Associations of resistin with inflammation and insulin resistance in patients with type 2 diabetes mellitus

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.

Salivary resistin level and its association with insulin resistance in obese individuals

The escalating global burden of type 2 diabetes mellitus necessitates the implementation of strategies that are both more reliable and faster in order to improve the early identification of insulin resistance (IR) in high-risk groups, including overweight and obese individuals. The use of salivary biomarkers offers a promising alternative to serum collection because it is safer, more comfortable, and less painful to obtain saliva samples. As obesity is the foremost contributory factor in IR development, the adipocytokines such as leptin, adiponectin, resistin, and visfatin secreted from the adipose tissue have been studied as potential reliable biomarkers for IR. Measurement of salivary adipokines as predictors for IR has attracted widespread attention because of the strong correlation between their blood and salivary concentrations. One of the adipokines that is closely related to IR is resistin. However, there are conflicting findings on resistin’s potential role as an etiological link between obesity and IR and the reliability of measuring salivary resistin as a biomarker for IR. Hence this study reviewed the available evidence on the potential use of salivary resistin as a biomarker for IR in order to attempt to gain a better understanding of the role of resistin in the development of IR in obese individuals.

Mechanistic insight into high-fat diet-induced metabolic inflammation in the arcuate nucleus of the hypothalamus

A high-fat diet (HFD) is linked with cytokines production by non-neuronal cells within the hypothalamus, which mediates metabolic inflammation. These cytokines then activate different inflammatory mediators in the arcuate nucleus of the hypothalamus (ARC), a primary hypothalamic area accommodating proopiomelanocortin (POMC) and agouti-related peptide (AGRP) neurons, first-order neurons that sense and integrate peripheral metabolic signals and then respond accordingly. These mediators, such as inhibitor of κB kinase-β (IKKβ), suppression of cytokine signaling 3 (SOCS3), c-Jun N-terminal kinases (JNKs), protein kinase C (PKC), etc., cause insulin and leptin resistance in POMC and AGRP neurons and support obesity and related metabolic complications. On the other hand, inhibition of these mediators has been shown to counteract the impaired metabolism. Therefore, it is important to discuss the contribution of neuronal and non-neuronal cells in HFD-induced hypothalamic inflammation. Furthermore, understanding few other questions, such as the diets causing hypothalamic inflammation, the gender disparity in response to HFD feeding, and how hypothalamic inflammation affects ARC neurons to cause impaired metabolism, will be helpful for the development of therapeutic approaches to prevent or treat HFD-induced obesity.

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.

Insulin Resistance and Colorectal Cancer Risk: the Role of Elevated Plasma Resistin Levels

PURPOSE

Given the important role of resistin in insulin resistance (IR) and obesity, as well as the associations between both IR and obesity and increased risk of colorectal cancer (CRC), we investigated whether plasma resistin levels were associated with CRC risk. Furthermore, the possible correlations between resistin and insulin, IR, and obesity in patients with CRC and controls were explored.

METHODS

This study was conducted as a case-control study and 170 subjects, including 88 controls and 82 cases with CRC, were enrolled and their plasma levels of glucoe, insulin, and resistin were measured using glucose oxidase or ELISA methods. Moreover, IR was calculated according to HOMA-IR index.

RESULTS

The cases with CRC had a higher HOMA-IR than the controls (1.8 ± 0.4 versus 1.4 ± 0.3, P < 0.001). Additionally, after the stratification of the cases with CRC by tumor site, higher levels of resistin and insulin, and a higher HOMA-IR in the cases with rectal cancer than in the controls were observed (resistin 5.9 ± 1.2 versus 5.4 ± 1.3, P = 0.043; insulin 5.9 ± 1.2 versus 5.4 ± 1.3, P = 0.039; HOMA- IR 1.9 ± 0.4 versus 1.3 ± 0.3, P < 0.001). Furthermore, resistin was positively correlated with insulin in the controls (r = 0.737, P < 0.001), the cases with CRC (r = 0.881, P < 0.001), the cases with colon cancer (r = 0.811, P < 0.001), and the cases with rectal cancer (r = 0.990, P < 0.001). All these differences remained significant after adjustment for confounding factors.

CONCLUSIONS

The findings of the present study reinforce the hypothesis that higher plasma levels of resistin in connection with insulin resistance play a role in susceptibility to colorectal, notably rectal, cancer. Nevertheless, further studies with bigger sample sizes are required to validate these findings.

Relation between resistin, PPAR-γ, obesity and atherosclerosis in male albino rats

Obesity and atherosclerosis are inflammatory states involving variable metabolic signals. The adipokine resistin is implicated in adipose tissue dysfunction and is modulated by PPARγ. In this study, resistin and PPARγ role is investigated in the development of CVS disease. Forty-eight Adult male albino rats were divided into control, obesity and atherosclerotic groups; each group is divided into two subgroups; with and without PPARγ agonist administration for 8 weeks. To assess pathological changes; lipid profile, inflammatory mediator, serum resistin level and resistin expression in adipose tissue were measured. Aorta is histopathologically evaluated. It was found that resistin expression is significantly correlated with lipid profile and inflammatory status in obesity and atherosclerotic groups, and PPARγ agonist administration significantly improves inflammatory status and dyslipidemic profile across studied groups (p < .05). Aortic wall shows histopathological evidence of atherosclerosis in obesity group which is more evident in atherosclerotic group, and milder changes upon receiving PPARγ agonist.

Structure and hypoglycemic activity of a novel exopolysaccharide of Cordyceps militaris

A novel neutral exopolysaccharide (EPS-III) was isolated from culture broth of Cordyceps militaris (C. militaris). The EPS-III was a homogeneous polysaccharide with M_w of 1.56 × 10³ kDa. The yield of EPS-III from culture broth was 123.2 ± 3.1 mg/L and the sugar content was 93.32 ± 0.87%. The backbone of EPS-III was mainly consisted of →4)-α-D-Galp-(1→, while →3, 6)-α-D-Manp-(1→, →4)-α-D-Manp-(1→, →3)-β-D-Galp-(1→ and →3)-α-D-Glcp-(1→ were distributed in the backbone or in the branch chains. The EPS-III had helix structure when dissolved in weak alkaline solution. It also had branched and intertwined form on the surface. The inhibition of α-glucosidase significantly increased as the increase of purity of exopolysaccharides. The EPS-III had effective inhibition on the α-glucosidase with dose-effect relationship. Besides, the results of hypoglycemic activity analysis in vivo indicated that EPS-III can alleviate weight loss, reduce plasma glucose concentration, improve glucose tolerance, protect immune organs and repair dyslipidemia to relieve diabetes in STZ-induced diabetic mice. The manuscript first studied the hypoglycemic activity of exopolysaccharide of by C. militaris, proving and promoting the application value of culture broth. The structure characterization of EPS-III laid experimental foundations on the exploration of structure-activity relationship.

Relation of Circulating Resistin to Insulin Resistance in Type 2 Diabetes and Obesity: A Systematic Review and Meta-Analysis

Background: Resistin, a cysteine-rich polypeptide encoded by the RETN gene, which plays an important role in many mechanisms in rodent studies, including lipid metabolism, inflammation and insulin resistance. Nevertheless, the relationship between resistin and insulin resistance in humans is under debate. The present study was designed to clarify the correlation between resistin and insulin resistance. Methods: A systematic literature search was performed using PubMed, Embase and Cochrane Library until March 3, 2019 with the keywords "resistin" and "insulin resistance." Funnel plots and Egger's test were used to detect publication bias. A random-effects model was used to calculate the pooled effect size. Subgroup analysis and meta regression was performed to identify the sources of heterogeneity. Results: Fifteen studies were included in our systematic review. Among them, 10 studies with Pearson coefficients were used for meta-analysis. We found resistin levels were weakly correlated with insulin resistance in those with T2DM and obesity (r = 0.21, 95% CI: 0.06-0.35, I 2 = 59.7%, P = 0.003). Nevertheless, subgroup analysis suggested that circulating resistin levels were significantly positively correlated with insulin resistance in individuals with hyperresistinemia (≥14.8 ng/ml) (r = 0.52, 95% CI: 0.35-0.68, I 2 = 0.0%, P = 0.513). And there was no relationship between circulating resistin and insulin resistance in those with normal circulating resistin levels (<14.8 ng/ml) (r = 0.08, 95% CI: -0.01-0.18, I 2 = 0.0%, P = 0.455). Publication bias was insignificant (Egger's test P = 0.592). Conclusion: In T2DM and obese individuals, resistin levels were positively correlated with insulin resistance in those with hyperresistinemia, but not in those with normal circulating resistin levels.

Resistin up-regulates LPL expression through the PPARγ-dependent PI3K/AKT signaling pathway impacting lipid accumulation in RAW264.7 macrophages

Resistin is a cysteine-rich cytokine, which has been indicated as a mediator of insulin resistance and inflammation. Previous studies demonstrated that lipoprotein lipase (LPL) was an important enzyme that could mediate lipid accumulation in macrophages. Additionally, the intracellular molecules phosphatidylinositol 3-kinase (PI3K)/serine-threonine protein kinase (AKT)/peroxisome proliferator-activated receptor (PPARγ) were supposed to be involved in the lipid accumulation process in cells. However, it remains unclear whether resistin was correlated with the dysregulation of lipid metabolism in macrophages. The present study investigated that resistin could up-regulate the expression of LPL and increase the contents of intracellular triglyceride (TG) and total cholesterol (TC) in RAW264.7 macrophages. In addition, intracellular molecules PI3K, AKT and PPARγ were significantly up-regulated and activated in resitin-stimulated RAW264.7 macrophages (P < 0.05). In contrast, the effects of resistin on RAW264.7 macrophages could be abrogated by specific inhibitors for LPL (LPL-siRNA) and PI3K/AKT signaling pathway (LY294002). All together, this study demonstrated that resistin could up-regulate the expression of LPL and induce lipid accumulation in RAW264.7 macrophages. More importantly, the PPARγ-dependent PI3K/AKT signaling pathway was relevant to the lipid accumulation process in resistin-stimulated macrophages.

The Anti-Inflammatory Effects of Testosterone

Low plasma testosterone (T) levels correlated with metabolic syndrome, cardiovascular diseases, and increased mortality risk. T exerts a significant effect on the regulation of adipose tissue accumulation, and in the glucose and lipids metabolism. Adipocytes are the primary source of the most important adipokines responsible for inflammation and chronic diseases. This review aims to analyze the possible effect of T on the regulation of the proinflammatory cytokines secretion.

A systematic literature search on MEDLINE, Google Scholar, and Cochrane using the combination of the following keywords: “testosterone” with “inflammation,” “cytokines,” “adiponectin, CRP, IL-1B, IL-6, TNFα, leptin” was conducted. Sixteen articles related to the effect of low T level and 18 to the effect of T therapy on proinflammatory cytokine were found.

T exerts a significant inhibitory effect on adipose tissue formation and the expression of various adipocytokines, such as leptin, TNF-α, IL-6, IL-1, and is positively correlated with adiponectin level, whereas a low T level is correlated with increased expression of markers of inflammation. Further studies are necessary to investigate the role of T, integrated with weight loss and physical activity, on its action on the mechanisms of production and regulation of proinflammatory cytokines.

Resistin inhibits neuronal autophagy through Toll-like receptor 4

Autophagy is a non-selective degradation pathway induced in energy-deprived cells and in non-starved cells by participating in cellular inflammatory responses mainly through the elimination of injured and aged mitochondria that constitute an important source of reactive oxygen species. We have previously reported that resistin/TLR4 signaling pathway induces inflammation and insulin resistance in neuronal cell. However, the impact of resistin-induced inflammation on neuronal autophagy is unknown. In the present study, we hypothesized that resistin-induced neuroinflammation could be attributed, at least partially, to the impairment of autophagy pathways in neuronal cells. Our data show that resistin decreases neuronal autophagy as evidenced by the repression of the main autophagy markers in SH-SY5Y human neuroblastoma cell line. Furthermore, the silencing of TLR4 completely abolished these effects. Resistin also inhibits AMPK phosphorylation and increases that of Akt/mTOR contrasting with activated autophagy where AMPK phosphorylation is augmented and mTOR inhibited. In vivo, resistin treatment inhibits the mRNA expression of autophagy markers in the hypothalamus of WT mice but not in Tlr4-/- mice. In addition, resistin strongly diminished LC3 (a marker of autophagy) labeling in the arcuate nucleus of WT mice, and this effect is abolished in Tlr4-/- mice. Taken together, our findings clearly reveal resistin/TLR4 as a new regulatory pathway of neuronal autophagy.

Resistin increases the expression of NOD2 in mouse monocytes

Previous studies have indicated that resistin, a type of adipokine, contributes to the development of insulin resistance and type 2 diabetes mellitus, and mediates inflammatory reactions. However, a specific receptor for resistin has not yet been identified. In this study, the relationship between resistin and nucleotide-binding oligomerization domain-like receptors, as well as resistin signal transduction, was examined through transfection, quantitative polymerase chain reaction, western blot analysis and ELISA. The mRNA expression of nucleotide-binding oligomerization domain-containing protein 2 (NOD2), a key immune receptor related to insulin resistance, was significantly increased by resistin treatment at concentrations of 100, 150 and 200 ng/ml (P<0.05, P<0.01 and P<0.01, respectively). The mRNA expression of downstream signaling molecules in the NOD2 signaling pathway, receptor-interacting serine/threonine-protein kinase 2 (RIP2; P<0.01 at 6, 12 and 24 h) and inhibitor of NF-κB kinase subunit beta (P<0.01 at 3, 6, 12 and 24 h) were significantly increased by resistin treatment compared with the control. The mRNA expression of key proinflammatory cytokines, tumor necrosis factor α, IL (interleukin)-6 and IL-1β, were also significantly increased by resistin treatment compared with the control (P<0.01). NOD2 knockdown by small interfering RNA (siRNA) significantly decreased the expression of NOD2 and RIP2 (P<0.01), and there was no significant increase in the levels of cytokines, as compared with treatment with control siRNA. These findings indicate that the inflammatory reaction induced by resistin involves the NOD2-nuclear factor (NF)-κB signaling pathway. The inhibition of NF-κB significantly decreased the secretion of key inflammatory cytokines (P<0.01), suggesting that NF-κB signaling mechanisms are essential to the resistin-induced inflammatory response.

Association of +62 G>A Polymorphism in the Resistin Gene with Type 2 Diabetes Mellitus among Thais: Case-Control Study

INTRODUCTION

Resistin gene (RETN) polymorphisms in humans may have a role in the pathogenesis of Type 2 Diabetes Mellitus (T2DM) and insulin resistance. There is still lack of evidence on association between +62 G>A polymorphism in the RETN and T2DM among Thais.

AIM

To determine the effect of polymorphisms at +62 G>A of RETN on Thai T2DM.

MATERIALS AND METHODS

This matched case control study was conducted with a total of 360 samples from all regions of Thailand (180 Thai new T2DM cases and 180 non-T2DM Thais for control) were enrolled. The RETN +62G>A polymorphism were detected using the Polymerase Chain Reaction (PCR) method. Conditional logistic regression was performed to test the association between +62 G>A polymorphism and T2DM.

RESULTS

Among 360 samples that were enrolled, only 350 samples completed molecular analysis. It was found that GA+AA genotype frequencies in T2DM cases was higher than control by 16% (95% CI: 6.0%, 27.0%, p-value=0.002). After adjustments for possible confounders, multivariable analyses by conditional logistic regression showed that the RETN+62 G>A polymorphism was statistically associated with Thai T2DM (OR_adjusted =1.84, 95% CI: 1.03, 3.31, p-value=0.04). Other factors such as; low educational attainment (OR_adjusted=3.87, 95%CI: 1.60, 9.36), hypertension (OR_adjusted=3.07, 95%CI: 1.56, 6.04), had both obese father and mother (OR_adjusted=1.94, 95%CI: 1.06, 3.56) and triglyceride≥150 (OR_adjusted=2.18, 95% CI: 1.18, 4.02) were statistically associated with Thai T2DM (p-value<0.05). While regular consumption of glutinous rice was found to be a protective factor (OR_adjusted=0.29, 95%CI: 0.13, 0.64).

CONCLUSION

These findings suggest that RETN polymorphism at position +62 G>A may increase the susceptibility to T2DM in Thais.

Obesity-associated digestive cancers: A review of mechanisms and interventions

The prevalence of obesity has steadily increased over the past few decades. Previous studies suggest that obesity is an oncogenic factor and that over 20% of all cancers are obesity-related. Among such cancers, digestive system malignancies (including esophageal adenocarcinomas, colorectal cancers, and cancers of the gastric cardia, liver, and pancreas) are reported most frequently. While the 5-year survival rates of cancers of the breast and prostate are 90%, that rate is only 45% for digestive cancers. In this review, the mechanisms of obesity-associated digestive cancers are discussed, with an emphasis on obesity-related gene mutations, insulin and insulin-like growth factor signaling pathways, chronic inflammation, and altered adipokine levels. Evidence that these factors often function interdependently rather than independently in carcinogenesis is presented. Recommended interventions that may reduce the burden of obesity-associated digestive cancers, such as participation in physical activity, diet modulation, and calorie restriction, are also described.

Increased circulating resistin is associated with insulin resistance, oxidative stress and platelet activation in type 2 diabetes mellitus

Resistin is an adipokine that promotes inflammation and insulin resistance by targeting several cells including platelets. We hypothesised that in type 2 diabetes (T2DM), resistin may foster in vivo oxidative stress, thromboxane-dependent platelet activation and platelet-derived inflammatory proteins release, key determinants of atherothrombosis. A cross-sectional comparison of circulating resistin, sCD40L, as a marker of platelet-mediated inflammation, asymmetric dimethylarginine (ADMA), endothelial dysfunction marker, Dickkopf (DKK)-1, reflecting the inflammatory interaction between platelets and endothelial cells, and urinary 8-iso-PGF_2α and 11-dehydro-TxB₂, reflecting in vivo lipid peroxidation and platelet activation, respectively, was performed between 79 T2DM patients and 30 healthy subjects. Furthermore, we investigated the effects of the α-glucosidase inhibitor acarbose and the PPARγ agonist rosiglitazone, targeting hyperglycaemia or insulin resistance, versus placebo, in 28 and 18 T2DM subjects, respectively. Age- and gender-adjusted serum resistin levels were significantly higher in patients than in controls. HOMA (β=0.266, p=0.017) and 11-dehydro-TXB₂ (β=0.354, p=0.002) independently predicted resistin levels. A 20-week treatment with acarbose was associated with significant reductions (p=0.001) in serum resistin, DKK-1, urinary 11-dehydro-TXB₂ and 8-iso-PGF_2α with direct correlations between the change in serum resistin and in other variables. A 24-week rosiglitazone treatment on top of metformin was associated with significant decreases in resistin, DKK-1, 11-dehydro-TXB₂ and 8-iso-PGF_2α, in parallel with HOMA decrease. In conclusion, resistin, antagonising insulin action in part through PPARγ activation, may favour insulin resistance and enhance oxidative stress, endothelial dysfunction and platelet activation. The adipokine-platelet interactions may be involved in platelet insulin resistance and their consequent pro-aggregatory phenotype in this setting.

Circulating Resistin Levels and Risk of Colorectal Cancer: A Meta-Analysis

Objectives. Published data on resistin levels in patients with colorectal cancer (CRC) were conflicting and heterogeneous. We conducted a meta-analysis of observational studies to examine the association of circulating resistin levels with carcinogenesis of the CRC. Methods. Potentially eligible studies published up to November 2015 were searched through MEDLINE, EMBASE, Science Citation Index Expanded database, CNKI, and WanFang database. The pooled weighted mean differences (WMDs) with 95% confidence intervals (CIs) calculated by fixed- or random-effect model were used to estimate the effects. Results. A total of 11 studies involving 965 patients were admitted in our meta-analysis. The pooled effects indicated that resistin levels were higher in CRC patients compared to healthy controls (WMD: 1.47 ng/mL; 95% CI: 0.78 to 2.16), with significant heterogeneity across the studies (I² = 72%, p < 0.0001). Subgroup analyses and sensitivity analyses revealed that study quality, design, sample type, and resistin assays may account for this heterogeneity. No publication bias was observed. Conclusions. Our meta-analysis suggests that increased circulating resistin levels are associated with greater risk of colorectal cancer. Given the limited number of available studies and significant heterogeneity, larger well-designed randomized studies are warranted.

Resistin is a predictor of asthma risk and resistin:adiponectin ratio is a negative predictor of lung function in asthma

BACKGROUND

Adipokines, such as resistin and adiponectin, modify inflammation and may contribute to increased asthma risk and severity in obese people.

OBJECTIVE

To examine plasma resistin and resistin:adiponectin ratio (i) in asthmatics compared to healthy controls, (ii) according to asthma severity, obesity and gender (iii) following weight loss in obese asthmatics.

METHODS

In a cross-sectional observational study of asthmatic adults (n = 96) and healthy controls (n = 46), plasma resistin and adiponectin were measured. In a separate intervention study, obese asthmatic adults (n = 27) completed a 10-week weight loss intervention and plasma resistin and adiponectin concentrations were analysed.

RESULTS

Plasma resistin and resistin:adiponectin ratio were higher in asthma compared to controls and were higher again in subjects with a severe vs. mild-to-moderate asthma pattern. Amongst asthmatic subjects, resistin was not modified by gender or obesity, while adiponectin was lower in males and obese subjects. As a result, resistin:adiponectin ratio was higher in obese males, non-obese males and obese females, compared to non-obese females. In a logistic regression model, plasma resistin concentration was a predictor of asthma risk. In a multiple linear regression model, plasma resistin:adiponectin ratio was a negative predictor of FEV1 in asthma. Following weight loss, neither resistin, adiponectin nor resistin:adiponectin ratio was changed. However, the change (∆) in %body fat was associated with ∆ resistin:adiponectin ratio. Post-intervention ∆ resistin was negatively correlated with both ∆FRC and ∆RV.

CONCLUSION AND CLINICAL RELEVANCE

This study demonstrates that resistin and resistin:adiponectin ratio are higher in asthma and are higher again in subjects who have more severe disease. Resistin:adiponectin ratio is highest in obese male asthmatics. As resistin is a predictor of asthma risk and resistin:adiponectin is a predictor of FEV1 in asthma, these adipokines may be contributing to the obese asthma phenotype, thus providing a potential therapeutic target for obese asthma.

Associations of Resistin Levels with Resistin Gene Polymorphism and Metabolic Syndrome in Thais

Background

Metabolic syndrome (MS) is a clinical constellation comprising risk factors associated with developing cardiovascular disease and type 2 diabetes. Resistin has been suggested as a linkage between obesity, inflammation and type 2 diabetes. This study aimed to investigate resistin concentrations and hematological-biochemical parameters in MS subjects and controls, and to determine whether two resistin gene (RETN) polymorphisms (−420C>G & +299G>A) are linked to resistin levels and MS among Thais.

Methods

This case-control study was performed with 322 Thai volunteers: 160 MS subjects and 162 controls. Anthropometric parameters and hematological-biochemical variables were determined. The RETN −420C>G (rs1862513) and +299G>A (rs3745367) polymorphisms were genotyped by PCR-RFLP technique.

Results

The resistin levels of the MS group were significantly higher than those of the control group. Resistin levels were positively correlated with anthropometric parameters and WBC count in the MS group. According to RETN −420C>G polymorphism, MS subjects with the G allele (CG/GG) (3.9 μg/L) had significantly higher resistin concentrations than in subjects with the CC genotype (2.4 μg/L); with regard to RETN +299G>A polymorphism, carriers with the A allele (GA/AA) (3.8 μg/L) had significantly higher resistin levels than subjects with the GG genotype (2.7 μg/L), after adjusting for potential covariates. However, the RETN −420C>G and +299G>A polymorphisms were not found to be associated with MS, hematological-biochemical parameters and anthropometric variables.

Conclusions

These findings suggest resistin levels are linked with MS and the RETN −420C>G and +299G>A polymorphisms have impacted the circulating resistin concentrations. However, these two RETN polymorphisms probably do not influence susceptibility to MS among Thais.

Obesity and colorectal cancer: Role of adipokines in tumor initiation and progression

Obesity-associated diseases account for a large portion of public health challenges. Among obesity-related disorders, a direct and independent relationship has been ascertained for colorectal cancer (CRC). The evidence that adipocyte hypertrophy and excessive adipose tissue accumulation (mainly visceral) can promote pathogenic adipocyte and adipose tissue-related diseases, has led to formulate the concept of “adiposopathy”, defined as adipocyte and adipose tissue dysfunction that contributes to metabolic syndrome. Adipose tissue can, indeed, be regarded as an important and highly active player of the innate immune response, in which cytokine/adipokine secretion is responsible for a paracrine loop between adipocytes and macrophages, thus contributing to the systemic chronic low-grade inflammation associated with visceral obesity, which represents a favorable niche for tumor development. The adipocyte itself participates as a central mediator of this inflammatory response in obese individuals by secreting hormones, growth factors and proinflammatory cytokines, which are of particular relevance for the pathogenesis of CRC. Among adipocyte-secreted hormones, the most relevant to colorectal tumorigenesis are adiponectin, leptin, resistin and ghrelin. All these molecules have been involved in cell growth and proliferation, as well as tumor angiogenesis and it has been demonstrated that their expression changes from normal colonic mucosa to adenoma and adenocarcinoma, suggesting their involvement in multistep colorectal carcinogenesis. These findings have led to the hypothesis that an unfavorable adipokine profile, with a reduction of those with an anti-inflammatory and anti-cancerous activity, might serve as a prognostic factor in CRC patients and that adipokines or their analogues/antagonists might become useful agents in the management or chemoprevention of CRC.

Oral Angiotensin-(1-7) prevented obesity and hepatic inflammation by inhibition of resistin/TLR4/MAPK/NF-κB in rats fed with high-fat diet

Obesity is characterized by a pro-inflammatory state commonly associated with type 2 diabetes and fat-liver disease. In the last few years, different studies pointed out the role of Angiotensin (Ang)-(1-7) in the metabolic regulation. The aim of the present study was to evaluate the effect of oral-administration of Ang-(1-7) in metabolism and inflammatory state of high-fat feed rats. Twenty-four male Sprague Dawley rats were randomized into three groups: High Fat Diet (HFD); Standard Diet (ST); High Fat Diet+Angiotensin-(1-7) [HFD+Ang-(1-7)]. Glycemic profile was evaluated by glucose tolerance and insulin sensitivity tests, plasmatic glucose and insulin. Cholesterol, HDL and triglycerides analyses presented lipidic profile. RT-PCR evaluated mRNA expression to ACE, ACE2, resistin, TLR4, IL-6, TNF-α and NF-κB genes. The main results showed that oral Ang-(1-7) decreased body weight and abdominal fat-mass. In addition, HFD+Ang-(1-7) treated rats presented enhanced glucose tolerance, insulin-sensitivity and decreased plasma-insulin levels, as well as a significant decrease in circulating lipid levels. These alterations were accompanied by a marked decreased expression of resistin, TLR4, ACE and increased ACE2 expression in liver. Furthermore, Ang-(1-7) decreases phosphorylation of MAPK and increases NF-κB expression. These alterations diminished expression of interleukin-6 and TNF-α, ameliorate inflammatory state in liver. In summary, the present study showed that oral-treatment with Ang-(1-7) in high-fat feed rats improved metabolism down-regulating resistin/TLR4/NF-κB-pathway.

What about non-alcoholic fatty liver disease as a new criterion to define metabolic syndrome?

Non-alcoholic fatty liver disease (NAFLD) is currently not a component of the diagnostic criteria for metabolic syndrome (MetS); however, the development of NAFLD has some common mechanisms with the development of MetS, as they share the pathophysiologic basis of insulin resistance. It is also recognized that NAFLD is the hepatic manifestation of MetS. To define MetS, the presence of at least three of the proposed criteria is required, and sometimes it is sufficient to have only one laboratory value, modified by diet or drugs, for the classification of MetS. Ultrasonographically-detected NAFLD (US-NAFLD) is more stable, only changing during the middle- to long-term. Although controversies over MetS continue, and considering that abdominal ultrasonography for diagnosing NAFLD has high specificity and guidelines to modify the natural course of NAFLD by diet composition or lifestyle have not yet been established, why should we not introduce US-NAFLD as a new criterion to define MetS?

Leptin, resistin and visfatin: the missing link between endocrine metabolic disorders and immunity

Adipose tissue is still regarded as a principle site for lipid storage and mobilizing tissue with an important role in the control of energy homeostasis. Additionally, adipose tissue-secreted hormones such as leptin, visfatin, resistin, apelin, omentin, sex steroids, and various growth factors are now regarded as a functional part of the endocrine system. These hormones also play an important role in the immune system. Several in vitro and in vivo studies have suggested the complex role of adipocyte-derived hormones in immune system and inflammation. Adipokines mediate beneficial and detrimental effects in immunity and inflammation. Many of these adipocytokines have a physiological role in metabolism. The uncontrolled secretions of several adipocytokines were associated with the stimulation of inflammatory processes leading to metabolic disorders including obesity, atherosclerosis, insulin resistance and type 2 diabetes. Obesity leads to the dysfunction of adipocytes andcorrelated with the imbalance of adipokines levels. In obese and diabetic conditions, leptin deficiency inhibited the Jak/Stat3/PI3K and insulin pathways. In this review, ample evidence exists to support the recognition of the adipocyte's role in various tissues and pathologies. New integral insights may add dimensions to translate any potential agents into the future clinical armamentarium of chronic endocrine metabolic and inflammatory diseases. Functional balance of both adipocytes and immune cells is important to exert their effects on endocrine metabolic disorders; furthermore, adipose tissue should be renamed not only as a functional part of the endocrine system but also as a new part of the immune system.

Central resistin overexposure induces insulin resistance through Toll-like receptor 4

Resistin promotes both inflammation and insulin resistance associated with energy homeostasis impairment. However, the resistin receptor and the molecular mechanisms mediating its effects in the hypothalamus, crucial for energy homeostasis control, and key insulin-sensitive tissues are still unknown. In the current study, we report that chronic resistin infusion in the lateral cerebral ventricle of normal rats markedly affects both hypothalamic and peripheral insulin responsiveness. Central resistin treatment inhibited insulin-dependent phosphorylation of insulin receptor (IR), AKT, and extracellular signal-related kinase 1/2 associated with reduced IR expression and with upregulation of suppressor of cytokine signaling-3 and phosphotyrosine phosphatase 1B, two negative regulators of insulin signaling. Additionally, central resistin promotes the activation of the serine kinases Jun NH(2)-terminal kinase and p38 mitogen-activated protein kinase, enhances the serine phosphorylation of insulin receptor substrate-1, and increases the expression of the proinflammatory cytokine interleukin-6 in the hypothalamus and key peripheral insulin-sensitive tissues. Interestingly, we also report for the first time, to our knowledge, the direct binding of resistin to Toll-like receptor (TLR) 4 receptors in the hypothalamus, leading to the activation of the associated proinflammatory pathways. Taken together, our findings clearly identify TLR4 as the binding site for resistin in the hypothalamus and bring new insight into the molecular mechanisms involved in resistin-induced inflammation and insulin resistance in the whole animal.

Clinical implications of adipocytokines and newly emerging metabolic factors with relation to insulin resistance and cardiovascular health

Adipose tissue is known to secrete hormones actively and produces many biologically active proteins called adipocytokines. Typically, obesity is followed by low-grade inflammation, which is characterized by increased circulating levels of pro-inflammatory cytokines. Macrophages play a role in the inflammatory process by secreting many cytokines such as tumor necrosis factor alpha, interleukin-6, resistin, and retinol binding protein-4. These cytokines and chemokines participate in low-grade pro-inflammatory processes leading to insulin resistance, metabolic impairment, and cardiovascular diseases. More metabolic regulators, such as fibroblast growth factor (FGF)21, FGF19, FGF1, vaspin, and visfatin have now been discovered but their exact roles in human diseases are still unclear. This review focuses on recent research regarding the role of adipokines and new metabolic factors in metabolic derangement or cardiovascular disease.

Relationship between adipocytokines and cardiovascular risk factors in patients with type 2 diabetes mellitus

The aim of this study was to explore the relationship between serum profiles of adiponectin, leptin, resistin and visfatin and traditional and non-traditional cardiovascular risk factors in patients with type 2 diabetes mellitus (T2DM). A total of 85 patients with T2DM and 30 non-diabetic controls were enrolled in the study. Levels of adipocytokines (adiponectin, leptin, resistin and visfatin), lipids (total cholesterol, triglycerides), lipoproteins [HDL-cholesterol, LDL-cholesterol, lipoprotein (a)], apolipoproteins (Apo-A1 and Apo-B), non-traditional cardiovascular risk markers [asymmetric dimethylarginine (ADMA), homocysteine] and the inflammatory marker hs-CRP were measured, and anthropometric variables were determined. Serum adiponectin levels were decreased and leptin, resistin and visfatin levels were increased in T2DM patients compared to controls. They were associated with obesity (BMI), insulin resistance (HOMA-IR) and various markers of glucose/lipid profile, inflammation and endothelial dysfunction markers. These results suggest that decreased serum adiponectin and increased leptin, resistin and visfatin levels in T2DM may be novel biochemical risk factors for cardiovascular complications.

Inflammation and oxidative stress in obesity-related glomerulopathy

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

The plasma level and gene expression of resistin in polycystic ovary syndrome

OBJECTIVES

To investigate the relationship between plasma resistin, polycystic ovary syndrome (PCOS), and insulin resistance (IR). To compare the mRNA level of resistin in mononuclear cells and monocyte-derived macrophages in women with PCOS and controls.

MATERIALS AND METHODS

Patients with PCOS and controls were enrolled and IR was considered as the stratified factor for subgroups. Fasting blood was collected to determine the levels of sex hormones, insulin, glucose, blood lipid, and resistin. Resistin gene expression was evaluated by quantitative real-time RT-PCR in mononuclear cells and monocyte-derived macrophages cultured with or without rosiglitazone for 96 h.

RESULTS

No significant difference of plasma resistin levels was found among PCOS-IR, PCOS-non-IR, control-IR, and control-non-IR groups. There were no significant differences in resistin mRNA expression between participants with and without PCOS and with and without IR. Resistin mRNA expression in monocyte-derived macrophages was higher than that in mononuclear cells (p = 0.04), and could be reduced by rosiglitazone (p < 0.001).

CONCLUSIONS

Plasma resistin does not correlate with normal weight PCOS or IR. Resistin gene expression in mononuclear cells and monocyte-derived macrophages in PCOS and IR is the same as controls. Further researches on the role of resistin in the pathogenesis of PCOS or IR should concentrate on the tissue level.

Serum resistin as a novel marker of erythropoietin resistance in nondiabetic patients on hemodialysis

The use of higher erythropoietin (EPO) doses is associated with an increased risk of an adverse outcome and increased mortality in patients with renal failure. Resistin is related to heart disease, and may contribute to an increased atherosclerotic risk. We hypothesized that a link between resistin and EPO responsiveness may exist. We therefore investigated the relationship between resistin and the EPO resistance index (ERI) in nondiabetic hemodialysis (HD) patients. Fifty-seven patients enrolled in the study underwent HD for ≥ 3 months and intravenous EPO therapy to maintain a target hemoglobin (Hb) level of 11.0 g/dl. The ERI was defined as the weekly EPO dose per unit Hb per body weight. The mean patient age was 52.6 ± 11.9 years and the mean time on dialysis was 4.9 ± 4.4 years. Serum Hb and ERI were 10.4 ± 0.7 g/dl, and 13.3 ± 7.0 (IU/kg/week/g/dl), respectively. Serum resistin levels were 23.6 ± 9.3 µg/L. EPO resistance is associated with low body mass index (BMI) (coefficient β =-0.393, p = 0.002) and with high serum resistin levels (coefficient β = 0.332, p = 0.018). According to a multiple regression analysis, the serum resistin level was a significant independent factor related to EPO resistance (p = 0.017). The results suggest that serum resistin levels reflect EPO responsiveness in nondiabetic HD patients. Resistin may therefore be considered as a new marker of EPO responsiveness in HD patients.

Macrophage migration inhibitory factor is a therapeutic target in treatment of non-insulin-dependent diabetes mellitus

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in the pathogenesis of a variety of autoimmune inflammatory diseases. Here, we investigated the role of MIF in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM) using MIF(-/-) mice and a mouse model of streptozotocin (STZ)-induced NIDDM. Following single injection of STZ, MIF(+/+) BALB/c mice showed a significant increase in blood glucose levels, developed polyuria, and succumbed to disease. In contrast, no such increase in blood glucose was observed in MIF(-/-) BALB/c mice treated with STZ. These mice produced significantly less inflammatory cytokines and resistin as compared with MIF(+/+) mice and failed to develop clinical disease. Finally, oral administration of a small-molecule MIF antagonist, CPSI-1306, to outbred ICR mice following induction of NIDDM significantly lowered blood glucose levels in the majority of animals, which was also associated with a significant reduction in the levels of the proinflammatory cytokines IL-6 and TNF-alpha in the sera. Taken together, these results demonstrate that MIF is involved in the pathogenesis of NIDDM and is a therapeutic target to treat this disease.

Resistin as a cardiovascular and atherosclerotic risk factor and uremic toxin

Resistin is a 12.5 kDa protein originally found to be secreted by mouse adipocytes. Whereas in rodents adipose tissue is the main source of resistin, in humans resistin is expressed primarily in macrophages. In a variety of pathophysiologic states, particularly in type 2 diabetes mellitus and in chronic kidney disease, the serum concentration of resistin is increased. Resistin reduces the glucose uptake in adipose tissue and skeletal muscle cells and may be involved in insulin resistance. A positive correlation between resistin levels and inflammatory markers has been described. Resistin has a potential role in cardiovascular disease and may contribute to an increased atherosclerotic risk by modulating the activity of endothelial cells. We recently found that resistin in concentrations measured in uremia is able to interfere with the chemotactic movement and the oxidative burst of neutrophils, cells of the first-line nonspecific immune defense. Therefore, resistin may also contribute to the disturbed immune response and as a consequence to the increased risk of infections in uremic and diabetic subjects.

Cytokine biomarkers, endothelial inflammation, and atherosclerosis in the metabolic syndrome: emerging concepts

In recent years, an explosion of research related to the cellular and vascular accompaniments of the metabolic syndrome has generated intense interest and controversy. Attention has focused on the vascular endothelium, where heightened, low-grade inflammatory processes lead to a continuum of vascular insults ranging from early endothelial derangements to advanced atherosclerosis. Inflammatory biocytokines, such as C-reactive protein, have been speculated to be both markers and mediators of oxidative stress and endovascular toxicity. Adipocytokines originating from fatty tissue have reinforced the concept that fat is a metabolically active organ rather than inert tissue. To fully elucidate its complex pathogenetic mechanisms, further inquiry into the inflammatory components of the metabolic syndrome is warranted. Unraveling the role of emerging proinflammatory markers has the promising potential to shed light into the underlying pathophysiology of the epidemic of obesity and the metabolic syndrome and thus help devise effective therapies.

Polymorphism in resistin promoter region at -420 determines the serum resistin levels and may be a risk marker of stroke in Japanese type 2 diabetic patients

Resistin, which appears to be related to insulin resistance, is secreted mainly from macrophages in human and some of its polymorphisms have been reported. Based on recent in vitro studies, resistin may be associated with atherosclerosis by mediating endothelial hyperactivity. We investigated whether resistin polymorphism at -420C>G is associated with serum resistin levels and diabetic macroangiopathy (coronary heart disease, arteriosclerosis obliterans, and stroke) in 349 Japanese type 2 diabetic patients (DM) and 286 non-diabetic controls (non-DM). Serum resistin levels in DM with a history of stroke were significantly higher than those without, 19.6+/-2.1 and 12.4+/-0.5 ng/ml (P<0.001), respectively. Furthermore, the levels were significantly increased in a genotype-dependent manner (CC, CG, GG) based on the polymorphism at -420C>G (P<0.001) in both DM and non-DM. The prevalence of stroke in DM significantly increased according to the presence of mutations (P<0.035). In multivariate logistic-regression analysis, individuals with the CG or GG genotypes were significantly more likely to have had a stroke than individuals with the CC genotype (vs. CG; OR 2.99, P=0.024, vs. GG; OR 4.49, P=0.010). These data suggested that the genotyping of resistin polymorphism at -420(C>G) can be a risk marker for stroke susceptibility in Japanese type 2 diabetic patients.

The metabolic syndrome

The "metabolic syndrome" (MetS) is a clustering of components that reflect overnutrition, sedentary lifestyles, and resultant excess adiposity. The MetS includes the clustering of abdominal obesity, insulin resistance, dyslipidemia, and elevated blood pressure and is associated with other comorbidities including the prothrombotic state, proinflammatory state, nonalcoholic fatty liver disease, and reproductive disorders. Because the MetS is a cluster of different conditions, and not a single disease, the development of multiple concurrent definitions has resulted. The prevalence of the MetS is increasing to epidemic proportions not only in the United States and the remainder of the urbanized world but also in developing nations. Most studies show that the MetS is associated with an approximate doubling of cardiovascular disease risk and a 5-fold increased risk for incident type 2 diabetes mellitus. Although it is unclear whether there is a unifying pathophysiological mechanism resulting in the MetS, abdominal adiposity and insulin resistance appear to be central to the MetS and its individual components. Lifestyle modification and weight loss should, therefore, be at the core of treating or preventing the MetS and its components. In addition, there is a general consensus that other cardiac risk factors should be aggressively managed in individuals with the MetS. Finally, in 2008 the MetS is an evolving concept that continues to be data driven and evidence based with revisions forthcoming.

Resistin inhibits essential functions of polymorphonuclear leukocytes

The serum levels of resistin, a 12-kDa protein primarily expressed in inflammatory cells in humans, are increased in patients with chronic kidney disease and in those with diabetes mellitus. Both groups of patients have an increased risk of infections mainly as a result of disturbed polymorphonuclear leukocyte (PMNL) functions. Therefore, we investigated the influence of resistin on human PMNLs. Serum resistin concentrations were determined with a sandwich enzyme immunoassay. Using PMNLs from healthy subjects, chemotaxis was tested by the under-agarose method. Flow cytometric assays to measure oxidative burst and phagocytosis were conducted in whole blood. The uptake of deoxyglucose was determined as measure of the PMNL activation state. The activity of intracellular kinases was assessed by Western blotting and by in vitro kinase assays. Resistin inhibited PMNL chemotaxis and decreased the oxidative burst stimulated by Escherichia coli and by PMA, but did not influence PMNL phagocytosis of opsonized E. coli and PMNL glucose uptake. The inhibition of PMNLs by resistin was observed at concentrations found in serum samples of uremic patients, but not in concentrations measured in healthy subjects. Experiments with specific signal transduction inhibitors and measurements of intracellular kinases suggest that PI3K is a major target of resistin. In conclusion, resistin interferes with the chemotactic movement and the stimulation of the oxidative burst of PMNL, and therefore may contribute to the disturbed immune response in patients with increased resistin serum levels such as uremic and diabetic subjects.

The effect of obesity on heart rate (heart period) and physiologic parameters during pregnancy

Obesity and excess gestational weight gain (EGWG) in pregnancy increase the risk for adverse maternal and infant outcomes. Along with careful monitoring of weight gain during pregnancy, early identification of a maladaptive response to the changes of pregnancy may help to avoid adverse outcomes. Simple physiologic markers such as resting heart rate (HR), heart period (HP), and blood pressure (BP) may be powerful predictors of cardiovascular adaptation to pregnancy. This article summarizes the current state of the science regarding the effect of obesity (body mass index [BMI] > or =30 kg/m(2)) and EGWG in pregnant women at rest in laboratory settings. The impact of differences in weight gain (kg and BMI) on pregnancy outcomes is also examined. A search was conducted for articles published from 1985 to 2006 reporting data on body weight and HR or HP at rest from randomized controlled trials or controlled trials conducted in laboratory settings involving pregnant women at low or high risk for adverse pregnancy outcomes who were obese or had EGWG. A meta-analysis was conducted on the 23 studies meeting inclusion criteria to explore the relation of BMI to HR, HP, and physiologic parameters. Autonomic responsiveness was found to be diminished in obese women with a BMI > 30 kg/m(2) and in women with high risk for adverse pregnancy outcomes, which may indicate a maladaptive autonomic response that is imbalanced and disorganized and that reduces adaptation to environmental demands.

Central resistin induces hepatic insulin resistance via neuropeptide Y

Sensing of peripheral hormones and nutrients by the hypothalamus plays an important role in maintaining peripheral glucose homeostasis. The hormone resistin impairs the response to insulin in liver and other peripheral tissues. Here we demonstrate that in normal mice resistin delivered in the lateral cerebral ventricle increased endogenous glucose production during hyperinsulinemic-euglycemic clamp, consistent with induction of hepatic insulin resistance. In agreement, central resistin inhibited Akt phosphorylation and increased the expression of glucose-6-phosphatase, the enzyme regulating glucose output in the liver. Central resistin induced expression of proinflammatory cytokines as well as suppressor of cytokine signaling-3, a negative regulator of insulin action in liver. Central infusion of resistin was associated with neuronal activation in the arcuate, paraventricular and dorsomedial nuclei, and increased neuropeptide Y (NPY) expression in the hypothalamus. The effects of central resistin on glucose production as well as hepatic expression of proinflammatory cytokines were abrogated in mice lacking NPY. Pretreatment of wild-type mice with antagonists of the NPY Y1 receptor, but not the Y5 receptor, also prevented the effects of central resistin. Together, these results suggest that resistin action on NPY neurons is an important regulator of hepatic insulin sensitivity.