HDL cholesterol levels as well as with the anti-inflammatory adipokine adiponectin. During the 2 h following glucose ingestion, a significant rise in circulating CAMP concentrations was observed in considerable contrast to reduced quantities of fatty acid binding proteins (FABP) 2 and 4 and dipeptidyl peptidase 4 (DPP4). In SGBS adipocytes, neither differing glucose levels nor insulin or incretin treatment significantly induced CAMP mRNA levels. According to our data, glucose represents a positive postprandial regulator of systemic CAMP. This effect apparently is not mediated by the regulatory impact of glucose metabolism on adipocyte CAMP expression. [ABSTRACT FROM AUTHOR]

The anti-inflammatory adipokine CTRP-3 might affect innate immune reactions such as NOD1. The impact of CTRP-3 on NOD1-mediated inflammation in adipocytes and monocytic cells as well as on NOD1 expression was investigated. Murine 3T3-L1 pre-adipocytes and adipocytes as well as human THP-1 monocyte-like cells were co-stimulated with the synthetic NOD1 agonist Tri-DAP and recombinant CTRP-3. Gonadal adipose tissue and primary adipocytes were obtained from a murine model carrying a knockout (KO) of CTRP-3 in adipocytes but not in stroma-vascular cells. Wildtype mice with lipopolysaccharide (LPS)-induced elevated NOD1 expression were treated with CTRP-3. Secreted inflammatory cytokines in cell supernatants were measured by ELISA and mRNA levels were quantified by RT-PCR. Pro-inflammatory chemokine and cytokine secretion (MCP-1, RANTES, TNFα) was induced by NOD1 activation in adipocytes and monocyte-like cells, and MCP-1 and RANTES release was effectively inhibited by pre-incubation of cells with CTRP-3. CTRP-3 also antagonized LPS-triggered induction of NOD1 gene expression in murine adipose tissue, whereas adipocyte CTRP-3 deficiency upregulated NOD1 expression in adipose tissue. CTRP-3 is an effective antagonist of peptidoglycan-induced, NOD1-mediated inflammation and of LPS-induced NOD1 expression. Since basal NOD1 expression is increased by adipocyte CTRP-3 deficiency, there have to be also inflammation-independent mechanisms of NOD1 expression regulation by CTRP-3. [ABSTRACT FROM AUTHOR]

Recent data argue for a pro-inflammatory role of CAMP (cathelicidin antimicrobial peptide) in adipocytes and adipose tissue (AT) and for regulatory circuits involving TLRs. In order to investigate regulatory effects of TLR2 and TLR4, 3T3-L1 adipocytes were stimulated with TLR2 agonistic lipopeptide MALP-2 and with TLR4 agonist LPS in presence or absence of signal transduction inhibitors. CAMP gene expression was analysed by quantitative real-time PCR in adipocytes and in murine AT compartments and cellular subfractions. CAMP expression was higher in gonadal than in subcutaneous AT and there was a gender-specific effect with higher levels in males. Adipocytes had higher CAMP expression than the stroma-vascular cell (SVC) fraction. MALP-2 up-regulated CAMP expression significantly, mediated by STAT3 and PI3K and potentially (non-significant trend) by NF-κB and MAPK, but not by raf-activated MEK-1/-2. Moreover, LPS proved to act as a potent inducer of CAMP via NF-κB, PI3K and STAT3, whereas specific inhibition of MAPK and MEK-1/-2 had no effect. In conclusion, activation of TLR2 and TLR4 by classical ligands up-regulates adipocyte CAMP expression involving classical signal transduction elements. These might represent future drug targets for pharmacological modulation of CAMP expression in adipocytes, especially in the context of metabolic and infectious diseases. [ABSTRACT FROM AUTHOR]

Adipocytes express various pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) and actively participate in anti-bacterial and anti-viral host defence. Obesity is associated with adipose tissue PRR expression. The potential role of Toll-like receptor 9 (TLR9) in adipocytes has not yet been investigated. Here, we evaluated TLR9 expression during adipocyte differentiation (AD) of 3T3-L1 adipocytes, in primary murine adipocytes and in different murine and human adipose tissue depots by real-time PCR, immunocytochemistry and immunohistochemistry. TLR9 expression was inhibited using specific siRNA-mediated knockdown, and TLR9 signaling was induced using specific class A, B and C agonistic CpG-oligodeoxynucleotide (ODN) treatment vs ODN controls in 3T3-L1 adipocytes and in primary murine adipocytes from Tlr9wt/wt vs Tlr9-/- mice. We found that TLR9 gene expression is induced during AD and that T LR9 protein is expressed in murine gonadal and human visceral adipocytes. AD depends on intact TLR9 expression. Tlr9-/- mice demonstrate significantly reduced adiponectin serum levels, while siRNAmediated TLR9 knockdown led to reduced adiponectin mRNA expression in adipocytes. TLR9 ligands (CpG-ODNs) inhibit pro-inflammatory resistin secretion in mature 3T3-L1 adipocytes. Tlr9-/- as compared to Tlr9wt/wt adipocytes exhibit increased resistin and MCP1 secretion and reduced adiponectin secretion into cell culture supernatants, while TLR9 ligands (ODNs) show differential effects in Tlr9-/- vs Tlr9wt/wt primary murine adipocytes. TLR9 expression is significantly increased in visceral compared to subcutaneous adipose tissue depots in non-diabetic obese patients and correlates with systemic resistin levels in a compartment-specific manner. Thus, adipocytic TLR9 is a putative, new protective factor during (obesity-associated) adipose tissue inflammation. [ABSTRACT FROM AUTHOR]

Background C1q/ TNF-related protein-3 ( CTRP-3) represents a novel anti-inflammatory and antidiabetic adipokine secreted by adipose tissue. The physiological and postprandial regulation of CTRP-3 remains obscure and it is not known whether CTRP-3 is permeable to the brain. The postprandial regulation of CTRP-3 during an oral glucose tolerance test ( n = 100) and an oral lipid tolerance test ( n = 100) in humans was investigated. Moreover, CTRP-3 concentrations were measured in paired serum and cerebrospinal fluid ( CSF) samples of patients ( n = 270) undergoing neurological evaluation. The expression of CTRP-3 mRNA was investigated in adipocytes upon stimulation with glucose, sex hormones and a broad panel of fatty acids. Materials and methods Serum and CSF CTRP-3 concentrations were measured by ELISA. 3T3-L1 adipocytes were used for stimulation experiments. CTRP-3 mRNA expression was quantified by using real-time PCR analysis. Results CTRP-3 is present in human cerebrospinal fluid with a mean CSF/serum ratio of 110 ± 64 × 10−3. CTRP-3 is not regulated postprandially by carbohydrates or lipids in the healthy state. Females have slightly higher levels of CTRP-3 when compared to males. A significant and positive correlation of CTRP-3 to LDL cholesterol serum levels is reproducible in several cohorts and deserves further mechanistic investigation. Whereas glucose concentrations do not influence CTRP-3 mRNA expression in 3T3-L1 adipocytes in vitro, fatty acids differentially modulate CTRP-3 expression. Conclusions The novel adipokine CTRP-3 is detectable in human cerebrospinal fluid (proof of principle). Due to its blood-brain barrier permeability, CTRP-3 represents a novel putative candidate for a physiological regulator molecule affecting central nervous functions. [ABSTRACT FROM AUTHOR]

Background and aim: The C1q/TNF-related protein (CTRP) family represents a growing family of adiponectin paralogous proteins. CTRP-5 was detected in adipose tissue of mice and plays a role in the context of the metabolic syndrome. It was the aim to investigate the detailed expression profile of CTRP-5 in a variety of adipocytic cells and to determine whether CTRP-5 circulates in human serum. Moreover, regulation and function of CTRP-5 was studied in the context of adi-pocyte biology. Material and methods: CTRP-5 serum levels were measured in 50 healthy subjects by ELISA. Genotype analysis was performed by direct sequencing in 200 probands. CTRP-5 mRNA and protein expression was analyzed by RT-PCR, realtime RT-PCR and Western blot. Recombinant CTRP-5 and fatty acids were used for stimulation experiments in 3T3-L1 adipocytes. siRNA-mediated knockdown of CTRP-3 was performed during adipocyte differentiation. Results: CTRP-5 mRNA and protein was strongly expressed in a wide variety of human and murine adipocytic cells and was induced during adipocyte differentiation. Saturated fatty acids increased CTRP-5 expression in adipocytes. siRNA-mediated cellular knockdown of CTRP-3 in adipocytes resulted in an upregulation of CTRP-5 expression. CTRP-5 inhibited the release of resistin and adiponectin dose-dependently. CTRP-5 circulates abundantly in human sera with a broad interindividual variation. The SNP 1014 T/A was not associated with type 2 diabetes mellitus in 200 Caucasian probands. Conclusions: CTRP-5 might be a novel adipok-ine that circulates abundantly in human sera. CTRP-5 is functionally involved in adipocyte biology and there might exist a counter-regulatory connection with its family member, CTRP-3. [ABSTRACT FROM AUTHOR]

OBJECTIVES:Adipocytes of peripancreatic and intrapancreatic adipose tissue secret adipocytokines such as leptin, adiponectin, and resistin. For resistin, a role as an early predictor of peripancreatic necrosis and clinical severity in acute pancreatitis has been reported. It was the aim of this study to investigate whether the adipocytokine visfatin is able to serve as an early marker predicting peripancreatic necrosis and clinical severity.METHODS:A total of 50 patients (20 females and 30 males) with acute pancreatitis were included in this noninterventional, prospective, and monocentric cohort study on diagnostic accuracy. Clinical severity was classified by the Ranson score and APACHE-II (Acute Physiology and Chronic Health Evaluation II) score. Pancreatic and peripancreatic necrosis were quantified by the computed tomography-based Balthazar score, the Schroeder score, and the pancreatic necrosis score. Visfatin was measured at admission and daily for 10 days by enzyme-linked immunosorbent assay (ELISA).RESULTS:Visfatin values were significantly and positively correlated with clinical severity (APACHE-II score and Ranson score) and with clinical end points such as death and need for interventions. Admission visfatin levels were significantly elevated in patients with higher pancreatic and extrapancreatic necrosis scores. It was shown by receiver operator characteristics that admission visfatin concentration provides a positive predictive value of 93.3% in predicting the extent of peripancreatic necrosis (area under the curve (AUC): 0.89, P<0.001, sensitivity: 93.3%, specificity: 81.8%, likelihood ratio: 5.1, post-test probability: 93%) by using a cutoff value of 1.8 ng/ml.CONCLUSIONS:Admission visfatin concentration serves as an early predictive marker of peripancreatic necrosis and clinical severity in acute pancreatitis. Visfatin may have potential for clinical use as a new and diagnostic serum marker. [ABSTRACT FROM AUTHOR]

OBJECTIVES:Peripancreatic necrosis determines clinical severity in acute pancreatitis. Early markers predicting peripancreatic necrosis and clinical severity are lacking. Because adipocytes of peripancreatic adipose tissue secret highly active adipocytokines, the aim of the study was to investigate whether adipocytokines are able to serve as early markers predicting peripancreatic necrosis and clinical severity.METHODS:A total of 50 patients (20 women, 30 men) with acute pancreatitis were included in this noninterventional, prospective, and monocentric cohort study on diagnostic accuracy. Clinical severity was classified by the Ranson score and the APACHE (Acute Physiology And Chronic Health Evaluation) II score. Pancreatic and peripancreatic necrosis were quantified by using the computed tomography-based Balthazar score, the Schroeder score, and the pancreatic necrosis score. Adiponectin, leptin, and resistin were measured at admission and daily for at least 10 days by enzyme-linked immunosorbent assay.RESULTS:In contrast to admission C-reactive protein values, admission resistin values were significantly correlated with clinical severity and even with clinical end points such as death and need for interventions. Admission resistin levels were significantly elevated in patients with higher pancreatic and extrapancreatic necrosis scores. It was shown by receiver-operator characteristics that admission resistin concentration provides a positive predictive value of 89% in predicting the extent of peripancreatic necrosis (area under the curve, 0.8; P=0.002; sensitivity, 80%; specificity, 70%) by using a cutoff value of 11.9 ng/ml.CONCLUSIONS:Admission resistin concentration serves as an early predictive marker of peripancreatic necrosis and clinical severity in acute pancreatitis. Resistin may have potential for clinical use as a new and diagnostic serum marker. [ABSTRACT FROM AUTHOR]

Background Increasing data support the hypothesis of a local and systemic crosstalk between adipocytes and monocytes mediated by fatty acids. The aim of this study was to characterize the immunomodulatory effects of a large panel of fatty acids on cytokines and chemokines in monocytic THP-1 cells and primary human monocytes. We tested whether anti-inflammatory fatty acids are able to inhibit the binding of lipopolysaccharide (LPS) to its receptor, toll-like receptor/MD-2 (TLR4/MD-2). Materials and methods Resistin, monocyte chemoattractant protein-1 (MCP-1) and tumour necrosis factor (TNF) were measured by enzyme-linked immunosorbent assay. Proteins were analysed by Western blot. A designed Flag-tagged TLR4/MD-2 fusion protein (LPS trap) was used to investigate the effect of fatty acids on binding of LPS to its receptor. In 30 patients with type 2 diabetes mellitus (T2D), the correlation of serum triglyceride levels with LPS-induced monocyte activation was analysed. Results Eleven fatty acids investigated exerted differential effects on the monocytic release of cytokines and chemokines. Eicosapentaenoic acid had potent anti-inflammatory effects on human primary monocytes and THP-1 cells; 100 and 200 μM eicosapentaenoic acid dose-dependently inhibited LPS binding to the LPS trap. LPS-induced release of monocytic MCP-1 and TNF was significantly and positively correlated with serum triglyceride levels in 30 patients with T2D. Conclusions Monocytic activation is differentially regulated by fatty acids and depends on triglyceride levels in T2D. The main finding of the present study shows that eicosapentaenoic acid inhibits the specific binding of LPS to TLR4/MD-2. Eicosapentaenoic acid represents a new anti-inflammatory LPS-antagonist. [ABSTRACT FROM AUTHOR]

Background: Adiponectin is a circulating protein with hepatoprotective effects. Aims: To study the relationship of excessive alcohol consumption and serum adiponectin levels (SAL). Patients and Methods: The SAL were determined in (i) heavy drinkers without advanced liver damage during the course of alcohol withdrawal, (ii) patients with chronic hepatitis C virus (HCV) infection, (iii) patients with alcohol-associated cirrhosis, and (iv) healthy volunteers that consumed excessive amounts of alcohol for only a short period of time. Further, primary human hepatocytes (PHH) and adipocytes were incubated in vitro with alcohol or serum of patients. Results: Patients with chronic alcohol consumption had significantly higher SAL than HCV-patients with comparable degrees of liver damage. In alcoholics, but not in HCV patients, SAL positively correlated with serum levels of aminotransferases. Further, SAL correlated with the amount of alcohol consumption but declined during the course of alcohol abstinence. After short-term excessive alcohol consumption SAL were not elevated in healthy individuals. Adiponectin mRNA was detectable in adipocytes but not in hepatocytes, and alcohol failed to induce adiponectin in both cell types. In contrast, serum of active drinkers induced adiponectin expression in adipocytes while serum from the same individuals collected after alcohol withdrawal had no effect. Conclusions: Alcohol exhibits a specific effect on SAL that is dose and time dependent, and correlates with the degree of hepatic damage. Alcohol does not seem to affect adiponectin expression directly in adipocytes but potentially via mediators systemically released as a result of the chronic alcohol intake. [ABSTRACT FROM AUTHOR]

The aim of this study was to analyze Toll-like receptor (TLR) expression in preadipocytes and mature adipocytes and to investigate whether TLR ligands influence the release of cytokines, chemokines, and adipokines. Murine 3T3-L1 preadipocytes and mature adipocytes were used for stimulation experiments. The effects of lipopolysaccharide (LPS), flagellin, Poly (U), Poly (I:C), macrophage-activating lipopeptide-2 (MALP2), Pam3Cys, and CpG on the release of interleukin-6 (IL-6), resistin, and monocyte chemoattractant protein-1 (MCP-1) were determined by enzyme-linked immunosorbent assay (ELISA). Nuclear translocation and promoter binding of NFκB were analyzed by electrophoretic mobility shift assays. TLR expression was investigated by reverse-transcriptase (RT-PCR). All TLRs except TLR5 and TRL7 are expressed in the stromal vascular cell (SVC) fraction and in mature adipocytes of different fat stores. Whereas basal and LPS-induced IL-6 release is higher in preadipocytes, basal and LPS-induced MCP-1 release is higher in mature adipocytes. Mature adipocytes respond to corticosterone regarding MCP-1 and resistin release. The ligands for TLRs influence IL-6, MCP-1, and resistin release differentially. Some of these ligands induce nuclear translocation and promoter binding of NFκB. Besides TLR5, that is not expressed in mature adipocytes, all TLR family members are involved. There exists a functional TRL pathway in adipocytes that connects innate immunity with adipocyte function. As a consequence, the role of the adipose tissue in both immunity and metabolism has to be investigated in future studies. The results of this approach will help to explain the metabolic changes such as insulin resistance observed during infection and the immunological phenomena such as macrophage infiltration of adipose tissue seen in obesity.Obesity (2009) 17 4, 648–656. doi:10.1038/oby.2008.607 [ABSTRACT FROM AUTHOR]

Background Visceral adipose tissues secret a variety of adipokines; however, it is not known whether they are present in the peritoneal fluid. It was the aim of this study to investigate peritoneal fluid concentrations of novel (cartonectin, omentin) and classical adipokines (leptin, adiponectin, resistin, visfatin) in patients with ascites. Material and methods Ninety-six patients (71 men and 25 women) undergoing paracentesis were included. Of these, 76 suffered from liver cirrhosis. Adipokines were measured by enzyme-linked immunosorbent assay or Western blot. Results Each adipokine was detected in ascites with a broad range. Serum–ascites ratios (SAR) correlated with clinical and laboratory parameters. The main variables influencing peritoneal fluid adipokine concentrations were body mass index (BMI), local inflammation, systemic inflammation and serum adipokine concentrations. Resistin was significantly higher in patients with peritonitis and showed a positive correlation with peripheral leucocytes (white blood cell count). Leptin was correlated with the underlying disease. Visfatin correlated with peripheral white blood cell and C-reactive protein levels. Omentin expression was correlated with ascitic leucocyte count, ascitic albumin concentration and low albumin SAR. BMI was correlated positively with ascitic leptin levels and cartonectin protein levels. Conclusions Peritoneal fluid adipokine concentrations are characterized by individual SARs, depend on the presence of peritonitis, and correlate with underlying disease, BMI and systemic inflammation. The data open a new field of research on the role of the peritoneum and visceral adipokines in gastrointestinal diseases. [ABSTRACT FROM AUTHOR]

Meteorin-like protein (Metrnl) is an adipo-myokine with pleiotropic effects in adipose tissue (AT). Its systemic regulation in obesity and under weight loss is unclear. Circulating Metrnl concentrations were analyzed by ELISA in severely obese patients undergoing bariatric surgery (BS) or low calorie diet (LCD). Metrnl mRNA expression was analyzed in human and murine tissues and cell lines by quantitative real-time PCR. About 312 morbidly obese individuals underwent BS (n = 181; BMI 53.4 + 6.8 kg/m2) or LCD (n = 131; BMI 43.5 + 6.7 kg/m2). Serum samples were obtained at baseline and 3, 6, and 12 months after intervention. AT specimen from subcutaneous and visceral adipose tissue were resected during BS. Serum Metrnl levels were lower in type 2 diabetic patients and negatively correlated with HbA1c. In BS and LCD patients, Metrnl concentrations significantly increased after 3 months and returned to baseline levels after 12 months. There was no gender-specific effect. Metrnl mRNA expression did not differ between visceral and subcutaneous AT in n = 130 patients. In contrast, Metrnl gene expression in mice was highest in intra-abdominal AT followed by subcutaneous, peri-renal, and brown AT. In the murine 3T3-L1 cell line, Metrnl expression was high in pre-adipocytes and mature adipocytes with a transient downregulation during adipocyte differentiation. Metrnl expression remained unaffected upon treatment with glucose, insulin, fatty acids, bile acids, and incretins. Polyunsaturated omega-3 and omega-6 fatty acids downregulated Metrnl expression. Systemic Metrnl is transiently upregulated during massive weight loss and gene expression in adipocytes is differentially regulated. [ABSTRACT FROM AUTHOR]

The article presents a study which investigated the effects of recombinant cartonectin on the secretion of adipokines from adipocytes of human and murine origin. Adipokines include adiponectin, leptin and resistin. For stimulation experiments, adipocytes from pooled lead and preobese healthy individuals and murine adipocytes were used. Results showed that cartonectin in higher doses stimulates adiponectin and resistin secretion.

Background and Aim: Severe acute pancreatitis is characterized by lipase-induced peripancreatic fat cell necrosis. Because adipocytes secret several highly active molecules, the aim of the present study was to investigate the hypothesis that adipocytokines could serve as potential markers predicting peripancreatic necrosis and severity in acute pancreatitis. Methods: A total of 23 patients (11 females, 12 males) with acute pancreatitis were included and a computed tomography (CT) examination was available in 20 patients. Balthazar score, Schröder score, pancreatic necrosis score, Ranson score and APACHE II score were calculated, correlated with biochemical parameters and analyzed using receiver-operator characteristics (ROC) analysis. Adipocytokine serum levels were measured daily by enzyme-linked immunosorbent assay (ELISA) over 10 days after admission. Results: Resistin and leptin were significantly elevated in patients with severe pancreatitis and were correlated with a radiological scoring system for extrapancreatic necrosis. Whereas resistin correlated positively with clinical scoring systems, time until discharge and the need for interventions, leptin was correlated positively with C-reactive protein (CRP) levels. Resistin levels measured on the day of admittance had a positive predictive value of 93.3% (cut-off: >6.95 ng/mL) in predicting a Schröder score >3. Conclusion: Resistin, and to a lesser extent leptin, but not adiponectin levels are novel potential markers for extrapancreatic necrosis and severity of acute pancreatitis and should therefore be tested in larger cohorts of patients. [ABSTRACT FROM AUTHOR]

Abstract: The adipose tissue signals to the brain via its secretory products. However, it is unknown whether the brain itself can directly contact the fat tissue. In order to test this hypothesis, the adipocytic expression of receptors for pituitary hormones and hypothalamic peptides was investigated. Besides FSH- and LH-receptors, adipocytes do express the specific receptors for ACTH, TSH, GH, prolactin, oxytocin and the three receptor subtypes for vasopressin. Thus, the adipose tissue might no longer be regarded as an inert and steady tissue but as a fast acting player downstream of and under the control of the brain. Based on this, the potential existence and clinical impact of a hypothalamic–pituitary–adipose axis should further be investigated. [Copyright &y& Elsevier]

Aims/hypothesis. The human adipocyte-specific apM-1 (adipose most abundant gene transcript-1) gene encodes for a secretory protein of the adipose tissue that seems to play a role in the pathogenesis of obesity-related insulin resistance and its expression is inhibited by TNF-α. Our aim was to characterize the tissue-specific regulation of the recently cloned apM-1 promoter and the mechanisms of TNF-α-induced downregulation of the apM-1 gene. Methods. We characterised the apM-1 gene by electrophoretic mobility shift assays (EMSA) and luciferase reporter gene assays (LRA). Results. Although several putative binding sites for transcription factors known to be involved in adipogenesis such as C/EBP and PPARγ are present in the promoter, we could not detect any binding of these nuclear proteins from differentiated adipocytes. However, a proximal SP1 binding site specifically binds both, recombinant SP1 protein and SP1 derived from adipocyte nuclear extracts. Since the expression of SP1 during adipocyte differentiation has not yet been analysed, we could show by using EMSA, that binding activity of SP1 is increased during adipocyte differentiation. The stimulatory activity of SP1 was confirmed in LRA by cotransfection experiments in S2 Schneider cells lacking endogenous SP factors. An inhibitory activity of SP3 on the stimulatory effect of SP1 could be confirmed in LRA by contransfection experiments in adipocytes. Nuclear extracts from adipocytes incubated with TNF-α showed a reduced binding activity of SP1. Conclusion/interpretation. SP1 is expressed and its binding activity is enhanced during adipocyte differentiation. SP1 has stimulatory effects, SP3 has inhibitory effects on apM-1 promoter activity, mediated by a proximal SP1 binding site. The mechanism of TNF-α-induced inhibition of apM-1 gene expression is, at least in part, due to a decrease of transcriptional SP1 binding activity caused by TNF-α and thus provides a new mechanism of TNF-α-dependent signalling. [ABSTRACT FROM AUTHOR]

The C1q/TNF-related protein 3 (CTRP3) represents a pleiotropic adipokine reciprocally associated with obesity and type 2 diabetes mellitus and exhibits anti-inflammatory properties in relation to lipopolysaccharides (LPS)-mediated effects in adipocytes, as well as monocytes/macrophages. Here, we focused on the influence of CTRP3 on LPS-mediated effects in endothelial cells in order to expand the understanding of a possible anti-inflammatory function of CTRP3 in a setting of endotoxemia. An organ- and tissue-specific expression analysis by real-time PCR revealed a considerable Ctrp3 expression in various adipose tissue compartments; however, higher levels were detected in the aorta and in abundantly perfused tissues (bone marrow and the thyroid gland). We observed a robust Ctrp3 expression in primary endothelial cells and a transient upregulation in murine endothelial (MyEND) cells by LPS (50 ng/mL). In MyEND cells, CTRP3 inhibited the LPS-induced expression of interleukin (Il)-6 and the tumor necrosis factor (Tnf)-α, and suppressed the LPS-dependent expression of the major endothelial adhesion molecules Vcam-1 and Icam-1. The LPS-induced adhesion of monocytic cells to an endothelial monolayer was antagonized by CTRP3. In C57BL/6J mice with an LPS-induced systemic inflammation, exogenous CTRP3 did not affect circulating levels of TNF-α, ICAM-1, and VCAM-1. In conclusion, we characterized CTRP3 beyond its function as an adipokine in a setting of vascular inflammation. CTRP3 inhibited LPS-induced endothelial expression of adhesion molecules and monocyte cell adhesion, indicating an important vascular anti-inflammatory role for CTRP3 in endotoxemia. [ABSTRACT FROM AUTHOR]

CTRP-3 (C1q/TNF-related protein-3) is an adipokine with endocrine and immunological function. The impact of adipocyte CTRP-3 production on systemic CTRP-3 concentrations and on adipocyte biology is unknown. A murine model of adipocyte CTRP-3 knockout (KO) was established (via the Cre/loxP system). Serum adipokine levels were quantified by ELISA and adipose tissue (AT) gene expression by real-time PCR. Preadipocytes were isolated from AT and differentiated into adipocytes. Comparative transcriptome analysis was applied in adipocytes and liver tissue. Body weight and AT mass were reduced in CTRP-3 KO mice together with decreased serum leptin. In primary cells from visceral AT of KO mice, expression of adiponectin, progranulin, and resistin was induced, while peroxisome proliferator activated receptor γ (PPARγ) was decreased. M1/M2 macrophage polarization markers were shifted to a more anti-inflammatory phenotype. CTRP-3 expression in AT did not contribute to serum concentrations. AT and liver morphology remained unaffected by CTRP-3 KO. Myelin transcription factor 1-like (Myt1l) was identified as a highly upregulated gene. In conclusion, adipocyte CTRP-3 has a role in adipogenesis and AT weight gain whereas adipocyte differentiation is not impaired by CTRP-3 deficiency. Since no effects on circulating CTRP-3 levels were observed, the impact of adipocyte CTRP-3 KO is limited to adipose tissue. Modified AT gene expression indicates a rather anti-inflammatory phenotype. [ABSTRACT FROM AUTHOR]

The adipokine CTRP-3 (C1q/TNF-related protein-3) exerts anti-inflammatory and anti-diabetic effects. Its regulation in obesity and during weight loss is unknown. Serum and adipose tissue (AT) samples were obtained from patients (n = 179) undergoing bariatric surgery (BS). Moreover, patients (n = 131) participating in a low-calorie diet (LCD) program were studied. CTRP 3 levels were quantified by ELISA and mRNA expression was analyzed in AT and in 3T3-L1 adipocytes treated with bile acids and incretins. There was a persistent downregulation of CTRP-3 serum levels during weight loss. CTRP-3 expression was higher in subcutaneous than in visceral AT and serum levels of CTRP-3 were positively related to AT expression levels. A rapid decrease of circulating CTRP-3 was observed immediately upon BS, suggesting weight loss-independent regulatory mechanisms. Adipocytes CTRP-3 expression was inhibited by primary bile acid species and GLP 1. Adipocyte-specific CTRP-3 deficiency increased bile acid receptor expression. Circulating CTRP-3 levels are downregulated during weight loss, with a considerable decline occurring immediately upon BS. Mechanisms dependent and independent of weight loss cause the post-surgical decline of CTRP-3. The data strongly argue for regulatory interrelations of CTRP-3 with bile acids and incretin system. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor which discusses research into adipocytokines in synovial fluid. How adipocytes secrete several highly active molecules including leptin, adiponectin, and resistin; Adiponectin as belonging to the tumor necrosis factor family; Study conducted of synovial fluid of cancer patients.

Abstract Background and aim Bile acids (BA) are increasingly recognized as pleiotropic and hormone-like signaling molecules with metabolic and endocrine functions. However, the role of BA in white adipocyte physiology remains somewhat obscure. It was the aim to investigate the BA receptors (FXR, TGR5) and FGFR1 (Fibroblast growth factor receptor 1) as well as Bsep (bile salt export pump) in white adipocytes and in murine and human adipose tissue (AT) and to investigate effects of different BA species in adipocyte physiology. Patients, material and methods Receptor mRNA expression was quantified by real-time PCR in mice, humans and during 3T3-L1 pre-adipocyte differentiation. Adipokines were measured by ELISA upon stimulation by several BA. Effects of BA on TNF- and LPS-induced MCP-1 secretion and lipolysis were analyzed. TNF-induced lipolysis was investigated by glycerol assay. Results The present data provide for the first time a detailed expression profile of FXR, TGR5, FGFR1, and Bsep during adipocyte differentiation and in murine and human AT. FGFR1 expression is upregulated in adipose tissue of LPS-injected animals. Several BA regulate secretion of adipokines such as adiponectin and resistin differentially. Importantly, TNF- and LPS-induced MCP-1 release from adipocytes as well as TNF-induced lipolysis can be antagonized by cholic acid (CA) and deoxycholic acid (DCA). Conclusions The present data provide evidence of functional BA signaling pathways in adipocytes and argue for certain MCP-1 related anti-inflammatory effects of BA in TNF- and LPS-induced inflammation, whereas pro-inflammatory resistin is induced by CA and glycocholic acid (GCA). Systemic bile acids might represent a hormonal network regulating white adipocyte physiology including lipolysis. Graphical abstract Image 1 Highlights • Bile acid receptors FXR and TGR5 are expressed in pre-adipocytes, adipocytes and adipose tissue. • Bsep and FGFR1 are expressed in pre-adipocytes, adipocytes and adipose tissue. • Bile acids exert differential effects on adipocyte expression and secretion profile. • Certain bile acid species attenuate LPS- and TNF-induced inflammation in adipocytes. • Cholic acid and deoxycholic acid antagonize TNF-driven induction of lipolysis. [ABSTRACT FROM AUTHOR]

Background and aim Natriuretic peptides (NPs) and their receptors gain attention regarding adipocyte function. It was the aim to investigate the expression of natriuretic peptide receptors NPR-A, NPR-B and NPR-C during adipocyte differentiation (AD), upon stimulation with fatty acids (FA), and in murine and human adipose tissue depots (AT) of patients undergoing bariatric surgery (n = 44). Patients, material and methods The postprandial regulation of NT-proANP and NT-proBNP levels was measured by ELISA and was studied in two cohorts of healthy individuals undergoing an oral glucose tolerance test (OGTT) (n = 100) and an oral lipid tolerance test (OLTT) (n = 100). Adipocyte mRNA expression was investigated by quantitative real-time PCR. Results During AD, an early expression pattern could be described for NPR-C, a bimodal expression for NPR-B and a late expression pattern for NPR-A. NPR-A and NPR-B expression was high in epididymal and subcutaneous AT but low in peri-renal AT of mice. NPR-C showed a differential expression profile. FA stimulation caused a significant and differential regulation of NPRs in adipocytes. Serum NT-proANP and NT-proBNP concentrations did not change during OGTT, whereas NT-proANP significantly declined during OLTT. Basal NT-proANP and NT-proBNP concentrations were positively correlated with each other and with FGF-19 and FGF-21 levels. Conclusion Adipocytes and AT show a characteristic expression of NPRs. FA are able to regulate NPR expression differentially. There is a postprandial and negative regulation of serum NT-proANP concentrations after OLTT and of NPR-A after FA stimulation. Both effects could represent a novel hypothetical negative feedback mechanism on adipocyte lipolysis. [ABSTRACT FROM AUTHOR]