Resistin is an inflammatory marker of atherosclerosis in humans

Obesity, inflammation, and insulin resistance

Weight gain and obesity are major risk factors for conditions and diseases ranging from insulin resistance and type 2 diabetes mellitus to atherosclerosis and the sequelae of nonalcoholic fatty liver disease. A chronic, subacute state of inflammation often accompanies the accumulation of excess lipid in adipose tissue and liver (hepatic steatosis), evidenced by changes in both inflammatory cells and biochemical markers of inflammation. These changes can be seen in the involved tissues and systemically, in terms of elevated circulating levels of inflammatory markers. The link between obesity and inflammation has therefore raised the important question of whether obesity-induced inflammation plays a pathogenic role in the development and progression of these disorders. We review the rapidly expanding body of animal and clinical data that support potential roles for inflammation in the pathogenesis of insulin resistance and type 2 diabetes mellitus.

Effects of pioglitazone on fasting and postprandial levels of lipid and hemostatic variables in overweight non-diabetic patients with coronary artery disease

OBJECTIVES

To evaluate the effects of pioglitazone on insulin sensitivity and levels of biomarkers associated with thrombotic risk in overweight and obese, non-diabetic subjects with coronary artery disease.

BACKGROUND

Little information is available regarding the effects of thiazolidinediones in the absence of diabetes. Further, although postprandial hyperlipemia is a risk factor for cardiovascular diseases, there is limited information about the postprandial effects.

METHODS

Twenty overweight and obese, non-diabetic patients with coronary artery disease were enrolled in a randomized, placebo-controlled, double-blind study. Subjects were on atorvastatin for the duration of the study and received either placebo or pioglitazone (45 mg day(-1)) for 12 weeks and then crossed over to the alternative therapy for an additional 12 weeks. Insulin sensitivity, fasting and postprandial levels of lipid, hemostatic, and inflammatory variables were measured, and endothelial function was assessed.

RESULTS

Insulin sensitivity improved from 0.03 micromol kg(-1) x min pM(-1) on placebo to 0.04 on pioglitazone (P = 0.0002), and there were decreases in fasting levels of factor (F) VII:C (102 +/- 17% to 92 +/- 18%, P = 0.001), FVII:Ag (68 +/- 12% to 60 +/- 14%, P = 0.01) and in von Willebrand factor (VWF) (174 +/- 94% to 142 +/- 69%, P = 0.01). Pioglitazone lowered postprandial levels of FVII:Ag, FVII:C, plasminogen activator inhibitor-1, VWF, and triglycerides, and increased high-density lipoproteins (+9%, P = 0.02).

CONCLUSIONS

Pioglitazone improves insulin sensitivity and favorably modifies fasting and postprandial lipid, hemostatic and inflammatory markers of the metabolic syndrome in overweight and obese non-diabetic patients with coronary artery disease.

Association between serum resistin and carotid intima media thickness in hypertension patients

BACKGROUND

Resistin is an adipocytokine belonging to the family of cysteine rich secretory proteins. We sought to determine if a correlation between resistin levels and carotid atherosclerosis exists in hypertensive patients.

METHODS

This study consisted of 307 treated hypertensive patients. Subjects were grouped into tertiles according to their resistin level.

RESULTS

Carotid intima media thickness (IMT) was significantly highest in the third tertile. The first tertile had a mean carotid IMT and a mean of maximum carotid IMT of 0.63+/-0.08 and 0.81+/-0.10 mm, respectively. The 2nd tertile had measurements of 0.63+/-0.08 and 0.81+/-0.12 mm, and the 3rd tertile 0.67+/-0.12 and 0.86+/-0.11 for the same parameters. (p=0.002). Resistin levels were independently associated with the carotid IMT (mean carotid IMT: R(2)=0.159, p<0.001 and mean of maximum carotid IMT: R(2)=0.162, p<0.001) after controlling for age, gender, HDL cholesterol, triglyceride, LDL cholesterol, smoking and DM. The tertile level of resistin was significantly associated with (odds ratio=3.097, p=0.004) risk of coronary artery disease after controlling for age, gender, HDL cholesterol, triglyceride, LDL cholesterol, smoking, DM and carotid IMT.

CONCLUSION

Serum resistin is independently associated with increasing carotid IMT in treated hypertensive patients.

Adiponectin and resistin plasma levels in healthy individuals with prehypertension

Prehypertension seems to be related to increased cardiovascular risk in healthy subjects, while hypoadiponectinemia and hyperresistinemia may contribute to insulin resistance and accelerated atherogenesis. This study investigated whether plasma levels of adiponectin (known to increase insulin sensitivity) and resistin (a protein possibly involved in inflammatory activities) are affected in healthy individuals with prehypertension, and to compare the findings to those of healthy normotensives matched for age, gender, and body mass index. Twenty-six (14 men and 12 women) healthy individuals with prehypertension (mean age, 52+/-5 years; mean body mass index, 23+/-1.5 kg/m2) and 24 healthy normotensives (13 men and 11 women; mean age 53+/-6 years; body mass index 23.2+/-1.4 kg/m2) were studied. The adiponectin and resistin plasma levels were determined by the enzyme-linked immunosorbent assay method. Plasma resistin levels were significantly higher, while adiponectin plasma levels were significantly lower, in prehypertensive subjects compared with normotensive subjects (10.62+/-3.17 ng/mL vs. 6.72+/-3.15 ng/mL and 6.26+/-2.18 mg/mL vs. 12.12+/-4.8 mg/mL; p < 0.01, respectively). The findings suggest that healthy individuals with prehypertension have significantly higher resistin plasma levels and significantly lower adiponectin plasma levels compared with healthy normotensives. These findings may represent another possible mechanism that may increase the cardiovascular risk in this special group of patients, needing further investigation.

Plasma and urine levels of resistin and adiponectin in chronic kidney disease

BACKGROUND

Subjects with chronic kidney disease (CKD) have an increased risk of developing coronary atherosclerosis. Adipocyte hormones, resistin and adiponectin are implicated in insulin resistance and atherosclerosis. However, few studies in the literature address the role of adipocyte hormones in CKD. The aim of this study was to compare the levels of resistin, adiponectin and other inflammatory markers in subjects with CKD with those of the control subjects.

MATERIALS AND METHODS

In a cross-sectional study, we measured basal metabolic panel, fasting lipid panel and levels of glucose, resistin, adiponectin, insulin, C-reactive protein (CRP) and TNF-alpha in 43 subjects with CKD compared with those of 34 control subjects. We also measured the resistin and adiponectin levels in urine samples (16).

RESULTS

Subjects with CKD have increased insulin levels and insulin resistance index (IRI). Compared with controls, subjects with CKD had increased levels of resistin (5.12+/-3.2 vs.7.5+/-5.9; p<0.05), CRP (1.7+/-2.2 vs. 5.97+/-6.0; p<0.0005), and TNF-alpha (3.4+/-2.0 vs. 5.2+/-3.5; p<0.005). Resistin levels correlate with CRP and TNF-alpha, even with BMI as a covariate. Although 60% of subjects with CKD have CAD, e plasma levels of adiponectin were not decreased in subjects with CKD compared with controls (17.02+/-9.8 vs. 16.40+/-9.0 with p value 0.78). Urinary adiponectin levels correlate inversely with GFR (r=-0.4; p<0.05) and plasma adiponectin levels (r=0.9; p<0.0001).

CONCLUSIONS

Subjects with CKD had normal levels of plasma adiponectin despite the adverse metabolic environment for CAD. In addition, this study demonstrates the relationship between resistin and TNF-alpha in subjects with CKD and suggests that resistin may play a role in the sub-clinical inflammation associated with CKD, suggesting that adiponectin clearance may be decreased as shown by the inverse correlation of urinary adiponectin with GFR.

Metabolic syndrome, inflammation and atherosclerosis

The inflammatory component of atherogenesis has been increasingly recognized over the last decade. Inflammation participates in all stages of atherosclerosis, not only during initiation and during evolution of lesions, but also with precipitation of acute thrombotic complications. The metabolic syndrome is associated with increased risk for development of both cardiovascular disease and type-2 diabetes in humans. Central obesity and insulin resistance are thought to represent common underlying factors of the syndrome, which features a chronic low-grade inflammatory state. Diagnosis of the metabolic syndrome occurs using defined threshold values for waist circumference, blood pressure, fasting glucose and dyslipidemia. The metabolic syndrome appears to affect a significant proportion of the population. Therapeutic approaches that reduce the levels of proinflammatory biomarkers and address traditional risk factors are particularly important in preventing cardiovascular disease and, potentially, diabetes. The primary management of metabolic syndrome involves healthy lifestyle promotion through moderate calorie restriction, moderate increase in physical activity and change in dietary composition. Treatment of individual components aims to control atherogenic dyslipidemia using fibrates and statins, elevated blood pressure, and hyperglycemia. While no single treatment for the metabolic syndrome as a whole yet exists, emerging therapies offer potential as future therapeutic approaches.

Implications of resistin plasma levels in subjects undergoing coronary angiography

BACKGROUND

The adipokine resistin, which is thought to serve as a link between obesity and insulin resistance, was recently shown to exert proatherosclerotic features.

OBJECTIVE

Our study aimed to explore the involvement of resistin in cardiovascular disease by investigating the associations of resistin with angiographic coronary artery disease (CAD), cardiovascular risk factors and mortality.

DESIGN

The Ludwigshafen Risk and Cardiovascular Health (LURIC) study is a prospective study of white subjects who had undergone coronary angiography.

PATIENTS AND MEASUREMENTS

Resistin levels were determined in 1162 subjects with (n = 911) and without (n = 251) angiographic CAD. During a mean follow-up period of 5.47 years, 198 deaths occurred among our probands.

RESULTS

Resistin was positively correlated with C-reactive protein (CRP; r = 0.245, P < 0.001), vascular adhesion molecule-1 (VCAM-1; r = 0.327, P < 0.001) and intercellular adhesion molecule-1 (ICAM-1; r = 0.197, P < 0.001) and was negatively correlated with glomerular filtration rate (GFR; r = -0.438, P < 0.001) and high density lipoprotein (HDL; r = -0.196, P < 0.001). Multiple regression analysis revealed that GFR was the strongest predictive variable for resistin. Angiographic CAD, type 2 diabetes, smoking, hypertension and body mass index (BMI) were not associated with resistin. Compared to the first quartile, we observed an increased risk for cardiovascular and noncardiovascular mortality at the fourth quartile of resistin, but only the association between resistin and noncardiovascular mortality remained significant after multivariable adjustments [hazard ratio (HR) 4.92, 95% confidence interval (CI) 1.66-14.6, P = 0.004].

CONCLUSIONS

Resistin plasma concentrations are related to inflammatory processes and renal function but our study does not support the hypothesis of resistin as an independent cardiovascular risk factor. The unexpected association of resistin with noncardiovascular mortality still warrants further study.

Obesity, metabolic syndrome and sleep apnoea: all pro-inflammatory states

Obesity is associated with significant morbidity and mortality and is increasing in prevalence worldwide. Associated conditions include insulin resistance (IR), diabetes, hypertension and dyslipidaemia; a clustering of these has recently been termed as metabolic syndrome. Weight gain is a major predictor of the metabolic syndrome with waist circumference being a more sensitive indicator than body mass index as it reflects both abdominal subcutaneous adipose tissue and visceral adipose tissue (VAT). VAT has more metabolic activity and secretes a number of hormones and pro-inflammatory cytokines which are linked with the metabolic abnormalities listed above. Central obesity also increases the risk of obstructive sleep apnoea syndrome (OSAS), where the sleep disordered breathing may also independently lead to/or exacerbate IR, diabetes and cardiovascular risk. The contribution of OSAS to the metabolic syndrome has been under-recognized. The putative mechanisms by which OSAS causes or exacerbates these other abnormalities are discussed. We propose that activation of nuclear factor kappa B by stress hypoxia and/or by increased adipokines and free fatty acids released by excess adipose tissue is the final common inflammatory pathway linking obesity, OSAS and the metabolic syndrome both individually and, in many cases, synergistically.

Adipose tissue and atherosclerosis: exploring the connection

The prevalence of obesity, especially among the young, is dramatically increasing in the United States. Obesity is associated with accelerated atherosclerosis and increased rates of cardiovascular death. There are many plausible mechanisms by which an increase in adipose tissue could adversely affect the vessel wall. These include the changes in blood pressure, glucose level, lipid/lipoprotein metabolism, and systemic inflammation. In addition, factors secreted by adipose tissue may directly influence vessel wall homeostasis by influencing the function of endothelial cells, arterial smooth muscle cells, and macrophages in the vessel wall. There is general agreement that central, as opposed to peripheral, adipose tissue confers the most cardio-metabolic risk. Although the basis of this differential risk has not been not established, the pattern of gene expression and secretory products in visceral fat would be predicted to be more atherogenic compared with that in subcutaneous peripheral fat. Numerous studies have shown the beneficial effects of weight loss on markers of cardiovascular risk but fewer have demonstrated improvement in direct measures of large vessel disease. The unfolding role of adipose tissue as an important metabolic and secretory organ provides new opportunities for developing more effective approaches for preventing obesity and its atherosclerotic complications.

Adipokines and vascular disease in diabetes

Adipokines, in particular adiponectin, have been highlighted in the pathogenesis of obesity-related illnesses, including type 2 diabetes, because of their role in the regulation of insulin sensitivity as well as vascular endothelial function. Since cardiovascular disease accounts for an overwhelming proportion of the morbidity and mortality suffered by patients with diabetes, researchers are actively seeking a better understanding of the role that adipokines play in the vasculature with the hope that the use of these agents, or activation of their signaling pathways, might help prevent micro- and macrovascular complications. This brief review highlights recent work on the vascular effects of circulating adipokines, focusing on adiponectin, and includes some recent findings with leptin and resistin. This highly active area of investigation has identified novel hormonal mechanisms by which the adipose tissue mass can influence vascular function with important consequences for cardiovascular risk.

Ethnicity, insulin resistance, and inflammatory adipokines in women at high and low risk for vascular disease

OBJECTIVE

We sought to compare the relationship between body composition, insulin resistance, and inflammatory adipokines in Aboriginal Canadian women, who are at high risk of vascular disease, with white women.

RESEARCH DESIGN AND METHODS

A subgroup of the First Nations Bone Health Study population, consisting of 131 Aboriginal women and 132 matched white women, was utilized. Body composition was determined by whole-body dual X-ray absorptiometry, and blood analytes were measured after an overnight fast.

RESULTS

After excluding individuals with diabetes, A1C, BMI, percent trunk fat, and homeostasis model assessment of insulin resistance (HOMA-IR) were greater in First Nation women compared with white women, whereas adiponectin, retinol binding protein (RBP)4, and insulin-like growth factor binding protein-1 (IGFBP-1) were lower. First Nation women had more trunk fat for any given level of total fat than white women. There were no differences in resistin, leptin, tumor necrosis factor (TNF)-alpha, or C-reactive protein (CRP) levels between First Nation and white women. Insulin resistance correlated with leptin and inversely with adiponectin levels in both First Nation and white women. There were weak correlations between insulin resistance and TNF-alpha, interleukin-6, and CRP, but these were not significant after correction for body fat. No correlation was found between RBP4 and insulin resistance. ANCOVA revealed a higher HOMA-IR adjusted for total body fat in First Nation women than in white women (P = 0.015) but not HOMA-IR adjusted for trunk fat (P > 0.2).

CONCLUSIONS

First Nation women are more insulin resistant than white women, and this is explained by trunk fat but not total fat. Despite the increased insulin resistance, inflammatory adipokines are not significantly increased in First Nation women compared with white women.

Update on advances in atherothrombosis

The study of atherothrombosis is a rapidly evolving field, and significant progress was achieved in various aspects of the disease during the past year. In the area of diagnostic imaging, MRI and multidetector CT were actively used to evaluate the characteristics of the arterial wall, including calcified and noncalcified lesions, and both in the coronary and extracoronary vascular territories. There was also extensive research into the application of imaging modalities to visualize cellular or molecular disease processes, known as molecular imaging. Considerable efforts were devoted to the identification of novel biomarkers that reflect different components of atherothrombosis, namely inflammation, thrombogenicity, oxidative stress and reparative ability, predicting the presence of early disease or the risk of clinical events. In the therapeutic arena, substantial evidence accumulated on the beneficial effects of several pharmacologic agents, most significantly statins. Finally, important advances were also made in the understanding of the roles of immunity and neovascularization in atherogenesis, including the development and progression of disease at different stages. Awareness of these recent advances and new lines of active research is fundamental for health professionals involved in the care of patients with atherothrombosis. In this Review we present an overview of data in these areas.

Relationship of serum adiponectin and resistin levels with breast cancer risk

Obesity is one of the well-known risk factors of breast cancer. We evaluated the relationship between serum adiponectin and resistin levels and breast cancer risk in 41 biopsy-proven breast cancer patients and 43 age- and body mass index-matched controls. The mean serum adiponectin level was lower in the breast cancer group than the control group (6.93+/-3.2 microg/mL, vs. 7.60+/-3.5 microg/mL), but this difference did not reach statistical significance (p=0.37). There was a statistically significant difference in serum resistin levels between the groups (breast cancer group 5.23+/-6.9 ng/mL vs. control 1.46+/-2.0 ng/mL; p<0.001). The risk of breast cancer was significantly increased in the highest tertile group for serum resistin level compared to the lowest tertile group (adjusted odds ratio 2.77 [95% CI 1.40-5.50]). The lymph node metastasis was significantly increased in the patients with less than the median adiponectin level (p=0.017). In the patients whose resistin level was higher than the median, the frequency of tumor with the highest histological grade was significantly increased (p=0.025). In conclusions, both the low serum adiponectin levels and high resistin levels are likely to be associated with increased breast cancer risk in Korean women.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Resistin as an intrahepatic cytokine: overexpression during chronic injury and induction of proinflammatory actions in hepatic stellate cells

Obesity and insulin resistance accelerate the progression of fibrosis during chronic liver disease. Resistin antagonizes insulin action in rodents, but its role in humans is still controversial. The aims of this study were to investigate resistin expression in human liver and to evaluate whether resistin may affect the biology of activated human hepatic stellate cells (HSCs), key modulators of hepatic fibrogenesis. Resistin gene expression was low in normal human liver but was increased in conditions of severe fibrosis. Up-regulation of resistin during chronic liver damage was confirmed by immunohistochemistry. In a group of patients with alcoholic hepatitis, resistin expression correlated with inflammation and fibrosis, suggesting a possible action on HSCs. Exposure of cultured HSCs to recombinant resistin resulted in increased expression of the proinflammatory chemokines monocyte chemoattractant protein-1 and interleukin-8, through activation of nuclear factor (NF)-kappaB. Resistin induced a rapid increase in intracellular calcium concentration, mainly through calcium release from intracellular inositol triphosphate-sensitive pools. The intracellular calcium chelator BAPTA-AM blocked resistin-induced NF-kappaB activation and monocyte chemoattractant protein-1 expression. In conclusion, this study shows a role for resistin as an intrahepatic cytokine exerting proinflammatory actions in HSCs, via a Ca2+/NF-kappaB-dependent pathway and suggests involvement of this adipokine in the pathophysiology of liver fibrosis.

Redefining Risk in Acute Coronary Syndromes Using Molecular Medicine

Acute coronary syndromes represent a complex phenotype involving the interplay of many elements. The risk of developing an acute coronary syndrome and related complications has been defined by variables such as age, diabetes, smoking history, serum creatine phosphokinase, or electrocardiographic findings. However, in the past 5 years the wide-scale acceptance of a protein--troponin--has changed the diagnostic profile. With advances in molecular medicine, this protein is a segue to a panel of molecular assays that will improve screening and tailored intervention. We expound upon some of these factors and the potential they may carry in changing clinical medicine.

The in vitro effects of resistin on the innate immune signaling pathway in isolated human subcutaneous adipocytes

CONTEXT

Obesity-associated inflammation is a contributory factor in the pathogenesis of type 2 diabetes mellitus (T2DM); the mechanisms underlying the progression to T2DM are unclear. The adipokine resistin has demonstrated proinflammatory properties in relation to obesity and T2DM.

OBJECTIVES

The objectives of this study were to characterize resistin expression in human obesity and address the role of resistin in the innate immune pathway; to examine the influence of lipopolysaccharide, recombinant human resistin (rhResistin), insulin, and rosiglitazone in human adipocytes; and, finally, to analyze the effect of rhResistin on the expression of components of the nuclear factor-kappaB pathway and insulin signaling cascade.

METHODS

Abdominal sc adipose tissue was obtained from patients undergoing elective liposuction surgery (n = 35; age, 36-49 yr; body mass index, 26.5 +/- 5.9 kg/m2). Isolated adipocytes were cultured with rhResistin (10-50 ng/ml). The level of cytokine secretion from isolated adipocytes was examined by ELISA. The effect of rhResistin on protein expression of components of the innate immune pathway was examined by Western blot.

RESULTS

In vitro studies demonstrated that antigenic stimuli increase resistin secretion (P < 0.001) from isolated adipocytes. Proinflammatory cytokine levels were increased in response to rhResistin (P < 0.001); this was attenuated by rosiglitazone (P < 0.01). When examining components of the innate immune pathway, rhResistin stimulated Toll-like receptor-2 protein expression. Similarly, mediators of the insulin signaling pathway, phosphospecific c-Jun NH2-terminal kinase (JNK) 1 and JNK2, were up-regulated in response to rhResistin.

CONCLUSION

Resistin may participate in more than one mechanism to influence proinflammatory cytokine release from human adipocytes, potentially via the integration of nuclear factor-kappaB and JNK signaling pathways.

Serum Resistin is Associated With High Risk in Patients With Congestive Heart Failure A Novel Link Between Metabolic Signals and Heart Failure

BACKGROUND

Resistin is derived from fat tissue in rodents, and serum levels are elevated in animal models of obesity and insulin resistance. Recent studies have reported that resistin is correlated with markers of inflammation and oxidative stress and is predictive of coronary atherosclerosis in humans. However, clinical significance of serum resistin has not been examined in heart failure. Therefore, the purpose of this study was to examine whether: (1) resistin is correlated with the severity of heart failure; and (2) resistin can predict clinical outcomes of patients with heart failure.

METHODS AND RESULTS

Serum levels of resistin in 126 patients hospitalized for heart failure and 18 control subjects were measured. The patients were followed up with end-points of cardiac death and re-hospitalization caused by worsening of heart failure. The serum resistin level was higher in patients with heart failure than in control subjects and increased with advancing New York Heart Association functional class. The normal upper limit of the resistin level was determined as the mean +2 standard deviation value of control subjects (14.1 ng/ml). In heart failure patients, the cardiac event rate was higher in patients with a high resistin level than in those with a normal level. Among age, body mass index, serum levels of resistin, brain natriuretic peptide, loop diuretics selected by the univariate Cox regression hazard analysis, age and resistin were significant predictors of future cardiac events by multivariate Cox analysis.

CONCLUSION

Serum resistin was related to the severity of heart failure and associated with a high risk for adverse cardiac events in patients with heart failure.

The metabolic syndrome: metabolic changes with vascular consequences

Despite criticism regarding its clinical relevance, the concept of the metabolic syndrome improves our understanding of both the pathophysiology of insulin resistance and its associated metabolic changes and vascular consequences. Free fatty acids (FFA) and tumour necrosis factor-alpha (TNF-alpha) play prominent roles in the development of insulin resistance by impairing the intracellular insulin signalling transduction pathway. Obesity is an independent risk factor for cardiovascular disease and strongly related to insulin resistance. In case of obesity, FFAs and TNF-alpha are produced in abundance by adipocytes, whereas the production of adiponectin, an anti-inflammatory adipokine, is reduced. This imbalanced production of pro- and anti-inflammatory adipokines, as observed in adipocyte dysfunction, is thought to be the driving force behind insulin resistance. The role of several recently discovered adipokines such as resistin, visfatin and retinol-binding protein (RBP)-4 in the pathogenesis of insulin resistance is increasingly understood. Insulin resistance induces several metabolic changes, including hyperglycaemia, dyslipidaemia and hypertension, all leading to increased cardiovascular risk. In addition, the dysfunctional adipocyte, reflected largely by low adiponectin levels and a high TNF-alpha concentration, directly influences the vascular endothelium, causing endothelial dysfunction and atherosclerosis. Adipocyte dysfunction could therefore be regarded as the common antecedent of both insulin resistance and atherosclerosis and functions as the link between obesity and cardiovascular disease. Targeting the dysfunctional adipocyte may reduce the risk for both cardiovascular disease and the development of type 2 diabetes. Although lifestyle intervention remains the cornerstone of therapy in improving insulin sensitivity and its associated metabolic changes, medical treatment might prove to be important as well.

Effect of growth hormone therapy on serum adiponectin and resistin levels in short, small-for-gestational-age children and associations with cardiovascular risk parameters

BACKGROUND

Adiponectin and resistin are fat cell-derived hormones, which are thought to be respectively protective and disadvantageous with regard to the development of cardiovascular disease and diabetes mellitus type 2. Low birth weight has been associated with increased risks for the development of these diseases. In short, small-for-gestational-age (SGA) children, GH therapy has several positive effects regarding cardiovascular risk factors. On the other hand, concern has been expressed about the effects of GH therapy on insulin sensitivity.

METHODS

We measured adiponectin and resistin levels in 136 short prepubertal children born SGA and their association with cardiovascular risk parameters and growth factors. Also, we compared the levels with normal-statured controls. The effect of GH treatment was evaluated in 50 short SGA children vs. baseline and vs. an untreated sex- and age-matched SGA control group.

RESULTS

Short SGA children had similar adiponectin and lower resistin levels, compared with normal-statured controls. In GH-treated SGA children, neither adiponectin nor resistin levels changed significantly during 2 yr of GH treatment. Compared with untreated sex- and age-matched SGA controls, GH-treated SGA children had similar adiponectin and lower resistin levels. Adiponectin correlated inversely with age but not any cardiovascular risk parameter or growth factor. Higher IGF-I levels in GH-treated children were associated with lower resistin levels.

CONCLUSIONS

Compared with normal-statured controls, short prepubertal SGA children had similar adiponectin and lower resistin levels. Two years of GH treatment had no effect on their adiponectin and resistin levels.

Resistin increases lipid accumulation and CD36 expression in human macrophages

Excessive lipid accumulation in macrophages plays an important role in the development of atherosclerosis. Recently, several studies have implied that resistin, an adipocytokine which is mainly expressed in human peripheral blood monocytes, may take part in the pathogenesis of atherosclerosis. In this study, we investigated the effects of resistin on lipid accumulation as well as oxLDL on resistin expression in human macrophages. Treatment of macrophages with oxLDL significantly increased resistin mRNA expression, whereas native LDL had no such effect. Resistin pre-treated macrophages contained more and larger lipid droplets stained by Nile red. Resistin increased the expression of CD36 at both mRNA and protein levels, without affecting those of class A macrophage scavenger receptor (SR-A). These results suggest that resistin promotes lipid accumulation in human macrophages through its upregulating CD36 cell surface expression. Also, it is suggested that resistin may act as a modulator for macrophage-to-foam cell transformation.

Relationship between serum resistin concentrations and inflammatory markers in patients with type 2 diabetes mellitus

To examine whether serum resistin concentrations are associated with metabolic or inflammatory markers in patients with type 2 diabetes mellitus, we examined serum concentrations levels and metabolic or inflammatory markers in 56 patients with type 2 diabetes mellitus and 41 healthy subjects. Serum levels of resistin, serum amyloid A, and soluble vascular cell adhesion molecule-1 were measured by enzyme-linked immunosorbent assay. Serum resistin levels were significantly elevated in diabetic patients compared with those in healthy subjects. Serum resistin concentrations did not correlate with body mass index; however, there was a significant positive correlation between resistin and soluble vascular cell adhesion molecule-1 in diabetic patients. Based on the present results, we conclude that resistin appears to be associated with vascular inflammatory markers in patients with type 2 diabetes mellitus.

Resistin, a New Adipokine, Is Related to Inflammation and Renal Function in Kidney Allograft Recipients

BACKGROUND

Among patients without chronic kidney disease, resistin, an adipocytokine, has been related to inflammatory markers, coronary artery disease, and cardiovascular disease in the metabolic syndrome. Moreover, resistin up-regulates adhesion molecules. Since inflammation and endothelial cell damage or injury are invariably associated with thrombosis, atherosclerosis, and their major clinical consequences, resistin may play a role to link inflammation and CVD. The aim of this study was to correlate resistin with markers of inflammation and endothelial cell injury in 96 kidney allograft recipients.

METHODS

We measured resistin and the following markers of endothelial function/injury: vWF, thrombomodulin, VCAM, hsCRP, tumor necrosis factor alpha (TNFalpha), and interleukin-6 (IL-6).

RESULTS

Triglycerides, CRP (assessed by high-sensitivity method), phosphate, creatinine, IL-6, TNFalpha, vWF, prothrombin fragments 1 + 2, and resistin were elevated among kidney transplant recipients compared with the control group. Kidney allograft recipients with coronary artery disease displayed significantly higher resistin levels than those in patients without this complication. Upon univariate analysis resistin levels in kidney allograft recipients were related to hsCRP, IL-6, thrombomodulin, red blood cell count, white blood cell count, platelet count, creatinine, urea, VCAM, CSA, dose and eGFR. Upon multiple regression analysis, resistin was independently related only to creatinine, hsCRP, and white blood cell count in kidney allograft recipients.

CONCLUSIONS

The relation of elevated resistin levels to markers of inflammation may represent a novel link between these conditions and adipocytokines. Renal function was a major determinant of elevated resistin in kidney allograft recipients.

Brain adipocytokine action and metabolic regulation

Adipose tissue secretes factors that control various physiological systems. The fall in leptin during fasting mediates hyperphagia and suppresses thermogenesis, thyroid and reproductive hormones, and immune system. On the other hand, rising leptin levels in the fed state stimulate fatty acid oxidation, decrease appetite, and limit weight gain. These divergent effects of leptin occur through neuronal circuits in the hypothalamus and other brain areas. Leptin also regulates the activities of enzymes involved in lipid metabolism, e.g., AMP-activated protein kinase and stearoyl-CoA desaturase-1, and also interacts with insulin signaling in the brain. Adiponectin enhances fatty acid oxidation and insulin sensitivity, in part by stimulating AMP-activated protein kinase phosphorylation and activity in liver and muscle. Moreover, adiponectin decreases body fat by increasing energy expenditure and lipid catabolism. These effects involve peripheral and possibly central mechanisms. Adipose tissue mediates interconversion of steroid hormones and secretes proinflammatory cytokines, vasoactive peptides, and coagulation and complement proteins. Understanding the actions of these "adipocytokines" will provide insight into the pathogenesis and treatment of obesity and related diseases.

[Is essential hypertension essentially metabolic?]

Hypertension is one of the most prevalent cardiovascular risk factors. Most of the cases are not due to secondary causes and are diagnosed as essential hypertension, although a common physiopathologic link underlies for diabetes and dyslipidemia that are usually present. Most hypertensive patients have also obesity and insulin resistance and this may be more than an epidemiologic association, but one of the main physiopathologic basis of essential hypertension.

Prognostic significance of plasma resistin levels in patients with atherothrombotic ischemic stroke

BACKGROUND

Resistin (RSN) is an adipocytokine involved in insulin resistance, obesity and atherosclerosis. This study aimed to investigate the association between plasma RSN and outcome after ischemic stroke.

METHODS

RSN measured within 24 h after the event was related to functional outcome and 5-year survival in 211 subjects with first-ever atherothrombotic ischemic stroke. Prognosis was assessed by the Kaplan Meier and the Cox techniques.

RESULTS

The probabilities of death were 80.4%, 46.2% and 15.7% (p<0.001) for patients stratified according to tertiles of RSN (>30 ng/mL, 20-30 ng/mL and<20 ng/mL, respectively). The proportion of dependency (modified Rankin Scale score>or=3) was greater in 5-year survivors with RSN in the upper tertile (6/11 [54.5%]) compared to the middle (20/56 [35.7%]) and the lowest tertile (8/43 [18.6%]; p<0.01). C-reactive protein levels (hazard ratio [HR] 3.96 [95% CI 2.06, 8.91]; p<0.001), coronary heart disease (2.69 [1.62, 6.23]; p<0.001), RSN levels (2.12 [1.31, 5.08] p<0.001), National Institute of Health Stroke Scale score (2.02 [1.23, 4.49]; p<0.01) and age (1.84 [1.19, 3.93]; p<0.01) were independent predictors of death.

CONCLUSIONS

High plasma RSN appears to be associated with increased risk of 5-year mortality or disability after atherothrombotic ischemic stroke, independently of other adverse predictors.

Increase in glucose-6-phosphate dehydrogenase in adipocytes stimulates oxidative stress and inflammatory signals

In adipocytes, oxidative stress and chronic inflammation are closely associated with metabolic disorders, including insulin resistance, obesity, cardiovascular disease, and type 2 diabetes. However, the molecular mechanisms underlying these metabolic disorders have not been thoroughly elucidated. In this report, we demonstrate that overexpression of glucose-6-phosphate dehydrogenase (G6PD) in adipocytes stimulates oxidative stress and inflammatory responses, thus affecting the neighboring macrophages. Adipogenic G6PD overexpression promotes the expression of pro-oxidative enzymes, including inducible nitric oxide synthase and NADPH oxidase, and the activation of nuclear factor-kappaB (NF-kappaB) signaling, which eventually leads to the dysregulation of adipocytokines and inflammatory signals. Furthermore, secretory factors from G6PD-overexpressing adipocytes stimulate macrophages to express more proinflammatory cytokines and to be recruited to the adipocytes; this would cause chronic inflammatory conditions in the adipose tissue of obesity. These effects of G6PD overexpression in adipocytes were abolished by pretreatment with NF-kappaB inhibitors or antioxidant drugs. Thus, we propose that a high level of G6PD in adipocytes may mediate the onset of metabolic disorders in obesity by increasing the oxidative stress and inflammatory signals.

Increased subcutaneous and epicardial adipose tissue production of proinflammatory cytokines in cardiac surgery patients: possible role in postoperative insulin resistance

CONTEXT

Hyperglycemia and insulin resistance frequently occur in critically ill patients even without a history of diabetes.

OBJECTIVE

Our objective was to study the role of adipose tissue hormonal production in the development of insulin resistance in cardiac surgery patients. PARTICIPANTS, INTERVENTIONS, AND SETTINGS: Fifteen patients with elective cardiac surgery underwent blood sampling before, at the end, and 6, 12, 24, 48, and 120 h after the end of their operation. Epicardial and sc adipose tissue sampling was done at the beginning and at the end of surgery in the Department of Cardiac Surgery.

MAIN OUTCOME MEASURES

We measured serum concentrations and sc and epicardial adipose tissue mRNA expression of IL-6, monocyte chemoattractant protein-1 (MCP-1), TNF-alpha, leptin, resistin, and adiponectin and sc and epicardial adipose tissue mRNA expression of CD14, CD45, and CD68.

RESULTS

The rate of insulin infusion required to maintain euglycemia increased up to 7-fold 12 h after the operation, suggesting the development of insulin resistance. Serum IL-6 levels increased 43-fold 12 h after surgery. MCP-1 peaked 6-fold at the end of surgery. Smaller peaks of TNF-alpha and leptin appeared 6 and 12 h after surgery, respectively. Resistin levels peaked 4-fold 24 h after surgery, but adiponectin levels were not significantly affected. TNF-alpha and CD45 mRNA expression increased markedly during the operation in sc adipose tissue. IL-6, resistin, and MCP-1 mRNA expression increased in both sc and epicardial adipose tissue. Leptin, adiponectin, CD14, and CD68 mRNA expression did not change significantly.

CONCLUSIONS

Both sc and epicardial adipose tissue is a source of proinflammatory cytokines in cardiac surgery patients and may contribute to the development of postoperative insulin resistance.

Relationship between serum resistin concentration and proinflammatory cytokines in obese women with impaired and normal glucose tolerance

The aim of this study was to investigate the possible role of resistin in obese women with and without insulin resistance. We compared serum concentrations of resistin with interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha), soluble TNF receptors 1 and 2, and certain anthropometric and metabolic parameters in 26 obese women (body mass index [BMI], 35.8 +/- 4.12 kg/m2) and 15 healthy control women (BMI, 22.32 +/- 1.89 kg/m2). Fasting serum resistin and inflammatory cytokine levels were measured by enzyme immunoassay. Insulin resistance was measured by the homeostasis model assessment of insulin resistance (HOMA-R) formula. Compared with lean controls, obese women showed higher HOMA-R values and levels of insulin and increased values of TNF-alpha, soluble TNF receptors, and IL-6. There was no significant difference in resistin levels between the investigated groups of obese women and lean subjects. The results showed that serum resistin concentrations did not correlate with BMI, HOMA, fasting plasma glucose level, or fasting plasma insulin level. Serum resistin correlated with fat mass and IL-6 in the group with impaired glucose tolerance (obese group) (r = 0.51, P < .05, and r = 0.37, P < .05, respectively) and with low-density lipoprotein cholesterol (r = -0.39, P < .05) in the same group. The groups we examined are relatively small; it is likely that with a larger number of subjects, the correlation in other obese women groups may achieve statistical significance. It seems that resistin may be linked with inflammation and obesity and, indirectly, with insulin resistance.

Loss of resistin improves glucose homeostasis in leptin deficiency

Resistin levels are increased in obesity, and hyperresistinemia impairs glucose homeostasis in rodents. Here, we have determined the role of resistin in ob/ob mice that are obese and insulin resistant because of genetic deficiency of leptin. Loss of resistin increased obesity in ob/ob mice by further lowering the metabolic rate without affecting food intake. Nevertheless, resistin deficiency improved glucose tolerance and insulin sensitivity in these severely obese mice, largely by enhancing insulin-mediated glucose disposal in muscle and adipose tissue. In contrast, in C57BL/6J mice with diet-induced obesity but wild-type leptin alleles, resistin deficiency reduced hepatic glucose production and increased peripheral glucose uptake. Resistin deficiency enhanced Akt phosphorylation in muscle and liver and decreased suppressor of cytokine signaling-3 level in muscle, and these changes were reversed by resistin replacement. Together, these results provide strong support for an important role of resistin in insulin resistance and diabetes associated with genetic or diet-induced obesity.

Relation of improvement in endothelium-dependent flow-mediated vasodilation after rosiglitazone to changes in asymmetric dimethylarginine, endothelin-1, and C-reactive protein in nondiabetic patients with the metabolic syndrome

The mechanisms by which thiazolidinediones exert beneficial effects on the endothelium are still not clear. We examined the effects of rosiglitazone on the plasma markers of metabolic control (glucose, insulin, adiponectin, resistin, and lipid profiles), markers of inflammation (high-sensitivity C-reactive protein [CRP], interleukin-6, soluble CD40 ligand, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1), and markers of vasoreactivity (asymmetric dimethylarginine [ADMA] and endothelin-1) and analyzed the relations between changes in endothelium-dependent flow-mediated dilation of the brachial artery and changes in these markers to elucidate their roles in mediating the vascular protective effects of rosiglitazone. Of 70 nondiabetic patients who met a modified National Cholesterol Education Program definition of the metabolic syndrome, 35 were randomized to receive rosiglitazone (4 mg/day) and 35 to receive placebo for 8 weeks. At study end, treatment with rosiglitazone had significantly reduced plasma insulin (-25%, p = 0.004) and resistin (-16%, p <0.001), increased adiponectin (164%, p <0.001), low-density lipoprotein cholesterol (16%, p = 0.005), and apolipoprotein-B (14%, p = 0.003), and decreased CRP (-30%, p = 0.005), soluble CD40 ligand (-20%, p = 0.014), ADMA (-16%, p <0.001), and endothelin-1 (-11%, p <0.001) concentrations and systolic and diastolic blood pressures. Rosiglitazone treatment significantly improved flow-mediated dilation (p <0.001) and nitroglycerin-induced vasodilation (p = 0.001) of the right brachial artery. On multivariate analysis, changes in ADMA, endothelin-1, and CRP were independent predictors of improved endothelial reactivity with rosiglitazone. In conclusion, we have, for the first time, demonstrated the independent associations between the improvement in flow-mediated dilation and reductions in ADMA, endothelin-1, and CRP after 8 weeks of treatment with rosiglitazone in nondiabetic patients with the metabolic syndrome. These findings suggest that decreases in ADMA, endothelin-1, and CRP may serve as possible mechanisms for the improvement in endothelial function conferred by rosiglitazone treatment.

Resistin in rheumatoid arthritis synovial tissue, synovial fluid and serum

BACKGROUND

Resistin is a newly identified adipocytokine which has demonstrated links between obesity and insulin resistance in rodents. In humans, proinflammatory properties of resistin are superior to its insulin resistance-inducing effects.

OBJECTIVES

To assess resistin expression in synovial tissues, serum and synovial fluid from patients with rheumatoid arthritis, osteoarthritis and spondylarthropathies (SpA), and to study its relationship with inflammatory status and rheumatoid arthritis disease activity.

METHODS

Resistin expression and localisation in synovial tissue was determined by immunohistochemistry and confocal microscopy. Serum and synovial fluid resistin, leptin, interleukin (IL)1beta, IL6, IL8, tumour necrosis factor alpha, and monocyte chemoattractant protein-1 levels were measured. The clinical activity of patients with rheumatoid arthritis was assessed according to the 28 joint count Disease Activity Score (DAS28).

RESULTS

Resistin was detected in the synovium in both rheumatoid arthritis and osteoarthritis. Staining in the sublining layer was more intensive in patients with rheumatoid arthritis compared with those with osteoarthritis. In rheumatoid arthritis, macrophages (CD68), B lymphocytes (CD20) and plasma cells (CD138) but not T lymphocytes (CD3) showed colocalisation with resistin. Synovial fluid resistin was higher in patients with rheumatoid arthritis than in those with SpA or osteoarthritis (both p<0.001). In patients with rheumatoid arthritis and SpA, serum resistin levels were higher than those with osteoarthritis (p<0.01). Increased serum resistin in patients with rheumatoid arthritis correlated with both CRP (r=0.53, p<0.02), and DAS28 (r=0.44, p<0.05), but not with selected (adipo) cytokines.

CONCLUSION

The upregulated resistin at local sites of inflammation and the link between serum resistin, inflammation and disease activity suggest a role for resistin in the pathogenesis of rheumatoid arthritis.

Relationship between adipokines, inflammation, and vascular reactivity in lean controls and obese subjects with metabolic syndrome

PURPOSE

Metabolic syndrome is an important risk factor for cardiovascular disease. Adipokines interfere with insulin action and endothelial cell function. We investigated the relationship among adipokines, metabolic factors, inflammatory markers, and vascular reactivity in obese subjects with metabolic syndrome and lean controls.

METHODS

Cross-sectional study of 19 obese subjects with metabolic syndrome and 8 lean volunteers evaluated as controls. Vascular reactivity was assessed by venous occlusion pletysmography measuring braquial forearm blood flow (FBF) and vascular resistance (VR) responses to intra-arterial infusions of endothelium-dependent (acetylcholine-Ach) and independent (sodium nitroprusside-SNP) vasodilators. Blood samples were obtained to evaluate C reactive protein (CRP), plasminogen activator inhibitor 1 (PAI-1), fibrinogen, adiponectin, resistin, and lipid profile. Patients were classified with regard to insulin resistance through the HOMA-IR index.

RESULTS

PAI-1, CRP and fibrinogen were higher and adiponectin was lower in metabolic syndrome subjects compared to controls. Metabolic syndrome subjects had impaired vascular reactivity. Adiponectin and PAI-1 were associated with insulin, HOMA-IR, triglycerides, and HDLc; and resistin with CRP. Adiponectin was associated with VR after Ach in the pooled group and resistin with D FBF after Ach in the metabolic syndrome group.

CONCLUSION

Metabolic syndrome subjects exhibited low levels of adiponectin and high levels of CRP, fibrinogen, and PAI-1. Adiponectin and PAI-1 correlated with insulin resistance markers. Adiponectin and resistin correlated with vascular reactivity parameters. An adipocyte-endothelium interaction might be an important mechanism of inflammation and vascular dysfunction.

Resistin worsens cardiac ischaemia-reperfusion injury

We provide the first report of direct effects of resistin upon haemodynamic and neurohumoral parameters in isolated perfused rat heart preparations. Pre-conditioning with 1 nmol L-1 recombinant human resistin prior to ischaemia significantly impaired contractile recovery during reperfusion, compared with vehicle-infused hearts (P<0.05, n=12). This was accompanied by a significant increase in both A-type and B-type natriuretic peptides (P<0.05, n=12 both ANP and BNP vs vehicle), creatine kinase, and tumour necrosis factor-alpha (TNF-alpha) release in resistin-infused hearts. Resistin had no significant effect on myocardial glucose uptake. Co-infusion of resistin with Bay 11 7082 (an NF-kappaB inhibitor) improved contractile recovery following ischaemia and reduced both natriuretic peptide and creatine kinase release. This is the first evidence indicating resistin impairs cardiac recovery following ischaemia, stimulates cardiac TNF-alpha secretion, and modulates reperfusion release of natriuretic peptides and biochemical markers of myocardial damage. A TNF-alpha signalling related mechanism is suggested as one component underlying these effects.

Low-dose rosiglitazone exerts an antiinflammatory effect with an increase in adiponectin independently of free fatty acid fall and insulin sensitization in obese type 2 diabetics

BACKGROUND

We have previously demonstrated an early and potent antiinflammatory effect of troglitazone and rosiglitazone.

HYPOTHESIS

Because inflammatory mediators interfere with insulin signal transduction, we have now hypothesized that rosiglitazone exerts an initial antiinflammatory effect independently of its metabolic actions including the suppression of the plasma concentration of free fatty acids (FFAs), insulin, and glucose after which insulin sensitization occurs.

PATIENT AND METHODS

Fourteen patients with type 2 diabetes were included in the study. Eight patients were given 2 mg daily of rosiglitazone for 6 wk, whereas the other six patients were given a placebo for the same period.

RESULTS

After a 2-mg dose of rosiglitazone, plasma FFAs, insulin, and glucose concentrations and homeostasis model assessment of insulin resistance did not change. Plasma C-reactive protein, serum amyloid A, and matrix metalloproteinase concentrations fell significantly at wk 1 and continued to be significantly lower than the baseline levels by 25, 29, and 24%, respectively, at wk 6. Leukocyte count was significantly lower at wk 6 after rosiglitazone, whereas there was no change in the control group. Plasma adiponectin concentrations increased significantly at wk 2 and continued to increase during the treatment period with rosiglitazone. Resistin concentrations fell significantly by 10% at wk 6 only. There were no changes in any of these indices in the placebo group.

CONCLUSIONS

A low dose of rosiglitazone exerts an early and potent antiinflammatory effect with an increase in adiponectin and a fall in resistin concentrations without causing any metabolic changes (fall in plasma glucose, FFAs, and insulin concentrations) over a 6-wk period. The increase in adiponectin and the decrease in resistin after rosiglitazone are thus related primarily to its antiinflammatory effects rather than its metabolic actions. These observations have implications in relation to the mode of action of this drug as an insulin-sensitizing agent and also its use as a potential antiinflammatory and antiatherogenic drug in the future.

Resistin impairs endothelium-dependent dilation to bradykinin, but not acetylcholine, in the coronary circulation

Elevated plasma levels of fat-derived signaling molecules are associated with obesity, vascular endothelial dysfunction, and coronary heart disease; however, little is known about their direct coronary vascular effects. Accordingly, we examined mechanisms by which one adipokine, resistin, affects coronary vascular tone and endothelial function. Studies were conducted in anesthetized dogs and isolated coronary artery rings. Resistin did not change coronary blood flow, mean arterial pressure, or heart rate. Resistin had no effect on acetylcholine-induced relaxation of artery rings; however, resistin did impair bradykinin-induced relaxation. Selective impairment was also observed in vivo, as resistin attenuated vasodilation to bradykinin but not to acetylcholine. Resistin had no effect on dihydroethidium fluorescence, an indicator of superoxide (O(2)(-)) production, and the inhibitory effect of resistin on bradykinin-induced relaxation persisted in the presence of Tempol, a superoxide dismutase mimetic. To determine whether resistin impaired production of and/or responses to nitric oxide (NO) or prostaglandins (e.g., prostacyclin; PGI(2)), we performed experiments with N(omega)-nitro-L-arginine methyl ester (L-NAME) and indomethacin. The effect of resistin to attenuate bradykinin-induced vasodilation persisted in the presence of L-NAME or indomethacin, suggesting resistin may act at a cell signaling point upstream of NO or PGI(2) production. Resistin-induced endothelial dysfunction is not generalized, and it is not consistent with effects mediated by O(2)(-) or interference with NO or PGI(2) signaling. The site of the resistin-induced impairment is unknown but may be at the bradykinin receptor or a closely associated signal transduction machinery proximal to NO synthase or cyclooxygenase.

Increased subcutaneous and epicardial adipose tissue production of proinflammatory cytokines in cardiac surgery patients: possible role in postoperative insulin resistance

CONTEXT

Hyperglycemia and insulin resistance frequently occur in critically ill patients even without a history of diabetes.

OBJECTIVE

Our objective was to study the role of adipose tissue hormonal production in the development of insulin resistance in cardiac surgery patients. PARTICIPANTS, INTERVENTIONS, AND SETTINGS: Fifteen patients with elective cardiac surgery underwent blood sampling before, at the end, and 6, 12, 24, 48, and 120 h after the end of their operation. Epicardial and sc adipose tissue sampling was done at the beginning and at the end of surgery in the Department of Cardiac Surgery.

MAIN OUTCOME MEASURES

We measured serum concentrations and sc and epicardial adipose tissue mRNA expression of IL-6, monocyte chemoattractant protein-1 (MCP-1), TNF-alpha, leptin, resistin, and adiponectin and sc and epicardial adipose tissue mRNA expression of CD14, CD45, and CD68.

RESULTS

The rate of insulin infusion required to maintain euglycemia increased up to 7-fold 12 h after the operation, suggesting the development of insulin resistance. Serum IL-6 levels increased 43-fold 12 h after surgery. MCP-1 peaked 6-fold at the end of surgery. Smaller peaks of TNF-alpha and leptin appeared 6 and 12 h after surgery, respectively. Resistin levels peaked 4-fold 24 h after surgery, but adiponectin levels were not significantly affected. TNF-alpha and CD45 mRNA expression increased markedly during the operation in sc adipose tissue. IL-6, resistin, and MCP-1 mRNA expression increased in both sc and epicardial adipose tissue. Leptin, adiponectin, CD14, and CD68 mRNA expression did not change significantly.

CONCLUSIONS

Both sc and epicardial adipose tissue is a source of proinflammatory cytokines in cardiac surgery patients and may contribute to the development of postoperative insulin resistance.

Adipose tissue resistin levels in patients with anorexia nervosa

OBJECTIVE

Resistin is a specific fat-derived hormone that affects fuel homeostasis and insulin action in rodents. However, its role in human physiology and pathophysiologic conditions, such as malnutrition, remains uncertain.

METHODS

To enhance understanding of the role of resistin in the pathophysiology of anorexia nervosa (AN), we measured plasma resistin levels in 13 women with a restrictive type of AN and in 16 healthy age-matched women (control). Further, we measured resistin levels in the subcutaneous adipose tissue of eight women from the AN group and eight women from the control group with an in vivo microdialysis technique (CMA/107 pump, CMA/60 catheters, CMA Microdialysis AB, Solna, Sweden).

RESULTS

Body mass index, percentage of body fat, fasting plasma leptin and insulin, and homeostasis model assessment index for insulin resistance were severely decreased in patients with AN compared with the control group. Plasma resistin levels were significantly decreased in patients with AN (P < 0.05), whereas subcutaneous adipose tissue resistin levels were significantly increased in patients with AN compared with the control group (P < 0.05). In both groups, plasma resistin levels showed no significant relation to resistin in dialysate, percentage of body fat, body mass index, homeostasis model assessment index for insulin resistance, and fasting plasma leptin levels.

CONCLUSION

We demonstrated that AN is associated with decreased plasma resistin levels and increased resistin levels in extracellular space of the abdominal adipose tissue. Plasma resistin levels in patients with AN or in healthy normal-weight women were not directly related to body mass index, percentage of body fat, plasma leptin levels, and insulin sensitivity.

Elevated resistin levels in cirrhosis are associated with the proinflammatory state and altered hepatic glucose metabolism but not with insulin resistance

The adipokine resistin has been implicated in obesity and insulin resistance. Liver cirrhosis is associated with decreased body fat mass and insulin resistance. We determined plasma resistin levels in 57 patients with cirrhosis, 13 after liver transplantation, and 30 controls and correlated these with hemodynamic as well as hepatic and systemic metabolic parameters. Patients with cirrhosis had, dependent on the clinical stage, an overall 86% increase in resistin levels (P < 0.001) with hepatic venous resistin being higher than arterial levels (P < 0.001). Circulating resistin was significantly correlated with plasma TNF-alpha levels (r = 0.62, P < 0.001). No correlation was observed between resistin and hepatic hemodynamics, body fat mass, systemic energy metabolism, and the degree of insulin resistance. However, plasma resistin in cirrhosis was negatively associated with hepatic glucose production (r = -0.47, P < 0.01) and positively with circulating free fatty acids (FFA; r = 0.40, P < 0.01) and ketone bodies (r = 0.48, P < 0.001) as well as hepatic ketone body production (r = 0.40, P < 0.01). After liver transplantation, plasma resistin levels remained unchanged, whereas insulin resistance was significantly improved (P < 0.01). These data provide novel insights into the role of resistin in the pathophysiological background of a catabolic disease in humans and also indicate that resistin inhibition may not represent a suitable therapeutic strategy for the treatment of insulin resistance and diabetes in patients with liver cirrhosis.

Increased serum resistin in elite endurance athletes with high insulin sensitivity

AIMS/HYPOTHESIS

Resistin is an adipokine associated with obesity and type 2 diabetes in animal models, but in humans its role remains uncertain. This study was undertaken to test whether serum resistin is related to insulin resistance and markers of low-grade inflammation in elite athletes taken as a model of extreme insulin sensitivity. SUBJECTS MATERIALS AND METHODS: In 23 elite athletes (sprinters, middle-distance and marathon runners) and in 72 sedentary men including lean and obese individuals with NGT, and obese individuals with IGT or new-onset type 2 diabetes, we assessed insulin sensitivity using a whole-body insulin-sensitivity index (WBISI) derived from a 3-h OGTT; energy homeostasis was also assessed by means of indirect calorimetry, along with circulating adipokines and low-grade pro-inflammatory cyto-chemokines.

RESULTS

Professional athletes had increased WBISIs (p<0.001) and lipid oxidation (p<0.03); they also showed higher serum resistin concentrations (p<0.001), although the pro-inflammatory chemokines were not increased in comparison with the other study groups. Resistin was independently associated only with fasting plasma NEFA. Increased resistin was detected in the middle-distance and marathon runners, but not in the sprinters when compared with the lean, young, sedentary individuals.

CONCLUSIONS/INTERPRETATION

Serum resistin concentration is increased in elite athletes, providing evidence against the notion that resistin levels reflect insulin resistance in humans, as seen in animal studies. Increased resistin was observed in aerobic-endurance, but not sustained-power athletes and this feature appeared to be independently associated with parameters of fatty acid metabolism.

Increased expression of the adipokine genes resistin and fasting-induced adipose factor in hypoxic/ischaemic mouse brain

Adipose tissue is the primary source of the adipokines resistin and fasting-induced adipose factor (FIAF). We reported that the brain is also a site of adipokine expression, although their function there is unknown. Peripheral resistin and fasting-induced adipose factor are reported to be inflammatory markers, and we hypothesized that they would be induced in the brain by hypoxia/ischaemia. We show that neonatal hypoxia/ischaemia rapidly increased fiaf mRNA in the injured cortex and hippocampus at 2 and 7 days after hypoxia/ischaemia. In contrast, resistin (retn) mRNA was increased in the cortex only at 21 days after hypoxia/ischaemia. As a lipopolysaccharide-induced inflammatory response did not increase brain fiaf and retn mRNA levels, we conclude that brain injury may be responsible for the novel hypoxia/ischaemia-induced changes in adipokine gene expression. In summary, our results indicate that brain injury, or an inflammatory stimulus, regulates the central expression of two genes normally considered to be adipose tissue-specific. These observations add to our previous evidence that the brain is an important site of adipokine gene expression.

Elevated resistin levels in chronic kidney disease are associated with decreased glomerular filtration rate and inflammation, but not with insulin resistance

In the present study, we explore the role of decreased renal function and a genetic polymorphism on the recently discovered protein resistin, apparently able to inhibit hepatic insulin action in mice. We also investigate possible links with inflammation and the insulin resistance present in patients with chronic kidney disease (CKD). This is a post hoc, cross-sectional study comparing 239 prevalent CKD patients with varying degrees of renal function impairment with an age- and gender-matched randomly selected control group of 25 individuals. Glomerular filtration rate (GFR) was estimated by the mean of urea and creatinine clearance (24-h urine samples) (n=204) or by iohexol clearance (n=60). Plasma analysis of blood lipids, insulin, glucose, inflammatory markers (high-sensitivity C-reactive protein, interleukin-6, tumor necrosis factor-alpha, vascular cellular adhesion molecule, intercellular adhesion molecule) and resistin (kit from LINCO Research, St Charles, MS) was performed using commercially available assays or routine methods. Insulin resistance was estimated by quantitative insulin-sensitivity check index (QUICKI) and homeostasis model assessment for insulin resistance (HOMA-IR) and body composition by dual-energy X-ray absorptiometry. Genotyping of a C/G promoter single nucleotide polymorphism (n=168) at position -180 of the resistin gene was performed by PyroSequencing. Serum levels of resistin were markedly elevated in the CKD patients with both advanced (39.9+/-1.3 ng/ml) and mild to moderate (23.2+/-1.0 ng/ml) renal function impairment, as compared to controls (8.5+/-0.7 ng/ml; P<0.001). In a multiple linear regression model in patients (adjusted r(2)=0.60), only GFR (beta=3.4; P<0.0001), lean body mass (beta=2.2; P<0.001) and the inflammatory markers were independently associated with circulating resistin levels. There was a weak but significant impact of -180 C/G genotype on plasma levels of resistin (median 43.0+/-2.4 ng/ml in CC, 37.5+/-2.0 ng/ml in CG, and 41.1+/-4.9 ng/ml in GG; P<0.05). Univariate analysis of non-diabetic patients and controls showed that serum resistin was associated with markers of glucose metabolism. However, in a multiple regression model, resistin, as well as all the measured markers of inflammation, was only associated with insulin resistance if GFR was not taken into account. Circulating resistin levels are strongly associated with both GFR and inflammatory biomarkers in CKD. As the significant relationship between plasma resistin levels and insulin resistance was lost following the correction for GFR, resistin is not a likely mediator of insulin resistance in patients with CKD. Renal function is an important factor to take into account in clinical studies relating insulin sensitivity to inflammatory biomarkers in CKD as well as in patients with diabetes mellitus, who often have an impaired renal function.

Resistin and adiponectin levels in subjects with coronary artery disease and type 2 diabetes

BACKGROUND

Resistin and adiponectin are implicated in insulin resistance and atherosclerosis. The objective of this study was to evaluate the association between plasma resistin levels and the presence of coronary artery disease (CAD) or diabetes compared to the controls. In a cross-sectional study, we measured glucose, fasting lipid panel, resistin, adiponectin, insulin, C-reactive protein (CRP) and TNF-alpha in 57 subjects with CAD, 58 subjects with diabetes compared to 45 normal control subjects.

RESULTS

Subjects with CAD compared to the control subjects had increased insulin resistance index (39+/-32 vs. 13.45+/-12.73 with p<0.0001), CRP levels (3.8+/-4.03 vs. 2.0+/-2.0 with p<0.05) and decreased levels of adiponectin (12.5+/-4.8 vs. 17.26+/-10.4 with p<0.0003). Subjects with diabetes compared to the controls had had increased insulin resistance index (69+/-19 vs. 13.45+/-12.73 with p<0.001), CRP levels (4.1+/-4.8 vs. 2.0+/-2.0 with p<0.01) and decreased levels of adiponectin (11.58+/-4.8 vs. 17.26+/-10.4 with p<0.001). Compared to the controls, there was no significant difference in the levels of resistin in subjects with CAD (4.92+/-3.2 vs. 4.1+/-2.4) as well as diabetes (4.92+/-3.2 vs. 4.6+/-2.6). Both CRP and resistin levels correlate with TNF-alpha (r=0.557, p<0.000001; r=0.84, p<0.000001).

CONCLUSIONS

The present study shows decreased plasma adiponectin levels in subjects with diabetes as well as in subjects with CAD is similar to the literature. Plasma levels of resistin in subjects with CAD or diabetes are similar to the controls. However, there was a strong correlation of resistin levels with inflammatory markers. This suggests resistin as an inflammatory marker associated with CAD.

Oxidative Stress and Adverse Adipokine Profile Characterize the Metabolic Syndrome in Children

Thirty-four children were assessed for body composition, blood pressure, lipids, glucose tolerance, markers of insulin resistance, oxidative stress, and adipokines. Children were divided into 3 groups: (1) normal weight, (2) overweight but otherwise healthy, and (3) overweight with the metabolic syndrome. There were no differences among any of the groups for age or Tanner stage, and anthropometric variables were similar between the overweight and the overweight with the metabolic syndrome groups. Differences across groups were found for high-density lipoprotein cholesterol (P < .001), triglycerides (P < .01), fasting insulin (P < .001), homeostasis model assessment (P < .01), adiponectin (P < .05), leptin (P < .0001), C-reactive protein (P < .0001), interleukin 6 (P < .0001), and 8-isoprostane (P < .001). In children, oxidative stress and adipokine levels worsen throughout the continuum of obesity and especially in the presence of components of the metabolic syndrome. Overweight children with components of the metabolic syndrome may be at elevated risk for future cardiovascular disease.

High plasma resistin level is associated with enhanced highly sensitive C-reactive protein and leukocytes

OBJECTIVES

Resistin is a newly described hormone with a suggested role in insulin resistance. In humans, inflammatory cells seem to be the major source of resistin. The aim of this study was to find out whether plasma resistin concentration associates with carotid artery atherosclerosis and the risk factors of atherosclerosis.

METHODS

Plasma resistin concentrations were measured in 525 Finnish middle-aged subjects among our population-based cohort. Intima-media thickness was measured from the internal carotid artery, the bifurcation enlargement, and the common carotid artery.

RESULTS

Among all the subjects, the median resistin concentration was 7.07 ng/ml (interquartile range, 5.82-8.84), women having higher levels than men (P < 0.001) with median values of 7.56 ng/ml (6.18-9.19) and 6.67 ng/ml (5.63-8.31), respectively. Resistin level correlated negatively with mean intima-media thickness, internal carotid artery, and common carotid artery, but the association did not remain significant after adjustments. Plasma resistin concentration was associated positively with leukocytes (P < 0.001), highly sensitive C-reactive protein (P = 0.009), and IGF binding protein 1 (P < 0.001), but not with plasma insulin or glucose levels in analysis of covariance after adjustments for age, sex, and body mass index.

CONCLUSIONS

The results imply that inflammatory factors are more important in the determination of plasma resistin concentration than plasma insulin or glucose values. Resistin is associated with proatherogenic inflammatory markers but not independently with early atherosclerosis.

Heritability of serum resistin and its genetic correlation with insulin resistance-related features in nondiabetic Caucasians

CONTEXT

Serum levels of resistin are believed to modulate insulin resistance in humans.

OBJECTIVE

The aim of this study was to investigate whether serum resistin levels are genetically controlled and whether this control is shared with other insulin resistance traits.

DESIGN AND METHODS

The study cohort included 264 nondiabetic probands, Caucasian from Italy, and their 473 adult family members. Phenotypic characterization included anthropometric variables, blood pressure, fasting glucose and insulin, lipid profile, and resistin levels. Genotypes were determined at position g.-420C-->G (rs1862513), IVS2+181G-->A (rs3745367), and GAT((n)) polymorphisms of the resistin (RETN) gene.

RESULTS

In the 264 unrelated probands, resistin levels were significantly (P < 0.01) correlated with adiposity, blood pressure, C-reactive protein, and the metabolic syndrome score. In a variance component analysis of the 264 probands and their 473 relatives, about 70% of the observed variation of serum resistin levels was heritable (P < 0.0001). A small, but significant (P = 0.004) proportion of this variance was explained by the G-->A variation at position IVS2+181 of the RETN gene. Significant genetic correlations (P < 0.05) were observed between resistin and body mass index (rho(g) = 0.30), waist circumference (rho(g) = 0.32), the insulin resistance index HOMA(IR) (rho(g) = 0.28), and the metabolic syndrome score (rho(g) = 0.35).

CONCLUSIONS

These data indicate that serum resistin is highly heritable and has some common genetic background with traits related to insulin resistance, reinforcing the hypothesis that this adipokine may play a pathogenic role in insulin resistance-related abnormalities, including type 2 diabetes and cardiovascular disease.

Resistin, acute coronary syndrome and prognosis results from the AtheroGene study

OBJECTIVE

Resistin, an adipocyte and macrophage derived cytokine, causes insulin resistance and glucose intolerance. We investigated the impact of resistin as a diagnostic marker in patients with acute coronary syndrome and its prognostic value for future cardiovascular events.

METHODS

Resistin levels were determined in 1153 patients with stable angina (SAP), 380 patients with unstable angina, 278 patients with non-ST-elevation myocardial infarction (NSTEMI) and 111 patients with ST-elevation myocardial infarction (STEMI). All patients have been followed up for a median follow-up of 2.6 years. During follow-up, 70 patients died from cardiovascular causes.

RESULTS

Compared to SAP, resistin levels (5.1 ng/mL in SAP) were elevated in patients with angina at rest (5.89 ng/mL, P=0.001), in patients with NSTEMI (6.00 ng/mL, P<0.001), and in patients with STEMI (5.98 ng/mL, P<0.001). Resistin levels rose at 3-6h after chest pain onset (5.46 ng/mL), persisted elevated among those individuals presenting between 6 and 12h after chest pain onset (5.57 ng/mL) and peaked in individuals presenting more than 12h after chest pain onset (5.74 ng/mL). An increase of one standard deviation of resistin levels was associated with a 1.22-fold (95% CI 1.04-1.43; P=0.02) risk for future fatal cardiovascular events in a model adjusted for risk factors and clinical and therapeutic variables. When adjustment for renal function was applied, this association lost its statistical significance.

CONCLUSIONS

Resistin levels are elevated in patients presenting with unstable angina, NSTEMI and STEMI and might play a role as a diagnostic marker. In addition, systemic resistin level is moderately associated with future cardiovascular death in patients with documented coronary artery disease.