Resistin is secreted from macrophages in atheromas and promotes atherosclerosis

Role of adipokines in atherosclerosis: interferences with cardiovascular complications in rheumatic diseases

Patients with rheumatic diseases have an increased risk of mortality by cardiovascular events. In fact, several rheumatic diseases such as rheumatoid arthritis, osteoarthritis, systemic lupus erythematosus, and ankylosing spondylitis are associated with a higher prevalence of cardiovascular diseases (CVDs). Although traditional cardiovascular risk factors have been involved in the pathogenesis of cardiovascular diseases in rheumatic patients, these alterations do not completely explain the enhanced cardiovascular risk in this population. Obesity and its pathologic alteration of fat mass and dysfunction, due to an altered pattern of secretion of proinflammatory adipokines, could be one of the links between cardiovascular and rheumatic diseases. Indeed, the incidence of CVDs is augmented in obese individuals with rheumatic disorders. Thus, in this paper we explore in detail the relationships among adipokines, rheumatic diseases, and cardiovascular complications by giving to the reader a holistic vision and several suggestions for future perspectives and potential clinical implications.

Resistin: functional roles and therapeutic considerations for cardiovascular disease

Resistin, originally described as an adipocyte-specific hormone, has been suggested to be an important link between obesity, insulin resistance and diabetes. Although its expression was initially defined in adipocytes, significant levels of resistin expression in humans are mainly found in mononuclear leukocytes, macrophages, spleen and bone marrow cells. Increasing evidence indicates that resistin plays important regulatory roles apart from its role in insulin resistance and diabetes in a variety of biological processes: atherosclerosis and cardiovascular disease (CVD), non-alcoholic fatty liver disease, autoimmune disease, malignancy, asthma, inflammatory bowel disease and chronic kidney disease. As CVD accounts for a significant amount of morbidity and mortality in patients with diabetes and without diabetes, it is important to understand the role that adipokines such as resistin play in the cardiovascular system. Evidence suggests that resistin is involved in pathological processes leading to CVD including inflammation, endothelial dysfunction, thrombosis, angiogenesis and smooth muscle cell dysfunction. The modes of action and signalling pathways whereby resistin interacts with its target cells are beginning to be understood. In this review, the current knowledge about the functions and pathophysiological implications of resistin in CVD development is summarized; clinical translations, therapeutic considerations and future directions in the field of resistin research are discussed.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

Resistin: functional roles and therapeutic considerations for cardiovascular disease

Resistin, originally described as an adipocyte-specific hormone, has been suggested to be an important link between obesity, insulin resistance and diabetes. Although its expression was initially defined in adipocytes, significant levels of resistin expression in humans are mainly found in mononuclear leukocytes, macrophages, spleen and bone marrow cells. Increasing evidence indicates that resistin plays important regulatory roles apart from its role in insulin resistance and diabetes in a variety of biological processes: atherosclerosis and cardiovascular disease (CVD), non-alcoholic fatty liver disease, autoimmune disease, malignancy, asthma, inflammatory bowel disease and chronic kidney disease. As CVD accounts for a significant amount of morbidity and mortality in patients with diabetes and without diabetes, it is important to understand the role that adipokines such as resistin play in the cardiovascular system. Evidence suggests that resistin is involved in pathological processes leading to CVD including inflammation, endothelial dysfunction, thrombosis, angiogenesis and smooth muscle cell dysfunction. The modes of action and signalling pathways whereby resistin interacts with its target cells are beginning to be understood. In this review, the current knowledge about the functions and pathophysiological implications of resistin in CVD development is summarized; clinical translations, therapeutic considerations and future directions in the field of resistin research are discussed.

LINKED ARTICLES

This article is part of a themed section on Fat and Vascular Responsiveness. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.165.issue-3.

A novel pro-inflammatory mechanism of action of resistin in human endothelial cells: up-regulation of SOCS3 expression through STAT3 activation

Resistin is a significant local and systemic regulatory cytokine involved in inflammation. Suppressors of cytokine signaling (SOCS) proteins are intracellular regulators of receptor signal transduction induced by several cytokines in a cytokine and cell specific manner. Resistin up-regulates SOCS3 expression in mice adipocytes but it is not known whether this is a common occurrence in other cells. We questioned whether resistin-induces SOCS3 in human endothelial cells and if signal transducer and activator of transcription (STAT) proteins are involved in the process. The Real-Time PCR and Western blot analysis showed that in resistin-activated HEC the gene and protein expression of SOCS3 were significantly increased. Furthermore, resistin induced activation of STAT3 as characterized by increased tyrosine phosphorylation. Resistin-induced SOCS3 expression was blocked by specific inhibitors of STAT3 signaling and by the transfection of siRNA specific for STAT3. Silencing of SOCS3 gene expression by transfection with SOCS3 siRNA reduced the expression of resistin induced-P-selectin and fractalkine in HEC. Together, our results demonstrate that in HEC (1) resistin up-regulates SOCS3 expression and activates STAT3 transcription factor; (2) the increase in SOCS3 mRNA and protein expression as well as STAT3 activation have a long-lasting effect (up to 18h); (3) inhibition of SOCS3 function prevents resistin-induced expression of cell adhesion molecules P-selectin and fractalkine and thus activation of endothelial cells. The data uncover a new resistin-mediated mechanism in human endothelial cells and designate SOCS3 as a novel therapeutic target to modulate resistin-dependent inflammation in vessel wall diseases.

Sirt1 inhibits resistin expression in aortic stenosis

The development of human calcified aortic stenosis (AS) includes age-dependent processes that have been involved in atherosclerosis, such as infiltration of macrophages in aortic valves, which then promote production of many pro-inflammatory cytokines, including resistin. However, the molecular mechanisms contributing to these processes are not established. Since Sirt1 has been shown to modulate macrophage biology and inflammation, we examined its levels in human AS and tested its impact on resistin expression. Sirt1 mRNA (p = 0.01) and protein (p<0.05) levels were reduced in explanted valves from AS patients (n = 51) compared to those from control (n = 11) patients. Sirt1 mRNA levels were negatively associated with resistin mRNA levels quantified in AS valves (p = 0.02). Stimulation of Sirt1 by resveratrol or virus-driven overexpression robustly diminished resistin mRNA and protein expression in macrophages, whereas down-regulation of Sirt1 triggered a large increase in resistin expression. These effects were direct, as chromatin immunoprecipitation assays showed that Sirt1 physically interacted with the resistin promoter region at an AP-1 response element. Moreover, Sirt1 blocked c-jun-induced resistin transactivation in gene reporter assays. These findings demonstrate that, in calcified AS, levels of Sirt1 are reduced whereas those of resistin are increased within aortic valve leaflets. Our results also suggest that this loss of Sirt1 expression alleviates its inhibition of resistin transcription in macrophages. Although the overall contribution of this process to the underlying mechanisms for AS disease development remains unresolved, these observations suggest that modification of Sirt1 expression and/or activity could represent a novel approach against inflammation in AS.

Inflammation and oxidative stress in obesity-related glomerulopathy

Obesity-related glomerulopathy is an increasing cause of end-stage renal disease. Obesity has been considered a state of chronic low-grade systemic inflammation and chronic oxidative stress. Augmented inflammation in adipose and kidney tissues promotes the progression of kidney damage in obesity. Adipose tissue, which is accumulated in obesity, is a key endocrine organ that produces multiple biologically active molecules, including leptin, adiponectin, resistin, that affect inflammation, and subsequent deregulation of cell function in renal glomeruli that leads to pathological changes. Oxidative stress is also associated with obesity-related renal diseases and may trigger the initiation or progression of renal damage in obesity. In this paper, we focus on inflammation and oxidative stress in the progression of obesity-related glomerulopathy and possible interventions to prevent kidney injury in obesity.

Inflammation and metabolic dysfunction: links to cardiovascular diseases

Abdominal obesity is a major risk factor for cardiovascular disease, and recent studies highlight a key role of adipose tissue dysfunction, inflammation, and aberrant adipokine release in this process. An increased demand for lipid storage results in both hyperplasia and hypertrophy, finally leading to chronic inflammation, hypoxia, and a phenotypic change of the cellular components of adipose tissue, collectively leading to a substantially altered secretory output of adipose tissue. In this review we have assessed the adipo-vascular axis, and an overview of adipokines associated with cardiovascular disease is provided. This resulted in a first list of more than 30 adipokines. A deeper analysis only considered adipokines that have been reported to impact on inflammation and NF-κB activation in the vasculature. Out of these, the most prominent link to cardiovascular disease was found for leptin, TNF-α, adipocyte fatty acid-binding protein, interleukins, and several novel adipokines such as lipocalin-2 and pigment epithelium-derived factor. Future work will need to address the potential role of these molecules as biomarkers and/or drug targets.

Potential effect of resistin on the ET-1-increased reactions of blood pressure in rats and Ca2+ signaling in vascular smooth muscle cells

Resistin and endothelin-1 (ET-1) are upregulated in people with type II diabetes mellitus, central obesity, and hypertension. ET-1 signaling is involved in Ca(2+)-contraction coupling and related to blood pressure regulation. The aim of this study is to investigate the role of resistin on ET-1-increased blood pressure and Ca(2+) signaling. The blood pressure and cytosolic Ca(2+) of vascular smooth muscle cells (VSMCs) of Sprague-Dawley rats were detected. The data demonstrated that resistin accelerated and prolonged ET-1-induced increases in blood pressure and had significant effects on ET-1-increased Ca(2+) reactions. Resistin-enhanced ET-1-increased Ca(2+) reactions were reversed by blockers of store-operated Ca(2+) entry (SOCE) and extracellular-signal-regulated kinase (ERK). The endogenous expression of Orai and stromal interaction molecular (STIM) were characterized in the VSMCs. Furthermore, resistin-enhanced ET-1 Ca(2+) reactions and the resistin-dependent activation of SOCE were abolished under STIM1-siRNA treatment, indicating that STIM1 plays an important role in resistin-enhanced ET-1 Ca(2+) reactions in VSMCs. Resistin appears to exert effects on ET-1-induced Ca(2+) increases by enhancing the activity of ERK-dependent SOCE (STIM1-partcipated), and may accelerate and prolong ET-1-increased blood pressure via the same pathway.

Adipose tissue in the pathophysiology of cardiovascular disease: Who is guilty?

Epidemiological evidence has shown how abdominal obesity is closely associated with the development of cardiovascular disease. It has been demonstrated that patients with extensive adipose tissue usually have other concomitant cardiovascular risk factors, such insulin resistance, hypertension and dyslipidemia. Moreover, obese patients have a significantly higher risk of developing thrombophilic events compared with the non-obese. Thus, obesity is actually considered an independent cardiovascular risk factor. The pathophysiological mechanisms responsible for the association between obesity and cardiovascular disease remain largely unknown. However, it has been postulated that obese patients have an “inflammatory milieu” responsible for their metabolic disorders and vascular disease. In this context, adipocyte-derived molecules with inflammatory activity might play a pivotal role in the development of these mechanisms. In the present report, we provide an updated overview on the molecules produced by adipose tissue that are potentially involved in cardiovascular pathophysiology.

Dietary strawberry powder reduces blood glucose concentrations in obese and lean C57BL/6 mice, and selectively lowers plasma C-reactive protein in lean mice

The purpose of the present study was to test the anti-inflammatory and blood glucose (BG)-regulating capacity of strawberries in a mouse model of diet-induced obesity. A total of thirty-six male C57BL/6J mice were randomly divided into four groups (nine mice per group). Mice were fed a low-fat diet (LF, 13 % fat), the LF supplemented with 2·6 % freeze-dried strawberry powder (LFSB), a high-fat diet (HF, 44 % fat) or the HF supplemented with 2·6 % strawberry powder (HFSB). Blood samples were collected to measure BG, inflammation and systemic markers for endocrine function of pancreas and adipose tissue. Splenocytes were harvested at the end of the study and activated with either anti-cluster of differentiation (CD) 3/anti-CD28 antibodies or lipopolysaccharide to test immune responsiveness. The HF increased non-fasted BG, insulin, soluble intracellular adhesion molecule-1, E-selectin, leptin, resistin and plasminogen activator protein-1 (P < 0·05). High dietary fat decreased IL-4 production from activated splenocytes (P < 0·05). BG concentrations were lower in the mice supplemented with SB (10·64 mmol/l) compared to the non-supplemented mice (11·37 mmol/l; P = 0·0022). BG values were approximately 6·5 % lower in the supplemented mice. Additionally, SB lowered plasma C-reactive protein in the LFSB group compared to the other three groups (P < 0·05). The dietary intake of SB approximated one human serving of strawberries. These results, although modest, support a promising role for dietary strawberries in reducing the risks associated with obesity and diabetes, and regulating the levels of inflammatory markers in non-obese individuals.

Circulating chemerin level is independently correlated with arterial stiffness

AIM

Adipokines have been implicated in the pathogenesis of obesity and obesity-related disorders, including atherosclerosis. Chemerin is a recently discovered adipokine which is closely correlated with various metabolic phenotypes in humans. We examined the association between circulating chemerin levels and arterial stiffness, as represented by the brachial ankle pulse wave velocity (baPWV).

METHODS

Fifty-eight obese and 62 non-obese individuals participated in the study. We measured the serum chemerin and high sensitivity C-reactive protein (hsCRP) levels, and the homeostasis model assessment of insulin resistance (HOMA-IR), as well as other cardiovascular risk factors. Vascular health was assessed by the baPWV and carotid intima-media thickness (IMT).

RESULTS

The serum chemerin level was significantly increased in obese individuals compared with lean controls (120.14±19.43 ng/mL vs. 106.81±23.39 ng/mL, p = 0.001). The circulating chemerin level had a significant positive correlation with the body mass index, waist circumference, HOMA-IR, and low-density lipoprotein-cholesterol, triglycerides, and hsCRP levels. The serum chemerin level was significantly associated with the baPWV (r= 0.280, p= 0.002), but not the carotid IMT (r= 0.065, p= 0.504). Multiple stepwise regression analysis showed that age (p < 0.001), waist circumference (p= 0.038), systolic blood pressure (p < 0.001), and serum fasting glucose (p= 0.003) and chemerin levels (p= 0.017) were definitive risk factors for arterial stiffness (r(2)=0.457).

CONCLUSIONS

The circulating chemerin level was an independent risk factor for arterial stiffness even after adjusting for other cardiovascular risk factors.

Resistin induces monocyte-endothelial cell adhesion by increasing ICAM-1 and VCAM-1 expression in endothelial cells via p38MAPK-dependent pathway

Resistin, firstly reported as an adipocyte-specific hormone, is suggested to be an important link between obesity and diabetes. Recent studies have suggested an association between resistin and atherogenic processes. The adhesion of circulating monocytes to endothelial cells is a critical step in the early stages of atherosclerosis. The purpose of the present study was to investigate the effect of resistin on the adhesion of THP-1 monocytes to human umbilical vein endothelial cells (HUVECs) and the underlying mechanism. Our results showed that resistin caused a significant increase in monocyte adhesion. In exploring the underlying mechanisms of resistin action, we found that resistin-induced monocyte adhesion was blocked by inhibition of p38MAPK activation using SB203580 and SB202190. Furthermore, resistin increased the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) by HUVECs and these effects were also p38MAPK-dependent. Resistin-induced monocyte adhesion was also blocked by monoclonal antibodies against ICAM-1 and VCAM-1. Taken together, these results show that resistin increases both the expression of ICAM-1 and VCAM-1 by endothelial cells and monocyte adhesion to HUVECs via p38MAPK-dependent pathways.

Human resistin: found in translation from mouse to man

The discovery of resistin 10 years ago as a fat cell-secreted factor that modulates insulin resistance suggested a link to the current obesity-associated epidemics of diabetes and cardiovascular disease, which are major human health concerns. Although adipocyte-derived resistin is indisputably linked to insulin resistance in rodent models, the relevance of human resistin is complicated because human resistin is secreted by macrophages rather than adipocytes, and because of the descriptive nature of human epidemiology. In this review, we examine the recent and growing evidence that human resistin is an inflammatory biomarker and a potential mediator of diabetes and cardiovascular disease.

Adipokine resistin is a key player to modulate monocytes, endothelial cells, and smooth muscle cells, leading to progression of atherosclerosis in rabbit carotid artery

OBJECTIVES

We investigated the effects of human resistin on atherosclerotic progression and clarified its underlying mechanisms.

BACKGROUND

Resistin is an adipokine first identified as a mediator of insulin resistance in murine obesity models. But, its role in human pathology is under debate. Although a few recent studies suggested the relationship between resistin and atherosclerosis in humans, the causal relationship and underlying mechanism have not been clarified.

METHODS

We cloned rabbit resistin, which showed 78% identity to human resistin at the complementary deoxyribonucleic acid level, and its expression was examined in 3 different atherosclerotic rabbit models. To evaluate direct role of resistin on atherosclerosis, collared rabbit carotid arteries were used. Histological and cell biologic analyses were performed.

RESULTS

Rabbit resistin was expressed by macrophages of the plaque in the 3 different atherosclerotic models. Peri-adventitial resistin gene transfer induced macrophage infiltration and expression of various inflammatory cytokines, resulting in the acceleration of plaque growth and destabilization. In vitro experiments elucidated that resistin increased monocyte-endothelial cell adhesion by upregulating very late antigen-4 on monocytes and their counterpart vascular cell adhesion molecule-1 on endothelial cells. Resistin augmented monocyte infiltration in collagen by direct chemoattractive effect as well as by enhancing migration toward monocyte chemotactic protein-1. Administration of connecting segment-1 peptide, which blocks very late antigen-4 × vascular cell adhesion molecule-1 interaction, ameliorated neointimal growth induced by resistin in vivo.

CONCLUSIONS

Our results indicate that resistin aggravates atherosclerosis by stimulating monocytes, endothelial cells, and vascular smooth muscle cells to induce vascular inflammation. These findings provide the first insight on the causal relationship between resistin and atherosclerosis.

Resistin level is positively correlated with thrombotic complications in Southern Chinese metabolic syndrome patients

BACKGROUND

The metabolic syndrome (MetS) has been found to be closely related with thrombotic diseases. The mechanism, however, is far from elucidated.

AIM

This study was designed to investigate the relationship between endogenous resistin and thrombosis mediating factors, as well as its potential effects on the gene expression of cardiovascular disease biomarkers.

METHODS

Ninety patients satisfied the MetS criteria, and 55 healthy subjects were recruited as part of a single-center clinical study. Plasma levels of resistin, tissue factor (TF), tissue factor pathway inhibitor (TFPI), tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1) were measured by enzymelinked immunosorbent assays. The effect of resistin on the expression of cardiovascular disease biomarkers in human umbilical vein endothelial cells (HUVEC) was assayed by gene microarray.

RESULTS

1) The average levels of resistin in MetS patients with or without acute myocardial or cerebral infarction were significantly higher than those of the controls. 2) The TF and TFPI increase was higher in MetS with infarction patients than in MetS patients. 3) In MetS with infarction patients, resistin was positively correlated with TF and PAI-1 (r=0.313, p=0.008; r=0.401, p=0.002, respectively). 4) In HUVEC, the microarray showed that apolipoprotein C-I, ACE, tumor necrosis factor receptor superfamily member 1A (TNFRSF1A) and member 5 (CD40) genes expression were dramatically increased by resistin.

CONCLUSION

In patients with MetS, resistin is strongly associated with hypercoagulative and hypofibrinolitic activities. Moreover, resistin may induce thrombotic complications via mediating the lipoprotein metabolism and stimulating inflammation.

Matrix metalloproteinases modulated by protein kinase Cε mediate resistin-induced migration of human coronary artery smooth muscle cells

BACKGROUND

Emerging evidence showed that resistin induces vascular smooth muscle cell (VSMC) migration, a critical step in initiating vascular restenosis. Adhesion molecule expression and cytoskeletal rearrangement have been observed in this progress. Given that matrix metalloproteinases (MMPs) also regulate cell migration, we hypothesized that MMPs may mediate resistin-induced VSMC migration.

METHODS

Human VSMCs were treated with recombinant human resistin at physiologic (10 ng/mL) and pathologic (40 ng/mL) concentrations for 24 hours. Cell migration was determined by the Boyden chamber assay. MMP and tissue inhibitor metalloproteinase (TIMP) mRNA and protein levels were measured with real-time PCR and ELISA. MMP enzymatic activity was measured by zymography. In another experiment, neutralizing antibodies against MMP-2 and MMP-9 were coincubated with resistin in cultured VSMCs. The regulation of MMP by protein kinase C (PKC) was determined by εV1-2, a selective PKCε inhibitor.

RESULTS

Resistin-induced smooth muscle cell (SMC) migration was confirmed by the Boyden chamber assay. Forty nanograms/milliliter resistin increased SMC migration by 3.7 fold. Additionally, resistin stimulated MMP-2 and -MMP9 mRNA and protein expressions. In contrast, the TIMP-1 and TIMP-2 mRNA levels were inhibited by resistin. Neutralizing antibodies against MMP-2 and MMP-9 effectively reversed VSMC migration. Furthermore, resistin activated PKCε, but selective PKCε inhibitor suppressed resistin-induced MMP expression, activity, and cell migration.

CONCLUSIONS

Our study confirmed that resistin increased vascular smooth muscle cell migration in vitro. In terms of mechanism, resistin-stimulated cell migration was associated with increased MMP expression, which was dependent on PKCε activation.

Resistin contributes to neointimal formation via oxidative stress after vascular injury

Resistin may play a major potential role in vascular remodelling and may contribute to atherogenesis. However, the role of VSMC (vascular smooth muscle cell)-derived resistin in neointimal formation is not well understood. We hypothesize that endogenous resistin derived from VSMCs may contribute to neointimal formation after vascular injury. VSMCs from thoracic aorta of adult Wistar rats were cultured. The carotid artery from adult Wistar rats was injured by balloon catheter. Resistin significantly increased migration and proliferation of VSMCs. Resistin siRNA (small interfering RNA) and resistin antibody significantly inhibited migration and proliferation of VSMCs induced by conditioned medium from stretched VSMCs. Resistin protein and mRNA expression significantly increased at 14 days after carotid injury. Resistin siRNA and NAC (N-acetylcysteine) significantly reduced resistin protein and mRNA expression induced by balloon injury. Carotid artery injury increased ROS (reactive oxygen species) production. Treatment with NAC and resistin siRNA decreased ROS production. The neointimal area was significantly increased after carotid injury and was significantly reduced by resistin siRNA and NAC. In conclusion, resistin increases migration and proliferation of VSMCs, and expression of resistin in carotid artery significantly increases after injury. Resistin siRNA attenuates neointimal formation after carotid injury partly through an antioxidative mechanism. Resistin may play a pivotal role in the pathogenesis of neointimal thickening after mechanical injury.

Failure of the Adipocytokine, Resistin, to Protect the Heart From Ischemia-Reperfusion Injury

Experimental studies have linked the adipocytokines with acute cardioprotection. Whether the adipocytokine, resistin, confers protection is, however, debatable. In the current study, the actions of resistin, administered at reperfusion, were investigated in in vivo and in vitro rodent and in vitro human models of myocardial ischemia-reperfusion (I/R) injury. Resistin did not reduce infarct size in Langendorff-perfused rat hearts or murine hearts perfused in vivo. Resistin also did not protect human atrial muscle subjected to hypoxia-reoxygenation. Although cyclosporin A delayed mitochondrial permeability transition pore (MPTP) opening in murine cardiomyocytes, resistin was ineffective. Western blot analysis revealed that resistin treatment was associated with enhanced phosphorylation of Akt, at both the serine-473 (+ 51.9%, P = .01) and threonine-308 (+107%, P < .01) phosphorylation sites, although not to the extent seen with ischemic preconditioning (+132.5%, P = .002 and +389.1%, P < .01, respectively). We conclude that resistin administered at reperfusion at concentrations/doses equivalent to normal (upper end) and pathological serum levels does not protect against I/R injury or inhibit MPTP opening.

Insulin suppresses endotoxin-induced oxidative, nitrosative, and inflammatory stress in humans

OBJECTIVE

To investigate whether insulin reduces the magnitude of oxidative, nitrosative, and inflammatory stress and tissue damage responses induced by endotoxin (lipopolysaccharide [LPS]).

RESEARCH DESIGN AND METHODS

Nine normal subjects were injected intravenously with 2 ng/kg LPS prepared from Escherichia coli. Ten others were infused with insulin (2 units/h) for 6 h in addition to the LPS injection along with 100 ml/h of 5% dextrose to maintain normoglycemia.

RESULTS

LPS injection induced a rapid increase in plasma concentrations of nitric oxide metabolites, nitrite and nitrate (NOM), and thiobarbituric acid-reacting substances (TBARS), an increase in reactive oxygen species (ROS) generation by polymorphonuclear leukocytes (PMNLs), and marked increases in plasma free fatty acids, tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), macrophage migration inhibition factor (MIF), C-reactive protein, resistin, visfatin, lipopolysaccharide binding protein (LBP), high mobility group-B1 (HMG-B1), and myoglobin concentrations. The coinfusion of insulin led to a total elimination of the increase in NOM, free fatty acids, and TBARS and a significant reduction in ROS generation by PMNLs and plasma MIF, visfatin, and myoglobin concentrations. Insulin did not affect TNF-α, MCP-1, IL-6, LBP, resistin, and HMG-B1 increases induced by the LPS.

CONCLUSIONS

Insulin reduces significantly several key mediators of oxidative, nitrosative, and inflammatory stress and tissue damage induced by LPS. These effects of insulin require further investigation for its potential use as anti-inflammatory therapy for endotoxemia.

Serum resistin: physiology, pathophysiology and implications for heart failure

Resistin, a 12.5-kDa polypeptide, has been associated with both insulin resistance and inflammation in animal models. Although initially discovered in the adipocytes, it has subsequently been found in other tissues. In humans, controversy still exists regarding the role of resistin but serum resistin concentration has been correlated with risk factors for coronary heart disease, renal dysfunction and outcomes among stroke patients. Both inflammation and insulin resistance are associated with the development of incident heart failure, with worse outcomes among those with prevalent cardiomyopathy. Therefore, it is interesting to note that recent literature suggests a significant relationship between serum resistin concentrations and heart failure. In this article, we discuss the physiology, pathophysiology, and the direct and indirect role of resistin in determining heart failure risk and worse outcomes among these patients. Some of the salient points reviewed include the possible association of resistin with hyperglycemia and substrate metabolism, inflammation through TNF-alpha and direct cardiac effects.

In Vivo Study on the Expression Pattern of Resistin in Patients With Abdominal Aortic Aneurysm

Objective: To study the expression pattern of resistin in abdominal aortic aneurysms and to correlate its plasma levels to aneurysm size and statin therapy. Patients and Methods: From 25 patients on regular and 38 patients without statin therapy tissue specimen and plasma samples were obtained for analysis. Results: Demographic data, past medical history, and body mass index showed no significant differences between the statin and no statin group. Immunohistochemistry showed positive stainings for resistin in all sections and in part colocalization to CD 68 positive cells. Patients with large aneurysms showed significant correlation of C-reactive protein (CRP) and interleukin 10 (IL-10) levels; patients on statin medication had significantly lower plasma levels of resistin and CRP. Conclusion: In contrast to IL-10 and CRP plasma levels of resistin are not correlated to aneurysm diameter; yet statin therapy results in decrease of resistin and CRP, suggesting an anti-inflammatory action in patients with abdominal aortic aneurysms (AAAs).

Impaired glucose tolerance and insulin resistance in heart failure: underrecognized and undertreated?

BACKGROUND

A link between diabetes mellitus (DM) and heart failure (HF) has been well-recognized for more than a century. HF is also closely linked to abnormal glucose regulation (AGR) and insulin resistance (IR) in patients without DM and, similarly, these conditions commonly coexist. In epidemiological studies, each condition appears to predict the other. The prevalence of AGR/IR in HF patients without DM is significantly underrecognized and, as yet, the optimal method for screening for these abnormalities in the outpatient setting is unclear.

METHODS AND RESULTS

The purpose of this review is to overview the prevalence and prognostic impact of AGR and IR in HF patients without DM and discuss potential pathophysiological pathways that link these conditions with HF. The severity of glucose intolerance in patients with HF correlates with functional and clinical severity of HF and is an independent predictor of an adverse outcome. It is thought that changes in cardiac metabolism, including a switch from glucose metabolism toward fatty acid metabolism, may in part contribute to the pathophysiological processes associated with HF patients with AGR/IR.

CONCLUSIONS

We discuss how pharmacological targeting of metabolic pathways in the myocardium of these patients with HF may represent novel therapeutic strategies in these at-risk patients.

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.

Association of resistin with urinary albumin excretion in nondiabetic patients with essential hypertension

BACKGROUND

Evidence suggests that resistin, a recently described protein, is associated with subclinical atherosclerosis in different clinical settings. In this study, we investigated the relationship of increased resistin levels with urinary albumin excretion, expressed as the albumin-to-creatinine ratio (ACR), an established index of diffuse vascular damage, in hypertensives.

METHODS

Our population consisted of 132 untreated nondiabetic subjects with stage I-II essential hypertension (49 males, mean age = 54 years, mean office blood pressure (BP) = 159/100 mm Hg). In all patients, ACR was determined as the average of three nonconsecutive morning spot urine samples, and venous blood sampling was performed for estimation of resistin concentrations. The distribution of resistin was split by the median (4.63 ng/ml), and accordingly, subjects were stratified into those with high and low values.

RESULTS

Hypertensive patients with high (n = 66) compared to those with low resistin (n = 66) exhibited higher ACR values (21.8 + or - 15.3 vs. 10.3 + or - 3.8 mg/g, P < 0.01), even after adjustment for 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 ACR (r = 0.499, P < 0.01). Multiple regression analysis revealed that age (b = 0.193, P = 0.02), body mass index (b = 0.237, P = 0.02), 24-h systolic BP (b = 0.338, P < 0.0001), 24-h heart rate (b = 0.169, P = 0.04), and resistin (b = 0.77, P < 0.01) were independently associated with ACR (R(2) = 0.471, P < 0.01).

CONCLUSIONS

Hypertensive subjects with augmented resistin levels exhibit higher albuminuria, independently of established risk factors. Moreover, the association of resistin with ACR suggests a link between resistin and microvascular disease in the early stages of essential hypertension.

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.

Resistin decreases expression of endothelial nitric oxide synthase through oxidative stress in human coronary artery endothelial cells

Resistin is a newly discovered adipocyte-derived cytokine that may play an important role in insulin resistance, diabetes, adipogenesis, inflammation, and cardiovascular disease. However, it is largely unknown whether resistin impairs endothelial functions by affecting the endothelial nitric oxide synthase (eNOS) system. In this study, we determined the effect of human recombinant resistin protein on eNOS expression and regulation in human coronary artery endothelial cells (HCAECs). When cells were treated with clinically relevant concentrations of resistin (40 or 80 ng/ml) for 24 h, the levels of eNOS mRNA, protein, and activity and eNOS mRNA stability were significantly reduced. Cellular nitric oxide levels were also decreased. In addition, the cellular levels of reactive oxygen species (ROS), including superoxide anion, were significantly increased in resistin-treated HCAECs. Mitochondrial membrane potential and the activities of catalase and superoxide dismutase were reduced. Three antioxidants, seleno-L-methionine, ginsenoside Rb1, and MnTBAP (superoxide dismutase mimetic), effectively blocked resistin-induced eNOS downregulation. Meanwhile, resistin activated the mitogen-activated protein kinases p38 and c-Jun NH(2)-terminal kinase (JNK), and the specific p38 inhibitor SB-239063 effectively blocked resistin-induced ROS production and eNOS downregulation. Furthermore, immunoreactivity of resistin was increased in atherosclerotic regions of human aorta and carotid arteries. Thus resistin directly induces eNOS downregulation through overproduction of ROS and activation of p38 and JNK in HCAECs. Resistin-induced mitochondrial dysfunction and imbalance in cellular redox enzymes may be the underlying mechanisms of oxidative stress.

Novel adipokines, high molecular weight adiponectin and resistin, are associated with outcomes following lower extremity revascularization with autogenous vein

OBJECTIVE

A significant portion of patients undergoing lower extremity bypass surgery (LEB) for peripheral arterial disease (PAD) will have cardiovascular or graft-related events. It has been previously demonstrated that systemic inflammation is associated with PAD and its clinical outcomes. We hypothesized that serum biomarkers of insulin resistance and inflammation would identify a subgroup at elevated risk for graft failure, limb loss, and mortality.

METHODS

This was a prospective longitudinal study of patients (n = 225) undergoing LEB using autogenous vein. Baseline blood samples were obtained prior to surgery in the fasting state. High-sensitivity C-reactive protein (hsCRP) and the adipokines resistin and high-molecular weight adiponectin (HMWA) were measured by enzyme-linked immunosorbent assay (ELISA). Median follow-up was 893 days. The major endpoints of primary patency (PP) and amputation-free survival (AFS) were examined using multivariable methods. Endpoints were screened against biomarkers and patient characteristics for univariate associations. Promising explanatory variables (P < .1) were included in multivariable Cox proportional hazard models.

RESULTS

The mean age of subjects was 67.6 years; 71.6% were male and 87.1% were Caucasian. One hundred thirty-three (59.1%) subjects underwent bypass for critical limb ischemia (CLI) and 73 (32.4%) had tissue loss. Patients with CLI and diabetes demonstrated elevated resistin and hsCRP levels. HMWA levels correlated with CLI and with a measure of insulin resistance (HOMA-IR) but not with clinical diabetes. Baseline biomarkers were higher in those presenting with tissue loss and in patients with postoperative events (mortality, limb loss). After multivariable analysis (including CLI, diabetes, age, estimated glomerular filtration rate [eGFR], adiponectin, resistin, and CRP), resistin (hazard ratio [HR] 1.75, 95% confidence interval [CI], 1.07-2.85; P = .025) and CRP (HR 2.39, 95% CI, 1.30-4.39; P = .005) were independently predictive of reduced AFS. However, only resistin maintained its significance when restricted to the diabetic cohort (HR 2.10, 95% CI, 1.10-3.99; P = .025). Higher levels of HMWA were found to be associated with primary graft patency (HR 0.73 for graft failure; 95% CI, 0.55 to 0.97; P = .031) in a multivariable model adjusting for diabetes, CRP, African-American race, CLI, high-risk conduits, and redo bypass procedures.

CONCLUSION

These findings suggest that serum biomarkers of insulin resistance and inflammation may be predictive of clinical outcomes following LEB. Improving the systemic milieu of insulin resistance and inflammation in these high-risk patients may lead to reduced morbidity and mortality.

Resistin: a newly identified chemokine for human CD4-positive lymphocytes

AIMS

Increased levels of resistin, a peptide secreted by adipocytes and inflammatory cells, circulate in patients with insulin resistance and early type 2 diabetes, a high-risk population for the development of a diffuse and extensive pattern of arteriosclerosis. Recent data suggest that resistin may activate vascular cells such as smooth muscle cells and endothelial cells, but hitherto nothing is known about the role of resistin in CD4-positive lymphocytes. Therefore, the present study examined the effect of resistin on CD4-positive lymphocyte migration, an important process in early atherogenesis.

METHODS AND RESULTS

Resistin stimulated CD4-positive cell chemotaxis in a concentration-dependent manner with a maximal induction of 2.25 +/- 0.54 at 100 ng/mL (P < 0.05, n = 7). This process involves pertussis toxin-sensitive G-proteins as well as activation of Src- and phosphoinositide 3-kinase (PI 3-K). Biochemical analysis showed that resistin induces phosphorylation of Src and PI 3-K activation in human CD4-positive cells. In addition, resistin activates RhoA, Rac-1, and Cdc42 in these cells as shown by affinity precipitation experiments. Finally, resistin-induced phosphorylation of myosin light chain was inhibited by Src short interference RNA transfection, underscoring the importance of the upstream signalling molecule Src in resistin-induced migration.

CONCLUSION

These data support an active role of resistin in CD4-positive lymphocyte chemotaxis and elucidate molecular mechanisms in resistin-induced cell migration.

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.

Increased expression and secretion of resistin in epicardial adipose tissue of patients with acute coronary syndrome

The purpose of this study was to test the hypothesis that specific epicardial adipose tissue (EAT) proinflammatory adipokines might be implicated in acute coronary syndrome (ACS). We compared expression and protein secretion of several EAT adipokines of male ACS with those of matched stable coronary artery disease (CAD) patients and controls with angiographically normal coronary arteries. The effect of supernatant of cultured EAT on endothelial cell permeability in vitro was also evaluated in the three study groups. EAT of ACS patients showed significantly higher gene expression and protein secretion of resistin than patients with stable CAD. Interleukin-6, plasminogen activator inhibitor-1, and monocyte chemoattractant protein-1 genes were also significantly overexpressed in ACS compared with the control group but not when compared with stable CAD. Immunofluorescence of EAT sections revealed a significantly greater number of CD68(+) cells in ACS patients than stable CAD and control groups. The permeability of endothelial cells in vitro was significantly increased after exposure to supernatant of cultured EAT from ACS, but not control or stable CAD groups, and this effect was normalized by anti-resistin antiserum. We found that EAT of patients with ACS is characterized by increased expression and secretion of resistin and associated with increased in vitro endothelial cell permeability.

Crosstalk between perivascular adipose tissue and blood vessels

Crosstalk between cells in the blood vessel wall is vital to normal vascular function and is perturbed in diseases such as atherosclerosis and hypertension. Perivascular adipocytes reside at the adventitial border of blood vessels but until recently were virtually ignored in studies of vascular function. However, perivascular adipocytes have been demonstrated to be powerful endocrine cells capable of responding to metabolic cues and transducing signals to adjacent blood vessels. Accordingly, crosstalk between perivascular adipose tissue (PVAT) and blood vessels is now being intensely examined. Emerging evidence suggests that PVAT regulates vascular function through numerous mechanisms, but evidence to date suggests modulation of three key aspects that are the focus of this review: inflammation, vasoreactivity, and smooth muscle cell proliferation.

Similar effects of resistin and high glucose on P-selectin and fractalkine expression and monocyte adhesion in human endothelial cells

Resistin and high glucose (HG) are concomitantly present at elevated concentration in diabetic's plasma; both are pro-inflammatory agents acting on vascular cells by mechanisms that are not fully understood. We questioned whether resistin and HG affect the expression of major adhesion molecules, P-selectin and fractalkine in human endothelial cells (HEC). The results showed that in HEC (i) resistin increased P-selectin expression; (ii) HG up-regulated Fk expression; (iii) P-selectin and fractalkine were functional increasing monocyte adhesion to activated cells. Co-stimulation with resistin and HG increased P-selectin and fractalkine mRNA and protein and induced monocyte adhesion, generated an increase in NADPH oxidase activity and of the intracellular reactive oxygen species and activated the NF-kB and AP-1 transcription factors at similar values as those of each activator. In conclusion in HEC, resistin and HG induce the up-regulation of P-selectin and fractalkine and the ensuing increased monocyte adhesion by a mechanism involving oxidative stress and NF-kB and AP-1 activation.

High serum resistin level may be an indicator of the severity of coronary disease in acute coronary syndrome

OBJECTIVE

To investigate the correlation between serum resistin level, cardiovascular risk factors and severity of coronary disease in acute coronary syndrome (ACS).

METHODS

After evaluated by clinical history, electrocardiography, exercise tolerance tests, laboratory tests, and coronary angiography, 220 consecutive patients with suspected chest pain were divided into normal control group, stable angina pectoris (SAP) group, and ACS group, respectively. Baseline clinical characteristics, including height, weight, waist circumference, hip circumference, white blood cell count, high-sensitive C-reactive protein (hsCRP), total cholesterol, triglyceride, low-density lipoprotein cholesterol and high-density lipoprotein cholesterol, were compared among three groups. ELISA was used to detect serum resistin levels. Pearson's correlation coefficient analysis was used to assess association between resistin and other traditional cardiovascular risk factors. Multinomial logistic regression analyses were used to define the relationship between serum resistin level and SAP or ACS.

RESULTS

Serum resistin level in ACS group (1.18+/-0.48 microg/L) was significantly higher than that in normal control and SAP groups (0.49+/-0.40 and 0.66+/-0.40 microg/L; P<0.01). Only in ACS group, increased serum resistin level was significantly correlated with hsCRP (r=0.262, P=0.004) and white blood cell count (r=0.347, P=0.001). Furthermore, serum resistin levels showed a stepwise increase with the number increase of > 50% stenosed coronary vessels. Multinomial logistic regression test demonstrated that serum resistin was a strong risk factor for ACS (OR=29.132, 95 % CI: 10.939-77.581, P<0.001).

CONCLUSION

These findings suggested the potential role of resistin in atherosclerosis and especially its involvement in ACS.

Resistin competes with lipopolysaccharide for binding to toll-like receptor 4

Toll-like receptors (TLRs) are a family of cellular structures activated by recognition of pathogen associated molecular sequences. The activation of TLRs triggers a variety of intracellular mechanisms aiming to protect the host from the invading microorganisms. Lipopolysaccharide (LPS) is the main ligand for TLR4. Here we show that resistin, a cystein-rich protein believed to regulate carbohydrate metabolism, competes with LPS for binding to TLR4. Binding of recombinant resistin to human myeloid and epithelial cells was assessed by flow cytometry and its co-precipitation with TLR4 was demonstrated. Antibodies against TLR4 abolished resistin binding to human leucocytes and cytokine production by peripheral blood mononuclear cells in response to resistin stimulation. In contrast, isotype-matched murine IgG or TLR2 antibodies were unable to prevent binding of resistin to the cells. Similarly, TLR4-dependent pattern of resistin binding was observed in epithelial cell line HEK293 (human epithelial kidney cell), where TLR4 transfected, but not myeloid differentiation factor 2/CD14-transfected, TLR2 transfected or HEKnull cells, responded functionally to resistin stimulation. Intracellular signalling of resistin was assessed using inhibitors of transcription factors mitogen activated protein kinases, nuclear factor-kappaB, phosphoinositide 3-kinase and siRNA targeting TLR4 and human myeloid differentiation factor 88. Results demonstrate that TLR4 serves as a receptor for the pro-inflammatory effects of resistin in human cells. This may partly explain the multifunctional role of resistin in chronic inflammation, atherosclerosis and insulin resistance.

The role of resistin as a regulator of inflammation: Implications for various human pathologies

Resistin was originally described as an adipocyte-secreted peptide that induced insulin resistance in rodents. Increasing evidence indicates its important regulatory roles in various biological processes, including several inflammatory diseases. Further studies have shown that resistin in humans, in contrast to its production by adipocytes in mice, is synthesized predominantly by mononuclear cells both within and outside adipose tissue. Possible roles for resistin in obesity-related subclinical inflammation, atherosclerosis and cardiovascular disease, non-alcoholic fatty liver disease, rheumatic diseases, malignant tumors, asthma, inflammatory bowel disease, and chronic kidney disease have already been demonstrated. In addition, resistin can modulate several molecular pathways involved in metabolic, inflammatory, and autoimmune diseases. In this review, current knowledge about the functions and pathophysiological implications of resistin in different human pathologies is summarized, although there is a significant lack of firm evidence regarding the specific role resistin plays in the "orchestra" of the numerous mediators of inflammation.

Adipose tissue: the new endocrine organ? A review article

Fat is either white or brown, the latter being found principally in neonates. White fat, which comprises adipocytes, pre-adipocytes, macrophages, endothelial cells, fibroblasts, and leukocytes, actively participates in hormonal and inflammatory systems. Adipokines include hormones such as leptin, adiponectin, visfatin, apelin, vaspin, hepcidine, chemerin, omentin, and inflammatory cytokines, including tumor necrosis factor alpha (TNF), monocyte chemoattractant protein-1 (MCP-1), and plasminogen activator protein (PAI). Multiple roles in metabolic and inflammatory responses have been assigned to adipokines; this review describes the molecular actions and clinical significance of the more important adipokines. The array of adipokines evidences diverse roles for adipose tissue, which looms large in the mediators of inflammation and metabolism. For this reason, treating obesity is more than a reduction of excess fat; it is also the treatment of obesity's comorbidities, many of which will some day be treated by drugs that counteract derangements induced by adipokine excesses.

Neutrophil-derived hyperresistinemia in severe acute streptococcal infections

The concept of neutrophil activation and degranulation as important contributors to disease pathology in invasive group A streptococcal infections has recently been emphasized. This study focuses on two of the most severe streptococcal manifestations, toxic shock syndrome and necrotizing fasciitis, and the newly described proinflammatory molecule resistin, known to derive from adipocytes and monocytes. We demonstrate for the first time that these conditions are characterized by hyperresistinemia in circulation as well as at the local site of infection. Importantly, analyses of patient tissue biopsies and whole blood revealed that neutrophils represent a novel and dominant source of resistin in bacterial septic shock. This was confirmed by the identification of resistin within neutrophil azurophilic granules. In vitro assays using primary neutrophils showed that resistin release was readily triggered by streptococcal cell wall components and by the streptococcal M1 protein, but not by the potent streptococcal superantigens. This is the first report demonstrating that resistin is released from neutrophils in response to microbial stimuli, which adds resistin to the neutrophil granule proteins that are likely to contribute to the pathologic inflammatory responses associated with severe streptococcal infections.

Association of polymorphism of estrogen receptor-alpha gene with circulating levels of adiponectin in postmenopausal women with type 2 diabetes

AIM

Menopause is a risk factor for cardiovascular disease (CVD) in women because of the reduction in endogenous estrogen. Recently, single nucleotide polymorphisms (SNPs) of the estrogen receptor alpha (ESR-1) gene (c.454-397T>C) associated with the prognosis of myocardial infarction in postmenopausal women were identified; however, the mechanism by which genetic variation of ESR-1 contributes to the pathogenesis of CVD is unknown. Circulating levels of adipokines and inflammatory cytokines predict CVD risk; hence, this study aimed to investigate whether ESR-1 genotypes (c.454-397T>C) might influence circulating levels of adipokines and inflammatory cytokines in postmenopausal women with type 2 diabetes.

METHODS

Sixty-three postmenopausal women with type 2 diabetes were recruited. Serum levels of adiponectin, resistin, interleukin-6 (IL-6), and high-sensitive C-reactive protein (hs-CRP) were determined.

RESULTS

The genotype of ESR-1 was closely associated with serum adiponectin, which was decreased in subjects with the T allele and was lowest in those with the T/T genotype. Multiple logistic regression analysis revealed independent contribution of the homozygote for the T allele to low serum levels of adiponectin.

CONCLUSION

The T allele of the c.454-397T>C SNP of ESR-1 is associated with low serum levels of adiponectin, which may lead to a high risk of CVD in postmenopausal women.

Mechanism of inhibitory effect of atorvastatin on resistin expression induced by tumor necrosis factor-alpha in macrophages

Atorvastatin has been shown to reduce resistin expression in macrophages after pro-inflammatory stimulation. However, the mechanism of reducing resistin expression by atorvastatin is not known. Therefore, we sought to investigate the molecular mechanisms of atorvastatin for reducing resistin expression after proinflammatory cytokine, tumor necrosis factor-α (TNF-α) stimulation in cultured macrophages. Cultured macrophages were obtained from human peripheral blood mononuclear cells. TNF-α stimulation increased resistin protein and mRNA expression and atorvastatin inhibited the induction of resistin by TNF-α. Addition of mevalonate induced resistin protein expression similar to TNF-α stimulation. However, atorvastatin did not have effect on resistin protein expression induced by mevalonate. SP600125 and JNK small interfering RNA (siRNA) completely attenuated the resistin protein expression induced by TNF-α and mevalonate. TNF-α induced phosphorylation of Rac, while atorvastatin and Rac-1 inhibitor inhibited the phosphorylation of Rac induced by TNF-α. The gel shift and promoter activity assay showed that TNF-α increased AP-1-binding activity and resistin promoter activity, while SP600125 and atorvastatin inhibited the AP-1-binding activity and resistin promoter activity induced by TNF-α. Recombinant resistin and TNF-α significantly reduced glucose uptake in cultured macrophages, while atorvastatin reversed the reduced glucose uptake by TNF-α. In conclusion, JNK and Rac pathway mediates the inhibitory effect of atorvastatin on resistin expression induced by TNF-α.

The expression of human resistin in different leucocyte lineages is modulated by LPS and TNFalpha

OBJECTIVE

Human resistin has been linked to several inflammatory diseases such as atherosclerosis. This study aimed to clarify the expression of resistin in different inflammatory cells and its effect on endothelial cells.

RESULTS

In this study, RNA and protein expression of resistin were detected in human primary neutrophils, monocytes, and T cells as well as in human Jurkat T cells, RPMI-8226 B cells, monocytic U937, and myeloblastic HL-60 cell lines. The highest resistin protein and mRNA level were detected in neutrophils, primary monocytes, and monocytic U937 cells. The RNA expression of resistin was upregulated both in neutrophils and in U937 cells after exposure to LPS. Also TNFalpha induced resistin RNA expression in neutrophils, U937, T-lymphocytic Jurkat cells, and B-lymphocytic RPMI-8226 cells. The RNA and protein expression of resistin decreased as the monocytic U937 cells differentiated into macrophage-like cells. In endothelial EA.hy 926 cells, resistin increased the expression of MCP-1 and PECAM-1 and adhesion of monocytes to endothelial cells.

CONCLUSIONS

The wide-ranging expression of resistin in white blood cells and the upregulation of its expression by inflammatory reagents LPS and TNFalpha support the fact that increased resistin could be involved in several inflammatory diseases.

Association of -394C>G and -420C>G polymorphisms in the RETN gene with T2DM and CHD and a new potential SNP might be exist in exon 3 of RETN gene in Chinese

Genetic variations of the human RETN gene are associated with metabolic phenotypes, including obesity, insulin sensitivity, diabetes, and coronary heart disease (CHD). There are few studies of two gene variants, -394C>G and -420C>G, in Chinese population. This study investigated the distribution of RETN gene, single nucleotide polymorphisms (SNPs), in Chinese Han population and the association of the polymorphisms with type 2 diabetes mellitus (T2DM) and CHD. In a population-based, case-control genetic association study, a total of 961 subjects were recruited from the community, including 318 T2DM patients, 273 CHD patients, and 370 unrelated healthy control individuals. Serum lipid levels were detected. Two SNPs of RETN gene, -394C>G and -420C>G, were genotyped by PCR-RFLP. Unknown Polymorphisms were screened with the technique of denaturing high performance liquid chromatography (DHPLC). The frequencies of RETN -394G allele in T2DM group, CHD group, and control group were 0.3066, 0.3555, and 0.3481, respectively, which are met with the Hardy-Weinberg equilibrium. There is a significant difference of the comparison of sex in T2DM group of RETN gene SNP-394C>G (P < 0.05). Compared with controls, there was no significant difference in the distribution of genotypes and allele frequencies of -394C>G polymorphic site in T2DM patients and CHD patients, respectively. No direct association was found between the -394C>G polymorphism and T2DM or CHD. The frequencies of RETN -420G allele in T2DM group, CHD group, and control group were 0.4009, 0.3725, and 0.3859, respectively, which are met with the Hardy-Weinberg equilibrium. The frequencies of RETN -420G allele in T2DM groups and control groups of Chinese population are significantly different from those in European population (0.40 vs. 0.27, 0.39 vs. 0.26) (P < 0.01). Compared with controls, there was no significant difference in distribution of genotypes and allele frequencies of -420C>G polymorphic site in T2DM patients and CHD patients, respectively. No direct association was found between the -420C>G polymorphism and T2DM or CHD. In addition, we found new potential SNP +593G>C in exon 3 of RETN gene using DHPLC. The RETN gene exhibits sex and ethnic differences. +593G>C of RETN gene might be a new potential SNP in exon 3 of RETN gene. Association between SNP -394C>G and -420C>G of RETN gene with T2DM and CHD in Chinese needs more exploration.

Serum resistin concentrations and risk of new onset heart failure in older persons: the health, aging, and body composition (Health ABC) study

OBJECTIVE

Resistin is associated with inflammation and insulin resistance and exerts direct effects on myocardial cells including hypertrophy and altered contraction. We investigated the association of serum resistin concentrations with risk for incident heart failure (HF) in humans.

METHODS AND RESULTS

We studied 2902 older persons without prevalent HF (age, 73.6+/-2.9 years; 48.1% men; 58.8% white) enrolled in the Health, Aging, and Body Composition (Health ABC) Study. Correlation between baseline serum resistin concentrations (20.3+/-10.0 ng/mL) and clinical variables, biochemistry panel, markers of inflammation and insulin resistance, adipocytokines, and measures of adiposity was weak (all rho <0.25). During a median follow-up of 9.4 years, 341 participants (11.8%) developed HF. Resistin was strongly associated with risk for incident HF in Cox proportional hazards models controlling for clinical variables, biomarkers, and measures of adiposity (HR, 1.15 per 10.0 ng/mL in adjusted model; 95% CI, 1.05 to 1.27; P=0.003). Results were comparable across sex, race, diabetes mellitus, and prevalent and incident coronary heart disease subgroups. In participants with available left ventricular ejection fraction at HF diagnosis (265 of 341; 77.7%), association of resistin with HF risk was comparable for cases with reduced versus preserved ejection fraction.

CONCLUSIONS

Serum resistin concentrations are independently associated with risk for incident HF in older persons.