Resistin: molecular history and prognosis

Aging and Adiposity-Focus on Biological Females at Midlife and Beyond

Menopause is a physiological phase of life of aging women, and more than 1 billion women worldwide will be in menopause by 2025. The processes of global senescence parallel stages of reproductive aging and occur alongside aging-related changes in the body. Alterations in the endocrine pathways accompany and often predate the physiologic changes of aging, and interactions of these processes are increasingly being recognized as contributory to the progression of senescence. Our goal for this review is to examine, in aging women, the complex interplay between the endocrinology of menopause transition and post-menopause, and the metabolic transition, the hallmark being an increasing tendency towards central adiposity that begins in tandem with reproductive aging and is often exacerbated post menopause. For the purpose of this review, our choice of the terms 'female' and 'woman' refer to genetic females.

Resistin stimulates PC-3 prostate cancer cell growth through stimulation of SOCS3 and SOCS5 genes

Resistin and suppressors of cytokine signaling (SOCSs) have been reported to regulate prostate cancer (PCa) cell proliferation and survival, respectively. Whether any of the SOCS molecules mediate the mitogenic effect of resistin on PCa cells is unknown. Using PC-3 human PCa cells, we found that resistin upregulates the expression of SOCS3 and SOCS5 mRNA, but not SOCS7 mRNA, in a dose- and time-dependent manner. The resistin-induced increases in SOCS3 and SOCS5 expression and cell proliferation were prevented by pretreatment with specific inhibitors of the TLR4, ERK, p38 MAPK, JNK, PI3K, and JAK2 proteins. However, pretreatment with a TLR2 inhibitor had no effect on resistin-mediated SOCS3 and SOCS5 expression. In addition, the effects of resistin on SOCS3, SOCS5, and SOCS7 mRNA levels were cell type-specific. Overexpression of either SOCS3 or SOCS5 enhanced further resistin-stimulated growth of PC-3 cells, whereas silencing SOCS3 or SOCS5 antagonized resistin-increased cell growth. Further PCa tissue analysis demonstrated higher levels of RETN, TLR4, SOCS3, and SOCS5 mRNAs in cancer tissues than benign prostate hyperplasia and indicated positive correlations among RETN, TLR4, and SOCS5. These data suggest that SOCS5, TLR4, and, to a lesser extent, SOCS3 can mediate the mitogenic effect of resistin on PC-3 PCa cells.

What Is the Role of Gut Microbiota in Obesity Prevalence? A Few Words about Gut Microbiota and Its Association with Obesity and Related Diseases

Obesity is becoming the most dangerous lifestyle disease of our time, and its effects are already being observed in both developed and developing countries. The aim of this study was to investigate the impact of gut microbiota on the prevalence of obesity and associated morbidities, taking into consideration underlying molecular mechanisms. In addition to exploring the relationship between obesity and fecal microorganisms with their metabolites, the study also focused on the factors that would be able to stimulate growth and remodeling of microbiota. Assessed articles were carefully classified according to a predetermined criterion and were critically appraised and used as a basis for conclusions. The considered articles and reviews acknowledge that intestinal microbiota forms a multifunctional system that might significantly affect human homeostasis. It has been proved that alterations in the gut microbiota are found in obese and metabolically diseased patients. The imbalance of microbiome composition, such as changes in Bacteroidetes/Firmicutes ratio and presence of different species of genus Lactobacillus, might promote obesity and comorbidities (type 2 diabetes mellitus, hypertension, dyslipidemia, depression, obstructive sleep apnea). However, there are also studies that contradict this theory. Therefore, further well-designed studies are needed to improve the knowledge about the influence of microbiota, its metabolites, and probiotics on obesity.

The Inflammatory Profile of Obesity and the Role on Pulmonary Bacterial and Viral Infections

Obesity is a globally increasing health problem, entailing diverse comorbidities such as infectious diseases. An obese weight status has marked effects on lung function that can be attributed to mechanical dysfunctions. Moreover, the alterations of adipocyte-derived signal mediators strongly influence the regulation of inflammation, resulting in chronic low-grade inflammation. Our review summarizes the known effects regarding pulmonary bacterial and viral infections. For this, we discuss model systems that allow mechanistic investigation of the interplay between obesity and lung infections. Overall, obesity gives rise to a higher susceptibility to infectious pathogens, but the pathogenetic process is not clearly defined. Whereas, viral infections often show a more severe course in obese patients, the same patients seem to have a survival benefit during bacterial infections. In particular, we summarize the main mechanical impairments in the pulmonary tract caused by obesity. Moreover, we outline the main secretory changes within the expanded adipose tissue mass, resulting in chronic low-grade inflammation. Finally, we connect these altered host factors to the influence of obesity on the development of lung infection by summarizing observations from clinical and experimental data.

Assessment of Inflammatory Markers in Children with Cow's Milk Allergy Treated with a Milk-Free Diet

Background: The aim of the study was to establish whether the use of a strict milk-free diet in children with cow’s milk allergy, resulting in the resolution of clinical symptoms of the disease, also extinguishes the inflammatory reaction induced by the allergy. Methods: We examined 64 children (aged 3–6 years) with a diagnosed cow’s milk allergy who had been treated with an elimination diet for at least six months and showed remission of the disease’s clinical symptoms as a result of the treatment. The control group consisted of 30 healthy children of the same age following an unrestricted age-appropriate diet. Concentrations of cytokines, calprotectin, and adipokines (leptin, resistin, chemerin, neutrophilic lipocalin associated with gelatinase—NGAL) were determined in the serum samples obtained from the studied children by immunoenzymatic assays. Results: Patients with CMA had significantly higher median values of serum IL-6, TNF-α, resistin, chemerin and NGAL in comparison to the healthy children (p < 0.05, p < 0.001, p < 0.05, p < 0.01, p < 0.001, respectively). Serum concentrations of IL-10, leptin, calprotectin and CRP as well as in WBC count were in the same range in both studied groups. We observed direct statistically significant correlations between levels of IL-10 and CRP (p = 0.005), IL-10 and WBC (p = 0.045), TNF-α and WBC (p = 0.038), calprotectin and WBC (p < 0.001), chemerin and CRP (p < 0.001) as well as between NGAL and WBC (p = 0.002) in children with CMA. Conclusion: The use of a strict milk-free diet by children with CMA, resulting in the resolution of clinical symptoms of the disease, does not seem to extinguish the inflammation induced by the allergy. The findings of this study—elevated IL-6, TNF-α, resistin, chemerin and NGAL levels in patients with CMA—suggest that these parameters seem to be involved in the generation of a low-grade proinflammatory environment observed in cow‘s milk allergy and could be used to monitor the effectiveness of treatment.

Association of Adipose Tissue and Adipokines with Development of Obesity-Induced Liver Cancer

Obesity is rapidly dispersing all around the world and is closely associated with a high risk of metabolic diseases such as insulin resistance, dyslipidemia, and nonalcoholic fatty liver disease (NAFLD), leading to carcinogenesis, especially hepatocellular carcinoma (HCC). It results from an imbalance between food intake and energy expenditure, leading to an excessive accumulation of adipose tissue (AT). Adipocytes play a substantial role in the tumor microenvironment through the secretion of several adipokines, affecting cancer progression, metastasis, and chemoresistance via diverse signaling pathways. AT is considered an endocrine organ owing to its ability to secrete adipokines, such as leptin, adiponectin, resistin, and a plethora of inflammatory cytokines, which modulate insulin sensitivity and trigger chronic low-grade inflammation in different organs. Even though the precise mechanisms are still unfolding, it is now established that the dysregulated secretion of adipokines by AT contributes to the development of obesity-related metabolic disorders. This review focuses on several obesity-associated adipokines and their impact on obesity-related metabolic diseases, subsequent metabolic complications, and progression to HCC, as well as their role as potential therapeutic targets. The field is rapidly developing, and further research is still required to fully understand the underlying mechanisms for the metabolic actions of adipokines and their role in obesity-associated HCC.

The Effect of the Ultra-Marathon Run at a Distance of 100 Kilometers on the Concentration of Selected Adipokines in Adult Men

Pro-inflammatory adipokines have a multifunctional role in adipogenesis, angiogenesis, glucose homeostasis, and inflammation. The aim of the present study is to evaluate the effect of running a 100 km ultra-marathon on serum levels of two adipokines: resistin and chemerin. Fifteen male participants complete a medical questionnaire and their body composition is assessed. Serum resistin, chemerin, high sensitivity C-reactive protein (hs-CRP), glucose, and lactate levels are measured at baseline and post-race. During-race data on fluid and food consumption and energy expenditure are calculated. There is a higher (p < 0.001) post-race concentration of resistin and hs-CRP compared with resting values, with no change in chemerin levels. There is an inverse correlation of the change in resistin levels with post-run glucose values (r = 0.742, p < 0.001) and a positive correlation between changes in hs-CRP and energy expenditure (r = 0.782, p < 0.001). The present results show the impact of running an ultra-marathon on serum levels of pro-inflammatory markers released by adipose tissue. It is difficult to establish whether these results may be due to the stress of exercise, high energy expenditure or caloric deficit. However, we suggest that an addition of resistin to traditional pro-inflammatory markers (including CRP) may improve the assessment of inflammation in conditions of high-energy expenditure.

Comparison between Tibetan and Small-tailed Han sheep in adipocyte phenotype, lipid metabolism and energy homoeostasis regulation of adipose tissues when consuming diets of different energy levels

This study aimed to gain insight into how adipose tissue of Tibetan sheep regulates energy homoeostasis to cope with low energy intake under the harsh environment of the Qinghai-Tibetan Plateau (QTP). We compared Tibetan and Small-tailed Han sheep (n 24 of each breed), all wethers and 1·5 years of age, which were each divided randomly into four groups and offered diets of different digestible energy (DE) densities: 8·21, 9·33, 10·45 and 11·57 MJ DE/kg DM. When the sheep lost body mass and were assumed to be in negative energy balance: (1) adipocyte diameter in subcutaneous adipose tissue was smaller and decreased to a greater extent in Tibetan than in Small-tailed Han sheep, but the opposite occurred in the visceral adipose tissue; (2) Tibetan sheep showed higher insulin receptor mRNA expression and lower concentrations of catabolic hormones than Small-tailed Han sheep and (3) Tibetan sheep had lower capacity for glucose and fatty acid uptake than Small-tailed Han sheep. Moreover, Tibetan sheep had lower AMPKα mRNA expression but higher mammalian target of rapamycin mRNA expression in the adipocytes than Small-tailed Han sheep. We concluded that Tibetan sheep had lower catabolism but higher anabolism in adipose tissue and reduced the capacity for glucose and fatty acid uptake to a greater extent than Small-tailed Han sheep to maintain energy homoeostasis when in negative energy balance. These responses provide Tibetan sheep with a high ability to cope with low energy intake and with the harsh environment of the QTP.

Adiponectin and resistin in acutely ill and weight-recovered adolescent anorexia nervosa: Association with psychiatric symptoms

Objectives: Anorexia nervosa (AN) is a chronic illness where restriction of food intake results in decreased adipose tissue. The aim of this study was to measure the concentration of adiponectin and resistin in acute and partially weight-recovered anorectic inpatients. The associations of their levels with eating disorder symptoms were also assessed.Methods: A longitudinal study was conducted on 76 adolescent patients (ANG) and 30 age-matched healthy girls (CG). Selected adipokines serum levels, as well as the severity of depressive, obsessive-compulsive and disturbed eating behaviours, were analysed in the group of anorectic patients before (accAN) and after weight gain (recAN) and compared with the CG.Results: The concentration of adiponectin in the accAN was higher than in the CG (P = 0.05) and increased in recAN (P = 0.01). Resistin concentrations were lower in accAN and recAN than in the CG (P = 0.00). A negative correlation between adiponectin and the scores in Yale-Brown Obsessive Compulsive Scale as well as positive between resistin and Beck Depression Inventory were found.Conclusions: In the acute AN, adiponectin and resistin levels are impaired and partial weight recovery fails to normalise them thus we suggest that they can be involved in the chronicity of certain symptoms. The level of adiponectin is associated with obsessive and compulsive symptoms and resistin with depressive symptoms, which indicates their potential contribution to the regulation of emotions and behaviours in AN.

Mechanistic Links Between Obesity, Diabetes, and Blood Pressure: Role of Perivascular Adipose Tissue

Obesity is increasingly prevalent and is associated with substantial cardiovascular risk. Adipose tissue distribution and morphology play a key role in determining the degree of adverse effects, and a key factor in the disease process appears to be the inflammatory cell population in adipose tissue. Healthy adipose tissue secretes a number of vasoactive adipokines and anti-inflammatory cytokines, and changes to this secretory profile will contribute to pathogenesis in obesity. In this review, we discuss the links between adipokine dysregulation and the development of hypertension and diabetes and explore the potential for manipulating adipose tissue morphology and its immune cell population to improve cardiovascular health in obesity.

Visfatin and resistin in gonadotroph cells: expression, regulation of LH secretion and signalling pathways

Visfatin and resistin appear to interfere with reproduction in the gonads, but their potential action at the hypothalamic-pituitary level is not yet known. The aim of the present study was to investigate the mRNA and protein expression of these adipokines in murine gonadotroph cells and to analyse the effects of different concentrations of recombinant mouse visfatin and resistin (0.01, 0.1, 1 and 10ngmL^-1) on LH secretion and signalling pathways in LβT2 cells and/or in primary female mouse pituitary cells. Both visfatin and resistin mRNA and protein were found in vivo in gonadotroph cells. In contrast with resistin, the primary tissue source of visfatin in the mouse was the skeletal muscle, and not adipose tissue. Visfatin and resistin both decreased LH secretion from LβT2 cells after 24h exposure of cells (P<0.03). These results were confirmed for resistin in primary cell culture (P<0.05). Both visfatin (1ngmL^-1) and resistin (1ngmL^-1) increased AMP-activated protein kinase α phosphorylation in LβT2 cells after 5 or 10min treatment, up to 60min (P<0.04). Extracellular signal-regulated kinase 1/2 phosphorylation was transiently increased only after 5min resistin (1ngmL^-1) treatment (P<0.01). In conclusion, visfatin and resistin are expressed in gonadotroph cells and they may affect mouse female fertility by regulating LH secretion at the level of the pituitary.

Adipose tissue and metabolic and inflammatory responses to stroke are altered in obese mice

Obesity is an independent risk factor for stroke, although several clinical studies have reported that obesity improves stroke outcome. Obesity is hypothesised to aid recovery by protecting against post-stroke catabolism. We therefore assessed whether obese mice had an altered metabolic and inflammatory response to stroke. Obese ob/ob mice underwent a 20-min middle cerebral artery occlusion and 24-h reperfusion. Lipid metabolism and expression of inflammatory cytokines were assessed in the plasma, liver and adipose tissue. The obese-specific metabolic response to stroke was assessed in plasma using non-targeted ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) metabolomics coupled with univariate and multivariate analysis. Obesity had no effect on the extent of weight loss 24 h after stroke but affected the metabolic and inflammatory responses to stroke, predominantly affecting lipid metabolism. Specifically, obese mice had increases in plasma free fatty acids and expression of adipose lipolytic enzymes. Metabolomics identified several classes of metabolites affected by stroke in obese mice, including fatty acids and membrane lipids (glycerophospholipids, lysophospholipids and sphingolipids). Obesity also featured increases in inflammatory cytokines in the plasma and adipose tissue. Overall, these results demonstrate that obesity affected the acute metabolic and inflammatory response to stroke and suggest a potential role for adipose tissue in this effect. These findings could have implications for longer-term recovery and also further highlight the importance of considering comorbidities in preclinical stroke research, especially when identifying biomarkers for stroke. However, further work is required to assess whether these changes translate into long-term effects on recovery.

Summary: Obesity, a co-morbidity for stroke, affected the acute metabolic and inflammatory response to stroke, highlighting the importance of considering comorbidities in preclinical stroke research, especially when identifying biomarkers.

The role of selected adipokines and ghrelin in the prognosis after myocardial infarction in a 12-month follow-up in the presence of metabolic syndrome

INTRODUCTION

The aim of this study was to evaluate the predictive value of selected adipokines in the improvement in the ejection fraction and in the development of adverse cardiac remodeling during 12 months of follow-up among patients with an ST-segment elevation acute myocardial infarction (STEMI) in the presence of metabolic syndrome (MeS).

MATERIAL AND METHODS

The study population consisted of 69 patients (49 male; mean age: 59 ±10 years) with a first STEMI that was treated with a primary percutaneous coronary intervention (pPCI). In this group, 36 patients (18 male; mean age: 60 ±15 years) had MeS according to the definition of the International Diabetes Federation. The baseline clinical evaluation included a clinical examination and evaluation of the blood levels of C-reactive protein, ghrelin, resistin, and fasting glucose. Within 72 h after the STEMI, an echocardiographic examination was performed. A complete clinical evaluation was repeated after 12 months. Adverse cardiac remodeling was defined as an increase in the left ventricular end-diastolic volume of ≥ 8%. An improvement of the ejection fraction (EF) was defined as an increase of more than 5% in the EF.

RESULTS

A concentration of ghrelin ≤ 160.46 pg/ml (AUC = 0.71, p = 0.032) had a good predictive value for the occurrence of adverse left ventricular remodeling but only in the patients without MeS. Among the patients with MeS, a concentration of resistin ≤ 5196 pg/ml (AUC = 0.073, p = 0.024) had a good predictive value for the occurrence of left ventricular remodeling. A concentration of leptin > 52.18 pg/ml (AUC = 0.81, p < 0.0001) and resistin > 4419.27 ng/ml (AUC = 0.67, p = 0.049) had a good predictive value for improvement of the LVEF in the patients without MeS.

CONCLUSIONS

The selected adipokines had a good predictive value for the development of adverse cardiac remodeling and for improvement of the ejection fraction among patients after a STEMI in the presence of metabolic syndrome.

Secretory function of adipose tissue

There are two kinds of adipose tissue in mammals: white adipose tissue - WAT and brown adipose tissue - BAT. The main function of WAT is accumulation of triacylglycerols whereas the function of BAT is heat generation. At present, WAT is also considered to be an endocrine gland that produces bioactive adipokines, which take part in glucose and lipid metabolism. Considering its endocrine function, the adipose tissue is not a homogeneous gland but a group of a few glands which act differently. Studies on the secretory function of WAT began in 1994 after discovery of leptin known as the satiation hormone, which regulates body energy homeostasis and maintainence of body mass. Apart from leptin, the following belong to adipokines: adiponectin, resistin, apelin, visfatin and cytokines: TNF and IL 6. Adiponectin is a polypeptide hormone of antidiabetic, anti-inflammatory and anti-atherogenic activity. It plays a key role in carbohydrate and fat metabolism. Resistin exerts a counter effect compared to adiponectin and its physiological role is to maintain fasting glycaemia. Visfatin stimulates insulin secretion and increases insulin sensitivity and glucose uptake by muscle cells and adipocytes. Apelin probably increases the insulin sensitivity of tissues. TNF evokes insulin resistance by blocking insulin receptors and inhibits insulin secretion. Approximately 30% of circulating IL 6 comes from adipose tissue. It causes insulin resistance by decreasing the expression of insulin receptors, decreases adipogenesis and adiponectin and visfatin secretion, and stimulates hepatic gluconeogenesis. In 2004, Bays introduced the notion of adiposopathy, defined as dysfunction of the adipose tissue, whose main feature is insulin and leptin resistance as well as the production of inflammatory cytokines: TNF and IL 6 and monocyte chemoattractant protein. This means that excess of adipose tissue, especially visceral adipose tissue, leads to the development of a chronic subclinical inflammatory condition, which favours the development of insulin resistance and Type 2 diabetes. Obesity is a systemic illness caused by energy transformation homeostasis disorder which results in an increase in the amount of body fat mass. It effects approximately 40% of dogs and 20% of cats. Illnesses which accompany obesity result, to a great extent, from the secretive role of adipose tissue, which is still little known, which should be included when planning treatment of an obese animal.

Candesartan cilexetil prevents diet-induced insulin resistance via peroxisome proliferator-activated receptor-γ activation in an obese rat model

Angiotensin II type 1 receptor (AT1R) blockers (ARBs) have been shown to reduce the incidence of type 2 diabetes mellitus; however, the underlying molecular mechanism is unknown. Peroxisome proliferator-activated receptor γ (PPARγ) is the central regulator of insulin and glucose metabolism, which improves insulin sensitivity. Whether candesartan cilexetil, as a prodrug of the AT1R blocker candesartan, has PPARγ-activating properties remains to be elucidated. The aim of the present study was to investigate the effects of oral administration of candesartan cilexetil on glucose tolerance and the actions of PPARγ on liver and adipose tissue in the insulin-resistant obese rat induced by high-fat diet. Animals treated with candesartan cilexetil showed an improved glucose tolerance after oral glucose challenge. Whole-body insulin sensitivity was evaluated using the hyperinsulinemic-euglycemic clamp technique. During high-fat feeding in high-fat diet (HF) rats, the glucose infusion rate (GIR) was 52.3% lower than that in normal chow (NC) rats. However, the GIR was significantly enhanced following candesartan cilexetil treatment. Angiotensin II receptor antagonism also resulted in significant increases in PPARγ protein expression in adipose and liver tissue. These results indicate that PPARγ activation by candesartan cilexetil may provide novel therapeutic options in the treatment of patients with metabolic syndrome.

Cardiovascular risk in Egyptian healthy consumers of different types of combined oral contraceptives pills: A comparative study

This study aimed to evaluate the associated cardiovascular risk in Egyptian healthy consumers of different types of combined oral contraceptives pills (COCPs) via determination of lipids profiles, Castelli index I, leptin, adiponectin, and resistin concentrations as cardiovascular risk factors. In this cross-sectional study, the study groups consisted of control group that represented by 30 healthy married women who were not on any contraceptive mean or any hormonal therapy and had normal menstrual cycles, group two consisted of 30 women who were users of Levonorgesterl 0.15 mg plus Ethinylestradiol 0.03 mg as 21 days cycle, group three consisted of 30 women who were users of Gestodene 0.075 mg plus Ethinylestradiol 0.03 mg as 21 days cycle, and group four consisted of 30 women who were users of Drospirenone 3 mg plus Ethinylestradiol 0.03 mg as 21 days cycle. One-way analysis of variance followed by LSD post hoc test was used for comparison of variables. P value <0.05 was considered to be significant. The comparison of the studied groups revealed that COCPs containing levonorgestrel plus ethinylestradiol resulted in significantly lower adiponectin level, and significantly higher leptin and resistin levels with more atherogenic lipid profile presented by significantly higher LDL-C, significantly lower HDL-C concentrations, and significantly higher atherogenic index. Formulation containing ethinylestradiol combined with gestodene neither altered adipose tissue function nor showed deleterious effect on lipid panel. Formulation containing ethinylestradiol combined with drospirenone resulted in significantly higher HDL-C and adiponectin concentrations. In conclusion, the uptake of COCPs containing levonorgestrel plus ethinylestradiol is associated with high cardiovascular risk since this formulation showed significantly lower adiponectin concentration, significantly higher leptin, resistin, and atherogenic index as compared to other studied groups. By contrast, the formulations containing ethinylestradiol combined with third generation progestin gestodene or fourth generation progestin drospirenone are associated with low cardiovascular risk since they neither altered adipose tissue function nor impaired lipoprotein metabolism as experienced by their favorable effect on leptin, adiponectin, and resistin, with non-changed atherogenic index, higher HDL-C levels and lower LDL-C levels as compared to levonorgestrel plus ethinylestradiol formulation.

Atherosclerotic Cardiovascular Disease Risk in the HAART-Treated HIV-1 Population

Atherosclerotic cardiovascular disease (CVD), a leading cause of morbidity and mortality in the general population, is also an increasing cause for concern for HIV-infected patients. A number of risk factors for CVD are also associated with HIV disease and HIV therapy, particularly insulin resistance, metabolic dyslipidemia, and inflammation. For example, atherogenic dyslipidemia, a side effect of HIV therapy, is an established risk for CVD in the non-HIV-infected population. As our understanding of atherosclerotic disease evolves, new markers of CVD risk have been identified, including metabolic syndrome definitions and C-reactive protein, a marker of inflammation. Use of these markers, in association with established risk factor guidelines, may serve as important tools in helping HIV physicians implement drug regimens that allow optimum management of metabolic complications associated with HIV and HAART, and thereby reduce CVD risk. The objective of this article is to review the mechanisms of atherosclerotic CVD and to discuss risk factors and markers that can be applied in the evaluation and treatment of CVD in the HIV-positive population.

Obesity and coronary microvascular disease - implications for adipose tissue-mediated remote inflammatory response

It is believed that obesity has detrimental effects on the coronary circulation. These include immediate changes in coronary arterial vasomotor responsiveness and the development of occlusive large coronary artery disease. Despite its critical role in regulating myocardial perfusion, the altered behavior of coronary resistance arteries, which gives rise to coronary microvascular disease (CMD) is poorly understood in obesity. A chronic, low-grade vascular inflammation has been long considered as one of the main underlying pathology behind CMD. The expanded adipose tissue and the infiltrating macrophages are the major sources of pro-inflammatory mediators that have been implicated in causing inadequate myocardial perfusion and, in a long term, development of heart failure in obese patients. Much less is known the mechanisms regulating the release of these cytokines into the circulation that enable them to exert their remote effects in the coronary microcirculation. This mini review aims to examine recent studies describing alterations in the vasomotor function of coronary resistance arteries and the role of adipose tissue-derived pro-inflammatory cytokines and adipokines in contributing to CMD in obesity. We provide examples of regulatory mechanisms by which adipokines are released from adipose tissue to exert their remote inflammatory effects on coronary microvessels. We identify some of the important challenges and opportunities going forward.

Obesity and its metabolic complications: the role of adipokines and the relationship between obesity, inflammation, insulin resistance, dyslipidemia and nonalcoholic fatty liver disease

Accumulating evidence indicates that obesity is closely associated with an increased risk of metabolic diseases such as insulin resistance, type 2 diabetes, dyslipidemia and nonalcoholic fatty liver disease. Obesity results from an imbalance between food intake and energy expenditure, which leads to an excessive accumulation of adipose tissue. Adipose tissue is now recognized not only as a main site of storage of excess energy derived from food intake but also as an endocrine organ. The expansion of adipose tissue produces a number of bioactive substances, known as adipocytokines or adipokines, which trigger chronic low-grade inflammation and interact with a range of processes in many different organs. Although the precise mechanisms are still unclear, dysregulated production or secretion of these adipokines caused by excess adipose tissue and adipose tissue dysfunction can contribute to the development of obesity-related metabolic diseases. In this review, we focus on the role of several adipokines associated with obesity and the potential impact on obesity-related metabolic diseases. Multiple lines evidence provides valuable insights into the roles of adipokines in the development of obesity and its metabolic complications. Further research is still required to fully understand the mechanisms underlying the metabolic actions of a few newly identified adipokines.

The forkhead transcription factor FOXO1 stimulates the expression of the adipocyte resistin gene

Resistin is known as an adipocyte-specific hormone that can cause insulin resistance and decrease adipocyte differentiation. It can be regulated by transcriptional factors, but the possible role of forkhead transcription factor FOXO1 in regulating resistin gene expression is still unknown. Using 3T3 fibroblast and C3H10T1/2 and 3T3-L1 adipocytes, we found that transient overexpression of a non-phosphorylatable, constitutively active FOXO1, but not the wild type of FOXO1 or a DNA binding-deficient FOXO1, activated resistin promoter-directed luciferase expression. However, transient overexpression of a dominant-negative FOXO1 inactivated resistin promoter activity and reduced resistin mRNA expression. These observations indicate that the action of FOXO1 on resistin gene expression requires the activation of FOXO1 and that the effect of FOXO1 depends on the phosphorylation and dephosphorylation of FOXO1. The FOXO1 protein target sites on the resistin promoter were localized to the proximal -3545 to -787bp of 5'-flanking region of the resistin promoter. A chromatin immunoprecipitation assay also showed that FOXO1 bound the resistin promoter at nucleotide regions of -1539 to -1366bp and -1016 to -835bp, but not at the regions of -795 to -632bp. Results of this study suggest that FOXO1 transcription factor likely activates the expression of adipocyte resistin gene via direct association with the upstream resistin promoter.

Resistin protects against 6-hydroxydopamine-induced cell death in dopaminergic-like MES23.5 cells

Resistin is originally reported as an adipose tissue-specific hormone and is thought to represent a link between obesity and insulin-resistant diabetes. Adipokines exert energy-regulation and has been reported to have neuroprotective effect like leptin, adiponectin, and ghrelin. However, the role of resistin in neuroprotective effect has not been explored. 6-hydroxydopamine (6-OHDA), one of the most investigated Parkinson's disease neurotoxins, is widely used to study mechanisms of cell death in dopaminergic neurons. In the present study, our results show that treatment of resistin protects 6-OHDA-induced cell death in dopaminergic-like MES23.5 cells. Resistin also antagonizes 6-OHDA-induced apoptotic cell death measured by fluorescence-activated cell sorter (FACS) analysis and Hochest 33342 staining. Furthermore, treatment of resistin also dramatically reduces 6-OHDA-mediated ROS production and mitochondria transmembrane potential dissipation. Moreover, expression of 6-OHDA-induced apoptotic markers, such as Bcl-2 degradation, Bax expression, PARP degradation and caspase 3 activity increase, are all attenuated by resistin treatment. Our results also show that resistin induces up-regulation of heat shock protein (Hsp) 32 (heme oxygenase-1, HO-1) and Hsc (heat shock cognate) 70. The protective effect of resistin on 6-OHDA-induced cell death is abolished by HO-1 inhibitor zinc protoporphyrin IX and HSP inhibitor KNK437. These results suggest the neuroprotective effects of resistin against 6-OHDA-induced cell death with the underlying mechanisms of inhibiting oxidative stress and apoptosis. Therefore, we suggest that resistin may provide a useful therapeutic strategy for neurodegenerative diseases such as Parkinson's disease.

Resistin gene expression in visceral adipose tissue of postmenopausal women and its association with insulin resistance

AIM

The present study evaluates resistin mRNA expression in visceral adipose tissue (VAT) and its correlation with insulin resistance (homeostatic model assessment) in postmenopausal obese women.

MATERIALS & METHODS

A total of 68 (nonobese = 34 and obese = 34) age-matched (49-70 years) postmenopausal women were recruited for the study. Fasting blood samples were collected at admission and abdominal VAT were obtained during surgery for gall bladder stones or hysterectomy. Physical parameters (age, height, weight and BMI) were measured. Biochemical parameters (plasma insulin, plasma glucose and serum resistin) were estimated by enzymatic methods. The VAT resistin mRNA expression was evaluated by real-time PCR.

RESULTS

The relative mean (± standard deviation) VAT resistin mRNA expression in postmenopausal obese women lowered significantly by 20.4% compared with postmenopausal nonobese women (0.029 ± 0.011 vs 0.023 ± 0.013; p = 0.047). Furthermore, VAT resistin mRNA expression in postmenopausal obese women was downregulated by 0.69-fold when compared with age-matched postmenopausal nonobese women. Furthermore, the relative VAT resistin mRNA expression in postmenopausal obese women showed significant inverse association with insulin resistance (r = -0.48; p < 0.01) and serum resistin (r = -0.84; p < 0.001), while in postmenopausal nonobese women it did not show any association with both insulin resistance (r = 0.03; p > 0.05) and serum resistin (r = -0.03; p > 0.05).

CONCLUSION

The VAT resistin mRNA expression in postmenopausal obese women is associated to insulin resistance.

Relations of circulating resistin and adiponectin and cardiac structure and function: the Framingham Offspring Study

Obesity is associated with pathological cardiac remodeling and risk of heart failure (HF). Adipocytokines (ADKs) may mediate the increased risk of cardiovascular disease associated with excess adiposity. Yet data relating ADKs to cardiac remodeling phenotypes are sparse. We related two circulating ADKs, resistin and adiponectin, to three important echocardiographic markers of cardiac remodeling, left ventricular mass (LVM), left atrial diameter (LAD), and LV fractional shortening (LVFS) in 2,615 participants (mean age 61 years, 55% women) in the Framingham Offspring Study. Adiponectin concentrations were inversely related to LVM in multivariable linear regression models adjusting for key clinical correlates including BMI (regression coefficient per s.d.-increment in ln-adiponectin = -3.37, P = 0.02; P for trend across quartiles = 0.02). Adiponectin was not associated with LAD or LVFS (P > 0.56). Resistin concentrations were inversely related to LVFS (regression coefficient per s.d.-increment in ln-resistin = -0.01, P = 0.03; P for trend across quartiles = 0.04). Resistin was not associated with LVM or LAD (P > 0.05). In our moderate-sized, community-based sample, higher circulating concentrations of adiponectin and resistin were associated with lower LVM and lower LVFS, respectively. In conclusion, these associations identify potential mechanisms by which excess adiposity may mediate adverse cardiac remodeling and HF risk.

Over expression of resistin in adipose tissue of the obese induces insulin resistance

AIM: To compare resistin mRNA expression in subcutaneous adipose tissue (SAT) and its correlation with insulin resistance (IR) in postmenopausal obese women.

METHODS: A total of 68 postmenopausal women (non obese = 34 and obese = 34) were enrolled for the study. The women of the two groups were age matched (49-70 years). Fasting blood samples were collected at admission and abdominal SAT was obtained during surgery for gall bladder stones or hysterectomy. Physical parameters [age, height, weight, body mass index (BMI)] were measured. Biochemical (plasma insulin and plasma glucose) parameters were estimated by enzymatic methods. RNA was isolated by the Trizol method. SAT resistin mRNA expression was done by real time- reverse transcription polymerase chain reaction (RT-PCR) by using Quanti Tect SYBR Green RT-PCR master mix. Data was analyzed using independent Student’s t test, correlation and simple linear regression analysis.

RESULTS: The mean weight (52.81 ± 8.04 kg vs 79.56 ± 9.91 kg; P < 0.001), BMI (20.23 ± 3.05 kg/m²vs 32.19 ± 4.86 kg/m²; P < 0.001), insulin (8.47 ± 3.24 μU/mL vs 14.67 ± 2.18 μU/mL; P < 0.001), glucose (97.44 ± 11.31 mg/dL vs 109.67 ± 8.02 mg/dL; P < 0.001) and homeostasis model assessment index (2.01 ± 0.73 vs 3.96 ± 0.61; P < 0.001) were significantly higher in postmenopausal obese women compared to postmenopausal non obese women. The mean serum resistin level was also significantly higher in postmenopausal obese women compared to postmenopausal non obese women (9.05 ± 5.15 vs 13.92 ± 6.32, P < 0.001). Furthermore, the mean SAT resistin mRNA expression was also significantly (0.023 ± 0.008 vs 0.036 ± 0.009; P < 0.001) higher and over expressed 1.62 fold (up-regulated) in postmenopausal obese women compared to postmenopausal non obese women. In postmenopausal obese women, the relative SAT resistin mRNA expression showed positive (direct) and significant correlation with BMI (r = 0.78, P < 0.001) and serum resistin (r = 0.76, P < 0.001). Furthermore, the SAT resistin mRNA expression in postmenopausal obese women also showed significant and direct association (r = 0.45, P < 0.01) with IR, while in postmenopausal non obese women it did not show any association (r = -0.04, P > 0.05).

CONCLUSION: Increased SAT resistin mRNA expression probably leads to inducing insulin resistance and thus may be associated with obesity-related disorders in postmenopausal obese women.

Enamel matrix derivative stimulates expression and secretion of resistin in mesenchymal cells

In this study we wanted to identify the effect of enamel matrix derivative (EMD) on adipocytokines, so-called adipokines. Primary human cells of mesenchymal origin (osteoblasts, periodontal ligament cells, mesenchymal stem cells, and pulp cells) and hematopoietic origin (monocytes) were incubated with EMD. The levels of adipokines in cell culture medium were quantified using the Lincoplex human adipocyte panel (Luminex) and by real-time PCR of mRNA isolated from cell lysates. Rats were injected with 2 mg of EMD or saline intramuscularly every third day for 14 d. Blood samples were taken before and after injections, and the level of resistin in rat plasma was measured by ELISA. We found a dramatic increase in the secretion of resistin from mesenchymal stem cells, and verified this result in all the cells of mesenchymal origin tested. However, we observed no significant changes in the amount of resistin secreted from monocytes exposed to EMD compared with the control. Injections of EMD significantly enhanced the circulating levels of resistin in rats, and EMD also significantly enhanced the activity of the resistin promoter in transfected mesenchymal stem cells, indicating a direct effect on resistin expression. Our results indicate that resistin may play a role in mediating the biological effect of EMD in mesenchymal tissues.

Relations of circulating resistin and adiponectin and cardiac structure and function: the Framingham Offspring Study

Obesity is associated with pathological cardiac remodeling and risk of heart failure (HF). Adipocytokines (ADKs) may mediate the increased risk of cardiovascular disease associated with excess adiposity. Yet data relating ADKs to cardiac remodeling phenotypes are sparse. We related two circulating ADKs, resistin and adiponectin, to three important echocardiographic markers of cardiac remodeling, left ventricular mass (LVM), left atrial diameter (LAD), and LV fractional shortening (LVFS) in 2,615 participants (mean age 61 years, 55% women) in the Framingham Offspring Study. Adiponectin concentrations were inversely related to LVM in multivariable linear regression models adjusting for key clinical correlates including BMI (regression coefficient per s.d.-increment in ln-adiponectin = -3.37, P = 0.02; P for trend across quartiles = 0.02). Adiponectin was not associated with LAD or LVFS (P > 0.56). Resistin concentrations were inversely related to LVFS (regression coefficient per s.d.-increment in ln-resistin = -0.01, P = 0.03; P for trend across quartiles = 0.04). Resistin was not associated with LVM or LAD (P > 0.05). In our moderate-sized, community-based sample, higher circulating concentrations of adiponectin and resistin were associated with lower LVM and lower LVFS, respectively. In conclusion, these associations identify potential mechanisms by which excess adiposity may mediate adverse cardiac remodeling and HF risk.

The expression of rat resistin isoforms is differentially regulated in visceral adipose tissues: effects of aging and food restriction

Two variants of the adipose hormone resistin are generated by alternative splicing in Wistar rats. Here we analyzed the expression of these resistin variants in 2 main visceral adipose depots, epididymal and retroperitoneal, as well as the resistin serum concentration during aging and food restriction. Total protein levels of resistin were also analyzed in extracts from both visceral adipose depots. Resistin variants show similar patterns of relative expression in visceral adipose tissues in 3-month-old rats, representing the short variant, s-resistin, which is 15% of the full-length transcript. However, only epididymal, but not retroperitoneal, fat pad shows a decrease in both messenger RNA and protein levels of resistin isoforms with aging. Food restriction decreases adiposity index in 8- and 24-month-old animals to values even lower than those of 3-month-old animals. Food restriction decreases resistin expression in both adipose tissues in 8-month-old but not in 24-month-old rats. Interestingly, concomitant with the improvement of insulin sensitivity asserted by homeostasis model assessment, resistin serum levels decrease only in food-restricted 8-month-old animals. In contrast, food restriction up-regulates s-resistin messenger RNA in epididymal adipose tissue, whereas no significant changes are appreciated in retroperitoneal adipose tissue. These data indicate that both forms of resistin are differentially regulated by fat depot location, aging, and even nutritional status, suggesting that alternative splicing plays a key role in this differential regulation.

Fat poetry: a kingdom for PPAR gamma

Adipose tissue is not an inert cell mass contributing only to the storage of fat, but a sophisticated ensemble of cellular components with highly specialized and complex functions. In addition to managing the most important energy reserve of the body, it secretes a multitude of soluble proteins called adipokines, which have beneficial or, alternatively, deleterious effects on the homeostasis of the whole body. The expression of these adipokines is an integrated response to various signals received from many organs, which depends heavily on the integrity and physiological status of the adipose tissue. One of the main regulators of gene expression in fat is the transcription factor peroxisome proliferator-activated receptor gamma (PPARgamma), which is a fatty acid- and eicosanoid-dependent nuclear receptor that plays key roles in the development and maintenance of the adipose tissue. Furthermore, synthetic PPARgamma agonists are therapeutic agents used in the treatment of type 2 diabetes.This review discusses recent knowledge on the link between fat physiology and metabolic diseases, and the roles of PPARgamma in this interplay via the regulation of lipid and glucose metabolism. Finally, we assess the putative benefits of targeting this nuclear receptor with still-to-be-identified highly selective PPARgamma modulators.

White adipose tissue as endocrine organ and its role in obesity

Due to the public health problem represented by obesity, the study of adipose tissue, particularly of the adipocyte, is central to the understanding of metabolic abnormalities associated with the development of obesity. The concept of adipocyte as endocrine and functional cell is not totally understood and can be currently defined as the capacity of the adipocyte to sense, manage, and send signals to maintain energy equilibrium in the body. Adipocyte functionality is lost during obesity and has been related to adipocyte hypertrophy, disequilibrium between lipogenesis and lipolysis, impaired transcriptional regulation of the key factors that control adipogenesis, and lack of sensitivity to external signals, as well as a failure in the signal transduction process. Thus, dysfunctional adipocytes contribute to abnormal utilization of fatty acids causing lipotoxicity in non-adipose tissue such as liver, pancreas and heart, among others. To understand the metabolism of the adipocyte it is necessary to have an overview of the developmental process of new adipocytes, regulation of adipogenesis, lipogenesis and lipolysis, endocrine function of adipocytes and metabolic consequences of its dysfunction. Finally, the key role of adipose tissue is shown by studies in transgenic animals or in animal models of diet-induced obesity that indicate the contribution of adipose tissue during the development of metabolic syndrome. Thus, understanding of the molecular process that occurs in the adipocyte will provide new tools for the treatment of metabolic abnormalities during obesity.

Plasma resistin associated with myocardium injury in patients with acute coronary syndrome

BACKGROUND

Resistin, a novel adipocytokine, has been suggested as representing a link between metabolic signals, inflammation and atherosclerosis. The aim of the present study was to investigate the alteration in level of plasma resistin in patients with acute coronary syndrome (ACS) to uncover the role of resistin.

METHODS AND RESULTS

The 39 patients with ACS and 26 age-matched healthy subjects in this cross-sectional study were investigated. Plasma resistin levels were measured using radioimmunoassay. Plasma resistin levels were significantly increased in patients with ACS at 24 h after symptoms onset and remained at a high level for 1 week, and were significantly higher in patients with acute myocardial infarction than in those with unstable angina. In addition, plasma resistin level was correlated positively with peak plasma creatine kinase (CK), the MB isoform of CK and troponin I, and was correlated negatively with left ventricular ejection fraction. No correlation was found between plasma resistin level with level of metabolic parameters or inflammatory markers.

CONCLUSIONS

Plasma resistin levels in patients with ACS are elevated significantly within the first week after symptoms onset. Increased resistin levels may be a marker of myocardial ischemia and injury in ACS.

Plasma adiponectin levels in primary biliary cirrhosis: a novel perspective for link between hypercholesterolemia and protection against atherosclerosis

INTRODUCTION

Hypercholesterolemia is a common finding in primary biliary cirrhosis (PBC), but the risk of cardiovascular events in PBC patients is not increased in respect to the general population. High serum adiponectin levels appear to play a protective role in the development of either metabolic syndrome or cardiovascular disease.

AIM

To investigate factors potentially preventing atherosclerosis in PBC patients.

METHODS

Circulating levels of adiponectin, resistin, leptin, and tumor necrosis factor-alpha (TNF-alpha) were measured in 137 consecutive PBC patients (125 women, 12 men; mean age 61.6 +/- 12.3 yr), 137 sex- and age-matched healthy controls, and 30 female patients with nonalcoholic steatohepatitis (NASH) and associated metabolic syndrome.

RESULTS

The body mass index (BMI) was comparable in the three groups, whereas total cholesterol was significantly higher in both PBC and NASH cases than in controls (221.6 +/- 50.5 mg/dL in PBC vs 221.7 +/- 39.7 mg/dL in NASH vs 209.8 +/- 39.2 mg/dL in controls, P < 0.05). Serum concentrations of adiponectin, resistin, and leptin were significantly higher in PBC patients than in either NASH cases or controls (P < 0.05). Among the PBC patients, only adiponectin correlated positively with histological progression of the disease (P= 0.001) and negatively with BMI (P= 0.01). Logistic regression analysis revealed that adiponectin correlated independently with age, BMI, Mayo score, and gamma-glutamyl transpeptidase.

CONCLUSIONS

The high adiponectin concentrations observed in PBC patients should be regarded as a possible protective factor against atherogenesis. The search for further protective factors should be encouraged.

Octylphenol stimulates resistin gene expression in 3T3-L1 adipocytes via the estrogen receptor and extracellular signal-regulated kinase pathways

Resistin is known as an adipocyte-specific secretory hormone that can cause insulin resistance and decrease adipocyte differentiation. It can be regulated by sexual hormones. Whether environmental estrogens regulate the production of resistin is still not clear. Using 3T3-L1 adipocytes, we found that octylphenol upregulated resistin mRNA expression in dose- and time-dependent manners. The concentration of octylphenol that increased resistin mRNA levels by 50% was ∼100 nM within 6 h of treatment. The basal half-life of resistin mRNA induced by actinomycin D was lengthened by octylphenol treatment, suggesting that octylphenol decreases the rate of resistin mRNA degradation. In addition, octylphenol stimulated resistin protein expression and release. The basal half-life of resistin protein induced by cycloheximide was lengthened by octylphenol treatment, suggesting that octylphenol decreases the rate of resistin protein degradation. While octylphenol was shown to increase activities of the estrogen receptor (ER) and MEK1, signaling was demonstrated to be blocked by pretreatment with either ICI-182780 (an ERα antagonist) or U-0126 (a MEK1 inhibitor), in which both inhibitors prevented octylphenol-stimulated phosphorylation of ERK. These results imply that ERα and ERK are necessary for the octylphenol stimulation of resistin mRNA expression. Moreover, U-0126 antagonized the octylphenol-increased resistin protein expression and release. These data suggest that the way octylphenol signaling increases resistin protein levels is similar to that by which it increases resistin mRNA levels; it is likely mediated through an ERK-dependent pathway. In vivo, octylphenol increased adipose resistin mRNA expression and serum resistin and glucose levels, supporting its in vitro effect.

The multiple facets of the fat tissue

After a long history of relative neglect by the scientific community, white adipose tissue is finally emerging as a central component of body homeostasis. Indeed, the explosion of obesity statistics worldwide encouraged the study of adipose tissue and the complications of increased adiposity, such as insulin resistance, type 2 diabetes, and accelerated vascular disease. Far beyond merely furnishing free fatty acids from triglyceride depots, a growing list of fat tissue-derived mediators has increased the understanding of the regulatory role of adipose tissue in metabolic control. Recently, inflammation within the obese adipose tissue has surfaced as another important link of obesity to its undesirable metabolic consequences.

Explant cultures of white adipose tissue

Obesity is characterized by increased adiposity of visceral and subcutaneous depots as well as other organs, including the vasculature. These fat depots secrete various hormone-like proteins implicated in metabolic homeostasis (e.g., adiponectin, resistin), the central control of appetite (e.g., leptin) and the increased production of cytokines. These molecules act either in a paracrine or endocrine manner, contributing to the metabolic and cardiovascular complications of obesity. Explant cultures of white adipose tissue are an important step in analyzing the secretory mechanisms of adipose tissue by preserving the physiological in vivo cross-talk between the various types of cells.

Mouse models for atherosclerosis and pharmaceutical modifiers

Atherosclerosis is a multifactorial highly-complex disease with numerous etiologies that work synergistically to promote lesion development. The ability to develop preventive and ameliorative treatments will depend on animal models that mimic the human subject metabolically and pathophysiologically and will develop lesions comparable to those in humans. The mouse is the most useful, economic, and valid model for studying atherosclerosis and exploring effective therapeutic approaches. Among the most widely used mouse models for atherosclerosis are apolipoprotein E-deficient (ApoE-/-) and LDL receptor-deficient (LDLr-/-) mice. An up-and-coming model is the ApoE*3Leiden (E3L) transgenic mouse. Here, we review studies that have explored how and to what extent these mice respond to compounds directed at treatment of the risk factors hypercholesterolemia, hypertriglyceridemia, hypertension, and inflammation. An important outcome of this survey is that the different models used may differ markedly from one another in their response to a specific experimental manipulation. The choice of a model is therefore of critical importance and should take into account the risk factor to be studied and the working spectrum of the compounds tested.

The adipocyte as an active participant in energy balance and metabolism

Obesity is responsible for the mounting incidence of metabolic disease in adult and pediatric populations. Understanding of the pathogenesis and maintenance of the obese state has advanced rapidly over the past 10 years. Bodily energy reserves are managed actively by complex systems that regulate food intake, substrate partitioning, and energy expenditure. An underlying assumption that circulating factors released from storage organs were able to signal bodily energy reserves was confirmed with the discovery of the leptin system. This proof of concept has spurred on the discovery of a multitude of other adipocyte-generated factors. These circulating factors signal to the brain and other organs of metabolic importance, including adipose tissue, liver, muscle, and the immune system. Adipose-derived factors have numerous implications for the basic biology of obesity and provide prospective targets for the amelioration of obesity and its adverse metabolic consequences. In this review we detail the current understanding of leptin as a prototypical adipose tissue-derived hormone related to appetite and obesity. We also describe other important adipose-derived factors in relation to their metabolic effect.

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.

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.

Resistin concentrations before and after weight loss in obese children

OBJECTIVE

The influences of gender, puberty, and obesity on resistin levels and the longitudinal relationships between insulin resistance, weight loss, and resistin have not yet been studied in childhood.

METHODS

Age, pubertal stage, gender, weight status (standard deviation score-body mass index (SDS-BMI)), resistin levels, and insulin resistance index calculated by homeostasis model assessment (HOMA) were evaluated in 63 obese children and compared to 36 lean children of same age, gender, and pubertal stage. Furthermore, we analyzed the changes of weight status (SDS-BMI, percentage body fat based on skinfold measurements), waist-to-hip ratio, resistin, and HOMA over a 1-year period in 38 obese children.

RESULTS

The resistin levels did not significantly (P = 0.079) differ between obese (median resistin 8.7 ng/ml) and lean children (median resistin 9.7 ng/ml). Resistin concentrations were independent of age and pubertal stage, but girls demonstrated significantly higher resistin levels than boys (P = 0.021). There were no significant correlations between changes of resistin and changes of SDS-BMI (r = 0.14, P = 0.198), changes of percentage body fat (r = -0.01, P = 0.466), changes of waist-to-hip ratio (r = 0.17, P = 0.141), and changes of insulin resistance index (r = 0.01, P = 0.472) over the 1-year period. The weight loss of > or = 0.5 SDS-BMI in 16 children was associated with a significant decrease in HOMA (P = 0.030), while there was no significant change in resistin levels (P = 0.878).

CONCLUSIONS

Girls demonstrated higher resistin concentrations than boys. Our data do not support a relationship between resistin, insulin resistance index, and weight status in childhood.

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.

17 beta-estradiol stimulates resistin gene expression in 3T3-L1 adipocytes via the estrogen receptor, extracellularly regulated kinase, and CCAAT/enhancer binding protein-alpha pathways

Resistin is known as an adipocyte-specific secretory hormone that can cause insulin resistance and decrease adipocyte differentiation. It can be regulated by sexual hormones, but the mechanism of estrogen's actions is still not clear. Using 3T3-L1 adipocytes, we found that 17 beta-estradiol (E2) up-regulated resistin mRNA expression in a dose- and time-dependent manner. The concentration of E2 that increased resistin mRNA levels by 100-250% was approximately 1 nM for a range of 1-24 h of treatment. Treatment with either actinomycin D or cycloheximide prevented E2-stimulated resistin mRNA expression, suggesting that the effect of E2 requires new mRNA and protein synthesis. Although E2 was shown to increase activities of the estrogen receptor (ER) and MAPK kinase 1 and the association of nuclear ER alpha and CCAAT/enhancer binding protein-alpha with the resistin gene promoter, signaling was demonstrated to be blocked by pretreatment with either ICI182780 or PD98059. Neither SB203580 nor LY294002 changed the E2-increased levels of resistin mRNA, but they respectively inhibited E2-stimulated phosphorylation of p38 MAPK and Akt. These results imply the ER alpha, ERK, and CCAAT/enhancer binding protein- are necessary for the E2 stimulation of transcription from the resistin promoter. Moreover, PD98059, but not SB203580 or LY294002, antagonized E2-increased resistin protein release. These data suggest that E2 likely modifies the distribution of the resistin protein between the intracellular and extracellular compartments via an ERK-dependent pathway.

Molecular mechanisms of insulin resistance and associated diseases

Insulin resistance is a state in which higher than normal concentrations of insulin are required for normal response. The most common underlying cause is central obesity, although primary insulin resistance in normal-weight individuals is also possible. Excess abdominal adipose tissue has been shown to release increased amounts of free fatty acids which directly affect insulin signalling, diminish glucose uptake in muscle, drive exaggerated triglyceride synthesis and induce gluconeogenesis in the liver. Other factors presumed to play the role in insulin resistance are tumour necrosis factor alpha, adiponectin, leptin, IL-6 and some other adipokines. Hyperinsulinaemia which accompanies insulin resistance may be implicated in the development of many pathological states, such as hypertension and hyperandrogenaemia. Insulin resistance underlies metabolic syndrome and is further associated with polycystic ovary syndrome and lipodystrophies. When beta-cells fail to secrete the excess insulin needed, diabetes mellitus type 2 emerges, which is, besides coronary heart disease, the main complication of insulin resistance and associated diseases.

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.