Resistin, an adipokine with potent proinflammatory properties

Reliability of leptin, but not adiponectin, as a biomarker for diet-induced weight loss in humans

Calorie restriction (CR)-induced weight loss has been shown to lower the risk of chronic disease in obese individuals. Although the mechanisms that link weight loss to disease risk reduction remain unclear, evidence suggests adipokines may play a role. What has yet to be determined, however, is the dose-response effect of body weight loss and visceral fat mass loss on adipokines. Accordingly, this review examines how varying degrees of CR-induced weight loss (i.e., >10%, 5-10%, and <5% from baseline) impact plasma levels and expression of adiponectin, leptin, resistin, interleukin 6 (IL-6), interleukin 8 (IL-8), monocyte chemotactic protein 1 (MCP-1), and retinol-binding protein 4 (RBP-4). The dose-response relationship between visceral fat mass loss and adipokine profile improvement will also be explored. Results from this review demonstrate that even mild weight loss induced by CR may have beneficial effects on leptin levels, but it has no clear impact on adiponectin, resistin, IL-6, IL-8, MCP-1, or RBP-4 concentrations.

Adipokines in inflammation and metabolic disease

The worldwide epidemic of obesity has brought considerable attention to research aimed at understanding the biology of adipocytes (fat cells) and the events occurring in adipose tissue (fat) and in the bodies of obese individuals. Accumulating evidence indicates that obesity causes chronic low-grade inflammation and that this contributes to systemic metabolic dysfunction that is associated with obesity-linked disorders. Adipose tissue functions as a key endocrine organ by releasing multiple bioactive substances, known as adipose-derived secreted factors or adipokines, that have pro-inflammatory or anti-inflammatory activities. Dysregulated production or secretion of these adipokines owing to adipose tissue dysfunction can contribute to the pathogenesis of obesity-linked complications. In this Review, we focus on the role of adipokines in inflammatory responses and discuss their potential as regulators of metabolic function.

Geranylgeranyltransferase type I (GGTase-I) deficiency hyperactivates macrophages and induces erosive arthritis in mice

RHO family proteins are important for the function of inflammatory cells. They are modified with a 20-carbon geranylgeranyl lipid in a process catalyzed by protein geranylgeranyltransferase type I (GGTase-I). Geranylgeranylation is viewed as essential for the membrane targeting and activity of RHO proteins. Consequently, inhibiting GGTase-I to interfere with RHO protein activity has been proposed as a strategy to treat inflammatory disorders. However, here we show that mice lacking GGTase-I in macrophages develop severe joint inflammation resembling erosive rheumatoid arthritis. The disease was initiated by the GGTase-I-deficient macrophages and was transplantable and reversible in bone marrow transplantation experiments. The cells accumulated high levels of active GTP-bound RAC1, CDC42, and RHOA, and RAC1 remained associated with the plasma membrane. Moreover, GGTase-I deficiency activated p38 and NF-κB and increased the production of proinflammatory cytokines. The results challenge the view that geranylgeranylation is essential for the activity and localization of RHO family proteins and suggest that reduced geranylgeranylation in macrophages can initiate erosive arthritis.

The effects of adipokines on cartilage and meniscus catabolism

Obesity is one of the primary risk factors for osteoarthritis. Increased adiposity is associated not only with alterations in joint loading, but also with increased systemic and joint concentrations of adipose tissue-derived cytokines, or "adipokines", that promote a state of chronic, low-grade inflammation that may act in concert with other cytokines in the joint to increase joint degeneration. However, the direct effect of adipokines, such as leptin, visfatin, and interleukin-6 (IL-6), on joint tissues, such as articular cartilage and meniscus, are not fully understood. In this study, we examined the hypothesis that these adipokines act synergistically with interleukin-1 (IL-1) to increase catabolism and the production of proinflammatory mediators in cartilage and meniscus. Explants of porcine cartilage and meniscus were treated with physiologically relevant concentrations of leptin, IL-6, or visfatin, alone or in combination with IL-1. Visfatin and IL-1 promoted the catabolic degradation of both cartilage and meniscus, as evidenced by increased metalloproteinase activity, nitric oxide production, and proteoglycan release. However, leptin or IL-6 at physiologic concentrations had no effect on the breakdown of these tissues. These findings suggest that the effects of obesity-induced osteoarthritis may not be through a direct effect of leptin or IL-6 on cartilaginous tissues, but support a potential role for increased visfatin levels in this regard. These data provide an important first step in understanding the role of adipokines in regulating cartilage and meniscus metabolism; however, these adipokines may have different effects in the context of the whole joint and must be evaluated further.

Mood disorders and obesity: understanding inflammation as a pathophysiological nexus

The aim of this review is to evaluate the evidentiary base supporting the hypothesis that the increased hazard for obesity in mood disorder populations (and vice versa) is a consequence of shared pathophysiological pathways. We conducted a PubMed search of all English-language articles with the following search terms: obesity, inflammation, hypothalamic-pituitary-adrenal axis, insulin, cognition, CNS, and neurotransmitters, cross-referenced with major depressive disorder and bipolar disorder. The frequent co-occurrence of mood disorders and obesity may be characterized by interconnected pathophysiology. Both conditions are marked by structural and functional abnormalities in multiple cortical and subcortical brain regions that subserve cognitive and/or affective processing. Abnormalities in several interacting biological networks (e.g. immuno-inflammatory, insulin signaling, and counterregulatory hormones) contribute to the co-occurence of mood disorders and obesity. Unequivocal evidence now indicates that obesity and mood disorders are chronic low-grade pro-inflammatory states that result in a gradual accumulation of allostatic load. Abnormalities in key effector proteins of the pro-inflammatory cascade include, but are not limited to, cytokines/adipokines such as adiponectin, leptin, and resistin as well as tumor necrosis factor alpha and interleukin-6. Taken together, the bidirectional relationship between obesity and mood disorders may represent an exophenotypic manifestation of aberrant neural and inflammatory networks. The clinical implications of these observations are that, practitioners should screen individuals with obesity for the presence of clinically significant depressive symptoms (and vice versa). This clinical recommendation is amplified in individuals presenting with biochemical indicators of insulin resistance and other concurrent conditions associated with abnormal inflammatory signaling (e.g. cardiovascular disease).

The serum levels of resistin in ankylosing spondylitis patients: a pilot study

Resistin is a recently described adipokine which is a member of cysteine-rich secretory protein family. Although it has been primarily defined in human adipocytes, it has been identified that its level was higher in mononuclear leukocytes, macrophages, spleen, and bone marrow cells. Because ankylosing spondylitis is an inflammatory disease, it is suspected that upregulation of proinflammatory cytokines is effective in its immunopathogenesis. The aim of our study is to determine the serum resistin levels in patients with AS and to research the relationship with disease activity markers. A total of 30 patients with AS and 30 healthy controls were included in this study. Serum resistin concentrations, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), Bath AS Disease Activity Index (BASDAI) were evaluated. In results resistin levels in ankylosing spondylitis group were significantly higher than in control group. But, there was no correlation between resistin and ESR, CRP, BASDAI. In conclusion, higher serum resistin levels in patients with AS compared to healthy subjects give clues that resistin could have a role in the pathogenesis of AS.

The Relationship of Proinflammatory and Antiinflammatory Adipokines in the Development of Metabolic Syndrome in Centrally Obese Men

BACKGROUND: The increased prevalence of obesity worldwide is correlated with increasing prevalence of metabolic syndrome. Studies of adipose tissue have been improved from an inert energy storage to a metabolic active endocrine organ. Adipokines secreted by this tissue play a role in maintaining metabolic homeostasis. The large mass of visceral fat tissue causing the imbalance of these adipokines leading to metabolic abnormality known as the metabolic syndrome (MetS). This study was performed to understand relationship of proinflammatory adipokines (resistin, TNF-α, RBP4 and visfatin) and anti-inflammatory adipokines (adiponectin and vaspin) in the development of MetS.METHODS: This was a cross-sectional study using 122 central obesity men with waist circumference >90 cm, age from 30–60 years old. Proinflammatory adipokines (resistin, TNF-α, RBP4 and visfatin) and anti-inflammatory adipokines (adiponectin and vaspin) was measured by ELISA method.RESULTS: The crosstab study showed that subjects who have >2 high proinflammatory adipokines (17.3%) has higher MetS prevalence (OR = 1.16; p = 0.72) compare to subjects with <2 high proinflammatory adipokines (14.8%), subjects with low anti-inflammatory adipokines profile (18.9%) has higher prevalence of MetS (OR=1.38; p=0.22) compare to subjects with high anti-inflammatory adipokines (13.7%) and the prevalence of MetS became 1.49 times higher (p=0.24) when we combine the high RBP4 and low adiponectin profile (21.1%) compare to subjects with low RBP4 and high adiponectin (14%).CONCLUSIONS: This study showed that each adipokine was not strong enough to induce MetS, so the interaction between proinflammatory and antiinflammatory adipokines were needed to induce a systemic metabolic abnormality. Thus, the adipokines equilibrium was important to prevent MetS especially in centrally obese subjects.KEYWORDS: obesity, metabolic syndrome, adipokines, resistin, TNF-α, RBP4, visfatin, adiponectin, vaspin

Resistin is associated with mortality in patients with traumatic brain injury

INTRODUCTION

Recently, we reported that high levels of resistin are present in the peripheral blood of patients with intracerebral hemorrhage and are associated with a poor outcome. However, not much is known regarding the change in plasma resistin and its relation with mortality after traumatic brain injury (TBI). Thus, we sought to investigate change in plasma resistin level after TBI and to evaluate its relation with disease outcome.

METHODS

Fifty healthy controls and 94 patients with acute severe TBI were included. Plasma samples were obtained on admission and at days 1, 2, 3, 5 and 7 after TBI. Its concentration was measured by enzyme-linked immunosorbent assay.

RESULTS

Twenty-six patients (27.7%) died from TBI within 1 month. After TBI, plasma resistin level in patients increased during the 6-hour period immediately after TBI, peaked within 24 hours, plateaued at day 2, decreased gradually thereafter and was substantially higher than that in healthy controls during the 7-day period. A forward stepwise logistic regression selected plasma resistin level (odds ratio, 1.107; 95% confidence interval, 1.014-1.208; P = 0.023) as an independent predictor for 1-month mortality of patients. A multivariate linear regression showed that plasma resistin level was negatively associated with Glasgow Coma Scale score (t = -6.567, P < 0.001). A receiver operating characteristic curve identified plasma resistin cutoff level (30.8 ng/mL) that predicted 1-month mortality with the optimal sensitivity (84.6%) and specificity (75.0%) values (area under curve, 0.854; 95% confidence interval, 0.766-0.918; P < 0.001).

CONCLUSIONS

Increased plasma resistin level is found and associated with Glasgow Coma Scale score and mortality after TBI.

Obesity in rheumatoid arthritis

Obesity is a major threat for public health and its study has attracted significant attention in the general population, predominantly due to its association with significant metabolic and cardiovascular complications. In RA research, BMI is frequently reported as a demographical variable, but obesity, as such, has received little interest. This is surprising, in view of the clear associations of obesity with other arthritides, particularly OA, but also in view of the now-clear association of RA with increased cardiovascular morbidity and mortality. In this review, we summarize the studies that have looked into obesity in the RA population, evaluate their findings, identify knowledge gaps and propose directions for future research. We also pose a question of high clinical and research significance: is the use of BMI still a valid way of assessing obesity in RA?

Response of swine spleen to Streptococcus suis infection revealed by transcription analysis

Astract

Diagnosis and treatment of osteoarthritis

Osteoarthritis (OA) is a common disease in aging dogs and cats but frequently goes undiagnosed and untreated. Although OA cannot be cured, long-term management of the disease can be very rewarding for the veterinary medical team as well as pet owners. Managing pain with pain medications is an essential first step. There are a wealth of pain medications available, including nonsteroidal antiinflammatory drugs, gabapentin, amantadine, and tramadol. There are also physical modalities available for pain reduction. Weight management and nutritional joint support are also important in aspects of managing OA in dogs and cats. Finally, physical rehabilitation is a great way to improve mobility and keep pets active as they age.

Usefulness of assessing circulating levels of resistin, ghrelin, and IL-18 in alcoholic acute pancreatitis

OBJECTIVES

Acute pancreatitis (AP) is a severe inflammatory disease with high mortality and morbidity rates. We have previously demonstrated that resistin may represent an early marker of inflammation in AP. It was also revealed that ghrelin may have anti-inflammatory potential. However, the role of adipohormones in AP-resistin and ghrelin as well as the proinflammatory cytokine interleukin (IL)-18-has not yet been fully elucidated.

METHODS

The study group comprised 32 patients with alcoholic AP and 30 controls matched for age, sex, and body mass index (BMI). In all cases AP was classified as grade C according to Balthazar's computed tomography (CT) score and as severe (3 points) according to Ranson's criteria. Serum levels of resistin, ghrelin, and IL-18 were measured on first, third, and fifth day of hospitalization by enzyme-linked immunosorbent assay (ELISA).

RESULTS

On first day of hospitalization the mean serum resistin concentration in AP patients was significantly higher than in controls (P < 0.05) and further increased on third and fifth day of hospitalization (17.4 ± 4.23 ng/ml and 25.8 ± 8.14 ng/ml, respectively). On first day of hospitalization the mean serum IL-18 concentration in AP patients was significantly higher than in controls (P < 0.05), on third day its level further increased, and on fifth day it decreased to a level similar to that observed on admission. The serum ghrelin concentrations on first, third, and fifth day of hospitalization were comparable, and significantly higher than in controls (P < 0.01). Significant correlation between C-reactive protein (CRP) and resistin levels (r = 0.43; P < 0.05) and between CRP and IL-18 (r = 0.58; P <0.05) on day of admission was found.

CONCLUSIONS

Serum concentration of IL-18 and resistin may contribute to inflammatory response and may be useful as an early marker of inflammation in AP. We also suspect that ghrelin affects the course of AP and plays an important role in inflammatory response.

Is plasma 25(OH) D related to adipokines, inflammatory cytokines and insulin resistance in both a healthy and morbidly obese population?

To analyse in a cohort of healthy subjects and in a group of morbidly obese patients, we studied the association amongst 25(OH) D and plasma concentrations of adipocytokines, inflammatory cytokines and insulin resistance. We also aimed to determine whether vitamin D-deficient patients showed a greater inflammatory profile. In the observational study that the authors conducted, plasma concentrations of 25(OH) D, leptin, resistin, adiponectin and interleukine-18 were determined in 134 healthy men and 127 women. In the population consisting of 44 patients with morbid obesity, plasma concentrations of 25(OH) D, leptin, resistin, adiponectin, interleukine-18, soluble tumor necrosis factor receptors 1 and 2 and C-reactive protein were analysed. In the healthy population, plasma 25(OH) D showed a negative correlation with body mass index, body fat, waist, hip circumference and with leptin. However, no significant associations were found amongst 25(OH) D and plasma concentrations of resistin, adiponectin or interleukine-18. Patients with vitamin D deficiency showed higher body mass index, fat mass percentage and higher leptin concentrations compared with subjects with normal 25(OH) D concentrations. In the morbidly obese subjects, 25(OH) D did not correlate with leptin, resistin, adiponectin, interleukine-18, soluble tumor necrosis factor receptors 1 and 2 or with C-reactive protein. In patients with morbid obesity, no differences were found in adipokines and inflammatory cytokines concentrations regarding 25(OH) D status. No associations were found either between 25(OH) D and plasma glucose and insulin resistance or with lipid profile. Plasma 25(OH) D concentrations are associated with adiposity markers but not with adipocytokines implicated in inflammation. This lack of association does not support a major role of 25(OH) D in the pro-inflammatory environment observed in morbidly obese subjects. In addition, subjects with vitamin D deficiency are not characterized by a greater inflammatory state.

Targeting inflammation-induced obesity and metabolic diseases by curcumin and other nutraceuticals

Extensive research within the past two decades has revealed that obesity, a major risk factor for type 2 diabetes, atherosclerosis, cancer, and other chronic diseases, is a proinflammatory disease. Several spices have been shown to exhibit activity against obesity through antioxidant and anti-inflammatory mechanisms. Among them, curcumin, a yellow pigment derived from the spice turmeric (an essential component of curry powder), has been investigated most extensively as a treatment for obesity and obesity-related metabolic diseases. Curcumin directly interacts with adipocytes, pancreatic cells, hepatic stellate cells, macrophages, and muscle cells. There, it suppresses the proinflammatory transcription factors nuclear factor-kappa B, signal transducer and activators of transcription-3, and Wnt/beta-catenin, and it activates peroxisome proliferator-activated receptor-gamma and Nrf2 cell-signaling pathways, thus leading to the downregulation of adipokines, including tumor necrosis factor, interleukin-6, resistin, leptin, and monocyte chemotactic protein-1, and the upregulation of adiponectin and other gene products. These curcumin-induced alterations reverse insulin resistance, hyperglycemia, hyperlipidemia, and other symptoms linked to obesity. Other structurally homologous nutraceuticals, derived from red chili, cinnamon, cloves, black pepper, and ginger, also exhibit effects against obesity and insulin resistance.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Effects of resistin on skeletal glucose metabolism

Resistin is an adipokine highly related to insulin resistance (IR). The purpose of our research was to investigate how resistin influences skeletal glucose metabolism and explore its mechanisms. We constructed the recombinant plasmid pcDNA3.1 expressing resistin and then transfected it into C2C12 myocytes. The expression of resistin in C2C12 myocytes was detected by Western blotting. Glucose uptake was measured by 3H labeled glucose; glucose oxidation and glycogen synthesis was detected with 14C-labeled glucose. GLUT4 mRNA was measured by reverse transcription polymerase chain reaction (RT-PCR). We observed that resistin was expressed in transfected myocytes, and resistin decreased insulin induced glucose uptake rate by 28%-31% and inhibited the expression of GLUT4 mRNA. However, there was no significant difference in basal glucose uptake, and glucose oxidation and glycogen synthesis remained unchanged in all groups. It is concluded that resistin inhibits insulin induced glucose uptake in myocytes by downregulating the expression of GLUT4 and it has no effects on glucose oxidation and glycogen synthesis. Our findings may provide a clue to understand the roles of resistin in the pathogenesis of skeletal IR.

Relation of resistin levels with cardiovascular risk factors, insulin resistance and inflammation in naïve diabetes obese patients

BACKGROUND

The aim of the present study was to explore the relationship of resistin levels with cardiovascular risk factors, insulin resistance and inflammation in naïve diabetic patients.

SUBJECTS

A population of 66 naïve diabetic patients with obesity was analyzed. A complete nutritional and biochemical evaluation was performed.

RESULTS

The mean age 56.9+/-11.6 years and the mean BMI was 37.8+/-6.3. Patients were divided in two groups by median resistin value (3.3ng/ml), group I (patients with the low values, average value 2.5+/-0.5) and group II (patients with the high values, average value 4.8+/-1.8). Patients in the group I had lower waist circumference, total cholesterol, LDL-cholesterol and C-reactive protein than patients in group II. Correlation analysis showed a significant correlation among resistin levels and the independent variables; BMI (r=0.26; p<0.05), waist circumference (r=0.38; p<0.05), fat mass (r=0.28; p<0.05), LDL-cholesterol (r=0.3; p<0.05), C-reactive protein (r=0.28; p<0.05). In the multivariate analysis, resistin concentration increase 0.024ng/ml (CI 95%: 0.006-0.42) for each mg/dl of C-reactive protein.

CONCLUSION

Circulating resistins are associated with C-reactive protein in an independent way in naïve diabetic patients.

Resistin induces expression of proinflammatory cytokines and chemokines in human articular chondrocytes via transcription and messenger RNA stabilization

OBJECTIVE

To elucidate the effects of resistin on human articular chondrocytes and to generate a picture of their regulation at the transcriptional and posttranscriptional levels.

METHODS

Human articular chondrocytes were cultured with resistin. Changes in gene expression were analyzed at various doses and times. Cells were also treated with the transcription inhibitor actinomycin D after resistin treatment or with the NF-kappaB inhibitor IKK-NBD before resistin treatment. Gene expression was tested by quantitative real-time polymerase chain reaction. Computational analysis for transcription factor binding motifs was performed on the promoter regions of differentially expressed genes. TC-28 chondrocytes were transfected with CCL3 and CCL4 promoter constructs, pNF-kappaB reporter, and NF-kappaB and CCAAT/enhancer binding protein beta (C/EBPbeta) expression vectors with or without resistin.

RESULTS

Resistin-treated human articular chondrocytes increased the expression of cytokines and chemokines. Levels of messenger RNA (mRNA) for matrix metalloproteinase 1 (MMP-1), MMP-13, and ADAMTS-4 also increased, while type II collagen alpha1 (COL2A1) and aggrecan were down-regulated. The cytokine and chemokine genes could be categorized into 3 groups according to the pattern of mRNA expression over a 24-hour time course. One pattern suggested rapid regulation by mRNA stability. The second and third patterns were consistent with transcriptional regulation. Computational analysis suggested the transcription factors NF-kappaB and C/EBPbeta were involved in the resistin-induced up-regulation. This prediction was confirmed by the cotransfection of NF-kappaB and C/EBPbeta and the IKK-NBD inhibition.

CONCLUSION

Resistin has diverse effects on gene expression in human chondrocytes, affecting chemokines, cytokines, and matrix genes. Messenger RNA stabilization and transcriptional up-regulation are involved in resistin-induced gene expression in human chondrocytes.

Gene expression profiling in the lungs of pigs with different susceptibilities to Glässer's disease

Background

Haemophilus parasuis is the causative agent of Glässer's disease in pigs. Currently, little is known about the molecular mechanisms that contribute to disease susceptibility. This study used a porcine oligonucleotide microarray to identify genes that were differentially expressed (DE) in the lungs of colostrum-deprived animals previously characterized as being either 'Fully Resistant' (FR) or 'Susceptible' to infection by H. parasuis in a bacterial challenge experiment.

Results

Gene expression profiles of 'FR' and 'Susceptible' animals were obtained by the identification of genes that were differentially expressed between each of these groups and mock-inoculated 'Control' animals. At 24 hours post-inoculation, a total of 21 and 58 DE genes were identified in 'FR' and 'Susceptible' animals respectively. At 72 hours, the numbers of genes were 20 and 347 respectively. 'FR' animals at 24 hours exhibited an increased expression of genes encoding extracellular matrix and TGF-β signalling components, possibly indicative of tissue repair following the successful early resolution of infection. The gene expression profile of 'FR' animals at 72 hours supported the hypothesis that higher levels of antibacterial activity were responsible for the 'FR' phenotype, possibly due to an increase in natural immunoglobulin A and decrease in signalling by the immunoregulatory transcription factor peroxisome proliferator-activated receptor gamma (PPAR-γ). The expression profile of 'Susceptible' animals at both time-points was characterized by an imbalance in signalling between pro and anti-inflammatory cytokines and an increased expression of genes involved in biological processes associated with inflammation. These include the pro-inflammatory cytokine genes resistin (RETN) and interleukin 1-beta (IL1B). At 72 hours, a reduction in the expression of genes involved in antigen presentation by both MHC class I and II molecules was observed, which could have contributed to the inability of 'Susceptible' animals to clear infection.

Conclusions

This study is the first to have identified discrete sets of DE genes in pigs of differing susceptibility to H. parasuis infection. Consequently, several candidate genes and pathways for disease resistance or susceptibility phenotypes have been identified. In addition, the findings have shed light on the molecular pathology associated with Glässer's disease.

Increased apelin serum levels and expression in human chondrocytes in osteoarthritic patients

Apelin is a recently discovered hormone secreted by adipocytes. The aim of this study, therefore, was to evaluate the distribution of apelin in paired serum and synovial fluid (SF) of osteoarthritis (OA) patients, as compared to that in healthy controls, and to characterise the expression profile of apelin and its cognate receptor APJ in human chondrocytes. Apelin levels in serum and SF were analysed by enzyme-linked immunosorbent assay (ELISA). Expression of apelin and APJ in human chondrocytes was determined by real-time quantitative polymerase chain reaction (PCR). Apelin was found to be present in OA SF, and concentrations were positively correlated with the severity of OA. OA serum exhibited significantly elevated levels of apelin (2.18 ± 0.22 ng/ml) as compared to normal serum (1.31 ± 0.12 ng/ml) (p < 0.05), and serum apelin levels exceeded those in paired SF (p < 0.001). The apelin and APJ transcripts were identified in chondrocytes, and levels were significantly higher in OA cartilage than in healthy donors. These findings suggest that apelin may contribute to the onset and/or progression of OA, and may provide new insights into the pathophysiology of OA.

Maternal plasma retinol binding protein 4 in acute pyelonephritis during pregnancy

OBJECTIVE

Adipokines have been implicated in metabolic regulation and the immune response thus providing a molecular mechanism for the interaction between these two systems. Retinol binding protein 4 (RBP4) is a novel adipokine that plays a role in the pathophysiology of obesity-induced insulin resistance, as well as in the modulation of inflammation. The aim of this study was to determine whether there are changes in maternal plasma concentrations of RBP4 in pregnant women with acute pyelonephritis.

STUDY DESIGN

This cross-sectional study included pregnant women in the following groups: 1) normal pregnancy (n=80); 2) pyelonephritis (n=39). Maternal plasma RBP4 concentrations were determined by enzyme-linked immunoassays. Non-parametric statistics were used for analyses.

RESULTS

1) The median maternal plasma RBP4 concentration was lower in patients with acute pyelonephritis than in those with a normal pregnancy (3709.6 ng/mL, interquartile range (IQR) 2917.7-5484.2 vs. 9167.6 ng/mL, IQR 7496.1- 10,384.1, P<0.001; 2) the median maternal plasma RBP4 concentration did not differ significantly between patients with acute pyelonephritis who had a positive blood culture and those with a negative culture (3285.3 ng/mL, IQR 2274.1-4741.1 vs. 3922.6 ng/mL, IQR 3126.8-5547.1, respectively, P=0.2); and 3) lower maternal plasma RBP4 concentrations were independently associated with pyelonephritis after adjustment for confounding factors.

CONCLUSIONS

In contrast to what has been reported in preeclampsia, acute pyelonephritis during pregnancy is associated with lower maternal plasma RBP4 concentrations than in normal pregnancy. This finding suggests that the acute maternal inflammatory process associated with pyelonephritis is fundamentally different from that of the chronic systemic inflammatory process suggested in preeclampsia, in which RBP4 concentrations were found to be elevated.

Resistin enhances the expansion of regulatory T cells through modulation of dendritic cells

Background

Resistin, a member of adipokine family, is known to be involved in the modulation of immune responses including inflammatory activity. Interestingly, resistin is secreted by adipocytes in mice and rats whereas it is secreted by leukocytes in humans. However, the mechanism behind the effect of resistin on the expansion of regulatory T cells (Tregs) remains poorly understood. Therefore, we examined regulatory effect of resistin on the induction and cellular modification of Tregs.

Results

Both protein and mRNA expression of FoxP3, a representative marker of Tregs, increased in a dose-dependent manner when peripheral blood mononuclear cells were treated with resistin. At the same time, resistin had no direct effect on the induction of FoxP3 in CD4⁺ T cells, suggesting an indirect role through other cells type(s). Since DCs are an important player in the differentiation of T cells, we focused on the role of DCs in the modulation of Tregs by resistin. Resistin suppressed the expression of interferon regulatory factor (IRF)-1 and its target cytokines, IL-6, IL-23p19 and IL-12p40, in DCs. Furthermore, FoxP3 expression is increased in CD4⁺ T cells when co-cultured with DCs and concomitantly treated with resistin.

Conclusion

Our results suggest that resistin induces expansion of functional Tregs only when co-cultured with DCs.

Adipocytokines in atherothrombosis: focus on platelets and vascular smooth muscle cells

Visceral obesity is a relevant pathological condition closely associated with high risk of atherosclerotic vascular disease including myocardial infarction and stroke. The increased vascular risk is related also to peculiar dysfunction in the endocrine activity of adipose tissue responsible of vascular impairment (including endothelial dysfunction), prothrombotic tendency, and low-grade chronic inflammation. In particular, increased synthesis and release of different cytokines, including interleukins and tumor necrosis factor-α (TNF-α), and adipokines—such as leptin—have been reported as associated with future cardiovascular events. Since vascular cell dysfunction plays a major role in the atherothrombotic complications in central obesity, this paper aims at focusing, in particular, on the relationship between platelets and vascular smooth muscle cells, and the impaired secretory pattern of adipose tissue.

Biological agents targeting beyond TNF-alpha

Biological agents represent an important addition to the therapies for immuno-inflammatory conditions and have a great impact on the disease course and quality of life of these patients. However, recent reports of serious infections like tuberculosis, demyelinating and neurodegenerative diseases, pancytopenia, cardiovascular diseases, etc. after anti-TNF therapy raised questions on their safety. Hence, focus is shifted towards drugs targeting cytokine checkpoints in the inflammatory cascades beyond TNF-α. Existing therapeutic targets include the biological agents acting as antagonists of various inflammatory cytokines (Anakinra, Tocilizumab, Atlizumab) and modulators of CD80 or CD86-CD28 co-stimulatory signal (Abatacept), CD2 receptors on T-cells (Alefacept), CD11a, subunit of leukocyte function-associated antigen 1 (Efalizumab), vitronectin receptor and CD20 antigen on pre-B, immature and mature B cells (Rituximab). With the introduction of these novel molecules the future for immunomodulatory intervention in rheumatology, asthma, crohn's disease, septic shock etc. looks very promising. These novel therapeutic agents could truly give a new hope to the clinician to modify the disease and achieve tangible improvements in the lives of the patients.

The emerging role of adipokines in osteoarthritis: a narrative review

Osteoarthritis (OA) is a most common multifactorial degenerative joint disease in elderly individuals. OA is affecting severely the quality of life of patients, while the causes of OA are not completely understood. Age, obesity, the female sex, and previous injury are considered as significant risk factors. Recently, increased levels of adipokines which are mainly produced by adipocytes have been detected in patients with osteoarthritis. Moreover, studies on different adipokines all reveal that they have played proinflammatory and catabolic/anabolic roles during the pathophysiology of OA. In the present review, we summarize current data on the effect of the adipose tissue-derived hormones leptin, adiponectin, resistin and visfatin on initiation and progression of OA.

Peritoneal adipocytes and their role in inflammation during peritoneal dialysis

Adipose tissue is a major site of chronic inflammation associated with peritoneal dialysis (PD) frequently complicating peritonitis. Adiposity-associated inflammation plays a significant contributory role in the development of chronic inflammation in patients undergoing maintenance PD. However, the molecular and cellular mechanisms of this link remain uncertain. Adipose tissue synthesizes different adipokines and cytokines that orchestrate and regulate inflammation, insulin action, and glucose metabolism locally and systemically. In return, inflammation retards adipocyte differentiation and further exacerbates adipose dysfunction and inflammation. An understanding of the inflammatory roles played by adipose tissue during PD and the healing mechanism of injured mesothelium will help to devise new therapeutic approach to slow the progression of peritoneal damage during peritoneal dialysis. This article reviews the roles of peritoneal adipose tissue in chronic peritoneal inflammation under PD and in serosal repair during PD.

Hyperresistinemia - a novel feature in systemic infection during human pregnancy

PROBLEM

Resistin, originally described as an adipokine, has emerged as a potent pro-inflammatory protein associated with both acute and chronic inflammation. Moreover, resistin has been proposed as a powerful marker of sepsis severity, as well as a predictor of survival of critically ill non-pregnant patients. The aim of this study was to determine whether pyelonephritis during pregnancy is associated with changes in maternal plasma resistin concentrations.

METHODS OF STUDY

This cross-sectional study included the following groups: (i) normal pregnant women (n = 85) and (ii) pregnant women with pyelonephritis (n = 40). Maternal plasma resistin concentrations were determined by ELISA. Non-parametric statistics was used for analyses.

RESULTS

(i) The median maternal plasma resistin concentration was higher in patients with pyelonephritis than in those with a normal pregnancy (P < 0.001); (ii) among patients with pyelonephritis, the median maternal resistin concentration did not differ significantly between those with and without a positive blood culture (P = 0.3); (iii) among patients with pyelonephritis who were diagnosed with systemic inflammatory response syndrome (SIRS), those who fulfilled > or =3 criteria for SIRS had a significantly higher median maternal plasma resistin concentration than those who met only two criteria; and (iv) maternal WBC count positively correlated with circulating resistin concentration (r = 0.47, P = 0.02).

CONCLUSION

Hyperresistinemia is a feature of acute pyelonephritis during pregnancy. The results of this study support the role of resistin as an acute-phase protein in the presence of bacterial infection during pregnancy.

Serum resistin concentrations in children with Kawasaki disease

OBJECTIVE

Human resistin is expressed strongly in monocytes or macrophages rather than in adipocytes and may play a pivotal role in inflammation. We hypothesize that resistin levels are elevated in patients with Kawasaki disease (KD) in the acute phase and may be associated with the disease severity.

DESIGN AND SUBJECTS

Serum resistin concentrations were measured in 44 Japanese children with KD and 17 age-matched healthy children. All the KD patients were given both aspirin and a single dose of intravenous immunoglobulin (IVIG).

RESULTS

The serum resistin levels at baseline in KD children were significantly higher than those in controls [33.0 (21.6-45.3) vs. 14.8 (12.4-18.6) ng/mL, P < 0.001]. After IVIG therapy, serum resistin levels were significantly decreased to normal control levels. No significant difference in baseline resistin levels was found between the high-risk group and the low-risk group of coronary artery aneurysms.

CONCLUSIONS

We confirmed that resistin was an acute inflammatory protein, but its concentrations were unlikely to predict the prognosis of disease in acute KD patients.

Plasma resistin levels associate with risk for hypertension among nondiabetic women

Emerging evidence suggests a role for resistin in inflammation and vascular dysfunction, which may contribute to the pathogenesis of hypertension, but the association between resistin levels and incident hypertension is unknown. We examined the association between plasma resistin levels and the risk for incident hypertension among 872 women without a history of hypertension or diabetes from the Nurses' Health Study. We identified 361 incident cases of hypertension during 14 years of follow-up. After adjustment for potential confounders, resistin levels in the highest tertile conferred a 75% higher risk for hypertension than the lowest tertile (relative risk [RR] 1.75; 95% confidence interval [CI] 1.19 to 2.56). Further adjustment for other adipokines did not change the RR substantially. In stratified analysis, resistin levels in the highest tertile significantly increased the risk for hypertension among women aged >or=55 years (adjusted RR 2.40; 95% CI 1.55 to 3.73) but not among women aged <55 years (adjusted RR 0.64; 95% CI 0.25 to 1.62). In a subset analysis of 362 women who also had measurements of inflammatory and endothelial biomarkers, plasma resistin levels significantly correlated with IL-6, soluble TNF receptor 2, intercellular adhesion molecule 1, vascular adhesion molecule 1, and E-selectin after controlling for age and body mass index. After further adjustment for these biomarkers and C-reactive protein, resistin levels remained significantly associated with incident hypertension. In conclusion, higher plasma resistin levels independently associate with an increased risk for incident hypertension among women without diabetes.

Transcription of human resistin gene involves an interaction of Sp1 with peroxisome proliferator-activating receptor gamma (PPARgamma)

BACKGROUND

Resistin is a cysteine rich protein, mainly expressed and secreted by circulating human mononuclear cells. While several factors responsible for transcription of mouse resistin gene have been identified, not much is known about the factors responsible for the differential expression of human resistin.

METHODOLOGY/PRINCIPAL FINDING

We show that the minimal promoter of human resistin lies within approximately 80 bp sequence upstream of the transcriptional start site (-240) whereas binding sites for cRel, CCAAT enhancer binding protein alpha (C/EBP-alpha), activating transcription factor 2 (ATF-2) and activator protein 1 (AP-1) transcription factors, important for induced expression, are present within sequences up to -619. Specificity Protein 1(Sp1) binding site (-276 to -295) is also present and an interaction of Sp1 with peroxisome proliferator activating receptor gamma (PPARgamma) is necessary for constitutive expression in U937 cells. Indeed co-immunoprecipitation assay demonstrated a direct physical interaction of Sp1 with PPARgamma in whole cell extracts of U937 cells. Phorbol myristate acetate (PMA) upregulated the expression of resistin mRNA in U937 cells by increasing the recruitment of Sp1, ATF-2 and PPARgamma on the resistin gene promoter. Furthermore, PMA stimulation of U937 cells resulted in the disruption of Sp1 and PPARgamma interaction. Chromatin immunoprecipitation (ChIP) assay confirmed the recruitment of transcription factors phospho ATF-2, Sp1, Sp3, PPARgamma, chromatin modifier histone deacetylase 1 (HDAC1) and the acetylated form of histone H3 but not cRel, C/EBP-alpha and phospho c-Jun during resistin gene transcription.

CONCLUSION

Our findings suggest a complex interplay of Sp1 and PPARgamma along with other transcription factors that drives the expression of resistin in human monocytic U937 cells.

Circulating resistin is increased with decreasing renal function in a general Japanese population: the Hisayama Study

BACKGROUND

The purpose of this study is to investigate the relationship between serum resistin levels and chronic kidney disease (CKD).

METHODS

A total of 3192 community-dwelling subjects (1377 men, 1815 women), aged ≥40 years and without renal failure, were divided into four groups according to quartiles of serum resistin concentrations: ≤7.1, 7.2-9.9, 10.0-14.7 and ≥14.8 ng/mL. The associations of resistin levels with renal function status were examined cross-sectionally. The estimated glomerular filtration rate (eGFR) was calculated using the equation from the Modification of Diet in Renal Disease Study, and CKD was defined as an eGFR of <60 mL/min/1.73 m(2).

RESULTS

The age- and sex-adjusted mean values of eGFR decreased significantly with elevating quartiles of resistin (P for trend <0.001). The age- and sex-adjusted odds ratios (ORs) for the presence of CKD increased progressively with higher quartiles of resistin. This trend remained robust even after controlling for age, sex, body mass index, diabetes, homeostasis model assessment of insulin resistance (HOMA-IR), high-sensitivity C-reactive protein (hs-CRP), triglycerides, high-density lipoprotein and total cholesterol, hypertension, current smoking, current drinking, and regular exercise [second quartile: OR 1.44, 95% confidence interval (CI) 1.05-1.99; third quartile: OR 2.15, 95% CI 1.58-2.92; fourth quartile: OR 2.32, 95% CI 1.71-3.16; P for trend <0.001]. In stratified analyses, high resistin level (≥7.2 ng/mL) was a significant relevant factor in CKD, independent of HOMA-IR or hs-CRP level. Conclusion. Our findings suggest that elevated resistin level is significantly associated with the likelihood of CKD in the general Japanese population.

Maternal plasma concentration of the pro-inflammatory adipokine pre-B-cell-enhancing factor (PBEF)/visfatin is elevated in pregnant patients with acute pyelonephritis

PROBLEM

Visfatin/pre-B-cell-enhancing factor (PBEF) has been implicated in the regulation of the innate immune system, as well as in glucose metabolism. Specifically, visfatin plays a requisite role in delayed neutrophil apoptosis in patients with sepsis. The aim of this study was to determine whether pyelonephritis during pregnancy is associated with changes in maternal plasma visfatin concentration in normal weight and overweight/obese patients.

METHOD OF STUDY

This cross-sectional study included the following groups: (1) normal pregnant women (n = 200) and (2) pregnant women with pyelonephritis (n = 40). Maternal plasma visfatin concentrations were determined by ELISA. Non-parametric statistics was used for analyses.

RESULTS

(1) The median maternal plasma visfatin concentration was significantly higher in patients with pyelonephritis than in those with a normal pregnancy; (2) among overweight/obese pregnant women, those with pyelonephritis had a significantly higher median plasma visfatin concentration than women with a normal pregnancy; and (3) pyelonephritis was independently associated with higher maternal plasma visfatin concentrations after adjustment for maternal age, pre-gestational body mass index, smoking status, gestational age at sampling, and birthweight.

CONCLUSION

Acute pyelonephritis during pregnancy is associated with a high circulating maternal visfatin concentration. These findings suggest that visfatin/PBEF may play a role in the regulation of the complex and dynamic crosstalk between inflammation and metabolism during pregnancy.

Retinol binding protein 4--a novel association with early-onset preeclampsia

OBJECTIVE

Dysregulation of maternal circulating adipokines has been implicated in several "great obstetrical syndromes" including preeclampsia (PE), small-for-gestational age (SGA) neonate and fetal death (FD). It has been suggested that adipokines provide a molecular link between metabolic derangements and inflammatory response in complicated pregnancies. Retinol binding protein 4 (RBP4), a novel adipokine, plays a role in obesity-related disorders, as well as in the regulation of the immune response. The aim of this study was to determine whether there are changes in maternal plasma concentrations of RBP4 in patients with PE and in those with an SGA neonate or FD.

STUDY DESIGN

This cross-sectional study included patients in the following groups: 1) normal pregnancy (n=134); 2) PE (n=104); 3) SGA neonate (n=28); and 4) FD (n=37). Maternal plasma RBP4 concentrations were determined by ELISA. Non-parametric statistics were used for analysis.

RESULTS

1) The median maternal plasma RBP4 concentration was higher among patients with PE than in those with a normal pregnancy (P=0.03); 2) The median maternal plasma RBP4 concentrations of patients with preterm PE (<37 weeks) was higher than that of those with term PE (P=0.017) and than that of those with a normal pregnancy (P=0.002); 3) The median maternal plasma RBP4 concentration did not differ significantly between patients with a normal pregnancy and those with an SGA neonate or with an FD; 4) Among normal pregnant women, the maternal plasma RBP4 concentrations did not correlate with pre-pregnancy body mass index, gestational age at blood sampling and neonatal birthweight.

CONCLUSIONS

1) Preeclampsia, but not pregnancy with an SGA neonate or an FD, is associated with a higher median maternal plasma concentration of RBP4 than normal pregnancy; 2) Preterm PE, and specifically early-onset PE, is associated with higher median RBP4 concentrations in maternal plasma compared to term PE. These findings suggest a role for RBP4 in the pathogenesis of preterm PE, but not in SGA and FD.

Adipocytokine resistin and breast cancer risk

Adipocytokine resistin is a member of the newly discovered family of cysteine-rich protein. Recent data suggest that macrophages are a major source of human resistin. Given the obesity-breast cancer link and convergence of adipocyte and macrophage function, resistin may provide unique insight into links between obesity, inflammation, and breast cancer risk in humans. We conducted a hospital-based case-control study to evaluate whether plasma resistin levels were associated with breast cancer risk in women. We also examined the modification effect of estrogen exposures on the resistin-breast cancer link. Questionnaire information, anthropometric measures, and blood samples were taken before treatment from 380 incident cases with breast cancer and 760 controls admitted for health examination at the Tri-Service General Hospital, Taipei between 2004 and 2008. Plasma levels of resistin were measured by enzyme immunoassay. Cumulative exposure to estrogens were estimated according to the age at menarche and age at enrollment for premenopausal women and age at menarche and age at menopause for postmenopausal women. Cases with breast cancer had significantly elevated resistin concentrations as compared with control subjects. Compared with those in the lowest quartile, the adjusted odds ratios of breast cancer for women in the second, third, and highest quartiles were 1.48 [95% confidence interval (CI) = 0.65-3.38], 1.76 (95% CI = 1.00-4.73), and 2.08 (95% CI = 1.04-3.85), respectively. Furthermore, the biological gradient of breast cancer risk by plasma resistin levels remained after adjustment for measures of adiposity. The dose-dependent relationship of resistin levels with breast cancer risk was notably pronounced among women with excess exposure to estrogens. Adipocytokine resistin may have an adiposity-independent role in breast carcinogenesis. Mechanistic studies to fully elucidate the mechanisms underlying resistin's effects should be pursued in future investigations.

Resistin up-regulates COX-2 expression via TAK1-IKK-NF-kappaB signaling pathway

The hormone resistin, which was originally shown to induce insulin resistance, has been implicated in the regulation of inflammatory processes, but the molecular mechanism underlying such regulation has not been clearly defined. The goal of our study was to determine whether the expression of COX-2 can be induced by resistin and what the potential signaling pathway involved in this process is. Compared with controls, resistin significantly upregulated COX-2 expression in RAW264.7 macrophage cells. Administration of anti-resistin antibody could significantly reduce this effect. Induction of COX-2 by resistin was also markedly reduced in the presence of either dominant negative mutant IkappaBalpha or PDTC, a pharmacological inhibitor of NF-kappaB. On the other hand, NF-kappaB subunit p65 was upregulated by resistin. Moreover, we found that transforming growth factor-beta-activated kinase 1 (TAK1), a mitogen-activated protein kinase kinase kinase (MAPKKK), could be activated in response to resistin. These results suggest that resistin enhances COX-2 expression in mouse macrophage cells in a TAK1-IKK-NF-kappaB-dependent manner and therefore plays a critical role in inflammatory processes.

Regulation of resistin by cyclic mechanical stretch in cultured rat vascular smooth muscle cells

Resistin has a potential role in atherosclerosis; however, the molecular mechanism underlying the increase in resistin expression in atherosclerosis remains unclear. As mechanical stretch plays an important role in atherosclerosis, in the present study we sought to investigate the cellular and molecular mechanisms underlying the regulation of resistin by cyclic mechanical stretch in VSMCs (vascular smooth muscle cells). VSMCs from thoracic aorta of adult Wistar rats were cultured and subjected to cyclic stretch. Cyclic mechanical stretch significantly increased resistin protein and mRNA expression as compared with control cells without stretch. The specific p38 MAPK (mitogen-activated protein kinase) inhibitor SB203580, the antioxidant N-acetylcysteine and p38 MAPK siRNA (small interfering RNA) attenuated the induction of resistin protein by cyclic stretch. Cyclic stretch significantly increased the phosphorylation of p38 MAPK, whereas pre-treatment with SB203580 and N-acetylcysteine significantly inhibited this effect. Cyclic stretch significantly increased ROS (reactive oxygen species) production, and pre-treatment with N-acetylcysteine significantly inhibited stretch-induced ROS production. Cyclic stretch also increased STAT3 (signal transducer and activator of transcription 3)-binding activity and resistin promoter activity, and resistin promoter activity was abolished when STAT3 in the promoter area was mutated. Pre-treatment with SB203580 and N-acetylcysteine significantly attenuated resistin promoter activity induced by cyclic stretch. Cyclic stretch increased the secretion of AngII (angiotensin II) and resistin from cultured VSMCs. Exogenous AngII increased resistin expression, and AngII receptor inhibition attenuated this effect. In conclusion, cyclic mechanical stretch increases resistin expression in cultured rat VSMCs. Stretch-induced resistin expression is mediated through ROS, and the p38 MAPK and STAT3 pathways. Therefore resistin induced by cyclic stretch may contribute to the pathogenesis of atherosclerosis under haemodynamic overload.

Retinol binding protein 4: an adipokine associated with intra-amniotic infection/inflammation

OBJECTIVE

Retinol binding protein 4 (RBP4), a specific carrier for retinol in the blood, is a novel adipokine that has been implicated in the pathophysiology of insulin resistance, and its gene expression has been associated with adipose tissue inflammation. Recently, proteomic profiling of amniotic fluid (AF) from women with preterm labor (PTL) revealed over-expression of RBP4 in those who delivered preterm. The aim of this study was to determine whether RBP4 is present in AF, and if its concentrations change with gestational age, in the presence of labor, and intra-amniotic infection/inflammation (IAI) in patients with spontaneous PTL.

STUDY DESIGN

This cross-sectional study included pregnant women in the following groups: (1) mid-trimester (n = 30); (2) term not in labor (n = 31); (3) term in labor (n = 30); (4) spontaneous PTL without IAI who delivered at term (n = 60); (5) PTL without IAI who delivered preterm (n = 64); and (6) PTL with IAI (n = 56). RBP4 concentrations in AF were determined by ELISA. Non-parametric statistics were used for analyses.

RESULTS

(1) RBP4 was detected in all AF samples; (2) among patients with PTL, women with IAI had a higher median AF RBP4 concentration than those without IAI who delivered preterm (1268.9 ng/ml, interquartile range (IQR) 900.3-1970.1 vs. 815.8 ng/ml, IQR 592.4-1098.1; p < 0.001) and at term (828.7 ng/ml, IQR 499.7-1119.6; p < 0.001); (3) the median AF RBP4 concentration was higher in women in the mid-trimester than in those at term not in labor (1861.1 ng/ml, IQR 1486.2-2034.3 vs. 766.1 ng/ml, IQR 608.5-1154.1; p < 0.0001; (4) the median AF RBP4 concentration did not differ significantly between patients with PTL without IAI who delivered preterm and those who delivered at term (p = 0.7); and (5) among women at term, the median AF RBP4 concentrations was not significantly different between those in labor and those not in labor (p = 0.4).

CONCLUSIONS

RBP4 is a physiologic constituent of the AF. Among patients with PTL, the median AF concentration of immunoreactive RBP4 is elevated in pregnancies complicated by IAI. These results suggest that RBP4 may participate in the host response against IAI.

Resistin is associated with biomarkers of inflammation while total and high-molecular weight adiponectin are associated with biomarkers of inflammation, insulin resistance, and endothelial function

OBJECTIVE

Adiponectin and resistin have been linked to inflammation, endothelial dysfunction, and/or insulin secretion or resistance. It remains to be elucidated which of these adipokines is associated primarily with biomarkers of all or only some of these categories, i.e. biomarkers of inflammation, endothelial dysfunction, and/or insulin secretion or insulinemia.

DESIGN AND METHODS

We studied 1065 healthy women, Nurses' Health Study participants, who provided blood samples in 1989-1990. A cross-sectional analysis was conducted to assess the relationships between total and high-molecular weight (HMW) adiponectin and resistin with inflammatory markers and biomarkers of endothelial dysfunction, insulin secretion, and insulinemia.

RESULTS

Resistin was positively associated with the inflammatory markers soluble tumour necrosis factor-alpha receptor II and interleukin-6 but not with any biomarkers of endothelial function, glycemia, insulinemia, or markers of insulin secretion after multivariate adjustment for age and body mass index (BMI). In both crude and multivariate analyses, total adiponectin was inversely associated with insulin, proinsulin, C-peptide, HbA1c, sE-selectin, and C-reactive protein (CRP) levels. HMW adiponectin was inversely associated with circulating insulin, proinsulin, C-peptide, HbA1c, sE-selectin, and CRP concentrations, even after adjustment for age, BMI, lifestyle factors, exercise, the use of medications as well as the other biomarkers of interest. Total and HMW adiponectin demonstrated negative associations with soluble intercellular adhesion molecule-1, which became nonsignificant after adjustment for confounders, whereas positive associations between soluble vascular cell adhesion molecule-1 and total adiponectin became significant only after multivariate adjustment.

CONCLUSIONS

Total and HMW adiponectin are inversely associated with markers of insulin secretion/insulinemia, endothelial function, and inflammation. Resistin is positively associated only with markers of inflammation.

Differential effect of saturated and unsaturated free fatty acids on the generation of monocyte adhesion and chemotactic factors by adipocytes: dissociation of adipocyte hypertrophy from inflammation

OBJECTIVE

Obesity is associated with monocyte-macrophage accumulation in adipose tissue. Previously, we showed that glucose-stimulated production by adipocytes of serum amyloid A (SAA), monocyte chemoattractant protein (MCP)-1, and hyaluronan (HA) facilitated monocyte accumulation. The current objective was to determine how the other major nutrient, free fatty acids (FFAs), affects these molecules and monocyte recruitment by adipocytes.

RESEARCH DESIGN AND METHODS

Differentiated 3T3-L1, Simpson-Golabi-Behmel syndrome adipocytes, and mouse embryonic fibroblasts were exposed to various FFAs (250 micromol/l) in either 5 or 25 mmol/l (high) glucose for evaluation of SAA, MCP-1, and HA regulation in vitro.

RESULTS

Saturated fatty acids (SFAs) such as laurate, myristate, and palmitate increased cellular triglyceride accumulation, SAA, and MCP-1 expression; generated reactive oxygen species (ROS); and increased nuclear factor (NF) kappaB translocation in both 5 and 25 mmol/l glucose. Conversely, polyunsaturated fatty acids (PUFAs) such as arachidonate, eicosapentaenate, and docosahexaenate (DHA) decreased these events. Gene expression could be dissociated from triglyceride accumulation. Although excess glucose increased HA content, SFAs, oleate, and linoleate did not. Antioxidant treatment repressed glucose- and palmitate-stimulated ROS generation and NFkappaB translocation and decreased SAA and MCP-1 expression and monocyte chemotaxis. Silencing toll-like receptor-4 (TLR4) markedly reduced SAA and MCP-1 expression in response to palmitate but not glucose. DHA suppressed NFkappaB translocation stimulated by both excess glucose and palmitate via a peroxisome prolifterator-activated receptor (PPAR) gamma-dependent pathway.

CONCLUSIONS

Excess glucose and SFAs regulate chemotactic factor expression by a mechanism that involves ROS generation, NFkappaB, and PPARgamma, and which is repressed by PUFAs. Certain SFAs, but not excess glucose, trigger chemotactic factor expression via a TLR4-dependent pathway.

Adipokine signaling in inflammatory bowel disease

While the incidence of inflammatory bowel disease (IBD) is still increasing, the etiology has not finally been dissected. The main hypothesis suggests that the mucosal immune system is hyperresponsive to dietary factors and commensal bacteria in genetically predisposed individuals. Burrill Crohn himself described a local hypertrophy of the mesenteric fat tissue adjacent to the segments of inflamed intestine. In addition, more recent data indicate altered local expression and serum levels of some adipocyte-derived mediators (adipokines) with immune-modulating capacities in IBD. This review focuses on the role of adipose tissue and adipokines in the immune system, with particular focus on the mucosal immune system. The available data will serve to establish a working hypothesis on how the mesenteric fat tissue contributes to the pathogenesis of Crohn's disease.

Diabetes and hypertension markedly increased the risk of ischemic stroke associated with high serum resistin concentration in a general Japanese population: the Hisayama Study

Background

Resistin, secreted from adipocytes, causes insulin resistance in mice. The relationship between resistin and coronary artery disease is highly controversial, and the information regarding resistin and ischemic stroke is limited. In the present study, the association between serum resistin concentration and cardiovascular disease (CVD) was investigated in a general Japanese population.

Methods

A total of 3,201 community-dwelling individuals aged 40 years or older (1,382 men and 1,819 women) were divided into quintiles of serum resistin, and the association between resistin and CVD was examined cross-sectionally. The combined effect of either diabetes or hypertension and high serum resistin was also assessed. Serum resistin was measured using ELISA.

Results

Compared to those without CVD, age- and sex-adjusted mean serum resistin concentrations were greater in subjects with CVD (p = 0.002) or ischemic stroke (p < 0.001), especially in those with lacunar and atherothrombotic infarction, but not elevated in subjects with hemorrhagic stroke or coronary heart disease. When analyzed by quintile of serum resistin concentration, the age- and sex-adjusted odds ratio (OR) for having CVD and ischemic stroke increased with quintile of serum resistin (p for trends, 0.02 for CVD, < 0.001 for ischemic stroke), while such associations were not observed for hemorrhagic stroke or coronary heart disease. Compared to the first quintile, the age- and sex-adjusted OR of ischemic stroke was greater in the third (OR = 3.54; 95% confidence interval [CI], 1.17-10.67; p = 0.02), fourth (OR = 4.48; 95% CI, 1.53-13.09; p = 0.006), and fifth quintiles (OR = 4.70; 95% CI, 1.62-13.61; p = 0.004). These associations remained substantially unchanged even after adjustment for other confounding factors including high-sensitivity C-reactive protein. In the stratified analysis, the combination of high serum resistin and either diabetes or hypertension markedly increased the risk of ischemic stroke.

Conclusion

Elevated serum resistin concentration appears to be an independent risk factor for ischemic stroke, especially lacunar and atherothrombotic infarction in the general Japanese population. The combination of high resistin and the presence of either diabetes or hypertension increased the risk of ischemic stroke.

Diabetes and hypertension markedly increased the risk of ischemic stroke associated with high serum resistin concentration in a general Japanese population: the Hisayama Study

BACKGROUND

Resistin, secreted from adipocytes, causes insulin resistance in mice. The relationship between resistin and coronary artery disease is highly controversial, and the information regarding resistin and ischemic stroke is limited. In the present study, the association between serum resistin concentration and cardiovascular disease (CVD) was investigated in a general Japanese population.

METHODS

A total of 3,201 community-dwelling individuals aged 40 years or older (1,382 men and 1,819 women) were divided into quintiles of serum resistin, and the association between resistin and CVD was examined cross-sectionally. The combined effect of either diabetes or hypertension and high serum resistin was also assessed. Serum resistin was measured using ELISA.

RESULTS

Compared to those without CVD, age- and sex-adjusted mean serum resistin concentrations were greater in subjects with CVD (p = 0.002) or ischemic stroke (p < 0.001), especially in those with lacunar and atherothrombotic infarction, but not elevated in subjects with hemorrhagic stroke or coronary heart disease. When analyzed by quintile of serum resistin concentration, the age- and sex-adjusted odds ratio (OR) for having CVD and ischemic stroke increased with quintile of serum resistin (p for trends, 0.02 for CVD, < 0.001 for ischemic stroke), while such associations were not observed for hemorrhagic stroke or coronary heart disease. Compared to the first quintile, the age- and sex-adjusted OR of ischemic stroke was greater in the third (OR = 3.54; 95% confidence interval [CI], 1.17-10.67; p = 0.02), fourth (OR = 4.48; 95% CI, 1.53-13.09; p = 0.006), and fifth quintiles (OR = 4.70; 95% CI, 1.62-13.61; p = 0.004). These associations remained substantially unchanged even after adjustment for other confounding factors including high-sensitivity C-reactive protein. In the stratified analysis, the combination of high serum resistin and either diabetes or hypertension markedly increased the risk of ischemic stroke.

CONCLUSION

Elevated serum resistin concentration appears to be an independent risk factor for ischemic stroke, especially lacunar and atherothrombotic infarction in the general Japanese population. The combination of high resistin and the presence of either diabetes or hypertension increased the risk of ischemic stroke.

Adiponectin is a mediator of the inverse association of adiposity with radiographic damage in rheumatoid arthritis

OBJECTIVE

Recent reports have suggested that increasing adiposity may protect against radiographic damage in rheumatoid arthritis (RA). We explored the role of serum adipokines (adiponectin, resistin, and leptin) in mediating this association.

METHODS

Patients with RA underwent total-body dual x-ray absorptiometry for measurement of total and regional body fat and lean mass, abdominal computed tomography for measurement of visceral fat area, and radiographs of the hands and feet scored according to the modified Sharp/van der Heijde (SHS) method. Serum levels of adipokines were measured and cross-sectional associations with radiographic damage were explored, adjusting for pertinent confounders. The associations of measures of adiposity with radiographic damage were explored with the introduction of adipokines into multivariable modeling as potential mediators.

RESULTS

Among the 197 patients studied, adiponectin demonstrated a strong association with radiographic damage, with the log SHS score increasing by 0.40 units for each log unit increase in adiponectin (P = 0.001) after adjusting for pertinent predictors of radiographic damage. Adiponectin independently accounted for 6.1% of the explainable variability in SHS score, a proportion comparable with rheumatoid factor, and greater than HLA-DRB1 shared epitope alleles or C-reactive protein levels. Resistin and leptin were not associated with radiographic damage in adjusted models. An inverse association between visceral fat area and radiographic damage was attenuated when adiponectin was modeled as a mediator. The association of adiponectin with radiographic damage was stronger in patients with longer disease duration.

CONCLUSION

Adiponectin may represent a mechanistic link between low adiposity and increased radiographic damage in RA. Adiponectin modulation may represent a novel strategy for attenuating articular damage.

Dysregulation of maternal serum adiponectin in preterm labor

OBJECTIVE

Intra-amniotic and systemic infection/inflammation have been causally linked to preterm parturition and fetal injury. An emerging theme is that adipose tissue can orchestrate a metabolic response to insults, but also an inflammatory response via the production of adipocytokines, and that these two phenomenons are interrelated. Adiponectin, an insulin-sensitising, anti-inflammatory adipocytokine, circulates in multimeric complexes including low-molecular weight (LMW) trimers, medium-molecular weight (MMW) hexamers and high-molecular weight (HMW) isoforms. Each of these complexes can exert differential biological effects. The aim of this study was to determine whether spontaneous preterm labor (PTL) with intact membranes and intra-amniotic infection/inflammation (IAI) is associated with changes in maternal serum circulating adiponectin multimers.

STUDY DESIGN

This cross-sectional study included patients in the following groups: (1) normal pregnant women (n=158); (2) patients with an episode of preterm labor and intact membranes without IAI who delivered at term (n=41); (3) preterm labor without IAI who delivered preterm (n=27); and (4) preterm labor with IAI who delivered preterm (n=36). Serum adiponectin multimers (total, HMW, MMW and LMW) concentrations were determined by ELISA. Non-parametric statistics were used for analyses.

RESULTS

(1) Preterm labor leading to preterm delivery or an episode of preterm labor that does not lead to preterm delivery was associated with a lower median maternal serum concentration of total and HMW adiponectin, a lower median HMW/total adiponectin ratio and a higher median LMW/total adiponectin ratio than normal pregnancy; (2) among patients with preterm labor, those with IAI had the lowest median concentration of total and HMW adiponectin, as well as the lowest median HMW/total adiponectin ratio; (3) the changes in maternal adiponectin and adiponectin multimers remained significant after adjusting for confounding factors such as maternal age, BMI, gestational age at sampling and parity.

CONCLUSION

(1) Preterm labor is characterised by a change in the profile of adiponectin multimers concentrations and their relative isoforms. These changes were observed in patients with an episode of preterm labor not leading to preterm delivery, in patients with intra-amniotic inflammation, or in those without evidence of intra-amniotic inflammation. (2) The changes in adiponectin multimer concentrations reported in preterm labor are different from those previously reported in spontaneous labor at term, suggesting that there is a fundamental difference between preterm labor and labor at term. (3) The findings reported herein provide the first evidence for the participation of adiponectin multimer in preterm parturition. We propose that adiponectins and adipokines in general provide a mechanism to organise the metabolic demands generated by the process of preterm parturition regardless of the nature of the insult (intra-amniotic inflammation or not).

Independent association of circulating resistin with glomerular filtration rate in the early stages of essential hypertension

Resistin, a newly discovered protein, promotes endothelial dysfunction and proinflammatory activation, contributing to subclinical atherosclerosis in different clinical settings. In this study we sought to investigate the relationship of increased resistin levels with estimated glomerular filtration rate (eGFR), the most established marker of kidney impairment, in hypertensive subjects. Our population consisted of 132 untreated non-diabetic subjects with stage I-II essential hypertension (49 males, mean age=54 years, office blood pressure (BP)=159/100 mm Hg). In all patients eGFR was assessed by the Modification in Renal Disease equation and venous blood sampling was performed for estimation of resistin concentrations. The distribution of resistin was split by the median (4.63 ng ml(-1)) and accordingly subjects were stratified into those with high and low values. Hypertensive patients with high (n=66) compared to those with low resistin (n=66) exhibited lower eGFR values (77.1+/-9.4 vs 89.1+/-12.2 ml min(-1) per 1.73m(2), P<0.0001), even after adjustment for established confounders. In the total population, resistin was associated with 24-h systolic BP (r=0.244, P<0.05), serum creatinine (r=0.311, P=0.007) and eGFR (r=-0.519, P<0.0001). Multiple regression analysis revealed that age (b=0.379, P=0.01), body mass index (b=0.158, P=0.022), 24-h systolic BP (b=0.284, P=0.006) and resistin (b=0.429, P<0.0001) were independent predictors of eGFR (R(2)=0.436, P<0.0001). In essential hypertensive subjects, higher resistin levels are associated with renal function impairment, as reflected by decreased eGFR. Moreover, the independent association of resistin with eGFR suggests involvement of resistin in the progression of kidney damage in the early stages of hypertension.

Stress and body mass index each contributes independently to tumor necrosis factor-alpha production in prepubescent Latino children

This investigation extended prior work by determining if stress and body mass index (BMI) contributed independently to tumor necrosis factor-alpha (TNF-alpha) levels among prepubescent Latino children and if sex and family history of type 2 diabetes mellitus (T2DM) modified these relationships. Data were collected in South Florida from 112 nondiabetic school-aged Hispanic children, of whom 43.8% were obese (BMI >/= 95th percentile) and 51.8% presented with a family history of T2DM. Stressful life events were assessed via parental report using a life events scale. Plasma TNF-alpha levels were determined with enzyme-linked immunosorbent assay. The relative contributions of stress and BMI with TNF-alpha levels and the potential interaction effects of sex and family history of T2DM were analyzed with multiple linear regression analyses. Stress and BMI each accounted for a significant proportion of the unique variance associated with TNF-alpha. The association between stress and TNF-alpha was not modified by sex or family history of T2DM. These findings implicate BMI and stress as independent determinants of TNF-alpha (an inflammatory cytokine and adipocytokine) among Latino children. Future investigations should examine the potential roles of exercise, nutritional status, age, and growth hormone in explicating the relationship between TNF-alpha production and psychosocial distress and risk for infection among obese children.