Resistin: an adipocyte-derived hormone. Has it a role in diabetes and obesity?

Clinical impacts of sarcopenic obesity on chronic obstructive pulmonary disease: a cross-sectional study

BACKGROUND

Sarcopenia and obesity are two abnormal body composition phenotypes, and sarcopenic obesity (SO) is characterized by both low skeletal muscle mass (sarcopenia) and high adiposity (obesity). SO negatively influences the clinical status of patients with chronic obstructive pulmonary disease (COPD). However, the studies exploring the prevalence and clinical effects of SO in COPD patients are limited. Our study aimed to elucidate the prevalence and impact of SO on COPD patients.

METHODS

In this cross-sectional study, the pulmonary function, St. George's Respiratory Questionnaire, exercise tolerance, body composition, and serum levels of resistin and TNF-α were assessed in 198 COPD patients. The clinical value of serum resistin and TNF-α for predicting SO in patients with COPD was evaluated.

RESULTS

In the 198 patients with COPD, the prevalence rates of sarcopenia, obesity, and SO in COPD patients were 27.27%, 29.8%, and 9.6%, respectively. Patients with SO experienced more severe symptoms of dyspnea and worse health related quality of life. The expression of resistin increased in patients with SO compared to other patients. The AUC value of serum resistin level for predicting SO was 0.870 (95% CI: 0.799-0.940). BMI (OR: 1.474, 95% CI: 1.124-1.934) and resistin (OR: 1.001, 95% CI: 1.000-1.002) levels were independent risk factors of SO in patients with COPD in Multivariate analysis.

CONCLUSION

The prevalence rates of SO in COPD patients was 9.6%. COPD accompanied by SO is significantly associated with worse pulmonary function and poor physical performance. Serum resistin may be a potential adjunct for predicting SO in COPD patients.

Adipocytokines and High Blood Pressure in Mexican Children

Given that adipocytokines may play an important role in the pathophysiology of high blood pressure (HBP) and because related reports in children are scarce and controversial, we evaluated the relationship of leptin, resistin, tumor necrosis factor-α, interleukin-6, adiponectin, and interferon-γ with HBP. Materials and Methods. A total of 129 (53.8%) girls and 111 (46.2%) boys, with average ages of 10.8 ± 0.9 and 10.6 ± 1.0 years, respectively, were enrolled in a cross-sectional study. HBP was defined by systolic blood pressure (SBP) and/or diastolic blood pressure (DBP) between the 90th and 95th percentiles. A multivariate logistic regression backwards-stepwise analysis adjusted for body mass index, waist circumference, and triglyceride levels was performed to compute the association between adipocytokines and HBP. Results. Seventy-two (30.0%) participants showed HBP: 44 (61.1%) girls and 28 (38.9%) boys. Multivariate analysis showed that, irrespective of obesity, serum levels of adiponectin, but not those of other adipocytokines, are inversely associated with HBP (odds ratio 0.93; 95% CI 0.77 to 0.98, p = .04). Conclusions. Our results show that low serum adiponectin levels, but not those of other adipocytokines, are inversely associated with HBP; this association is independent of obesity.

Impact of pregravid obesity on maternal and fetal immunity: Fertile grounds for reprogramming

Maternal pregravid obesity results in several adverse health outcomes during pregnancy, including increased risk of gestational diabetes, preeclampsia, placental abruption, and complications at delivery. Additionally, pregravid obesity and in utero exposure to high fat diet have been shown to have detrimental effects on fetal programming, predisposing the offspring to adverse cardiometabolic, endocrine, and neurodevelopmental outcomes. More recently, a deeper appreciation for the modulation of offspring immunity and infectious disease-related outcomes by maternal pregravid obesity has emerged. This review will describe currently available animal models for studying the impact of maternal pregravid obesity on fetal immunity and review the data from clinical and animal model studies. We also examine the burden of pregravid obesity on the maternal-fetal interface and the link between placental and systemic inflammation. Finally, we discuss future studies needed to identify key mechanistic underpinnings that link maternal inflammatory changes and fetal cellular reprogramming events.

Prognostic biomarkers in renal cell carcinoma: is there a relationship with obesity?

Obesity is a recognized risk factor for renal cell carcinoma (RCC) the commonest form of kidney cancer. Both obesity and RCC are serious diseases with increasing incidence yearly. This review examined certain obesity associated measurements and adipokines as detection/prognostic indicators for RCC. The obesity related measurements such as body mass index (BMI), waist circumstance (WC), waist-hip ratio (WHR) in predicting RCC are valid when used in conjunction with other risk factors such as age and sex or with histological findings. The adipokine adiponectin holds promising outcomes as a predictive marker in assessing the risk of developing RCC. In addition, tissue leptin/leptin receptor may be a distinguishing marker for RCC subtypes. However, circulating leptin may not be a suitable detection or prognostic biomarker for RCC. The other less investigated adipokines; omentin, visfatin, apelin and resistin are also expressed in RCC but their prognostic capabilities are still inconclusive. BMI, WC and adipokines may be useful additions in a nomogram which includes TNM staging and pathological grading system to detect, confirm and follow-up RCC cases.

Maternal obesity and inflammatory mediators: A controversial association

The link between maternal obesity and inflammatory mediators is still unclear. Our aim was to summarize the main findings of recently published studies on this topic. We performed a search in Medline for studies published in the last years on obesity, human pregnancy, and inflammatory mediators. We report the findings of 30 studies. The characteristics and number of participants, study design, gestational age at sample collection, and type of sample varied widely. Approximately two-thirds of them investigated more than one mediator, and 50% included participants in only one trimester of pregnancy. The most frequently investigated mediators were leptin, tumour necrosis factor-alpha (TNF-α), and interleukin (IL)-6. Almost all studies reported an association between maternal obesity, leptin, and C-reactive protein (CRP) serum levels but not with IL-1β and IL-10. The association of IL-6, TNF-α, monocyte chemo-attractant protein-1 (MCP-1), adiponectin, and resistin with maternal obesity is still controversial. To clarify the physiopathological link between maternal obesity and inflammation, more high-quality studies are needed.

The role of sex steroids in white adipose tissue adipocyte function

With the increasing knowledge that gender influences normal physiology, much biomedical research has begun to focus on the differential effects of sex on tissue function. Sexual dimorphism in mammals is due to the combined effects of both genetic and hormonal factors. Hormonal factors are mutable particularly in females in whom the estrous cycle dominates the hormonal milieu. Given the severity of the obesity epidemic and the fact that there are differences in the obesity rates in men and women, the role of sex in white adipose tissue function is being recognized as increasingly important. Although sex differences in white adipose tissue distribution are well established, the mechanisms affecting differential function of adipocytes within white adipose tissue in males and females remain largely understudied and poorly understood. One of the largest differences in the endocrine environment in males and females is the concentration of circulating androgens and estrogens. This review examines the effects of androgens and estrogens on lipolysis/lipogenesis, adipocyte differentiation, insulin sensitivity and adipokine production in adipocytes from white adipose tissue with a specific emphasis on the sexual dimorphism of adipocyte function in white adipose tissue during both health and disease.

Insulin resistance in chronic kidney disease: a systematic review

Insulin resistance (IR) is an early metabolic alteration in chronic kidney disease (CKD) patients, being apparent when the glomerular filtration rate is still within the normal range and becoming almost universal in those who reach the end stage of kidney failure. The skeletal muscle represents the primary site of IR in CKD, and alterations at sites beyond the insulin receptor are recognized as the main defect underlying IR in this condition. Estimates of IR based on fasting insulin concentration are easier and faster but may not be adequate in patients with CKD because renal insufficiency reduces insulin catabolism. The hyperinsulinemic euglycemic clamp is the gold standard for the assessment of insulin sensitivity because this technique allows a direct measure of skeletal muscle sensitivity to insulin. The etiology of IR in CKD is multifactorial in nature and may be secondary to disturbances that are prominent in renal diseases, including physical inactivity, chronic inflammation, oxidative stress, vitamin D deficiency, metabolic acidosis, anemia, adipokine derangement, and altered gut microbiome. IR contributes to the progression of renal disease by worsening renal hemodynamics by various mechanisms, including activation of the sympathetic nervous system, sodium retention, and downregulation of the natriuretic peptide system. IR has been solidly associated with intermediate mechanisms leading to cardiovascular (CV) disease in CKD including left ventricular hypertrophy, vascular dysfunction, and atherosclerosis. However, it remains unclear whether IR is an independent predictor of mortality and CV complications in CKD. Because IR is a modifiable risk factor and its reduction may lower CV morbidity and mortality, unveiling the molecular mechanisms responsible for the pathogenesis of CKD-related insulin resistance is of importance for the identification of novel therapeutic targets aimed at reducing the high CV risk of this condition.

Obesity and Sepsis

Obesity has reached epidemic proportions over the last few decades. Obesity is associated with increased morbidity and mortality in hypertension, cardiovascular diseases, stroke, and cancer and is feared to decrease overall life expectancy over the next few decades. There is a growing body of evidence suggesting that obesity is a chronic inflammatory disease. Obesity is becoming a cause of concern in critically ill patients as well. Sepsis is the number one cause of morbidity and mortality in noncoronary artery disease critical care units all over the world and is associated with a high cost of care. An increase in morbidity in obese septic patients compared with lean people is a cause of growing concern. Laboratory evidence suggests that there is exaggeration in the inflammatory and prothrombogenic phenotype assumed by obese compared with lean septic animals. The exact mechanisms underlying this phenomenon are unknown. This article reviews some of the pathophysiological processes responsible for the underlying inflammation in obesity and sepsis and reviews the literature for the association of the two.

Effect of periodontal treatment on adipokines in type 2 diabetes

The association between adipokines and inflammatory periodontal diseases has been studied over the last two decades. This review was intended to explore the observation that periodontal therapy may lead to an improvement of adipokines in diabetic patients. In summary, substantial evidence suggests that diabetes is associated with increased prevalence, extent and severity of periodontitis. Numerous mechanisms have been elucidated to explain the impact of diabetes on the periodontium. However, current knowledge concerning the role of major adipokines indicates only some of their associations with the pathogenesis of periodontitis in type 2 diabetes. Conversely, treatment of periodontal disease and reduction of oral inflammation may have positive effects on the diabetic condition, although evidence for this remains somewhat equivocal.

Resistin derived from diabetic perivascular adipose tissue up-regulates vascular expression of osteopontin via the AP-1 signalling pathway

Perivascular adipose tissue (PVAT) is implicated in the development of vascular diseases; however, the roles of PVAT on OPN expression in diabetic vasculature remain to be determined. This study investigated the role of adipokines derived from diabetic PVAT in regulating the vascular expression of OPN and explored the mechanisms involved. Aortic sections of ob/ob and high-fat diet (HFD)-induced obese (DIO) mice showed an increased expression of OPN, which was paralleled by increased amounts of PVAT characterized by enlargement of adipocytes. In the earlier phase of HFD feeding, macrophage infiltration was mainly localized to the area of PVAT at which adipocytes were enlarged, suggesting a potential link of activated adipocytes to macrophage infiltration. PVAT sections of ob/ob and DIO mice revealed a significantly greater number of macrophages with increased expression of adipokines, including resistin and visfatin. The distribution of resistin in PVAT mostly co-localized with macrophages, while visfatin was expressed in macrophages and other cells. In in vitro studies, OPN expression in vascular smooth muscle cells (VSMCs) co-cultured with PVAT of DIO mice was significantly increased, which was attenuated by a resistin-neutralizing antibody. Likewise, resistin up-regulated expression of OPN mRNA and protein in cultured VSMCs and the pivotal role of AP-1 in resistin-induced OPN transcription was demonstrated. Resistin produced by PVAT plays a pivotal role in the up-regulated expression of OPN in the diabetic vasculature via a signalling pathway that involves activation of AP-1. © 2013 The Authors. Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Early effects of a hypocaloric, Mediterranean diet on laboratory parameters in obese individuals

Calorie restriction is a common strategy for weight loss in obese individuals. However, little is known about the impact of moderate hypocaloric diets on obesity-related laboratory parameters in a short-term period. Aim of this study was to evaluate the variation of laboratory biomarkers in obese individuals following a Mediterranean, hypocaloric (1400-1600 Kcal/die) diet. 23 obese, pharmacologically untreated patients were enrolled and subjected to the determination of anthropometric variables and blood collection at baseline, 1 and 4 months after diet initiation. After 4 months of calorie restriction, we observed a significant decrease in body weight and BMI (both P < 0.0001), insulin (P = 0.037), HOMA-IR (P = 0.026), leptin (P = 0.008), and LDH (P = 0.023) and an increase in EGF (P = 0.013). All these parameters, except LDH, varied significantly already at 1 month after diet initiation. Also, lower levels of insulin (P = 0.025), leptin (P = 0.023), and EGF (P = 0.035) were associated with a greater (>5%) weight loss. Collectively, our data support a precocious improvement of insulin and leptin sensitivity after a modest calorie restriction and weight reduction. Moreover, EGF and LDH may represent novel markers of obesity, which deserve further investigations.

Role of adipokines signaling in the modulation of T cells function

The field that links immunity and metabolism is rapidly expanding. Apparently non-immunological disorders such as obesity and type 2 diabetes have been linked to immune dysregulation, suggesting that metabolic alterations can be induced by or be consequence of an altered self-immune tolerance. In this context, adipose tissue produces and releases a variety of pro-inflammatory and anti-inflammatory factors, termed "adipokines," which can be considered as the bridge between obesity-related exogenous factors, such as nutrition and lifestyle, and the molecular events leading to metabolic syndrome, inflammatory, and/or autoimmune conditions. In obesity, increased production of most adipokines impacts on multiple functions such as appetite and energy balance, modulation of immune responses, insulin sensitivity, angiogenesis, blood pressure, lipid metabolism, and so on. This report aims to discuss some of the recent topics of adipocytokine research and their related signaling pathways, that may be of particular importance as could lead to effective therapeutic strategies for obesity-associated diseases.

Resistin concentration and gestational diabetes: a systematic review of the literature

Gestational diabetes (GD) exposes mothers and infants to the risk of immediate and later adverse outcomes. Increased insulin resistance is a common feature of GD and obesity. Because of its critical role in regulating insulin sensitivity, resistin has been implicated in the physiopathology of GD. The aim of this study was to review the existing literature on the relationship between circulating maternal resistin levels and GD. Three electronic databases (MEDLINE, EMBASE, and LILACS) were searched for pertinent studies published from 2001 to 2012, without language restrictions. Eleven studies, with a total of 639 participants between 23 and 41 weeks of gestation, were included. The number of GD patients per study ranged from 11 to 81, with varying degrees of disease severity and several different GD diagnostic criteria. Mean concentrations of resistin varied widely both in control women (0.05-22.21 ng/ml) and in GD patients (0.05-62.38 ng/ml). We performed a meta-analysis including a total of 10 studies, and also subgroup analyses according to gestational age at sample collection (up to 32 and >33 weeks). The pooled absolute mean difference (WMD) in resistin levels was slightly lower in GD patients than in controls, but this did not reach statistical significance (WMD=-0.02, 95% CI -0.07 to 0.04). According to the data from the 11 studies analyzed, there was no association between circulating resistin levels and GD. However, this result should be interpreted with caution owing to the large heterogeneity amongst the existing published studies.

Correlation of resistin with inflammatory and cardiometabolic markers in obese adolescents with and without metabolic syndrome

OBJECTIVE

The link between plasma resistin and obesity-related cardiometabolic disorders in children remains debatable. This study assessed the relationships of plasma resistin with cardiovascular risk factors, pro-inflammatory markers and insulin resistance index (HOMA-IR) in obese (Ob) adolescents and obese adolescents with metabolic syndrome (Ob-MS) compared to healthy controls (CO).

METHODS

114 obese adolescents (60 Ob, age 13.6 ± 0.9 years, BMI 28.0 ± 2.2 kg/m(2), and 54 Ob-MS, age 13.8 ± 1.0 years, BMI 32.5 ± 4.8 kg/m(2)) and 37 CO (age 13.7 ± 0.8 years, BMI 22.8 ± 0.8 kg/m(2)) were studied. Anthropometrics, cardiac variables as well as fasting plasma concentrations of lipids, glucose, insulin, and adipocytokines (resistin, tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), C-reactive protein (CRP)) were measured. HOMA-IR was calculated, and the presence of MS was assessed.

RESULTS

Plasma resistin was significantly higher in Ob-MS than in both Ob and CO and was correlated with anthropometric, cardiovascular, pro-inflammatory markers and several components of MS as was HOMA-IR in Ob and Ob-MS. With increasing the number of MS components, plasma resistin, pro-inflammatory markers, and HOMA-IR were also increased. Multiple regression models highlighted significant correlation between resistin and both HOMA-IR (r = 0.40, p < 0.05) and systolic blood pressure (r = 0.63, p < 0.01) in Ob-MS.

CONCLUSION

These results support the hypothesis that there is an association between circulating resistin and childhood obesity-related inflammatory and cardiometabolic events.

Therapeutic effect of carboxymethylated and quanternized chitosan on insulin resistance in high-fat-diet-induced rats and 3T3-L1 adipocytes

Owing to their distinct biochemical properties, chitosan and its derivatives have a great potential in a range of bioapplications. One such application is as a dietary antilipidemic supplement to be used in reducing obesity and to improve insulin resistance. The lipid-binding efficiency of chitosan and its derivatives, however, remains debatable. Accordingly, in this study we investigated the interaction of chitosan and its two derivatives, O-carboxymethyl chitosan (O-CMCs) and N-[(2-hydroxy-3-N,N-dimethylhexadecyl ammonium)propyl]chitosan chloride (N-CQCs), with plasma leptin, glucose, insulin and total cholesterol in a diet-induced insulin-resistant rat model, and further interaction with mRNA expression of adipocytokines and its related molecule PPAR-γ. The experiments were performed using the RT-PCR technique in cultured 3T3-L1 adipocytes, in which the mRNA expression of leptin, adiponectin, resistin and PPAR-γ was recorded in the absence and presence of chitosan, O-CMCs and N-CQCs. The experimental results proved that chitosan, O-CMCs and N-CQCs not only lowered the level of plasma leptin, glucose, insulin and total cholesterol in vivo, but down-regulated mRNA expression of leptin and resistin, and up-regulated mRNA expression of adiponectin and PPAR-γ in vitro, to achieve the desired insulin resistance therapy.

Green tea catechins ameliorate adipose insulin resistance by improving oxidative stress

Epidemiological data have suggested that drinking green tea is negatively associated with diabetes, and adipose oxidative stress may have a central role in causing insulin resistance, according to recent findings. The aim of this work is to elucidate a new mechanism for green tea's anti-insulin resistance effect. We used obese KK-ay mice, high-fat diet-induced obese rats, and induced insulin resistant 3T3-L1 adipocytes as models. Insulin sensitivity and adipose reactive oxidative species (ROS) levels were detected in animals and adipocytes. The oxidative stress assay and glucose uptake ability assay were performed, and the effects of EGCG on insulin signals were detected. Green tea catechins (GTCs) significantly decreased glucose levels and increased glucose tolerance in animals. GTCs reduced ROS content in both models of animal and adipocytes. EGCG attenuated dexamethasone and TNF-α promoted ROS generation and increased glucose uptake ability. EGCG also decreased JNK phosphorylation and promoted GLUT-4 translocation. EGCG and GTCs could improve adipose insulin resistance, and exact this effect on their ROS scavenging functions.

Adipokines, an adipose tissue and placental product with biological functions during pregnancy

Latter half of pregnancy is characterized by a "physiological diabetogenic state" since changes in insulin-sensitivity have been well documented. These changes ensure continuous supply of nutrients to the growing fetus. In the last years the role of adipocyte-derived signaling molecules, collectively known as adipokines has been object of different in vitro and in vivo studies. Of interest, adipokines and/or their receptors are expressed in the placental tissue which, therefore, can contribute to development of maternal insulin-resistance and, as a consequence, fetal growth. Leptin, adiponectin, and resistin represent the most well studied adipokines and, with the exception of adiponectin, their serum and placental levels increase as pregnancy progresses. High levels of adipokines have also been detected in umbilical plasma hence suggesting a possible role on fetal development and metabolism; however, it remains still unclear if such adipokines can directly stimulate fetal tissues development acting as growth factors. In addition to their well known metabolic effects, we also reported studies describing the role of adipokines in promoting proliferation and invasiveness of trophoblast cells and affecting local angiogenic processes. These observations strongly suggest that adipokines, by alternatively interfering with placental development, may affect pregnancy outcome and fetal growth. However, further studies are needed to better understand the local regulation of their expression. © 2012 International Union of Biochemistry and Molecular Biology, Inc.

Changes in metabolic profile and adipoinsular axis in morbidly obese premenopausal females treated with restrictive bariatric surgery

BACKGROUND

The aim of the present study was to evaluate the effects of surgically induced weight loss on the metabolic profile and adipocytokine levels in premenopausal morbidly obese females.

METHODS

Twenty premenopausal morbidly obese (MO) women with a median age of 34 years (range: 24-48 years) and a median body mass index (BMI) of 41.47 kg/m(2) (range: 38.0-56.73 kg/m(2)) were studied (13 women underwent gastric banding and 7 women underwent sleeve gastrectomy). In addition, 20 lean premenopausal women with a median age of 32 years (range: 22-44 years) and a median BMI of 20.0 kg/m(2) (range: 18.5-24.7 kg/m(2)) were also studied. Anthropometric measurements and metabolic parameters were analyzed in each patient, along with changes in leptin, adiponectin, resistin, and interleukin-6 (IL-6) before surgery, 6 months after surgery, and 12 months after surgery. Comparisons with the reference normal-weight subjects were also performed.

RESULTS

Both weight and BMI were found to be significantly decreased postoperatively. A 54.5% loss of excess BMI was observed 12 months after surgery, and was associated with significant improvement in all anthropometric and metabolic parameters. Twelve months after surgery we also observed decreased levels of serum leptin, resistin, and IL-6; increased levels of serum adiponectin; and a remarkable improvement in metabolic syndrome markers. Furthermore, postoperative serum resistin and IL-6 levels were found to reach those of normal-weight volunteers.

CONCLUSIONS

The results of this study suggest that weight loss through restrictive bariatric surgery results in a significant reduction in leptin, resistin, and IL-6 levels, and an increase in adiponectin levels, in addition to improving insulin sensitivity and glucose and lipid homeostasis in young morbidly obese female patients. These changes were significantly correlated with the magnitude of weight loss.

Interleukin-6 G-174C gene polymorphism and serum resistin levels in North Indian women: potential risk of metabolic syndrome

The present investigations were aimed to identify the possible association between genetic polymorphism in interleukin-6 (IL-6) G-174C gene, which confers susceptibility to metabolic syndrome, and serum level of resistin in North Indian women. The study population comprised 370 unrelated Indian women (192 having abdominal obesity and 178 controls). Polymorphism in genotype (CC+GC) of IL-6 G-174C gene was determined using a combination of polymerase chain reaction (PCR) and sequence-specific primer with restriction fragment length polymorphism (RFLP) technology. Insulin resistance (IR) and serum resistin level were also analyzed along with metabolic risk factors. Of 192 abdominal obese women, 147 (76.56%) were found to have mutant CC+GC (p = 0.001) genotype and allele frequency (p = 0.001), which was significantly higher 45 (23.44%) than non-obese and their respective wild type. The mutant genotype (CC+GC) of IL-6 gene was found to be associated significantly with high triglyceride (p = 0.025) and resistin level (p < 0.001), when compared with respective wild genotype (GG) in obese women. Non-obese women with no signs of metabolic risk factors were found to have significantly low level of serum resistin and IR in comparison to obese women having genetic polymorphism for IL-6 G-174C gene. Study suggests that IL-6 G-174C gene is one among the susceptibility loci for metabolic syndrome in North Indian women. Genotype for this polymorphism may prove informative for prediction of genetic risk for metabolic syndrome. Further, high level of serum resistin molecules may be targeted to correlate with metabolic syndrome risk factors and could be used as early prediction marker.

Age-related autocrine diabetogenic effects of transgenic resistin in spontaneously hypertensive rats: gene expression profile analysis

Increased circulating levels of resistin have been proposed as a possible link between obesity and insulin resistance; however, many of the potential metabolic effects of resistin remain to be investigated, including systemic versus local resistin action. We investigated potential autocrine effects of resistin on lipid and glucose metabolism in 2- and 16-mo-old transgenic spontaneously hypertensive rats (SHR) expressing a nonsecreted form of mouse resistin under control of the aP2 promoter. To search for possible molecular mechanisms, we compared gene expression profiles in adipose tissue in 6-wk-old transgenic SHR versus control rats, before development of insulin resistance, by digital transcriptional profiling using high-throughput sequencing. Both young and old transgenic rats showed moderate expression of the resistin transgene in adipose tissue but had serum resistin levels similar to control SHR and undetectable levels of transgenic resistin in the circulation. Young transgenic rats exhibited mild glucose intolerance. In contrast, older transgenic rats displayed marked glucose intolerance in association with near total resistance of adipose tissue to insulin-stimulated glucose incorporation into lipids (6 ± 2 vs. 77 ± 19 nmol glucose·g(-1)·2 h(-1), P < 0.00001). Ingenuity Pathway Analysis of differentially expressed genes revealed calcium signaling, Nuclear factor-erythroid 2-related factor-2 (NRF2)-mediated oxidative stress response, and actin cytoskeletal signaling canonical pathways as those most significantly affected. Analysis using DAVID software revealed oxidative phosphorylation, glutathione metabolism, pyruvate metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling as top Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. These results suggest that with increasing age autocrine effects of resistin in fat tissue may predispose to diabetes in part by impairing insulin action in adipose tissue.

Endocrinology of obesity

Obesity is a growing health concern in humans and companion animals. Obesity is highly associated with various endocrine abnormalities that are characterized by hormonal imbalance and/or resistance. Weight reduction generally normalizes these endocrine alterations, implicating obesity as a direct cause. Most data in this area have been derived from obese humans, with little data pertaining to hormonal changes in obese dogs and cats. Because the literature contains inconsistent results and because considerable hormone-hormone interactions occur, we have a limited understanding of the obesity-induced changes on the endocrine system in dogs and cats.

Plasma resistin levels associate with risk for hypertension among nondiabetic women

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

The Role of Adipokines in Understanding the Associations between Obesity and Depression

Objective. Two major causes of disability, major depression and obesity, share overlapping psychosocial and pathophysiological etiologies. Studies are now focused on biological mechanisms linking the two illnesses, and there is interest in the role that adipokines may have in mediating the association between obesity and depression. We reviewed the literature to look at what is currently known about this association, focusing on the adipokines leptin, adiponectin, and resistin. Methods. A MEDLINE search, citing articles from 1966 onward, supplemented by a review of bibliographies, was conducted to identify relevant studies. Results. This paper identified plausible pathways underlying a link between adipokines and depression. Only a few studies have yet been conducted specifically examining these biomarkers in patients with depression, but the results are intriguing. Conclusion. This paper is one of the first to examine the association between adipokines and depression. It provides an overview of the physiological role of adipokines and summarizes the data suggesting that they may be dysregulated in major depression. This area of research may become increasingly important as new treatment strategies are developed.

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.

Anthropometry, carbohydrate and lipid metabolism in the East Flanders Prospective Twin Survey: linkage of candidate genes using two sib-pair based variance components analyses

Insulin resistance and obesity are underlying causes of type 2 diabetes and therefore much interest is focused on the potential genes involved. A series of anthropometric and metabolic characteristic were measured in 240 MZ and 112 DZ twin pairs recruited from the East Flanders Prospective Twin Survey. Microsatellite markers located close to ABCC8, ADIPOQ, GCK, IGF1, IGFBP1, INSR, LEP, LEPR, PPARgamma and the RETN gene were genotyped. Univariate single point variance components linkage analyses were performed using two methods: (1) the standard method, only comprising the phenotypic and genotypic data of the DZ twin pairs and (2) the extended method, also incorporating the phenotypic data of the MZ twin pairs. Suggestive linkages (LOD > 1) were observed between the ABCC8 marker and waist-to-hip ratio and HDL-cholesterol levels. Both markers flanking ADIPOQ showed suggestive linkage with triglycerides levels, the upstream marker also with body mass and HDL-cholesterol levels. The IGFBP1 marker showed suggestive linkage with fat mass, fasting insulin and leptin levels and the LEP marker showed suggestive linkage with birth weight. This study suggests that DNA variants in ABCC8, ADIPOQ, IGFBP1 and LEP gene region may predispose to type 2 diabetes. In addition, the two methods used to perform linkage analyses yielded similar results. This was however not the case for birth weight where chorionicity seems to be an important confounder.

Cilostazol ameliorates metabolic abnormalities with suppression of proinflammatory markers in a db/db mouse model of type 2 diabetes via activation of peroxisome proliferator-activated receptor gamma transcription

In a previous study, cilostazol promoted differentiation of 3T3-L1 fibroblasts into adipocytes and improved insulin sensitivity by stimulating peroxisome proliferator-activated receptor (PPAR) gamma transcription. This study evaluated the in vivo efficacy of cilostazol to protect a db/db mouse model of type 2 diabetes against altered metabolic abnormalities and proinflammatory markers via activation of PPARgamma transcription. Eight-week-old db/db mice were treated with cilostazol or rosiglitazone for 12 days. Cilostazol significantly decreased plasma glucose and triglyceride levels, as did rosiglitazone, a PPARgamma agonist. Elevated plasma insulin and resistin levels were significantly decreased by cilostazol, and decreased adiponectin mRNA expression was elevated along with increased plasma adiponectin. Cilostazol significantly increased both adipocyte fatty acid binding protein and fatty acid transport protein-1 mRNA expressions with increased glucose transport 4 in the adipose tissue. Cilostazol and rosiglitazone significantly suppressed proinflammatory markers (superoxide, tumor necrosis factor-alpha, and vascular cell adhesion molecule-1) in the carotid artery of db/db mice. In an in vitro study with 3T3-L1 fibroblasts, cilostazol significantly increased PPARgamma transcription activity, as did rosiglitazone. The transcription activity stimulated by cilostazol was attenuated by KT5720 [(9R,10S,12S)-2,3,9,10,11,12-hexahydro-10-hydroxy-9-methyl-1-oxo-9, 12-epoxy-1H-diindolo[1,2,3-fg:3',2',1'-kl]pyrrolo [3,4-I][1,6]-benzodiazocine-10-carboxylic acid hexyl ester], a cAMP-dependent protein kinase inhibitor, and GW9662 (2-chloro-5-nitrobenzanilide), an antagonist of PPARgamma activity, indicative of implication of the phosphatidylinositol 3-kinase/Akt signal pathway. These results suggest that cilostazol may improve insulin sensitivity along with anti-inflammatory effects in type 2 diabetic patients via activation of both cAMP-dependent protein kinase and PPARgamma transcription.

The effect of energy restriction during pregnancy on obesity-related peptide hormones in rat offspring

It has been proposed that fetal exposure to environmental stressors, such as undernutrition, during critical periods of development may lead to adaptations that permanently change the structure and function of the body. These adaptations may be important for immediate survival during fetal development, but can predispose to disease in later life. We designed a pilot study investigating the effect of fetal undernutrition on the obesity-related peptides adiponectin, ghrelin, leptin and resistin levels in rat. We also wanted to explore changes in lipid and insulin metabolism. Sprague-Dawley rats were randomly assigned to three dietary treatment groups on day 4 of gestation. The control group was fed ad libitum and the food-restricted rats received either 75% or 50% of ad libitum food intake until parturition. Serum levels of obesity-related peptides as well as lipid and insulin levels were measured from 1-month-old pups. Serum resistin concentrations were higher in both food-restricted groups and serum adiponectin concentration was lower in the 50% food-restricted group compared to the control group. Serum total cholesterol levels were significantly higher in both food-restricted groups. These results indicate that undernutrition during fetal development may lead to unfavorable changes in obesity-related peptide hormones as well as evoking adverse changes in serum cholesterol levels. The observed changes may predispose to insulin resistance and significantly increase the risk of developing cardiovascular disease in later life.

Visfatin: a new player in mesangial cell physiology and diabetic nephropathy

Visfatin is an adipocytokine that improves insulin resistance and has an antidiabetic effect. However, the role of visfatin in the kidney has not yet been reported. In this experiment, the synthesis and physiological action of visfatin in cultured mesangial cells (MCs) were studied to investigate the role of visfatin in diabetic nephropathy. Visfatin was found synthesized in MCs as well as adipocytes. Visfatin synthesis was markedly increased, not by angiotensin II, but by high glucose stimuli. In addition, visfatin treatment induced a rapid uptake of glucose, peaking at 20 min after visfatin treatment in a dose-dependent manner. A small inhibiting RNA against insulin receptor significantly blocked visfatin-mediated glucose uptake. Visfatin stimuli also enhanced intracellular NAD levels, and treatment with FK866, which is a specific inhibitor of nicotinamide phosphoribosyltransferase (Nampt), significantly inhibited visfatin-induced NAD synthesis and glucose uptake. Visfatin treatment increased glucose transporter-1 (GLUT-1) protein expression in isolated cellular membranes, and pretreatment with cytochalasin B completely inhibited visfatin-induced glucose uptake. Moreover, immunofluorescent microscopy showed the migration of cytosolic GLUT-1 into cellular membranes after visfatin treatment. In accordance with these results, the activation of protein kinase B was detected after visfatin treatment. Furthermore, visfatin treatment dramatically increased the synthesis of profibrotic molecules including transforming growth factor-beta1, plasminogen activator inhibitor-1, and type I collagen, and pretreatment with cytochalasin B completely inhibited visfatin-induced upregulation of profibrotic molecules. These results suggest that visfatin is produced in MCs, which are a novel target for visfatin, and play an important role in the pathogenesis of diabetic nephropathy.

Angiotensin receptor blockers improve insulin resistance in type 2 diabetic rats by modulating adipose tissue

Adipose tissue is recognized as a pivotal organ in the development of insulin resistance. This study seeks to determine the effect of angiotensin receptor blockade (ARB) on insulin resistance of adipocytes in culture and in a rat model of type 2 diabetes. Treatment of Otsuka Long-Evans Tokushima Fatty rats with the ARB L158809 for six months significantly lowered fasting plasma glucose, cholesterol and triglyceride levels but led to higher plasma adiponectin levels. Insulin resistance, measured by an intraperitoneal glucose tolerance test, of the treated rats was significantly improved along with an increase in the number of small differentiated adipocytes; however, epididymal fat mass decreased. Treatment significantly lowered lipid peroxidation and MCP-1 expression while increasing adiponectin production by the adipose tissue. ARB treatment significantly improved insulin sensitivity and markedly suppressed AT2-induced oxidative stress, PAI-1 and MCP-1 levels and NF-kappaB activation of adipocytes in culture. Treatment increased adiponectin and PPARgamma expression along with intracellular triglyceride levels reflecting differentiation of the cultured adipocytes. Our study suggests that ARB treatment improves insulin resistance by modification of adipose tissue thereby blunting the development of diabetes.

Effects of the new C1q/TNF-related protein (CTRP-3) "cartonectin" on the adipocytic secretion of adipokines

BACKGROUND

Cartonectin (collagenous repeat-containing sequence of 26-kDa protein; CORS-26) was described as a new adipokine of the C1q/TNF molecular superfamily C1q/TNF-related protein-3 (CTRP-3), secreted by the adipocytes of mice and humans. The receptor and function of cartonectin are unknown and the recombinant protein is not commercially available.

OBJECTIVE

To investigate the effects of recombinant cartonectin on the secretion of adipokines such as adiponectin, leptin, and resistin from adipocytes of human and murine origin. The effect of the BMI of the adipocyte donor was also investigated.

METHODS AND PROCEDURES

Human adipocytes from pooled lean and preobese healthy individuals and murine 3T3-L1 adipocytes were used for stimulation experiments. Recombinant cartonectin was expressed in insect H5 cells. Adipokine secretion was measured using enzyme-linked immunosorbent assay. In addition, western blot analysis and luciferase reporter gene assays were employed.

RESULTS

Cartonectin (1, 10, 50, and 250 ng/ml) in higher doses stimulates the secretion of adiponectin and resistin from murine adipocytes. This effect is not caused by an induction of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) protein expression, as confirmed by western blot analysis. Also, luciferase reporter gene assay revealed that cartonectin failed to induce luciferase activity at the peroxisome proliferator-activated receptor responsive element site containing the adiponectin/luciferase promoter fragment. Human adipocytes from lean individuals secrete higher amounts of adiponectin and leptin when compared with adipocytes of individuals with a preobesity BMI (25-30 kg/m(2)). Cartonectin failed to stimulate adiponectin or leptin secretion from human adipocytes, irrespective of the BMI value.

DISCUSSION

Cartonectin is a new adipokine that differentially regulates the secretion of classical adipokines, with marked differences between the human and the murine systems. These effects are species-dependent, while basal adipokine secretion is influenced by the BMI.

Fatty acid-induced induction of Toll-like receptor-4/nuclear factor-kappaB pathway in adipocytes links nutritional signalling with innate immunity

To study the effects of fatty acids and the involvement of the Toll-like receptor-4/nuclear factor-kappaB (TLR-4/NF-kappaB) pathway with respect to the secretion of adipokines from adipocytes 3T3-L1 adipocytes were stimulated with increasing doses of fatty acids. The secretion of adiponectin, resistin and monocyte chemoattractant protein-1 (MCP-1) was measured by enzyme-linked immunosorbent assay. The NF-kappaB p65 nuclear translocation and TLR-4 expression were investigated by Western blot. The effects mediated by NF-kappaB were tested using a specific NF-kappaB-inhibitor and TLR-4-induced effects were analysed with a neutralizing TLR-4 antibody. Binding of (14)C-labelled fatty acids to TLR-4/MD-2 was investigated using a FLAG-tagged extracellular part of TLR-4 fused to full-length MD-2 via a linker (lipopolysaccharide-Trap). The messenger RNA (mRNA) expression of adipokines in abdominal adipose tissue of rats fed a standard chow or a high-fat diet was investigated by reverse transcription-polymerase chain reaction. The TLR-4 is induced during adipocyte differentiation and its expression is enhanced following fatty acid stimulation. The stimulatory effects of stearic and palmitic acids on MCP-1 secretion and of palmitoleic acid on resistin secretion are mediated via NF-kappaB. The stimulatory effects of stearic, palmitic and palmitoleic acids on resistin secretion and the stimulatory effect of stearic acid on MCP-1 secretion are mediated via TLR-4. Fatty acid-mediated effects are caused by an endogenous ligand because fatty acids were shown not to bind directly to TLR-4/MD-2. Adipose tissue mRNA expression and serum levels of adipokines did not differ in rats fed a high-fat diet. These data provide a new molecular mechanism by which fatty acids can link nutrition with innate immunity.

Beta cells in type 2 diabetes - a crucial contribution to pathogenesis

The healthy beta-cell has an enormous capacity to adapt to conditions of higher insulin demand (e.g. in obesity, pregnancy, cortisol excess) to maintain normoglycaemia with an increase in its functional beta-cell mass. This compensates in 80-90% of individuals for insulin resistance. However, in 10-20% of individuals, the beta-cells are unable to match the demands of insulin resistance and insulin levels are relatively insufficient to maintain normal glycaemic control. This eventually leads to glucose intolerance and type 2 diabetes (T2DM). Accordingly, preservation of functional beta-cell mass has become central in the treatment of type 1 diabetes as well as T2DM. The purpose of this review is to summarize the recently described mechanisms of beta-cell death in T2DM and to postulate possible new targets for treatment.

Role of fat mass and adipokines in chronic kidney disease

PURPOSE OF REVIEW

As traditional risk factors cannot alone explain the high prevalence and incidence of cardiovascular disease in chronic kidney disease, the complex of insulin resistance, oxidative stress, and endothelial dysfunction has increasingly been studied as an important non-traditional risk factor. Recent studies show that the adipose tissue is a complex organ with pleiotropic functions far beyond the mere storage of energy. Fat tissue secretes a number of adipokines including leptin and adiponectin, as well as cytokines, such as resistin, visfatin, tumor-necrosis factor-alpha and interleukin-6.

RECENT FINDINGS

Adipokine serum levels are markedly elevated in chronic kidney disease, likely due to a decreased renal excretion. Evidence suggests that these pluripotent signaling molecules may have multiple effects modulating insulin signaling, endothelial health and vascular outcome.

SUMMARY

Fat tissue is a storage depot for energy and a source of circulating signaling molecules. It plays an important role in the catabolic uremic milieu, and has been linked to systemic inflammation and uremic anorexia. Further research is needed to investigate the complex interactions between adipokine signaling networks and its effects on vascular health and outcome in chronic kidney disease.

Obesity in chronic kidney disease: good or bad?

Cardiovascular disease (CVD) remains the major cause of morbidity and mortality in chronic kidney disease (CKD) patients. As traditional risk factors cannot alone explain the high prevalence and incidence of CVD in this high-risk population, the complex of insulin resistance, oxidative stress, and endothelial dysfunction has increasingly been studied as important non-traditional risk factors. Recent studies show that the adipose tissue is a complex organ with functions far beyond the mere storage of energy. Indeed, it has recently been shown that fat tissue secretes a number of adipokines - including leptin, adiponectin and retinol-binding protein, as well as cytokines such as resistin, visfatin, tumor necrosis factor and interleukin-6. Adipokine serum levels are furthermore markedly elevated in CKD, likely due to a decreased renal excretion. Evidence suggests that these pluripotent signaling molecules may have multiple effects modulating insulin signaling, endothelial health and putatively CVD. As fat tissue is also a storage depot for energy, much needed in the catabolic milieu of uremia, further research is still needed to elucidate the likely complex interactions between these signaling networks, vascular health and outcome in this high-risk population.

Obesity and the polycystic ovary syndrome

Polycystic ovarian syndrome (PCOS) is extremely common among reproductive-aged women, but often goes undiagnosed. PCOS is associated with the metabolic syndrome and carries a greatly increased risk of impaired glucose tolerance and type 2 diabetes mellitus, and cardiovascular risks. Treatment of PCOS may provide relief of cosmetic problems and depression by improving patient self-esteem. In addition, because of its association with the metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease, its recognition and treatment can potentially be life saving. This article reviews the impact, pathophysiology, and associated risks of obesity and the metabolic syndrome in PCOS.

Serum leptin, resistin, and lipid levels in patients with end stage renal failure with regard to dialysis modality

Little information is available on the relationship between serum resistin levels and other adipokines with serum lipid levels and insulin resistance in uremic patients under different dialysis modalities.

METHODS

This study investigated the effects of dialysis modality on serum leptin, adiponectin, resistin, interleukin 6 (IL-6), and tumor necrosis factor (TNF) alpha levels in age, sex, and total adipose tissue mass (TATM); matched 30 hemodialysis (HD) patients, 30 continuous peritoneal dialysis (CAPD) patients, and 30 healthy controls; and evaluated the relationship between these adipokines and dyslipidemia and insulin resistance.

RESULTS

Serum resistin, adiponectin, IL-6, TNF-alpha, and high sensitive C reactive protein (hsCRP) levels were significantly increased in dialysis patients compared to controls (p < 0.05). In CAPD patients, serum leptin, resistin, triglycerides, and total cholesterol levels were higher than those in HD patients (p < 0.05). Leptin levels were positively correlated with TATM, serum triglycerides, total cholesterol, and low density lipoprotein (LDLc) levels in both dialysis groups. Resistin levels were found to positively correlate with TATM and triglycerides in CAPD patients. No relationship was found between the homeostasis model assessment-insulin resistance index (HOMA-IR) and adipokines studied.

CONCLUSION

Serum leptin, resistin, triglycerides, and total cholesterol levels were higher in CAPD patients. Leptin levels were positively correlated with TATM, serum triglycerides, total cholesterol, and LDLc levels in dialysis patients. Resistin levels were positively correlated with TATM and triglycerides in CAPD patients. Glucose load during CAPD may be an important factor in increased in leptin, resistin, triglycerides, and total cholesterol levels in CAPD patients. These results highlight the importance of leptin and resistin as determinants of dyslipidemia, especially in CAPD patients.

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.

Resistin: a hormone which induces insulin resistance is increased in normal pregnancy

AIMS

Resistin, a newly discovered adipokine, is thought to play a key role in the regulation of insulin resistance. The objectives of this study were to develop a nomogram of maternal plasma concentrations of resistin from 11 weeks of gestation to term and to determine whether resistin concentrations differ between normal and overweight pregnant women.

METHODS

In this cross-sectional study, plasma concentrations of resistin were determined in normal pregnant women of normal body mass index (BMI 18.5-24.9; n=261), overweight pregnant women (BMI > or =25; n=140), and non-pregnant women of normal BMI (n=40). Blood samples were collected once from each woman between the first trimester and term. Percentiles for resistin concentration were determined for five pre-specified windows of gestational age. Plasma resistin concentration was determined by immunoassay. Non-parametric statistics were used for analysis.

RESULTS

The median maternal plasma concentration of resistin between 11 to 14 weeks of gestation in women of normal weight was significantly higher than non-pregnant women; the plasma concentration of resistin increased with gestational age.

CONCLUSIONS

Normal pregnant women have a higher median plasma concentration of resistin than non-pregnant women and the concentration of this adipokine increases with advancing gestation. Alterations in the maternal plasma concentration of resistin during pregnancy could contribute to metabolic changes of pregnancy.

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.

Role of adipose tissue as an inflammatory organ in human diseases

Reviews on the inflammatory role of adipose tissue outside the field of metabolism are rare. There is increasing evidence provided by numerous basic research studies from nearly all internal medicine subspecializations that adipocytes and adipocytokines are involved in primary inflammatory processes and diseases. Therefore, it is the aim of the present review to discuss and to summarize the current knowledge on the inflammatory role of adipocytokines and special types of regional adipocytes such as retroorbital, synovial, visceral, subdermal, peritoneal, and bone marrow adipocytes in internal medicine diseases. Future clinical and therapeutic implications are discussed.

Insulin resistance, adipokines, and oxidative stress in nondiabetic, hypercholesterolemic patients: leptin as an 8-epi-prostaglandin F2alpha determinant

Limited data are available on the association of insulin resistance, adipokines, and in vivo lipid peroxidation. We investigated the relationships between insulin resistance, adipokines (leptin, adiponectin, and resistin), and oxidative stress in nondiabetic, hypercholesterolemic patients. Seventy-six nondiabetic patients with hypercholesterolemia participated in this cross-sectional study. Fasting glucose and insulin concentrations were analyzed. Serum leptin, adiponectin, and resistin concentrations and urinary excretion of 8-epi-prostaglandin F(2alpha) (8-epi-PGF(2alpha)) were determined using enzyme-linked immunosorbent assay. We divided all subjects into 3 groups, classified by the tertiles of homeostasis model assessment of insulin resistance (HOMA-IR) values, and clinical parameter comparisons were made among the 3 groups. The results showed that serum leptin (P < .001) and adiponectin levels (P < .05) were significantly different among the groups, although serum resistin was not different. Furthermore, the group with the highest HOMA-IR had a significantly higher urinary 8-epi-PGF(2alpha) excretion than the group with the lowest HOMA-IR (P = .017). Circulating leptin was positively correlated with urinary 8-epi-PGF(2alpha) (r = 0.323, P < .01) and HOMA-IR (r = 0.524, P < .001). Circulating adiponectin was negatively correlated with body mass index (r = -0.252, P < .05) and HOMA-IR (r = -0.228, P < .05). We could not find a relationship between circulating adiponectin or resistin and urinary 8-epi-PGF(2alpha) excretion. Stepwise multiple linear regression analysis showed that leptin was associated with the urinary 8-epi-PGF(2alpha) excretion after adjusting for age, sex, body mass index, blood lipids, and HOMA-IR (P = .002). In conclusion, our results show that more insulin-resistant state of nondiabetic, hypercholesterolemic patients is associated with decreased adiponectin and increased leptin and urinary 8-epi-PGF(2alpha) levels, although no relationship with resistin was observed. Furthermore, serum leptin independently contributed to urinary 8-epi-PGF(2alpha) excretion.

The obesity epidemic and its cardiovascular consequences

PURPOSE OF REVIEW

Obesity has reached global epidemic proportions because of an increasingly obesogenic environment. This review examines the association between obesity, and in particular visceral fat, as a risk factor for cardiovascular disease and mortality.

RECENT FINDINGS

The World Health Organization defines obesity based on the body mass index. Recently the waist-to-hip ratio has been shown to be a significantly stronger predictor of cardiovascular events than body mass index. The metabolic syndrome and its evolving definition represent a cluster of metabolic risk factors which help predict cardiovascular disease and mortality. Although insulin resistance plays a central role in the pathophysiology of the metabolic syndrome, there is limited support for therapy with insulin sensitizers, thiazolidinediones, in patients with coronary artery disease. The current anti-obesity drugs, orlistat and sibutramine, have only a modest effect on weight loss. The blockade of the endocannabinoid system with rimonabant, however, may be a promising new strategy.

SUMMARY

Obesity is associated with significant increase in cardiovascular risk. Lifestyle modification remains the cornerstone of management although anti-obesity medications may be indicated in high risk individuals with comorbid disease.

Adipocyte-derived hormones, cytokines, and mediators

Adipose tissue is responsive to both central and peripheral metabolic signals and is itself capable of secreting a number of proteins. These adipocyte-specific or enriched proteins, termed adipokines, have been shown to have a variety of local, peripheral, and central effects. These secreted proteins, which include tumor necrosis factor (TNF)-alpha, resistin, IL-6, IL-8, acylation-stimulating protein (ASP), angiotensinogen, plasminogen activator inhibitor-1 (PAI-1) ("bad" adipokines) and leptin, adiponectin ("good" adipokines) seem to play important regulatory roles in a variety of complex processes, including fat metabolism, feeding behavior, hemostasis, vascular tone, energy balance, and insulin sensitivity, but none is without controversy regarding its respective mechanism and scope of action. The present review is focused on the effects of free fatty acids and a restricted number of adipokines, which have been implicated in vascular (angiotensinogen, PAI-1) and energy and glucose homeostasis (ASP, TNFalpha, IL-6, resistin, leptin, adiponectin).