Resistin Induces Hypertension and Insulin Resistance in Mice via a TLR4-Dependent Pathway

Genetic variants in DBC1, SIRT1, UCP2 and ADRB2 as potential biomarkers for severe obesity and metabolic complications

Introduction

Obesity is a multifactorial disease associated with the development of many comorbidities. This disease is associated with several metabolic alterations; however, it has been shown that some individuals with obesity do not exhibit metabolic syndrome. Adipose tissue neutralizes the detrimental effects of circulating fatty acids, ectopic deposition, and inflammation, among others, through its esterification into neutral lipids that are stored in the adipocyte. However, when the adipocyte is overloaded, i.e., its expansion capacity is exceeded, this protection is lost, resulting in fatty acid toxicity with ectopic fat accumulation in peripheral tissues and inflammation. In this line, this study aimed to investigate whether polymorphisms in genes that control adipose tissue fat storage capacity are potential biomarkers for severe obesity susceptibility and also metabolic complications.

Methods

This study enrolled 305 individuals with severe obesity (cases, BMI≥35 kg/m2) and 196 individuals with normal weight (controls, 18.5≤BMI≤24.9 kg/m2). Demographic, anthropometric, biochemical, and blood pressure variables were collected from the participants. Plasma levels of leptin, resistin, MCP1, and PAI1 were measured by Bio-Plex 200 Multiplexing Analyzer System. Genomic DNA was extracted and variants in DBC1 (rs17060940), SIRT1 (rs7895833 and rs1467568), UCP2 (rs660339), PPARG (rs1801282) and ADRB2 (rs1042713 and rs1042714) genes were genotyped by PCR allelic discrimination using TaqMan® assays.

Results

Our findings indicated that SIRT1 rs7895833 polymorphism was a risk factor for severe obesity development in the overdominant model. SIRT1 rs1467568 and UCP2 rs660339 were associated with anthropometric traits. SIRT1 rs1467568 G allele was related to lower medians of body adipose index and hip circumference, while the UCP2 rs660339 AA genotype was associate with increased body mass index. Additionally, DBC1 rs17060940 influenced glycated hemoglobin. Regarding metabolic alterations, 27% of individuals with obesity presented balanced metabolic status in our cohort. Furthermore, SIRT1 rs1467568 AG genotype increased 2.5 times the risk of developing metabolic alterations. No statistically significant results were observed with Peroxisome Proliferator-Activated Receptor Gama and ADRB2 polymorphisms.

Discussion/Conclusion

This study revealed that SIRT1 rs7895833 and rs1467568 are potential biomarkers for severe obesity susceptibility and the development of unbalanced metabolic status in obesity, respectively. UCP2 rs660339 and DBC1 rs17060940 also showed a significant role in obesity related-traits.

Association of visceral adiposity index with hypertension (NHANES 2003-2018)

Objectives

This study focused on the association between visceral adiposity index (VAI) and the prevalence of hypertension in a nationally representative population of American adults.

Methods

The study obtained data from the National Health and Nutrition Examination Survey (NHANES) database from 2003-2018 for a large-scale study. This study incorporated participants ≥18 years of age. Multivariate logistic regression modelling and smoothed curve fitting were applied to investigate the existence of a correlation between VAI and hypertension prevalence. Subgroups were analyzed to confirm the stationarity of the association between VAI and hypertension prevalence. In addition, an interaction test was conducted in this study.

Results

In completely adapted sequential models, the risk of hypertension prevalence in the overall population increased 0.17-fold with each 1-unit increase in VAI [odds ratio (OR) = 1.17; 95% confidence interval (CI) 1.12-1.22]. In the wholly adapted categorical model, there was a 0.95-fold increased risk of hypertension in the population of VAI quartile 4 (Q4) vs. VAI quartile 1 (Q1) (OR = 1.95; 95% CI 1.62-2.35). These results indicate that VAI was strongly related to the occurrence of hypertension, and smoothed curve-fitting analysis showed nonlinearity. Adjustment for covariates revealed no apparent interactions in the subgroup analyses, and results were stable across subgroups.

Conclusion

This cross-sectional study suggests a nonlinear and positive correlation between elevated VAI and the adult risk of developing hypertension in U.S. adults.

Nicotinamide Mononucleotide (NMN) Works in Type 2 Diabetes through Unexpected Effects in Adipose Tissue, Not by Mitochondrial Biogenesis

Nicotinamide mononucleotide (NMN) has emerged as a promising therapeutic intervention for age-related disorders, including type 2 diabetes. In this study, we confirmed the previously observed effects of NMN treatment on glucose uptake and investigated its underlying mechanisms in various tissues and cell lines. Through the most comprehensive proteomic analysis to date, we discovered a series of novel organ-specific effects responsible for glucose uptake as measured by the IPGTT: adipose tissue growing (suggested by increased protein synthesis and degradation and mTOR proliferation signaling upregulation). Notably, we observed the upregulation of thermogenic UCP1, promoting enhanced glucose conversion to heat in intermuscular adipose tissue while showing a surprising repressive effect on mitochondrial biogenesis in muscle and the brain. Additionally, liver and muscle cells displayed a unique response, characterized by spliceosome downregulation and concurrent upregulation of chaperones, proteasomes, and ribosomes, leading to mildly impaired and energy-inefficient protein synthesis machinery. Furthermore, our findings revealed remarkable metabolic rewiring in the brain. This involved increased production of ketone bodies, downregulation of mitochondrial OXPHOS and TCA cycle components, as well as the induction of well-known fasting-associated effects. Collectively, our data elucidate the multifaceted nature of NMN action, highlighting its organ-specific effects and their role in improving glucose uptake. These findings deepen our understanding of NMN's therapeutic potential and pave the way for novel strategies in managing metabolic disorders.

Changes in adipokine indicators depending on A1166C polymorphism of the angiotensin II type 1 receptor gene as a predictor of the arterial hypertension

Objective. Genetic factors substantially contribute to the development and duration of arterial hypertension. The study of the A1166C polymorphism of the angiotensin II type 1 receptor gene (AGTR1) in arterial hypertension is an auspicious area for assessing the relationship between heredity, hypertension development, and adipokines, but it still remains debatable. The purpose of the current study was to investigate serum adipokines levels depending on the AGTR1 A1166C polymorphism. Methods. A total of 86 patients with arterial hypertension were examined, who underwent the evaluation of the allelic A1166C polymorphism of AGTR1 by polymerase chain reaction with electrophoretic detection and determination of serum adipokines levels using enzyme-linked immunosorbent assay. Results. In the group of patients with arterial hypertension, a significant increase in serum adipokines (resistin, adiponectin, and leptin) levels was found against the background of a decrease in the antianorexic hormone ghrelin with a predominance of CC genotype carriers compared with AA genotype carriers of the AGTR1. A statistically significant decrease in ghrelin and an increase in serum adipokines (resistin, adiponectin, and leptin) in CC genotype carriers compared with AA genotype carriers of the AGTR1 were found suggesting that CC genotype carriers may be predictors of the development of arterial hypertension in our patients. Conclusions. Statistically significant decrease in ghrelin and increase in serum adipokines (resistin, adiponectin, and leptin) were found in CC genotype carriers compared with AA genotype carriers of the AGTR1, which suggests that carriers of the CC genotype are predictors of the arterial hypertension development in our patients.

Inappropriate Activation of TLR4/NF-κB is a Cause of Heart Failure

Significance: Heart failure, a disease with extremely high incidence, is closely associated with inflammation and oxidative stress. The Toll-like receptor 4 (TLR4)/nuclear factor kappa-B (NF-κB) pathway plays an important role in the occurrence and development of heart failure.

Recent advances: Previous studies have shown that TLR4/NF-κB causes heart failure by inducing oxidative stress and inflammation; damaging the endothelia; promoting fibrosis; and inducing myocardial hypertrophy, apoptosis, pyroptosis, and autophagy.

Critical issues: Understanding the pathogenesis of heart failure is essential for the treatment of this disease. In this review, we outline the mechanisms underlying TLR4/NF-κB pathway-mediated heart failure and discuss drugs that alleviate heart failure by regulating the TLR4/NF-κB pathway.

Future directions: During TLR4/NF-κB overactivation, interventions targeting specific receptor antagonists may effectively alleviate heart failure, thus providing a basis for the development of new anti-heart failure drugs.

Free-radical oxidation as a pathogenetic factor of metabolic syndrome

The medical and social significance of cardiovascular diseases remains high. One of the factors that determine cardiovascular risks is metabolic syndrome. As a result of excessive accumulation of lipid and carbohydrate metabolism products in metabolic syndrome, oxidative (oxidative) stress develops. The article considers both domestic and foreign scientific studies, which highlight various aspects of the influence of reactive oxygen and nitrogen species, as well as other free radicals on the formation of oxidative stress in pathological conditions that are part of the metabolic syndrome complex. This describes the mechanisms of the formation of chronic inflammation through excessive secretion of pro-inflammatory cytokines and adipokines, activation of the transcription factor NF-kB, as well as damage to the antioxidant system in obesity. Separately, a number of mechanisms of the stimulating effect of adipokines: leptin, adiponectin, chimerine, omentin 1, resistin, on the formation of oxidative stress have been noted. The ways of activating the polyol pathway, as well as diacyl-glycerol — protein kinase C — the signaling pathway of oxidative stress, the formation of mitochondrial dysfunction is described. As a result of which there is an excessive production of free radicals in insulin resistance, diabetes mellitus and macroand microvascular complications of diabetes. In addition, the influence of oxidative stress directly on the formation of cardiovascular diseases of atherosclerotic genesis, as well as arterial hypertension, has been shown.

The Association between Serum Resistin Level, Resistin (-420C/G) Single Nucleotide Variant, and Markers of Endothelial Dysfunction, including Salt Taste Preference in Hypertensive Patients

Background: Resistin action links to conditions such as diabetes, obesity, but its role in hypertension is less well understood. This study aimed to estimate the relationship between resistin (−420G/C) single nucleotide variant (SNV) and markers associated with endothelial dysfunction in hypertension. Methods: The study enrolled 162 hypertensive patients (HT) and 165 non-hypertensive (NHT) patients. Resistin serum concentration was estimated with immuoenzymatic assay. Anthropometric measurements, blood pressure and arterial stiffness index (SI), uric acid (UA) serum concentration, and salty taste preference of normal (NS) or high (HS) were assessed in the study. Genotyping was achieved by polymerase chain reaction-restriction fragment length polymorphism. Results: Resistin concentration and SI do not differ significantly between HT and NHT individuals; UA significantly increased in HT subjects. Resistin, UA, and SI did not differ among particular resistin genotypes in HT, NHT, NS, or HS groups. GG and CG genotypes were more frequent (OR 1.57 (95% CI; 1.01–2.43); p = 0.04) in hypertensive individuals than the NHT group, but less frequent (OR 0.58 (95% CI; 0.37–0.91); p = 0.01) in HS patients compared to NS individuals. Concerning HT patients with different salt preferences, GG + CG genotypes were less frequent (OR 0.50 (95% CI; 0.26–0.97); p = 0.04) in the HS group than in NS individuals. HT carriers of GG and CG genotype have significantly increased UA concentrations compared to the respective NHT subjects. HS individuals carrying GG and CG genotypes have higher SI values than the NS group. Allele G of SNV (−420G/C) adjusted for age, BMI, serum resistin, UA concentration, salt taste preference, SI, and HR values increased the risk of developing hypertensive phenotype 1.8 fold. Conclusions: Resistin SNV (−420G/C) is related to several markers associated with endothelial dysfunction, including salt taste preference in hypertensive patients.

The correlation between serum resistin and toll-like receptor-4 with insulin resistance in hypertensive subjects with or without type 2 diabetes mellitus

Background: The most chronic disease prevalence in the Iraqi population are type-2 diabetes mellitus (T2DM) and hypertension (HT). One of the important causes of these chronic diseases is obesity. Resistin (RETN) is a major link between obesity and insulin resistance (IR) or T2DM (which induces IR). The action of RETN on IR is mediated by Toll-like receptor-4 (TLR4). TLR4 is a putative RETN receptor that has been suggested to participate in RETN-inducing inflammation and IR. Objectives: To study the association between serum RETN/TLR4 and IR in hypertensive patients with or without T2DM subjects. Methods: This cross-sectional study was conducted on 120 men that classified into four different groups. These groups consist of the following: 30 apparently control group, 30 patients with hypertension, 30 patients with T2DM but without HT and 30 hypertensive patients with T2DM. For all the subjects, serum RETN, TLR4 and serum insulin was estimated by using the ELISA technique. Results: Our results showed that mean levels of the serum RETN and TLR4 were significantly elevated in all patient groups when compared with the control group. Also, a positive correlation between serum RETN and TLR4 was found in hypertensive patients with T2DM patients. Conclusions: Serum RETN and TLR4 were higher in all patient groups when compared with the control group. In addition, a positive correlation between RETN and IR in all study groups was noted. Then, we suggested a close association between RETN and TLR4 and their positive correlations with IR.

Resistin: A journey from metabolism to cancer

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Resistin levels have been associated with several pathological disorders such as metabolic disorders, cancers etc.

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Resistin exists in three isoforms namely RELM-α, β and γ.

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High resistin level activates inflammatory pathways, promotes metabolic disorders and is associated with carcinogenesis.

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Increase in the resistin level impairs the therapeutic response by inducing stemness or resistance, in cancer cells.

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Conventional drugs which alter resistin level could have therapeutic implications in several pathological disorders.

Resistin, a small secretory molecule, has been implicated to play an important role in the development of insulin resistance under obese condition. For the past few decades, it has been linked to various cellular and metabolic functions. It has been associated with diseases like metabolic disorders, cardiovascular diseases and cancers. Numerous clinical studies have indicated an increased serum resistin level in pathological disorders which have been reported to increase mortality rate in comparison to low resistin expressing subjects. Various molecular studies suggest resistin plays a pivotal role in proliferation, metastasis, angiogenesis, inflammation as well as in regulating metabolism in cancer cells. Therefore, understanding the role of resistin and elucidating its’ associated molecular mechanism will give a better insight into the management of these disorders. In this article, we summarize the diverse roles of resistin in pathological disorders based on the available literature, clinicopathological data, and a compiled study from various databases. The article mainly provides comprehensive information of its role as a target in different treatment modalities in pre as well as post-clinical studies.

Obesity, Adipose Tissue and Vascular Dysfunction

Cardiovascular diseases are the leading cause of death worldwide. Overweight and obesity are strongly associated with comorbidities such as hypertension and insulin resistance, which collectively contribute to the development of cardiovascular diseases and resultant morbidity and mortality. Forty-two percent of adults in the United States are obese, and a total of 1.9 billion adults worldwide are overweight or obese. These alarming numbers, which continue to climb, represent a major health and economic burden. Adipose tissue is a highly dynamic organ that can be classified based on the cellular composition of different depots and their distinct anatomical localization. Massive expansion and remodeling of adipose tissue during obesity differentially affects specific adipose tissue depots and significantly contributes to vascular dysfunction and cardiovascular diseases. Visceral adipose tissue accumulation results in increased immune cell infiltration and secretion of vasoconstrictor mediators, whereas expansion of subcutaneous adipose tissue is less harmful. Therefore, fat distribution more than overall body weight is a key determinant of the risk for cardiovascular diseases. Thermogenic brown and beige adipose tissue, in contrast to white adipose tissue, is associated with beneficial effects on the vasculature. The relationship between the type of adipose tissue and its influence on vascular function becomes particularly evident in the context of the heterogenous phenotype of perivascular adipose tissue that is strongly location dependent. In this review, we address the abnormal remodeling of specific adipose tissue depots during obesity and how this critically contributes to the development of hypertension, endothelial dysfunction, and vascular stiffness. We also discuss the local and systemic roles of adipose tissue derived secreted factors and increased systemic inflammation during obesity and highlight their detrimental impact on cardiovascular health.

The paradox of the role of resistin in early-onset obesity hypertension: A comparative study among four Chinese adult subgroups

Objective: To explore the role of resistin in the onset and development of obesity-related hypertension.Methods: Resistin serum levels were tested by ELISA in 153 adult subjects among four characteristic Chinese adult physical examination groups. Waist circumference (WC), body mass index (BMI), systolic blood pressure (SB), diastolic blood pressure (DB), and other clinical laboratory data were collected. Following, correlations between research index and differences between groups were analyzed using SPSS.Results: Serum resistin levels statistically significantly negatively correlated with SB, DB and BMI, but statistically significantly positively correlated with serum creatinine (SCR) and serum albumin (ALB), even after adjustment for age and/or gender. The serum level of resistin in the normal healthy subject group (NH) was higher than in other groups.Conclusions: Resistin's role in the onset of obesity-related hypertension may be more important than what has been previously assumed. More pathway substances in the early onset of obesity-related hypertension should be tested.Abbreviations: WC, waist circumference; GGT, Gamma-glutamyltransferase; ALB, Albumin; ALT, Alanine aminotransferase; LDL, Low density lipoprotein cholesterol; TG, Triglyceride; HDLC, High density lipoprotein cholesterol; FA Fructosamine; SCR, serum creatinine; IB, Indirect bilirubin; ALP, Alkaline phosphatase; CB, Conjugated bilirubin; UREA, Urea; Ua, Uric acid; FBG, fasting blood glucose; TC, Total cholesterol; TB, Total bilirubin; TP, Total protein; TC/HDLC, TC/HDLC ratio; SB, systolic blood pressure; DB, diastolic blood pressure.

Resistin induces cardiac fibroblast-myofibroblast differentiation through JAK/STAT3 and JNK/c-Jun signaling

Cardiac fibrosis is characterized by excessive deposition of extracellular matrix proteins and myofibroblast differentiation. Our previous findings have implicated resistin in cardiac fibrosis; however, the molecular mechanisms underlying this process are still unclear. Here we investigated the role of resistin in fibroblast-to-myofibroblast differentiation and elucidated the pathways involved in this process. Fibroblast-to-myofibroblast transdifferentiation was induced with resistin or TGFβ1 in NIH-3T3 and adult cardiac fibroblasts. mRNA and protein expression of fibrotic markers were analyzed by qPCR and immunoblotting. Resistin-knockout mice, challenged with a high-fat diet (HFD) for 20 weeks to stimulate cardiac impairment, were analyzed for cardiac function and fibrosis using histologic and molecular methods. Cardiac fibroblasts stimulated with resistin displayed increased fibroblast-to-myofibroblast conversion, with increased levels of αSma, col1a1, Fn, Ccn2 and Mmp9, with remarkable differences in the actin network appearance. Mechanistically, resistin promotes fibroblast-to-myofibroblast transdifferentiation and fibrogenesis via JAK2/STAT3 and JNK/c-Jun signaling pathways, independent of TGFβ1. Resistin-null mice challenged with HFD showed an improvement in cardiac function and a decrease in tissue fibrosis and reduced mRNA levels of fibrogenic markers. These findings are the first to delineate the role of resistin in the process of cardiac fibroblast-to-myofibroblast differentiation via JAK/STAT3 and JNK/c-Jun pathways, potentially leading to stimulation of cardiac fibrosis.

[Refractory and resistant hypertension in patients with type 2 diabetes mellitus: differences in metabolic profile and endothelial function]

AIM

To determine the prevalence of refractory hypertension (RfH) in patients with and without type 2 diabetes mellitus (DM), as well as to evaluate whether diabetic patients with RfH significant differ from those with uncontrolled resistant hypertension (RH) in clinical phenotype, metabolic profile and endothelial function.

MATERIALS AND METHODS

The study included 193 patients with RH: RH 74 patients with diabetes and 119 patients without DM. Uncontrolled RH and RfH were defined by the presence of uncontrolled blood pressure BP (140 and/or 90 mm Hg) despite the use of 3 but 5 antihypertensive drugs (for RH) and 5 antihypertensive drugs, including a mineralocorticoid receptor antagonist (for RfH). Clinical examination, lab tests were performed. Flow-mediated dilation (FMD) and vasoreactivity of middle cerebral artery (MCA) using both breath-holding and hyperventilation test were measured by high-resolution ultrasound.

RESULTS

The prevalence of refractory hypertension in patients with and without DM was similar (30% vs 28%, respectively). No differences in BP levels, data of echocardiography and clinical phenotype were found between the diabetic groups, but value of HOMA index, plasma resistin level and postprandial glycaemia were higher in patients with RfH. FMD and MCA reactivity to the breath-holding test were worse in patients with RfH, and they had a more pronounced vasoconstrictor response of MCA to the hyperventilation test compared to patients with RH.

CONCLUSION

The prevalence of RfH is the same in patients with and without diabetes. Diabetic patients with refractory hypertension have a more unfavorable metabolic profile and greater impairment of endothelial function than patients with uncontrolled resistant hypertension.

Remodeling of whole-body lipid metabolism and a diabetic-like phenotype caused by loss of CDK1 and hepatocyte division

Cell cycle progression and lipid metabolism are well-coordinated processes required for proper cell proliferation. In liver diseases that arise from dysregulated lipid metabolism, hepatocyte proliferation is diminished. To study the outcome of CDK1 loss and blocked hepatocyte proliferation on lipid metabolism and the consequent impact on whole-body physiology, we performed lipidomics, metabolomics, and RNA-seq analyses on a mouse model. We observed reduced triacylglycerides in liver of young mice, caused by oxidative stress that activated FOXO1 to promote the expression of Pnpla2/ATGL. Additionally, we discovered that hepatocytes displayed malfunctioning β-oxidation, reflected by increased acylcarnitines (ACs) and reduced β-hydroxybutyrate. This led to elevated plasma free fatty acids (FFAs), which were transported to the adipose tissue for storage and triggered greater insulin secretion. Upon aging, chronic hyperinsulinemia resulted in insulin resistance and hepatic steatosis through activation of LXR. Here, we demonstrate that loss of hepatocyte proliferation is not only an outcome but also possibly a causative factor for liver pathology.

Mgll Knockout Mouse Resistance to Diet-Induced Dysmetabolism Is Associated with Altered Gut Microbiota

Monoglyceride lipase (MGLL) regulates metabolism by catabolizing monoacylglycerols (MAGs), including the endocannabinoid 2-arachidonoyl glycerol (2-AG) and some of its bioactive congeners, to the corresponding free fatty acids. Mgll knockout mice (Mgll-/-) exhibit elevated tissue levels of MAGs in association with resistance to the metabolic and cardiovascular perturbations induced by a high fat diet (HFD). The gut microbiome and its metabolic function are disrupted in obesity in a manner modulated by 2-arachidonoyl glycerol (2-AG's) main receptors, the cannabinoid CB1 receptors. We therefore hypothesized that Mgll-/- mice have an altered microbiome, that responds differently to diet-induced obesity from that of wild-type (WT) mice. We subjected mice to HFD and assessed changes in the microbiomes after 8 and 22 weeks. As expected, Mgll-/- mice showed decreased adiposity, improved insulin sensitivity, and altered circulating incretin/adipokine levels in response to HFD. Mgll-/- mice on a chow diet exhibited significantly higher levels of Hydrogenoanaerobacterium, Roseburia, and Ruminococcus than WT mice. The relative abundance of the Lactobacillaceae and Coriobacteriaceae and of the Lactobacillus, Enterorhabdus, Clostridium_XlVa, and Falsiporphyromonas genera was significantly altered by HFD in WT but not Mgll-/- mice. Differently abundant families were also associated with changes in circulating adipokine and incretin levels in HFD-fed mice. Some gut microbiota family alterations could be reproduced by supplementing 2-AG or MAGs in culturomics experiments carried out with WT mouse fecal samples. We suggest that the altered microbiome of Mgll-/- mice contributes to their obesity resistant phenotype, and results in part from increased levels of 2-AG and MAGs.

Adipose Tissue Immunomodulation: A Novel Therapeutic Approach in Cardiovascular and Metabolic Diseases

Adipose tissue is a critical regulator of systemic metabolism and bodily homeostasis as it secretes a myriad of adipokines, including inflammatory and anti-inflammatory cytokines. As the main storage pool of lipids, subcutaneous and visceral adipose tissues undergo marked hypertrophy and hyperplasia in response to nutritional excess leading to hypoxia, adipokine dysregulation, and subsequent low-grade inflammation that is characterized by increased infiltration and activation of innate and adaptive immune cells. The specific localization, physiology, susceptibility to inflammation and the heterogeneity of the inflammatory cell population of each adipose depot are unique and thus dictate the possible complications of adipose tissue chronic inflammation. Several lines of evidence link visceral and particularly perivascular, pericardial, and perirenal adipose tissue inflammation to the development of metabolic syndrome, insulin resistance, type 2 diabetes and cardiovascular diseases. In addition to the implication of the immune system in the regulation of adipose tissue function, adipose tissue immune components are pivotal in detrimental or otherwise favorable adipose tissue remodeling and thermogenesis. Adipose tissue resident and infiltrating immune cells undergo metabolic and morphological adaptation based on the systemic energy status and thus a better comprehension of the metabolic regulation of immune cells in adipose tissues is pivotal to address complications of chronic adipose tissue inflammation. In this review, we discuss the role of adipose innate and adaptive immune cells across various physiological and pathophysiological states that pertain to the development or progression of cardiovascular diseases associated with metabolic disorders. Understanding such mechanisms allows for the exploitation of the adipose tissue-immune system crosstalk, exploring how the adipose immune system might be targeted as a strategy to treat cardiovascular derangements associated with metabolic dysfunctions.

The Adipokine Network in Rheumatic Joint Diseases

Rheumatic diseases encompass a diverse group of chronic disorders that commonly affect musculoskeletal structures. Osteoarthritis (OA) and rheumatoid arthritis (RA) are the two most common, leading to considerable functional limitations and irreversible disability when patients are unsuccessfully treated. Although the specific causes of many rheumatic conditions remain unknown, it is generally accepted that immune mechanisms and/or uncontrolled inflammatory responses are involved in their etiology and symptomatology. In this regard, the bidirectional communication between neuroendocrine and immune system has been demonstrated to provide a homeostatic network that is involved in several pathological conditions. Adipokines represent a wide variety of bioactive, immune and inflammatory mediators mainly released by adipocytes that act as signal molecules in the neuroendocrine-immune interactions. Adipokines can also be synthesized by synoviocytes, osteoclasts, osteoblasts, chondrocytes and inflammatory cells in the joint microenvironment, showing potent modulatory properties on different effector cells in OA and RA pathogenesis. Effects of adiponectin, leptin, resistin and visfatin on local and systemic inflammation are broadly described. However, more recently, other adipokines, such as progranulin, chemerin, lipocalin-2, vaspin, omentin-1 and nesfatin, have been recognized to display immunomodulatory actions in rheumatic diseases. This review highlights the latest relevant findings on the role of the adipokine network in the pathophysiology of OA and RA.

Resistin and adenylyl cyclase-associated protein 1 (CAP1) regulate the expression of genes related to insulin resistance in BNL CL.2 mouse liver cells

Resistin is an adipokine produced in white adipose tissue that is thought to modulate insulin sensitivity in peripheral tissues (such as liver, skeletal muscle or adipose tissue). Human and murine resistin molecules share only about 60% sequence homology. [1] Contrary to humans, in which resistin is secreted mostly by macrophages, Park and Ahima 2013 resistin in rodents is produced primarily by the mature adipocytes of the white adipose tissue. Although resistin can bind to toll-like receptor 4 (TLF4) activating proinflammatory responses in human and rodents, [3], [4], [5], [6], [7], [8] the inflammatory actions of resistin in human monocytes were found to be mediated by resistin binding to adenylyl cyclase-associated protein 1 (CAP1). [9] In this study, we aimed to investigate the in vitro effects of resistin on the expression of various genes related to insulin resistance in mouse liver cells. Using BNL CL.2 cells, we investigated the effect of resistin in untransfected or CAP1 siRNA-transfected cells on the expression of 84 key genes involved in insulin resistance.

Resistin Mediates Sex-Dependent Effects of Perivascular Adipose Tissue on Vascular Function in the Shrsp

Premenopausal women are relatively protected from developing hypertension compared to men. Perivascular adipose tissue (PVAT) has been shown to mediate vasoactive effects; however, a sex-dependent difference in PVAT function in the setting of hypertension has not yet been explored. We investigated the effect of PVAT on resistance vessel biology in male and female 16 week old stroke prone spontaneously hypertensive rats (SHRSP). This preclinical model of hypertension exhibits a sex-dependent difference in the development of hypertension similar to humans. Wire myography was used to assess vascular function in third-order mesenteric arteries. K_ATP channel-mediated vasorelaxation by cromakalim was significantly impaired in vessels from SHRSP males + PVAT relative to females (maximum relaxation: male + PVAT 46.9 ± 3.9% vs. female + PVAT 97.3 ± 2.7%). A cross-over study assessing the function of male PVAT on female vessels confirmed the reduced vasorelaxation response to cromakalim associated with male PVAT (maximum relaxation: female + PVAT_female90.6 ± 1.4% vs. female + PVAT_male65.8 ± 3.5%). In order to explore the sex-dependent differences in PVAT at a molecular level, an adipokine array and subsequent western blot validation identified resistin expression to be increased approximately 2-fold in PVAT from male SHRSP vessels. Further wire myography experiments showed that pre-incubation with resistin (40 ng/ml) significantly impaired the ability of female + PVAT vessels to relax in response to cromakalim (maximum relaxation: female + PVAT 97.3 ± 0.9% vs. female + PVAT + resistin_[40ng/ml]36.8 ± 2.3%). These findings indicate a novel role for resistin in mediating sex-dependent vascular function in hypertension through a K_ATP channel-mediated mechanism.

The Impact of OMEGA-3 Fatty Acids Supplementation on Insulin Resistance and Content of Adipocytokines and Biologically Active Lipids in Adipose Tissue of High-Fat Diet Fed Rats

It has been established that OMEGA-3 polyunsaturated fatty acids (PUFAs) may improve lipid and glucose homeostasis and prevent the "low-grade" state of inflammation in animals. Little is known about the effect of PUFAs on adipocytokines expression and biologically active lipids accumulation under the influence of high-fat diet-induced obesity. The aim of the study was to examine the effect of fish oil supplementation on adipocytokines expression and ceramide (Cer) and diacylglycerols (DAG) content in visceral and subcutaneous adipose tissue of high-fat fed animals. The experiments were carried out on Wistar rats divided into three groups: standard diet-control (SD), high-fat diet (HFD), and high-fat diet + fish oil (HFD+FO). The fasting plasma glucose and insulin concentrations were examined. Expression of carnitine palmitoyltransferase 1 (CPT1) protein was determined using the Western blot method. Plasma adipocytokines concentration was measured using ELISA kits and mRNA expression was determined by qRT-PCR reaction. Cer, DAG, and acyl-carnitine (A-CAR) content was analyzed by UHPLC/MS/MS. The fish oil supplementation significantly decreased plasma insulin concentration and Homeostatic Model Assesment for Insulin Resistance (HOMA-IR) index and reduced content of adipose tissue biologically active lipids in comparison with HFD-fed subjects. The expression of CPT1 protein in HFD+FO in both adipose tissues was elevated, whereas the content of A-CAR was lower in both HFD groups. There was an increase of adiponectin concentration and expression in HFD+FO as compared to HFD group. OMEGA-3 fatty acids supplementation improved insulin sensitivity and decreased content of Cer and DAG in both fat depots. Our results also demonstrate that PUFAs may prevent the development of insulin resistance in response to high-fat feeding and may regulate the expression and secretion of adipocytokines in this animal model.

Central Administration of Insulin Combined With Resistin Reduces Renal Sympathetic Nerve Activity in Rats Fed a High Fat Diet

Insulin receptors are widely distributed in the central nervous system and their activation by insulin elicits renal sympatho-excitatory effects. Resistin, an adipokine, promotes resistance to the metabolic effects of insulin. Resistin also induces increases in renal sympathetic nerve activity (RSNA) by acting in the brain, but whether it can influence insulin’s actions on RSNA is unknown. In the present study we investigated, in male Sprague-Dawley rats (7–8 weeks of age), the effects of central administration of insulin combined with resistin on RSNA following a normal diet (ND) and a high fat diet (HFD) (22% fat), since HFD can reportedly attenuate insulin’s actions. RSNA, mean arterial pressure (MAP) and heart rate (HR) responses were monitored and recorded before and for 180 min after intracerebroventricular injection of saline (control) (n = 5 HFD and ND), resistin (7 μg; n = 4 ND, n = 5 HFD), insulin (500 mU; n = 6 ND, n = 5 HFD), and the combination of both resistin and insulin (n = 7 ND, n = 5 HFD). The key finding of the present study was that when resistin and insulin were combined there was no increase in RSNA induced in rats fed a normal diet or the high fat diet. This contrasted with the sympatho-excitatory RSNA effects of the hormones when each was administered alone in rats fed the ND and the HFD.

Physiological roles and molecular mechanisms of K+ -Cl- cotransport in the mammalian kidney and cardiovascular system: where are we?

In the early 80s, renal microperfusion studies led to the identification of a basolateral K⁺ -Cl^- cotransport mechanism in the proximal tubule, thick ascending limb of Henle and collecting duct. More than ten years later, this mechanism was found to be accounted for by three different K⁺ -Cl^- cotransporters (KCC1, KCC3 and KCC4) that are differentially distributed along the renal epithelium. Two of these isoforms (KCC1 and KCC3) were also found to be expressed in arterial walls, the myocardium and a variety of neurons. Subsequently, valuable insights have been gained into the molecular and physiological properties of the KCCs in both the mammalian kidney and cardiovascular system. There is now robust evidence indicating that KCC4 sustains distal renal acidification and that KCC3 regulates myogenic tone in resistance vessels. However, progress in understanding the functional significance of these transporters has been slow, probably because each of the KCC isoforms is not identically distributed among species and some of them share common subcellular localizations with other KCC isoforms or sizeable conductive Cl^- pathways. In addition, the mechanisms underlying the process of K⁺ -Cl^- cotransport are still ill defined. The present review focuses on the knowledge gained regarding the roles and properties of KCCs in renal and cardiovascular tissues.

An Update on the Emerging Role of Resistin on the Pathogenesis of Osteoarthritis

Background

Resistin may be involved in the pathogenesis of osteoarthritis (OA), but a systematic understanding of the role of resistin in OA is lacking.

Methods

We reviewed studies that evaluated the role of resistin in OA. The expression levels of resistin in vitro experiments and OA/rheumatoid arthritis (RA) patients were analyzed. We also studied potential resistin receptors and the signaling pathways that these receptors activate, ultimately leading to cartilage degeneration.

Results

Resistin levels in both the serum and synovial fluid were higher in OA and RA patients than in healthy subjects. Overall, resistin levels are much higher in serum than in synovial fluid. In human cartilage, resistin induces the expression of proinflammatory factors such as degradative enzymes, leading to the inhibition of cartilage matrix synthesis, perhaps by binding to Toll-like receptor 4 and the adenylyl cyclase-associated protein 1 receptor, which then activates the p38-mitogen-activated phosphate kinase, protein kinase A–cyclic AMP, nuclear factor-κB, and C/enhancer-binding protein β signaling pathways.

Conclusion

Resistin levels are higher in OA patients than in healthy controls; however, the precise role of resistin in the pathogenesis of OA needs to be studied further. Resistin may be a novel therapeutic target in OA in the future.

Resistin-Inhibited Neural Stem Cell-Derived Astrocyte Differentiation Contributes to Permeability Destruction of the Blood-Brain Barrier

Neuroinflammation is an important part of the development of neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson's and amyotrophic lateral sclerosis. Inflammatory factors destroy the balance of the microenvironment, which results in changes in neural stem cell differentiation and proliferation behaviour. However, the mechanism underlying inflammatory factor-induced NSC behavioural changes is not clear. Resistin is a proinflammatory and adipogenic factor and is involved in several human pathology processes. The neural stem cell microenvironment changes when the concentration of resistin in the brain during an inflammatory response disease increases. In the present study, we explored the effect and mechanism of resistin on the proliferation and differentiation of neural stem cells. We found that intracerebroventricular injection of resistin induced a decrease in GFAP-positive cells in mice by influencing NSC differentiation. Resistin significantly decreased TEER and increased permeability in an in vitro blood-brain barrier model, which is consistent with the results of an HBMEC-astrocyte coculture system. Resistin-inhibited astrocyte differentiation is mediated through TLR4 on neural stem cells. To our knowledge, this is the first study reporting the effect of resistin on neural stem cells. Our findings shed light on resistin-involved neural stem cell degeneration mechanisms.

Molecular Mechanisms Underlying Obesity-Induced Hypothalamic Inflammation and Insulin Resistance: Pivotal Role of Resistin/TLR4 Pathways

Low-grade inflammation and insulin resistance are among the clinical features of obesity that are thought to promote the progressive onset of type 2 diabetes. However, the underlying mechanisms linking these disorders remain not fully understood. Recent reports pointed out hypothalamic inflammation as a major step in the onset of obesity-induced insulin resistance. In light of the increasing prevalence of obesity and T2D, two worldwide public health concerns, deciphering mechanisms implicated in hypothalamic inflammation constitutes a major challenge in the field of insulin-resistance/obesity. Several clinical and experimental studies have identified resistin as a key hormone linking insulin-resistance to obesity, notably through the activation of Toll Like Receptor (TLR) 4 signaling pathways. In this review, we present an overview of the molecular mechanisms underlying obesity-induced hypothalamic inflammation and insulin resistance with peculiar focus on the role of resistin/TLR4 signaling pathway.

Resistin effects on pancreatic cancer progression and chemoresistance are mediated through its receptors CAP1 and TLR4

Resistin, secreted by macrophages in tumor microenvironment, has never been investigated in pancreatic cancer models, despite a vibrant tumor microenvironment around pancreatic tumors. We evaluated serum resistin levels in healthy individuals versus pancreatic cancer patients representing different tumor grades. In vitro mechanistic analysis involved MiaPaCa-2 and SW1990 cells. Resistin signaling depends on binding of resistin to its cognitive receptors. Therefore, we silenced adenylyl cyclase-associated protein 1 (CAP1) and toll-like receptor 4 (TLR4), its two known receptors, individually as well as in combination, by short hairpin RNA (shRNA). Effect of resistin on cell proliferation, migration, invasion, cell cycle, and sensitivity to gemcitabine was studied without or with silencing of resistin receptors CAP1 and/or TLR4. The results were also confirmed in vivo in mice xenografted with MiaPaCa-2 cells without or with receptor silencing. We report high resistin levels in pancreatic cancer patients which correlate positively with tumor grades. We observed a marked reduction in the resistin-induced proliferation, migration, invasion, and cell cycle of pancreatic cancer cells MiaPaCa-2 and SW1990 when the receptors were silenced. The results were confirmed in vivo wherein resistin effects were significantly attenuated in MiaPaCa-2 xenografts with silenced receptors. The combined silencing of CAP1 and TLR4 was found to be most effective in vitro and in vivo. We found activation of STAT3 by resistin in vivo and in vitro which was dependent on the presence of CAP1 and TLR4. Further, resistin was found to induce resistance to gemcitabine through its receptors. Our results describe novel functional roles of resistin with implications toward a better understanding of pancreatic tumor microenvironment.

Here, there and everywhere: Resistin-like molecules in infection, inflammation, and metabolic disorders

The Resistin-Like Molecules (RELM) α, β, and γ and their namesake, resistin, share structural and sequence homology but exhibit significant diversity in expression and function within their mammalian host. RELM proteins are expressed in a wide range of diseases, such as: microbial infections (eg. bacterial and helminth), inflammatory diseases (eg. asthma, fibrosis) and metabolic disorders (eg. diabetes). While the expression pattern and molecular regulation of RELM proteins are well characterized, much controversy remains over their proposed functions, with evidence of host-protective and pathogenic roles. Moreover, the receptors for RELM proteins are unclear, although three receptors for resistin, decorin, adenylyl cyclase-associated protein 1 (CAP1), and Toll-like Receptor 4 (TLR4) have recently been proposed. In this review, we will first summarize the molecular regulation of the RELM gene family, including transcription regulation and tissue expression in humans and mouse disease models. Second, we will outline the function and receptor-mediated signaling associated with RELM proteins. Finally, we will discuss recent studies suggesting that, despite early misconceptions that these proteins are pathogenic, RELM proteins have a more nuanced and potentially beneficial role for the host in certain disease settings.

The role of adipokines in skeletal muscle inflammation and insulin sensitivity

Background

There is currently an unmet clinical need to develop better pharmacological treatments to improve glucose handling in Type II Diabetes patients with obesity. To this end, determining the effect of obesity-associated adipokines on skeletal muscle insulin sensitivity has emerged as an important area of drug discovery research. This review draws together the data on the functional role of adipokines on skeletal muscle insulin signalling, highlights several understudied novel adipokines and provides a perspective on the direction of future research.

Main body

The adipokines leptin, resistin, visfatin and adiponectin have all been shown to affect skeletal muscle insulin sensitivity by impacting on the activity of components within insulin signalling pathways, affecting GLUT4 translocation and modulating insulin-mediated skeletal muscle glucose uptake. Furthermore, proteomic analysis of the adipose tissue secretome has recently identified several novel adipokines including vaspin, chemerin and pref-1 that are associated with obesity and insulin resistance in humans and functionally impact on insulin signalling pathways. However, predominantly, these functional findings are the result of studies in rodents, with in vitro studies utilising either rat L6 or murine C2C12 myoblasts and/or myotubes. Despite the methodology to isolate and culture human myoblasts and to differentiate them into myotubes being established, the use of human muscle in vitro models for the functional validation of adipokines on skeletal muscle insulin sensitivity is limited.

Conclusion

Understanding the mechanism of action and function of adipokines in mediating insulin sensitivity in skeletal muscle may lead to the development of novel therapeutics for patients with type 2 diabetes. However, to date, studies conducted in human skeletal muscle cells and tissues are limited. Such human in vitro studies should be prioritised in order to reduce the risk of candidate drugs failing in the clinic due to the assumption that rodent skeletal muscle target validation studies will to translate to human.

Association between serum resistin concentration and hypertension: A systematic review and meta-analysis

Objectives

Recent studies have suggested the involvement of adipokines in the pathogenesis of cardiovascular diseases, including hypertension. In this study, we evaluated the significance of serum resistin levels in hypertensive patients using a meta-analysis approach.

Materials and Methods

Relevant articles were retrieved by searching the following databases: PubMed, Embase, Ovid Medline, ISI Web of Knowledge. The retrieved studies were subjected to a thorough screening procedure to identify case-control studies that contained the required data. Data were extracted from each study and analyzed by Stata software and Review Manager software. In total, 14 case-control studies, containing 718 hypertensive patients and 645 normotensive controls, were included in this study. The major result of the meta-analysis revealed a statistically significant association between serum resistin concentration and hypertension (SMD = 0.85, 95% CI: [0.15, 1.54]), and the association was more obvious in Asian and Hispanic populations, diabetic population and studies with larger size cohorts. Publication bias was a low probability event for overall comparisons.

Conclusions

Based on our results, we conclude that serum resistin level in hypertensive patients is higher than normotensive controls, indicating resistin might be a risk factor for hypertension.

Activation of the porcine alveolar macrophages via toll-like receptor 4/NF-κB mediated pathway provides a mechanism of resistin leading to inflammation

Resistin, a previously discovered cysteine-rich adipokine known to regulate glucose metabolism, has been emerged as a mediator in inflammation and immunity. Its level was supposed to be related to the expression of indicators, such as interleukin-1β (IL-1β), IL-6 and tumor necrosis factor-α (TNF-α) in inflammation. Toll-like receptor 4 (TLR4) was reported to be a receptor for resistin in cells, like leukocytes and peripheral blood mononuclear cells (PBMC). However, the pro-inflammatory role of resistin and its intracellular mechanisms in alveolar macrophages have not been thoroughly validated. Here we found that the pro-inflammatory cytokine expression in porcine alveolar macrophages (PAMs) was positively correlated with resistin. Our results also showed that resistin induced the expression of TLR4, intracellular molecules myeloid differentiation primary response protein 88 (MyD88), TRIF-related adaptor molecule (TRAM) and nuclear factor κB (NF-κB) in PAMs. In contrast, inhibition of TLR4, MyD88, TRAM and NF-κB abrogated the pro-inflammatory effect of resistin on PAMs. Additionally, the associations among TLR4, MyD88/TRAM and NF-κB were investigated by introducing TLR4-siRNA, MyD88-siRNA and TRAM-siRNA respectively into PAMs prior to the treatment with resistin. Taken together, our findings demonstrated that resistin promoted the production of pro-inflammatory cytokine in PAMs via TLR4/NF-κB-mediated pathway (TLR4/MyD88/TRAM/NF-κB).

α-Lactalbumin-oleic acid complex kills tumor cells by inducing excess energy metabolism but inhibiting mRNA expression of the related enzymes

Previous studies have demonstrated that the anti-tumor α-lactalbumin-oleic acid complex (α-LA-OA) may target the glycolysis of tumor cells. However, few data are available regarding the effects of α-LA-OA on energy metabolism. In this study, we measured glycolysis and mitochondrial functions in HeLa cells in response to α-LA-OA using the XF flux analyzer (Seahorse Bioscience, North Billerica, MA). The gene expression of enzymes involved in glycolysis, tricarboxylic acid cycle, electron transfer chain, and ATP synthesis were also evaluated. Our results show that α-LA-OA significantly enhanced the basal glycolysis and glycolytic capacity. Mitochondrial oxidative phosphorylation, including the basal respiration, maximal respiration, spare respiratory capacity and ATP production were also improved in response to α-LA-OA. The enhanced mitochondrial functions maybe partly due to the increased capacity of utilizing fatty acids and glutamine as the substrate. However, the gene expressions of pyruvate kinase M2, lactate dehydrogenase A, aconitate hydratase, and isocitrate dehydrogenase 1 were inhibited, suggesting an insufficient ability for the glycolysis process and the tricarboxylic acid cycle. The increased expression of acetyl-coenzyme A acyltransferase 2, a central enzyme involved in the β-oxidation of fatty acids, would enhance the unbalance due to the decreased expression of electron transfer flavoprotein β subunit, which acts as the electron acceptor. These results indicated that α-LA-OA may induce oxidative stress due to conditions in which the ATP production is exceeding the energy demand. Our results may help clarify the mechanism of apoptosis induced by reactive oxygen species and mitochondrial destruction.

Effects of Sex Hormone Treatment on the Metabolic Syndrome in Transgender Individuals: Focus on Metabolic Cytokines

CONTEXT

Hormonal treatment in transgender persons affects many components of the metabolic syndrome (MS).

OBJECTIVE

To determine the role of direct hormonal effects, changes in metabolic cytokines, and body composition on metabolic outcomes.

DESIGN, SETTING, AND PARTICIPANTS

24 transwomen and 45 transmen from the European Network for the Investigation of Gender Incongruence were investigated at baseline and after 12 months of hormonal therapy.

OUTCOME MEASURES

Best predictors for changes in components of MS, applying least absolute shrinkage and selection operator regression.

RESULTS

In transwomen, a decrease in triglyceride levels was best explained by a decrease in fat mass and an increase in fibroblast growth factor 21 (FGF-21); the decrease in total and low-density lipoprotein cholesterol levels was principally due to a decrease in resistin. A decrease in high-density lipoprotein cholesterol depended on an inverse association with fat mass. In contrast, in transmen, an increase in low-density lipoprotein cholesterol was predicted by a decrease in FGF-21 and an increase in the waist/hip ratio; a decrease in the high-density lipoprotein/total cholesterol ratio depended on a decline in adiponectin levels. In transwomen, worsened insulin resistance and increased early insulin response seemed to be due to a direct treatment effect; however, improvements in hepatic insulin sensitivity in transmen were best predicted by a positive association with chemerin, resistin, and FGF-21 and were inversely related to changes in the waist/hip ratio and leptin and adipocyte fatty acid-binding protein levels.

CONCLUSIONS

The effects of hormonal therapy on different components of the MS are sex-specific and involve a complex interplay of direct hormonal effects, changes in body composition, and metabolic cytokine secretion.

TLR4 regulates insulin-resistant proteins to increase apoptosis in the mouse retina

OBJECTIVE AND DESIGN

Work in multiple organs has suggested that toll-like receptor 4 (TLR4) may play a role in insulin resistance. Additional studies have shown a negative role for TLR4 on retinal health. We have previously reported that β-adrenergic receptors can regulate both TLR4 signal transduction, as well as insulin signaling in the retina and in retinal endothelial cells. Thus, we hypothesized that TLR4 would regulate retinal insulin signaling.

MATERIALS AND METHODS

We used endothelial cell-specific TLR4 knockout mice, as well as TLR4-overexpressing mice for these studies.

METHODS

Western blotting and ELISA analyses were done for investigations of insulin receptor, insulin receptor substrate 1 (IRS-1) serine 307, and Akt phosphorylation, as well as cleaved caspase 3 levels in the mouse retina.

RESULTS

We found that loss of TLR4 led to increased insulin receptor and Akt phosphorylation, as well as decreased IRS-1^Ser307 levels. In support of these results, TLR4 overexpression decreased insulin signaling and the cleavage of caspase 3.

CONCLUSIONS

Therefore, these results suggest that TLR4 plays a key role in insulin signaling in the retina. Reduction of TLR4 levels may be protective to the retina.

Adiponectin/resistin interplay in serum and in adipose tissue of obese and normal-weight individuals

BACKGROUND

The interplay between adiponectin and resistin, the two adipokines of opposite effects, may determine the metabolic profile of obese individuals and development of obesity-related complications. The current study was conducted to assess how adiponectin/resistin interplay in sera and adipose tissues may influence the metabolic profile of obese and normal-weight subjects.

METHODS

Concentrations of adiponectin and resistin were measured on protein level by immunoassay in visceral and subcutaneous adipose tissues from 50 obese (body mass index > 40 kg/m²) and 28 normal-weight (body mass index 20-24.9 kg/m²) individuals. Simultaneously expression of ADIPOQ and RETN (encoding adiponectin and resistin, respectively) was assessed on mRNA level by real-time PCR.

RESULTS

ADIPOQ mRNA (P = 0.0001) and adiponectin protein (P = 0.0013) levels were lower, while RETN mRNA (P = 0.0338) and resistin (P < 0.0001)-higher in subcutaneous adipose tissues of obese subjects. ADIPOQ and RETN mRNA levels did not correlate with protein concentrations in the investigated adipose tissues. In obesity adiponectin serum concentrations correlated positively with ADIPOQ mRNA in subcutaneous adipose tissue (P = 0.005) and negatively with protein levels in visceral adipose tissue (P = 0.001). Obesity was associated with higher adiponectin-resistin index value in sera (P < 0.0001) and decreased in subcutaneous adipose tissue (P < 0.001), but only adiponectin-resistin index measured in sera was significantly higher in obese with the metabolic syndrome (P = 0.04).

CONCLUSIONS

Obesity affects synthesis of adiponectin and resistin mainly in subcutaneous adipose tissue. The adiponectin-resistin index assessed in the adipose tissues has a different prognostic value compared to the adiponectin-resistin index in serum and does not reflect a metabolic risk in obese individuals.